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.     

脉石矿物在细粒煤浮选过程的夹带回收特性研究

以脉石矿物高岭石为研究对象,通过浮选速度实验研究了其在单独及掺配浮选条件下的回收特性,探究了起泡剂用量、浮选浓度、搅拌转速对浮选过程中高岭石回收率Rs、水回收率Rw、夹带率eg的影响.实验结果表明:单独浮选时,高岭石夹带率eg在浮选过程中基本不变,表现出"随水分配"的特征;掺配浮选时疏水性煤粒促进了高岭石回收,高岭石回...     

Gas dispersion measurements in industrial flotation cells

For nearly 100 years, the flotation plant metallurgist has often wondered what is happening ‘beneath the froth’. To assist in unravelling this mystery, new technology has been developed as part of the Australian Mineral Industries Research Association (AMIRA) P9 project, to measure gas dispersion characteristics (such as gas hold-up, superficial gas velocity and bubble size) in industrial flotation cells. These measurements have been conducted in a large number of cells of different types and sizes by researchers from the Julius Kruttschnitt Mineral Research Centre (JKMRC) and JKTech. A large database has been developed and the contents of this database are described in this paper.Typical cell characterization measurements show a wide spread in values, even in the same cell types and sizes performing similar duties. In conventional flotation cells, the typical gas hold-up values range from 3% to 20%, bubble sizes range between 1 and 2 mm, and superficial gas velocity ranges from 1 to 2.5 cm/s.The ranges of cell characterization measurements given in this paper will enable plant personnel to compare their operation to other similar types of operations from around Australia and the rest of the world, giving opportunities for further improvement to flotation plant operations.     

Effect of entrainment in bubble load measurement on froth recovery estimation at industrial scale

Froth recovery was calculated in a 130 m³ mechanical cell of a rougher flotation circuit. This was done by bubble load determinations along with mass balance surveys. Valuable grade in the bubble load decreased in the −38 μm due to fine particles entrained to the chamber of the device. The effect of fine particle entrainment on froth recovery was evaluated. A comparison between results from the raw bubble load data (assuming all particles were transported by true flotation) with those from corrected bubble load information (subtracting fine particle entrainment) was carried out. Entrainment occurred due to hydraulic transport in the bubble rear, which corresponds to the worst case scenario for froth recovery estimation. Results showed that the relative error was less than 0.3%, which allowed validation of the bubble load measurement as an effective methodology for froth recovery estimation at industrial scale.     

煤泥浮选过程中的细泥夹带与罩盖机理

选用开滦矿区钱家营矿的高灰难选煤泥和大同塔山选煤厂煤系高岭石,通过单矿物和混合矿物浮选试验研究了影响高灰细泥夹带和罩盖的主要因素。研究发现：影响高灰细泥夹带的主要因素为细泥粒度、起泡剂用量和矿浆浓度,捕收剂用量对其影响较小;矿浆pH值接近8时,可燃体回收率最大。EDLVO理论计算发现：微细粒的高岭石与煤粒间存在着“能垒”,当颗粒间距约为30 nm时,“能垒”达到最大值;高岭石的粒度越细,“能垒”越低。外界能量输入可以打破“能垒”,使细泥颗粒发生罩盖。试验表明：强烈的机械搅拌使混合煤样的精煤产率和可燃体回收率分别降低10.87%和13.16%。     

Effects of hydrodynamic parameters on entrainment and flotation performance

The separation selectivity and efficiency of the flotation process depends not only on differences in the physico-chemical surface properties of various minerals within an ore, but also on the hydrodynamics of flotation. The hydrodynamics relate directly to many sub-processes of the flotation, such as suspension of particles in the pulp, dispersion of the air into bubbles and the probability of particle–bubble collision. Mechanical entrainment plays a major role in the quality of the flotation concentrate and the separation selectivity. Therefore, the effects of some important hydrodynamic parameters on both the entrainment and the flotation performance were investigated by means of a fractional factorial experimental design. Furthermore, many flotation tests were performed in order to generate sufficient data for use in empirical modelling and neural network based modelling, in light of the results of the experimental design. The adaptability and reliability of the models developed, depending on the treatment of available experimental data, have been studied comprehensively. Evaluation of the observed and predicted results demonstrated that the effect of some chemical and hydrodynamic parameters of the flotation process on both the metallurgical performance and entrainment in the training region, can successfully be predicted, with an error of less than 6%, by using the developed neural networks models without particular assumptions and additional experiments. In order to prove the validation of the empirical and neural networks models developed and to compare their performances, a few additional tests were conducted under predetermined flotation conditions. The results of these additional flotation tests indicated that the neural network models were consistently more accurate than the empirical models with a negligible error.     

