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Chemical engineering education

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Title:
Chemical engineering education
Alternate Title:
CEE
Abbreviated Title:
Chem. eng. educ.
Creator:
American Society for Engineering Education -- Chemical Engineering Division
Publisher:
Chemical Engineering Division, American Society for Engineering Education
Publication Date:
Frequency:
Quarterly[1962-]
Annual[ FORMER 1960-1961]
quarterly
regular
Language:
English
Physical Description:
v. : ill. ; 22-28 cm.

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Subjects / Keywords:
Chemical engineering -- Study and teaching -- Periodicals ( lcsh )
Genre:
serial ( sobekcm )
periodical ( marcgt )

Notes

Citation/Reference:
Chemical abstracts
Additional Physical Form:
Also issued online.
Dates or Sequential Designation:
1960-June 1964 ; v. 1, no. 1 (Oct. 1965)-
Numbering Peculiarities:
Publication suspended briefly: issue designated v. 1, no. 4 (June 1966) published Nov. 1967.
General Note:
Title from cover.
General Note:
Place of publication varies: Rochester, N.Y., 1965-1967; Gainesville, Fla., 1968-

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University of Florida
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All applicable rights reserved by the source institution and holding location.
Resource Identifier:
01151209 ( OCLC )
70013732 ( LCCN )
0009-2479 ( ISSN )
AA00000383_00018 ( sobekcm )
Classification:
TP165 .C18 ( lcc )
660/.2/071 ( ddc )

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Chemical Engineering Documents

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FJN/E 1966M
JUN/E 1966A


CHANGING ATTITUDES
TO REACTOR DESIGN























chemical engineering

texts from Prentice-Hall


New for 1968...
INTRODUCTION TO FLUID MECHANICS by
Stephen Whitaker, University of California
at Davis. Provides an exceptionally thor-
ough treatment of the macroscopic (or
integral) momentum and mechanical energy
equations. February 1968, approx. 480 pp.,
$12.00

MATHEMATICAL METHODS IN CHEMICAL
ENGINEERING: MATRICES AND THEIR AP-
PLICATION by Neal R. Amundson, Univer-
sity of Minnesota. Outlines the elementary
theory of matrices discussing eigenvalue
problems, Hamilton-Cayley's theorem, and
systems of linear differential equations and
algebraic equations. 1966, 270 pp., $12.50

FOUNDATIONS OF OPTIMIZATION, by
Douglass J. Wilde, Stanford University and







For approval copies, write: box 903

PRENTICE-HALL


Charles S. Beightler, University of Texas.
Covers both the direct and indirect optimi-
zation techniques; extends the new non-
linear technique of geometric programming
to functions with negative signs and re-
versed inequalities. 1967, 480 pp., $12.95

KINETICS OF CHEMICAL PROCESSES by
Michel Boudart, Stanford University. Ex-
plains the kinetic analysis of elementary
steps, single reactions, and reaction net-
works for chemists interested in reactivity
and chemical engineers interested in re-
actors. April 1968, approx. 220 pp., $7.50


Englewood Cliffs, New Jersey 07632









0#EM/sffw






Contents for Volume 1, No. 4, June '66



55 Changing Attitudes To
Reactor Design

0. Levenspiel


70 The Chemical Engineering
Approach To Entropy

J. L. Throne


72 The Integrity of
Chemical Engineering

J. M. Douglas
and S. A. Miller


DEPARTMENTS


iii Editors' Corner


63 Speaking Out


R. G. Thorpe


EDITORS' I a

Chemical engineering curricula today face the
sternest confrontation of their entire history, a
challenge from inside the world of engineering
itself that amounts to questioning their raison
d'etre. Yet if the discipline of chemical engineer-
ing is reality and if the chemical process industry
is not illusion, there should be no doubt about
the reasonable purpose of chemical engineering
education. The core of that purpose is three-
kerneled: to prepare its graduates at all levels
to solve the engineering problems of chemical
processing, from research to marketing; to pro-
vide clear educational leadership in chemical en-
gineering in both academic and industrial spheres;
and to share strongly the technical leadership
of chemical engineering. The central kernel is, of
course, the first.
A not inconsiderable piece of the student's
equipment with which his chemical engineering
education should outfit him is attitude. He must
be conditioned to seek creative solutions to com-
plex, real-world problems. He must be able to
look at whole systems and not merely the com-
ponents thereof. He must be stimulated to sus-
tain a lifetime of continued learning. And he
must be aware of his field, recognize its power,
and sense the satisfaction it can yield to its
practitioners. Indeed, perhaps the most signifi-
cant burden laid upon late-twentieth-century fac-
ulties of chemical engineering is one of attitude.
We who teach must impress our undergraduate
and graduate students with the imperative of
continued scholarship and the reward that goes
with it. We must find ways to encourage disci-
plined originality. Above all, we must reflect
the genuine excitement of the real-life engineer-
ing problem. Without such inspiration, our stu-
dents can be expected to view the world of chem-
ical engineering toward which their college ex-
perience should direct them with mild interest
at best, and possibly with distaste. The persistent
maintenance of infectiously zestful attitude is a
demand of inestimable importance that we edu-
cators cannot evade.


ENGINEERING


b0ULAATION


The official journal of the


Chemical Engineering Division, American Society for Engineering Education


Editor Shelby A. Miller
Consulting Editor Albert H. Cooper
Assistant Editor John W. Bartlett
Publications Committee of CED
L. Bryce Andersen Chairman
Charles E. Littlejohn
E. P. Bartkus
James H. Weber
Executive Committee of CED
Chairman John B. West
Chairman-elect J. A. Bergantz
Secretary-Treasurer William H. Honstead
Elected Committeemen J. T. Banchero
W. H. Corcoran
Past Chairman George Burnet


CHEMICAL ENGINEERING EDUCATION is pub-
lished four times during the academic year
by the Chemical Engineering Division, Ameri-
can Society of Education. Publication months:
October, January, April, June. Publication
and editorial offices: 201 Gavett Hall, Uni-
versity of Rochester, Rochester, N. Y. 14627.
Title registered U. S. Patent Office.
Subscription rates: To Chemical Engineering
Division members, $3.00 per year; to non-
members in the Western Hemisphere, $4.00
per year; to non-members'outside the West-
ern Hemisphere, $5.00 per year; single issue
price, $1.50. Advertising rates quoted upon
request.


JUNE 1966


CHIEMICAL






THE AMERICAN SOCIETY FOR ENGINEERING EDUCATION


FOURTH ANNUAL

CHEMICAL ENGINEERING DIVISION

LECTURESHIP AWARD

to

Dr. Octave Levenspiel







SHE CHEMICAL ENGINEERING Division Lectureship
Award of the American Society for Engineering
Education is an annual award of $1000 to a distinguished
engineering educator for outstanding achievement in funda-
mental chemical engineering theory or practice. It is spon-
sored by the 3-M Company.
The recipient of the Fourth Annual Award, presented
on June 22, 1966, was Octave Levenspiel, Professor of
Chemical Engineering at Illinois Tnstitute of Technology,
who responded with an address on "Changing Attitudes to
Reactor Design." Previous award winners and the subjects
of their lectures were:
1965, Leon Lapidus, Princeton University
"Aspects of Modern Control Theory and
Application"
1964, C. R. Wilke, University of California (Berkeley)
"Mass Transfer in Turbulent Flow"
1963, A. B. Metzner, University of Delaware
"Non-Newtonian Fluids"


CHEM ENG ED








Changing Attitudes

TO REACTOR DESIGN


Octave Levenspiel
Professor of Chemical Engineering
Illinois Institute of Technology, Chicago, Illinois

Exciting things are happening today in
the field loosely covered by the terms
chemical technology, reactor design, and
kinetics, for, without fanfare, study re-
ports, or discussion in ASEE or in AIChE,
a new way of looking at this subject was
recently introduced. The new view may be
characterized by the phrase Chemical Re-
action Engineering, and its friendly recep-
tion by the profession is causing a remark-
able change in our approach to and our
teaching of chemical technology.
I should like to discuss this new develop-
ment, to sketch its strategy as opposed to
the traditional approach, to give a few ex-
amples to illustrate what I mean, to show
how it has affected our pattern of educa-
tion, and finally to consider what I feel is
its place in the main line evolution of our
profession.
In the traditional approach, we engineers
were more concerned with the peculiar and


unique features of this or that reacting
system than with the similarities and com-
mon characteristics among such systems.
It is true that the unique features make
for the success of a particular process. It
is also true that what is useful for the pro-
cesses of tomorrow are the analogies and
generalizations which we are able to extract
from the technology of today. Thus for
predictive and design purposes we need
generalizations; in the past, however, we
have emphasized the particular and the
unique.
In the U.S. of the forties we saw the
first break with this philosophy. The gen-
eral approach was brought forward; how-
ever, it was soon channelled, narrowed, and
dominated by the problems and interests
of the oil industry. Hence there was an
overwhelming emphasis on catalytic re-
actions and a rather unhealthy preoccupa-
tion with developing models to account for
their kinetics. Little wonder that this sub-
ject was known and is still known as applied
kinetics, chemical engineering kinetics, or
just kinetics, despite the fact that finding


JUNE 1966







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the rate of reaction is only one phase in the
over-all problem of scale-up and proper
reactor design.
In the late fifties a bolder attempt at
generalization was started in Europe. To
emphasize its concern with the over-all
problem it was termed Chemical Reaction
Engineering or CRE for short. As the name
suggests, we are here concerned with the
"engineering" of chemical reactions, or
their efficient exploitation. The philosophy,
then, is to seek common factors to link
processes and to develop broad methods of
attack for problems, and this is done with
the conviction that these methods can be
used as a basis for design in all areas of
application, whether it be in polymer pro-
cessing, industrial metallurgy, pharmaceu-
tical manufacture, foods, biological pro-
cesses, high-temperature reactions, or any
other operation in fact wherever a new
material or chemical species is to be pro-
duced economically on a commercial scale.
In a nutshell the concern of CRE is shown
in Figure 1. Thus we engineers must deter-
mine how to treat a feed stream so as to
obtain most economically a most desirable
product stream. More specifically we must
decide what temperature, pressure, and
contacting pattern to use, and in general
this decision requires knowledge of the
stoichiometry, thermodynamics and kine-
tics of the systems.
It is convenient to classify reacting sys-
tems according to the phases participating
in the reaction. As shown in Figure 2 the
broad division is between homogeneous and
heterogeneous systems. In the former, one
fluid phase alone moves through the reactor


and only chemical kinetic factors influence
the rate. In the latter classification, we may
have to deal with additional problems aris-
ing as a direct consequence of the hetero-
geneity of the system, such as phase equili-
brium, mass transfer from phase to phase
or from phase to interface, and contacting
pattern of the phases. As may be expected,
heterogeneous systems represent a more
complex situation.
Next we see that homogeneous systems
may be divided into systems where only
one reaction occurs and into systems where
two or more reactions occur simultaneously.
The reason for this split is that different
questions are pertinent in these two situa-
tions. With one reaction all we ask is to
maximize conversion with a most economi-
cal reactor arrangement; with multiple
reactions we ask how (by what tempera-
ture, pressure, and contacting pattern) to
promote the formation of the desired
product and depress the formation of all
other undesired materials. The primary
concern is not the same in the two cases.
And so it is with heterogeneous systems,
where we have (in what I consider to be
the order of complexity) solid-catalyzed
gas-phase reactions, non-catalyzed fluid-
solid reactions (reduction of metal oxides,
burning of coal), fluid-fluid systems (ab-
sorption with reaction), and finally the
catch-all et cetera classification which in-
cludes all other multiphase systems. These
systems can be horribly messy to treat, and
in the interest of simplicity I shall avoid
them in this paper, even though they in-
clude many processes of great industrial
importance.
CHEM ENG ED


