Application of neural networks to predict locked cycle flotation test results

The performance of a continuous flotation circuit is influenced by the flotation variables and the number of stages of a flotation circuit is dependent on flotation conditions, such that the interrelation between the flotation conditions and the number of stages must be carefully determined to obtain acceptable metallurgical performance from the circuit. The locked cycle test is a useful tool for simulation of continuous flotation circuits. However, it is a time-consuming and tedious procedure. A simulation method used to predict locked cycle test results from data from individual batch tests is available in the literature. In order to develop an optimum circuit configuration for a specific ore, several batch flotation tests for the first cycle of the locked cycle test have to be conducted to predict the metallurgical performance of various circuit types. Therefore, an integrated simulation method, which uses experimental data and the results of this simulation method has been developed to structure a neural network model for prediction of locked cycle tests results without additional experiment and calculation. In training and testing of the neural network model, results of the simulation method were used as the output data set and the flotation conditions of the batch tests were used as the input data set. Apart from the training and testing data, results of the LCT for several circuit types were predicted in order to validate the neural network model and to determine its performance on both: interpolation and extrapolation. Because the neural network model was trained using results of the simulation method, the use of the neural network model did not lead to any improvement in predictions of actual LCT results. However, the results of this study indicate that the neural network model can be used to simulate various circuit types with an error of less than 4%, instead of the simulation method. Consequently, the neural network model, as an alternative to the simulation method, can be used to determine the effects of changes in certain flotation variables on the number of cleaner and scavenger stages in a flotation circuit.     

Estimation of platinum flotation grades from froth image data

Features extracted online from froth images on flotation plants are potentially useful to the development of advanced control for flotation systems, provided that these features can be related to the key indicator variables of the plant, such as valuable metal loadings and recovery. Although such relationships have been established in a number of base metal plants in industry, this is not the case in the platinum industry. In this paper, estimation of flotation grades and recoveries from froth image data is therefore considered based on laboratory and industrial plant data. It is shown that grades and recoveries can be reliably estimated from a number of different features by use of linear and nonlinear models. This includes simple colour information that on the industrial plant showed a strong correlation with grade measurement.     

Monitoring of mineral processing systems by using textural image analysis

In the last few decades, developments in machine vision technology have led to innovative approaches to the control and monitoring of mineral processing systems. Image representation plays an important role in the performance of the recognition systems used in these approaches, where the use of feature representations based on second-order statistics of the image pixels have predominated. However, these representations may not adequately capture or express the visual textural structure associated with the observed patterns in images. In this study, the use of texton and complex multiscale wavelet representations (steerable pyramids) that exploit higher-order statistical regularities, is investigated. These techniques are applied to two image data sets: industrial platinum group metals froth flotation, and coal particles on a conveyor belt. Compared to grey level co-occurrence matrix and classical wavelet representations, these are observed to improve performance when used as input in the pattern recognition phase.     

Effect of ultrasonic treatment on zinc removal from hydroxide precipitates by dissolved air flotation

The effect of ultrasonication on the precipitation of zinc hydroxide, as well as the separation of zinc hydroxide and gypsum precipitates by use of dissolved air flotation are considered in this paper. Both ultrasonic treatment and the addition of carboxymethyl cellulose (CMC) resulted in flocculation of the zinc hydroxide formed during precipitation. The best flotation results could be obtained by using the CMC during precipitation of the hydroxides, followed by ultrasonic conditioning prior to flotation. Apart from flocculating the zinc hydroxide particles, expediting precipitation and enhancing reagent adsorption, ultrasonic treatment also promoted the mechanical removal of the zinc hydroxide from the surfaces of the gypsum particles.     

A new SEM-EDS based automated mineral analysis solution for PGM-bearing ores and flotation products

Reliable automated PGM identification is a consistent challenge on SEM-EDS based automated mineral analysis systems. The main reason for this is the size of the PGM grains, which are often smaller than 3 μm in diameter, particularly in chromitite ores of the Bushveld Complex. This leads to “mixed” X-ray (EDS) spectra, in which the relative PGM: gangue elemental contribution is variable. This is further complicated by the fact that PGM species often occur in the form of a solid solution series, and ideal chemical formulae of these minerals cannot be relied upon for automated mineral identification. These conditions make it difficult to automatically identify PGM species based on spectral matching or “windowed” elemental EDS X-ray analysis schemes.Mintek’s Mineralogy Division has developed and tested an algorithm that can identify PGM species from raw EDS spectral data, and largely overcomes the problem of mixed spectra. This PGM identification algorithm is being integrated as a plug-in into the Carl Zeiss SmartPI™ particle analysis software by the Carl Zeiss software team in Cambridge, UK, to provide a reliable automated PGM analysis system.     

