Prediction of mineral liberation characteristics of comminuted particles of high grade ores

In mineral processing, the liberation of valuable mineral is of key importance in achieving high recoveries from downstream separation processes such as froth flotation and gravity concentration. To quantify mineral liberation, information on ore texture of the parent rock as well as properties of comminuted particles is essential. These properties have been quantified by statistical measures such as the proximity function and covariance function, which were extracted from SEM images of parent rock and particle polished sections, using convenient and efficient image analysis techniques based on Labview™ software. To quantify fully liberated particles, a phase specific line segment function has been introduced and evaluated by placing random line segments on the image. It was also found that the ore texture assumptions made by Barbery are not valid for the high grade sulphide ore tested and the general applicability of these assumptions is therefore questionable. Using the measured information above, predictive liberation models to quantify volumetric grade distribution of particles in 1D and 3D have been developed based on Barbery’s work. Results show that the grade distributions of composite particles predicted from the proposed 1D model is closest to measured data than those of Barbery’s 1D model. The predictions using the proposed 3D model are similar to those predicted from Barbery’s model and are considered more realistic as the model does not rely on assumed ore texture but on measurements made on the parent rock and particle sections.     

Evaluation of mineral processing by assessment of liberation and upgrading

A model is presented to evaluate mineral processing on basis of gangue recovery and valuables recovery. It combines mineralogical limiting curves with upgrading curves in the Fuerstenau diagram. These curves are used to assess mineral liberation and mineral beneficiation compared with the ideal result. Two new parameters (ratio of separation and ratio of liberation) are calculated based on a comparison of areas enclosed by the mineralogical limiting curve, the upgrading curve, the curve representing a total liberation of valuables, and the curve representing a perfect mixture of valuables and gangue.An assessment of the success of mineral processing is possible using these parameters. The assessment shows whether the quality of a separation product is influenced by the separation process itself or by the achieved liberation of the feed.A series of experiments on the magnetic separation of a greisen-type ore proves the applicability of this model to mineral processing. SEM-based image analysis and ICP-OES measurements have been used to obtain the necessary data.     

Mathematical models of the column flotation process a review

Mathematical modelling is a valuable quantitative instrument, which is being effectively employed to the column flotation process in order to predict its metallurgical performance. This paper presents an up-to-date assessment of the various mathematical models for column flotation currently available under the categories of kinetic models and non-kinetic models and also identifies a number of associated shortcomings.     

Determining a dynamic model for flotation circuits using plant data to implement a Kalman filter for data reconciliation

Data reconciliation is extensively applied to improve the accuracy and reliability of plant measurements. It relies on process models ranging from simple mass and energy conservation equations to complete causal models. The precision of reconciled data mainly depends on the complexity and quality of plant models used to develop data reconciliation observers. In practice, the difficulty of obtaining detailed models prevents the application of powerful observers like the Kalman filter. The objective of this study is to propose a methodology to build a model for a flotation circuit to support the implementation of a Kalman filter for dynamic data reconciliation. This modeling approach extracts essential information from the plant topology, nominal operating conditions, and historical data. Simulation results illustrate that applying a Kalman filter based on a rough empirical model that has been correctly tuned gives better estimates than those obtained with sub-model based observers.     

某低品位钼矿煤油气溶胶浮选特性的研究

针对某低品位钼矿,将捕收剂煤油气溶胶化进行加药,试验从粗选、精选和扫选三个阶段分别进行了气溶胶浮选特性的研究。试验主要考查了气溶胶加药技术对各浮选阶段煤油用量、浮选速度和钼回收率的影响情况,并将其与常规浮选技术进行对比。试验结果表明：气溶胶浮选在粗选和精选阶段表现出了独特的优势,而在扫选阶段没有表现出良好的优越性。与常规浮选相比,在粗选阶段,气溶胶浮选使钼回收率提高了2.01%,煤油用量节省40%左右,浮选时间缩短40%左右;在精选阶段,气溶胶浮选使钼回收率提高了1.12%,煤油用量节省50%左右,浮选时间缩短37%左右。气溶胶浮选具有提高药剂作用效果,减少药剂用量,加快浮选速度,提高浮选指标等优点。     

A relationship between the bubble-particle attachment time and the mineralogy of a copper-sulphide ore

Flotation performance depends on bubble-particle attachment which is controlled by the particle surface properties which include the particle composition and the surface liberation of valuable minerals. This paper discusses the contribution of liberation of valuable minerals to bubble-particle attachment time measurements, under constant chemical conditions. The bubble-particle attachment time measurements were performed using a sized fraction from concentrates obtained at different times and tails by flotation of a copper-gold sulphide ore (Northparkes Mine, Australia) in a mechanically agitated batch flotation cell. All products and tails were analyzed using quantitative mineral liberation analysis. The results showed that there was a relationship between the time of the concentrate collected, the Cu grade of the sample and the bubble-particle attachment time, and that the measurements were most sensitive to the amount of unliberated material. The fast floating material was higher grade, with a lower attachment time indicating that the measured bubble-particle attachment time could be used to characterize flotation performance of an ore.     