Homosemeous


mu ltiple|
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i ermo cre ion s
Fig. 2 Classification of Reacting Systems





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JUNE 1966







The line at the bottom of Figure 2 shows
the usual stages in our control of reacting
systems all the way from initial studies on
thermodynamics and stoichiometry to a
search for optimum operation.
Our ability to handle problems is quite
different in the different classifications. For
example in homogeneous single-reaction
systems we are at the stage of selecting
optimum set-ups. In catalytic systems we
would be just about as far along if it were
not for the obstinate problem of represent-
ing and properly accounting for the kine-
tics of the reaction. With fluid-fluid sys-
tems our difficulties are everywhere: how
to represent the rate usefully, how to ac-
count for movement of reacting species in
the flowing phases, and in general how to
predict the extent of reaction given all
kinetic and equilibrium information. This
means that except for special cases we have
trouble trying to develop a design equation
for this classification. And so it is with the
other classifications shown in Figure 2; in
each there are particular difficulties to be
overcome.
Let me next offer three examples of re-
cent research activities in CRE. They must
be brief for this review to conform to rea-


sonable length. Nevertheless I hope that
they will provide a feeling for the sort of
thing that is going on.
The first example concerns the search for
an optimum set-up for the single catalylic
reaction whose thermodynamics and stoi-
chiometry are known, and let us restrict
ourselves to adiabatic operations in packed
beds. Now there are many possible ways of
running such a reaction for example,
single-stage operations in one packed bed
reactor, multistage packed-bed operations
with interstate heat transfer, operations
with recycle of fluid between stages or with
bypassing of certain stages with fresh feed.
And for every set-up we can choose the
temperature of fluid entering the various
stages. With all these factors at our con-
trol, are we to make a computer search of
every possibility that comes to mind, or
are there methods which give us a feel for
the situation and allow us to reject quickly
many of the alternatives while retaining
those few which are promising? Since I
favor the latter approach let me outline a
graphical method which does just that.
Figure 3 shows the design equations for
the flow patterns of interest: the ideals of
plug flow and backmix flow and the inter-


CHEM ENG ED






mediate of recycle flow. It should be noted
that plug and backmix flows represent the
extremes of recycle flow when the recycle
ratio m becomes zero and infinite, respec-
tively. These equations indicate that the
four quantities, V (size of reactor), FAO
(feed rate of reactant A), -rA (rate of
reaction), and XA (conversion of reaction)
*


.-U1

0~I
-c


0)


are all interrelated, and knowing any three
of these quantities gives the fourth. The
sketches in Figure 3 are a graphical repre-
sentation of these equations for any ar-
bitary kinetics and the shaded areas are a
measure of the size of reactor needed for a
given duty. These expressions are quite
basic to CRE.


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JUNE 1967


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Figure 4 is the temperature-conversion
graph for typical exothermic and endo-
thermic reactions when starting with a
given feed. Shown in this figure are the
equilibrium curves obtained from ther-
modynamic considerations and typical re-
action paths starting with feed at tempera-
ture To, both for isothermal and adiabatic
operations. In the succeeding figures we


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shall build on this plot. I shall discuss only
the exothermic situation, but I include in
the figures the corresponding endothermic
reaction for the reader who wishes to pur-
sue that case on his own. The logic of the
two situations is somewhat similar.
Now to Figure 5: the dotted lines show
the locus of constant reaction rate, and this
general shape again is typical of all re-


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CHEM ENG ED







actions. Next, to minimize the size of re-
actor we want to choose the temperature
where the rate is maximum for that com-
position. The heavy line in this figure shows
the progression of temperatures which
satisfy this condition. Comparing with
Figure 4 we see that the slope of this opti-
mum line is opposite that for adiabatic
operations.
Because of the opposite slopes the way


all


to approach this optimum with plug flow
units is shown in Figure 6. Abiabatic stages
with intercooling are required. It is appar-
ent that intercooling simply shifts the
operating line horizontally to the left on
this graph.
Since it is impractical to use a large
number of stages, we may start by examin-
ing one-stage, two-stage, and then three-
stage operations. Figure 7 illustrates how


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JUNE 1966 61


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to find the minimum size of a two-stage
plug-flow unit to achieve a given conversion
XA,. The procedure is a one dimensional
trial-and-error where To alone is guessed.
Points a and c are found by the integral
given in the figure and point b has the same
rate as point a. Figures 8 and 9 sketch
analogous plots for recycle and for backmix
flow.
Again we ask if we must search all these


possibilities. Figure 10 indicates that this
is not necessary and that the key to the
proper contacting is given by the slope of
the adiabatic operating line. For the shal-
low slope of case a the rate of reaction is
extremely low at low conversions; hence we
should avoid operating in this range of con-
ditions. This immediately suggests that we
use backmix flow or recycle flow with a high
(continued on page 64)
CHEM ENG ED


U -


1'







R. G. Thorpe
Associate Professor of Chemical Engineering SPEAKING
Cornell University, Ithaca, New York


About-The Industry-University Interface

The classical conception of an interface, bounded
by several high resistance films and across which
mass and energy are transported under the in-
fluence of a driving force, has undoubtedly been
of more value in the solution of real problems
than any other concept one could name. Engineers
have always been singularly perceptive, if not
ruthless, in the adaptation of engineering ter-
minology to the description of human behavior.
It is not surprising then, to find "interface" being
used ir a particularly appropriate sense to de-
scribe the transfer of intellectual capacity between
groups which have quite different responsibilities
and interests. No empty verbalism this, for the
use carries with it the connotation that a re-
sistance to the transfer process does in fact exist.
I have returned to the academic cloister from a
most interesting and exciting sabbatic leave dur-
ing the 1965-66 academic year as a full-time en-
gineering consultant in the Engineering Tech-
nology and Services Branch of Monsanto's new
Central Engineering Department. I functioned
during the entire period directly with Monsanto
professionals in the solution of short-term prob-
lems and in the development of new technology
for long-term application. I now can see the pro-
cess industry-engineering college interface in de-
tail. The resistance on the industrial side is mini-
mal, but it is certain that the academic side re-
sistance is much too high for the single reason
that there appears to be much more concern in
the engineering colleges with advancing science
than with making the advances of science useful.
Clearly, there has been serious abrogation of re-
sponsibility by the colleges in the teaching of
analysis, synthesis, and design to meet modern
day demands both at the undergraduate and
more seriously, at the Ph.D. level.
In the broad spectrum of engineering activity,
research has rightly been the pivot between prac-
tice and theory. Massive infusion of the colleges
with government contract research funds over a
period of several academic generations has
brought us to the point where the design naivete
of the instructor is producing students who are
design deprivates. Undergraduate students, in
general, are not being properly prepared to cope
with the very real and extremely complex en-
gineering design problems of today, and if the
present trend toward greater acceptance of the
non-experimental or "paper" thesis continues, the
engineering Ph.D. degree is in danger of becoming
an anachronism. Development of acceptable de-
sign competence in the student is an enormously
difficult task in comparison to the development of
research and theoretical competence. Even if the
engineering professor did not exist in a design

JUNE 1966


Immediately upon receipt of the B.Ch.E.
degree from Rensselaer, Raymond G.
Thorpe was ordered to active duty in the
U. S. Navy and served for four wartime
years. After the war had ended and he had
received his discharge, he pursued and
earned the M.Ch.E. degree at Cornell. He
joined Monsanto's Plastics Division, but
ultimately was drawn back to Cornell where
he has remained for over ten years.
A year of academic leave spent consult-
ing with Monsanto's Central Engineering
Department crystallized thoughts about the
relationship between engineering academe
and industry that Professor Thorpe had
been forming for some years. His observa-
tions were first published in the Monsanto
Technical Review, whose permission to re-
print them here CHEM ENG ED gratefully
acknowledges.



and technology void, the task would still be
difficult and expensive. The industrial sabbatic
leave is one mechanism by which the engineering
professor may, it would seem, acquire the neces-
sary insight and skill for design teaching. All
too often, however, the young engineering pro-
fessor is merely transplanted from his own limited
academic research surroundings to a broad-based
industrial research environment. He gains in re-
search experience, fulfills both his academic and
industrial objectives, and returns to the campus.
His research-conscious academic administrators
are satisfied, but his students continue to remain
design cripples.
Monsanto engineering management believes
that technological upgrading of the young en-
gineering professor is not only necessary, but pos-
sible. What is required is that the professor be
temporarily absorbed into an engineering organi-
zation and permitted to function as a permanent
employee without restriction. Monsanto does not
subscribe to the concept of the prolonged guided
tour, but feels that mutual maximum benefit can
only occur if complete professional interaction
takes place in a climate in which the professor is
not only permitted free access to company per-
sonnel and technology, but most importantly he is
exposed to real economics and encouraged to
make a genuine contribution in decision making
processes. It is assumed that the professor, from
a new vantage point comparable to that of the
process designer, may reach certain inescapable
conclusions with regard to the limitation of the
purely theoretical approach and the true worth

(continued on page 69)







(continued from page 62)
recycle rate. On the other hand plug flow
is quite satisfactory for the steep slope of
case b. The numerical values shown on this
slide represent a heat of reaction of 30 Kcal.
So, simply by making this type of graph we
can tell what class of contacting schemes to
examine and what class to reject.
Other alternative arrangements can also
be considered, for example the cold-shot
cooling of Figure 11. This arrangement


-I


eliminates all the interstate heat ex-
changers; however it is only practical to use
this scheme under the conditions shown in
the figure.
Only a detailed cost study of exchangers,
catalyst, pumping, and the like will tell
which set-up is best in a specific situation;
however, I like this graphical procedure be-
cause it is rapid and simple to use, it is
general, and it is easily extended to non-
abiabatic and to homogeneous reactions. It


h 0


CHEM ENG ED






also gives a visualization, a feel, for what
is going on. I can't help thinking that its
role in reactor design is somewhat like that
of the McCabe-Thiele method in distilla-
tion.
But enough. Let us look at another area
where a search for generalizations is going
on. This concerns multiple reactions and
the question of product distribution.
Suppose we have a feed consisting of the


two dichloro compounds shown on the left
side of Figure 12 and we want to know how
to contact this stream with chlorine so as
to maximize the formation of the desired
trichloro compound. Should we use counter-
current contacting, concurrent contacting,
a vigorously agitated vat through which
chlorine is bubbled, or some other arrange-
ment? The direct way of answering this
question is to evaluate the five rate con-


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JUNE 1966





stants and then to solve the design equa-
tions for the various contacting patterns. It
would be very nice, however, if we had some
general rules allowing us to find the best
contacting pattern, not only for the reaction
shown in Figure 12 but for other reactions
as well, without going through the detailed
calculations, or better still, without even


knowing the values of the rate constants.
Such rules would be a useful guide and a
great timesaver.
A number of such rules have indeed been
proposed to date. Some have been proved,
while others are still conjectures. Let me
present a few of them.
Rule 1. For reactions in parallel, for ex-


a.


