An evaluation of the role of particle size in the flotation of coal using different cell technologies

A large variety of new flotation cells has been introduced in the last few years, probably as a result of the successful introduction of column flotation in the minerals processing industry. In common with the column cell, a number of these new cells employ an essentially quiescent separation zone. However, a number of novel cell designs have been introduced that use agitation mechanisms similar to those employed on conventional flotation cells. The aim of this investigation was to evaluate flotation behaviour in both an agitated and non-agitated environment, particularly with respect to particle size. A hybrid ‘agitated’ column cell was designed for the investigation, and the operation of this unit was compared to that of a column cell, and to a batch flotation cell, on a laboratory scale. The testwork was conducted on coal fines, as problems with the flotation of coarse coal particles in a column cell had previously been identified. It was demonstrated that the addition of an agitated stage to a column cell can significantly improve the coarse particle recovery in comparison to the conventional column cell, while maintaining good selectivity in the fine sizes.     

A comparative evaluation of rock strength measures

The variation in strength is investigated for eight lithologically similar, Silurian sedimentary rock units from the northeastern United States. The tests used for this investigation include the fracture toughness, uniaxial compression, point load index and Brazil tensile tests.The results show that the amount of variation associated with each test and formation is similar, although fracture toughness tests appear to give more consistent results. The strength and in situ location correlations indicate that the variation in strength within a unit is of the same order of magnitude as the variation associated with each test. Existing correlations among the tests are examined in the framework of the data, and new correlations for predicting fracture toughness are presented.The variation in strength with saturation for the sandstone is also examined; generally, the strength decreases with saturation. Lastly, the variation in strength as a function of lithological differences within one formation is evaluated. The results indicate that it may be more important to sample a rock unit selectively in a number of different locations than to do extensive testing in one location.     

浮选技术比武考核标准的探讨

技术比武是选煤厂搞好劳动竞赛的重要手段,制定规范合理的考核标准是技术比武的关键。针对选煤厂浮选技术比武中存在的问题,从浮选入料、浮选精煤滤液、药剂与浮选效率等方面入手,综合分析了各项指标对技术比武结果的影响。通过提出应用浮选完善指标考核,综合考虑药剂用量的技术比武思路,杜绝了单一定量指标考核的弊端,规范了技术比武流程,有利于反映岗位工操作的真实水平,对促进浮选生产具有积极的意义。     

A continuous pilot-scale flotation rig for the systematic study of flotation variables

A pilot-scale flotation apparatus has been developed for the purpose of determining floatability parameters for an ore. It has the capability to vary many of the important flotation variables allowing them to be investigated independently. Adjustable factors include: cell size, froth depth, feed, tailings and air volumetric flow rates and reagent addition rates.The flotation rig was commissioned successfully at BHP Billiton’s Cannington mine in North-West Queensland, Australia. It was found to supply a stable feed stream with air well distributed across the cell. At the test conditions, the relative standard deviation of the calculated galena overall recovery was found to be only 1%.Such an apparatus could prove invaluable in flotation research, allowing live streams from an operating industrial flotation plant to be processed continuously. The versatility of the design and accuracy of performance allow the investigation of most major flotation variables with confidence.     

焦化废水深度处理新技术及其相互耦合特征研究

焦化废水具有水量大、难降解、水质复杂和处理成本高等特点,且随着"两山论"、"零排放"和GB 16171—2012《炼焦化学工业污染物排放标准》等新理念、新标准的提出,传统深度处理技术已难以使焦化废水处理达标;为了使焦化废水稳定达标排放,探讨了以非均相臭氧催化氧化技术、磁混凝技术和聚瓷膜分离技术为核心的单元深度处理新技术及其相互耦合深度处理新技术;分析了新型臭氧催化剂和新型臭氧反应设备、新型重介质、新型膜材料和新型膜结构分别作为非均相臭氧催化氧化技术、磁混凝技术和聚瓷膜分离技术的重要特征;介绍了3种单元新型深度处理技术及其分别耦合技术的应用现状,并指出耦合新型处理技术可以使焦化废水处理后稳定达到废水排放标准或废水回用标准,总结了不同技术的绿色环保、处理成本低、矿化程度高、处理效果好、短流程和运行稳定等技术优势。根据单元深度处理新技术及其分别耦合新技术的特点,形成了完善和成熟的集成技术工艺包,这将是今后焦化废水深度处理新技术发展的新趋势。     

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.     

