Force Field Simulation,Design And Study On Separating Performance Of The Rotational-flow Multiple-gradient Magnetic Separator

There are larges amounts of weak magnetic mineral resources,such as red iron ore, manganese ore, black tungsten, tantalum and niobium ore,and so on, magnetic and gravity separation are important technology to recover these resources. Increasing magnetism by its high-gradient magnetic field, high gradient magnetic separator improves recovery ratio of weak magnetic mineral; strengthening "gravity" of particle by its centrifugal force field, centrifugal separator improves recovery ratio of weak magnetic mineral having the quality of high density.With the magnetic and gravity separator appearing, weak magnetic mineral separation have made some progress, however, there are a few problems:①the dispersion of pulp is poor and grain inclusions are serious in the sorting area of high gradient magnetic separator, which will influence the quality of magnetite concentrates,especially,when the high gradient magnetic separator is used for concentrate, the extraction efficiency is low and lowing magnetic intensity always is the only way to improve its efficiency;②the centrifugal force field of centrifugal separator increases the forces on the objective mine while increasing the forces on the gangue mineral, nevertheless, the size of some gangue particles are bigger than the value mineral’s because that the value mineral is fragile and argillization, so, its hard to separate the value mineral from the gangue mineral;③although the centrifugal separator could lower size limit of the objective mine, it must be based on strict particle classification, while, the strict particle classification always is very hard to the feebly magnetic minerals. So, the main of these problems is that the single force field and narrow separation field lead to be poor selectivity in the separating process.A new compound force field equipment (centrifugal force field and magnetic field) named rotational-flow multiple-gradient magnetic separator has been designed in this paper, which could significantly improve the efficiency of separating the magnetic mineral from non magnetic based on making the most of the differences of density and magnetic susceptibility. This separator benefits from the vertical centrifugal separator that the centrifugal force field has been generated by rotating separation cavity while also absorbing the advantage of high-gradient magnetic separator that there is very high gradient on the ferromagnet media placed in separation cavity where the background magnetic field has been generated by the magnetic system, which increases the catching force to weak magnetic mineral.Compare rotational-flow multiple-gradient magnetic separator with conventional gradient magnetic separators, the theory of new separator is that which can provide two kinds of gradient separating force field:①the centrifugal gradient force field, the force on particle is higher near the inner wall of separation cavity than in the center;②tthe magnetic gradient force field, the background magnetic field generated by the magnetic system has the feature that magnetic field intensity is higher near the inner wall of separation cavity than in the center and higher near the top of separation cavity than near the bottom, it’s easier to move towards the inner wall or the bottom of separation cavity for magnetic mineral, the weak magnetic mineral can be caught by the ferromagnet media placed in separation cavity.Study contents of this paper include:3-D Fluent simulation of the rotational-flow multiple-gradient magnetic separator,3-D Ansys magnetic simulation, design of the separation cavity and the magnetic system, analysis of forces on particles, experiments of single force separator(the centrifugal force field or the magnetic force field)on ore simples,the model derivation of separating performance as force field, the separating performance prediction of the rotational-flow multiple-gradient magnetic separator and the structural design of complete machine, and so on.Take the different diameter wolframite and quartz particle for example, under the specific conditions (the background magnetic field strength is0.978T and the centrifugal field strength is13.98G),the forces on particles have been analysed in separator, the results show:①when the particle diameter is more than10μm, magnetic force on wolframite is the most important factor influencing on its recovery, the second factor is centrifugal force, radial compound force on wolframite particle has a larger magnitude than on quartz particle because the differences of density and magnetic susceptibility, so, this separator makes good separation between wolframite and quartz particle;②the week magnetic particles can form magnetic agglomeration which is the equivalent of increasing diameter of magnetic particles during the movements, that can improve the efficiency of separating magnetic materials from nonmagnetic in the radial motion, when particles reach the surface of ferromagnet media, the force different between magnetic and nonmagnetic particles grow because of magnetic force on magnetic particles;③centrifugal force not only helps material dispersed, magnetic particles contacting with ferromagnet media and avoid inclusion and blockage, but also to lengthen moving distance of particles in separation cavity, these are helpful to increase the capture probability to magnetic particles.The single force field experiments on a wolframite mine have been made, through1stopt software, the theory model has been got, which describe relationships between grade and recovery of wolframite concentrate and compound forces, the separation results that this wolframite mine is treated with rotational-flow multiple-gradient magnetic separator have been predicted, the results show:under low centrifugal force field, though regulating the background magnetic field strength and the back flush water pressure, the concentrate grade can be improved greatly using the difference mainly in magnetic susceptibility, a concentrate with WO3recovery of over70%and grade of over8%will be obtained from the sample with WO3grade of about0.4%; under high centrifugal force field, though using the differences of density and magnetic susceptibility together, the concentrate recovery can be improved greatly, a concentrate with WO3recovery of over90%and grade of over1%will be obtained,the separation performance of new separator is significantly better than traditional magnetic and centrifugal separator’s.