SO2 ABSORPTION IN A BUBBLING REACTOR USING LIMESTONE SUSPENSIONS

In the present work attention was focused on a wet flue gas desulfuriz ation process using limestone suspensions, which is the most common me thod used to reduce SO2 emissions from power plant exhaust gases. The SO2 absorption rate was measured varying both the SO2 concentration in the gas phase and the limestone concentration in the suspension. The experiments were performed by bubbling mixtures of sulfur dioxide and nitrogen in the continuous limestone aqueous suspension. The absorptio n phenomenon was studied by making use of the film theory to describe the liquid-side mass transfer. It was assumed that the liquid-phase di ffusional resistance is concentrated in a layer the thickness of which depends on fluid dynamics, but which is independent of the nature of the reactions taking place. The equations considered by the model desc ribe conditions of thermodynamic equilibrium as well as material and e lectrical balances. Furthermore, they take into account the effect of the gradient of the electric potential of diffusion on the diffusive t ransport of ions and molecules in the film surrounding the gas-liquid interface. The SO2 absorption rate and the limestone dissolution rate experimentally determined were used to integrate the model equations, yielding the value of the film thickness, and allowing the determinati on of the concentration profiles of the different species in the liqui d film and of the enhancement factor for chemical absorption. Consiste ncy between model and experimental results, on the basis of the hypoth esis of the model, was found.