Understanding the Software Options

TABLE 8. PURCHASE COST (C PCS) OF OTHER TYPES OF EQUIPMENT
Centrifuges CapCost DFP CCEP
EconExpert
AspenPEA
Dia., m
Material
CPCS ∆% ∆% ∆% ∆%
CS3-Ct-101 2 CS 303,600 n/a +
n/a +
n/a +
49%
CS3-Ct-102 2 CS 303,600 n/a +
n/a +
n/a +
Crystallizers
49%
CS3-Cr-101 21.9 CS 139,150 n/a +
–76% n/a +
Fired heater
210%
CS6-H-101 26,800 CS 1,078,700 63% 112% –46% 59%
CS5-H-101
Mills
360,000 CS 6,405,500 –23% –15% –13% –35%
CS7-C-101 0.00035 SS 67,100+ n/a +
n/a +
–90% n/a +
Filtering centrifuges
CS7-S-103 0.00002 SS 53,900+ n/a +
n/a +
181% n/a +
Filters
CS7-S-104 0.0075 SS 18,600* n/a +
n/a +
–99%* –98%
CS7-S-101 1.5 SS 18,600* n/a +
n/a +
–89% –47%
CS7-S-102 55 SS 131,000 n/a +
n/a +
n/a #
–37%
CS7-S-105 80 SS 170,200 n/a +
n/a +
n/a #
31%
CS7-S-106 90 SS 184,000 n/a +
n/a +
n/a #
33%
CS7-S-107 90 SS 184,000 n/a +
n/a +
n/a #
33%
Reactor-jacketed agitated
CS3-R-101 28.4 CS 109,135 n/a +
n/a +
–70% n/a +
CS3-R-102 28.4 CS 109,135 n/a +
n/a +
–70% n/a +
* cost of minimum size as size is less than the minimum size
+ not available in this program and so taken from another program
# purchase cost not available in EconExpert
TABLE 9. TOTAL MODULE COST (C TM) OF
EQUIPMENT
Total module
cost CapCost DFP CCEP
Econ-
Expert
and agitated reactors are only available
in CapCost and EconExpert. The
results obtained from these two are
comparable (Table 8).
Total purchase and module cost
We also compared total purchase and
total module costs for all pieces of
equipment in each case study given
by the different programs. For all programs,
if a piece of equipment had a size
above the valid range, it was divided
into multiple units of smaller size and
the costing was done by summing C TM
for multiple smaller units. If a piece of
equipment had a specification below
the valid range, then its cost was estimated
by taking the lower limit of the
valid range. Similarly, if the flowrate
was less than the minimum required
for costing, the minimum flowrate was
used (not actual). Since layers of silver
wire gauze inside the reactor cannot be
Aspen-
PEA
CTM ,
Case study $million ∆% ∆% ∆% ∆%
1 4.3 –6% –4% –36% –3%
2 1.0 16% 71% –5% 68%
3 2.5 6% –11% –14% 81%
4 4.1 79% 19% –29% 28%
5 33.3 27% –23% –28% –36%
6 17.0 94% 14% 2% –11%
7 9.4 34% 7% 8% 14%
mapped to any equipment
in the programs, it is not
evaluated in case four. For
similar reasons, the cost
of catalyst pellets is also
excluded in the total fixed
capital cost in case five.
The five programs give
comparable purchase and
total module costs for the
whole plant in each case
study (Table 9 and online
table VIII), with DFP giving
a slightly higher cost
in some cases. In case study two, both
the purchase and total module costs
obtained by ApenPEA are more than
60% higher than those by CapCost.
This is mainly due to the high costs
of towers and vessels in AspenPEA.
In case three, there is good agreement
among different programs except for
AspenPEA, which shows higher purchase
and total module costs due to
the high costs of crystallizers and vessels.
In case studies four and six, the
high deviations (more than 80%) in
both purchase and total module cost
in DFP are mainly due to cost differences
in vessels and packing towers.
Conclusions
Although based on different methods
and developed in different platforms,
all five programs are user friendly
and are useful tools for estimating
the capital cost of chemical process
plants. AspenPEA has the most equipment
types available out of the five
programs. DFP is the most limited in
that regard. Based on our analysis,
the overall plant cost does not deviate
much among the different programs
studied. However, equipment capital
costs for different programs may not
be comparable. There is generally
good agreement for the purchase costs
of floating-head heat exchangers.
For fixed-head heat exchangers and
pumps, there is greater deviation in
both purchase and total module costs
among different programs studied.
Also, there is significant deviation for
most vessels and towers in total module
cost. Since material, pressure and
installation factors vary in different
methods in calculating total module
cost, capital cost estimates may differ.
Hence, while evaluating plant design
alternatives, it is important to use
only one program for cost evaluation
of process design options to maintain
consistent results. ■
Edited by Scott Jenkins
Editor’s note: Additional tables for total module
cost of equipment are included in the online
version of this article (www.che.com).
Authors
Ying Feng is currently a
technologist at Shell Chemicals
Seraya Pte. Ltd. She received
a B.S.Ch.E. and a B.S.
(economics) from the National
University of Singapore in
2010, with first-class honors
in both degrees. She received
a scholarship for her performance
at the university, and
also received a Baden-Württemberg
Scholarship during
her student exchange program at Karlsruhe
Institute of Technology, in Germany. Feng’s research
interests are capital cost estimation and
optimization of petrochemical processes.
G.P. Rangaiah has been with
the National University of Singapore
(21 Lower Kent Ridge
Rd., Singapore 119077; Phone:
+65 6516 2187; Email: chegpr@
nus.edu.sg) since 1982, and is
currently professor and deputy
head for student and academic
affairs in the Dept. of Chemical
& Biomolecular Engineering.
He received bachelor’s,
master’s and doctoral degrees
in chemical engineering, from Andhra University,
IIT Kanpur and Monash University, respectively.
Rangaiah worked at Engineers India Ltd. for two
years before his doctoral study. His research interests
are in control, modeling and optimization
of chemical, petrochemical and related processes.
Rangaiah has supervised ten research fellows
and 35 graduate theses. He has edited two books,
published 120 papers in international journals
and presented 100 papers in conferences. Rangaiah
has received several teaching awards, including
the Annual Teaching Excellence Awards from
the National University of Singapore for four consecutive
years.
CHEMICAL ENGINEERING WWW.CHE.COM AUGUST 2011 29