Patent ID: 8765009

Claim:
A process for preparing nitric acid in a concentration of from 50 to 77.8% by weight, the process comprising: (I) catalytically oxidizing ammonia in the gas phase with a superstoichiometric proportion of process air, to obtain a gas mixture comprising NO and O 2 ; (II) cooling and condensing the gas mixture, thereby oxidizing NO with O 2 in the gas mixture, to obtain a gas stream comprising NO 2 /N 2 O 4 and an aqueous solution comprising nitric acid; and (III) countercurrently absorbing the NO 2 /N 2 O 4 from the gas stream in an absorber with process water (H 2 O), to obtain the nitric acid in a concentration of from 50 to 77.8% by weight and an NO x -comprising absorber offgas, wherein the water content of the process air is continuously measured and, as a function thereof, the amount of process water, (Q-H 2 O), fed to the absorber is adjusted, such that the concentration of the nitric acid is from 50 to 77.8% and the NO x content of the NO x -comprising absorber offgas is from 20 to 500 ppm.