Gypsum is a monoclinic mineral and a hydrate whose main chemical component is calcium sulfate (CaSO4). Gypsum is a widely used industrial material and building material. It can be used as cement retarder, gypsum building products, model making, medical food additives, sulfuric acid production, paper filler, paint filler, etc.

Ore type and quality

Diverse ore types: There are many types of gypsum ores, including anhydrite, ordinary gypsum, fibrous gypsum, etc. Among them, China's gypsum resources are mainly ordinary gypsum and anhydrite, anhydrite accounts for more than 60% of the total, but high-quality resources (special and first-grade gypsum) only account for 8% of the total, and fibrous gypsum is even rarer, accounting for only 1.8% of the total.

Large differences in quality: Gypsum mines in different regions vary in quality. High-quality gypsum mines are mainly used in high-end building materials and chemical fields, while ordinary gypsum mines are mostly used in construction and cement production.

Major consumer sectors

Cement production: Gypsum is used as a retarder in cement production and is one of the important raw materials for cement production. In China cement production accounts for a considerable proportion of the gypsum consumption structure. According to past data, about 84% of China’s gypsum consumption is used as a retarder for cement production, which shows that the cement industry is the main consumer of gypsum mines.

Ceramic molds: Gypsum is also widely used in the production of ceramic molds. The ceramic industry requires a large number of molds in the production process, and gypsum is an ideal material for making ceramic molds due to its good formability and easy demoulding. In China, part of gypsum consumption is used for the production of ceramic molds, but the specific proportion may vary depending on the year and industry changes.

Gypsum products and wall materials: With the development of the construction industry and the improvement of people's requirements for the quality of living environment, the demand for gypsum products and wall materials has gradually increased. Gypsum products such as gypsum boards and gypsum blocks are widely used in interior decoration and wall construction due to their excellent properties such as light weight, high strength, fire resistance and sound insulation. In addition, gypsum can also be used as wall materials, such as gypsum plastering. In China’s gypsum consumption structure, gypsum products and wall materials account for a certain proportion.

Chemical and other industries: Gypsum also has certain chemical properties and can be used in the production of chemical products. For example, gypsum can be used as one of the raw materials for the production of sulfuric acid. In addition, gypsum can also be used in agricultural fertilizers, medicine, papermaking and other fields. Although the demand for gypsum in these industries is relatively small, it is also an important part of the gypsum consumption structure.

Mining and mineral processing technology

Diverse mining methods: The mining methods of gypsum mines in China vary from region to region. Gypsum mines in the western region generally have thick coal seams and shallow burial depths, which are suitable for open-pit mining; while gypsum mines in the central and eastern regions are buried deeper and are mostly thin-layer mines, requiring underground mining, which is more difficult to mine.

Gypsum ore beneficiation process is a complex and delicate process, which aims to increase the content of useful minerals in gypsum ore to meet different application requirements, which can be roughly divided into crushing-sorting-grinding-calcination. The following is a detailed overview of gypsum ore beneficiation process

Crushing: The gypsum ore is first crushed by a crusher (such as a jaw crusher) to break it into small pieces that meet the requirements. This step is to facilitate subsequent handling and processing.

Sorting:

1) Manual sorting:In some small-scale mining companies with low production output and low quality requirements, manual sorting is still used for sorting. Workers sort out different grades of gypsum ore and gangue according to the appearance characteristics of the ore, such as color and shape.

2) Photoelectric sorting:Photoelectric sorting is a method of separating gypsum ore and impurities by using the difference in optical properties. Photoelectric sorters (color sorters, artificial intelligence sorters) convert the optical differences of ore into electrical signals through photoelectric conversion, and then control the actuators (such as high-speed air valves) to separate useful ore from waste rock. Photoelectric sorting has the advantages of high efficiency and precision. The main manufacturer is MINGDER.

3) Flotation method:The flotation method is to use the difference in physical and chemical properties between gypsum ore and impurities for sorting. In the flotation process, by adding flotation agents, the surface of the gypsum ore becomes aerophilic, so that it floats to the surface of the slurry under the action of bubbles and is separated from the impurities. The flotation method is suitable for the sorting of fine-grained gypsum ore, but the selection and dosage of flotation agents have a great influence on the sorting effect.

4) Heavy medium separation:Heavy medium separation is a separation method based on the density difference between mineral particles. In heavy media (such as heavy liquid or heavy suspension), mineral particles of different densities are subject to different buoyancy, thus achieving separation. Heavy medium separation is suitable for the separation of coarse-grained gypsum ores, but the equipment is complex and the operation is difficult.

Gypsum ore sorting process is a complex process involving multiple steps and links. In practical applications, it is necessary to comprehensively consider factors such as the properties of the ore, application requirements, and production costs to select appropriate sorting methods and process flows. At the same time, with the advancement of technology and the upgrading of equipment, the gypsum ore sorting process will continue to be optimized and improved.