GB602453A - Synthetic forsterite materials - Google Patents

Abstract

Synthetic magnesium orthosilicate for use in the manufacture of refractory materials is prepared by mixing together in the correct proportions magnesia and silica of sufficient fineness to unite without fusion, and heating the mixture to reaction temperature. The silica in particular and, preferably, the magnesia also, should comprise a considerable amount of particles approaching colloidal fineness. The silica which is preferably amorphous, may be that obtained as a waste product from the production of ferro-silicon, or the natural, finely divided materials such as chalcedony, geyserite or diatomaceous earth, or rice hull ashes may be used; alternatively, it may be obtained by reducing relatively-pure siliceous material such as quartz by heating with carbon, allowing the silicon to reoxidize, and collecting the product. The magnesia may be the dust obtained by electrostatic precipitation or otherwise from the flue gases of furnaces for calcining magnesite, precipitated magnesia, particularly that obtained by the treatment of seawater or brine with lime or calcined dolomite, or powdered calcined magnesite or brucite. In order to convert any lime and iron present in the ingredients into monticellite and magnesioferrite respectively, a slight excess of magnesia is employed, the proportions being 60 MgO to 40 SiO2. The ingredients are mixed together with a small amount of water, and cold-setting bonds, such as waste sulphite liquor, tar, sulphite pitch, molasses, or magnesium chloride or sulphate, may be incorporated. If magnesia precipitated from brine is employed, the mixture of the ingredients may be prepared by adding the finely-divided silica to the brine either before or after treatment with the lime. After mixing, the product may be shaped if desired, and the mixture is finally burnt at approximately 1450 C., or clinkers may be produced which are subsequently ground and bonded by the same or a different material. Specifications 579,098 and 602,454, [both in Group V], and U.S.A. Specifications 852,908 and 1,659,476 are referred to.ALSO:Synthetic magnesium orthosilicate for use in the manufacture of refractory materials is prepared by mixing together in the correct proportions magnesia and silica of sufficient fineness to unite without fusion, and heating the mixture to reaction temperature. The silica in particular and, preferably, the magnesia also, should comprise a considerable amount of particles approaching colloidal fineness. The silica, which is preferably amorphous, may be that obtained as a waste product from the production of ferro-silicon, or the natural, finely divided materials such as chalcedony, geyserite or diatomaceous earth, or rice hull ashes may be used; alternatively, it may be obtained by reducing relatively-pure siliceous material such as quartz by heating with carbon, allowing the silicon to reoxidise, and collecting the product. The magnesia may be the dust obtained by electrostatic precipitation or otherwise from the flue gases of furnaces for calcining magnesite, precipitated magnesia, particularly that obtained by the treatment of seawater or brine with lime or calcined dolomite, or powdered calcined magnesite or brucite. In order to convert any lime and iron present in the ingredients into monticellite and magnesioferrite respectively, a slight excess of magnesia is employed, the proportions being 60 MgO to 40 SiO2. The ingredients are mixed together with a small amount of water, and cold-setting bonds, such as waste sulphite liquor, tar, sulphite pitch, molasses, or magnesium chloride or sulphate, may be incorporated. If magnesium precipitated from brine is employed, the mixture of the ingredients may be prepared by adding the finely-divided silica to the brine either before or after treatment with the lime. After mixing, the product may be shaped if desired, and the mixture is finally burnt at approximately 1450 DEG C., or clinkers may be produced which are subsequently ground and bonded by the same or a different material. Specifications 579,098 and 602,454, and U.S.A. Specifications 852,908 and 1,659,476 are referred to.