Modeling of a fluidized catalytic cracking process

Abstract

The purpose of this study is to develop a detailed dynamic model of a typical fluidized cracking (FCC) unit that consists of the reactor, regenerator, catalyst transport lines, and several auxialiary units (pre-heater, catalyst cooler, and blowers). Hydrodynamic descriptions for the crucial parts of the unit are incorporated into the model. Special attention has been paid to the reactor riser to predict the velocity distributions of the catalyst and gas phases, the molar concentrations of 10-lump species, and the temperature profile by utilizing momentum, mass, and energy balances. The regenerator is modeled in such detial that the two-regime (dense bed and freeboard), two-phase (emulsion and bubble) behavior of typical fluidized beds can be described. The models for cylcones, valves, and several auxiliary units of the FCC unit are also applied to investigate their dynamic effects on the overall systems. The resulting model equations are grouped into 14 molecules each of which corresponds to a specific part of the unit and type of equations, and then an efficient iterative scheme is employed for convergence of all the modules. The model solver is constructed on the basis of a modular approach and then implemented by a Fortran code. Finally, to validate the developed simulator, the steady-state simulation results are compared with those in the literature and the dynamic responses of the process are predicted and analyzed.