Fluid Catalytic Cracking Power Recovery Computer Simulation

Abstract

Fluidic cat crackers using the catalyst regeneration cycle have significant power recovery potential. Typically, the regenerator takes the spent coked catalyst and burns off the coke in an air pressurized atmosphere. The hot pressurized flue gas, leaving the regenerator section, contains the potential for power conversion from the heat energy and pressure head. Many existing systems recover the heat energy by means of carbon monoxide or waste heat boilers, but fail to utilize the pressure energy which can be recovered by the use of high temperature, dirty gas expanders. The use of an expander in the regenerator system introduces additional complexity. Analysis of the system operation during "off-design" conditions must be determined in order to properly design and size all turbo machinery and process components. A computer simulation model has been developed which allows the equipment vendor to size the air string components and assist the process designer in the evaluation of the many possible operating conditions. The digital computer model simulates the performance of the axial compressor, power recovery expander, regenerator section, and system pressure drops. The program can simulate the process system design conditions for compatibility with the axial compressor and the power recovery expander. It can predict off-design operation, such as the variation of ambient air inlet temperature and its effect on the compressor-expander power balance. It can test the startup procedures so that component design limitations are not exceeded. This paper will cover some of the basic modeling concepts for the axial compressor, regeneration and hot gas expander.