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CHEM ENG ED





ample A the concentration level
of materials is the key to proper control
of product distribution: a high concen-
tration of a component favors the re-
action of higher order with respect to
that component, a low concentration
favors the reaction of lower order.
This rule is easy to prove for parallel re-
actions of all kinds including catalytic and
autocatalytic.
Rule 2. For reactions in series, say
A --e R --* S --- T, keeping the composi-
tion homogeneous, thus not allowing
material of different composition to mix,
will allow a maximum amount of any
intermediate to be formed.
This rule has also been proved in general
for any stoichiometry and reaction kinetics
and for any intermediate in the reacting
chain.
Rule 3. Multiple reactions can be looked
upon as a combination of their constitu-


ent series and parallel reactions, as far
as product distribution is concerned. For
example, the consecutive competitive re-
action scheme
A + B--R
R + B---S
can be looked upon as the sum of
A -*R --S and B S
This rule is useful and allows us to break
down complex reaction schemes into their
building blocks, from which the optimum
contacting pattern can easily be found.
Rule 4. With respect to product distribu-
tion every non-continuous contacting set-
up has its steady-state continuous-flow
analog and vice versa.
This rule suggests, for example, that if you
can produce a polymer with a specific mo-
lecular weight distribution in batch opera-
tions then you should be able to design a


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Fig. 12 Multiple-Reaction System

JUNE 1966 67


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continuous process which will give the same
quality product. Also beer, traditionally
batch-prepared, should be produceable con-
tinuously*. I suggest this rule with some
hesitation because it has occasioned rather
antagonistic responses, with counterex-
amples quoted from the literature. In fact,
none of the counterexamples have held up.
Thus, the rule is still open to question -
it has yet to be proved or disproved.
Rule 5. For a given set of reactions,
optimum contacting is independent of
the value of the rate constants.
This rule certainly holds for some of the
simpler reaction schemes, such as those
indicated in Rules 1, 2, and 3. It can be
shown by counterexample, however, that it
does not hold for all reaction schemes. My
opinion is that it holds if reactants enter
in separate feed streams and if their in-
troduction can be controlled, thus
A
Reactor -> Product
B
but that it does not hold if the reactants
enter or are present in the reactor in a
fixed ratio which we are not able to control,
say if they enter in one stream
(A + B ) -! Reactor -4 Product
Rule 6. The steady-state optimum can
never be surpassed by unsteady-state
operations.
This is an interesting rule because recently
a number of papers have appeared suggest-
ing that unsteady state operations can raise
conversions and improve product distribu-
tion. All right then, in terms of general
classes of reacting systems what are the
limitations to this rule? Is it applicable to
homogeneous systems? To those with mass-
transfer-controlled kinetics? This is what
we need to know.
I could suggest others, but I think that
these six are enough to indicate the sort
of thing we are looking for. Actually we
are just beginning timidly to probe this
area, uncertain even of the questions to be
asked, never mind the answers. What we
need is our own modem day Euclid for
this area of CRE.
The examples cited have been intended
to demonstrate that the concern and em-
phasis in CRE is quite different from the
*It is being so produced. Ed.


approaches used in the past. Also, with all
the discussion in educational circles about
what constitutes proper research, I cannot
escape the conclusion that this type of
activity, this search for generality which is
useful for design and prediction, is indeed
engineering research in the proper sense of
the term.
Now to engineering education: here we
must ask how best to prepare students for
prediction and design for the problems of
tomorrow. Well, the basis of all experience
has shown that generalizations and uni-
versals are our best bet, not the details and
particulars of this or that phenomenon or
process. Generalizations constitute teach-
able knowledge, whereas the teaching of
facts that stand alone and outside of any
general conceptual framework is simply the
passing on of today's art. In fact, I may
go as far as to say that until a general point
of view is taken a subject cannot be taught
effectively.
To show that CRE does constitute such
teachable knowledge let us see what hap-
pened to the educational pattern after
CRE appeared on the scene. First of all
the first congress on CRE, where its pro-
gram was first spelled out, was held in 1957.
The 1962 ASEE survey of under-graduate
chemical engineering education in the US
gave these figures:
In 1957 18.5% of schools taught "Kinetics"
In 1961 53.2% of schools taught "Kinetics"
Professor Thatcher, who prepared this re-
port, considered this large jump to be the
most significant shift in the chemical en-
gineering curriculum in this period. Why
the increase? Is it a coincidence that not
long after the CRE approach was intro-
duced this subject which had always
been important all of a, sudden became
teachable? I'm convinced that it is no
coincidence. And if you compare the sub-
ject matter before and after in these
courses I'm confident that you too will say
that the CRE approach was largely respon-
sible for this shift.
As of today my guess is that the 53%
figure has risen to over 80%. This is a re-
markable development especially in view of
the fact, as I mentioned earlier, that it has
taken place without major discussion in
ASEE or AIChE.
CtIEM ENG ED






Finally I'd like to say a few words about
CRE and the main line evolution of the
profession. Early in this century the unit
operations approach was the unifying prin-
ciple which brought order to the study of
the physical operations of chemical tech-
nology, and it became the focal point about
which chemical engineering as a profession
achieved its identity, flourished, and grew.
Now, fifty years later, in the midst of much


Octave Levenspiel was born in 1926 in
Shanghai, China, and grew to manhood
there. He came to the United States in
1946, became a citizen
in 1958, is now married
and has three children.
He attended a German
elementary school, Brit-
ish secondary school and
French University (Uni-
versite l'Aurore) all in
Shanghai. Dr. Leven-
spiel received his B.S.
degree in chemistry in
1947 from the University
of California at Berkeley and his M.S. and
Ph.D. degrees in chemical engineering in
1949 and 1952 from Oregon State University.
Except for one year in research at Uni-
versity of California (1951-52), Dr. Leven-
spiel has been continuously in engineering
education. He taught at Oregon State Uni-
versity (1952-54), Bucknell University


(continued from page 63)
of his own academic research. The student will
inherit a long overdue legacy if administration in
the engineering colleges will recognize that the
intangible non-research activity so necessary for
analysis, synthesis, and design is not only aca-
demically legitimate, but important.
Many industrial managers hold the view that
the market for highly theoretical and research
trained engineering Ph.D.'s in narrow specialty
areas is rapidly becoming saturated. Progressive
graduate schools might very well either: 1, con-
sider adoption of a requirement that a portion
of the engineering doctoral candidates demon-


questioning in the profession about identity
and purpose, I see the promise of a similar
but broader unification, this time encom-
passing the chemical operations and with
CRE as its vehicle. Such is the role in our
ever-changing profession which I envision
for CRE, an approach whose name and
program were clearly spelled out a short
nine years ago. Only time will tell whether
we will shape CRE to fulfill this promise.


(1954-58) and Illinois Institute of Tech-
nology (1958 to the present), where he is
now Professor of Chemical Engineering. In
1963-64 he spent a year at Cambridge Uni-
versity as a National Science Foundation
Senior Post-doctoral Fellow.
In research and scholarly activities his
interests have centered about the use of
knowledge and the development of the gen-
eral approach for prediction and design. In
this line he has published articles on heat
transfer, fluidization, the design of chemical
reactors and flow patterns of fluids in ves-
sels. He has written a review on the last
named subject in "Advances in Chemical
Engineering", Vol. IV. In 1962 he wrote
"Chemical Reaction Engineering" to in-
troduce students to the method of design of
chemical reactors.
Dr. Levenspiel is a Professional Engineer
(State of Oregon) and has strong interests
in the philosophy and history of science,
and in statistics.


C


state an acceptable degree of competence in de-
sign, or 2, adopt curricula which will produce
broadly trained design professionals at the ad-
vanced degree level who are able to utilize
modem computational facilities to the fullest ex-
tent. Training of our young people cannot be
done by professors who are themselves design
illiterates.
Solutions to the problem of design instruction
will not fall out easily. We do, however, have an
effective way of using a new dimension in in-
dustry-university cooperation to scaledown the
problem.


P-I
(f-I


JUNE 1966







THE CHEMICAL ENGINEERING

APPROACH TO ENTROPY

Views of A Non-Thermodynamicist


James L. Throne
Assistant Professor of Chemical Engineering
Ohio University, Athens, Ohio


In a recent article (2), Bates sets forth some
"canonical statements" in an attempt to clarify
some of the irrational concepts and misleading
labels which have evolved with thermodynamics,
probably beginning with Black and the concept
of caloriess" (5). I wish to take issue not only
with Bates' approach to the healing of thermo-
dynamics, but with the entire philosophy of
teaching thermodynamics on the undergraduate-
first year graduate level. In this paper, I would
like to present what might be called a "non-
thermodynamicist" viewpoint to the problems of
teaching thermodynamics, my focal point being
the concept of entropy and its abuse in chemical
engineering. In a subsequent paper, I intend to
present a course outline for thermodynamics on,
say, a first year graduate level in chemical en-
gineering. Such a course has been taught success-
fully at Ohio University by non-thermodynami-
cists.
Forests and Trees
While Bates' arguments regarding misconcep-
tions and irrational nomenclature are well taken,
I am not convinced, first, that his introduction of
another set of nomenclature (regardless of its
rationality) is "first aid," and second, that even
if adoption of a standard set of symbols, de-
finitions, axioms, canonical statements, and what
have you, does take place (highly improbable,
when, for example, Tribus (1) introduces; through
information theory, concepts such as "temper"),
that this type of first aid will not result in direct
application to thermodynamics of the old saw,
"the operation was successful, but the patient
died."
I think that the dying patient, which I prefer
to call mechanical thermostatics (bowing to Tri-
bus' careful definitions here), needs radical sur-
gery, transfusions, and miracle drugs rather than
simple first aid. Perhaps the time has come for
the engineer who utilizes thermodynamics (in its
true sense, i.e., transport of heat, mass, and
momentum) in his work with physical and chemi-
cal phenomena (and here it must be understood
that I am referring to a much greater scope of
problems than those outlined by Bird, Stewart,
and Lightfoot (3)) to render advice and, if neces-
sary, to step in and perform the necessary sur-
gery himself. It may well be that those who now
apply first aid may see only single trees where
entire forests (mostly unexplored) lie waiting.


Philosophy and Thermodynamic Concepts
As is well known, there are two major ways of
approaching the developments of the major cor-
ner-stones of thermodynamics: through classical
or macroscopic developments and through "statis-
tical" or molecular developments. Both paths or-
iginate in physics and both require the person
following the development to make some form of
idealizing assumption. While I will have more to
say on this point in the subsequent paper, I want
to point out two recent important changes in
emphasis, one in each approach. In classical
thermodynamics, much work is being carried out
in "moleculeless" continuum mechanical thermo-
statics. While we seldom use this title, the de-
velopment of the energy equation explicitly de-
pends .upon this approach. In statistical thermo-
dynamics, Tribus' work and that of others dealing
with the development of a thermodynamics which
relies on information theory alone must be con-
sidered as a novel way of developing the same
principles one can obtain from "classical" (as
opposed to quantum) statistical thermophysics.
Undergraduate chemical engineering thermo-
dynamics courses are apparently so crowded now
(too many trees?), that aside from isolated ex-
perimental attempts (1) to introduce statistical
concepts, only the macroscopic approach is
emphasized.
Since we are dealing here only with under-
graduate thermodynamics, and since we must
recognize that thermodynamics is truly a building
block in the over-all concept of chemical engineer-
ing process and product design (or if you prefer,
systems and materials engineering), the pragmatic
philosophy must control the way in which we
present the three laws of thermodynamics and
their applications to real engineering problems.
Let me point out that, unlike Bates, I believe
that the first law of thermodynamics is the
"canonical statement" of temperature, the second,
of energy, and the third, of entropy. My position,
incidently, places me directly in the path of cross-
fire from the mechanicists who choose work and
power for the second and third laws and the
thermodynamicists who choose internal energy and
reversibility. It is not true, in my opinion that the
concept of entropy is more abstract than that of
energy, which in turn, is more abstract than that
of temperature. All concepts are abstract, if one
follows the Platonic philosophy; as a result, if we
are to use these concepts in any pragmatic (and
hence, engineering) way, we must make approxi-
mations to them. The student thinks he knows
what temperature is; he makes a "heat" balance
and thus has some connection, on paper or by

CHEM ENG ED






relation to some physical process such as heat
transfer, with the engineer's idea of conservation
of energy. However, what makes entropy mys-
terious (and thus, to the student at least, "more
abstract") is not the abstract concept, but our in-
ability to measure it with a meter!

