MECHANISMS OF ADAPTATION PERICLASE-SPINEL REFRACTORIES TO THERMAL SHOCKS

Abstract

In the group of periclase spinel refractories, the dynamics of demand for magnesite-chromite and chromium-magnesite refractories, which contain MgCr2O4 – magnesia-chromium spinel – in their phase composition, is changing, due to the environmental hazard of any hexavalent chromium compounds. These reasons stimulate the search for alternative refractories to replace chromium-containing ones. Periclase-spinel refractories of the MgO – MgAl2O4 system are poorly wetted by cement clinker melt and the lining made of them does not gain a garnish (coating), which is a mandatory technical requirement. It was necessary to develop a new type of periclase-spinel refractories based on more multicomponent oxide systems. At the same time, the task of ensuring their high heat resistance should be solved. Thus, the study of the mechanisms of adaptation of materials of the MgO – Al2O3 – FeO – TiO2 system, which counteract thermal stresses in refractories, is relevant. A new periclase-spinel refractory material has been developed, the phase composition of which is modified by a FeO- and TiO2-containing pre-synthesized additive. Refractories made of the developed material meet the technical requirements that determine operational reliability when used for lining high-temperature zones of rotary kilns for firing Portland cement clinker. The thermal resistance of a material is determined by its ability to withstand thermal stresses caused by the involuntary expansion/contraction of individual structural blocks of the material and causing its breakdown and subsequent destruction. Some mechanisms of adaptation are demonstrated and discussed based on the results of the analysis of X-ray and electron microscopic studies. Some of the discussed mechanisms are unconventional for the technological practice of refractory nonmetallic materials and complement the toolkit of materials scientists. The achieved results and some technological methods of ensuring thermal stability have signs of universality and can be used for various types of heterophase refractory nonmetallic materials