GB744708A - Process for recovering sulphuric acid and iron oxide from iron sulphate - Google Patents

Abstract

Sulphuric acid and iron oxide are obtained in a single stage from iron sulphate, e.g. such as is obtained by cooling or concentrating exhausted pickling baths, by heating to not less than 600 DEG C. in the presence of water vapour and an oxidizing agent, as defined, in a chamber substantially devoid of air. The oxidizing agent may be mixed with the water vapour, e.g. hydrogen peroxide, nitrous or nitric acids, or mixed with the iron sulphate, e.g. <PICT:0744708/III/1> barium peroxide, or potassium chlorate. Ferric or ferrous sulphate may be used with any content of water of crystallization, although the monohydrate is preferred. Iron sulphate enters heated vessel 1 at 12 and is contacted with a mixture of H2O and HNO3 from vapour generator 2. The iron oxide, which may be FeO, Fe2O3 or a mixture thereof, may be withdrawn to 11 and reduced therein to iron. Vaporous products from 1 pass to receiver 3 containing hot water or aqueous sulphuric acid. Since 3 is immediately after vessel 1, the temperature of the absorption liquid therein will be such that the absorbed sulphuric acid is free from nitrous compounds, and water vapour, nitrous or nitric acids, and NO and NO2 will pass on to condenser 4, where unused HNO3 and water vapour are condensed. Remaining gases are drawn by suction pump 10 through oxidation chamber 5, where they are contacted with air, drawn in at 14, to oxidize NO to NO2, further oxidation chamber 6 and absorption towers 7, 8, 9, where they may be contracted with part of the condensate from condensers 4 which is withdrawn through oxidation chamber 5 at 15. The condensates from 15 and from towers 7, 8, 9, are recycled to vapour generator 2. Specification 425,291 is referred to.