Enhancement of gas–liquid mass transfer by small reactive particles at realistically high mass transfer coefficients: absorption of sulfur dioxide into aqueous slurries of Ca(OH) 2 and Mg(OH) 2 particles

Abstract

Chemical absorption of pure SO 2 into aqueous slurries of fine and reactive Ca(OH) 2 and Mg(OH) 2 was studied in a stirred vessel at 298 K at realistically high mass transfer coefficients. The absorption process was theoretically analyzed using two different models. For the SO 2–Ca(OH) 2 system, a single reaction plane model was used to estimate the theoretical enhancement factor and for the SO 2–Mg(OH) 2 system, a two-reaction plane model incorporating the solids dissolution promoted by the reactions with the absorbed SO 2 in the liquid film was employed. For the later system, the theoretical results could be more accurately predicted by a correct approach to estimate the enhancement caused due to suspended solids and the overall enhancement factor. The extra enhancement observed for the SO 2–Mg(OH) 2 system could be explained from the reaction between SO 2 and the dissolved [SO 3] 2−.