ALUMINA PRODUCTION PROCESS Russian patent published in 2001 - IPC

FIELD: nonferrous metallurgy. SUBSTANCE: alumina appropriate for electrolytic production of aluminum is prepared from variety of types inexpensive alumina-containing raw materials, in particular from kaolin clays and concentrates, anorthosites, nepheline syenites, high-silica bauxites, etc. Raw material is mixed with ammonium hydrodifluoride or fluoride at weight ratio from 1: 2.5 to 1:3.3, mix is heated to 170-210 C, and held at this temperature to attain complete fluoridation of all rock-forming components to give powderlike cake. The latter is sublimed in oxidative medium while being blown by steam at temperature at least 400 C to remove volatile ammonium hexafluorosilicate, hexafluorotitanate, and fluoride and to yield alumina as nonvolatile residue. EFFECT: reduced produce cost price. 2 cl, 3 ex