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微细粒矿物浮选颗粒−气泡碰撞的湍涡作用机理及过程强化
  • Title

    Function mechanism of turbulent eddy and process intensification of particle-bubble collision in fine mineral flotation

  • 作者

    李晓恒王海楠郑恺昕王利军闫小康张海军刘炯天

  • Author

    LI Xiaoheng;WANG Hainan;ZHENG Kaixin;WANG Lijun;YAN Xiaokang;ZHANG Haijun;LIU Jiongtian

  • 单位

    中国矿业大学 化工学院中国矿业大学 国家煤加工与洁净化工程技术研究中心中国矿业大学 低碳能源与动力工程学院郑州大学 河南资源与材料产业河南省协同创新中心

  • Organization
    School of Chemical Engineering and Technology, China University of Mining & Technology
    National Engineering Research Center of Coal Preparation & Purification, China University of Mining & Technology
    School of Low-carbon Energy and Power Engineering, China University of Mining & Technology
    Henan Province Industrial Technology Research Institute of Resources and Materials, Zhengzhou University
  • 摘要

    微细矿物分选一直是困扰业界的难题,浮选是分选细粒矿物的主要方法,微细粒矿物质量小、惯性低、动能低,遇气泡易随流线绕流气泡而过,难以摆脱流线与气泡发生接触,与气泡的碰撞概率极低,是导致微细颗粒浮选回收困难的重要原因之一。强湍流流动因能提高颗粒动能以及颗粒−气泡碰撞频次,成为微细粒浮选的必要条件,然而,受制于湍流高频脉动及多尺度涡特征,颗粒、气泡在湍流环境中的运动及矿化过程与层流中差异极大,碰撞机理并不明晰。利用高频粒子图像测速技术(Particle Image Velocimetry, PIV)和高速显微摄像技术测量了各向同性湍流场中流体、颗粒及气泡的微尺度动力学行为,借助小波变换等数学手段,对湍流场的多尺度涡特性进行数学分解,从微观湍流层面解析了湍流小尺度涡运动对颗粒、气泡运动及碰撞过程的影响规律。研究发现:湍流场中微细颗粒运动受制于湍流小尺度涡运动,两者尺度具有相关性,在研究尺度范围内,流场所能够产生的Kolmogorov涡尺度越接近颗粒尺寸,颗粒滑移速度越大,颗粒摆脱流线与气泡发生碰撞的可能性越大;湍涡也会短暂“捕获”气泡且并影响气泡速度及轨迹;与常规碰撞矿化认知不同,大多颗粒在随流场主流宏观运动的过程中,局部跟随微观小尺度涡旋转,气泡在高涡量区内随涡体旋转且自转过程中裹挟颗粒,通过剪切碰撞的方式与颗粒发生矿化。基于此,提出了冲击流、涡流发生器等高涡量小尺度涡场的构涡方法,使浮选流场湍涡运动能有效作用到微细尺度颗粒上,提高微细颗粒−气泡碰撞概率,降低浮选有效回收粒度下限;不同类型纯矿物及实际矿物的浮选试验表明,通过对流场的湍涡调控,切实有效提高了微细矿物颗粒的浮选性能。研究将微细粒矿物浮选的过程强化从“调粒/调泡/调药”扩展到“调涡”,为低品质贫杂难选矿产资源的强化回收提供了新的思路和方法。

  • Abstract

    The separation of fine minerals has always been a difficult problem in the mineral industry, and flotation is the main method for separating fine-grained minerals. Fine minerals have small mass, low inertia, and low kinetic energy. When encountering bubbles, fine particles are prone to flow around the streamline and are difficult to detach from the streamline and contact with bubbles. The low probability of collision with bubbles is one of the challenges in the flotation of fine particles. Strong turbulent flow can increase the kinetic energy of particles and the frequency of particle-bubble collision, which is a necessary condition for fine particle flotation. However, due to the high-frequency fluctuations and multi-scale eddy characteristics of turbulence, the movement and mineralization processes of particles and bubbles in the turbulent environment differ greatly from laminar flow, and the collision mechanism is not clear. In this study, the microscale dynamic behavior of fluids, particles, and bubbles in an isotropic turbulent field was measured using high-frequency particle image velocimetry and high-speed microscopic camera technology. With the help of mathematical methods such as wavelet transform, the multi-scale eddy characteristics of the turbulent flow field were mathematically decomposed, and the influence of small-scale eddy motion on the particle and bubble motion and collision processes was analyzed at the micro turbulence level. The study found that the motion of fine particles in the turbulent flow fields is constrained by the motion of small-scale turbulent eddies, and the scales of the two are correlated. In the scale scope of the study, the closer the Kolmogorov eddy scale generated by the flow field is to the particle size, the greater the particle slip velocity, and the greater the possibility of particle detachment from the streamline and collision with bubbles. Turbulent eddies briefly “capture” bubbles and affect their velocity and trajectory. Unlike conventional collision mineralization, particles locally follow micro-scale eddies during macroscopic motion with the mainstream flow field, while bubbles rotate with the eddy body in the high vorticity region and carry particles during their rotation. Bubbles and particles achieve mineralization through shear collision. Based on this, the vortex construction methods for the high vorticity small-scale eddy fields such as shock flow and vortex generators have been proposed, which enable the turbulent eddy motion of flow field in flotation to effectively act on fine particles, improve the probability of collision between fine particles and bubbles, and reduce the lower limit of effective recovery particle size in flotation. The flotation experiments of different types of pure minerals and actual minerals show that the flotation performance of fine mineral particles is effectively improved by regulating the turbulent eddies in the flow field. The study extends the fine mineral flotation process intensification from “particle adjustment”, “bubble adjustment”, and “reagent adjustment” to “eddy adjustment”, providing a new thought and method for the enhanced recovery of poor, miscellaneous and difficult-to-select mineral resources.

  • 关键词

    微细粒矿物气泡碰撞湍涡矿化浮选流体动力学过程强化

  • KeyWords

    fine minerals;bubbles collision;turbulent eddy;mineralization;flotation;fluid dynamics;process intensification

  • 基金项目(Foundation)
    国家自然科学基金资助项目(52225405)
  • DOI
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  • 图表
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    • 小波分解树(以采样频率f=1 000 Hz为例)

    图(15) / 表(2)

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