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Table 4 Overflow particle size correction coefficient Kβ value
Selection and application of spiral classifier
Conventional mineral grading plant equipment spiral classifier, hydrocyclone, a hydraulic classifier, a fine sieve. The choice is mainly based on the required processing capacity, material properties, grading granularity, equipment configuration conditions and equipment performance.
First, the choice of spiral classifier
The spiral classifier is widely used in the classification of the grinding circuit of the concentrator and the operations of washing, de-sludge and dewatering. Its main advantages are simple structure, reliable operation and convenient operation. It can be connected with the mill in the closed-circuit grinding circuit. Compared with the hydrocyclone, the power consumption is lower. The main disadvantages are low classification efficiency, heavy equipment and large floor space. Due to the limitation of equipment specifications and production capacity, it is generally impossible to form a closed circuit with a ball mill with a specification above Ñ„3.6m.
The spiral classifier is structurally divided into two types: sorghum type and submerged type. The high-grade classifier is suitable for coarse-grain classification. The maximum particle size of the overflow is generally 0.4~0.15mm. The sunken classifier is suitable for fine-grain classification. The maximum particle size of the overflow is generally below 0.2mm.
Second, the calculation of the spiral classifier
The processing capacity of the spiral classifier is mainly related to the equipment type, specification, installation angle, overflow particle size, overflow concentration, material density and other factors.
A commonly used calculation methods and formulas
(1) The specification of a spiral classifier is known, and the amount of treatment by the amount of solids in the overflow is calculated.
Sorghum spiral classifier: q 1 =mK 1 K 2 (94D 2 +16D)/24 (1)
Submerged spiral classifier: q 1 =mK 1 K' 2 (75D 2 +10D)/24 (2)
Where q 1 - the amount of treatment by weight of solids in the overflow, t / h;
M——the number of spirals of the classifier;
D——the diameter of the classifier spiral, m;
K 1 - ore density correction factor, see Table 1 or calculated as K 1 =1+0.5 (Ï-2.7);
K 2 , K′ 2 —— graded particle size correction coefficient, see Table 2;
Ρ——ore density, t/m 3 .
Table 1 ore density correction coefficient K 1 value
Ore density Ï/t·m -3
2.00
2.30
2.50
2.70
2.80
3.00
3.30
3.35
4.00
4.50
K1
0.65
0.80
0.90
1.00
1.05
1.15
1.30
1.40
1.65
1.90
Table 2 Classification granularity correction coefficient K 2 , K′ 2 values
Graded overflow particle size (d 95 )/mm
1.17
0.83
0.59
0.42
0.30
0.20
0.15
0.10
0.074
0.061
0.053
0.044
K 2
K' 2
2.50
2.37
2.19
1.96
1.71
1.41
3.00
1.00
2.30
0.67
1.61
0.46
1.00
0.72
0.55
0.36
A spiral classifier with a diameter D > 1200 mm can also be calculated by the following formula:
Sorghum spiral classifier: q 1 =mK 1 K 2 (65D 2 +74D-27.5)/24 (3)
Submerged spiral classifier: q 1 =mK 1 K' 2 (50D 2 +50D-18)/24 (4)
(2) It is known that the processing amount of the solid weight in the overflow is calculated, and the specification of the spiral classifier is calculated.
Approximate treatment of equations (1) and (2) yields the following formula for calculating the diameter of the spiral:
(3) After calculation by the above method, it is generally necessary to check the amount of solids in the return sand according to the following:
q 2 =135mK 1 nD 3 /24 (7)
Where q 2 - the amount of solids in the mass of the returned sand, t / h;
n - the number of revolutions, r / min;
The remaining version number - the same as before. [next]
B The calculation formula of the former Soviet Union Razumov et al., the “Design of the Concentrator†(1982 edition), which is waiting for the Razmo House, gives the following formula for the calculation of the sorghum spiral classifier.
(1) The amount of treatment q 1 based on the weight of solids in the overflow:
q 1 = 4.55mKaK β K Ï KcKsD 1.765 (8)
Where K a is the correction coefficient of the installation angle of the bottom of the classifier, see Table 3;
K β -- the overflow particle size correction factor, see Table 4;
K Ï â€”â€” grading material density correction coefficient, when density production Ï=2.2~5.0, K Ï =Ï/2.7;
K c ——overflow concentration correction factor, see Table 5;
K s -- the mud content coefficient of the graded material. When the mud content is high, Ks=0.75~0.8; when the mud content is medium, Ks=1.0; when the mud content is low, Ks=1.1~1.2;
q, m, D - the meaning of the symbol is the same as before.
Table 3: Spiral classifier groove bottom inclination angle a correction coefficient Ka value
Inclination a/(°)
14
15
16
17
18
19
20
Ka value
1.12
1.10
1.06
1.03
1
0.97
0.94
Overflow particle size (d 95 )/mm
1.17
0.83
0.59
0.42
0.3
0.21
0.15
0.10
0.074
Gradient content in overflow /%
-0.074mm
17
twenty three
31
41
53
65
78
88
95
-0.045mm
11
15
20
27
36
45
50
72
83
Standard liquid to solid ratio (by weight) R 2.7
1.3
1.5
1.6
1.8
2.0
2.33
4.0
4.5
5.06
Overflow concentration /%
43
40
38
36
33
30
20
18
16.5
Coefficient Kβ
2.50
2.37
2.19
1.96
1.70
1.41
1.0
0.67
0.46
Table 5 Overflow concentration correction coefficient Kc value
Ore density
Ï/t·m -3
R T /R 2.7 ratio
0.4
0.6
0.8
1.0
1.2
1.5
2.7
3.0
3.3
3.5
4.0
4.5
0.6
0.63
0.66
0.68
0.73
0.78
0.73
0.77
0.82
0.85
0.92
1.00
0.86
0.93
0.98
1.02
1.12
1.22
1.00
1.07
1.15
1.20
1.32
1.45
1.13
1.23
1.311
1.37
1.52
1.66
1.33
1.44
1.55
1.63
1.81
1.99
Note: 1.R T - the classifier overflow liquid to solid ratio required for the process conditions;
2.R 2.7 - standard liquid to solid ratio, see Table 4.
(2) The treatment amount according to the weight of solids in the return sand: q 2 = 5.45mD 2 nKaÏ/2.7 (9)
The meaning in the formula is the same as before.