Citation
Kinetics of processing asphaltic residues

Material Information

Title:
Kinetics of processing asphaltic residues
Creator:
Holmgren, John Daniel, 1927-
Publication Date:
Copyright Date:
1954
Language:
English
Physical Description:
87 leaves : ; 28 cm.

Subjects

Subjects / Keywords:
Asphalt ( jstor )
Calibration ( jstor )
Gas analysis ( jstor )
Gulfs ( jstor )
Mathematical constants ( jstor )
Oxygen ( jstor )
Precipitators ( jstor )
Reaction kinetics ( jstor )
Storage tanks ( jstor )
Velocity ( jstor )
Asphalt ( lcsh )
Chemistry thesis Ph. D
Dissertations, Academic -- Chemistry -- UF
City of Gainesville ( local )
Genre:
bibliography ( marcgt )
non-fiction ( marcgt )

Notes

Thesis:
Dissertation (Ph.D.) - University of Florida, 1954.
Bibliography:
Bibliography: leaves 85-86.
General Note:
Manuscript copy.
General Note:
Vita.

Record Information

Source Institution:
University of Florida
Holding Location:
University of Florida
Rights Management:
Copyright [name of dissertation author]. Permission granted to the University of Florida to digitize, archive and distribute this item for non-profit research and educational purposes. Any reuse of this item in excess of fair use or other copyright exemptions requires permission of the copyright holder.
Resource Identifier:
022286213 ( AlephBibNum )
13640460 ( OCLC )
ACZ2581 ( NOTIS )

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KINETICS OF PROCESSING

ASPHALTIC RESIDUES





By
JOHN DANIEL HOLMGREN


A DISSERTATION PRESENTED TO THE GRADUATE COUNCIL OF
THE UNIVERSITY OF FLORIDA
IN PARTIAL FULFILMENT OF THE REQUIREMENT FOR THE
DEGREE OF DOCTOR OF PHILOSOPHY


UNIVERSITY OF FLORIDA
JUNE, 1954


*1




























ACKNOWLEDGEMENT


The author wishes to thank Dr. H. E. Schweyer for his help-

ful guidance in directing this research. The author is also indebted

to Dr. Mack Tyner for his suggestions on kinetics and to the other

members of his Supervisory Committee, Professor T. L. Bransford,

Dr. W. F. Brown and Dr. A. H. Gropp for their counsel and criticism.

The author wishes to thank Mr. Douglas Baldwin, Jr. for his work on

the drawings, Mr. E. A. J. Warshyk for his help on the construction of

the equipment, The Texas Company for supplying the asphalt and the

Engineering and Industrial Experiment Station for sponsoring this

project.


- ii -












TABLE OF CONTENTS


Page

ACKNOWLEDGME . . . . . . L. . . .

LIST OF FIURES .................. .

LIST OF TABLES ................ vii

I. INTRODUCTION ...... ............ 1

II. THEORY ................ ... 5

A. The Asphalt Blowing Reaction . . . . 5

B. Heterogeneous Reactions . . . . . 6

III. MATERIALS ..................... 10

IV. APPABATU ......... ............ 11 .

A. Processing Equipment . . . . . .. 11

1. Asphalt storage tank . . . .. 11
2. Asphalt reactor . . . . .. 14
3. Electrical precipitator . . . .. 17
4. Flow panel board . . . . .. 19
5. Temperature panel board . . . .. 21
6. Piping ................ 23

B. Analysis Equipment . . . . . . 24

1. Gas analysis unit . . . . 24
2. Gas analysis calibration . . .. 25

V. PROCEDURES ........... ....... . 30

A. Operating Procedure . . . . . . 31

B. Analytical Procedure . . . . ... 37

VI. CALCULATIONS ................... /0.

A. Kinetics .................. 40

B. Reaction Mechanism . . . . ... .. 43

C. Scale Up ............... .. 48

ii -












TABE OF CONTENTS


Page

VII. RESULTS AND DISCUSSION . . . . . . . 50

A. Kinetics ............ ...... 50

B. Reaction Mechanism . . . . . .. 62

C. Scale Up ................... 74

VIII. CONCLUSIONS .................. .. 80

IX. NOMENCLATURE .................... 83

X. BIBLIOGRAPY .................. .. 85

XI. APPENDICES ..................... 87

A. Drawings ....... ...... ..... 87

B. Experimental Data . . . . . . . 94

C. Calibration Curves .... ......... 102

XII. BIOGRAPHY OF ATHOR . . . . . . .. .. 110


- iv -













LIST OF FIGURES


Figure Page
No.

1. Asphalt Blowing Pilot Plant . . . . .... .12

2. Asphalt Storage Tank, Reactor and Electrical
Precipitator .......... ......... .. 20

3. Asphalt Blowing Flow Panel Board and Gas Analysis
Unit . .. .. ... . .. .. . . .. 22

4. Thermal Conductivity Cell Calibration Curve for
Ternary System of Oxygen, Nitrogen and Carbon Dioxide 29

5. Softening Point and Reaction Time Relation for Batch
Runs Using Gulf Coast Asphalt TA-1023-2 . . .. 51

6. Reproducibility of Batch Run Data, Gulf Coast
Asphalt TA-1023-2 . . . . . . . .... .53

7. Reaction Rate and Product Consistency for Batch
Runs, Gulf Coast Asphalt TA-1023-2 . . . .. 55

8. Evaluation of Rate Equation Exponent, a ...... 57

9. Evaluation of Rate Equation Exponent, p, and Pseudo
Reaction Velocity Constant, k . . . . . . 57

10. Variation of the Pseudo Reaction Velocity Constant,
k, with Temperature for Gulf Coast Asphalt TA-1023-2 60

11. Oxygen Utilization and Product Consistency for
Gulf Coast Asphalt TA-1023-2 . . . . .... .64

12. Oxygen Utilization and Product Consistency for
East Texas Asphalt TA-1024 . . . . . . 64

13. Oxygen Utilization and Product Consistency for
East Central Texas Asphalt TA-1025 . . . .. 65

14. Oxygen Utilization and Product Consistency for
South Texas Heavy Asphalt TA-1026 . . . ... 65

15. Cumulative Oxygen Balance for Low Space Gas
Velocity and Low Oxygen Concentration,
Gulf Coast Asphalt TA-1023-2 . . . . . .. 70

v -












LIST OF FIGURES


Figure Page
No.

16. Cumulative Oxygen Balance for High Space Gas
Velocity and High Oxygen Concentration,
Gulf Coast Asphalt TA-1023-2 . . . . .... "0

17. Properties of Asphalt Products, Gulf Coast TA-1023-2 "2

18. Properties of Asphalt Products, East Texas TA-1024 72

19. Properties of Asphalt Products,
East Central Texas TA-1025 . . . . . ..

20. Properties of Asphalt Products,
South Texas Heavy TA-1026 . . . . . . 73

21. Asphalt Blowing Flow Diagram . . . . ... 88

22. Asphalt Blowing Piping Diagram . . . ... 89

23. Asphalt Blowing Wiring Diagram . . . . .. 90

24. Asphalt Blowing Storage Tank . . . . .... .91

25. Asphalt Blowing Reactor .. . . . . . 92

26. Asphalt Blowing Electrical Precipitator . . .. q3

27. Air Feed Rotameter Calibration Curve, Schutte and
Koerting 3F Tube and Number 2 Aluminum Float . . 10b

28. Oxygen Feed Rotameter Calibration Curve, Schutte
and Koerting 1R Tube and Stainless Steel Float . 177

29. Converter Gas Rotameter Calibration Curve, Sehutte
and Koerting 3F Tube and Number 1 Aluminum Float . 108

30. Gas Analysis Rotameter Calibration Curve, Fisher
and Porter 01-N-15A Tube with Pyrex Glass and
Stainless Steel Floats . . . . . . . 109


- vi -












LIST OF TABLES


Table Page
No.

1. Properties of Asphaltic Residues . . ... 10

2. Calibration Data for Gas Analysis Instruments . . 27

3. Asphalt Processing Conditions . . . . ... 30

4. Gas Properties .............. ..... 46

5. Reproducibility of Batch Run Data . . . ... 52

6. Slope and Intercept Values from Figure 7 . . . 54

7. Slope and Intercept Values from Figure 8 . . .. 58

8. Pseudo Reaction Velocity Constants . . . ... 59

9. Variation of the Pseudo Reaction Velocity Constant
with Agitation ........ ........... 61

10. Percentage Error for Reaction Rate Equation .... . 62

11. Oxygen Utilisation for Processed Residua . . .. 66

12. Unaccountable Oxygen Losses to 200 OF. Ring and Ball
Product Consistencies ................ 68

13. Fume Oil Reaction Products to 200 OF. Ring and Ball
Product Consistencies . . . . . . . . 74

14. Comparison of Experimental Batch and Continuous Data 76

15. Operating Conditions for All Asphalt Blowing Runs . 95

16. Experimental Data . . . . . .... ..... 98

17. Air Feed Rotameter Calibration Data . . . ... 103

18. Converter Gas Rotaaeter Calibration Data . . . 104

19. Oxygen Feed Rotameter Calibration Data ...... 105

20. Gas Analysis Rotameter Calibration Data ...... 105


- vii -












I. INTRODUCTION


In 1951 13,000,000 short tons of petroleum asphalt were produced

in the United States at a value of 216 million dollars (19). Of this

total 70 per cent was used for paving, 24 per cent for roofing and water-

proofing and 6 per cent for specialty products as rubber, molding com-

pounds and paints. These materials are processed by a variety of

methods, one of the most important of which is by subjecting a residual

stock to air at elevated temperatures. The processing of asphaltic

residua obtained from the distillation of petroleum oils with oxygen

containing gases at elevated temperatures is known as air blowing

and has been practiced commercially for over sixty years (7).

According to the present practice the asphalt residuum is blown

at about 450 to 575 OF. at a rate of 30 to 50 cubic feet of air per

minute, per ton of asphalt, for a period of 5 to 12 hours in a suitable

reactor vessel (1). Air blowing the residuum is carried out in either

a batch or continuous operation. In a batch operation the asphalt is

contacted with air by either blowing or sucking the air through the

asphalt charge. In continuous blowing the stock is moved through one

or more vessels in series each having a reaction zone. The finished

asphalt is removed continuously and part of it can be recycled with

fresh feed. The asphalt is reacted until the desired product consis-

tency is obtained.

Asphalts as a class are non-aqueous colloidal systems of very

high viscosity, which may have the character of either a sol or gel.

-1-










-2 -

They consist principally of hydrocarbons and hydrocarbon derivatives

and may contain groups of saturated allphatics, naphthenies or cyclo-

paraffins, aliphatics with olefinic double bonds and eromatics (16).

Exact knowledge of the chemical composition of asphalts is

not known but there has been recognition of distinct constituent

groups as asphaltous acids and anhydrides, asohaltenes, esphaltic resins,

petroleum resins, petroleum oils, carbenes, carboids and inorganic a-

terial.

The resulting reaction of oxygen with asphalt residuum is gen-

erally called an oxidation process. Actually this term oxidation is

a misnomer, because the reaction has been characterized as essentially:

(a) the removal of a small amount of hydrogen to fore eater followed by

condensation and polymerization of the hydrocarbons (13), (b) the addition

of oxygen which forms unstable compounds from which water is eliminated

leaving unsaturated compounds which polymerize (18), or (e) slow poly-

merisation of the oils and resins to asphaltenes (9).

Air blowing of asphalts changes the physical properties of the

residuum which results in increased hardness, gravity, softening point

and lower ductility. The extent of these changes depend on the original

asphalt and the processing and conditions to which it is subjected. The

chemical and polymerization reactions which cause these effects are very

complex and very little is known about the mechanism, stoichiometry or

kinetics of the reaction. It is known that the air blowing process is

an exethermie reaction (6) and that among the water and carbon dioxide

that are eliminated are also oxygenated hydrocarbons, oil vapor and










-3-

mechanically entrained oil. In the work reported by Thurston and Knowles

(18) on one asphalt, 68 per cent of the weight of the oxygen that Eas

used reacted to form water and 14 per cent formed carbon dioxide. The

remaining unaccounted for oxygen apparently formed other oxygenated

compounds. Kats (13) found that oxygen and nitrogen are present in the

products in very small amounts at Ring and Ball softening points up to

200 OF. and only to an extent of approximately 2 per cent in very high

melting samples. Similar results (9) were also obtained for a different

residuum where the oxygen content and the change in quantities of oils,

resins and asphaltenes were determined for the air blowing process.

The literature on the air blowing of asphalt is very limited

outside of the references given by Abraham (1) on patents. A series

of articles by Holland (11) and more recently a staff article by Hoiberg

(10) constitute about the only detailed discussions on the asphalt blowing

process from a manufacturer's view point. Blakely, I.Ajl. (5) have re-

ported the effect of agitation on air blowing Venezuelan and Mexican

asphalts on a pilot plant scale.

Because of the complex nature of the reactants and reaction mecha-

nism for the air blowing process, the degree of reaction is generally

described by some physical property of the residuum. The rate of change

of this property in turn is a function of several process variables as

the type of asphalt residuum, volume of the reactor, feed gas flow rate,

temperature, degree of agitation and oxygen content in the feed gas.

There is no suitable pilot plant or laboratory data presently available

to correlate and relate the proceeding process variables for design










4-

considerations of commercial asphalt blowing units. Therefore, it is

the object of this investigation to present principles that may serve

as the basis for design and operation of commercial asphalt blowing

equipment. These principles include: (a) kinetic equations and eva-

luation of reaction rate constants, (b) reaction mechanism including

kinetic order and oxygen utilization, (o) scale up procedures from

pilot plant equipment to industrial processing equipment.














II. THEORY


A. The Asphalt Blowina Reaction

The gross chemical reaction for the asphalt blowing process

might be described as follows:

A, + 02 + inerts----- Ax + L + C002 + H20 + 02 + inerts + AH

where

Ar = the asphalt charge stock

Aox the composite air blown asphalt product
not removed from the reacting zone

Lx a the composite condensed product removed
overhead minus C02, H20 and other fixed gases

AH = the heat of reaction

To arrive at this gross reaction, the actual mechanism could

consist of a series of progressive reactions described in the following

diagram:

Ar + 02-Ao01 + 02---A2 + 02 -+Ao + C02 + 1H20 ...

Ll L2 L3 + LX

Each step of this progressive reaction probably yields oxygenated

compounds of unknown and complex composition, some of which remain in

the blown asphalt and some appear as overhead products as designated

by L. The residual material is dehydrogenated and decarbonized as

shown by the appearance of H20 and CO2. Polymerization also occurs to

produce a product with an increase in viscosity as evidenced by the

increase in Ring and Ball softening point. No information is available

on the exact chemical reactions occurring either as the above gross reaction

5 -










6-

or as the progressive reaction. It is necessary, therefore, to study

the degree of chemical reaction in terms of a change in a physical pro-

perty of the system as suggested by Frost and Pearson (8). For this

study the physical property is determined as the Ring and Ball softening

point by the A. S. T. M. method D 36-26 (4).to evaluate the gross reac-

tion from Ar to Ag.

B. Heteroeneous Reactions

Gas-liquid reactions may be typified as a gas-absorption opera-

tion in which a chemical reaction occurs. The actual reaction may

occur at the interface separating the gas and liquid phase or in

either the gas or liquid films adjacent to the interface. In either

case, a problem of mass transfer of reacting materials from one phase

to another phase or to the interface is involved. The net rate of reac-

tion is then determined by the rate of chemical reaction itself and

by the rates of mass transfer of reacting materials (12).

Rates of gas absorption accompanied by chemical reaction in the

liquid have been calculated kinetically for certain simple cases, for

example, the absorption of carbon dioxide with ethanolamine. No esti-

mates have been made for cases involving second order chemical kinetics.

The differential equations involving transient accumulations, diffusions

and reaction are known, but the mathematical solutions are too involved

for practical solutions. Perry and Pigford (15) used a digital computer

to calculate the solutions of a number of theoretical second order cases.

The results were represented as the ratio of the local mass transfer










7 -

coefficient with reaction to the mass transfer without reaction. These

results were found todtpend on the rate and chemical equilibrium constants,

the ratio of reactants and the time exposure of the liquid surface.

Sherwood and Pigford (17) present a more general treatment for the process

of simultaneous absorption and chemical reaction.

The process of blowing asphalt residuum canbe classified as a

heterogeneous and exothermic reaction of a liquid phase and a gas phase.

It is a flow system where the active agent in the gaseous phase (oxygen)

reacts with the liquid asphalt to form asphalt products of increasing

consistency. A consideration of the physical system in the asphalt

blowing process leads to a concept of two possible controlling mechanisms

or a combination of both. As the feed gas is exposed to the liquid asphalt,

the chemical reaction may occur at the interface of the gas-liquid or in

the gas or.liquid films adjacent to the interface. If the chemical reac-

tion takes place very rapidly at the gas-liquid interface, it then becomes

necessary to replace the oxygen used from the film with fresh oxygen for

the process to continue. This fresh oxygen must diffuse from inside a

gas bubble, through the gas film to the interface where the reaction

is occurring. When this diffusion rate is slow compared to the bhemi-

cal reaction rate, the diffusion resistance will control the gross rate

of reaction. Conversely, if the chemical reaction rate at the interface

is slow relative to diffusion, then the chemical reaction is the controlling

rate. The effect on the gross reaction rate for a combination of the

diffusion and chemical reaction mechanism might be expressed as

driving potential
gross reaction rate =
diffusion resistance + chemical resistance










8 -

Considering the possible progressive type of reaction and physical sys-

tem involved, it is conceivable that the diffusion resistance might

control for some of the steps while the chemical resistance might control

for other steps.

The gross reaction rate is the degree of chemical reaction with

time and is measured as the change of Ring and Ball softening point with

reaction time. The driving potential for the gross reaction is assumed

to be a combination diffusion and chemical reaction driving force. The

driving force for the diffusion mechanism is the difference of partial

pressure of the oxygen in the gas bubble and at the gas-liquid interface.

The driving force for the chemical reaction is the concentration of reac-

ting materials. Assuming the driving potential to be a combination of

diffusion and chemical reaction, the resistance for the gross reaction

rate will also be a function of these two mechanisms.

A general rate equation might be derived to relate the processing

variables in terms of a gross reaction rate. This equation is

dR/dt kPPSSRr (1)

where

dR/dt = the gross reaction rate measured as
Ring and Ball softening point

The diffusion driving force is PPSa which is the oxygen concentration

and space gas velocity for the feed gas. The asphalt concentration term

is related to the instantaneous value of softening point, R, at any time,

t. The value, k, is a pseudo reaction velocity constant and is a func-

tion of the gross reaction rate resistance. The value of k also includes











9-

a factor that accounts for a decrease in driving potential as the reac-

tion proceeds. The data for this investigation was evaluated in terms

of this proposed rate equation.












III. MATERIALS


The asphaltic residues used in this investigation were sup-

plied through the courtesy of The Texas Company. The samples represent

four different types of asphalt having substantially different proper-

ties. The properties of the residues used in this study are tabulated

in Table 1.

TABLE 1

PROPERTIES OF ASPHALTIC RESIDUES


Sample TA-1023-2 TA-1024 TA-1025 TA-1026


Identification Gulf Coast East East South
Naphthenio Texas Central Texas
Texas Heavy

Density 0 60 oF. 0.9670 1.0215 1.0203 0.9908

Viscosity, Saybolt
Fural Seconds, 210 oF. 106 .... .... 85

Ring and Ball Softening
Point, OF. 70* 100 98 73*

Penetration, 77 oF. .... 227 283 ....


*Estimated by extrapolating values
time curves to sero time.


of Ring and Ball versus reaction


-10-












IV. APPARATUS


The asphalt blowing unit was designed and constructed to blow

asphalt in either a continuous or a batch operation. The asphalt appa-

ratus consists of an asphalt storage tank, asphalt reactor, electrical

precipitator, flow panel board, temperature panel board and a continuous

gas analysis unit. A picture of the unit is shown in Figure 1 and a

flow diagram in Figure 21. Cdplete piping and wiring diagrams are

shown in Figures 22 and 23.


A. Processing Eauiment

1. Asphalt storage tank. The asphalt storage tank is a

heated tank used to store and preheat the asphalt reactor feed. Cir-

culation is maintained in the storage tank by pumping the asphalt through

a closed piping system.

The storage tank shell was fabricated from a piece of 12 inch

steel pipe and fitted with ring flanges on both ends. A flanged dished

bottom with a centered 3/4 inch outlet drain was bolted to the lower

shell flange. A round 1/4 inch transit cover was fastened to the top

shell flange.

The tank is heated with eight 500 watt electrical strip heaters

bolted to the outside shell. They are alternated one long and one short.

The dished bottom is heated with a 1,000 watt ring heater. The heaters

are wired in parallel and connected to a three-heat snap switch. High

heat position on the switch utilizes the long, short and bottom heaters.

Medium heat uses only the short and bottom heaters. Low heat turns on

n-











:3.
-U2-



i'
r -





Iiud
|n. r-;










-13-

only the bottom heater. The heaters were selected and arranged in this

manner to permit changing the heated length of the storage tank as deter-

mined by the height of the liquid asphalt in the tank. A General Electrio

Thermostat is.used to control the temperature of the asphalt in the tank

and directly controls the electrical line load to the heaters. Thermo-

stat and thermocouple protection tubes were made from steel pipe and

welded in the side of the reactor shell. The tank was insulated on the

side and bottom surfaces with block magnesia insulation and then covered

with a sheet metal protective cover. The entire assembly was mounted on

four angle iron legs. It was then placed on a Toledo platform scale. The

scale is used to measure mass feed rates of the asphalt to the reactor.

The hot asphalt in the storage tank is circulated and trans-

ferred to the asphalt reactor with a Viking pump. This is a positive

displacement gear type pump which is mounted on the floor below and to the

side of the asphalt storage tank. Asphalt is pumped from the storage tank

with a free suspension suction pipe that is inserted into the storage tank

through the transit cover and extends close to the bottom. The recircula-

tion return pipe is also freely suspended and discharges asphalt near the

top of the tank. An auxiliary three-heat immersion heater, thermostat

control and thermocouple are placed in the recirculation line to indicate

and prevent any appreciable temperature drop in the asphalt while it is

being recirculated and adjusted to the reactor asphalt temperature. The

recirculation piping is steam traced with 1/4 inch copper tubing and the

asphalt reciroulation lines are preheated to prevent any asphalt freeze-

up during initial recirculation. Drain valves are suitably located to










-14 -

completely drain the recirculation lines. A detail of the asphalt. storage

tank is shown in Figure 24.

2. Asphalt reactor. The asphalt reactor is a heated and agi-

tated tank which permits blowing reacting gas through the hot asphalt.

It is possible to blow the asphalt as a batch operation with no fresh

asphalt feed or as a continuous operation where fresh asphalt feed is

pumped in and asphalt product continuously removed. The reacting asphalt

occupies only 60 per cent of the total reactor volume. The remaining

40 per cent is used as a vapor space for entrainment separation.

The asphalt reactor was made froa a piece of 8 inch steel pipe

that was flanged on both top and bottom. The bottom is fitted with a

dished plate with a 3/4 inch center drain pipe. The top 1/4 inch steel

plate cover is used to support the agitator assembly, themocouple pro-

tection tubes, asphalt feed line and entrainment baffle plate. The

reactor has welded pipe fittings for the reactor gas feed, converter gas

product and reacted asphalt product.

The reactor is heated wLth five 500 watt strip heaters equally

spaced and bolted to the outside surface of the reactor pipe. The lengths

of the heaters were selected so that they would provide heat directly

to the height of the reactor pipe that would be filled with liquid asphalt.

This prevent localised heating in the vapor section and reduces the

amount of coke formed on the reactor walls. The temperature of the reacting

asphalt is controlled with a Minneapolis-Honeywell-Brown Pyr-0-Vane pro-

portional temperature controller.










15-

The agitator assembly for the asphalt reactor is a laboratory

model Turbo Mixer Agitator. The combination used for this investigation

was a hooded ring cover and aerator impeller. The hooded ring is sup-

ported from the top cover of the reactor by two guide rods. The impel-

ler is located 4 inches from the bottom of the reactor and is fastened

to a shaft that extends through the top cover and packing gland into the

agitator head and pulley assembly. The agitator pulley is a four step

cone pulley and is matched with a similar pulley on the 3/4 horsepower

1750 r.pA. agitator drive motor. This pulley arrangement permits variable

agitator speeds with a V-belt drive. The minimum agitator speed is ?00

r.p.m. and the next speed is 1300 r.p.a..

