Abstract: The invention is directed to a process for oxidizing gaseous pollutants in a flue gas stream composed of flue gases, water vapour and one or more gaseous pollutants selected from the group consisting of SO2, NO, NO2, H2S, and mercury vapour, the oxidized form of the pollutants being more readily removable from the flue gas stream by water absorption than the non-oxidized form thereof, comprising: (a) injecting sufficient chlorine in a gaseous form, a liquid form, or as a chlorine water solution, into the flue gas stream while the flue gas stream is at a temperature greater than 100° C.

Abstract: Chlorine is injected in a gaseous liquid or solution form into a hot (greater than 100.degree. C.) gas stream for the purpose of oxidizing objectionable components in the gas stream, such as, but not restricted to, SO.sub.2 and NO.sub.x, when the oxidized form of the gases is more readily removed from the gas stream. After sufficient reaction time, the gas stream mixture passes through water scubbers for the further removal of the components from the gas stream. Acidic and basic compounds of the gas stream and halogens, including excess chlorine, are also removed in the scrubbers. The pollutants remain as the corresponding oxidized acids or salts in the process effluent solution.