Fluidized catalytic cracking (FCC) riser reactors have been widely used by the refining industry to convert heavy oil to more valuable products such as gasoline. The conversion process involves multi-phase hydrodynamics, heat and mass transfer, and cracking reactions. A computational fluid dynamic (CFD) computer code has been developed and validated to simulate the cracking processes of commercial-scale FCC units and investigate the effects of operating and design conditions on product yields and selectivity. The code solves an Eulerian formulation of the liquid, solid, and gas flow in a riser reactor. Phenomenological models of particle-solid interaction, particle-droplet collision heat transfer, spray vaporization, cracking kinetics, and coke formation were developed and added to the CFD code. A hybrid approach was adopted to integrate the flow calculation with the detailed cracking kinetics calculation. A unique methodology was developed to extract rate constants of the selected cracking reactions from a limited number of experimental test data sets. The code was validated with test data of the pilot- and commercial-scaled FCC units. Parametric and optimization studies were performed to investigate the impacts of operating/design parameters on the product yields of an existing commercial FCC riser reactor. Conceptual advanced FCC units were also evaluated. The results showed that optimized product yields and selectively could be achieved by using a CFD tool to guide the design of geometry and adjustment of operating parameters. Examples of the studies and optimizing opportunities are shown in this paper.
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