SO2 absorption and desorption by an accelerating water droplet undergoing vaporization

Heat and mass transfer between a water droplet and polluted air has been studied during the beginning of its free fall. Experimental results are compared with predicted ones from a model based on the Whitman film theory. The purpose of this article is to extend our previous model to predict the SO2 absorption and desorption by drops (1–5 mm) falling in air containing low gas concentration and including the natural droplet vaporization and cooling. The measured droplet temperature and sulfur concentration after small contact time (0.35–2.43 s) concords with model predictions. It is observed that the initial vaporization and its corresponding cooling effect increase the initial SO2 absorption rate and decrease the initial SO2 desorption rate.