Higher kaolin recovery with a water-injection cyclone

In kaolin classification, the final product is isolated from the overflow of a 50 mm hydrocyclone with an underflow containing fine sand and residual kaolin. For a higher kaolin recovery, the underflow is usually further treated using a washing cyclone. This paper presents a new development in fine sand washing using water injection in the conical section of the classifying cyclone. This washing results in a 45-50% reduction of the kaolin fraction (<10 μm) in the underflow. Thus, water injection into the classifying cyclone leads to a separation comparable to downstream washing.     

Mechanism of hydrocyclone separation with water injection

In hydrocyclones, the particle separation efficiency is limited by the suspended fine particles, which are discharged with the coarse product in the underflow. It is well known that injecting water in the conical part of the cyclone reduces the fine particle fraction in the underflow.This paper presents a mathematical model that simulates the water injection in the conical component. The model accounts for the fluid flow and the particle motion. The stationary concentration distributions result from superpositioning the turbulent particle diffusion and particle settling. Particle interaction, due to hindered settling caused by increased density and viscosity of the suspension, and fine particle entrainment by settling coarse particles are included in the model. Water injection in the conical part of the hydrocyclone is performed to reduce fine particle discharge in the underflow. This added water transports the fine particles of the sediment to the center, where they are directed to the overflow. The model demonstrates the impact of the injection rate, injection velocity, and injection location on the shape of the partition curve. Under optimal conditions, the so-called “fish hook” of the curve is reduced without changing the cut size. The simulations are compared with experimental data of a 50-mm cyclone.     

Classification evaluation of water injected hydrocyclone

The performance of hydrocyclone with a truncated cone and water injection facility at its apex has been studied. It was found that the flow rate of water in the overflow of the cyclone is higher when smaller cone is used. However on injecting water at the apex, the overflow water rate is minimum when smallest cone is used, implying localised effect of injection of water in the displacement of fines. Experiments using silica as feed, along with water injection, showed that the weight percent of particles less than a particular size in the underflow is reduced, this size being a function of inlet pressure and truncated cone diameter.     

高效节能旋流器在酒钢选烧厂的工业应用

酒钢选烧厂一段磨矿分级采用高效节能旋流器,强化了分级过程,提高了分级效率,高效节能旋流器溢流细度比螺旋分级机和常规旋流器溢流细度分别提高了4.22%和1.9%,沉砂夹细分别降低了3.19%和1.29%,分级效率分别提高了8.28%和3.5%,有效解决了酒钢选烧厂分级系统沉砂夹细偏多,分级效率偏低的问题,有效提高球磨机台时处理量,从而达到节能降耗的目的。     

Numerical study of particle–fluid flow in hydrocyclones with different body dimensions

This paper presents a numerical study of the gas–liquid–solid multiphase flow in hydrocyclones with different dimensions of body construction, which include the lengths of cylindrical and conical parts and cyclone body size. The turbulent flow of gas and liquid is modelled using the Reynolds stress model, the interface between the liquid and air core is modelled using the volume of fluid multiphase model, and the results are then used in the simulation of particle flow described by the stochastic Lagrangian model. The flow features are examined in terms of flow field, pressure drop, split ratio reported to the underflow, particle trajectories and separation efficiency. The proposed model is first validated by the good agreement between the measured and predicted results, and then used to study the effects of cyclone size and length. The results show that the flow fields in the hydrocyclones with different size and length are different, which results in different performance. A smaller cyclone is helpful to higher efficiency. The cylindrical section plays an inessential role in collecting particles. A long conical section can improve the performance of hydrocyclone considerably.     

采用水力旋流器和螺旋分选机处理粉煤的1艺计算与选择

水力旋流器和螺旋分选机是国外常用的粉煤分选设备.对于高灰或者难选粉煤,宜采用两段分选.文章通过对四种常用流程的模拟计算,确定了适宜的流程和条件,并分析了其优、缺点和适用范围.将此种工艺加在重介旋流器与浮选之间,为国内选煤厂设计和管理提供了新的思路.     

