Patent ID: 8083518

Claim:
A combustion method, comprising: a concentration ratio adjusting step of adjusting a concentration ratio K of nitrogen oxides, carbon monoxide, and oxygen in a gas free of hydrocarbons but containing nitrogen oxides, carbon monoxide, and oxygen from a gas generation source to a predetermined reference concentration ratio K 0 ; and a hazardous-substance decreasing step of decreasing nitrogen oxides, using an oxidation catalyst having characteristics of coming into contact with the gas to oxidize carbon monoxides by oxygen and reduce nitrogen oxides by carbon monoxide, and decreasing concentrations of nitrogen oxides and carbon monoxide on a secondary side to substantially zero when the concentration ratio K on a primary side is set to the predetermined reference concentration ratio K 0 , wherein the concentration ratio adjusting step detects a concentration of oxygen on the secondary side of the oxidation catalyst to control the concentration ratio K to the predetermined reference concentration ratio K 0 so that a detected oxygen concentration becomes a set oxygen concentration substantially close to zero, the predetermined reference concentration ratio K 0 satisfying the following formulas (1) and (2): ([NO x]+ 2[O 2 ])/[CO]═K (1) 1.0≦K=K0≦2.0 (2) in the formula (1), [CO], [NOx], and [O 2 ] represent the concentrations of carbon monoxide, nitrogen oxides and oxygen, respectively, and [O 2 ] is larger than 0.