Design and Application of Banana Screen in Coal Preparation Plants
Introduction
In recent years, with the development of coal processing technology, vibrating screens, due to their high efficiency, high reliability, and strong batch processing capacity, have been applied in coal processing operations such as classification, dehydration, and dewatering. As a type of vibrating screen, banana screen, when used in coal processing plants, not only reduces the purchase cost and subsequent management expenses, but also saves the floor area of the factory. Moreover, banana screen, with its high efficiency, large processing capacity, and high reliability, is widely used in the coal processing industry. This article takes a single-layer banana screen as an example to explain its application in coal processing plants.
Analysis of the single-layer banana screen structure
The single-layer banana screen is a 5-angle screen surface high-efficiency linear vibrating screen. This equipment is used for desliming of raw coal, desilting of clean coal, and desilting of gangue in coal preparation plants. It has been optimized through the application of the principle of equal thickness screening and the theory of linear vibration. The vibration parameters such as amplitude, frequency, and excitation force are set appropriately and reasonably. The side supports, main beams, cross beams, and various structural components have high rigidity, strength, and long service life.
A pair of box-type vibration exciter is installed on the main beam of the exciter, and is connected to the driving mechanism through coupling and spline transmission shafts. It reliably and smoothly transmits power and linear vibration force, causing the screen body to vibrate the materials at the predetermined frequency, causing the materials to be excited and separated layer by layer and advancing forward. From the material inlet to the discharge outlet, the screening treatment is carried out through the screen surface.
The screen body is mainly composed of side supports, cross beams, excitation beams, lifting beams, and back plates. Each component is precisely manufactured using high-quality structural steel. The cross beams, excitation beams, and lifting beams are all subjected to heat treatment after welding. The screening body is machined using high-precision CNC machines. Then, high-quality imported steel is selected and an advanced assembly process is used to rivet the screen body. The side plates have no weld seams, and the cross beams and excitation beams have large cross-sectional coefficients and high rigidity.
The surface of the cross beams is coated with polyurethane wear-resistant material, and the surface of the screen body is treated to Sa2.5 level and then sprayed with polyester protective paint. Each process of the screen body manufacturing is strictly inspected and controlled. The screen body structure has been optimized for design, with a light weight. The screen body can avoid cracking and wear of various components under high-load and high-frequency vibration conditions, and has higher fatigue resistance, reliability, and service life.
Design of single-layer banana screen structure
Considering the material properties and efficiency, reliability and other factors applicable to banana screen, in order to meet the above requirements, the structure form of banana screen needs to be determined first. The width of the screen surface of banana screen is 3.6m, and the length is 6.1m. The screen surface of banana screen is composed of multiple sections, and its shape is concave arc; the structure form of the screen plate is an elastic rotating rod structure, and its driving path is dual-side motor – belt – transmission device.
Design of the screen frame
In order to ensure that banana screen can meet the requirements of impact, bending and welding in actual production, the screen frame needs to have certain anti-wear, anti-fatigue and corrosion resistance properties. In summary, on the basis of ensuring that banana screen can normally perform its function, there are also higher reliability requirements. Therefore, the banana screen screen frame uses low-alloy special plates. Through simulation analysis, using this low-alloy special plate can meet the actual production requirements. In addition, using this low-alloy plate can also reduce the weight of banana screen to a certain extent.
Selection of exciter
The type of exciter used in traditional banana screen is self-synchronous and forced synchronous vibrationers. Practice shows that using synchronous exciter causes greater destructive force as the length and width of the screen frame increase, resulting in a sharp decline in the lifespan of banana screen. The exciter is installed on the upper beam of the screen box, and the active shaft and the driven shaft of the exciter are both installed inside the screen box. Equal mass eccentric blocks are installed on both the active shaft and the driven shaft to generate a large centrifugal force when rotating in the opposite direction.
Screen surface of banana screen
The screen surface is an important component of banana screen and the most easily damaged part. Therefore, the quality of the screen surface directly plays a decisive role in the production cost. Banana screen has strict requirements for its own screen surface, and must select high-capacity, high-maintenance material, and effectively ensure its corrosion resistance.
To truly meet the actual needs of banana screen for the screen mesh, the screen mesh uses steel frame polyurethane cast screen mesh. While meeting the high-capacity requirements, it significantly extends the service life of banana screen. To prevent the screen plate from generating secondary vibration, special materials are used to compress the structure (polyurethane) around it, effectively ensuring the service life of banana screen screen mesh, and providing a strong basic guarantee for banana screen screening work.
Conclusion
This article takes the single-layer banana screen as an example, and discusses its structure analysis and the design of each core component. It clarifies the structural parameters and component selection schemes suitable for the production conditions of coal preparation plants. By using low-alloy special plates to make the screen frame and adopting eccentric block exciter combined with steel skeleton polyurethane poured screen mesh, the designed single-layer banana screen can not only meet the production requirements of coal classification, dehydration, and desilting in coal preparation plants, but also effectively reduce the overall weight of the equipment, extend the service life of the equipment, and reduce production maintenance costs and the floor area of the plant.
