In the coal preparation industry, vibrating screen is the most widely used classification, dewatering, de-intermediation and de-sludge equipment. It is also a key screening equipment. The graded dewatering effect is good or bad, and the screening quantity directly affects the coal preparation. Quality and efficiency. In terms of coal processing, screening technology and sorting technology are equally important. Therefore, studying the principle, structure and design method of vibrating screen has important practical significance in China's coal preparation industry.
According to the different methods of generating vibration, it can be divided into three types: eccentric vibrating screen, inertial vibrating screen and electromagnetic vibrating screen. Due to the simple structure of the inertial vibrating screen, the work performance is good, the development is fast, the structure is getting better and better, and the performance is getting better and better. The inertial vibrating screen can be divided into a circular vibrating screen and a linear vibrating screen according to different vibration paths. The circular vibrating screen is a kind of screening machine that is used more in the coal preparation plant. Such sieves and other sieves
Compared with machinery, the structure is simple, the cost is low, and the maintenance workload is small. The eccentric circular vibrating screen has been gradually eliminated. The simple inert vibrating screen is only available from a few manufacturers, and the most widely used is the self-centering circular vibrating screen. Compared with other sieves, linear vibrating screen has the advantages of simple structure, reliable use, easy manufacture, good screening effect, etc. It is the most widely used screening equipment in coal preparation plants in China.
The quality and efficiency of the vibrating screen screening process is actually affected by many factors, but mainly related to material properties and equipment performance.
1 Effect of material properties on the screening process
The properties of materials that have an impact on the screening process are: particle size characteristics, water content, mud content, particle formation and density.
(1) The effect of particle size composition. In the actual production process, it is obvious that the particle size of the material is compared with the mesh size. In the case of a certain amount of processing, the more fine particles in the material, the higher the screening efficiency; conversely, the larger the fine particle content, the larger the sieve The lower the efficiency.
(2) The influence of material temperature. When the moisture of the material is very small, the screening process is little affected by moisture; as the moisture content increases gradually
Adding, the sieving process is affected by the increase of moisture, and the sieving efficiency is reduced. However, when the water is increased to a certain value, the sieving process is most affected by the water, and the sieving efficiency is minimized. When the water is large, the sieving process is gradually reduced by the influence of moisture, and the screening efficiency is gradually increased.
(3) The influence of the mud content of the material. The more the mud content of the material, the more difficult it is to screen the material; the less the mud content, the easier the material is to be sieved. This is mainly because the mud is easy to block the mesh hole. For desmear screening, it is generally necessary to add water spray or use electric heating screen to improve the screening conditions.
(4) The influence of the shape of the particles. The degree of influence of particle formation on the screening process has a great relationship with the shape of the mesh, square or round
The mesh hole is easy to make the particles form a spherical, cubic or polygonal material through the sieve, but it is not easy to pass through the strip shape and the plate shape; the strip-shaped and plate-shaped particles are easy to pass through the rectangular mesh hole, that is, It is said that the sieving material is permeable to mesh openings similar in shape to the granules.
(5) The influence of material density. If all the particles of the material are of the same density, there is no effect on the screening. However, when the material is composed of particles of different densities, it will have an impact on the screening process. The high density of the material will affect the screening of the density, but the effect is not significant.
2 Screening impact on the screening process
The performance of the equipment includes the screening process performance and mechanical properties of the equipment, mainly discussing process performance. The process performance of the screening equipment is concentrated in the main working part of the screening equipment - the screen surface.
(1) The influence of the movement of the screen surface. The types of screening equipment we use are fixed screen, vibrating screen and shaking screen. The fixed screen with fixed screen surface has low screening efficiency. On the screen surface of the vibrating screen, the particles are in the direction of the larger angle with the screen surface. It is shaken, the vibration frequency is appropriate, and the screening efficiency is high.
(2) The influence of the length and width of the screen surface on the screening process. The wider the sieve surface, the larger the treatment volume, the longer the sieve surface, the longer the retention time of the particles on the sieve surface, the higher the screening efficiency of the sieve, but the sieve efficiency increases after the sieve surface length increases to a certain extent. It is very slow, so the sieve does not have to be too long. Generally, the aspect ratio of the sieve is 2 to 3.
(3) The influence of the screen inclination angle on the screening process. The angle α between the screen surface and the horizontal plane is the inclination angle of the screen surface, the inclination angle is large, the production capacity is large, and the screening efficiency is low (mainly because the material group moves forward on the screen surface at a fast speed, and the channel when the particles are sieved is correspondingly narrowed) Conversely, the smaller the angle of inclination, the smaller the production capacity and the higher the screening efficiency. Generally, the inclination of the sieve is fixed after it is installed.
(4) The influence of the shape of the mesh on the screening process. The rectangular sieve holes easily pass through the strip-shaped particles, and the circular sieve holes easily pass through the square particles. When the nominal pore size of the sieve openings is the same, the size of the sieved product passing through the sieve openings of various shapes is different. The shape of the screen surface also has a certain influence on the screening efficiency. The multi-stage slope screen has higher efficiency than the plane screen.
With the improvement of the requirements for coal products, the vibrating screen screening is also developing with a large amount of processing and finer particle size, and the demand for vibrating screens is also increasing. Therefore, in order to make the vibrating screen play a better role in the coal preparation industry, Sanjiang Electric Co., Ltd. has been continuously improving and innovating the technology to produce better products to better serve the production.