泡沫相对疏水矿粒的捕收

本文研究了在浮选中泡沫相对疏水颗粒的捕收。研制了能将泡沫相与矿浆分隔开的连续浮选机。粒度为d80 =87μm的赤铁矿在矿浆中用常规的油酸钠浮选 ,将类似粒度的 (d80 =82 μm)玻璃颗粒在添加清洗水时添加到泡沫相中。用接触角 0°～ 82°的 4种玻璃颗粒作为试验样品。研究结果表明 ,泡沫对疏水颗粒的捕收效率是很高的。颗粒的疏水性和泡沫中适于颗粒附着的表面积对该过程影响很大。对泡沫相浮选捕收玻璃颗粒推荐了一些参数 ,特别是以接触角描述的疏水性、泡沫厚度、向泡沫给料的固体浓度、空气流速和清洗水流速     

浮选泡沫相中现象及机理研究进展

泡沫相(层)是浮选重要组成部分之一,决定了最终精矿品位和整体浮选效率。由于泡沫相中的气泡与颗粒的相互作用比较复杂,近些年国内外学者围绕浮选泡沫层开展了大量相关研究。本综述在介绍浮选泡沫的结构和性质后归纳了浮选泡沫失稳的机理,即排液、粗化和兼并在现阶段的研究进展。对颗粒强化泡沫稳定性的相关机理进行了分析和总结,且归纳出颗粒疏水性、粒度和形状是颗粒影响泡沫层稳定的主要因素。之后回顾了泡沫层中常见的泡沫夹带现象,分析总结了泡沫夹带的三个主要机理;颗粒物理性质、水回收率、湍流强度、矿浆浓度、泡沫层性质和表观气速是影响泡沫夹带的主要因素;夹带模型的建立对脉石夹带程度的有效预测以及浮选工艺流程的优化具有重要意义。最后提出在今后的研究中加强泡沫相流体力学研究和推进泡沫层颗粒追踪技术是浮选泡沫相研究的方向之一。     

表面极性对微细石英颗粒沉降速度的影响

通过对微细石英颗粒的表面进行变性处理，研究表面极性对微细石英颗粒沉降速度的影响。石英砂粒群在水中的干涉沉降试验结果,干涉沉降速度的对数与松散度的对数基本保持直线关系。在相同的松散度下，疏水后的沉降速度比疏水前明显增大。疏水前后的直线斜率相等，均为4．0208，疏水前后的截距发生了变化。疏水前颗粒的自由沉降末速为2．277cm/s，疏水后为2．411cm/s，说明石英表面疏水性提高加快其沉降速度。     

铅-锌和铜矿石浮选过程中泡沫特性与品位——回收率之间的关系

浮选泡沫的特性取决于起泡剂类型与浓度、矿物粒度、疏水性能以及矿泥含量。在细颗粒存在的条件下,捕收剂的选择性差,主要因为颗粒被机械挟杂而回收,回收率虽高,但品位低。亲水的和疏水颗粒给予泡沫以稳定性。该稳定性取决于矿物颗粒粒度和     

铝土矿浮选三相泡沫稳定性研究

针对铝土矿浮选精矿三相泡沫体系,研究了表面疏水的一水硬铝石对铝土矿三相泡沫稳定性的影响规律。研究表明,影响三相泡沫稳定性的因素主要有颗粒大小、固体浓度和颗粒的疏水性。     

疏水性煤尘综掘工作面降尘技术研究及应用

针对疏水性煤尘在综掘过程中降尘效率低的难题,以王坡煤矿疏水性煤尘为研究对象,对煤尘进行润湿性测试。测试结果表明,快速渗透剂T溶液表面活性剂对王坡煤矿疏水性煤尘具有较好的润湿性和保水效果,能有效降低疏水性煤尘的湿润接触角,且浓度越高越有利于被低能的煤尘颗粒吸附;喷洒快速渗透剂T溶液表面活性剂能够在煤样表面形成固化层,使煤粉颗粒紧密连接、缩小间隙,煤尘之间的空隙被表面活性剂填充,使得尘粒相互黏结,更为紧凑,从而抑制煤尘飞扬。现场采用掘进机泡沫降尘与含0.03%快速渗透剂T溶液表面活性剂的气水喷雾降尘措施,可有效提高掘进工作面疏水性煤尘的降尘率,在掘进机后方一定范围内,全尘降尘率为63.35%～74.96%,呼尘降尘率为58.77%～71.50%。     

