Preparation, Evaluation And Characterization Of Sulfur-Transfer Additives For SO_X Removal From FCC Flue Gas

In fluid catalytic cracking(FCC) process, the burn-off of coke deposited on catalysts in FCC regenerator produces SOX(90%SO2 and 10%SO3). SO2 is one of the most hazardous atmospheric pollutants. SO2 and SO3 are acid rain precursors. And SO2 erodes FCC unit. Due to heavier feedstock and more and more stringent environmental regulations, it becomes urgent to cut down the emissions of SO2. In order to meet the requirement of environmental protection policies, sulfur-transfer additives are used in FCC process. If sulfur-transfer additives can highly effectively remove SO2, still can have good CO combustion activity, it will not only arouse people's initiative but also save the cost. New sulfur-transfer additives were designed in my thesis, and the additives were modified to remove SO2 and CO.First, sulfur-transfer additives were prepared by systematic studies on active components, MgAl2O4 and preparation conditions in the self-made desulfurization unit in the laboratory. The experimental results demonstrated that the role of ceria was mainly reflected in SO2 oxidation. The role of iron was mainly reflected in SO2 reduction. The content of MgO in additives had an optimum value. The sulfur-transfer additives were ceria and iron-containing magnesia-excess spinels. The additives could completely remove SO2 from mixed reaction gas in the self-made desulfurization unit. The additives had very good SO2 oxidation–reduction performance and high hydrothermal stability.Then, sulfur-transfer additives were evaluated in riser pilot unit and FCC unit of Dagang Petrochemical Company. The riser test proved when appending 2% sulfur-transfer additives, SO2 in the flue gas was reduced by 88%. Moreover, it had no unfavorable effect on distributions of riser products. Industrial trial in Dagang'FCC unit showed when appending 2% sulfur transfer additives, sulfur-transfer additives'desulfuring activity was 90%. And it had no significant effect on distributions of FCC products and qualities of FCC gasoline. Finally, Cu as a combustion promoter was added into the sulfur-transfer additives, and the modified additives were tested in self-made fixed bed system. The experimental results showed that the weight content of CuO in the modified additives was 1%. The influence of CuO (1%) to sulfur-transfer additives was very small in additives'composition and structure. But additives'CO complete combustion temperature was reduced obviously, and additives'CO combustion activity was noticeably improved. Additives'combustion activity was 100% at 200℃and additives'SO2 saturation capacity increased. In a word, modified additives could simultaneously remove SO2 and CO.