The Screening Efficiency Of The Banana Screen In Coal Mining

Introduction

When traditional screening equipment and methods are confronted with complex and variable coal, the coal with high moisture content and high viscosity is prone to clogging the screen holes, resulting in the interruption of the screening process and a reduction in output. The screening accuracy of fine-grained coal is difficult to guarantee, and a large amount of qualified fine-grained coal is mixed into coarse-grained products, resulting in resource waste and economic losses. The processing capacity of conventional screening equipment is limited and is difficult to meet the demands of large-scale production in modern coal mines. As an innovative screening device, Banana Screen, with its unique design and outstanding performance, provides new ideas and methods for solving the problem of screening efficiency in coal mines and has gradually been widely applied in the coal industry.

Unique design of Banana Screen

Banana Screen structure

The Screen surface of Banana Screen is not a single planar structure, but is ingeniously combined by multiple screen sections with different inclination angles. From the feeding end to the discharging end, the inclination Angle of the screen surface shows a changing trend from large to small, and the overall shape is just like a curved banana, which is highly recognizable. This unique geometric structure embodies a sophisticated design concept. In terms of space utilization, Banana Screen has demonstrated a huge advantage. Compared with the traditional horizontal Screen surface or single-inclination screen surface equipment, the “banana-shaped” structure of Banana Screen can achieve a longer screening path in a limited space.

The large-inclination-angle feeding end enables the material to quickly gain a large initial velocity when entering the screen surface, rapidly disperse and initially stratify, laying a good foundation for the subsequent screening process. The small-angled discharge end provides sufficient residence time for materials close to the screening particle size, ensuring that these key materials can fully pass through the screen and improving the screening accuracy.

Screening effect

When coal enters the screen surface from the feeding end, the larger inclination Angle endows the material with a higher movement speed. Under the action of gravity and inertia, it will slide forward rapidly. Meanwhile, due to the vibration of the screen surface, the material will be thrown up and quickly spread out, achieving rapid stratification. Large and small particle materials are initially separated during the rapid movement, and small particle materials can approach the screen surface more quickly.

As the material moves towards the middle section, the inclination Angle of the screen surface gradually decreases, and the movement speed of the material also slows down accordingly. The thickness of the material layer is relatively stable, allowing fine-grained materials more time to undergo sieving. At this stage, the movement of the material on the screen surface is more stable, allowing it to fully contact the screen mesh and increasing the chance of passing through the screen.

At the discharge end, the inclination Angle of the screen surface is the smallest, and the movement speed of the material is the slowest. The low-speed movement and longer residence time at the discharge end can maximize the screening rate of critical particles, ensure the accuracy of screening, and reduce the waste of resources. Through the synergistic effect of different inclination angles at the feeding end, the middle section and the discharging end, Banana Screen optimizes the movement state of the materials, thereby significantly improving the screening effect and providing a strong guarantee for the precise classification of coal.

The key factors affecting screening efficiency

Amplitude, frequency and mode shape

The amplitude determines the height and force with which the material jumps on the screen surface, while the frequency controls the speed at which the material jumps. When the two achieve an appropriate match, the vibration intensity generated can keep the material in a loose state all the time. When dealing with highly viscous coal, a larger amplitude can subject the material to a greater impact force, thereby effectively overcoming the viscous force and preventing fine particles from aggregating. By appropriately increasing the frequency, the number of times the material comes into contact with the screen surface can be increased, enabling the material to pass through the screen more quickly.

Different vibration modes will also have a significant impact on the screening effect. The common vibration modes of Banana Screen include linear vibration and circular vibration, etc. Linear vibration causes the material to move back and forth in a straight line on the screen surface. This mode of motion is conducive to the rapid conveying and initial screening of the material. Circular vibration causes the material to move in a circular motion on the screen surface, increasing the length of the material’s movement trajectory on the screen surface. This enables the material to come into more thorough contact with the screen mesh, thereby enhancing the accuracy of screening.

Sieve holes and opening ratio

Banana Screen different-shaped sieve holes, such as square holes and rectangular holes, have obvious differences in the screening effect of coal. During the screening process, square-hole screen mesh can perform relatively regular classification of coal particles and is suitable for screening operations with strict requirements for particle size. Rectangular hole screens, on the other hand, have a higher screening efficiency and perform well when dealing with coal with large output and relatively low requirements for particle size accuracy.

