Gypsum (CaSO4·2H2O) is also called raw gypsum. After calcination and grinding, β-type hemihydrate gypsum (2CaSO4·H2O), that is, building gypsum, also known as plaster and plaster. If the calcination temperature is 190 ° C, the model gypsum can be obtained, and its fineness and whiteness are higher than that of the building gypsum. If the gypsum is calcined at 400-500 ° C or higher, the floor gypsum will be solidified and hardened, but the strength, wear resistance and water resistance after hardening are better than ordinary building gypsum. Usually white, colorless, colorless transparent crystal called transparent gypsum, sometimes due to impurities such as gray, light yellow, light brown and other colors. The streak is white. Transparent. Glass luster, cleavage surface pearl luster, fibrous aggregate silky luster. The cleavage is extremely complete, and medium, and the cleavage piece is split into a diamond with an angle of 66 and 114. Crisp. Hardness 1.5~2. The directions are slightly different. The relative density is 2.3. Under the polarizer: colorless. Biaxial crystal (+). 2V = 58. Ng=1.530, Nm=1.523, Np=1.521. 2V decreases with increasing temperature, and 2V is zero at approximately 90 °C.
When heating, there are 3 stages of discharging crystallization water: 105~180°C, first discharging one water molecule, then immediately discharging half of the water molecules, and converting into calcined gypsum Ca[SO4]·0.5H2O, also called plaster or hemihydrate gypsum. . At 200~220 °C, the remaining half of the water molecules are discharged and converted into type III anhydrite Ca[SO4]·εH2O (0.06 < ε < 0.11). At about 350 ° C, it is converted to type II gypsum Ca [SO4]. Further converted to type I anhydrite at 1120 °C. The melting temperature was 1450 °C.
Gypsum is a monoclinic mineral whose main chemical component is calcium sulphate (CaSO4) hydrate. Gypsum is a widely used industrial and building material. It is a world-recognized environmentally-friendly and energy-saving material with a wide range of raw materials, good product performance, high strength, and ultra-high-strength gypsum with superior performance. It is an environmentally friendly and healthy material commonly used in industrialized countries.
The gypsum falls into the center of the grinding mill disc through the feeding tube, and the disc rotating at a constant speed uniformly disperses and flattens the raw material outward by the action of centrifugal force to form a layer of a certain thickness, and the material simultaneously undergoes multiple grinding on the grinding disc. Roller. Rolling and crushing. Under the continuous driving force of the centrifugal force, the material continuously moves toward the outer edge of the disk. The material leaving the disk encounters hot gases that enter the mill through the air ring and rise. In the process, it enters the separator through the intermediate casing of the vertical mill. The material is completely heat exchanged with the hot gas and the water evaporates quickly. Vertical roller mill. Particles larger than the specified size are separated and dropped back onto the grinding disc. The gypsum powder that meets the fineness requirements enters the finished product warehouse through the sorter.