浮选机内矿浆停留时间分布研究

矿浆在浮选机的停留时间是浮选回路的重要参数,研究矿浆停留时间有利于了解浮选机内的流动特性、搅拌混合程度,能指导浮选机的操作,优化浮选机的设计。以实验室30L浮选机为研究对象,运用实验流体力学方法对30L浮选机液相进行停留时间分布研究,试验采用刺激响应法,得到了浮选机的停留时间分布,与理想停留时间进行了对比;运用双参数模型对试验处理分析,研究了槽体内的短路和死区的概率及短路和死区在浮选机中出现的区域。结果表明试验的平均停留时间与理想平均停留时间相差很小,短路和死区的概率分别为5.6%和2.7%。     

KYF型浮选机气泡特征参数分析与探讨—KYF浮选机流场测试与仿真研究(五)

浮选机内气泡特征参数和流动规律的研究一直是浮选机研究的重点和难点。本文利用电导探针法和CFD数值方法研究了浮选机内气泡特征参数及其分布特性。通过电导探针法获取了浮选机内气泡直径、速度和气含率等气泡特征参数。利用CFD数值方法揭示了浮选机内气含率的分布特征,预测结果同试验观察一致。并进一步研究了浮选机关键运转参数对气含率分布的影响规律。试验结果表明,CFD预测的气含率同试验测试结果吻合。     

KYF型浮选机内气泡特征参数分析与探讨——KYF浮选机流场测试与仿真研究(五)

浮选机内气泡特征参数和流动规律的研究一直是浮选机研究的重点和难点.本文利用电导探针法和CFD数值方法研究了浮选机内气泡特征参数及其分布特性.通过电导探针法获取了浮选机内气泡直径、速度和气含率等气泡特征参数.利用CFD数值方法揭示了浮选机内气含率的分布特征,预测结果同试验观察一致.并进一步研究了浮选机关键运转参数对气含率分布的影响规律.试验结果表明,CFD预测的气含率同试验测试结果吻合.     

机械搅拌式浮选机的流体动力学分析

利用计算流体动力学分析软件Fluent模拟计算机械搅拌式浮选机的内部流场。计算结果标明,矿浆在槽体内螺旋上升和螺旋下降的循环流动,存在流动死区和短路现象,湍流强度分布呈现对称性,最大湍流强度出现在叶片流道内,进出口对其影响不大。     

KYF型浮选机三相流仿真研究初探

CFD方法在浮选机三相流动仿真中的应用,对于揭示浮选过程和优化浮选设备具有重要意义。本文以大型浮选机KYF-160为研究对象,揭示了浮选机内三相流动特征以及气、固两相含率的分布。本文研究了矿石不同单一粒径下,固相含率的分布特点及其影响。矿石颗粒固相含率的分布特点与工程实际一致。矿石粒径的增大,会导致浮选机底部矿粒沉积现象严重,顶部固相含率变低。本文探究了多粒径体系下,浮选机内固相含率的分布特点。较粗的颗粒更难悬浮,因此,浮选机对于矿石入选粒径有一定要求。     

矿浆在大容积工业型单槽浮选机中的停留时间分布

研究了液体和不同粒度的固体(-45, 45-150和 150 μm)在自吸气式机械搅拌浮选机捕收区内的停留时间分布(RTD).结果表明采用LTST模型(大槽与小槽串联模型)和间竭时间,可以表征目前工业上应用的130～250 m3单槽浮选机的特性,从按比例放大观点来看,容积为130m3工业浮选机的混合特性与容积为250 m3浮选机的特性相近.同样地,单檀机械搅拌式浮选机的混合特性(RTD)与大容积充气浮选柱的混合特性类似.研究结果表明,用经典的N槽串联模型可以表征由3个或3个以上槽子组成的浮选机组的混合条件.     

基于数值计算的浮选机内颗粒流动行为研究

浮选机内矿浆动态流动性能研究对于优化浮选机具有重要意义。利用CFD数值模拟方法研究了浮选机内矿浆动态流动特性,并讨论了不同粒径矿石颗粒的分布特点,矿浆的动态流动并未破坏浮选机的循环流场结构,固相颗粒也形成了循环特征流场。单一固相粒径分析表明,随着给矿粒径的增加,浮选机槽底的沉积现象加重。多固相粒径分析表明,浮选机对不同粒级颗粒的提升能力和搅拌混合能力是不同的,为提高粗颗粒的回收能力,需要提高颗粒的提升高度。     

