Influencing factors and control measures of SO₂ emission from sulfur recovery unit of Zhongxian Branch

Through the analysis on the desulfurization and sulfur recovery unit, it was concluded that the main process influence factors of SO₂ emission in flue gas were the fluctuation of feed gas composition and volume flow, the acid gas composition, the performance of desulfurization solution and catalyst. In order to reduce the SO₂ emission of the sulfur recovery unit and meet the national environmental protection requirements, the following technical measures were taken: (1) Improve the selectivity of MDEA solution by controlling the mass fraction of desulfurization solution and the solution temperature entering the absorption tower, and appropriately reduce the solution circulation. (2) Replace the deactivated catalyst in time. (3) Add SO₂ selective hydrogenation catalyst to the third-stage reactor of the conventional Claus section to reduce the SO₂ content entering the super Claus section. (4) Optimize the sulfur removal scheme, and shorten the sulfur removal time during plant production and shutdown. The results showed that after adopting the above measures, the sulfur recovery rate of the natural gas purification unit was stable high and the SO₂ mass concentration in the flue gas met the standard requirements.