What Is the Mainly Use of Various Gypsum?
From : clirik Date : 2019-01-11 13:17
what is the Use of various gypsums?
A. Indoor plastering and painting of building gypsum with water, sand and retarder mixed with gypsum mortar for indoor plastering. The surface after plastering is smooth, delicate, white and beautiful. Gypsum mortar can also be used as a primer for paints, etc., and can be directly painted or pasted with wall coverings or wallpaper. The building gypsum is added with water and a retarder to form a gypsum slurry, which can be used as an indoor stucco paint.
B, gypsum board
a. The gypsum board is made of building gypsum as the main raw material, with appropriate amount of fiber material and retarder as core material, paperboard as reinforcing protective material, after stirring, forming (rolling), cutting and drying. be made of. The length of the gypsum board is 1800 ~ 3600mm, the width is 900 ~ 1200mm, the thickness is 9, 12, 15, 18mm; the longitudinal bending load can reach 400 ~ 850N. The gypsum board is mainly used for partition walls, interior walls, etc., and its weight is only 1/5 of the brick wall. Water-resistant paper gypsum board is mainly used in humid environments such as kitchens and bathrooms. The refractory gypsum board is mainly used for indoor partition walls and ceilings with high fire resistance requirements.
b. Fiber gypsum board Gypsum board made of fiber material (using glass fiber) as reinforcing material and construction gypsum, retarder and water through special process. The strength of the fiber gypsum board is higher than that of the gypsum board, and the specifications are basically the same. In addition to partition walls and interior walls, fiber gypsum board can also be used to make furniture instead of wood.
c. Decorative gypsum board It is made by building gypsum, appropriate amount of fiber material and water, etc. by stirring, pouring, trimming and drying. The decorative gypsum board is beautiful in appearance, decorative, and has good functions of sound absorption and fire prevention. It is mainly used for interior walls and ceilings of public buildings.
d. Hollow gypsum board is mainly made of building gypsum. It is made by adding appropriate amount of lightweight porous material, fiber material and water by stirring, pouring, vibrating forming, core pulling, demoulding and drying. Mainly used for partition walls, interior walls, etc., without the need for keels.
C, gypsum block
Gypsum block is a lightweight building gypsum product made of building gypsum as the main raw material, stirred by water, cast and dried. Fiber reinforcement or light aggregates may be added during production, and a blowing agent may also be added. Gypsum block has many advantages such as sound insulation and fireproof, convenient construction, etc. It is a new type of wall material with low carbon environmental protection, health and meeting the development requirements of the times. [1]
Food industry application of gypsum :
According to the hygienic standard for the use of food additives in China, gypsum is used as a coagulant in the production of canned and soy products, and the dosage is added according to the normal production needs. It is used to make tofu. The amount of soy milk is 2~14g/L. The excess will produce bitterness. That is, the gypsum in summer is about 2.25% of the raw material, and the winter is about 4.1% of the raw material. When used to make dry tofu, the amount of gypsum used in summer is about 2% of the raw material, and in winter it is about 4.3% of the raw material. Calcium sulphate can be used as a tissue fortifier in the production of canned tomatoes and potatoes, and 0.1% to 0.3% should be added according to the production formula.
use in Industrial application of gypsum
Gypsum is a monoclinic system with high degree of cleavage and easy to split into thin slices. The gypsum is heated to 100 to 200 ° C, and part of the crystal water is lost to obtain hemihydrate gypsum. It is a gas-hardening gelling material with both alpha and beta forms, all of which are rhombohedral but have different physical properties. The α-type hemihydrate gypsum crystallizes well and is solid; the β-type hemihydrate gypsum is a plate-like and cracked crystal, the crystal is very fine, and the specific surface area is much larger than that of the α-type hemihydrate gypsum.
When producing gypsum products, α-type hemihydrate gypsum requires less water than β-type, and the product has higher density and strength. Usually, it is made by steaming autoclave in a saturated steam medium, which is α-type hemihydrate gypsum, also called high-strength gypsum. It is made of β-type hemihydrate gypsum by using a wok or rotary kiln open device. plaster. Industrial by-product chemical gypsum has the same properties as natural gypsum and does not require excessive processing. The slurry of semi-hydrated gypsum and water is re-formed into dihydrate gypsum, which is rapidly coagulated and hardened during the drying process to obtain strength, but softens when exposed to water.
Gypsum is the main raw material for the production of gypsum cementitious materials and gypsum construction products, and also a retarder for Portland cement. After the gypsum is calcined at 600-800 ° C, a small amount of lime and other catalysts are added to grind together to obtain an anhydrite cement (also known as Jin's cement); after calcination at 900-1000 ° C and grinding, high-temperature calcined gypsum can be obtained. . The products made of these two kinds of gypsum have higher strength than the construction gypsum products, and the anhydrite cement has better heat insulation, and the high temperature calcined gypsum has better wear resistance and water resistance.