采用水力旋流器和螺旋分选机处理粉煤的工艺计算与选择

水力旋流器和螺旋分选机是国外常用的粉煤分选设备。对于高灰或者难选粉煤,宜采用两段分选。文章通过对四种常用流程的模拟计算,确定了适宜的流程和条件,并分析了其优、缺点和适用范围。将此种工艺加在重介旋流器与浮选之间,为国内选煤厂设计和管理提供了新的思路。     

新型加冲洗水式水力旋流器的研究

 本文在分析影响水力旋流器分级效率因数的基础上,提出通过降低底流中细粒级含量来增大旋流器的分级效率的方法,并对旋流器做了一些改进。新型旋流器采用加冲洗水的方式对矿浆进行二次分级,利用独特的底流口旋转筛分分级技术对底流进行三次分级,减少底流中细粒含量,以满足高效分级的要求。     

基于正交试验法的筛网旋流器分级性能研究

简要介绍了筛网旋流器的基本工作原理。通过对入料压力、底流口大小和溢流管插入深度3个影响因素进行了正交试验设计,同时利用正交分析法得出结论。结果表明:影响筛网旋流器分级粒度大小的主要因素为溢流管插入深度,底流口和溢流管插入深度交互作用显著。     

Volume split control of a hydrocyclone group

Experience obtained with a new hydrocyclone control system is reported. As command variable of the control serves an optical sensor detecting the underflow shape (rope or spray). These signals are transmitted to the computer and the control loop is completed with the pump power input, pressure in the feed and in the overflow. A volume split control of the hydrocyclone is performed by regulation of the overflow using a control valve. Groups of hydrocyclones can be controlled by installing only one control valve in a collecting pipe of all overflows. This control system stabilizes the separation at the transition point between spray and rope discharge at the cyclone underflow which in most cases is the operational optimum. One of the first applications was the regeneration of bentonite suspensions in tunnel driving. Since excavation of the material is discontinuous the solids content of the hydrocyclone feed varies over a wide range. By controlling the 150 mm hydrocyclone group it was possible to compensate for feed fluctuations and to stabilize the separation.     

磁铁矿粉旋流重选提铁降硅试验

通过采用水力旋流器,大锥角水介质旋流器与旋流重选柱对屯兰选煤厂选煤用磁铁矿粉进行分选对比试验,试验结果表明：随着单锥结构水介质旋流器底锥锥角增大,底流粗粒产品全铁品位提高,SiO₂含量降低。对于粗粒级磁铁矿粉,复锥结构的旋流重选柱提铁降硅效果优于单锥120°锥角结构水介质旋流器。     

Numerical analysis of hydrocyclones with different conical section designs

Hydrocyclones generally follow a conventional design and may have some limitations on separation performance. This paper presents a numerical study of hydrocyclones with different conical configurations by a recently developed computational fluid dynamics method. The feed solids concentration considered is up to 30% (by volume), which is well beyond the range reported before. The numerical results show that the cyclone performance is sensitive to both the length and shape of the conical section, as well as the feed solids concentration. A longer conical section length leads to decreased inlet pressure drop, cut size d₅₀, and Ecart probable E_p, and at the same time, an increased water split (thus larger by-pass effect). When conical shape varies from the concave to convex styles gradually, a compromised optimum performance is observed for the cyclone with a convex cone, resulting in a minimum E_p and relatively small inlet pressure drop and water split. Almost all these effects are pronounced with increasing feed solids concentration. Based on the numerical experiments, a new hydrocyclone featured with a long convex cone is proposed. It can improve the performance of the conventional cyclone at all the feed solids concentrations considered.     

Fundamentals on the spigot capacity of dense medium cyclones

The capacity of dense medium cyclones is often restricted by the solids-carrying capacity of the underflow, referred to as spigot capacity. Cyclone manufacturers normally recommend the spigot capacity for a cyclone of a particular size; however, it is not clear how these capacities are determined and whether they can be increased. In the literature, spigot capacity has previously been associated with roping flow at the underflow, although this notion has neither been clearly proven nor disproved. Furthermore, the effect of overloading the spigot on the operation of a dense medium cyclone has not been adequately studied.In this study, test-work on a 165 mm diameter dense medium cyclone was performed to investigate its spigot overloading behaviour. This work established clearly that spigot capacity was reached at the onset of roping flow, and that there was a critical underflow ore concentration at which roping/spigot overloading occurred. This ore concentration was shown to be a useful tool in anticipating and avoiding spigot overloading. Spigot capacities obtained in this study were higher than those specified in the DSM handbook, indicating that dense medium cyclone could possibly be operated at higher spigot capacities. However, separation efficiencies were not monitored during this investigation.     

Dynamic characterization of column flotation process laboratory case study

The objective of metallurgical column control is to achieve the economic optimum combination of concentrate grade and mineral recovery for any given feed. Metal prices and the cost of consumables will dictate the metallurgical concentrate and mineral recovery targets. Furthermore, experience has shown that collection zone height, air holdup and bias water flow rate are key parameters (controlled variables) that affect metallurgical performance. The collection zone height is related, mainly, with the residence time of the particles inside the collection zone, air holdup is correlated to the available surface area of air bubbles and bias water flow rate is an indirect measure of the cleaning action of the froth zone. However, these variables cannot be directly manipulated. Instead, wash water, air and underflow flowrates are the directly manipulated variables [1]. Therefore, if dynamic relationships could be established between the three manipulated variables and the three controlled variables, column metallurgical control may be improved. This study was an attempt to model these relationships using a tool known as System Identification, that includes Transient Analysis.The study consists in experimental tests, transient response analysis and identification of black box type models with cross validation.The experimental work was performed in a pilot scale laboratory flotation column of 3.2 m high by 80 mm of diameter. This flotation column operates in a plant with all the required instrumentation installed. The study considers the operation of the two phase air-water system.     

