Page 253 - Analysis, Synthesis and Design of Chemical Processes, Third Edition

c. By how much would the cost of cooling water increase if the cost of make-up water were to
double?

Determine the cost of producing a refrigerant stream at –50°C using propane as the working fluid in a
noncascaded system. You may wish to refer to Example 8.5 to do this problem. The steps you should
follow are as follows.

a. Determine the pressure at which propane can be condensed at 45°C, which assumes that cooling
water with a 5°C temperature approach will be used as the condensing medium.

b. Determine the pressure to which the propane must be throttled in order to liquefy it at –50°C.

12.
c. Use the results of Parts (a) and (b) to set the approximate pressure levels in the condenser and
evaporator in the refrigeration system.

d. Determine the amount of propane necessary to extract 1 GJ of heat in the evaporator.

e. Assuming a 5kPa pressure drop in both heat exchangers and that a single-stage compressor is
used with an efficiency of 75%, determine the cost of electricity to run the compressor, determine the
cooling water cost, and from this determine the cost of providing refrigeration at –50°C using
propane as the working fluid.

Repeat the process described in Problem 12 using a simple refrigeration loop to determine the cost of
providing 1 GJ of refrigeration at –50°C using the following working fluids:

a. Propylene

b. Ethane
13.

c. Ammonia

Determine whether any of the working fluids given above cannot be used in a simple (noncascaded)
refrigeration loop. For these fluids, would using a cascaded refrigeration system to provide –50°C
refrigerant make sense? Explain carefully your answers to these questions.

Estimate the cost of operating labor (C ), the cost of utilities (C ), and the cost of manufacturing
OL UT
14. (COM ) for the ethylbenzene process given in Project B.2 of Appendix B. You must do Problem 7.21
d
in order to estimate COM .
d

Estimate the cost of operating labor (C ), the cost of utilities (C ), and the cost of manufacturing
OL
UT
15. (COM ) for the styrene process given in Project B.3 of Appendix B. You must do Problem 7.22 in
d
order to estimate COM .
d

Estimate the cost of operating labor (C ), the cost of utilities (C ), and the cost of manufacturing
OL
UT
16. (COM ) for the drying oil process given in Project B.4 of Appendix B. You must do Problem 7.23 in
d