Abstract: The main difference between the tail gas of sulfur recovery units in refinery and coal chemical industry is the difference of CO₂ content. In this paper, the hydrogenation reduction and absorption process were used, and the solvent was methyl diethanolamine (MDEA) solution. Three types of typical sulfur recovery tail gas from refinery sulfur recovery unit, coal chemical oxygen-enriched sulfur recovery unit and coal chemical pure oxygen sulfur recovery unit were studied, and the effects of CO₂ on the absorption of tail gas and the regeneration of solvent were investigated. The results showed that the CO₂ affected the absorption of H₂S by MDEA solution. With the increase of content of CO₂, the required circulation amount of MDEA solution and the concentration of MDEA solution increased, steam consumption also increased during solvent regeneration. For the tail gas of sulfur recovery from coal chemical industry with high CO₂ content, high concentration and high efficient solvent should be used to reduce the amount of solution circulation and steam consumption, and to reduce the absolute amount of acid gas returning to sulfur making furnace, or choose a short-process sulfur recovery process.

Key words: sulphur recovery unit, tail gas, methyldiethanolamine, carbon dioxide, hydrogen sulfide