1. CONCEPTUAL
DESIGN OF
CHEMICAL
PROCESSES
•
James M. Douglas
ｕｮｾｲｳｩｬｙ of Massodwsttts
McGraw-Hili Rook Company
New York 51 Louis San Frlnciseo !lockland 80101. Cliracu Colorado Springs
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2. CONCEPTUAL DESIGN OF CHEMICAL PROCESSES
INTERNATIONAL EOIlION 1988
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Copyright G1988 by McGraw-Hill, nco All rights reserved.
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The production supervisors were Diane Renda and LDuise Karam.
Ubl'ary of Congress Cataloging-in-Publieation Dala
Douglas,James M.(James Merrill)
CoooeptuaJ design 01 chemical processes.
(McGraw-Hili chemical engineering series)
Bibliography:p.
Includes index.
1. O'Iemical prooesse5. I. Tille. II. Series.
TPl55.7.D67 1988 660.2'81 87-21359
ISBN D-OHl1n62·7
When ordering this title use ISBN 0-07·100195--6
Printed In Singapore
ABOUT THE AUTHOR
James M. Douglas, Ph.D.. is currently a professor of chemical engineering at the
University of Massachusclls. Previously he taught at the University of Rochester
and at the University of [klaware. Before entering leaching, he spent five years at
ARea, working on reactor design and control problems. l-Ie has published
extensively in areas of reacting engineering, process control (including two books).
and conceptual process design. He won the Post-Doctoral FellowshIp Award at
ARea, the Faculty Fellowship Award at the University of Massachuselts, and the
Computing and ChemIcal EnglOeerlOg Award of AIChE.
3. DEDICATED TO:
The loves of my life,
My lovely wife. Mary E. (Belsy) Douglas,
My mOlher, Carolyn K., and the memory of my
falher. Merrill H. Douglas,
My two wonderful kids, Lynn and Bob,
aod to my colleagues, who have taught me so much aboul
design and control,
Mike Doherty, Mike Malone, Ka Ng, and Erik Ydstie,
and to my students, who have suffered so much.
4. CONTENTS
Preface ..
Part I A Strategy for Process Synthesis and
Analysis
The Nature of Process Synthesis and Analysis I
I-I Creau,·c Aspcc;:u of Proo:;;ess Onlg" 3
1-' A IhcraKhlCal Approach to Conccplual Iks.lgn
•
1-3 Summary. Eac:rcue5, and Nomcnclil1urc
"
2 Engineering Economics 2J
'-I Cost Informalioo Requned
"
,-, Estimating Capital and OpelaliDg Costs 32
'-3 Toral Capital 'nvestment and TOIII ｐｲｯ､ｵｾ Costs 37
'-4 Time Value of Money
"
,-, Measures of Process Profitabllll)'
"
,-. Simphfymg the economIC AnalysIs for Conceptual Designs ...
'-7 Summary, Eacrciscs. and Nomenclature ..
3 Economic Decision Making: Design of a
Solvent Recovery System 72
3-1 Problem Dclimllon and General ConsideratlODS 72
3-' Design ora Gas Absorber. FlowshcCl, Malena! and Energy
Balances, and Stream COSIS
"
3-3 equipment Design Conslderauons
"
3-4 Rules of Thumb
"
3-' Summary, eXerCISeS, and Nomenclature 90
x;
5. xii ｾＮ ｲｯｾ xiii
Part II Developing a Conceptual Design and 9 Cost Diagrams and the Qujck Screening of
Finding the Best Flowsheet 97 Process Alternatives 28.
'-1 Cost Diagrams 28.
4 Input Infonnation and Batch versus Continuous 99 '-2 CQ5t Diagraml for Complex Processes
'"
Input (nfonnabon 99 '-3 QUl<:k Screenmg of Process Ahemalh"es JOJ
'-1
'4 HDA Process J08
.-, u'"el·! DecIsion 8atdl venus Continuous 107
.-, Summary, uerasc. and Nomenclature Jll
'-J Summary, Elercues., and Nomenclature 111
5 Input-Output Structure of the Flowsheet 116 Part 11 Other Design Tools and Applications 317
'-1 Decisions for lhe Input-OulPUI Siructure 116
ｾＬ Deslgn Variables, Overall Malerial Balaooes. and Su"am Costs 123 10 Preliminary Process Optimization JI9
'-J Process Altc:malives IJ2
10-1 DesIgn Vanabla and Economic Trade-oll"s J20
'4 Summary, EJ.erriscs" and Nomc:oclaturc IJ2
10-2 Cost Models ror Prooess Units J27
Io-J A Cost Model ror a SImple Process m
6 Recycle Structure of the Flowsheet 137 104 Approlimate Optlmiution Analysis J40
10-' Summar). Exercises. and Nomenclature
".
..1 DeCIsions that l)etermme the Recycle Structure 137
.., Recycle Material Balances 14' II Process Retrofits
..3 RuetOf Hut Etreeu 14' m
... EA:juilibnum L!mltalJOns 14. II-! A Systematic Plocedure for Process PeHofilS ".
.., Compressor Design and Costs 13J 11·2 HDA Process Jl8
.-. Reaelor DesIgn 13. 11-3 Summary and ExerCIses 368
'-7 Recycle F.oonomlC EvaluatIOn 138
"8 Summary. berClSeS,. and NOOlCnclature 13. 12 Computer-Aided Design Programs
(FLOWTRAN) J69
7 Separation System 16J 12·1 General Struclure of Computer-AIded Design Programs J70
12-2 Malenal 8alaoo: CalculatiOns J7l
7-1 General Slructure or the SeparatIon Syslem 16J
12·] Comp1ele Planl Simulation J97
7-' Vapor Reoovery System 168
124 Summary and Exercises '04
7-J Uquid Separalion SYSlem 172
14 AZC'olroptC Systems 189
13 Summary or the Conceptual Design Procedure
7-' Rigorous Material BaJances 204
7-' SummaI"}'. ElerCJSCS. and Nomenclature 211 and Extensions of the Method 40'
13-1 A RevlC"" 01 the HIerarchICal Decision Proa:dure for
Pelrochemical Processes 406
8 Heat-Exchanger Networks 21' 1]-2 Design of Solids Processes and Batch Processes 408
8-1 Minimum Heating and Cooling Requirements 21' 1]-] Olher SignifICant Aspe<:ls or lhe Design Problem 412
8-' MInimum Number of ElchangeD '30
8-J Area Estlm.ates 2JJ
84 Design of Mlnrmum-Enerl)" Heat-EJ.cbanger Networks '36 Part IV Appendixes 42J
8-' Loops and Paths 248
8-' Reducing the Number of ｅｬ｣ｨ｡ｮｾｄ 231
8-1 A More Complele Design Algorithm Stream Splilting 231 A Shortcut Procedures for Equipment Design 42l
8-8 Heal and Power Integration 261 A-I Number of Trays ror a Gas Absorber ."
8-' Ileal and DIstillatIOn '64 A-' Dist.illation Columns" Number or TraY$ 4]'
8-10 HDA Proass 27J A-J Design of Gas AbsorbeD and Dlslillauon Columns
."
8-11 SummaI"}'. EJlerasc::s, and Nomendature: '84 A4 DIstillation Column Sequencing 461
6. xit' CONTEP'lT$
A·' Complex Distillalion Columns 466
... Energy Integralion of DiSllllalion Columns .18
A·7 Heal_Exchanger Design .86
... Gas Compressors .90
A·' Design of Refrigeration SySlems .90
A,IO Reactors S07
A-II Summary of Shortcut Equipment Design GUldel.tncs and
Nomenclalure for Appendix A S07
B HDA Case Study
'"
C Design Data 543
C·I Hydrocarbon Vapor-Liquid Equilibria 543
C·, Temperature Ranges for some Materials 547
D FLOWTRAN Input forms 548
D·I Component List 548
D·' IFLSH
""
D·3 AFLSH SSl
D4 SEPR
'"
D·' ADD '54
D·6 SPLIT
'"
D·7 PUMP
,,.
D·8 GCOMP
'"
D·' SCVW ",
D-IO DSTWU '6'
D·ll REACT
""
E Cost Data S6S
E·I Operating Costs
'"
E·' Summary of Cost Correlallons
,.,
F Conversion Factors S78
Indexes "I
Author Index "3
Subject Index so,
PREFACE
llLis book describes a systematic procedure for the conccptual design of a limned
class of chemical processes. The goal of a conceptual design is to find the best
process f1.owsheet (i.e., to select the process units and the interconnections among
these: units) and estimate the optimum design conditions. The problem is dif-
ficult because very many process alternatives could be considered. In additIOn,
experience indicates that less than I % of ideas for new designs ever become
commercialized. Thus, there are many possibilities to consider with only a small
chance of sUCGCss.
In man} cases the processing costs associated with the various process
alternalives differ by an order of magnitude or man:, so that we can use shortcut
calculations to screc:n the alternatives. However, we must be certain that we are in
the neighborhood of the optimum design condilions for each alternative, 10 prevent
discarding an alternative because of a poor choice of design variables. Hence, we
use cost studies as an initial screc:ning to eliminate ideas for designs that are
unprofitable. If a process appears to be profitable, then we must consider other
factors, including safelY, environmental constraints, conlrollability, ele.
We approach the synthesis and analysis problem by c:stablisWng a hierarchy
of design decisions. With this approach, we decompose: a very large and complex
problem into a number of smaller problems that are much simpler to handle. By
focusing on the decisions that must be made at each level in the hierarchy (e.g.. Do
we want to add a solvent recovery system?), we can identify the existing
technologies that could be used to solve the problem (e.g., absorption, adsorption.
condensation) without precluding the possibility that some new technology (e.g., a
membrane process) might provide a better solution. Moreover, by 'listing the
ahemative solutions we can propose: for each decision, we can systematically
generate a lisl of process alternatives.
In some cases it is possible to use: design guidelines (rules of thumb or
heurislics) 10 make some deciSIOns about the structure of the flowshect and/or to
set the values of some of the design variables. We use order-of-magnitude
"
7. arguments to denve many of these heunsucs, and we use a simple analys15 of this
type to identify the limllatlOns of the heuristics. In many cases. no heuristics are
available, and therefore we develop shortcut design methods that can be used as a
baSIS for making decislons_
B) follOWing this hierarchical decision pr()(X(Jure. a bt=ginmng designer can
substitute the e'aIUalion of a number of exIra calculations for experience dunng
the dC'elopment of a conceptual desIgn Since shortcut calculatIOns are used.
however. the penalty paid in the lime required to screen more alternallves is nol
'cry high Of course, as a designer gaUlS experience, she or he will be able to
recognize what alternatles do not need to be conSidered for a particular type of
process and thereby obtalO an increase m effiCiency, Note also that expenence
normally IS required for assessing lhe operability of a design. and lherefore a
begmner should always get an experienced designer to review the resulls of the
design study
ｏｲｾ｡ｮｩｺ｡ｴｩｯｮ of Ihe Text
The text is meant to be used in a one·semester, seDlor-levei course in process design
for chemical engineenng students. We present the material as a Iccture course. A
single case study is carried throughout the te.:l.l 10 illustrate the ideas, and the
homework assignments mclude lhe evaluation of alternatIves for the oc:ntral case
study, as lIell as sevcral other case studies. The purpose of these Olher case studies
is to Iw':lp the student undcrstand the similarities and differences betwttn 'arious
t)·pes of processes (e.g.• smgle reactIOns 'ersus product distnbutlon problems. cases
where gas·reg·cle costs domlOate. cases where liquid separation costs dominate.
the choice between recychng or removlOg by-products formed by reverSible
reactions, the economic trade-offs encountered when a gas recycle and a purge
stream is used, etc.). The focus is on scrttning calculations, although a ｣ｯｭｰｵｴ･ｲｾ
aided design program is eventually used to verify the apprOllim3liQos
Part I discusses a slrategy Qfsynthesis and analysis.. In Chap. I it is nQled lhat
only about I % of ideas for new designs ever become commercialized, SQ thai we
need an efficient procedure for eliminating poor projects Similarly. sinoc: design
problems arc always underdetined and we can orten generate 10- to 10' alternati'·e
processes even for a single·product plant. we oeed an efficient way of screening
process alternatives. These discussions provide the motivation for the use of
shortcut calculations. Also, a procedure for decomposing process nowshecls into a
hierarchical sct of simpler problems is presented.
Otapter 2 presents an mtroduction to engineering economics, including a
discussion of various measures of profitability. In addltioo. a simple economic
model thaI is useful for conceptual designs IS de'e1opcd
Chapter 3 presents a very simple design problem (actually a subsystem of
what could be a larger dC"ign problcm) This example ｩｬｬｵｾｴｲ｡ｴ･ｳ how simple it ｩｾ lQ
generate proocss alternatives. the need for design heunstlcs. the: origll' of dcslgn
heuristics, the IImltallOnS of design heUristiCS, the IOleractiolls among prQOCSSlOg
units, the need for a systems Viewpoint in place of a unit operatIOns viewpolOt. and
ｨｯｾｴ shorlcut design melhods can be developed
Part II presents the details of the hierarchical decision procedure for the
synthesis and analySIS of conceptual designs. Chapter 4 describes the infonnation
needed to get started, and lhe decision of designing a balch versus a continuous
process is discussed Chapter 5 presents the important decisions for the input and
output structure, the identification of the important design variables at this level of
complexity, and shortcut procedures 10 calculate the stream cosls and the costs ofa
feed compressor (if one IS reqUired). Chapter 6 introduces the additional deciSIOns
required to fix the overall recycle structure of the f1owsheel. i.e., the interaction of
the reactor system(s) with the remainder of the process The reactor cost and any
gas-recyck compressor costs are evalualed in terms of the design variables This
discussion is limlled to single-product plants.
