涡流场强化管流矿化机理研究

The proposed research is in the area of fine-grained mineral recovery. The main focus of the proposed research is the study of intensive recovery of fine-grained mineral. Intensive research during the past 10 years proved that the cyclonic-static micro bubble flotation column is a novel kind of efficient floatation device useful for fine-grained mineral separation. The highly-turbulent flow field of the pipe flow in the floatation column is the main reason to strengthen the recovery of fine-grained mineral. With the decreasing of fine-grained mineral diameter, the turbulent intensity in the pipe flow should be increased in order to strengthen the recovery of fine-grained mineral. In this proposed research the intensification mechanism of pipe flow mineralization with the effect of eddy will be studied. There are two main themes within the proposed research. The first is to explore drag coefficient, which is crucial importance for the simulation of gas-solid-liquid three-phase flow with CFD software FLUENT, of bubble movement. Thus the detailed study on the movement of single bubble with the effect of different type and amount of frother is required. The second theme is to explore the intensification mechanism of pipe flow mineralization with the effect of eddy. Some experiments should be done to proved mechanism. At first, the small column or square column is inserted into the pipe along radial direction to induce different eddy flow field which will greatly increase the turbulent intensity in the pipe flow. Then, the movement and distribution of mineral particles and bubbles are studied by the laser particle image velocimetry (PIV) and numerical simulation. Hydrodynamic model of particle and bubble movement in the eddy will be established according to the experiment and numerical simulation result of flow field information. At last the intensification mechanism of pipe flow mineralization with the effect of eddy will be got by comparing the flow field information with mineral flotation test. At the same time, the result of proposed research is also available for the other separation equipment to recover valuable fine mineral.

旋流-静态微泡浮选柱是一种高效的细粒矿物浮选设备，其管流段的高紊流环境是难浮细粒矿物与气泡发生碰撞并粘附的主要场所；随着入浮矿物粒度进一步变细，需要增大管流段的紊流强度，目前提高流速增大管内紊流强度方法导致管壁的严重磨损。本项目将以管流段的流动环境为研究对象，以提高气泡和颗粒之间碰撞概率及相对速度为目标，在流速不变条件下，利用内置混合元件诱发涡流流场强化管流段紊流强度。首先研究不同起泡剂种类及用量条件下单个气泡的运动规律，修正其运动曳力系数，作为后期数值模拟正确表达流场信息的基础；然后利用PIV技术及数值模拟方法研究混合元件诱发的涡流流场中矿物颗粒及气泡的运动规律，建立涡流场中矿物颗粒及气泡运动的流体动力学模型，并结合矿物分选试验，揭示涡流流场强化管流矿化的机理，因而具有重要的理论价值；同时本项目研究成果对于其它对其他分选设备强化微细粒矿物回收也具有指导意义。

管流段的高紊流环境是难浮细粒矿物在旋流-静态微泡浮选柱主要场所，为了应对矿物粒度的进一步变小这一问题，需要进一步增加管流段的湍流强度。本项目针对这一目标主要完成了以下几部分的工作：.1）建立清水以及起泡剂作用下气泡运动的曳力系数计算模型。单气泡运动曳力模型的建立是后续数值模拟研究的基础，文中采用实验方法，研究了不同直径气泡在清水和起泡剂（仲辛醇）作用下运动的曳力系数计算模型，在实验的雷诺数范围内（550≤Re≤1000），所建立模型的预测值与实验值的相对误差最大值为4.3%。.2）完成了气泡发生器结构的优化。气泡发生器结构将直接影响到管流段的流场，首先实验测量得到气泡发生器水流量和吸气量之间的关系，然后利用FLUENT 14.0对其进行三维流场模拟，模拟值与实验结果误差最大为7.6%，验证了所使用计算模型的正确性，利用该模型，研究了气泡发生器关键参数喉嘴距对气泡发生器性能的影响，研究结果表明，当喉嘴距为1.25 ~2.5 时候，其吸气量、气泡发生器出口气泡直径最小、气泡分布最均匀，即最有利于细粒矿物的浮选。.3）利用内置涡流发生器诱发涡强化管流段紊流强度。采用数值模拟的方法研究了涡发生器（VGs）对管流段紊流强度的影响，结果表明，当涡发生器的最佳间距为20mm，在不增加管内流速的情况下，管内平均紊流强度由0.015 m2/s2 增加到0.05 m2/s2当涡发生器的排数由0增加到5是，二湍流耗散率由1.99 m2/s3 增加到了11.8 m2/s3。根据矿物浮选理论可知，紊流强度和紊流耗散的增加是有利于细粒矿物的回收的。.4）进行了矿物浮选实验，验证了涡流发生器对细粒矿物回收强化的效果。进行分选实验，分别对对光管、1#管-单排布置、3#管-三排布置、5#管-5 排布置的管流段进行分选实验，实验结果表明：四种管流结构下的精煤产率呈现递增趋势由50.89%增加到55.42%，可燃体回收率有了明显提高，且精煤灰分差异不显著，强化了煤泥浮选效果。