摘要 |
The invention relates to a method for reducing the concentration of NOx nitrogen oxides in residual gas which accumulates when starting up a system for producing nitric acid. The residual gas contains NOx, and the residual gas is accumulated when starting up the system and is heated from a starting temperature T0 to a final operating temperature TB, passing through a threshold temperature TG, as the result of the measures taken for producing nitric acid (T0<TG<TB). A stationary operation of the system is then carried out at the operating temperature. The method has the following steps: (a) conducting the residual gas containing NOx over a storage medium for NOx and storing at least one part of the NOx in the storage medium for NOx as long as the temperature of the residual gas is lower than the threshold temperature TG; (b) optionally releasing the NOx stored in step (a) preferably when the temperature of the residual gas has reached the threshold temperature TG; and (c) combining the NOx with a reduction agent for NOx in the presence of an SCR catalyst after the temperature of the residual gas exceeds the threshold temperature TG but not before, whereby at least one part of the NOx is catalytically reduced, preferably to N2. |