What Good is Entropy?
To this question I am tempted to answer
"none," at least as entropy is presently taught
to undergraduate chemical engineers. If we deal
solely with the macroscopic mechanical thermo-
static developments, the classical development of
the concept is through Kelvin refrigerators or
Clausius (Carnot) heat engines, via the TS
versus PV diagrams, to the second law relating
a new variable, called entropy, to a measure of
reversible heat and temperature. The next step
is to rush into irreversible systems, to "prove"
that entropy in any conservative system must
either remain constant or increase with time.
Siedel (6) at one time collected some 25 state-
ments said to define entropy. At this point, rein-
forcement of the concept is needed (again because
we can't measure entropy) and in desperation
and with trepidation, the thermodynamicist dips
into statistical thermodynamics and extracts the
statement that entropy is a measure of the dis-
order of the system. Thereby he escapes cross-
examination either because the student is too
confused to ask for clarification or because no
real use is made of the pseudo-concept anyway.
Now I wish to raise two questions:
1. Why, if statistical thermodynamics is
to be referred to at all, must it be emascu-
lated only to support an archaic approach to
the ideas of teaching entropy?
2. Why is it necessary to teach mechanical
thermostatics to chemical engineers at all?
Carnot engines and Kelvin refrigerators are
great devices for making simple heat balances,
but certainly more realistic examples like
fuel cells, air liquefaction, and fresh water
recovery are more vital. The tired answer to
this is, of course, that the subject has been
presented this way for years, so why rock the
boat?
Boat-rocking notwithstanding, I would now pro-
pose the pragmatic approach to the concept of
entropy, leaning heavily on the recent work of
Coleman (4). Rather than 1) wasting time and
increasing confusion by introducing statistical
thermodynamics and 2) spinning wheels playing
with cycles and reversibility-irreversibility, I sug-
gest that the engineer's approximation to the con-
cept of entropy be put to work. From classical
thermodynamics we can determine whether a pro-
cess is reversible or irreversible, but we have no
idea of the rate at which a process is approaching
an equilibrium state (if ever), or the rate at
which conservative (reversible) energy is being
converted into dissipative (irreversible) energy.
At the risk of sounding like an "Onsagarist," I
propose that entropy be used not as a measure

JUNE 1966


of the reversibility of a system, but as a measure
of conversion of 'recoverable energy into nonre-
coverable or dissipative energy. Furthermore, that
the pragmatic approach to the utilization of
entropy be not in the calculation of the conversion
from stored energy to energy in motion, but rather
in the determination of the time rate of dissipa-
tion of energy in the form of heat. This means
that we are not restricted to Bates' PV versus TS
diagrams, but can now consider interactions be-
tween forces and fluxes (in a general way, or if
preferred, in the linear Onsagar Law way).
Entropy considerations will tell us not .only what
the system will or will not do but will enable us to
obtain a measure of the rate of energy dissipation.
To the student who has suffered through in-
numerable PV versus TS reversible-irreversible
problems and lectures, this "moleculeless con-
tinuum mechanical thermodynamics" approach
appears as an oasis in a desert of sand and
bleached bones of archaic thermodynamicists.

Conclusion
If I seem unkind to present approaches to the
teaching of thermodynamics, it is because my own
experiences as a student are healing very slowly.
Thermodynamics, or classical mechanical thermo-
statics, needs more than first aid. It is dying, and
unless non-thermodynamicists recognize the mal-
ady as malignant consumption and act quickly,
the do-gooders with their adhesive tape will short-
ly embalm the still-warm body.
I have tried to give an example of an entirely
pragmatic approach to a very simple concept,
entropy, and, more importantly, an illustration
with regard to the direct engineering application
of this concept to modern chemical engineering.
This approach would almost certainly allow
Gibbs to rest quietly and I doubt that he is
resting quietly now.
It is admitted that no mention has been made,
either by Bates or me, of chemical thermostatics.
For my part, I support the philosophies of Gibbs
and Denbigh. Additional comments will be forth-
coming.

REFERENCES
1. Balch, C., University of Toledo, personal com-
munication, 1967.
2. Bates, H. T., Chem. Eng. Ed., 1, 37-43, (1966).
3. Bird, R. B., Stewart, W. E., and Lightfoot, E.
N., "Transport Phenomena," John Wiley, New
York, 1960.
4. Coleman, B. D., and Noll, W., Arch. Rational
Mech. Anal., 4, 97-128, (1960).
5. Roller, D., The Early Development of the
Concepts of Temperature and Heat: "The
Rise and Decline of the Caloric Theory," Har-
vard University Press, Cambridge, Mass.,
1955.
6. Siedel, B., University of Delaware, personal
communication, 1963.
7. Tribus, M., "Thermostatics and Thermo-
dynamics," D. Van Nostrand, Princeton, N. J.,
1961.








The Integrity of Chemical Engineering


J. M. Douglas
Associate Professor of
Chemical Engineering


S. A. Miller
Professor of
Chemical Engineering


University of Rochester, Rochester, N. Y.


Chemical engineering is a chemistry-and-physics
based discipline. Chemical equilibria and kinetics
share equal importance with physical equilibria
and transport rates. The conservation statements
about chemical systems are as significant as those
about physical ones. Furthermore, the processing
that accompanies chemical reactions in the manu-
facturing setting depends heavily on diffusive
transport of molecular matter, an aspect of
physical chemistry exploited predominantly by
the chemical engineer. In this kind of physical
operation there has developed peculiar identifica-
tion with the chemical engineering discipline.
By combining chemical (stoichiometry, thermo-
dynamics, kinetics), physico-chemical (diffusion,
phase transformation), and physical (heat trans-
fer, fluid mechanics, strength of solids) principles
under the constraints of practical economics,
chemical engineering has produced processes of
great complexity, carried out in plants that are
often enormous (ten million gallons of product
per day) and costly (hundreds of millions of
dollars). Chemical engineers are responsible for
the entire plant and process-their conception,
development, design, and economic operation -
every component of which must operate properly
with respect to all the others if success is to result.
This is true systems engineering.
The history and present status of engineering
and the engineering industries demonstrate that
there is a distinct need and proper place for the
peculiar educational experience that a chemical
engineering curriculum affords, and for the pro-
duct of that education. Chemical engineering
problems are characterized, indeed, by a degree of
complication greater than those usually identified
with the other traditional engineering fields. The
evolution of our discipline has brought with it
methods of attacking such problems, and concepts
of exceptional power and wide usefulness. A con-
sequence is that chemical engineers, essential to
the process industry, are in demand in a variety
of other environments, industrial and extra-
industrial. One of their great assets is their
ability to work unusually effectively with repre-
sentatives of other disciplines in the solution of
problems of great scope and interdisciplinary
character.
Notwithstanding the success of past advances,
the techniques and insight provided by chemical


engineering are still evolving, and there is strong
reason to believe that contributions arising out of
them will be even greater in the future. Chemical
engineering originated from the consolidation of
the principles common to a number of previously
isolated use-centers: the paper industry, petro-
leum refining technology, acid manufacture, et
cetera. Its great strength derived from its capacity
to unify and establish bonds between these other-
wise diverse, discrete industries, and to provide
education and training that make the chemical
engineer effective in all of them. Today there
seems to be some tendency again to fragment the
field into use areas with new names but distinct
identities: environmental engineering, food en-
gineering, and the like. A competing tendency
would generalize certain of the subdisciplines
shared by several of the engineering fields into
new disciplines: thermal engineering, materials
science, and systems engineering are examples.
In both cases, the identification of interest centers
at which competence from a number of disci-
plines can converge for the attack of broad super-
problems is useful and salutary. But to suggest
that they should subordinate or supplant the
established discipline of chemical engineering is
to suggest the destruction of the burgeoning
promise of tremendous future contributions ori-
ginating in our field.
We submit that future society will benefit
most from the maintenance and continued evolu-
tionary development (at the most fundamental
level consistent with the definition of the field)
of an academic discipline erected on the subject
matter at the core of chemical engineering today.
Simultaneously, vigorous effort should be directed
to those developments at or near the diffuse
boundaries where other currently defined disci-
plines, basic and applied, and chemical engineer-
ing merge. We believe that such a frankly disci-
plinary approach optimizes the task of conserving
and extending the treasure of knowledge, under-
standing, and skill for which chemical engineering
has become a particular repository; of applying
that treasure to new creative goals in the world
of the process industry; and of sharing major
interdisciplinary challenge with others in a sig-
nificant effort which, in using without sacrificing
its contributing collaborators, is enduringly
synergistic.
CHEM ENG ED















h#EMJ I7




fe1 A7


INDEX FOR VOLUME 1 (1965-1966)


AUTHOR INDEX


SUBJECT INDEX


Abraham, W. H. ..--
Bates, H. T. ----.--
Berg, L. ---- ......-
Burkhart, L. E. -----
Burnet, G. -------..--.-
Burr, A. A. ---- ....--
Chilton, T. H ........--
Christensen, J. J ......-
Douglas, J. M ---. ..-
Genereaux, R. P. ----
Griffith, D. E. ------
Hamielec, A. E. .---
Hubbard, R. M ---....-
Kenyon, R. L. ..----------
Kiser, K. M. ------..
Levenspiel, 0 --...--------.
Madonna, L. A. ----.---
Miller, S. A. -------
Murphy, G. -------
Pfeffer, R ...---- ...
Schmidt, A. X. .....----
Snyder, J. R. ------.
Thorpe, R. G. -----.
Throne, J. L. ---...--
Wheelock, T. D. ..--
Willis, M. T....... ------
Wise, D. L. ------ ..-
Woods, D. R. ----.-
Yerazunis, S. ------. ...--.--


-------------.... 12,
------------------..........
---------------- .(1)


.....-----------------.-.-------
............................
............................











1
------.----------------------
----------------------------







1
.... ...... .
---.----...........-----
-...----- -----.......






--1------------------------
............................
............................
............................

............................
............................
............................








----------------------------


--------------. 19,


Bifurcation ------.......------ ---------..... 1, 5, 3, 7
Career choice ----------...... .......---------------- 12
Chemical Engineering Division -- (1) iii, (1) iv


1
iv
7
9
14
72
27
1
52


Cooperative programs
Core curricula --..-
Curricula -
Design
Engineering science
Entropy -
Five-year programs
"Goals" Report ....---
Industry, relations with


...-------- ... 14
--- -----... 24
--- 1, 3, 5, 7, 14, 25
(3) iii, 19, 52, 55
-----....--. 24
-- ------- 70
--------- 14
------- (2) iii
------- 9, 27, 63


10 Integrity of Chemical Engineering
15 Interdisciplinary programs ....-.
48 Job choice --------------
55 Laboratory demonstrations ......---
24 Multifurcation -------... ...--
72 Option, curricular ..-----
3 Overhead projector ----..... ------
13 Process control (book review)
13 Professional challenge ..-------
11 Professional practice ----....---
53 Reactor design ---- --------
70 Reactor design (book review) ---
5 Rensselaer program ---....--------...
16 Science-oriented curricula ---- .
24 Teaching aids ----------- ...
52 Teaching load -----.-------
7 Thrmodynamics -----------
Transport phenomena -------
Trouble-shooting ---..-------...
Unit operations --..--......--.....
Visual aids ...---- ..............-------------


--- 72
1, 24
12,44
---- 10
--... 1,3
1,3,5, 24
---.... 11
---- 30
---- 45
-- 9,44
-- .. 55
--- 48
... 7
3, 7, 24
- 10, 11
-. .... 13
_ 37, 70
---. 46
- ---- 19
- --- 46
--.... 10


JUNE 1967







CHEMICAL ENGINEERING EDUCATION
? / 201 Gavett Hall,
University of Rochester,
Rochester, N.Y. 14627.


November 17, 1967



Dear Subscriber:

No, there's nothing wrong with your mail
service. It is your editors who are responsible
for your receiving Volume 1, Number 4 of CHEMical
ENGineering EDucation in November, 1967, instead of
June, 1966. But although the masthead date shown
on this issue is technically correct, you may be
assured that the contents are contemporary. Copy
for all of the material that it carries except the
feature article was received within the last six
months -- some of it, notably advertising copy,
only a fortnight ago. And Professor Levenspiel's
fine paper is certainly as readable today as it
was in mid-66.