Thermocouple protection tubes were made from 1/8 inch steel

pipe and were threaded into welded couplings on the top reactor cover

plate. There are three thermocouple tubes; one for the Minneapolis-

Honeywell-Brown reactor temperature controller and two for the Bristol

temperature recorder. The lasttwo were fabricated with a differential

height of 1 inch so that they could be used to indicate asphalt liquid

level in the reactor. The long thermocouple indicates the liquid tem-

perature while the short thermoeouple indicates the vapor temperature.

Since the gas temperature is several degrees lower than the liquid tem-

perature, a differential reading between the two thermocouples indicates

that the liquid level is between these two thermocouple positions.

The asphalt feed line extends through the top of the reactor

cover and through the edge of the agitator hood ring. The feed line was

reduced to 1/4 inch nominal pipe inside the reactor to prevent any excessive










16 -

asphalt feed holdup. The bottom of the asphalt feed line is flush with

the bottom of the agitator hood ring. Thus the asphalt is fed directly

into the side of the rotating aerator impeller. A needle valve on the

asphalt storage recirculation line controls the asphalt feed to the reae-

tor and a thermocouple measures the asphalt feed temperature.

Reactor feed gas is introduced beneath and into the aerator

impeller through a T-tube sparger. The feed gas line comes into the

reactor in a 3/8 inch pipe directly above the bottom reactor flange.

This pipe extends into the reactor and then branches into a horizontal

"T" directly under the impeller. Two 1/8 inch vertical pipe tips are

located on the end of this *T" at a distance of 1/2 the radius of the

aerator impeller. The feed gas line to the reactor is piped as an in-

verted "U" stand pipe to prevent any asphalt from flowing through the

distributor tips back into the air feed line.

The reacted gas or converter gas is removed from the reactor

through a 1-1/2 inch pipe located directly beneath the top reactor flange.

The exit gases from the reactor first pass over an entrainment separator

baffle plate that is fitted below the converter gas outlet. This baffle

plate prevents swirling of the hot asphalt by agitation into the converter

gas outlet pipe. The baffle plate is fastened to the bottom side of the

top reactor cover. After leaving the reactor, the converter gases pass

through a short heat exchanger before entering the electrical Drecipitator.

This heat exchanger or cooler is used to help break any foaa that may form

in the reactor and flow up into the converter gas discharge pipe. The cooler

is a 3 inch steel pipe that is welded around the 1-1/2 inch converter gas










17 -

outlet pipe. The annular area between the pipes is fitted with 1/2 inch

pipe fittings for inlet and outlet cooling water. A thermocouple at

the top of the converter gas cooler measures the exit reactor converter

gas temperature.

During a batch or continuous run the reactor asphalt product

or asphalt samples are removed from the reactor through the 3/8 inch

pipe reactor aide drain. This drain is located beneath the converter

gas outlet line and has a quick-opening valve.

The reactor shell is insulated with asbestos insulation and

enclosed in a protective sheet metal cover. The top and bottom of the

reactor are not insulated. These surfaces were purposely left uncovered

so that the exothermic heat of reaction of the reacting asphalts would be

dissipated. Closer temperature control can be obtained when this heat

is dissipated and the temperature controller and reactor heaters are used

to maintain the desired temperature.

The reactor and agitator drive motor are arranged on a special

stand. The length of the asphalt piping from the asphalt storage tank

is as short as possible to reduce the amount of asphalt in the recir-

culation lines. Details of the asphalt reactor are shown in Figure 25.

3. Electrical precipitator. The purpose of the electrical or

Cottrell electrostatic precipitator is to remove the mechanically entrained

mist and smoke from the reactor converter gases.

The precipitator unit was fabricated from a piece of 3 inch

steel pipe and welded to inlet and outlet gas chambers. A round 1/8 Lnch

steel rod is used as a high voltage electrode with a steel ball welded










-18-

to the bottom of the electrode. The entire assembly is supported by a

high voltage insulator bushing and the insulator bushing is mounted on a

1/4 inch Bakelite plate which serves as the top of the outlet gas chamber.

A baffle plate is placed over the inlet feed gas line in the bottom gas

chamber to prevent the gas from impinging directly on the high voltage

electrode. A drain on the bottom gas chamber permits removal of the

condensed and precipitated smoke and fog products.

Access panels on the front of the gas chambers are provided to

allow alignment of the high voltage electrode and cleaning of the preci-

pitator. The panels are covered with Lucite plastic windows aqd it is

possible to observe the smoke content of the converter gas entering and

leaving the precipitator.

The precipitator pipe shell is wrapped with 1/4 inch copper tubing

on a 2 inch coil spacing. Cooling water passes through the tubing. As

a result water condenses out of the converter gas as it cools in the

precipitator. The condensed water is collected through the bottom drain

together with the precipitated oils. The cooled converter gases from

the precipitator pass through another heat exchanger to lower the tempera-

ture of the gases below room temperature and to prevent any condensation

from occurring in the gas rotameters. The electrical precipitator after-

cooler is a coil of 1/4 inch copper tubing placed inside a piece of 3 inch

steel pipe 12 inches in length. The converter gases pass across the

water cooled copper coil and the condensed water is removed from a bottom

drain on the cooler. Both the electrical precipitator and after-cooler

are insulated with air cell asbestos pipe insulation.

The laboratory model high tension rectifier used to obtain the










19 -

high voltages necessary for the electrical precipitator is a Carpco

Engineering Company Model RL High Voltage Rectifier. This rectifier

unit permits variable direct current output voltages from 0 to 40,000

volts. The current output is variable from 0.1 to 15.0 milliamperes.

Figure 26 is a detail of the electrical precipitator and Figure 2 Is

a picture of the storage tank, reactor and electrical precipitator.

4. Flow panel board. A1 the instruments necessary to control

and aeter the gas flows in the asphalt blowing process are grouped to-

gether on the gas flow panel board.

Three rotameters measure the air feed, oxygen feed and conver-

ter gas floor rates. The air feed and converter gas rotameters are standard

Schutte and Koerting 3? tubes with millimeter scales. The rotanmters are

calibrated with specially made aluminum floats for the gas flow rates

required in this study. The oxygen feed rotameter to a standard Sehutte

and Koerting 1R tube and stainless steel float. Gas flow control for the

metered feed gases is obtained by using bronae needle valves. Gas pressures

in the asphalt reacting system are measured by using panel mounted, well

type manometers. The feed gas manometers measure the pressure drop across

the gas rotameters. These indicated pressures are also the reactor gas

pressures. The feed gas manometer indicates the pressure of the reactor

feed gas; the converter gas manometer measures the pressure of the gas in

the reactor vapor space or back pressure in the reactor. For constant

feed gas flow rates the feed gas pressure changes with any change in the

reactor asphalt liquid level height. Therefore, during continuous operation

this feed gas manometer is used to control the asphalt product rate and to




-20 -


4


-r-i


Figure 2. ialtM Storage Tak, Reactor ad
'-eqatrioal Precipitator


-I.-










21-

maintain a constant asphalt reactor liquid level height. The converter

gas back pressure is controlled by the depth of imaersioq of the conver-

ter gas stand pipe in a tank of water. A slight back pressure is required

to allow for pressure drop of the saaple gas through the gas analysis

unit. The eagnitude of this back pressure is about 5 inches of water.

The back pressure regulator that is used is a small tank mounted

on tripod legs and provided with an overflow line to a drain. A constant

water liquid level is maintained in the tank by running the cooling water

used in the copper coil heat exchangers into the back pressure tank and

letting the water drain out through the overflow pipe. To prevent ex-

ceasive bubbling in the back pressure tank for high converter gas rates

a by-pass needle valve is piped into the exit converter gas line so that

only a small portion of the converter gas passes through the dip leg.

The inlet air feed line is fitted with a pressure reducing

valve and sedient separator. The air then passes through a Tel-Tale

silica gal dryer before it is metered to the reactor. The dryer oolum

1t a piece of 3 inch by 36 inch Pyrex glass pipe.

The entire assembly of rotameters, manometers, control valves

and dryers are mounted n a sovable panel board. A picture of the panel

board Is shown in Figure 3.

5, Temperature panel board. The asphalt blowing temperature

recorder and temperature controller are located on the temperature panel

board.

Chroael-aleal thermocouples are used to measure all process

streak temperatures in the asphalt blowing system. The thermocouples




- 22 -


O*
e. *

9
0,

p


-I
MT~










-23-

are mounted in protection tubes and these unlts are incorporated in the

process piping. Temperatures are recorded with a Bristol Dynaaster

12 point Pyrometer using 10 points as indicated on the diagraa in

Figure 22.

The temperature controller that is used for the asphalt reactor

is a Minneapolla-Honeyell-Brown Pulse Pyr-O-Vane Controller. This is

a tima-proportioning-tndicating type controller that eliminates any tem-

perature cycling or "hunting effects. The wiring on the temperature

controller is such that the controlled output goes through both 110 volt

and 220 volt outlets. The 220 volt outlet is used in this investigation

to control the reactor beaters. Two other outlets for continuous 110

and 220 volts are also provided on the panel board.

The temperature recorder, controller, outlets and circuit breakers

are mounted on a movable panel similar to the ga flow panel board. A

picture of the temperature panel board is shown in Figure 1.

6. Piping. The majority of theequlpment piping is 1/2 inch

steel pipe. Larger 3/. inch pipe is used for the converter gas lines,

the asphalt drains on the asphalt storage tank and the asphalt reactor.

Gas cock valves are used for the asphalt piping while globe and needle

valves are used for the asphalt blowing gas piping. All hot asphalt lines

are insulated with air cell asbestos insulation. A piping diagram to

shown in Figure 22.










-24-
B. Analysis EQaulpent

1. Gas analysis unit. The gas analysis unit provides a con-

tinuous volume analysis of oxygen and carbon dioxide of either the asphalt

blowing feed gas or converter gas. Dew points of these gases may also

be determined.

The analysis cells for the gas train are as follows: (a) sBek-

man Oxygen Analyzer Model C, 0-100 per sent Oxygen; (b) 'ao-Mao Thermal

Conductivity Cell for Carbon Dioxide; (c) Pittsburgh Ilectrodryer Dew

Point Apparatus. The Beckman analyzer gives volume percentage oxygen

as a direct reading while the output of the thermal conductivity call

is measured in millivolts.

In the gas analysis train the continuous gas sample for the oxy-

gen and carbon dioxide analysis cells is first dried by passing the gas

through a tube of Tel-Tale silica gel. Then the total flow rate is

measured with a rotameter. The sample gas is now divided into two streams

and the flow rate for each stream is determined with two additional rota-

et.ers. One gas stream is for the oxygen analyzer and the other streak

is for the carbon dioxide analysis cell. Constant gas flow rates are

maintained to the analysis cells to prevent the introduction of an analysis

error because of the effect of a change in gas velocity in the analysis

cells. The feed gas line and converter gas line have separate sample lines

and dryer tubes. After the sample gas passes through the dryer tube it

flows into a common header and then to the rotameter measuring the total

gas flow. With the two sample lines it is possible to select either the

feed gas or the converter gas for analysis. Only one gas can be analysed

at any particular tine.










-25 -

A constant 6 volt direct current source for the thermal coo-

ductivity cell is provided with a small Mallory power supply. The ther-

mal conductivity cell output is measured with a Weston direct current

aillivoltmeter. The Electrodryer dew point apparatus is a rectangular

metal box fitted with a removable polished hollow cylinder cup which

screws into the top of the box. A window in the front of the box isi ned

for observing the asrface of the cylinder. The hollow cylinder is filled

with a liquid so that the temperature of the cylinder nay be lowered

by cooling the liquid. The dew point of a sample gas is obtained by

impinging the gas on the liquid cooled cylinder and recording the liquid

temperature at the first appearance of fog or mist on the polished surface

of the cylinder. The hollow cylinder may be cooled with a mixture of

aceton and dry ice for extremely low dew points or water and ice for

higher dew points. Dw point temperature are measured with an alcohol

thermometer and dew points oan be made on either the asphalt feed gas or

the converter gas. A flow diagram and picture of the analysis unit may

be seao in Figures 21 and 3.

2. Gas analysis calibration. The thermal conductivity cell and

oxygen analyer are calibrated for a ternary system of dry gases; oxygen,

nitrogen and carbon dioxide. The range of the calibration is 0-4 per

cent carbon dioxide in a residual gas of nitrogen and oxygen, 0-100 per

cent oxygen.

The instruments were calibrated by measuring the thermal condus-
tivity cell output and reading the Beckman oxygen analyzer for known lIx-

tures of the ternary gas system. The individual gases were metered fro











-26 -

gas cylinder using a pressure reducing valve and rotamaterr for each gas

stream. After the flow rate for each gas stream was determined, the in-

dividual gases were ixed together to foar the gas sample for the instru-

ment allbration. The analysis of this sample gas was determined with

the use of an Orsat analyzer that determines the concentration of carbon

dioxide. The concentration of oxygen was Seterained through the use of

the Beckman oxygen analyser and the concentration of nitrogen was cal-

culated by subtracting the oxygen and carbon dioxide concentration from

100. The sample gas flow rates for the analysis Instruments were main-

tained at about 900 cc./minute for the thermal conductivity cell and

125 cc./linute for the oxygen analyser. Excess sample gas was exhausted

to the atmosphere. The output of the thermal conductivity cell was meas-

ured as millivolts and the reference point for this unit was zero milli-

volts for dry air.

Table 2 is a tabulation of the calibration data for the oxygen

analyzer and thermal conductivity cell. Figure 4 is a plot of the ternary

calibration data as a function of thermal conductivity cell millivolt

readings and oxygen concentration with parameters of volume per cent

carbon dioxide.










-27 -

TABLE 2

CALIBRATIOI DATA FOR GAS ANALYSIS INSTROUBTS

Run Gas Concentration Thermal Beo]san
so. Volume % Conductivity Oxygsa

02"* c02 N2 million a A


20.9
40.7
61.0
81.4
90.0
100.0
69.8
49.9
30.5
9.9
10.0
10.0
10.1
10.0
9.9
20.1
19.9
20.9
20.9
20.1
19.9
20.0
20,0
20.0
20.0
20.0

30.0
30.0
30.0
30.0
30.0
30.0
30.0



40.0


21.0





10.6
15.0
27.5
34.2
40.6
6.0



10.0
17.1
36.9
47.1
26.8
4.8

9.1
25.5
37.2
47.0
30.8
15.1

42.8
12.9


79.1
59.3
39.0
18.6
10.0

30.2
50.1
69.5
90.1
79.4
75.0
62.4
55.8
49.5
83.9
80.1
79.1
79.1
79.9
70.1
62.9
43,1
32.9
53.2
75.2
100.0
70.0
60,9
44.5
32.8
23.0
39.2
54.9
100.0
100.0
57.2
47.1


0.0
-11.7
-20.6
-28.0
-30.7
-34.0
-24.2
-16.0
- 6.3
2.8
23.9
33.2
59.2
74.2
88.5
15.1
- 1.6
0.3
0.0
- 1.9
17.8
31.8
72.8
93.0
51.1
6.4
7.1
- 6.3
9.8
44.3
69.8
88.6
55.8
23.0
7.2
7.1
97.0
13.5


20.9
40.7
61.0
81.4
90.0
100.0
69.8
49.9
30.5
9.9
10.0
10.0
10.1
10.0
9.9
10.1
19.9
20.9
20.9
20.1
19.9
20.0
20.0
20.0
20.0
20.0

30.0
30.0
30.0
30.0
30.0
30.0
30.0
30.0


40.0











28-

TABLE 2--Contijnau


Run Gas Concentration Thermal Beckman
No. Volume % Conduetivity Oxygen
Cell Analyzer
02" C02 1 N2 Millivolts


39.9
40.0
40.0
40.0
40.0
40,0
50.0
50,0
50.0
50.0
50.0
50.0
60.0
60.0
60.0
60.0
10.0
0** *
70.1
70.0
70.0
70.1
80.0
30.0
30.0
30.0
30.0
30.1
10.1
10.0
20.9

100.0


26.1
35.8
46.,
17.2
6.1

18.1
28.0
49.7
39.5
7.6

12.8
20.2
31.4
41.0


8.1
15.0
20.9

10.7

14.1
311
41.4
45.0
30.4
*.. *


60.1
33.9
24.2
13.3
42.8
53.9
50.0
31.9
22.0
0.3
10.5
42.4
40.0
27.2
19.8
8.6
44.0
100.0
100.0
21.9
15.0
9.0
19.9
9.3
70.0
55.9
38.9
28.5
44.9
69.6
79.1
100.0
*..e


-11.8
41.0
61.8
85.2
23.0
0.6
-16.2
20.2
41.7
89.0
66.2
- 1.3
-19.8
5.2
21.0
44,2
86.5
7.0
-24.0
- 7.4
5.8
18.0
-28.0
- 6.1
- 6.2
21.0
56.7
77.7
93.8
64.3
.*. *
*.. *


39.9
40.0
40.0
40.0
40.0
50.0
50.0
50.0
50.0
50,0
50.0
50.0
60.0
60.0
60.0
60.0
10.0

70.0
70.0
70.1
80.1
80.0
30.0
30.0
30.0
30.1
10.1
.10.0
20.9
0.0
100.5


*Beckmn oxygen analysis for runs 1-68.






-29 -


90



80



70







50 \

Volume





30 -



20



10 -


0
-40 20 0 20 40 60 80 100
Thersal Conductivity Cell Output Millivolta
Figure 4. Thermal Conductivity Cell Calibration Curve for Ternary System
of Oxygen, Nitrogen and Carbon Dioxide












V. PROCEDURES


The following is an outline of the conditions and procedures that

are used to operate the asphalt blowing equipment. The method is applicable

to either continuous or batch operation, with the exception that during

the continuous operation a constant asphalt feed is fed to the reactor

and a product is continuously removed.

The five variables under consideration in this investigation are

temperature, feed gas space velocity, feed gas oxygen concentration, agi-

tator speed and continuous or batch operation. The effect of these variables

were determined by making runs at essentially atmospheric pressure wond

fixing all but one variable. A total of 39 runs was made under the

following conditions to determine the overall effect of the variables on

each other. The extent to which the conditions were changed for any of the

materials under consideration is shown in Table 3.
e

TABLE 3

ASPHALT PROCESSING CONDITIONS

Material TA-1023-2 TA-1024 TA-1025 TA-1026


Temperatue Of. 450-550 500 500 500

Air Space Velocity
CFT 25-200 25-100 25-100 25-100

Oxygen Concentration
Per Cent 21-50 21-50 21-50 21-50

Agitator R.P.M. 700-1300* 700 700 700


*25CFM, 21% and 50% oxygen, 500 oF. only.


- 30-










- 31 -


A. Operating Procedure

The operating procedure for the asphalt blowing apparatus is

composed of the following steps (a) heating a charge of asphalt in the

reactor, (b) blowing with a feed gas, (c) measuring the gas flow rates,

(d) recording the gas analysis, (e) taking asphalt product samples.

The first step in the start of the asphalt blowing unit is to

heat a charge of reside to a temperature of 475-500 OF. in the asphalt

storage tank. To charge the storage tank, the asphalt auction and reeir-

culation return lines era removed and the transit cover taken off.

After the storage tank is charged with asphalt, the cover and pipes are

replaced and the asphalt storage heaters turned on by turning the three-

heat switch to the high position. While the asphalt charge is being warned

in the tank, the asphalt circulation line is preheated by turning on the

steam to the copper tubing trace line. When the temperature of the asphalt

in the storage tank has reached 225-250 of., it may be recirculated with

the pump to provide some degree of agitation in the storage tank. The

recirculation procedure is to open the asphalt suction line valve, close

the recirculation line bottom drain valve, close the reactor feed valve,

open the recirculation valve to the asphalt storage tank, close the vent

valve above the asphalt suction line valve, and turn on the pump. The

pump is a gear type pump and there is a sufficient residuua seal so that

it *ill pull a small vacuum on the asphalt suction line until the asphalt

flow ai started from the storage tank. Once the reeirculation asphalt

flow is started, the steam say be turned off to the steal trace line and

the auxiJlary heater in the recirculation line turned on. This heater










32 -
must not be turned on unless there is a flow of asphalt in the recircula-

tion line. Heating and recirculation of the asphalt is continued until

the temperature of the asphalt is 475-500 o.

A charge of asphalt is transferred to the reactor by first closing

the reactor drain valves, closing the air feed valve, reading a groes

weight on the Toledo scales, and then pumping the asphalt to the reactor

by opening the reactor feed valve and closing the recirculation valve to

the storage tank. The last few pounds of asphalt charged to the reactor

may be controlled with more precision by opening the recirculation valve

to the storage tank and throttling the asphalt reactor feed valve. When

the desired charge has been transferred to the reactor, the reactor feed

valve is closed and a final reading as net weight is taken trom the Toledo

scales. The difference in the weight readings of the scale is the mass of

asphalt charged to the reactor. If a continuous run is made, the asphalt

in the storage tank is continually recirculated at the desired reactor

temperature. If a batch run is made, the recirculation is discontinued

and the asphalt lines drained. The lines are drained by turning off the

recirculation heater, opening the vent valve, allowing the pump to run

several minutes, opening the recirculation line bottom drain valve and

shutting off the pump. An asphalt feed run sample may be taken from the

draining residuum.

Immediately after the charge of asphalt has been pumped to the

reactor the reactor temperature controller and agitator are turned on.

The reactor is continuously heated and agitated until the desired opera-

ting temperature is obtained. To pre-cool the condensers cooling water

may be circulated through the reactor cooler, electrical precipitator coil










33 -
and water condenser. While the reactor asphalt charge is being heated,

the analysis instruments are turned on and the calibration point checked

with dry air. The instruments are calibrated for a specified flow rate

of gas: the oxygen analyzer flow rate is 125 cc. per minute and the

thermal conductivity cell flow rate is 800900 cc. per minute. The zero

point for the oxygen analyzer is a 21 per cent oxygen scale reading for

dry air. The zero point for the thermal conductivity cell is a sero

millivolt reading on the Weston Millivoltaeter for dry air. The elec-

trical input to the thermal conductivity cell is always maintained at

6 volts d. e. and 138 milliamperes using a lallory power supply. The

thermal conductivity cell sero adjustment and current control are located

on the panel mounted remote control unit. The knob marked 'C" is for

current adjustment and the one marked "A" is for millivoltmeter indicator

adjustment. The instruments are permitted to operate with a continuous

dry air sample until a constant zero reading is obtained on the thermal

conductivity cell and the oxygen analyzer is up to operating temperature.

Care should be taken when opening the rotameter feed valve on the panel

board for the air gas sample, because the air feed valve to the reactor

is closed and the feed gas manometer can be blown readily with a sudden

surge of air.

When the gas analysis instruments have been zeroed and the tempera-

ture of the reactor charge is up to the conditions desired, the actual

blowing operation may be started. The valving on the panel board is checked

to insure the flow of two separate gas streams and also to eliminate the

possibility of any closed valves. The power source for the electrostatic

precipitator is turned on and the voltages adjusted to 29,000-31,000 volts










34 -
d. c.. The gas feed valve to the reactor is then opened and the flow

rate of feed gas to the reactor is started and adjusted to the desired

rate at the flow panel board. For a batch operation the time that the

gas flow is started to the reactor is considered zero time for the run.

The drain valves on the precipitator and water condenser are closed and

the valving is changed on the gas analysis unit so that a continuous

sample of converter gas may be taken. Gas flow rates are continuously

checked and adjusted to maintain the desired flow rate. The needle valve

on the converter gas discharge back pressure line is adjusted to give a

slight gas flow through the back pressure dip tube, This back pressure

of 5 to 6 inches of water provides a driving force for the gas sample

to the gas analysis unit. At frequent intervals flow rate, gas analysis

and instrument readings are recorded. For some of these readings asphalt

reactor samples and precipitator samples are taken. The reactor asphalt

samples are taken from the side drain allowing a small flush to flow from

the reactor (2-3 ounces) to remove the previous product. The weight of

sample and flush is recorded so that a material balance can be obtained

and the residence weight of asphalt in the reactor at the sample time can

be calculated. Precipitator and water samples are taken by closing the

top drain valves and opening the bottom valves. The sample is in the

stand pipe between the valves. Two valves are provided so that it is

possible to take the samples without lowering the pressure in the reactor.

