MODELING, SIMULATION AND OPTIMIZATION OF TWO STAGE FCCU RISER

Abstract

Fluid Catalytic Cracking (FCC) is an industrial process that converts heavy hydrocarbons (namely gas oil), coming from primary refining, to lower molecular weight products. The role of FCC unit in a modem refinery is to maximize gasoline production. As a result, a tremendous number of technological developments have been made since the installment of the first unit in 1942. A FCC unit is composed of a riser reactor where all the endothermic cracking reactions occur and a regenerator where air is used to burn off the coke on catalyst. But, the major disadvantage of the risers used at present in FCC units is that they are too long and it has been proved in literature that catalyst loses most of it's activity by the time it reaches half the riser height, so in the next half it almost act's like a conveyor. Recently, the concept of Two-stage riser has been proposed by researchers according to which a single long riser is divided into two risers in-order to increase the yie3d of gasoline. In the present work, a case study of single stage riser was taken from literature and it's model equations were modified to develop the model equations for two stage riser. Optimization was performed using NSGA-II technique and optimal operating conditions for the operation of two-stage riser were estimated. Furthermore, simulation results for single stage and two-stage riser were compared.