The effect of the reagent suite on froth stability in laboratory scale batch flotation tests

In batch flotation tests conducted on ores from the Merensky reef, changes in froth stability invariably occur with variations in the reagent suite. The main reagents are collectors (primary and secondary), activators, depressants and frothers. Since the particles entering and leaving the froth in a batch flotation system are continuously changing, the stability of the froth can vary. Under these conditions the simplest measure of froth stability is the measure of water recovery at a fixed froth height. The batch flotation system developed at UCT allows for the separation of gangue which is entrained relative to gangue which is floated. It has been found that the presence of naturally floatable gangue (NFG) leads to froth stabilisation, whereas the presence of hydrophobic sulfide minerals may lead to destabilisation of the froth depending on the hydrophobicity (contact angle) of the sulfide minerals. This can vary with ore type since particle shape and amount of particles present can influence the extent of destabilisation. At low depressant dosages sodium isobutyl xanthate (SIBX) always results in lower froth stability than sodium ethyl xanthate (SEX). The frothing nature of dithiophosphate leads to increased froth stability and the addition of copper sulfate results in destabilised froths. Increasing depressant dosage reduces the stabilising influence of NFG and the depressant type (guar gum or CMC) also affects froth stability. Frother can be used in an attempt to overcome the destabilising effects of high depressant dosage. This work examines the effect of variations in the reagent suite and uses water recovered at a fixed froth height as an indication of froth stability in order to analyse these effects on the recovery of sulfide minerals, floatable gangue and entrained gangue.     

Cu-S flotation separation via the combination of sodium humate and lime in a low pH medium

The flotation separation of chalcopyrite and pyrite was studied in the presence of sodium humate. The results of flotation tests indicated that pyrite can be selectively depressed by sodium humate, and the activity of sodium humate was strongly affected by the pH of the pulp. At high pH values, pyrite was strongly depressed by sodium humate; however, the content of chalcopyrite was not affected. Ore flotation tests were successfully conducted in the laboratory and at the Dexing Copper Mine by applying sodium humate as a pyrite depressant. By adding 40-60 g/t of sodium humate to the pulp and adjusting the pH to 10-10.5 with CaO, a concentrate with a Cu content of 24% was obtained without reducing the Cu recovery rate. In addition, the dosage of CaO was reduced, and the recovery of Au, Ag and Mo in the copper concentrate was enhanced due to the reduced pH of the pulp. The zeta potential, adsorption of xanthate and contact angle of the mineral surface were measured, and the results from surface measurements indicated that there was a strong hydrophilic interaction between sodium humate and the surface of pyrite. Moreover, the results revealed that the interaction between sodium humate and chalcopyrite was weak. Infrared (IR) spectra of pyrite and sodium humate were obtained, and the results indicated that sodium humate was chemically adsorbed on the surface of pyrite.     

The behavior of N,N-dipropyl dodecyl amine as a collector in the flotation of kaolinite and diaspore

The flotation behaviors of kaolinite and diaspore were investigated using N,N-dipropyl dodecyl amine (PN). Maximum recoveries of kaolinite and diaspore were about 90% and 50%, respectively. Both recoveries of kaolinite and diaspore increased with the increasing dosage of PN. On the basis of the zeta potential and FT-IR spectra, the ionization of surface hydroxyl and the isomorphic exchange of surface ions account for the charging mechanisms of surfaces of kaolinite and diaspore. The adsorption mechanism of PN on the surface of two minerals was mainly electrostatic. After reacting with PN, the zeta potential of kaolinite and diaspore both increased, and comparing with the original zeta potentials, potential of kaolinite increased much more than that of diaspore, this can explain why recovery of kaolinite is higher than that of diaspore.     

Distribution of Sb minerals in the Cu and Zn flotation of Rockliden massive sulphide ore in north-central Sweden

The Rockliden massive sulphide Zn–Cu deposit contains minor amounts of Sb minerals. The Sb mineralogy is complex in terms of composition, micro textures and mineral associations. The main Sb minerals comprise tetrahedrite, bournonite, gudmundite and Sb–Pb sulphides such as meneghinite. The presence of these minerals is especially critical to the quality of the Cu–Pb concentrate. To study how they are distributed in a simplified flotation circuit and what controls their process behaviour Sb-rich drill core samples were selected from the Rockliden deposit and a standard laboratory flotation test was run on the composite samples. Scanning electron microscope-based automated mineralogy was used to measure the Sb mineralogy of the test products, and the particle tracking technique was applied to mass balance the different liberation classes to finally trace the distribution of liberated and locked Sb minerals. The mineralogical factors controlling the distribution of Sb minerals are mineral grain size, the degree of liberation, and associated minerals. Similarities in the distribution of specific particle types from the tested composites point towards systematics in the behaviour of particles and predictability of their distribution which is suggested to be used in a geometallurgical model of the deposit.     

