The general term for gypsum refers to two minerals, calcite and anhydrite. Gypsum is calcium dihydrate (Ca[SO4]·2H2O), also known as dihydrate gypsum or plaster of paris. Anhydrite is calcium sulfate anhydrous. It is a very important industrial raw material and is widely used in many industries and applications such as construction, building materials, industrial and artistic models, chemical industry (sulfuric acid production, paper fillers, paint fillers), agriculture, food processing, pharmaceuticals, etc.
The world's major gypsum producers are the United States, Iran, China, Brazil, Canada, Mexico, Spain, Thailand, etc. The United States, Brazil, China and Canada are rich in gypsum resources.
The largest consumption area of gypsum is the building decoration material industry, which is mainly used to manufacture gypsum board for building decoration. In many countries, slab manufacturing accounts for more than 80% of gypsum consumption.
Fineness: Under normal circumstances, super anhydrite is generally around 1100 mesh, while gypsum gypsum is around 300 mesh.
Compressive strength: The 3-hour compressive strength of general building gypsum is about 4.9MPa. 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 types of gypsum powder is different.
The production process of gypsum powder
Building gypsum powder production line is usually divided into gypsum mining process, crushing, grinding and calcining process according to technical requirements.
Gypsum mining process
Gypsum mining technology is divided into two categories: fibrous gypsum mining and alabaster, common gypsum, and anhydrite mining. Due to the different physical and mechanical properties of ore and surrounding rock, the mining techniques of these two gypsum mines are very different.
Fiber gypsum has low hardness, and its rock consolidation coefficient is 1.2 for parallel fiber gypsum and 1.5 for vertical fiber gypsum. Because it is very brittle, it can easily turn into concentrate and run off. Due to the high price of ore, most of the fiber gypsum mines adopt the longwall method and the selective mining and filling method.
The mining process of alabaster, common gypsum and anhydrite is similar. The room-and-pillar mining method (generally 8-12m in width) and the chest mining method are adopted. Gypsum mines are easy to drill, but the consumption of explosives is large, generally 0.34 kg/ton.
Rotary drilling rig
Roller drilling rig is a new type of modern drilling equipment. It is suitable for drilling of minerals and rocks of various hardness, and has the characteristics of high perforation efficiency, low operation cost, high degree of mechanization and high degree of automation. At present, it has become a perforating equipment widely used in open pit mines around the world.
Excavator
Excavators are ideal stripping equipment for large open pit coal mines, iron ore, non-ferrous metal and building materials mines. The excavator is composed of power unit, working unit, slewing mechanism, control mechanism, transmission system, moving mechanism, auxiliary equipment, etc. After the excavator is replaced, it can also perform operations such as pouring, lifting, installation, piling, compaction, and pile pulling. its working device.
Gypsum crushing process
Large pieces of gypsum of 300-500 mm need to be crushed into gypsum stone particles of 30-50 mm by a crusher.
After being screened by the vibrating screen equipment, the finished materials that meet the particle size are sent to the finished product area, and the bulk materials are returned to the crusher to be crushed again until the required particle size is reached.
Gypsum crushing equipment commonly used are jaw crusher, cone crusher, impact crusher, roller crusher, hammer crusher, etc.
Primary gypsum crushing equipment
The common gypsum crushing equipment is jaw crusher with a crushing ratio of 4-6. Jaw crushers are often used as primary crushing equipment for gypsum, which can crush large pieces of gypsum into 150 mm particle size.
Secondary gypsum crushing equipment
If the gypsum crushed by the jaw crusher cannot meet the particle size requirements, it can be equipped with secondary gypsum crushing equipment such as cone crusher, hammer crusher and impact crusher to further medium and finely crush the gypsum. The specific equipment configuration should be determined according to the actual needs of customers.
hammer crusher
impact crusher
cone crusher
Gypsum grinding process
Raymond mill
Raymond mill is suitable for the processing of various non-flammable and explosive ore materials with Mohs hardness not greater than 9.3 and humidity below 6%. The equipment has high efficiency, low power consumption, small footprint, high sieving rate and fine mesh, and the finished product is in the range of 80-400 mesh.
Gypsum calcination process
The gypsum material is lifted by the elevator and transported to the top silo of the rotary kiln preheater. Then, the gypsum material is evenly distributed into each room of the preheater through the feeding pipe.
In the preheater, the gypsum is heated to about 900°C by the flue gas of the roasting kiln at 1150°C, of which about 30% is decomposed. Then it is pushed into the rotary kiln by hydraulic push rod to produce beta hemihydrate gypsum (180～240℃), anhydrous gypsum (350℃) and burnt gypsum (450～700℃).
The gypsum produced after being calcined and decomposed in the rotary kiln is sent to the cooler, and the cold air blown in by the cooler is cooled to below 100°C and discharged. The gypsum from the cooler is sent to the product warehouse via vibratory feeders, bucket elevators and belt conveyors.
