Spinel refractory aggregates from natural raw materials

Utilization of the magnesium aluminate spinel in refractory applications is briefly reviewed. The synthesis of a magnesia aluminate spinel aggregate from natural raw materials is considered in terms of the crystal chemistry of the spinel structure and expected impurities. Principles for the formation of this spinel refractory aggregate from different natural raw materials are presented. The basic concepts were then applied to the reaction of a bauxitic clay with a natural magnesite. This combination of raw materials has the potential to produce a low-cost refractory aggregate that is a composite of spinel and forste rite. Experimental results are reported to produce a spinel refractory aggregate containing a small amount of forsterite. It possesses low apparent porosity and high bulk density suitable for industrial refractory applications, including steelmaking, aluminum and copper foundries and cement production.