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本文提出了用流态化方法来分选石棉,并认为石棉的流态化选矿是根据石棉纤维和脉石之间的干涉沉降速度的差异进行的。在相同的空隙度时,干涉沉降速度小的纤维随上升流体进入溢流产品中,而干涉沉降速度大的脉石则逆上升流体向下排入尾矿。根据这一分选原理,本文提出了石棉流态化选矿的物理模型,并依据流体力学的原理,建立了物料和流体在分选管内各个区域中运动的数学解析式。通过求解流体的运动方程,得到了无限长圆柱体的沉降末速方程,再借助于试验建立了石棉纤维的自由沉降末速方程。通过试验本文还研究了纤维和脉石颗粒的空隙度指数n值和分选等问题。分选试验不但验证了本文提出的流态化分选原理,而且分选的较好结果还表明用流态化分选石棉是今后石棉选矿的发展方向之一。本文的理论分析和试验结果还得出了三点新的结论:(1)粗细均匀和质量均匀的圆柱形纤维在作自由沉降时,无论初始时它以何种形式在静水中下沉,最后总是取其受流体阻力最大的方向——即平行于水面的形式稳定地下沉。(2)长径比1/d≥15的圆柱纤维在作自由沉降时,由于流体从柱体两边的绕流阻力对纤维沉降末速的影响远远大于它从柱体两端的绕流的影响,所以纤维的长度不再影响它的沉降末速,决定纤维自由沉降末速大小的因素是纤维的直径、密度和流体的粘度、密度。本文所建立的圆柱纤维的自由沉降末速方程适合于计算雷诺数Re=1～17.601,长径比1/d≥15时各种材料的圆柱纤维在各种流体中的自由沉降末速。(3)圆柱纤维在自由沉降时是以水平状态下沉,在干涉沉降时由于纤维间的相互碰撞而倾斜下沉。基于纤维在流体中倾斜下沉时所受到的流体阻力小于水平下沉时的阻力,所以纤维的干涉沉降速度大于其自由沉降末速,它们的空隙度指数为负值。
This paper proposes the use of fluidization methods to sort asbestos, and believes that fluidized beneficiation of asbestos is based on the difference in the velocity of intervenient sedimentation between asbestos fibers and gangue. At the same voidage, fibers with low interferometric sedimentation velocity enter the overflow product with rising fluid, while gangues with large interferometric sedimentation velocity flow downward into the tailings. According to this sorting principle, the physical model of asbestos fluidized beneficiation is proposed in this paper. Based on the principle of fluid mechanics, the mathematical analytical formulae for the movement of materials and fluids in various regions within the sorting tube are established. By solving the equation of motion of the fluid, the equation of the final velocity of the infinite cylinder is obtained, and the free-settling velocity equation of the asbestos fiber is established by means of experiments. Through experiments, the voidage index n and separation of fibers and gangue particles were also studied. The sorting test not only validates the principle of fluidized sorting proposed in this paper, but also shows that the better sorting result shows that the use of fluidized sorting asbestos is one of the development directions of asbestos beneficiation in the future. The theoretical analysis and experimental results of this paper also yielded three new conclusions: (1) When a cylindrical fiber of uniform thickness and uniform quality is used for free-sinking, whatever form it sinks in still water at the beginning, finally Always take the direction in which the fluid resistance is greatest—that is, parallel to the surface of the water to stabilize the sink. (2) When the cylindrical fiber with aspect ratio 1/d≥15 is free to settle, the effect of the fluid flow resistance from both sides of the cylinder on the final velocity of fiber settling is much greater than the effect of the flow around the cylinder. Therefore, the length of the fiber does not affect its final settling velocity. The factors that determine the final size of fiber free settlement are the fiber diameter, density, and fluid viscosity and density. The free settlement velocity equation of the cylindrical fiber established in this paper is suitable for the calculation of Reynolds number Re=1 to 17.601, and the ratio of length to diameter 1/d≥15. (3) Cylindrical fibers sink in a horizontal state when they are free-sinking, and tilt and sink due to the mutual collision between fibers during the interferometric settlement. Since the fluid resistance of the fiber when it sinks obliquely in the fluid is less than the resistance when it sinks horizontally, the interferometric sedimentation velocity of the fiber is greater than its free-sinking velocity, and their voidage index is negative.