At present. lhe systematic preliminary design procedure is also limited to
vapor·liquid processes. For this class of processes. the structure of the separation
system (i.e.• the general structure. vapor recovery system alternatives, and the
decisions fQr the liquid separation system) is described in Chap. 7. Chapter g then
presents a synthesis procedure for the heat-exchanger network. At this point, a
base-case design and an estimate of the oplimum design conditions arc available
Our basic design strategy is to develop a base-case design as rapidly as
possible. simply listing the process alternativcs as we go along. to determine
...hether there is SQmething about the process that will make all Ihe alternatives
unprofitable. Provided that our base-case design appcan to bt= promising. ｾＧｃ ｵｾ
the methods in Chap 9 to screen the process allernativcs. Thus. at this POlOt we
allempt to identify the best process flowsheet.
Part III presents some other desIgn tools and apphcations. In the procedure
presented in Chaps 4 through 9. we used ｣｡ｳ｣Ｚｾｳｴｵ､ｹ cakulations to estimate the
oplimum design conditions because we were contlOually changing the structure of
the ftowshtt,.. Once we have identified the best flowshect, we can use more
sophisticated optimization procedures. However, to assess the degree ofsophistica-
tion that is desirable, we present an approlfimate oplimizatiQn analysis in Chap. 10.
This approllimate optimization procedure helps 10 identify the dominant econQmic
trade-offs for each design variable, the dominant design variables, and an indica-
tion of how far a design variable IS a.....ay from the optimum without knowing thc
exact value of the optimum This approll:imale optimization analysis is also very
useful for retrofit studies and for oplimum sleady-state control calculations.
In Chap. II we use the same techniques for process retrofits thai we used to
develop a design for a new plant. A systematic procedure is presented for
retrofilting processcs, mcluding completely replacing the ell:isting plant wilh either
the same or a beller process alternative. The approximate optimization procedure
is used to help idenlify the dominant opcratlOg variables and the equipment
constraints that pre'ent the opcratmg costs from being minimi7.ed. Then, based on
these results, additional equipmenl capacity is added until the incremental,
annualized equipment coS! balances the incremental decrease in operating
""" In Chap 12 ｾ･ diSCUSS Ihe use of a compuler-alded design program 10
Improve lhe accuracy of the shQrteul calculations Chapler 13 presents a summar)'
of the design procedure, briefoutlines of hierarchical decision procedures for ｳｯｬｩ､ｾ
8. x"iii HUAU
and balch processes. and a brief dIscussIOn of what remams to be done after a
conceptual design has been completed
The appendixes present some auxlhary information. The shortcut mOt.lels for
equipment design are dISCussed in AppendIx A, and the complete details of a case
study aregnen in AppendIX B Some samples ofdesign data and cost data are gIven
in Appendixes C and E.
AcknoMledgmenls
I am 'ery appreciative of the etrorls of A Ene Anderson (formerly with ARCO).
Duncan Woodcock of Imperial ChemIcal Indusllies, Edward C. Haun of UOP
Inc., JetrKantor. University ofNotre Dame; Carl F. King from duPont, E. L Sherk
from Euon, R. Hoch (formerly with Hakon International), John Scinfeld,
California Institute of Ta;hnology and J. J Sirola from Tennessee Eastman Co. for
their careful review of the texl. Similarly. I am grateful to the chemical enginccnng
students at the University of Massachusetts and to tbe students from Imperial
Chemical Industries (United Kingdom), Rohm and Haas, Monsanto, Union
CarbIde and Celanese, for many valuable comments concerning the course
material. In addition, I must acknowledge the numerous conlfibutions that my
colleague Mike Malone made to the text, and I want to thank my other colleagues
Mike Doherty, Erik Ydstic, and Ka Ng for their feedback when they taught the
material. The contributions of my graduate students, particularly Wayne Fisher
and Bob Kirkwood. also need to be ackno.... ledged.
Of course, I am especially grateful to 01) lovely .....ife. Betsy, to my children.
Lynn and Bob, and to my mOl her, Carolyn K.. Douglas, for [hel! support dunng
the preparation of the text. SImilarly, Pat Le.....IS. my admmistrative assistant. and
Pat 8arscheoski. who did the typmg, proldcd mucb oeeded support.
James M. Douglas
CONCEPTUAL DESIGN OF
CHEMICAL PROCESSES
10. CHAPTER
1
THE
NATURE
OF PROCESS
SYNTHESIS
AND A ALYSIS
J.I CREATIVE ASI'ECfS OF PROCESS
DESIGN
The purpose of engmeenng is 10 create new malenal wealth We auempt to
accomplish this goal in chemical engmeering via the chemical (or bIological)
transfonnation and/or separation of malcrials.. Process and plant design is the
creative activity whereby we generate ideas and then translate them inlO equipment
aDd processes for producing new malerials or for significantly upgradmg the value
of cJ:isling materials..
In any panicular company. we might Iry 10 generate ncw Ideas.
To produce a purchased ra..... malenal
To cantrt a waste by-product 10 a valuable product
To create a completely new malenal (synthetic fibers, food. bioproccs£mg)
To lind a lIew way of producing an cxlsting product (a new catalyst. a
bioprocessing allernative)
To exploH a new technology (genetic engmeenng. expert systems)
To exploit a new material or construction ＨｨｬｧｨＮｴ｣ｭｾｲ｡ｴｵｲ･ﾷ or hlgh-
prc:ssure-operalion, Specialty polymers)
J
11. As an indIcatIon of the ｉｾ｣ｭ･ｮ､ｯｵｳ suc«ss of the engineering effort, we note Ihal
over ＵＰｾ oflhe products sold by mosl chemical companies ｷ･ｾ･ developed during
the last decade or Iwo_
SUCCe<iS ｒ｡ｴｾ
Despite thiS ucdlcnt record of SUct%S5.....e should realize that very few ne.... ideas.
either fljr Improvmg Clllsting processes or fordevdoping new prOttSs«.lead 10 new
....-eahh In fact, lhe chano:::s of commercialization at the research stage for a new
process arc only about I to ｊｾ .. at thedee1opment stage they arc about 10 to Ｒｓｾ｟
and al the pilot plant stage lhey arc about 40 to 60%· Of course, we expect that
the success rale for process modifications Will be higher than that for completel)
new proocsscs. but the economic rewards associated with these safer projects will
have a Significantly lower potential
It is not surprising that so few ideas 10 engrneering ever prove to be fruitful:
the same paltern holds for any type of creative activilY. Sincc experience mdicates
lhat only a small number of ideas e,,'er will ha ve a payout, we see that et'olUalion IS
one of the most slgmficant components ofany design methodology. In fact. process
synlhesis. i.e.. the selection of equipment and the interconnections belween that
equipment which will achieve a certain goal, is really a combination of a synthesis
and analysis activity.
S)·nthesi.. and Anallsis
Perhaps the major feature thai dlStlllgulshcs dcslgn problems from olher t)pes of
engmeenng problems 15 that they are underdefined: i_c.. only a very small fraction
of the mformatlon needed to define a design problem is available from the problem
statemenl_ For example. a chemISt might discover a new reaction to make an
eKistmg product or a new catalyst for an existing, ｣ｯｭｾｲ｣ｩ｡ｬ reaction. and we
want to translate these discoveries to a new process. Thus, we slart with only a
knowledge of the reaction conditions that ....-c: obtain from the chemist, as well as
some infonnation about available raw materials and products that we obtain from
our marketing organization, and then we need to supply all the other information
that we need to define a design problem.
To supply this missing information. we must make assumptions about what
types of process units should be used, how those procc:ss unils will be ｩｮｴ･ｲｾｮﾭ
nected, and what temperatures., pressures. and process flow rates will be required.
This is the synthesis activity. Synthesis is difficult because there arc a vcry large
number (10· to 10') of ways that we might consider to accomplish the same goal
1-leIlCC. design problems arc very ｯｰ･ｮｾｮ､｣､
• Thes<: values rerrest.nr the ｡ｾＮ｡ｾ of CSl"nalei supplied by ｓｬｾ r.>n><b worl I'll In Konom,c
evalua!r('ln I'ours of maJO' chemrcal and I"'I,olwm OOm",,"1tS
S£CTION 'I CIlUTIVI! ASl'fCTll ｏｾ I'llocas ｾｓｉｇｎ 5
Nonnally......e wanl 10 find the process alternative (OUI of the 10· to 10
0
possibilities) that has Ihe lowest cost, but .....e must also ensure that the process IS
safe. will satisfy environmental ｣ｯｮｳｴｾ｡ｩｮｴｳＮ is easy to start up and operate. etc. In
sotnC cases, we can usc: rules of thumb (heuristics) 10 eliminate certain process
alternatives from further conSIderation., bUI in many cases it is ne:ttSsary to design
V.lnous altemati'es and Ihen 10 compare their costs Experienced designers can
mmlmlze the effort rtquircd for thIS type ofevaluation because they can often guess
the costs of a parhcular unit. or group of units. by analogy 10 another ｰｲｾ
However, beginmng desIgners normally must design and evaluate more altema-
tu-es in order to find the best altemati-e_
When experienced designers coDSider new types of problems, where they lack
experiencc and where they cannot idenlify analogies. they try to use shortcut (back-
of.the-envelope) design procedures as the basis for comparing altemati·cs. These
back-of-the-envelope calculations are used only to screen alternatives.. Then if the
process appears to be profitable, more rigorous design calculations an: used to
develop a final design for the best alternative. or the best few alternatives.
Because of the underdefined and open-ended nature of design problems, and
because of the low success rates. it is useful to develop a strategy for solving design
problems. We expeet that the strategy that a beginnmg designer would use fOI
synthesis and analysis would be different from that of an experienced designer.
because a beginner must evaluate many more process alteroatives. However. b}
usmg shortcut design procedures .....e can minimize the effort required to undertake
lhese additional calculations
Engineering Mefhod
If we reflect on the nature of process synthesis and analysis. as discussed above, '·..e
recognize that process design aClually is an art., ie., a creatn'C process. ｔｨ･ｲ･ｾｯｲ･Ｎ
l..e might try to approach design problems in much the same way as a pamter
de-c:lops a painting. In other words. our original design procedures should
oorrespond to the development of a pencil sketch, where we want to suppress all
but the most significant details of the design; i.e., we want to disco..-c:.r the most
expensh'c parts of a prooess and the significant economic trade-offs. An artist next
c-.aluates thc preliminar} painting and makes modifications. using only gross
outlines of the subjects SImilarly. we want to evaluate our first guess at a design
and generatc a number of process alternatives that might lead to imprO'o'emcnts. In
this way, we hope to ger...::ratc a "reasonable-looking," rough process ､ｾｩｧｮ before
we Slart adding much detail.
Then lhe artist adds ｣ｯｬｯｾＮ shading, and the details of various objocts in the
painting and reevaluales the results. Major modifications ｾ｡ｹ be ｩｮｴｲｯ､ｵ｣･ｾ if the}'
soem to be wflrranted. In an analogous manner, the engmecr uses more rigorous
design and costing procedures for the most expensive e(luipment items, improves
the accuracy of the approximate-material and energy-balance calculations, and
adds detail in terms of the small. inexpensive equipment items that are necessary for
12. 6 SECTJO'II I I CIU. TlVE ASPECTS or PlOCESS OESIGN
the process operations but do not hae a major impact on the total plant cost, e g,
pumps. ftash drums, elc,
Thus, .....e s..e thai bolh a palnllng and a process design proceed through a
scnes ofsuccessively more detailed synthesis and evaluation stages. Thatcher refen
to a solution sirategy of this type as SUCCeS!MC refinements, and he: call!> It ｴｾ
rngltli'erltlg mf'lhod· otc that as .....c malc successivc refinemcnts, ""c should
always mainlalO a focus on the ol}f!rall problrm.
If wc accept thiS analogy betwccn cnglDeering design and art, then wc can
recognize some other IOterestlOg fealures of the design process. An artist never
really completes a painling; normally the work is termlOatcd whenever the
additional effort reaches a point of diminishing rcturns; i.e., if little added value
comes from much additional effort, the effort is DOl worthwhile. Another feature of
art is that therc is never a single solution to a problem; i.e... thcre arc a variety of
ways of painting a "great" Madoona and Child or a landscape; and in pr0ces5
engir-cering nonnally different proc:essing routes can be used to produce the same
chemICal for essentially the same cost. Slill another analogy between cngineering
design and art is thai it requires judgment to decide how much dClaii should be
included in thc various stages of painung. just as it docs in a process design.
Of course, numerous SClcntific pnnciples arc used ID the dcvdopment of a
design, bUllhc overall activity is an art In fact, it is this combinatton ofsocncc and
art in a creative activity that helps 10 make process design such a fascinatlDg
challcnge to an englOcer.
u·els of Enginei.'ring Designs
Now we sec that there arc a number of levels of engmcering designs and cost
estimalc:s that wc cxpect 10 undcrtakc. These vary from very simple and rapid, but
not very accurate, estlmatcs to very detailed calculations thai are as accuratc as we
can make. Pikuhlr. and Diazt e1assify these dcslgn estimates by the categories given
in Table 1.1-1.
They also givc the relativc costs required 10 oblain these eslimatcs. as shown
in Table 1.1-2. From tbis table we sec how rapidly cng!Decrio& costs increase as we
!Delude more detail In the calculations, Obviously, we wanl to noid Iargc dcslgn
costs unless thcy can be economically Justified.
