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By S. M. Bradshaw

In order to assess the requirements for online matching when using a transverse electric field (E-field) applicator to treat mineral ores continuously, the effect of varying load properties on matching has been investigated by simulation. The effective permittivity of the ore to be treated is expected to show variation on both short (< 1 s ) and long (minutes) time scales. By modelling the ore as a series of slices with alternating effective permittivity values, it was shown that permittivity variations on the scale of the expected particle size are attenuated significantly and matching is not required. For variations in permittivity on the length scale of the free-space wavelength, variations in reflected power are at most within ±10% of the mean. This is not considered operationally significant, as extreme permittivity variation over this length scale is unlikely, given the expected distribution of ore particle sizes to be treated. At typical ore transport speeds through the applicator, these variations occur on a time scale an order of magnitude shorter than the response time of typical industrial online matching equipment. This implies that online matching is neither required nor possible for short time scale variation. Long-term variations in dielectric properties can be adequately compensated for by current matching technologies. It is concluded that the transverse E-field applicator is robust to changes in the dielectric properties of crushed ores within the expected range of their variation.

Jan 1, 2012

By B. Zlender

ABSTRACT: The paper presents investigation of carboniferous slates from the Trojane hilly area performed on series of samples of equal material. The results of static loading tests show that carboniferous slate is heterogeneous and yields on slate layers. Where that kind of heterogeneity is distinctive the strength results are essentially lower of commonly tests results. The results of dynamical loading tests show that the slate surfaces have the essential meaning for the stability of the material. When those surfaces are moistened the material become unstable. RÉSUMÉ: L&apos;article présente une épreuve des ardoises carbonifères de la région montagneuse de Trojane sur une série des échantillons des matériaux identiques. Les résultats des tests de charge statique montrent que l&apos;ardoise carbonifère est hétérogène et qu&apos;elle cède sur les couches d&apos;ardoise. Quand l&apos;hétérogénéité est distinctive, les résultats de stabilité sont essentiellement plus bas que les résultats obtenus par des tests ordinaires. Les résultats des tests de charge cyclique montrent que les surfaces d&apos;ardoise sont très importantes pour la stabilité du matériel. Quand ces surfaces sont mouillés, le matériel devient instabile. ZUSAMMENFASSUNG: Der Artikel präsentiert die Forschung von Karbonschiefersteinen im Bereich des Bergland Trojane, ausgeführt durch Serien von Proben aus den gleichen Erdmaterial. Die Resultate der statischen Belastungsprüfungen zeigen, das die Karbonschiefersteine heterogen sind und die Schieferflächen nachlassen. Wo bei dieser Art der Heterogenität die Festigkeitsergebnisse wesentlich niedriger sind als bei gewöhnlichen Testergebnissen. Die Ergebnisse der zyklischen Belastungsprüfungen zeigen das die Schieferflächen eine wesentliche Bedeutung für die Stabilität des Erdmaterials haben. Wen diese Schieferflächen befeuchtet sind, wird das Erdmaterial unstabil.

Jan 1, 2003

By R. Gurung, S. Asokan, Ch. V. G. K. Murty, R. Upadhyay

Tata Steel Limited which is Asia?s first and India?s largest integrated private sector steel company, as part of its vision to grow in related industries is also undertaking the Titania project. The project will involve mining, separation of ilmenite and other valuable minerals from the inland heavy mineral sands deposit in the Indian state of Tamil Nadu. The raw material will be beneficiated to synthetic rutile, titanium dioxide pigment and ultimately to titanium metal. The recently concluded feasibility study revealed that the deposit under consideration has 10.4%of total heavy mineral content and 15.2% slimes of the size below 63 µm, over an average sand thickness of 6.9 metres. The presence of about 15% slimes in ROM sand coupled with scarcity of water at the project site complicates the slimes handling/disposal system, requiring the development of an innovative, efficient and effective system for disposal of slimes. Mineral characteristics of slimes revealed the presence of kaolinite clay, which poses its own challenges in thickening/dewatering of slimes. This paper outlines the detailed studies conducted, including slime characterization, settling and thickening characteristics, and ge-technical studies to arrive at an efficient and effective slime handling/disposal system, with a view to plant saplings on the mined-out reclaimed land with species typically suitable to that environment.

