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- ~
MAGINE A WORLD where penicillin and
other antibiotics are rarer and more
expensive than the finest diamonds.
Imagine countries gripped by famine as dwin-
dling supplies of natural guano and saltpeter
cause fertilizers to become increasingly scarce.
Imagine hospitals and clinics where kidney
dialysis is as risky and as uncertain over the
long term as today's artificial heart program.
Imagine serving on a police force or in the
infantry without a lightweight bulletproof vest.
Imagine your closet with no wash-and-dry,
wrinkle-free synthetic garments, or your home
without durable, easy-cleaning, mothproof syn-
thetic rugs. Imagine cities choked with smog
and soot from millions of residential coal fur-
naces and millions of automobiles without emis-
sion controls. Imagine an "information society"
trying to function on vacuum tubes and ferrite
core storage for data processing. Imagine paying
$25 or more for a gallon of gasoline, if you can
even buy it. This world, in which few of us
would want to live, is what a world without
chemical engineering would be like.
Chemical engineers have made so many im-
portant contributions to society that it is hard
FROA'T{~{AIN C}~'/~L ~1~-~'.''Wi~
to visualize modern life without the large-vol-
ume production of antibiotics, fertilizers and
agricultural chemicals, special polymers for
biomedical devices, high-strength polymer com-
posites, and synthetic fibers and fabrics. How
would our industries function without environ-
mental control technologies; without processes
to make semiconductors, magnetic disks and
tapes, and optical information storage devices;
without modern petroleum processing? All these
technologies require the ability to produce spe-
cially designed chemicals and the materials
based on them economically and with a min-
imal adverse impact on the environment. De-
veloping this ability and implementing it on a
practical scale is what chemical engineering is
all about.
The products that depend on chemical engi-
neering emerge from a diverse array of indus-
tries that play a key role in our economy (Table
2.11. These industries produce most of the
materials from which consumer products are
made, as well as the basic commodities on
which our way of life is built. In 1986, they
shipped products valued at nearly $585 billion.
They had a payroll of 3.3 million employees, or
TABLE 2.1 The Chemical Processing Industries in the United Statesa
Number of Value ofValue Added by
Employees ShipmentsManufacture
Industryb(thousands) ($ millions)($ millions)
Food and beverages378 73,63324,370
Textiles99 7,6492,897
Paper322 51,14519,871
Chemicals1,023 197,93295,258
Petroleum169 129,36517,112
Rubber and plastics340 31,07815,390
Stone, clay, and glass354 34,37217,449
Nonferrous metals49 21,920524
Other nondurables577 37,59424,291
TOTAL
Chemical processing
industries' share of
total manufacturing
a Data for employment and value of shipments are for 1986. Data for value added by
manufacture are for 1985. SOURCE: Data Resources, Inc.
b The definition of the chemical processing industries (CPI) used in this table is the
one used by Data Resources and Chemical Engineering in compiling their statistics on
these industries. For several of the industries listed, only a part is considered to be in
the CPI and data are presented for this part only. A list of the Standard Industrial
Classification codes used to define the CPI for this table is given in Appendix C.
3,321
584,689
217,161
17.5% 25.7% 21.7%
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WHAT IS CHEMICAL ENGINEERING?
17.5 percent of all U.S. manufacturing employ-
ees. They generated over $217 billion in value
added in 1985, or 21.7 percent of all U.S.
manufacturing value added. The chemicals por-
tion of the CPI is one of the most successful
U.S. industries in world competition, producing
an export surplus of $7.8 billion in 1986, in
contrast to the overall U.S. trade deficit of $152
billion.
But chemical engineering is more than a group
of basic industries or a pile of economic statis-
tics. As an intellectual discipline, it is deeply
involved in both basic and applied research.
Chemical engineers bring a unique set of tools
and methods to the study and solution of some
of society's most pressing problems.
TRADITIONAL PARADIGMS OF
CHEMICAL ENGINEERING
Every scientific discipline has its character-
istic set of problems and systematic methods
for obtaining their solution that is, its para-
digm. Chemical engineering is no exception.
Since its birth in the last century, its fundamental
intellectual model has undergone a series of
dramatic changes.
When the Massachusetts Institute of Tech-
nology (MIT) started a chemical engineering
program in 1888 as an option in its chemistry
department, the curriculum largely described
industrial operations and was organized by spe-
cific products. The lack of a paradigm soon
became apparent. A better intellectual founda-
tion was required because knowledge from one
chemical industry was often different in detail
from knowledge from other industries, just as
the chemistry of sulfuric acid is very different
from that of lubricating oil.