浮游选煤精选作业工艺效果评定方法的探讨

对浮游选煤精选作业工艺效果评定方法进行学术性探讨,初步提出将精选完善指标作为主要评价指标,浮选精煤可燃体回收率和浮选精煤非可燃体脱除率作为辅助评价指标。依据数理统计分析,在一定条件下,精选完善指标和浮选精煤相对降灰率存在良好的正相关关系。     

3D打印技术及先进应用研究进展

对3D打印的主要技术原理及特点进行了介绍,综述了3D打印技术在航空航天、生物医学和陶瓷制造等先进领域的研究现状,并指出了我国发展3D打印技术存在的问题,展望了其美好前景.     

A strategy for the identification of optimal flotation circuits

This article presents a strategy for the identification of optimal flotation circuits based on experimental data and the assumption that the flotation circuit structure are not very sensitive to stage recovery. The main objective is to find a set of optimal flotation circuit configurations, including the best metallurgical conditions for the process and cell design. The optimization process maximizes the Net Present Value (NPV). This methodology consists of two steps. The first step of the methodology entails obtaining data from the laboratory. Different metallurgical conditions are tested for different flotation stages. Each metallurgical condition is evaluated to determine its kinetics. The second step of the methodology is the optimization process. The optimization process achieves the best solution by optimizing cell design, flotation circuit structure and metallurgical conditions. The optimization process has three phases. The first phase assumes that every flotation stage has the same residence time and calculates feasible flotation circuits, metallurgical conditions and cell volumes. This process is performed for several residence times and, therefore, a set of feasible solutions is generated. The second phase takes the previous set of feasible solutions and calculates the residence time at each flotation stage. Then, for each phase two solution, the optimal flotation circuit, metallurgical conditions and cell design are calculated. The final product is a set of optimal solutions than can be considered for further study. The procedure is illustrated by the design of a zinc flotation plant, considering seven flotation stages and five species.     

A conceptual model for gold flotation

This paper is aimed at producing a conceptual model for gold flotation based on the discussion of a number of experimental results where the behaviour of free and refractory gold has been studied under different chemical and physical conditions. A review of the literature suggests that there have been numerous studies on the flotation of free gold particles and refractory sulphides, but these investigations have typically focused on the individual flotation behaviour of each gold bearing species in synthetic mixtures and not when they are present together in “real” ores in the same pulp. The model discussed here shows that the flotation of refractory gold follows a similar trend to the recovery of refractory pyrite and pyrrhotite and is mainly affected by chemical conditions in the pulp such as redox potential, aeration conditions, copper activation, reagent synergism and galvanic interaction. Refractory gold is usually recovered by true flotation that is hydrophobic particle-bubble attachment, unless under certain conditions the physical transport of water and gangue provides a washing effect and detaches some of the sulphide material from the air bubbles. The flotation recovery of free gold is largely affected by physical constraints like the shape and size of the particles, the degree of water and gangue transport to the froth, the stability of the froth, and the extent of bubble loading of sulphide particles which can provide a barrier towards the hydrophobic bubble attachment of free gold. In each individual study the results suggest that the recovery of free gold follows a proportional trend with regard to water and gangue recovery. However, there is an inverse relationship between the true flotation of free and refractory gold due to the fact that free gold particles cannot attach to air bubbles properly in the presence of physical barriers.     

A model to relate the flotation rate constant and the bubble surface area flux in mechanical flotation cells

Two recent flotation models developed by the authors are discussed, viz. the bubble population balance model and the attachment-detachment model. The bubble population balance model describes the history of a bubble population in a flotation cell in terms of the sub-processes of bubble breakage and coalescence. The attachment-detachment model allows for the presence of a gas phase in the flotation cell, both in terms of a gas residence time and the attachment and detachment of mineral particles to/from bubbles. When combined the two models predict a near-linear region about a point of inflexion on the (simulated) response between the flotation rate constant (k) and the flux of bubble surface area through the flotation cell (S_b). It is proposed by the authors that this region corresponds to the linear k−S_b relationship observed in a recent research project on flotation kinetics in mechanical flotation cells by Gorain et al. (1997).     

