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By G Malherbe, J Gonzalez, D C. Franklin, J Bassan, C T. Farrelly

To respond to ever-increasing challenges, mining companies have been experimenting with new business models and technologies in order to speed mine development, production, processing and transport. The various experiments involve mobile access to data, intelligent sensors, advanced analytics, virtual collaboration, virtual reality, automated equipment, remote operations centres and strategic partnerships. A synthesis of all these components creates a ænetwork effectÆ that can dramatically improve the overall effectiveness the entire operation. The concept of the Network Centric Mine borrows from a variety of industries, including defence, aerospace, aviation, petroleum, utilities and manufacturing. Central to the concept are improvements to the way we connect people, process, information and technology, resulting in a more highly collaborative business model, with roles and processes designed to take advantage of new technology. The components of the mining operation act as a connected network aimed at a common goal, regardless of the boundaries of organisation and location.The design of this new organisational ecosystem needs to take into account the recent advances that enable the æplug and playÆ integrated collaborative environment, including cloud computing, mobile devices and social networking, as well as advances in augmented reality, robotics, geo-location, digital labelling, simulation and analytics. However, the most consistent lesson from other industries is the need to properly enable the behaviour and process changes necessary for success.Benefits from adopting a network centric approach include the more effective use of scarce expertise, improved data and information analysis, reduced process variance, and more informed and faster decision-making. The future of mining will see more technology savvy workers who will drive the adoption of new processes. The operations will shift from a relatively static and disparate set of functions, to a digitally aware, dynamic, automated, integrated and interactive environment, with increased agility, lower operating costs, higher productivity and improved safety.CITATION:Farrelly, C T, Malherbe, G, Gonzalez, J, Bassan, J and Franklin, D C, 2012. The network centric mine, in Proceedings International Mine Management 2012, pp 143-160 (The Australasian Institute of Mining and Metallurgy: Melbourne).

Nov 20, 2012

By P Holt, M Allen

On the first of July, 2012, the Australian GovernmentÆs Clean Energy Act commenced. From this point, a price of $23/t of CO2-e will apply to facilities that trip the liability threshold. This first part of this paper concentrates on the mechanics of the Clean Energy Future legislation and how it will be applied to the mining and mineral processing industry.The second part of this paper contains analysis of the data presented for typical mine operations. Methodologies for constructing a carbon strategy are also presented. This will entail determining what the objectives of the carbon strategy are, and defining what the strategic priorities for a business should be. An action plan to address the risks identified from the Clean Energy Act is also developed as part of the strategy.Details such as the advantages and disadvantages of opting into the carbon price scheme for liquid fuels are shown. Other considerations such as the ability to acquire permits through the carbon farming initiative or through overseas clean development mechanism projects are explained.CITATION:Allen, M and Holt, P, 2012. Implications of the carbon price and developing a carbon strategy, in Proceedings International Mine Management 2012, pp 105-114 (The Australasian Institute of Mining and Metallurgy: Melbourne).

Nov 20, 2012

By T Trott, G Lumley

"The mining industry suffers from a shortage of professional and other workers. Research and analysis has demonstrated a close correlation between high performance in productivity, maintenance and safety. There is also a significant correlation between engagement and performance. It is the hypothesis of the authors that mines can use a strategy of establishing themselves as a high-performance mine to attract and retain high caliber professional people: step 1 is to become best practice in equipment performance (productivity, maintenance and safety) step 2 is to brand the mine as æbest practiceÆ by sharing what has been confidential performance and outcome information with the general industry.Previous research has shown that many professional people are attracted by the prospect of a high achieving site because of the learnings and the support for continually doing better. In addition, a link has been established in previous research between productivity and safety. Operators and drivers are attracted to sites which have fewer dangerous people operating or driving. Good management delivers exceptional performance and a work site which high caliber managers and operational personnel people want to work at. The strategy requires commitment and proper execution but it can work. The strategy needs a specific approach and this paper will discuss this. A case study is provided from a mine which over a nine month period increased dragline performance by 15 per cent and reduced stress on the boom by 30 per cent. This mine paid the employees (professional and operational) $25 000/a less than the major mines but the operators and professional people would not leave; in fact, people were happy to be paid less to work there.CITATION:Lumley, G and Trott, T, 2012. Using best practice operations as a strategy for attracting and retaining professional people, in Proceedings International Mine Management 2012, pp 35-52 (The Australasian Institute of Mining and Metallurgy: Melbourne)."

