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In the factory production, many mine owners have encountered the problem of low screening efficiency of the vibrating screen. As an important screening equipment, vibrating screen will directly affect the quality and investment cost of the final product.
Generally, the screening efficiency of vibrating screen is related to many factors, such as material properties, equipment structure and various performance parameters. In addition to the hard factors of material properties and equipment structure, we mainly start from the performance parameters of the vibrating screen, and analyze in detail the influence of amplitude, vibration frequency, vibration direction angle, screen surface inclination angle and projectile angle on its efficiency, so as to provide reference for shaker operators.
Generally, the bigger the vibrating screen type, the choice of amplitude. Because the amplitude of the vibrating screen is larger, the phenomenon of screen hole blockage will be less, which is more conducive to the screening of ore stratification, to obtain better screening production capacity. But note that if the size of the vibrating screen is too big, strong vibration will cause big damage of vibrating screen itself. The vibration screen amplitude selection is usually determined by the ore size and properties, when the ore particles are small, wet and also have a certain viscosity, we need to use low frequency, large amplitude.
In addition, the corresponding amplitudes and frequencies should be selected for different screening stages. For example, screening operations before selection generally use low frequency, large amplitude of vibration, dehydration, deintermediation operations to use high frequency, small amplitude.
The vibration frequency has direct influence on the pulsation state of ore particles on the screen surface. Taking high frequency vibrating screen as an example, its high frequency can well break the tension of pulp surface, make fine material oscillate at high speed on the screen surface, accelerate the separation of useful minerals, and increase the probability of contact between material with less than separated particle size and sieve hole, thus creating good screening conditions. Too high or too low vibration frequency is not beneficial to screening efficiency.
According to the study, no matter what screening operation the shaker carries out, the vibration frequency is maintained at 850-1000 times/is an ideal choice. If the frequency is too low and the vibration intensity is the same, the weight of the eccentric block of the vibrator will increase accordingly, which is not economical enough. At the same vibration intensity, the higher frequency will greatly affect the running speed of the ore, which means that the processing capacity is reduced. Therefore, the vibration frequency is not adjusted at will, must be adjusted to the appropriate range according to the actual situation of the selection plant, in order to make the vibrating screen to play the ideal performance.
Screen slope Angle refers to the included Angle between screen surface and horizontal plane. The size of its Angle is closely related to the processing capacity and screening efficiency of the vibrating screen. When the inclination Angle of the screen surface increases, the movement speed of ore particles on the screen surface becomes faster, and the processing capacity increases accordingly. However, at the same time, the residence time of ore particles on the screen surface is correspondingly shorter, which affects the screening efficiency, and vice versa.
Vibrating screen Angle is according to the material used and the actual production needs. Horizontal vibrating screen is recommended for fine screening; If the granularity of screening material is large and the screening rate is good, the dip Angle of 5-10° can be adopted. If the particles are large and overdud, the range of 15° can be used. The reasonable range of shaker inclination is based on the uniform distribution of material particles. Installation inclination of different types of vibrating screen is different, the installation inclination of high frequency vibrating screen is about 30°, the general purpose vibrating screen inclination is 0-15°, and the vibrating screen for dehydration is the upward tilt of the discharge end (often said negative Angle).
The vibration direction Angle mentioned here refers to the included Angle between the screen motion direction and the screen surface, which is generally denoted by matrix. The first consideration in determining the direction of vibration is the nature of the ore being sifted. For high density or fine particle size, easy to crush the ore, the vibrating screen vibration direction Angle should be large; For those minerals with large water content, strong viscosity or abrasion resistance, the vibration direction Angle should be small.
In actual production, most linear vibrating screen adopt 30°, 45° and 60° vibration direction angle, which can not only better adapt to various screening performance, but also obtain better moving speed and screening efficiency; The vibration direction angle is 90°, so the round vibraitng screen needs to be installed at an angle, otherwise the minerals will not move forward.
According to the screening theory and practice, the size and strength of the throwing angle of the vibrating screen have direct influence on the screening of the ore on the screen surface. When the ore projectile strength increases, the inertial force is also larger, the ore can be thrown higher, more conducive to ore screening. However, too much projectile strength will inevitably affect the screen box, making it premature damage. Therefore, in the production practice of plant selection, the size and strength of the projection angle should consider the structural strength of the vibrating screen.
In the actual use of the process, different types of vibrating screen will certainly have some differences, this is inevitable. It is suggested that all mine owners look for equipment manufacturers with the overall qualification of the screening plant to purchase appropriate vibrating screen, and determine the value of each parameter according to the actual situation of the screening plant, so as to obtain the ideal screening efficiency of the vibrating screen.