Page 213 - Fluid Catalytic Cracking Handbook

Unit Monitoring and Control 181

mined by direct sampling of the reactor overhead line or by conducting
a unit test run,
The heat balance exercise provides a tool for in-depth analysis of
the unit operation. Heat balance surveys determine catalyst circulation
rate, delta coke, and heat of reaction. The procedures described in this
chapter can be easily programmed into a spreadsheet program to
calculate the balances on a routine basis.
The pressure balance provides an insight into the hydraulics of
catalyst circulation. Performing pressure balance surveys will help the
unit engineer identify "pinch points." It will also balance two common
constraints: the air blower and the wet gas compressor.
Finally, process control systems allow the unit to operate smoothly
and safely. At the next level, an APC package (whether within the DCS
framework or as a host-based multivariable control system) provides
more precise control of operating variables against the unit's con-
straints. It will gain incremental throughput or cracking severity.

REFERENCES

1. Davison Div., W.R. Grace & Co., "Cat Cracker Heat and Material Balance
Calculations," Grace Davison Catalagmm, No. 59, 1980.
2. Hsieh, C. R. and English, A. Ar., "Two Sampling Techniques Accurately
Evaluate Fluid-Cat-Cracking Products," Oil & Gas Journal, June 23, 1986,
pp. 38-43.