Design of robust optimal controllers for a fluid catalytic cracking unit in petroleum refineries

Abstract

Fluid Catalytic Cracking Unit (FCCU) is a technique where raw crude oil is transformed into lighter petroleum products. It is a challenging problem in the refining industry. The FCCU has become the benchmark for many advanced control techniques in recent decades. It involves a complex series of steps, starting with the preheating of the heavy fuel oil and ending with the production of lighter products, such as gasoline and kerosene. The problem statement is that the FCCU process is expensive and has a low yield of the desired products. This can lead to significant economic losses. In this study, a control system for an FCCU has been designed. The FCCU is a non-linear and interactive process as they are interdependent on one another. The main control objective of FCCU is to maintain the desired temperature of reactor and regenerator temperature respectively. However, because of manipulating variables, air flow rate and regenerator catalyst flow rate will change both reactor and regenerator. Hence, Gain Scheduling Decentralized Proportional-Integral (GSD-PI), Gain Scheduling Decentralized PID (GSD-PID), Gain Scheduling Decentralized Fuzzy Logic Controller newline(GSD-FLC), and Gain Scheduling Mixed Fuzzy Logic Control scheme (GSMFLC) need to be utilized by FCCU process. The PID controllers are more often used in industry for the standardized control. A PID control scheme is a closed-loop control process that is a more stable and accurate controller newline newline