GB590693A - Corrected magnesia products and method of making the same - Google Patents

Abstract

Crystalline refractory periclase is produced by intimately mixing magnesium oxide or other magnesia-yielding material with silica which is in a state of sub-division finer than can be obtained mechanically and which, together with any silica present as an impurity in the magnesia does not amount to more than 10 per cent., and heating to sintering temperature. The magnesia employed may be obtained by precipitation from seawater, by electrostatic precipitation from the flue dust of rotary furnaces used in the calcination of magnesia, or from powdered brucite. The silica is obtained in a state of subdivision approaching colloidal size and preferably of an amorphous character from the fumes resulting from the production of ferrosilicon or from the reoxidation of volatilized silicon produced in the reduction of silica in the presence of carbon or reducing gases. At least a part of the silica may be incorporated in the seawater prior to precipitation or in the precipitate before final separation of the mother liquor or washing-water; alternatively, it may be incorporated in the partially or completely dried hydroxide either in the dry state or as a slurry respectively. Specifications 498,183 and 579,098, [both in Group V], and U.S.A. Specifications 792,882 and 2,206,131 are referred to.ALSO:Crystalline, refractory periclase is produced by intimately mixing magnesium oxide or other magnesia-yielding material with silica which is in a state of subdivision finer than can be obtained mechanically and which, together with any silica present as an impurity in the magnesia, does not amount to more than 10 per cent., and heating to sintering temperature. The magnesia employed may be obtained by precipitation from seawater, by electrostatic precipitation from the flue dust of rotary furnaces used in the calcination of magnesite, or from powdered brucite. The silica is obtained in a state of subdivision approaching colloidal size and preferably of an amorphous character from the fumes resulting from the production of ferrosilicon or from the reoxidation of volatilized silicon produced in the reduction of silica in the presence of carbon or reducing gases. At least a part of the silica may be incorporated in the seawater prior to precipitation or in the precipitate before final separation of the mother liquor or washing water; alternatively, it may be incorporated in the partially or completely dried hydroxide either in the dry state or as a slurry respectively. Specifications 498,183 and 579,098 and U.S.A. Specifications 792,882 and 2,206,131 are referred to.