Mechanical entrainment is an important mechanism responsible for the low selectivity in high gradient magnetic separation (HGMS). Previous studies on mechanical entrainment mainly focused on particle motion behaviors or interparticle forces, a very important factor attributing entrainment was neglected, namely the effect of gravitational force. In this paper, the role of gravitational force on mechanical entrainment was systematically investigated with varying feeding direction, fluid velocity, size and density of nonmagnetic particles. Results indicated that gravity played a vital role in mechanical entrainment. Nonmagnetic particles were preferentially entrained in deposits of upper surface (relative to gravity direction) rather than upstream surface (relative to flow direction) due to gravity. Mechanical entrainment became more serious with increasing gangue mineral density. Mechanical entrainment of low-density gangue could easily be eliminated with moderate fluid velocity or pulsating frequency, but that caused by large density gangue in upper deposit could hardly be eliminated, even with high fluid velocity or high strength pulsating. Weakening the effect of gravity with nonmagnetic heavy medium (or heavy suspension) should be promising method to enhance selectivity in HGMS, which will be conducted theoretically and experimentally in near future.

机械夹带是导致高梯度磁分离（HGMS）选择性低的重要机制。以往对机械夹带的研究主要集中在粒子运动行为或粒子间力上，而忽略了一个非常重要的归因于夹带的因素，即万有引力的影响。在本文中，系统地研究了重力对机械夹带的作用，不同的进料方向、流体速度、尺寸和非磁性颗粒的密度。结果表明，重力在机械夹带中起着至关重要的作用。由于重力，非磁性颗粒优先夹带在上表面（相对于重力方向）而不是上游表面（相对于流动方向）的沉积物中。随着脉石矿物密度的增加，机械夹带变得更加严重。低密度脉石的机械夹带在中等流速或脉动频率下很容易消除，但上层矿床大密度脉石引起的机械夹带即使在高流速或高强度脉动下也很难消除。用非磁性重介质（或重悬浮液）减弱重力的影响应该是提高 HGMS 选择性的有前途的方法，这将在不久的将来在理论上和实验上进行。即使有高流体速度或高强度脉动。用非磁性重介质（或重悬浮液）减弱重力的影响应该是提高 HGMS 选择性的有前途的方法，这将在不久的将来在理论上和实验上进行。即使有高流体速度或高强度脉动。用非磁性重介质（或重悬浮液）减弱重力的影响应该是提高 HGMS 选择性的有前途的方法，这将在不久的将来在理论上和实验上进行。