进气速度与质量流率对多密度颗粒分离性能的影响研究

通过建立多密度颗粒在康达效应下的分离模型,利用不同密度颗粒在康达壁附近迁移轨迹不同而实现不同颗粒间的分离。基于计算颗粒流体力学(CPFD)方法模拟混合颗粒在该模型下的流动迁移特征,反映出不同密度颗粒在不同进气速度与质量流率的分离特性。研究表明,进气速度与质量流率对不同密度颗粒在康达壁下的迁移轨迹及分布均具有重要影响,当气流速度为2.8 m/s,质量流率为10 g/s时,在420～480 mm区间,矿粒铜的回收率可达65%,品位可达78%,富集比可达9.75,在480～520 mm区间,矿粒钨回收率可达59.50%,品位可达72%,富集比可达18,说明在康达效应下可以有效的分选富集高密度金属矿粒铜和钨,对多密度颗粒的分选具有借鉴作用,同时可为我国西北水资源贫乏地区金属矿的分选提供新的思路。     

A preliminary investigation into magnetic separation process using CFD

The performance of magnetic separation units relies on the interaction between magnetic, hydrodynamic, gravitational, and inter particle forces. These forces are controlled by process as well as design parameters. In order to get a better understanding of the separation process we have developed a mathematical model using a computational fluid dynamics framework to follow the separation behavior of particles as in a wet high intensity magnetic separator. A three-dimensional, Eulerian-Eulerian model has been developed to predict the flow profile, as well as the concentration profile of solid particles between two parallel plates. The Navier-Stokes equations are used to predict the flow profile for the liquid phase. The model equations have been solved using the finite volume solver available in the commercial computational fluid dynamics (CFD) software, Fluent, to estimate the volume fraction of magnetic particles captured by the plates. Simulation results show that most of the magnetic particles are trapped on the magnetic plate which has also been observed experimentally.     

基于CG VOF-DEM和CG Mixture-DEM模型的水力旋流器多相流数值模拟

针对水力旋流器进料固体颗粒的分离过程内部流场复杂,颗粒运动规律难以掌握的问题.基于颗粒动力学理论并引入粗颗粒(CG)概念,提出了两种数值模型来对水力旋流器中的多相流进行建模:一种是将多相流(VOF)模型与离散元法(DEM)结合起来的CG VOF-DEM模型;另一种是将混合(Mixture)模型和DEM模型结合起来的CG...     

水力旋流器内部流场及分选过程的研究进展

论述了水力旋流器内部流场特性研究的发展历程及研究现状。详细介绍了数值试验方法在旋流器模型建立、内部流场特性描述、颗粒在其流场中的分离过程以及旋流器结构参数优化设计等方面的应用。在此基础上,提出了今后的研究方向与重点,即对于轴向零速包络面（LZVV）及空气柱的特性仍需进一步研究;在高浓度矿浆中,颗粒形状及颗粒与颗粒、颗粒与流体、颗粒与器壁之间相互作用对分离效率的影响仍是下一个时期的研究重点。     

高梯度磁选中非磁性颗粒的机械夹杂行为研究

非磁性矿物颗粒的机械夹杂是影响高梯度磁选选择性的重要因素。基于自主设计的高梯度磁选试验装置,对磁介质上、下游累积物进行冷冻-剥离和独立分析,系统研究了各种关键参数对非磁性颗粒机械夹杂行为的影响。结果表明,磁介质下游捕集的选择性都优于上游。非磁性矿物的机械夹杂主要发生在介质上游,增加给矿流速和减小非磁性颗粒的粒度可以提高高梯度磁选的选择性,磁场强度对介质上下游机械夹杂的影响较小。在较低流速条件下,弱化上游捕集和强化下游捕集具有重要意义,并提出了提高选择性的两种潜在技术方案。     

