Research On The Influence Of Coaxial Rotating Magnetic Field On The Separation Effect Of Dense Medium Cyclone

In recent years,the study of using an external magnetic field to adjust the separation effect of the dense medium cyclone has achieved certain results,but the static magnetic field cannot control the tangential velocity of the dense medium suspension,and the static magnetic field controls the dense medium cyclone is not comprehensive.In order to further optimize the on-line control of the magnetic field on the separation density of the dense-medium cyclone,the author tried to influence the internal flow field and density field of the dense-medium cyclone by adding a rotating magnetic field to adjust the separation characteristics of the cyclone.Adopt the method of coaxially placing the permanent magnet at the barrel of the dense medium cyclone,at different positions of the cone,and at the underflow port.A three-phase asynchronous motor is used to control the rotation speed and direction of the magnet.The-3mm coarse coal slime separation test was carried out under four conditions:the magnetic field,the rotation direction of the permanent magnet is consistent with the rotation direction of the slurry,and the rotation direction of the permanent magnet is opposite to the rotation direction of the slurry.Selected four:no magnetic field,static magnetic field at a distance of 120mm from the interface of the barrel and cone,the rotation speed of the permanent magnet is 851r/min when the rotation direction of the permanent magnet is consistent with the rotation direction of the slurry,and the rotation speed is 421r/min when the rotation direction of the permanent magnet is opposite to the rotation direction of the slurry.The reselection effect of the test points was evaluated,and the static magnetic field was simulated and analyzed by Ansys Maxwell analysis software.When the permanent magnet is placed in each position of the dense-medium cyclone,the ash content of the clean coal and tail coal of each particle size is reduced in the static magnetic field compared with the absence of the magnetic field.When the permanent magnet is placed on the cylinder,there is no significant difference in the test results when the rotation direction of the permanent magnet is consistent with the rotation direction of the slurry and the opposite.When the permanent magnet rotates,compared with the static magnetic field,the ash content of each particle size is reduced.The ash content of the tailings of the particle size is increased;when the permanent magnet is located on the upper part of the cyclone cone,the specific position is that the permanent magnet is 80mm,120mm,and 160mm away from the barrel-cone interface.The test results are basically the same,and the rotation direction of the magnet is consistent with the rotation direction of the slurry.Compared with the static magnetic field,the ash content of the clean coal and tailings of each particle size are increased.When the rotating direction of the permanent magnet is opposite to the direction of slurry feeding,the ash content of each particle size of the cleaned coal is reduced,and the ash content of the tailing coal of each particle size is reduced compared with the static magnetic field.When the permanent magnet is located at the lower part of the cyclone cone,240mm away from the cone-cone interface,when the magnet rotation direction is consistent with the pulp rotation direction,compared with the static magnetic field,the ash content of the clean coal and tailings of each particle size are increased.When the rotation direction of the permanent magnet is opposite to the rotation direction of the slurry,the ash content of the clean coal of each particle size is reduced compared with the static magnetic field,and the fluctuating change of the ash content of the tailings of each particle size is not much different from the ash content of the tailings under the static magnetic field;When the interface is 300mm,the test results when the rotating direction of the permanent magnet is the same and opposite to the rotating direction of the slurry are basically the same.When the permanent magnet rotates,compared with the static magnetic field,the ash content of the clean coal and tailings of each particle size are increased;when the permanent magnet When placed at the underflow port,there is no significant difference in the test results when the rotation direction of the permanent magnet is consistent with the rotation direction of the slurry and the test results are opposite.Compared with the rotation of the permanent magnet,the ash content of clean coal and tailings are both improved.From the evaluation results of the reselection effect,we can see:?p(non-magnetic)>?p(+851)>?p(-421)>?p(static);Ep(non-magnetic)>Ep(static)?Ep(+851)>Ep(-421).The separation density under static magnetic field is 0.09g/cm~3 lower than that without magnetic field,Ep value is reduced by 0.0134 g/cm~3,and the separation accuracy is improved;the rotation direction of the permanent magnet is consistent with the rotation direction of the pulp and the speed is 851 r/min,the separation density is0.03g/cm~3 higher than the separation density in static magnetic field,and the separation accuracy is basically unchanged;when the rotating direction of the permanent magnet is opposite to that of the pulp and the speed is 421 r/min.Compared with the static magnetic field,the separation density is increased by0.012g/cm~3,the Ep value is reduced by 0.0103 g/cm~3,and the separation accuracy is greatly improved.Using Ansys Maxwell analysis software,it is initially revealed that the permanent magnet placed in the cone can reduce the separation density of the dense medium cyclone.The reason is that the oblique downward magnetic force attracts more magnetite powder to the bottom flow port and from the bottom flow port.Elimination thereby reducing the separation density of the dense medium cyclone.