Nov 20, 2012

By J Joy, D Griffiths, A Bye, G V. Kizil

Poor standards of electrical installation and maintenance continue to contribute to electrical related fatalities and injury risk in the mining industry. Electrical isolation has the potential to initiate major unwanted events (MUEs) and as such requires thorough analysis to demonstrate adequate management. There have been 719 incidents related to accidental contact with electricity over the past five years in the Queensland mining industry (Queensland Government DME, 2012a, 2012b) with the last fatality being recorded in 1997 (MESA, 2012).A project funded by the Australian Coal Association Research Program (ACARP) has developed a form of a safety case using the four-layered æCoal Mine Safety Regime (CMSR)Æ approach. The CMSR is transparent and robust as it includes full site risk assessment and special issues risk assessment to be demonstrated as part of the process.The practical application of the CMSR has been demonstrated using a longwall mining case study site, where a unique 11 kV armoured face conveyor (AFC) is in operation. The case study has involved progressive application of the requirements of each layer of the CMSR (see Figure 1) to high voltage (HV) electrical isolation related issues. The project has specifically concentrated on understanding and analysing two high priority MUEs, electric shock and unplanned movement of equipment, through Layer 1 analysis. These two MUEs are an important part of the project as they have demonstrated the steps that may be taken to satisfy the risk management processes at Layer 1 of the CMSR and have contributed to resolving issues at the other three layers of the CMSR.The analysis of HV electrical isolation has been used as an exemplar to demonstrate the CMSR process and its practical application. The CMSR is applicable to major/principal hazards management as identified by the New South Wales and Queensland jurisdictions.This paper provides an overview of the development of a form of safety case using the CMSR and introduces the case study application for HV electrical isolation risk management at underground coal mines focusing on the major unwanted event of electric shock.This project provides the mining industry with a documented, publicly accessible, form of safety case using the CMSR approach for the first time.CITATION:Kizil, G V, Griffiths, D, Bye, A and Joy, J, 2012. Using a coal mine safety regime approach to the management of high-voltage electrical isolation, in Proceedings International Mine Management 2012, pp 59-74 (The Australasian Institute of Mining and Metallurgy: Melbourne).

Nov 20, 2012

By J E. Wheeler, S B. Valine, L G. Albuquerque

It has long been known that closed circuit grinding with a classifier improves grinding efficiency, reduces unit specific power consumption, and reduces over grinding. The classification device removes material from the circuit that has reached the desired size and returns coarse material back to the mill for further grinding. The efficiency of the classifier is an important factor in the overall performance of a grinding circuit. The classifier affects the capacity of the grinding circuit and the metallurgical performance of downstream operations. A review of historical research and modern case studies is used to demonstrate the benefits of high frequency screens for classification in grinding circuits.CITATION:Valine, S B, Wheeler, J E and Albuquerque, L G, 2012. Applications of fine screens in grinding circuits, in Proceedings 11th AusIMM Mill OperatorsÆ Conference, pp 389-394 (The Australasian Institute of Mining and Metallurgy: Melbourne).

