Modeling and simulation of a downer-type FCC unit

FCC process is becoming increasingly important as a potentially flexible means of responding to changes in petrochemical product demand. This process will play a major role as producer not only of gasoline, but also of light olefins, thus integrating refining and petrochemical industries. Mathematical models were developed for a downer-type FCC unit, in which conservation equations for nonisothermal downer and regenerator reactors were linked with applicable hydrodynamic findings, 4-lump cracking kinetics in the downer, and complete combustion kinetics in the regenerator. The models were validated against experimental data collected in a pilot plant, in which the downer and regenerator were 1 and 3.6 m in length, respectively, and operating temperatures of ~ 875 K were achieved. Detailed parametric sensitivity studies, including the analysis of key operating, design, and model parameters, were performed using different catalysts.