Chemical Engineerings Grand Adventura

8/17/2019 Chemical Engineerings Grand Adventura

1/9

Chemical Engineering Science, Vol. 43, No. 7. pp 1427-1435.1988.

0009-2509188 $3.00 + 0.00

Printed in Cheat Britain.

0 1988 Pergamon Press plc

THIRD P. V. DANCKWERTS

MEMORIAL LECTURE

PRESENTED AT THE INSTITUTE OF DIRECTORS, LONDON, U.K.

4 MAY 1988

CHEMICAL ENGINEERING’S GRAND ADVENTURE

OCTAVE LEVENSPIEL

Chemical Engineering Department.

Oregon

State University, Corvallis, OR 97331-2702, U.S.A.

Fellow chemical engineers, I am honored that you

have invited me to speak to you today. On this

occasion, most memorable for me, I ask that you

join me in exploring an important but little con-

sidered aspect of our activities.

Let me start by proposing that the mission and

essence of chemical engineering is to come up with

processes to make materials wanted by man-new

or improved processes to replace older less efficient

ones, and processes to make completely new

materials. In a nutshell we are the chefs of science

and technology, and as I put it here, it’s a two-step

affair-conceiving or dreaming up a scheme, and

then making it come real.

The second step of this affair, transforming the

idea into reality and teaching how to go about it is

what concerns most of us most of the time, and we

are very good at this. But what about the first step of

this two-step affair, the creative or inventive step,

the dreaming up of a scheme? Who does this and

how does the doer go about doing it? Can this be

taught and if so how is it taught today, and who

teaches it? It is this first step in the development of a

process that I wish to talk about today.

Let me illustrate what I mean with a quick

example. A while ago Japanese chemists discovered

that hot (450°C) liquid indium was a versatile

catalyst, capable of making a variety of useful

reactions go, as shown in Slide 1. However, in all

Dehydrogenotion reaction

I-

5

Reactant -

I-z

+

cOnverSIOn

Liquid lndlum

-450=X

ethanol - acetaldehyde

2 - butanol

- MEK

cyclohexonol

- cyc10hexon0ne

I sopropanol

- acetone

Slide 1

cases, conversion to product was low, between 1 and

5%. With this information let’s try to come up with a

good scheme to treat 1 ton/day of feed (iZiG =

0.1 kg/mol) to 90% conversion, if experiments give

2% conversion for a gas feed rate of 1 cm3/s over a

reaction boat containing 1 g of liquid catalyst.

The first thought is to directly scale up from

experiment. However, a quick back-of-the-envelope

calculation shows that this would require about 6800

tubes in parallel, each containing over 110 boats of

catalyst, as sketched in Slide 2. But at fl.Yg, the

cost of catalyst alone comes to about fl million.

And how would you like to engineer such a process?

I think you will agree that we should be able to do

better.

A second thought is to try the bathtub reactor of

Slide 3. This would require 12 tons of catalyst

costing f18 million? Out of the question.

A third idea would use the spray tower, as shown

in Slide 4. This would use less catalyst, about

f500,OOO worth, but this still is awfully costly. And

how would we overcome the mechanical problems

of dealing with a hot liquid?

These direct approaches just don’t seem practical.

So let us put on our innovative thinking caps. If we

are imaginative enough we may come up with the

scheme of Slide 5. Mix, pelletize, calcine, reduce,

pack and then run with hot gas. What a simple idea

No need to handle hot liquid, and all it requires is

Direct scale up

, ton/day

of feed

Ll3 reactIonboats

per tube

Slide 2

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OCT VE LEVENSPIEL

Bath tub reactor

12 tons of indium

,,f-at 450-C

/ .

1

:

Slide 3.

Spray

column

Everything --

at 450°C

Slide 4.

SLC - supported liquid

catalysts

MIX -

PelW 1ze

- carc1ne

-8CUs:

WS

>

8

%

mvers,o”

I

Reduce wth Hz

-4oo’C

Specks of In

03- 20$.,,

Pack and hecat

to 350°C

Reactant

US Pat 4.224.190

Slide 5.

just a few grams of indium for the whole operation,

costing not much more than a good dinner in

London today.

Why didn’t I think of it? A team at the Danish

Technical University headed by Professor John

Villadsen did, and I wonder what

it was

in their

background that led them away from the traditional

thinking about bubble columns, spray columns and

the like to come up with this unconventional and

neat idea, so simple and obvious in hindsight.

