Preparation And Properties Of Li₂O-Al₂O₃-SiO₂ System High Temperature Glaze For The Outlet Castable In Cement Rotary Kiln

The new dry-process cement rotary kiln has good potential for the harmless and resource reusing treatment of industrial waste and domestic waste,therefore using industrial waste and domestic waste as alternative fuels has been applied.However,alternative fuels may lead to the enrichment of alkali,sulfur,chlorine,et al.,which aggravates the damage of refractories in the outlet of cement kiln and shorten their service life.Glaze is a continuous glass layer or a mixed layer comprising of glass and crystal.It attached on the surface of ceramic substrate and exhibited the well bonding with the substrate,which can remarkably enhance the integrity and corrosion resistance of the substrate.This research of developing high temperature glaze for the outlet castable has important application value in enhancing the alkali resistance of kiln castables and prolonging its life.In this work,typical Al₂O₃ castable and mullite-silicon carbide castable for kiln were selected as substrate,a series of high temperature glazes of Li₂O-Al₂O₃-SiO₂ systems was firstly designed according to the empirical formula for the initial melting temperature of the glaze and the environment of the kiln site.With the aid of high temperature physical analyzer,scanning calorimetry and thermodynamic simulation analysis,the application range of high temperature glaze was investigated and the factors affecting the quality of glaze layer was also exploded;On this basis,the appropriate high temperature glaze was chosen to cover the surface of Al₂O₃ castable and mullite-silicon carbide castable,effects of glaze composition and treating temperature on the mechanical properties,thermal stability and alkali resistance of the castable were studied systematically.Based on the above researches,the following conclusions could be drawn:1.Glaze layer was evenly spread and well bonded with substrate after firing one step in this work.The quality of surface glaze on the castables surface is closely related to the amount of liquid phase and the viscosity of the liquid phase,which formed in the interaction between glaze and matrix.2.There is a good combination between the designed high temperature glaze and the substrate of corundum castable.The formed glaze blocked the pores and cracks on the surface of castables,thus decreasing its apparent porosity.This significantly reduced the penetration of alkali as well as improved the alkali resistance of corundum castables.3.Compared with the unglazed mullite-silicon carbide castable,less Si C was oxidized in the glazed-silicon carbide castable.In addition,the cold modulus of rupture?CMOR?of glazed-silicon carbide castable was lower,but its thermal shock resistance was greatly improved.Similarly to the glazed corundum castable,the glaze layer can block pores and micro-cracks on the specimen surface,thus significantly improving the alkali resistance.