Gypsum powder is mainly used for making tofu products, where the arsenic content is strictly limited. Otherwise, people who eat tofu with excessive arsenic content will have different degrees of nausea, vomiting, gastrointestinal discomfort and other symptoms, and even lead to bigger lesions caused by arsenic poisoning.
Types and Uses of gypsum The most commonly used type of gypsum in construction is construction gypsum, followed by model gypsum, as well as high strength gypsum, anhydrous gypsum cement and floor gypsum. The main raw material for the production of gypsum is natural dihydrous gypsum, also known as soft gypsum or gypsum, which is calcium sulfate containing two crystalline waters. Natural dihydrous gypsum can be made of various properties of gypsum.
The main processes of gypsum production are heating and grinding. Due to the different heating temperature and method, different properties of gypsum can be produced. (1) Building gypsum Building gypsum is a white powder made by calcining mature gypsum and other raw materials such as natural hydra gypsum at the temperature of 107℃ ~ 170℃, and then grinding fine. Its main component is b - type semi - hydrous gypsum. After hardening, the building gypsum has good thermal insulation, sound absorption and better fire resistance and moisture absorption. White color, can be used for interior painting construction, especially suitable for making a variety of. White, smooth and delicate floral decoration, such as the addition of pigments can make the product with a variety of colors. Construction gypsum should not be used for outdoor projects and high temperature projects above 65℃. In short, architectural gypsum can be used for interior painting, making decorative products, porous gypsum products and gypsum board, etc. (2) The gypsum of Paris produced by calcining dihydrous gypsum of model gypsum is called model gypsum if the impurity content is less and the SKI is finer than that of white powder grinding. It sets faster and has higher strength than building plaster. It is mainly used for making models, sculptures, decorative ornaments and so on. (3) High strength gypsum The H hydrogypsum is placed in a pressure steamer and steamed at l.3 atmosphere (124℃). Type a semi-hydrous gypsum, finely ground for high strength. This gypsum has a high density and strength after hardening. High strength gypsum is suitable for plaster works, decorative products and gypsum board with high strength requirements. After adding water repellent, the products can be used in high humidity environment. It can also be added to the organic solution to be used as a binder. (4) When the natural dihydrous gypsum is heated to 400℃ ~ 750℃, the gypsum will completely lose water and become insoluble anhydrous gypsum. After mixing and grinding it with an appropriate amount of activator, it will become anhydrous gypsum cement. Anhydrous gypsum cement is suitable for indoor use, mainly used to make gypsum board or other products, can also be used as indoor plaster. (5) Floor gypsum if the natural dihydrous gypsum is calcined above 800℃, so that part of the calcium sulfate is decomposed into calcium oxide, the product after grinding is called high temperature calcined gypsum, also known as floor gypsum. After hardening, floor plaster has high strength, wear resistance and water resistance, so it is mainly used as plaster floor for indoor floor decoration. The gypsum commonly referred to as CaS04·2H20 includes gypsum and anhydrite, two natural calcium sulfate products. Gypsum is calcium sulfate dihydrate, anhydrous gypsum is anhydrous calcium sulfate CaS04·2H20.
