Page 219 - Analysis, Synthesis and Design of Chemical Processes, Third Edition

When designing equipment for high-temperature and high-pressure service, the maximum allowable
stress as a function of temperature of the material of construction is of great importance. Consider a
cylindrical vessel shell that is to be designed for pressure of 150 bar (design pressure). The diameter
13. of the vessel is 3.2 m, it is 15 m long, and a corrosion allowance of 6.35 mm (1/4″) is to be used.
Construct a table that shows the thickness of the vessel walls in the temperature range of 300 to
500°C (in 20°C increments) if the materials of construction are (a) ASME SA515-grade carbon steel
and (b) ASME SA-240-grade 316 stainless steel.

Using the results of Problem 13, determine the relative costs of the vessel using the two materials of
construction (CS and 316 SS) over the temperature range. You may assume that the cost of the vessel

14. is directly proportional to the weight of the vessel and that the 316 SS costs 3.0 times that of CS.
Based on these results, which material of construction is favored over the temperature range 300–
500°C for this vessel?

The following problems may be solved either by using hand calculations or by using CAPCOST (use
a value of CEPCI = 500).

Determine the bare module cost of a 1-shell pass, 2-tube pass (1-2) heat exchanger designed for the
following operating conditions:

Maximum operating pressure (tube side) = 30 barg

Maximum operating pressure (shell side) = 5 barg
15.

Process fluid in tubes requires stainless steel MOC

Shell-side utility (cooling water) requires carbon steel MOC

Heat exchange area = 160 m 2

Repeat Problem 15, except reverse the shell-side and tube-side fluids. Are your results consistent
16.
with the heuristics for heat exchangers given in Chapter 11? Which heuristic is relevant?

In Chapter 15, the concepts of heat-exchanger networks and pinch technology are discussed. When
designing these networks to recover process heat, it is often necessary to have a close temperature
approach between process streams, which leads to large heat exchangers with multiple shells.

Multiple-shell heat exchangers are often constructed from sets of 1-2 shell and tube exchangers
stacked together. For costing considerations, the cost of the multiple-shell heat exchanger is best
estimated as a number of smaller 1-2 exchangers. Consider a heat exchanger constructed of carbon
17. steel and designed to withstand a pressure of 20 barg in both the shell and tube sides. This equipment
2
has a heat exchange area of 400 m . Do the following.
a. Determine the bare module cost of this 4-shell and 8-tube pass heat exchanger as four, 1-2
2
exchangers, each with a heat-exchange area of 100 m .
b. Determine the bare module cost of the same exchanger as if it had a single shell.
c. What is the name of the principle given in this chapter that explains the difference between
the two answers in (a) and (b)?