Objective A natural gas purification plant has completed the transformation of carbonyl sulfur(COS) hydrolysis in process gas, and the problem of excessive total sulfur content in commercial gas has been completely solved. However, the low carbon dioxide(CO₂) mole fraction in commercial gas seriously restricts the effective improvement of commercial gas yield. Exploring suitable stimulation measures can reduce cost and increase benefit of the plant.

Methods The two-stage absorber model of the plant was constructed by using HYSYS process simulation software. The effects of the absorber plates numbers, the solution circulation rate, and the desulfurizer composition on natural gas purification were investigated, and the effect on the CO₂ mole fraction in commercial gas was mainly explored.

Results (1) Under the premise of not adjusting the composition of the desulfurizer, a total of 5 plates in the two-stage absorber were reduced, meanwhile the flow rate of lean and semi-rich amines was decreased to the lower limit of operation, the hydrogen sulfide(H₂S) mass concentration in the commercial gas could not exceed the standard, and the CO₂ mole fraction increased to 0.87%. (2) Under the premise of adjusting the composition of the desulfurizer, a total of 5 plates in the two-stage absorbers were reduced, meanwhile the flow rate of lean and semi-rich amines was decreased to the lower limit of operation, the H₂S mass concentration in the commercial gas still could not exceed the standard, and the CO₂ mole fraction eventually increased to 2.47%.

Conclusions The study of absorber simulation and stimulation measures can guide the technological transformation of the plant, improve the commercial gas yield, and provide a reference for the technological transformation of large-scale natural gas purification plants with high sulfur content.