Often the volume of the sample collected is larger than the volume of the

standpipe, and it will be necessary to repeat the sampling procedure until

the complete ample is obtained. To obtain an exact sample at a specified










35 -
time, this procedure is followed prior to the sample time so that when

the top valve is closed at the sample time no part of the sample is

omitted. The run is continued in this manner until the asphalt charge

in the reactor is at the desired consistency. For batch runs the final

product consistency is approximately 200 OF. Ring and Ball. This point

must be estimated from the consistency of the reactor asphalt samples.

Often when the asphalt in the reactor is approaching 200 OF. Ring and Ball

the side asphalt sample line plugs with the hard asphalt. In this case the

asphalt samples may either be taken from the bottom reactor drain valve

or By heating the side reactor valve with a small gas torch and melting

the solidified asphalt. When the asphalt is at or above 200 OF. Ring and

Ball, final readings and samples are taken and the reactor contents drained

into a previously tared 5 gallon steel bucket. The agitator and the reao-

tor temperature controller are turned off. The reactor feed gas is allowed

to flow for a few minutes to clear the air feed line of any asphalt.

The reactor feed gas is shut off and the power source to the elec-

trical precipitator is also turned off. The feed gas valve to the reactor

is closed and clean air is again turned on to the analysis instruments

to sweep them ot any residual converter gas and also to check the calibra-

tion sero point. The analysis instruments and air flow are turned off and

the asphalt drain bucket weighed to obtain the final weight of asphalt for

a material balance. This ends the operating part of a batch run.

The conditions and procedure for making a continuous run are simi-

lar to a batch run. In effect they are a combination of both a batch and

continuous operation. The reactor is charged, heated and blown as a batch










36-

operation to a predetermined Ring and Ball consistency as estimated from

an analysis of a previous batch run. When the desired consistency is

obtained, the reactor charge is blown as a continuous operation by sisul-

taneously introducing fresh asphalt feed and removing asphalt product at

a similar, constant rate. The feed rates are determined by the equiva-

lent residence time that the fresh asphalt must remain in the reactor to

be blown to the desired Ring and Ball consistency. The continuous run

is continued in this manner until a constant converter gas analysis is

obtained for fixed gas flow rates and asphalt feed rates. The continuous

run may then be discontinued and the reactor charge again blown as a batch

operation to a new asphalt product consistency. A continuous run may be

repeated again with decreased asphalt feed flow rates. The run is ter-

minated in the same manner as a batch run.

During continuous or batch runs an indication of the asphalt liquid

level in the reactor may be obtained by observing the manometer pressure

reading for the inlet reactor feed gas. This is particularly useful for

continuous runs when the asphalt feed and product flow rates are being

adjusted. Best results are obtained for controlling a continuous asphalt

feed to the reactor when the feed valve to the reactor is opened slightly

and the recirculation valve to the storage tank carefully throttled. A

great deal of caution must be used to prevent closing the recirculation

line valve, because the displacement pump would be damaged.

For fortified oxygen runs .additional amounts of pure oxygen is

metered into the asphalt reactor gas to increase the oxygen feed gas con-

centration. A pressure reducing valve on the oxygen cylinder reduces the










37 -
pressure to a low value and the flow rate of the gas is then metered with

the oxygen rotameter. The composition of the feed gas is checked several

times during a run by closing the converter gas sample line and opening

the feed gas sample line to the analysis unit. The composition of the

feed gas is indicated when consistent readings are obtained from the

analysis unit.

As a run progresses the mass of the asohalt charge in the reactor

decreases due to losses by blowing and from sampling. To maintain a con-

stant gas to asphalt ratio for the particular run conditions, the reactor

feed gas flow rate is continuously adjusted for the estimated asphalt mass

in the reactor. Dew points of the converter gas are obtained with the dew

point apparatus at the gas analysis unit during batch runs and at the panel

board converter rotameter during continuous runs. The converter rotameter

is used to prevent any change in reactor gas pressure during a continuous

run. A drop in the reactor gas pressure generally results in an increased

asphalt feed flow rate. The double valve sampling device on the electrical

precipitator and water condenser was developed to eliminate this pressure

drop while sampling. All equipment drain valves are left open when the

equipment is not in operation.


B. Analytical Procedures

In this study the extent of reaction in the asphalt reactor charge

was determined by the converter gas analysis and the change in physical

properties of the asphalt product. The asphalt properties that were meas-

ured were softening point and penetration while the volume per cent oxygen,

carbon dioxide and water were determined for the converter gas. The electrical










38-

precipitator and water condenser products were separated into an oil

and aqueous sample. Acid numbers were determined for these fractions.

The softening point of the asphalt product and feed samples were

run by the A. S. T. M. Ring and Ball method, designation D 36-26 (4).

The standard method was followed and a quadruple holder unit was used to

pemrit attachment of four brass rings. A water bath was used for mate-

rials having softening points below 176 OF. and a glycerin bath for the

higher softening point asphalts. A small air agitator was used to provide

agitation when using the more viscous glycerin. The values of Ring and

Ball are reported as temperature degrees Fahrenheit. Asphalt penetration

values were measured with a standard penetration apparatus and needle

according to the A. S. T. M. procedure designation D 5-25 (3). The load

time and temperature for the penetration tests were 100 ga., 5 seconds

and 77 O9. (25 OC.) respectively.

The oil and water mixtures from the electrical precipitator and

condenser were separated into two samples, one aqueous and one oil, by

centrifuging and decantation. The volume of each water sample was measured

and likewise the weight of the oil sample was determined. The acid numbers

for the electrical precipitator and condenser products were evaluated for

the purpose of completing an oxygen material balance for the asphalt blow-

ing products. The aqueous fraction of the sample was titrated with O.1l

sodium hydroxide using phenolpbthalein for an end point indicator. The

acid number for the oil fraction of the sample was obtained by a color

indicator titration following the A. S. T. M. procedure D 663-46T (2).

A standard 0.1N sodium hydroxide solution was used instead of the suggest-

ed potassium hydroxide solution.










39-

The gas composition of the converter gases was measured with the

gas analysis unit instruments. The Beckman oxygen analyzer gave a direct,

continuous reading in volume per cent oxygen. The thermal conductivity

cell ternary calibration plot was used to obtain the carbon dioxide content

in the converter gases. The conductivity cell aillivolt output and the

oxygen analysis were the only parameters required to estimate directly

the percentage of carbon dioxide gas. The partial pressure of water vapor

in the exit converter gas was determined from the dew point analysis.

The volume per cent of water in the converter gas is equal to the partial

pressure of the water divided by the total pressure. The total pressure

was assumed to be equal to one atmosphere at all times. Since the oxygen

and carbon dioxide analysis was made using a dried converter gas, it was

necessary to correct the indicated analysis of those gases for the effect

of water vapor.

As the concentration of carbon dioxide in the converter gas was

very small, no corrections were made for the oxygen analyzer analysis.

Orsat analyses for percentage oxygen and carbon dioxide in the converter

gas were measured at intervals to check the operation of the gas analysis

unit. The Orsat gas analyzer was used to obtain the original thermal

conductivity cell calibration and ternary plot for gaseous mixtures of

oxygen, nitrogen and carbon dioxide.










VI. CALCULATIONS


The experimental data for the batch and continuous runs wore

analysed fors (a) kinetics, development of rate equations and evalua-

tion of reaction rate constants: (b) reaction mechanism, kinetic order,

oxygen balance and utilisation, and reaction products; (c) scale up,

comparison of batch and continuous data and practical application. A

tabulation of the calculated results for all experimental runs is n-

eluded in the Appendix.

A. Kinetics

The general rate equation for the reaction rate of the processed

asphalt was assumed to be related to various physical process variables

in the form of the expression

dB/dt kPP r (1)
where

dR/dt rate of change of softening point or
gross asphalt blowing reaction rate
R = asphalt Ring and Ball softening point, OF.

S = process gas space velocity, (ft.3)/(in.)(ton asphalt)
at (70 oF., 1 ata.)

P original process gas oxygen concentration, vol. %

t process reaction time, hours

p, s, r = exponents on the process variables
k a pseudo reaction velocity constant

This form of the rate equation suggests that the rate of reaction

is a function of the space gas velocity and the feed gas oxygen concentra-

tion. Temperature is another variable but is included in the pseudo

40 -












reaction velocity constant, k. The values of the exponents, p, r, and

a indicate the reaction order for the process variables. The degree of

variation of the pseudo reaction velocity constant, I, with temperature

will indicate certain conclusions regarding the rate controlling mecha-

nism. The resulting equation with all constants evaluated, can be used

for scale up and design considerations for larger commercial processing

units.

The exponents and constants in the general rate equation may be

evaluated by putting the equation in the logarithmic form as

In(dR/dti In(kcPP'sR) (2)

or

In(dR/dt) In(kPpSs) + rlnR (3)

If the logarithm of the reaction rate (dR/dt) is plotted on the ordinate

against the logarithm of asphalt consistency (R) on the abscissa, and

the plot results in a straight line, the slope of the line is the expo-

nent, r, and the intercept is In(kPPSB). Each batch run may be plotted

as a line to give a measured value of elope and an intercept value at

lnR 0. For this general treatment of the data to be of any value, the

value of the slope for all runs must be the same. However, the intercept

values will not be constant because the intercept is a function of k,

S and P.

The values of the remaining exponents p, s,and constant, k, may

be obtained from the intercept data as

I a in(kPPS) (4)










-42 -
and

I = In(kP) 4 lasn (5)
where

I intercept of In(dR/dt) versus
InR plot at lnR = 0
The intercept, I,a is now plotted as the ordinate value and lnS

on the abscissa. The resulting curves should be plotted as straight

lines with parameters of oxygen concentration. The slopes of this plot

should again be constant and will be the value of the exponent, s. The

intercept will be equal to the ln(k,Pp) at the value of InS 0.

The intercept equation from this second logarithm plot may now

be written as

Ib In (kP1) (6)
or

Ib = Ink 4 plnP (7)
where

Ib intercept of the I. versus laS plot
at nS 0.
The intercept values for this equation are again plotted on the

ordinate against abscissa values of InP. The resulting curve for this

plot should be a straight line with a slope value of p and an intercept

value of Ink at InP ? 0. The value of k is then

I -* Ink (8)

k e(9)










43 -
where

Ic intercept of the Ib versus lnP plot
at InP 0.

e a base of natural logarithms

The pseudo reaction velocity constant, k, will be a specific value for

any given temperature. In the preceding analysis only the data at one

given temperature are evaluated together to derive the desired values

of exponents and constants.

This procedure is repeated for treatment of data at different

temperatures. The resulting values of the exponents p, r, and a, should

be constant and independent of the temperature if a general reaction rate

expression is to be developed. The only variable constant is k, the

pseudo reaction velocity constant, which is a function of the reaction

temperature.


B. Reaction Mechanis

The reaction mechanism for the asphalt blowing reaction can be

described by the order of the process variables in the general reaction

rate equation, by the variation of the reaction velocity constant with

temperature, and by the oxygen utilization and oxygen balance for the

reacting asphalt.

The order of reaction for the previously described rate equation

(Equation 1) is the sum of all the exponents, p, r, and s, on the process

variables, P, R, and S. The order with respect to each variable is the

value of the exponent for that variable. The exponents are usually simple

positive integers, but they may be fractional or even negative, depending

upon the complexity of the reaction.










-44-
For a true chemical reaction rate the specific reaction rate

constant, k', is a function of the processing temperature and is related

to the temperature by the Arrhenius equation

k' Ae-E/ (10)

or

Ink' --E/RT + In (11)

where

k' specific reaction velocity constant

E = the olal energy of activation

A proportionality factor characteristic of the system
and termed the frequency factor

R a gas constant

T = absolute temperature

If the Ink' is linear with 1/T the molal energy of activation

can be evaluated by plotting the Ink' against reciprocal absolute tem-

perature, 1/T. It is usually found that this plot is nearly linear with

a negative slope, and the value of the slope is equal to -E/R. High

values of the activation energy, E, is typical of reactions where the

chemical reaction step is the rate controlling mechanism. Low values of

the activation energy, E, indicate a reaction where the rate of diffusion

is the controlling mechanism. A pseudo molal energy of activation for

the asphalt blowing process can be evaluated if k from Equation 9 is

substituted for k in Equation 11. This pseudo energy of activation can

be used to derive certain conclusions regarding the rate controlling

mechanism. *










45 -
Oxygen utilization for the asphalt blowing process is determined

by the disappearance of gaseous oxygen from the process gas streams. AM

oxygen balance for the process is an accounting and comparison of the

oxygen in the feed gas against the oxygen in the reacted products. This

balance includes the accounting of oxygen in the converter gas and pre-

cipitator products as oxygen (02), carbon dioxide (002), water vapor

(H20 ), water (H201) and acids. The mass weight of oxygen is calculated

for specified time intervals by using an average gas concentration over

the time interval used. Cusulative oxygen results are used and reduced

to a basis per one pound of asphalt reacted.

The values for the oxygen balance for the gaseous products are

calculated from the general equation

(G)(C)((t)(f) lbs. oxygen (12)

where

G a gas flow rate, CPM, 70 of., 1 atmosphere

C a gas concentration, volume per cent

At = time interval, hours

d = gas density, lbs./ft.3

f conversion factor, lbs. oxygen/bs. gas

Table 4 is a listing of some of the gas properties that were used in

this equation. The conversion factor, f, is the equivalent weight of

oxygen, 02, per unit weight of carbon dioxide, air and water.










- 46-


TABLE 4

GAS PROPERTIES


Density, d Conversion Factor, f
Gas Lb./yt.3 Lbs. 02/Lb. Gas
70 O., 1 Ata.


02 0.0892 1.0
C02 0.1235 0.728

H20 (g) 0.0501 0.888

Air 0.0808 0.231

N2 0.0780 .....

The amount of oxygen in the condensed liquid water from the pre-

cipitator was determined by the relation

0.001956(v) a lbs. oxygen (13)

where

v = the volume of water, cc.

The oil and aqueous precipitated samples were titrated for acid deter-

mination by assuming that the acid was formic acid. The equivalent

amount of oxygen as acid was then calculated by the relationship

7.05 x 10'5(V)(B)) () lbs. oxygen (4)

where

V = volume of water or weight of oil sample,
co. and gas. respectively

B = volume of sodium hydroxide per cc. of
water or per g. or oil, ca.

N = normality of the sodiau hydroxide










47 -
-A7-

The feed and converter gas flow rates were obtained from the gas

rotameter data. Since the metered gas temperatures and pressures were

essentially 70 OF. and 1 atmosphere, no rotameter correction factors

were used. The amount of oxygen in the feed gases was very easily cal-

culated from the rotameter data because the concentration of oxygen was

either 21 per cent for air or 100 per cent for pure oxygen. The gas

concentrations in the converter gas were those values that were recorded

from the gas analysis unit and corrected from a dry basis to a wet gas

basia by the following relationship

Pp. (c02. S, 02) ?(70-1r H2ag) (15)
where

D a concentration of gas on dry basis,
volume per cent

Pp. 20g partial pressure of the water vapor in the oonver-
ter gas as determined from the dew point

Pp.(CO2, S2, 02) partial pressure of the converter gases on
a wet gas basis
The partial pressure of the various gases on a dry basis was calculated

from the gas analysis data by the expression

Pp. gas 760D (16)
The gas concentration, C, Is determined from the partial pressure of

the converter gas on a wet basis by the relation

C Pp.(cO2, N2, 02)/760 (17)

A constant pressure of 1 atmosphere or 760 mm. Hg. was assumed

for all calculations. For the feed gas oxygen balance the weight of

oxygen as 02 and equivalent weight of 02 as air was added for each time










48 -
interval to give the total pounds of oxygen feed. For the converter

gas oxygen balance the weight of oxygen as 02 and the equivalent weights

of 02 as C02, H20 and acide were added for eaoh time interval to give

the pounds of oxygen in the converter gas. The amount of xygen used or

the oxygen utilization was the difference between the oxygen in the

feed gas and the oxygen as oure 02 it the converter gas. The difference

between the total oxygen feed and the ana of the oxygen and equivalent

oxygen in the converter gas ti the oxygen loss or unaccountable oxygen.

The amount of oxygen calculated in the previous equations was based on the

total asphalt charge in the reactor. This charge decreased during the

course of a batch reaction and did not remaLn constant, because of samp-

ling, entraLnaent and reaction losses. The amount of asphalt in the

reactor at any time during the reaction was determined by a material

balance. The calculated values of oxygen for any time nterval were

reduced to a basis of one pound of asphalt by dividing the Mass of oxyge

by the average weight of the asphalt reactor charge for the sme time

interval. The results were plotted as a cumulative plot of pounds of

oxygen per pound of asphalt versus elapsed reacting time,


C. Scale Up
All batch runs were analyzed and calculated by the preceding reac-

tion rate and oxygen balance methods. Continuous run were also evaluated

by these methods and compared to the batch ran resulted. The two tynes

of operation can be compared only at a similar asphalt residence tiae,

using a differential treatment for continuous operation and as integral

treatment for batch operation.









49-
For continuous runs there was a continuous asphalt feed and siaul-

taneous removal of asphalt product. As the mass of the asphalt charge

in the reactor was kept constant, the asphalt residence time in the reae-

tor was equal to the mass of the asphalt charge divided by the asphalt

feed rate, that is

to Ma/a (18)

where

to asphalt residence time, hours

,a a mass asphalt in the reactor, pounds

F, feed rate of fresh asphalt, pounds per hour

The asphalt residence time, to, for continuous operation is equivalent

to the elapsed reacting time, t, for batch operation. The differential

analysis for continuous operation requires only a material balance around

the reactor while the integral evaluation requires determining areas

under curves plotted from the initial to the final reaction time, t.

The batch and continuous runs were compared for product consisten-

cies and oxygen utilization at equivalent residence times. In a subse-

quent section practical application of the developed rate equation is

illustrated by a sample calculation for the design of a commercial reac-

tor vessel. The calculated results using the developed rate equation

are compared with the actual commercial reactor data.










VII. RESULTS AND DISCUSSION


The majority of the batch and continuous runs were made by using

the Gulf Coast Asphalt, TA-1023-2. A total of thirty run were made

for this residuum. The process conditions that were studied Included

temperature, feed gas space velocity (flow rate), feed gas oxygen con-

centration and agitator speed. Nine additional runs using the East Texas

TA-102I, East Central Texas TA-1025 and the South Texas Heavy TA-1026

residua were made for purposes of comparison with the TA-1023-2 Gulf

Coast material. These four types of materials represent four different

types of asphalt.

The analysis of the data was made according to: (a) kinptlio,

(b) reaction mechanism, and (c) scale up.


A. Kinltles
The general rate equation relating the process variables to the
reaction rate was evaluated to describe the reaction rate of the processed

asphalt. This equation

dR/dt k9SRr (1)
was put in the logarithami form and the exponents and reaction rate con-

stants were evaluated as outlined in the calculation procedures.

Reaction rate data is obtained by plotting a urve of Ring and Ball

softening point against reaction time. The slope at any point on the

resulting curve is the reaction rate dR/dt when R is plotted on the abscissa

and t as the ordinate. A typical set of batch runs are plotted in this

manner and shown in Figure 5. Each curve in Figure 5 indicates a batch


-50 -








- 51 -


200
4.14

















I'
4j




a












50 i -- -- ----
50
1 2 3 4 5 6 7
Reaction Time (t) Hours

Figure 5. Softening Point and Reactlon Tlm Relation for Batch Runms Using
Gulf Coast Asphalt TA-1023-2










52 -
run for given process conditions of space gas velocity, oxygen concen-

tration, agitation rate and reaction temperature.

Each curve shown in Figure 5 is the result of one batch run.

The reproducibility of the data for the batch runs was checked by making

duplicate runs for similar process conditions. Figure 6 is a comparison

of two batch runs for the Gulf Coast asphalt, TA-1023-2, which were

processed under similar conditions of temperature, feed gas space velocity,

oxygen concentration and agitation rate. The results for the two batch

runs shown in Figure 6 check within the limits of experimental error for

Ring and Ball analysis. Table 5 is a tabulation of the results when

the two batch runs in Figure 6 are compared.


TABLE 5
REPRODUIBILITY OF BATCH RUN DATA

Run Reaction Softening Oxygen Unaccountable
No. Time, t Point Utilisation Oxygen
Hour* oF. Lb. 02/Lb. Asphalt Lb. 02/Lb. Asphalt

406 2.1 120 0.040 0.011
3.1 160 0.056 0.020
4.0 200 0.068 0.019

42 2.2 120 0.035 0.017
3.2 160 0.060 0.028
4.0 200 0.070 0.021


From Figure 5 the slopes of the batch run curves at various values

of R are plotted in the logarithmic Equation 3

In(dB/dt) = ln(kPPS8) + rlnR (3)








-53-







200



O






S150 -








S* 0 aon 406

100 Run 442









50 I I ,
0 1 2 3 4 5 6 7
Reaction Time (t) Hours

Figure 6. Reproducibility of Batch Run Data, Gulf Coast Asphalt TA-1023-2










54 -
as the In(dR/dt) against the InR. The resulting straight line plots are

those given in Figure 7. In all the batch runs the asphalt was reacted

to consistencies of 190-220 oF. Ring and Ball. The limits of the curves

in Figure 7 are product consistencies of 200 oF. Ring and Ball which were

selected as the upper limits for the processing analysis of this inves-

tigation. The average of the slopes of the curves was equal to one and

each curve was adjusted to this value to give a corrected intercept value

at InR = 0. A tabulation of the original slopes and the intercept values

based on a common slope of one are listed in Table 6 for the runs shown

in Figure 7.


TABLE 6

SLOPE AND INTERCEPT VALUES FROM FIGURE 7

GULF COAST ASPHALT TA-1023-2

TEMPERwTURE 500 oF.

AGITATOR SPEED = 700 R.P.M.

Run S P Slopes Intercepts
No. CFMI % 02 (Slope a 1.0, InR 0)

404 25 21 1.16 -1.60
406 100 21 0.91 -1.28

407 200 21 0.60 -1.06

414 25 50 1.28 -0.91

415 100 50 0.95 -0.64

421 100 35 1.01 -0.81

423 25 35 1.10 -1.16











- 55 -


150





100


80



60 0


I

40 44

414

S 30
423
406


1 20



15 1404





10
70 TO 90 100 120 10 160 180 200
Ring and Ball (R) oF.

Figure 7. Reaction Rate and Product Consistency for Batch Runs, Gulf Coaat
Asphalt TA-1023-2










-56 -

The experimental values of the slopes show an average variation

of 15.6 per cent with a maximum of 40 per cent for run L07. The use of

a common slope of one is believed valid for this analysis. As will be

shown later, the average observed data are within 7.2 per cent of predict-

ed values by the procedure used. The slope variations found do not show

trends for space gas velocity and oxygen concentration. Since all the

slopes have approximately the same value, this provides the basis for

the use of a common slope. The selection of a common slope greatly aim-

plifies the correlation of the data. The important point is to recog-

nize the limitations of the relations presented for design application.

The intercept values from Table 6 were plotted against laS according to

Equation 5,

I, a In(kPp) 4 alnS (5)
This data gave a family of straight lines with a constant slope value

of a equal to 0.23. The parameter for this set of curves is the value

of oxygen concentration, P. The curves are plotted in Figure 8 and the

intercept values at InS = 0 are tabulated in Table 7.

The intercept values from Table 7 were next plotted against the

InP as indicated in Equation 7

Ib z Ink 4 plnP (7)
to evaluate the remaining rate equation constants, p and k. The slope

of this straight line plot was equal to the exponent, p, and the value

was 0.83. The value of the intercept, Ink, was evaluated at laP 0

and the value of k was equal to 0.0064. Figure 9 is a plot of the intercept






- 57 -


r- 0
t
-1.0






n -2.0


10 25 50 100 200
Space Gas Velocity (S) CMPT

Figure 8. Evaluation of Rate Equation Exponent, a


300


-3.0
21 35 50
Oxygen Concentration (P) %

Figure 9. Evaluation of Rate Equation Exponent, p, and Pseslo
Reaction Velocity Constant, k


L


0










58 -

data in Table 7 versus InP The remaining batch runs for different tempera-

tures and asphalts were analysed and evaluated by this same procedure.

The data for all the runs was plotted according to Figures 7, 8 and 9

and the values of the exponents, p, r, and a, were determined.