Maybe this is a good place to look at what we do

teach future chemical engineers and see where we

encourage this kind of creative thinking. Put simply,

Slide 6 shows what we do in typical chemical

engineering programs. At the BS level we prepare

the young chemical engineer primarily for plant

operations. Then in postgraduate programs we focus

on research in a variety of areas: physicochemical

information, theory for predicting behavior, design

methods, ways of optimizing operations, and so on.

All this has as its final goal the transformation of a

design concept into an efficient reliable process for

making a product material.

But what about the breakthroughs which lead to

new and better processes. As shown in Slide 6 this

can follow the discovery of a new chemical pathway

or the creation of a new catalyst. It can also come

from dreaming up a new contacting concept.

Gossett’s twig-filled windmill to give Britain’s first

industrial absorber, and Villadsen’s supported liquid

catalyst are such examples. This third step in Slide 6

is something which we in the educational world in

large part ignore. Why? Maybe we don’t know how

to teach it, maybe we consider it to be unteachable.

Let us see whether we can gain an insight into this

activity by seeing how our profession actually goes

about doing it. For this let’s select two examples,

pertinent today, for which there are many possible

routes from given reactants to given products.

First consider the production of liquid fuel from

shale rock. The concept is simple and is shown in

Slide 7. In step 1 shale rock is heated to about

500°C. This drives off the organics but leaves some

fixed carbon on the rock.

One

may follow this

primary operation with a second step in which the

fixed carbon is burned off the rock with air. This

releases heat which is then recycled to heat the raw

, Operate with understanding

1

* Handle emergencies

I

Tmlnlng

I

* Make lmpmvements

of

i

* Theory

developing

.

.

Language new processes

Innovations

- New catalyst

* New reoctlon pathways

* New contoctlng patterns

Slide 6.


3/9

Chemical engineering’s grand adventure

Downflow moving

Raw shale

beds

0

1429

Liquid fuels from shale

RCIW

shale

rnck

step

I

Heat,

no

q

lr

.

1

t

I

I

tieat

released In step

2

)

X-e-- may be used to

_____-x

feed stepl

Slide 7.

shale in the first step. Without step 2 one has to use

some other source of energy, usually a part of the

volatiles produced, to heat the shale rock.

This looks like a simple straightforward operation

so why shouldn’t one single design concept emerge?

With autos we have settled on four wheels, for

railroads two tracks, for commercial aircraft one

body with just one wing on either side, so shouldn’t

we all agree on moving beds or multifluidized beds,

or something else? Well, many large organizations

have worked on this and a whole host of distinctly

different design concepts have been selected, as

listed in Slide 8.

Let me sketch some of these concepts to show you

how different they are. First of all there is the

downflow moving bed of solids. As shown in Slide 9,

there are a number of commercial processes operat-

ing today which have opted for this approach. These

are not small pilot scale operations. For example the

Petrosix uses an 11 m i.d. unit, and the Brazilians

are planning to build 19 more of these giants. Slide

10 shows a horizontal moving bed design, in

operation today in Mexico. And to complete the

picture of moving-bed designs Slide 11 shows a U.S.

Counterflow

moving beds

cross

f low

n-wing beds

Clrculoting

solid schemes

IGT

Poroho

Occidental

union 011

Pet robros

c

Kerr - McGee

Kwiter

Superior Oit

Cities

Chevron

LUrQl

AX0

Shell

I

Rod iont heot

M~crowove heat

Vacuum extraction

Molten solt

From “Oil Processing TechnOloQy” (Edited by V. D. Allred 1

Center for Professional Advancement. 1982

Slide 8.

Paroho

Klviter

Tosco

8 Petrosix

(II rn i.d.1

Volotiles

Air or product

go=

Cold product

gas

Spent shale

Slide 9.

Superior Oib

horizontal

moving bed

(merry

-go - round)

ws

Slide 10.

Unocal’s upflow moving bed

Hot recycle ~0s

Downflow

of

Qas

Shale + C

ze *---Rock

pump pushes

shale upward

Slide 11


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OCTAVE LEVENSPIBL

upflowing-solids process which just produced its first

barrel of comm ercial product la st year. Up flow,

downflow, horizontal flow-shouldn’ one be best?