Jan 1, 2007

By S. Potgieter-Vermaak

The main mineral components of the so-called heavy sands (or black sand) are the titanium, zirconium and iron-bearing minerals, rutile, zircon and illmenite, accompanied by various minor and trace amounts of silicates or phosphates, often present together with the rare earth elements. The investigated samples originated from Richards Bay Minerals (RBM) in South Africa, which is jointly owned by BHP Billiton and Rio Tinto, the largest titanium slag producer in the world. The present study focused on the characteristics of samples originating from various points in the separation plant. The heavy-mineral fractions and concentrates of a representative suite of samples were investigated using various analytical techniques to establish the differences in morphological and elemental compositions at the different points in the plant. These techniques included: reflected light microscopy, micro-raman spectrometry (MRS), scanning electron microscopy coupled with energy dispersive X-ray analysis (SEM/EDX) and structural and chemical analyser (SCA). All samples comprised a heterogeneous population of zircon and rutile grains with diverse physico-chemical properties, expressed by large differences in colour and trace element chemistry of single grains. The elemental composition proved the presence of the rare earth elements that appeared to coexist with both Ti and Zr minerals. The percentage of grains hosting inclusions, such as anatase, monazite, quartz, spessartine, augite, epidote and actinolite, varied for each sample and could be uniquely characterized by Raman investigations. Keywords: heavy mineral sands, micro-ram an spectrometry, elemental analysis

By H. Wagner

The discovery of the gold-rich Main Reef Group of reefs on the farm Langlaagte in 1886 marked the opening of the richest and most extensive goldfield in history. Mining of the narrow reefs progressed from the outcrops to more than 3,5 km, and has made South Africa the foremost mining country in the world. Changes in the political and socio-economic climate create a new challenge to the gold-mining industry. The most significant of these is the emergence of Black trade unions, with their demands for higher wages, improved safety, job advancement, and abolition of discriminatory legislation. Industrial conflicts on gold mines have risen significantly in the past ten years, and are likely to continue in the future, although the causes of these conflicts may change. Events largely outside the control of the gold-mining industry, such as the improved dollar price for gold and the depreciation of the value of the rand relative to major currencies, have enabled the industry to meet the demands for higher wages and to narrow the wage gap. However, labour productivities have improved insignificantly and are a cause of major concern for the future development of the industry. Continued pressure in the industrial-relations area, the inflation of working costs, and the extension of mining operations to greater depths and more difficult areas create major challenges to mine managements and mining engineers. Significant improvements in mining technology, environmental control, and safety will have to be made to ensure the long-term survival of the industry. The unavoidable introduction in deep gold mines of mechanization on a larger scale to meet the requirements of higher labour productivities and a better and safer underground environment will have a major impact on the cost and management structure of these mines. Engineering will assume a more important role on deep gold mil1es, and management styles and structures will have to be adapted to accommodate these changes. The supply of suitably qualified engineers, technicians, and artisans will be a crucial factor controlling the rate of technological change. The industry is well-geared through its Group system to meet these challenges, and to benefit from the experience gained in the operation of highly mechanized mines. However, changes take time to implement and there is very little time left.

Jan 1, 1986

The statistical methods described in the previous chapter permit the estimation of the average value p of a deposit, and the calculation of confidence limits for this value. They are based on the assumption of independence of sample values. As soon as a reasonable number of samples has been obtained from a deposit, local valuation, or estimation of blocks of ore within the mineral deposit, becomes necessary. The assumption of independence of values must then be rejected. Local valuation is possible only if there is a relationship between the value of a sample and the value of the surrounding ore, provided this relationship is a function of the position of the sample with respect to the blocks of ore to be valued. Whichever method is used for the valuation of a block of ore, the following assumptions are always made: ? The values of samples located near or inside the block are related to the value of the block. ? The values of the samples located closest to the block are most closely related to the value of the block. These assumptions will hold true only if the following assumption can also be made: ? There exists a relationship between sample values which is a function of the distance between samples. We are saying that the value x (z) of a sample centred at a point z has properties which are functions of this point. A certain spatial structure exists in the sample distribution. We are therefore dealing with a regionalized phenomenon, and we must treat x (z) as a regionalized variable. This can be done statistically by means of a model chosen to represent the spatial structure of the phenomenon. We shall see that the relationship between block values and sample values can be deduced from the relationship between sample values, and all local valuation problems can be solved using the statistical model obtained from the analysis of the sample values. It is important to realize that this statistical model is obtained by analysing the properties of known sample values, and will be used for the estimation of unknown block values. Such a statistical inference is valid only if the model developed represents the properties of both the sampled section of the ore body and the section to be valued: some stationarity conditions must be satisfied, and the model with the least restrictive conditions is preferred. In the following chapters, the most important models used in spatial geostatistics are presented. The models which can be used when there is no significant drift (trends) in values are described in Chapters 3-1 1. These models can also be used to solve some specific valuation problems when a linear drift is present. A general study of the more difficult problem of analysis of an ore body whose values present a drift is described in Chapter 12. Note that the area considered for local valuation of a block of ore is often small enough for any drift which might be present to be ignored.

