H2S absorption via carbonate solution in membrane contactors: Effect of species concentrations

The reaction mechanism of hydrogen sulfide absorption into aqueous carbonate solution is considered to be complicated due to the various species involved in the reaction. These species can undergo reversible reactions depending on its concentrations and reaction rate constants, and hence affect the absorption rate of H2S. The previously developed comprehensive 2D mathematical model was modified to account for the reversible reactions of all species involved in the chemical absorption of H2S in aqueous carbonate solution using hollow fiber membrane contactors. The model predictions agreed well with experimental data provided from the literature for 2 M carbonate solution under non-wetting conditions. The model results showed that as the initial gas concentration increases, the removal rate of H2S decreases and remain unchanged for the case of chemical and physical absorption, respectively. As the concentration of the solvent increases, the absorption rate of H2S increases initially and then decreases at high concentrations of carbonate solutions due to the salting-out effect. As the initial concentration of bicarbonate increases, the absorption rate of H2S decreases due to enhancement of the reversible reaction. The absorption rate was enhanced by increasing the solvent velocity for both physical and chemical absorption.