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By P. T. Nguyen

The analysis of particle capture by an air bubble by two separate phenomena of collision and attachment has been difficult due to the uncertainty in determining when and where the two phenomena begin and terminate at the bubble surface, respectively. Therefore, a unified analysis was developed by solving the motion equation for the particle capture as one process. No distinction be-tween collision and attachment was made. Both the liquid film described by the micro-hydrodynamic resistance functions and the surface forces were included in the new model. The model predictions with the DLVO (Derjaguin-Landau-Verwey-Overbeek) surface forces did not agree with the experimental trajectories of latex and silica spheres. The model predictions with the inclusion of the non-DLVO attractive surface force agreed with the experimental data. The non-DLVO force reduced the repulsion between the non-attaching particle and the bubble, and significantly increased the attraction between the attaching particle and the bubble. The unified analysis is capable of predicting particle capture without the use of the induction time. The unified analysis also shows significant influence of the short-range hydrodynamic interactions on the collision which has been previously ignored.

Jan 1, 2014

By T. Wajima

We tried to convert paper sludge ash (PSA) into zeolitic product with high cation exchange capacity (CEC) through acid leaching. Typically, PSA from incineration of paper sludge contains a high percentage of calcium in the form of anorthite (CaAl2Si2O8) and gehlenite (Ca2Al2SiO7). It is difficult to convert the ash with a high Ca content into zeolites, or at least into more desirable zeolite phases. Acid leaching with HCl was applied to reduce the Ca content to synthesize zeolitic product with high CEC. The raw ash was treated with 1 M, 3 M, and 5 M HCl solution for 0.5~24 hours (the ratio of the ash to volume of HCl solution was 1/4), and then zeolitic product was synthesized from leached ash through the reaction with 2.5 M NaOH solution at 80 oC for 24 hours. During acid leaching, gehlenite is readily dissolved in a lower HCl concentration solution than anorthite. With increasing HCl concentration, the amounts of Ca, Mg, Si, Al, Fe and Ti extracted from the ash increased. Ca and Mg contents were easily extracted from ash than other elements. The contents of Ca and Mg extracted rapidly at initial stage, and then levelled off. The saturation times of Mg and Ca are almost 0.5 h using all concentrations of HCl solutions. After the synthesis from leached ashes, zeolite-A and -P were synthesized from ash leached in 1 M HCl solution, and 3 M and 5 M HCl solutions, respectively, regardless of leaching time. With in-creasing HCl concentration, the Ca content eluted from the product decreased, due to the removal of Ca via acid leaching before the synthesis, while the Na content eluted from the product increased to 3 M HCl and then decreased, which was almost similar to the CEC of the product, due to the ion exchange of Na-type zeolitic phase in the product. The change of zeolite phases in the product and the CEC of the product depend on the concentrations of Si and Al in the solution during the synthesis. The highest CEC of the product is about 220 cmol/ kg, which was synthesized from the ash leached in 3 M HCl solution.

Jan 1, 2014

By J. J. Lui

Surfactant plays a critical role in many industrial processes such as petroleum, mining, environment and food processing, and daily life. For ionic surfactant systems, adsorption of surfactant at oil-water interface imposes a net charge to the interface. The nature and magnitude of the charges at the oil-water interface depend on charge characteristics of surfactant molecules, concentration of surfactant and solution pH. In our previous study, zeta potential measurement of hexadecane drop-lets in industrial process water was shown to be a simple, yet powerful method for identifying various types of ionic surfactants present in the aqueous system. In this paper, the site-binding model was applied to prediction of zeta potential of oil droplets in aqueous solutions containing a mixture of cationic and anionic surfactant molecules. The total number of interfacial sites for various types of surfactant involved was determined by applying the Gibbs adsorption equation to the measured interfacial tension-surfactant concentration profiles. The distribution of various types of surfactant molecules at the interfaces was evaluated by Langmuir isotherm constants. With the ionization constant of surfactant taken from the literature, the predicted zeta potentials of oil droplets in surfactant solutions from site binding model were shown in a reasonable agreement with the measured zeta potential values.