Jan 1, 1978

By P. T. L. Koh, M. P. Schwarz

A series of parametric studies were carried out for a flotation cell using computational fluid dynamic (CFD) modelling to determine the local response of hydrodynamic performance measures to change in operating conditions. As an example, an Outotec cell was used to carry out the response analysis. The hydrodynamics of the flotation cell has been previously investigated by laboratory measurements presented by Schwarz et al (2019), and a CFD model of the cell was developed and validated using these measurement data (Schwarz et al., 2019). In this work, parametric studies have been performed by modelling the flotation cell at different stirring speeds and gas flowrates, varying above and below standard conditions. Predictions of void fraction, bubble size, bubble surface area flux and particle–bubble collision rate are presented showing the effects of increasing and decreasing stirring speed and gas flowrate around the base case. Generally, the total gas holdup in the flotation cell was found to increase with increasing gas flowrate. The bubble diameter was found to decrease with increasing stirring speed and increase with increasing gas flowrate. The collision rate increased with both stirring speed and gas flowrate. The parametric results show that there is a correlation between the bubble surface area flux Sb which is affected by stirring speed and gas flowrate, and the particle–bubble collision rate. With the collision rate as an indication of flotation collection, it is also possible to show that cell performance can improve more by increasing stirring speed than by increasing gas flowrate in a situation where everything else remains constant. The CFD results can form the basis for a Response Surface Method (RSM) analysis which can then be used for automated optimization of cell performance. Keywords: Flotation kinetics, computational fluid dynamics, bubble surface area flux, particle-bubble collision rate

Jan 1, 2020

By J. P. Harrison, J. A. Hudson.

ABSTRACT: When considering the rock stress component of rock mechanics design, the basic procedure is to consider the pre-existing stress-state in the rock mass and then estimate the disturbance to this stress state as a result of engineering excavation. Failure criteria are applied to the final stress state to establish whether failure will occur. However, during the evolution of the stress state, the failure locus may be reached before the anticipated failure state and, in this case, failure will occur unexpectedly. This indicates that the complete stress path (defined as the variations in magnitudes and orientations of the stress tensor components resulting from engineering-induced or natural changes) must be considered. We list a set of stress path principles with their corollaries and then introduce a new and powerful method for simultaneously illustrating changes in the six independent components of the stress tensor. This method plots the magnitudes of the principal stresses above their orientational paths on the hemispherical projection, to provide a three-dimensional stress path locus for each of the three principal stress components. In connection with this presentational device, we illustrate a number of concepts associated with the stress path in rock engineering. For example, we show how the minor principal stress approaches zero at an unsupported excavation face, the interchange of the trajectories of two principal stresses when their magnitudes become equal, and the influence of the bounds on the principal stresses given by strength criteria. RESUME: Si on s’interesse à la composante “contrainte” lors d’un dimensionnement en mécanique des roches, la méthode de base consiste à considérer l’état de contrainte pré-existant dans le massif rocheux, puis d’estimer la perturbation à cet état générée par l’excavation projetée. Des critères de rupture sont appliqués à l’état de contrainte final pour établir si une rupture va se produire. Cependant, lors de l’évolution de l’état de contrainte, la surface critique peut être atteinte ce qui provoquera une rupture anticipée et, dans ce cas, cette dernière sera inattendue. Cela indique que le chemin de contrainte complet (défini par les variations de l’intensité et de l’orientation des composantes du tenseur des contraintes liées à des causes anthropiques ou naturelles) doit être pris en compte. Nous présentons un ensemble de règles pour les chemins de contraintes ainsi que leurs corollaires et, ensuite, nous introduisons une méthode, nouvelle et puissante, pour présenter simultannement les changements des six composantes du tenseur des contraintes. Cette méthode consiste à tracer l’intensité des contraintes principales sur le chemin d’orientation des contraintes à l’aide d’une projection hémisphérique afin d’obtenir le lieu, en trois dimensions, de chaque contrainte principale. En relation avec cet outil de représentation, nous illustrons certains concepts associés au chemin de contrainte en ingénierie au rocher. Par exemple, nous montrons comment la contrainte mineure tend vers zero à la surface d’une excavation sans soutenement, le changement de direction des deux contraintes principales quand leur intensité deviennent égales, et l’influence des conditions aux limites sur les contraintes fournies par un critère de rupture. ZUSAMMENFASSUNG: Bei ingenieurmassigen Taetigkeiten in Felsgesteinen ist es noetig die ungestoerten Gesteins Stress Componenten, die vor einem anthropogen Eingriff im Gestein vorhanden waren, zu kennen und erst dann Vorhersagen ueber Stoerung des Stress Zustandes, der durch einen ingenieurmaessigen Eingriff hervorgerufen wird, herzuleiten. Kriterien fuer das Versagen werden im letzten Stadium, des Stress Zustandes angewendet, um zu erfahren ob ein Versagen wohl eintreten wird. Es ist jedoch zu beachten, dass waehrend des Stress Aufbaus ein oertliches Versagen eintreten kann, welches vor dem eigentlichen, erwarteten Versagens Zustand auftritt. Diese Moeglichkeit weist darauf hin, dass der gesammte “Stress Path” (definiert durch die Variationen der Stress Tensor Komponenten in Richtung und Groesse, hervorgerufen durch ingenieurmaessig hervorgerufene oder natuerlich Vorgaenge) betrachtet werden muss. Wir fuehren eine Liste der “Stress Path” Prinzipien auf und stellen dann eine neue und wirksame Methode zur gleichzeitigen Darstellung der sechs unabhaegigen Komponenten des Stress Tensors vor. Diese Methode stellt die Groesse der “Principal Stresses” in Abhaengigkeit von ihrem rauemlichen Weg auf einer hemispherischen Projektion dar und erlaubt hiermit eine drei dimensionale Darstellung fuer jeden Ort des “Stress Path’s” in die drei Haupt Stress Komponenten. Im Zusammenhang mit der hier gegebenen Darstellungsart, verdeutlichen wir eine Reihe von Konzepten in der Felsmechanik. Wir zeigen zum Beispiel, wie der “Minor Principal Stress” Null zustrebt an einer Wand von einer nicht abgestuetzten Ausschachtung, den Austausch von Trajektorien zweier “Principal Stresses” wenn ihre Groessen sich gleichen, und den Einfluss der Groesse von “Principal Stresses” bei gegebenen Kriterien des Festgkeits Versagens.

