Processes to remove acid forming gases from exhaust gases

An improved process for reducing the concentration of one or more nitrogen-oxygen-containing compounds in a gas, which process comprises:

• (a) contacting a gas containing NO and SO.sub.2 with a gaseous oxidizing agent selected from O.sub.3, ClO.sub.2, the product of the reaction of P.sub.4 and O.sub.2, or combinations thereof to produce NO.sub.2 in the gas phase,
• (b) contacting the oxidized gas of step (a) with an aqueous reagent which first converts NO.sub.2 to HNO.sub.2, said aqueous reagent comprising bisulfite in admixture with sulfite formed by the reaction of SO.sub.2 and water, and a compound selected from urea, sulfamic acid or combinations thereof to reduce the formation of any compounds comprising both nitrogen and sulfur, at between about 5.degree. and 95.degree. C. at a pH of between about 1 and 7 for between about 0.01 and 60 sec in an amount sufficient to substantially convert the nitrogen atom present in the HNO.sub.2 to nitrogen;
• and
• (c) producing a gas having a reduced concentration of NO.

An improved process for reducing the concentration of NO in a gas, which process comprises:

• (A) contacting a gas containing NO and SO.sub.2 with a gaseous oxidizing agent to oxidize the NO to NO.sub.2 ;
• (B) contacting the oxidized gas of step (A) comprising NO.sub.2 with an aqueous reagent of bisulfite in admixture with sulfite formed from the reaction of SO.sub.2 and water, and
• a compound selected for urea, sulfamic acid, hydrazinium ion, hydrazoic acid, nitroaniline, sulfanilamide, sulfanilic acid, mercaptopropanoic acid, mercaptosuccinic acid, cysteine or combinations thereof to reduce the formation of any compounds comprising both nitrogen and sulfur, at between about 0 .degree. and 100.degree. C. at a pH of between about 1 and 7 for between about 0.01 and 60 sec;
• (B') producing a gas having a reduced concentration of NO.sub.2 ;
• and
• (C) contacting the reaction product of step (B) with means to reduce the concentrations of the organic products of the reaction of step (B).