Simulation of an industrial riser for catalytic cracking in the presence of coking using Single-Event MicroKinetics

A relumped Single-Event MicroKinetic model for the catalytic cracking of hydrocarbons and coke formation on a RE-USY equilibrium catalyst is used to simulate an industrial riser. In contrast to previous publications on the modeling of riser reactors for catalytic cracking, the current mode includes a fundamental description of the reaction pathway to catalytic coke, resulting in a slightly higher number of lumps, i.e., 677 + 1 for coke rather than 670. Coke formation occurs via alkylation of di and triaromatics, which are coke precursors formed during cracking or contained in the feed, with alkenes in LPG and gasoline fractions. A one-dimensional reactor model which is pseudo-homogeneous with respect to concentrations but heterogeneous with respect to temperature is used. Feed conversion as well as LPG, gasoline and coke yield profiles along the riser position are in line with published results showing a vigorous cracking and a moderate to fast coke deposition in the first meters. For a riser of 30 m length, about 70% of the cracked product yields and feed conversion is established during the first 3 m. The effect of operating conditions, feed composition and riser dimensions on the product distributions is assessed. The regenerated catalyst temperature and the catalyst to oil ratio are identified as the key operating parameters affecting the conversion and the cracked product distributions.