Economic and Control Performance of a Fluid Catalytic Cracking Unit: Interactions between Combustion Air and CO Promoters

Abstract

The presence of CO combustion promoters significantly affects the heterogeneous CO combustion in the regenerator of a fluid catalytic cracking (FCC) unit. Neglecting the quantitative correlation between the heterogeneous CO combustion and the amount of added CO combustion promoters in the previous models makes it impossible to predict the steady-state and the dynamic behaviors of the system with respect to the CO combustion promoters. Therefore, an augmented dynamic model of an FCC unit with high-efficiency regenerator incorporating the quantitative correlation between heterogeneous CO combustion and the CO combustion promoters is developed, and the corresponding closed-loop dynamic responses are obtained. Since CO combustion in the regenerator is affected by both the combustion air flow rate and the CO combustion promoters, a sensitivity analysis of some important variables related to the combustion air flow rate and the amount of added CO combustion promoters is carried out and the overall operating map of the system is developed by selecting the conversion of the riser, the integrated absolute errors of the controllers, and the temperature rise between the dense bed and the outlet of the freeboard to represent the concerns of economics, control, and safety.