TABLE 7

SLOPE AND INTERCEPT VALUES FROM FIGURE 8

GULF COAST ASPHALT TA-1023-2

TEMPERTURa E 500 oF.

AGITATOR SPEED 700 R.P.M.

P Slope Intercept
% 02 laS 0

21 0.23 -2.66

35 0.23 -2.23

50 0.23 -1.73



The values of the exponent constants that best fit the data for

the four different processed residues are

r 1.0

a 0.2

p a 0.9

The corresponding values for the pseudo reaction velocity constant, k,

are tabulated in Table 8 for one asphalt at three different temperatures

and the other three asphalt at 500 oF.










- 59 -


TABLE 8

PSEUDO ACTION VELOCITY COSTATS

AGITATOR SPEED 700 R.P.J.

Pseudo Reaction Velocity Constant, k
Teap.
O TA-1023-2 TA-102/ TA1025 TA-1026

450 0.0045 ....... ....... .......

500 0.0061 0.0090 0.0070 0.0056

550 0.00 ....... ....... .......


The pseudo energy of activation, was determined by plotting
the Ink versus the reciprocal of the absolute temperature 1/ and measur-

ing the slope of the resulting straight line. According to Equation 11

Ink -E/RT + lA (1)

the negative slope of the plot is equal to -E/R. The value of E deter-

ained from the slope of the curve in Figure 10 was 5800 calories per

gn. aole.

The effect of agitation was evaluated by changing the agitator

speed from 700 r.p.r. to 1300 r.p.m. and making batch runs at similar

process conditions. An increase in the value of the peaudo reaction

velocity constant is the only variation to be expected for batch runm

with a higher degree of agitation. It was determined that the batch runs

using a higher agitator speed followed the same general rate equation

and the values of the reaction velocity constant varied as shown in Table 9.











-60-


0.0100


0.0090


0.0080 -


0.0070 -



0.0060



0.0050


0. 00C0


0.0030


0.0017 0.0018 0.0019
I/T f'.


0.0020 0.0021


Figure 10. Variation of Pseudo Reaction Velocity instantnt, k, with
Temperature for Gulf Coast Asphalt TA-1023-2.


I










- 61-


TABLE 9

VARIATION OF THE PSEUDO REACTION VELOCITY CONSTANT
WITH AGITATION

TEMPERATURE 500 oF.

ASPHALT TA-1023-2

Agitator Speed
R.P,M. k

700 0.0061

1300 0.0062

The small increase in the value of k for the increased agitator

speed suggests that the degree of agitation that was used in this inves-

tigation was above the maximum agittion threshold. When this threshold

value is obtained, the degree of agitation is no longer a process vari-

able. The rate of reaction will then depend upon other process variables.

The rate equation that was developed for the asphalt blowing pro-

ceas was checked by substituting process conditions and reaction times

to calculate final asphalt consistencies. The calculated values were

checked against the experimentally determined values for the batch runs.

The agreement of the developed equation as cheeked for all batch runs

using the equation

dR//t a kS.2p'1.9R (19)
or in the integrated fora

lnRVl/ ktS0.2P0'9 (20)










62-

The values of k and Ro that were used for the different process condi-

tions and asphalt were taken from Tables 8 and 1 respectively. The

average percentage variation of the calculated consistencies baaed on the

experimental values are tabulated in Table 10.


TABLE 10

PERCENTAGE ERROR FOR REACTION RATE EQUATION

EQUATION ln(R/R,) = kt30.2p0.9

Per,Cent Error for Asphalt
Temp.
OF. TA-1023-2 TA-1024 TA-1025 TA-1026

450 4.1 ......

500 7.1 3.4 3.6 9.5

550 15.1 .....


For all batch runs the overall percentage variation for agree-

ment to the developed rate equation was 7.2 per cent.

B. Reaction Mechanism

The order of the reaction for the asphalt blowing process is the

sum of the exponents on the process variables and is approximately a pseudo

second order reaction. The order with respect to each variable is the

value of the exponent for that particular variable. The developed rate

equation suggests that the mechanism is 0.2 order with space gas velocity,

0.9 order with oxygen concentration and first order with Ring and Ball

consistency. These are all pseudo order values based on physical variables.










63-

The evaluated constant, 3, the pseudo molal energy of activation,

was 5800 calories/ga. mole. This is a rather low value for the activa-

tion energy and indicates a reaction mechanism with diffusion controlling.

The reaction rate for this mechanism depends on the rate at which the

active reacting gaseous agent (oxygen) is transferred to the liquid asphalt

interface. Process conditions that would increase this mass transfer of

oxygen would be increased agitation, increased gas space velocity and

increased oxygen concentration in the feed gas.

The oxygen utilization for the four different types of residue

was a function of the asphalt product consistency and was independent

of the processing conditions. The pounds of oxygen utilized per pound

of asphalt processed was plotted against the change in Ring and Ball

consistency of the asphalt. This average ourve for the Gulf Coast re-

siduu is shown in Figure 11. Curves for the other three residue are

indicated in Figures 12, 13 and 14. Table 11 is a tabulation of the

average values of oxygen utilization for specific changes in asphalt

product consistency.

The oxygen utilization data indicates that the change in consis-

tency, or the degree of reaction of the asphalt, is a stoichlometrie

relationship with the amount of oxygen that is used. The four residua

that were used required different amounts of oxygen for a given change

in asphalt consistency. The South Texas Heavy Asphalt TA-1026 utilized

the most oxygen for a given change in product consistency while the East

Texas Asphalt TA-1024 required the least oxygen for a similar change.





-64-

0.12


0.10 -
o.4 o

0.08


0.06

g0

C .0 -0
-3



0.02




0 20 40 60 80 100 120 140O
Change In Ring and Ball Softening Point oF.

Figure 11. Oxygen Utilization and Product Conslatency for Gulf
Coast Asphalt TA-1023-2
0.12 i


0.10



0.08



0.06 -


0.04 -


20 40 60 80 100 120 140
Change in Ring and Ball Softening Point oP.
Figure 12. Oxygen Utilization and Produat Consistenoy for East
Texas Asphalt TA-1024






-65-

0.12



0.10


S0.08


a 0.06 -
I


0 0.04 -


0.02



0 20 40 60 80 100 120 UO
Change in Ring and Ball Softening Point OF,

Figure 13. Oxygen Utilisation and Produot Consistency for East
Central Texas Asphalt TA-1025

0.12









S0.06



0.04 -



0.02



0 20 40 60 80 100 120 140
Change in Ring and Ball Softening Point OF.

Figure 14. Ozygen Utilisation and Product Consistency for South
Texas Heavry Asphalt TA-1026
Texas Heavy Asphalt TA-1026











66t. -

The data also indicate that as the reaction proceeds in the four different

residua, lees oxygen Is required for a given change in product consistency.

TABLE 11

OXYGEN UTILIZATION FOR PROCESSED RESIDUA

Asphalt Change in Ring and Oxygen Utilizatton**
Ball Consistency" Lb. 02/Lb. Asphalt
oF.

TA-1023-2 30 0.034
80 0.061
130 0.075

TA-1024 50 0.U1
100 0.025

TA-1025 52 0.023
102 0.037

TA-1026 27 0.044
77 0.079
127 0.100

*Change in consistency froa original residuum.
**Cumulative oxygen required for the given change in Ring and Ball
consistency.

The reaction products from the air blowing process are

the air blown asphalt and the converter gas containing water vapor,

carbon dioxide, oxygen, nitrogen and an oil smoke and entrainment mist.

A considerable portion of the water and essentially all the snoke and

entrainment products were separated from the converter gas in the Cottrell

electrical precipitator. The water and oil products that were condensed

and precipitated in the Cottrell unit were called fune oil products.

When calculating an oxygen balance for batch and continuous

runs, an unaccountable disappearance of oxygen occurred for each run.










67 -

The oxygen balance was made by comparing the amount of oxygen in the pro-

oaes feed gas to that calculated in the converter gas as oxygen, carbon

dioxide, water vapor, liquid water and acids. The equivalent amount of

oxygen as acids in the precipitator fume oil products was mall and these

values were not included in the calculation. The resulting oxygen balance,

therefore, was based on the remaining converter gas constituents of oxy-

gen, carbon dioxide, water vapor and liquid water. Nitrogen balances were

calculated for all the runs on the feed and converter gas streams to make

certain that the gas flow rates or analyses of the feed and converter gases

were not responsible for the unaccountable oxygen loss. The average varia-

tion for the cumulative nitrogen balances on the feed and converter gas

streams was 1 2.9 per cent by weight. This low variation for nitrogen

balances indicates satisfactory flow rate measurements and analyses for

the feed and convertor gas streams with no significant losses.

In Table 12 are listed the average emulative unaccountable oxy-

gen losses for batch runs where the final product consistency was 200 OF

Ring and Ball.

A comparison of the data in Table 11 and Table 2, for the total

oxygen used to produce a 200 oF. Ring and Ball product, shows that between

0 and 55 per cent of the oxygen appears as an unaccountable loss. The

unaccountable oxygen could have been absorbed in the liquid asphalt,

reacted to form oxygenated compounds in the fume oil products, or appeared

as oxygenated compounds in the converter gas stream. The previous inves-

tigation by Kats (13) proved that less than 1 per cent by weight of oxygen

is absorbed in liquid asphalt at Ring and Ball consistencies of 200 OF.










-68 -
or less. If it is assumed that 1 per cent of the oxygen was absorbed

by the asphalt, 0.01 lb. 02/1b. asphalt would be accounted for. This

value is approximately 100 per cent of the average losses for the harder

TA-1024 and TA-1025 asphalts and 26-53 per cent for the softer TA-1023-2

and TA-1026 asphalts.


TABLE 12

UNACCOUNrABLE OrXYG LOSSS TO 200 F.
RING AND BALL PRODUCT CONSISTECIES

Total Oxygen Losses Average Oxygen Losses
Lb. 0Lb. aLphalt i. O/Lb. Asphalt
Asphalt
minimum Maximum Average

TA-1023-2 0.000 0.064 0.082

TA-1024 0.000 0.016 0.006

TA-1025 0.000 0.019 0.011

TA-1026 0.020 0.052 0.035


Considering the loa variation for the cuulative nitrogen balances

on the process gases, it is assumed that the remainder of the unaccount-

able oxygen reacted to form oxygenated products that could occur as

vapors in the converter gas or as precipitated fume oil products. The

appearance of oxygenated compounds in the fue oil products seems to be

a more feasible explanation, because the Orsat analyzer indicated similar

converter gas analysis as given by the gas analysis unit.

The appearance of water and carbon dioxide in the converter gas

substantiate the dehydrogenation and deearbonisation reactions. With










69-
this mechanism, it is possible that the oxygenated materials in the fume

oil are organic compounds auch as aldehydes, katones and ethers.

Typical cumulative curves of the oxygen balance for batch runs

are plotted in Figures 15 and 16. Figure 15 shows the data for a low

gas space velocity and low oxygen concentration run. Almost all the

available oxygen is used for the reaction with the result of very

little oxygen in the converter gas. Figure 16 is the plotted data for

a high space gas velocity and high oxygen content run. Only a small frac-

tion of the available oxygen is used for the reaction and the curves are

close to each other. These curves may be used to determine the amount

of oxygen used by the reacting asphalt to produce a specified degree of

consistency. The data for Table 11 was obtained in this manner. The

remaining batch runs gave similar plots depending on the processing

conditions.

The fume oil products were collected for each batch and continuous

run. At the end of a run, the various samples taken were separated into

an aqueous and an oil fraction. The volume and weight of these samples

were determined and then the samples were titrated for acid numbers.

Table 13 shows the average amount of fume oil collected for the

various asphalt residue used and processed at different conditions to a

final product consistency of 200 oF. Ring and Ball softening point. The

amount of fue oil products that was collected for these batch runs was

independent of the process gas oxygen concentration but was dependent

on the gas space velocity, reaction temperature and the type of asphalt

processed. It may be noticed that for all the residue used, the percentage






- 70 -


0.15



6.
S 0.10 0 Fooed






i 002 Out

0
1 2 3 4 5 6
Reaction Tim (t) Hours
Figure 15. Cumulative Oxygen Balance for Low Space Gas Velocity and Low
Oxygen Concentration, Gulf Coast Asphalt TA-1023-2

0.4

|02 Feed



2 Dut



I
I 0.2 -
a
m


0.1



SI I I I I
0 1 2 3 4 5 6
Reaction Time (t) Hours
Figure 16. Cumulative Oxygen Balance for High Space Gas Velocity and High
Oxygen Concentration, Gulf Coast Asphalt TA-1023-2










71-

of the oil fraction increases with increasing reaction temperature and

feed gas space velocity. The total amount of fume oil produota collected

for asphalt processed to 200 OF. Ring and Ball consistencies was not

constant. The total amount of fume oil products per batch run was

greatest for the South Texas Heavy Asphalt TA-1026 and smallest for the

East Texas Asphalt TA-1024. The fraction of the fue oil products as oil

was only 15 weight per cent for the East Texas Asphalt TA-1024 with a

aximm of 50 weight per cent for the Bast Central Texas Asphalt TA-1025.

The total weight of fue oil in Table 13 includes the weight of the pre-

cipitated oils and the um of the weight of water as condensed water and

water vapor in the converter gas.

The penetration values for the asphalt products were determined

by the standard A. S. T. M. test D 5-25 (3) using a penetrometer. This

penetration data for asphalts is generally used in conjunction with sof-

tening point data to determine the adaptability of bituminous materials

for specific uses and for quality control. Figures 17, 18, 19 and 20

show the relationship between Ring and Ball softening point and penetra-

tion values for the asphalt residues used in this investigation. The

relation of Ring and Ball softening point and penetration is almost

identical for the four different residues.






- 72-


100 120 140 160 180 200
Ring and Ball Softening Point 0F.
Figure 1. Properties of Asphalt Producta, Gulf Coast TA-1023-2


230 ,


200




150




100


S 12 10 1I I


100 120 140 160 130 200
Ring and Ball Softening Point oF.

figure 18. Properties of Asphalt Products East Texas TA-102A






-73 -
230


200



150
i

fr
a100


Io-






100 120 140 160 180 200 220
Ring and Ball Softening Point OF.
Figure 19. Properties of Asphalt Products, East Central Texas TA-1025


230


200

o0

150
0



8 0


I 5o

0
0

0 III II
100 120 14O 160 180 200 220
Ring and Ball Softening Point o.

Figure 20. Properties of Asphalt Products, South Texas Heavy TA-1026










-74 -


TABLE 13

FUME OIL REACTION PRODUCTS TO 200 oF.
RING AND BALL PRODUCT CONSISTENCIES

Asphalt Temp. S Total Wt.* Oil Water
OF. CFT Fume Oil, for Wt. Wt. %
Batch Runs, Gas.

TA-1023-2 450 25 339 15 85
450 100 470 17 83
500 25 332 16 84
500 100 457 25 75
500 200 491 38 62
550 25 467 27 73
550 100 585 36 64

TA-1024 500 25 94 15 85
500 100 403 15 85

TA-1025 500 25 241 50 50
500 100 472 52 48

TA-1026 500 21 704 31 69
500 100 1023 43 57

*Average value for batch runs independent of feed gas oxygen concentration.


C Scale Up
The preceding analysis and development of the rate equation was

based on batch run data. Several continuous runs were made at similar

batch run processing conditions, to compare the batch or integral treat-

ment against the continuous or differential treatment. The comparison

was made by determining equivalent residence reaction time for the two

types of operation and then comparing the asphalt product consistency

and oxygen utilization. The reaction residence time used as the basis

of comparison was calculated from the continuous operation data by










75 -

Equation 18

to a Maa (18)

This same value for reaction time was used for the batch operation

data to estimate Ring and Ball softening points and oxygen utilization

data from plots similar to Figures 5 and 15. Table 14 indicates the

results for the batch and continuous runs where the processing conditions

were the same for both types of operation. When the equivalent reaction

times are equal for the two types of operation, the agreement of the oxy-

gen utilization data is within 15 per cent and the product consistencies

check within 10 per cent. These results indicate that the same product

and oxygen consumption may be expected from either batch or continuous

runs.

The practical application for the developed rate equation is

paramount for the calculation of processing times and design capacities

for commercial ephalt blowing equipment. A sample calculation to demon-

strate the use of the rate equation is included to illustrate its use-

fulness,

Assume that it is required to determine the processing time and

production capacity of an agitated reactor vessel 10 feet in diameter

and 17 feet high. The ieptn of the asphalt charge is 12 feet. The reactor

is agitated with a Turbo-Wixer agitator of the type used in the pilot plant

experiments. The size of the agitator impeller is 42 inches. By select-

ing process conditions and substituting them in the developed rate equation,

the processing time, process gas requirements and production capacity

can be calculated for a product having a 100 OF. softening point rise.









- 76-


TABLES 14

COMPARISON OP EXPREMMAL BATCH AND CONTINUOUS DATA

GULF COAST ASPHALT TA-1023-2
TEMPERATURE = 500 OF.

AGITATOR SPEED = 700 R.P.M.

Corntiuous S P Residence Product 02 Used
Runs CFMT % 02 Time, Hrs. R, oF. Lb. 02/Lb. Aaph.

411 25 21 3.1 110 0.0335
412 25 21 4.2 146* 0.098
413 25 21 4.65 170 0.0600

429 100 21 1.63 97 .0.0317
430 100 21 2.48 124 0.0434
431 100 21 3.33 150 0.0500

408 200 21 1.28 95 0.0303
409 200 21 1.77 131 0.0318
.10 200 21 2.54 161 0.0408

Batch
Rmns

404 25 21 3.1 108 0.037
404 25 21 4.2 137 0.050
404 25 21 4.6 153 0.056
406 100 21 1.6 106 0.034
406 100 21 2.5 135 0.046
406 100 21 3.3 167 0.060

407 200 21 1.3 111 0.039
L.07 200 21 1.8 133 0.054
407 200 21 2.5 173 0.063











-77 -
The residuum to be used in this sample calculation is the Gulf Coast

Asphalt TA-1023-2.

The processing conditions are selected as follows:

Temperature 500 OF.

Feed gas space velocity, S = 28CPMT

Feed gas oxygen concentration, P = 21
The reaction time necessary to change the product consistency by 100 PF.

Ring and Ball can be calculated from the integrated form of the rate

equation (Equation 20)

In1/Ro. ktP'.9S0,2 (20)

For the Gulf Coast Asphalt processed at 500 of., k a 0.0061 and Ro, "0.

The remaining variables are substituted into Equation 20 and solved for

the reaction time, t.

Ro 70 F.

R1 100 + 70 = 170 OF.

k 0.0061

S 28CFIT

P a 21% 02

ln(170/70) 0.0061(21)0.9(28)02t

t 4.9 hours
The value of t is the reaction time necessary to change the

product consistency from 70 OF. to 170 OF. Ring and Ball. This value

is 4.9 hours for the process conditions .hosen.

The process gas requirements are determined from the feed gas

space velocity and the mass of reacting residuum. The mass of asphalt










-9-
charge per batch is

Mass asphalt = (reactor volume)(asphalt density)

(r) ()2 (12)(62.4)(0.967)/(4)(2000)
= 28.4 tons asphalt

The corresponding feed gas flow rate is

Gas feed rate a (mass asphalt)(feed gas space velocity)

28.4(28)

a 795 ft.3 air/min.
The calculated feed gas requirement for the reactor is 795 ft.3 air/min.

The daily production capacity for the reactor can be determined

from the total cycle time required to process one batch. The operating

cycle includes; time necessary to heat the charge to the reacting teopera-

ture, time necessary for the desired reaction, holding time for analysis

and time to discharge to a product tank. If the sum of the time for all

the operations except the reaction time is assumed to be 6 hours, the total

cycle time is approximately 11 hours. The daily batch production would

be 2.2 batches per day or 62 tons of Gulf Coast Asphalt having a final

product consistency of 170 OF. Ring and Ball. A variation of the processing

conditions would change the reaction time but would not anpreciably affect

the relaning cycle time.

When the feed gas space velocity and oxygen concentration is
increased to 100 CFMT and 50 per cent respectively, the reaction time

for the reactor is reduced to 1.7 hours. The total cycle time is now

7.7 hours and the daily production is increased to 89 tons of 170 oF.

Ring and Ball asphalt. The production has been increased but at the











79-

expense of a greater feed gas flow rate and oxygen concentration. An

economic analysis must be considered to arrive at justified operating

conditions.

The calculated results for the initial conditions selected for

the design problem may be compared with actual finery data as supplied

by the Turbo-Mixer Corporation (14). The comparison sl based on the same

size reactor and similar operating conditions. The commercial data for

refinery "A" lists a reaction time of 5.5 hours for increasing the soften-

ing point of an asphalt 100 O. Ring and Ball. By assuming that this

asphalt is similar to the Gulf Coast Asphalt TA-1023-2, the calculated

reaction time of 4.9 hours may be compared with the 5.5 hours reaction

time. The error is approximately 13 per cent. The agreement of these

results verify the use of the general rate equation for design calculations

of commerolal asphalt blowing units.












VIII. CONCLUSIONS


From the results of the asphalt blowing process using four

different kinds of residua, the following conclusions may be made con-

cerning the Kinetics of the asphalt slowing process within the limits

of the conditions covered by this investigation:

1. The general rate equation for the reaction rate is

di/dt kP0.30S.Z

where

dR/dt u gross asphalt reaction rate as rate
of change of softening point

R w asphalt Ring and Ball softening point,
OF.

S process gas apace velocity,
ft.o/(min.)(ton asphalt) at (70 OF.,
1 atm.)

P = original process gas concentration,
volume %

k a pseudo reaction velocity constant

t a process reaction time, hours

2. The values of the pseudo reaction velocity constants are a

function of the type of residua and the reacting temperatures.

The corresponding values for the pseudo reaction velocity con-

stants are:

Tep. Pseudo Reaction Velocity Constant, k
oF. TA-1023-2 TA-1024 TA-1025 TA-1026

450 0.0045 ...... ......
500 0.006L 0.0090 0.0070 0.0056
550 0.0081 ...... ....... ......


- 80 -










81 -

3. The reaction rate controlling step is a diffusion process

based on the low pseudo molal energy of activation, E, of

5800 calories/gm. mole.

4. The gross asphalt blowing reaction may be considered a coa-

plex dehydrogenation, decarbonization and polymerization

reaction. This is substantiated by the appearance of water

and carbon dioxide in the converter gas and by the increased

softening point for the asphalt products.

5. The asphalt blowing fume oil reaction products collected in

the Cottrell precipitator contain a mixture of unknown oils

and water. For asphalt residues reacted to 200 OF. Ring and

Ball, the amount of fume oil products vary from 4-11 per cent

of the weight of residue reacted.

6. The fraction of oil in the fume oil products was a minimum of

15 weight per cent for the East Texas Asphalt TA-1024 and a

maximum of 50 weight per cent for the East Central Texas

Asphalt TA-1025.

7. The change in asphalt consistency is related to the amount

of oxygen used in the asphalt blowing reaction. The amount

of oxygen used for a given change in product consistency was

different for the four residua used. The East Texas Asphalt

TA-1024 used a minimum amount of oxygen while the South Texas

Heavy TA-1026 used the maximum amount of oxygen.

8. Of all the oxygen used in the asphalt blowing reaction, 0-56

per cent could not be accounted for in the converter gas and










82 -

fuhe oil products. It is assumed that the unaccountable oxy-

gen reacted to form oxygenated products that could appear as

vapors in the converter gas or as liquids in the fume oil

products.

9. For the same residence reaction times, integral batch opera-

tion is equivalent to differential continuous operation.

10. The general rate equation may be used for the calculation

and design of commercial asphalt blowing units.












IX. NOMENCLATURE


A = Arrhenius frequency factor

Arp asphalt charge stock

Aq, A2 t intermediate asphalt products

Ax = composite air blown asphalt product not removed from
the reacting sone

B = volume of sodium hydroxide per on. of water or ga. of oil,
cc.

C = gas concentration on a wet gas basis, volume per cent

D = concentration of gas on dry gas basis, volume per cent

d = ga density, lbs./ft.3

E = molal energy of activation

e = base of natural logarithms

a feed rate of fresh asphalt, Ibs./hr.

f a conversion factor, lbs. oxygen/lbs. gas

G = gas flow rate, ft.3/min. @ 70 oF. and 1 atm.

