Selective H2S removal by nonaqueous methyldiethanolamine solutions in an experimental apparatus

An experimental apparatus consisting of adiabatic packed absorption and regeneration columns was established to simulate the H2S removal process. With this apparatus, nine nonaqueous methyldiethanolamine (MDEA) solutions were evaluated under fixed operating conditions such as circulating solution flow rate and heating power of regeneration. The results indicated that the selectivity of H2S removal increased by 3.31 and 2.74 times with N-methylpyrrolidone and ethylene glycol as the nonaqueous solvents, respectively, but that the efficiency of desulfurization was somewhat lower compared with aqueous MDEA solutions. However, it is necessary to keep a limited amount of water in nonaqueous solutions that can cause stripping steam in the reboiler to prevent the solutions from overheating. For ethylene glycol and diethylene glycol as examples, the effect of the water content on the selectivity, efficiency of desulfurization, and stripping temperature were studied, and the results indicated that the efficiency of desulfurization would decrease significantly as a result of insufficient regeneration if the water content were lower than 0.5 mol/mol of amine.