In the suspended-solid approach, Slide 12 shows

an all-fluidized circulating solid system ; Slide 13

shows a variation of this in which hot and cold sh ale

are intimately contacted in a screw conveyer; and

Slide 14 shows the ball mill design wherein heat is

fed to cold fresh shale by circulating hot balls.

Most of the moving-bed processes are simple from

the engineerin g standp oint, but do not try to recover

the energy in the fixed carbon. Thus spent shale is

returned to the waste dump with a portion of its

l l

Chevron’s STB

m

staged turbubnt bed)

-bust aon

lift p*pe

_ Downflow of soltds

=

I

-3cm/s

Solids recycle

rotio = 2- 5

Slide 12

Lurgi

- Ruhrgas

IL1

meatgrinder)

Solid recycle rotio = 2 - 4

and fuel

Tosco II

n

ball miW

3:

“I

Elevator

i

.I

_ Lift pipe

Raw shale

/

c I-bt waste gas

carbon burn

UP

Slide 14.

energy unextracted. On the other hand, the

fluidized-bed processes are more complicated, but

in most cases they are designed to extract all the

energy from the shale.

Some designs go to great lengths to recover the

energy from the fixed carbon. As an example Slide

15 shows U.S. Shell’s concept. The left half of the

slide with its two fluidized beds and its circulating

heat-carrying steel balls has just one purpose, to

transfer heat from hot spent shale to fresh cold

shale.

Look at the designs of Slides 12, 13 and 15. In

their very differen t ways they all try to recycle heat

from spent shale to fresh shale. Thus solid-solid

heat exchange is the problem here, and an efficient

way of doing this may then be the key to a good

shale process.

We chemical engineers are quite comfortable with

fluid-fluid heat exchange. There are books upon

books on this subject. But what about solid-solid

heat exchange? There is hardly anything

on

this

Shell’s Spher 3 bed concept

_..-..

Hot balls

Ti

‘-/

Slide 13.

Siide 15.


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1431

topic in the literature, and not one word on it in

Perry’s Handbook. So let us probe in the literature

to see what is available.

Slide 16 shows Professor Leung and Chong’s

proposed shell-and-tube design. Unfortunately, for

shale processing,

temperature limitations and

stability of operations would be serious problems

with this design. Slide 17 shows a somewhat simpler

alternative proposed by Professor Potter which uses

side-by-side fluidized beds, and this design could

possibly be incorporated into a shale process.

But now let our minds wander and explore other

ideas. Why not consider using heat pipes? These

devices were made practical about 25 years ago, and

are widely used today in consumer electronics and in

space applications. Even the Alaska pipeline uses

close to 100,000 of them. They are most efficient

heat transfer devices which can be designed to

operate in various temperature ranges from below

room temperature to 1000°C and higher, and in any

orientation-vertical, horizontal or around corners.

Slide 18 shows how heat pipes could be used in a

solid-solid heat exchanger. Sketch A shows what

happens when we just pour solids down past finned

heat pipes. Heat transfer is rapid, but unfortunately

Leung and Chong’s SBT exchanger

Slide 16.

Cooted fluidized

solids out

Hwted fluldized

solids out

Potter’s fluidized exchanger

l-lot

solids

Cold

sol Ids

Slide 17.

Heat pipe s/s heat

(A)

0°C

100°C

exchanger

48°C

52°C

(El

Upflow of condensate

Slide 18.

this arrangement represents cocurrent heat ex-

change for which the maximum heat recovery

efficiency is only 50%.

Of course if we are able to coax one stream of

solids to flow upward then we could approach 100%

efficiency. But how do you coax solids to flow

upward on their own? However, there is a simple

alternative. Rearrange the heat pipes as in sketch B

of Slide 18. This results in a downflow of both solid

streams with counterflow heat exchange and close to

100% heat recovery efficiency. Even better still,

locate the cold unit above the hot unit, as shown in

sketch C. Then the working fluids in all the heat

pipes condense in the upper unit and flow down to

the lower unit, a more efficient arrangement.

So why not consider incorporating heat pipes into

a shale process. Slide 19 shows a possible design.

With no need for very fine solids, no fluidizing gas,

gravity flow of solids throughout the exchanger

section, a process with this type of heat exchanger

should be much simpler than many of the present

designs on which so much effort and money have

been spent.

