Patent attributes
An apparatus is provided for treatment of process gas formed during nitric acid production by catalytic oxidation of NH3. The apparatus includes a reactor, a first catalyst bed for N2O decomposition, an absorption tower to react the NOx formed with an absorption medium downstream of the first catalyst bed, a device for adding NH3 added to tailgas entering the second catalyst bed, and a second catalyst bed for NOx reduction and further decrease in N2O in the tailgas exiting the absorption tower. The second catalyst bed contains at least one iron-loaded zeolite catalyst. N2O removal in the first catalyst bed is limited such that the process gas exiting the first catalyst bed exhibits a N2O content of >100 ppmv and a molar N2O/NOx ratio of >0.25. Treated gas exiting the second catalyst bed has a NOx concentration of <40 ppmv and a N2O concentration of <200 ppmv.
