GB279515A - Improvements in or relating to the production of aluminium compounds from raw materials - Google Patents

Abstract

279,515. Clay Reduction Co., (Assignees of Svendsen, S. S.). Oct. 25, 1926, [Convention date]. Silica; ammonium titanic or vanadic fluoride; ammonium silicofluoride; silicon fluoride ammonia.-Bauxite, felspar or other material containing aluminium is heated at 34-100‹ C. with a solution of ammonium fluoride or bifluoride to form ammonium silicofluoride, ammonium titanic or vanadic fluoride, and aluminium and other fluorides. The solution is dried and the residue is heated to 400-500‹ C. to volatilize silicon fluoride ammonia, and vanadium and titanium fluorides. The residue is treated with a reducing gas to aid volatilization and reduce iron to the ferrous state, and then with dry ammonia and hydrochloric acid gases at a temperature above that of the dissociation of ammonium chloride, so that the remaining non-volatile aluminium, potassium and other metallic fluorides become chlorides, and ammonium fluoride is formed. The vapours of aluminium chloride and ammonium fluoride pass off and are cooled first to 200-300‹ C. to separate the ammonium fluoride and then further to condense aluminium chloride. The latter may be heated with steam to produce alumina and hydrochloric acid, the alumina being subsequently heated to 1000‹ C. to dehydrate it. The fluorides first volatilized are treated with aqueous ammonia below 34‹ C., whereby silica gel and ammonium fluoride are formed. Any waste of fluorine is met by adding fluorspar. The non-volatile chlorides such as potassium chloride remain on volatilization of the aluminium chloride. Hydrofluoric acid may be used in place of ammonium fluoride.