We are sorry for the delay. We hope that
you find the issue rewarding in spite of having to
wait for it so long.

The official publication of ASEE's Chemical
Engineering Division will come to you in the future
under new, extremely competent editorial leadership.
I know that bright days lie ahead for all of us readers
who are interested in chemical engineering education.
Meanwhile John Bartlett, Al Cooper, and I are grate-
ful for the privilege we've had to serve you and the
Division during an interim period in the life of
CHEMical ENGineering EDucation.

Sincerely yours,


S. A. Miller
Editor

SAM: sm




CHEMICAL ENGINEERING EDUCATION Non-Profit Organization
201 Gavett Hall, U. S. POSTAGE
University of Rochester, PAID
Rochester, N. Y. 14627. ROCHESTER, NEW YORK
Permit No. 780




Full Text

PAGE 1

CHEMl/@1{} ENGl!li!/!l!llllllli!l!B ED!!IJ@l{Jll!l!lJ!i!I JUNE1966

PAGE 2

chemical engineering texts from Prentice-Hall New for 1968 ... INTRODUCTION TO FLUID MECHANICS by Stephen Whitaker, University of California at Davis. Provides an exceptionally thor ougb treatment of the macroscopic ( or integral I momentum and mechanical energy equations. February 1968, approx. 480 pp., $12.00 MATHEMATICAL METHODS IN CHEMICAL ENGINEERING: MATRICES AND THEIR AP PLICATION by Neal R. Amundson, Univer sity of Minnesota. Outlines the elementary theory of matrices discussing eigenvalue problems, Hamilton -Cayley's theorem, and systems of linear differential equations and algebraic equations. 1966, 270 pp., $12.50 FOUNDATIONS OF OPTIMIZATION, by Douglass J. Wilde, Stanford University and For approval copies, write: box 903 PRENTICE-HALL Charles S. Beightler, University of Texas. Covers both the direct and indirect optimi zation techniques; extends the new non linear technique of geometric programming to functions with negat[ve signs and re versed inequalities. 1967, 480 pp., $12.95 KINETICS OF CHEMICAL PROCESSES by Michel Boudart, Stanford University. Ex plains the kinetic analysis of elementary steps, single reactions, and reaction net works for chem i sts interested in reactivity and chemical engineers interested in re actors. April 1968, approx. 220 pp., $7.50 Englewood Cliffs, New Jersey 07632 -----------------,.1

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CHEM!l@JfJ!l ENG!lli!!!l!llllllli!!!B ED!ll@JfJlll!(JJli!J Contents for Volume 1, No. 4, June '66 55 Changing Attitudes To Reactor Design 0. Levenspiel 70 The Chemical Engineering Approach To Entropy J. L. Throne 72 The Integrity of Chemical Engineering DEPARTMENTS iii Editors' Corner 63 Speaking Out J. M. Douglas and S. A. Miller R. G. Thorpe EDITORS' mm Chemical engineering curricula today face the sternest confrontation of their entire history, a challenge from inside the world of engineering itself that amount s to questioning their raison d'etr e. Yet if the discipline of chemical engineer ing is reality and if the chemical process industry is not illusion, there should be no doubt about the reasonable purpose of chemical engineering e ducation The core of that purpose is three kerneled: to prepare its graduates at all levels to solve the engineering problems of c hemical processing, from research to marketing; to pro vide clear educational leadership in chemical en gineering in both academic and industrial spheres; and to share strongly the technical leadership of chemica l engineering. The central kerne I is of c ours e, the first. A not inconsiderable piece of the student's equipment with which his chemical engineering education should outfit him is attitude He must be conditioned to seek creative solutions to com plex, real-world problems. He must be able to look at whole systems and not merely the com ponents thereof. He must be stimulated to sus tain a lifetime of continued learning And he must be aware of his field recognize its power, and sense the satisfaction it can yield to its practitioners Indeed perhaps the most signifi cant burden laid upon late-twentieth-century fac ulties of chemical engineering is one of attitude. We who teach must impress our undergraduate and graduate students with the imperative of continued scholarship and the reward that goes with it. We must find ways to encourage disci plined originality. Above all we must reflect the genuine excitement of the real life engineer ing problem. Without such inspiration, our stu dents can be expected to view the world of chem ical engineering toward which their college ex perience should direct them with mild interest at best, and possibly with distaste. The persistent maintenance of infectiously zestful attitude is a demand of inestimable importance that we edu cators cannot evade. ,------------CHEMICAL ENGINEERING EDUCATION--------The official journal of the Chemical Engineering Div isi on American Soc ie ty for Engineering Education JUNE 1966 Editor Shelby A Miller Consulting Editor Albert H. Cooper Assistant Editor John W Bartlett Publications Committee of CED L. Bryce Andersen Chairman Charles E. Littlejohn E P. Bartkus James H. Weber Executive Committee of CED Chairman John B. West Chairman-elect J. A. Bergontz Secretory-Treasurer William H Honsteod Elected Committeemen J T. Banchero W H. Corcoran Past Chairman George Burnet CHEMICAL ENGINEERING EDUCATION i s pub lished four times during the academic year by the Chemical Engineering Division, Ameri can Society of Education. Publication months: October, January, April, June. Publication and editorial offices: 201 Gavell Holl, Uni versity of Rochester, Rochester, N. Y. 14627. T i tle registered U. S. Potent Office Subscription rates: To Chemical Engineering Division members, $3 00 per year ; to no members in the Western Hemisp here, $4.00 per year ; to non members outside the Wes t ern Hemisphere, $5 00 per year; single issue price, $1.50. Advertis i ng rates quoted upon request. iii

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iv THE AMERICAN SOCIETY FOR ENGINEERING EDUCATION FOURTH ANNUAL CHEMICAL ENGINEERING DIVISION LECTURESHIP AWARD to Dr. Octave Levenspiel HE CHEMICAL ENGINEERING Division Lectureship U Award of the American Society for Engineering Education is an annual award of $1000 to a distinguished engineering educator for outstanding achievement in funda mental chemical engineering theory or practice. It is spon sored by the 3-M Company. The recipient of the Fourth Annual Award, presented on June 22, 1966, was Octave Levenspiel, Professor of Chemical Engineering at Illinois Jnstitute of Technology, who responded with an address on "Changing Attitudes to Reactor Design." Previous award winners and the subjects of their lectures were: 1965, Leon Lapidus, Princeton University "Aspects of Modern Control Theory and Application" 1964, C. R. Wilke, University of California (Berkeley) "Mass Transfer in Turbulent Flow" 1963, A. B. Metzner, University of Delaware "Non-Newtonian Fluids" CHEM ENG ED

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Changing Attitudes TO REACTOR D ESIGN Octave Levenspiel Professor of Chemical Engineering Illinois Institute of Technology, Chicago, Illinois Exciting things are happening today in the field loosely covered by the terms chemical technology, reactor design, and kine.tics, for, without fanfare, study re ports, or discussion in ASEE or in AIChE, a new way of looking at this subject was recently introduced. The new view may be characterized by the phrase Chemical Re action Engineering, and its friendly recep tion by the profession is causing a remark able change in our approach to and our teaching of chemical technology. I should like to discuss this new develop ment, to sketch its strategy as opposed to the traditional approach, to give a few ex amples to illustrate what I mean, to show how it has affected our pattern of educa tion, and finally to consider what I feel is its place in the main line evolution of our profession. In the traditional approach, we engineers were more concerned with the peculiar and unique features of this or that reacting system than with the similarities and com mon characteristics among such systems. It is true that the unique features make for the success of a particular process. It is also true that what is useful for the pro cesses of tomorrow are the analogies and generalizations which we are able to extract from the technology of today. Thus for predictive and design purposes we need generalizations; in the past, however, we have emphasized the particular and the unique. In the U.S. of the forties we saw the first break with this philosophy. The gen eral approach was brought forward; how ever, it was soon channelled, narrowed, and dominated by the problems and interests of the oil industry. Hence there was an overwhelming emphasis on catalytic re actions and a rather unhealthy preoccupa tion with developing models to account for their kinetics. Little wonder that this sub ject was known and is still known as applied kinetics, chemical engineering kinetics, or just kinetics, despite the fa.ct that finding IN Stoich lh.ermo ( Reactor I OUT ( Con.ta.cting pattern. a.nd. con.clU:lons Fig. 1 Schematic of Chemical Reactor Engineering JUNE 1966 55

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Homo9e.n..eous He.l:e:ro5 e.n.eo us M~~le. F-Scnt J f~FJl~-slf~c.j Stc,c~ ) \GLnet,csjeontactiMI fh~r:m~n.ce '1 Opt,m. Tn.ermo -.J frtcl,ctio~ Fig. 2 Classification of Reacting Systems the rate of reaction is only one phase in the over-all problem of scale-up and proper reactor design. In the late fifties a bolder attempt at generalization was started in Europe. To emphasize its concern with the over-all problem it was termed Chemical Reaction Engineering or CRE for short. As the name suggests, we are here concerned with the "engineering" of chemical reactions, or their efficient exploitation. The philosophy, then, is to seek common factors to link processes and to develop broad methods of attack for problems, and this is done with the conviction that these methods can be used as a basis for design in all areas of application, whether it be in polymer pro cessing, industrial metallurgy, pharmaceu tical manufacture, foods, biological pro cesses, high-temperature reactions, or any other operation in fact wherever a new material or chemical species is to be pro duced economically on a commercial scale. In a nutshell the concern of CRE is shown in Figure 1. Thus we engineers must deter mine how to treat a feed stream so as to obtain most economically a most desirable product stream. More specifically we must decide what temperature, pressure, and contacting pattern to use, and in general this decision requires knowledge of the stoichiometry, thermodynamics and kine tics of the systems. It is convenient to classify reacting sys tems according to the phases participating in the reaction. As shown in Figure 2 the broad division is between homogeneous and heterogeneous systems. In the former, one fluid phase alone moves through the reactor 56 and only chemical kinetic factors influence the rate. In the latter classification, we may have to deal with additional problems aris ing as a direct consequence of the hetero geneity of the system, such as phase equili brium, mass transfer from phase to phase or from phase to interface, and contacting pattern of the phases. As may be expected, heterogeneous systems represent a more complex situation. Next we see that homogeneous systems may be divided into systems where only one reaction occurs and into systems where two or more reactions occur simultaneously. The reason for this split is that different questions are pertinent in these two situa tions. With one reaction all we ask is to maximize conversion with a most economi cal reactor arrangement; with multiple reactions we ask how (by what tempera ture, pressure, and contacting pattern) to promote the formation of the desired product and depress the formation of all other undesired materials. The primary concern is not the same in the two cases. And so it is with heterogeneous systems, where we have (in what I consider to be the order of complexity) solid-catalyzed gas-phase reactions, non-catalyzed fluid solid reactions (reduction of metal oxides, burning of coal), fluid-fluid systems (ab sorption with reaction), and finally the catch-all et cetera classification which in cludes all other multiphase systems. These systems can be horribly messy to treat, and in the interest of simplicity I shall avoid them in this paper, even though they in clude many processes ofgreat industrial importance. CHEM ENG ED

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JUNE 1966 'I.cc X -l$-< en C: 0 -~ ::, w C: O> "iii Q) C in C: ... I a.. u. ... 0 ..... (.) :3 cc I M C'l u:: 57

