Radiation chemical reactions in NO x and SO 2 removals from flue gas

Abstract

For the purpose of elucidation of radiation chemical reactions of No x and SO 2 removals in irradiation of flue gas, the reactions of NO x and SO 2 were studied under irradiation with electron beams in various systems ranging from a simple system (NO-nitrogen) to the complex (NO-SO 2-water vapour-oxygen-nitrogen) which was close to the composition of an flue gas. Reaction mechanisms of NO x and SO 2 were changed markedly by oxygen and water vapour. In nitrogen, NO was decomposed to oxygen and nitrogenthrough reactions with N atom and NO 2 was also decomposed to NO, dinitrogen oxide, oxygen and nitrogen. The decompositions were retarded markedly in the presence of oxygen, and an oxidation of NO and a reduction of NO 2 became predominant reactions. In the moist mixture of oxygen and nitrogen, fast oxidation of NO took place through the reactions with O, OH and HO 2 radicals, leading to the formation of NO 2, followed by oxidation of NO 2 to produce HNO 3. The SO 2 was also oxidized to H 2SO 4 through the reactions with O and OH radicals in the moist mixture. An addition of ammonia enhanced markedly the NO x and SO 2 removals in the moist mixture. Reactions of NO and SO 2 with NH 2 radical took place in irradiation of the moist mixture containing ammonia in addition to the oxidations of No and NO 2. The HNO 3 and H 2SO 4 produced through the oxidations were converted to solid NH 4NO 3 and (NH 4) 2SO 4 and some parts of SO 2 itself reacted with ammonia, leading to the SO 2 removal.