In looking at all these different ways of extracting

oil from shale rock-in fluidized beds or moving

beds, using upflow, downflow or horizontal flow of

shale, with or without using inert heat-carrying

solids-it should be evident that it is the first

step

in

the development of a process, the choice of process

concept, that we are considering here. Maybe you’ll

agree with me that this is the crucial step in the

development of a process, because once the process

concept is chosen it determines the path to be taken

in all the supporting research, testing, development

and design which follows.

In general terms, not just for shale processing,

what I’d like to suggest is that before starting work


6/9

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OCTAVE LEVENSPIEL

DMB.HPC -

downf low moving

bed heat pipe

Cold row stale

concept

(+I

No C remains

on solids

(+) No N2 I”

VOlOtlleS

I+1 No fuel neede d

(+) Can handle Large

solids

(+) S1mpte

Cold spent shale

Slide 19.

on a particular process concept one should set out

the criteria for the ideal-never mind whether

practical or not-and then see how close one can get

to the ideal. This requires “thinking” research,

sitting around in easy chairs, discussing and dis-

cussing-all this before building even the smallest of

pilot plants.

Let’s try this type of thinking with another system,

the production of synthesis gas from coal. This is

likely to become one of the most important pro-

cesses worldwide by early next century as coal will

progressively replace petroleum as the feedstock for

organic chemicals.

Slide 20 shows. in simple terms, that two reactions

are involved: the desired reaction of coal with steam

which is endothermic, and a combustion reaction

which supplies the heat for the desired reaction.

And since this would be a large-volume operation

we’d like to use only cheap easily obtainable

feeds-air, water and coal, and nothing else.

Synthesis gas

from coal

The rdeat process should only use

COAL. AIR

and

WATER

Desired

\

Cool +

steam e

CO + H,

+Q

Coat + t;;:r,

- CO, + N,)

-

30

How to run these two reactions ?

Slide 20.

In considering this operation we spot a number of

potential problems:

If coal is reacted with air and steam at the same

time then nitrogen is present in the product gas,

and this is costly to remove.

If we try to avoid this problem by reacting with

oxygen instead of air, then we would need an

oxygen plant-again cost1 y.

We can avoid the nitrogen problem by running

the two reactions in different locations, but then

we have the problem of transferring heat from

one location to the other.

And in all of these schemes if the product gases

are rapidly cooled then a lot of tar forms and this

also is costly to remove. To avoid this we must

keep the product gases hot for a while to let the

tars crack into lower molecular weight com-

pounds.

These considerations lead us to jot down the

requirements for an ideal gasification process, as

shown in Slide 21. Let me comment on the last two

items on this list. Thermodynamics, reinforced by

common sense, suggests that if we want to squeeze

the most from a process then ideally all the product

streams should leave the process at ambient con-

ditions.

The last item on this list is most important, for to

dream up a process which is basically complex is

risky. An example of this is the CO,-Acceptor

process in the U.S. for coal gasification. It was a

beautiful concept and many millions were spent on

its development. However, the developers had to

call it quits precisely because of its complexity.

Slide 22 shows that all sorts of schemes have been

dreamed up for coal gasification. As you can see

there is no agreement on the best way to gasify coal.

Well, just for fun let us look at the four main

schemes and see how they compare with our six

criteria for the ideaI.

Scheme 1 Slide 23) uses air and countercurrent

gas-solid contacting with both reactions taking

place in one bed. During reaction a narrow hot zone

forms and the product gas quickly cools. The main

problems with this design are shown in Slide 23.

Requirements for an ideal synthesis gas process

(+I Onky “se AIR. WATER and COAL

(+I No N, leaves with product gas

+I No tar or liquid formed

(+I No O2 plant to be used

(+I A11 flow streams Leave at room tempemture

(+I Proc ess must be slmpk, procticol, and easy

to opemte and control

SIide 21.


