Abstract: FCCU flue gas desulfurization process is now in a boom period. There are sulfur transfer additive and wet flue gas desulfurization (WFGD) that can be selectively considered for a 1.80 Mt/a catalytic cracking unit with two risers for prolific propylene. The cost of additives, recycling product and alkali waste treatment, equipment investment, operating cost and occupied areas of schemes were compared comprehensively. The results show that under the present environmental requirements, the scheme adopting sulfur transfer additive is more economical than the WFGD when the SOx content in flue gas to be treated is less than 1000 mg/Nm3, while in the case of more than 1000 mg/Nm3 SOx, the combination of above two schemes or only the WFGD may well be adopted.

Key words: FCC, sulfur transfer additive, wet flue gas desulfurization, economics