AH 2 asphalt blowing heat of reaction

I& a intercept of In(dR/dt) versus InR plot at lnR a 0

Ib 2 intercept of the I, versus lnS plot at InS s 0

Ig intercept of the Ib versus InP plot at InP 2 0
k s peudo reaction velocity constant

k's specific reaction velocity constant

L, L2, L3 = intermediate condensed reaction products

Lx a composite condensed reaction products

Ma mass of asphalt in reactor, pounds

N = normality of sodium hydroxide

83 -














P a feed gas oxygen concentration, volume per cent

p a exponent for P

Pp. partial pressure, am,. Hg.

R asphalt Ring and Ball softening point, oF.

Ro = Ring and Ball softening point for charge stock, "F.

1I a Ring and Ball softening point at any reaction
ties, oF.

r = exponent for R

S = feed gas space velocity, ft.3/min. ton asphalt at
70 *F. and 1 atm.

a 2 exponent for S

T = absolute temperature, "o

t = batch process reaction time, hours

at a time interval, hours

to a continuous process residence time, hours

V volume of water or weight of oil, cc. or gas.

S= volume of water, cc.


- 8U-











X. BIBLIOGRAPHY


(1) Abraham, H., "Asphalts and Allied Substances," 5th ed., D. Van
Nostrand Co., New York, 1945.

(2) "American Society for Testing Materials," Tentative Method of Test

for Acid and Base Numbers of Petroleum Oils By Color-Indicator

Titration, D 663-46T, A. S. T. M. Standards on Petroleum Products

and Lubricants, 336 (1947).

(3) Ibid., Standard Method of Test for Penetration of Bituminous Materials,
D 5-25, 4.

(4) Ib., Standard'Method of Test for Softening Point of Bituminous

Materials, D 36-26, 12.

(5) Blakely, A. R., Forney, W. F., Frino, V. J., and Rescorla, A. R.,
"Asphalt Oxidation with Agitation," Paper presented at the A. C. S.

Meeting in Miniature, Hotel Essex House, Newark, New Jersey, Janu-

ary 25, 1954.
(6) Brooks, B. T., "Non-Bensenoid Hydrocarbons," Chemical Catalog Co.,

New York, 1922.

(7) Byorly, F. X., U. S. Patent 524,130 (August 7, 1894).
(8) Frost, A. A., and Pearson, R. C., *linetics and Mechanism,"

John Wiley and Sons, New York, 1953.

(9) Graham, W., Cudmore, W. J. C., and Heyding, R. D., Canadian J.

binol.., 01, 143 (1952).
(10) Hoiberg, A. J., and Shearon, W. H. Jr., Ind. Eng. Chem., /,

2122 (1953).

85 -









86-

(11) Holland, C. J., Pstr. Eag., S, Nos. 2-11, (1935).
(12) Hougen, 0. A., and Watson, K. M., "Chemical Prooes Principles,"
Part III, John Wiley and Sons, New York, 1947.

(13) Kats, I., an. J. Research, 2, 435 (1934).
(14) Parker, H., Turbo Mixer Corp., Private Communieation, April 30, 1954.
(15) Perry, R. H., and Pigford, R. L., Ind. Eng. Chem., j, 1247 (1953).
(16) Pfeiffer, J. P. H., "Properties of Asphaltic Bitumen," Elsevier
Publishing Co., New York, 1950.

(17) Sherwood, T. I., and Pigford, R. L., *Absorption and Extraction,"
McGraw Hill Book Co., New York, 1952.

(18) Thurston, R. R. and Knowles, E. C., Ind. Eng. Chem., 2a, 88 (1936).

(19) U. S. Department of Commerce, 'Statitical Abstract of the United
States," 74th ed., Government Prining Office, Washington, 1953,
p. 736.
































APPENDIX A


DRAWINGS















atrinKnt (ser Rotameter R or







pil & Wate
Analya er



co2
o |- .

Dryers
Roactor


sce Botaaeter.
Beaced
Asphalt


Scale





Notametere Doew
Point













ERIAL
ERAASPH IALT BLOWING FLOW DZAMAU

RAWNCHEC BY: i ENGINEERING AND INDUSTRIAL EXPERIMENT STATION
LERANCES UNLESS OTHERWISE SPECIFIED DATE: 327-5 UNIVERSITY OF FLORIDA
ECIMAL FRACTIONS RCALE: GAINESVILLE












Precipitator


Seale


O heru=oeaple

O mbiaslt


H;. 1aiiy

rti I' -


Reactor


7 aet-- er



1,- Manomter


Back Pressure
Regulhtor










-----[?"--7e
02 ~2 I


Oxygen


Oas Panel Board


Pppeatre Rehoing e


E" V.ve


ASPHALT BLOWING PIPING DIAORAM

ENGINEERING AND INDUSTRIAL EXPERIMENT STATION
UNIVERSITY OF FLORIDA
OAINESVILLE


-~-- I-~-













CONTINUOUS
OUTPUT
r---- 1


MAIN FUSE
SWITCH


I V D.C.
S 138 M.A.

L--_____


CONTROLLED
OUTPUT


1.





L tI I


I -EreRe
i^.-".^Mol. _
-+*"^^ ^


110 V
OUTLETS


I -- 7


S THERMOSTAT

THREE HEAT
SWITCH
HIGH- IL,4,5; 2L3
MED.2L,3; IL 5
LOW 2L,5;IL4

[ I.-1 BLACK


I
I

** w\


0- 50,000 voc
I 20 MA
L- ___ __
ELECTRICAL PRECIPITATOR


I4- 500W, 230V
I SHORT STRIP
I HEATERS


I 1000W, 230V
RINu HEATER


L __ _
ASPHALT STORAGE
HEATERS


y,
/\ I.
/, \ I,


I!!!


DATE i MATERIAL ASPHALT BLO

DRAWN BY D. B.
CHECKcED r J H.
TOLERANCES UNLESS OTHERWISE SPECIFIED DATE 4- 5- 54
DECIMAL FRACTIONS SCALE


WIRING DIAGRAM


ENGINEERING AND INDUSTRIAL EXPERIMENT SIAIION DRAWING NUMBER
UNIVERSIlr OF FLORIDA 5302- 3
GAINESVILLE


GAINEVILL


:t


REVISION


.. II


I Y
r/ira~
Ir

L







Thermostat Bulb -s
Protection Tube


Thercouple -
Protection Tube


- Strip Heaters- Alternate
Long and Short


Translte Cover -


T-,








Storage Shell -
12" Steel Pipe


T-


-- Inaulbtion


Theramotat Control


-- Three Beat Snap
Switch


- Sheet Metal Cover
and Boz


Ring Beater


Figure 24

ASPHALT HLOWIO STORAGE TAHI

ENGINEERING AND INDUSTRIAL EXPERIMENT STATION DRAWING NUMBER
UNIVERSITY OF FLORIDA 520o3-
OAINESVILLE
DATE MATERIAL







0




o 6

-0'


Air Feed DMetributor
3/g" steel pipe
1/8' pipe 9ip


, o
C-
C. O ] ^


Thermocouple Welle


Asphalt Feed


3m Steel Pipe


1)" IPS Pipe Fittings


1s Steel Pipe


Strip Heaters
/, 5-Bqually Spaced


U
12D


Shaft
Support


Asphalt Outlete
3/9a Pipe Couplinge


Turbo Mizer Aerator Hood Ring
and Impeller #~-2.4-3


Agitator Assembly


ASPHALT BLOWIHO REACTOR

ENGINEERING AND INDUSTRIAL EXPERIMENT STATION
UNIVERSITY OF FLORIDA
GAINEBVILLE


Agitator
Assembly


Air feeo
Distributor


Beactor Assembly














High Voltage
Bushing Insulator


Flow
ff ~1 "


Aooss Panel &
Oberrvation
window


37 Steel Pipe


- Hih Toltage
/ lectroe


/-Ueatrode pension
S Weiht


ASPHALT BLOWID ILICTRICAL FZCIPITATO

ENGINEERING AND INDUSTRIAL EXPERIMENT STATION
UNIVERSITY OF FLORIDA
GAINESVILLE
ON DATE MATERIAL


) 6L -




Full Text

PAGE 1

KINETICS OF PROCESSING P ^ ASPHALTIC RESIDUES 7^ By JOHN DANIEL HOLMGREN A Dissertation Presented to the Graduate Council of The University of Florida In Partial Fulfilment of the Requirements for the Degree of Doctor of Philosophy UNIVERSITY OF FLORIDA JUNE, 1954

PAGE 2

Cis. / SCIENCES LIBRARY

PAGE 3

ACKNOIVLSDGEWENT The author wishes to thank Dr. H. E. Schweyer for his helpful guidance In directing this research. The author is also indebted to Dr. Mack Tyner for his suggestions on kinetics and to the other members of his Supervisory Conmlttee, Professor T. L. Bransford, Dr. W. F. Brown and Dr. A. H. Gropp for their counsel and criticism. The author wishes to thank Mr. Douglas Baldwin, Jr. for his work on the drawings, Mr. E. A, J. ffarshyk for his help on the construction of the equipment, The Texas Company for supplying the asphalt and the Engineering and Industrial Experiment Station for sponsoring this project. ii -

PAGE 4

TABLE OF CONTENTS Page ACKNOWLEDGEMENT H LIST OF FIGURES v LIST OF TABLES vii I. INTRODUCTION 1 II. THEORY 5 A. The Asphalt Blowing Reaction 5 B. Heterogeneous Reactions 6 III. MATERIALS 10 IV. APPARATUS 11 A. Processing Equipment , 11 1, Asphalt storage tank 11 2, Asphalt reactor H 3, Electrical precipitator 17 U. Flow panel board 19 5. Temperature panel boaH 21 6. Piping 23 B. Analysis Equipment 2U 1. Gas analysis vmit 24. 2. Gas analysis calibration 25 V. PROCEDURES 30 A. Operating Procedure 31 B. Analytical Procedure 37 VI. CALCULATIONS 4.0. A. Kinetics 40 B. Reaction Mechanism 43 C. Scale Up 48 Ill-

PAGE 5

TABLE OF CONTENTS Page VII. RESULTS AND DISCUSSION 50 A. Kinetics 50 B. Reaction Mechanism 62 C. Scale Up '^U VIII. CONCLUSIONS 80 IX. NOMENCLATURE 83 X. BIBLIOGRAPHY 85 XI. APPENDICES 87 A. Drawings 87 B. Experimental Data ^U C. Calibration Curves 102 XII. BIOGRAPHY OF AUTHOR 110 Iv -

PAGE 6

LIST OF FIGURES Figure Page No. 1. Asphalt Blowing Pilot Plant 12 2. Asphalt Storage Tank, Reactor and Electrical Precipitator 20 3. Asphalt Blowing Flow Panel Board and Gas Analysis Unit 22 U. Thermal Conductivity Cell Calibration Curve for Ternary System of Oxygen, Nitrogen and Carbon Dioxide 29 5. Softening Point and Reaction Time Relation for Batch Runs Using Gulf Coast Asphalt TA-1023-2 51 6. Reproducibility of Batch Run Data, Gvdf Coast Asphalt TA-1023-2 53 7. Reaction Rate and Product Consistency for Batch Runs, Gulf Coast Asphalt TA-1C23-2 55 8. Evaluation of Rate Equation Exponent, s 57 9. Evaluation of Rate Equation Exponent, p, and Pseudo Reaction Velocity Constant, k 57 10. Variation of the Pseudo Reaction Velocity Constant, k, with Temperature for Gulf Coast Asphalt TA-1023-.2 60 11. Oxygen Utilization and Product Consistency for Gulf Coast Asphalt TA-1023-2 6^ 12. Oxygen Utilization and Product Consistency for East Texas Asphalt TA-1C2-C 64. 13. Oxygen Utilization and Product Consistency for East Central Texas Asphalt TA-1025 65 14. Oxygen Utilization and Product Consistency for South Texas Heavy Asphalt Ta-1026 65 15. Cumulative Oxygen Balance for Low Space Gas Velocity and Low Oxygen Concentration, Gulf Coast Asphalt TA-1023-2 70 v -

PAGE 7

LIST OF FIGURES FigTire Page Mo. 16. Cumulative Oxygen Balance for High Space Gas Velocity and High Oxygen Concentration, Gulf Coast Asphalt TA-1023-2 70 17. Properties of Asphalt Products, Gulf Coast TA-1023-2 72 18. Properties of Asphalt Products, East Texas TA-102^ . 72 19. Properties of Asphalt Products, East Central Texas TA-1025 73 20. Properties of Asphalt Products, South Texas Heavy TA-1026 73 21. Asphalt Blowing Flow Diagram 88 22. Asphalt Blowing Piping Diagram 89 23. Asphalt Blowing Wiring Diagram 90 24.. Asphalt Blowing Storage Tank 91 25. Asphalt Blowing Reactor 92 26. Asphalt Blowing Electrical Precipitator 93 27. Air Feed Rotameter Calibration Curve, Schutte and Koerting 3F Tube «ind Number 2 Aluminum Float .... 106 28. Oxygen Feed Rotameter Calibration Curve, Schutte and Koerting IR Tut>e and Stainless Steel Float ... 107 29. Converter Gas Rotameter Calibration Curve, Schutte and Koerting 3F Tube and Number 1 Aluminum Float . . 108 30. Gas Analysis Rotameter Calibration Curve, Fisher and Porter 01-N-15A Tube with Pyrex Glass and Stainless Steel Floats 109 vi -

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LIST OF TABLES Table Page No. 1. Properties of Asphaltic Residues 10 2. Calibration Data for Gas Analysis Instruments .... 27 3. Asphalt Processing Conditions 30 4,. Gas Properties A^ 5. Reproducibility of Batch Run Data 52 6. Slope and Intercept Values from Figui-e 7 5A 7. Slope and Intercept Values from Figure 3 58 8. Pseudo Reaction Velocity Constants 59 9. Variation of the Pseudo Reaction Velocity Constant with Agitation 61 10. Percentage Error for Reaction Rate Equation 62 11. Oxygen Utilization for Processed Residua 66 12. Unaccovintable Oxygen Losses to 200 °F. Ring and Ball Product Consistencies 68 13. Fune Oil Reaction Products to 200 ^. Ring and Ball Product Consistencies 7^ 1^.. Comparison of Experimental Batch and Continuous Data 76 15. Operating Conditions for All Asphalt Blowing Runs . . 95 16. Experimental Data 98 17. Air Feed Rotameter Calibration Data 103 18. Converter Gas Rotameter Calibration Data 10^. 19. Oxygen Feed Rotameter Calibration Data 105 20. Gas Analysis Rotameter Calibration Data 105 vil -

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I. INTRODUCTION In 1951 13,000,000 short tona of petroleum asphalt were oroduced in the United States at a value of 216 million dolDars (19). Of this total 70 per cent was used for paving, 24 per cent for roofing and waterproofing and 6 per cent for specialty products as rubber, molding compounds and paints. These materials are processed by a variety of methods, one of the most important of which is by subjecting a residual stock to air at elevated temperatures. The processing of asphaltlc residua obtained from the distillation of petroleum oils with oxygen containing gases at elevated temperatures is known as air blowing and has been practiced commercially for over sixty years (7). According to the present practice the asphalt residuum Is blown at about 450 to 575 °F. at a rate of 30 to 50 cubic feet of air per minute, per ton of asphalt, for a period of 5 to 12 hours in a suitable reactor vessel (l). Air blowing the residuum is carried out in either a batch or continuous operation. In a batch operation the asphalt Is contacted with air by either blowing or sucking the air through the asphalt charge. In continuous blowing the stock is moved through one or more vessels in series each having a reaction zone. The finished asphalt is removed continuously and part of it can be recycled with fresh feed. The asphalt is reacted until the desired product consistency is obtained. Asphalts as a class are non-aqueous colloidal systems of very high viscosity, which may have the character of either a sol or gel. 1 -

PAGE 10

2 They consist principal] y of hydrocarbons and hydrocarbon derivatives and may contain groups of saturated aliphatlcs, naphthenics or cycle— paraffins, aliphatlcs with oleflnlc double bonds and aromatlcs (16). Exact knowledge of the chemical composition of asphalts is not known but there has been recognition of distinct constituent groups as asphaltous acids and anhydrides, asphaltenes, asphaltlc resins, petroleum resins, petroleum oils, carbenes, carbolds and Inorganic material. The resulting reaction of oxygen with asphalt residuiim is generally called an oxidation process. Actually this term oxidation Is a misnomer, because the reaction has been characterized as essentially: (a) the removal of a small amount of hydrogen to form water followed by condensation and polymerization of the hydrocarbons (13), (b) the addition of oxygen which forms xinstable compounds from which water is eliminated leaving unsaturated compounds which polymerize (18), or (c) slow polymerization of the oils and resins to asphaltenes (9). Air blowing of asphalts changes the physical properties of the residuum which results in increased hardness, gravity, softening point and lower dvictillty. The extent of these changes depend on the original asphalt and the processing and condltlona to which it is subjected. The chemical and polymerization reactions which cause these effects are very complex and very little is known about the mechanism, stoichiometry or kinetics of the reaction. It is known that the air blowing process is an exothermic reaction (6) and that among the water and carbon dioxide that are eliminated are also oxygenated hydrocarbons, oil vapor and

PAGE 11

3 mechanically entrained oil. In the work reported by Thurston and Knowles (18) on one asphalt, 68 per cent of the weight of the oxygen that was used reacted to form water and lA per cent formed carbon dioxide. The remaining unaccounted for oxygen apparently formed other oxygenated compounds, Katz (13) found that oxygen and nitrogen are present in the products in very small amounts at Ring and Ball softening points up to 200 *^. and only to an extent of approximately 2 per cent In very high melting samples. Similar results (9) were also obtained for a different residuum where the oxygen content and the change in quantities of oils, resins and asphaltenes were determined for the air blowing process. The literature on the air blowing of asphalt is very limited outside of the references given by Abraham (l) on patents. A series of articles by Holland (11) and more recently a staff article by Hoiberg (10) constitute about the only detailed discussions on the asphalt blowing process from a manufacturer's view point. Blakely, et al . (5) have reported the effect of agitation on air blowing Venezuelan and Mexican asphalts on a pilot plant scale. Because of the complex nature of the reactants and reaction mechanism for the air blowing process, the degree of reaction is generally described by some physical property of the residutm. The rate of change of this property in turn is a function of several process variables as the type of asphalt residuum, volume of the reactor, feed gas flow rate, temperature, degree of agitation and oxygen content in the feed gas. There is no suitable pilot plant or laboratory data presently available to correlate and relate the preceedlng process variables for design

PAGE 12

4 considerations of commercial asphalt blowing units. Therefore, it is the object of this investigation to present principles that may serve as the basis for design and operation of commercial asphalt blowing equipment. These principles include: (a) kinetic equations and evaluation of reaction rate constants, (b) reaction mechanism including kinetic order and oxygen utilization, (c) scale up procedures from pilot plant equipment to industrial processing equipment.

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II . THEORY A. The Asphalt Blowing Reaction The gross chemical reaction for the asphalt blowing process might be described as follows: Aj. f O2 + inerts > A^^ * ^c "*" ^^2 ^ ^2^ • "^2 ^ inerts AH where Aj. = the asphalt charge stock Aqx the composite air blown asphalt product not removed from the reacting zone Lt( = the composite condensed product removed overhead minus CO2, H2O and other fixed gases AH = the heat of reaction To arrive at this gross reaction, the actual mechanism could consist of a series of progressive reactions described in the following diagram: Ar + 02-*A + 02-^A * °2— "V * ^^°2 •»• ^HaO + ... v \ \ ^Ll ^L2 ^h^^ Each step of this progressive reaction probably yields oxygenated compounds of unknown and complex composition, some of which remain in the blown asphalt and some appear as overhead products as designated by L. The residual material is dehydrogenated and decarbonized as shown by the appearance of H2O and CO2. Polymerization also occurs to produce a product with an increase in viscosity as evidenced by the increase in Ring and Ball softening point. No information is available on the exact chemical reactions occuring either as the above gross reaction

PAGE 14

6 or as the orogresalve reaction. It Is necessary, therefore, to study the degree of chemical reaction in terms of a change in a physical property of the system as suggested by Froat and Pearson (8). For this study the physical property is determined is the Ring and Ball softening point by the A. S. T. M. method D 36-26 (^).to evaluate the gross reaction from A_ to A^^ . B. Heterogeneous Reactions Oas-liquid reactions may be typified as a gas-absorption operation in which a chemical reaction occurs. The actua] reaction may occur at the interface separating the gas and liquid phase or in either the gas or liquid films adjacent to the interface. In either case, a problem of mass transfer of reacting materials from one phase to another phase or to the interface is involved. The net rate of reaction is then determined by the rate of chemical reaction itself and by the rates of mass transfer of reacting materials (12). Rates of gas absorption accompanied by chemical reaction in the liquid have been calculated kinetlcally for certain simple cases, for example, the absorption of carbon dioxide with ethanolamine. No estimates have been made for cases involving second order chemical kinetics. The differential equations involving transient accumulations, diffusions and reaction are known, but the mathematical solutions are too involved for practical solutions. Perry and Plgford (15) used a digital computer to calculate the solutions of a number of theoretical second order cases. The results were represented as the ratio of the local mass transfer

PAGE 15

7 coefficient with reaction to the mass transfer without reaction. These results were found to Apend on the rate and chemical equilibrium constants, the ratio of reactants and the time exposTire of the liquid surface. Sherwood and Pigford (17) present a more general treatment for the process of simultaneous absorption and chemical reaction. The process of blowing asphalt residuum can be classified as a heterogeneous and exothermic reaction of a liquid phase and a gas phase. It is a flow system where the active agent in the gaseous phase (oxygen) reacts with the liquid asphalt to form asohal^ products of increasing consistency. A consideration of the physical system in the asphalt blowing process leads to a concept of two possible controlling mechanisms or a combination of both. As the feed gas is ejcposed to the liqxiid asphalt, the chemical reaction may occur at the interface of the gas-liquid or in the gas or liquid films adjacent to the interface. If the chemical reaction takes place very rapidly at the gas-liquid interface, it then becomes necessary to replace the oxygen used from the film with fresh oxygen for the process to continue. This fresh oxygen must diffuse from inside a gas bubble, through the gas film to the Interface where the reaction is occurring. When this diffusion rate is slow compared to the chemical reaction rate, the diffusion resistance will control the gross rate of reaction. Conversely, if the chemical reaction rate at the Interface is slow relative to diffusion, then the chemical reaction is the controlling rate. The effect on the gross reaction rate for a combination of the diffusion and chemical reaction mechanism might be expressed as driving potential gross reaction rate = diffusion resistance + chemical resistance

PAGE 16

8 Considering the possible progressive type of reaction and physical system involved, it is conceivable that the diffusion resistance might control for some of the steps while the chemical resistance might control for other steps. The gross reaction rate is the degree of chemical reaction with time and is measured as the change of Ring and Ball softening point with reaction time. The driving potential for the gross reaction is assumed to be a combination diffusion and chemical reaction driving force. The driving force for the diffusion mechanism Is the difference of partial pressure of the oxygen in the gas bubble and at the gas-liquid Interface. The driving force for the chemical reaction is the concentration of reacting materials. Assuming the driving potential to be a combination of diffusion and chemical reaction, the resistance for the gross reaction rate will also be a function of these two mechanisms. A general rate equation might be derived to relate the processing variables in terras of a gross reaction rate. This equation is dR/dt kF^S^R^ (1) where dR/dt the gross reaction rate measured as Ring and Ball softening pol«t The diffusion driving force Is r S which Is the oxygen concentration and space gas velocity for the feed gas. The asphalt concentration terra Is related to the Instantaneous value of softening point, R, at any time, t. The value, k, Is a pseudo reaction velocity constant and Is a function of the gross reaction rate resistance. The value of k also Includes

PAGE 17

9 a factor that accounts for a decrease In driving potential as the reaction proceeds. The data for this Investigation was evaluated in terms of this proposed rate equation.

