In the refining and natural gas purification industries, mainstream Claus sulfur recovery units generally adopt activated alumina and titanium-based special catalysts. Catalyst activity degradation stands as a core factor restricting sulfur recovery efficiency and long-cycle stable operation of facilities. Based on actual operating conditions, catalyst deactivation falls into four major categories: elemental sulfur pore deposition, carbon deposition from feed impurities, oxygen-induced sulfate poisoning, and thermal sintering. Comprehensive prevention shall be implemented from feedstock control, process condition adjustment, operation & maintenance and graded protection to slow down activity degradation and cut down catalyst replacement frequency.
Strictly control feed gas quality to block irreversible deactivation at the source. Optimize the acid gas pretreatment unit by installing coalescing filters and hydrocarbon removal equipment to intercept heavy aromatics, colloids, amine liquid droplets and inorganic salts entrained in raw materials. This prevents macromolecular hydrocarbons from cracking and coking on high-temperature catalyst beds, which would block microporous active sites. Ammonia content in acid gas shall be tightly controlled to achieve complete ammonia decomposition in the incinerator, avoiding ammonium salt crystallization on catalyst surfaces that impairs interfacial reaction efficiency.
Precisely regulate process parameters to mitigate chemical poisoning. Accurately adjust process gas composition and maintain the molar ratio of H₂S to SO₂ at 2:1 through closed-loop control. Online trace oxygen analyzers are deployed to limit excess oxygen volume fraction in reactor beds below 0.3%, which stops the irreversible reaction between SO₃ and alumina support forming sulfates that permanently cover active centers. Hierarchical temperature control is adopted for reactors: the primary high-temperature reactor operates at 220–240 °C, while the temperature of the final low-temperature reactor is kept over 30 °C above sulfur dew point. This balances Claus reaction performance and avoids pore blockage by condensed liquid sulfur at low temperatures as well as crystal phase sintering of supports under excessive heat.
Standardize startup, shutdown and regeneration maintenance to reduce operation-caused degradation. Follow a gradient heating schedule during unit startup to prevent sharp temperature rises that crack catalyst supports and reduce specific surface area. Low-oxygen inert nitrogen purge is applied for sulfur stripping during shutdown; high-temperature sulfur burning under oxygen-rich conditions is prohibited. Regular low-temperature thermal regeneration at 280–300 °C decomposes surface sulfur deposits via reduction to restore pore permeability for reversible sulfur deposition deactivation. A protective catalyst cushion layer is laid at the bottom of catalyst beds to adsorb heavy metals and dust poisons and share the load of main catalysts.
Carry out regular monitoring and establish an early warning system for catalyst degradation. Periodically test catalyst specific surface area, bed pressure drop and sulfur species in tail gas. Evaluate the degradation degree combined with conversion rate data to dynamically optimize air distribution and temperature control parameters. Integrated prevention measures can extend catalyst service life by more than 30% and sustain stable compliance of sulfur recovery efficiency.