Data from the USGS "Mineral Yearbook" states that 106 million tons of natural gypsum were mined and consumed globally in 2004. The United States has the largest mining volume, reaching 18 million tons, accounting for 17% of the global mining volume; followed by Iran (10.8%), Canada (8.5%), Spain (7.1%), and China (6.5% or 6.9 million tons) (But according to the statistics of relevant Chinese authorities, it is 29 million tons, mainly used for cement production). The other top 10 countries include Thailand, Australia, France and Germany, which together account for 72% of the global mining volume.
According to the German OneStone consulting company, about 45% of the global natural gypsum mining volume is processed mature gypsum. The world's annual output of plaster of paris is about 66.5 million tons, of which 60%, or 40 million tons, comes from natural gypsum, and 40%, or 26.5 million tons, comes from synthetic gypsum and recycled waste gypsum. It is estimated that the annual output of synthetic gypsum in the world is about 160 million tons, of which about 35 million tons come from desulfurization gypsum produced by the desulfurization system of power stations, about 110 million tons are phosphogypsum by-products of phosphate fertilizer production, and about 15 million tons are titanium gypsum and other chemical plaster. 90% of the synthetic gypsum used in the gypsum industry is derived from desulfurized gypsum.
For the gypsum industry, approximately 80% of the plaster of paris is used to produce building siding. About 20% is used to produce gypsum plaster or other gypsum products.
The short setting time of gypsum is important for gypsum board factories. Flash burning, grinding and calcining co-production processes are commonly used. For the use of desulfurized gypsum, the calciner and related supporting hammer mills are designed by each factory according to its own process. Grinding and calcining systems and their matching vertical roller mills account for about 40% of the market. The market leader is Claudius Peters Process, who has received nine orders for EM pulverizer systems in the past two years. The MPS gypsum mill from Gebr.Pfeiffer AG can meet virtually any production requirement and allows the addition of up to 45% desulfurized gypsum during calcination.
Gypsum board factories are dried by a co-current dryer or a counter-current dryer. For fiber gypsum board drying, it is dried by a dry screen machine. The gypsum board has a retention time of 32 to 40 minutes in a dryer that takes up as little space as possible. Each group is designed with 6 to 16 board surfaces and 3 drying areas. The accuracy of the downstream dryer feeder is very important. First, the boards are cut and then arranged on a series of board surfaces, and then the stacking begins; the boards immediately following must maintain the principle of "follow in, follow out" and maintain stable quality.
Drywall plant machine operations are increasingly important. This involves the coordination of wet end equipment, dry feeding equipment and depalletizing equipment, as well as the coordination of drying end equipment and stacking equipment. The equipment must be able to operate flexibly to produce gypsum boards of different sizes, thicknesses and qualities. Manual operations must meet safety requirements when producing different products. Although the transition to mechanized production methods in modern factories almost guarantees raw meal preparation and paper handling, board handling is fully automated. However, high production rates also require sophisticated palletizing systems at the end of production.