• C. M Thald",r. 1M ｆｾＬＮＬ ..1s ｲ［ｻｃｾＬＢＱｎＱ EttgI-wr,"'fI. Mcrrill Columbus, OhIO. 1962, chap J
I A Ptkuhk and H E. D.u., ·COSI &umaunl Major P,oec:ss ｅｱｵｬｰｭ｣ｮｲＮｾ CIlnn. ｅｮｧｾ 84(21): 106
(11I17). ｎｏｉｾ These accu,aey bounds ..,11 var, "0111 one: eompany 10 anOther, and Ihc .ccuncy of Ihoc
dclalkd ｃｾｬｬｭ｡ｬ｡ｩ Will nO{ be Ih.s good dunn. ｰｭｯ､ｾ ofh.gb 1IIftallon (Ihc cnon mlghl be as much as 8
1010'""
.. even for a delalled cslmulle) Abo, nOrmall) Ihe ch4ncc 01 oblalmDI poIlu.e cnon Il; I,,:alcr
than lhal for nellamc urorl., 50 Ihal 11M: order-ol·maSlUlu<!e esl,malc, I c. Ilcm I. ViOuld be rcportcd itS
+40 10 - 25 %(des.gn enIJrtCI"s seldom Overc:lilUnatc COSlJ,) S,mlla,I" hlpr eolltlrtgcOC' kcs rna, be
tndudcd III Ibc arloc' Icvcls(lhal J$, 10 10 2S}; In lIem } dropplDllO 10% ID .tcm oi) 10 accounl rorCOlls
not Included In tnc anal)'UI (.. hlCh IS somc:.. ta..l d.tre:rcnl r"ltD Ihc KCUnley 011"" c::IlUDalc)
SECTION I I Cll!A1WE ASI'ECT'S Of PlOClSS DESION 7
TABU: I.t-t
Types of desiCn estim.tcs
1_ Ord,u-ol-mapuludc ,""l1m.Ile(nbOc:lilunale) based oa .m"lar preVlOUI Wsl cia.... p,obabk aocunq
uaocdJi ＱＴＰｾ［
2. Slud, elumalc (rad""cd a.lJm.llc) bued On Ir.DO... J.cdJf- 01 D.lIJOI I!Cm!l 01 eqwpmUII. probabk
....."'t, up 10 ｩＲＵｾｾ
1. Prdlllllnary ail'male (budget aulltonuUon ,""umalc. ICOpc ct.llIIU.!c) based oa sulliocr.l dala UI
pclmll ItIt aiUmalc 10 be budaclcd. p,obabk accuracy WIthin ＮＱＱＲｾＮ
(. DclinlUVoc c:lillmatc (pro}Cd control e1illma!c) hued OQ almost compkle datI, bul bdorc compktlOll
ordnwlngl and Ipce:,jiQlllolU. probabk a<:cUUC, Wllhln :I. Ｖｾ
So DclaiJ.cd eltlffillc (CODtnldOI'1 csumalc) baled on compklc cnll_nnl dn"'mp. Ipco;tfiallOM.
aIld Nle .urve,s; probabl, &CQInq ",.thln ±J%
F,om It.. f"Ikulilr. ud H E. DIu, ·COll Eit.....lIDI Majol PtOCCSl Equ;pmcM,· CIu-..... bot, IotIll) 106 /1'77)
For the case o! a ncw process. whcrc prcvious cost dala are nOI availablc, it
seems as if it would Dot be possible to dcvelop an order-o!-magnitude estimate
However, an cxpcric:oced designer can o'crcomc this difticully by drawing analo-
gies between thc new proocss and other existing processes for which some data arc
available in the company files. Procedures for dc,·eloping order-of-magnitudc
estimates have been described 10 the literature,· but normally it requircs some
cxperience 10 cvaluate the results obtamed from Ihis t)'pe of calculatiOn.
For a beglOning dcslgner, with little or no experience. It would be useful to
ha'·c a systcmalic approach for ､｣ｾｬｯｰｬｏｧ order-of.magmtude estimates We can
usc: order-of-magnitude arguments to Simplify man)' of the design calculations, and
.....e can limn our allcntlon to Ihe major pieces of process equipment as we carr)' out
a prehmmary process design The goal of this lext IS 10 develop a systematic
• J. H ｔ｡ＬｾＬ - Pr(l(;C:$$ Step-Soonn, Mclhod fOf Makln& Quick Capllal EallmalQ,- C-.J' £log., P. 207,
J:l1,·AuJII5I 1910 0 H AIIc:n. and II; C Pace. PRcV!Kd Tcdtn>quc for P<aiallll Cosl Eaumallo,,-
CM""- ﾣｎｊｾ 12(5) loi2 (March J, Ins).
TABU: 1.1-1
EagiDeC:ring costs 10 ｰｴＢｾｰｵ･ estim.tes (1977)
.........
51 lIIiIIi.- SI-$.! oniltiooo S5-s.5O MiItiooo
Typt of ntimalc ..... ..... ....
Siudy (S lhouurtds)
," 02)0 ,0<O
Prclunmary ($ IhotlSdrtd.1 IS JS )060 lO90
Dcli...uvt (S .hOWoiln,hl
"'" 60 020 100230
F..- It.. P'ihli. uod 1I E. o.a.. .ea.. Eou....' .... Ma)Ol Procea Equ,.........• ""'"
&rr, Iot(ll) 106 11'71)
13. 8 SECTION II ... HIU....CHlCAl ..,....(M,CH TO CONCEI'TUA.L OI:$IGI<
ｓｾｏｉｯｬ I J ... ｈｉｅｾｃｍｉｃａＮｌ ...rPRO..CM TO CONcrI'TUA.L I>EllION .,
procedure of this type and then to show how the results can be extended to a study
estimate.
Detailed estImates are considered 10 be beyond the scope of this text
However, as noted before,the chance that a new idea ever becomes commercialized
is only about I ｾ .. so that .....e expect to undertake roughly 100 preliminary designs
for every detailed design. Hence. the methodology of conceplUal process design
should be mastered in considerable detail.
Other Applications of fhe l1ethooology
Despite the fact thaI our primary focus is dllcctro to lhe design and evaluation of
new processes, much of the melhodology .....e develop is useful for other engineering
tasks. including basic research and technical service. In basic research, we want to
spend most of our effort studying those variables that wjJl have the greatest
economic impact on the process. and rough prooess designs will help to identify the
hlgh--cost parts of tbe process and the dominant design variables. Sinularly. in
technical service activities., .....e look for ways of improving an existing process. To
accomplish this goal, we need to understand the significant economic trade-offs in
the process, and it is useful to have procedures available for obtaining quick
estimates of the potential payout of new ideas. Thus, the methodology we: develop
will have numerous applications in the process industries.
IHeal
Ccmp....... I
Purge
""tH.. I
IHcat I
Reactor CooIllDl
- Ft""
IHcat I IHca' I H2, CH",
I )- 1- Benune
•
u
" Jj
Toluene ]. "
ｾ
"& :D
• •
ｾ ｾ
i
Diphenyl T
ncURE 1.2-1
HDA process lAfttrJ M DDt.gloJ. AlOE J. JJ JH (l9&.S).]
Tbe e.xample we consider is the hydrodealkylal1on of toluene: to produce ｢･ｮｺｾｮｾＮﾷ
The: reactions of Interest are
1.2 A HIERARCHICAL APPROACH TO
CONCEPT AL DESIGN
Example: Hldrodealkylatioo of ｔｯｬｾｮ･ (HDA
Process)
• TIlls CIl"" .Iu<!y rC-p'nC'nIS" mod.fiecl "t'ntOll 01 1M 1961 ａｾｮ｣｡ｮ tmhlule 01 Cberwcal En&,,,",,s
(AIChE) Siudenl ｃｯｮｬｾＱ Problem. J« J J McKC"lIa. bc)"C"kJ"rd,o t>f Clw"'lC'oJ PrOCtssutQ _tl/N",,,.
vol "". Dekker, New York, t9n, pin. ror lhe on&,nli problem.oo • .mUlIon
The homogeneous reactions take place In the range from IISOoF (below this
temperature the reactIOn rate 15 too slow) to ＱＳＰＰｾｆ (abo'e this temperature a
significant amount of h}drocrackmg takes place) and at a pressure of about
500 psia. An e:xcxss of h}"drogen (a 5/1 ratio) is oc:c:ded to prevent coklOg. and the
reactor effluent gas must Ix rapidly quenched to I 15O"F in order to pre'ent cokmg
m the: heat exchanger following the reactor.
One: possIble: fJowshc:c:t for the: process is shown in Fig.. 1.2-1. The toluene and
bydrogen raw-material streams are: heated and combined with recycled toluene
and hydrogen streams before they are fed to the reactor. The product stream
leaving the reactor contains hydroge:n, methane, benzene, toluene, and the unwant-
ed diphenyl. We attempt to separate most of the hydrogen and methane hom the
aromatics by wing a partial condenser to coodense the aromatics., and the:n we
flash away the light gases We: use the liquid leaviog this flash drum to supply
quench cooling of the hot reactor gases (not shown on the 80wshee:t).
We would like to recycle the hydrogen leaving in the: flash vapor, but the
methane:.. which enters as an impurity io the hydrogen feed stream and is also
produced by reactioo 1.2-1, will accumulate in lhe gas-reeycle loop. Heooe, a purge
stream is required to remove both the feed and the: product methane .from the
proceSS. Note that no rules of thumb (design guidelines) can Ix used to estlma.te the
optimum cona:ntration of methane that should be allowed to ｡｣｣ｵｭｾｬ｡ｴ･ m the
gas-rec}"C1e loop_ We discuss Ihis design variable in much greater ､･ｴ｡ｬｬｬｾｴ･ｾＮ
Not all the hydrogen and methane can beseparated from the aromatics 10 the
flash drum, and therefore we remove most of the remainlllg amount in a distIllation
column (the stabilizer) to pre'ent them from contaminating our benzene product
(12-1)
(I 2-2)
Toluene + HJ ....... Benzeoe + CH..
Ｒｂ･ｮｺ･ｮ･ｾｄｩｰｨ･ｮｹｬ + Hz
The engulec:nng method (or the: artist's approach) indicates that we should sohe
design problems by first de'eloping vcry simple solutions and then adding
sua:essi'e layers ofdelail. To see hoYt we can ｾ this approach for process design
problems. we consider a typtcal fJowshc:c:t for a petrochemical process, and Ihen we
look for ways of stripping away layers of detail until we obtain the simplest
problem of interest. By applying this procedure to a number of different types of
procc:ssc:s, we: might be able to recognize a general pattern that we can use as the
basis for synthesizing Dew processes.
aod
14. 10 5EClION U A HIE.....CHlCAl AI'f'lOACH 10 COIICEPTI,IAl OfSlGN
The benzene is then recovered in a second dlstlllation column, and finally, the
recycle toluene is separated from the unwanted diphenyl. Other, alternative
flowsheets can also be drawn, and we discuss some of these as we go through the
analysis.
Energ:r Integration
The process f10wsheet shown III Fig 12-1 IS not very reahsllc because: II implies
that the heating and coohng requirements for every process stream will take place
In separate heat exchangers uSing external utilities (coohng water, steam, fuel. etc.).
In the lasl decade, a new design procxdure has been developed that makes II
possible 10 find tbe minimum healing and cooLlIlg loads for a proa:ss and the heat-
exchanger network that gnes the "best" energy integration. This procedure is
described In detail in Chap. 8.
To apply thIS new design procedure, we must know the flow rate aDd
composition of each process stream and the inlet and outlet temperatures of each
process stream. One alternative f10wsheetthat results from this energy tIllegratlon
analySIS IS shown 10 Fig. 1.2·2.· Now we see that first the: reactor product slream IS
used to partially preheat the feed entering the reactor. Tbc:n tbe: hot reactor lases
arc: used to dnve the toluene: recycle column reboiler. to preheat some more foc:d, to
drive the stabdi7.c=r column reboiler,to supply part of the benzene: product column
reboiler load, and to preheat some more feed before the gases enter the partial
condenser_ Also the toluene column is prc:ssurized. so that the condenslllg
temperature for toluene is higher than the: boiling point of the: bollom Slream in the
benzene column With this arrangement, conde::mmg toluene can be used to supply
some:: of the benzene rc:bollc::r load. ins-lead of using steam and cooling water from
external sources of utllltlcs.
II we compare the energy-lIlu:gratc:d f10wsbect (Fig.. 1.2-2) with the flowshec:t
indicating only the need for heating and cooling (Fig. 1.2-1), then we see that the
energy integration analysis makes the flowshcct morc: complicated (i.e.. there arc
many more interconnections). Moreover. to apply the energy integration analysis,
we must know the flow rate and composition of every process stream, i.e.• all the
process heat loads including those of the separation systc:m as well as all the stream
temperatures. Since we need to fix almost aU the Bowshcct before we can design the
energy integration system and since it adds the greatcst complication to the process
flowsheet, we consider the energy integration analysis as Ihe last step in our proocss
design procedure.
Distillation Train
Let us now consider the train ofdistiUation columns shown in Fig. 1.2-1. Since: the
unwanted dlphenyl is rormed by a reversible reaction (Eq. 1.2.2), we could recycle
• ThUi wlUllon WH developed by 0 W To..·n!iCnd al lmpenal ChcmlCllllndLl$lf1CS, Runcom., Unlled
Kmldom
ｾ
.l!
"
:t
ｾｾ 1" u
u
.- ･ｾ
" !'. ] tl
2"u
. ｾ
-' " 0-
I;
l"
"
u
•
0-
E
0
ｾ
" 'T ｾ
•
•
,f u:
ｾ " ｾｾ
u ,
ｾＢｂ
.ll ｾ
p
r
ｾ
1
ｾＺ
,
t
uwnjO:) Ｚｉｕｾｾ ( ) )
c1
uwnlOO In!llqllflS ;)
• ..
:t
ｾ
U r
;.. I
'"
,
I 1
uwnlOO ＺＩ｜ｊｾｮｬﾰＮｌ
,
,
>.
T
e r
u I
ｾ
0- L
is
+
0
"
ｾ
'"
"
u
"
u
• -
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, •
"- ｾ
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0
"II
15. 12 s£CTKm 1.;1 Il NIElIllllCHIClll IlPPIIOM'H 10 C'OI'I("(I'Tl'lll DESIGN SECTION 11 Il HlE....IICHlCIll ""PlIOlleH 10 CONO:I'TlJIll DESIGN 13
Benzene
Toluene
(To recycle)
might be chealXr than uSing Ihe configuration shown in the original flowsheet
(Fig. 1.2-1).