Unit Operations
The first paradigm for the discipline was based
on the unifying concept of "unit operations"
proposed by Arthur D. Little in 1915. It evolved
in response to the need for economic large-scale
manufacture of commodity products. The con-
cept of unit operations held that any chemical
manufacturing process could be resolved into a
coordinated series of operations such as pul
1i
verizing, drying, roasting, crystallizing, filter-
ing, evaporating, distilling, electrolyzing, and
so on. Thus, for example, the academic study
of the specific aspects of turpentine manufacture
could be replaced by the generic study of
distillation, a process common to many other
industries. A quantitative form of the unit op-
erations concept emerged around 1920, just in
time for the nation's first gasoline crisis. The
rapidly growing number of automobiles was
severely straining the production capacity for
naturally occurring gasoline. The ability of
chemical engineers to quantitatively character-
ize unit operations such as distillation allowed
for the rational design of the first modern oil
refineries. The first boom of employment of
chemical engineers in the oil industry was on.
During this period of intensive development
of unit operations, other classical tools of chem-
ical engineering analysis were introduced or
were extensively developed. These included
studies of the material and energy balance of
processes and fundamental thermodynamic
studies of multicomponent systems.
Chemical engineers played a key role in
helping the United States and its allies win
World War II. They developed routes to syn-
thetic rubber to replace the sources of natural
rubber that were lost to the Japanese early in
the war. They provided the uranium-235 needed
to build the atomic bomb, scaling up the man-
ufacturing process in one step from the labo-
ratory to the largest industrial plant that had
ever been built. And they were instrumental in
perfecting the manufacture of penicillin, which
saved the lives of potentially hundreds of thou-
sands of wounded soldiers. An in-depth look at
this latter contribution shows the sophistication
that chemical engineering had achieved by the
1940s.'
Penicillin was discovered before the war, but
could only be prepared in highly dilute, impure,
and unstable solutions. Up to 1943, when chem-
ical engineers first became involved with the
project, industrial manufacturers used a batch
purification process that destroyed or inacti-
vated about two-thirds of the penicillin pro-
duced. Within 7 months of their involvement,
chemical engineers at an oil company (Shell
Development Company) had applied their
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q ~
knowledge of generic engineering principles to
build a fully integrated pilot plant that processed
200 gallons of fermentation broth per day and
achieved nearly 85 percent recovery of penicil-
lin. When this process was installed by four
penicillin producers, production soared from a
rate in 1943 capable of sustaining the treatment
of 4,100 patients per month to a rate in the
second half of 1944 equivalent to treatments for
nearly 250,000 patients per month.
A second challenge in getting penicillin to the
front was its instability in solution. A stable
form was needed for storage and shipment to
hospitals and clinics. Freeze drying- in which
the penicillin solution was frozen to ice and
then subjected to a vacuum to remove the ice
as water vapor seemed to be the best solution,
but it had never been implemented on a pro-
duction scale before. A crash project by chem-
ical engineers at MIT during 1942-1943 estab-
lished enough understanding of the underlying
phenomena to allow workable production plants
to be built.
The Engineering Science Movement
The high noon of American dominance in
chemical manufacturing after World War II saw
the gradual exhaustion of research problems in
conventional unit operations. This led to the
rise of a second paradigm for chemical engi-
neering, pioneered by the engineering science
movement. Dissatisfied with empirical descrip-
tions of process equipment performance, chem-
ical engineers began to reexamine unit opera-
tions from a more fundamental point of view.
The phenomena that take place in unit opera-
tions were resolved into sets of molecular events.
Quantitative mechanistic models for these events
were developed and used to analyze existing
equipment, as well as to design new process
equipment. Mathematical models of processes
and reactors were developed and applied to
capital-intensive U.S. industries such as com-
modity petrochemicals.
THE CONTEMPORARY TRAINING OF
CHEMICAL ENGINEERS
Parallel to the growth of the engineering
science movement was the evolution of the core
>~ ~ ~ tY A' 'rS I`/\ ~ Delphi i CAL ~1\'6 [~RA;161JO
chemical engineering curriculum in its present
form. Perhaps more than any other develop-
ment, the core curriculum is responsible for the
confidence with which chemical engineers in-
tegrate knowledge from many disciplines in the
solution of complex problems.