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1433

Large

moving

bed

Cool gasification concepts

one

fluldized

bed

1

Two

ftuidired

I

beds

I

Mutt i

fluldized

beds

c

- Brltlsh Gas/Lurgi SlagQlnQ

With 0,

Dry ash Lurgl

Air. 02

Gas lntegrote

A1r

IGI - two stage

Air. O2

~erpely (USBM)

Air

Leuno

0,

Power go*

Air

Thyssen Galoczy

02

UGI water gos

A1r

Weltmon GoCusho

A1r

Wellman - Incandescent

Air

Woodoll Duckham

Air

Exxon

Onty steam

Hoffman

Only steam

HRI fast fluldized

Air

Synthone

0,

u - gas

Air

Wlnkter

Air

Battelle osh agglomerating Air

CD, - acceptor

Air

Cogas

Air

ICI moving turden

Air

Westinghouse

Air

IGT hygos

(3 stogesj

02

TrIgas

(3 stages) Air

CQQos

(5 stages)

Air

Babcock - W11cox

0,

Entrained

flow

gasi f iers

Bell - Aerospace

A,lr, 0,

Bionchi

0,

01 - gas

i2 stages)

0,

Combustion Engineering

Air

Foster - Wheeler (2 stages) Air

Koppers - Totzek

4

Ponindco

Air, 0,

Ruhrgas VOrtex

Air

Shell - Koppers

Air, 0,

Texo co

Air, 0

z

Also :

Molten baths

From “Cool Goslflcation Concepts:’ NoyeS

Doto Corp., krk Ridge, NJ, 1981

Slide 22.

Coal %

_ CO+Hz.

Scheme I

l l o t

zon

N,

tar

(+) Simple

(+I No O2 plant

Slide 25

.-

- Ropld

cooll”g

(+ 1 Cool products

(-1 Tar

(-1 N, with

product

Scheme 4

CO+Hz

N, + COz

Ash

+ air

Slide 23.

Cool

CO+ a.

Scheme 2

tar

“0 0,000

$2 “0

R

(+I

No N, with product

008

Hot zone

,“g

%o _,’

(+I Simple

*

,.oea 4

NZ

(+ 1 Cool product

&@$@

&3$x8

(-1 Tars

V

-Air

(- ) O2 plant

1

Ash

02

Slide 24.

Scheme 3 (Slide 2s) shows that nitrogen separ-

ation is the problem with single fluidized bed

processes, but not tar production, because the

product gases stay hot for a reasonably long time.

Scheme 4 (Slide 26) keeps the reactions separate

in two or more tluidized beds. Its main problem

concerns complexity, and the CO*-Acceptor process

shows what happens when this question is taken

lightly.

There are many variations of these four basic

designs, and we will not go into them. It suffices to

note that none of the processes proposed or

operating today approach, in principle, the ideals

listed in Slide 21. This means that it may be

worthwhile trying to conceive a radically different

and better concept, and not just an improvement of

existing technology.

So, keeping the ideal in mind, let’s see what we

can come up with. Here are two of more than a

dozen ideas that our easy-chair research group in far

CO + H,. N,

Scheme 3

Cool

==%I

(+I No tar

(+I No 0, plant

(+I Sample

(-1 N, with product

(-1 Hot products

Air + steam

(+I No N,

In

product

(+I No tar

(+ ) No Oz plant

needed

(-1 Not simple

(-1 Hot product

Scheme

(Slide 24) shows how the nitrogen

problem is avoided, but unfortunately at the cost of

an upstream oxygen plant.

Steam

Ajr

Slide 26.


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OCT VE LEVENSPIEL

away Oregon plus one Missourian, Professor Mike

Dudukovic, came up with.

First, how about treating powdered coal-gas

mixtures in parallel flow channels which are forested

with finned heat pipes, or more properly, with

finned thermosiphons, as shown in Slide 27? This

would mean treating only slightly dusty gases-a

simple matter. W e haven’ yet made the calculations

on this type of operation, in fact we don’ even know

whether cocurrent or countercurrent flow of the two

stream s is better, but it would be interesting to look

into this concept because of its simplicity.

Slide 28 show s a comp letely different idea.

Instead of running the two reactions at the same

time but in different reactors, why not run them in

the same reactor but at different times? This leads to

the RE-GAS process, standing for regenerator-

gasifier.

In this operation the reactor con sists of a large

long vertical vessel with insulated walls and packed

with structured solid. It operates like this.

In the first step of the cycle feed fine coal powder

suspended in air again very dilute in solids) to

the vessel. The coal burns, heats the bed solids,

and a hot front slowly moves up the vessel;

EX-GAS exchanger - gasifier) concept

/COz Nz

Slide 27.

