How to improve the thermal insulation properties of mullite insulation brick

With the progress of Al2O3 content in mullite bricks, its high temperature performance is improved, and the flux increases, and the high temperature function is reduced. Therefore, strict control of impurity oxide content, especially K2O, Na2O and Fe2O3 content, is to obtain high-performance mullite brick important measures. In the use of alkali-containing components of the slag or gas environment, the use of mullite brick are a serious corrosive effect.

 

Fe2O3 in the high temperature of mullite and corundum in a certain solid solubility, the formation of limited solid solution. Its solid solubility in corundum is higher than that in mullite because of the formation of solid solution, which grows the lattice of mullite and corundum. The effect of Fe2O3 on the initial melting temperature of Al2O3-SiO2 system is related to the Al2O3 / SiO2 ratio in the system. When Al2O3 / SiO2, the initial melting temperature is 1380 ℃. When Al2O3 / SiO2> 2.55, Melting temperature to 1460 ℃, and with its A12O3 content progress and gradually progress. In the reducing atmosphere, Fe2O3 was reduced to FeO and dissolved into the glass phase, and the initial melting temperature of the system decreased, respectively, down to 1240 ℃ and 1380 ℃.

 

Mullite insulation brick usually contains TiO2, Fe2O3, CaO, MgO, K2O and Na2O and other impurities in the oxide, natural raw materials produced mullite impurity content than synthetic raw materials. These impurity oxides play a role in mullite, reduce the temperature and viscosity of the melt, increase the amount of liquid phase, increase the dissolution rate and dissolution of the melt to the solid phase, but the impurity oxides The effect of K2O and Na2O on the liquid formation temperature was the highest, and K2O and Na2O decreased the temperature of the non-variable point by 513 ~ 724 ℃, respectively, and also decomposed the effect of mullite. Among these impurity oxides, the effect of TiO2 is the smallest, only the temperature of the variable point is reduced by 101 ~ 107 ℃. When the TiO2 content is less, in addition to the Department of solid solution in the mullite to form a limited solid solution to promote the development of mullite and crystal growth, there are departments at high temperatures into the liquid phase to form vitreous.