Research On Magnetic Manipulation Method And Its Law Of Separation Density In Dense Medium Cyclone

As the main equipment of coal washing and processing,the large diameter three products dense medium cyclone(DMS) is one of the most effective technologies and methods to realize the utilization of the clean coal. But the shortcoming, as the separation effect is difficult to manipulate online – is still restricting the long-term sustainable development of coal preparation plant, and had become the main technical problem to be solved for coal preparation plant. Based on the above problems, this paper has made a deep exploration based on the preliminary research of the early stage of the research personnel. This paper take-3 mm coal slime as the research object, with bottom flow, overflow product ash content of dense medium cyclone under different magnetic field characteristics as macro indicators, by changing the positions, intensity and magnetic gradient and operating conditions of cyclone, comprehensive consideration of medium distribution experiment, separation effect, and the result of its separation effect, with magnetic field simulation method, indicate the corresponding relation of magnetic field characteristics and separation effect, determine the key technique to manipulate separation density under the condition of given slurry density.Bying locating the large diameter coil and small coil diameter on cyclone column section and cone section, respectively, got the conclusion that the clean coal ash content and tailing coal ash content can be improved at the same time under the action of magnetic field. By comparing the dense medium separation effect of two positions, the separation density generally can be increased 0.2 g·cm-3. The separation accuracy Ep slightly reduced when the coil was located in the column section and decreased a little when the coil was located in the cone section. Medium distribution test results show that the introduction of the magnetic field enhanced suspension stability and the test under coil combination show that different locations of the same function coil combination can strengthen the separation result. The test on another diameter cyclone proved the universal practicability of the above conclusion. Combination magnetic field produced by two or more magnetic system that have similar effects could promote the cyclone separation density.Too large magnetic field force destroys the stability of the flow field in the cyclone, and the separation effectdecreased.According to the principle of magnetic aggregation, introducing the magnetic structure, by studying the settling process of steel ball and distribution of magnetic medium in a cyclone under different magnetic aggregation, simultaneously on the basis of the analysis of forces, getting the settlement rule of a ball and medium distribution rule under different magnetic structure, and ultimately verified the reinforcement to separation process of the magnetic structure by experiment with coal.By changing the magnetic location, intensity of magnetic field, magnetic field gradient features, etc., studied the separation effect of cyclone when coil was located below the bottom spigot under different magnetic field strength and magnetic field gradient characteristics, it can be concluded that the clean coal and tailing coal ash can be reduce when the coil is located below the bottom spigot, and, with the increasing of the feed slurry density, the magnetic field strength required also need to be improved accordingly.The magnetic system used in the test was simulated. The simulation results show that the radial magnetic force and the axial magnetic force improved the separation density at the same time work: magnetic medium accumulate in coil center under the action of axial magnetic force and increased local concentration, and, at the same time, move to the cyclone side wall motion under the action of centrifugal force which was strengthened by the radial magnetic force. The "separation surface" moved outward and downward, leading to a higher separation density. To reduce the cyclone separation density, the radial magnetic force was to weaken and strengthen the axial force, trapping the magnetic medium to the bottom spigot under the action of axial force, and increasing the bottom flow discharge.This paper provides a new control method of cyclone separation density by magnetic fields, has the advantages of contactless with pulp, no blocking, convenient to adjustment and easy to realize mechanization and automation, etc. and will eventually solve the problem, which difficult to adjust separation density online of three products dense medium cyclone separation density in coal preparation industry. This method will reduce the cost of coal separation, and improve dense medium cyclone coal preparation efficiency and automation level. It is of great importane to improve coal preparation technology automatic control online level.