Chemical Engineering August 2011 - 35

centrifugal pumps
CS4-P-101
CS5-P-104
CS6-P-101
CS5-P-105
CS2-P-102
CS1-P-102
CS4-P-102
Table 5. purchase cosT (CPCS) of pumps
capcost Dfp
ccep
power, kW material CPCS
0.3
0.38
0.46
0.75
1.12
1.7
1.7
CS5-P-102/103 2
CS2-P-101
CS5-P-106
CS1-P-101
CS6-P-102
CS5-P-101
CS1-P-103
CS4-P-103
CS6-P-105
CS7-P-101
CS6-P-106
CS6-P-104
CS3-P-105
CS3-P-103
CS3-P-101
CS3-P-102
CS6-P-103
CS7-P-103
CS7-P-102
CS7-P-104
2.24
2.65
2.8
5.84
6.4
24
0.5
1.08
2.3
3.69
10.4
reciprocating pumps
CS3-P-104
0.2
0.24
0.6
22.4
29.6
0.16
Diaphragm pumps
CS7-P-105
1
1.9
3.7
60
CS
CS
CS
CS
CS
CS
CS
CS
CS
CS
CS
CS
CS
CS
SS
SS
SS
SS
SS
CS
CS
CS
CS
CS
SS
SS
SS
SS
SS
3,554*
3,554*
3,554*
3,554
3,577
3,726
3,726
3,807
3,876
3,979
4,025
4,807
4,934
8,257
3,554*
3,565
3,887
4,267
5,808
7,659
7,613
9,258
47,380
57,500
7,176
10,730
13,455
17,710
95,105
econexpert
aspenpea
Δ%
Δ% Δ% Δ%
152% 50%* 7% 55%
156%* 49%* 14%* 57%*
152%* 62%* 21% 57%
165% 46% 39% 60%
164% 48%* 57% 35%
165% 27%* 73% 53%
110% 46%* 73% 53%
166% 54%* 79% 50%
176% 28%* 83% 37%
209% 53% 89% 76%
251% 26% 91% 89%
297% 120% 110% 123%
289% 75% 112% 107%
204% 24% 117% 10%
146% 59%* 24% 57%
143% 223% 56% 57%
163% 51%* 84% 50%
145% 294% 99% 132%
438% 140% 118% 58%
n/a+
n/a+
n/a+
n/a+
n/a+
n/a+
n/a+
n/a+
n/a+
n/a+
-25%* 11% -9%*
-24%* 11% -8%*
-55% 22% -24%*
-21% 22% -38%*
-35% 22% -49%*
-29%* 4% -3%*
45%* 26% -50%
182%* 27% -50%
-36% 27% -51%
17% 25% -87%
*cost of minimum size as size is less than the minimum size
+ not available in this program and so taken from another program
Compressors
Major compressor types are trunkpiston
and crosshead reciprocating
compressors, diaphragm compressors,
centrifugal compressors and axial
compressors. Case studies 4-7 involve
compressors, and purchase costs of
these compressors at base conditions
are presented in Table 2. Total module
cost is shown in online table I.
In these and subsequent tables, the
cost estimate by CapCost is given, and
the cost estimate by other methods is
expressed as the percent difference
from that by CapCost, such that Δ =
100 × (cost using other method - cost
using CapCost) / cost using CapCost).
Hence, a positive (or negative) Δ
value means the cost estimate by that
method is more (or less) than that determined
by CapCost.
Results in Table 2 indicate that compressor
purchase cost estimates by
CapCost, CCEP and AspenPEA are
comparable, while the purchase costs
given by EconExpert increase very
fast with increasing size. In fact, DFP
gives a very high cost compared to all
other programs, which is mainly due to
the cost equation given in Ref. 2. From
this equation, even the lower limit
(power of 75 kW) gives a cost as high
as $714,050. Such a high cost may be
due to the data source for calculation
of empirical constants. Differences in
total module cost of compressors by different
programs are larger than those
in purchase costs (Table online), which
is due to differences in installation and
other factors used for CTM.
Heat exchangers
Common heat-exchanger types are
shell-and-tube, double-pipe, air-cooled
fin fan, and compact heat exchangers,
including plate-and-frame and spiral
plate types. Because heat exchangers
are common, the data available from
vendors and other sources are voluminous.
The wealth of data results in
relatively more-accurate cost estimation.
For example, the purchase cost
and total module costs of floatinghead
and fixed-head heat exchangers
predicted by all programs are comparable,
with somewhat lower cost
by CCEP and EconExpert (Table 3).
For kettle reboilers, CapCost predicts
50 to 80% higher purchase and total
module costs than the other four programs.
For double-pipe heat exchangers,
all programs predict comparable
purchase cost. However, AspenPEA
predicted a total module cost three
times that by CapCost (online table
II). The most significant factor contributing
to the high total module cost
in AspenPEA is the piping cost. While
other programs calculate piping cost
as a small fraction of purchase cost,
AspenPEA model calculates piping
cost based on respective equipment.
For double-pipe heat exchangers,
the piping cost is around three times
the purchase cost, which contributes
10×CPCS to CTM.
Figure 1 shows the total module cost
of floating-head heat exchangers calculated
in all five programs as a function
of heat transfer area. Since only the
U-tube shell-and-tube heat exchanger
cost equation is given in Ref. 2, the DFP
estimate in Figure 1 is for this type.
Since floating-head heat exchangers
are generally costlier than the U-tube
type, the floating-head heat exchanger
cost by DFP is expected to be slightly
higher than that in Figure 1.
For smaller heat transfer areas (up
to 400 m2), all five programs predict
total module cost for floating-head exchangers
with less than 50% deviation
using the CapCost value as a reference.
As the area increases, the deviations
become more significant. In the seven
case studies, many of the floating-head
heat exchangers have areas below 400
m2. Hence, all five programs predicted
similar costs. However, when the heat
transfer area is large, CapCost and
DFP predict a relatively higher cost
than the other programs.
Figure 2 shows the variation in the
total module cost of fixed-head heat
exchangers calculated by all five programs,
with heat transfer area. Since
only the U-tube shell-and-tube heat
exchanger cost equation is given in
Ref. [2], the DFP estimate in Figure
1 is for this type. CCEP and EconExpert
predict lower costs than the
other three programs for all sizes of
fixed-head heat exchanger. However,
for smaller areas, (up to 300 m2) the
percent deviation is relatively small.
In the case studies, most of the fixedhead
heat exchangers have areas
below 300 m2. Hence, all five programs
predicted a similar cost. As the area
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