CHAPTER 1. INTRODUCTION
Chemical Engineering design of new chemical plants and the expansion or revision of
existing ones require the use of engineering principles and theories combined with a
practical realization of the limits imposed by industrial conditions.
A plant-design projects moves to completion through a series of stages as is shown in
the following:
1. Introduction (a beginning of something)
2. Preliminary evaluation of economics and market
3. Development of data necessary for final design
4. Final economic evaluation
5. Detailed engineering design
6. Procurement (supply, acquirement, obtainment. 획득, 조달)
7. Erection (or construction)
8. Startup and trial runs
9. Production
Skills required: research, market analysis, design of individual pieces of equipment, cost
estimation, computer programming, plant-location surveys
A. CHEMICAL ENGINEERING PLANT DESIGN
-
General term “plant design” includes all engineering aspects involved in the
development of either new, modified, or expanded industrial plant.
-
Therefore, although one person cannot be an expert in all the phases involved
in plant, it is necessary to be acquainted with the general problems and
approach in each of the phases.
-
Close team work is necessary
-
The most effective teamwork and coordination of efforts are obtained when
each of the engineers in the specialized groups is aware of the many functions
in the overall design project.
B. PROCESS DESIGN DEVELOPMENT (Chapter 2)
i) The first, of course, must be the inception of the basic idea.
 For example, the engineering department of the company may originate a new
process or modify an existing process to create new products.
ii) If the initial analysis indicates that the idea may have possibilities of developing into
a worthwhile project, a preliminary research or investigation program is initiated.
 General survey of the possibilities for a successful process is made considering
the physical and chemical operations involved as well as the economic aspects.
iii) Process-research phase
 Preliminary market surveys, laboratory-scale experiments and production of
research samples of the final product
iv) Development phase (after when potentialities of the process are fairly well
established)
 Pilot plant or a commercial development plant may be constructed
 Pilot plant: small replica of the full-scale final plant
 Commercial development plant

made from odd (짜두리, 끄트러기) pieces of equipment which are already
available

not meant to duplicate the exact setup to be used in the full-scale plant
 Design data and other process information are obtained
 Complete market analysis
 Sample of final product are sent to prospective customers

Satisfactory?

Sales potential?
 Capital-cost estimates for the proposed plant are made
 Probable returns on the required investment are determined
 A complete cost-and-profit analysis of the process is developed
Expensed Engineering
- Distinction is used for tax purpose
- Management will decide if further funds should be provided for the project
Capitalized Engineering
Capitalized engineering costs can be amortized (write off expenditure by prorating
(divide) over a certain period) over a period of several years.
v) Final stage
 All the design details are worked out in this phase including controls, services,
piping layouts, firm price quotations, specifications and designs for individual
pieces of equipment, and all other design information necessary for the
construction of the final plant.
 A complete construction design is then make with elevation drawings, plantlayout arrangement, and other information required for the actual construction
of the plant.
 Procurement of the equipment, construction of the plant, startup of the plant,
overall improvements in the operation, and development of standard operating
procedures -> to give the best possible results.
 Many projects are discarded as soon as the preliminary investigation or
research on the original idea is completed.
 Engineers must maintain a realistic and practical attitude in advancing through
the various stages of a design projects -> exclude personal interests and
desires -> ability to eliminate unprofitable ventures before final-proposal stage.
C. GENERAL OVERALL DESIGN CONSIDERATIONS (Chapter 3)
 Failure to include theses considerations in the overall design project may, in
many cases, alter the entire economic situation so drastically as to make the
venture “unprofitable”.
 Plant location, plant layout, materials of construction, structural design, utilities,
buildings, storage, materials handling, safety, waste disposal, federal, state and
local laws or codes (regulations), and patents.
* COMPUTER-`AIDED DESIGN (Chapter 4) – will not be not covered
D. COST AND ASSET ACCOUNTING (Chapter 5)
 Record keeping and accounting procedures are important
 Be familiar with general terminology and approach used by accountants
E. COST ESTIMATION (Chapter 6)
 As soon as the final process-design stage is completed accurate cost
estimations become possible: detailed equipment specification and definite
plant-facility information based.
 However, cost estimates should be made throughout all the early stages of the
design even when complete specifications are NOT available.
 Predesign cost estimation (guesstimation): evaluation of costs in the preliminary
design phases.
 Provide a basis for company management to decide if further capital should be
invested in the project.
 Chemical engineer should consider all possible factors: fixed costs, direct
production costs for raw materials, labor, maintenance, power, and utilities,
costs for plant and administrative overhead, distribution of the final products
plus other miscellaneous items.
 Chapter 6 covers many techniques for making predesign cost estimations
 The final test as to the validity of any cost estimation can come only when the
completed plant has been put into operation. However, it is still possible to
make remarkably close cost estimations before the final process design.
F. FACTOR AFFECTING PROFITABILITY OF INVESTMENTS (Chapter 7 & 10)
 A ultimate goal is to maximize the long-term profit.
 A decision to invest in fixed facilities carries with it the burden of “continuing
interests”, “insurance”, “taxes”, “depreciation”, “manufacturing costs”, etc. and
also reduces the fluidity of the company’s future action.
 Money has a time value and expected to receive a return “during” the time
money is being used.
 The amount of return demanded usually depends on the degree of risk that is
assumed.
 The risk depends on;

