Objective The aim is to develop a low-cost sodium hydrosulfide (NaHS) production process for treating acid gas containing hydrogen sulfide and carry out industrial applications, to achieve the up-to-standard emission of tail gas.

Method The acid gas feed and the mixed caustic solution were counter currently contacted and reacted in the column type first-stage reactor, and the crude NaHS solution, circulating caustic solution, and first-stage purified gas after the reaction were respectively entered into the stripping column, circulating cooler, and stirred tank type second-stage reactor. The second-stage caustic solution and second-stage purified gas from the second-stage reactor entered the semi-finished product tank and the static mixer type third-stage reactor, respectively. The gas-liquid two-phase reaction product from the third-stage reactor entered the semi-finished product tank. The semi-finished caustic solution separated from the semi-finished product tank was mixed with the circulating caustic solution and returned to the first-stage reactor as a mixed caustic solution. The third-stage purified gas was contacted with the desalted water in the water washing separator and produced ammonia water.

Result It had been verified by the industrial unit that the process could effectively remove ammonia and other impurities from NaHS products without pre-treatment of acid gas feed. It could flexibly produce different specifications of NaHS products according to market needs, and ensure that purified gas met the emission standards. It could also produce ammonia water.

Conclusion This process has the characteristics of high resource utilization, high selectivity of NaHS, flexible operation, and low equipment and operating costs, which can provide a reference for other acid gas treatment units.