The core curriculum provides a background
in some of the basic sciences, including math-
ematics, physics, and chemistry. This back-
ground is needed to undertake a rigorous study
of the topics central to chemical engineering,
including:
~ multicomponent thermodynamics and ki-
netics,
· transport phenomena,
· unit operations,
. . .
· reaction englneerlng,
· process design and control, and
· plant design and systems engineering.
This training has enabled chemical engineers
to become leading contributors to a number of
interdisciplinary areas, including catalysis, col-
loid science and technology, combustion, elec-
trochemical engineering, and polymer science
and technology.
A NEW PARADIGM FOR CHEMICAL
ENGINEERING
Over the next few years, a confluence of
intellectual advances, technological challenges,
and economic driving forces will shape a new
model of what chemical engineering is and what
chemical engineers do (Table 2.21.
A major force behind this evolution will be
the explosion of new products and materials
that will enter the market during the next two
decades. Whether from the biotechnology in-
dustry, the electronics industry, or the high-
performance materials industry, these products
will be critically dependent on structure and
design at the molecular level for their usefulness.
They will require manufacturing processes that
can precisely control their chemical composition
and structure. These demands will create new
opportunities for chemical engineers, both in
product design and in process innovation.
A second force that will contribute to a new
chemical engineering paradigm is the increased
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WHAT IS CHEMICAL E~-~NEERt\G?
TABLE 2.2 Enduring and Emerging Characteristics of Chemical Engineering
Enduring Characteristics
~3
Emerging Characteristics
Serves industries whose products are quickly superseded
in the marketplace by improved ones
Serves industries that compete on the basis of quality and
product performance
Serves industries whose products remain unchanged on
the market for long periods
Serves industries that compete mainly on the basis of
price and availability
Expertise in the manufacture of homogeneous materials
from small molecules
Expertise in the manufacture of commodity materials
Expertise in process design
Expertise in designing large-volume processes
Expertise in designing continuous processes
Expertise in designing industrial plants dedicated to a
single product or process
Practitioners use simple models and approximations to
solve problems
Practitioners have access to only a few simple analytical
instruments
Practitioners build their careers around a single product
line or process
Expertise in the manufacture of composite and structured
materials from large molecules
Expertise in the manufacture of high-performance and
specialty materials
Expertise in designing products with special performance
characteristics
Expertise in designing small-scale processes
Expertise in designing batch processes
Expertise in designing flexible manufacturing plants
Practitioners use more complete models. better
approximations, and large computers to solve problems
rigorously
Practitioners have access to many sophisticated analytical
instruments
Practitioners have multiple career changes
Academic research is mostly performed by single principalAcademic research is also performed by multidisciplinary
investigators within chemical engineering departmentsgroups of principal investigators, sometimes in centers
or other organizational environments
Research and education focus on the mesoscale
(equipment level)
Research and education also include the microscale
(molecular level) and macroscale (systems level)
competition for worldwide markets. Product
quality and performance are becoming more
important to global competition than ever be-
fore. If the United States is to remain compet-
itive in world chemical markets, it must find
new ways to lower costs and improve product
quality and consistency. Similarly, a strong
domestic energy-producing industry is needed
to preclude foreign domination of this vital
sector of the economy. The key to meeting
these challenges is innovation in process design,
control, and manufacturing operations. It is
particularly important that the United States
maintain a vigorous presence in commodity
chemical markets. Commodities are at the base
of industries that employ millions of Americans,
provide basic necessities for our society, and
generate valuable export earnings. Thriving
commodity businesses are also vital to specialty
chemical businesses. The technical expertise
and financial resources that commodities pro-
vide is crucial to the long-term research and
development efforts that specialties require.
The third force shaping the future of chemical
engineering is society's increasing awareness of
health risks and environmental impacts from
the manufacture, transportation, use, and ulti-
mate disposal of chemicals. This will be an
important source of new challenges to chemical
engineers. Modern society will not tolerate a
continuing occurrence of such incidents as the
release of methyl isocyanate at Bhopal (in 1985)
and the contamination of the Rhine (in 1986~.
It is up to the chemical engineering profession
to act as the cradle-to-grave guardian for chem-
icals, ensuring their safe and environmentally
sound use.
The fourth and most important force in the
development of tomorrow's chemical engineer-
ing is the intellectual curiosity of chemical
engineers themselves. As they extend the limits
of past concepts and ideas, chemical engineering
researchers are creating new knowledge and
tools that will profoundly influence the training
and practice of the next generation of chemical
engineers.
