Sulfur-recovery units in oil refining and coal-chemical industries commonly adopt the Claus process to recover elemental sulfur. Restricted by chemical equilibrium, the tail gas from the Claus unit still contains considerable sulfur-dioxide, carbonyl sulfide, carbon disulfide and other organic sulfur compounds. These components cannot be directly discharged to meet emission standards. Therefore, a tail-gas hydrogenation treatment unit must be equipped to convert various non-hydrogen-sulfide sulfur compounds into hydrogen sulfide, which is then recycled through amine absorption to satisfy environmental-protection emission requirements.
Within the whole tail-gas treatment process, hydrogenation-conversion catalyst serves as the core determining the overall operating efficiency of the unit. During actual operation, the unit is confronted with practical challenges such as fluctuating working conditions, varying temperature ranges and complex feed compositions, which set multiple requirements for the comprehensive performance of catalysts. On one hand, catalysts shall deliver favorable low-temperature activity to complete hydrogenation reduction and organic-sulfur hydrolysis reactions under relatively mild operating temperatures, so as to cut heating energy consumption of the unit. On the other hand, they need sufficient specific surface area and pore volume to ensure uniform distribution of active components for handling feedstock with complex compositions. Meanwhile, excellent mechanical strength is required to resist gas-flow erosion, lower attrition loss, extend catalyst service life and reduce shutdown-replacement frequency.
Numerous industrial project practices indicate that improper catalyst selection may lead to incomplete organic-sulfur conversion, rapid activity decline and sharp rise in bed pressure drop. These issues will directly result in excessive tail-gas emissions and increase operation-and-maintenance burdens for enterprises. Shandong Xunda Chemical Industrial Group Co., Ltd. has long been engaged in the R&D of sulfur-recovery catalysts. It has developed dedicated catalysts for sulfur tail-gas hydrogenation service with continuous optimization on carrier structure and active-component ratio, which are applicable to sulfur-recovery tail-gas treatment units under diverse overseas working conditions.
From the perspective of global industry trends, environmental-protection regulations worldwide are getting increasingly stringent. When operating sulfur-recovery units, enterprises no longer merely pursue overall sulfur-recovery efficiency. More attention is paid to catalysts' long-term operational stability, tolerance against working-condition fluctuations and total-life-cycle comprehensive cost. Reliable performance of the hydrogenation-conversion section not only ensures the unit complies with emission standards, but also acts as an important approach for enterprises to realize sulfur-resource recycling and improve overall economic benefits.