Makeup & Purge

Consider the hydrodesulfurization process used in petroleum refining. This process has a large recycle hydrogen stream. In addition, there are two small stream branches on the recycle.

A "makeup" stream is required to replace losses to leaks, carryover, etc. within the recycle loop.

A "purge" stream is a small stream bled off from a recycle loop to prevent buildup of inerts or impurities in the system. Often, the purge flow is so much smaller than the recycle flow that it can be neglected in the steady state overall material balance.

Proper sizing and location of makeup and purge streams can prevent many problems with process plants.

References:

1. Felder, R.M. and R.W. Rousseau, Elementary Principles of Chemical Processes, 2nd Edition, John Wiley, 1986, pp. 113, 138.
2. Felder, R.M. and R.W. Rousseau, Elementary Principles of Chemical Processes, 2005 3rd Edition, 2005, p. 138-42.
3. Himmelblau, D.M., Basic Principles and Calculations in Chemical Engineering, 6th Edition, Prentice-Hall, 1996, pp. 218-19.

R.M. Price
Original: 6/14/94
Modified: 9/14/95, 10/30/95; 1/6/2005

Copyright 2005 by R.M. Price -- All Rights Reserved