锥角对水力旋流器流场及分离性能影响的数值试验研究

为了考察锥角对水力旋流器内部流场和分离性能的影响，针对实验室[?]50 mm水力旋流器，采用Fluent软件中RSM湍流模型、VOF和Mixture多相流模型进行了系统的数值试验研究。流场模拟结果表明，在相同操作条件下，增大锥角，空气柱直径增大，湍流强度增加，压强和压强梯度均明显增加，从而导致整体能耗增加；切向速度随锥角增大明显升高，轴向速度变化不大，但LZVV逐渐向器壁移动，分流比逐渐降低。颗粒分离模拟结果表明，增大锥角会导致分离粒度增加，各粒级分离效率降低；小锥角容易造成“底流夹细”现象，大锥角容易引起“溢流跑粗”现象。研究结果为水力旋流器锥体的结构选择和设计提供了参考。     

Mechanics of coal spirals

Separation of liberated, organic contaminants from polluted soil has been simulated both numerically and experimentally. Simulation of the motion of the individual particles shows that the organic contaminants accumulate in the middle of the trough while soil particles move to the inner rim. The results suggest that the separation is determined by segregation in the first turn of the spiral. It was found that the separation is optimal when the spiral is operated close to the maximum capacity. Both a high slurry density and slurry flow rate are found to be beneficial.     

基于CPFD多密度矿物颗粒选择性分离行为研究

基于Barracuda仿真计算平台计算颗粒流体力学(CPFD)方法,建立多密度矿物颗粒干法选矿装置内部流场有限元模型,通过试验验证有限元模型的正确性,研究多密度矿物颗粒选择性分离行为对矿物颗粒分选富集效果的影响。结果表明:多密度矿物颗粒干法选矿装置可以有效的分选富集高密度有价金属钨、锰和铜;多密度矿物颗粒组分钨的品位随着粒径的增加而提高;当风速4.2m/s,矿物颗粒钨在分布距离170mm处分选品位较好,在开口为4mm时品位可达10.655%;矿物颗粒锰在分布距离270mm处富集程度最佳,开口为3mm时品位达到最大值48.3%。     

宽粒级煤炭颗粒在三相流化床中的分选实验研究

拓宽浮选粒度上限是浮选领域挑战的难题之一。应用三相流化床技术,在上升水流中引入气泡流,对比有无气泡对煤炭颗粒床层膨胀度的影响,得出气泡流的引入能够加强低密度颗粒的流化。并在单独上升水流、上升水流+气泡流和上升水流+气泡流+捕收剂(煤油)3种水流条件下,进行煤炭分选实验。结果表明,气泡流的引入,能够大幅减少低密度级颗粒悬浮所需的上升水流速度,气泡流对低密度级颗粒的影响强于高密度级,气泡的存在强化了颗粒密度、弱化了粒度对分选的影响;在上升气泡流中添加捕收剂后,低密度级颗粒与气泡形成颗粒-气泡结合体,低密度级颗粒便能够在较低的上升水流速度下进行分选,低速上升水流稳流度较低,保证了大颗粒与气泡的稳定性。添加捕收剂后,各粒级颗粒分选所需上升水流速度较为接近,各粒级精煤灰分在10%左右。     

Fine coal preparation using novel tribo-electrostatic separator

Dry coal beneficiation has been examined by tribo-electrostatic method using Indian thermal coal sample from Ramagundam coal mines. The process of tribo-electric coal/ash cleaning is carried out with a newly built cylindrical fluidised bed tribo-charger with internal baffles, made up of copper metal. The charge transfer in coal maceral and mineral particles after repeated contact with copper plate tribo-charger is measured. Separation of particles in an electrostatic separator according to the polarity of particle charge generated during tribo-electrification is discussed with respect to gas flow rate and residence time in fluidised bed tribo-charger and the applied electric field.The coal and mineral particles charge with positive and negative polarities respectively. The magnitude of particles charge found to be relatively high illustrating greater efficiency of contact electrification in fluidised bed tribo-charger. The separation results with ?300 μm size fraction of coal containing 43% ash showed that the ash content can be reduced to 18% and 33% with an yield of about 30% and 67%, respectively. These results are comparable to the maximum separation efficiency curve of washability studies on this coal sample. Since the ash percentage of coal particles collected in the bins close to positive and negative electrodes are about 70% and 20%, a better yield with low ash content can be accomplished on recycling the material.     

