Abstract: The reasons for the poor combustion of off-gas in generator of FCCU with capacity of 2.0 Mt/a in SINOPEC Yangzi Petrochemical Co. Ltd, were analyzed from factors of coke make, catalyst fluidized state in the regenerator, catalyst amount in circulation, external heat quantity, and combustion promoter used. These factors are proved to influence on the coke burning temperature in coke burning tank, the coke oxidation reaction time and the carbon distribution on the catalyst, resulting in incomplete combustion CO entering into the dilute phase and occurring a violent reaction. By adjusting the coke make of device, the air flow in the transportation pipeline for the regenerated catalyst, control the appropriate amount of catalyst in circulation and external heat, the burning of tail gas can be alleviated.

Key words: catalytic cracking, regenerator, carbon burning, afterburing