本文選題：浮選機 + 計算流體力學��； 參考：《廣西大學》2016年碩士論文

【摘要】：在浮選工藝中,浮選機的性能對浮選指標和浮選效率有著至關重要的影響,而浮選機內(nèi)物料的停留時間分布是浮選機性能的重要表現(xiàn)之一。由于浮選機內(nèi)固-液-氣三相流動復雜,很難直接進行數(shù)學求解,而使用實驗方法得到數(shù)據(jù)不全面并且會耗費大量的時間和成本。本文利用基本多相流理論和計算流體力學的方法,對KYF-0.2浮選機內(nèi)礦漿的停留時間分布進行了數(shù)值模擬,考察了浮選機的葉輪轉(zhuǎn)速、礦漿流量、礦漿濃度、粒度等參數(shù)對礦漿停留時間分布的影響,也對浮選機內(nèi)短路和停滯區(qū)現(xiàn)象作出一定分析。本文的主要研究內(nèi)容包括：1) 將實際的物理模型進行簡化和合理的假設,并使用歐拉-歐拉多項模型、k-ε湍流模型、WenYu曳力模型等,建立了起了KYF-0.2浮選機內(nèi)部礦漿的流動模型；2) 對單相流和固液兩相流在浮選機內(nèi)部流動過程進行了模擬,得到了礦漿在浮選機內(nèi)的停留時間分布,分析并研究了固相及液相在整個浮選機中的流動規(guī)律；3) 根據(jù)得到的停留時間分布,建立了合適停留時間分布模型對其進行了研究,對流動中可能存在的短路和停滯區(qū)情況進了相關描述和解釋；4) 考察了葉輪轉(zhuǎn)速對于礦漿停留時間分布的影響。模擬結果表明,葉輪轉(zhuǎn)速的提高對于單相流停留時間影響不大,這可能是由于在轉(zhuǎn)速達到200rpm后已經(jīng)建立了較為完整的流場,而在兩相流中對于固相停留時間有一定影響,轉(zhuǎn)速從200rpm增大到300rpm,固相平均停留時間由102s提升至164s,短路和停滯區(qū)比率有所改善；5)考察了礦漿流量對于對于停留時間分布的影響。模擬結果表明,礦漿流量減半后,單相流上循環(huán)中心可能形成流速較緩慢區(qū)域,無量綱平均停留時間由0.89將至0.85。在兩相流中,固體顆粒則可能由于流出速度減慢,停滯區(qū)現(xiàn)象有所好轉(zhuǎn),無量綱平均停留時間由0.64提升至0.78。6) 考察了礦漿濃度和顆粒粒度對兩相流固相停留時間分布的影響。模擬結果表明,礦漿濃度從12%提升至18%,固相平均停留時間從164s下降至153s。而當顆粒粒度從0.074mm增大到0.15mm后,平均停留時間從164s下滑至118s,存在著較為嚴重的停滯區(qū)。7) 對固-液-氣三相流停留時間分布進行了初步的探索。模擬結果表明,氣泡的平均停留時間在2s左右,并且停留時間基本一致。氣泡的存在對于固相的停留時間有一定影響但與實際有一定區(qū)別,原因可能是模型設置不完善、氣含率過高造成的軸功率降低、模擬步長的選擇等等。具體還有待進一步討論和實驗的驗證。
[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.
【學位授予單位】：廣西大學
【學位級別】：碩士
【學位授予年份】：2016
【分類號】：TD456

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