Concentrated nitric acid Process comprises catalytically burning ammonia in oxygen in the presence of water vapour; condensing the water vapour to form a dilute HNO3; adding oxygen to the remaining gases containing nitrogen oxides; and contacting the resulting gas mixture in a liquid film absorber with dilute HNO3 or water to form concentrated HNO3. The oxygen added to the gases may be preliminarily used to blow out the nitrogen oxides from the concentrated nitric acid. By this method the absorption of nitrogen oxides can be carried out in a small space without evoking an excession temperature increase.
