GB547959A - Improvements relating to the production of highly concentrated nitric acid - Google Patents

Abstract

547,959. Nitric acid. BAMAG, Ltd., and MANNING, A. H. March 20, 1941, No. 3831. [Class 1 (ii)] Concentrated nitric acid is produced by 'oxidation of a solution or admixture of nitrogen tetroxide in nitric acid of medium concentration by means of oxygen in excess passed, in counter flow to the mixture, through a long reaction tube, the excess oxygen being led to the lower part of a pressure feed vessel above the tube so that the oxygen bubbles through an acid mixture in the feed vessel to effect partial oxidation of nitrogen oxide and to raise pressure therein to promote the flow of the mixture into the reaction tube. The process is carried out cyclically in an apparatus comprising a reaction tube 14, a storage vessel 1 for a mixture of nitric acid and nitrogen tetroxide, a pump 2 and constant level tank 4, and a number, e.g. 3, of pressure feed vessels 36-38. Oxygen is passed into the tube 14 from a tube 30 and the unabsorbed excess is allowed to flow, for example into the middle feed vessel 37, through a dip pipe 17, some being absorbed and the remainder causing a rise of pressure whereby the liquid in the feed vessel flows by gravity through a valve 1'2 into the reaction tube. After most of the liquid in vessel 37 has passed into the reaction tube a valve 20 is opened and liquid in the vessel 38 passes into the reaction tube. The valves 12, 19 are then closed and the oxygen remaining in vessel 37 is allowed to pass into vessel 36 through a tube 17. When the pressure in vessels 36, 37 is equalized connection between them is broken, the vessel 37 vented to atmosphere through a valve 29 and liquid from tank 4 allowed to flow into it. The operation is then continued seriatim.