刚柔组合桨搅拌强化锰矿浸出数值模拟

通过CFD软件对以SO₂气体为还原剂的锰矿浸出过程进行数值模拟,对比刚性单桨、刚性双桨及刚柔组合桨对于气-固-液三相混合强化作用。通过对固相及气相浓度云图分析,比较三种不同结构配置的搅拌反应器对固体颗粒悬浮和气体分散的作用大小,并对搅拌反应器内宏观、介观及其微观混合性能通过轴向和纵向的速度、湍动能及湍动能耗散率进行对比分析。结果表明：刚柔组合桨流场内并未出现颗粒团聚、气体分散不均等现象,并在流场上部对于颗粒悬浮及气体分散作用明显要强于单轴单桨及单轴双桨;刚柔组合桨的宏观、介观及其微观混合性能的表现均优于单轴单桨及单轴双桨。     

Turbulence Dissipation in Stirred Jars

A two-compartment analytical model was developed to estimate the turbulent dissipation rates in a standard jar stirred by a radial impeller. A simple numerical simulation was also performed to support the analytical arguments. Results of the numerical model showed that away from the impeller, the turbulent dissipation rate rapidly decays proportionally with z?2, where z is the axial distance. The turbulent velocity away from the impeller region showed a decay proportional to z?0.5. Although the dissipation rates at the wall boundary layer were higher compared to those in the tank interior, the total energy dissipated in the boundary layer is smaller compared to that expended in the impeller zone.     

三层桨搅拌槽内三维流场的数值模拟

采用计算流体动力学(CFD)的方法,对稀土萃取过程中上两层为平直叶、底层为涡轮桨叶的三层组合桨搅拌槽内三维流场进行了研究。利用标准的k-epsilon双方程模型对无机相(水)和有机相(P507)的混合液在搅拌槽中产生的流场进行数值计算,得到这种搅拌桨以恒定转速300r/min在搅拌槽内转动时产生的速度场和压力场,以及速度分布云图、速度矢量图以及压力云图,为搅拌桨的设计与改进提供理论基础。     

梯形通道中扰流柱沿流向叉排布置的流动和换热

应用湍流模型对涡轮叶片尾缘扰流柱通道的换热与流动进行了三维数值模拟研究。为了研究通道内扰流柱排列方式对换热与流动的影响，对扰流柱沿流向叉排布置的通道和几何叉排通道进行了数值模拟计算，并对两种排列的传热和阻力特性进行了综合分析和比较，结果表明扰流柱沿流向叉排通道对换热的影响比几何叉排通道的影响更显著，说明沿流向叉排是一种好的扰流柱排布方式。并计算了直径与平均间距比在不同工况下对流动和换热的影响。     

两段强制搅拌调浆的混合特性及对煤泥浮选的影响

基于强化煤泥浮选前的矿浆预处理过程,设计了具有折叶开启式涡轮的两段强制搅拌装置.通过分析两段强制搅拌体系的流量准数、功率准数、剪切特性、循环特性以及混合效率来评价搅拌体系的混合特性,并对永城矿区的无烟煤煤泥进行了两段强制模式的调浆浮选试验.随着转速的增加,输入两段强制搅拌体系的能量以及混合效率增加,单位能耗的矿浆循环性能和剪切性能均减小,剪切性能减小的趋势小于循环性能减小的趋势.在相同转速下,大直径叶片的单位能耗具有较强的剪切特性及混合效率、较小的循环/剪切比.在两段强制搅拌调浆模式下,旋流静态微泡浮选床可获得较好的浮选指标和较大的处理能力.大直径和高转速条件下的能量输入可促进矿浆中难浮颗粒的回收,在合适的处理能力条件下能够加强粗颗粒的回收,而在处理能力较强的条件下可以提高浮选尾煤中的细颗粒灰分.      

