Abstract: FCC plays a key role in the process of resid cracking to light hydrocarbons. In this study, HYSYS software was employed to set up FCC mechanism model, and the model was calibrated by plant data. The influence of reactor size, feed properties, catalysts and operation conditions on product yield was analyzed systematically, and the maximum or minimum product yields were taken as the target for variable optimization. The results show that the four key parameters influencing the product yield are feed characterization factor, conradson carbon residue (CCR) content, catalyst micro-activity and reaction temperature. LPG yield is positively correlated with feed characterization factor, catalyst micro-activity and reaction temperature and negatively correlated with CCR content. The relation between diesel yield and multiple variables is just the opposite. The relation of gasoline yield and total liquid yield with the variables is the same as that of LPG yield except that the gasoline yield and total liquid yield increase firstly and then decrease with the incrase of the reaction temperature. For gasoline yield, diesel yield and total liquid yield, feed characterization factor shows the highest optimization degrees of 18.91%, -41.23% and 4.85%, respectively. For LPG yield, reaction temperature shows the highest optimization degree of 23.19%. Catalyst micro-activity presents the lowest optimization degrees for gasoline, LPG and diesel yields, which are 1.59%, 1.77% and -3.25%, respectively. For total liquid yield, reaction temperature presents the lowest optimization degree of 0.26%. The obtained results could provide theoretical basis for the optimization of process design and the operation adjustment in refinery plant

Key words: FCC, HYSYS, mechanism model, process parameter, product yield, optimization