Oct 29, 2012

By K Evtiminova, G Jobson, M Nolte, S Meik

Chelopech Mining EAD (CMEAD) is a wholly owned subsidiary of Dundee Precious Metals Inc (DPM) and operates the Chelopech underground mine and processing facility located in Bulgaria. The final product sold is a flotation concentrate containing copper minerals with associated gold and silver. The increase in production from 0.6 to 1.0 Mt/a by 2009 occurred with the original (1975) secondary/tertiary crushing, and primary/secondary ball mill circuits. As part of the mine/mill upgrade project to 2.0 Mt/a, a new single stage semi-autogenous (SAG) mill and ancillary equipment was installed, replacing the original circuits, with commissioning occurring during the first half of 2011. Aspects of the design, commissioning and operation of the new comminution facility are the subjects of this paper.An extensive program of comminution characterisation test work was completed in 2004/2005, which indicated moderate hardness and competency characteristics. The characteristics were considered suitable for a range of comminution approaches which were assessed with respect to power requirements and capital and operating costs. Retention of the existing primary crushing facility, and installation of a new single stage SAG mill located within the existing mill building, was selected as the design for the expansion.An extended ramp-up schedule for the overall concentrator upgrade turned out to be necessary as the comminution and flotation circuits were completed prior to several downstream unit processes (concentrate filtration and tailings thickening), which were required to reach the design mill feed throughput rate on a sustainable basis. This resulted in the opportunity to gradually increase the SAG mill ball charge as necessary, to obtain the throughput corresponding to the various downstream processing constraints.A relatively fine cyclone overflow stream particle size distribution is a feature of the Chelopech comminution circuit that has not been fully overcome with increasing ball charge conditions. However, design throughput has been met even under the finer product size conditions and will be consistently achieved following the commissioning of two further process improvement projects scheduled for late 2012.CITATION:Jobson, G, Nolte, M, Evtiminova, K and Meik, S, 2012. The modernisation and upgrade of concentrator operations at the Chelopech Mine, Bulgaria - Design, installation and operation of the 250 tonnes per hour comminution circuit, in Proceedings 11th AusIMM Mill OperatorsÆ Conference, pp 325-332 (The Australasian Institute of Mining and Metallurgy: Melbourne).

Oct 29, 2012

By S Girard, L Rowland, V Lawson, Y Shields

Since 1948, ValeÆs Matte Separation Plant has been successfully using magnetic separation and froth flotation to separate the copper sulfide, nickel sulfide and Ni-Cu metallic alloy contained in Bessemer matte for downstream processing. Though some equipment upgrades have been performed over the years, the flow sheet has generally remained unchanged since the early 1970s. The need to improve metallurgical performance led to the trial of a scalping flotation column to produce a final copper concentrate ahead of the cleaner circuit feed to take advantage of a high degree of copper mineral liberation, reduce cleaner-recleaner circulating loads and decrease the associated loss of selectivity. Plant results indicated that 50 per cent of copper contained in the rougher concentrate could be recovered at final grade target. Results indicate that up to a 1.5 per cent increase in copper recovery to copper concentrate was achieved during the scalper trial due to a reduction in the generation of fine chalcocite which has historically been observed to report to flotation tailings due to surface contamination. Deficiencies are currently being addressed and a long-term trial is scheduled to confirm the benefits of copper scalping.CITATION:Girard, S, Rowland, L, Shields, Y and Lawson, V, 2012. Copper scalping at ValeÆs matte separation plant, in Proceedings 11th AusIMM Mill OperatorsÆ Conference, pp 299-308 (The Australasian Institute of Mining and Metallurgy: Melbourne).

Oct 29, 2012

By Y Peng, D J. Bradshaw, G Long

As copper reserves deepen, they are becoming increasingly less pure. Penalty elements such as arsenic, antimony and bismuth are occurring in increasing concentrations. Environmental issues with smelters are leading to increases in penalty rates for these elements such that some concentrates may become difficult to sell. Arsenic concentration in Rosebery copper concentrates during 2010 varied between 3000 and 8500 ppm. Arsenic levels above 5000 ppm can preclude import to some customer countries. Optical mineralogy has indicated that arsenic in Rosebery copper concentrates is most commonly associated with tennantite (Cu12As4S13) in solid solution with tetrahedrite (Cu12As4S13). In addition, silver reports to concentrate as freibergite (Cu12As4S13 ). A reduction in arsenic content will therefore lead to a concurrent reduction in the silver content.A literature review by Long, Peng and Bradshaw (2012) indicated that arsenic bearing minerals could be removed using potential controlled flotation. Some success in reducing the amount of arsenic had also been reported using either roasting or chemical depression using reagents such as lime and cyanide. Due to the location of the Rosebery concentrator adjacent to world heritage listed temperate rainforest, the use of a roaster or cyanide was immediately discounted. Lime is already used as a reagent in the Rosebery flow sheet, so could be considered as a potential arsenic depressant.In order to determine a method of separating out the high arsenic bearing minerals, two series of flotation tests were conducted. The first series investigated the effect of pulp potential on the recovery of copper, silver and arsenic minerals; a second series investigated the effect of pH, froth depth and regrind.CITATION:Long, G, Peng, Y and Bradshaw, D J, 2012. Production of a low arsenic copper concentrate at MMG Rosebery, in Proceedings 11th AusIMM Mill OperatorsÆ Conference, pp 347-354 (The Australasian Institute of Mining and Metallurgy: Melbourne).

