GB594065A - Improvements in and relating to the preparation of magnesium oxide-containing material for reduction purposes - Google Patents

Abstract

A method of preparing magnesium oxide-containing material for treatment with a predetermined quantity of solid reducing agent, comprises uniformly incorporating the solid reducing-agent with a precipitate resulting from the treatment of convertible magnesium salt-containing brines with reagents capable of effecting the precipitation of magnesium hydroxide therefrom. Carbon may be used as the precipitant and may be prepared from carbonaceous material capable of forming carbon at a calcining temperature under non-oxidising conditions. Suitable precipitants are calcium hydroxide and calcined dolomite. Mixing of reducing agent and magnesium hydroxide is preferably done just prior to the separation of the precipitate from the mother liquor, or from the washing water, should such be used to wash the precipitate. The mixture is then conditioned for subsequent treatment at a reduction temperature by heating to between 800 DEG C. and the reduction temperature. When coal or coke is used as reducing agent the mixing may be performed in a paint-mixing machine, the resultant mixture being then extruded, say from a plodding machine, into cylindrical or other suitable form, and is subjected to a temperature not greater than 800 DEG C. for removal of the free water, and then to a temperature between 800 DEG C. and 1250 DEG C. for the removal of combined water and for leaving the mixture in the form of irregular pieces. Additional reducing-agent, above that amount stoichiometrically satisfying the magnesium salts present in the brine, may be used to compensate for potential losses during calcination. Calcination is preferably effected under reduced pressure and in a non-oxidising atmosphere.