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The line at the bottom of Figure 2 shows the usual stages in our control of reacting systems all the way from initial studies on thermodynamics and stoichiometry to a search for optimum operation. Our ability to handle problems is quite different in the different classifications. For example in homogeneous single-reaction systems we are at the stage of selecting optimum set-ups. In catalytic systems we would be just about as far along if it were not for the obstinate problem of represent ing and properly accounting for the kine tics of the reaction. With fluid-fluid sys tems our difficulties are everywhere: how to represent the rate usefully, how to ac count for movement of reacting species in the flowing phases, and in general how to predict the extent of reaction given all kinetic and equilibrium information. This means that except for special cases we have trouble trying to develop a design equation for this classification. And so it is with the other classifications shown in Figure 2; in each there are particular difficulties to be overcome. Let me next offer three examples of re cent research activities in CRE. They must be brief for this review to conform to reaExothermic \ I sot-he.rma.\ To sonable length. Nevertheless I hope tha t they will provide a feeling for the sort of thing that is going on. The first example concerns the search for an optimum set-up for the single catalylic reaction whose thermodynamics and s t oi chiometry are known, and let us restrict ourselves to adiabatic operations in packed beds. Now there are many possible ways of running such a reaction for example single-stage operations in one packed bed reactor, multistage packed-bed operations with interstage heat transfer, operations with recycle of fluid between stages or with bypassing of certain stages with fresh f eed. And for every set-up we can choose the temperature of fluid entering the various stages. With all these factors at our con trol, are we to make a computer search of every possibility that comes to mind or are there methods which give us a feel for the situa t ion and allow us to reject quickly many of the alternatives while retaining those few which are promising? Since I favor the latter approach let me outline a graphical method which does just that. Figure 3 shows the design equat i ons for the flow patterns of interes t : the ideals of plug flow and backmix flow and the inter\Erd&m~c \s~r,~o .. \ t\cl,obo.+~ Fig. 4 Typical Temperature-Conversion Graphs 58 CHEM ENG ED

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mediate of recycle flow. It should be noted that plug and backmix flows represent the extremes of recycle flow when the recycle ratio m becomes zero and infinite, respec tively. These equations indicate that the four quantities, V (size of reactor), FAo (feed rate of reactant A), -r A (rate of reaction), and XA (conversion of reaction) \ \ ,.._ __ --are all interrelated, and knowing any three of these quantities gives the fourth. The sketches in Figure 3 are a graphical repre sentation of these equations for any ar bitary kinetics and the shaded areas are a measure of the size of reactor needed for a given duty. These expressions are quite basic to CRE. -I' ' -g\ --..... ,J ........ _, ......... I E ,,-.......... oJ -..... o i \ E ...9! .... ' -0 :l 1 d '--Jj f en !,,_. C: CL u E ____. o E E d QI d +-' f en 0 ... 'Q) 0.. e C ::::, ~o ... 0 CQ ... Q) v a. II E E Q) Iv ::> E .~ ::::, 4 E Q_ -~ -4a. .,,_ !l0 o> 0 II I 0 ,,,.It) \ c5.2> u. \ ff') ' '--" .... \ ......... 0 c..+\ ----.-.. II ' ' ..... ........ ---'"jj'11c.f ~< I II x< JUNE 1967 59

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Figure 4 is the temperature-conversion graph for typical exothermic and endo thermic reactions when starting with a given feed. Shown in this figure are the equilibrium curves obtained from ther modynamic considerations and typical re action paths starting with feed at tempera ture T 0 both for isothermal and adiabatic operations. In the succeeding figures we c t -i .,, d LL \-E ~ ---. ~ --4..._ __ f j 'i, I '.:) E E I 'i,,. P0 "' w _ ,.. __ olu~ shall build on this plot. I shall discuss only the exothermic situation, but I include in the figures the corresponding endothermic reaction for the reader who wishes to pur sue that case on his own. The l ogic of the two situations is somewhat similar. Now to Figure 5: the dotted lines show the locus of constant reaction rate, and this general shape again is typical of all re.a. a (!J ,. Cl en ,.... 0 .... CJ ca Q) l a: := 00 J; t LL en :::, I a: ,.... 0 -'ca ., E 0.,i:i C. 0 I co .5?> LL c a I ----------160 ...c X CHEM ENG ED

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actions. Next, to minimize the size of re actor we want to choose the temperature where the rate is maximum for that com position. The heavy line in this figure shows the progression of temperatures which satisfy this condition. Comparing with Figure 4 we see that the slope of this opti mum line is opposite that for adiabatic operations. Because of the opposite slopes the way a) E ::, ':> 0 ~o (.\1 > I) c:.J0 < >< 75 < -1 ~4': 1a,-d .. ~I/""b..---0 ...______, p "-It< ] '-) .. 0 )... Lt: d (/) 'X s.d: to approach this optimum with plug flow units is shown in Figure 6. Abiabatic stages with in.tercooling are required. It is appar ent that intercooling simply shifts the operating line horizontally to the left on this graph. Since it is impractical to use a large number of stages, we may start by examin ing one-stage, two-stage, and then three stage operations. Figure 7 illustrates how 3: .,J,.. ::, 0 0 u. (!J' C> :::, C: Q) N ui 0 .... CJ Ica Q) a: Q) C) ca .... (/) 6 3: I IE :::, E C: I ..... .2> u. f0 II<( >< .c 0. -.... ..... ..... -.-,/IIIIIIP ""' x'X' 0 JUNE 1966 61

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,,, ..,. ---..E. <11 (/) ~N ...... "' / --1 ~< / _.;_,. -' u Q) a: Q) .!:::! (/) lo.. 0 +-' u ca Q) a: Cl) C) ca +-' (/) 6 IE ::::, E C: I co ,, I \ .2> t>I x
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R. G. Thorpe Associate Professor of Chemical Engineering Cornell University, Ithaca, New York About-The Industry-University Interface The classical conception of an interface, bounded by several high resistance films and across which mass and energy are transported under the in fluence of a driving force, has undoubtedly been of more value in the solution of real problems than any other concept one c.ould name. Engineers have always been singularly perceptive, if not ruthless, in the adaptation of engineering ter minology to the description of human behavior It is not surprising then, to find "interface" being used ir a particularly appropriate sense to de scribe the transfer of intellectual capacity between groups which have quite different responsibilities and interests. No empty verbalism this for the use carries with it the connotation th'at a re sistance to the transfer process does in fact exist. I have returned to the academic cloister from a most interesting and exciting sabbatic leave dur ing the 1965-66 academic year as a full-time en gineering consultant in the Engineering Tech nology and Services Branch of Monsanto's new Central Engineering Department. I functioned during the entire period directly with Monsanto professionals in the solution of short-term prob lems and in the development of new technology for long-term application. I now can see the pro cess industry-engineering college interface in de tail. The resistance on the industrial side is mini mal, but it is certain that the academic sid e re sistance is much too high for the single reason that there appears to be much more concern in the engineering colleges with advancing science than with making the advances of science useful Clearly, there has been serious abrogation of re sponsibility by the colleges in the teaching of analysis, synthesis, and design to meet modern day demands both at the undergraduate and more seriously, at the Ph.D. level. In the broad spectrum of engineering activity research has rightly been the pivot between prac tice and the<>l"y. Massive infusion of the colleges with government contract research funds over a period of several academic generations has brought us to the point where the design naivete of the instructor is pr:oducing students who are design deprivates. Undergraduate students, in general, are not being properly prepared to cope with the very real and extremely complex en gineering design problems of today, and if the present trend toward greater acceptance of the non-experimental or "paper" thesis continues, the engineering Ph.D degree is in danger of becoming an anachronism. Development of acceptable de sign competence in the student is an enormously difficult task in comparison to the development of research and theoretical competence Even if the engineering professor did not exist in a design JUNE 1966 SPEAKING Immediately upon receipt of the B.Ch.E. degree from Rensselaer, Raymond G. Thorpe was ordered to active duty in the U. S. Navy and served for four wartime ye ars. After the war had ended and he had received his discharge, he pursued and earned the M.Ch.E degree at Cornell. He joined Monsanto's Plastics Division, but ultimately was drawn back to Cornell Vl-1-lere he has remained for over ten years. A year of academic leave spent consult ing with Monsanto's Central Engineering Department crystallized thoughts about the relationship between engineering academe and industry that Professor Thorpe had been forming for some years. His observa tions were first published in the Monsanto Technical Review whose penni.ssion to re print them here CHEM ENG ED gratefully acknowledges. and technology void, the task would still be difficult and expensive. The industri1d sabbatic leave is one mechanism by which the engineering pr:ofessor may, it would seem, acquire the neces sary insight and skill for design teaching. All too often, however the young engineering pro fessor is merely transplanted from his own limited academic research surroundings to a broad-based industrial research environment. He gains in re search experience, fulfills both his academic and industrial objectives and returns to the campus. His research-conscious academic administrators are satisfied, but his students continue to remain design cripples. Monsanto engineering management believes that technological upgrading of the young en gineering professor is not only necessary, but pos sible What is required is that the professor be temporarily absorbed into an engineering organi zation and permitted to function as a permanent employee without restriction Monsanto does not subscribe to the concept of the prolonged guided tour, but feels that mutual maximum benefit can only occur if complete professional interaction takes place in a climate in which the professor is not only permitted free access to company per sonnel and technology, but most importantly he is exposed to real economics and encouraged to make a genuine contribution in decision making processes. It is assumed that the professor, from a new vantage point comparable to that of the process designer, may reach certain inescapable conclusions with regard to the limitation of the purely theoretical approach and the true worth ( continued on page 69) 63

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( continued from page 62) recycle rate. On the other hand plug flow is quite satisfactory for the steep slope of case b. The numerical values shown on this slide represent a heat of reaction of 30 Kcal. So, simply by making this type of graph we can tell what class of contacting schemes to examine and what class to reject. Other alternative arrangements can also be considered, for example the cold-shot cooling of Figure 11. This arrangement \ ... \ eliminates all the interstage heat ex changers; however it is only practical to use this scheme under the conditions shown in the figure. Only a detailed cost study of exchangers, catalyst, pumping and the like will tell which set-up is best in a specific situation; however, I like this graphical procedure be cause it is rapid and simple to use it is general, and it is easily extended to non abiabatic and to homogeneous reactions. It Q) N en ... 0 ti IU Q) a: Q) C) IU ..... CJ) 6 IE ::, E C \ ......... \. ,---I CJ) .!2> 64 \ '--\ ... ... \ \ \ \ \ \ \ \ \ \ \ C: u. C!r CHEM ENG ED

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also gives a visualization, a feel, for what is going on. I can't help thinking that its role in reactor design is somewhat like that of the McCabe-Thiele method in distilla tion. But enough. Let us look at another area where a search for generalizations is going on. This concerns multiple reactions and the question of product distribution. Suppose we have a feed consisting of the ""' two dichloro compounds shown on the left side of Figure 12 and we want to know how to contact this stream with chlorine so as to maximize the formation of the desired trichloro compound. Should we use counter current contacting, concurrent contacting, a vigorously agitated vat through which chlorine is bubbled, or some other arrange ment? The direct way of answering this question is to evaluate the five rate conle C 0 0 0 ('() ,. gl l('(? ..J Cl C -~ f! Q) 0. 0 (.) -~ n, JUNE 1966 0 ol ('("J II ii a... 0 if) I I I II Q) Q_ 0 C/J ----1 ----+--t\fl. C) d .c ~ "C I 0 .... !ii LL 65

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stants and then to solve the design equa tions for the various contacting patterns. It would be very nice, however, if we had some general rules allowing us to find the best contacting pattern, not only for the reaction shown in Figure 12 but for other reactions as well, without going through the detailed calculations, or better still, without even \ \ \ \ \ \ \ \ \ \ \ knowing the values of the rate constants. Such rules would be a useful guide and a great timesaver. A number of such rules have indeed been proposed to date. Some have been proved, while others are still conjectures. Let me present a few of them. Rule 1. For reactions in parallel, for exC) C: 0 0 u \ \ .... 0 ..c: en 66 \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ I \ I I \ I 1 X ----+-6 0 u I .!2> LL CHEM ENG ED

