GB510536A - Improvements in the production of aluminates and sulphur dioxide - Google Patents

Abstract

510,536. Aluminates ; sulphur dioxide. GROVES. W. W. (I.G. Farbenindustrie Akt. Ges.). Feb. 2, 1938, No. 3249. [Classes 1 (ii) and 1 (iii)] In the production of aluminates and sulphur dioxide a mixture of bauxite, alunite, aluminium sulphate, or aluminium sulphite with an alkali sulphate and/or an alkaline-earth sulphate is reduced in an internally heated furnace in stages at temperatures up to 1,200-1,300‹C. with avoidance of sintering until the reduction is finished, the main reduction being conducted at a temperature below about 1,000‹C. with carbon in deficiency and the final reduction being effected with a gaseous reducing agent. As the furnace is internally heated, steam and/or carbon dioxide are also present in the final stage. The process may be carried out in a shaft, or preferably in a rotary furnace, having means for introducing gas and air at various positions, so that the mixture may be heated in a slightly oxidizing preheating zone to 600-700‹C, the main reduction being then effected in a neutral zone up to 800-1,000‹C, and the final reduction be effected in a gas-reducing zone up to 1,200- 1,300‹C. 0.5 to 1 mol of carbon may be used per mol SO4, the ratio Al2O3 to Na2O be 1:1 when sodium sulphate is used, and the ratio Al2O3 to CaO be 1:1-3 when calcium sulphate is used. Examples relate to the reduction of aluminium sulphate with sodium or calcium sulphate or a mixture of the two in a rotary furnace. The Provisional Specification is not limited to the use of the aluminiferous materials specified above, nor to the use of a solid reducing agent such as carbon, nor to the use of an internally heated furnace.