The heurisllcs (design guidelines) for separation ｾｹｳｴ･ｭｳ require a knowledge
of the feed composition of the Slream entering the distillation tram. Thus. before we
conSider the ､･｣ｩｾｩｯｮｳ associated v.lth the design of the distillation train, we must
ｾｰ･｣ｬｦｹ the remalOder of the llov.shcct and esllmate the process ftows. For thiS
reason ....e consider the design of the distIllation train before we consider the design
of the heat-<:ltchanger network
Diphenyl
FIGURE t.2--3
Altcmale dislillalion IralOS,
ｴｨｾ diphenyl with ｴｨｾ ｴｯｬｵｾｮ･ and lei it build up 10 an equilibrium le'eL ThiS
alternative would make il powble 10 eliminate one of the distillation columns.,
although the flow Tate Ihrough the reactoT would ｩｮ｣ｲｾ
If we decide: to r«over the diphenyl as Fig. 12-1 indlC3le:s, ....·e expect Ihallhc
toluene-diphenyl spill 1,1,'111 be er)' easy. Therefore. v.e might be able 10 use a
sldestream column to accomplish a benzene-toluene-diphenyl spht. That is, we
could recover the benttne oerhead. remove the toluene as a sidestream below lhe
feed, and reco'er the dlphenyl as a bollom Slream (sec Fig. 1.2.3) We can still
obtain very pure benzene Oerhead if we take the toluene sldestream olf below the
feed. The purity of the toluene reqcle will ､･｣ｦｬｾ｡ｳ･Ｌ howe'er, if It IS reco'ered as a
sidcstream, as compared to an overhead producL Since: there is no specification for
the recycle toluene. the purity might not be important and the savings might be
worthwhile. Similarly, we ellpc:ct that the methane-benzene split in the stabilizer IS
easy. Then, recovering benzene as a sidestream in a H1 and CI-I.
benzene-toluene and diphenyl spliner (a pasteurization column) (see Fig. 1.2-4)
Condensallon (high pressure, or low lemper-Hllre. or both)
Absorption
Adsorption
A membrane process
To estimate", hether a vapor recovery system can be economically justified.
"C muSI estimale Ihe flow rates or the aromatics lost in the purge as well as the
ｨｾ､ｲｯｧ･ｮ and methane flow in the purge. Hence, before we consider the necessity
and/or the design of a vapor recovery system. we must specify the remainder of the
ftowshcct and "'e must eSllmale the process flows. We consider lhe design or the
'apor ra;overy system before that for Ihe liquid separalion system because the nit
streams from the options for a vapor rcco'ery system listed above (e.g.. a gas
absorber) normally include a liquid stream that is sent to the liquid separation
system.
Simplified Flowsheet for dw Stoparation Systems
Our goal is to find a way of simplifying f1owsheets. It is obvious that Fig. 1.2·1 is
much simpler than FIg. 1.2·2, and therefore we decided 10 do the energy integration
last. Similarly, since we have (0 know the process flow ratcs to design thC vapor and
hquid recovery systems, .....e decided to consider Ihese design problems just berore
lhe energy integration. Thus, we can simplify the flowsheet shown in Fig. 1.2-1 by
drawing it as shown In Fig. 1.2-5, The connections between the vapor and liquid
recovery systems ｾｨｯｷｮ 10 Fig. 12-5 are discussed in more detadlater.
We now ask ourselves whether all processes can be represented by the
Simplified f10wsheet shown m Fig.. 12-5. Sma: this flowsheet CQntaiOs both gas- and
Vapor Reco'ery S)'SlenJ
Referring again 10 Fig 1.2-1. we consider the vapor flow leaving lhe flash drum. We
know that we never obtain sharp splits in a flash drum and therefore that some of
the aromalics will leave with the flash vapor. Moreover. some or these aromatics
",ill be lost in the purge stream. Of course, we could recover these: aromatiCS by
IOslalling a vapor recovery system either on the flash vapor stream or on the purge
<ITeam
As a apor reco'eT}' SYSlem we could use one of these
FIGURE 1.1-4
A11cnl.ale d,mllatiOfllrams
Diphe.nyl
Toluene
(To recycle)
16. 14 SECTlON' H A HfE...ICHk4t 4''''0AQl TO C'ONl:(P'TU4t OESK.N
FIGURE U-S
HDA Jc:par1lllOn s)'$1cm.. [Aft.... J M Dovgla. Aloe J, 31 JjJ (JSlIj).]
Benzene:
I I
tl2, CH4
---.r-'-----'-i-
' - - - - - ' -
Toluene
FIGURE L1-7
HDA ｭｰｵｉｾｬｰｵｴ Slruchne (Af/IO' J M Ou,,!/I,u, Alo.e J, JI JH (/lI8j)]
to understand whal design questions arc importanl to obtalO Ihls simplified
ｲ･Ｚｰｲ･ｳ･ｾｬ｡ｴｩｯｮＬ wilhom worrying aboul the addItIonal complexitIes caused by the
separation syslem or Ihe: energy integralion network For example, we can siudy
the factors thai determine Ihe number of recycle: strcams., heal effects in the reactor
equilIbrium limitatIons in the reactor, etc. Thus, conllnuing 10 stnp away levels or
detail, we sec that we want 10 stud) the recycle Slrul.:ture of Ihe flowshcct before
considering the details of the separallon system
,
CH,
phenyl
Vapor recovery Pu<g
system H1,
, CH4
Reactor Phase
system Splil
luene:
"'
LiquKt separalion
SYSlem
D;
To
liquid-recycle loops. but somc processes do not contain any gaseous componenlS-,
.....e do oot eXp«1 the resulls to be general (Sec Sec. 7.1 for other altemam·cs.)
However, .....e can slmphfy Ihe ftolo'Jhcct stili more by lumping lhe vapor and hquid
separation systems in a slIIgle box (sec Fig. 1.2-6). Thus, Ioe consider the
specification of the general structure of the separatIOn system before we consider
tbe specificalion of either the vapor or the liquid recovery systems.
Recycle Structurc of the Flowsbeel
Now we have obtained a very simple ftolo'Jhcet for the process (Fig. J.2-6). We can
use this simple representation to eslimate the recycle flows and their effect on the
reactor cost and the cost of a gas-recycle compressor, if any. Moreover, we can try
Input-OufPUI Siructure of the Flowshecl
ｆｩｧｵｾ･ 1.2-6 provides a 'erJ simple ftolol>hect. bUI we consider Ihe possibility of
obtaining an even SImpler representatIon Ob·iousl}. If wc dra", a box around the
compkte process, we 10'111 be left Wilh the feed and product Slreams. Al first glance
(sec FIg 1.2-7), IhlS representation might seem 10 be too SImple, but II 10111 aid us m
understanding Ihe deSign ...anablcs lhat affect the overall malenal balances withoul
Inlroducmg any other eomplicalions Since raw-malerial COSiS normally rail in rhe
range from 33 fO 85 ｾｾ of the 10lal product costs,· thc o'erall material balances are
a ､ｯｭｩｾ｡ｮｴ ｦ｡ｾｴｯｲ in adesIgn Also, we do not want to spend any lime investigating
Ihe dcslgn vanables In the rangcs where Ihe products and by-products are worth
less than thc raw materials. Thus, we consider the input-output Slfucturc of the
ftowsheel and the decisions that affcci this structure before we consider any recycle
syslems.
Possible Limitalions
By ｳｵｾｳｳｩｶ､ｹ simplifying a f1owshcct, we can dee1op a general procedure for
auaclnng design problems. However, our onglOal ftowshcet described a contin-
uous, vapor-liqUId process lhat produced a single product and involved only
SImple chemicals (no polymers or hydrocarbon CULS) There are a large number of
processes Ihal saIIS() these hmllaltOns, and so we Iry 10 develop Ihis systematic
Diphenyl
Benzene
Purge
H,
I I H1, C
- Rcaao, Separation -
- system system
-
I I
Gas ｲｾｬ･
Toluene
Toluene: recycle
FIGURE U-6
HDA,cqdewuclu,IO (Aft,.,.J M ｾａｉｃｉｯｅｊＮｊｉ JH(/98,S)]
• E L Grurm., wScltma ｐｮ｡Ｂｾ b .. Mllenil ｃｯｳｉＬｾ ｃｾｭ Utg,19(9) 190 (April I", 1967) Abo
sec II E. Kyle, CMm Eng p,,,,.Il1(Il) 17 (1986). lor SOnIC dall ｣ｯｭｾｮｄｉ commOOIlY dlCmlQlI
prodlKUQn to ｾｰ｣｡ｉｊｊｬＩＧ d1CmlQlb
17. 16 SfcnOI'l 1.1 A lllUAIlCltICAl A"rIlOACH TO CQNl::ErruAI OBION
procedure In greatcr detail. Howevcr. batch processes may hac a somcwhat
difTercnt underlying structure (v,c often carry out mull1ple operations In a single
essel). and certainly they are described dlfTerentl)' in terms of mathcmatlCal
models (normally ordinary diffcrential or partial diffcrcnllal equations Ins1ead of
31gebraic equations or ordinary differcntlal equations) lienee. our first deciSion
probabl) should be to distinguish bctv,een batch and continuous processes.
Hierarchy of Decisions
If we collect the results dISCUssed abo'e. we can develop a systematic approach to
process design by reducing thc deSign problem to a hierarchy of deoSlons; see
Table 1.2·. One greal advantage of this approach to design is that it allows us to
calculate equipment sizes and to estimate costs as we proceed through the levels In
the hierarchy. Then if the potential profit becomes negative at some level, we can
look for a process alternative or terminate the design project WIthout baying to
obtain a complete solution to the problem.
Another advantage of the proocdure arises from the fact that as we make
dectSlons about the structure of the flo.....sheet at various 1c"e1s, .....e know that if v,e
change these decisions. we .....iIl generate process altematl·cs. Thus, with a
systematic desIgn procedure for idenlifymg ahematives Ioe are much Icss hkel} 10
O'erlook some important cholttS, The goal of a conceptual design is to find the
.. best- alternati"e
Shortcut Solutions
Experience indicates that it is usually possible to generate a very large number (i.e..
often 10'" to 10°) of alternative f10wsheets for any prOttSs if all the possibilities are
considered. Hence, it is useful to be able to quickly reduC'C the number of
alternatives that we need to consider. We nonnally screen these alternatives, using
order-of-magnitude arguments 10 simplif)' tbe process malerial balanccs, Ihe
equipment design equations, and the cost calculations. These shortcut calculations
often are sufficiently accurate to eliminate the ＹＰｾ or so, of tbe alternatives that
do nOI correspond to profitabk operation Then if our synthesis and analysis lead
TABtE t.J.1
I-tmrchy of decisions
t. tbleh venus conunllOlS
Z. InJlul-ouCpul ｾｬｲｵ｣ｵｭＺ of the 1Io.'sheec
J. Recycle Ilructure of the no,",sheel
.. Geneul sCructurc of che ｳ･ｊｬｾＧＮｬｩｯｮ sySlerl
If. Va po. recovcry ｾｹｳｲ｣ｭ
b trquld reoo,ely system
So IIUl-Ucbanl"'r no:lWOTlc
SEcnON I J A HlF.llAkCHlCAl """.0"01 TO CQl'fC£l'TU4l OESION 11
to a profitable solutIOn, wc repeat all the calculations more rigorously, because
thcn we can justify the additional engIneering effort
TIle use of shortcut solutions and tbe hierarchical decision procedure also
makes it possible to provide mOTe .-apid feedback to the chemist who is allemptmg
to de'elop a rrootSs. That is. alternate chemical routes could be used to make the
same product, Yo Ith a laTgc number of flowsheet alternati'es fOT each .-outc. l-kntt.
quick estimates of the range ofconersions. molar ratios of reactants. etc.., that are
dose to the economic optimum for the various routes help the chemist to take data
m the Tangc WhCTC thc most pTofitable opcTation might be obtained and to
tcnmnate expcTiments thilt ilTC outside the range of profitable opcTation.
Decomposition Procedures for Existing Processes
Of course, we can also use the approach presented above as a decomposition
procrdure for existmg processes, to simplify the understanding of the process. to
understand the dttisions made to develop the process, or to systematically develop
II list of prooess alternatl·es. The decomposition proocdure we suggest is as follows'
I. Remove all the heat exchangers. drums, and storage '·csscls.
2. Group all the dlSlillation columns (liqUid separation system block).
J. Simplify the general structure of the separation system (similar to Fig.. 1.2-5).
4. Lump (group all units In a smgle box) the complete separation system (similar
to Fig. 1.2-6)
5. Lump the completc process
This dttomposition procedure is different from those that break down Ihe
f10wsheet into discrete subsystems which always retain their identity, i.e" into
individual unit operations. To develop process alternatives, we want to modify the
subsystems. With our approach we accomplish this lask within a framework where
we aJways consider the total plant, altbough the amount of detail included at
various levels changes.
Hierarchical Planning
Our strategy of sucassi,·e refinemcnts and our bierarchical design procedure are
similar to the hlerarchlC3l planmng stTategy discussed in the artificial intelligence
(AI) literature. Sacerdoti- states,
The essence of Ihis approach IS to utilize a means for discnminating between
imponanl Information and details In problem space By planning in a hierarchy of
abstraction spaces in which suca:ss.ive levels of detail are introduced. Slgnlficanl
increases in problem-solving power have been achieved
• E. D. Sau,doll. -Ptanmn,ln a Hierarchy or Ab!;lradKm Splloes.- AIIr/t..,d. 5 lIS (197").
18. 18 SECTION U SUI.HUn ''"0 £XElClSfS
0 c-;::::L
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u
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ｾ uwnlOO pnpoJd
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y
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• Ol
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Cool water
ｾｉＭ ---.J
.. ｉＭＭＭＭＭＭｾ
1.3 SUMMARV AND EXERCISFS
Summary
Process design problems are underdefined, and only about I ｾｾ of the K1eas for new
designs ever become commercialized Hence., an efficient strategy for developing a
design is initially to consider only rough, screening-lype calculations; l-e., .....e
eliminate poor proFls and poor prOOC$S alternatives witb a mmimum of effort.
