GB365949A - Improvements in and relating to the denitration of acid which contains nitro-bodies dissolved therein - Google Patents

Abstract

<PICT:0365949/III/1> Waste acid comprising sulphuric and nitric acid and dissolved nitro-bodies, such as obtained in nitro-toluene manufacture, is denitrated by treatment with steam with or without hot gases, the amount of steam being such that a nitric acid is obtained in the condensing stage of such concentration, say 20-30 per cent by weight, that complete separation of nitro-bodies therefrom can be attained by cooling. Alternatively, the necessary concentration may be attained by diluting the condensed nitric acid. Waste acid is led by a tube 1 to a column 2 down which it flows in counter-current to steam introduced by a conduit 3 and hot air by a lower conduit 4. Denitrated sulphuric acid passes out through tube 28. 30 per cent nitric acid condenses in a condenser 6 and passes to alternately employed cooling and clarifying chambers 8, 9. The nitro-bodies are removed after standing through a conduit 10. The gases passing from the condenser 6 proceed through a tube 11 to a tower 12 irrigated with 50-60 per cent nitric acid which absorbs their remaining content of nitrobodies. The acid from the tower 12 is maintained in constant circulation, being in part led to a cooling chamber 14 where it is freed from excess of nitro-bodies and in part returned to the tower 12; or it can be conveyed through a conduit 36 to the separating vessels 8, 9 and there freed from nitro-bodies, provided the acid in the separating vessels is kept below 30 per cent. The nitrous gases freed from nitro-bodies issuing from the tower 12 are led successively to towers 16, 17, 18 whereby treatment with water and nitric acid in counter-current they are converted into 50-60 per cent nitric acid. Water flows through a conduit 19 and down the tower 18, the acid liquid being in part recirculated and in part led to the tower 17. The acid derived from the tower 17 is in part recirculated in this tower and in part led to the tower 16. The towers 16, 17 are also fed via a conduit 25 with 30 per cent acid from the separators 8, 9. 50-60 per cent nitric acid passes out through tube 30.ALSO:Waste acid comprising sulphuric and nitric acid and dissolved nitro-bodies, such as obtained in nitrotoluene manufacture, is denitrated by treatment with steam, with or without hot gas, the amount of steam being such that a nitric acid is obtained in the condensing stage of such a concentration, say 20-30 per cent by weight, that complete separation of nitro bodies therefrom can be attained by cooling. Alternatively, the necessary concentration may be attained by diluting the condensed nitric acid.