Study On The Preparation And Properties Of Spinel Insulation Refractory

With the rapid development of high energy consumption industry in China, energy problem has been increasingly severe. Nowadays much focus has been placed on how to realize the industrial energy consumption. Heat insulating refractory has excellent high temperature performance, high porosity, low bulk density and low thermal conductivity, which can significantly reduce the heat loss of kilns and improve the thermal efficiency when used in high temperature kilns.In this paper, ?-Al₂O₃, fused magnesia and ?-Al₂O₃ were employed as raw material to prepar spinel heat insulating refractory with bulk density of 1.0g/cm3 and 0.5g/cm3.The hydration characteristics of ?-Al₂O₃ in different hydration medium were studied firstly. The results showed that alkaline medium will accelerate hydration of ?-Al₂O₃ while acidc medium will slow it down. It tends to generate boehmite and gibbsite under acidic condition in the hydration of ?-Al₂O₃ but bayerite and single water aluminum stone in neutral and alkaline condition. After heat treatment at 500? all of those hydration products that generated in different hydration medium will dehydration to ?-Al₂O₃. With the temperature rises to 1100?, hydration products generated in water will convert to ?-Al₂O₃, hydration products generated in hydrogen nitrate will convert to ?-Al₂O₃ and ?-Al₂O₃ and hydration products generated in sodium carbonate solution will convert to ?-Al₂O₃ and ?-Al₂O₃. When the temperature rises to 1500?, all those hydration products will convert to ?-Al₂O₃ ultimately except the hydration products generated in sodium carbonate solution which will convert to ?-Al₂O₃ finally.Then, corundum spinel thermal insulation refractory of 1.0g/cm3 bulk density was prepared by using ?-Al₂O₃ fine powder and fused magnesia as raw materials, ?-Al₂O₃ as binder. The effect of amounts of ?-Al₂O₃ and fused magnesia, sintering temperature and holding time on phase and properties of the heat insulating material was investigated. It has been showed that the cold crushing strength and the firing line change rate increased with the increase of amount of ?-Al₂O₃, and all samples have the same phase composition of corundum + spinel. With the increase of amount of fused magnesia, the firing line change rate gradually changed from shrinkage to expansion,the cold crushing strength attained its maximum at 20wt% fused magnesia, phase composition changed from “corundum + spinel” to “spinel” and then to “spinel + periclase”. Higher sintering temperature can obviously promote sintering and the cold crushing strength can be enhanced when prolonging holding time.Next, slurry dispersant and ceramic body reinforcing agent were added to prepare spinel heat insulating refractory with ultra low bulk density. The effection of addition of slurry dispersant and mass concentration of ceramic body reinforcing agent on the preparation and properties of sample was investigated. The results show that mass concentration of ceramic body reinforcing agent had significant effect on the curing of foam slurry, the best mass concentration is 3%. Hydration controlling agent can reduce the drying shrinkage and promote the sintering of samples, the appropriate addition is 0.1%. After optimizing processing parameters, spinel heat insulating refractory with spherical structure?120?m? was prepared, which shows better properties than alumina hollow ball products.Finally,the properties and morphology of spinel heat insulating refractory were studied. The results show that the spinel heat insulating refractory with bulk density of 0.5g/cm3 and 1.0g/cm3, its porosity were 57.6% and 76%, cold compressive strength is 0.4¹.0MPa and 1.6².1MPa, reheating linear change rate is ±0.5% and ±0.5%, thermal conductivity?1000?? is 0.175 W·m-1·K-1 and 0.216 W·m-1·K-1 respectively. The material shows better thermal shock resistance when its pase composition is S+M.