浮选中颗粒-气泡间相对运动研究进展

颗粒-气泡间相对运动的研究对浮选机理的认知至关重要,对新型浮选机的开发和提高浮选效率均具有指导意义,本文系统综述了颗粒-气泡间相对运动的研究进展。早期研究过程中,研究者忽略了颗粒和气泡性质的影响,将颗粒视为随流线运动的点,气泡视为刚性球体,利用流线方程对颗粒-气泡间的相对运动展开研究;随着认知过程的不断深入,颗粒和气泡物理化学性质的影响逐步得到了关注,研究者分别从颗粒惯性力、重力、形状和粗糙度以及气泡表面流动性等方面并展开了大量研究;颗粒-气泡间相对运动的试验研究多通过颗粒沉降法进行,研究对象由单个玻璃微珠发展为大量矿物颗粒,且出现了关于运动玻璃球与上升气泡之间相对运动的研究。研究表明,当颗粒粒度较细、密度较小时,利用流线方程对颗粒-气泡间相对运动的研究具有一定的适用性;当颗粒粒度较粗、密度较大时,需考虑正负惯性力、重力等因素对颗粒-气泡间相对运动的影响。此外,颗粒形状的不规则性会影响颗粒周围液体对颗粒的作用力,导致临界碰撞半径减小,且颗粒表面不规则的凸起会促进颗粒-气泡间水化膜的破裂,减少诱导时间,增大颗粒表面粗糙度有助于增强颗粒-气泡间的黏附强度。气泡表面的流动性可采用"滞留帽"模型进行分析,具有较好的适用性。对于颗粒-气泡间相对运动的试验研究主要采用颗粒沉降法,亲水玻璃微珠只能在气泡上半球滑行,到达气泡赤道位置附近后便离开气泡,疏水玻璃微珠会刺破颗粒-气泡间的水化膜,越过气泡赤道后会继续沿气泡表面滑行并最终黏附在气泡底部,煤颗粒与气泡的黏附效率随碰撞角和密度的增大而减小。然而目前的试验研究多集中于静水领域,对于浮选流场中颗粒-气泡间相对运动的试验研究尚需进一步探索。

Research progress of relative motion between particles and bubbles in froth flotation

The study of the relative motion between particles and bubbles is critical to the understanding of froth flotation mechanism,and has a guiding significance for the development of new flotation machines and the im-provement of flotation efficiency. In this paper,the research progress of relative motion between particles and bubbles was reviewed. In the early research,some researchers ignored the effects of particle and bubble property. Particles were regarded as points moving along the streamline and bubbles were regarded as rigid spheres. Streamline equations were used to study the relative motion. With the continuous research,the effects of physical and chemical properties of particles and bubbles have gradually received extensive attention. Researchers have done a lot of researches on particle inertial force,gravity,shape and roughness,and the mobility of bubbles surface. Particle sedimentation method was used to study the relative motion between particles and bubbles. The research object was developed from a single glass bead to a large number of mineral particles,and the relative motion between the moving glass bead and the rising bubble has been studied. Research shows that the streamline equation is applicable to the study of the relative motion between particles and bubbles when the particle size is fine and the density is small,and the influence of inertial force and gravity on the relative motion should be considered when the particle size is coarse and the density is large. In addition,the irregularity of particle shape will affect the force of the liquid around the particle,resulting in the decrease of the critical collision radius,and the irregular surface protrusion will accelerate the rupture of the liquid film between particles and bubbles. Increasing the surface roughness of particles can help to enhance the adhesion strength between particles and bubbles. The “stagnant-cap” model can be used to analyze the bubble surface mobile. Particle sedimentation method is mainly used to study the relative motion between particles and bubbles. The hydrophilic glass beads can only slide in the upper hemisphere of the bubble,and then leave the bubble near the equator of the bubble. The hydrophobic glass beads will pierce the thin liquid film between particle and bubble. After crossing the bubble equator,it will continue to slide along the bubble surface and attach to the bottom of the bubble. The adhesion efficiency of coal particles decreases with the increase of collision angle and coal density. However,the current research focuses on the field of still water. The relative motion between particles and bubbles in the flotation flow field needs a further investigation.