Application of kaolin in refractory industry

Kaolin has a high degree of refractoriness and is commonly used to produce refractory materials. Its products have the ability to withstand high temperatures and withstand loads at high temperatures without deformation. Kaolin, which is mainly composed of kaolinite, and bentonite and bauxite, are collectively referred to as refractory clay according to their high temperature resistance. China's clay with a refractoriness of more than 1580 ° C, bauxite with a refractoriness of more than 1770 ° C, is commonly known as refractory clay. The former is divided into hard clay, soft clay, semi-soft clay, and the latter is called high alumina clay. Some colored kaolins cannot be used in ceramics and papermaking, but are good raw materials for refractory materials. Therefore, refractory materials are an important market for the comprehensive application of kaolin.

There are two main types of kaolin used as refractory products: refractory bricks, silicon aluminum wool. The former has a refractoriness of not less than 1730 ° C, a softening start temperature of 2 × 105 Pa load is not lower than 1350 ° C, and the refrigerating line shrinkage is less than 0.5% (1400 ° C, 2 h), and can be made into various sizes and shapes as needed. brick. The latter is a lightweight refractory insulation material, which is manufactured by kaolin, calcined at 1000 to 1100 ° C, and then melted with an electric arc furnace at 2000 ° C to be blown into cotton under high-speed air flow.

The quality requirements of refractory materials for kaolin are not very strict, but the ratio of the ratio of Al2O3 and SiO2 in kaolin directly affects the change of refractoriness. The value of Al2O3/SiO2 in high quality kaolin is generally between 0.7 and 0.8 or slightly higher. The ratio of Al2O3/SiO2 in pure kaolin is 0.85. When the ratio is greater than 0.85, there is an aluminum-rich mineral, which will improve the refractoriness. When it is less than 0.7, the kaolin content is low, and there is quartz, which will reduce the refractoriness. In addition, the high content of Fe2O3, TiO2 and K2O in kaolin will reduce the refractoriness and have certain harmfulness.