Iron is a magnetic field that produces a strong attraction device, its use in the raw material is mixed in iron and other magnetic materials is removed, to ensure delivery system crusher, ball mill and other mechanical equipment be safe to work .
The iron removal efficiency of iron separators in China is generally not high. In order to improve the efficiency of iron removal, some sorting plants usually adopt the second or third grade iron removal method, but still can not meet the requirements of the plant selection. The main reason is that they are in coal. The iron material at the bottom of the layer is subjected to less electromagnetic force and is also subjected to the pressure of the upper coal, so the iron removal effect is not good.
In recent years, a method to improve the efficiency of iron removal has been developed. The electromagnet is subjected to "short-time strong excitation", that is, a sensor is installed on the front side of the electromagnet pole piece and below the conveyor belt, and the purpose is to detect the distance by using the sensor. The magnetic material that is the farthest pole of the pole piece and attracts the weakest effect, and then transmits the detected signal to the strong excitation rectifier through the sensor, so that when the magnetic substance passes under the pole piece, the magnet ring is temporarily applied with a high supply voltage. This produces a strong magnetic flow, which causes the electromagnetic attraction to increase sharply for a short period of time, so that the magnetic material buried in the depth can be sucked out, and then the voltage is restored to the normal power supply state.
The purpose of the sensor installed in front of the pole piece is to avoid the interference of the magnetic field of the electromagnet. Under normal circumstances, when the iron substance is in the upper part or the middle part of the coal seam, the sensor is not allowed to send an effective signal, only when the iron is buried in the bottom of the coal seam. A valid signal can be sent.
The sensor has the following links:
Normal excitation trigger control
Mainly for the normal excitation control of the electromagnet, it is necessary to have the trigger pulse phase shift adjustment function to control the main thyristor KP1 and KP2 to achieve the normal excitation current regulation.
Strong excitation delay control
It provides time delay from the detection of the iron matter signal to the time when the iron material just runs to the front end of the electromagnet pole piece, then starts the strong excitation control signal, activates the strong excitation trigger link, and strengthens at the best moment. Reinforce, and try to reduce the time of strong excitation, do not miss the purpose of capturing good opportunities.
Strong excitation time control
Mainly to control the length of the application of the strong excitation time, the strong excitation time is controlled at the front end of the running pole piece, and the time after the running of the rear end of the pole piece can control the strong excitation time within the optimal range.
Strong excitation trigger control
It is mainly under the control of strong excitation delay and strong excitation time, and the strong excitation excitation pulse is issued to the thyristor KP3 and KP4 of the strong excitation main circuit in time to carry out strong excitation. In addition, it is not necessary to perform phase shift control on the trigger pulse, and it is only necessary to control the trigger angle to the minimum value, so that a larger strong excitation current can be obtained.
In the current situation that the iron removal effect of the electromagnetic iron remover is not satisfactory, the method of “short-time strong excitation†greatly improves this situation and has great application potential.
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