Jan 1, 2003

By A. M. Venter

"SynopsisThe availability of advanced characterization techniques is integral to the development of advanced materials, not only during development phases, but in the manufactured components as well. At Necsa, two modern neutron diffractometers equipped with in-situ sample environments, as well as complementary X-ray diffraction instruments, are now available as User Facilities within the National System of Innovation in support of the South African research and industrial communities. Neutrons and X-rays, owing to their different interaction mechanisms with matter, offer complementary techniques for probing crystalline materials. Both techniques enable nondestructive investigation of phenomena such as chemical phase composition, residual stress, and texture (preferred crystallite orientation). More specifically, the superior penetration capabilities of thermal neutrons into most materials allows for the analysis of bulk or localized depth-resolved properties in a wide variety of materials and components. Materials that can be investigated include metals, alloys, composites, ceramics, and coated systems. In particular, depth-resolved analyses using neutron diffraction complements surface investigations using laboratory X-rays in many scientific and engineering topics. The diffraction techniques can add significant downstream value to the anticipated nuclear industry development activities.IntroductionMaterials characterization is central in understanding the relationship between the structure, properties, and performance in order to engineer materials that fit the performance criteria for specific applications. This is conveniently represented in the form of a tetrahedron, generally known as the material science paradigm (Figure 1).The availability of advanced characterization techniques is integral to the development of advanced metals, not only during development phases, but in the form of manufactured components. At Necsa (South African Nuclear Energy Corporation), modern X-ray and neutron diffraction instruments are now accessible to the South African research and industrial communities. These facilities enable nondestructive investigations of materials and components that could add significant downstream value to the anticipated nuclear industry development activities."

