D centrifugal force F c
When sorting on the drum type electric sorter, the centrifugal force F c is directly related to the rotational speed of the drum. This is the mechanical force that affects the sorting effect except for the electric power. The following formula indicates:
Where F c ——— centrifugal force, N;
m———mineral mass, kg;
V—the drum line speed, m/s;
R———bulk radius, m.
E Gravity F g
F g =mg (13)
Where m—the mass of the object (mineral), kg;
g———Gravity acceleration 9.8m/s 2
When the ore particles are sorted on the drum type electric sorter, the radial and tangential component forces of the gravity are changed with the angle of rotation. When starting to feed the drum, the direction of gravity is completely perpendicular to the drum surface. After the rotation of the crucible, the radial and tangential component forces constantly change. When turned to 180°, the direction is exactly opposite to the feeding.
In addition to the above five kinds of forces, there are also inter-molecular forces, the friction between the ore and the drum surface and the air resistance, but they are small compared to the above various forces, and can be ignored, only the fine particles are sorted. At the level, the forces between molecules must be considered.
According to the electric and mechanical forces of the ore particles on the drum surface, the conductivity is good, and the relationship is:
F 1 +F C >F 2 +F g (14)
Therefore, the ore particles will fall within the range of AB in Figure 1.17.
Non-conducting ore particles with poor conductivity, the relationship is:
F 1 +F 2 >F c +F g (15)
This will fall within the scope of the CD.
Medium-mineral with medium conductivity, the relationship is:
F c +F g >F 1 +F 2 (16)
This will fall within the BC range.
The interaction effect of the sorting voltage, the drum speed and the electrode structure is very significant. If the electrode structure is determined, the voltage and the speed of the interaction are very prominent, which is essentially the power F 1 F 2 in the above relationship. And the problem of centrifugal force F c , that is, how to choose and cooperate with the key issues. [next]
(4) The various forces that the ore particles are subjected to in the free fall electric sorter
In addition to the drum type, such a free fall type electric sorter is a more used electric sorting apparatus . The ore is first subjected to contact collision and friction or directly rubbed with the ore tank to obtain electric charge, and then enters the equipment for sorting.
If the effects of air friction and Coulomb force between adjacent particles are neglected, the ore particles are only affected by electricity and gravity, then the power F e =QE (17)
Gravity F g =mg (18)
The symbols and units are the same as above.
It can be seen from the above figure 10 that after the trigeminal is charged and charged, it is subjected to electric power and enters the X-axis after entering the electric field; it is dropped by the gravity along the Y-axis, so the above two equations can be written as
Where t————time, s o minus sign indicates the direction of the drop.
And Q=Σ σ s (21)
Where σ s ———the surface charge density on the ore particles after the frictional contact is charged, C/m 2 . Obviously the initial velocity and displacement of the ore particles are zero, and the movement along the X axis due to electricity will be 19 After the integral is obtained:
Under normal circumstances, the processing particle size of this electric sorter is medium-grained, that is, 48-60 mesh. According to the particle size and density, the m value of the ore particles can be obtained, so that Q/m≈9×10 can be obtained. -6 . Coulomb / kg. The electric field strength E of this electric sorter is 4 × 10 5 volt / m, substituted into 22 to get X = 1.8t 2 (24)
If the drop height is 0.5 m, it is sufficient to obtain X = 0.18 m from 24 and 25. The X value is the distance from the center line (the position at the time of falling), so that the lateral width of the entire device is about 0.36 m. Therefore, when sorting the particle size, the height of the device is 0.5 m and the width is 0.36 m, which can meet the requirements, and the sorting fine particles should be appropriately changed.
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