SYSTEM FOR ABSORBING NITROGEN OXIDE IN NITRIC ACID-DISSOLVED EXHAUST GAS

摘要

PROBLEM TO BE SOLVED: To provide a method and a system for removing NOx, in each of which NOx in the nitric acid gas generated at a nitric acid dissolution step is removed effectively to prevent the diffusion of the nitric acid gas to the outside.

SOLUTION: The method for removing NOx in nitric acid-dissolved exhaust gas comprises the steps of: bringing the nitric acid gas generated in a nitric acid dissolution tank into contact with ammonia water to react NOx in the nitric acid gas with the ammonia water and produce ammonium nitrate; and bringing the ammonium nitrate-containing gas into contact with an alkaline solution to absorb the ammonium nitrate contained in the gas in the alkaline solution. It is preferable that the pH value of the ammonia water contacted with the nitric acid gas is measured, the pH of the pH value-measured ammonia water is adjusted to become within an objective pH range, the pH-adjusted ammonia water is added to the existing ammonia water and the nitric acid gas is brought into contact with the resulting ammonia water to react NOx with the resulting ammonia water.

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