Improvements in method and apparatus for denitrating mixtures of nitric acid and sulphuric acid and concentrating nitric acid

摘要

333,264. Hercules Powder Co., (Assignees of Bonnett, J. L.). Oct. 26, 1928, [Convention date]. Nitric acid.-Nitric acid is concentrated by passing a mixture of aqueous nitric acid and a dehydrator, e.g. sulphuric acid, phosphoric acid or anhydrous sodium sulphate, in counterflow with a mixture of steam and nitric acid vapour to effect partial denitration of the former mixture, heating the partially denitrated mixture to generate steam and nitric acid vapour and using a portion of the generated steam to denitrate further quantities of the acid mixture, and effecting the separation of nitric acid from the balance of the steam generated, the quantity of steam passing into the tower in which the counterflow takes place being limited to an extent necessary for avoiding excessive dilution of the concentrated nitric acid. The acid mixture is passed from a vessel a down a packed tower c to a boiler g, heated by a steam jacket h and coils l, and divided by partitions k into compartment j, j1, and j11. Steam containing nitric acid vapour from the first compartment j passes up the column c, from the top of which concentrated nitric acid vapours pass to a condenser w. Steam, containing small quantities of nitric acid vapour, passes from the compartments j1 and j11 through pipes o, p upwards through a packed column n and reflux condenser s. Dilute nitric acid condensed in column n passes by a trapped pipe 2 into the first compartment j of the boiler. The apparatus may be used for denitrating acid mixtures by passing the latter down the column c.