Investigation of gas dispersion characteristics in stirred tank and flotation cell using a corrected CFD-PBM quadrature-based moment method approach

In this study, the population balance model (PBM) is coupled with computational fluid dynamics (CFD) to investigate the steady-state bubble size distribution in two types of process equipment namely, a standard Rushton turbine stirred tank reactor and a generic lab-scale flotation cell. The coupling is realized using Fluent 15.07 software, and the numerical model is validated for the stirred tank reactor. The population balance equation (PBE) is solved using the quadrature method of moments (QMOM) technique along with a correction procedure implemented to check and correct invalid moment sets. The breakage and coalescence of bubbles due to turbulence are considered. The breakage rate and daughter size distribution models proposed by Laakkonen et al. (2007) are considered. For modeling coalescence rate, models proposed by Coulaloglou and Tavlarides (1977) are considered. The interaction between the phases is handled by considering the drag model proposed by Lane et al. (2005) while ignoring the other interphase forces. The correction algorithm has been successfully implemented, and improved predictions of gas volume fraction and Sauter mean diameter (SMD, d₃₂) have been observed with a good match between the predictions and experimental measurements. The local SMD predictions are compared against predictions from the past studies and the superiority of the current approach for moderate gassing rates is established. The CFD-PBM approach is then used to study and characterize different flow regimes occurring in a generic mechanical flotation cell at different aeration rates and impeller rotation speeds. Also, power numbers are calculated from torque data and are found to drop considerably with an increase in aeration rate and impeller rotation speed as the flow regime approaches recirculating flow. The predicted SMD for flotation cell indicates that smaller bubbles are concentrated near the high turbulence impeller stream, the lower recirculation region, and close to the tank walls. On the other hand, large bubbles are formed in the upper tank region and are concentrated around the shaft during the flooding, loading, and transition flow regimes. In the future, the corrected QMOM approach will be further extended by implementing kinetic models capable of predicting the flotation rate constant using local bubble size information obtained from CFD-PBM simulations.     

Prediction of the metallurgical performances of a batch flotation system by image analysis and neural networks

It is now generally accepted that froth appearance is a good indicative of the flotation performance. In this paper, the relationship between the process conditions and the froth features as well as the process performance in the batch flotation of a copper sulfide ore is discussed and modeled. Flotation experiments were conducted at a wide range of operating conditions (i.e. gas flow rate, slurry solids%, frother/collector dosage and pH) and the froth features (i.e. bubble size, froth velocity, froth color and froth stability) along with the metallurgical performances (i.e. copper/mass/water recoveries and concentrate grade) were determined for each run. The relationships between the froth characteristics and performance parameters were successfully modeled using the neural networks. The performance of the developed models was evaluated by the correlation coefficient (R) and the root mean square error (RMSE). The results indicated that the copper recovery (RMSE = 2.9; R = 0.9), concentrate grade (RMSE = 1.07; R = 0.92), mass recovery (RMSE = 1.94; R = 0.94) and water recovery (RMSE = 3.07; R = 0.95) can be accurately predicted from the extracted surface froth features, which is of central importance for control purposes.     

Prediction of the disc wear in a model IsaMill and its effect on the flow of grinding media

Mill wear is a critical issue in mineral industries. It affects mill performance and the cost of replacing worn parts is high. Understanding wear and its effect would provide a useful insight for process optimisation. This paper combines the discrete element method (DEM) with a commonly used wear model to predict the wear pattern of stirring discs in a model IsaMill. The results show that wear is more severe at the outer face of discs and the lifting side of holes. The simulated wear pattern has been compared with those observed in practice. The effect of disc wear on the flow of grinding media is also examined, showing that with the increasing wear, impact energy increases while power draw shows a mix of slight increase and decrease. The findings would be useful to the improvement in the design and control of IsaMills.     

某重型矿用自卸车侧置式驾驶室悬置系统的振动特性试验研究

采用试验测试法,研究了某重型矿用自卸车侧置式驾驶室悬置系统在不同车速下的振动情况。按国标计算方法,将试验加速度数据进行加权均方根与隔振性计算,得出驾驶室内部各区域的振动情况。再结合频谱分析,获得了驾驶室各测点的振动特性与车速之间的变化规律。结果表明:该型矿用自卸车侧置式驾驶室悬置系统对高频段振动的减振性较好,而座椅悬置系统对低频振动的减振性较好,两种悬置系统相互配合使用能保证驾驶室驾乘的舒适性。     

金属矿床开采岩体移动预测系统的开发

分析目前岩体移动预测的各类方法,指出每一类方法适用条件和存在的问题,提出了以工程类比、数值分析与现场监测三者相结合的综合预测理论,进行了"金属矿床开采岩体移动预测辅助系统"的结构设计与开发。     

某矿山矿石爆破相似试验模型强度力学测试分析

某矿山采用无底柱分段崩落法,中深孔爆破,矿体节理裂隙发育,矿石物理力学性质比较复杂,矿石爆破相似试验模型材料的强度难以确定。因此,本文根据相似理论针对矿石进行相似性分析,并设置三组不同配比的模型试件进行力学测试,通过对模型试件的测试结果进行数据处理得到三组试件的σ-ε曲线图,分析三组试件的破坏形式,计算出三组试件的物理力学参数,并结合相似理论对矿石物理力学性质分析的理论值,最终得到满足矿石爆破相似试验的模型强度。     

Effect of seepage control on stability of a tailings dam during its staged construction with a stepwise-coupled hydro-mechanical model

Seepage flow renders tailings dams vulnerable to failure during their staged construction. Draining is one of the most effective measures in improving dam stability. In this study, a stepwise-coupled hydro-mechanical model is employed to examine the effect of seepage control on the stability of a tailings dam during its staged construction. The settlement and deformation of the tailings under gravity load are modelled using the Duncan–Chang non-linear elastic E–B model, and the seepage flow through the tailings with drains is characterised by a variational inequality formulation of Signorini’s condition. The Kozeny–Carman equation is calibrated to illustrate the dependence of hydraulic conductivity on the porosity and volumetric deformation of the tailings. The proposed model was applied to assess the performance of the drains designed for the Luogou tailings disposal in Luanchuan County, Henan Province, China. Numerical results show that the stress-induced variation in tailings permeability could be of 1–2 orders of magnitude, and a proper design of the drainage system is of great importance in lowering the phreatic surface and protecting the tailings from seepage erosion.