| 摘要 |
<p>1500014 Magnesium oxide VEREENIGING REFRACTORIES Ltd 20 March 1975 [22 March 1974] 11675/75 Heading CIA Magnesium oxide is obtained from a material containing a magnesium compound by treating a slurry thereof with sulphur dioxide to form a solution of magnesium bisulphite which is separated from the insoluble residue containing undissolved impurities, a magnesium sulphite hydrate is then precipitated from the solution and is separated off and dehydrated before being subjected to flash decomposition by rapidly introducing the sulphite into a heated furnace at a temperature of at least 600‹ C. to form magnesium oxide and sulphur dioxide. The oxide may be obtained from magnesium carbonate and/or silicate or magnesite contaminated with silica in which case the starting material is calcined before formation of the aqueous slurry. If the starting material is calcareous or dolomitic magnesite the slurry may be treated with SO 2 at a pH above 3 to form soluble magnesium bisulphite and insoluble calcium sulphite which is separated from the solution before precipitation of the magnesium sulphite. The MgSO 3 may be formed by adding a base to the solution, e.g. magnesia, magnesium hydroxide or ammonia.</p> |