PAGE 18

III. MATERIALS The asphaltlc residues used In this Investigation were supplied through the courtesy of The Texas Company, The samples represent four different types of asphalts having substantially different properties. The properties of the residues used in this study are tabulated In Table 1. TABLE 1 PROPERTIES OF ASPHALTIC RESIDUES Sample

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IV. APPARATUS The asphalt blowing unit was designed and constructed to blow asphalt in either a continuous or a batch operation. The asphalt apparatus consists of an asphalt stor^ige tank, asphalt reactor, electrical precipitator, flow panel board, temperature panel board and a continuous gas analysis unit. A picture of the unit is shown in Figure 1 and a flow diagran in Figure 21. Complete piping and wiring diagrams are shown in Figures 22 and 23. A. Processing Equipment 1. Asphalt storage tank. The asphalt storage tank is a heated tank used to store and preheat the asphalt reactor feed. Circulation is maintained in the storage tank by pumping the asphalt through a closed piping system. The storage tank shell was fabricated from a piece of 12 inch steel pipe and fitted with ring flanges on both ends. A flanged dished bottom with a centered 3A inch outlet drain was bolted to the lower shell flange. A round 1/4. inch trans Ite cover was fastened to the top shall flange. The tank is heated with eight 500 watt electrical strip heaters bolted to the outside shell. They are alternated one long and one short. The dished bottom is heated with a 1,000 watt ring heater. The heaters are wired in parallel and connecl.ed to a three-heat snap switch. High heat position on the switch utilizes the long, short and botto« heaters. Mediim heat uses only the short and bottom heaters. Low heat turns on n -

PAGE 20

• 12 -

PAGE 21

-13only the bottom heater. The heaters were selected and arranged in this manner to permit changing the heated length of the storage tank as determined by the height of the liquid asphalt in the tank. A General Electric Thennostat is. used to control the temperature of the asphalt in the tank and directly controls the electrical line load to the heaters. Thermostat and thermocouple protection tubes were made from steel pipe amd welded in the side of the reactor shell. The tank was insulated on the side and bottom surfaces with block magnesia insulation and then covered with a sheet metal protective cover. The entire assembly was mounted on four angle iron legs. It was then placed on a Toledo platform scale. The scale is used to measure mass feed rates of the asphalt to the reactor. The hot asphalt in the storage tank is circulated and transferred to the asphalt reactor with a Viking pump. This is a positive displacement gear type pump which is mounted on the floor below and to the side of the asphalt storage tank. Asphalt is pumped from the storage tank with a free suspension suction pipe that is inserted into the storage tank through the transite cover and extends close to the bottom. The recirculation return pipe is also freely suspended and discharges asphalt near the top of the tank. An auxiliary three-heat immersion heater, thermostat control and thermocouple are placed in the recirculation line to indicate and prevent any appreciable temperature drop in the asphalt while it is being recirculated and adjusted to the reactor asphalt temperatiure. The recirculation piping is steam traced with I/4 inch copper tubing and the asphalt recirculation lines are preheated to prevent any asphalt freezeup during initial recirculation. Drain valves are suitably located to

PAGE 22

-ucorapletely drain the recirculation lines. A detail of the asphalt storage tank is shown in Figure 24.. 2. Asphalt reactor. The asphalt reactor is a heated and agitated tank which permits blowing reacting gas through the hot asphalt. It is possible to blow the asphalt as a batch operation with no fresh asphalt feed or as a continuous operation where fresh asphalt feed is pumped in and asphalt product continuously removed. The reacting asphalt occupies only 60 per cent of the total reactor volume. The remaining 4.0 per cent is used as a vapor space for entrainment separation. The asphalt reactor was made from a piece of 8 inch steel pip)e that was flanged on both top and bottom. The bottom is fitted with a dished plate with a 3/4 inch center drain pipe. The top 1/4 inch steel plate cover is used to support the agitator assembly, thermocouple protection tubes, asphalt feed line and entrainment baffle plate. The reactor has welded pipe fittings for the reactor gas feed, converter gas product and reacted asphalt product. The reactor is heated with five 500 watt strip heaters equally spaced and bolted to the outside surface of the reactor pipe. The lengths of the heaters were selected so that they would provide heat directly to the height of the reactor pipe that would be filled with liquid asphalt. This prevents localized heating in the vapor section and reduces the amount of coke formed on the reactor walls. The temperature of the reacting a'sphalt is controlled with a Minneapolis-Honeywell-Brown Fyr-0-Vane proportional temperature controller.

PAGE 23

15 The agitator assembly for the asphalt reactor is a laboratory model Turbo Mixer Agitator. The oombination used for this investigation was a hooded ring cover and aerator impeller. The hooded ring is supported from the top cover of the reactor by two guide rods. The impeller is located ^ inches froa the bottom of the reactor and is fastened to a shaft that extends through the top cover and packing gland into the agitator head and pulley assembly. The agitator pulley is a four step cone pulley and is matched with a similar pulley on the 3A horsepower 1750 r.FUB. agitator drive motor. This pulley arrangement permits variable agitator speeds with a V-belt drive. The minimum agitator speed is 700 r.p.m. and the next speed is 1300 r.p.m.. Thermocouple protection tubes were made from 1/8 inch steel pipe and were threaded into welded couplings on the top reactor cover plate. There are three thermocouple tubes; one for the MinneapolisHoneywell-Brown reactor temperature controller and two for the Bristol temperattire recorder. The lasttwo were fabricated with a differential height of 1 inch so that they could be used to indicate asphalt liquid level in the reactor. The long thermocouple indicates the liquid temperature while the short thermocouple indicates the vapor temperature. Since the gas temperature is several degrees lower than the liquid temperature, a differential reading between the two thermocouples indicates that the liquid level is between these two thermocouple positions. The asphalt feed line extends through the top of the reactor cover and through the edge of the agitator hood ring. The feed line was reduced to \/U inch nominal pipe inside the reactor to prevent any excessive

PAGE 24

16 asphalt feed holdup. The bottom of the asphalt feed line is flush with the bottom of the agitator hood ring. Thus the asphalt is fed directly into the side of the rotating aerator impeller, A needle valve on the asphalt storage recirculation line controls the asphalt feed to the reactor and a thermocouple measures the asphalt feed temperature. Reactor feed gas is introduced beneath and into the aerator impeller through a T-tube sparger. The feed gas line comes into the reactor in a 3/8 inch pip>e directly above the bottom reactor flange. This pipe extends into the reactor and then branches into a horizontal "T" directly under the impeller. Two 1/8 inch vertical pipe tips are located on the end of this "T" at a distance of 1/2 the radius of the aerator impeller. The feed gas line to the reactor is piped as an inverted "U" stand pipe to prevent any asphalt from flowing through the distributor tips back into the air feed line. The reacted gas or converter gas is removed from the reactor through a 1-1/2 inch pipe located directly beneath the top reactor flange. The exit gases from the reactor first pass over an entrainment separator baffle plate that is fitted below the converter gas outlet. This baffle plate prevents swirling of the hot asphalt by agitation into the converter gas outlet pipe. The baffle plate is fastened to the bottom side of the top reactor cover. After leaving the reactor, the converter gases pass throxigh a short heat exchanger before entering the electrical orecipitator. This heat exchanger or cooler is used to help break any foam that may form in the reactor and flow up into the converter gas discharge pipe. The cooler is a 3 inch steel pipe that is welded around the 1-1/2 inch converter gas

PAGE 25

17 outlet pipe. The annular area between the pip)es is fitted with l/2 inch pipe fittings for inlet and outlet cooling water. A thermocouple at the top of the converter gas cooler measures the exit reactor converter gas temperattire . During a batch or continuous run the reactor asphalt product or asphalt samples are removed from the reactor through the 3/8 inch pipe reactor side drain. This drain is located beneath the converter gas outlet line and has a quick-opening valve. The reactor shell is insulated with asbestos insulatlcn and enclosed in a protective sheet metal cover. The top and bottom of the reactor are not insvilated. These surfaces were purposely left uncovered so that the exothermic heat of reaction of the reacting asphalts would be dissipated. Closer temperature control can be obtained when this heat is dissipated and the temperature controller and reactor heaters are used to maintain the desired temperature. The reactor and agitator drive motor are arranged on a special stand. The length of the asphalt piping from the asphalt storage tank is as short as possible to reduce the amount of asphalt in the recirculation lines. Details of the asphalt reactor are shown in Figure 25. 3. Electrical precipitator. The piu-pose of the electrical or Cottrell electrostatic precipitator is to remove the mechanically entrained mist and smoke from the reactor converter gases. The precipitator unit was fabricated from a piece of 3 inch steel pipe and welded to inlet and outlet gas chambers. A round 1/8 inch steel rod is used as a high voltage electrode with a steel ball welded

PAGE 26

13 to the bottom of the electrode. The entire assembly Is supported by a high voltage insulator bushing and the insulator bushing is mounted on a \/U inch Bakelite plate which serves as the top pf the outlet gas chamber. A baffle plate is placed over the inlet feed gas line in the bottom gas chamber to prevent the gas from impinging directly on the high voltage electrode. A drain on the bottom gas chamber permits removal of the condensed and precipitated smoke and fog products. Access panels on the front of the gas chambers are provided to allow alignment of the high voltage electrode and cleaning of the precipitator. The panels are covered with Luclte plastic windows and it la possible to observe the smoke content of the converter gas entering and leaving the precipitator. The precipitator pipe shell is wrapped with \/U inch copper tubing on a 2 inch coil spacing. Cooling water passes through the tubing. As a result water condenses out of the converter gas as it cools in the precipitator. The condensed water is collected through the bottom drain together with the precipitated oils. The cooled converter gases from the precipitator pass through another heat exchanger to lower the temperature of the gases below room temperatvire and to prevent any condensation from occurring in the gas rotameters. The electrical precipitator aftercooler is a coll of \/k inch copper tubing placed inside a piece of 3 inch steel pip© 12 inches in length. The converter gases pass across the water cooled copper coil and the condensed water is removed from a bottom drain on the cooler. Both the electrical precipitator and after-cooler are insulated with air eel] asbestos pipe insulation. The laboratory model high tension rectifier used to obtain the

PAGE 27

19 high voltages necessary for the electrical precipitator is a Carpco Engineering Company Model RL High Voltage Rectifier. This rectifier unit permits variable direct current output voltages from to 4.0,000 volts. The current output is variable from 0.1 to 15.0 milliamperes. Flgxire 26 is a detail of the electrical precipitator and Figure 2 is a pictvure of the storage tank, reactor and electrical precipitator. U» Flow panel board. All the instruments necessary to control and meter the gas flows in the asphalt blowing process are grouped together on the gas flow panel board. Thr«e rotameters measure the air feed, oxygen feed and converter gas flow rates. The air feed and converter gas rotameters are standard Schutte and Koerting 3F tubes with milllBeter scales. The rotameters are calibrated with specially made aluminvun floats for the gas flow rates required in this study. The oxygen feed rotameter is a standard Schutte and Koerting IR tube and stainless steel float. Gas flow control for the metered feed gases is obtained by using bronze needle valves. Gas pressures in the asphalt reacting system are measured by using panel mounted, well type manometers. The feed gas manometers measure the pressure drop across the gas rotameters. These indicated pressures are also the reactor gas pressures. The feed gas manometer indicates the pressure of the reactor feed gas; the converter gas manometer measures the pressia^e of the gas in the reactor vapor space or back pressure in the reactor. For constant feed gas flow rates the feed gas pressure changes with any change in the reactor asphalt liquid level height. Therefore, during continuous operation this feed gas manometer is used to control the asphalt nroduct rate and to

PAGE 28

20 >J.'>'R4^

PAGE 29

21 maintain a constant asphalt reactor liquid level height. The converter gas back pressiore is controlled by the depth of immersion; of the converter gas stand pipe in a tank of water, A slight back pressxire is required to allow for pressure drop of the sample gas through the gas analysis unit. The magnitude of this back pressure is about 5 inches of water. The back pressure regulator that is used is a small tank mounted on tripod legs and provided with an overflow line to a drain, A constant water liquid level is maintained in the tank by running the cooling water tiaed in the copper coll heat exchangers into the back pressure tank and letting the water drain out through the overflow pipe. To prevent excessive bubbling In the back pressure tank for high converter gas rates a by-pass needle valve is piped into the exit converter gas line so that only a small portion of the converter gas passes through the dip leg. The inlet air feed line Is fitted with a pressure reducing valve and sediment separator. The air then passes through a Tel-Tale silica gel dryer before it is metered to the reactor. The dryer column is a piece of 3 inch by 36 inch Pyrex glass pipe. The entire assembly of rotameters, manometers, control valves and dryers are mounted on a movable panel board, A picture of the panel board is shown in Figure 3. 5. Temperature panel board. The asphalt blowing temperature recorder and temperature controller are located on the temperature panel board. Chromel-alumel thermocouples are used to measure all process stream temperatures in the asphalt blowing system. The thermocouples

PAGE 30

22 -

PAGE 31

23 are mounted in protection tubes and these units are incorporated in the process piping. Temperatures are recorded with a Bristol Dynamaster 12 point Pyrometer using 10 points as indicated on the diagram in Figure 22. The temperature controller that is used for the asphalt reactor is a Minneapolis-Koneywell-Broim Pulse Pyr-O-Vane Controller. This is a time-proportioning-indicating type controller that eliminates any temperature cycling or "hunting" effects. The wiring on the temperature controller is such that the controlled output goes through both 110 volt and 220 volt outlets. The 220 volt outlet is used in this Investigation to control the reactor heaters. Two other outlets for continuous 110 and 220 volts are also provided on the panel board. The temperature recorder, controller, outlets and circuit breakers are mounted on a movable panel similar to the gas flow panel board. A picture of the temperature panel board is shown in Figure 1. 6, Piping. The majority of the equipwent piping is 1/2 inch steel pipe. Larger 3/4 Inch pipe is used for the converter gas lines, the asphalt drains on the asphalt storage tank and the asphalt reactor. Gas cock valves are used for the asphalt piping while glot-e and needle valves are used for the asphalt blowing gas piping. All hot asphalt lines are insulated with air cell asbestos Insulation, A piping diagram is shown in Figure 22.

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B. Analysis Equipment 1. Gas analysis unit. The gas analysis unit provides a continuous voltune analysis of oxygen and carbon dioxide of either the asphalt blowing feed gas or converter gas. Dew points of these gases may also be determined. The analysis cells for the gas train are as follows: (a) Beckman Oxygen Analyzer Model C, 0-100 per cent Oxygen; (b) Gow-Mac Thermal Conductivity Cell for Carbon Dioxide; (c) Pittsburgh Electrodryer Dew Point Apparatus. The Beclcnan analyzer gives volume percentage oxygen as a direct reading while the output of the thermal conductivity cell is measured in rallllvolts. In the gas analysis train the continuous gas sample for the oxygen and carbon dioxide analysis cells is first dried by passing the gas through a tube of Tel-Tale silica gel. Then the total flow rate is measured with a rotameter. The sample gas is now divided into two streaas and the flow rate for each stream is determined with two additional rotameters. One gas stream is for the oxygen analyzer and the other stream is for the carbon dioxide analysis cell. Constant gas flow rates are maintained to the analysis cells to prevent the introduction of an analysis error because of the effect of a change in gas velocity in the analysis cells. The feed gas line and converter gas line have separate sample lines and dryer tubes. After the sample gas passes through the dryer tube it flows into a common header and then to the rotameter measuring the total gas flow. With the two sample lines it is possible to select either the feed gas or the converter gas for analysis. Only one gas can be analyzed at any particular time.

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25 A constant 6 volt direct current soiurce for the thermal conductivity cell Is provided with a small Mallory power supply. The thermal conductivity cell output is raeastired with a Weston direct current millivoltmeter. The Electrodryer dew point apparatus is a rectangular metal box fitted with a removable polished hollow cylinder cup which screws into the top of the box, A window in the front of the box Is used for observing the surface of the cylinder. The hollow cylinder is filled with a liquid so that the temperature of the cylinder may be lowered by cooling the liquid. The dew point of a sample gas is obtained by impinging the gas on the liquid cooled cylinder and recording the liquid temperature at the first appearance of fog or mist on the polished surface of the cylinder. The hollow cylinder may be cooled with a mixture of acetone and dry ice for extremely low dew points or water and ice for higher dew points. Dew point temperatures are measured with an alcohol theriDometer and dew points can be made on either the asphalt feed gas or the converter gas. A flow diagram and pictvire of the analysis unit may be seen in Figures 21 and 3. 2. Gas analysis calibration. The thermal conductivity cell and oxygen analyzer are calibrated for a ternary system of dry gases; oxygen, nitrogen and carbon dioxide. The range of the calibration is 0-4.0 per cent carbon dioxide in a residual gas of nitrogen and oxygen, 0-100 per cent oxygen. The instruments were calibrated by measuring the theraal conductivity cell output and reading the Beckman oxygen analyzer for known mixtures of the ternary gas system. The individual gases were metered froa

PAGE 34

26 gas cylinders using a pressure reducing valve and rotameter for each gas strean. After the flow rate for each gas stream was determined, the Individual gases were mixed together to form the gas sample for the instrument calibration. The analysis of this sample gas was determined with the use of an Orsat analyzer that determines the concentration of carbon dioxide. The concentration of oxygen was determined through the use of the Beckraan oxygen analyzer and the concentration of nitrogen was calculated by subtracting the oxygen and carbon dioxide concentration from 100, The sample gas flow rates for the analysis instruments were maintained at about 900 cc. /minute for the thermal conductivity cell and 125 cc. /minute for the oxygen analyzer. Excess sample gas was exhausted to the atmosphere. The output of the thermal conductivity cell was measured as millivolts and the reference point for this unit was zero millivolts for dry air. Table 2 is a tabulation of the calibration data for the oxygen analyzer and thermal conductivity cell. Figure 4. Is a plot of the ternary calibration data as a function of thermal conductivity cell millivolt readings jind oxygen concentration with parameters of volume per cent carbon dioxide.

PAGE 35

27 TABLE 2 CALIBRATION DATA FOR GAS ANALYSIS INSTRUMENTS Run

PAGE 36

28 TABLE 2— Continued Run

PAGE 37

29 100 t (D oi >. C I" 40 -40 20 20 ^0 60 ThemiAl Conductivity Cell Output Millivolts 80 100 Figure A. Thermal Conductivity Cell Calibration Curve for Ternary System of Oxygen, Nitrogen and Carbon Dioxide

PAGE 38

V. PROCEDURES The following is an outline of the conditions and procedures that are used to operate the asphalt blowing equipment. The method is applicable to either continuous or batch operation, with the exception that during the continuous operation a constant asphalt feed is fed to the reactor and a product is continuously removed. The five variables under consideration in this investigation are temperature, feed gas space velocity, feed gas oxygen concentration, agitator speed and continuous or batch operation. The effect of these variables were determined by making runs at essentially atmospheric pressure ^nd fixing all but one variable. A total of 39 runs was made under the following conditions to determine the overall effect of the variables on each other. The extent to which the conditions were changed for any of the materials under consideration is shown in Table 3. • TABLE 3 ASPHALT PROCESSING CONDITIONS Material

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31 A. Operating Procedure The operating procedure for the asphalt blowing apparatus is composed of the following steps: (a) heating a charge of asphalt in the reactor, (b) blowing with a feed gas, (c) measuring the gas flow rates, (d) recording the gas analysis, (e) taking asphalt product samples. The first step in the start of the aschalt blowing unit is to heat a charge of residuum to a temperature of ^75-500 °F. in the asphalt storage tank. To charge the storage tank, the asphalt suction and recirculation return lines are removed and the transite cover taken off. After the storage tank is charged with asphalt, the cover and pipes are replaced and the asphalt storage heaters turned on by turning the threeheat switch to the high position. While the asphalt charge is being warmed in the tank, the asphalt circulation line is preheated by turning on the steam to the copper tubing trace line. When the temperature of the asphalt in the storage tank has reached 225-250 °F., it may be recirculated with the pump to provide some degree of agitation in the storage tank. The recirculation procedure is to open the asphalt suction line valve, close the recirculation line bottom drain valve, close the reactor feed valve, open the recirculation valve to the asphalt storage tank, close the vent valve above the asphalt suction line valve, and turn on the oump. The pump Is a gear type pump and there is a sufficient residuum seal so that it will pull a smaJl vacuum on the asphalt suction line until the asphalt now is started from the storage tank. Once the recirculation asphalt flow is started, the steam may be turned off to the steam trace line and the auxiliary heater in the recirculation line turned on. This heater

PAGE 40

32 must not be turned on unless there is a flow of asphalt in the recirculation line. Heating and recirculation of the asphalt is continued iintil the tempera tiire of the asphalt is (4.75-500 HP, A charge of asphalt i« transferred to the reactor by first closing the reactor drain valves, closing the air feed valve, reading a gross weight on the Toledo scales, and then pumping the asphalt to the reactor by opening the reactor feed valve and closing the recirculation valve to the storage tank. The last few pounds of asphalt charged to the reactor may be controlled with more precision by opening the recirculation valve to the storage tank and throttling the asphalt reactor feed valve. When the desired charge has been transferred to the reactor, the reactor feed valve is closed and a final reading as net weight is taken from the Toledo scales. The difference in the weight readings of the scale is the mass of asphalt charged to the reactor. If a continuous run is made, the asphalt in the storage tank is continually recirculated at the desired reactor temperature. If a batch run is made, the recirculation is discontinued and the asphalt lines drained. The lines are drained by turning off the recirculation heater, opening the vent valve, allowing the pump to mn several minutes, opening the recirculation line bottom drain valve and shutting off the piimp. An asphalt feed run sample may be taken from the draining residutm. Immediately after the charge of asphalt has been pumped to the reactor the reactor temperatxire controller and agitator are tiumed on. The reactor is continuously heated and agitated until the desired operating temperature is obtained. To pre-cool the condensers cooling water may be circulated through the reactor cooler, electrical precipitator coil

PAGE 41

33 and water condenser. While the reactor asphalt charge is being heated, the analysis Instruments are turned on and the calibration point checked with dry air. The instruments are calibrated for a specified flow rate of gas: the oxygen analyzer flow rate is 125 cc. per minute and the thermal conductivity eel] flow rate is 800-900 cc. per minute. The zero point for the oxygen analyzer la a 21 per cent oxygen scale reading for dry air. The zero point for the thermal conductivity cell is a zero millivolt reading on the Weston Mlllivoltmeter for dry air. The electrical input to the thermal conductivity cell is always maintained at 6 volts d. c. and 138 milllaoperes using a Mallory power supply. The thermal conductivity cell zero adjustment and current control are located on the panel mounted remote control unit. The knob marked "C" is for current adjustment and the one marked "A" is for millivoltmeter indicator adjustment. The instruments are permitted to operate with a continuous dry air sample until a constant zero reading is obtained on the thermal conductivity cell and the oxygen analyzer is up to operating temperature. Care should be taken when opening the rotameter feed valve on the panel board for the air gas sample, because the air feed valve to the reactor is closed and the feed gas manometer can be blown readily with a sudden surge of air. When the gas analysis instruments have been zeroed and the t emperature of the reactor charge is Tip to the conditions desired, the actual blowing operation may be started. The valving on the panel board is checked to insure the flow of two separate gas streams and also to eliminate the possibility of any closed valves. The power source for the electrostatic precipitator is tumod on and the voltages adjusted to 29,000-31,000 volts

PAGE 42

3^ d, c. The gas feed valve to the reactor is then opened and the flow rate of feed gas to the reactor is started and adjusted to the desired rate at the flow panel board. For a batch operation the time that the gas flow is started to the reactor is considered zero time for the run. The drain valves on the precipitator and water condenser are closed and the valving is changed on the gas analysis unit so that a continuous sample of converter gas may be taken. Gas flow rates are continuously checked and adjusted to maintain the desired flow rate. The needle valve on the converter gas discharge back pressure line is adjusted to give a slight gas flow through the back pressure dip tube. This back pressure of 5 to 6 inches of water provides a driving force for the gas sample to the gas analysis unit. At frequent intervals flow rate, gas analysis and instrvmient readings are recorded. For some of these readings asphalt reactor samples and precipitator samples are taken. The reactor asphalt samples are taken from the side drain allowing a small flush to flow from the reactor (2-3 ounces) to remove the previous product. The weight of sample and flush is recorded so that a material balance can be obtained and the residence weight of asphalt in the reactor at the sample time can be calculated. Precipitator and water samples are taken by closing the top drain valves and opening the bottom valves. The sample is in the stand pifje between the valves. Two valves are provided so that it is possible to take the samples without lowering the pressure in the reactor. Often the volume of the sample collected is larger than the volume of the standpipe, and it will be necessary to repeat the sampling procedure until the complete sample is obtained. To obtain an exact sample at a specified

