KYF-0.2型浮选机停留时间分布的数值模拟研究

发布时间：2018-06-21 10:26

本文选题：浮选机 + 计算流体力学　；参考：《广西大学》2016年硕士论文

【摘要】：在浮选工艺中,浮选机的性能对浮选指标和浮选效率有着至关重要的影响,而浮选机内物料的停留时间分布是浮选机性能的重要表现之一。由于浮选机内固-液-气三相流动复杂,很难直接进行数学求解,而使用实验方法得到数据不全面并且会耗费大量的时间和成本。本文利用基本多相流理论和计算流体力学的方法,对KYF-0.2浮选机内矿浆的停留时间分布进行了数值模拟,考察了浮选机的叶轮转速、矿浆流量、矿浆浓度、粒度等参数对矿浆停留时间分布的影响,也对浮选机内短路和停滞区现象作出一定分析。本文的主要研究内容包括：1) 将实际的物理模型进行简化和合理的假设,并使用欧拉-欧拉多项模型、k-ε湍流模型、WenYu曳力模型等,建立了起了KYF-0.2浮选机内部矿浆的流动模型；2) 对单相流和固液两相流在浮选机内部流动过程进行了模拟,得到了矿浆在浮选机内的停留时间分布,分析并研究了固相及液相在整个浮选机中的流动规律；3) 根据得到的停留时间分布,建立了合适停留时间分布模型对其进行了研究,对流动中可能存在的短路和停滞区情况进了相关描述和解释；4) 考察了叶轮转速对于矿浆停留时间分布的影响。模拟结果表明,叶轮转速的提高对于单相流停留时间影响不大,这可能是由于在转速达到200rpm后已经建立了较为完整的流场,而在两相流中对于固相停留时间有一定影响,转速从200rpm增大到300rpm,固相平均停留时间由102s提升至164s,短路和停滞区比率有所改善；5)考察了矿浆流量对于对于停留时间分布的影响。模拟结果表明,矿浆流量减半后,单相流上循环中心可能形成流速较缓慢区域,无量纲平均停留时间由0.89将至0.85。在两相流中,固体颗粒则可能由于流出速度减慢,停滞区现象有所好转,无量纲平均停留时间由0.64提升至0.78。6) 考察了矿浆浓度和颗粒粒度对两相流固相停留时间分布的影响。模拟结果表明,矿浆浓度从12%提升至18%,固相平均停留时间从164s下降至153s。而当颗粒粒度从0.074mm增大到0.15mm后,平均停留时间从164s下滑至118s,存在着较为严重的停滞区。7) 对固-液-气三相流停留时间分布进行了初步的探索。模拟结果表明,气泡的平均停留时间在2s左右,并且停留时间基本一致。气泡的存在对于固相的停留时间有一定影响但与实际有一定区别,原因可能是模型设置不完善、气含率过高造成的轴功率降低、模拟步长的选择等等。具体还有待进一步讨论和实验的验证。
[Abstract]:In flotation process, the performance of flotation machine has a vital effect on flotation index and flotation efficiency, and the residence time distribution of material in flotation machine is one of the important performances of flotation machine. Because of the complexity of solid-liquid-gas three-phase flow in flotation machine, it is difficult to solve the problem directly, but the experimental method is not comprehensive and will cost a lot of time and cost. In this paper, the residence time distribution of pulp in KYF-0.2 flotation machine is numerically simulated by using the basic multiphase flow theory and computational fluid dynamics method. The impeller speed, pulp flow rate and pulp concentration of the flotation machine are investigated. The effect of particle size and other parameters on the residence time distribution of slurry is also analyzed, and the phenomena of short circuit and stagnation zone in flotation machine are also analyzed. The main research contents of this paper include: (1) simplifying the actual physical model and making reasonable assumptions, and using the Euler-Euler multi-term turbulence model / WenYu drag model, the flow model of the inner pulp of KYF-0.2 flotation machine is established. 2) the flow process of single-phase flow and solid-liquid two-phase flow in flotation machine is simulated, the residence time distribution of slurry in flotation machine is obtained, and the flow law of solid phase and liquid phase in the whole flotation machine is analyzed and studied. 3) based on the obtained residence time distribution, a suitable residence time distribution model is established, and the possible short-circuit and stagnation regions in the flow are described and explained. 4) the influence of impeller speed on the residence time distribution of slurry was investigated. The simulation results show that the increase of impeller speed has little effect on the residence time of single-phase flow, which may be due to the fact that a relatively complete flow field has been established after the speed has reached 200rpm, while in the two-phase flow, it has a certain effect on the residence time of solid phase. The effect of slurry flow rate on the residence time distribution was investigated by increasing the rotational speed from 200rpm to 300rpm, increasing the mean residence time from 102s to 164s, and improving the ratio of short circuit and stagnation zone. The simulation results show that after the slurry flow is halved, the flow velocity may be slower in the circulation center of single-phase flow, and the dimensionless mean residence time will range from 0.89 to 0.85. In the two-phase flow, the phenomenon of stagnant zone may be improved due to the slow down of the outflow rate of solid particles. The effects of slurry concentration and particle size on the distribution of residence time of solid phase in two-phase flow were investigated by increasing the average residence time (RTD) from 0.64 to 0.78.6). The simulation results show that the average residence time of solid phase decreases from 164s to 153s when the slurry concentration is raised from 12% to 18%. When the particle size increased from 0.074mm to 0.15mm, the mean residence time (RTD) declined from 164s to 118s, and there was a serious stagnation region. 7) the residence time distribution of solid-liquid-gas three-phase flow was preliminarily explored. The simulation results show that the average residence time of the bubble is about 2 s, and the residence time is basically the same. The existence of bubble has a certain influence on the residence time of solid phase, but it is different from the actual one. The reasons may be that the model is not perfect, the axial power is reduced due to the high gas holdup, the selection of simulation step and so on. Further discussion and experimental verification are needed.
【学位授予单位】：广西大学
【学位级别】：硕士
【学位授予年份】：2016
【分类号】：TD456

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