GB808234A - Improvements in or relating to processes for the manufacture of nitric acid by catalytic combustion of ammonia - Google Patents

Abstract

<PICT:0808234/III/1> In the production of nitric acid by the successive operations, each carried out under pressure, of catalytic oxidation of ammonia to produce water vapour and oxides of nitrogen, condensation of the water vapour, further oxidation of the oxides of nitrogen, and absorption of the resulting oxides of nitrogen in aqueous nitric acid, the water vapour is condensed by absorption in aqueous nitric acid of such strength that substantially no oxides of nitrogen are absorbed, the resulting solution being passed to the absorption operation. The nitric acid may be of such strength that oxides of nitrogen are evolved therefrom on condensation. Absorption may be effected in a multistage absorption system, the last stage being fed with water which is passed as nitric acid of increasing strength from one absorption stage to another, nitric acid for the condensation being recycled from an appropriate absorption stage. The condensation may be effected by spraying the nitric acid into a scrubber tower. As shown a mixture of air and ammonia is passed under pressure through a condenser scrubber 4, an oxidizer 5, and six absorption scrubbers 6-11 connected in series at their lower ends so that nitric acid of increasing strength may pass through the system from scrubbers 11 to 6. Acid is recirculated from the bottom to the top of each of scrubbers 6 and 8-11 via a pump 12-16 and water cooler 17-21. Acid is recirculated from the bottom to the top of scrubber 7 via a pump 22, scrubber 4, pump 23 and water cooler 24. The exhaust gases pass off through line 25 while the nitric acid product is obtained from line 26.