Jan 1, 2015

By S. Krishnannair

Singular Spectrum Analysis (SSA) is an effective data-adaptive multimodal tool for monitoring chemical processes. However, monitoring multiscale signals using principal component analysis obtained from the multilevel decomposition of process signals using basic SSA assume the upper control limits of monitoring charts (" ) to have a Gaussian distribution. This assumption deteriorates the performance of basic SSA when applied to the monitoring of nonlinear processes. To address the issue in this paper, the kernel density estimation (KDE) was used to estimate upper control limits of monitoring charts for basic SSA based nonlinear process monitoring techniques. The monitoring performance of the resulting basic SSA-KDE approach was then compared with a basic SSA approach of which upper control limits of the monitoring charts were determined based on a Gaussian distribution. Application on nonlinear dynamic simulated process and base metal flotation plant chemical processes showed that the SSA-KDE approach provided better overall performance than the SSA approach with Gaussian assumption-based upper control limits for its monitoring charts. Keywords: Fault detection, singular value decomposition, singular spectrum analysis, kernel density estimation

Jan 1, 2020

By D. K. Weatherley, T. P. Oladele, L. B. Bbosa

Comminution is a critical stage of mineral processing which aims to reduce the size of ore particles through breakage, consequently increasing the likelihood of liberation of valuable minerals. Several factors, such as pre-existing cracks, mineralogical composition and particle size, are known to affect ore breakage behaviour. While investigating the contributing role of each factor is essential to improve understanding of breakage, isolating individual factors by experiment is typically impractical. Numerical techniques such as the Bonded Particle Model-Discrete Element Method (BPM-DEM) have been developed as a means of studying closely controlled breakage conditions. This study evaluates this technique in modelling the effect of pre-existing cracks breakage behaviour for synthetic ore specimens during impact breakage in a short impact load cell (SILC). Synthetic ore was modelled as a collection of discrete entities connected by brittle-elastic beams. Model parameters were calibrated against macroscopic material properties of a conventional homogenous synthetic ore. The extent of pre-existing cracks within specimens was prescribed by varying discontinuities between the connecting entities. An approach with the insertion of seed points was used to model the mineralogy of the specimens. Results showed that pre-existing cracks resulted in a decrease in the fracture force as the crack density increased. Additionally, the irregularity of fracture patterns within rock specimens after impact became more apparent as the crack density increased. The findings were used to emphasise some of the attributable causes of the variation observed between ore hardness characterisation tests and in situ ore behaviour. Keywords: Element Method; Bonded Particle Model, synthetic rock sample; rock fracture, preexisting cracks

Jan 1, 2020

By L. E. Salinas-Farran, S. J. Neethling

Key variables in heap leaching include permeability, mechanical stability and mass transport. All of these properties can be manipulated by agglomerating and curing the ore before stacking it into heaps. The chemical and structural evolution of the agglomerates during curing is key to improving agglomerate properties and, ultimately, heap performance. It is possible to image the internal structure of agglomerates using SEM/EDX (e.g. QEMSCAN or MLA), although these methods are destructive and do not represent the 3D structure of the agglomerates. A non-destructive alternative is to image the agglomerates using X-ray Microtomography (XMT). Not only does this provide 3D information, it also allows the same samples to be repeatedly scanned, allowing the time evolution of the agglomerate structure and chemical composition to be tracked. In this paper we compared the behaviour of ores agglomerated using a combination of sulphuric acid and ferric sulphate with ones in which chloride ions are added to the recipe, since chloride leaching is gaining in popularity as a chemical alternative to bioleaching for sulphide ores. We tracked the curing process beyond the typical time scales to see the impact that this has on both the agglomerate structure and the subsequent leaching behaviour. Keywords: Heap leaching, curing extent impact, leaching kinetics, ferric-chloride leaching

Jan 1, 2020

Council for 1998/99 President R.P. Mohring President Elect J.R. Dixon Vice Presidents Senior junior M.H. Rogers Dr L.A. Cramer Immediate Past President Honorary Treasurer Dr N.A. Barcza J.A. Cruise

Jan 1, 1985

By W. K. C. Boemer, G. A. Davies

Vanadium slag production in the shaking ladles started in April 1968, steelmaking was begun in July 1968 and the first continuously cast blocks were produced soon after on the 29th July, 1968. Nominal monthly production of over 20 000 tons was reached in seven months and by December 1970 about 12 000 heats were cast and a monthly production of 35000 tons has been achieved.

By R. Rubin, P. A. Laxen, G. S. M. Becker

An account is given of developments in the use of activated carbon for the recovery of gold from cyanide solutions. The carbon-In-pulp process employed at the Homestake Mine is described, and its various applications in South Africa and their effectiveness are discussed. Probable future work on the carbon-in-pulp process and other possible applications of carbon for the recovery of gold are outlined.

