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KINETICS OF PROCESSING
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
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
- ii -
TABLE OF CONTENTS
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
TABE OF CONTENTS
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
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
LIST OF FIGURES
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
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 -
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.
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-
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
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
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.
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
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
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
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
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
gross reaction rate =
diffusion resistance + chemical resistance
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)
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
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.
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.
PROPERTIES OF ASPHALTIC RESIDUES
Sample TA-1023-2 TA-1024 TA-1025 TA-1026
Identification Gulf Coast East East South
Naphthenio Texas Central Texas
Density 0 60 oF. 0.9670 1.0215 1.0203 0.9908
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
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
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
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
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.
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
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
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
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
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
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
Figure 2. ialtM Storage Tak, Reactor ad
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
Chroael-aleal thermocouples are used to measure all process
streak temperatures in the asphalt blowing system. The thermocouples
- 22 -
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
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.
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
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.
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
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
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
CALIBRATIOI DATA FOR GAS ANALYSIS INSTROUBTS
Run Gas Concentration Thermal Beo]san
so. Volume % Conductivity Oxygsa
02"* c02 N2 million a A
Run Gas Concentration Thermal Beckman
No. Volume % Conduetivity Oxygen
02" C02 1 N2 Millivolts
*Beckmn oxygen analysis for runs 1-68.
-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
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.
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
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.
- 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
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
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
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
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
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
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
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
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
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.
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.
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.
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)
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
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
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)
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)
I = In(kP) 4 lasn (5)
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)
Ib = Ink 4 plnP (7)
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)
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
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
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.
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)
Ink' --E/RT + In (11)
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
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)
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.
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)
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)
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
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)
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
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.
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)
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.
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
- 51 -
50 i -- -- ----
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
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.
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)
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
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.
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 -
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
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
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 -
10 25 50 100 200
Space Gas Velocity (S) CMPT
Figure 8. Evaluation of Rate Equation Exponent, a
21 35 50
Oxygen Concentration (P) %
Figure 9. Evaluation of Rate Equation Exponent, p, and Pseslo
Reaction Velocity Constant, k
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.
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
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 -
PSEUDO ACTION VELOCITY COSTATS
AGITATOR SPEED 700 R.P.J.
Pseudo Reaction Velocity Constant, k
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
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.
0.0017 0.0018 0.0019
Figure 10. Variation of Pseudo Reaction Velocity instantnt, k, with
Temperature for Gulf Coast Asphalt TA-1023-2.
VARIATION OF THE PSEUDO REACTION VELOCITY CONSTANT
TEMPERATURE 500 oF.
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)
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.
PERCENTAGE ERROR FOR REACTION RATE EQUATION
EQUATION ln(R/R,) = kt30.2p0.9
Per,Cent Error for Asphalt
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.
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
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.
C .0 -0
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
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
a 0.06 -
0 0.04 -
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 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
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.
OXYGEN UTILIZATION FOR PROCESSED RESIDUA
Asphalt Change in Ring and Oxygen Utilizatton**
Ball Consistency" Lb. 02/Lb. Asphalt
TA-1023-2 30 0.034
TA-1024 50 0.U1
TA-1025 52 0.023
TA-1026 27 0.044
*Change in consistency froa original residuum.
**Cumulative oxygen required for the given change in Ring and Ball
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.
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.
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.
UNACCOUNrABLE OrXYG LOSSS TO 200 F.
RING AND BALL PRODUCT CONSISTECIES
Total Oxygen Losses Average Oxygen Losses
Lb. 0Lb. aLphalt i. O/Lb. 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
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
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 -
S 0.10 0 Fooed
i 002 Out
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
I 0.2 -
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
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.
100 120 140 160 180 200
Ring and Ball Softening Point 0F.
Figure 1. Properties of Asphalt Producta, Gulf Coast TA-1023-2
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
100 120 140 160 180 200 220
Ring and Ball Softening Point OF.
Figure 19. Properties of Asphalt Products, East Central Texas TA-1025
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
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
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
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-
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.
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
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
The residuum to be used in this sample calculation is the Gulf Coast
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.
P a 21% 02
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
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)
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
expense of a greater feed gas flow rate and oxygen concentration. An
economic analysis must be considered to arrive at justified operating
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.
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
dR/dt u gross asphalt reaction rate as rate
of change of softening point
R w asphalt Ring and Ball softening point,
S process gas apace velocity,
ft.o/(min.)(ton asphalt) at (70 OF.,
P = original process gas concentration,
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-
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 -
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
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
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
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.
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,
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
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
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.
(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., /,
(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,
atrinKnt (ser Rotameter R or
pil & Wate
o |- .
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
rti I' -
7 aet-- er
02 ~2 I
Oas Panel Board
Pppeatre Rehoing e
ASPHALT BLOWING PIPING DIAORAM
ENGINEERING AND INDUSTRIAL EXPERIMENT STATION
UNIVERSITY OF FLORIDA
I V D.C.
S 138 M.A.
L tI I
I -- 7
HIGH- IL,4,5; 2L3
MED.2L,3; IL 5
[ I.-1 BLACK
0- 50,000 voc
I 20 MA
L- ___ __
I4- 500W, 230V
I SHORT STRIP
I 1000W, 230V
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/, \ 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
ENGINEERING AND INDUSTRIAL EXPERIMENT SIAIION DRAWING NUMBER
UNIVERSIlr OF FLORIDA 5302- 3
Thermostat Bulb -s
- Strip Heaters- Alternate
Long and Short
Translte Cover -
Storage Shell -
12" Steel Pipe
-- Three Beat Snap
- Sheet Metal Cover
ASPHALT HLOWIO STORAGE TAHI
ENGINEERING AND INDUSTRIAL EXPERIMENT STATION DRAWING NUMBER
UNIVERSITY OF FLORIDA 520o3-
Air Feed DMetributor
3/g" steel pipe
1/8' pipe 9ip
C. O ] ^
3m Steel Pipe
1)" IPS Pipe Fittings
1s Steel Pipe
/, 5-Bqually Spaced
3/9a Pipe Couplinge
Turbo Mizer Aerator Hood Ring
and Impeller #~-2.4-3
ASPHALT BLOWIHO REACTOR
ENGINEERING AND INDUSTRIAL EXPERIMENT STATION
UNIVERSITY OF FLORIDA
ff ~1 "
Aooss Panel &
37 Steel Pipe
- Hih Toltage
ASPHALT BLOWID ILICTRICAL FZCIPITATO
ENGINEERING AND INDUSTRIAL EXPERIMENT STATION
UNIVERSITY OF FLORIDA
ON DATE MATERIAL
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