Patent ID: 7449157

Claim:
An exhaust gas decomposition method, comprising the steps of: forming a spiral flow of a reactant gas and an exhaust gas containing therein a substance to be decomposed; rectifying said spiral flow; and introducing said spiral flow to a catalyst bed after rectification, and without changing substantially the direction of flow of the rectified spiral flow into the catalyst bed so as to maintain substantially rectification of the spiral flow, to allow said substance to be decomposed to react with said reactant gas; wherein said spiral flow is formed within a passage having an inner wall and a baffle plate located in the passage substantially perpendicular to the inner wall, and part of said spiral flow exists at said baffle plate near the inner wall of the passage after rectification, wherein said spiral flow is passed through at least one through hole provided at a portion near a center of baffle plate, and then passed through an enlarged section of a flow path downstream of the through hole before being introduced into said catalyst bed.