浮选过程中的泡沫夹带研究进展

细粒矿物浮选过程中,亲水的脉石矿物泡沫夹带进入精矿中,导致精矿品位降低。揭示泡沫排液及排脉石过程中的相关理论,可以为浮选泡沫结构及泡沫夹带行为的研究提供理论基础。浮选过程中的脉石泡沫夹带是一种普遍现象,脉石夹带回收率与精矿水回收率呈线性关系;两相泡沫排液受重力、毛细作用力(表面张力)、黏滞力控制,不同含液率的两相泡沫排液遵循不同的排液公式;三相泡沫的排脉石过程遵循对流—扩散模型,脉石的夹带回收率受三相泡沫排液速率及脉石颗粒浓度分布控制。浮选操作条件、亲水脉石的特性、矿浆特性以及泡沫结构是影响泡沫夹带的主要因素;优化浮选操作条件,改变浮选流程结构和改变药剂制度可以有效降低脉石的泡沫夹带,提高浮选选择性。未来,还需开发表征浮选三相泡沫特征的方法、装置或仪器,三相泡沫的结构及形态、疏水矿物颗粒与亲水脉石颗粒在泡沫中的运动路径及分布规律、浮选三相泡沫排液及排脉石的数学模型还需要进一步的细致研究。另外,降低脉石泡沫夹带的技术对于部分浮选体系虽有一定效果,但脉石的泡沫夹带尚难以消除,须开发一些革命性的技术。     

浮选油泡稳定性试验研究

为了研究浮选油泡的性质,采用自制油泡生成装置,进行了泡沫稳定性试验以及精煤水回收率试验,分析了不同试验条件下,两相泡沫和三相泡沫的衰变过程、不同粒级对油泡层稳定性的影响和油泡与普通气泡表面水流夹带。     

超声乳化煤油乳滴尺寸对泡沫性质及隐晶质石墨浮选的影响

本文提出采用乳化煤油的方法强化泡沫排液,改变泡沫性质,从而降低在隐晶质石墨浮选中脉石颗粒夹带的思路。将乳化剂、煤油和氯化钠溶液以2.5%、2.5%和95%的比例通过不同的复配方法混合,采用超声波处理制备出不同乳滴尺寸的乳化煤油,并探究了不同方法获得的乳化煤油对泡沫性质(如气泡尺寸、泡沫层高度和水回收率)和隐晶质石墨浮选过程中脉石矿物夹带的影响。研究结果表明:随着乳化煤油乳滴尺寸的减小,泡沫层高度和水回收率降低,隐晶质石墨浮选过程中脉石矿物的夹带量减少,浮选精矿品位和回收率均提高。     

浮选泡沫细粒脉石夹带与充气量的关系

为更好地揭示并合理利用浮选过程中细粒脉石的泡沫夹带与充气量的内在联系,采用自制的泡沫特性测试系统,模拟了浮选中充气量对泡沫的特性及脉石的泡沫夹带行为的影响规律。结果表明：在两相体系中,充气量的增大会明显降低泡沫层中气泡的兼并速度,增大泡沫的含液率及泡沫柱表观液流速度,显著提高泡沫水回收速率;在三相体系中,充气量的增大会显著降低泡沫中脉石的回流速度,显著提高顶部泡沫层的脉石质量分数。因此,在浮选过程中,在保证精矿有效回收的前提下,控制充气量是有效控制精矿泡沫夹带脉石的有效手段。     

基于极限树回归的浮选泡沫层厚度预测研究

泡沫浮选是一种重要的选矿方法，不同表面物理化学性质的矿物颗粒在药剂的作用下借助浮选机实现分离。浮选机的控制变量包括充气量、泡沫层厚度和药剂添加量等。泡沫层厚度是影响浮选指标的一个重要控制参数，同样，泡沫层厚度的准确测量也至关重要。传统的泡沫层厚度测量方式一般是采用传感器等装置来实现的，由于这些传感器往往需要与矿浆直接接触，所以有时会因机械故障或信号干扰而造成测量值的误差。 针对传统测量手段存在的问题，本文提出了一种浮选泡沫层厚度的软测量方法。运用极限树回归ETR方法，以浮选过程中原矿品位、入料流量、入料浓度、入料粒度、充气量、泡沫稳定度和泡沫移动速度为输入变量，建立预测模型，实现了浮选泡沫层厚度的有效预测。     

无机盐对气液两相泡沫特性的影响研究

为更好地揭示并合理利用浮选过程中无机盐对浮选泡沫特性的影响,采用自制的泡沫特性测试系统,通过对两相泡沫不同高度处泡沫的静压强、气泡直径、泡沫柱的溢流流量进行测定,深入研究了无机盐对泡沫特性参数的影响规律.结果表明:在两相体系中,NaCl、Na2SO4、MgSO4及AlCl3这四种无机盐可显著减小各泡沫层高度下的气泡直径,增大泡沫含液率以及泡沫柱表观溢流速度,从而增大微细粒亲水脉石的泡沫夹带,而NaClO3的添加对泡沫特性参数均无显著影响.     

