In the actual beneficiation plant, many mine owners have encountered the problem that the vibrating screen fail to reach the predetermined processing capacity and the screening efficiency of the vibrating screen is low. As an important vibrating screen, the screening efficiency of the vibrating screen will directly affect the quality and investment cost of the final product. When it comes to the screening efficiency of vibrating screen, many factors will make a difference, such as material properties, equipment structure and various performance parameters.
Irrespective of the hard factors of material properties and equipment structure, we mainly analyze the influence of various parameter indexes on the efficiency of the vibrating screen, including amplitude, vibration frequency, vibration direction angle, screen tilt angle and the throwing angle, these are the reference for the vibrating screen operation.
Use the table of contents below to navigate through the guide:
Generally, the larger the vibrating screen model, the greater the vibrating screen amplitude chosen. Because the amplitude of the vibrating screen is larger, the screen plugging phenomenon will be less, which is more conducive to the screening and stratification of the ore, and obtain better screening production capacity. However, it should be noted that if the amplitude of the vibrating screen is too large, strong vibration will cause greater damage to the vibrating screen itself. In general, the amplitude of the vibrating screen is chosen by the ore size and nature. When the minerals are of small particle sizes, moist and also have a certain viscosity, we need to use low frequency and large amplitude. In Addition, amplitudes and frequencies vary in the different screening stage. For example, low frequency and large amplitude are normally used in screening operation before mineral beneficiation; while high frequency and small amplitude will be applied in dewatering and de-media operation.
The vibration frequency has a direct effect on the beating state of the ore particles on the screen surface. Taking the high-frequency vibrating screen as an example, its high frequency well destroys the tension of the slurry surface, causing the fine-grained material to oscillate at a high speed on the screen surface, accelerating the separation of useful minerals, and increasing the material and sieve smaller than the separation granularity. The probability of screen pore contact, thus creating a good screening condition. Excessive or too low vibration frequencies of the vibrating screen are not beneficial for screening efficiency. According to research, regardless of the screening operation of the vibrating screen, the vibration frequency is maintained at 850-1000 beats/min is the best choice. If the frequency is too low, the weight of the eccentric mass of the vibrator of the vibrating screen will increase with the same vibration intensity, which is not economical. Under the same vibration intensity of the vibrating screen, the higher frequency will greatly affect the running speed of the ore, which means reduced processing power. Therefore, the vibration frequency of the vibrating screen is not arbitrarily adjusted, and must be adjusted to the appropriate range according to the actual conditions of the plant, in order to make the vibrating screen perform optimally.
The inclined angle of the vibrating screen refers to the angle between the screen surface and the horizontal plane, and the angle of the vibrating screen is closely related to the processing capacity of the vibrating screen and the screening efficiency of the vibrating screen. When the inclination angle of the screen surface is increased, the movement speed of the ore particles on the screen surface becomes faster, and the treatment capacity increases accordingly, but at the same time, the residence time of the ore particles on the screen surface is correspondingly shorter, thereby affecting screening efficiency of the vibrating screen and vice versa.
Generally, ideal screening efficiency of the vibrating screen can be achieved with a tilt angle range between 5° to 25°. Of course, there will be some differences between different models and screening operations. When the ore particles are above 50mm, the screen inclination angle of the linear vibrating screen is usually maintained at 5° to 10°; and when the ore particles are below 40mm, the screen tilt angle is 0°.
The vibration direction angle mentioned here refers to the angle between the direction of the screening motion and the screen surface, and is generally expressed by β. When determining the direction of the vibration direction of the vibrating screen, the primary consideration is the nature of the sieved ore. For ore with high density or finer size and easy to pulverize, the vibration direction angle of the vibrating screen should be large; and for those ores with large water content, strong viscosity or wear resistance, the vibration direction angle of the vibrating screen should be small. In actual production, most linear vibrating screen use 30°, 45° and 60° vibration direction angles. This direction angle of the vibrating screen not only can better adapt to various screening performance, but also obtain the best moving speed and screening efficiency; and the vibrating direction of the circular vibrating screen is 90°. Therefore, the circular vibrating screen needs to be installed obliquely, otherwise the mineral will not move forward.
According to the screening theory and practice, the size and strength of the vibrating screen throwing angle have a direct impact on the screening work. When the ore's projectile strength increases, the inertial force is also increased, and the ore is thrown higher, which is more conducive to the ore permeable. However, if the projectile strength is too large, it will inevitably affect the screen box and cause it to be damaged prematurely. Therefore, in the actual beneficiation plant, the size and strength of the projectile angle should consider the structural strength factor of the vibrating screen box.
In actual use, there will be some differences between different types of vibrating screens, which is unavoidable. It is recommended that all mine owners consult professional vibrating screen manufacturers before plant operation to adjust the vibrating screens according to the actual beneficiation plant conditions, in order to achieve the desired performance of the vibrating screen and obtain the best screening efficiency.