Study On Flow Characteristics And Particles Separation Behavior In Spiral

Nowadays,the environmental consciousness of energy conservation and emissions reduction is growing.As a kind of typical gravity equipment which uses the compound force field of centrifugal inertia force and gravity force to separate,the spiral receives much concern,because it has many advantages such as low power consumption,covering low area,easy-maintenance,simple operation,no moving parts,and large capacity per unit area and so on.However,the movement behavior and separation rule of mineral particles in the spiral are not learned comprehensively and accurately by people,which only stay in qualitative analysis phase.Therefore,it is particularly important to detailedly research internal flow field and the movement behavior of particles in spiral.In the paper,lots of research methods are applied,such as the flow-field test and numerical simulation,monomineralic separation tests,and numerical simulation of particles motion behavior.The flow field and particles separation in spiral are studied systematically,and characteristics of them with the diameter of 300mm are found.And the influence of main structural parameters and operating conditions on characteristics of the flow field and particles separation behavior is researched,and results are as follows:(1)The flow characteristics in spiral are that,the water flow mainly collects on the outer rim,the water thickness increases gradually firstly from inner to outer,and after a sharp increasing,it decreases closing to side walls.The water flow velocity increases gradually from the bottom of the spiral to the water surface,and reaches its maximum on the water surface.Besides the water flow velocity levels off gradually at some water depth which varies depending on the radial position,and this result is consistent with experimental data trend.The turbulent kinetic energy basically decreases gradually from the bottom of the spiral to the water surface,and the difference between them are relatively small at each radical distance except for closing to the water surface.In spiral,the lateral secondary circulation flow exits obviously,and the demarcation point of the radical velocity is effected by the radical distance.(2)Based on the influence of the inlet flow rate and screw pitch on characteristics of the flow field in spiral,from the end of the first turn to the end of the fifth turn,the water thickness of inner rims are affected by them relatively slight increasing the inlet flow rate,but the outer rims are affected obviously.In other words,with the increasing of water flow rate,the flow velocity increases,the secondary circulation flow phenomenon,is more obvious,and the demarcation point of the radical velocity is changed.However,the turbulent kinetic energy varies depending on radial positions and relative water depth.Increasing the screw pitch,the water velocity and turbulent kinetic energy increase significantly,but the inlet flow rate and screw pitch have little influence on the distribution characteristics of the flow velocity and the turbulent kinetic energy.(3)The results of monomineralic separation tests show that the pulp flow is mainly discharged from the tailing belt,and the volume production rate is more than 90%.Increasing the feed mass flow,the secondary circulation flow phenomenon is more obvious,which are consistent with the test results of water thickness.And it is conducive to the flow layer spreading along the groove increasing the feed concentration.(4)The simulation results of the particles motion behavior in spiral show that,particles with different sizes and densities zone completely along the spiral downward process,which is dispergated at the inlet.And the radial distribution rule of different property particles at the outlet is consistent with separation results of hematite and quartz particles.(5)Monomineralic separation tests and simulation results of motivation behavior show that,the feed concentration and mass flow have obvious interaction on movement and separation behavior of hematite and quartz particles.With low feed concentration,increasing the feed mass flow is conducive to the separation of coarse particles,and at low feed mass flow,increasing the feed concentration is beneficial to the separation of fine particles.