The effect of a new polysaccharide on the depression of talc and the flotation of a nickel–copper sulfide ore

The effect of the depressant galactomannan (KGM) on the depression of talc and the flotation of a nickel–copper sulfide ore have been investigated through microflotation, batch flotation and industrial flotation tests, zeta potential and infrared spectrum measurements. The flotation results indicated that KGM had a straining influence on the depression of talc while had little effect on nickel minerals flotation. Compared with the depressant carboxymethyl cellulose (CMC) and guar gum, the KGM increased the nickel recovery dramatically, it not only negated the need for a talc removal process, but also achieved a significant decrease in the depressant consumption by half. Zeta-potential and infrared spectrum measurements illustrated that chemical adsorption was seen between KGM and talc, and a possible weak physical adsorption was seen between KGM and pentlandite. This was the reason why KGM had high depression selectivity for talc and little depression effect on nickel minerals.     

难选煤泥可浮性分析及解离浮选工艺研究

以选煤厂细粒煤泥为研究对象,分析了该煤泥的煤质特征。探索了改变充气量对浮选结果的影响,结果表明该煤泥为难选煤泥,常规浮选很难得到低灰分的精煤产品。对浮选精煤产品进行粒度与密度组成分析,表明解离不充分与细泥夹带是造成精煤灰分偏高的主要原因。采用原煤分级 粗粒级磨矿浮选工艺,可有效降低精煤产品的灰分。     

BFIPS—Ⅰ型浮选泡沫图像处理系统的应用与研究

结合在大山选矿厂的具体应用,从系统方案、软硬件平台、模型建立等方面详细分析介绍了BFIPS—Ⅰ型浮选泡沫图像处理系统。系统可以准确快速提供泡沫图像的特征参数并建立数学模型,并使得模型预测的精矿品位值与实验室化验值的平均相对误差小于10%,最终得到成功应用。     

The influence of the oxidation state of pyrite and arsenopyrite on the flotation of an auriferous sulphide ore

In this paper, the influence of the oxidation state of pyrite and arsenopyrite on the flotation of an auriferous sulphide ore was investigated by different techniques, including electrode, pulp potentials, DRIFT spectroscopy and microflotation tests. In addition, the gold and sulphide recoveries were also investigate, in a laboratory-scale cell, as a function of pulp potential and reagent concentration. It was verified that the presence of oxidation products on the sulphide mineral surface demands a higher collector concentration in order to achieve a satisfactory sulphide recovery. The electrochemical behaviour of pyrite and arsenopyrite indicated that a nitrogen atmosphere can lead to a low pulp potential, which inhibits the formation of oxidation products, enhancing both the free gold and sulphide recoveries. Although copper sulphate activates even oxidised sulphide surfaces, it does not improve free gold recovery.     

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.     

Assessment of the floatability of chalcopyrite,molybdenite and pyrite using biosolids and their main components as collectors for greening the froth flotation of copper sulphide ores

Biosolids and representative compounds of their main components – humic acids, sugars, and proteins – have been tested as possible environment-friendly collectors and frothers for the flotation of copper sulphide ores. The floatability of chalcopyrite and molybdenite – both valuable sulphide minerals present in these ores – as well as non-valuable pyrite was assessed through Hallimond tube flotation tests. Humic acids exhibit similar collector ability for chalcopyrite and molybdenite as that of a commercial collector (Aero 6697 promoter). Biosolids show more affinity for pyrite. The copper recovery (85.9%) and copper grade (6.7%) of a rougher concentrate obtained using humic acids as main collector for the flotation of a copper sulphide ore from Chile, were very similar to those of a copper concentrate produced by froth flotation under the same conditions with a xanthate type commercial collector. This new and feasible end-use of biosolids and humic acids should be new environment-friendly organic froth flotation agents for greening the concentration of copper sulphide ore. Now, further research is needed in order to scale current laboratory assays to operational mining scales to determine efficiencies to industrial scale.     

神经网络技术与小波分析相结合的故障诊断方法

提出了一种将神经网络技术与小波分析相结合的故障诊断方法,对诊断对象进行时域信号采集,通过小波分析,获得所需参数,再将此参数作为神经网络的输入量,从而达到故障诊断的目的.     