Oct 29, 2012

By MáAndrusiewicz, M M. Hilden, M S. Powell, P D. Kay, B Foggiatto

Circuits with unconventional and potentially more complex designs are predicted to become more common in the future as plant designers and operators look to process ores more efficiently. Ideas have been presented on how circuit design may be changed to utilise todayÆs technology to address tomorrowÆs challenges (Powell and Bye, 2009; Powell, Benzer and Mainza, 2011a). High pressure grinding roll (HPGR) installations in various configurations; application of preconcentration plants eg sorting, magnetic or gravity separation; and preweakening devices eg microwave processing; are all examples of technologies having the potential to deliver a significant reduction in comminution energy for ores amenable to these processes. Not only will future novel circuits contain equipment for which models are not as well developed (if at all), many will likely require the ability to respond to variations in feed, and interact with geometallurgical models requiring process adjustments when the ore characteristics change.In order to confidently simulate more complex circuits and accommodate variations in feed type, a significant advancement in modelling and simulation capability is required. This includes dealing with multiple components in the feed, accommodating different competencies of ore, utilising physical separation opportunities and tracking the grade reporting along the different potential processing routes. Developing the means to simulate complex circuits has been a key priority of a collaborative group of comminution researchers working to solve these challenges.Simulations are presented utilising a new configurable simulation interface called the model developers kit (MDK). The MDK is designed to accommodate multi-components and incorporate new models under development. These will be used to demonstrate the potential of flexible circuit design, based on measured ore properties and equipment performance.CITATION:Foggiatto, B, Hilden, M M, Powell, M S, Kay, P D and Andrusiewicz, M, 2012. Simulation of flexible circuits, in Proceedings 11th AusIMM Mill OperatorsÆ Conference, pp 291-298 (The Australasian Institute of Mining and Metallurgy: Melbourne).

Oct 29, 2012

By R Crosbie, K C. Runge, E Tabosa, J K. McMaster

Flotation feed density is an operating parameter which is currently not well understood. Most models of flotation only incorporate its effect on particle residence time, but it is likely to have additional effects within both the pulp and froth phases of the machine. Test work was performed in MetsoÆs 3 m3 RCS test rig to investigate the effect of flotation feed density on metallurgical performance. The rig was operated at Rio TintoÆs Northparkes operation using flotation feed and scavenger tail. For each feed, tests were performed at different feed densities, and measurements were performed to estimate the pulp and froth recovery as well as other key flotation parameters (eg bubble size, turbulence and froth stability). Results of this test work have shown that the pulp density does affect key parameters of the flotation process in both the pulp and froth phases. Pulp phase kinetic rates decrease at high density and this is attributed to a reduction in the turbulence within the cell. Froth phase recovery, however, improves presumably because of a stabilising effect due to a greater loading of solids on bubble surfaces.There is a need for more research to be done to better understand these interactions so that metallurgists can determine the optimum flotation feed density to use at a particular operation, or within a section of a flotation circuit.CITATION:Runge, K C, Tabosa, E, Crosbie, R and McMaster, J K, 2012. Effect of flotation feed density on the operation of a flotation cell, in Proceedings 11th AusIMM Mill OperatorsÆ Conference, pp 171-178 (The Australasian Institute of Mining and Metallurgy: Melbourne).

Oct 29, 2012

By C McHugh, F Oppolzer, B Rogers, A Stokes

Rio Tinto has embarked on a journey to use automation to improve the performance of its surface mines. The driver for automation has more to do with improving the accuracy and consistency of mining processes and less to do with cost savings through labour reduction.A key task in most surface mines is blasthole drilling. The degree to how well this is done cascades through the downstream mining process. It impacts scheduling, excavation, slope stability, material handling, beneficiation, ore loss and final product blending. Improved blasthole drilling was identified as an objective that has a significant business case in most of Rio TintoÆs surface mines.This paper describes Rio TintoÆs multi-drill automation project, which has developed a robust system for automating most of the functions on several Caterpillar SKSS16 drill rigs. Automated drilling is currently being trialled in production at the West Angelas iron ore mine in the Pilbara region of Western Australia. A description of the essential elements of the automated multi-drill system is given together with an overview of how automated drilling is performed remotely from the operating bench.A review of the performance and benefits of the automated multi-drill system is given together with future plans to extend the functionality of automated drills.CITATION:McHugh, C, Stokes, A, Oppolzer, F and Rogers, B, 2012. Automated multi-drills in Rio Tinto, in Proceedings Eighth Open Pit OperatorsÆ Conference , pp 83-88 (The Australasian Institute of Mining and Metallurgy: Melbourne).

