GB169301A - A process for the preparation of alumina from clay - Google Patents

Abstract

Sulphur oxides; alkali metal compounds, obtaining from complex silicates. Potash-bearing clay, or similar impure aluminous material is decomposed with sulphuric acid and potash alum is obtained by cooling the liquor resulting from the hot lixiviation of the treated mass. Potassium sulphate recovered at a later stage is then added to produce a further yield of alum and the latter is calcined to give alumina, potassium sulphate and oxides of sulphur. In an example, air-dried clay is ground and mixed with rather less than the equivalent of chamber acid. The reacting mass is allowed to stand 24 hours and the action is completed and the silica rendered filterable by heating to 200 DEG C. The resulting mass is lixiviated with hot water to give a solution of about 35 DEG B<\>ae which on cooling deposits potash alum. A further crop of crystals is obtained by adding powdered recovered potassium sulphate to the cold liquor. The combined yields after de-hydration are calcined and the sulphur oxides evolved worked up into sulphuric acid for treating fresh quantities of clay. The residue after calcination is extracted at 100 DEG C. with an aqueous solution of potassium sulphate saturated in the cold. On cooling, the liquor yields potassium sulphate crystals and a mother liquor which is used repeatedly.ALSO:Potash-bearing clay, or similar impure aluminous material is decomposed with sulphuric acid, and potash alum is obtained by cooling the liquor resulting from the hot lixiviation of the treated mass. Potassium sulphate recovered at a later stage is then added to produce a further yield of alum, which is calcined to give alumina, potassium sulphate, and oxides of sulphur. In an example, air-dried clay is ground and mixed with rather less than the equivalent of chamber acid. The reacting mass is allowed to stand 24 hours and the action is completed and the silica rendered filterable by heating to 200 DEG C. The resulting mass is lixiviated with hot water to give a solution of about 35 DEG B<\>ae which on cooling deposits potash alum. A further crop of crystals is obtained by adding powdered recovered potassium p sulphate to the cold liquor, and the combined yields after re-crystallization from water are calcined. The alum is introduced into the hottest part of a furnace, which is preferably of the revolving-tube type in order to avoid the formation of a tough, hard mass during the dehydration of the crystals. The latter are finally heated to 700-800 DEG C. in the same kind of furnace, to expel oxides of sulphur which are worked up into sulphuric acid for treating fresh quantities of clay. The residue after calcination is extracted at 100 DEG C. with an aqueous solution of potassium sulphate saturated in the cold. On cooling, the liquor yields potassium sulphate which is mainly used for the production of alum as described above.