Page 47 - Plant design and economics for chemical engineers

30 PLANT DESIGN AND ECONOMKS FOR CHEMICAL ENGINEERS

TABLE 1
Equipment specifications for alkylation unit?

No. req’d. Item and description Size Mat’l. const.
T-l, storage tank for benzene 10,000 gal Carbon steel
T-Z, storage tank for dodecene 25,000 gal Carbon steel
T-3, holding tank for alkylate 6,000 gal Carbon steel
P-l, pump (centrifugal) for benzene 30 gpm Carbon steel
transfer from T-l to R-l (up to 50 psi)
1 P-2, pump (centrifugal) for dodecene 70 gpm Carbon steel
transfer from T-2 to R-l (up to 50 psi)
1 P-3, pump (centrifugal) for pumping 45 gpm Carbon steel
cooling water to jacket of R-l (up to 50 psi)
1 P-4, pump (positive displacement) for 10 iw Cast iron
alkylate transfer from T-3 to C-l (150 psi)
1 R-l, reactor (stirred) alkylator 1,300 gal Glass-lined
Wee Fig. 2-5.

Select a 70-gpm centrifugal pump, carbon steel construction. The alkylate pump
used to transfer alkylate from the holding tank to the benzene fractionator must
operate continuously. Thus,
(1670 + 4160)
clf(alkylate) = (24)(60) = 4 k?Pm
Select a lo-gpm positive displacement pump, carbon steel construction. A
summary of the equipment needs for the alkylation unit in this preliminary
process design is presented in Table 1. The preparation of similar equipment
lists for the other process units completes the equipment selection and design
phase of the preliminary design. Figure 2-5 shows a simplified equipment
diagram for the proposed process and includes the specified size or capacity of
each piece of process equipment.

Economics
The purchased cost of each piece of process equipment may now be estimated
from published cost data or from appropriate manufacturers’ bulletins. Regard-
less of the source, the published purchased-cost data must always be corrected
to the current cost index. This procedure is described in detail in Chap. 6.
For the alkylation unit, purchased-equipment costs may be estimated
using the equipment-specification information of Table 1 and the cost data
presented in Chaps. 14 through 16 of this text. Table 2 presents these costs
updated to January 1, 1990. The required fixed-capital investment for the
nonbiodegradable detergent manufacturing process may be estimated from the
total purchased-equipment cost using the equipment-cost ratio method outlined
in Table 17 of Chap. 6. The total purchased-equipment cost is, presented in