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Gypsum is a widely used industrial material and building material. It can be used for cement retarder, gypsum building products, model production, medical food additives, sulfuric acid production, paper filler, paint filler, etc.
Gypsum mined in nature is mainly divided into hydrogypsum and anhydrite:
Hydrogypsum, also known as soft gypsum or raw gypsum, is mainly composed of calcium sulfate and two crystallizing water.
Anhydrite is used to make models, crafts and other products, because of its low price, easy to obtain, non-toxic odor free, fast solidification speed, and has a certain strength, is mainly used in the field of industrial building materials and building materials.
Powdered gypsum can be used in construction industry, building materials industry, chemical industry, medicine and medical treatment industry, light industry, etc.
In construction industry, powdered gypsum can be used to produce cementing material, floor material, and interior wall putty and functional putty, and fireproof materials.
In building materials industry, powdered gypsum can be used as cement additives, additive or active activator.
In chemical industry, powdered gypsum can be used to produce sulfuric acid and cement, and produce chemical fertilizer.
In medicine and medical treatment industry, powdered gypsum can be used to produce plaster bandage, fixing device, etc. and to produce traditional Chinese medicine.
In light industry, powdered gypsum can be used for producing gypsum mold and papermaking.
To apply gypsum in the above mentioned industries, gypsum powder is needed. Gypsum powder production process is to grind the natural gypsum ore or industrial by-product gypsum through grinding mill and calcine it at a certain temperature to dehydrate and decompose to get the β hemihydrate gypsum as the main product.
In general, the production process of gypsum powder mainly includes the following 5 types:
1. Calcine the gypsum blocks and then crush them
In this method, the block gypsum is first calcined in the earth kiln, chamber kiln or vertical kiln, and then crushed and screened in the grinding equipment such as wheel mill or ball mill to obtain the gypsum powder with the required size.
The advantage of this method is simple equipment and high crushing and grinding efficiency. The disadvantage is that the gypsum calcination is uneven, which is easy to cause local dead burning and raw burning, and it is also easy to mix with impurities such as coal ash.
2. Calcination of pulverized gypsum powder
In this method, the raw gypsum is first crushed in a wheel mill or cage crusher, and then sent to the frying pan or rotary kiln for calcination, and then screen it for use.
The advantage of this method is that the ground particles are burned completely and the quality is higher. The disadvantage is that the water content of gypsum is high, the crushing efficiency is low, and it is not easy to stir evenly when frying the gypsum.
3.The grinding and calcining of gypsum are carried out simultaneously
In this method, the block gypsum after coarse crushing is sent to the wind sweep type fast rotary grinding mill for grinding. The suspended gypsum powder is calcined in the hot gas tube, and then the required gypsum powder is produced by wind power powder separation.
This method has the advantages of large output, high frying efficiency, fast coagulation and low strength, but the equipment is complex.
4. The gypsum is first crushed into fine granular sand, and then roasted, and then crushed and screened
Adopt cage crusher to crush the gypsum blocks and then conduct air separation and screening. This method has the advantages of the previous two methods, but the process is relatively complex.
5. Pressure steaming method to fry the gypsum
In this method, the raw gypsum with the size of 25-50mm after coarse crushing is preheated in the hot gas of 60 ℃, and then placed in the pressure cooker for closed cooking for 5-7 hours, and then the hot dry gas of 200 ℃ is introduced until the hot dry gas is discharged, and the vapor pressure hemihydrate gypsum is obtained.
According to the process requirements, the construction gypsum production line is usually divided into 5 parts, which are crushing system, grinding system, calcining system, material storage and transportation system and electric control system.
1. Crushing system
The gypsum raw material enters the crusher through the vibrating feeder, and be crushed into small particles less than 30mm. According to the size of gypsum raw materials and different production needs, different types and models of crushers can be selected.
For gypsum crushing, ZENITH recommends jaw crusher, impact crusher and cone crusher. And in order to protect the environment, dust removal equipment can be equipped to meet the requirements of environmental protection emissions.
2. Material storage and transportation system
The crushed gypsum particles are transported to the storage bin by the elevator for further process. The storage bin is designed according to the requirements for the storage time of gypsum materials to ensure the stable supply. At the same time, elevators are used for material turnover of all parts to reduce the floor area.
3. Grinding system
Gypsum raw materials in the storage bin enter the grinding mill for finish processing through the vibrating feeder, which is set under the storage bin. This equipment is interlocked with the mill, and the supply volume of materials can be adjusted according to the operation condition of the grinding mill.
The materials are fed into the grinding mill uniformly and continuously through the electromagnetic vibration feeder for grinding. The ground gypsum raw powder is blown out by the airflow from the blower and graded by the analyzer above the main machine. The powder with the required fineness enters the cyclone collector with the wind flow, and is discharged through the powder outlet pipe after collection. The finished product falls into the screw conveyor and is transported to the next system for calcination.
Through the grinding system, the size of the material changed from 0-30mm to 80-120 mesh or other sizes, which meets the fineness requirements of gypsum powder.
4. Calcining system
The raw powder transported from the grinding system is transported to the calcining furnace for calcining, and the cooked powder after calcining is transported to the finished product warehouse by the elevator. The system mainly includes hoist, calcining furnace, electrostatic dust removal device, Roots fan and other equipment.
5. Electric control system
The electric control system adopts the current advanced centralized control, DCS control or PLC control.
In the above 5 systems, grinding system is the core system, which determines the fineness of powdered gypsum. With over 30 years’ experience, ZENITH kept on developing and optimizing the grinding equipment for better service and has mature process technology and professional mechanical design team to help you make better application of gypsum!
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