JPS54131569A - Treatment of exhaust gas containing carbon monoxide and nitrogen oxides - Google Patents

Abstract

PURPOSE: To make exhaust gas harmless effectively at a comparatively low temperature by the procedure in which H₂ is added to exhaust gas containing CO and NO_x in the presence of O₂, the gas is kept at a definite temperature to convert CO into CO₂, and then NH₃ is added to the gas to decompose NO_x.

CONSTITUTION: Hydrogen (H₂) is added to an exhaust gas containing CO and NO_x, e.g., those from internal combustion engines, etc., in the presence of O₂ and the gas is kept at 400 to 800°C to oxidize CO to CO₂. Then, NH₃ is added to the gas in the presence of O₂ and H₂ and kept at 490 to 800°C to decompose NO_x. In this case, the preferred concentration of O₂ is 0.1 to 20 volumetric %, more preferably 1 to 10 vol. %, and the preferred amount of H₂ to add is more than 0.05 mole, more preferably 0.5 to 10 mole, on the basis of one mole of CO present in exhaust gas. And, the preferred temperature to be kept is 500 to 750°C. The preferred amount of NH₃ to add at later stage is more than 0.4 in molal ratio, more preferably 1 to 10, on the basis of NO_x present, and the preferred amount of H₂ to add is more than 0.5 in molal ratio on the basis of NH₃.

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