Model of oxygen absorption into calcium sulfite solutions

Wet limestone scrubbing is the most common flue gas desulfurization process, and in this process sulfite oxidation plays a major roledetermining the dewatering properties of the sludge produced and leading to the production of gypsum of high quality. A literature analysisshowed that the results obtained for sulfite oxidation under homogeneous conditions are relatively easily interpreted, while the results relativeto heterogeneous reaction conditions (i.e. conditions in which gaseous oxygen and a sulfurous solution are brought in contact) are muchmore difficult to interpret, owing to the interaction between mass transfer and chemical reaction. In this work a model is proposed to describethe interaction between oxygen absorption and the oxidation reaction under heterogeneous conditions, which takes into account the peculiarcharacteristics of absorption with zero order reaction. A kinetic equation of order zero in dissolved 02, 3/2 in HSO; and 3/2 in the catalystconcentration was used to match experimental results presented in the literature and model results. Integration of the model equations led toevaluation of the oxygen absorption rate as a function of the catalyst concentration together with the concentration profiles in the liquid filmfor the different species.