1. Ordinary magnesia alumina brick. It is a spinel alkaline refractory containing about 85% MgO and 5%~10% Al2O3. The crystal phase of it is mainly composed of periclase and magnesia-alumina spinel as matrix. The crystal network is formed after crystallization of spinel aggregate, which makes the brick structure compact. Because no coarse aggregate is used in the manufacturing, the overall brick structure is uniform and the pores are loose.
2. Magnesia-alumina spinel brick is a kind of magnesia brick with magnesium and aluminum as the main mineral resources. It is made by adding alumina in the ingredient to improve the thermal stability of magnesia brick. Magnesia-alumina spinel brick has the advantage of good thermal stability, and it will react with clinker during use. Then a thin layer of calcium aluminate protective layer is formed on the outside of the brick, and its anti-falling performance is better than that of directly bonded magnesia-chrome brick.
3. Modified magnesia-alumina spinel brick. Magnesia-alumina spinel brick has been successfully applied in the transition zone of cement reverse kiln, but it is easy to arrange embrittlement and fall off in the firing zone, the kiln skin is not easy to hang, the cement clinker has poor resistance to alkali vapor and liquid phase permeability, and the mechanical stress caused by the deformation of the kiln body is poor, which limits its application in the firing zone. For this reason, a modified magnesia-alumina spinel brick suitable for sintering zone in cement reverse kiln was developed.
Application of it: magnesia alumina brick is widely used in non-ferrous metallurgical furnace, magnesia-alumina spinel brick is widely used in cement conversion, and modified magnesia-alumina spinel brick is widely used in cement reverse kiln sintering zone. The thermal shock resistance of it is better than that of magnesia brick, the softening temperature under load is higher than 1580 ℃, and the softening temperature of high-purity it under load can reach 1600~1750 ℃. In addition to the impurity content in it with the addition of A1203, the starting temperature of load softening generally increases, and there is a higher value when the content of A1203 is 3%~10%. When the content of A1203 exceeds 10%, it begins to decrease. When the temperature is lower than 1000 ℃, the elastic modulus of magnesia alumina brick increases with the increase of temperature, but when the temperature is higher than 1000 ℃, the elastic modulus decreases significantly.