The amcepl CIIn be readily eltended 10 a hierarchy ofspace:li. each deahns wllh
fewer details than the ground space below It and with more delalls than lbe:
abslr1l.CtlOn space above II. By wrwdenns details only when a sl.lCttSSful plan in a
bJ&ber k"eIlipace Jlves Iiuona eVldeQCC of Ihen unportanoc,. beumuc scarcll process
..'I1J mvestlgale a peally reduced ponlOJi of lbe search spice.
In our hierarchy, the ground state represents the energy-mtegrated flowshcet,
and each le-el abo-e It contains fc....er delaib. Moreoer, if the process appears to
be unprofitable as ....e proceed through the levels in Table 12-1, we look for a
profitable alternative or ....e teminate the project before ....e proceed to the next
level. As noted by Sacerdoti, the hierarchy provides an efficienl approach for
developing a design.
Wlller __J
FIGURE 1.]..1
IPA planL (A/ler 1947 AIC"£ $'...., CDftlut Probk... )
19
19. 20 SintoN I 1 ｾＧｊｯｬＢＧＧＧＧＧＧＧＧＧＧＧＧ nnosF.S
Thcn If the result.. Oflhls preliminary analysIs seem luomislOg. we add del all 10 Ihe
calculations and we use more ngorous compulallonal procedures.
We can simplify the deSIgn problem by breallng it down into a hierarchy of
decisions, as In Table 1.2-1 In this text ....e discuss this hierarchy of decisions In
detail
Exercise<i
Recommended eu,cises are preceded by an aSlensk '
1.3-1. If engin«l1ng l'01e C0515 SIOO/hr. cstnnale the worker-hour'i requIred to complete
each type of dCSlgn 5tud) In Table I 1-1 for a smalt plant
1.3-2. Aa:ordmg to the engmeerln! melhod. what would be the best Will' to read a
telilbook thilt OOtn a field you ｨ｡ｾ･ not sluched before. Ｈｩ･ｾ bloteo::hllOlo&)',
elccuoc:hemlStry, etc.}'!
·1.3-3. If the diphenyl In the hydrodealkylahon or loluene (BOA) proca.s is recycled to
ntlncllon, ln51ead of being ｲ･ｯＺＺｯｾ･ｲ･､Ｎ show one alt"'mallve for the hierarchy of
nowsheets, 'c:.. Input-outpul, recycle, scparauon sySlem, dlstillallon train (do not
consider enerl'S integration).
1.J-.4. A Oowsheel for a proa::ss 10 produce acetone from ISOpropanol is Jlve.n In FiB- 13-1
The reaCllon IS ISOpropanol_ acetone + Ii" and an IIZCOUOplC m.i:l.lure. of
IPA-H10 IS used as the feed stream_ The reactIOn takes place at 'aim and Sn'F
Show the hierarchy of no'"'sheets,
1.3-5. An encr&),-mlegrated IIowshec:l for the production or eth)Ibe:ru:e-nc: IS JI'en In Fig
I -1 The pH",ary reaCllons ue
Ethylene: + Benzene -, Ethylbenl.cne
Ethylene ... Ethylbenunc ｾ Dtethylbenunc
Elhyknc: + D?ethylbcnnne ｾｔｮ･ｬｨｹｬ｢｡ｵｲｮ･
2Elbylbe:nzenc:;:::. Benzene of ｄ＿･ｴｨｹｲｾｮ･
The reaCllon IS ,un ..·,th iln ucess of benzene and a1lnO$t complete COn"enlon
of the ethylene, to try to mmlmlze the formation of dt- ilnd triethylbenune. and it
takes place It 300 psig ilnd 82O"F over a catalysL Two re:adOI$ are required (one on
sHearn and the other being regenerated because orooke formation). There 15 ＰＮＹＴｾＮ
or elhanc: In tbe elhylcnc feed and O.28X water In the bc:nzcne rc:cd.. Develop the
hlCf1lrchy or nowsbccts for Ihis process.
1.3-4. A nowshcct for eth.a.nol synthesis is shown In fiB- I)·). The primary reactiOns af':
Elhylene of ｬｉｊｏｾｅｴｨｬｬｮｯｬ
1 ｅｴｨ｡ｮｯｬｾｄｬ･ｴｨｹｬ Eth('r + HlO
The reaClJon takes platt al S60 K and 69 ban., and about 7" conversion or lhe
elh)lcnc 15 obt:uned. The equdibnum constant fo, dicthyl ether produclJon ilt thdc:
oonchtions is aboul K .02. The: feed streams are pure Willer ilnd iln ethylene stream
contamrng ＹＰｾｾ ethylene, g" ethane, and 1'7. melhane. Show the hierilrchy or
f1owshects.
Reaction section
HealC'r Reactor ¶lor ｾ __.., Scrubber Vent
Condensate
Water
Benzoic add
Benzoic acid
rectification
ToluC'De
stripping
Reactor
<
e
"
8
DEE
ｓｬ｡ｲｴｬｨＭＭＭＭｾｉ｟Ｍﾭ
Feed elhylenC'
FlCUlIt.: I.J..J
Eth..1101 synlliats
FlCURE 1.J.4
Beuooc llad JlfodOChOll. [Afi... lIyJ'ocft Ptoc_ 41(11) 156 (N... IllIU) J
20. 22 Sl:CTlOH U ｓｕｾ .....UY Ai'<O UOClSU
1.3-7. A nowshcct for bcnl:CIIC aod prodocllon '" liho.....n In h&- 1}-4 (from S IA
VISCOSA ｉＧｲｾＬ ｬｉＩＧ､ｲｾｬｊｲ｢ P'IJ< .• 48(11); 156 (No..... 1964» The prlm..r)
rea"uon I)
Toluene -t 150: ｾ lkJUotCAad + lI J O
lIo..e:e:r. reerslble by-pn)(hu:b (beno.1dchydc and beruyl...: .100001) as ...:II .b
heauer ones (as.sumc phenyl benzoale and benzyl ｢｣Ｚｮｬｾｬ･ｬ ate also formed al the
reaL1l0n condillons of 16O'"C and 10 aIm Pure wluc:ne and au are used as Ihe ra....
matenalli. and Ihe toluene CODerSlOn 110 1.epl at 30 10 ｝ＵｾＮ As shown on Ihe
Iowshc:el. lhe IOluene IS rccovered and recycled in one column. and the reC:r)Ible by-
products are recyclc:d from Ihe ovcrhead of a second The produclls rcco'ercd as a
vapor sidestream (""1Ih greater Ihan 99Xpumy), and the heavy componenrs :.Ire senl
10 fud. Show Ihe hierarchy of 10wsheCI5.
1.3-8. Select a Iowshcc:t from HydroctJrf)(JI1 P,ocusing (liOC the Novcmber issue: of any
year). Develop the hiel1Hchy of Iowshccts for Ihe proces.s
CHAPTER
2
ENGINEERING
ECONOMICS
In Chap I Ilo'e descnbed a SYSlemallc approach thai can be used 10 declop a
conceptual design In add ilion. we hsted the Iypc::s ofdesign esllmatcs lhal nonnal!)'
are undertalen oer the hfe of a proJCCL The goal of lhese esumates is 10 generate
cost data, although Ibe alXuracy of tbe calculation procedures and the amount of
detail consKkred arc different for each Iypc of csumalt.
Since. COSI estimates arc the dn'·lng force for any design studl. Iloe need to
uDdc:rsland the 'anous faclon to Include. We descflbe a procedure for general109 a
cost estllnate for a concc:plUal deSIgn 10 IhlS chapler We begm by presentlng the
results from a published case Stud}. In order to gam an o"crall pcrspc:cll'e on the
t)pes of eOSI dala required, and Ihen we discuss Ihe details of Ihe COSI analysis.
Remember Ihat the cost models Ihal we develop should be used OIlly for
screeDlng process alternalives. The cost estimates that arc reported to management
should be prepared by the appropriate economic specialists in the company,
because they will mclude contIngency facton based on expenence and WIll include
the costs of more ilems than ..e consider. Thus, our oost eStimates Donnally will be
100 optimiStic, and they should be kept confidential untillhey have been venfied
2.1 COST I FORMAno REQUIRED
By considering the results of a published case study. Ilo·e caD I!'et an overview of the
kind ofinformation thai we nttd to de'dop a cost eSllmate for a ｣ｯｾｰｬｵ｡ｬ design.
Moreover, the framewor.. rdatmg the material and energy balances, eqUipment
sizes and ulility flows. capItal and operating costs, and procc:ss profilability should
become more apparen!. Tbc: parllcular case sludy we consider 1O.,.01ve5 the
production of cyclohexane by Ihe hydrogenation of benzene"
Iknu:ne + 3H:;:: Cyclohexane (2.1-1)
• J R. Fall, ｃｊＢｾＮｴｊｉｉｉ Mom.flX,wn. WashlOlloD UDlYC....I)' Dcslp Ca", Stud)' No 4, ･､ｬｬｾ by B
D Smllb, WllJlua,lan IJm...·u'ly. St I OUlS, Ma.• Aug. I. 1%7
23
22. Il:
TARLE 2.1-2
Oper1lling COSI summary: Cydohtnnt-bue cast
ESTIMATED PRODUCTION COST AT ARNOLD, CONSOLIDATED CHEMICAL CO
C.H II OUTPUT • 10,000.000 GAL (65.000.000 LR)
PRODUCT DELIVERED AS LIQUID, 99.9+ %
PPR "rAR (8322 HOURS)
TOTAL MFG CAPITAL _ S510.('J('(I
!oj
TOTAL FIXED &I WORKING CAPITAL. 693.000
UNIT
QUflNTlT"
UNIT I'RI(.'li
COST COST
I'HIt yrAR PER YEAR P['R 100 LII
RAW MATERIALS
-
RI'NZENE "I ｾＮＲＱＰＮＰＰＰ SO,D SI.R93.CXXl
HYDROGEN MeF '.100.000 0,23 207.000
CATALYST Ih 10.Mm '00 21.600
It M HANDLING
TOTAL R M
CREDITS SPENT CATALYST Ib IO,Roo 'SO - 5.400
NH RAW MATI:RlAI.S 2.116.200 Sl26
DIRECT EXPENSE
Lobo. "300
ｓｵｰ･ｲｾｉｉｉｏｉｬ 9.600
Paytoll CharllU
'''OIl
Steam (SO PSIG-CREDIT) Mlh 4$.SOO 'SO -22,1100
ｅｬ･｣ｴｮｾｬＱｹ kwh 2.119.000 001 21.200
Camp Air
Repalrl@4%MFG CAP 20.""
Waler-Coohllil Mgal 141.000 O.OIS ｾＲＰＰ
Water-Process
Waler-BOILER FEEDWATFR Mgal >'000 OJO 1.500
Fuel-Ga.-Oil
Fuel-Coal
ｆ｡ｾｬｯｲｹ SUPPheJ} 10.200
2% MF(i C.... p
Laboratory ,
TOT.... L DE- W.OOO 012
(CO",,"wtd)
23. SEClION U £'05T ｲｬＧ＼ｲｯＮｾｈｬｑＬＮ If:QUllFO 29
Profitability Estimate
We combine the operatlng and capllat costs. along With some other costs. and "'e
use these results to estimate the profitability or the process (see Table 2.1-7). The
return on investment IS used as criterion of profitability in the case study, but a
number of othcr critcrla can be used. These arc ､ｩｳ｣ｵｾｳ･､ in Sec 24
Engine-ering Economics
Now thatll.'c can see what types ofcosts are mcluded in an economic analYSIS. how
can we genenlle thcse cost data" First wc consider some of the mcthods for
"IE')I RnclOf<'Oohnfcoil 41OR'
r._ J R r." """-"_ ｕＢ＾｡Ｑｉｉｾ Oo$>p c.... Sl.tJ No 4......... bJ
• 0 SmotIt. IouJ.,.- U",n1'I'. So. l-. 1010.. 1961
Capital Costs
After .....e have determined the stream no101o's and slream temperatures. we can
calculate the equipment sizes; see Table 2.1-3. Then we can use cost correlations
(which arc dISCussed in Sec. 2.2) 10 estimate the delivered equipment coslS. NCXI we
use installation factors to estimate the installed equipment costs (see Tabk 2.1-4),
We must also estimate the working capital required for the plant (see Table 2.1-5)
Combinmg allthe:se costs. we obtain an estimate of the tolal capital requirements
(see Table 2.1-6).
TABLE l-I.J
Equipment schetluk
ＬＬｾ
'.
ｾＬ rqi<llued ＢＮｾ Sin (ncb)
R1 , Rnao,· 45-," d,am " 28 r.
CI , r «d comp'OIOI <l(lI) bhp. t ..o-I!agc
C·, 1 ileo;)ck o;omplcssor ｾ bhp
"
, ｃｯｯｫｬＭ＼ｏｦｷｫｾｲ ＢＲｾ fl'
E' 1 InlucooIn' 15511'
EJ , Aftrn:ookr usn'
PO , &nzcnc ked pump 11 IP"'. 860 n
p., , tk"k. fotd pump lllpm.116ft
p.) , RenU1 p"mp 13 gpm. 93 n
P4 , rille' pump 2S !pm, 62 n
T·, , Iknttnl' ｳｵｲｾ 57,000 gat
T·' , R.,nU1 dlllm 930 pi
T·) , ....no: tepllralOl' 11.,a.. dlam. " J n
T4 , Siumdrum 150 pi
,., , P,odlJd storal" IS&.OOO 'II
ｔｾ
, FIller ｣ｨ｡ｲｾ link 300 ..'
"
, Calal}'st filu:. JS ft'
•
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8
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o
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ｾ
ｾ
•
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u
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t:
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,
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•
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ｾ
1--1-+-+-+----11---+-+--1 0
•
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•
•
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o
•
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18
24. JO ｓｾｃｔｉｏｎ 1.1 con INlO"',ATION ｬｴｑｈｉｾｅｉｬ
TAIU Ie: 2.1-4
1111nurllcu.ring Capilllll: 8a ｃｊｉｾ
ｾｅ｣ｮｯｎ II cosr ISrolMUION lEQUIUIl 31
TABU 1.1...
