Oxidation chemistry of chloric acid in NOx/SOx and air toxic metal removal from gas streams

Chloric acid, HClO3, is a new oxidizer which has recently been shown to be an effective agent in the simultaneous removal of NOx and/or SOx from combustion flue gases and various chemical processes, including nitrations and metal pickling. Aqueous chloric acid readily reacts with NO and SO2 even in dilute solutions at ambient temperatures. Chlorine dioxide, ClO2, is formed as a chemical intermediate in the solution phase oxidation reactions. The oxidation by-products of NO generated from include NO2 and nitric acid. The ClO2 generated from the solution phase reactions also participates in gas phase oxidation reactions with NO and NO2. The combined solution phase and fast gas phase reaction chemistries provide the means for creating a new type of high performance NOx/SOx removal process. Wet scrubber based pilot plant tests have demonstrated up to 99% removal of NO. Additional recent research work has shown that chloric acid is an effective reagent for the removal of air toxic metals, such as elemental mercury, which are present in the waste gas output streams from incinerators, hydrogen from mercury cell chlor-alkali plants, and flue gases of coal-fired power plants. Work in this area is being conducted by Argonne National Laboratories and Olin. This paper discusses the oxidation chemistry of choric acid and its unique solution and gas phase reactions with NO, SO2, and air toxics in wet scrubber type process equipment.