Kinematic parameters and process parameters of the vibrating screen

1. Kinematic parameters of the vibrating screen
(1) Amplitude A. Generally, different vibrating screen amplitudes are selected according to the following conditions:
Circular vibrating screen used for pre-screening A=2.5~3.5mm
Circular vibrating screen used for final screening A=3~4mm
Linear vibrating screen A=3.5~5.5mm
Resonance screen A=6~15mm
(2) The number of vibrations n. The number of vibrations of different vibrating screens can be roughly selected as follows:
Circular vibrating screen n=800~1200r/min
Linear vibrating screen n=700~900r/min
Resonance screen n=400~800s/min
(3) Slope angle α of the screen surface. The slope angle of the screen is related to the screening ability and efficiency. The larger the angle of inclination, the greater the screening capacity, but the lower the screening efficiency, and vice versa. The reasonable angle of the screen surface selected according to practical experience is generally as follows:
Circular vibrating screen for pre-screening α=15°~25°
Circular vibrating screen for final screening α=12.5°~20°
Linear vibrating screen or resonant screen for screening α=0°~10°
Linear vibrating screen or resonant screen for dehydration and desorption α=-50°~O°
(4) Vibration tilt angle β. The linear vibrating screen and the resonating screen are mounted substantially horizontally, and only the given angle of vibration is applied to move the screened material forward. The vibration tilt angle is large, the material throwing is high, and the screening efficiency is improved, which is suitable for difficult-to-screen materials. The vibration tilt angle is small, the material movement speed is fast, the screening ability is increased, and it is suitable for easy screening materials. The selection range of the vibration tilt angle is usually 30 ° ~ 65 °, currently used is 45 °, for difficult-to-screen materials such as gravel, coke , sinter, etc., up to 60 °.
(5) The moving speed of the material along the screen surface and the thickness of the material layer. The moving speed of the material along the screen surface is generally 0.12~0.4m/s, and the maximum is 1.2m/s. For the circular vibrating screen, the moving speed of the material along the screen surface has the following relationship with the inclined angle of the screen surface:
Screen angle of inclination 18° 20° 22° 25°
Movement speed of material along the screen surface (m/s) 0.305 0.41 0.51 0.61
The relationship between the thickness of the layer and the size a of the mesh can be calculated according to the thickness ≤ (3~4) α. The relationship between the thickness of the layer and the average particle size D 0 of the material on the sieve can be calculated according to the thickness ≈ (2~2.5) D 0 .
2. Process parameters of the vibrating screen
(1) Screen length and width. When the thickness of the layer is constant, the width of the screen directly affects the productivity of the sieve, and its length directly affects the screening efficiency. Generally, the sieve vibrating screen of the mine vibrating screen is generally about 4 m in length and has an aspect ratio of about 2. The coal vibrating screen used for final classification, dewatering and de-intermediation has a screen length of about 6 m and an aspect ratio of about 1.5 to 2.5. 25米。 The width of the sieve may not be too wide, the minimum width may be 1. 25m. The vibrating screen for mining is increased into a series of screen widths at intervals of 0.3 m, and the vibrating screen for coal is increased to a series of screen widths at intervals of 0.25 m.
(2) Productivity calculation. The productivity of vibrating screens is generally calculated based on the amount of feed. There are usually two calculation methods:
1) Flow method
Q=3600Bhυγ(t/h)
Where, B - screen width (m); h - sieve fabric layer thickness (m); υ - material movement average speed (m / s); γ - material loose density (t / m 3 ).
2) Average method
Productivity calculation formula for coal vibrating screen:
Q=Fq(t/h)
Where, F - screen area (m 2 ); q - unit screen area productivity (t / m 2 · h), the values ​​are listed in Table 1. [next]
Table 1 Unit sieve area productivity
Job name
Grading
Dehydration
Decoupling
Screen size / mm
100
80
50
25
13
End coal
Slime
Lump coal
End coal
q/(t/m 2 ·h)
110
90
60
30
12~17
7
2
7~9
3.5~4.5
Productivity calculation formula for mine vibrating screen:
Q=FqγKLMNOP(t/h)
Where F is the working area of ​​the screen surface (m 2 ); q is the productivity of the unit screen area (m 3 /m 2 .h), the values ​​of which are listed in Table 2; γ——the bulk density of the material (t/m 3 ); K, L, M, N, 0, P - correction factors are listed in Table 3.
Table 2 Unit sieve area productivity
Screen size / mm
q value / (m 3 /m 2 ·h)
Screen size / mm
q value / (m 3 /m 2 ·h)
Screen size / mm
q value / (m 3 /m 2 ·h)
0.16
0.2
0.3
0.4
0.6
0.8
1.17
1.9
2.2
2.5
2.8
3.2
3.7
4.4
2
3.15
5
8
10
16
20
5.5
7
11
17
19
25.5
28
25
31.5
40
50
80
100
31
34
38
42
56
63
(3) Screening efficiency. During sieving, for some reasons, a part of the fine-grained material fails to pass through the sieve hole and is mixed with the coarse-grained grade and is discharged with the product on the sieve. Therefore, the screening efficiency refers to the weight of the actually obtained sieved product and the person. The ratio of the weight of the material contained in the sieve material to the size of the mesh. Screening efficiency is generally expressed as a percentage and is usually calculated as follows:

In the formula, α—the percentage of the content of the sieved product in the feedstock; β—the percentage of the sieve fraction in the product on the sieve.
By sieving the feedstock and the product on the sieve, the fractional content α and β of the sieve can be calculated, so that the sieve efficiency E can be calculated.
In screening operations, screening efficiency is a measure of the quality of the screening process and is therefore as important as the productivity of the indicator of the number of screening processes. In actual industrial production, screening efficiency and material particle size characteristics, humidity, mesh shape, screen surface tilt angle, screen surface type, screen surface length and width, screen wear condition, screen surface motion characteristics, productivity, and feedstock Whether it is uniform and the amount of feed is related to many factors.

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