NUMERICAL-CALCULATION OF SIMULTANEOUS ABSORPTION OF H2S AND CO2 IN AQUEOUS HYDROXIDE SOLUTIONS

Simultaneous absorption of H2S and CO2 in aqueous hydroxide solutions is studied numerically, considering reversibility effects of all reactions involved. A finite-difference scheme based on film theory is developed, which exhibits excellent convergence characteristics. The effect of finite CO2 reaction rate is examined, and the role of the second dissociation of CO2 in enhancing the kinetic selectivity toward H2S absorption is demonstrated. Under certain conditions, forced desorption of CO2 is predicted. The effect of temperature on the selectivity of the system at hand is investigated. It is shown that, as the temperature increases, the effect of the accelerated CO2 reaction is gradually reversed by the increased CO2 back-pressure and by forced desorption effects. In fact, the results suggest that the selectivity at temperatures around 200-degrees-C may be significantly greater than that attained at room temperature.