基于Euler-Lagrange方法的细粒煤脉动气流分选数值模拟

传统的欧拉模型和离散相模型难以准确模拟细粒煤气流分选过程,为此采用DDPM(Dense Discrete Phase Model)模型,引入相体积分数和软球碰撞模型,提出了一种基于离散相体积分数和颗粒间碰撞作用的新的细粒煤气流分选过程数值模拟方法。通过数值模拟与实验室连续分选实验,研究了分选机内流场分布和6~3 mm细粒煤脉动气流分选效果。结果表明:采用DDPM模型可有效模拟细粒煤气流分选过程中颗粒相对流场的扰动作用;分选柱内流场受被分选物料的影响,速度分布和压降值较加入颗粒前变化明显,且分选机处理量越高,压降变化越明显;实验条件范围内,DDPM模型模拟得到的各密度级重产物分配率均方根误差低于3%,且相同风量时,分选机处理量越大,分选密度越高。     

给料参数对螺旋溜槽内流层铺展及颗粒分离行为的影响

为了查明螺旋溜槽内流层形态及不同性质颗粒的分离行为,采用激光多普勒测速仪对螺旋溜槽内的清水流场进行测试,并考查入口水量对水层深度的影响,进一步对赤铁矿和石英进行螺旋溜槽分离试验,考查给料流量及固体质量浓度对矿浆流动和颗粒分离行为的影响。结果表明,清水在螺旋槽面中完全铺展,水深沿槽面分布呈现内中薄、外缘厚的特点,提高入口水量,水层铺展深度增大,且槽面中部及外缘处水层受到的影响更显著;矿浆均主要汇聚于螺旋溜槽外缘,提高给料浓度可使流层向槽内铺展,使中部分流比增大;提高赤铁矿的给料浓度可以削弱给料流量对流体运动的影响;在较低的给料浓度和给料流量下,石英主要在螺旋溜槽中矿带和尾矿带排出,粒度越小,石英在外缘尾矿带中的分配率越高,赤铁矿则主要集中于中矿带和精矿带,粒度越小,赤铁矿在內缘精矿带中的分配率越高,然而粒度过细会导致少量赤铁矿迁移到尾矿带中;螺旋溜槽给料条件对颗粒运动行为均有明显交互作用,在较低浓度下增加给料流量,石英颗粒因受力改变而向外缘迁移,而在高浓度下增加给料流量,则同时使流层向内汇聚及颗粒向内迁移,提高给料浓度和给料流量对赤铁矿回收具有不利影响,但在较低流量下提高给料浓度可减少赤铁矿在外缘尾矿带中的损失,在一定程度上起到提高处理量的作用。研究结果可以螺旋溜槽操作参数的选取提供依据。     

基于CPFD多密度电子垃圾颗粒分离影响研究

基于电子垃圾绿色、高效的分离回收需求,利用barracuda仿真软件建立电子垃圾颗粒气固分离模型,模拟电子垃圾颗粒在气流作用下的分选特性,探讨在不同气流参数及不同物料流量、不同粒径下电子垃圾各组分颗粒的分离效率和回收率。研究表明,电子垃圾颗粒下落流量与粒径对贵金属回收分离有显著影响,当一次进风的气流速度为3.8m/s、二次进风的气流速度为4.6m/s、入料开口宽度为4mm,颗粒粒径为75~100um时,Au的品位率和回收可达87.1%和99.1%,Cu的品位为70.8%,回收率为85.8%。说明在二次进风的作用下,改变电子垃圾流量和控制粒径大小可以有效提升电子垃圾中贵金属的品位和回收率,同时对多密度颗粒的分选提供参考和借鉴。     

