高含硫天然气净化厂Cansolv尾气处理工艺优化OA

Objective This study aims to solve issues in the Cansolv tail gas treatment unit of the high-sulfur natural gas purification plant:high levels of heat-stable salts and thiosulfate in the DS lean solution,an increased pH of the DS lean solution,and a large volume of high-COD wastewater.Method Problems such as the deterioration of DS solution quality,high startup frequency of the amine purification unit(APU),and excessive solvent consumption were solved by adjusting the combustion temperature in the reaction section of the tail gas combustion furnace and optimizing the process flow and key operating parameters.As a result,the average mass concentration of SO2 in the flue gas remained below 50 mg/m3 over the long term,being far below the limit of the GB 39728—2020 Emission standard of air pollutants for onshore oil and gas exploitation and production industry(800 mg/m3 for a sulfur recovery unit with capacity＜200 t/d).Result After optimizing the key operating parameters,the process performance of the unit was as follows:First,the combustion section temperature of the tail gas combustion furnace was adjusted from 800℃to 710-740℃,and the volume fraction of oxygen in the process gas after combustion was controlled within 1.5%-2.5%.The molar ratio of heat-stable salts to organic amine in the DS solvent decreased from 1.5:1-1.7:1 to 1.1:1-1.6:1,and the APU startup frequency dropped from the design value of 6 times per day to 1-2 times per day.Second,the outlet temperature of the Venturi combination tower was reduced from 50℃to 30-35℃,maintaining the system water balance.The consumption of DS solution was reduced by about 0.4 t/a,and the volume of high-COD wastewater requiring treatment was reduced by about 180 m3/a.Conclusion Parameter adjustment and process flow optimization can compensate for the design defects of the unit,restore the pH of the DS lean solution to the normal operating range,and reduce the risk of disproportionation reactions,thereby improving the performance of the DS solvent.