Electrochemical desulfurization of waste gases in a batch reactor

To meet the increasing need for reduction of exhaust emissions from stationary sources, many technologies have been developed to remove S[O.sub.2] from flue gas. In this study the anodic oxidation of sulfur dioxide in aqueous solutions of sulfuric acid with a unique reactor design and electrode configuration has been investigated. An electrochemical absorption column larger than laboratory scale was employed. A titanium rod cathode and platinum expanded mesh anode separated by a cation exchange membrane were used as electrodes in the cylindrical electrochemical reactor. The effects of current densities of 10, 1, and 0.1 [Am.sup.-2], initial S[O.sub.2] concentrations of 500, 2,500, and 5,000 ppm, gas flow rates of 0.75, 1.5, and 5 L [min.sup.-1], sulfuric acid concentrations of 1, 5, and 10% (w), gas composition, and electrolysis time on removal efficiency, current efficiency, energy consumption, and mass transfer coefficient were reported. Removal efficiency of 94% was obtained with a high current efficiency of 94%, energy consumption of 2.22 x [10.sup.-2] kW [hm.sup.-3], and mass transfer coefficient of 5.9 x [10.sup.-5] [ms.sup.-1] without additives or pretreatment. At the current densities of 0.1, 1, and 10 [Am.sup.-2], the removal efficiencies were 10, 94, and 98%, respectively. Removal efficiency was observed to decrease as inlet S[O.sub.2] concentration, gas flow rate, and electrolyte concentration increased. The presence of C[O.sub.2] in the gas mixture led to a decrease in the S[O.sub.2] removal efficiency. During electrochemical absorption of S[O.sub.2] into the [H.sub.2]S[O.sub.4] solution, the concentration of acid is increased from 5 to 10%. At the end of the studies, electrochemical desulfurization succeeded in meeting the regulation requirement, and the absorbing liquid remained in a reusable form. DOI: 10.1061/(ASCE)0733-9372(2007)133:1(13) CE Database subject headings: Absorption; Air pollution; Gas; Reactors.