This improved for disposal of oxides of sulphur and / or nitrogen oxides from gas uses

摘要

1505169 Purifying waste gases FUJI KASUI ENG CO Ltd and SUMITOMO METAL INDUSTRIES Ltd 9 July 1975 [2 Nov 1974 25 Nov 1974] 28971/75 Heading C1A Nitrogen oxides are removed from a waste gas containing nitrogen oxides and oxygen by adding chlorine dioxide or ozone to the gas whereby nitrogen monoxide contained in the gas is converted into nitrogen dioxide and/or dinitrogen trioxide and, then, contacting the gas with an aqueous scrubbing solution of at least one sulfite selected from alkali metal sulphites and ammonium sulphite in a scrubber wherein (a) the scrubbing solution contains at least one oxidation retardant selected from thiourea, or an alkali metal or ammonium sulphide, polysulphide or thiosulphate in an amount of at least 0À03 mol/1 in the scrubbing solution and (b) the pH of said scrubbing solution is at least 5. The scrubbing solution may also contain copper and/or iron ions in an amount of at least 0À003 mol/1. The Cu and Fe may be in the form of copper sulphate, copper chloride, iron sulphate, iron chloride or as a chelate or complex. Specified chelating agents are ethylene diamine tetraacetic acid, citric acid, tartaric acid and gluconic acid. Specified complexes are The waste gas may also contain sulphur oxides, in which case the scrubbing solution may contain the hydroxide, carbonate or bicarbonate of an alkali metal or NH 4 OH, so that SO 3 SP2-/SP is produced by reaction of the sulphur oxides. When an alkali metal or ammonium hydroxide is used, any CO 2 present in the gas is also removed.