PAGE 43

35 ' time, this procedure is followed prior to the sample time so that when the top valve is closed at the sample time no part of the sample is omitted. The run is continued in this manner until the asphalt charge in the reactor is at the iesired consistency. For batch runs the final product consistency is aporoxlraately 200 °F. Ring and Ball. This point must be estimated from the consistency of the reactor asphalt samples. Often when the asphalt in the reactor is approaching 200 °• . Ring and Ball the side asphalt sample line plugs with the hard asphalt. In this case the asphalt samples may either be taken from the bottom reactor drain valve or by heating the side reactor valve with a small gas torch and melting the solidified asphalt. When the asphalt is at or above 200 °P. Ring and Ball, final readings and samples are taken and the re-ictor contents drained into a previously tared 5 gallon steel bucket. The agitator and the reactor temperature controller are turned off. The reactor feed gas is allowed to flow for a few minutes to clear the air feed line of any asphalt. The reactor feed gas is shut off and the power source to the electrical precipitator is also turned off. The feed gas valve to the reactor is closed and clean air is again turned on to the analysis instruments to sweep them of any resldioal converter gas and also to check the calibration zero point. The analysis instruments and air flow are turned off and the asphalt drain bucket weighed to obtain the final weight of asphalt for a material balance. This ends the operating part of a batch run. The conditions and orocedure for making a continuous run are similar to a batch run. In effect they are a coir.bination of both a batch and continuous operation. The reactor is charged, heated and blown as a batch

PAGE 44

36operation to a predetermined Ring and Ball consistency as estimated from an analysis of a previous batch rxin. 7/hen the desired consistency is obtained, the reactor charge is blown as a continuous operation by simultaneously Introducing fresh asphalt feed and removing asphalt product at a similar, constant rate. The feed rates are determined by the equivalent residence time that the fresh asphalt must remain in the reactor to be blown to the desired Ring and Ball consistency. The continuous run is continued in this manner until a constant converter gas analysis is obtained for fixed gas flow rates and asphalt feed rates. The continuous run may then be discontinued and the reactor charge again blown as a batch operation to a new asphalt product consistency. A continuous run may be repeated again with decreased asphalt feed flow rates. The ran is terminated in the same manner as a batch run. During continuous or batch runs an indication of the asphalt liquid level in the reactor may be obtained by observing the manometer pressure reading for the inlet reactor feed gas. This is particularly useful for continuous runs when the asphalt feed and product flow rates are being adjusted. Best results are obtained for controlling a continuous asphalt feed to the reactor when the feed valve to the reactor is opened slightly and the recirculation valve to the storage tank carefully throttled, A great deal of caution must be used to prevent closing the recirculation line valve, because the displacement pump would be damaged. For fortified oxygen inins additional amounts of pure oxygen is metered into the asphalt reactor gas to Increase the oxygen feed gas concentration. A pressure reducing valve on the oxygen cylinder reduces the

PAGE 45

37 pressure to a low value and the flow rate of the gas is then metered with the oxygen rotameter. The composition of the feed gas is checked several times during a run by closing the converter gas sample line and opening the feed gas sample line to the analysis unit. The composition of the feed gas is indicated when consistent readings are obtained from the analysis unit. As a run progresses the mass of the asohalt charge in the reactor decreases due to losses by blowing and from sampling. To maintain a constant gas to asphalt ratio for the particular run conditions, the reactor feed gas flow rate Is continuously adjusted for the estimated asphalt mass in the reactor. Dew points of the converter gas are obtained with the dew point apparatus at the gas analysis unit during batch nans and at the panel board converter rotameter during continuous runs. The converter rotameter is used to prevent any change in reactor gas pressure during a continuous run. A drop in the reactor gas pressure generally results in an increased asphalt feed flow rate. The double valve sampling device on the electrical precipitator and water condenser was developed to eliminate this pressure drop while sampling. All equipment drain valves are left open when the equipment is not in operation. B. Analytical Procedure^ In this study the extent of reaction in the asphalt reactor charge was detennined by the converter gas analysis and the change in physical properties of the asphalt product. The asphalt properties that were measured were softening point and oenetration while the volume per cent oxygen, carbon dioxide and water were determined for the converter gas. The electrical

PAGE 46

38 precipitator and water condenser products were separated into an oil and aqueous sample. Acid numbers were determined for these fractions. The softening point of the asphalt product and feed samples were run by the A. S. T. M. Ring and Ball method, designation D 36-26 (U) . The standard method was followed and a quadruple holder unit was used to permit attachment of four brass rings. A water bath was used for materials having softening points below 176 °F. and a glycerin bath for the higher softening point asphalts. A small air agitator was used to provide agitation when using the more viscous glycerin. The values of Ring and Ball are reported as temperature degrees Fahrenheit. Asphalt penetration values were measured with a standard penetration apparatus and needle according to the A. S. T. M. procedure designation D 5-25 (3). The load time and temperature for the penetration tests were 100 gm., 5 seconds and 77 °F. (25 °C.) respectively. The oil and water mixtures from the electrical precipitator and condenser were separated into two samples, one aqueous and one oil, by centrifuglng and decantatlon. The volume of each water sample was measured and likewise the weight of the oil sample was determined. The acid numbers for the electrical precipitator and condenser products were evalixated for the purpose of completing an oxygen material balance for the asphalt blowing products. The aqueous fraction of the sample was titrated with O.IN soditun hydroxide using phenolphthalein for an end point indicator. The acid number for the oil fraction of the sample was obtained by a color indicator titration following the A. S. T. M. procedure D 663-4.6T (2). A standard O.IN sodium hjrdroxide solution was used instead of the suggested potassium hydroxide solution.

PAGE 47

39 The gas composition of the converter gases was measured with the gas analysis unit instruments. The Beckraan oxygen analyzer gave a direct, continuous reading in volume per cent oxygen. The thermal conductivity cell ternary calibration plot was used to obtain the carbon dioxide content in the converter gases. The conductivity cell millivolt output and the oxygen analysis were the only parameters required to estimate directly the precentage of carbon dioxide gas. The partial pressure of water vapor in the exit converter gas was determined from the dew point analysis. The volume per cent of water in the converter gas is equal to the partial pressure of the water divided by the total pressure. The total pressure was assumed to be equal to one atmosphere at all times. Since the oxygen and carbon dioxide analysis was made using a dried converter gas, it was necessary to correct the indicated analysis of those gases for the effect of water vapor. As the concentration of carbon dioxide in the converter gas was very small, no corrections were made for the oxygen analyzer analysis. Orsat analyses for percentage oxygen and carbon dioxide in the converter gas were measured at intervals to check the operation of the gas analysis unit. The Orsat gas analyzer was used to obtain the original thermal conductivity cell calibration and ternary plot for gaseous mixtures of oxygen, nitrogen and carbon dioxide.

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VI. CALCULATIONS The experimental data for the batch and continuous iruns were analyzed for; (a) kinetics, development of rate equations and evaluation of reaction rate constants: (b) reaction mechanism, kinetic order, oxygen balance and utilization, and reaction products; (c) scale up, comparison of batch and continuous data and practical application, A tabulation of the calculated results for all experimental runs is included in the Appendix. A. Kinetics The general rate equation for the reaction rate of the processed asphalts was assiraed to be related to various physical process variables in the form of the expression dR/dt kP^S^n'^ (1) wher« dR/dt * rate of change of softening point or gross asphalt blowing reaction rate R ~ asphalt Ring and Ball softening point, °F. S = process gas space velocity, (ft.)/(min. ) (ton asphalt> at (70 °F., 1 atra.) P original process gas oxygen concentration, vol. % t • process reaction time, hours p, s, r = exponents on the process variables k = pseudo reaction velocity constant This form of the rate equation suggests that the rate of reaction is a function of the space gas velocity and the feed gas oxygen concentration. Temperature is another variable but is included in the pseudo ^0 -

PAGE 49

a ' reaction velocity constant, k. The values of the exponents, p, r, and 3, indicate the reaction oirder for the process variables. The degree of variation of the pseudo reaction velocity constant, k, with temperature will indicate certain conclusions regarding the rate controlling mechanism. The resulting equation with all constants evaluated, can be used for scale up and design considerations for larger commercial processing units. The exponents and constants in the general rate equation may be evaluated by putting the equation in the logarithmic form as ln(dR/dt) In(kP^sV) (2) or ln(dR/dt) In(kpV) + rlnR (3) If the logarithm of the reaction rate (dR/dt) is plotted on the ordinate against the logarithm of asphalt consistency (R) on the abscissa, and the plot results in a straight line, the slope of the line is the exponent, r, and the intercept is ln(kP^S ). Each batch run may be plotted as a line to give a measured value of slope and an intercept value at InR " 0. For this general treatment of the data to be of any value, the value of the slope for all runs must be the same. However, the intercept values will not be constant because the intercept is a function of k, S and P. The values of the remaining exponents p, s, and constant, k, may be obtained from the intercept data as I^ In(kpPs') U)

PAGE 50

42 and I^ = In(kP^) + sins (5) where I intercept of ln(dR/dt) versus InR plot at InR = The intercept, I^, is now plotted as the ordinate value and InS on the abscissa. The resulting curves should be plotted as straight lines with parameters of oxygen concentration. The slopes of this plot should again be constant and will be the value of the exponent, s. The intercept will be equal to the ln(k,P^) at the value of InS 0. The intercept equation from this second logarithm plot may now be written as lb In(kpP) (6) or I^ Ink + plnP (7) where I^ = intercept of the I^ versus InS plot at InS 0. The intercept values for this equation are again plotted on the ordinate against abscissa values of InP. The resulting curve for this plot should be a straight line with a slope value of p and an intercept Value of Ink at InP 0. The value of k is then Ic Ink (8) k = e^c (9)

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' U3 where I(, Intercept of the I^ versus InP plot at InP » 0. e = base of natural logarithms The pseudo reaction velocity constant, k, will be a specific value for any given temperature. In the preceding analysis only the data at one given temperature are evaluated together to derive the desired values of exponents and constants. This procedure is repeated for treatment of data at different temperatures. The resulting values of the exponents^ p, r, and s, should be constant and independent of the temperature if a general reaction rate expression is to be developed. The on]y variable constant is k, the pseudo reaction velocity constant, which Is a function of the reaction temperature . B. Reaction Mechanism The reaction mechanism for the asphalt blowing reaction can be described by the order of the process variables in the general reaction rate equation, by the variation of the reaction velocity constant with temperature, and by the oxygen utilization and oxygen balance for the reacting asphalts. The order of reaction for the previously described rate eqtiatlon (Equation 1) is the sura of all the exponents, p, r, and s, on the process variables, P, R, and S. The order with respect to each variable is the value of the exponent for that variable. The exponents are usually simple positive Integers, but they may be fractional or even negative, depending upon the complexity of the reaction.

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u For a true chemical reaction rate the specific reaction rate constant, k', is a function of the processing temperature and is related to the temperature by the Arrhenius equation kAe-^/^^ (10) or where Ink' -E/RT + InA (U) k' specific reaction velocity constant E = the molal energy of activation A proportionality factor characteristic of the system and termed the frequency factor R » gas constant T = absolute temperature If the Ink' is linear with l/T the molal energy of activation can be evaluated by plotting the Ink' against reciprocal absolute temperature, l/T. It is usually found that this plot is nearly linear with a negative slope, and the value of the slope is equal to -E/R. High values of the activation energy, E, is typical of reactions where the chemical reaction step is the rate controlling mechanism. Low values of the activation energy, E, indicate a reaction where the rate of diffusion is the controlling mechanism. A pseudo molal energy of activation for the asphalt blowing process can be evaluated if k from Equation 9 is substituted for k in Equation 11. This pseudo energy of activation can be used to derive certain conclusions regarding the rate controlling mechanism. ^

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U5 ' Oxygen utilization for the asphalt blowing process is determined by the disappearance of gaseous oxygen from the process gas streams. An oxygen balance for the process Is an accounting and comparison of the oxygen in the feed gas against the oxygen in the reacted products. This balance includes the accounting of oxygen In the converter gas and precipitator products as oxygen (Og), carbon dioxide (CO2), water vapor (HjO ), water (HjO-^ ) and acids. The mass weight of oxygen Is calculated for specified time intervals by using an average gas concentration over the time Interval used. Cumulative oxygen results are used and reduced to a basis per one pound of asphalt reacted. The values for the oxygen balance for the gaseous products are calcxilated from the general equation (G)(C)(At)(f) • lbs. oxygen (l2) where G « gas flow rate, CFM, 70 OF., 1 atmosphere C « gas concentration, volume per cent At = time Interval, hours d gas density, lbs. /ft. f conversion factor, lbs. oxygen/lbs. gas Table 4. Is a listing of some of the gas properties that were used In this equation. The conversion factor, f, Is the equivalent weight of oxygen, O2, per unit weight of carbon dioxide, air and water.

PAGE 54

-^6TABLE A GAS PROPERTIES Gas

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47 The feed and converter gas flow rates were obtained from the gas rotameter data. Since the metered gas tempera tiires and pressures were essentially 70 °F. and 1 atmosphere, no rotameter correction factors were used. The amount of oxygen in the feed gases was very easily calculated from the rotameter data because the concentration of oxygen was either 21 per cent for air or 100 per cent for pure oxygen. The gas concentrations in the converter gas were those values that were recorded from the gas analysis unit and corrected from a dry basis to a wet gas basis by the following relationship Pp.(G02, Nj, O2) D (760Pp. H20g) (15) where D » concentration of gas on dry basis, volume per cent Pp. H2O partial pressure of the water vapor in the converter gas as determined from the dew point Pp. (CO2, N2, O2) • partial pressure of the converter gases on a wet gas basis The partial pressure of the various gases on a dry basis was calculated from the gas analysis data by the expression Pp. gas 760D (16) The gas concentration, C, is determined from the partial pressure of the converter gas on a wet basis by the relation G Pp.(C02, N2, 02)/760 (17) A constant pressure of 1 atmosphere or 760 mm. Hg. was assumed for all calculations. For the feed gas oxygen balance the weight of oxygen as O2 and equivalent weight of O2 as air was added for each time

PAGE 56

A8 interval to give the total pounds of oxygen feed. For the converter gas oxygen balance the weight of oxygen a s O2 and the equivalent weights of O2 as CO2, HpO and aciis were added for each time interval to give the pounds of oxygen in the converter gas. The amount of oxygen used or the oxygen utilization was the difference between the oxygen In the feed gas and the oxygen as pure O2 in the converter gas. The difference between the total oxygen feed and the san of the oxygen and equivalent oxygen in the converter gns is the oxygen loss or unaccountable oxygen. The a-nount of oxygen calculated in the previous equations was based on the total asphalt charge in the reactor. This charge decreased during the course of a batch reaction and did not remain constant, because of sampling, entrainraent and reaction losses. The amount of asphalt In the reactor at any time duirlng the reaction was determined by a material balance. The calculated values of oxygen for any time interval were reduced to a basis of one pound of asphalt by dividing the mass of oxygen by the average weight of the asphalt reactor charge for the sane time interval. The results were plotted as a cumulative plot of pounds of oxygen per pound of asphalt versus elapsed reacting time. C. Scale Up All batch runs were analyzed and calculated by the preceding reaction rate and oxygen balance methods. Continuous runs were also evaluated by these methods and compared to the batch run results. The two types of operation can be compared only at a similar asphalt residence time, using a differential treatment for continuous operation and an integral treatment for batch operation.

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' A9 For continuous runs there was a continuous asphalt feed and simultaneous removal of asphalt product. As the mass of the asphalt charge in the reactor was kept constant, the asphalt residence time in the reactor was equal to the mass of the asphalt charge divided by the asphalt feed rate, that is tc Ma/Fa (l8) where tg asphalt residence time, hours M^ = mass asphalt in the reactor, pounds Fg^ * feed rate of fresh asphalt, pounds per hour The asphalt residence time, t^, for continuous operation is equivalent to the elapsed reacting time, t, for batch operation. The differential analysis for continuous operation requires only a material balance around the reactor while the integral evaluation requires determining areas vmder curves plotted from the initial to the final reaction time, t. The batch and continuous runs were compared for product consistencies and oxygen utilization at eqtiivalent residence times. In a subsequent section practical application of the developed rate equation is illustrated by a sample calculation for the design of a commercial reactor vessel. The calculated results using the developed rate equation are compared with the actual commercial reactor data.

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VII. RESULTS AND DISCUSSION The majority of the batch and continuous runs were made by using the Gulf Coast Asphalt, TA-1023-2. A total of thirty runs were made for this residuum. The process conditions that were studied included temperature, feed gas space velocity (flow rate), feed gas oxygen concentration and agitator speed. Nine additional runs using the East Texas TA-102/^, East Central Texas TA-1025 and the South Texas Heavy TA-1026 residua were made for purposes of con;->arison with the TA-1023-2 Gulf Coast material. These four types of materials represent four different types of asphalt. The analysis of the data was made according to: (a) kin
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51 200 150 100 2 3 L Reaction Tim© (t) Hours Figure 5. Softening Point and Reaction Time Relation for Batch Runs Using Gulf Coast Asphalt TA-1023-2

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52 run for given process conditions of space gas velocity, oxygen concentration, agitation rate and reaction temperature. Each cxirve shown in Figure 5 is the result of one batch run. The reproducibility of the data for the batch runs was checked by making duplicate runs for similar process conditions. Figure 6 is a comparison of two batch runs for the Gulf Coast asphalt, TA-1023-2, which were processed under similar conditions of temperature, feed gas space velocity, oxygen concentration and agitation rate. The results for the two batch runs shown in Figure 6 check within the limits of experimental error for Ring and Ball analysis. Table 5 is a tabulation of the resiilts when the two batch runs in Figiire 6 are compared, TABLE 5 REPRODUCIBILITY OF BATCH RUN DATA Run

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53 50 O Run ^06 • Run U2 2 3 4 5 Reaction Time (t) Hours Figure 6. Reproducibility of Batch Run Data, Gulf Coast Asphalt TA-1023-2

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5U as the ln(dR/dt) against the InR. The resulting straight lino plots are those given in Figure 7. In all the batch runs the asphalt was reacted to consistencies of 190-220 °F. Ring and Ball. The limits of the curves in Figure 7 are product consistencies of 200 °F. Ring and Ball which were selected as the upper liniits for the processing analysis of this investigation. The average of the slopes of the curves was equal to one and each curve was adjusted to this value to give a corrected intercept value at InR =0. A tabulation of the original slopes and the intercept values based on a common slope of one are listed in Table 6 for the runs shown in Figure 7. TABLE 6 SLOPE AND INTERCEPT VALUES FROM FIGURE 7 GULF COAST ASPHALT TA-1023-2 TEMPERATURE 500 ^. AGITATOR SPEED = 700 R.P.M. Run No.

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55 150 100 80 60 50 ^ ^0 30 20 15 10 90 100 120 UO Ring and Ball (R) op. 160 180 200 Figure 7. Reaction Rate and Product Consistency for Batch Runs, Giilf Coast Asphalt TA-1023-2

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56 The experimental values of the slopes show an average variation of 15.6 oer cent with a maximum of ^0 per cent for run 4.07. The use of a common slope of one is believed valid for this analysis. As will be shown later, the average observed data are within 7.2 per cent of predicted values by the procediire used. The slope variations found do not show trends for space gas velocity and oxygen concentration. Since all the slopes have approximately the seutoe value, this provides the basis for the use of a common slope. The selection of a common slope greatly simplifies the correlation of the data. The important point is to recognize the limitations of the relations presented for design application. The intercept values from Table 6 were plotted against InS according to Equation 5, la = In(kpP) 4 slnS (5) This data gave a family of straight lines with a constant slope value of 3 equal to 0.23. The parameter for this set of curves is the value of oxygen concentration, P. The curves are plotted in Figure 8 and the intercept values at InS = are tabulated in Table 7. The intercept values from Table 7 were next plotted against the InP as indicated in Equation 7 1^ Ink 4 plnP (7) to evaluate the remaining rate equation constants, p and k. The slope of this straight line plot was equal to the exponent, n, and the value was 0.83. The value of the intercept, Ink, was evaluated at InP and the value of k was equal to 0.006^. Figure 9 is a plot of the intercept

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57 ^ -1.0 c -2.0 25 50 100 Space Gas Velocity (S) CFMT 200 300 Figure 8. Evaluation of Rate Equation Exponent, s -1.0 o. « o u 0) c 2.0 -3.0 21 35 Oxygen Concentration (P) % 50 Figure 9. Evaluation of Rate Equation Exponent, p, and PseuJo Reaction Velocity Constant, k

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58 data in Table 7 versus InP The remaining batch runs for different temperatures and asphalts were analyzed and evalxiated by this same procedure. The data for all the runs was plotted according to Figures 7, 8 and 9 and the values cf the exponents, p, r, and s, were determined. TABLE 7 SLOFE AND INTERCEPT VALUES FROM FIGURE 8 GULF COAST ASPHALT TA-1023-2 TEMPERATURE = 500 °F. AGITATOR SPEED » 700 R.P.M, p % ©2

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59 TABLE 8 PSEUDO REACTION VELOCITY CONSTANTS AGITATOR SPEED • 700 R.P.M. Temp.

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60 0.0100 r, 0.0050 ^' 0.0040 0.0030 0.0017 O.OOIM 0.0019 1/T f K . 0.0020 0.0021 Figure 10. Variation of Pseudo Reaction Velocity Constant, k, with Temperature for Gulf Coast Asphalt TA-1023-2.

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61TABLE 9 VARIATION OF THE PSEUDO REACTION VELOCITY CONSTANT WITH AGITATION TEMPERATURE $00 °F. ASPHALT TA-1023-2 Agitator Speed R.P.M. ^ 700 0.0061 1300 0.0062 The small increase In the value of k for the increased agitator sjseed suggests that the degree of agitation that was uaed in this investigation was above the maximum agitation threshold. When this threshold value is obtained, the degree of agitation is no longer a process variable. The rate of reaction will then depend upon other process variables, The rate equation that was developed for the asphalt blowing process was checked by substituting process conditions and reaction times to calculate final asphalt consistencies. The calculated values were checked against the experLnentally determined values for the batch runs. The agreement of the developed equation vias checked for all batch runs using the equation dR/dt kS^^'^P^-'^R (19) or in the integrated form InRj^/Rg = kts'^-'-p^*^ (20)

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62 The values of k and R that were used for the different process conditions and a3i:>halt3 were taken from Tables 8 and 1 respectively. The average percentage variation of the calculated consistencies based on the experimental values are tabtilated In Table 10. TABLE 10 PERCENTAGE ERROR FOR REACTION RATE EQUATION EQUATION InCRi/a^) = kt3'"^*^P°'^

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63The evaluated constant, E, the pseudo raolal energy of activation, was 5800 calorles/gra. mole. This is a rather low value for the activation energy and indicates a reaction mechanism with diffusion controlling. The reaction rate for this mechanism depends on the rate at which the active reacting gaseous agent (oxygen) is transferred to the liquid asphalt interface. Process conditions that would increase this mass transfer of oxygen would be increased agitation, increased gas space velocity and increased oxygen concentration in the feed gas. The oxygen utilization for the four different types of residvia was a function of the asphalt product consistency and was independent of the processing conditions. The pounds of oxygen utilized per pound of asphalt processed was plotted against the change in Ring and Ball consistency of the asphalt. This average curve for the Gulf Coast reslduvan is shown in Figure 11. Curves for the other three residua are indicated in Figures 12, 13 and U. Table 11 is a tabulation of the average values of oxygen utilization for specific changes in asphalt prod-uct consistency. The oxygen utilization data indicates that the change in consistency, or the degree of reaction of the asphalt, is a stoichiometric relationship with the amount of oxygen that is used. The four residua that were used required different amounts of oxygen for a given change in asphalt consistency. The South Texas Heavy Asphalt TA-1026 utilized the most oxygen for a given change in product consistency while the East Texas Asphalt TA-1024. required the least oxygen for a similar change.