三产品重介质旋流器结构参数的计算

文章在研究二段底流口直径与其流量关系的基础上,建立了二段底流口直径与其流量的关系方程;根据原煤被分选后矸石的数量及悬浮液分配体积,求出了二段底流口直径;依据二段溢流口、底流口直径与流量的关系,求出了二段溢流口直径;再根据相关经验公式,求出了一段溢流口直径,从而确定出了三产品重介质旋流器结构参数中最重要的三个口径,为合理、准确地确定三产品重介质旋流器结构参数提供了科学的依据。     

对武安高岭土除铁工艺研究

河北武安硬质高岭土粉含Fe2O31.23%，经高梯度磁选后降至0.77%，再用Na2S2O3进行还原溶解后降至0.62%，白度提高了13％，本文介绍了流程及条件试验过程和结果。     

大锥角水介质旋流器分选粒控旋流器底流的可行性研究

用大锥角水介质旋流器对粒控旋流器底流进行了分选试验,结果表明,可从中回收近50%的合格精煤,Ep<0.1,分选不完善度I<0.2,并分析了工业应用的技术与经济可行性。     

某金矿两段分级超细尾砂静态沉降与半工业浓密试验研究

某金矿对分级细尾砂进行旋流分级,得到+37μm含量25%以下、-19μm含量60%以上的超细尾砂。基于该两段分级超细尾砂开展了室内静态絮凝沉降试验和半工业浓密试验。静态沉降试验分析了砂浆浓度、絮凝剂单耗对絮团沉降行为的影响,试验发现絮团沉降速度随着砂浆浓度的增加而减小,而絮凝剂单耗存在最优值,高于或低于该值,絮团沉降速度反而变慢。半工业浓密试验探究了泥层高度对浓密的影响,研究了固体通量对溢流水含固量和底流浓度的影响,试验结果表明:泥层高度与浓密的底流浓度呈非线性,底流浓度随着泥层高度的增加呈先增大后最终趋于平稳;随着固体通量的增加,溢流水含固量逐渐增大,而底流浓度与固体通量呈线性负相关。试验数据成功应用到1 000 m³无动力高效浓密机,实现了工业应用。     

单、双溢流管旋流器流场特征及分离性能研究

普通旋流器完成一次分级只能得到细颗粒的溢流和粗颗粒的底流,无法实现窄粒级精细分级要求。为了使一次分级可以获得多个细粒径、窄粒级产品,提出了一种双溢流管旋流器,为探明旋流器内流场特 征及分离性能,采用数值模拟和试验研究对比研究了双溢流管旋流器和普通单溢流管旋流器内速度场、压力场、粒度场及分离性能。数值模拟结果表明：具有双溢流管结构的旋流器经过一次分离可以获取内溢流、外 溢流和底流3种粒级产品。相比于单溢流管旋流器,双溢流管旋流器的切向速度和内部静压力更大;径向速度、轴向速度和湍动能更小,说明双溢流管旋流器可以强化分离过程,有利于分离性能的提高。试验验证结果 表明：相较于单溢流管旋流器,双溢流管旋流器底流浓度降低了8.3个百分点,底流产率增大了3.25个百分点,内外溢流产品中-45 μm的颗粒累积含量增加了1.15个百分点,综合分级效率提高了1.26个百分点。研究 结果可为多产品窄粒级旋流分离装备及工艺的研发提供一定的参考。     

Air core formation in the hydrocyclone

Air core formation has been investigated in hydrocyclones operated with clear water and a lucid suspension of glass balls. Hydrocyclones form a central air core which extends over the complete hydrocyclone length. Air is sucked in the core at the underflow discharge. The air core diameter can be determined balancing the positive pressure gradient and the centrifugal force in the rotational flow field. In dense flow separation (high feed solids content) the air core in the conical part of the hydrocyclone is suppressed. The hydrocyclone operates as it is air sealed because the solids are discharged trough the underflow as a rope. Then, air can be introduced to the hydrocyclone only on the feed side. In practice, feed suspension always contains more or less dissolved or dispersed air. Observations in a transparent hydrocyclone show that dissolved gas is released due to the pressure drop inside the hydrocyclone. The generated micro bubbles grow by coalescence and move in the centrifugal field toward the centre, where an air core is formed.