The smaller the particle size is, the higher the whiteness is. The coarser the particle size is, the more difficult it is to remove carbon, especially the carbon inside the particle is not easy to volatilize, which affects the whiteness of the calcined product. The raw material is fine, the surface area is large, the carbon is easy to remove, the carbon is easy to volatilize, and the whiteness of the calcined product is high

In the process of calcining product whiteness, kaolin has a slow down trend with the increase of calcination temperature. Compared with 900 ℃, 850 ℃ kaolin calcination, kaolin products not only remove crystal water, increase pore size, but also maintain flaky, high whiteness, belonging to calcination temperature, reduce investment cost and environmental pollution, so 850 ℃ is the best calcination temperature

The whiteness of the product increases with the constant temperature time, but the trend is slow. When the temperature is too short, the carbon in kaolin is not easy to remove. After more than 4 hours of constant temperature, the degree of decarburization and dehydration of the product is small, so the whiteness of the product is improved, but the improvement is very small. In order to improve the thermal efficiency, the constant temperature control of calcined product is more suitable for 4 hours

By using different calcining additives, the production process is simplified, the cost is reduced, and the whiteness of calcined products is greatly improved. Among them, sodium chloride is the most effective additive. The introduction of urea as intercalation agent also increases the whiteness of calcined kaolin

The control of calcination atmosphere has a great influence on the whiteness and yellowness of calcined products. To meet the needs of carbon removal of coal series kaolin, calcination in oxidizing atmosphere results in low iron oxide and high price, which will inevitably lead to the increase of carbon removal and yellowness of kaolin products. Therefore, calcination at 850 ℃ in high temperature and reducing atmosphere can reduce low iron and high iron, control the calcination atmosphere, reduce the whiteness and improve the yellowness of products