Jan 1, 1979

By A. W. S. Schumann

SYNOPSIS The most economic exploitation of South African coal resources requires sustained study of the balance between known resources and the predicted rate of consumption, against the background of the development of other sources of energy in South Africa and relevant developments elsewhere in the world. A number of the major issues which would arise in such a study are discussed, including the need for a standardized South African definition for coal resources, the merits of sectoral forecasts of consumption compared with global forecasts, the encouragement of a higher recovery from reserves, and the development of an export market for South African coal.

PREFACE During the past year, considerable effort was devoted to the implementation of the strategic plan that was adopted by the SAIMM in 1986. Good progress was made in a number of areas, while in others the foundation was laid for future progress. Key Objective of the Institute The key objective of the SAIMM is as follows: To identify the needs of its members and to initiate and give effect to the means whereby the requirements for technology and scientific knowledge of the minerals and metals section of the South African economy are satisfied; and to represent and promote the interests of its members.

Jan 1, 1987

By H. Ruthert

An understanding of wear in systems conveying solids is extremely important from the standpoints of design and economics. The lifetime of any bulk solids-handling system depends on the type of solids present and the operating parameters of the transportation system. The relationship between wear in backfill pipelines on South African gold mines and the transportation system&apos;s operating parameters is well understood. However, the effect of the transported solids on the pipe wear is less well understood, because of an inability to characterize particle sharpness. The sharpness of the particles, together with their size and hardness, is responsible for the aggressivity of particles, or their ability to cause damage and wear. This paper presents a novel method for the characterization of particle sharpness. The results presented rank particles according to the sharpness of their surfaces.

Jan 1, 1993

By F. H. Deist, H. D. Small, J. D. Austin, L. F. Duvel

The development and application of a Computer System to aid in the planning of production in mines By F. H. Deist, L. F. Duvel, J. D. Austin, H. D. Small A computer system to aid in the planning of production in mines and its application to a complex colliery are descrIbed, The system consists of three phases, the data base maintenance program the &apos;production simulator&apos; and the report generation facility, In the first part of the paper the categories of information kept on the data base and the functions of the simulator are described in general terms. The application of the system to a multi-product colliery operating a variety of mining methods in a number of superimposed seams is described m the second part. In conclusion some comments are made on further applications and intended future developments.

By M. Tang, X. Tong

"SynopsisSlime coating is one of the most common ways for serpentines to contaminate metallic mineral concentrates during traditional flotation of coarse sulphide particles. This could pose quite a complicated and challenging problem in the case of some types of low-grade and finely disseminated Cu-Ni ores bearing high serpentine contents. This is the case for the copper and nickel sulphides from the Yunnan Mine, China. Previous batch flotation tests of this ore resulted in satisfactory recoveries of 86.92% Cu, 54.92% Ni, and 74.73% Pt+Pd, and concentrate grades of 4.02% Cu, 3.24% Ni, and 76.61 g/t Pt+Pd. However, the MgO content in these concentrates was more than 19%. In the current study, microflotation tests and settling rate tests were introduced to investigate the effects of a combination of strong collectors (a 2:1 weight ratio of butyl xanthate and butyl ammonium dithophosphate) on entrainment of serpentines in metallic mineral concentrate, as well as visual observations of the concentrates in suspension using still photography. All test results indicated the presence of serpentines entrapped in the hydrophobic flocs that resulted from these collectors, even with the use of effective gangue depressants. These strong collectors are used to flocculate the ultra-fine sulphides by forming loose and ‘fluffy’ hydrophobic flocs. However, these hydrophobic flocs may also be able to load or entrap some serpentine slimes into the concentrate, and this entrained serpentine could be harder to remove by using depressants or intensified conditioning than serpentine slime coating on the particle surfaces.IntroductionSerpentine minerals, which have the generalized composition (Mg,Fe)3Si2O5(OH)4, can be easy to crush and grind due to their convoluted and bent layered structures. These serpentines can hinder the enrichment of some metallic minerals and dilute their concentrates by entrainment during flotation. The resulting high pulp viscosities, slime coatings, and high content of dissolved ions adversely affect the flotation recoveries of copper and nickel sulphides, and high levels of MgO entrained in the concentrates lead to heavy penalties from smelters. Since the quality of nickel flotation concentrate depends heavily on its MgO content (generally less than 6–7% for No.1 or 2 grade nickel concentrate according to the standard requirement from National Nonferrous Industry), reducing the entrainment of serpentine during flotation is becoming more and more pressing. Previous research has focused on the collectors and depressants that are commonly used in copper-nickel flotation, as well as their interaction mechanisms."

Jan 1, 2015