The mining and processing of gypsum is a straightforward process that enables this versatile mineral to be utilized in everything from construction materials to agricultural soil treatments.
Gypsum Mining
Gypsum is commonly found in sedimentary rock formations. It's extracted from open-pit mines or underground mines using large drills and blasting with explosives. The way gypsum is mined depends on the hardness of the gypsum and the size and depth of the deposit. If the gypsum is located close to the surface and the deposit is small, simple strip mining technology is employed. In strip mining, overburden is removed from above the gypsum layer by large trucks equipped with shovels. The gypsum is then scraped off the surface using scrapers and graders. Where the gypsum deposit extends deep below the surface, open-pit mining is conducted from the surface down using specialized drills, trucks and shovels. For very deep gypsum deposits, underground mining may be employed using tunneling and shaft technology. Care is taken during gypsum mining to avoid contamination with clay and other impurities.
Gypsum Processing
After gypsum mining, the rocks undergo an industrial processing. The first stage is crushing the gypsum which is done in a large crushing machine. The crushed gypsum is then screened to ensure uniform sizing of the gypsum granules. It is then sent through a roller mill where it is ground down into a fine powder. The powdered gypsum is now ready to start being processed into gypsum products.
For building plasters, the gypsum powder is mixed with water in a continuous mixer. Additives such as calcite and potassium sulfate may also be added to improve certain properties in the plaster. The resultant plaster mixture is pumped into a plaster calcining kettle where it is heated to evaporate excess water. The plaster slurry that comes out of the kettle is fed onto a conveyor belt and between rollers that shape it into sheet form. As the sheet travels down the conveyor line, it hardens as the excess water evaporates. At the end, the gypsum plaster sheet is cut into desired sizes.
Gypsum powder is also processed into a variety of drywall products. The powder is mixed with water and other additives to form a slurry which is fed between continuous layers of recycled paper on a long board machine. As the board moves down the line, the calcium sulfate recrystallizes or reconstitutes, water evaporates and the board hardens. Cutters slice the continuous gypsum board into panels of different sizes for use in ceilings or walls. Gypsum boards provide excellent fire resistance and sound absorbency.
So through open-pit or underground mining, crushing, screening, grinding, mixing, pumping and reconsolidating, gypsum is transformed into a myriad of products that are utilized in homes, schools, hospitals and commercial buildings. Its versatile properties and abundance in nature contribute to gypsum's widespread use in construction and industry.
