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Selection and application of vibrating screen
Beneficiation plant screening equipment commonly used types are: vibrating screen, grate, roller screen, fine screen and a cylindrical sieve. The main factors considered in the selection of screening equipment are material characteristics (such as maximum particle size, material content under the sieve level, material density, material moisture and mud content, etc.), beneficiation process requirements, and screening equipment performance and application conditions.
The vibrating screen has different movement trajectories, and can be divided into two categories: circular motion and linear motion. The main types, performance, applicable conditions and characteristics of domestic vibrating screens are shown in Table 1.
Table 1 Main models, performance, applicable conditions and characteristics of vibrating screen
Motion track
Shaker name
model
Working area / m 2
Maximum feed size / mm
Screen size / mm
Applicable conditions
Circular motion
Circular vibrating screen
YA
YAH
(heavy)
DYS
(large)
4~14
22~26
≤200
≤400
≤300
6~50
30~150
Large block and medium and fine grain material bulk material screening; there are seat type, hanging type, single layer, double layer; reasonable structure and vibration parameters; maximum treatment, high screening efficiency, convenient maintenance, low noise, application Wide range; YA type is the introduction of American R·S company technology
Circular motion
Custom center
Vibrating screen
SZZ
0.29~6.48
40~150
1~50
Medium and fine grain material screening; there are seat type, hanging test, single layer, double layer; simple structure, convenient adjustment, strong vibration of screen surface, material not easy to block sieve hole, high screening efficiency, but not stable enough, amplitude is affected Greater impact on the amount of minerals
Heavy vibrating screen
H
6~10
300~400
25~150;
20~50
Large block, high-density material screening; solid structure, can withstand large impact loads, screen is bar
Inertial vibrating screen
SZ
3.1~4.5
100
6~40
Medium and fine grain material screening; there are seat type, hanging type, single layer, double layer; the vibrator is placed on the screen frame with the screen frame moving up and down, the center of the pulley is moving in space, the belt is tight when tight, and the motor load is not even enough. Affect the life, the screening efficiency is unstable, and the variation of the ore amount affects the amplitude.
Single-axis vibrating screen
DD
ZD
0.7~1.6
1.6~6.5
100
1~25
6~50
The medium and fine particles are sieved; there are seat type, hanging type, single layer and double layer; the structure is simple, the movement is stable, and the work is reliable.
Linear motion
Linear vibrating screen
ZKX
DZS
(Big)
3~14
17~28
100~300
300
0.5~13
3~80
Screening, dehydration and de-intermediation of bulk and medium- and fine-grained materials; single layer and double layer, ZKX type is introduced to American R·S company technology
Vibrating fine screen
ZKBX
6.23~14.4
≤13
0.4~1.5
Grade fine materials, dehydration, mud, off-mediated; mainly used in metal ore grinding and classification to the first paragraph of plant operations
Straight line equal thickness screen
ZD
7.7
15
300
150
6~25
6~13
The bulk and medium- and fine-grained materials are classified, and the screen surface adopts a fold line of different inclination angles, and the thickness of the material layer from the feed end to the discharge end is constant or increasing. The moving speed of the material on the screen surface is decreasing, it is not easy to block the screen hole, and the processing capacity is large, but the installation height is large.
Resonance screen
GL
6
15
30
100
150
300
13 (upper punch)
0.5
(lower seam)
Medium and fine-grained material grading, de-sludge, de-intermediation; single layer, double layer, stable work, small dynamic load, compact structure, large processing capacity, high screening efficiency, but high precision in manufacturing and installation. Uniform material requirements
First, the calculation of the amount of vibrating screen processing
Common empirical formula
q=φAq 0 Ï s K 1 K 2 K 3 K 4 K 5 K 6 K 7 K 8 (1)
Where q - the amount of processing of the vibrating screen, t / h;
A——the nominal area of ​​the screen surface, m 2 ;
Φ——effective screening area coefficient: the upper sieve surface of single or multi-layer sieve φ=0.9~0.8; the lower sieve surface of double-layer sieve φ=0.7~0.6;
q 0 —— the volumetric processing capacity per unit sieve area, m 3 /(m 2 ·h), approximated according to the value of Table (2) or the following formula: fine particle sieving (screening a<3mm) q 0 = 41ga/0.08; medium sieve (a=4~40mm)q 0 =24lga/1.74; coarse sieve (a>40mm) q 0 =51lga/9.15;
Ï s - the same meaning as before;
K 1 ~ K 8 - the correction factor of the influencing factors, see Table (3).
