GB149662A - Improved manufacture of sulphur dioxide by heating sulphates of alkaline earths magnesium and iron - Google Patents

Abstract

Sulphur dioxide is prepared by reducing sulphates of the alkaline earths, of iron and magnesium by means of a mixture of a heavy metal, or the lower oxide of a heavy metal, which is reduced by hydrogen, with carbon or a reducing-gas. The reducing-agent may be present in sufficient quantity to carry the reduction only to the sulphite stage, or sufficient may be added to convert the sulphate to sulphide. In the latter case the reduction is followed by treatment with air and steam at a higher temperature. The reduction to sulphite may also be carried out in two stages. The reduction is first effected in the presence of nitrogen or some other neutral gas or in a vacuum, and sulphur dioxide is driven off at a higher temperature. The higher oxides of the heavy metals may also be employed, the lower oxides or metals being produced in the process itself, and the metal is recovered from the residual mass by reducing e.g. by water-gas and washing out the lime with water. In the first of two examples, hepatite, iron powder and anthracite are heated alone, and, in the other, similar materials are first heated to 600 DEG C. and then sulphur dioxide obtained by heating to 900 DEG C. in the presence of steam and air. The Specification as open to inspection under Sect. 91 (3) (a) states that the reduction may be effected by metals, their low oxides or substances which can produce these compounds; no carbon or reducing gas being necessary. In additional examples, iron and iron protoxide are respectively used. This subject-matter does not appear in the Specification as accepted.