Abstract: A method and apparatus to remove acid gases from a flue gas containing sulphur dioxide and oxides of nitrogen. There is a heat exchanger to reduce incoming flue gas temperatures. Gas from the heat exchanger are oxidized to their higher oxidation state. A reaction tower receives the oxidized gases. The reaction tower includes a reaction surface. There is a first inlet for gases adjacent the base of the reaction tower and a second inlet for a basic compound in the reaction tower above the first inlet. The arrangement allows counter current flows of the gas and the basic compound to enable scrubbing of the gas. There is an outlet for scrubbed gas and an outlet for liquids at the tower base.