基于CFD的浓密机给料井停留时间分布模拟

采用CFX软件对浓密机给料井内的流体流动进行模拟,附加无反应组分输运方程研究流体停留时间分布(RTD),并考察了操作参数和结构的变化对RTD的影响。结果表明,随着给料流量的逐渐增大,给料井内的死区会减少,混合流与柱塞流会逐渐增多。此外,隔板安装高度的变大与过流面积的减少都会减少给料井内的死区区域,提高给料井的利用效率。     

工业型浮选回路自动控制的流体动力学特性和选矿指标研究

工业浮选回路由5排平行的粗选浮选机组成，每排由9台容积为42．5m^3的浮选机构成。用一个可连续测量局部充气量的简单装置直接测定浮选机单位横截面气体流速，其值范围为0．8～1．2cm/s。用一个矿浆取样器测定了矿浆的含气量，其值为15％～20％。用UCT气泡尺寸分析仪测定了气泡的尺寸分布，将测定出的平均气泡尺寸与矿浆－泡沫界面附近观察到气泡尺寸分布进行了比较。观察到的平均气泡Santer尺寸为0．9～1．1mm。用放射性示踪法测定了液相和固相的有效停留时间（RTD）。结果表明，固体的RTD比液体的短5％。也测定了不同粒级不可浮矿物RTD。对各列每一台浮选机顶部到底部矿浆的品位、浓度、各粒级的产率分布进行了测定，并对不同矿浆深度处的粒度分布和混合情况进行了全面地对比。考查了用强制充气和调节液面高度对各列浮选机动力学的影响。因此，建立了工业化浮选机精矿产率与富集比之间有用的关系模型，该模型可用于控制目的。     

BGRIMM浮选机放大方法与技术

低品位矿产资源高效开发对大型浮选装备技术有强烈需求。几十年来,世界范围内浮选装备的研究主要致力于设备的大型化。浮选机放大方法是浮选装备大型化的关键问题。简要分析了世界上主要浮选装备的大型化历程及其放大方法。阐述了我国BGRIMM系列浮选机的放大方法。BGRIMM系列浮选机的放大方法从相似放大理论、计算流体力学仿真优化和工业试验验证三个方面实现浮选装备的大型化。提出了以平均叶轮搅拌雷诺数相等、以几何相似及悬浮相似为核心的浮选设备放大方法。通过动力学准数分析论证了系列浮选机一致的动力学特性。建立了准确的浮选机CFD仿真优化模型,通过CFD辅助放大设计实现了大型浮选机细节优化。工业试验研究作为浮选机放大研究的关键环节,验证了大型浮选机优良的动力学性能。放大方法指导了BGRIMM系列浮选机的大型化,推动了低品位矿产资源的高效开发。     

基于数值示踪试验的浮选柱停留时间分布模型分析

浮选柱是实现泡沫浮选的核心技术装备。由于对细粒矿物优异的分选性能和较低的能耗,使得浮选柱得到了广泛应用。因此,研究揭示浮选柱内流动特性具有重要意义。轴向扩散模型和多槽串联模型是常用的反应器理论分析模型。本文应用轴向扩散模型和多槽串联模型分析了浮选柱流动特性,特别是物料的停留时间分布。采用计算流体力学方法研究了实验室浮选柱内示踪物的浓度变化。基于数值示踪试验,确定了轴向扩散模型和多槽串联模型的特征参数Pe和N。应用轴向扩散模型和多槽串联模型理论预测的浮选柱停留时间分布同试验结果吻合。     

Analysis of the residence time distribution in large flotation machines

Residence time in a single flotation machine is one of the most important parameters necessary to properly design a flotation circuit. The mean residence time for any particular cell design is usually determined from residence time distribution (RTD) experimental results. The comparison of the measured mean residence time with the expected residence time, as well as analysis of the shape of the RTD curve, give the most useful and valid information about the mixing properties in the cell.Experimental RTD results for three large flotation cells (Dorr-Oliver, Outokumpu and WEMCO^®) discussed in this publication were released by the Chuquicamata Division of CODELCO as a part of the competitive rougher flotation test report (CODELCO (National Copper Corporation of Chile), Chuquicamata Division, 2000, Project IM2, No. 19/99; Final Report of the Evaluation of Large Volume Flotation Cells). Evaluation of the results by CODELCO as well as by authors is provided. “Approximation of the theoretical curve of a perfect mixer,” used by CODELCO as a base for cell categorization is analyzed and critiqued after comparing to the criteria used by many authorities in the field.Conclusions are drawn based on the multi-parameter flow model, showing existence of stagnant volume of 45% in Outokumpu, 35% in Dorr-Oliver, and 7% in WEMCO^® flotation cell volumes.     

