Fluid catalytic cracking (FCC) is one of the most important conversion processes in petroleum refineries, and the FCC regenerator is a key part of an FCC unit utilized in the recovery of solid catalyst reactivity by burning off the deposited coke on the catalyst surface. A three-dimensional multiphase, multispecies reacting flow computational fluid dynamics (CFD) model was established to simulate the flow and reactions inside an FCC regenerator. The Euler–Euler approach, where the two phases (gas and solid) are considered to be continuous and fully interpenetrating, is employed. The model includes gas–solid momentum exchange, gas–solid heat exchange, gas–solid mass exchange, and chemical reactions. Chemical reactions incorporated into the model simulate the combustion of coke which is present on the catalyst surface. The simulation results were validated by plant data.