Gypsum is a kind of monoclinic system ore, and itsmain chemical component is CaSO4. Dihydrate gypsum(CaSO4•2H2O) is also called plaster stone, and hemihydrate gypsum could be got through burning process. If temperature is 190 °C, mould plaster could be got which has higher fineness and whiteness than building plaster. If plaster stone is calcined in 400-500 °C or above 800 °C, floor gypsum could be got. It takes long time to congeal and harden, but it has better strength, abrasive resistance and water tolerance than ordinary building gypsum’s. Gypsum is usually white or colorless. Colorless and transparent crystal is called selenite, sometime presents grey, pale yellow and light brown. Gypsum is crisp and its hardness is in the range of 1.5-2, relative density is 2.3.
Building plaster powder production project (raw material: natural gypsum ore, flue gas desulfurization gypsum, ardealite) is divided into 4 steps: crushing, grinding, calcining and loading. Detailed process: after being exploited, raw material will be taken to crusher to be crushed, then elevator will take material to stock bin, vibrating feeder will feed material. Roller and grinding ring grind material to different size. Because of different heating condition, dehydration gypsum's structure and characters are different. Being dried under ordinary pressure, hemihydrates gypsum(building gypsum) will be formed. Different type of grinding machine could be selected: YGM high pressure medium grinder and Raymond mill are used to process material to 15-425 mesh(fineness adjustable); HGM three ring medium superfine powder grinding mill could process material to 325-2500 mesh; coarse grinding machine processes material to 1-3 mm.
Gypsum is kind of widely applied industrial material and construction material. It could be used in cement retarder, gypsum building products, modeling, food additive, sulfuric acid manufacture, filler and paint filler areas. Gypsum and relevant products have good sound insulation, thermal insulation and fire protection performance. By different heating methods, different gypsum like building gypsum, mould plaster, high strength gypsum could be produced. building plaster has good sound isulation and fire protection and moisture absorption performance; it could be used for interior coating and all kinds of craft production. Mould plaster has better intensity than building gypsum does, it's used for modeling, sculpture, decorate area. A type hemihydrate gypsum could be fine grinded to get high intensity gypsum. This gypsum has high degree of density and intensity. Gypsum could be applied in plasterer industry, which is high level standard. It could be mixed with water-proofing agent to be applied in high moisture environment, also, it could be put into organic solution to be blended with binder.