Individual and simultaneous desorption of H2S and CO2 from synthetic green liquor

Selective desorption of H2S from green liquor has been investigated using a batch stirred tank reactor. It was found that the gas and liquid side resistances are dependent on the stirrer velocity. In this equipment for physical absorption and desorption of H2S or CO2 the resistance in the liquid side is dominant. Within the pH interval researched, the individual desorption rate of CO2 as well as H2S is mainly determined by the liquid side mass transfer rate and is not enhanced by any reaction in the film. For the desorption of H2S from a Na2S solution, an equilibrium model based on the film theory was evaluated. Another model also based on the film theory with finite reaction rate in the film as well as in the bulk was evaluated for the desorption of CO2 from NaHCO3 solution. Both models show values which are in good agreement with the experimental results. For the desorption of H2S from synthetic green liquor a model was taken from the literature [M. Wallin, S. Olausson, Chem. Eng. Commun. 123 (1993) 43-59] and modified. The modified model takes into account that the desorption of H2S from synthetic green Liquor is enhanced by the chemical reaction from hydrogencarbonate to carbonate. The desorption of CO2 from synthetic green liquor is well described by the model evaluated for the individual desorption of CO2 from NaHCO3 solution. (C) 1999 Elsevier Science S.A. All rights reserved.