Ultrasonic enhanced limestone dissolution: experimental and mathematical modeling

Stricter emission regulations require the improvement of SO2 scrubbing efficiency and energy usage. In this work, the dissolution of two very pure limestone samples under the effect of ultrasound (US) was compared to their dissolution in silent conditions. The aim of this work was to assess experimentally whether this method could be adopted as a process intensification technique for Wet Flue Gas Desulfurization (WFGD) applications. A pH-stat method with vigorous agitation, coupled with in situ particle size distribution measurements was developed for evaluating the effect of US in limestone dissolution. The samples were characterized in detail, the experiments were modeled mathematically and, a chemical reaction constant was determined and used to compare quantitatively the use of US and the silent case. The results indicate that US does enhance limestone dissolution, and that the degree of enhancement depends largely on the type of sample, i.e. the geological origin and the particle size. The developed mathematical model was implemented satisfactorily; the model was able to fit the data with high degrees of accuracy (> 94%). The degree of enhancement, quantified in terms of the increase in the estimated chemical reaction constant, ranged from 18% to 150%.