密度对细粒煤颗粒与气泡间相对运动的影响

颗粒与气泡间相对运动的研究对浮选机理的认识十分重要,目前关于颗粒与气泡间相对运动的研究多为理论推导,试验研究比较匮乏且试验对象多为形状规则,表面性质均匀的颗粒。以内蒙古公乌素原煤为研究对象,利用自行设计搭建的试验装置研究了粒级为0.100～0.074 mm、密度级分别为-1.3,1.4～1.5和+1.7 g/cm~3的煤样与气泡间的相对运动。试验通过追踪大量煤颗粒的运动轨迹,研究了颗粒沉降阶段、运动轨迹偏离阶段和碰撞阶段中颗粒运动特征参数的变化规律。试验结果表明:颗粒当量直径均值为0.092 mm,颗粒经短暂加速后便达到沉降末速,颗粒沉降末速随颗粒当量直径和密度的增大而增大。气泡会影响颗粒的运动轨迹,同一初始沉降区间内,竖直方向上煤样轨迹偏离点到气泡的距离随煤样密度的增大而减小。静水条件下颗粒和气泡碰撞角的主分布区间为20°～50°,且碰撞区间和颗粒集中分布区间随初始沉降区间向外扩展而扩展。颗粒和气泡的碰撞角小于50°时,碰撞点处颗粒速度减小比例随碰撞角增大近似直线减小,碰撞角大于50°时,碰撞点处颗粒速度减小比例趋于平稳,低密度颗粒的速度减小量大于高密度级颗粒的速度减小量,然而差异并不明显。理论计算发现,颗粒初始沉降位置距气泡中轴较近时理论碰撞速度较小,且颗粒理论碰撞速度随颗粒初始沉降位置向外扩展而增大,与试验规律较为吻合。

Effect of density on relative motion between particles and bubbles

The study of the relative motion between particles and bubbles is critical to the understanding of flotation mechanism.At present,the research on the relative motion between particles and bubbles is mostly based on theoretical analyses.The experimental research is relatively limited and the test objects are particles with regular shape and homogeneity properties.In this experiment,the coal samples from Gongwusu mining area in China was taken,and the relative motion between particles and bubbles with the particle size of 0.100-0.074 mm and densities of -1.3,1.4-1.5,+1.7 g/cm3 was studied by self designed experimental device.During the test,the trajectories of a large number of coal particles were traced.The change laws of particle motion parameters during the settlement stage,the deviation stage and the collision stage were studied.The experimental results show that the equivalent diameter of particle is 0.092 mm.The particles reach the terminal velocity after transient acceleration and the terminal velocity of particle increases with the increase of particle’s equivalent diameter and density.Bubble will affect the trajectory of particle.In the same initial settlement interval,the vertical distance between the deviation point of particle trajectory and bubble decreases with the increase of particle density.The main dis tribution interval of collision angle is 20°-50° in hydrostatic conditions.The collision interval and particle con centration interval expand outward with the expend of initial settlement interval.When the collision angle is less than 50°,the reduction ratio of particles collision velocity decreases linearly with the increases of collision angle.When the collision angle is greater than 50°,the reduction ratio of particle velocity tends to plateau.The velocity reduction of low density particles is greater than that of high density particles,but the difference is not obvious.The theoretical calculation shows that the theoretical collision velocity is small when the particle initial settlement position is closer to the central axis of bubble.The particle theoretical collision velocity increases with the expend of initial settlement interval,which has a good agreement with the experimental results.