Thermal Energy Correction Based Model Predictive Control for Fluid Catalytic Cracking Riser

Abstract

A model predictive control (MPC) method optimizing the temperature distribution along the fluid catalytic cracking (FCC) riser reactor is proposed to precisely control the reactions in the FCC riser reactor for improving the economic performance. In the proposed MPC, a novel cost function considering the thermal energy consumption is constructed to cope with the disturbances, e.g., the variations of the inlet temperature or quality of feedstock, since the disturbances may make the original outlet temperature set point lose its economical optimality. Taking advantage of the feature that the thermal energy consumption indicates the conversion rate, the proposed MPC ensures the yield of the FCC reaction when the disturbances occur. Besides, a moving horizon estimator is employed to estimate the temperature distribution of the riser reactor since there is only a limited number of thermocouples placed on the FCC riser. A numerical study based on an industrial FCC unit was completed, and the results show that even if the disturbances exist, compared with the method which controls the outlet temperature to a fixed set point, the desired conversion rate is improved by the proposed method.