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In recent years, as the amount of imported sour crude oil processed by domestic refineries has increased, the sulfur content of catalytic cracking (FCC) raw materials has also continued to increase. This has led to a significant increase in the concentration of SO2 and SO3 in the regeneration flue gas of the FCC unit. This has not only aggravated environmental pollution, but also caused serious equipment corrosion. According to reports, a large number of cracks have occurred in the regenerators or three-rotation shells of more than a dozen FCC devices across the country due to dew point stress corrosion. ； There are also installations that have experienced dew point stress corrosion in waste heat boiler systems and flue gas pipeline expansion joints, which has seriously threatened the safety, stability, long-term, full and optimal operation of the installation. At the same time, due to the increase in SOx content in the flue gas, the dew point temperature of the regeneration flue gas increases. In order to avoid dew point corrosion, the exhaust gas temperature has to be increased, which wastes a lot of heat sources and increases the energy consumption of the device. The use of sulfur transfer additives is a low-cost solution. This method only requires a small increase in additive costs and does not require the addition of new facilities to effectively reduce the concentration of SOx. It is especially suitable for devices with flue gas SOx content not exceeding 2500 μg/l. The SOx transfer agent is physically mixed with the cracking catalyst and circulated between the reactor and the regenerator of the FCC unit. In the regenerator, the SOx transfer agent reacts with SO3 and forms stable metal sulfates on the surface of the transfer agent. The transfer agent after forming sulfate is circulated to the reactor together with the regenerated cracking catalyst. The sulfur adsorbed in the form of sulfate on the transfer agent is directly released in the form of H2S or converted into metal sulfide under the reducing conditions of the reactor, and is converted and released in the stripper. This part of H2S, together with the H2S generated by the cracking reaction, is used as the raw material for the sulfur recovery device. The sulfur transfer agent after desorbing sulfur is recycled to the regenerator for re-adsorption of SOx. This principle has been successfully applied in industry. The main product in the world that produces sulfur transfer agents is the DeSOx industrial SOx transfer agent developed by Katalistiks. After use, it can meet the requirements of SOx emission regulations for FCC devices formulated in California, without adversely affecting the product yield and particle emissions of the device. Generally, when the amount of SOx transfer agent added reaches 15% of the total catalyst in the device, the catalyst activity will be reduced by 3.5 units. However, using the above DeSOx agent can reduce the activity of the catalyst by 3.5 units. * * This dilution effect is reduced, which is mainly due to the unique activity of the Mg-Al spinel contained in the DeSOx agent. In addition, under the same SOx reduction efficiency, the dosage of DeSOx agent is less than that of general alumina-based SOx transfer agents. Industrial tests show that when the FCC unit feed is 3180 t/d and the regenerator operation mode is complete combustion of CO, adding alumina-based SOx transfer agent A (454kg/d) within the first 90 days reduces SOx emissions from 400PPm to 200PPm. After 90 days, DeSOx agent was added, and SOx emissions remained at 200PPm. At this time, the amount of DeSOx agent is 1.5% of the catalyst bed amount in the device. ； The SOx transfer agent A accounts for 10% of the catalyst bed. This shows that the efficiency of DeSOx agent in reducing SOx emissions is 6 to 7 times higher than that of alumina-based sulfur transfer agent. my country Petrochemical Research Institute has established experimental and pilot-scale evaluation methods in the research of developing SOx transfer agents. The evaluation results of the developed RSOx-7 transfer agent on Arco's small riser FCC device show that as the amount of RSOx transfer agent added increases, the SOx concentration in the flue gas decreases. When the addition amount is increased to 5% of the device bed capacity, the SOx in the flue gas is 245PPm, and the SOx is reduced by 83%. While the gasoline and coke yields remain at the same level, the diesel yield does not change much, and the conversion rate has no significant difference. It is expected that after industrial use testing, it can be put into large-scale use. The Refining Research Institute of Luoyang Petrochemical Engineering Company has successfully developed a liquid sulfur transfer aid, and has completed industrial application tests at Maoming Petrochemical Company and Zhenhai Refining and Chemical Company. The tests show that the SOx concentration in the flue gas has dropped by more than 80%, reaching emission standards. This post was last edited by ali2004 on 2007-12-23 10:22 ]