Kinetic modeling of FCC process

Catalytic cracking of petroleum fractions a process termed as FCC is usually carried out in a reactor block with somewhat complicated hydrodynamic regime. The reactor block is considered as a combination of two different reactors. The riser is a near ideal plug-flow displacement of the catalyst and reaction mixture, while the main reactor vessel (separator) is considered as an ideal mixing CSTR. Temperature gradient along the plug-flow riser can vary on a linear and non-linear dependence. This is reflected by the thermal effect on the cracking products, along the altitude of the riser. Moreover, it can exert a considerable influence on the selectivity of the process in general, as characterized by the diversity of different hydrocarbon groups both in the gaseous and liquid products. The fluid catalytic cracking (FCC) is a process of conversion of a heavy oil fraction into lighter products in a catalytic fluidized reactor. The chemical composition and the structure of the feed are reflected on the catalyst's selectivity and the amount of coke deposited. It is, therefore, necessary to consider the feed type on modeling the process. Cracking reaction in the model was represented as a five-stage process. Reaction rates for the plug-flow riser and the ideal mixing separator are described mathematically in differential and algebraic forms. The model takes into account, exponential dependence of the specific reaction rate on temperature, as well as reflects the influence of the real and bulk catalyst densities, circulation rate, equilibrium and fresh catalyst's activities, reactor pressure, feed rate and unit construction. The model was developed based on a data taken from an industrial FCC unit, that were used to compute the kinetic constants and other parameters. Concrete computed kinetic parameters were compared with corresponding experimental data for adequacy. FCC process is in constant technological development with modernization of especially the riser reactor. Kinetic modeling of the catalytic FCC reactor will give a further understanding of the process and explain the complicated mechanism involved for an efficient and optimal conversion of the feed stock.