Jan 1, 2014

By Aidan Giblett, Karen McCaffery, Robert Dunne

"A worldwide decline in competency levels of practicing metallurgists over recent decades has become clearly evident and is a common topic of discussion among senior practitioners and professional associations. The associated impacts on the industry are material and include operational inefficiencies, missed optimisation opportunities and suboptimal new plant designs. There are many contributing factors to this condition. Decrease in competency is particularly evident both in regions where imbalance between supply and demand has led to a general reduction in experience levels for comparable roles over time and in emerging regions where a rapid rise in demand for practitioners has occurred in conjunction with rapid economic development and industrialization. The context, depth and breadth of education curricula and levels vary with location such that solutions to the technical competency dilemma may need to be developed specifically for each region with these influences in mind. Delivering, demonstrating and maintaining competencies are a critical requirement of undergraduate training and ongoing professional development. Other factors such as generational and cultural characteristics and expectations, political influences, role requirements and employment reward and recognition systems all play a critical role in determining if core competencies can be effectively developed, applied and subsequently maintained. This paper reviews factors impacting and some common approaches to competency development. The authors’ experiences in the management of professional development efforts within the global industry are reviewed and a blueprint proposed to address industry requirements in this area."

Jan 1, 2014

By Erico Tabosa

The turbulence characteristics and measurement techniques for agitated tanks are well established for liquid and liquid-gas systems. However, the literature shows that the overall energy dissipation rate (related to turbulence) is affected not only by air addition, but also by the concentration of solids. Unfortunately, there are no reliable measurement techniques for characterizing turbulence in a three phase (liquid-solids-gas) environmental system, which is the case in a flotation cell. Therefore, the effect of turbulence on flotation kinetics is very much one of conjecture. The aim of this work was to develop a sensor to characterize the degree of velocity fluctuation, which is related to turbulence, in a flotation cell operating with slurry and air. This sensor comprises a piezoelectric film transducer that converts mechanical to electrical energy. Hence, when the sensor deflects backwards and forwards an AC voltage is created. Flotation studies carried out using this sensor in a 3m3 Metso RCS cell processing a copper sulphide ore showed a highly turbulent impeller zone with transition to a significantly less turbulent zone in the upper portion of the cell. The transition region moves as the cell operating variables are changed, for instance the impeller speed, impeller size, air rate and feed solids concentration. Keywords: mechanical flotation cell hydrodynamics, turbulence characterization

Sep 1, 2012

By de Vaux. Deryck, Natalie J. Shackleton, Vratislav Malysiak Cyril T. O. Connor

"The major losses of PGM and base metals in the beneficiation of platinum group deposits occur during the separation of gangue from the value minerals by selective flotation. A number of studies have shown that this negative impact on flotation is due to surface passivation, caused by various ions that may originate from the external water supply or, as is likely in the majority of cases, from the oxidation of the mineral surfaces and the grinding media. This investigation aimed at reducing surface passivation of pentlandite and inadvertent activation of pyroxene, thereby improving ultimate valuable mineral recovery and selectivity. Both synthetic minerals and plant ores were studied in order to determine the effect surface passivation and inadvertent activation have on mineral surface alteration and floatability. Zeta potential determinations, microflotation, ToF-SIMS (Time of Flight Secondary Ion Mass Spectrometry) analyses, laboratory batch flotation tests and continuous flotation testwork were used as tools to study the surface alteration and/or floatability.Zeta potential determinations and ToF-SIMS analyses showed that copper adsorption is non-selective. Both pentlandite and pyroxene become copper (II)-activated in the presence of copper sulphate and subsequently, in the presence of xanthate, adsorption of the collector will occur onto copper activated mineral surfaces. Zeta potential determinations also showed an alteration of the surface charge in the presence of polyphosphate, thereby inhibiting surface passivation of sulphides by slime coatings due to surface repulsion.The addition of diethylenetriamine (DETA) reduces the copper concentration on both minerals, predominantly on the pyroxene surfaces and polyphosphate further enhances the selectivity at pH 6.The microflotation and batch flotation data obtained has shown a significant improvement in the ultimate flotation response of valuable mineral recovery and concentrate grade compared to the standard reagent regime, while the continuous flotation results significantly improved the selectivity, however, at a similar ultimate recovery."

Jan 1, 2003

By E. V. Manlapig, M. C. Harris

"The complexity of the flotation process has made the identification of an appropriate model structure, for use in the prediction of flotation circuit performance, far from obvious. Work performed under the auspices of the AMIRA P9 flotation program has indicated that the metallurgical performance achieved from a flotation cell arises from the interaction of two essentially independent property classes, namely the cell operating conditions and the properties of the cell feed stream. These observations have led to the development of a model structure that associates a constant set of flotation parameters to the streams of the circuit, which are transformed into a flotation response depending on the operating conditions within the flotation cell.A variety of alternative model structures exist within the literature which do not make this distinction between cell and stream flotation properties, and many of these models are in widespread use for flotation optimisation and design studies, both in industry and academia.In this paper, data collected from an industrial flotation circuit is used to derive the parameters associated with two different types of flotation models. Simulations performed using these models demonstrate the need to differentiate between cell and feed properties. A model that does not differentiate between these two properties fails to successfully predict the metallurgical performance of a flotation circuit after a disturbance."

