Abstract: To diagnose the cause of amine solution blackening leading absorption column blockage in a petrochemical sulfur recovery unit, a systematic analysis was conducted using methods such as filter disassembly, scale element detection, and amine composition analysis. The results indicated that the black substances were primarily composed of iron sulfide (FeS). The study found that when lean and rich amine streams cross-contaminate, iron sulfide initially forms a protective film on the surfaces of pipelines and equipment. However, changes in tail gas composition or operating conditions can cause the film to detach, allowing FeS particles to circulate with the amine solution into the absorber, leading to a rise in differential pressure. Based on process characteristics and safety risk assessments, measures such as stream isolation, passivation cleaning, and amine replacement were proposed and implemented. Following these actions, the absorber differential pressure significantly decreased, and the acid gas processing capacity returned to normal levels. This study provides a practical engineering approach and technical reference for preventing amine blackening and tray blockage in similar sulfur recovery units.

Key words: sulfur recovery, amine solution blackening, blockage, iron sulfide, passivation cleaning