Parametric Sensitivity Studies in a Commercial FCC Unit

Abstract

A steady state model was developed for simulating the performance of an industrial fluid catalytic cracking (FCC) unit which was subsequently used in parametric sensitivity studies. The simulator includes kinetic models for the riser reac-tor and the regeneration systems. Mass and energy balances were performed for each of these sections and simulation results were compared with the plant data available in the literature. Model predictions were found to be in close agreement with the reported data. Finally this validated model was used for studying the effects of independent vari-ables such as feed preheat temperature (Tfeed) and feed flow rate (Ffeed) on the unit performance at either fixed regener-ated catalyst temp/regenerator temp (Trgn) or constant reactor outlet temperature (ROT). The catalyst circulation rate (CCR) was automatically adjusted to keep the ROT constant with varying the independent variables feed preheat tem-perature while the air rate adjusted for keeping the regenerator temperature constant which consequences the depend-ency of both dependent and independent variables on the unit performance. The air flow rate to the regenerator was also an independent variable during the parametric sensitivity analysis and its effect on FCC performance was investigated at constant Tfeed, Ffeed and CCR. Combining all the sensitivity analysis, it has been found to increase gas oil conversion and product yields by 5 to 6 percent with decrease of say, 10 K, in the feed preheat temperature (Tfeed) and correspond-ing increase in air rate (Fair) and catalyst circulation rate (Frgc) at constant reactor outlet temperature (ROT) and rege- nerated catalyst temperature (Trgc).