Table 2 vibrating screen unit area volume processing amount q 0 value
Screen size / mm
0.15
0.2
0.3
0.5
0.8
1
2
3
4
5
6
8
q 0 /m 3 ·m -2 ·h -1
1.1
1.6
2.3
3.2
4.0
4.4
5.6
6.3
8.7
11.0
12.9
15.9
Screen size / mm
10
12
14
16
20
25
30
40
50
60
80
100
q 0 /m 3 ·m -2 ·h -1
18.2
20.1
21.7
23.1
25.4
27.8
29.5
32.6
37.6
41.6
48.0
53.0
Table 3 K 1 ~ K 8 correction factor
influences
factor
Screening conditions and coefficient values
Fine grain
influences
Less than half the size of the end hole in the feedstock
Particle content /%
<10
10
20
30
40
50
60
70
80
90
K 1
0.2
0.4
0.6
0.8
1.0
1.2
1.4
1.6
1.8
2.0
Coarse grain
influences
Particle content greater than mesh size in the feedstock /%
<10
10
20
30
40
50
60
70
80
90
K 2
0.91
0.94
0.97
1.03
1.09
1.18
1.38
1.55
2.00
3.36
Screening
effectiveness
End efficiency E/%
85
87.5
90
92
92.5
93
94
95
96
K 3 = (100-E) / 8
1.87
1.56
1.25
1.00
0.94
0.88
0.75
0.63
0.50
Material type and particle shape
Material type and particle shape
Broken ore
Round particles (sea gravel)
coal
K 4
1.0
1.25
1.50
materials
humidity
Screen size / mm
<25
>25
Material humidity
Dry ore
Wet ore
Bonded ore
K 5
1.00
0.25~0.75
0.20~0.60
0.90~1.00
Screening
the way
Screen size / mm
<25
>25
Screening method
Dry sieve
Wet screen (spray water)
K 6
1.00
1.25~1.40
1.00
Sieve motion parameters
2 m value 1
6000
8000
10000
12000
K 7
0.65~0.70
0.75~0.80
0.85~0.90
0.95~1.00
Screen surface and mesh shape
Screen type
Woven screen
Punching sieve
Rubber sieve
Sieve shape
Square
rectangle
Square
Round
Square
Slot
K 8
1.00
1.20
0.85
0.70
0.90
1.20
1r-sieve amplitude (single amplitude); mm; n-number of revolutions of the sieve axis, r/min.[next]
The total area of ​​the required vibrating screen is calculated as follows:
Where A t - the total area of ​​the required vibrating screen, m 2 ;
q t —— total amount of vibrating screen, t/h;
Other symbols are the same as (1).
After calculating the total area of ​​the sieve, the specifications and number of sieves can be determined according to the process conditions and equipment configuration.
The amount of the double-layer or multi-layer vibrating screen should be calculated layer by layer. After the area of ​​each layer of sieve is determined, the maximum size and number of sieves are selected.
The calculation of the upper sieve area of ​​the double-layer vibrating screen is the same as that of the single-layer vibrating screen. The product under the upper sieve is the feed of the lower sieve. The lower sieve also uses formulas (1) and (2) to calculate the throughput and screen area. In order to determine the correction factors K 1 , K 2 and K 3 in the formula, it is necessary to determine the screening efficiency of the lower sieve (for example, if there is a requirement for the content of the sieve under the sieve on the lower sieve, it must be calculated by formula (3)); (4) and (5) respectively calculate the content of the semi-particles smaller than the mesh size and the excessively large particle content larger than the mesh size in the lower sieve feed.
Where E 2 - lower sieve screening efficiency, %;
β(1,-d 2 )——the content of the lower sieve level in the lower sieve, expressed in decimals;
β(2,-d 2 )—The allowable content of the sub-screen grade in the product on the lower sieve, expressed as a decimal.
Wherein β(1,-d 2 /2)——the content of the particles in the lower sieve given to the ore, which is less than half the size of the mesh, expressed in decimals;
β(1,+d 2 )——the content of oversized particles larger than the mesh in the lower sieve feed, expressed in decimals;
β(-d 1 ), β(-d 2 ), β(-d 2 /2)—in the upper sieve feed, the content of sieve fractions smaller than d 1 , d 2 , and d 2 /2 is expressed as a decimal ;
E 1 - the screening efficiency of the upper sieve in terms of -d 1 particle size, expressed in decimals;
d 1 , d 1 —— the size of the upper sieve and the lower sieve mesh, mm.
The yield of entering the lower sieve according to the original ore meter is calculated by formula (6):
γ=β(-d 1 )E 1 (6)
Where γ——the yield of entering the lower sieve according to the original ore, %;
β(-d 1 )E 1 - is the same as (5).
The upper sieve screening efficiency in terms of d 2 /2 and d 2 fractions is generally close to one.
The double-layer sieve can be used as a single-layer sieve to increase the amount of sieve treatment and protect the lower screen and extend the service life of the lower screen. However, when the final sieve has a grain size of more than 50%, more difficult sieve particles or high ore water content, the double layer sieve should not be used as a single layer sieve. When the double-layer sieve is used as a single-layer sieve, the upper sieve hole must be correctly selected to solve the problem of load distribution of the upper and lower screen surfaces. The size of the upper sieve mesh is determined according to the grain size characteristics of the ore. At the same time, it is necessary to consider the requirement that the amount of the upper sieve is 55%~65% of the ore supply. The q 01 value can also be roughly calculated according to formula (7), and then the corresponding mesh size can be found from Table 2.
Where q 01 - the unit sieve volume handling capacity of the corresponding sieve size of the upper sieve, m 3 /(m 2 ·h);
q 02 —— the unit sieve volume handling capacity of the corresponding sieve size of the lower sieve, m 3 /(m 2 ·h);
Β—the content of the upper sieve that is smaller than the upper sieve level in the upper sieve, expressed in decimals;
E 1 - the same formula (4).
After determining the mesh size according to the above method, the upper and lower mesh areas are respectively calculated. If the difference between the two is large, the upper mesh size should be adjusted until the two are close.
Second, the shape of the vibrating screen and the size of the product under the sieve
The size of the undersize product is related to the shape of the mesh. The maximum particle size d max (mm) of the different shape mesh d(mm) can be calculated according to the formula d max =K a , and K is the mesh shape coefficient, as shown in Table 4.
Table 4 mesh shape factor K
Sieve shape
Round
Square
rectangle
Long strip
K
0.8
0.9
1.15~1.25 1
1.2~1.7 1
1 pair of slat-like ore takes a large value.