Medium Magnetic Field Analysis And Parameter Optimization Design For High-gradient Magnetic Separation

High-gradient Magnetic Separator(HGMS)is a kind of high-efficiency physical separating equipment,which uses magnetic medium contained in its magnetic field to realize the effective separation of minerals.It has been widely used in the separation of fine weak magnetic minerals and produced enormous economic and social benefits.Because high gradient magnetic separation is affected by many factors,relevant theory for practice guidance is still very scarce.Gaining in-depth knowledge of the magnetic field distribution of magnetic medium and its relationship with separation efficiency is helpful to analyze the integrated mechanical for the selection of suitable magnetic media and the optimization of the design of the separation parameters.It is also of great significance to enhancing the efficiency of high gradient magnetic separation and advancing the development of new equipment.Conformal mapping refers to the transformation from physical plane to computational plane with the use of analytic complex function,which has been applied in many fields of physics.This thesis described the basic process for solving the high gradient magnetic field with complex boundary by means of conformal mapping.The distribution of magnetic field strength,magnetic field gradient and magnetic force density per unit volume of single-wire and multi-wire medium,the shape of cross-section is circular,diamond,ellipse,polygon,etc.,are calculated by direct solution method and numerical analysis combined method respectively.Then,a construction principle of high gradient magnetic separation model is proposed to reveal the relationship between magnetic field distribution and separation efficiency of HGMS.The results of theoretical calculation show that:(1)Numerical analysis combined method of conformal mapping exhibits high accuracy,small amount of data and strong applicability,which can accomplish the vector calculation of complex boundary conditions in a unified form,so as to accurately calculate the magnetic field distribution in HGMS.(2)The magnetic force density per unit volume on the medium surface has an important influence on the particle trapping.For circular multi-wire,its appropriate horizontal and vertical spacing should be determined according to the medium radius.the vertical spacing(D)should be approximated as 2R,and the horizontal spacing(L)should be determined according to the nature of ore feeding and the results of magnetic field analysis of hexagon element.(3)The distribution of magnetic field in HGMS follows the law of conservation of energy.When the medium becomes sharp along the direction of background magnetic field intensity,the magnet congregate effect can be enhanced.The medium with rough surface and angular surface fluctuates greatly due to the distribution of magnetic field,which is more conducive to the recovery of magnetic minerals.In addition,the concept of specific magnetic force variance ratio of circular multi-wire is derived from gradient matching calculation method of single wire.Based on the corresponding two peaks in the variance ratio of specific magnetic force,the formula for calculating the competitiveness of ore particles leaving the trapping area and the experimental results of high gradient magnetic separation of high-phosphorus oolitic hematite,the constraint equation of medium on the size of ore feeding is proposed.In order to verify the validity of the particle size constraint equation,a practical experiment was carried out on a periodic pulsating HGMS(SLon-100)for titanium recovery from a titanium-containing iron tailings owned by Panzhihua Steel.By quantitatively analyzing iron tailings,calculating gradient matching of medium and measuring the effect of particle size on slurry viscosity,the particle size range matching with the medium and Optimized parameters for equipment operation were determined.Iron tailings with original grade(Tio₂)of 13.44%were treated by weak magnetic field and classification as samples.Its grade(Tio₂)arrived up to 18.55%,the maximum particle size was 106 micron,and the content of minimum controlled particle size was 19.77%.High gradient magnetic separation test was carried out based on the calculation results of the equation.Titanium concentrate with grade(Tio₂)of 29.46%and a recovery rate of 91.36%could be obtained by one-stage separation.Both two indexes were superior to those in other processes.The experimental results show that pyroxene and ilmenite with similar specific magnetic susceptibility can be effectively separated by precise controlling feed size,which provides a new way to solve this kind of problem.