Process used: well established or a complete innovation

Product to be made: staple (steady in demand) or a completely new product

Sales forecasts: whether sales will be outside the company or a significant
fraction internally
G. TAXES AND INSURNACE (Chapter 8)
 Expenses for various taxes and insurance can materially (substantially,
significant degree) affect the economic situation for any industrial process.
 Modern taxes may amount to a major portion of a manufacturing firm’s net
earnings:
Chemical
engineers
must
be
conversant
(familiar)
with
the
fundamentals of taxation.
 Profitability should be based on income after taxes.
 However, insurance costs, normally only a small part of the total operational
expenditure of an industrial enterprise.
 Before any operation can be carried at on a sound economic basis, necessary to
determine the insurance requirement to provide adequate coverage against
“unpredictable” emergencies or development.
H. DEPRECIATION (loss in value)(Chapter 9)
 Physical assets of an industrial facility decreases in value with age, therefore, it
is normal practice to make periodic charges against earnings so as to distribute
the first cost of the facility over its expected service life.
 No current outlay of cash (unlike other expense), engineering firm needs
available, additional funds (additional to net profit) corresponding to the
depreciation expense in a given accounting periods.
 Called “capital recovery”: a partial regeneration of the first cost of the physical
assets.
I. OPTIMUM DESIGN (Chapter 11-will not be not covered)
i) Optimum Economic Design
 If there are two or more methods for obtaining exactly equivalent final results,
the preferred method would be the one involving the least total cost.
 Figure 1-1. Pumping a given amount of fluid.
 Pumping cost goes up as pipe diameter decreases: frictional effects.
 Fixed charge goes down as pipe diameter decreases: reduced capital
investment.
 Often choose the final design on the basis of least total cost: consider quality of
the product or operation
 Optimum economic requirement: various types; 1) maximum profit per unit of
time, 2) minimum total cost per unit of production
ii) Optimum Operation Design
 Require definite conditions; temp., pressure, contact time, etc.
 Partial
separation
of
these
optimum
conditions
from
direct
economic
considerations: optimum operation design
 Usually meaningless: economic considerations ultimately determine most
quantitative decisions.
J. PRACTICAL CONSIDERATIONS IN DESIGN
 Must never loose sight of the practical limitations
 For example, exact diameter of the pipe calculated from optimum economic
design not necessarily “must” be used in final design

If optimum I.D. = 3.43 in (8.71 cm) not practical to fabricate this. Instead,
purchase readily available standard 3 and 1/2 in diameter pipe (I.D. = 3.55
in = 9.02 cm)
 Physical problems involved in final operation and maintenance of the designed
equipment

Crucial (extremely important) control valves at easily accessible to the
operators

Sufficient space must be available for maintenance personnel to check, take
apart, repair equipment
 For example, theoretical designing of a distillation unit may indicate (suggest)
that the feed should be introduced on one particular tray in the tower. Instead of
specifying a tower with only one feed inlet on the calculated tray, the practical
engineer will include inlets on several trays above and below the calculated
feed point: actual operating conditions for the tower will vary and the
assumptions included in the calculations make it “impossible” to guarantee
absolute accuracy.
K. THE DESIGN APPROACH
 Computers can solve problems in process development and design rapidly with
a higher degree of completeness, which generally, can reduce overdesign and
safety factors: consequently a substantial savings in capital investment.
 However, at no time, should the engineer be led to believe that plants are
designed around computers.
 The general approach in any plant design involves a carefully balanced
combination of theory, practice, originality and plain common sense.
 To be prepared to make many assumptions: no absolutely accurate values or
methods of calculation are available.
 Realize the uncertainties in design
 Economic conditions and limitations: always better to sell many units at a low
profit per unit then a few units at a high profit per unit.