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Abstract

The mixture of aqueous nitric and nitrous acids which is produced by the absorption of nitrogen oxides with water in the manufacture of nitric acid is conducted to a closed vessel, where the acid mixture is reacted with oxygen, preferably under pressure, and is then returned to the absorber. This treatment has been found to enhance the absorption of the nitric oxide (NO) component of the gas mixture of NO and NO.sub.2 which is supplied to the absorber in the production of nitric acid. Normally, nitric oxide has a low solubility in the mixture of nitric and nitrous acids. Because nitric oxide oxidation is the controlling factor in the operation of nitric acid plants, this enhanced absorption provides for more efficient and economic nitric acid manufacture, as well as for the reduction of emissions of nitrogen oxides in the acid plant tail gases. The same invention is also applicable to the removal of nitrogen oxides from emissions generated in processes other than nitric acid manufacture.

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First Claim