The dry drum type magnetic separator has single drum type and double drum type, Its magnetic field strength has weak magnetic and medium magnetic, which is the main permanent magnetic separator.Dry drum magnetic separators are the perfect choice for the recovery of iron ore in dry areas such as Chile, Mongolia, the Southwest of the US, the Northwest region of China and many other dry or desert areas. The application of a dry drum separator lowers the beneficiation plants reliance on water and is environmental friendly. Depending on the magnetic intensity needed the magnet system can be either ferrite or rare earth.
2.Structure of dry drum type magnetic separator
The dry type permanent magnetic separator mainly includes frame, tank, the magnetic drum, the adjusting mechanism of the magnetic system, the transmission system and the ore dividing plate. The structure of the permanent magnetic dry magnetic separator is shown as figure1.
Figure1.dry type magnetic separator
1.feeding port;2.tank ;3.magnetic drum;4.frame5.magnetic production discharge port;6. Non magnetic production discharge port 7.ore dividing plate;8.motor& gear box;9.magnetic system adjusting roller.
The magnetic system has a fixed (including sector) fixed magnetic system and a full circular magnetic field magnetic system. There are two forms of magnetic pole arrangement, one is that the magnetic poles are arranged alternately along the circumference of N and S poles, along the axial polarity, and the magnetic poles are arranged in the perimeter magnetic system as shown in Figure 2. The magnetic system can be designed into a small circumferential direction, distance, multi pole magnetic angle form, improve the magnetic stirring times, is more suitable for the separation of fine magnetite powder (-1.0mm), to improve the precision of separation; also can be designed into a larger magnetic pole distance, the number of small, more suitable for separation of coarse magnetite (-12mm) and can improve the recovery rate of magnetic products.
Figure2.Magnetic pole permutation magnetic system
Curve: 1. drum surface; 2. distance drum surface 20mmn, 3. distance drum surface 40mm
Another kind of magnetic system structure is the magnetic pole alternately arrayed along the axial N and S poles. As shown in Figure 3, the circumferential polarity is the same. The magnetic minerals in the magnetic system do not have magnetic reversal in the sorting process, which is more suitable for the iron removal and purification operation of non-metallic minerals. The magnetic system can be adjusted to the appropriate position and fixed by the adjustment mechanism.
Figure3. Magnetic pole permutation magnetic system
If the surface magnetic field strength is low and the drum sorting speed is low, the separating drum’s material can be non-magnetic stainless steel; if the surface magnetic field of high strength, high speed sorting cylinder (general line speed of more than 2.5m/s), in order to prevent metal materials by eddy heat generated and motor power increased, the drum material should be non metal materials. The rotating speed of the separation drum can be stepless speed regulation by the frequency modulator.
When the machine works, ore feeder directly to the drum separator on the ferromagnetic particles is influenced by the magnetic force is adsorbed on the cylinder or the suction side to the direction of the drumr, the products into the magnetic ore tank; weak magnetic or nonmagnetic particles are mainly affected by the centrifugal force and gravity is thrown into the non magnetic products tank, by adjusting the separating drum separation index and the speed of mine dividing plate position can be adjusted magnetic products and non magnetic products, the separation process is shown in figure 4. In a double drum magnetic separator, two sections of coarse selection & selection or coarse selection & cleaning can be completed on one device.
Figure4. Separating process of dry type magnetic separator
4. Operation and maintenance
The main factors affecting the separation index of dry magnetic separator are ore properties (grade, magnetism, grain size and moisture content, etc.), equipment performance and operation level. Under the condition of certain equipment performance, the operation regulation should be determined according to the properties of the ore treated and the requirements for the product index. The main factors of operation adjustment include the rotational speed of the cylinder, the location of the ore separating board and the size of the ore feed. Reasonable adjustment of these three factors can improve the sorting index and determine reasonable technical parameters through experiments. At the same time, the particle size has a great influence on the sorting index, the narrower the particle size is, the better the sorting index is. The moisture content of the selected material has great influence on the separation index. The high moisture content may deteriorate the sorting index. For coarse particle (-12mm) mineral separation, the moisture content in the ore is generally less than 3%. For the fine particle (-1.0mm) material sorting, the moisture content in the ore is generally less than 1%. In order to reduce the dust content in the working environment and ensure the workers' health, the dry magnetic separator is designed to be a closed structure. The dust collecting port is installed at the top part of the magnetic
5. Specification of dry drum type magnetic separator
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The efficient separation of magnetic minerals and non-magnetic (weak magnetic) minerals will be realized, and fine magnetic minerals and coarse magnetic minerals will not get lost.
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When the materials feeder transports the minerals to the separation area of the separation drum, the magnetic minerals will alternate rapidly and repeatedly within a short time through the N pole and S pole of the magnetic field, and the magnetic minerals will do magnetic rever?sal and magnetic agitation. The non-magnetic (weak) magnetic mineral mingled in the magnetic minerals is not or slightly affected by the adsorption of the magnetic force, moving to the outer layer gradually, and is thrown out by the centrifugal force, gravity and the joint action of magnetic turn and agitation of magnetic minerals. With the adsorption of the magnetic force and the joint action of the magnetic turn and agitation of magnetic minerals, the mag?netic minerals will move to the inter layer gradually. When the magnetic minerals rotate to the ore unloading area with the separation drum, as the rotation magnetic system is eccentric, the magnetic density of the ore unloading area for the separation cylinder is extremely weak, and most of the magnetic minerals can fall off automatically. A small quantity of magnetic minerals not falling off will be adsorbed to the external surface of the ore unloading cylinder with higher magnetic density when rotating to the position nearby the ore unloading cylinder so as to realize the automatic unloading of magnetic minerals.