Study On Selective Crushing Behavior Of Magnetite Under High-Voltage Pulse

Conventional mechanical crushing mainly uses impact,shearing and grinding to reduce the particle size of the ore while increasing the monomer dissociation degree of useful minerals.However,the crushing principle shows that the mechanical crushing is mainly through crystal crushing in the crushing process.It is difficult to effectively dissociate useful minerals from gangue minerals.Based on the differences in the electrical characteristics of minerals,highvoltage pulse technology can generate discharge channels at the mineral interface.The discharge channels accumulate a large amount of energy to generate a strong stress wave,which makes different minerals rupture and dissociate along the two mineral interfaces to achieve selective crushing.Research on the technological mineralogical characteristics of magnetite shows that the metal minerals in the ore are mainly magnetite,with a content of 32.91%;the non-metallic minerals are mainly quartz,with a content of 40.59%;magnetite,hematite,quartz or feldspar are mostly produced in granular form,and the minerals are interspersed with each other.The selective rupture behavior of artificial specimens under the action of high-voltage pulses shows that the filling of magnetite with higher relative permittivity in artificial specimens can promote the rupture of artificial specimens,and with the increase of the filling rate,the reduction of the filling particle size can further improve the promotion effect;for the addition of quartz with a relative dielectric constant similar to that of cement,the reduction of the particle size can also promote the rupture of the artificial specimen,but when the quartz is in contact with the high-voltage electrode or the ground electrode,it will prevent the rupture of the artificial specimen.The study of the electric field distribution law inside the ore under the action of highvoltage pulses shows that increasing the input voltage,reducing the particle size of the ore and the distance between the high-voltage electrode and the ore can increase the electric field inside the ore;In addition,minerals with a higher relative permittivity have a higher peak value of the internal electric field and stronger ability to attract electric fields;minerals with a low relative permittivity have a higher total internal electric field and are more prone to dielectric breakdown;at the mineral interface with a large difference in relative permittivity,the electric field increases greatly,and dielectric breakdown is likely to occur along the interface.The study on the development law of the internal discharge channel of the ore under the action of high-voltage pulses shows that the high relative permittivity mineral has an attractive effect on the electric field and can generate a discharge channel inside the artificial specimen,and as the filling rate increases or the filling particle size decreases,the number of discharge channels increases,thereby promoting the rupture of the artificial specimens,but the minerals with lower relative permittivity will hinder the development of the discharge channels in the artificial specimens and weaken Electric breakdown effect of artificial specimens.By studying the selective fracture behavior mechanism of magnetite under different treatment methods,it is concluded that both high-voltage pulse pretreatment and crushing methods can effectively promote the dissociation of magnetite and enrich it in-0.15mm.The promotion effect of the high-voltage pulse crushing technology is the most obvious.Among the crushed products-0.15mm size,the grade of TFe has increased by 4.66 percentage points,and the distribution rate has increased by 7.98 percentage points;the test results of the monomer dissociation degree show that the monomer dissociation degree of magnetite increases with the number of pulses,and the monomer dissociation degree of the high-voltage pulse crushing product is higher than that of other treatment methods;BET,SEM and EDS tests show that during the process of high-voltage pulse acting on magnetite,it promotes the dissociation of mineral monomers,while retaining the complete crystal form of the mineral.The particle size of the ore is relatively uniform without obvious fine particles.At the same time,during the crushing process,a large number of internally developed cracks are not caused in the ore,but the discharge channel develops along the interface between magnetite and quartz,and high temperature is generated on the dissociation surface,leading to high-temperature melting on the surface of the ore,and a large number of pore-like structures such as pores and pores appear.The research results of this thesis have certain guiding significance for the further study of the selective fracture behavior of metal ore under the action of high voltage electric pulse.