Mass transfer between a fixed bed of limestone particles and acid solutions

Limestone dissolution in acid solutions was experimentally studied by means of a fixed-bedreactor. A diffusive model was proposed to describe experimental results. The model, based onthe film theory, takes into account the effect of the electric potential of diffusion on the dissolutionrate. In order to validate the model, experiments were carried out to study the effect of bothparticle size and liquid-solid relative velocity on the dissolution rate. Furthermore, the limestonedissolution rate in aqueous solutions of SO2(aq), HCl, and H2SO4 was measured at different acidconcentrations. The results showed that the diffusive model, associated with the correlationproposed by Chu et al. [Chu, J. C.; Kalil, J.; Wetteroth, W. A. Chem. Eng. Prog. 1953, 49 (3),141] for the evaluation of the liquid-solid mass-transfer coefficient, is capable of describing thedependence of the dissolution rate on both the size of the limestone particles and the liquidsolidrelative velocity. In addition, it was found that, in agreement with the physical meaningof the film theory, the thickness of the liquid film is not dependent on the kind of acid presentin the solution nor on its concentration but only on the fluid dynamic conditions of the liquidsolidsystem.