GB124842A - Improved Process for the Manufacture of Sulphuric Acid from Sulphate of Lime. - Google Patents

Abstract

124,842. Basset, L. P. June 22, 1916, [Convention date]. Void [Published under Sect. 91 of the Act]. Sulphuric acid; ammonium sulphate and phosphate; ammonia; metaphosphoric acid. - Sulphurio acid is obtained from calcium sulphate by a series of operations in which ammonium sulphate is first prepared, and this is then treated to obtain ammonia and sulphuric acid by alternative methods. The calcium sulphate is treated with ammonia and carbonic acid to obtain ammonium sulphate, and this is then heated with an oxide, such as iron or chromium oxide, or a mixture of oxides, or with an alkali sulphate, ammonia being liberated and used again, and a residue of metal sulphate or alkali bisulphate remaining, from which sulphuric acid is recovered by further heating. An alkaline-earth sulphate may be mixed with the alkali bisulphate to facilitate its decomposition. Alternatively, the ammonium sulphate may be heated with metaphosphoric acid, when sulphuric acid is expelled and ammonium metaphosphate NH4HP2O6 is formed, which, on further heating, yields ammonia and metaphosphoric acid. The calcium sulphate is mixed with water in a mixer a and passed to tanks b<1>, b<2>, b<3>, which are used successively to supply a tower c into which ammonia and carbonic acid are led by pipes h, i, the gas escaping at j being led to an acid washer to recover remaining ammonia. The liquor is circulated between the tower e and tank b<1> until the reaction is finished, whereupon it is discharged to a filter l, and the next tank b<2> is used to supply the tower. The ammonium sulphate solution is collected in a tank m and passed to a drier n, the solid salt, together with iron oxide from a feed r, being led to a heater s The wash-waters of the calcium carbonate in the filter l are collected in a tank o and led back to the tank a for mixing with the next charge of calcium sulphate. The ferric sulphate discharged from the heater s is decomposed in a suitable furnace, for instance a furnace similar to a lime-kiln heated by an oxidizing-flame, or a mechanical furnace, of the kind used for roasting pyrites, the material passing downwards from floor to floor, being directly heated by oxidizing- gases; or the ferric sulphate may be heated in a closed vessel.