A process has been developed for the simultaneous removal of sulfur dioxide and nitrogen oxides from power plant flue gas at normal stack gas effluent temperatures. Sulfur dioxide removal is accomplished by oxidation with nitrogen dioxide followed by absorption of the resulting sulfuric acid and the oxides of nitrogen in a recycle stream of sulfuric acid. The acid is stripped of its nitrogen oxide content. The nitrogen oxides are reoxidized with the excess nitrogen dioxide being converted to nitric acid and the bulk of the oxide recycled for further sulfur dioxide oxidation. Thus the nitrogen dioxide acts as a reactive catalyst. A high temperature isothermal scrubber permits the scrubber to recover the sulfuric acid and the oxides of nitrogen without absorbing any diluent water (which would require heat to remove), and a catalytic stripper which rapidly oxidizes the oxides of nitrogen in the liquid phase. Activated charcoal was used as the catalyst to oxidize the NOx. In addition, kinetic studies of the sulfur dioxide oxidation reaction with nitrogen dioxide were conducted. A preliminary economic analysis based on an 800 megawatt power plant, producing 1.44 million standard cubic feet per minute of flue gas was made. (Author)