高泥化煤泥水的疏水聚团沉降试验研究

为探寻煤泥水聚团沉降新技术,以季铵盐类药剂为表面活性剂开展了高泥化煤泥水疏水聚团沉降试验研究,考察了药剂用量、动能输入、p H值等因素对高泥化煤泥水疏水聚团沉降的影响规律。结果表明:季铵盐能够改善颗粒表面疏水性,降低颗粒表面电负性,提高煤泥颗粒疏水聚团效果,季铵盐烷基链越长,药剂用量越大,对煤泥颗粒的聚团效果越强;高矿浆浓度煤泥水有利于煤泥颗粒形成疏水聚团;合适的动能输入能增强疏水聚团效果;随着p H值(p H=4~12)增大,沉降速度增大,但上清液透光率有所减小。当煤泥水质量浓度为26 g/L,采用p H=8.6、药剂1831用量3 000 g/t、搅拌强度750 r/min及搅拌时间10 min时煤泥水沉降效果较好,沉降速度达0.83 cm/min,透光率达78.6%。     

不同密度细粒煤泥对粗粒煤泥浮选的影响机理

分别将0.074 mm粒度以下的低密度(-1.4 g/cm3)、中间密度(1.4~1.8 g/cm3)和高密度(+1.8 g/cm3)细粒煤泥掺入到粗粒煤泥中进行浮选试验,研究不同密度细粒煤泥对粗粒煤泥浮选产率的影响,通过AFM测定低密度、高密度细粒煤泥颗粒与低灰粗颗粒煤之间的作用力,采用SEM观察浮选精煤、尾煤中粗颗粒煤的表面形貌,结合EDLVO理论对其影响机理进行了探讨。结果表明:中间密度细粒煤泥对粗粒煤泥浮选的抑制作用最大,低密度细粒煤泥次之,高密度细粒煤泥最小;粗粒煤泥的粒度越大,其浮选产率受中间密度细粒煤泥的影响越严重;AFM测定的作用力-距离曲线证实了疏水作用力的存在,颗粒疏水性越强,颗粒间的疏水力越大;通过SEM观察发现中间密度细粒煤泥在粗粒煤泥表面的罩盖现象显著。     

石墨尾矿沉降特性研究

研究了石墨尾矿浆在不同条件下的沉降特性,研究表明:石墨尾矿的沉降与颗粒细度、矿浆的浓度和外加剂有关:颗粒越细,沉降速度越慢;浓度越低,沉降速度越快,但颗粒的偏析和分级越明显。在矿浆中掺加促沉剂CBC-S时,在低掺量条件下具有加速微细颗粒沉降和改善水质的作用,在高掺量时有促使尾矿固化作用。     

疏水性微细矿粒在水中的沉降速度

微细矿粒表面性质对其在水中的沉降有重要的影响,通过理论分析与计算,得出了包含表面性质因素的颗粒沉降的介质阻力公式和沉降末速公式。试验测定了疏水前后的单颗粒和粒群在水中的沉降速度。结果表明,矿粒表面疏水化后,在水中的自由沉降速度和干涉沉降速度均上升,这与理论分析结果相一致。     

Effect of particle size on flotation performance of complex sulphide ores

Flotation processes occurring in the bulk and froth phases have a characteristic influence on the structural features and dynamics of the flotation froth. It is recognized that the structure and texture of a mineral froth is a good indicator of flotation separation performance. The surface froth feature and dynamics are presented by three features extracted from the digitized images of the froths, i.e. SNE, a rough indication of the average bubble size of the froth, froth stability and the average grey level of the froth, an indication of mineral loading. Particle size is an important parameter in flotation operation. Nowadays, particle size is often measured and controlled in flotation concentrators. In this study the dependence of the froth structures on the particle size variation was investigated on the batch flotation of a sulfide ore from the Merensky reef in South Africa, and the size by size recovery curves were studied as well. In general medium particles produced bubbles smaller than those observed in the presence of fine and coarse particles, and the recovery rates were larger. Entrainment was a contributory mechanism to the recovery of fine particles. The fluctuation of flotation indices on the particle size change can be diagnosed and predicted by the froth structures change with a high degree of accuracy.     