Numerical and experimental study of the effect of a froth baffle on flotation cell performance

In this work, the effect of a froth baffle on flotation performance is investigated both experimentally and numerically. Flotation experiments with an artificial ore comprised of 80% silica as gangue and 20% limestone as floatable component were carried out to compare the flotation performance of a baffled froth system against an un-baffled froth system. The effect of the baffle’s inclination angle to the horizontal was also studied. Results indicated that a froth baffle has a profound effect on both recovery and grade. The presence of a froth baffle resulted in an increase in grade at the expense of recovery. The decrease in limestone recovery with the introduction of a froth baffle was found to be a function of the baffle’s inclination angle i.e. recovery decreased as the inclination angle becomes more acute. Water recovery as well as entrainment recovery herein represented by silica recovery decreased with decrease in baffle’s inclination angle. Numerical techniques were employed to model the experimental results. The 2D stream function equation/Laplace equation which is known to be adequate in describing froth transport was solved subject to boundary conditions that represent the presence of baffles. A solution was developed using finite difference methods on a rectangular map obtained using Schwarz–Christoffel (SC) mapping. Results from the simulations indicated a change in particle residence time distribution in a manner that reduces spread. The changes in residence time distribution helped in developing an explanation of the experimental data.     

Influence of mineralogy and ore texture on pentlandite flotation at the Nkomati nickel mine,South Africa

The influence of ore mineralogy and ore texture on flotation response was studied for 29 samples from the main mineralised zone at Pit 3 of the Nkomati Ni mine, through laboratory scale flotation testing, laboratory assay, and mineral liberation analyser examination of the ore and the concentrates. The individual sample flotation responses vary widely in terms of Ni grade, and cumulative Ni recovery. It is demonstrated that this is a complex function of ore mineralogy and ore texture. Chalcopyrite is the first sulphide to float, followed by pentlandite and finally pyrrhotite, in ore samples with dominant chalcopyrite, or where pentlandite, pyrrhotite and chalcopyrite occur in equal abundance. However in samples with a high ratio of pyrrhotite to pentlandite and chalcopyrite, pyrrhotite floats earlier than expected, reports to concentrate over the entire flotation period, and depress and extend the flotation of pentlandite over the flotation interval with no clear peak of Ni recovery during flotation. Primary silicates (e.g. olivine and pyroxene) and alteration-related minerals (talc, tremolite and chlorite) are naturally floating, and hence affect the flotation of pentlandite in a similar manner to that of pyrrhotite. The most problematic ore at Nkomati in terms of Ni recovery is characterised by fine disseminated and fine bleb- or net-texture sulphides, contain abundant olivine, pyroxene, amphibole, talc and tremolite, and include abundant metamorphism-related country rock xenoliths (with calc-silicate minerals such as diopside and tremolite).     

Froth flotation of a Merensky Reef platinum bearing ore using mixtures of SIBX with a dithiophosphate and a dithiocarbamate

The Bushveld Igneous Complex (BIC) in northern South Africa has the largest deposit of platinum group elements (PGEs) in the world. In trace amounts, these are closely associated with base metal sulphides (BMS). Froth flotation is used as a bulk sulphide recovery to beneficiate these PGE ores. To maximise the recovery of the PGEs it is required to improve the recovery of the BMS. The chemical additives used largely determines the performance of the froth flotation process. Consequently, mixtures of collectors were used in batch froth flotation tests in an attempt to improve concentrate grades and recoveries of BMS from a Merensky Reef platinum ore. The mixtures consisted of a xanthate (SIBX) with a dithiophosphate (DTP) or a dithiocarbamate (DTC). Each mixture was tested at mole ratios of 80:20 and 60:40, with the xanthate the major component. An increase in nickel recovery was observed with all mixtures relative to pure SIBX at the expense of concentrate grade. The mixtures of DTC with SIBX increased the cumulative nickel recovery by 11%, while the mixtures with DTP increased it by 10%. Copper recovery increased by 6% with the DTP mixtures. No significant improvements in the copper recoveries and grades were observed with the mixtures of SIBX with DTC compared to pure SIBX.     

油酸钠浮选体系中硅线石与石英的分离机理

通过硅线石与石英的浮选规律试验、浮选药剂的溶液化学分析、矿物表面的动电位测定、红外光谱(FTIR)分析和X射线光电子能谱(XPS)分析,探讨硅线石和石英的分离机理.结果表明,在弱碱性矿浆中,元素Fe以形成氢氧化物沉淀形式在硅线石和石英表面吸附,与油酸根阴离子能够产生化学作用,说明元素Fe能够活化油酸钠与硅线石、石英表面...