Development And Mechanism Study Of A Compound Force Field Magnetic Belt Chute

Compound force field separation equipment is an important direction in the research and development of new efficient mineral processing equipment.The multiple force fields created inside the equipment take advantage of the differences between minerals,such as density,particle size,specific susceptibility and electrical conductivity.These differences enhance the differences in particle migration paths,improve the separating effect of the separation system and increase the selectivity of the separating.In this paper,a compound force field magnetic belt chute is developed by combining the magnetic and gravity fields based on the traditional re-election belt chute.The internal flow field of the belt chute and the movement of mineral particles and the law of stratification are studied theoretically.A laboratory prototype of CPL-8030 with a processing capacity of 0.3t/h was used to conduct a separating test study on Panzhihua ilmenite and Tieshanlong wolframite fine mud,and to investigate the separating performance of the equipment on weakly magnetic minerals and the influencing factors.This thesis analyses the forces on the clear water film and slurry flow film inside the chute and establishes the basic kinetic equations for the motion of the flow film.The velocity distribution of the flow film is obtained by solving the kinetic equations and the flow field inside the chute is simulated by Fluent software.The results show that the velocity distributions obtained under the viscous and no-approximation conditions are more accurate,while the turbulent approximation is more inaccurate and should not be used directly;the longitudinal velocities in both the clear water and slurry flow films increase with the relative depth,and increase rapidly when the relative depth is small,increase slowly when the relative depth is large,and then gradually level off;at the same depth,the longitudinal velocity of the slurry flow film is always larger than that of the clear water flow film The velocity gradient curve indicates that the difference in velocity gradient near the wall is the main reason for the difference in velocity distribution between the slurry and the clear water flow film;at a flow film thickness of h=1.34 mm and an average density of?(?)=1.3 g/cm3,the surface velocity of the slurry flow film is U_max=0.66 m/s,while that of the clear water flow film is 0.62 m/s.The thesis then calculates the longitudinal movement pattern of the actual mineral particles of quartz,pyroxene and ilmenite in the chute as well as the normal stratification pattern.The results show that:the lower limits of particle size for the three minerals are 25.9?m,17.6?m and 10.2?m respectively;the minimum separation distances for the recovery of 38?m ilmenite in the magnetic belt chute are between48.15cm and 83.89cm;the critical particle sizes for stable deposition of quartz and pyroxene on the magnetic belt are 180?m and 106?m respectively,and ilmenite of not less than 18?m All ilmenites up to 18?m can be deposited stably at the bottom of the belt.Both high density and coarse grain sizes have the same stratification pattern and are in the bottom layer,but the stratification effect of coarse grain sizes is more obvious in a certain range;when the inclination angle increases,the distribution of the same particles in the chute tends to expand towards the surface layer,which will facilitate the dispersion of the slurry.A laboratory-type magnetic belt chute with a compound force field has been developed.It has the following characteristics:(1)A magnetic belt with a uniform surface magnetic field distribution is used as the magnetic system.Compared to conventional permanent magnetic systems,the magnetic belt does not have a narrow or uneven magnetic field distribution,and the surface magnetic field consists of many tiny areas of varying magnetic field strength.This magnetic field distribution ensures that the magnetic mineral particles are effectively adsorbed while at the same time keeping the particles loose.(2)The strong magnetic roller device at the lower end of the plant separates the strongly magnetic minerals from the magnetic belt,so that the separation process is to some extent non-magnetic,weakly magnetic and strongly magnetic,which not only reduces the influence of residual strong magnetic minerals on the separation,but also greatly simplifies the separation process.(3)The compound force field magnetic belt chute can be adjusted to suit the sorting requirements of different minerals by adjusting the belt speed,tilt angle,flushing water and other operating variables in the process of sorting minerals,which has good adaptability and flexibility.The CPL-8030 compound force field magnetic belt chute was used to carry out a pilot study on the separation of a titanium-iron ore in Panzhihua and a fine wolframite mud in Tieshanlong.The influence of four operating parameters-feed size,belt speed,tilt angle and flushing water volume-on the sorting results was investigated and compared with several other heavy and magnetic separation equipment.The test results show that:the feed size needs to be suitable,too coarse feed and too fine feed will deteriorate the sorting effect;the increase of tilt angle and flushing water can improve the sorting accuracy of the equipment,the belt speed needs to match with the tilt angle and flushing water,and a faster belt speed is required for a large tilt angle and large flushing water.Compared with other equipment,the comprehensive sorting effect of magnetic belt chute is significantly better than that of shaking bed,re-election belt chute and plate high gradient magnetic separator;compared with the pulsating high gradient magnetic separator,the enrichment ratio is increased by 0.21,and the sorting process is more energy-saving and energy-consuming.