A Study of the Dynamics and Control of the Model IV Fluidized Catalytic Cracking Process

Abstract

Fluid catalytic cracking (FCC) is one of the most important chemical units in oil refineries due to its economic benefits. This research work concentrates on improving the control system of the Model IV FCC unit where dynamic modeling and the controllability based on the McFarlane et al. (1993) model. Different open-loop tests were carried out in the wash oil flow rate (F₁) and the furnace fuel flow rate (F₅) to find the FCC models using Sundaresan and Krishnaswamy (S&K) and fraction incomplete response (FIR) methods. The riser temperature (T_r) and the regenerator bed temperature (T_g) were chosen as the control variables while (F₁ and F₅) were selected as the corresponding manipulated variables based on the relative gain array (RGA).  PI controller tuning parameters were evaluated using the internal model control (IMC) method and different closed-loop control responses were examined for both set point tracking and disturbance rejection changes. Additional adjustments to the IMC filter constant were employed to further improve the closed loop responses for the system.