CONTACT REDUCING METHOD OF NITROGEN OXIDE

PROBLEM TO BE SOLVED: To improve reactivity and selectivity in the reduction reaction of nitrogen oxides by adding a reducing agent to part of exhaust gas, partially oxidizing the reducing agent under specified conditions to obtain a reducing agent gas, and adding the reducing agent gas to the exhaust gas to effect contact reduction of nitrogen oxides in the presence of a catalyst. SOLUTION: Part of exhaust gas containing nitrogen oxides is separated, to which at least one kind of reducing agent selected from hydrocarbons and oxygen-contg. org. compds. is added. The mixture gas is introduced to an oxidizing reactor, where the reducing agent is partially oxidized by keeping the gas at 350 to 800 deg.C in 5 to 50% oxygen concn. for 0.05 to 1sec. Then the reducing agent gas containing the partially oxidized reducing agent is added to the exhaust gas containing nitrogen oxides in such a manner that the amt. of the reducing agent in terms of C1 compds. is >=1.5 times for the amt. of nitrogen oxides. The mixture gas is introduced to a catalytic reactor, where the nitrogen oxides in the exhaust gas are subjected to contact reduction. Thereby, nitrogen oxides in the exhaust gas can be decomposed into nitrogen and water by the contact decomposition and the exhaust gas is changed into purified gas.