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ample A <_f the concentration level of materials is the key to proper control of product distribution: a high concen tration of a component favors the re action of higher order with respect to that component, a low concentration favors the reaction of lower order. This rule is easy to prove for parallel re actions of all kinds including catalytic and autocatalytic. Rule 2. For reactions in series, say A...,.. R S T, keeping the composi tion homogeneous, thus not allowing material of different composition to mix, will allow a maximum amount of any intermediate to be formed. This rule has also been proved in general for any stoichiometry and reaction kinetics and for any intermediate in the reacting chain. Rule 3. Multiple reactions can be looked upon as a combination of their constituent series and parallel reactions, as far as product distribution is concerned. For example the consecutive competitive re action scheme A+ B-R R + B-s can be looked upon as the sum of A ~R -s and B
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continuous process which will give the same quality product. Also beer, traditionally batch-prepared, should be produceable con tinuously*. I suggest this rule with some hesitation because it has occasioned rather antagonistic responses, with counterex amples quoted from the literature. In fact, none of the counterexamples have held up. Thus, the rule is still open to question it has yet to be proved or disproved. Rule 5. For a given set of reactions, optimum contacting is independent of the value of the rate constants. This rule certainly holds for some of the simpler reaction schemes, such as those indicated in Rules 1, 2, and 3. It can be shown by counterexample, however, that it does not hold for all reaction schemes. My opinion is that it holds if reactants enter in separate feed streams and if their in troduction can be controlled, thus A B Reactor Product but that it does not hold if the reactants enter or are present in the reactor in a fixed ratio which we are not able to conttol, say if they enter in one stream ( A + B ) Reactor Product Rule 6. The steady-state optimum can never be surpassed by unsteady-state operations. This is an interesting rule because recently a number of papers have appeared suggest ing that unsteady state operations can raise conversions and improve product distribu tion. All right then, in terms of general classes of reacting Sj'Stems what are the limitations to this rule? Is it applicable to homogeneous systems? To those with mass transfer-controlled kinetics? This is what we need to know I could suggest others, but I think that the s e s i x are enough to indicat e the s ort of thing we are looking for. Actually we are just beginning timidly to probe this area, uncertain even of the questions to be asked, never mind the an s wers. What we need is our own modem day Euclid for this ar e a of CRE. The e x amples cited have been intended to demon s trate that the concern and em phasis in CRE i s quite different from the It i s b e in g so pr o du ce d. E d. 68 approaches used in the past. Also, with all the discussion in educational circles about what constitutes proper research, I cannot escape the conclusion that this type of activity, this search for generality which is useful for design and prediction, is indeed engineering research in the proper sense of the term. Now to engineering education: here we must ask how best to prepare students for prediction and design for the problems of tomorrow. Well, the basis of all experience has shown that generalizations and uni versals are our best bet, not the details and particulars of this or that phenomenon or process. Generalizations constitute teach able knowledge, whereas the teaching of facts that stand alone and outside of any general conceptual framework is simply the passing on of today's art. In fact, I may go as far as to say that until a general point of view is taken a subject cannot be taught effectively. To show that CRE does constitute such teachable knowledge let us see what hap pened to the educational pattern after CRE appeared on the scene. First of all the first congress on CRE, where its pro gram was first spelled out, was held in 1957. The 1962 ASEE survey of under-graduate chemical engineering education in the US gave these figures: In 1957 18 5% of schools taught "Kinetics" In 1961 53.2 % of schools taught "Kinetics" Professor Thatcher, who prepared this re port, considered this large jump to be the most significant shift in the chemical en gineering curriculum in this period. Why the increase? Is it a coincidence that not long after the CRE approach was intro duced this subject which had always been important all of a. sudden became teachable? I'm convinced that it is no coincidence. And if you compare the sub j ec t matter before and after in these cour s es I'm confident that you too will say that th e CRE approach was largely respon sible for this shift. As of today my guess is that the 53 % figure has risen to over 80 % This is a re markable development especially in view of the fa c t a s I m e ntion e d earlier that it has taken place without major di s cus s ion in ASEE or AIChE. Cl;IEM ENG ED

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Finally I'd like to say a few words about CRE and the main line evolution of the profession. Early in this century the unit operations approach was the unifying prin ciple which brought order to the study of the physical operations of chemical tech nology, and it became the focal point about which chemical engineering as a profession achieved its identity, flourished, and grew. Now, fifty years later, in the midst of much Octave Levenspiel was born in 1926 in Shanghai, China, and grew to manhood there. He came to the United States in 1946, became a citizen in 1958, is now married and has three children. He attended a German elementary school Brit ish secondary school and French University (Uni versite l' Aurore) all in Shanghai. Dr. Leven spiel received his B.S degree in chemistry in 1947 from the University of California at Berkeley and his M.S and Ph.D degrees in chemical engineering in 1949 and 1952 from Oregon State University. Except for one year in research at Uni versity of California (1951-52) Dr. Leven spiel has been continuously in engineering education. He taught at Oregon State Uni versity (1952-54) Bucknell University (continued from page 63) of his own academic research The student will inherit a long overdue legacy if administration in the engineering colleges will recognize that the intangible non-research activity so necessary for analysis, synthesis, and design is not only aca demically legitimate but important Many industrial managers hold the view that the market for highly theoretical and research trained engineering Ph.D.'s in narrow specialty areas is rapidly becoming saturated. Progressive graduate schools might very well either: 1, con sider adoption of a requirement that a portion of the engineering doctoral candidates demonJUNE 1966 questioning in the profession about identity and purpose, I see the promise of a similar but broader unification, this time encom passing the chemical operations and with CRE as its vehicle. Such is the role in our ever-changing profession which I envision for CRE, an approach whose name and program were clearly spelled out a short nine years ago Only time will tell whether we will shape CRE to fulfill this promise. (1954-58) and Illinois Institute of Tech nology (1958 to the present), where he is now Professor of Chemical Engineering In 1963-64 he spent a year at Cambridge Uni versity as a National Science Foundation Senior Post doctoral Fellow. In research and scholarly activities his interests have centered about the use of knowledge and the development .of the gen eral approach for prediction and design. In this line he has published articles on heat transfer, fluidization, the design of chemical reactors and flow patterns of fluids in ves sels He has written a review on the l a st named subject in "Advances in Chemical Engineering" Vol. IV In 1962 h e wrote Chemical Reaction Engineering to in troduc e students to the method of design of chemical reactors. Dr Levenspi e l is a Professional Engin ee r (State of Oregon) and has strong interests in the philosophy and history of science, and in statistics strate an acceptable degree of competence in de sign or 2 adopt curricula which will produce broadly trained design professionals at the ad vanced degree level who are able to utilize modern computational facilities to the fullest ex tent. Training of our young people cannot be done by professors who are themselves design illiterates. Solutions to the problem of design instruction will not fall out easily. We do, however have an effective way of using a new dimension in in dustry-university cooperation to scaledown the problem. 69

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THE CHEMICAL ENGINEERING APPROACH TO ENTROPY Views of A Non-Thermodynamicist James L. Throne Assistant Professor of Chemical Engineering Ohio University, Athens, Ohio In a recent article (2), Bates sets forth some "canonical statements" in an attempt to clarify some of the irrational concepts and misleading labels which have evolved with thermodynamics, probably beginning with Black and the concept of "calorics" (5). I wish to take issue not only with Bates' appr oach to the healing of thermo dynamics, but with the entire philosophy of teaching thermodynamics on the undergraduate first year graduate level. In this paper, I would like to present what might be called a "non thermodynamicist" viewpoint to the problems of teaching thermodynamics, my focal point being the concept of entropy and its abuse in chemical engineering. In a subsequent paper, I intend to present a course outline for thermodynamics on say, a first year graduate level in chemical en gineering. Such a course has been taught success fully at Ohio University by non-thermodynami cists. Forests and Trees While Bates' arguments regarding misconcep tions and irrational nomenclature are well taken I am not convinced, first, that his introduction of another set of nomencla ture (regardless of its rationality) is "first aid," and second, that even if adoption of a standard set of symbols, de finitions, axioms, canonical statements, and what have you, does take place (highly improbable, when for example, Tribus (1) introduces,through information theory, concepts such as "temper"), that this type of first aid will not result in direct application to thermodynamics of the old saw, "the operation was successful but the patient died." I think that the dying patient, which I prefer to call mechanical thermostatics (bowing to Tri bus' careful definitions here), needs radical sur gery, transfusions, and miracle drugs rather than simple first aid. Perhaps the time has come for the engineer who utilizes thermodynamics (in its true sense, i.e., transport of heat, mass, and momentum) in his work with physical and chemi cal phenomena (and here it must be understood that I am referring to a much greater scope of problems than those outlined by Bird, Stewart, and Lightfoot (3)) to render advice and; if neces sary, to step in and perform the necessary sur gery himself. It may well be that those who now apply first aid may see only single trees where entire forests (mostly unexplored) lie waiting. 70 Philosophy and Thermodynamic Concepts As is well known, there are two major ways of approaching the developments of the maj or cor ner-stones of thermodynamics: through classical or macroscopic developments and through statis tical" or molecular developments. Both paths or iginate in physics and both require the person following the development to make some form of idealizing assumption. While I will have more to say on this point in the ~ubsequent paper, I want to point out two recent important changes in emphasis, one in each approach. In classical thermodynamics much work is being carried out in "moleculeless" continuum mechanical thermo statics. While we seldom use this title, the de velopment of the energy equation explicitly de pends .upon this approach In statistical thermo dynamics, Tribus' work and that of others dealing with the development of a thermodynamics which relies on information theory alone must be con sidered as a novel way of developing th e same principles one can obtain from "classical" (as opposed to quantum) statistical thermophysics. Undergraduate chemical engineering thermo dynamics courses are apparently so crowded now (too many trees?), that aside from isolated ex perimental attempts (1) to introduce statistical concepts, only the macroscopi c.. approach is emphasized. Since we are dealing here only with under graduate thermodynamics, and since we must recognize that thermodynamics is truly a building block in the over-all concept of chemical engineer ing process and product design (or if you prefer systems and materials engineering), the pragmatic philosophy must conbol the way in which we present the three laws of thermodynamics and their applications to real engineering problems Let me point out that unlike Bates, I believe that the first law of thermodynamics is the "canonical statement" of temperature, the second, of energy, and the third, of entropy My position, incidently, places me directly in the path of cross fire from the mechanicists who choose work and power for the second and third laws and the thermodynamicists who choose internal enefgy and reversibility. It is not true, in my opinion that the concept of entropy is more abstract than that of energy, which in turn, is more abstract than that of temperature. All concepts are abstract, if one follows the Platonic philosophy; as a result if we are to use these concepts in any pragmatic (and hence, engineering) way, we must make approxi mations to them. The student thinks he knows what temperature is; he makes a heat" balance and thus has some connection, on paper or by CHEM ENG ED

