PURIFICATION METHOD FOR EXHAUST GAS AND PURIFICATION DEVICE FOR EXHAUST GAS

摘要

PROBLEM TO BE SOLVED: To provide a purification method for exhaust gas designed to efficiently carry out purification of exhaust gas at a low temperature by maintaining constant rate of denitration when reduction denitration through contacting with ammonia is carried out by allowing the coexistence of NO2and NH3in exhaust gas containing NOx.

SOLUTION: (1) This method comprises feeding ammonia and nitrogen dioxide to a gas duct for exhaust gas containing nitrogen oxides and then contacting the exhaust gas with a catalyst to remove the nitrogen oxides through reduction. A part of the ammonia fed to the gas duct is contacted with an oxidation catalyst to produce the nitrogen dioxide, and the amount of the ammonia fed to the gas duct based on the amount of the ammonia used for production of the nitrogen dioxides is controlled to be in the molar ratio of 2-2.5. (2) The purification method for exhaust gas controls the amount of nitrogen dioxide to be fed to the gas duct to be an amount at most an equimolar amount of nitrogen oxides contained in the exhaust gas.

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