Modelling of residence time distribution of liquid and solid in mechanical flotation cells

This paper presents the results of modelling the residence time distribution (RTD) in mechanical flotation cells, measured in several plants, using the radioactive tracer technique. Results include mechanical cells of 100–300 m³ operated with effective residence times from 2 to 7 min. Data were obtained in forced air and self-aerated cells for liquid and non-floatable solids (per size classes). Different RTD model structures including perfect mixing, Large and Small Tanks in Series (LSTS) and by-pass flow plus perfect mixing were evaluated and compared for single cells. The actual mixing regimes were related to the effective residence times and cell designs based on the model fitting. By-pass flow percentages were typically lower than 10%, therefore the perfect mixing model plus a dead time was a suitable model structure in most cases.On the other hand, the arrangement of cells in series was in most cases effective in reducing the bypass flow observed in single cells. In addition, the N mixed tanks-in-series model was used to represent the mixing regime along flotation banks, which were operated with mean residence times in the range of 18–53 min. Results showed that the N equivalent tanks-in-series values were closer to the actual values in most cases. In some applications, slight by-pass propagation was observed because of circuit layout, problems with the level control system, solid settling and/or high flowrates.     

Short-cut method for flotation rates modelling of industrial flotation banks

The knowledge of the distributed performance of a flotation bank, consisting of a number of cells in series, is a key factor for different purposes such as process design, scale-up, diagnosis, operation, control and optimization. A common practice in plant operation is to develop mass balances around the whole flotation bank in order to characterize the overall recovery, typically in rougher flotation. However, testing to fit flotation rate models are seldom developed on industrial flotation banks because they are high consumers of human labor during sampling, mineral samples preparation and chemical analysis development. In this paper a short-cut method is proposed which allows obtaining the relevant information for flotation rate modeling in a flotation bank with minimum effort and cost, and within a reasonable accuracy (less than 1–2% error in estimating cell recovery along the bank). The procedure considers two mass balances, one around the first cell of the bank and the second is the overall mass balance around the whole flotation bank, with a total of only 5 sampling streams. Examples developed in four rougher flotation banks located in three industrial concentrators illustrate the merit of this procedure.     

The entrainment effect on the performance of iron ore reverse flotation

An iron ore mineral processing plant in Brazil treating Itabirite ore was assessed by sampling a circuit consisting of Wemco 144 mechanical cells, as part of the AMIRA P9P collaborative research project. This paper presents and discusses the results of entrainability, water recovery and quartz and hematite grades associated to hydrodynamic parameters. The results indicated strong correlation between water recovery and hematite losses which was intensified by the operating conditions of the circuit.A potential alternative to reduce the hematite losses through entrainment and to increase quartz removal was to modify the traditional circuit design to treat rougher and cleaner/recleaner tails in different stages. In addition, the scavenger residence time must be matched to the quartz floatability. Changes to design and operation of these circuits are needed to sustain concentrate recovery and grade as iron ores become finer.     

细粒锡石浮选的试验研究和工业化应用

对云南某选矿厂硫化矿系统的泥化矿进行了选矿试验研究,通过旋流器脱泥、浮选除硫、锡石浮选的工艺,从锡品位为0.380%的给矿中获得了品位和回收率分别为8.47%和43.10%的锡精矿,锡石浮选作业回收率为78.13%。工业生产试验取得了与室内试验较为接近的指标,其结果进一步证明了锡石浮选工艺处理此类细粒级锡石具有明显的优势。     

GAS holdup and RTD measurement in an industrial flotation cell

In this work, the measurement of the axial gas holdup profile and gas residence time distribution (RTD), in a 130 m³ self-aerated flotation cell, is presented. For this purpose, a radioactive tracer gas was activated in the Nuclear Reactor of the Chilean Commission of Nuclear Energy.The gas tracer, Freon 13B1, was injected as an impulse signal at the gas (air) inlet point, located at the top of the cell, from which the gas tracer circulates first through the rotor, where the bubble dispersion occurs, and then the gas becomes well distributed over the whole cross-sectional area before leaving the cell.The axial gas holdup profile was estimated from the transient gas concentration measurement at different depths inside the cell. From these experiments it was found that the air entering the cell was preferentially distributed in the upper half of the cell, while the gas entrainment into tailings was negligible. The mean gas holdup was 8.8%, and consequently the effective pulp volume of collection zone was 91.2%.The gas concentration on top of froth was recorded for RTD measurement of the gas leaving the cell. It was found that the mean gas residence time was around 42 s and the mixing condition for gas and pulp was similar.     

A new industrial mineral: Huntite and its recovery

Huntite is a new industrial mineral. The industrial utilization of huntite is not well known. Huntite formations include different types of minerals such as hydromagnesite, magnesite, clay minerals, aragonite and dolomite. Separation properties of these ores have not exactly been determined yet.In this study, characterization of huntite ores was made and separation conditions for huntite from the associated mineral, magnesite were investigated. The effect of modifying reagents like sodium silicate and carboxymethyl cellulose on surface properties of huntite were also examined. Electrokinetic measurements showed that the surface charge of huntite becomes positive in the presence of MgCl₂ and CaCl₂. On the other hand, carboxymethyl cellulose was found to be a strong depressing agent for huntite in the alkaline region. The result of flotation tests performed with run of mine ore sample, huntite concentrates were produced with 97–98% huntite contents and 76–86% recoveries.     

