Influence of by-product salts and Na 2 CO 3 contents on gas–liquid mass transfer process in wet desulfurization of water gas

Among the different methods of H 2 S removal, the wet desulfurization is widely used because of its unique advantages. Wet desulfurization usually employs alkaline Na 2 CO 3 –NaHCO 3 buffer solution as desulfurization agent, which can react with H 2 S in absorber tower to produce HS − . Then, HS − is oxidized into sulfur in the presence of a catalyst such as phthalocyanine dicaryon sulfonates or other desulfurization catalysts. But unfortunately, Na 2 S 2 O 3 , Na 2 SO 3 , NaSCN and other by-product salts are inevitably generated in the oxidation process. However, the desulfurization pH and the physical properties of the solution such as surface tension, density and viscosity are notably affected by the content in Na 2 CO 3 and by-product salts. Therefore, it is necessary to investigate the influence of by-product salts and Na 2 CO 3 on desulfurization efficiency. In this work, the effect of different by-product salts and Na 2 CO 3 content on the total volumetric mass transfer coefficient K G a of H 2 S absorption process is experimentally explored. The results revealed that the increase in the by-product salts content results in a decrease in K G a and pH values. On the contrary, with the increase in Na 2 CO 3 content, K G a and pH values increased. A mathematical model of the absorption process is proposed and analyzed; the mass transfer coefficient in gas phase k G and in liquid phase k L as well as secondary reaction constant k 2 is calculated. The results showed that K G a was changed mainly by k 2 which reflects the effect of pH. The surface tension, density and viscosity had relatively small effect on K G a . The present results provide the required theoretical guidance for practical industrial applications.