Removal of sulfur dioxide from industrial waste gases

Because of the wide occurrence of sulfur in fuels and mineral ores, sulfur dioxide (SO2) is one of the most prevalent gaseous air pollutants in stack gases from stationary sources. Removal of SO2 is essential in order to protect the environment.

An innovative SO2 removal technology has been experimentally demonstrated to reduce SO2 emissions within regulatory requirements. the SO2 removed from the stack gases can be recovered in the form of marketable liquid SO2. The objective of this research work was to investigate the feasibility of using aqueous buffered phosphate-based solutions for effective SO2 removal from industrial waste gases. Removal efficiency of greater than 99% SO2 and outlet SO2 gas concentration of below 100 parts per million by volume (ppmv) were observed using such solutions. The potential of SO2 desorption was also investigated. Desorption efficiency of 95% SO2 was achieved using such solutions. A 25% enhancement of SO2 loading was further achieved by the addition of trace quantities of adipic acid (H2Ad) as a buffer additive while maintaining SO2 desorption efficiency of greater than 80%. No loss in efficiency was observed in the presence of 30% carbon dioxide, a common stack gas constituent. A 4% net enhancement of overall SO2-removal efficiency considering both absorption and desorption was oberved using phosphate solutions with 0.01 M H2Ad as a buffer additive. These performance measures of SO2 absorption was adequately predicted using mathmetical correlation over a wide range of inlet SO2 concentrations and solution temperatures.

Thus, an innovative alternative SO2 removal process using aqueous buffered phosphate-based solutions has been developed with high SO2 absorption and desorption efficiencies. As a result, the proposed phosphate process is more economically attractive than a government-sponsored and publicly demonstrated process treating tail gas from industrial sources. The proposed phosphate process is also economically comparable with the most widely used commercial process treating flue gas from utility sources. A formal patent application has been filed for the invention of this SO2 removal technology.