Page 57 - Analysis, Synthesis and Design of Chemical Processes, Third Edition

Next, the size of the major process lines must be determined. In order to estimate these pipe sizes,
it is necessary to make use of some heuristics. A heuristic is a simple algorithm or hint that
allows an approximate answer to be calculated. The preliminary design of a piece of equipment
might well use many such heuristics, and some of these might conflict with each other. Like any
simplifying procedure, the result from a heuristic must be reviewed carefully. For preliminary
purposes, the heuristics from Chapter 11 can be used to estimate approximate pipe sizes.
Example 1.12 illustrates the heuristic for calculating pipe size.

Example 1.12

Consider the suction line to P-202 A/B, what should be the pipe diameter?

From Table 11.8, 1(b) for liquid pump suction, the recommended liquid velocity and pipe diameter are
related by u = (1.3 + D (inch)/6) ft/s.

From Table B.1.1, the mass flowrate of the stream entering P-202, = Stream 16 + Stream 10 = 2170 +
3
5970 = 8140 kg/h and the density is found to be 800 kg/m . The volumetric flowrate is 8140/800 = 10.2
3
3
3
m /h = 0.00283 m /s = 0.0998 ft /s.
The procedure is to calculate the velocity in the suction line and compare it to the heuristic. Using this
approach, the following table is constructed.