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     

泡沫稳定性研究进展

综述了近年来国内外学者们针对泡沫稳定性研究的进展。对各种测试方法和影响泡沫稳定性的主要因素进行了总结。对于泡沫衰变机理研究进行了讨论,指出调整泡沫体系液膜间通道的液相组成,或是改变液膜表面的界面层性质,是今后研究的发展方向。     

柴油对浮选泡沫稳定性影响的试验研究

泡沫稳定性是影响浮选过程效率的重要参数之一。为了探究柴油对浮选泡沫稳定性的影响,借助泡沫扫描分析仪(FOAMSCAN)研究了气液两相体系下不同浓度的柴油与体积分数20×10-6的甲基异丁基甲醇(MIBC)混合溶液的起泡能力与泡沫稳定性,采用动态液膜分析装置分析了泡沫间液膜的最终状态,进一步明晰了柴油对泡沫稳定性的影响机制,并通过细粒煤浮选及气液固三相泡沫稳定性试验探讨了柴油对实际浮选体系泡沫性质及浮选效果的影响。气液两相体系泡沫稳定性试验表明,随着柴油浓度的增加,溶液起泡能力和泡沫稳定性逐渐降低。泡沫间液膜测试结果说明,柴油浓度加大使得泡沫间液膜由最终的平衡状态转为破裂状态,液膜稳定性变差,气泡更容易兼并甚至破裂,该结论与气液两相泡沫稳定性试验结果保持一致。浮选结果表明,柴油用量较低时,随着柴油浓度增加,最大泡沫层高度和半衰期逐渐增大,浮选精煤产率也随之增大,这主要是由于柴油改善煤样表面疏水性以及细粒煤的稳泡作用所致;但当柴油用量增加到一定浓度后,最大泡沫层高度和泡沫半衰期减小,浮选精煤产率减小,一方面,柴油油滴进入泡沫间液膜中,在范德华力等力的驱使下,泡沫间的液膜逐渐薄化直至形成经典的油滴架桥现象,最终导致气泡兼并甚至破裂,另一方面,柴油油滴竞争吸附起泡剂分子,使得气液界面的起泡剂浓度降低,从而导致泡沫稳定性降低,柴油具有一定的消泡作用。     

充填式浮选柱的工艺优点

充填式浮选柱浮选是一种简单的且完全不同于其它浮选方法的新工艺。在浮选柱中添加填料能为颗粒与气泡的紧密接触提供窄小、曲折的通道。这些通道也使清洗水有效地通过厚泡沫层。充填式浮选柱采用填料撕碎气泡，不需要其它气泡发生器。不仅克服了回收细粒的困难，也能避免常规浮选枉中常遇到的轴向混合问题。试验表明，在Btu回收率为96．6%的情况下，可脱除86．1%的黄铁矿硫，其工艺优点主要在于大大地强化了泡沫分选。本文还讨论了细粒夹带机理。     

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.     

Modelling of entrainment in industrial flotation cells: Water recovery and degree of entrainment

Entrainment in flotation can be considered as a two-step process, including the transfer of the suspended solids in the top of the pulp region just below the pulp–froth interface to the froth phase and the transfer of the entrained particles in the froth phase to the concentrate. Both steps have a strong classification characteristic. The degree of entrainment describes the classification effect of the drainage process in the froth phase. This paper briefly reviews two existing models of degree of entrainment. Experimental data were collected from an Outokumpu 3 m³ tank cell in the Xstrata Mt. Isa Mines copper concentrator. The data are fitted to the models and the effect of cell operating conditions including air rate and froth height on the degree of entrainment is examined on a size-by-size basis. It is found that there is a strong correlation between the entrainment and the water recovery, which is close to linear for the fines. The degree of entrainment decreases with increase in particle size. Within the normal range of cell operating conditions, few particles coarser than 50 μm are recovered by entrainment. In general, the degree of entrainment increases with increase in the air rate and decreases with increase in the froth height. Air rate and froth height strongly interact with each other and affect the entrainment process mainly via changes in the froth retention time, the froth structure and froth properties. As a result, other mechanisms such as entrapment may become important in recovering the coarse entrained particles.     

粗颗粒浮选技术与装备研究进展与趋势

矿物的粒度是影响矿物浮选的关键因素之一,粗颗粒浮选 不仅对于缓解碎磨压力、节能降耗具有重大意义,而且有利于尾矿的资源化利用,为无尾或少尾矿山提供 了新的解决方案,因此粗颗粒浮选对于绿色矿山建设意义重大。从颗粒表面特性基因和泡沫特性基因的角度出发, 结合基因矿物加工工程的理念,综述了国内外对粗颗粒浮选技术与装备的研究进展,分别总结了机械搅拌式粗粒 浮选、粗颗粒流化床浮选和泡沫中分选（SIF 法）浮选技术的原理及其优势和不足。重点对影响粗颗粒浮选过程中的 因素进行了探讨,明确了影响粗颗粒浮选的关键因素,常规浮选技术难以从根本上提升矿石分选的粒度上限,复 合力场与浮选的结合为粗颗粒乃至超粗颗粒的浮选提供了可能,将推动矿物综合回收率的进一步提升和尾矿资源 的高消纳综合利用。     

Fundamental properties of flotation frothers and their effect on flotation

Froth flotation process requires the use of frothers. These important flotation agents are commonly characterized as either “selective” or “powerful” and are chosen following general guidelines and verification by laboratory and/or pilot plant tests.Fundamental properties of the flotation frothers have been extensively studied over the last few years. These studies have led to the development of standardised procedures to characterise frothers in terms of their ability to reduce bubble size and to increase foam stability.In this research project, the performance of five frothers in flotation of coal is evaluated and related to the fundamental properties of these agents. Since the recovery of water in the concentrate is closely related to the non-selective transport of solid particles by entrainment, the tested frothers are also assessed in terms of their ability to promote the transport of water towards the froth collection zone, both in absence and in presence of solids.     

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.     

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。     

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.