Producing synthetic ceramic magnesia — Alumina spinel for roof refractories

Conclusions Laboratory and technological studies to obtain magnesia spinel from raw materials of different qualities showed that, as regards the degree of activity, the magnesia constituents can be arranged in the following decreasing order: chemically pure magnesia metallurgical magnesite seawater magnesia. The use of technical alumina as the aluminous constituent is preferable to corundum.The minimum degree of sintering occurs in specimens of spinel having a stoichiometric composition.The sintering is improved with an increase both in the excess periclase and in the excess alumina over the stoichiometric ratio.A positive influence on the spinel formation and degree of crystallization is exerted by small (up to 5%) additions of chromite. The industrial significance of small (up to 2%) additions of TiO₂, B₂O₃, and V₂O₅ for the synthesis of spinels is not established.Thus, the spinel used as the batch constituent for making high quality magnesite spinel refractories should contain excess periclase and small quantities of chromite.Translated from Ogneupory, No. 2, pp. 41–49, February, 1972.