A mathematical model for catalyst regenerator of fluidized bed catalytic cracking process, including thermal effects, has been developed to simulate a regenerator having characteristics similar to that of the unit operated by Petrobras (Brazilian Oil Company). The proposed model was built up by splitting the regenerator into two regions : the first one was the jet region near the air distributor grid, the second one was the dense phase region (divided into bubbles and gas-solid emulsion phases). The jet region uas described taking into account experimental observations related to the dead zones between adjacent jets, jet expansion angle, gas and solids entrance effects as well as coalescence of neighboring jets. It was assumed heterogeneous carbon, hydrogen and carbon monoxide combustion on the catalyst, as well as the homogeneous carbon monoxide oxidation in the gas phase. The model equations are solved numerically, allowing the physical properties of the system and compounds concentration in emulsion and diluted phases to vary with belt height so that more realistic predictions are obtained.