If the size of the sieve holes is too large, it will cause a large amount of coarse-grained coal that does not meet the particle size requirements to pass through the sieve, reducing the product quality. Conversely, if the size of the sieve holes is too small, the screening efficiency will drop significantly and the output will decrease.

High opening rate screen plates, such as polyurethane or woven screen mesh, can provide a larger effective screening area, making it easier for coal particles to pass through the screen mesh and directly enhancing the screening capacity. Meanwhile, a high opening rate can also reduce the probability of screen hole clogging, as a larger screen hole area enables the material to pass through the screen more smoothly and is less likely to get clogged.

Uniformity of feeding

Uniform and continuous feeding can keep the thickness of the material layer on the screen surface stable, creating favorable conditions for the thorough screening of coal. When the materials are evenly distributed on the screen surface, each part of the materials can be fully screened, avoiding the problem of low screening efficiency caused by uneven material accumulation.

A stable thickness of the material layer also helps maintain the stability of the screening process. During the screening process, fluctuations in the thickness of the material layer will affect the movement state of the material on the screen surface and the screening effect. If the thickness of the material layer varies, it will cause unstable movement speed of the material, affecting the accuracy and efficiency of screening. By ensuring the uniformity of the feed and keeping the thickness of the material layer within an appropriate range at all times, the material can move smoothly on the screen surface, fully contact the screen mesh, increase the screening rate, and thus maintain a high screening efficiency.

The performance of Banana Screen in coal mines

Handle coal with high moisture content and high viscosity

When high-moisture and high-viscosity coal enters the feeding end of the Banana Screen, the large inclination Angle of the screen surface and the intense vibration endow the material with an extremely high movement speed, breaking the viscous constraints between coal particles and causing the material to disperse rapidly. Meanwhile, during the high-speed movement, the moisture on the surface of the coal is rapidly shed, achieving rapid dehydration. After rapid dehydration, the viscosity between the particles of coal is significantly reduced, making it looser. This creates favorable conditions for subsequent screening on the screen surface, effectively improving the screening efficiency and ensuring the efficient classification of coal.

Anti-clogging

On the Screen surface of the Banana Screen, the material undergoes a constantly changing motion state from the feeding end to the discharging end, always in the alternating process of acceleration and deceleration. At the feeding end, the accelerated movement of the material endows it with greater kinetic energy, enabling it to pass through the screen surface quickly. This reduces the residence time of the material on the screen surface and lowers the possibility of clogging. As the material moves towards the middle section and the discharge end, the inclination Angle of the screen surface gradually decreases, and the material speed slows down. However, at this time, the movement of the material on the screen surface becomes more stable and can fully contact the screen mesh.

In addition, the vibration characteristics of the Banana Screen also help prevent the clogging of the sieve holes. The appropriate amplitude and frequency cause the screen to generate high-frequency vibration. This vibration can promptly shake off the materials adhering to the edges of the screen holes, keeping the screen holes unobstructed.

Wear-resistant material

Common highly wear-resistant materials such as polyurethane and high manganese steel have excellent wear resistance. The wear resistance of polyurethane screen plates is 3 to 5 times that of ordinary metal screen plates. It can maintain the stability of the screen hole size during a long screening process, ensuring consistent screening accuracy. High manganese steel features high strength and excellent wear resistance. When subjected to the impact of coal, it can rapidly work harden and increase surface hardness, thereby resisting wear. Meanwhile, the screen plates made of highly wear-resistant materials have a long service life, reducing the replacement frequency of the screen plates, lowering the maintenance frequency and cost of banana screens, improving production efficiency, and laying a solid foundation for the continuous and stable production of coal mines.

Conclusion

In the practical application of coal mines, Banana Screen has the rapid dehydration ability when dealing with high-moisture and high-viscosity coal, excellent anti-clogging design, and long-term screening accuracy guaranteed by wear-resistant materials. In terms of technological innovation, further optimizing the vibration parameters and screen surface structure of the equipment to enhance the screening efficiency and accuracy will remain the focus of research.