A method for reducing the no.sub.x - oxygen in a operated under pressure, nitric acid plant during - and / or starting of the plant

摘要

With a process for the reduction of the no φ × φ - oxygen in a nitric acid plant operated under pressure, the exhaust gas exiting is subjected to a residual gas cleaning, during the - and / or start-up of the installation, a solution is to be provided, in which the no.sub.x φ × φ - oxygen during the - and / or starting of a nitric acid plant without residual gas purification can be reduced. Dollars a this is achieved by the fact that during a shutdown of the installation, directly after the caused by a drop in temperature or the like of a failure of the residual gas cleaning, the pressure prevailing in the installation temporarily maintained and the gas is subsequently expanded in a controlled manner and is diluted by means of air supplied from the outside and is emitted to the surrounding area.