Gypsum board
Building products produced using building gypsum mainly include:
1 Gypsum board. Add a small amount of adhesive, fiber, foaming agent, etc. to the building gypsum and mix it with water, then continuously cast between two layers of facing paper, and then roll, solidify, cut and dry. The plate thickness is 9-25 mm, and the dry bulk density is 750-850 kg/m3. The plate has good toughness, non-combustible, stable size, smooth surface, and can be sawed for easy construction. Mainly used for inner partition wall, interior wall veneer, ceiling, sound absorbing panel, etc., but poor water resistance, not suitable for use in humid environments.
2 fiber gypsum board. The gypsum slurry mixed with fibers and other admixtures is formed by entanglement, pressure filtration or rolling, and then cut, solidified and dried. The thickness is generally 8 to 12 mm. Compared with the gypsum board, it has high flexural strength, no need for facing paper and adhesive, but the bulk density is large, and the use is the same as that of the gypsum board.
3 Decorative plasterboard. The prepared building gypsum slurry is poured into a mold frame with a pattern of the bottom mold, which is smoothed, solidified, demolded and dried, and the plate thickness is about 10 mm. In order to improve the sound absorption effect, it can also be made into plates with perforations and blind holes, which are often used as ceilings and decorative walls.
4 Gypsum hollow slats and gypsum blocks. The gypsum slurry is poured into a mold, which is formed by vibration molding, solidification, demoulding and drying. The thickness of the hollow strip is generally 60-100 mm, and the hole rate is 30-40%; the size of the block is generally 600×600 mm, the thickness is 60-100 mm, and the periphery has a tongue and mouth, and sometimes it can be made into a hollow with a round hole. Block. Hollow slats and blocks are made of special plaster, which is convenient for construction and is often used as a non-load-bearing inner partition wall.
Industrial production made of gypsum :
Gypsum ore
Data from the USGS “Mineral Yearbook” stated that natural gypsum mined and consumed worldwide in 2004 reached 106 million tons. The United States has the largest amount of mining, reaching 18 million tons, accounting for 17% of global production; followed by Iran (10.8%), Canada (8.5%), Spain (7.1%), and China (6.5%, 6.9 million tons). (But according to the statistics of relevant Chinese departments, it is 29 million tons, mainly used for cement production). Other countries that have entered the top 10 are Thailand, Australia, France and Germany. The combined production of these 10 countries accounts for 72% of the world.
According to the German OneStone Consulting Company, approximately 45% of the global natural gypsum production is processed into mature gypsum. The annual production of world mature plaster is about 66.5 million tons, of which 60% or 40 million tons are from natural gypsum, and 40% or 26.5 million tons are from synthetic gypsum and recycled waste gypsum. It is estimated that the annual production of synthetic gypsum in the world is about 160 million tons, of which about 35 million tons are derived from desulfurization gypsum produced by power station desulfurization systems, about 11 million tons are phosphogypsum, a by-product of phosphate fertilizer production, and about 15 million tons are titanium gypsum and others. Chemical gypsum. 90% of the synthetic gypsum used in the gypsum industry is derived from desulfurized gypsum.
For the gypsum industry, approximately 80% of the plaster is used to produce building wall panels. About 20% is used to produce gypsum plasters or other gypsum products.
For gypsum board plants, the shorter set time of the gypsum is important. Flash, mill and calcination 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 their own process. Grinding and calcining systems and their matching vertical drum mills account for approximately 40% of the market. The market leader is the Claudius Peters process, and in the past two years he has received orders for nine EM pulverizer systems. Gebr.Pfeiffer AG's MPS gypsum mill can actually meet any production requirements and allows up to 45% of desulfurized gypsum to be added during the calcination process.
The gypsum board factory is dried by a downstream dryer or a countercurrent dryer. For the drying of the fiber gypsum board, it is dried by a dry sieve machine. The gypsum board has a retention time of 32 to 40 minutes in a dryer with as small space as possible, and each group is designed with 6 to 16 panels and 3 drying zones. The accuracy of the downstream dryer feeder is very important. First, after the board is cut, it is placed on a series of boards, and then stacking begins; the board that follows it must maintain the "follow-and-go" principle and maintain a stable quality.
Gypsum board factory machine operations are becoming more and more important. This involves the coordination of wet end equipment, dry feed equipment and depalletizing equipment, as well as coordinated dry end equipment and stacking equipment. These devices must be flexible to produce gypsum boards of different sizes, thicknesses and qualities. Manual operation must meet safety requirements when producing different products. Although the transformation of mechanized production methods in modern plants almost guarantees raw material preparation and paper handling, the operation of the board is fully automated. However, high speed production rates also require a well-established palletizing system at the end of the production.
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