Jan 1, 2003

Flinders Power, formerly NRG Flinders, is considering the possible use of low rank coal from Lake Phillipson, South Australia (SA) in its power stations at Port Augusta, SA. Typically, this coal contains about 35% moisture and 10% ash. Unfortunately, it also contains high levels of sodium (1% Na) and chloride (0.95% Cl) with a Na2O level in ash of 18.9%. Such levels cause serious problems during coal combustion, making the use of as-mined coal impractical for power generation. This paper describes the development of an aqueous leaching technique to remove 90% of the sodium and chloride and to yield a product with a Na2 O level in ash of less than 3%. Small-scale agitation leaching tests with good quality tap water at ambient temperatures showed that the coal needed to be crushed to minus 5.6 mm to obtain maximum removal of water-soluble sodium and chloride in 30 min. Leaching kinetics, but not the ultimate removal of salt, were enhanced by the use of higher temperatures (up to 150°C), but this was deemed uneconomic. Varying the pulp density between 20% and 50% had little effect on extractions and there was no benefit in multiple stage water washing. The best results by water leaching were 69%~74% extraction for sodium and 95%~97% for chloride, meaning that the sodium removal was well below the target level. From SEM examinations of the leached product it was concluded that the remaining sodium was organically bound to the carbon atoms in the coal. Further tests using aqueous solutions containing cation exchange additives such as calcium chloride (CaCl2) or ammonium chloride (NH4Cl) or sulphuric acid (H2SO4) showed that significantly enhanced sodium extractions were possible and target specifications were met. Two options, namely a single-stage and a two-stage leach, were then investigated. In a single-stage leach with additive, minus 5.6 mm coal was leached at 33%~50% solids for 30 min at ambient temperature and then filtered and washed with fresh water. This gave a sodium removal level of about 81% and a Na2O level in ash of about 5%. These levels do not quite meet tar-get specifications. In a two-stage leach, the coal was first leached with water alone without an additive as in the single stage leach, and the washed residue re-leached under similar conditions for about 5 min with an additive (CaCl2), and then filtered and washed. This gave a cumulative sodium removal of 96% and a Na2O level in ash of 1.4%~2.4%. These levels are well within target specifications.

Jan 1, 2014

By Caroline Olsen

The objective of this study was to achieve Zn activation control in an industrial Cu flotation circuit treating a complex Cu-Pb-Zn-Au-Ag sulphide ore at the LaRonde Division of Agnico-Eagle Mines Limited (Québec, Canada). In order to provide process relevant results, a laboratory testing methodology was developed to duplicate plant operational parameters. The action mechanisms of ZnSO4, TETA (triethylenetetramine) and NaHSO3used as depressants in order to limit ZnS activation were examined. Laboratory flotation tests with and without Cu2+ions (the ions responsible for ZnSactivation)were performed. All depressants showed equal or better flotation performance relative to baseline tests. For example, in the presence of Cu2+, the Zn recovery reduced from 32.2% to 17.5% in the copper rougher concentrate after adding ZnSO4(with a dosage of 50 g/t). TOF-SIMS analyses confirmed the relative decrease in surface Cu in the samples treated with ZnSO4and TETA. For the case with TETA, this indirectlyindicates the formation of a copper TETA complex in solution, thereby reducing available Cu for transfer. The TOF-SIMS and XPS data indicate that the addition of ZnSO4and NaHSO3resulted in an increase in surface metal hydroxides and SO3 on ZnS grains inhibiting both Cu and collector attachment.ZnSO4 was subsequently tested with success in the LaRonde concentrator. The addition of 40 g/t ZnSO4 at the conditioning (or cleaning) stage led to a 2% reduction in Zn content in the Cu and PM concentrate. Recently, improvements towards the control of copper sulfate addition in the downstream Zn flotation circuit resulted in the reduction of Cu2+ in process water. As this ?cleaner? water is recycled for Cu and PM flotation, the addition of ZnSO4 is now used only as required.