Arsenic-rejection flotation circuit design and selection based on a multiple-objective evaluation

This paper describes the application of a shortcut computational method to analyse and compare alternative flotation circuits developed to treat high-arsenic copper ores. The methodology uses a superstructure that considers the many different available elements of the flotation circuits and compares the results. The circuits were evaluated using radial/spider graphs, and were evaluated based on the metric indices of efficiency, capacity, quality, economics and environmental impact.The simulations were performed for a superstructure that considered 27 flotation circuits for an Australian sulphide ore containing chalcopyrite, tennantite, quartz and pyrite. The starting circuit corresponded to the flotation circuit described in previous work on this ore (Haque et al., 2010, Bruckard et al., 2010), and was used as the basis for comparison of the alternative flotation circuits.The key result of the analysis is that the base condition is one of the best circuits with respect to the copper grade in the concentrates, CO₂ emission, and fresh water usage. However, the base condition is one of the most inefficient circuits with respect to the percentage of arsenic in the products, profit, and copper recovery. This study shows that there are more suitable flotation circuits available than the stated base condition for a specific goal and/or multiple goals.     

A comparison of the predictability of batch flotation kinetic models

Batch flotation test data of a mixture of pyrite and calcite were used to compare regression parameters of four kinetic model structures. The work included the use of unoxidized or a mixture of partially oxidized pyrite (by microwave irradiation). The objective of floating oxidized pyrite was to have mineral particles with different floatability, closer to a real situation. The models considered include: single rate constant, distributed rate constants (i.e. rectangular and gamma distributions), and a recently introduced approach based on fractional calculus. Such models were selected due to their good tradeoff between simplicity and accuracy. The regressions were performed (1) taking all the data points and comparing the mean square error (MSE) and adjusted correlation factor $\left(R_{\mathit{Adj}}^2\right)$ as indicators of the goodness of fit; and (2) taking the first data points while neglecting the last ones (from 1 to 3) and observing the variability of the model parameters and the prediction of maximum recovery (R_∞). For the latter regression scheme, besides MSE and $R_{\mathit{Adj}}^2$, a predictive factor, E, was defined by subtracting the final measured recovery from the calculation obtained by the model. This allowed to measure the ability of each model to extrapolate the omitted points on the recovery vs. time curve.Results from this study showed that the single constant model had a satisfactory performance with the advantage of having the least parameters compared to the other structures. The gamma model was effective and robust. The rectangular model gave an acceptable goodness of fit but overestimated the maximum and final recovery. Finally, the fractional calculus approach gave the best goodness of fit, overall, but failed in predicting the maximum recovery, which occurred when the derivative order was greater than 1.     

青海某金矿浮选尾矿环保提金试验研究及实践

青海某金矿矿石性质属典型的难处理金矿,在生产初期处理混合矿石,浮选回收率较低。基于浮选尾矿矿石性质开展CIL环保提金剂浸出试验研究,环保提金剂浸出生产实践表明,浮选尾矿金的浸出率为53.95%,选矿总回收率达到92.7%,浸出生产成本降低6元/t,年经济效益增加378万元,实现了浮选尾矿环保浸出清洁化生产。      

A review of the effect of water quality on flotation

As water resources become scarcer and society’s demands to reduce freshwater extraction have increased, mine sites have been increasing water reuse and accessing multiple water sources for mineral processing to save freshwater, particularly in froth flotation. Implementation of either strategy may lead to water quality variation that may impact flotation efficiency. A large number of studies have been carried out to enhance the understanding of water quality variation in flotation. However, these studies tend to be performed on a case by case basis. There is a lack of a framework to put together these existing studies, which makes it difficult to understand the topic comprehensively and therefore difficult to identify gaps and directions for future research. This would eventually hinder the ongoing implementation of water conservation practices and thus lead to more pressure being placed on freshwater. In this paper, a review of the existing studies on water quality variation in flotation is given in three aspects: causes of water quality variation, consequences of water quality variation and solutions for problems caused by water quality variation. Based on the three aspects, a framework was developed, with which these studies were categorized and structured. Organizing literature in this way makes it possible to identify gaps in current research and future research directions.     