RE - GAS regenerator - gasif ier 1 concept

N, CO,

H, co

t t t t t t

tool

Hot

Powdered Coal

l,r

Powdered CQQL steam

Heating step

Gasif ication step

Slide 28.

however waste gases would leave at close to

ambient conditions. This is shown in the first

three sketches of Slide 28.

At the right time switch the feed to steam and

coal powder which on heating up and passing

through the hot solids produces the desired

product gas. During this operation a cold front

slowly moves up the bed, as shown in sketches

4-6 of Slide 28.

At the end of the cycle only the top of the bed

contains hot solid. One then repeats the whole

cycle of operations, but upside d own.

Now if we compare this scheme with the ideal of

Slide 21 we s ee that it does satisfy a ll the require-

men ts for an ideal process, especially the criterion of

simplicity sinc e there is no circulation of solids

needed and since all external piping and valving is at

close to ambient conditions.

At this point one can raise a number of questions

with this type of operation. For examp le:

would the unit plug up with ash?

would the spread of the heat front lower the

efficiency of operations drastically?

would tem peratur e instabilities occur, and if so

how could they be controlled?

0 A re suitable materials of construction available?

andsoon.

Of course such questions have to be considered.

However, answering these questions represents the

second step in the development of a process, and as

I mentioned at the beginning of this talk, this is

something that we chemical engineers are good at.

In any case, it should be noted that in principle the

RE-GAS process is superior to those mentioned

earlier, and so much sim pler since one is only

pumping cool slightly dusty gases. Shouldn’ it be

looked at?

Let me go back to the question of conceiving new

process concepts.

1)

2)

How does an organization come to its concept

for a process, wheth er it be the antigravity, or

meat grinder or merry-go-round or what have

you?

Does the director of research com e in one

morning and say “Okay-I’ve been think-

ing that we should look into ball mills”?

Is it the result of the deliberations of a

committee?

Does the researcher ask his technician for a

sma ll unit, which, if success ful, is then

scaled up again and again?

Does the researcher deliberately look for

something different so. as not to infringe on

o thers’ patents?

I don’ know what the answer is.

Maybe the search for a process concept is best

done by getting together a

group of

knowledgeable free thinkers of varied back-

ground and interests, including mavericks,

technicians and “wild men ”, and let them go

at it. Ideas need time to ferment, so let them


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1435

(3)

(4)

(5)

meet again and again

until they all enthusias-

tically agree that they’ve come up with the

very best.

tt may be risky to start out with small bench

scale pilot plants without thinking through the

whole operation, because as one progresses

one has more and more invested in following

the path which has already been chosen-not

just money invested, but intellectual effort

and reputation. A momentum is developed to

follow a given path which makes it more and

more difficult to change direction, to admit

that some other way may be better and that

one should maybe start afresh in a different

direction.

Some may suggest, especially after looking at

all the wildly different designs on Slides 8 and

22, that my whole discussion today may not

be pertinent because the difference in pro-

cessing costs may represent only a minor

factor in the overall economics. However, in a

large-scale operation I doubt that this is so.

To go back to the start of my talk, I pointed

out that the development of a process rep-

resents a two-step affair, thinking up a good

scheme and then transforming it into reality.

In chemical engineering education we focus

on the second step, and the way we teach this

is with courses of lectures. But would this

teaching method work with the first step?

(6)

Imagine trying to teach bicycle riding or

swimming in a course of lectures

In a way learning to swim and developing

the knack of inventing new processes is done

the same way-by practice, and then more

practice, not by lectures. For example, have

students work in teams trying to think up

schemes for making chemical y from x.

Encourage them to discuss, argue, throw out

the wildest ideas, but then have them rate

these schemes. I’ll wager that a most interest-

ing scheme will occasionally emerge from this

exercise.

This sort of program would be difficult to

set up, but isn’t this important enough for us

educators to try?

Finally, let me suggest that the driving force,

the “raison d ’ t re” of our profession is the

search for and the creation and development

of new processes to make materials wanted by

man. LeBlanc, Solvay, Haber-Bosch and

ammonia,

Ipatieff and platinum, FCC,

penicillin production, zeolites, these words

recall some highlights from the past. Who can

even dream of what will be tomorrow. This

then is the grand adventure of chemical

engineering.

Enough. 1 fear that I’ve left you with too many

questions and too few answers. It is time to stop. I

thank you for your attention.

Chemical Engineerings Grand Adventura

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