ｅｳｬｩｭｬｬｬｾ or capilliI requirtemtenls: Base C8 ｢ｬｬｬｾ､ on construction in 1967
f'''''' J It F••• W.."'n.'.... L"".nol) Do:o.lp ea", Sh.d) No 4 od,,'" b. B D Smllll.. ........""'.1<1.
l:...ｾｮＢＩＬ 51 Louu.. Mo_ 1967
TABLE 1.1.7
Profitabilily Or ｣Ｉ｣ｬｯ｢･ｸ｡ｄｾ manur.clure
o../h-UN Ib_
hat>_ ｾＬ
f"c'... ｔｾ ...
.. • •• .. S ·U,bIkj
C, 76.000
" 21l.llW
c.2 J."'"
" .""
E·' S,l00
" 20.'"
E2 '-"" .. 10.
E·J
'-"" .. 10,000
P-Ia
'-"" " '.
P-Ib
'-"" " <000
P·2a ')00
" '.""
P.2b ')00 .. ,.."
p.,. 100
" J.
P-lb 800
" l.700
ｰｾ
'.200
" '."'"
T·,
•."" ••• 20.000
T·2 2700
•• 12,qOO
T·]
"" .. 2300
ｔｾ 600 .. 2.100
T-Sa 10,800 .. ".000
T·Sb 10,800 .. ".000
H m
" ].600
'--I "00 .. II,SOO
SUJ.l70 SSIO.300
Uiot SSIOOOO
r.OOII J
• F".., "'''''''"'',.... l·....crll,) DeupI e"...
Sl...t) ,.... 4. Wl'od bj. B 0 s..u" '"••tln'II011 U....,-
..,_ 51 ｾ Me>... 1"7
I. Manufadlmnl Cal"lal
Equ,pment
kuel'"
COllIpres:...>r1i
E.o.ehan.....
PumJ-
Tallu
ｆｕｉｾｲ
TOIaI ptOOCU equlpmenl
Tout manufaclunn, capital buc:d on baod f.aclon
Toul UU1aufactunqaxl ･Ｑｩｕｭ｡ｬｾ
2.. NOnm.iUlWadunn, C.p,..1
ｐｲｯｰｯｲｬＮｬｏｬＺｕｬｬｾ libare ul'i'ling apow esumaled .1 ｉｓｾｾ InlOnwaetunn, ap"..]
l. TOlal Filled Capll.]
Sum of I .o.,l 2
... Y.'orl<lnS Capol.l
k.....·m.len..ｉｉｒＮｾｮｬｯｲｹ
Goods in prOCQS
FlRlshed p,oduc, ,n""nl0,)'
S,orc liuppha; and all olher Ilcrm a, ｝ＬＮｾ gross ulcs
TOlal ..orlan, cap".1
S. To,.1 F,.ed.nd ｗｯｲｾｬｮｾ C.polal
.........
10' ,.l/yr
TOlal COSI
S 9.700
".000
10.00J
'.000
32.670
2900
10.370
SlO.ooo
....000
'.600
...
29.000
12.000
107.000
S69J,OOIl
From J R F wuJwact_ Umwrw,y Dc..p Caoc 51""y No 4
Wllal by 8 U S "h, W....J""I'OII UBI_W'y, So lo.iol. ｍｯｾ 1967
F'..... J R F"". WlldulIl'01l UN••ｾＢ £k>,l" C.",
So""} No ... al".d by II I) SIIU.b, W••hIOIIQII Un,••r·
OI'J, S11.owo, Mo, 1%7
• F" W auo.)'l1Ir Coo- 6 d.1>d .....lrnl p".J
• SAkE ｋｮ＾ｮｾｭ Coo- la. ＮｾＢＮＬ re:ourch,
"od _nn'
TABLE 1.1-5
WOrkio& capilal
I. Rlw Qlltcnal Ｈｓｏｾｾ full)
e"lI. 24,jOO pl@SLt23
1. Goods ID prOCCSl
UI I1SO pi @ SO.u
J. PrOOUCI lo""nlory(SOY. full)
Cyclohuanc; I..S.ooo gal @SO.2Jesllmaled
... ｏｬｨｾｬＮ II SYo lVlUIi lilies
10,000,000(024)(0 OS)
'.600
]],000
120.000
SIS9,ooo
Muw..dunnl capital
Total F&.W capol&!'
Grou uIa per year
MllIluf"crunnll;Oll
Grou profil
SAkE' @ ｉｏｾＮ
.....Ｌｾ
Nel profit
ｒｾｬｕｲｐ on 10111 F&'W
S Slo.ooo
693,000
2""'-000
2.257.400
ＱＴｾＮＶＰＰ
14,JOO
128.JOO
";00
M.l00
9Jy'
25. calculating capllal and operating costs, then we descnbe the techniques for pUlling
capital and olXrating costs on the same basis, next we discuss profitability
measures, and fina!ly we pm>ent a simple model Ihat IS useful for screening process
alternatives when we develop a conceptual design
:u ESTIMATING CAPITAL AND
OPERATING COSTS
In Table 2.1-1 the ulihty loads for Ihe various pieces ofequIpment on the f10wsheel
Il.-ere itemized, and in Table 2.1-2 the ullhty costs were calculated. Similarly. in
Table 2.1-3 the eqUIpment SIZes for the f1owshoct were listed, and the COSts were
calc.ulated in ｔ｡｢ｬｾ 2.1-4..Thus, the first costs we consider are the operating and
capnal costs asSOCIated with the equipment on the fJowshocL
Operating Costs
0lXratmg costs are nonnaJly simple to estimate. Once we know the flows of tbe
raw·materials streams and the utility flows (fuel. sleam, cooling water. power), we
simply multiply the flow by the dollar value of that stream. In companies that
operate their ｵｴｾｬｾｴｾ systems. i.e.. steam and power production, as a separate
compan}'. lhe Ullhtlcs costs factors are simple to obtain. If this is Dot the case,
however, an analysis of the total site is needed to estimate tbe cost of steam at
various pressure levels. For our preliminary designs, we assume that a value is
available.
. Care ｭｾｴ be laken that the utility "alues are {t;1l'en on a thermodynamically
consistent baSIS; ｉＮｾ .• fuel and electricity should be more expensh'e than high-
pressure steam, whIch should be more expensive than low-pressure steam etc.
ｾ｢･ｲｲ｡ｾｩｯｮｳ in prices do occur at times, so that it might appear that there is a ｾｲｯｦｩｴ
III burrung feedstocks to make electricity or in using electricity to produce steam.
Howeve.r, ､･ｳｩｾｳ based on unusual market situations normaUy pay heavy
economIc penalties after a few years. One way to keep utility costs uniform is to
relate ｾｕ utility prices (electricity, various steam k"els, and cooling-water costs) to
an eqUivalent fuel value; see Appendix E.!.
The costs of chemicals can be obtained from the marketing department in a
company. For academic purposes, current prices for most chemicals can be found
in the ｃＢｾｭｩ｣ｑｉ A{wluting ＦｰｯＬｴｾＬ or many of tbe trade publications. Light gases,
for example. 01, N J , CO, etc.. arc not listed in the ｃｨｾｭｩ｣ｄｉ ｍｄｔｊ｣ｾＯｩｮｧ ｒｾｰｯｮｾＬ
beause most are sold locally on long.tenn contracts. The current prices available io
trade publications are often different from the price obtaiDcd from the marketing
department because of long-term contract arrangements.
Capilal Cosls
As :-'e mIght expect. there are a ...ancty of Il.ays of estlmating the capital costs or
･ｱｵｬｾｭ･ｮｴ that range from vcT}' quick calculations with Irmited accuracy to very
detailed calculatIons that arc lery time-consuming bUI more aecurate. The most
accurate estimate is simply to obtain a quote from a vendor; i.e., a heat-exchanger
manufacturer ｡ｾ to sell you a heat exchanger that has a specified perfonnance
and that will be delivered on a certain date for 8 specified price It pays to shop
around because a vendor's quote will depend on how much work is on hand. These
vendor's quotes arc used as the costs of a final design.
For conceptual designs we need a faster and simpler approach (i.e" we do nol
want to try to optimize a process based on vendor's quotes). Thus, "loe normally usc
equipment cost correlations. For ell8mple, the capital cost of a heal exchanger
normally is e.pressed in terms of the heat-c.xchanger area, and it is not neessary to
specif)' the number of tubes, the number of baffles, the baffle spacing. or any of the
details of the design. Similarly, tbe cost of. furnace is given in terms of the beat
duty required, and the cost of a distillation column is specified in tenns of the
column height and diameter. Tbe cost correlations are obtained by correlating a
large number of vendors quotes against the appropriate equipment size variable.
PURCHASED EQUIPMENT COST CORRELATIONS. A quite extensive set of
cost correlations is available in Peters and Timmerhaus.· Other correlations ofthis
type have been published by ChiltoD, Happel and Jordan, and Guthric.f The
correlations of Peters and Timmerhaus are amODg the most recent. although an
even more recent update is available in ASPEN. Several correlations for various
pieces of equipment that are taken from Guthrie can be found in Appendix E.2.
Of course, we are most interested in estimating the total processing costs.
Therefore, .....e must be able to predict the installed equipment costs. rather than the
purchased equipment costs. To accomplish this goal, we need to introduce a set of
installation factors.
INSTALLED EQUIPMENT COSTS. One of the earliest approaches for estimating
the installed equipment costs from the purchased equipment costs was proposed by
Lang.' He noted that the total installed equipment costs ....-ere approximately equal
to 4 times the total purchased costs, although different factors could be used for
different kinds of processing plants. Hand' found that more accurate cstimates
could be obtained by using different factors for different kinds of processing
equipment. For example. the purchased costs of distillation columns, pressure
ｶ･ｳｳ･ｬｾ pumps, and instruments should be multiplied by 4; heat exchangers should
be multiplied by 3.5; compressors by 2.5; fired heaters by 2; and miscellaneous
equipment by 2.5. The usc of Hand's factors is illustrated in Table 2.1-4.
• M S. Pdcrs and K. 0 TUIlIl1QlwlIJS, ''-t DaIfPl-" ELM_,na/or Cltmticlli bog_s. MeG,...•
Hill Nc.. YOlk. 1961. chaps. 13 loiS.
, C II ("h,lton. ·c_ Oala Correlalm.ｾ Cltnro Q,g_ 56(6)' 97 (Jan 1949), J IbJlpCland 0 G Jo,dan.
CIotom.ctJI f'rfKru u-....s. Oo:••c•. New York. t97S. chap ,. K M GUlhrx., ·Capolal COSI
&umalllll-- C'-t. ｅｉｉｦｾ 76(6) I J4 (t969).
I H J Ung. ·S,mpliflCd Arproach 10 Prchminarr Cosl EslJmalct,- Clatm ｅＮｮｻｬｾ SS(6)' 112 (1948)
, W E- H.nd. ｾｆｲｯｭ Flo.. Shccllo Cosl EsI;male.- rmol. ｦｱｦｩｾＧＬ 37(9), 3JI (195&)
26. 34 SECTION 11 ESTlloCAT1N{; C... I'tT...L "'1'10 OPU...TING COSTS
SECTION U fSTlloC ...TlNG C...PIT...L "'1'10 Ort:....UNti COSTS 35
-
-
iiiiiiiiiiiiii__.iiii,;;.iiiiiiiiiiiiiii=;.iiiii;';;
---_ _--_ ..
--_ -_ ,
_ _••••111_ _••••111
_ _••••111_-••••111
_ •••••III_•••ｬＺｩｾｉｾＺ
•••IIIIII.lIJi!lilll
ｾＱＱＱＱＱＡＡＡＮｬｩｬｩＡｉＡＡＡ
_. ...._---_....,
_ I Ｌｬｊｾ _ _••••lIl
_ _ ';11_ _•••1111
｟ｾ 1111__•••1111
｟ｾ UIl_••••1I11
.11 111I•••111111
.1111111I.111111I1
---
o •
---,..-...., ...
-"'-' .
- ..,0 ,
<- " '.0
__ " u
__ It. ,u
........ u ,.
.......... u ...
..... u "
..... _. n.' ,
_--.,.... 'I'-' ' ,
........,- .. .,
-- .. ..
-....-.. .... ."
_..,- •• .".•
._-- ..
-- .. ..
--- -,,,.,
-- - ,.
--.... .., ,.
---.... -••
-- - '.•
--- o. ,.
-..__............._.
"""'_.-......---'-
• • •
... .....
•• • • •.
- .. -
.. .. •
.. .. •
.. .. ..
.. .. ..
.. .. ..
.. .. ..
0' 0' .,
•• ., ••
Ｎｾ ... ".
.. .. ..
.. •• ｾ
,.. -. _
.
.. ..
--ｾ
... ｾＬ
-
,. '" u
'. u u
•• u u
- --
- ." -
exchanger can be read directly from the graph. Then a series of correction factors
can be used 10 accounl for the type of heal exchanger (fixed tubes. floating head.
etc.). the operating pressure of the exchanger, and the materials of construction for
both the wbcs and the shell.
Moreover, once the purchased cost of the e}[changer has been estimated,
there is another sct ｯｦｦ｡｣ｴｯｾ available which can be used to lind the installed cost.
The installation faclors provide separate accountings for the piping requirt:d,
concrete used for the structural supports, conventional instrumentation and
controllers, installation of the needed auxihary electrical equipment, insulation,
and paint. Simtlarly, factors for the labor costs reqUIred to inslallthe equipment are
listed as well as the indirect costs associated with rreight, insurance, taxes, and
other overhead costs.
