Simulation of hydrogen sulphide absorption in alkaline solution using a packed column

AbstractIn this work, a simulation tool was developed for hydrogen sulphide (H2S) removal in an alkaline solution in packed columns working at countercurrent. Modelling takes into account the mass-transfer enhancement due to the reversible reactions between H2S and the alkaline species (, and HO−) in the liquid film. Many parameters can be controlled by the user such as the gas and liquid inlet H2S concentrations, the gas and liquid flow rates, the scrubbing liquid pH, the desired H2S removal efficiency, the temperature, the alkalinity, etc. Since the influence of the hydrodynamic and mass-transfer performances in a packed column is well known, the numerical resolutions performed were dedicated to the study of the influence of the chemical conditions (through the pH and the alkalinity), the temperature and the liquid-to-gas mass flow rate ratio (L/G). A packed column of 3 m equipped with a given random packing material working at countercurrent and steady state has been modelled. The results show that the H2S removal efficiency increases with the L/G, the pH, the alkalinity and more surprisingly with the temperature. Alkalinity has a very significant effect on the removal efficiency through the mass-transfer enhancement and buffering effect, which limits pH decreasing due to H2S absorption. This numerical resolution provides a tool for designers and researchers involved in H2S treatment to understand deeper the process and optimize their processes.Keywords: hydrogen sulphidemass-transferabsorptionalkaline solutionpacked column