Sep 18, 2012

By T Laing, M A. Abdalla, P Hagan

Open pit operators are facing a number of challenges in the area of blasting and blasting processes, such as wall control, quality of fragmentation, explosives consumption and vibration. Remaining financially viable is one of the most significant objectives for mining professionals as they work through the blasting challenges within the mining chain of processes. This objective is such a significant challenge, primarily due to the high consumption of materials and the direct consequences on the downstream processes in the mining work flow, including loading, hauling, crushing, milling and mineral concentration. This paper reviews and discusses a technique to achieve this objective, namely air-decking. The performance in a number of mines around the world is reviewed focusing on the economic contributions of air-deck blasting. Various scenarios are investigated and simulated, covering both conventional and air-deck blasting, using JKSimblast software. The scenarios explore a range of issues and found that optimum results could be achieved with a minimum amount of explosives. The results obtained from the simulations were verified with blasts at Rixs Creek Coal Mine, Australia. Based on the verification results the simulations were then modified to more accurately model the actual conditions and parameters on site and to ensure that the models derived meet the production and control requirements at the mine site. Ultimately, overall analysis and comparisons were applied to the outcomes of the conventional and air-decking blasts revealing a reduction in material consumption of around 25 per cent with consequential savings and up to a 30 per cent reduction in ground vibration.CITATION:Abdalla, M A, Laing, T and Hagan, P, 2012. The contribution of air-deck blasting to open pit mining economics, in Proceedings Eighth Open Pit OperatorsÆ Conference , pp 7-12 (The Australasian Institute of Mining and Metallurgy: Melbourne).

Sep 18, 2012

By L Eriksson, D Penn, J Appelgren

Atlas Copco, a leading supplier of equipment and services to the mining and construction industries, is consistently pursuing its strategy to offer the most productive and economical solutions by continuously offering new innovative products. These are, in most cases, developed and tested in close cooperation with demanding end users before being officially launched on the international market. The demands for higher productivity and improved overall economy have resulted in systems for automation of the drilling cycle and also tools for integrating the drilling equipment to the production control system used by the customer. In terms of improving the blasted material quality, the company has placed emphasis on accuracy in the drilling process and documenting what has been drilled. By applying state of the art technology to the common automation platform, developed for the surface drilling market, major steps in improving overall drilling productivity and blasting performance have been achieved. This paper will give some examples derived from the latest development of solutions for the companyÆs surface drilling products.CITATION:Appelgren, J, Eriksson, E and Penn, D, 2012. Rotary drilling automation increasing operator productivity and drilling quality, in Proceedings Eighth Open Pit OperatorsÆ Conference , pp 13-18 (The Australasian Institute of Mining and Metallurgy: Melbourne).

Sep 18, 2012

By A. Pankewitz

The well-established on-line particle size analyzer OPUS manufactured by Sympatec GmbH, has been successfully implemented in several mining and industrial minerals project. OPUS monitors the particle size distribution in 31 fractions as well as the solid concentration in opaque and highly concentrated ore and mineral slurries on-line in real time e.g. behind mills or cyclones applying 31 ultrasonic frequencies for highest resolution. Ultrasonic extinction overcomes all limitations known from optical and mechanical systems like contamination, blockage and wear. OPUS measures slurries in their original state without any dilution, hence no extensive sampling procedure or sample conditioning is required thus no dilution errors occur. Due to the OPUS design and suitable algorithms entrained air bubbles do not affect the quality of analysis at all. The sensor covers particle size distributions from 0,01 to 3.000,00 µm and solid concentrations up to 70 % by volume and can be easily adapted to a number of production lines simultaneously. Jiangxi Copper?s Dexing Mine is one of the biggest copper mines in Asia and among the first users for OPUS on-line particle size and concentration analysis in mining industry. OPUS is connected to 2 process lines. Jiangxi Copper has implemented OPUS for into their central control system for the grinding & classifying circuit of one SAG mill and one ball mill. Analysis data and process control as well as optimization based on OPUS particle size and concentration measurements will be discussed Keywords: particle size analysis, ultrasonic extinction, concentration analysis, grinding control

