Individual and simultaneous desorption of H2S and CO2 from synthetic greenliquor

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 resi stances are dependent on the stirrer velocity. In this equipment for physic al absorption and desorption of H2S or CO2 the resistance in the liquid sid e 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 tr ansfer rate and is not enhanced by any reaction in the film. For the desorp tion of H2S from a Na2S solution, an equilibrium model based on the film th eory 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 des orption of CO2 from NaHCO3 solution. Both models show values which are in g ood 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 L iquor is enhanced by the chemical reaction from hydrogencarbonate to carbon ate. The desorption of CO2 from synthetic green liquor is well described by the model evaluated for the individual desorption of CO2 from NaHCO3 solut ion. (C) 1999 Elsevier Science S.A. All rights reserved.