Sep 1, 2012

By Carsten Gerold

The paper is giving an overview about successful operating Loesche Vertical ? Roller ? Mills (VRM) installations and summarises the main benefits of the dry compressive Loesche grinding technologies in Airflow- and Overflow-Mode. Some of these benefits are optimised energy efficiency of the grinding - classifying - circuits, increased mineral recoveries and decreased OPEX costs, at a parallel simplification of the process route. Within this paper the process values of the Loesche VRM are compared to existing or planned conventional grinding ? classifying circuits. Further advantages discovered in pilot trials and examples for new more efficient process route alternatives are given. The paper reports about production and pilot trial experiences obtained by crushing and grinding Iron Ore, Iron Ore Concentrates, Copper Shale, Copper Matte, Copper Slag, Titanium Slag, Tin Slag, Steel and Stainless Steel Slag with Loesche VRM.

Sep 1, 2012

By P. K. Sen, Mrinal K. Ghose

Tailing slurry is usually abrasive and possesses high viscosity. This paper examines the existing iron ore beneficiation process and focuses on some of the key environmental issues related to the disposal of tailings. It identifies that almost 32% of the iron ore extracted ends up as tailings and they are usually disposed in slurry form in tailing ponds. By the year 2000, 27 Mt of iron ore tailings were generated in India, which has become one of the biggest waste handling problems to the industry. Characteristics of the tailings vary widely. So the physical nature of tailings cannot be considered separately in isolation without considering the mill effluent from the beneficiation plant. In the present investigation, studies were carried out in three iron ore mines in India to evaluate the characteristics of tailings from the beneficiation plant. The tailing samples were collected from different locations during a time period of one year and analyzed. The results will be discussed and the characteristics of the tailings have been evaluated. The disposal system of tailings at the three mines was evaluated. The research on the settling characteristics of tailings indicates that the area provided in the existing tailing ponds in India is much more than that of the experimental results. This paper concludes that sedimentation tests are essential to design appropriate tailings pond with respect to size. In the proposed scheme it is suggested that an additional unit process, i.e. sedimentation tank be added to the process before the disposal of tailings to the tailing pond.

Jan 1, 2003

By Jim Petrie, Mary Stewart, Damien Giurco

This paper describes a generic approach to analysing the environmental and economic performance of a global mineral/metal value chain, with the express view of improving the quality of prospective decision-making within the industry in order to ensure more sustainable outcomes. The starting point for this analysis is the development of a global stocks flows and transformations model, for the metal of interest. Any aspect of the value chain, e.g. “metals refining, “goods manufacture”, “use and disposal”, can be assessed, either relative to other stages in the value chain, or in more detail by focusing on the technologies used within that stage. The use of this model as a decision support tool is explored here for the case of copper. Both primary and secondary production routes are enumerated, covering a range of processes, for seven distinct geographic regions round the globe. The value of the modelling approach is explored for different energy mixes. In particular, the case study examines the impact of increased recycling on the (re) distribution of global and regional environmental impacts for technologies-in-place in these different regions.

Jan 1, 2003

By Y. X. Yang

Bottom ash is a solid waste stream in a Waste-to-Energy (WTE) processing plant during the combustion of the municipal solid waste (MSW). In the Netherlands, bottom ash contains typically about 18% metals originated from the MSW, and current industrial practice could recover about 10% metals through magnetic and eddy current separators. The remaining 8% as the finer particles is difficult to recover through current physical separation technology. Among various alternatives, vitrification is one of the promising options to immobilize the ash and recover the remaining metals. During vitrification a homogeneous glassy slag and a Fe-Cu based alloy were obtained. In the cur-rent study, the metal alloy recovered from the bottom ash originated from a Dutch Waste-to-Energy plant contains about 82 wt% Fe, 12 wt% Cu and 6 wt% other alloying elements and impurities such as C, S, P, Ni etc. The generated alloy does not have direct commercial applications, and separation of copper from iron-based alloy is critical to obtain the market value of both copper and ferrous constituents. To find a suitable processing route of this metal alloy, various alternative approaches have been considered for an efficient removal of copper from the alloy, and the focus in the present study was on the sulphide treatment at elevated temperatures of 1400 ~ 1500oC. The tested sulphide systems include pure FeS, FeS containing sulphide mixture (such as Na2S and Al2S3), pyrite (FeS2) mineral, ZnS containing sludge as an industrial waste. It was found that the carbon saturation of the alloy is proved to be an essential condition for a proper phase separation. The results showed that FeS mixed with Na2S, ZnS containing sludge and pyrite are effective sulphide systems for copper removal with a removal efficiency of 92% by using pyrite and 95% by zinc sludge at a S/Cu ratio of around 7 times of the stoichiometry. The copper content drops from 12 wt% to about 2 wt%. However, it is still difficult to remove copper completely from the alloy in a single step, and a multi-step operation is needed. The present research is expected to contribute both to the utilization of the metal recovered from bottom ash, and to the general recycling of steel scrap where copper removal from the steel scrap is a critical issue.

