The Most Valuable Things You Need to Know about Gypsum
The general term gypsum refers to two minerals, raw gypsum and anhydrite. Raw gypsum is calcium dihydrate (Ca [SO4] ·2H2O), also known as dihydrate gypsum or plaster. Anhydrite is anhydrous calcium sulfate.
Gypsum is usually white, colorless and transparent crystals (called selenite). Gypsum has a dense massive structure or fibrous structure, with vitreous luster and pearl luster on the cleavage surface.
The applications of gypsum powder
It is a very important industrial raw material that is widely used in construction, building materials, industrial and artistic models, chemical industry (sulfuric acid production, paper filler, paint filler), agriculture, food processing, pharmaceutical, and many other industries and applications.
Uses of gypsum powder
Gypsum powder can be divided into the following 4 aspects according to its uses:
1. Gypsum powder for construction: At present, the gypsum powder on the market is divided into raw gypsum powder and plaster of Paris.
The plaster of Paris (also known as hemihydrate gypsum), divided into α-type gypsum powder and β-type gypsum powder, is formed from gypsum raw materials by heating at a high temperature of 105-200 ℃.
The plaster of Paris is a kind of rigid gelling material. It has two kinds of materials, both are orthorhombic crystals. The physical properties of the two gypsum powders are different.
The α-type gypsum powder has good crystallinity and solidity, so it can be used in ceramic molds, sculptures, gypsum lines and high-end buildings. The β-type gypsum powder is mainly used for mortar levelling, gypsum board production, painting, etc.
α-type gypsum powder VS β-type gypsum powder
Advantages of gypsum powder for construction:
- It has excellent fire resistance. Gypsum board is a non-combustible material with certain fire performance and some can even be used as the fire protection layer of a steel structure.
- It has the characteristics of keeping warm and breathing. It can meet the functional requirements of indoor heat preservation, sound insulation, fire protection, waterproof, flexible separation, etc. It is also a good indoor ornamental material.
- No environmental pollution. The production process of gypsum building materials does not emit waste gas, waste residue, wastewater and substances.
- It can be recycled. The discarded gypsum building materials can be used as raw materials for the production of gypsum building materials after being crushed, screened and calcined, without generating construction waste.
2. Gypsum powder for chemical industry: Gypsum powder can be used as Portland cement retarder in the concrete industry. In agriculture, because gypsum powder is alkaline, it is possible to sprinkle it into the acidic soil to integrate the ph value of the soil so as to make use of a lot of lands.
3. Gypsum powder for food: In the food industry, the official name of gypsum powder is called "food additive calcium sulfate", commonly known as "edible gypsum" and can also be used to make tofu.
The uses of gypsum powder
4. Gypsum powder for medicine: In the pharmaceutical industry, gypsum is the main medicine in the famous Chinese medicine " Baihu Tang ", which has a good effect in treating acute high fever and thirsty irritable. In addition, dentists use plaster to make models of gums, and surgeons also use plaster to repair the fractures.
Is gypsum harmful to humans? Is gypsum powder safe to eat? Will gypsum kill plants? Here is a video about how gypsum is used, including its uses in toiletries, food additive, fertilizer, chalks, etc. It also shows the process of gypsum.
Market demand for gypsum powder affects its price
In recent years, the gypsum industry has developed rapidly. Gypsum building materials are increasingly welcomed by the market and recognized by society with their applications becoming more and more widespread.
According to the US mining forecast, the world's gypsum demand will increase at a rate of 2.5% in the next few years. It is estimated that the world's gypsum demand will reach 300 million tons in 2030. The total annual consumption of the gypsum board will reach 2.04 billion square meters.
With the increase in the market demand for gypsum powder, the requirements for its production technology are getting higher and higher, so the price has risen accordingly. The price of gypsum powder is generally calculated in tons.
Its price varies with its accuracy and use. The price of gypsum powder is between $ 28.8-$ 403.6 per ton according to its whiteness and fineness. The cooked gypsum powder is about $ 28.8-$ 158.6 per ton, the cooking gypsum is about $ 72.1-$ 317.2 per ton, and the refined gypsum powder is about $ 201.8-$ 720.8 per ton.
