Production Technology
According to the technical requirements, building gypsum production line is usually divided into five gypsum powder machines parts. They are crushing system, calcining system, grinding machine system, packaging system and electronic control system.
Crushing System
The gypsum material is shoveled into the raw material hopper by a forklift.Then,the vibrating feeder at the lower part of the raw material hopper feeds the material uniformly into the crusher. And then, the crusher breaks the large-sized gypsum ore into small pieces of particles smaller than 8 mm. At the same time, the elevator and bracket machine transport the mineral materials to raw material warehouse. According to the size of gypsum raw materials and different output requirements, you can choose the corresponding specifications of the crusher. In order to protect the environment , the crusher can be equipped with dust removal equipment. The general operation of this section is 8-10 hours. storage bin according to the requirements of material storage time design specifications, to ensure a stable supply of materials, to meet the calcination system 24 hours of operation.
Calcining System
Ore material come from the storage bin will go to the silo before the rotary by impeller feeder screw conveyor and elevator. After that, the belt will take the mineral materials into the rotary for calcining. When calcining, the pulse bag dust collector in front of the rotary will collect the steam generated by calcining ;
Then,the crushed coal will go to the coal silo in the front of the fluidized bed furnace. And next, the impeller feeder will send the coal into the furnace chamber for fully being burned.The rotary kiln shell is heated, and the gypsum material is calcined through the shell conduction, the flue gas from calcination is collected by a water desert dust collector. The calcined cooked powder is transported to the semi-finished product bin by a hoist to be aged. And generally, it is aged for about 20 hours. The material is continuously dehydrated and homogenized in the aged Bin, so as to ensure the good stability of the cooked gypsum powder.
The fluidized bed furnace is the most widely used gypsum calcination equipment in China. It has the following characteristics: small equipment, large production capacity, simple structure, not easy to damage, compact equipment, less land, low energy consumption, easy operation, easy to achieve automatic control, good product quality, relatively ideal composition of plaster of Paris, stable physical performance, the capital construction investment is small, the running cost is low and so on. This system is widely used in the calcination of natural gypsum and chemical gypsum.
The method of Rotary Kiln calcining the gypsum can be divided into two types. The inside burning type and the outside burning type. The internal combustion type uses natural gas as fuel. The external combustion type uses pulverized coal as the fuel.
Grinding Machine System：
The gypsum in the semi-finished material bin is grinded by the impeller feeder and the screw conveyor.
The gypsum powder after grinding will be blown out by the air flow from the blower of the mill and graded by the analyzer above the main machine.
The qualified powder will flow into the big cyclone collector with the wind. After the collection, powder will be transported by tube. That is the finished powder.
The finished powder falls into the elevator and is transported to the next system package section. The air flow flows from the return air pipe of the large cyclone collector to the blower. The whole air path system is closed circulation and flows under negative pressure. As the ground material contains water and evaporates into gas during the grinding process, the air volume in the circulation wind path increases. The increased air volume is introduced into the bag filter from the pipe between the large cyclone collector and the blower, remove dust from the air and release it into the environment to ensure a clean environment. The material after grinding system changes from particle size 0 ~ 8mm to 80 ~ 200 Mesh, which meets the requirement of fineness of gypsum powder.
Packaging Machine System
The packing machine is installed at the bottom of the silo in the dolomite powder production line. According to the customer needs, there are two types of packaging:
1). Ton Bag packing (1000KG)
2). Small bag packing (25-100KG).
Finally, conveyor belt will transport the finished powder to the finished product storage area.
Electronic Control System
Technical specifications of gypsum powder
1). Powder quality: meet or exceed the national "building gypsum" standard (GB9776-2008).
2). Fineness: 80-250 mesh (adjustable), sieve remaining <10%.
3). Flexural strength (directly related to the raw material) : ≥ 1.6mpa;Compressive strength: ≥ 3.0mpa.
4). Main phase composition: hemihydrate gypsum content: ≥ 80% adjustable; Gypsum dihydrate content: < 5% adjustable; Soluble anhydrous gypsum content: < 5% adjustable
5). Initial setting time: adjustable from 3 to 8min; Final setting time: 6 ~ 15min adjustable.
6). Standard consistency: 78-85% adjustable.