高剪切搅拌调浆对细粒级黄铁矿的浮选强化研究

结合微细粒浮选过程强化理论,以江西铜业股份有限公司武山铜矿选铜尾矿中细粒级黄铁矿为研究对象,使用计算流体力学仿真方法对常规搅拌桶和高剪切改质机内部流场特征进行对比分析,同时开展半工业尺度的搅拌调浆浮选试验,研究了不同调浆方式和强度对细粒级黄铁矿浮选的影响规律。研究结果表明：高剪切改质机内湍动能的耗散率高且分布更为均匀,对武山铜矿细粒级黄铁矿起到了良好的活化改性效果,同常规搅拌桶相比硫回收率提高了9.76个百分点,且随着搅拌强度的提高,硫的回收率明显提高,尤其是细粒级硫可得到有效回收。     

Turbulence characteristics of a gas-stirred steel bath outside the bubble plume

In order to understand the turbulence characteristic in melts stirred with injected gas, the relations for effective diffusion coefficient, turbulent kinetic energy and mean size of energy containing eddies were derived from the energy equation with an extended flow field for the steel bath, where strong bubble plume and surface currents are present. 67 or 23% of the energy is dissipated in the bubble plume or surface flow zone. An increasing entrainment coefficient leads to higher values of energy dissipation factor, effective diffusion coefficient and mean size of energy containing eddies, but to low degrees of turbulence. With increasing bath aspect ratio the energy dissipation factor increases, but the degree of turbulence decreases. With increasing gas flow rate and bath height the effective diffusion coefficient enlarges. Increasing bath size leads to large mean size of energy containing eddies, which reaches 17% of the bath diameter at high gas flow rates.     

Numerical Simulation of Transient Flow Patterns of Upper Swirls in Continuous Slab Casting Moulds

The transient aspect of turbulent flow in a continuous slab casting mould is studied and the transient flow patterns of the upper rolls are investigated through the application of Large Eddy Simulation (LES), employing a static Smagorinsky sub‐grid scale (SGS) model. The unsteady and coherent features of the upper recirculation zones are found, and the mechanism causing vortices developing from the upper recirculation zones is described and analysed. Results show that the asymmetry of flow patterns of the upper rolls appears most of the time. The upper swirls may break into a series of relatively small scale vortices that are chaotically distributed, and large‐scale vortex shedding occurs during the switching process between flow patterns.     

含钒页岩浸出槽搅拌速度优化的数值模拟

含钒页岩浸出槽是钒页岩湿法提钒浸出段的主要操作单元,存在固相分布不均、槽底矿物易沉积等问题。通过数值模拟研究来对比分析搅拌桨叶双层同速以及异速方案下对搅拌浸出槽内固液两相流搅拌功率和效率的影响。结果表明,当搅拌桨叶双层同速由1.3 r/s改变至1.7 r/s时,死区由5.02 m³减少至2.03 m³,混匀时间由1 501 s降低至1 116 s,近自由液面平均速度也由0.32 m/s增大至0.56 m/s,因此搅拌桨转速选择1.7 r/s更为合适;搅拌桨叶双层异速可以得到与双层同速情况下基本一致的搅拌效果,当上层桨叶转速由1.5 r/s改变至1.7 r/s时,死区由2.95 m³减少至2.33 m³,混匀时间由1 261 s降低至1 146 s,近自由液面平均速度也由0.44 m/s增大至0.54 m/s。因此搅拌桨转速选择上层1.7 r/s、下层1.5 r/s能在保持较低的搅拌功率同时能得到较好的搅拌效率。     

半圆管挡板搅拌槽内的固液悬浮

为了提高固液悬浮性能,设计了一种半圆管挡板搅拌槽。采用数值模拟和试验测试相结合的方法,研究了半圆管挡板Rushton桨搅拌槽内石英砂—水的混合特性,分析了固液悬浮特征、固相浓度分布和功率消耗情况,并与标准平直挡板搅拌槽内的悬浮性能进行了对比。结果表明,同一搅拌转速时,半圆管挡板能改善悬浮性能,低固含率(5%)时效果更好。整体而言,半圆管挡板搅拌时石英砂的浓度分布比标准平直挡板搅拌时均匀,而且功率准数低13%左右,节能效应明显。研究结果为半圆管挡板的工业应用奠定了基础。