Mixing characteristics of industrial columns in rougher circuit

The rougher circuit at Miduk Copper Concentrator, Iran, includes five Microcel™ flotation columns in parallel, each 12 m in height and 4 m in diameter. The main objective of this communication was to describe the mixing conditions of rougher columns using residence time distribution (RTD) data. A liquid radioactive tracer was employed to trace the material reported to tailing and concentrate. External scintillation detectors were used to record the tracer intensity without disturbing the flow pattern. Data analysis showed that large and small tank-in-series and N perfect mixers in series were the best models to present the flow pattern of liquid transferred to tailing and concentrate, respectively. Solids mean residence time from a theoretical model for counter-current columns was estimated. A 1.4:1 ratio between the residence time of liquids and solids was achieved. In order to complete the diagnosis, solid content and grade profiles along the collection and froth zone of one of the columns were also measured. The results of the present study showed that despite the presence of vertical baffles, the mixing conditions of industrial rougher columns were close to well mixed ones. The possible causes for mixing in industrial columns were described. As expected by increasing gas flow rate, the mean residence times of liquid transferred to both tailing and concentrate streams reduced and the mixing degree increased.     

Modeling the RTD of an industrial overflow ball mill as a function of load volume and slurry concentration

The role of residence time distribution (RTD) in the accuracy of milling simulation is well appreciated in literature. Accordingly, the development of models that can accurately predict the RTD at various mill operating conditions would be of considerable benefit to the milling industry. In this paper, a 3-parameter RTD model has been derived using the concept of serial stirred mixers with a dead zone. The model parameters were optimized by minimizing the error between experimental tracer response data and model predictions using a MATLAB algorithm. Based on the optimum values of the model parameters, the mean residence time of slurry was evaluated and the effects of ball load volume and slurry concentration examined. The results revealed that the mean residence time of slurry inside the mill is affected to a larger extent by slurry concentration than the ball load volume. An empirical correlation was developed to predict the mean residence time as a function of slurry concentration, ball load volume and slurry feed rate. Over the range of conditions investigated, the mean residence time was observed to vary linearly with slurry concentration and ball load volume but inversely with feed flow rate. Lastly, a test case of the simulated mill product size distribution using the predicted RTD is presented displaying a close match with experimental data.     

Evaluation of residence time distribution and mineralogical characterization of the biooxidation of sulfide minerals in a continuous stirred tank reactor

The residence time distribution (RTD) of the liquid phase and the mineralogical characterization of the biooxidation of refractory gold mineral was studied in a continuous stirred tank reactor. The latter was achieved using a native mixed culture of acidophilic mesophiles. The RTD was assessed using a mathematical model of stirred tanks in parallel. The oxidation of sulfide and the phases generated through the biooxidation process were evaluated via X-ray diffraction (XRD).The results indicated that the experimental RTD fit to the model. The reactor has a high tendency to behave as a completely mixed reactor. However, the mixed flow inside the reactor has disturbances such as by-pass and dead zones. The estimated mean residence time for the model was approximately 36% greater than the theoretical residence time. It was probably caused by the delay in the outflow of the tracer due to gas hold-up, foaming at the top and the design of the reactor outlet structure. The XRD outcomes showed that the oxidation of arsenopyrite was greater than that of pyrite. Similarly, the formation of jarosite and brushite was observed. It was concluded that the dead zones could increase the probability of jarosite precipitations.     

Flotation rate distribution in the collection zone of industrial cells

The batch flotation process has been commonly characterized assuming a flotation rate distribution function F(k), e.g.: Dirac delta, Rectangular, Gamma or Weibull functions. The identification of F(k) for the collection zone of continuous industrial cells is more complex and to the authors knowledge, has not been reported yet.In this work, a novel procedure to estimate the flotation rate distribution from the collection zone of industrial flotation cells, using the radioactive tracer technique, is presented. The approach consists of measuring the impulse response of the floatable mineral tracer concentration, and non-floatable gangue tracer concentration (Residence Time Distribution, RTD), in the cell tailings. Then, the floatable tracer concentration can be compared with the model prediction, using the Gamma function and the RTD of the non-floatable tracer. Thus, the F(k) distribution parameters were obtained by means of the least-square estimation. The new approach was successfully tested in industrial rougher flotation cells of large size.     

射流闪速浮选机在铁精矿脱硫浮选中的试验研究

通过小型试验和工业试验,将安庆铜矿铁精矿脱硫浮选设备由XJK-2.8 m3浮选机改用SX-JLF-40-3高效射流闪速浮选机,脱硫率由70%提高到80%以上,取得了显著的经济效益和社会效益。