How to obtain the total cost of gypsum supply and use
1. The ex-factory price of Australian recycled gypsum is $ 35.00 per ton, plus $ 25 per ton freight, which is $ 60.00 per ton at the farm gate, and $ 10.00 per ton to spread. Its purity is measured at 17% S wet weight. Total cost of gypsum supply and application per ton of pure CaSO4.2H20 = (35+25+10) × 18.6 ÷ 17 = $ 76.59 per ton.
The total cost of gypsum in Australia
2. The ex-factory price of gypsum mined in New South Wales is $ 15 per ton, plus $ 40.00 per ton freight, which is $ 60.00 per ton at the farm gate, and $ 11.00 per ton to spread. Its purity is measured at 15% S wet weight. Total cost of gypsum supply and application per ton of pure CaSO4.2H20 = (15+40+11) × 18.6 ÷ 15 = $ 81.84 per ton.
Buying and using gypsum powder
The world's major gypsum producing countries are the United States, Iran, China, Brazil, Canada, Mexico, Spain, Thailand, etc. The United States, Brazil, China, and Canada are rich in gypsum resources.
Some countries have the highest reserves in the world, for example, there are 1.3 billion tons in Brazi, 700 million tons in the United States and 450 million tons in Canada.
The largest consumption area of gypsum is the building decoration material industry, which is mainly used to manufacture gypsum boards for construction and decoration. In many countries, the manufacture of slabs accounts for more than 80% of gypsum consumption.
Matters needing attention
- The fineness. In general, the extra-hard white plaster is usually about 1100 mesh, while the gypsum plaster is about 300 mesh.
- Strength. Generally, the 3-hour compressive strength of gypsum for construction is about 4.9 MPa. The compressive strength of different types of gypsum powder is different.
- Flexural strength. The flexural strength of gypsum powder for construction is 8.4 MPa.
- Bonding strength. The bonding strength of different kinds of gypsum powder is different.
The production process of gypsum powder
The building gypsum powder production line is usually divided into gypsum mining process, crushing, grinding and calcination processes according to technical requirements.
Gypsum powder production process
Gypsum mining process
The mining technology of gypsum ore is divided into two categories: the mining of fibrous gypsum ore and the mining of alabaster, ordinary gypsum and anhydrite mines. Due to the difference in physical and mechanical properties of the ore and surrounding rock, the mining technology of these two kinds of gypsum mines is very different.
Fibrous gypsum has low hardness and its rock consolidating coefficient is 1.2 for parallel fibrous gypsum and 1.5 for vertical fibrous gypsum. Because it is brittle, it will easily become fine ore to be lost. Due to the high price of the ore, most fibrous gypsum mines adopt the longwall method, selective mining and filling method.
The mining techniques of alabaster mine, ordinary gypsum mine and anhydrite mine are similar. The room and pillar mining method (generally 8-12 m in width) and breasting method are adopted. The drilling of gypsum ore is easy, but the explosive consumption is large, generally 0.34 kg/t.
Rotary drilling rig
The roller drilling rig is modern new drilling equipment. It is suitable for drilling operations of various hardness of minerals and rocks with the characteristics of high perforation efficiency, low operating cost, high mechanization and automation. At present, it has become a widely used perforation equipment in open-pit mines all over the world.
Excavators are ideal stripping and mining equipment for large open-pit coal mines, iron ore mines, non-ferrous metals and building materials mines.
The excavator is composed of the power plant, working device, swing mechanism, control mechanism, transmission system, moving mechanism, auxiliary equipment, etc. The excavator can also perform pouring, lifting, installation, piling, ramming, and pile pulling operations after changing its working device.
This is a video of gypsum powder production line on site with 100000t per year production capacity. If you are interested: Get Latest Price
Gypsum crushing process
Large blocks of gypsum of 300 to 500 mm need to be crushed by crushers to gypsum stone particles of 30 to 50 mm.
After sieving with the vibrating screen equipment, the finished material conforming to the size is sent to the finished product area, while the large material is returned to the crusher for being crushed again until it meets the required size.
Gypsum crushing equipment commonly includes the jaw crusher, cone crusher, impact crusher, roller crusher, hammer crusher and so on.
Primary gypsum crushing equipment
The common gypsum crushing equipment is the jaw crusher with a crushing ratio of 4-6. The jaw crusher, which is often used as the primary gypsum crushing equipment, can crush large pieces of gypsum into 150 mm particle size.