Jan 1, 2014

By Anuj Narang

Large-scale separation or flotation cells, used in the primary extraction in the oil sands industry, are integral parts of the overall process of bitumen extraction. Good regulation of the interface level between the bitumen froth and the middlings in these cells can result in a significant improvement in bitumen recovery and throughput, and heavily influence process economics. Automatic control of such industrial processes presents challenges such as multi-phase flow dynamics, variable process gain and time delays, poor quality of measurements and significant disturbances. This paper details a case study application of development of multiple models of the dynamics of the interface level and the design of model predictive controllers (MPC) for a separation cell process. A Model predictive controller (MPC) using linear models is designed and implemented in real time on an industrial separation cell. The industrial implementation results show that the MPC scheme provides significant benefits over the current operations which use a PID controller. The benefits include significant reduction in the variance of the interface level resulting in higher bitumen recovery and smoother downstream operation plus energy savings due to reduced underflow pump speed.

Sep 1, 2012

By Chris A. Fleming

"The ability to recover cyanide from gold plant tailings has been known almost as long as the cyanidation process has been practiced, but there has been little incentive to process tailings in this way in the past. With the development of technologies that make it possible to recover and recycle free or complexed cyanide directly from gold plant slurry tailings, which indicates, on paper at least, significant cost savings compared to cyanide destruction, coupled with the introduction of legislation to seriously limit the discharge of cyanide to the environment in most gold-producing regions of the world, many companies are evaluating the cyanide-recovery alternative.There is arguably an even more compelling reason for mining companies to consider cyanide recycling. With the growing storm of negative public opinion that the use of cyanide in the mining industry is attracting - following several highly publicized spills over the last couple of years - the time has come for the gold industry to demonstrate environmental diligence and stewardship in the use of this commodity that is so vital for their industry. There is no doubt that the widespread implementation of cyanide recycling will reduce the impact of the cyanidation process on the environment, both by reducing the risk of spills (with less cyanide being transported from manufacturing plants to gold mines), and by reducing the loading of toxic and nontoxic metals and ions in the tailings.This paper briefly discusses the pros and cons of the different processes that are available for the treatment of gold plant tailings to regenerate and recovery cyanide for recycling, and presents a techno-economic argument for the incorporation of this technology into many gold plant flowsheets today."

Jan 1, 2003

By M. Wierink

The lifecycle of a resource, specifically a metal, is often depicted as circle from primary production from mining to minerals processing and via manufacturing and use to disposal and recycling. When a material is recycled, it is considered as saved energy compared to producing the material from primary source. This is, however, a simplified representation. At each step of the life cycle, there are changes in the quality of the material due to different materials chemical and physical interaction, phase transformations due to diffusion, radiation etc. Due to these physical and chemical phenomena there are losses of material, which as determined by thermodynamics are not recoverable within the life cycle. This can be considered as an increase embodied energy per mass unit of substance and loss exergy from the material cycle. With low cyclic loss, the material will remain in the recycling loop for a long time, while with high cyclic loss it will disappear fast. Where you put the material determines how fast it disappears from the resource cycle. In this research paper the phenomena of quality degradation of material and idea of increase of embodied energy and exergy loss within a resource cycles is portrayed. The cyclic nature of material states and transitions and energy consequences of material quality degradation as well as the parameters affecting the length of the time scales of the material cycles are described. Currently the cyclic embedded energy and the history of material is not taken under consideration in generic life cycle assessment. This easily results into a conclusion that lifetime of product is optimized only in terms of how much energy an appliance uses during its lifetime, while ignoring the loss of embedded energy due to the effects caused by the environs the material is subjected to during the cycle. Better description of the time properties of material give us a possibility to design toward optimum lifetime of products in terms of resource efficiency. Keywords: product lifetime, material lifetime, recycling, cyclic resource efficiency, material state, material quality, exergy, embodied energy

