Numerical modelling of sulfur dioxide absorption for spray scrubbing

An increased concern for the environment and the stricter regulations necessitate the development of new technologies that curtail the harmful emissions from industry, energy and power sectors. Wet flue gas desulfurisation in scrubbers is a common approach for reducing the emissions of sulfur oxides, which have a detrimental effect on human health and nature. Although the idea of using seawater as a scrubbing liquid is not a novel one, recent studies on the advantages of seawater absorption and requests from the maritime sector prompted new investigations of its usage and the development of advanced modelling tools. Absorption of sulfur dioxide in the spray is a complex process consisting of two main phenomena. The first one is the interphase mass transfer of pollutants due to concentration differences, with mass transfer coefficient being the crucial factor determining the absorption dynamics. Another essential part is the chemical reactions of the absorbed pollutants in the aqueous phase, which enhance the absorption capabilities. In this work, a novel model for the absorption of sulfur dioxide in spray scrubbers is presented. It is based on a single droplet, concentrated-parameter approach that takes into account mass transfer coefficients and the in-droplet chemistry of the absorbed pollutants for pure water and seawater. The model was implemented in the computational fluid dynamics framework and validated against the available experimental data, with the relative error for removal efficiency within the +/- 10% for most of the operating points-a satisfactory result considering the uncertainties in the experimental setup. Therefore, with the results showing that the model is capable of correctly predicting the sulfur dioxide removal from flue gases, it presents a useful tool for designing more sustainable flue gas removal equipment.