| 摘要 |
What is proposed is a process for preparing nitric acid with a concentration in the range from 50 to 77.8% by weight by catalytic gas phase oxidation of ammonia (1) with a superstoichiometric proportion of process air (2) to obtain a gas mixture (3) comprising NO and O2, cooling/condensation of the gas mixture (3) comprising NO and O2, in the course of which NO is oxidized further by O2 to NO2/N2O4 to obtain an aqueous solution (4) comprising nitric acid and a gas stream (5) comprising NO2/N2O4 and countercurrent absorption of the NO2/N2O4 from the gas stream (5) comprising NO2/N2O4 in process water (H2O) in an absorber (A) to obtain the nitric acid (7) with a concentration in the range from 50 to 77.8% by weight and an NOx comprising absorber offgas (6), wherein the water content of the nitric acid (7) is regulated to a concentration in the range from 50 to 77.8% by weight and the NOx content of the absorber offgas (6) to a concentration in the range from 20 to 500 ppm, by continuously measuring the water content of the process air (2) supplied to the catalytic gas phase oxidation and, as a function of this, adjusting the amount of process water (Q-H2O) fed to the absorber (A).
|