银洞坡金矿氰渣浮选尾矿的综合回收

金精矿氰化渣经铅浮选后,尾矿再进一步综合回收铅、锌、金、银、硫,在资源不足的情况下,为矿山开辟了一条新的途径.试验中,采用Na2SiF6、纤维素联合强化抑制剂,重点抑制脉石矿物和黄铁矿,加入CuSO4活化剂活化强烈抑制的锌矿物,使铅、锌混合精矿达到了产品质量要求,取得了较好的技术指标.     

Flotation frother mixtures: Decoupling the sub-processes of froth stability,froth recovery and entrainment

The flotation process consists of two distinct phases: the pulp and froth phase. One of the main roles of the froth phase is to create a suitable environment for the separation of floatable, valuable minerals from non-selectively recovered, entrained gangue minerals. As a result the froth phase plays a significant role in the metallurgical performance of industrial flotation cells. Froth stability is important for the recovery of valuable minerals. However, a stable froth may contribute to increased entrainment and, consequently, a lower grade.This study compares the effect of frother mixtures with that of their single component frothers on the froth stability, froth recovery and entrainment of a platinum-bearing UG2 ore using polyglycol and alcohol frothers. The study showed that frother mixtures resulted in a greater froth stability than either of their component frothers. The increased froth stability was reflected in increased froth recoveries and greater overall recoveries. However, the important aspect in the use of frother blends was that they altered the froth structure and resulted in a lower degree of entrainment. This, together with the increased recovery, resulted in higher grades of valuable mineral recovered to the concentrate when using the frother mixtures.     

An evaluation of different models of water recovery in flotation

Water recovery is one of the key parameters in flotation modelling for the purposes of plant design and process control, as it determines the circulating flow and residence time in the individual process units in the plant and has a significant effect on entrainment and froth recovery. This paper reviews some of the water recovery models available in the literature, including both empirical and fundamental models. The selected models are tested using the data obtained from the experimental work conducted in an Outokumpu 3 m³ tank cell at the Xstrata Mt Isa copper concentrator. It is found that all the models fit the experimental data reasonably well for a given flotation system. However, the empirical models are either unable to distinguish the effect of different cell operating conditions or required to determine the empirical model parameters to be derived in an existing flotation system. The model developed by [Neethling, S.J., Lee, H.T., Cilliers, J.J., 2003, Simple relationships for predicting the recovery of liquid from flowing foams and froths. Minerals Engineering 16, 1123–1130] is based on fundamental understanding of the froth structure and transfer of the water in the froth. It describes the water recovery as a function of the cell operating conditions and the froth properties which can all be determined on-line. Hence, the fundamental model can be used for process control purposes in practice. By incorporating additional models to relate the air recovery and surface bubble size directly to the cell operating conditions, the fundamental model can also be used for prediction purposes.     

Froth zone characterization of an industrial flotation column in rougher circuit

In this investigation the froth zone of an industrial column (4 m “diameter” × 12 m “height”) in rougher circuit was characterized. Experiments were carried out at Miduk copper concentrator, Iran. Miduk is a unique copper processing plant which utilizes columns in rougher circuit. Cleaning and selectivity actions in the rougher froth were illustrated using solids and grade profiles along with RTD data. The impact of froth depth (FD) on overall rate constant (k) and k–S_b relationship was evaluated. Dependency of overall flotation kinetics on froth depth and gas velocity (J_g) was modeled by k = 4.97(FD)^?0.87(J_g)^0.80. Froth recovery (R_f) was estimated and modeled in terms of froth residence time of slurry (FRT_Slurry) as R_f = R_f,maxexp(?k × FRT_Slurry). Finally, the correlation between k, S_b (indicative of the collection zone performance) and FRT_Slurry (indicative of the froth zone performance) was modeled by k = 0.02 (FRT_Slurry)^?0.62(S_b)^0.82.     

核极限学习机在浮选回收率中的研究与应用

浮选回收率是浮选过程中重要的生产指标。需要通过人工检测得到的浮选回收率,可知性具有较大的时间延迟,使工人不能及时有效地对生产做出相应控制调整。由于浮选过程相当复杂,变量维数高、关联性强、噪声大、检测信号不完备等因素,难以建立较精确的回收率预测模型。然而,人工智能与机器学习技术能在机理不清楚、信息不完备的情况下,对复杂系统建立基于数据驱动的经验模型。因此,本文为提高回收率检测的及时性、有效性,在分析浮选过程相关因素影响的基础上,提出基于核极限学习机建立浮选回收率的预测模型。仿真实验结果表明,该建模方法可有效辨识浮选过程中,输入数据与回收率测量值之间的非线性关系,且具有更高的预测精度与训练性能。