Bauxite is raw material after being mined from bauxite, and these raw ore are processed through complicated procedures. Bauxite clinker is bauxite clinker after raw bauxite is calcined at high temperature (1200～1700℃).
What changes will the bauxite have after calcination? The main changes in the physical and chemical properties of bauxite from raw material to mature material are:
1. The appearance changes from the original gray, dark gray, gray-yellow, gray-white, red-yellow and other colors to white, beige, brown-red, and blue, and the blue becomes deeper as the aluminum content increases. The original earthy luster becomes corundum luster or grease luster, and sometimes slight melting stones or cracks appear on the surface;
2. The alumina content increases by 11-13, and the increase in other impurities is small;
3. Reduced size;
4. From monohydrate or monohydrate-kaolinite type to artificial corundum, mullite and a small amount of glass phase;
5. The hardness is increased from the original 1～3 to above 8;
6. The volume density is increased from the original 2.5g/cm3 to above 2.8～3g/cm3;
7. Crystal water, structural water, and attached water all overflow;
8. The structure changes from loose, loose, soft to dense and hard;
9. Enhanced slag resistance and alkali resistance;
10. The volatile ingredients, combustible ingredients and soil odor disappear completely;
11. The theoretical value of refractoriness can reach above 1780℃.
In summary, it is a complicated process for bauxite to change from raw material to mature material. As the calcination temperature increases and the holding time increases, the aluminum content increases and the grade of bauxite also increases.