粗细粒级差异化给矿对浮选柱选别性能的影响

粗细粒级矿物具有不同的浮选特性,浮选柱主要应用于精选作业的细粒级矿物分选,对粗颗粒矿物回收率较低,限制了浮选柱的应用。在泡沫层分选理论的基础上,以纯石英矿物(纯度大于99%)为代表矿样,将其分成150~280μm和-15μm粗细粒级两个组分,采用Ф100 mm×2 000 mm浮选柱开展试验考察粗细粒级差异化给矿对选别性能的影响。在一个试验中将粗细粒级矿物混合给入浮选柱泡沫层之下进行常规浮选,在另一个试验中将粗细粒级矿物差异化给入浮选柱泡沫层之上和泡沫层以下分别进行泡沫层分选和常规浮选。试验对比结果表明,粗细粒级差异化给矿提高了浮选柱精矿回收率,对粗颗粒矿物回收效果提升更为显著。     

Influence of coal particles on froth stability and flotation performance

Solid particles have significant effect on flotation froth. In this research, the effects of coal particles of different size and hydrophobicity on froth stability and flotation performance were studied. The froth stability was measured in both the froth formation and froth decay processes by maximum froth height, froth half-life time and water recovery. The results show that fine particles of moderate hydrophobicity contributed most to maximum froth height in the froth formation process and were most favorable for flotation. Fine hydrophilic particles stabilized the froth in the froth formation process but the froth half-life time was very short due to the high water solid ratio. High hydrophobic particles of both fine and coarse size fractions greatly increased the froth half-life time in the froth decay process. But the froths were very rigid and the maximum froth heights were very low. The presence of fine hydrophobic particles was very unfavorable for the recovery of coarse particles.     

The dynamic behaviour of coarse particles in flotation froths. Part II: Density tracer tests

A novel flotation cell was used in which hydrophobic particles act as film breakers and sink through the froth as concentrate, while hydrophilic particles are supported by the upward flow of froth and are recovered as a top product tailings. Experimental results on density tracers showed that the behaviour of particles (within the size range tested) in the froth phase of the cell is primarily dependent on the mass of a particle. In general, the higher the mass, the steeper is the trajectory of the particle in the froth, i.e., an increase in particle mass results in an increased recovery to the concentrate. The contact angle on the particle surface has only a secondary influence on the overall particle trajectory, in that an increase in the equilibrium contact angle will result in an increased recovery. However, the particle contact angle has very little influence on the behaviour of large, high-density particles, as well as small, low-density particles.Particles will therefore only separate on the basis of contact angle as long as their mass is between an upper and lower critical value. Any particle with a mass greater than the critical value will fall through the froth irrespective of the contact angle. Similarly, the upward force component acting on a particle with mass less than the lower critical value will dominate the force balance. The particle will therefore remain supported by the froth, irrespective of the particle contact angle and bubble film rupture time. For particles within these mass limits, the effect of the contact angle increases with a decreased mass.It was further concluded that these mass limits are dependent on the operating conditions of the cell as well as the particle shape. The particle shape determines the mass to cross-sectional surface area ratio (M/A₀). Where particles therefore have the same mass, the M/A₀ ratio would govern the particle trajectory. The higher the M/A₀ ratio, the more particles would be recovered to the concentrate, while a decrease in the M/A₀ ratio would result in flatter particle trajectories in the froth, thereby increasing the probability of a particle reporting to the tailings. A mathematical model provides an understanding of the interrelationship between the various parameters.     