The installation factors listed in the correlations are for carbon-steel ex-
changers, and we assume that the installation costs are essentially independent of
the correction factors for pressure, materials of construction, etc. Hence, we can
write the expressions
FIGURE 2.2-1
Sbcll·.nd-lUbe beal nchaog<:rs. (F,om K. M ｃｕｬｉｴｔｬｾＬ ｾｃ｡ｰｩｬＬＬＱ COli ulimDllng,· Chem. Eng., p_ JU,
Mar. 14, /969.)
GUTHRIE'S CORRELATIONS. An alternate approach was developed by
Guthrie," who published a set ofcost correlations which included mformation both
on the purchased cost and on the installed cosl of various pieces of process
equipment Guthrie's correlation for shell-and-tube heat exchangers is shown in
Fig. 22-1 We sec that the information for the purchased cost for a carbon-steel
(2.2--4)
(2.2-3)
(2.2-1)
Purchased Cost = (Base CostXF.Xlndex)
Installed Cost = (Base CostXlndexXIF + f. - I)
where IF is the installation factor and Index is lhe correction factor for inflation
Hence,
where F. corresponds to the correction factors for materials. pressure, elc.• and
Installed Cost = Installed Cost ofCarbon-Stecl Equipment
+ Incremental Cost for Materials, Pressure, etc.
= (IF)(Base CostXlndc}[) + (F, - IXBase CostXlndex) (2.2-2)
ruE ASPEN CORRELATIONS. Another new set of cost correlations has been
developed by Project ASPEN,· using data supplied by PDQS, Inc. These
correlations are part of a large. computer-aided design program. and therefore the
correlations are all in numerical ronn, rather than lhe graphs used in most other
sources. For example, the expression they use for heat exchangers is
Gutl:Jrie's correlations provide much more information than most other cost
correlations. although lhey arc as simple to use as other procedures. Moreover, if
we should wanl a breakdown of the tOlal COSI for piping, or instrumentation, for all
the process units, we could develop this infonnalion on a consistent basis. Some
additional examples of Guthrie's correlations are given in Appendix E.2.
-----,.........
_....._-..ｾ
｟ ..
---
--
_ ••, <>.'CO _ '" a.':U • ...,
.-.............
• o.
- -
--
•............ '-n
......_- ....
..........-.
""- '.'
.... '" _--
.. .It '"""-
_ '" u •• _
.. .... .......
ｾＭ ."
_e-. _ ,-'_
--
"'-'... "
. . . . . . R ｾＢ
._ .
u_ ."
....._--- ...
-......_,.
0-._ "'<:iI <:iI <:iI W<:iI-...lI Q/ ""
..... a_ ,., 11
.... .. '" ,.. '" '" ,.. ｾ ｾＢ ..
... "' u. ,.. ,It ,. ｾ ,......
.... u. u , "'''-'l
......- ,.. '." , p, U> Ul " ..
•_ . _ ... '-If ." " u. Ul " ......
• K M Glllhne, -Capll:;lJ COSI E!;IHllillrng." C/o,-m ｴＺｮｧｾ 76(6). tJ4 (1969).
• L B Evallli. ASPEN ProjeCt. Depanmcnl of Chcrrucal Englnccnng &. Encrr;y Labonlory, MIT,
Cambooge, Mus.
27. ....here C£ = 1979 ex&hanger cost; C. - base cost for a carbon-steel. floaung-head
eJ;chang...r with a tOO-psig dellgn pressure and ｢･ｴｷｾｮ 150 and 12.(lOOftl of
surface: ｡ｮｾ｡Ｌ FIJ - a dcslgn.typ..- correction: FMe - matenals·of-constructlon cor-
rection factor: and F,. = a pressure correction factor. The expression they U5C for
the base cost IS
SEC"llOI'I lJ 101...L OPl14L INY£STMEPl1 AND 101...L "oouct COSTS 37
separate factors for labor and materials, .... hteh often expenence dlfferentlOflatlon-
ary forces, Guthrie's correlations have the advantage that it l5 possible to update
the material and labor factors at dIfferent rates, or som... kind of uerage faclor can
be u'Cd to account for inflatIon
In C. = 8.202 + 0.01506 In A + 006811(ln A)l (2.2-5)
EquatIons for the correction factors arc available as well as the cost ......pressions fOI
a -anety of other pieces ofequIpment. SImIlarly, the installatIon factors arc gj'en In
the form of equatIons
Updating Cost Correlations
Chilton's correlations were published in 1949. Guthrie's were published in 1968.
and the Peters. Timmerhaus. and ASPEN correlations are more recent. ｈｯｾｶ･ｲＬ it
takes about three )'ears to build a chemical planl,and so ....·e must be able to predict
future costs. aearly the cost of almost everything increases with lime. and 50 .....e
must be able to update the cost correlations.. Several methods can be used for thIS
purpose., but they are all SImilar in that they involve multiplying the base cost in a
ccrtain year by the ratio ofa cost index for some other year to the cosl index for Ihe
base year.
One of lhe most poplliar cost indlC:C:$ of this Iype is published by Marshall
and ｓｾｩｦｴ (M&S) and is updated monthly in ｃｬｲｾｮｦｬ｣｡ｬ Engilluring. A plol of the
M&S ｬｾ･ｬ｛ IS shown 111 FIg 22-2 SImilar relationships are Ihe ﾣｉｉｧｊｮｾｾＢｬｉｧ ｎｾＢｪＮ
Rt'cora Indell. the Nelson refiner)' I1ldell. Ihe Cht'mtCol £IIglnurlllg plant constrlle-
tion indell. and the materials·and-Iabor cost indell Some of these I1ldu:c:s include
8OOr------------==----,
600
200
ｾｾｏＭＭＭＭ［Ｔ［Ｇ［［ｏＺＭＭＭ｣ＵＰ［Ｇ［［ＭＭＭＭＶＰ［Ｇ［［ＭＭｾＷＰＺＺＭＭＭ［ＺＸＰｾＭＭ［［ＡＹＰ
Years
FIGURE 1.2-2
Mti lIodel.
1...;'-fIOUSF COST CORREI ATlO....S. Man) companies ha'e developed their own
cost correlations and installatIon factors, These arc frequently updated hy uSlOg
endor's quotations and recent construction costs. These company cost correla·
tlons should alr"up be used If they arc available We UM: Guthr)c's corrclatiom
because they are avaIlable in the published hterature.
2.3 TOTAL CAPITAL INVESTMENT AND
TOTAL PRODUCT COSTS
There are numerous costs required 10 build and operale a chemical planl other
than the op..-rating costs and the installed equipment costs; sec Tables 2.1-2 and
2.1-6. Some of these costs add to Ihe capital investment, whereas others arc
operating ellpenses. Fortunately, most of theM: costs can be rdated direcily to the
instalJed equipment costs throllgh the use of variolls factors. Aver) conciM:
summary of these costs was prepared by Peters by Timmerhaus" and a modifted
erslon of their hst for the total capital 11l'estment is shown 10 Table 23-1 The
corresponding brea.kdo...·n for the tOlal product costs IS gien In Table 2.3-2.
It is common practlcc in the de'elopmenl of a design firsl to calculate the
sIZes of all the equipment and to eSlmlate the amOllnts of ulilmes reqllired, ellt.
the equipment costs arc determined. and the utility costs are calculated Then the
other COSI factors are added. and finally a profitability analym is llndertaken
Ho.....ever. for preliminary process design. we prefer to look for processs alternatives
as soon as a design appears to be unprofitable. Therefore., .....e would like to develop
simplified cost models for total invcstment. total processing costs. and process
profitability. We develop a simple model of this type as we discuss the mdlvidual
cost items.
Tot.1 C.pital IOl'e:stmenl
According to Table 2.3-1. the Iota) capital investment (Tot_ Inv.) isthc sum of the
fied capital investment (Filled Cap.) and the working capital (Work. ｾ｡ｰＩＺ
TOl- Inv - Filled Cap + Work. Cap.
• M S Pdcn.nd K 0 '1 'mJDI'rhaus. rlDftJ INJtgtl ..J u_.u ft/ll' C"'-_ Eit9UOfff'. 3d cd.
McGra..--HllI. I'lcw Yorl, t%9. chap ｾ
28. 38 SECTION 1) TOTAL CAI'ITAL IIft'UTMEl'lT ...,.,0 TOTAL 'lOOUCT COST'S
TOTAL ('A!'ITAL ｬｎｾｕｔｍｅｬＧｬｔ ANI> TOTAL ,lOOOCT COSTS 39
TA8LE 2.J-I
Breakd",,-n of lolal capilal iMeslmtnl ud slart-up cosu
I TOlol C<rfl,ta/ ",",SI_n' equab Ihe sum or lbc. fixed capital ｕＱｾ｡ｕｄ･ｮｬ plus !he wotllnl c:ap"al
II FlAd copll,,1 ",.,..SI,....n, (FCI) U lbe. COSli reqUired 10 build lbe: plOCCSli, equal to lhe s.uffi ollhe
doree' cosls and lhe Indlrecl cos...
A. D"UI cons equal the. iUm or II"" nlatenal Ind labor COSlli requored to build the complcle.
faclhly, about 10 IS Y. or FCI
I tftuUt rosu or ISSL (IIrJJM ofＢ｣ｕｬｾｹ /.""u) .rc tbc: C05I.5 or IMla1linilM eqwpmenl
sboWD on lbe. process 1owihc.c.1 '0 a spea&: FOPaphicalloo::allOD (Ibe. baUery bm1ls),
.boul SO ＶＰｾＮ 01 FCI_
" I'IuclvuIti t9"IIJ'"D"I!>duda.aII equ'pmc.ul bIilc.d on • complete: ｦｴｯｾＬ span:
pans and nofllnsl.a.lkd ･ｱｷｾＱ spafQ;'wptur; IlQWprMClI, wppba, and eqwp-
menl .11o noes; Inft.lIon COIl- .aIlo..."na, fn,gbl c:ba<JQ, ta.r.c.s. UUUl&lM:lCo.and
dUlICS, .Uo 1lOt' for modlficallon dunn, il.arl-UP; .bout ＲｏｾｙＮ of FCL
II f'urc/oosld·",q,,;pmr'" lfIJ'O/lOtlOn mcluda IlUill.llation or &II equipment IlSled on I
complele l0/4hec:1 includllliliructural supports, insulation, and painl ••boUI
7.)-26". or Fel 01 lS4Sy' or purchased eqwpmcnl c.oJl.
C I",-,,-w,,,o/lon WId c.."o/ "duda putdtul', IlliI.allaUOn..and callbrallOll, .boul
ｬＮｓＭＷＮＰｾＮ 0( Fel or 6 JOy. 01 purchased equlplDClll ｾｉ
J P","'fJ l!>dudes COQ 01. plpe.. plpc.lwlJeR. fitUDp. val¥'C$, IOSWaUOn. aDd eqUlpmc.ol,
:about) ｉｓｾＮ 01 FCI 01" 10-10% 01 purchased IlQwpmctll CXl5l.
r Ckc"fC'OI ""I"'pmDIl 0Ifd rrtOlt'taols inctu 1M purdI.asc aDd iDslaUallOn olille
rc.qu"cd clc.o::ln;;a1 equlpll>c.nl inctudtnll.-lIcbe:s.. moiOrs. condwl, WIre.. tittulp,
kcders, poundina. Illltrumenl and conl,oI wirin.. "J.hllnll paDC!J. .00 tiiOCialed
libor costs; aboul 2 SilO" 01 FCI o. 1-20% ol pu.chased eqUJpmCllI COSI.
2. OJfSllt COSIJ Of OSBL COJU (0,.",« ofbtl"",,)· /,mllS) U>elude C&.ril§ diroctly .c.laled 10
Ihe. prOCC5li bUl bu,lt ,n ｳ｣ＮｐｩＢｾｉＮ l"cOlloM from lhc.m.lll p'OCCSl.,nl equ'rmc.nl
" B"t/d,,.,. (",,:IOOmg iCr'ICCS)• .aboul 6 ＲｏｾＮ or Fa O' 10 10"or pu,,:b.ascd equ,p.
menl COSI
(I) "«"'u bo<,WM.fIS 'nclude ＢＢｾｬｮＮ･ｵＮｬｄＮ supc.ntrucI..rc.s. ｾﾷＮｰＮｬ｡､､｣ｦｬＢＮ
aa:ai ..-ars. cranes. moaorai/$, boasu. dc.>"lI1Gn. (Soaoc OOIl'IpaNCI uodudc
lhex 1a<:IOrt &Ii pan ollM ISBL -u. a.od DOl 1M OS8L"",IS)
(2) A...."I_}- ｾｊ lIldudc adllU-llOtrallOll aDd olficc, mcd>caI at dlSprlli:ll.l)',
eafcl",n.. pOll£. product ...."'hOU:SC. pam ...ｲ｣Ｎｨｯｷ｣Ｎｬｾｦ､ lind s.afcly, fire
51atlOn, chanJC house, pcnonnc.l buildJog, shipping ollioc and p1alform,
rc.sc.areh laboralory, conu-oll.bo••tory
(3) Moinr",rwnu shops include e.le.etne.al p;plDl. ShOCl mel.a.l. m.chine. we.lding.
carprnlJ'Y. IMlrumcnll,
(4) B"t/dong U'nIOCtS tnelude p1unlblna. bc.auna. "c.llldauoo.. dusl ooIlec1lOrt. a"
COOOluonUlg, build,n, bpunl. c.I.....lOn. c.ocaI.alOrs. Ickpbonc.s.. UlICfCOIllJllUru-
caloo-, system. pa.lluna. ipl1I1Uc.r .)'IJe....... liIc: alarm.
II Y",d....,.,---..u ＬｮｾｯｨＧｃ sUe docvdopawlll inctuduol Jlle deanna. p"lIdiaJ. roads.