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Secondary gypsum crushing equipment
If the gypsum crushed by the jaw crusher cannot meet the particle size requirements, secondary gypsum crushing equipment such as cone crushers, hammer crushers, and impact crushers can be equipped to carry out further medium and fine crushing of gypsum. Specific equipment should be configured depends on the actual needs of the customer.
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Gypsum grinding process
The crushed gypsum is sent to a ball mill for grinding until 90% of it is less than 149 μm (100 mesh). The ground gypsum powder leaves the mill in the form of airflow and is collected in the cyclone separator.
The process of grinding
The ball mill is mainly a machine for dry or wet grinding of the crushed gypsum. The machine is mainly used for repeated grinding of the raw materials in the barrel through the steel ball medium in the ball mill to complete the ball grinding operation.
Advantages of Fote ball mill
- The ball mill can control the grinding time flexibly and reduce the labor input.
- The barrel, liner, milling medium and other parts of the machine are all made of high-quality materials, with strong mechanical load-bearing capacity and long service life.
- The actuator has the characteristics of good technology, low operating current, short time, less power consumption, low cost.
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The cyclone separator adopts a vertical cylindrical structure, and the interior is divided into a liquid collection area, a cyclone separation area, and a clean room along the axial direction.
The cyclone separator is suitable for purifying non-viscous, non-fibrous dry dust larger than 1-3 microns. It is purification equipment with simple structure, convenient operation, high-temperature resistance and low equipment cost.
Separation effect of Fote cyclone separator
Under the design pressure and air volume conditions, solid particles ≥10 μm can be removed. At the operating point, the separation efficiency is 99%, and within ±15% of the operating point, the separation efficiency is 97%. Under normal working conditions, the pressure drop of a single cyclone separator at the operating point is not greater than 0.05 MPa.
This video shows how gypsum powder is produced in India with the capacity of 100 tons per day or 240 tons per day. If you are interested: Get Latest Price
Gypsum calcination process
The gypsum material is lifted by an elevator and transported into the top silo of the rotary kiln preheater. Then, the gypsum material is evenly distributed into rooms of the preheater through the feeding pipe.
In the preheater, gypsum is heated to about 900 °C by the flue gas of the roasting kiln at 1150 °C, and about 30% of it is decomposed. Then, it is pushed into the rotary kiln by a hydraulic push rod, and β-type hemihydrate gypsum (180～240 ℃), anhydrous gypsum (350 ℃) and overfired gypsum (450～700 ℃) can be produced.
Fote gypsum rotary kiln
The gypsum produced after calcining and decomposing in the rotary kiln is sent to the cooler to be cooled to below 100 °C by the cold air blown in the cooler and discharged. The gypsum from the cooler is sent to the product warehouse via a vibrating feeder, bucket elevator, and belt conveyor.
Gypsum rotary kiln
Gypsum rotary kiln is a kind of thermal equipment for calcining gypsum. Its appearance and shape are similar to lime rotary kiln and cement rotary kiln. Its main structure includes kiln head, kiln tail sealing device, rotary cylinder, supporting device, back-up roll device, etc.
The structure of rotary klin
The finished gypsum clinker calcined in the gypsum rotary kiln produced by Fote has the characteristics of high taste, high purity, easy to control during the production process, high mixing degree of raw materials, uniform raw meal composition, high strength grade of the clinker, with less dust in the grinding process, less fly ash in the calcining process and reasonable price.
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Bag dust collector
The bag dust collector can effectively reduce the waste of gypsum, to reduce the harm of dust to the human body and better protect the environment.
When producing gypsum powder, the gypsum factory will gradually heat it due to industrial needs. The heating will reach more than 250 degrees and the corrosiveness is particularly strong.
The large demand and wide application of gypsum powder have stimulated the prosperity of many industries and fields, so the production of high-quality gypsum powder is the general trend of the gypsum powder industry in the future.
Fote Heavy Machinery
Fote Heavy Machinery, as one of the three major mining machinery manufacturers in China, has 38 years of experience. We are always ready to provide you with high-quality milling equipment and the best service.
For any questions about gypsum powder, please ask our professional engineers. We are looking forward to your inquiry.