Combining Positron Emission Particle Tracking and image analysis to interpret particle motion in froths

Previous research into particle motion in the froth zone has focussed on constructing detailed CFD models that describe the behaviour of particle classes with different properties; density, size and hydrophobicity. These models have been reasonably successful in predicting trends in the separation behaviour and how it can be manipulated. Models of separation sub-processes cannot readily be verified experimentally due to the opacity and fragility of froth systems.Positron Emission Particle Tracking (PEPT) can be applied to particles in froth flotation systems to observe the behaviour of individual particles in a mixed particle–liquid–gas system. However, measuring the particle position alone is not adequate as its behaviour is also affected by instantaneous froth events such as bubble coalescence. To link the observed particle behaviour to the froth behaviour requires multi-modal measurements. Video footage of a rising foam column was recorded simultaneously with PEPT data, so that the PEPT tracer trajectory could be explained in terms of foam structure and events. A time weighting function of cubic splines with kernel width 200 ms was used to remove the effects of signal noise. An ascending 70 μm hydrophilic tracer accelerated within vertical Plateau borders and decelerated in Plateau borders angled away from vertical. The tracer trajectory showed velocity peaks and troughs when it was contained in nodes in a rising foam. When the tracer descended within a foam showing convective roll, coalescence events and subsequent foam deformation directly influenced the tracer trajectory.     

Froth recovery measurements in an industrial flotation cell

The froth phase serves an important role in upgrading the final concentrate in flotation. At present, the techniques that are used in the mineral industry to determine the effect of froth phase on the metallurgical performance of plant scale flotation cells have limitations.The aim of this paper is to investigate the performance of the froth in an industrial flotation cell. A unique device has been developed which is able to decouple the froth zone from the pulp zone. The device consists of two concentric tubes. The inner tube acts as a dropback collection chamber or catcher. The particles that return from the froth phase fall directly into the catcher and are collected as froth dropback. This technique is capable of measuring plant scale flotation cell froth recovery as well as providing valuable information on froth dropback particles.The froth recovery measurements were carried out in a rougher bank of a copper concentrator treating sulphide minerals. The dropback device is designed so that it can be immersed into an industrial size flotation cell and plant froth recovery measurements can be taken at any given location. During the experiments, the bubbles laden with valuable mineral particles entered the device from the flotation cell, subsequently rising to form a froth layer at the top of the device. The particles that detached or drained from the froth zone were collected in the dropback collection chamber whereas the concentrate sample was collected through a launder. By sizing and chemical analysis of the concentrate and dropback samples, the froth recovery was estimated on the basis of the valuable component. The effect of air rate on the froth recovery was also investigated. Metallurgical grades of the froth dropback device samples for different particle size ranges were compared to those of the concentrator to better understand the froth dropback mechanism.     

Investigating the effects of particle shape on chromite entrainment at a platinum concentrator

In flotation, entrainment is undesirable as it results in the recovery of hydrophilic gangue particles which reduces the concentrate grade. For UG2 ore, a South African platinum group mineral (PGM) ore, entrainment is particularly problematic because it leads to the recovery of chromite in the final concentrate which can cause severe problems in the smelter. It is therefore important to understand all factors affecting entrainment. These factors include froth characteristics, as well as particle size distribution and density, which have been studied widely. Theoretically, they should also include shape, as shape affects drag coefficients of particles and thus hindered settling rates of particles within plateau borders. In this study, detailed mineral-specific shape characterisation with Quantitative Evaluation of Minerals by Scanning Electron Microscopy (QEMSCAN) was used to assess the effect of particle shape on chromite entrainment during flotation of UG2 ore at a South African platinum concentrator. This plant-scale study suggests that shape does affect entrainment, with more rounded particles showing higher entrainment than angular, elongated particles.     

Evaluation of the selective detachment process in flotation froth

The improved selectivity between particles of varying degrees of hydrophobicity in flotation froths has been well documented in literature, especially in the deep froths utilized in flotation columns. The phenomenon is believed to be due to the selective detachment process whereby the least hydrophobic particles are released from the bubble surface upon bubble coalescence. To quantify the selective detachment process, column flotation experiments were performed under various operating conditions that provided varying amounts of reflux between the froth and collection zones. Entrainment was eliminated by the use of relatively coarse 250 × 75 micron material. The flotation column incorporated the ability to provide instantaneous stoppage of the process streams and separation between the collection and froth zones after ensuring steady-state operation of the column. The samples collected from the two zones and process streams were evaluated to quantify the flotation rate distribution of the particles comprising each sample. The flotation rate was used as an indicator of the degree of hydrophobicity and thus a relative measure of the binding force between the particle and bubble in the froth zone. The flotation rate data was used as input into well known flotation models to obtain the froth zone recovery rate and the quantity of material that refluxes between the collection and froth zones.