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When a discipline adopts a new paradigm,
exciting things happen, and the current era is
probably one of the most challenging and po-
tentially rewarding times to be entering chemical
engineering. How can the unfolding pattern of
change in the discipline be described?
The focus of chemical engineering has always
been industrial processes that change the phys-
ical state or chemical composition of materials.
Chemical engineers engage in the synthesis,
design, testing, scale-up, operation, control, and
optimization of these processes. The traditional
level of size and complexity at which they have
worked on these problems might be termed the
mesoscale. Examples of this scale include re-
actors and equipment for single processes (unit
operations) and combinations of unit operations
in manufacturing plants. Future research at the
mesoscale will be increasingly supplemented by
studies of phenomena taking place at molecular
dimensions the microscale and the dimen-
sions of extremely complex systems the ma-
croscale (see Table 2.31.
Chemical engineers of the future will be
integrating a wider range of scales than any
other branch of engineering. For example, some
may work to relate the macroscale of the en-
vironment to the mesoscale of combustion sys-
tems and the microscale of molecular reactions
and transport (see Chapter 7~. Others may work
to relate the macroscale performance of a com-
posite aircraft to the mesoscale chemical reactor
in which the wing was formed, the design of
the reactor perhaps having been influenced by
TABLE 2.3 Microscale-Mesoscale-Macroscale: Illustrations
FROAYTIERS IN CHEMICAL £.~INEERING
studies of the microscale dynamics of complex
liquids (see Chapter 54.
Thus, future chemical engineers will conceive
and rigorously solve problems on a continuum
of scales ranging from microscale to macroscale.
They will bring new tools and insights to re-
search and practice from other disciplines: mo-
lecular biology, chemistry, solid-state physics,
materials science, and electrical engineering.
And they will make increasing use of computers,
artificial intelligence, and expert systems in
problem solving, in product and process design,
and in manufacturing.
Two important developments will be part of
this unfolding picture of the discipline:
~ Chemical engineers will become more
heavily involved in product design as a com-
plement to process design. As the properties of
a product in performance become increasingly
linked to the way in which it is processed, the
traditional distinction between product and
process design will become blurred. There will
be a special design challenge in established and
emerging industries that produce proprietary,
differentiated products tailored to exacting per-
formance specifications. These products are
characterized by the need for rapid innovation,
as they are quickly superseded in the market-
place by newer products.
~ Chemical engineers will be frequent partic-
ipants in multidisciplinary research efforts.
Chemical engineering has a long history of
fruitful interdisciplinary research with the chem
Microscale (~10-3 m)
Atomic and molecular studies of catalysts
Chemical processing in the manufacture of integrated circuits
Studies of the dynamics of suspensions and microstructured fluids
Mesoscale (10-3-102 m)
Improving the rate and capacity of separations equipment
Design of injection molding equipment to produce car bumpers made from polymers
Designing feedback control systems for bioreactors
Macroscale (>10 m)
Operability analysis and control system, synthesis for an entire chemical plant
Mathematical modeling of transport and chemical reactions of combustion-generated air pollutants
Manipulating a petroleum reservoir during enhanced oil recovery through remote sensing of process data, development
and use of dynamic models of underground interactions, and selective injection of chemicals to improve efficiency of
recovery
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~T IS CHEMICAL E~.VEERiA-~?
ical sciences, particularly in industry. The po-
sition of chemical engineering as the engineering
discipline with the strongest tie to the molecular
sciences is an asset, since such sciences as
chemistry, molecular biology, biomedicine, and
solid-state physics are providing the seeds for
tomorrow's technologies. Chemical engineering
has a bright future as the "interracial discipline"
that will bridge science and engineering in the
multidisciplinary environments where these new
technologies will be brought into being.
Some things, though, will not change. The
underlying philosophy of how to train chemical
engineers emphasizing basic principles that
are relatively immune to changes in field of
application must remain constant if chemical
engineers of the future are to master the broad
spectrum of problems that they will encounter.
At the same time, the way in which this philos-
ophy finds concrete expression in course offer-
ings and requirements must be responsive to
changing needs and situations.
NOTE
1. Additional background and references on chemical
engineers and the effort to win World War II may
be found in Separation and Purification: Critical
Needs and Opportunities (Washington, D.C.: Na-
tional Academy Press, 1987), pp. 92-100.
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Representative terms from entire chapter:
unit operations
