(1) Product quality standards
In China's national standard for gypsum and anhydrite in cement (GB-5483-85), gypsum and anhydrite are classified into three grades according to their grades (grades are: greater than or equal to 80%, greater than or equal to 70) %, greater than or equal to 60%), and stipulates that it must not contain impurities harmful to the performance of cement and mixed with foreign inclusions, and the required water should not exceed 4%.
The ministerial standards formulated by the Ministry of Construction Materials Industry of China stipulate that the grades of medical, edible and art plasters are above 95%, the grades of plaster for building products and models are above 75%, and the grades of cement and agricultural gypsum are above 55% (see JC16 for details). -82), and the gypsum ore block is not more than 500mm, and the gypsum attached water content is not more than 5%.
(2) Processing method of mineral processing
Although heavy medium beneficiation, photo-selection, flotation, electro-election, etc. can be used for gypsum beneficiation, in China, these methods have not been widely used in industrial production. Most mines simply pick the gypsum ore that is mined and pick up the stone. Some mines with more complex ore types are selected by hand to extract fiber gypsum, plaster, ordinary gypsum and a small amount of anhydrite.
The calcination process of raw gypsum is divided into dry process and wet process. Dry calcination is the heating and dehydration of raw gypsum under normal pressure (or low partial pressure of water vapor), and Î²-type hemihydrate gypsum, type II anhydrite or burnt gypsum are formed depending on the temperature. This product is a plaster, cast gypsum or pre-product gypsum commonly used in construction. The wet calcination is to heat the raw gypsum under the pressure of water vapor in the autoclave or in a salt solution having a boiling point higher than 100 Â° C at a low pressure, and the product is Î±-type hemihydrate gypsum, which can be used as a special gypsum base material for pouring. .
The production process of Î²-type plaster is generally: ore storage â†’ crushing â†’ homogenization â†’ calcination dehydration â†’ aging â†’ grinding and mixing â†’ packaging, first calcined with a wok and then calcined.
The raw gypsum dry calcination process is as follows: raw gypsum is transported and selected from the quarry to ensure continuous feeding and stable quality. The feedstock is subjected to a section of crushing ( chopper crusher ) to below 8 cm, and then to a second stage of crushing ( hammer crusher ) to less than 2 cm, and then calcined into a calcining kiln through a Bucket Elevator. By controlling the temperature of the kiln, Î²-type hemihydrate gypsum, anhydrite gypsum and burnt gypsum can be separately produced.
The Î±-type wet calcination process and process are generally: gypsum raw material warehouse â†’ sieving machine â†’ autoclave autoclaving and drying â†’ broken pulverization â†’ homogenization storage â†’ Î± and Î² gypsum mixing â†’ packaging and handling. The process for producing Î±-type hemihydrate gypsum by hydrothermal method is:
Gypsum ore â†’ crushing â†’ milling â†’ reaction kettle (adding water and chemicals) â†’ cleaning â†’ dehydration drying â†’ packaging.
(4) Common technical equipment
Commonly used equipment for gypsum crushing are jaw crusher , cone crusher , impact crusher, roller crusher, hammer crusher, etc.
Dry calcination is commonly used in both direct calcination and indirect calcination. Direct calcination equipment such as rotary kiln, grinding and calcining integrated device (Peter mill, high temperature wind sweep, etc.). Indirect calcination equipment such as rotary calciner, wok (direct calcination of earth wok), horizontal calciner, vertical calciner, and the like.
The wet calcination equipment includes a horizontal type, a vertical autoclave, a vulcanization tank, and the like.
(5) Practice of mineral processing
The process flow of raw gypsum dry calcination in the Gineng Gypsum Mine Gypsum Products Factory in Jingmen City, Hubei Province is shown in Figure 4.18.6. Raw gypsum is transported and selected from the mining site to ensure continuous feeding and stable quality. The feedstock is subjected to a section of crushing (chopper crusher) to below 8 cm, and then to a second stage of crushing (hammer crusher) to less than 2 cm, and then calcined into a calcining kiln through a bucket elevator. The rotary kiln adopts a downstream type, and by controlling the temperature of the kiln, Î²-type hemihydrate gypsum (180-240 Â° C), anhydrite gypsum (350 Â° C) and burnt gypsum (450-700 Â° C) can be separately produced. After the calcined calcined gypsum is homogenized, it is ground to 200-325 mesh by a pendulum mill, and the pendulum mill is a 4R-3216 produced by Guilin Mining Machinery Factory.
1. jaw crusher; 2. hammer crusher; 3. raw material silo; 4. transport machine; 5. rotary kiln; 6. bucket elevator; 7. transport aircraft; 8. clinker silo; Crusher; 10. bagging
(6) Main types and uses of deep processed products
Used in cement production as cement retarder, special cement raw material; used in chemical industry for sulfuric acid, ammonium sulfate, etc.; used in agriculture to improve soil or soil fertilizer; paint, pigment, paper, textile and other industries Used as a coating and filler and as a filler for industrial products such as toothpaste, cream and chalk, and as a carrier for pesticides; used in the food industry to purify water in breweries, to control the clarity of wine, or to coagulate edible tofu Agents and animal feed additives. Finely ground gypsum powder can be used to clarify turbid sewage, oil refining, polishing glass and some precious metals, and other decorations. Naturally pure anhydrite powder can also be used as a flux in the glass industry in place of sodium sulfate. Raw gypsum is also known as condensate stone, (Taiyin) mysterious stone, salt root, etc. in ancient Chinese books. It has been used as a traditional Chinese medicine stone since ancient times. It has the effects of slowing the spleen and replenishing qi, quenching thirst and removing fire, and relieving hunger and sweat.
2. Plaster powder
Used in the construction industry as a stucco material for building walls, plastering materials and prefabricated parts for making plaster, which can be made into gypsum board, building partition wall, ceiling and other various gypsum prefabricated parts of various specifications; Used in the ceramic industry for the production of various ceramic molds; for the manufacture of molds in the foundry industry; for the manufacture of dental molds or surgical fixations in medicine. In the arts and crafts can be used as an art statue.
3. Gypsum products
Gypsum board has been an important wall material at home and abroad, including gypsum board, decorative gypsum board, fiber gypsum board, gypsum composite board, gypsum slag board, gypsum particle board, etc. Gypsum block is also emerging as wall material, gypsum Products have been widely used in building materials worldwide. Because of its non-toxicity and many other advantages, it is known as green building materials and has broad prospects.
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