GB337406A - Improvements in the manufacture and production of sulphuric acid and nitric acid - Google Patents

Abstract

337,406. Johnson, J. Y., (I. G. Farbenindustrie Akt.-Ges.). June 13, 1929. Ada@ tion to 301,232. Nitric and sulphuric acids. - In the simultaneous production of nitric and sulphuric acids by scrubbing gas mixtures containing nitrogen and sulphur oxides with sulphuric or nitrosyl sulphuric acid, as described in the parent Specification, so much nitrogen oxides are present that the whole of the sulphur dioxide is converted into sulphuric or nitrosyl sulphuric acid, or a mixture of sulphuric and nitric acids. Gas mixtures containing 2 molecular proportions of nitrogen oxides, calculated as nitric oxide, to each 1 to 2 molecular proportions of sulphur dioxide, such as are obtained by catalytic oxidation of ammonium sulphite, are suitable. The oxidation and absorption of the sulphur dioxide take place in the first part of the plant, and the remaining nitrogen oxides, after cooling and addition of oxygen if necessary, are recovered as pure nitric acid. The first tower may be fed with sulphuric acid, which is circulated and diluted with water or the aqueous condensate of the gases, to maintain a concentration of about 60 per cent, when a practically pure sulphuric acid is obtained. If the gas mixture contains suficient water no. scrubbing acid need be added. At higher concentrations nitrosyl sulphuric acid is formed and treated as in the parent Specification, while weaker acid gives a mixture of nitric and sulphuric acids, which can be treated to give sulphuric acid and nitrogen oxides. Pure nitric acid is obtained in the subsequent towers around which nitric acid is continuously circulated. The final washing may be effected with an alkali such as lime water. Specification 253,344 is referred to. Reference has been directed by the Comptroller to Srecification 301,232.