Sep 1, 2012

The ever increasing demand for energy and the progressive depletion of crude oil resources, have renewed interest in oil shale as an alternative fuel resource. Weathered oil shale samples were assembled from El-Nakheil phosphate mine in Quseir area, Eastern desert, Egypt. The oil shale samples were prepared and analyzed by XRD (X-ray diffraction), XRF (X-ray fluorescence spectrometry), and optical microscopic techniques. Rock-Eval pyrolysis and total organic carbon were used to study shale hydrocarbon potential. A leaching procedure using inorganic and organic acids was used to selectively dissolve the oil shale associated ash forming minerals. XRD results showed that calcite is the dominant carbonate mineral, whereas primary silicate minerals are quartz and montmorillonite. SEM (Scanning Electron Microscopy) observations indicated that the organic matter is dispersed throughout the rock matrix. The acid soluble fraction upon leaching was determined to be 37.59 and 42.74 wt% by using 5% HCl and 10% HCl, respectively. The TOC was increased from 20.78 to 29.88 and 34.09 wt% by using 5% HCl and 10% HCl, respectively. Keywords: el nakheil oil shale, characterization, xrd, xrf, sem, elemental analysis, proximate analysis, ultimate analysis, thin section, rock eval pyrolysis, acid leaching

Sep 1, 2012

By Steven Wright, Sharif Jahanshahi, Shouyi Sun

"While there is a large industry based on recovering platinum group metals (PGM) from complex sulphide ores containing Cu and Ni, there is little information on the thermodynamics of the matte phase formed on smelting the ore and in particular the behaviour of Pt in the matte.The equilibrium between metallic platinum and industrial mattes was studied in a series of experiments where a small quantity of matte (5g) and platinum foil of 150 µm thickness (0.5 g) were equilibrated in magnesia crucibles at 1400°C under conditions where the oxygen and sulphur partial pressures were fixed.The chemical composition of the phases was determined from EDS analysis using a scanning electron microscope. Line scans were initially used to confirm that the foils had attained a uniform composition across their thickness. The composition of the matte was determined from analysis of an area of matte including the small metallic droplets and dendrites.The results of the equilibrium study are presented in terms of how the oxygen and the sulphur pressure affect the distribution of Pt, between the matte and the alloy foil (Lmatte/alloy). Other variables investigated were matte chemistry, i.e., the Fe content and the temperature. The activities of platinum in the mattes were calculated using a regular solution model describing the activity-composition relationship in the alloy."

Jan 1, 2003

By M. M. Moghaddam

Charge motion is of prime importance in the efficiency of comminution in tumbling mills. Since direct observation of charge shape and its motion in industrial mill are not possible, a combination of analytical and physical studies was used to determine charge trajectory. Software packages, which predict charge motion such as the GMT (Grinding Media Trajectory) only consider the outermost layer of charge (single ball) and ignore the interactions of grinding elements. In this research, the measured charge trajectory in a 1m-diameter mill with the transparent end, called model mill, was compared with that of the GMT. Four types of polyurethane rings were accurately machined to scale down the liners arrangements at two industrial mills. To explore various charge shapes and trajectories, the model mill was operated at 55, 70 and 85% of critical speed for five levels of mill filling (10, 15, 20, 25 and 30% by volume). The angular displacement of the toe, toe departure, shoulder and charge impact point were determined from the photographs taken from the model mill. New relationships to predict charge shape and charge impact points were introduced to modify the GMT results. The relationships were validated by the model mill using the new liner of the Sarcheshmeh copper complex SAG mill. The relative error of prediction was found to be 1.1%. The results indicated that when the lifter face angle increased from 7 to 30º, the distance between the charge impact point and the toe decreased from 52 to 31º for 25% filling. This meant increasing the probability of charge impacting the toe not the liner which favoured more efficient comminution practice. After converting AG mills to SAG mills on account of liner profile change, 31% increase in throughput (from 419 to 548 t/h) in addition to 4% decrease in the product size (from 516 to 496 µm) were realized which was a significant contribution in the plant performance improvement.

Sep 1, 2012

By R. C. Dunne

A review of the current ?state of the art? of refractory gold treatment will be provided. This will include a global perspective of refractory processes past and present and the location of currently operating plants. Some discussion on the challenges that face the refractory gold industry will also be provided. Keywords: refractory gold treatment, flotation, roasting, pressure oxidation, bacterial oxidation, preg-robbing gold ores, fine grinding.

Sep 1, 2012