GB1195261A - Process for the Manufacture of Nitric Acid - Google Patents

Abstract

1,195,261. Nitric acid. FARBWERKE HOECHST A.G. 16 June, 1967 [18 June, 1966], No. 27831/67. Heading C1A. Nitric acid is made by passing nitrous gases, from the catalytic oxidation of ammonia with air in countercurrent flow with water and aqueous nitric acid in an absorption device, whereby nitrous gases are absorbed. with production of nitric acid, wherein the nitrous gases are introduced into the first half of the absorption device and in a zone in the second half of the absorption device nitrous gases are absorbed and oxidized by oxidizing nitric acid, which is conducted in a cycle separate from the said countercurrent flow, and the oxidized nitrous gases are blown out of solution by air in another part of this separate cycle and introduced into the first half of the absorption device. The nitrous gases entering the zone may have a concentration up to 3% by volume of NO and NO 2 , and preferably 0À5% by volume, and the nitric acid in the cycle has an HNO 3 content of at least 40% by weight and preferably more than 55% by weight. The process may be carried out at superatmospheric pressures, preferably 3 to 8 atmospheres, in the absorbtion device. The oxidizing nitric acid is preferably at a temperature between + 20‹ C. and - 30‹ C., the preferred range being + 10‹ to - 20‹ C. The absorbtion device is preferably a tray column or a packed column.