Removal of percentile level of H₂S from pressurized H₂S-CH₄ gas mixture using hollow fiber membrane contactors and absorption solvents

In the present paper, the removal of percentile level of H₂S from pressurized binary gas mixture (2% H₂S in CH₄) up to 50bar using hollow fiber membrane (HFM) contactors and absorption solvents is described. Unlike the related recent work on the removal of CO₂ from pressured gas streams [S.A.M. Marzouk, M.H. Al-Marzouqi, M.H. El-Naas, N. Abdullatif, Z.M. Ismail, Removal of carbon dioxide from pressurized CO₂-CH₄ gas mixture using hollow fiber membrane contactors, J. Membr. Sci. 351 (2010) 21-27], experiments with hazardous and highly toxic gas such as H₂S especially at high concentration (i.e., 20,000ppm) and pressures necessitated essential modifications of the previously described experimental setup to ensure safe operations. In addition, an improved module design was proposed to simplify the recycling of the stainless steel module body while retaining the essential advantage of operating at high pressures. The modules were equipped with expanded polytetrafluoroethylene (ePTFE) hollow fibers. H₂S absorption rates were investigated using distilled water (as a physical solvent) and aqueous sodium hydroxide and amine solutions of different concentrations as chemical solvents. The experimental results indicated that H₂S flux was enhanced by increasing the inlet gas pressure for both physical and chemical absorption solvents. Similar to the trend reported previously for CO₂, the increase of H₂S flux in case of physical absorption was more pronounced than that obtained with chemical absorption. The ratio between H₂S and CO₂ fluxes into water agreed very well with the solubility ratio of these two gases, respectively, which is expected for physical solvents such as water. Up to the authors' best knowledge, the present work is the first report on the experimental high pressure removal of percentile levels of H₂S from gas stream using HFM contactors and absorption solvents.