Sulfur dioxide absorption by charged droplets in electrohydrodynamic atomization

Abstract

This work presents and discusses the absorption of sulfur dioxide by charged calcium hydroxide aqueous solution droplets generated in electrohydrodynamic atomization (EHDA). The removal of sulfur dioxide is experimentally tested in a laboratory scale device, and the main factors affecting the absorption of sulfur dioxide, droplets diameter and specific charge, are obtained. The results indicated that the liquid-gas contacting interface area significantly increaes because droplets diameter decreases with an increase in electric potential. The specific charge increases as electric potential increasing, may lead to the uniform distribution of charged droplets in the spraying tower. The analysis of these findings indicated that the absorption rate and enhancement factor are improved in EHDA. The absorption efficiency can be significantly increased mainly because of the increase of contacting area between gas and liquid due to the disintegration of liquid in EHDA, and the uniform distribution of electrified droplets in the tower due to repulsive forces. Meanwhile, the activity of calcium ions can be improved due to electric field and charges on the droplets surface. There are also some interactions between the gas molecules near the droplet and the liquid molecules in electric field, which is difficult to characterize. In addition, the internal circulation induced by electric and flow fields inside the droplets may also enhance soluble gaseous pollutants transport.