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6^ (0 f-1 0.12 0,10 0.08 0.06 S O.OA 0.02 20 /^O 60 80 100 120 Change in Ring and Ball Softening Point ^. 1^0 Figure 11 0.12 Oxygen Utilization and Product Consistency for Gulf Coast Asphalt TA-1023-2 Figure 12. 20 /,0 60 80 100 120 UO Change in Ring and Ball Softening Point °? . Oxygen Utilization and Product Consistency for East Texas Asphalt TA-1024

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65 20 AO 60 80 100 120 Change in Ring and Ball Softening Point °T . UO Figxire 13. Oxygen Utilization and Product Consistency for East Central Texas Asphalt TA-1025 0.12 ST 0.10 0.08 0.06 0,0-; 0.02 c V Figure lA. 20 ^0 60 80 100 120 Change in Ring and Ball Softening Point °F. Oxygen Utilization and Product Consistency for South Texas Heavy Asphalt TA-1026

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66 The data also indicate that as the reaction proceeds in the four different residua, less oxygen is required for a given change in product consistency. TA.BI£ 11 OXYGEN liTILIZATTON FOR PROCESSED RESIDUA Asphalt

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67 The oxygen balance was made by comparing the amount of oxygen in the process feed gas to that calculated in the converter gas as oxygen, carbon dioxide, water vapor, liquid water and acids. The equivalent amount of oxygen as acids in the precipitator fume oil products was small and these values were not included in the calculation. The resulting oxygen balance, therefore, was based on the remaining converter gas constituents of oxygen, carbon dioxide, water vapor and liquid water. Nitrogen balances were calculated for all the runs on the feed and converter gas streams to make certain that the gas flow rates or analyses of the feed and converter gases were not responsible for the unaccountable oxygen loss. The average variation for the cumulative nitrogen balances on the feed and converter gas streams was i 2.9 per cent by weight. This low variation for nitrogen balances indicates satisfactory flow rate measurements and analyses for the feed and converter gas streams with no significant losses. In Table 12 are listed the average cumulative xmaccountable oxygen losses for batch runs where the final product consistency was 200 T". Ring and Ball. A comparison of the data in Table 11 and Table 1^ for the total oxygen used to produce a 200 °F. Ring and Ball product, shows that between and 66 per cent of the oxygen appears as an unaccountable loss. The unaccountable oxygen co\ild have been absorbed In the liquid asphalt, reacted to form oxygenated compounds In the fume oil products, or appeared as oxygenated compounds In the converter gas stream. The previous Investigation by Katz (13) proved that less than 1 per cent by weight of oxygen is absorbed in liquid asphalts at Ring and Ball consistencies of 200 °F.

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68 or less. If It la assxanpd that 1 per cent of the oxygen was absorbed by the asphalt, 0,01 lb. 02/lb, asphalt would be accounted for. This value Is approximately 100 per cent of the average losses for the harder Tk-IOZA and TA-.1025 asphalts and 25-35 per cent for the softer TA-1023-2 and TA-1026 asphalts. TABLE 12 UNACCOUNTABLE OXYGEN LOSSES TO 200 °F. RING AND BALL PRODUCT CONSISTENCIES Asphalt

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69 this mechanism. It is possible that the oxygenated materiaOs In the fume oil are organic compotmds such as aldehydes, ketones and ethers. Tjrpical cumulative curves of the oxygen balance for batch runs are plotted in Figures 15 and 16, Figure 15 shows the data for a low gas apace velocity and low oxygen concentration run. Almost all the available oxygen is used for the reaction with the result of very little oxygen in the converter gas. Figure 16 is the plotted data for a high apace gas velocity and high oxygen content nin. Only a small fraction of the available oxygen is used for the reaction and the curves are close to each other. These curves may be used to determine the amount of oxygen used by the reacting asphalt to produce a specified degree of consistency. The data for Table 11 was obtained in this manner. The remaining batch runs gave similar plots depending on the processing conditions. The fume oil products were collected for each batch and continuous run. At the end of a run, the various samples taken were separated into an aqueous and an oil fraction. The volume and weight of these samples were determined and then the samples were titrated for acid numbers • Table 13 shows the average amount of fume oil collected for the various asphalt residua used and processed at different conditions to a final product consistency of 200 °F. Ring and Ball softening point. The amount of fume oil products that was collected for these batch runs was independent of the process gas oxygen concentration but was depiendent on the gas space velocity, reaction temperature and the type of asphalt processed. It may be noticed that for all the residua used, the percentage

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70 o 0.15 0.10 0.05 Reaction Time Hours Figure 15. Cumulative Oxygen Balance for Low Space Gas Velocity and Low Oxygen Concentration, Gulf Coast Asphalt TA-1023-2 Ji Figvire 16. S 0.1 I1 2 3 -C 5 6 Reaction Time (t) Hours Cumulative Oxygen Balance for High Space Gas Velocity and High Oxygen Concentration, Gulf Coast Asphalt TA-1023-2

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71 of the oil fraction increases with increasing reaction tempera ttire and feed gas space velocity. The total amount of fume oil products collected for asphalts processed to 200 °F. Ring and Ball consistencies was not constant. The total amount of fume oil products per batch nin was greatest for the South Texas Heavy Asphalt TA-1026 and smallest for the East Texas Asphalt TA-102A. The fraction of the fume oil products as oil was only 15 weight per cent for the East Texas Asphalt TA-102^ with a maximvim of 50 weight per cent for the Rest Central Texas Asphalt TA-1025. The total weight of fume oil in Table 13 includes the weight of the precipitated oils and the sum of the weight of water as condensed water and water vapor in the converter gas. The penetration values for the asphalt products were determined by the standard A. S. T. M. test D 5-25 (3) using a penetrometer. This penetration data for asphalts is generally used in conjxinction with softening point data to determine the adaptability of bituminous materials for specific uses and for quality control. Figures 17, 13, 19 and 20 show the relationship between Ring and Ball softening point and penetration values for the asphalt residues used In this investigation. The relation of Ring and Ball softening point and penetration is almost identical for the four different residues.

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72 230 200 150 100 50 100 120 140 160 180 200 Ring and Ball Softening Point °F. Figure 17. Properties of Asphalt Products, Gulf Coast TA-1023-2 220 100 120 1^0 160 130 200 Ring and Ball Softening Point °? . 220 figure 18. Properties of Asphalt Products , East Texas TA-1024

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73 « 100 100 120 1^0 160 180 Ring and Ball Softening Point °F. 200 220 Figure 19. Properties of Asphalt Prodiicts, East Central Texas TA-1025 ^ P: 100 120 140 160 180 Ring and Ball Softening Point °F. 200 220 Figure 20. Properties of Asphalt Products, South Texas Heavy TA-1026

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-TAXABLE 13 FUME OIL REACTION PRODUCTS TO 200 °F. RING AND BALL PRODUCT CONSISTENCIES Asphalt

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75 Equation 18 tc Ma/Fa (18) This same value for reaction time was used for the batch ofieration data to estimate Ring and Ball softening points and oxygen utilization data from plots similar to Figtires 5 and 15. Table lU indicates the results for the batch and continuous runs where the processing conditions were the same for both tjrrjes of operation. When the equivalent reaction times are equal for the two types of opei^tion, the agreement of the oxygen utilization data is within 15 per cent and the product consistencies check within 10 per cent. These results Indicate that the same product and oxygen consumption may be expected from either batch or continuous runs. The practical application for the developed rate equation is paramount for the calculation of processing times and design capacities for commercial «phalt blowing equipment. A sample calculation to demonstrate the use of the rate equation is included to illustrate its usefulness. Assume that it is required to determine the processing time and production capacity of an agitated reactor vessel 10 feet in diameter and 17 feet high. The depth of the asphalt charge is 12 feet. The reactor is agitated with a Turbo-Mixer agitator of the type used in the pilot plant experiments. The size of the agitatoImpoller is ^ inches. By selecting process conditions and substituting them in the developed rate equation, the processing time, process gas requirements and production capacity can be calculated for a product having a 100 °F. softening point rise.

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-16TABLE \U COMPARISON OP EXPERIMENTAL BATCH AND CONTINUOUS DATA GULF COAST ASPHALT TA-1023-2 TEMPERATURE = 500 °F. .vaiTATOR SPEED = 700 R.P.W. Continuous Runs

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77 The residuum to be used In this sample calculation Is the Gulf Coast Asphalt TA-1023-2. The processing conditions are selected as follows: Temoeratxire 500 F. Feed gas space velocity, S = 28CFMT Feed gas oxygen concentration, P = 21 The reaction time necessary to change the product consistency by 100 °F. Ring and Ball can be calculated from the Integrated form of the rate equation (Equation 20) InRi/Ro ktP°'^S°-^ (20) For the Gulf Coast Asphalt processed at 500 °F., k » 0.0061 and Rq « 70. The remaining variables are substituted into Equation 20 and solved for the reaction time, t. Rq = 70 '•. R^ 100 70 = 170 °F. k 0.0061 S 28CFIfr P = 21^ O2 ln(l70/70) 0.006l(2l)'^'^(28)°'^t t A.9 hours The value of t is the reaction time necessary to change the product consistency from 70 °F. to 170 '^ . Ring and Ball. This value is A. 9 hours for the process conditions chosen. The process gas requirements are determined from the feed gas space velocity and the mass of reacting residuum. The mass of asphalt

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78charge per batch is Mass asphalt = (reactor volinne) (asphalt density) (tr)(l0)^(l2)(62.4)(0.967)/(^)(2000) = 2S.A tons asphalt The corresponding feed gas flow rate is Gas feed rate = (mass asphalt) (feed gas space velocity) « 28.4(2S) = 795 ft. 3 air/mln. The calculated feed gas requirement for the reactor is 795 ft. 3 air/min. The dally production capacity for the reactor can be determined from the total cycle time required to orocess one batch. The operating cycle Includes; time necessary to heat the charge to the reacting temperature, time necessary for the desired reaction, holding time for analysis and time to discharge to a product tank. If the sura of the time for all the operations except the reaction time is assumed to be 6 hours, the total cycle time Is approximately 11 hours. The daily batch production would be 2.2 batches per day or 62 tons of Gulf Coast Asphalt having a final product consistency of 170 ''F. Ring and Ball. A variation of the processing conditions would change the reaction time but would not appreciably affect the remaining cycle time. When the feed gas space velocity and oxygen concentration is increased to 100 CFMT and 50 per cent respiectlvely, the reaction time for the reactor is reduced to 1.7 hours. The total cycle time is now 7.7 hours and the daily production is increased to 89 tons of 170 *^. Ring and Ball asphalt. The production has been increased but at the

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79expense of a greater feed gas flow rate and oxygen concentration. An economic analysis must be considered to arrive at justified operating conditions. The calculated results for the initial conditions selected for the design problem may be compared with actual refinery data as supplied by the Turbo-Mixer Corporation (14), The comparison is based on the same size reactor and similar operating conditions. The commercial data for refinery "A" lists a reaction time of 5.5 hours for increasing the softening point of an asphalt 100 t' . Ring and Bal] . By assuming that this asphalt is similar to the Gulf Coast Asphalt TA-1023-2, the calculated reaction time of 4.9 hours may be compared with the 5.5 hours reaction time. The error is approximately 1] per cent. The agreement of these results verify the use of the general rate equation for design calculations of commercial asphalt blowing units.

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VIII. CONCLUSIONS From tfte results of the asphalt blowing process using four different kinds of residua, the following conclusions may be made concerning the Kinetics of the asphalt olowing process within the limits of the conditions covered by this investigation: 1. The general rate equation for the reaction rate is dR/dt kP°*'^S°'\ where dR/dt gross asphalt reaction rate as rate of change of softening point R s asphalt Ring and Ball softening point, °F. S = process gas space velocity, ft.V(tnin.)(ton asphalt) at (70 ^., 1 atm . ) P original process gas concentration, volvirae % k = pseudo reaction velocity constant t = process reaction time, hours 2. The values of the pseudo reaction velocity constants are a function of the type of residua and the reacting temperatures. The corresponding values for the pseudo reaction velocity constants are : Temp.

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81 3. The reaction rate controlling step is a diffusion process based on the low pseudo molal energy of activation, E, of 5800 calorles/gm. mole. U. The gross asphalt blowing reaction may be considered a complex dehydrogenation, decarbonlzation and poljnnerization reaction. This is substantiated by the appearance of water and carbon dioxide in the converter gas and by the increased softening point for the asphalt products, 5. The asphalt blowing fume oil reaction products collected In the Cottrell precipitator contain a mixture of unknown oils and water. For asphalt residues reacted to 200 °F. Ring and Ball , the amount of fume oil products vary from 4-11 per cent cf the weight of residue reacted. 6. The fraction of oil in the fume oil products was a minimun of 15 weight per cent for the East Texas Asphalt TA-102it and a maximum of 50 weight per cent for the East Central Texas Asphalt TA-1025. 7. The change in asphalt consistency is related to the amount of oxygen used in the asphalt blowing reaction. The amount of oxygen used for a given change in product consistency was different for the four residua used. The East Texas Asphalt TA-IO24 used a ininimum amount of oxygen while the South Texas Heavy TA-1026 used the maximum amount cf oxygen. 8. Of all the oxygen used in the asphalt blowing reaction, 0-66 per cent could not be accounted for in the converter gas and

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82 tvme oil products. It is assumed that the unaccountable oxygen reacted to form oxygenated products that could appear as vapors In the converter gas or as liquids in the fume oil products . 9. For the same residence reaction times, integral batch operation is equivalent to differential continuous operation. 10. The general rate equation may be used for the calculation and design of commercial asphalt blowing units.

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IX. NOMENCLATURE A = Arrhenius frequency factor A J. = asphalt charge stock Aq, , Ap_ = intermediate asphalt products Aj. = composite air blown asphalt product not removed from the reacting zone B = volume of sodium hydroxide per cc. of water or gm. of oil, cc. C ~ gas concentration on a wet gas basis, volume per cent D = concentration of gas on dry gas basis, volume per cent d = gas density, lbs. /ft.-' E = molal energy of activation e = base of natural logarithms F^ = feed rate of fresh asphalt, Ibs./hr. f = conversion factor, lbs. oxygen/lbs, gas G = gas flow rate, ft.-Zmin. (8 70 °F. and 1 atm. AH = asphalt blowing heat of reaction Ig = intercept of ln(dR/dt) versus InR plot at InR s Ijj = intercept of the I^ versus InS plot at InS = If, intercept of the I^, versus InF plot at InP = k pseudo reaction velocity constant k'« specific reaction velocity constant L, , L^, L^ = intermediate condensed reaction products L^ a composite condensed reaction products Mg * mass of asphalt in reactor, pounds N = normality of sodium hydroxide 83 -

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8^P s feed gas oxygen concentration, volume per cent p * exponent for P Pp.= partial pressure, mm, Hg, R s asphalt Ring and Bail softening point, °F, Rq = Ring and Ball softening point for charge stock, °F. R^ = Ring and Bal] softening point at any reaction time, °F. r exponent for R S feed gas space velocity, ft.'/min. ton asphalt at 70 **F. and 1 atm. 3 = exponent for S T = absolute temperature, "k t = batch process reaction tiire, hoiirs At = time interval, hours tg ~ continuous process residence time, hours V volume of water or weight of oil, cc. or gms. V = volume of water, cc.

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X. BIBLIOGRAPHY (1) Abraham, H., "Asphalts and Allied Substances," 5th ed., D. Van Nostrand Co., New York, 19i^5. (2) "American Society for Testing Materials," Tentative Method of Test for Acid and Base Nijmbers of Petroleum Oils By Color-Indicator Titration, D 663-4.6T, A. S. T. M. Standards on Petrol exan Products and Lubricants, 336 (19A7). (3) Ibid .. Standard Method of Test for Penetration of Bituminous Materials, D 5-25, U. (a) Ibid ., Standard Method of Test for Softening Point of Bituminous Materials, D 36-26, 12. (5) Blakely, A. R., Forney, W. F., Frino, M. J., and Rescorla, A. R., "Asphalt Oxidation with Agitation," Paper presented at the A. C. S. Meeting in Miniature, Hotel Essex House, Newark, New Jersey, January 25, 195A. (6) Brooks, E, T., "Non-Benzenoid Hydrocarbons," Chemical Catalog Co., New York, 1922. (7) Byerly, F. X., U. £. Patent 52/i,130 (August 7, 189^). (8) Frost, A. A., and Pearson, R. C, "Kinetics and f/'echanism," John Vfiley and Sons, New York, 1953. (9) Graham, W., Cudmoi'e, W. J. G., and Heyding, R. D., Canadia n J^ Technol. . 20, U3 (1952). (10) Hoiberg, A. J., and Shearon, W. K. Jr., Ind. Eng. Chem. . ^, 2122 (1053). 85 -

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86(11) Holland, C. J., Petr. Eng .. 6, Nos. 2-11, (1935). (12) Hougen, 0. A., and Watson, K. M., "Chemical Process Principles," Part III, John Wiley and Sons, New York, 19^7. (13) Katz, M., Can. J. Research . 10, A35 (193^). (1A) Parker, N. K., Turbo Mixer Corp., Private Communication, April 30, 1954.. (15) Perry, R. H., and Pigford, P.. L., Ind. Eng. Chem. . ^, 12^7 (1953). (16) Pfeiffer, J. P. K., "Properties of Asphaltic Bitumen," Elsevier Publishing Co., New York, 1950. (17) Sherwood, T. K., and Pigford, R. L., "Absorption and Extraction," McGraw Hill Book Co,, New York, 1952. (18) Thurston, R. R. and Knowlea, E. C. Ind. Eng. Chem.. 28, 88 (1936). (19) U. S. Department of Commerce, "Statistical Abstract of the United States," 74 th ed.. Government Printing Office, Washington, 1953, p. 736.

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APPENDIX A DRAWINGS

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88 Figure 21

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Cottrell Precipitator Bntralnmsnt Separator Asphalt Feed Piimp Oiygen Vuter Condenser ^eclpitated Oils & Vater Beacted Asphalt I Converter Oas Back Pressure Regulator Beckmui Oxygen Analyzer CO2 Analysis Dryer Botameters Den Point MATERIAL TOLERANCES UNLESS OTHERWISE SPECIFIED DECIMAL FRACTIONS ASPHALT BLOWING FLOW DIAQEAM DRAWN BY: JB CHECKED BY: jg DATE: 3-27_5U SCALE: ENGINEERING AND INDUSTRIAL EXPERIMENT STATION UNIVERSITY OF FLORIDA GAINESVILLE DRAWING NUMBER 5203-1

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89 Figure 22

PAGE 105

90 Figure 23

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230V, SINGLE PHASE 60 CYCLE ELECTRICAL PRECIPITATOR ASPHALT REACTOR HEATERS CONNECTOR PANELS ASPHALT STORAGE HEATERS LESS OTHERWISE ASPHALT BLOWING WIRING D. B. '>J.H, [NGINEEHIHG AND INDUSIRIAL exPERmEDT STAIION UHivEHsnr of Florida 5302

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91 Thermostat Bulb Protection Thibe Thermocouple Protection Tute Transit e Cover Storage Shell 12" Steal Pipe Figure 24 Strip HeatersAlternate Long and Short Insulation Thermostat Control Three Heat Snap -1 Switch Sheet Uetal Cover and Box Bing Heater ASPHALT BLOWING STORAQB TANK DRAWN BY JB CHECKED BY: jg DATE: 3-27-54 SCALE: ENGINEERING AND INDUSTRIAL EXPERIMENT STATION UNIVERSITY OF FLORIDA GAINESVILLE DRAWING NUMBER 5203-U MATERIAL TOLERANCES UNLESS OTHERWISE SPECIFIED DECIMAL FRACTIONS

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Beacti Shell Insula 92 Figure 25

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A^tator Assembly Air Feed Dlatrltnitor 3/8* Bteel pipe 1/S" pipe tips Sntrainnent Separator una Cooler 3" Steel Pipe li" IPS Pipe Fittings 8" Steel Pipe Strip Heaters 5-Equally Spaced Air Peed Distributor Thermocouple Wells Asphalt Feed Turbo Mixer Drive Assembly #U-10 Thermocouple Protection Tubes l/g* Pipe Asphalt Feed Line y/k" Pipe Notes For Agitator Drive Assembly See Turbo Mixer Co. Drawing No. U-18, 11-^0-^1. Asphalt Outlets 3/U» Pipe Couplings Turbo Uixer Aerator Hood Eing and Impeller #l|_2,U-3 Heactor Assembly Agitator Assembly TOLERANCES UNLESS OTHERWISE SPECIFIED DECIMAL FRACTIONS ASPHALT BLOWING RSaCTOS DRAWN BY:JP CHECKED BY: JH DATE: 3_?7_5U ENGINEERING AND INDUSTRIAL EXPERIMENT STATION UNIVERSITY OF FLORIDA GAINESVILLE DRAWING NUMBER 5203-5

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93 High Voltiige Bushing Insulator x^ V Baffle Plow / Plow Access Panel & Observation Window 3" Steel Pipe Hi^ Voltage Electrode Lectrode Tension Weight 3/U" Inlet, ^^ Outlet, and Drain Couplings Drain Figure 26 ASPHALT BlO'iVIMO ELECTRICAL PRECIPITATOR DRAWN BY J3 CHECKED BY: JH DATE: 5_27-5U SCALE: ENGINEERING AND INDUSTRIAL EXPERIMENT STATION UNIVERSITY OF FLORIDA GAINESVILLE DRAWING NUMBER 5203-6 REVISION DATE MATERIAL TOLERANCES UNLESS OTHERWISE SPECIFIED DECIMAL FRACTIONS

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APPENDIX B EXPERIMENTAL DATA

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95*J

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96 *>

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97 ••J rH « aj M •

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^^-

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Foldout too large for digitization May be added at a later date

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-99-

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APPENDIX C CALIBRATION CURVES

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-103TABLE 17 AIR FEED ROTAMETER CALIBRATION DATA SCHDTTE AND KOERTING 3F TUBE WITH MODIFIED ALUMINUM FLOAT NUMBER 2 Rotameter

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-lOitTABLE 18 CONVERTER GAS ROTAfJETER CALIBRATION DATA SCHUTTE AND KOERTING 3F TUBE WITH MODIFIED ALUMINUM FLOAT NUMBER 1 Roteuneter Scale

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-105TABLE 19 OXYGEN FEED ROTAMETER CALIBRATION DATA SCHUTTE AND KOERTING IR TUBE WITH STAINLESS STEEL ROTOR Rotsuneter Scale

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-106 o ro I 100 150 Rotameter Scale Reading 250 Flgiire 27. Air Feed Rotameter Calibration Curre, Schutte and Koerting 3F Tube and Number 2 Aluminum Float

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1073 o I C CO 0.5 0.4 0.3 0.2 0.1 50 100 150 Rotameter Scale Reading Figure 28. Oxygen Feed Rotameter Calibration Curve, Schutte and Koerting IR Tube and Stainless Steel Float

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10? o (S 2.5 2.0 1.5 1.0 0.5 50 100 150 Rotameter Scale Reading 200 Figure 29. Converter Gas Rotameter Calibration Curve, Schutte and Koerting 3F Tube and Number 1 Aluminxun Float

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-log's O 5 s r-i U U.iU

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XII. BIOGRAPHY OF AUTHOR John Daniel Holmgren was bom In Leadville, Colorado on March 20, 1927. Three months later he and his parents moved to Sllverton, another small mining town high in the moiintains of Southwestern Colorado. He graduated from the Sllverton High School in June 194j^, and entered the University of Colorado in October of that year. He graduated in June 19^3 with a Bachelor of Science degree in Chemical Engineering. After graduation he accepted a position as Chemical Engineer with the General Electric Company in Richland, Washington and was assigned as research engineer to a pilot plant development group. During this time he studied various phases of atomic energy, such as, pile technology, chemical processing of uranium and plutonium, and radio-active waste disposal. In order to complete extension work on a Master's degree, he resigned his position with the General Electric Company and entered the University of Washington In September, 1950. He completed the work on hla Master's degree in Chemical Engineering in September 1951 and transferred to the University of Florida to work towards a degree of Doctor of Philosophy. In June 1952 he received an appointment as Instructor at the University of Florida to work on a classified research oroject sponsored by the Department of Defense^ and he Is presently working on this project. He was married in June 1953. He is a member of the American Institute of Chemical Engineers, the American Chemical Society, Alpha Chi Sigma, and he is a Registered Professional Engineer in the State of Florida. 110 -

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-IllThis dissertation was prepared under the direction of the chairman of the candidate's supervisory coramlttee and has been aporcved by all members of the committee. It was submitted to the Dean of the College of Engineering and to the Graduate Council and was approved as partial fulfillment of the requirements for the degree of Doctor of Philosophy. June 7, 195^ JIU-^^'''-^ ^^ Dean/ College of Engineering Dean, Graduate School SUPERVISORY COMMITTEE: ^v. ff , S^JlocA-AgjuyiA Chairman