基于CFD立式离心分选机的内部流场数值模拟分析

针对离心选矿机内部流场分布、颗粒无规则运动等问题,构建矿机内部三维流场域模型,并结合有限元理论借助CFD对分选腔内物料的分布规律进行数值模拟研究。结果表明:分选区间存在一种水力特征流态效应对细粒分选具有强化作用;通过模拟富集槽内轻重颗粒运动规律得出影响分选效率的主要因素集中体现在富集槽的截面形状不同,设计了一种双弧形壁面缩短了选矿恶化时间周期,为进一步优化立式离心分选机结构参数及查明流场特征及其规律提供相应的理论指导。     

铅锌尾矿在旋流器超重力环境内分离特性研究

通过对颗粒分离理论、铅锌尾矿分选处理工艺等进行分析,提出适用于铅锌尾矿分选的反向流化结构旋流器,利用锥面反向流化作用,快速分离具有密度差异的铅锌尾矿。结果表明,轴向压力值在不同径向截面处对应的值不同,整体上随轴向距离的增大而降低,且在圆锥段获得最大压力值;轴向速度分布呈对称分布,不同轴向截面处的轴向速度增减趋势有区别,颗粒分布主要集中在锥段;随着反向流化速度的增加,PbO矿粒从主要集中分布于旋流器器壁逐渐扩散至整个旋流器流场范围内,大密度PbO颗粒在器壁富集量先增加后降低;当反向流化速度为0.01m/s、进料速度为4m/s时,PbO颗粒达到最大回收率86.7%和富集比22.5,铅锌尾矿颗粒间的分离性能最佳。该研究成果为国内外铅锌尾矿的回收利用提供依据与借鉴。     

Computer simulations of the Fish-Hook effect in hydrocyclone separation

This contribution is dedicated to the direct modelling the non-monotonic course of the separation function of a hydrocyclone. To calculate the separation curve it is necessary to know the concentration field of particles of each size fraction in the apparatus. The system of equations describing the steady-state turbulent flow of a polydisperse suspension consisting of a liquid phase (water) and N fractions of the dispersed phase (particles) in the hydrocyclone, in line with the “mixtures model” can be written in a form of conservation equations. This system is investigated numerically. The main feature of these calculations is that previously developed model for the settling velocity of a polydisperse suspension in a centrifugal field is used. The results can be summarised as following: The consideration of the interaction of particles in a polydisperse suspension can explain the non-monotonic character of the separation curve (the Fish-Hook-effect) by the deviation of the particles’ sedimentation rate from the law of Stokes. The magnitude of the Fish-Hook-effect depends on the concentration of the solid phase.     

Separation performance of double deck banana screens – Part 2: Quantitative predictions

Banana screens are often used for high capacity separation of iron ore, coal and aggregates into different size fractions. They consist of one or more curved decks that are fitted with screen panels with arrays of square or rectangular holes. The screen structure is vibrated while a dense stream of particles flows over it and is separated according to size. The material discharging from the top of the deck is the oversize and may become a coarse product or be crushed and recycled to the screen feed. The material falling through the deck can be further separated by additional decks below. Each lower deck returns a product stream and the material passing out through the bottom deck is the undersize. In this paper, Discrete Element Method (DEM) is used to explore the separation performance of a full industrial scale double deck banana screen for a peak acceleration of 5g. The separation efficiency of each deck is analysed and the individual contributions of each screen panel are assessed using outputs from the model. Residence time distributions for particles on each deck provide insight into both the transport characteristics along the deck and the separation performance through each deck. The top and bottom decks have very different flow behaviour with very different bed structure and motion. The stresses applied by the flowing particles to the screen cloths and the impact and abrasive wear on the screen surfaces are evaluated. Finally, the energy absorbed by particles provides insight into the extent of particle degradation produced by transiting the screen.     

