Absorption of sulfur dioxide into slurries containing fine limestone particles

Abstract

Chemical absorption mechanisms of sulfur dioxide into the slurry containing fine limestone particles was analyzed theoretically by applying the two-reactionplanes model in this work. As an experimental verification of the model, experimental enhancement factors for the liquid film mass transfer coefficients, which were obtained by the absorption using a stirred-tank absorber with a plane gasliquid interface at 20$^\circ$C were compared with the values predicted theoretically. As a result, it was shown that the absorption rates can be satisfactorily predicted by the proposed model. In addition, theoretical analysis of the desorption rate of carbon dioxide produced in the absorption of sulfur dioxide was suggested. Also, the effect of pH and the effect of $MgSO_4$ addition on the absorption were examined experimentally. The absorption rate of sulfur dioxide was slightly dependent on the pH value in the range of 7.0 to 8.2, and decreased rather steeply below the pH value of 7.0. The additon of $MgSO_4$ was desirable for the absorption which is strongly limited by the solid dissolution, that is, when the solid concentration in the limestone slurry is low and/or the sulfur dioxide concentration of inlet gas mixture is high.