Solubility of hydrogen sulfide in aqueous solutions of N-methyldiethanolamine at high pressures

• The solubility of H2S in aqueous MDEA at high pressures and in presence of methane as a makeup gas is experimentally measured with high accuracy.
• The data are measured at industrial conditions of H2S absorption process from natural gas.
• Data are measured at two different total pressures in order to quantify the effect of pressure on H2S solubility in aqueous MDEA.
• The Extended UNIQUAC model is used as a predictive tool for the measured data.
• The effect of total pressure on H2S solubility is modeled.

A static-analytic method was used to measure the H2S solubility in 50 wt% MDEA and in presence of methane as a makeup gas. The solubility was measured at 7000 kPa total pressure, and at 50 and 70 °C, for H2S partial pressures from 31 to 974 kPa. Measurements were also performed at 1500 kPa total pressure and 50 °C for H2S partial pressure span of 53–386 kPa. The measured data were compared to predictions using the Extended UNIQUAC model. The experimental data showed that the total pressure has a significant effect on H2S solubility in aqueous MDEA. The observed effect is shown to be dominated by the non-ideality of the gas, and it could be predicted by the pressure effect on the fugacity coefficient of H2S in the gas phase. The experimental data from this work are compared and shown to be consistent with earlier published data.