微细粒级钛铁矿的选矿预处理研究

攀枝花红格南矿区尾矿库钛铁矿TiO₂平均含量约为7.01%,钛主要集中在钛铁矿中,大部分以独立形式赋存,少部分与铁和钒以类质同像形式赋存在钛磁铁矿中。在成本较低的情况下,为了提高低品位微细粒级钛铁矿的选别指标,采用选择性分散絮凝—高冲次高梯度磁选新工艺对矿样进行预处理,并考察选择性分散絮凝药剂的种类、用量以及磁选的冲次等主要因素对低品位微细粒钛铁矿选别指标的影响。结果表明,在选择性分散絮凝药剂FX-3用量为700 g/t、强磁磁选冲次为350次/min的最佳试验条件下,获得的钛精矿TiO₂品位和回收率分别为24.93%和61.23%。在磁选试验前添加选择性分散絮凝药剂FX-3,使微细粒钛矿物和脉石颗粒稳定地分散在矿浆中,并相互作用形成不稳定的矿物颗粒,并通过“桥联”效应逐渐变成絮状物,在持续搅拌作用下形成更稳定的絮团,从而增加目标矿物颗粒的表观尺寸,有效地提高强磁分选效果和作用在钛矿物颗粒上的分选力。     

重介质旋流器分选过程的离散分析与数值模拟

重介质旋流器广泛应用于煤炭分选,分选过程十分复杂,试验测试研究重介质旋流器内部流场和颗粒运动特性费时费力,成本较高。随着数值计算技术的发展,国内外学者应用数值模拟方法研究旋流器内部的多相流流场。采用计算流体力学(CFD)与离散分析方法(DEM)耦合技术对重介质旋流器的分选过程进行数值模拟研究,为重介质旋流器的结构参数和操作参数的优化提供了一种新途径。用Fluent软件研究了旋流器内部悬浮液速度场、密度场、压力梯度场和黏度场,用EDEM软件研究了旋流分选过程中的煤粒运动行为及分选效果的评价。研究结果表明:悬浮液压力分布和压力梯度分布径向基本对称,溢流口和底流口处压力值最低。器壁沿径向形成了压力梯度,差值逐渐增大,空气柱边界处压力梯度最大;不同尺度的煤粒在旋流器内部的停留时间不同,相同密度的煤粒,粒度越小,停留时间越长。溢流中排出煤粒在旋流器中的停留时间明显长于从底流口排出的煤粒。溢流口排出的煤粒,密度越大,停留时间越长,底流口排出的煤粒,密度越大,停留时间越短。不同的旋流器结构参数对分选的影响程度不尽相同,其中溢流管直径的影响最为显著,溢流管直径超过500 mm时,不能形成完整的空气柱,无法分选。溢流管直径为300 mm时,分选效果较好;溢流管插入深度显著影响分选精度,插入深度为160 mm时,分选密度增大,细小高密度的煤颗粒将错配进入溢流,溢流管插入深度为320～800 mm时,分选密度接近悬浮液密度,分选指标E_p=0. 084～0. 100,分选效果较好。底流口直径对旋流器选精度影响较大,当底流口直径为272和306 mm时,分选密度与悬浮液密度接近,E_p值小于0.1,分选效果较好。圆柱段长度对于分选密度影响不明显。     

Numerical and experimental examination of swirl flow in a cylindrical container with rotating lids

Swirl flow is the primary mechanism for separation of particles in a hydrocyclone and hence influences the performance. The study of examining the basic swirl flow mechanism is accomplished by using a cylindrical apparatus with rotating lids. The upper and lower lids of the cylinder are able to rotate in the counter and clockwise direction at different angular velocities. In this study, the basic mechanisms of swirling in the laminar regime are investigated using an optically clear cylinder with rotating lids. The cylinder is filled with a liquid and the upper and lower lids of the cylinder are allowed to rotate in the clockwise and counter-clockwise directions. The induced flow is measured with a laser doppler anemometer and is compared to the velocity predictions from an in house developed software which solves the equations of motion. The results presented here constitute the first step in a series of experiments with the ultimate goal to improve the separation mechanism of hydrocyclones by means of controlling swirling flow characteristics.