浮选机－浮选柱联合分选某硫铁矿尾矿试验研究

以广东云浮某硫铁矿选矿厂的浮选尾矿为样品,采用浮选机-浮选柱联合分选工艺进行分选,充分利用浮选机和浮选柱两种设备的特性,在保证粗颗粒回收的同时强化了微细颗粒的回收。对原矿样品的粒度和硫含量进行了分析,结果表明硫主要分布于+74 μm和-10 μm两个粒级中。通过浮选机两次粗选、两次扫选、粗精矿再磨后两次精选流程的闭路试验,可从含硫6.91%的浮选入料中获得品位为33.42%、回收率为63.82%的硫精矿。在相同的药剂用量下,通过浮选机-浮选柱联合分选,可获得品位为32.68%、回收率为70.84%的硫精矿。粒级回收率分析表明,与单一浮选机工艺相比,浮选机-浮选柱联合分选后,-54 μm细粒级的回收率明显提高,尤其是-20 μm粒级,回收率提高了将近10个百分点。     

浮选试验标准不适应性讨论

浮选试验标准的根本作用是确定浮选"参数"与浮选"效果"的对应关系.为分析现行浮选试验标准的适应性问题,通过对新老浮选标准进行解读,并结合试验,指出了现行浮选标准存在的不适应性,如系统性较差、存在互相矛盾以及不适应生产实际的情况,从而使浮选效果评定缺乏整体性,主要体现在两方面:一是将无法获得理想分选误认为煤炭可浮性既包含...     

浮选回路配置的浮选动力学探讨

本文从浮选动力学的角度,对选矿厂浮选回路配置进行了探讨.认为采用目前性能先进的短柱型浮选机,单排配置槽数少,有利于矿物浮选性能的改善.     

A review of turbulence measurement techniques for flotation

Flotation is one of the most important primary separation processes in the minerals industry. As far as the mechanism of flotation is concerned, turbulence is one of the key parameters determining flotation performance because it affects three main processes: suspension of particles, air dispersion and particle-bubble collision, attachment and detachment. To study turbulence in industrial flotation cells, both numerical simulation and experimental measurement can be performed. Development of turbulence models and validation of Computational Fluid Dynamic (CFD) numerical simulation need experimental data obtained from turbulence measurement techniques that can be used in the three phase abrasive opaque environment present in a flotation cell. In this paper, the different techniques which have been used to characterise turbulence in the literature are reviewed in terms of their basic principles, system structure, range of application and limitations. Laser Doppler Anemometry (LDA), Particle Image Velocimetry (PIV), Constant Temperature Anemometer (CTA) and the Aeroprobe are all techniques that have been widely used to characterise the turbulence created in flotation machines operating with only fluid (or fluid and air). They cannot however be used when the concentration of solids is high as commonly occurs in a flotation machine. Techniques that have been identified that have the potential to be used to produce accurate measurements in three phase flows include Positron Emission Particle Tracking (PEPT), Piezoelectric Vibration Sensor (PVS) and Electrical Resistance Tomography (ERT). It is envisaged that applications of PEPT in three phase flotation cells will mostly be confined to studies at the laboratory scale. ERT has been tested in flotation cells filled with water and air but needs more development before it can be applied confidently in industrial scale flotation units. PVS, on the other hand, has been validated at laboratory scale and has been applied successfully for measuring turbulence in large scale operating flotation machines.     

A mixed collector system for phosphate flotation

Flotation has been used in industry for more than a half century as the primary technique for upgrading phosphate. While the flotation of phosphate was inefficient when oleic acid was used alone as a collector, therefore a mixed collector of oleic acid (HOl), linoleic acid (LA) and linolenic acid (LNA) was employed to improve the recovery of phosphate flotation. The batch flotation results showed that the optimal composition of the mixed collector was 54 wt.% HOl, 36 wt.% LA and 10 wt.% LNA. Additionally, the effect of pH on the mixed collector application was studied while considering the surface tension, contact angle and micro-flotation. The results showed that the mixed collector should be used at a pH of 9.5. Above a pH of 9.5, the adsorption of fatty acids dimers on the apatite surface hindered phosphate flotation. The influence of the mixed collector assembly on apatite flotation was also investigated. It was demonstrated that due to its low critical micelle concentration, a sufficiently hydrophobic apatite surface could be generated at a collector concentration of 60 mg/L. In addition, zeta potential experiments suggested that collector adsorption was governed by chemisorption. FTIR and XPS spectra studies further indicated that the chemical reaction involved the carboxyl groups of fatty acids and Ca species at the apatite surface for each fatty acid in the mixed collector.