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relation to some physical process such as heat transfer, with the engineer's idea of conservation of energy. However, what makes entropy mys terious (and thus, to the student at least, "more abstract") is not the abstract concept, but our in ability to measure it with a meter! What Good is Entropy? To this question I am tempted to answer "none," at least as entropy is presently taught to undergraduate chemical engineers. If we deal solely with the macroscopic mechanical thermo static developments, the classical development of the concept is through Kelvin refrigerators or Clausius (Carnot) heat engines, via the TS versus PV diagrams, to the second law relating a new variable, called entropy, to a measure of reversible heat and temperature. The next step is to rush into irreversible systems, to "prove" that entropy in any conservative system must either r e main constant or increase with time. Siedel (,6) at one time coll ected some 25 state m ents said to define entropy. At this point rein forcement of the concept is needed (again because we can't measure entropy) and in desperation and with trepidation, the thermodynamicist dips i nto statistical thermodynamics and extracts the statement that entr opy is a measure of the dis order of th e system. Th e reby he e scapes cross examination either because the student is too confused to ask for clarification or because no real use is made of the pseudo-concept anyway Now I wish to rais e two questions: 1. Why if statistical thermodynamics is to be ref e rr e d to at all must it be emascu lated only to support an archaic approach to th e ideas of teaching entropy? 2. Why is it necessary to teach mechanical th e rmo s tatics to chemical engineers at all? Carnot engines and Kelvin refrigerators are grea t d evices for making simple h e at balances, but certainly more realistic examples like fuel cells, air liquefaction and fresh water recovery are more vital. The tired answer to this is of co urse, that the subject has been presented this way for years, so why rock the boat? Boat-rocking notwithstanding I would now pro pose the pragmatic approach to th e concept of entropy, leaning heavily on the recent work of Coleman ( 4). Rath er than 1) wasting tim e and incr easi n g confusio n by introducing statistical th e rmodynami cs and 2) spinning wheels playing with cycles and reversibility-irreversibility, I sug gest that th e engi neer's approximation to the con cept of entropy be put to w.ork. From classical thermodynamics we can determine whether a pro cess is r e versibl e or irreversible, but we have no idea of th e rate at which a process is approaching an e quilibrium state (if ever), or the rate at which conservative (reversibl e ) energy is being converted into dissipativ e (irreversible) energy. At the risk of sounding like an "Onsagarist," I propos e that entropy be used not as a measure JUNE 1966 of the reversibility of a system, but as a measure of conversion of recoverable energy into nonre coverable or dissipative energy. Furthermore that the pragmatic approach to the utilization of entropy be not in the calculation of the conversion from stored energy to energy in motion, but rather in the determination of the time rate of dissipa tion of energy in the form of heat. This means that we are not restricted to Bates' PV versus TS diagrams but can now consider interactions be tween forces and fluxes (in a general way, or if preferred, in the linear Onsagar Law way). Entropy considerations will tell us not only what the system will or will not do but will enable us to obtain a measure of the rate of energy dissipation. To the student who has suffered through in numerable PV versus TS reversible-irreversible problems and lectures, this "moleculeless con tinuum mechanical thermodynamics" approach appears as an oasis in a desert of sand and bleached bones of archaic thermodynamicists Conclusion If I seem unkind to present approaches to the teaching of thermodynamics, it is because my own experiences as a student are healing very slowly. Thermodynamics, or classical mechanical thermo statics, needs more than first aid. It is dying and unless non-thermodynamicists recognize the' mal ady as malignant consumption and act quickly the do-gooders with their adhesive tape will short ly embalm the still-warm body I have tried to give an example of an entirely pragmatic approach to a very simple concept, entropy, and, more importantly an illustration with regard to the direct engineering application of this concept to modern chemical engineering. This approach would almost certainly allow Gibbs to rest quietly and I doubt that he is resting quietly now It is admitted that no mention has been made, ei th er by Bates or me, of c hemical thermostatics. For my part, I support the philosophies of Gibbs and D e nbigh. Additional comments will be forth coming. REFERENCES 1. Balch, C., University of Toledo personal com munication, 1967. 2. Bates, H T. Chem. Eng. Ed. 1 37-43, (1966). 3. Bird, R. B., Stewart W. E., and Lightfoot, E N. "Transport Phenomena," John Wiley, New York, 1960. 4. Coleman, B. D., and Noll, W ., Arch Rational Mech. Anal., 4, 97 128 (1960). 5. Roller, D., The Early Development of the Concepts of Temperature and Heat : "The Rise and Decline of the Caloric Theory," Har vard University Press Cambridge, Mass., 1955. 6. Siedel, B., University of Delaware, personal communication, 1963. 7 Tribus, M., "Thermostatics and Thermo dynamics," D Van Nostrand, Princeton, N. J ., 1961. 71

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The Integrity of Chemical Engineering J. M. Douglas Associate Professor of Chemical Engineering S. A. Miller Professor of Chemical Engineering University of Rochester, Rochester, N. Y. Chemical engineerings is a chemistry-and-physics based discipline. Chemical equilibria and kinetics share equal importance with physical equilibria and transport rates. The conservation statements about chemical systems are as significant as those about physical ones Furthermore the processing that accompanies chemical reactions in the manu facturing setting depends heavily on diffusive transport of molecular matter an aspect of physical chemistry exploited predominantly by the chemical engineer. In this kind of physical operation there has developed peculiar identifica tion with the chemical e ngineering dis c ipline. By combining chemical (stoichiometry thermo dynamics, kinetics), physico-chemical ( diffusion, phase transformation) and physical (h e at trans fer, fluid mechanics strength of solids) principles under the constraints of practical economics, chemical engineering has produced processes of great complexity, carried out in plants that are often enormous ( ten million gallons of product per day) and costly (hundreds of millions of dollars) Chemical engineers are responsible for the e ntire plant and process-their conception, development, design, and economic operation every component of which must operate properly with respect to all the others if success is to result. This is tru e systems engineering The history and present status of engineering and the e ngin ee ring industries demonstrat e that there is a distin c t need and proper place for the peculiar e ducational experience that a chemical engineering curriculum afford s and for the pro duct of that ed ucation. Chemical e n gi n ee rin g problems are c haracterized, indeed by a degree of complication greater than those usually identified with the other traditional engineering fi e lds. Th e evolution of our disciplin e has brought with it methods of attackin g such problems, and concepts of exceptional power and wide usefulness. A con sequence is that c hemical engineers, essential to the process industry, are in demand in a variet y of other e nvironments industrial and ex tra industrial. On e of their great ass ets is thei,r ability to work unusually effectively with repr e sentatives of other disciplines in th e solution of problem s of great scope and interdisciplinary character Notwithstanding the success of past advanc es, th e techniques and insight provided b y chemical 72 engineering are still evolving and there is strong reason to believe that contributions arising out of them will be even greater in the future. Chemical engineering originated from the consolidation of the principles common to a number of pr ev iously isolated use -c enters: the paper industry, petro leum refining technology, acid manufacture, et cetera Its great strength derived from its capacity to unify and establish bonds between these other wise diverse discrete industries and to pr ovide education and training that make the chemical engineer effective in all of them Today there seems to be some tendency again to fragment the field into use areas with new names but distinct identities: environmental engineering, food en gineering, and th e like. A competing tendency would generalize certain of the subdisciplines shared by several of the engineering fields into new disciplines: thermal engineering, materials science, and systems engineering are examples. In both cases, the identification of interest centers at which competences from a number of disci plines can c onverge for the attack of broad super problems is useful and s alutary. But to suggest that they should subordinate or supplant the established discipline of chemical engineering is to suggest the destruction of th e burgeoning promise of tremendous futur e contributions ori ginating in our field We submit that future society will benefit most from the maintenance and continued evolu tionary development (at the most fundamental level consistent with the definition of the field) of an academic discipline erected on the s ubject matt er at th e cor e of ch e mical e ngin ee ring today. Simultaneously, vigorous effort should be directed to thos e d eve lopments at or n e ar th e diffus e boundaries where other currently defined disci plines, basic and applied, and chemical e ngin ee r ing mer ge. We beli eve that such a frankly disci plinary approach optimizes the ta s k of conserving and e xtending the treasur e of knowledge, und e standing, and skill for which chemical engineering has be c ome a particular repository; of applying that treasure to new creative goals in the world of th e process industry; and of sharing major interdisciplinary challenge with others in a sig nificant e ffort which, in using without sacrificing its contributing co llaborat ors, is enduringly synergistic. CHEM ENG ED

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CHEMIJ@l{J!Z ENG!lli!/lllllllllli!IIB Ellll/J@l{Jl1!J@li!I INDEX FOR VOLUME 1 (1965-1966) AUTHOR INDEX SUBJECT INDEX Abraham, W. H. -------------------------------30 Bates, H. T. --------------------------------37 Berg, L. --------------------------------------12, 44 Burkhart, L E. --------------------------1 Burnet, G. ---------------------------------------( 1 ) iv Burr, A. A. -----------------------------------7 Chilton, T. H. ------------------------------9 Christensen, J. J. --------------------------------14 Douglas, J. M -----------------------------------72 Genereaux, R. P. ---------------------------------27 Griffith, D E -----------------------------------Hamielec, A. E. ----------------------------------52 Hubbard, R. M. ---------------------------------10 Kenyon, R. L. -------------------------------------45 Kiser, K. M. ----------------------------------48 Levenspiel, 0. -----------------------------55 Madonna, L. A ---------------------------24 Miller, S. A. ----------------------------------72 Murphy, G. --------------------------------------3 Pfeffer, R. -------------------------------------------13 Schmidt, A. X. -----------------------------------13 Snyder, J R. ------------------------------------11 Thorpe, R. G. __ _________ -------------------------63 Throne, J. L -----------------------------------70 Wheelock, T. D. -------------------------5 Willis, M. T. --------------------------------46 Wise, D. L. ------------------------------------24 Woods, D.R. -------------------------------19, 52 Yerazunis, S. -----------------------------7 JUNE 1967 Bifurcation ------------------------------1, 5, 3, 7 Career choice -----------------------------------12 Chemical Engineering Division ___ ___ ( 1 ) iii, ( 1 ) iv Cooperative programs ------------------------14 Core curricula ------------------ -----------24 Curricula --------------------------1, 3, 5, 7, 14, 25 Design -----------------(3) iii, 19, 52, 55 Engineering science -----------------------------24 Entropy -----------------------------------------------70 Five-year programs -------------------------14 "Goals" Report -------------------------------(2) iii Industry, relations with __ ____________________ 9, 27, 63 Integrity of Chemical Engineering ____________ 72 Interdisciplinary programs __ ____ ___ _______ __ __ 1, 24 Job choice ___ __ _________ _____ ------------------12, 44 Laboratory demonstrations ___ __________ __ __ __ ____ 10 Multifurcation -----------------------------1, 3 Option, curricular -----------------------1, 3, 5, 24 Overhead projector ----------------------------11 Process control ( book review) ____________ __ _____ 30 Professional challenge --------------------------45 Professional practice --------------------9, 44 Reactor design ------------------------------------55 Reactor design ( book review) ____ __ ___ __ _____ ___ 48 Rensselaer program --------------------------7 Science-oriented curricula __________________ 3, 7, 24 Teaching aids -----------------------------10, 11 Teaching load -------------------------------13 Thrmodynamics -----------------------------37, 70 Transport phenomena ----------------------46 Trouble-shooting ------------------------------19 Unit operations --------------------------------46 Visual aids ---------------------------------------10 V

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El r CHEMICAL ENGINEERING EDUCATION 201 Gavett Hall, University of Rochester, Rochester, N.Y. 14627. November 17, 1967 Dear Subscriber: No, there's nothing wrong with your mail service. It is your editors who are responsible for your receiving Volume 1, Number 4 of CHEMical ENGineeri~ El)lcation in November, 1967, instead of June, 1966. But although the masthead date shown on this issue is technically correct, you may be assured that the contents are contemporary. Copy for all of the material that it carries except the feature article was received within the last six months -some of it, notably advertising copy, only a fortnight ago. And Professor Levenspiel's fine paper is certainly as readable today as it was in mid-66. We are sorry for the delay. We hope that you find the issue rewarding in spite of having to wait for it so long. The official publication of ASEE's Chemical Engineering Division will come to you in the future under new, extremely competent editorial leadership. I know that bright days lie ahead for all of us readers who are interested in chemical engineering education. Meanwhile John Bartlett, Al Cooper, and I are grate ful for the privilege we've had to serve you and the Division during an interim period in the life of CHEMical ENGineering Erucation. SAM:sm CHEMICAL ENGINEERING EDUCATION 2 01 Gavett Holl University of Rochester, Rochester, N Y 146 27 Sincerely yours, S. A, Miller Editor Non-Profit Orgonization U. S. POSTAGE PAID ROCHESTER, NEW YORK Permit No. 780