..."ILwap. raiuoads. rc._ pallina areas. .. ｾ｣ＺｳＮｮ､ pen. rtcrUltwul fac;d,ue.s.
la.ndscaptlll; lboul ISS 0·" ol Fct
C s,f1J'u IlXi/JlIIS (jllSl.Ilc.d), aboul g 0 Ｉｓｏｾｾ ol FCI
(1) UI,/IIII'S Include. siram. waler, powe'. refnrcrallOn. coroprc.s.scd .... fuel, watt",
dlliPOUI.
(2) 1"«,I",,,,s 10clude. boiler plant. JrK:,nc.talOr, "'elb. liver UluLe, ",aler lTe.allnen!,
cKlhnglowcn. ,,"'ale' jto.ai:e. rlc.o::lT1C subnallon. ｲ･ｦｬｬｾｲ｡ｬｬｯｮ p1lnl, a" p1anl.
fuel _IOrage.. ...,,>le d,.poul pbnt. lire p'<>IcetlOU
(l) NOIII"IXIU ｉｾｮｬ cornpo$Cd of oltic:c ｲｕｬＱｬＯｉｕｾＮｮ､ eqwpcnt::ol, ukly .nd
medlCll CQUlpn!llll. shop CQwpmcnl, .ulomOfl'-c. c.qwpmc.nl, yard mllC.naJ-
ha",lhnl c.qulpmc.nl, 1.00ralory eqUipment, ｳｨ､ｾ｣ＮｳＮＮ bllli. paJkli, hand lrucks.
fire ｮｬｬｮｬｵｬｾｨ･ｲｳＮ bOK$, fire. c.nI'IU:S, Io"dlng c.qlllpme.lll.
(4) D,wlb"rron wuJ p"d.Gg,ng !Ddude I'lIw-malmal.nd prodtH;! slorlF and
handllnl cqulprnc.nt, plOdUCI pack.llnl equlpmenl. blcndllli r.cihlia;. loadlnl
it.UOIS..
d '-oJ.•bout I ＲｾＮｯｲｆｃｬｯｲＴ ＦｾＮｯｲｐｕｲ､ｬ｡ｳ｣Ｎ､･ｱｵｬｰＧｰＢｮｬｏｏｩｕ｟
(I) SuO'c)'i.nd recs
(2) PrGpen) ｾｉＤＭ
8_ IrulirtCl caw lire. uprMd 110I dJr-ealy lo"'ohul "'IlII matmlll and la.bor 01 ｡｡ｾｬｬｮｳｬ｡ｬｬＮﾭ
ｵｯｃｬＬｬｉ｢ｯｵｬｬｳＮＭｊｏｾＮｯｲｆｃｉ
I LtgllWlr"'fJ tJNI ｾｵ｟Ｌ .bout ＴｾＲＱ Y. or Fel or S-ISy' or duM ....1$-
11_ !Aimu,"'fJ COSTS Indude Ｎ､ｭｬｬｬｊｾｲ｡ｬＱｾ｣ＮＬ process d""'ICl and geucral c.nl'n«nng,
dmung, CO'it c.n&lnc.c.nng. proocsslng. ･ｾｰ･､ｬｬｬｏｬＬ reproducllon. communlCatlonli.
_Ie. modell.. consulI.nl rtts. lra"e1
II ErogutN''''fJ Sf'IN"u_ Qnd ｉｦｉｊｾＯｬｴｍｬ
2 CQIIJ'fJIC/I"" U/W'UU; IIboUI 4 8 21.0Y. 01. FCI
/J TtfPIIIO'/J'Y I«Jllln composed 01 COIlSINCIIOll. O-pcra11Oll., .nd IZAUlleMIlOt' 01
IaDpora.ry fllQbues; ofIiot::s, roads. parkllliiou. raliroacb. clec1nca1. p1p1nJ.
commUDOClUOns. kDan...
II Coru'TVCI_ ,oob <r..J ｾＬＭ
c C""Jlrvcl_ S"JWnu_ ｉｬｬｾｯｨｬｬｬｬＡ aCDDUnl1nJ, Illnd':ttplnJ. ｰｵｲ｣ｨ｡ｳｬｮｾ upe.o:htm,.
d Wo,rhOOlS<' JW'ltmnrllltld 1J,,'mJs
I Solnl'. ,..,d..-ol. QndIrmgt /H"tfi"
I I't,mm./itld ItJlS. sp"'u/ l'rtflHS
, T".us. UlS"'lltIrt, tmd mlt',tSI
1 C_lttK'or·s (tt_ abou' 1 S SO·. 01 Fel
" C..t"'9f"'C') 10 ｣ｯｭｾｬ･ for unprc.o:hetablc "enlS 'udl n "arms. ftoods. Ｂｮｾ･ｯＮ
pna: dt3nJCI. imall MIlD clgnp:s. ('fron ,n nlltrullCl., rIC ••boul S Xl·. 01 FCI
C AI't't_lt btnJ.:d/w" of FCI
I M-../oc-rllrlTOlJ c"p"oIInl'l'SI......nl-umc U 01Ul1a.
2. H_focIllTlTI(J CtlpluH /TIfIISI......,,1 Ii olfl,nc. plus mdlfCCI «>i1.5.
III W....klng coptlat is tM c:apll.al reqUITed 10 aetu.ally oprrale lhe. p1anl, aboUI ＱＰＭＲＰｾＮ 0I1be. 101.1
cap"al ,nvc.slmc.nl
A.. Ra...' """",.wl for. on",-momh supply_ (11le supply dcprnds on .vallabo"ly, .KISOII.I
deman4s. cle.)
B. F",1SIwJ ＬＬｾｉｓ III ,'oci. aad wm,filllShod producu, appco..,ma,e production C05I5for oM
monlh (Again. lbe amoUOllZAY vary.)
C Arcoo-u ClCtlC'Obll 10 I"e OISIomrn lO d.ays 10 pay lor coodt. aboul the productlOli
eoslS I'or one montb
o ClUit "'" IoDruJ 10 atttt oprraunl UprlliC5-salarlQ and waF' ra...·IMIc.naJ purrnasa.
E. AcC'OMIIu poy<Jbk -" ,urs ""yobl",
IV $,,,,r·"P CIUIS; :about ＱＰｪｾ 01 Fel
A. PHKtU wKJdljico,w#u needed 10 meel dc.s,&n speclficallolls
B Stan"p labo, more people a.e. n«ded 10 sra'l up plalll Ihan 1(1 ｾｴｴｰ 11 rumllnl
C J.,ou In prodwc,,<)tI 111'01'·0 lois of re'"(nuo durllli debull&'lIl (f( lhe pr00tli5
ｔＮｾ ... Ir_ M S ""'n...... I.. D l_'ba.... ,._ 0...., -.tIu_",,/- ｯＭＮＭＮｊｾｾ .. Mr:G....-lhll
ｾ V",l,I'"
29. 40 SOClION U TOlAl CArrrAI INVE5IMENT MoD TorAl ＬＮｾｯｬｊｕｃＧｔ COSH
SECTION l-J rOHI CAMIAl 1'IE5rMENT MoO rOTAl ｐｾｦＩｬ＾ｬｊｃＢｉ CQ5l·s 41
Start-up Costs
TA8U- 1J..2
Gross earnings lind lolal prodlK"t CCKts
T.k &_ M s. ｾ and K. D T......ba.... ,.... Duip...J ｾＯＢ aw-.ea._... Mc<lr.....H...
N York.. 1963
Many companies also include the start-up costs as part of the capital investmenl
Other companies conSider the fraction of the start-up costs that is allocated to
equipment modifications as part ofttle capital investment, whereas the funds used
for additional workforce: and malerials needed to start up tbe plant are considered
operating ･ｸｰ･ｮｾｳＮ The choice among ｴｨ･ｾ various possibilities depends on the
tax situalion of the company However. for our purposes we include the start-up
costs (Slart-up) as part of the inveslment. Hena:, Eq. 2.3-1 becomes
(2.3-4)
(2.3-7)
Offsite ... 045 ｏｮｾｬｴ･
Work. Cap. - O.I5(Tot lov.)
Working Capital
The working capital represents the funds required 10 actually operate the plant. i.e..
to pa) for raw materials., to pay salaries., etc. We allempl to replace the working
capital each month OUI of product revenues, NeH:rtheless, we must have money
available before we c0mmence operalions to rill up the lanks and to meet the Initial
payroll For this reason the working capital is considered 10 be part of the total
Incstmenl.
A breakdoy,n of the working capllalls glen m TaMe 2.3-1, and a reasonahle
first estimate of thIS cost can be taken as a 3-monlh supply of ray, malerials_ or
products We can greatly simphf) the mitial Inestment aoal)"sis. howecr. if we
assume thaI y,orkmg capital is related to the inestmenL For this reason, we leI
Fixed Capital 100-eslmenl
From Table 2.3-1 we set" Ihat the fixed captlal tnestment is the sum of Ihe dIrect
COSt and the IIIdlrecl casls:
The indirect costs dcscribed m the table often are lumped in two categories:
(I) the owner's costs, whleh include the engineenng, supervision, and construction
expenses; and (2) contingencIes and fees (Contlng,) which account both for tlems
The onsite costs correspond to the installed equipment COS!!i for the items shown
on the process flo""'sheet All these items are built III a specific geographical area.
called the bafUr)' IlmllS, We can eSlimate the onsite costs diTC{;II)' from Guthrie's
correlations.
The olfsite COSIS. or OSBl costs, refer to the steam plant, cooling towers. and
other items listed in Table 2.3-1 that are needed for the operation of the process but
are buill in a different geographical area, II is common ｰｲ｡｣ｴｩｾ to ha<e central
areas for cooling towers. steam generalion equipment. etc. We note from the table
Ihal the variation in the individual olfsite costs is much larger' than that in the
onsile costs. In facl, the offsite costs may vary from as little as 40 to ＵＰｯｾ of the
onsite costs for an elfpansion of an existing facility. up to 200 or 400% of the onsite
costs for the conslrUCIIOn of a grass-roots plant (a brand new facilily startmg from
scratch) or a major plant expansion. This situation is analogous 10 building an
addition to a ｨｯｵｾ versus building a new home. In OUf studies, we consider only
plant expansions, and we assume that
Fixed Cap. _ Direcl Cost of Indirect COSI (2,3-5)
The direct COSTS mclude the onslle costs (Onstle) or ISBL costs (inside batter)
limits). and the otrslle costs. or OSBL costs (oumde battery limits):
Oncct Cost = Onstte + Offstle (2,3-6)
(23-2)
(23-3)
I Gr0S5 arnlnp • 10t.1 UloCOme tot.1 produo;llon CO$l
II Tot.1 product CO$t _ m.nuf.etunnl COSI 1" p:oc:ral nrc:n5eS.
A M.nllr"etunn, eml _ dlr«l produchon costJ -+- hed ch.r,es .... rl.nt ovn-MJld
I I)UllC1 f'lodUClIOl1 costs t.boul ＶＰｾＧ［Ｌ otlhe tOlal product emt)
" R.... m.atefll" ,aboul 10 Xl·" of 100al prodUCI COSl)
b Ullllt," (about 10 20·. of tOlal p.oduct CO$I).
C MI,nlrna..... and rrpant (aboul 1 10·. or Fel).
J O""rJlllnr: supplors (aboul 10 20·.0( COit lor mlonlenance and rrp,,"rs o. 0.5 1".0(
rell
t Opellllnliabor (Iboul 10 ＲＰｾＮ 0(10111 product COSl).
f Orna su""rvlSlOfl and dmcailibol (lboUI 10-2S" 0( ｾｉｬｮｬＡ Iabot)
fI labontory chafFS (Ibout 10 20" 0( oprnlu"Ilabor).
4. PatmtJ and fO)"lltlC$ (about 0 Ｖｾ oClot" product C05I).
2. Fiud charr;es (Ibovl 10 20% 0( total product cost).
... l)epnaahOn (aboul ＱＰｾｾ of Fa).
II Loc:allun (aboul 1 4ｾｾ ol Fel).
c InsurJlllCJe (about 04 I·. of Fa).
J Rml (aboUI ＱＰｾＮ 0( ,.II.., 0( rrnled land .Dd bvrldinp).
r ｉｮｴｾ (about 0 7·" ollolal captal m>a.UDr-Dt).
} P1.anl ｯｾｨ｣｡､ (about SO ＱＰｾＧ［Ｌ ol!hl: oasI ror opcr1Iunr: labor. ｳｵｾ and ....onlrna.....
or 5 ＱＵｾＮ 0(10111 product COlli). costs IDdOCk rmc:ral pLmt upl-crp IDd o.....Mad. r-)"roll
ovnhad, pKkallna. ｾ Wl'YlCa, Aft'ly.nd protectIOn, rewt.UnrD!S, ucrca!lOll. S111'"lar.
laboralorxs. and ...orllt' r.alltx:s.
B Gt'nrral ｵｾ _ ｡､ｭｴｮｾｬｲ｡ｕＢＢ c:ostJ -+- dutnbuuon IlId sdlml! COitJ -+- Tt'SeIlch and dt'....I·
oproc:nt COSls [ali(! ca1It'd SARE (SIlks, adrtlllmlnltioD, ｾ IDd mplXftlJl!l]
I Admllu...rlllve QOIItJ (Iboul 1S% r:I ｾ for op«aUDI labor, supn-v!i1Oll, IIId mllnlrnana
or 2· ｓｾＮ ollotal produo:1 eost); lOOI.ldt'll COliIS for ua:uti,"t' w-na., c:kno::al ."I@t'S. kpl (<<II.,
offioe svppbr., and commU1lIC.IuonL
2. DttlflbutlOll.nd wlllnl costs (about 2-10" of total prodtJt:I COSI); irlclucks C:OS15 ror SIIkt
offica, S111t'$ sll1l', .lhIPPtnl. and IdVt'ItBUIJ.
3 Rt'teIrdt and dt'Ydoplllt'nl COSIII (aboul 2-S" of evefl' Wo:s dolLu or about 5% of tocal
product cost)
Tot Inv = Fixed Cap, + Work. Cap. + Start·up
From Table 2.3-1. item IV. we see lhal
Start-up ... 0, I(Fixed Cap,)
