Development of Models for Fluid Catalytic Cracking Fluidized Bed Reactor Using Four-Lump Kinetic Scheme

Abstract

Models' describing the steady state behavior of the fluidized bed reactor for catalytic cracking of gas oil has been presented. The four-lump kinetic scheme was used to describe the cracking reactions occurring in the reactor while the two-phase hypothesis comprising of the bubble and the emulsion phases of Kunii and Levenspiel was used to describe the fluidized bed models. The model equations consisted of sets of non linear first order differential equations and sets of quadratic equations. The differential equations were integrated numerically using the fourth order Runge-Kutta algorithm while the quadratic equations were solved using formulae method. Results predicted by the model were validated using data obtained from a operating plant, deviations of-21.99%, 9.85%, 5.27%, and 4.12% were obtained for the conversion of gas oil, yields of gasoline, gases and coke respectively. The results shows that plug flow-plug flow combination of the fluidized bed gave a higher conversion of gasoil than the plug flow-CSTR model. Sensitivity analyses showed that superficial velocity, bubble diameter, catalyst bed height, reactor temperature, catalyst-to-gasoil ratio and the diameter of reactor are important process variables that affect the yield of the products.