Sep 1, 2012

By B. Rai

Aluminum is produced by the Hall-Héroult process, which involves passing a current through a molten mixture of alumina dissolved in cryolite (Na3AlF6) to reduce the alumina to aluminum. This process occurs in an electrolytic cell comprising a steel shell lined with a carbon cathode and refractory bricks. After a certain period of operation, the carbon cathode deteriorates and is removed from the cell along with the refractory bricks. These removed materials are referred to as spent pot lining or ?SPL?. Typically, 30 Kg of SPL waste is generated for every ton of Aluminum produced. Globally aluminum smelters produce more than 500,000 tons of SPL each year. Even though SPL has a high fuel value (8000 to 9000 BTU/lb) and contains valuable metals, it is classified as a hazardous material due to its cyanide content and leachable fluorides. Various disposal/recycle techniques have been developed over the years for SPL but none of them is satisfactory. Thus, large quantities of SPL are still being dumped in landfills. In some countries, even the land filling of SPL is not permitted. The safe disposal of SPL thus remains a challenging problem to the aluminum industry and the search continues to find methods of converting SPL into a non-hazardous waste and/or recovering the valuable materials contained in the SPL. We have developed a process to produce hydraulic setting cements (eco-cement) containing a novel fluoride rich cementitious phase, from SPL by an energy efficient, low temperature clinkering route. A raw mix blend of SPL, lime/limestone, calcium sulfate and tailings sands based on a set of design criteria developed by us, is clinkered in a two stage process; 2 hours soak at 800 °C followed by clinkering at 1000 °C for another 2 hours, to produce a soft clinker. The SPL eco-cement is made by grinding the clinker to a fineness of 5000 cm2/g Blaine with 1% by weight borax as a set retarder. A good quality cement having as high as 20 % by weight of SPL in the raw mix (28 % by weight in the cement clinker) is thus produced. The physical properties of the SPL cements are found to be comparable to the Indian standard (IS) specifications for Ordinary Portland Cements (OPC). We have produced the cement in a few Kg batches and tested the reproducibility of results from batch to batch for further scale up. Once commercialized, this process has a potential of converting SPL into value-added cement products. Keywords: cement, spent pot lining, clinkering, fluoride, aluminum, ordinary portland cements

Sep 1, 2012

By Mario Gerards

Maturing populations create an increase in the demand for the type of non-ferrous metals, which are used in the manufacturing of electronic products. The depletion of existing high-grade deposits, make it necessary to boost the efficiency of beneficiation processes and most importantly the yield (recovery rate of the value commodities). Increasing demand now makes it worthwhile to tap into resources, which were previously considered waste, for example secondary deposits such as tailing ponds and electronic waste. In order to achieve increased yields, increasingly finer, or even ultra-fine fractions have to be treated. In most cases, mineral characteristics such as size and density call for non-mechanical, high-capacity technologies to be used. There are various technologies that allow for the separation of fines and ultra-fines. This paper outlines the dynamics and efficiency of pneumatic flotation with emphasis on its application to the recovery of non-ferrous metals, from electronic waste. The conventional agitator flotation technology of an electronic waste processing plant was not able to recover ultra-fine non-ferrous metals satisfactorily, due to losses within the tailings. Because of its adaptability and its inherent suitability for non-ferrous metals, pneumatic flotation has been incorporated to the existing process achieving excellent results. The merit of the process lies in the state of the art technology, which does not utilize compressed air and any rotating parts, which results in a reduction in wear and energy requirement, both features of this innovative technology. In addition, the use of pneumatic flotation resulted in a significant reduction in residence time, when compared to mechanical flotation. Pneumatic technology is able to influence air bubble size in a flotation cell, by changing the speed and pressure of the slurry stream. Higher slurry velocities lead to the formation of smaller air bubbles, which is required for the successful flotation of ultra-fine particles. Conversely, decreasing the slurry velocity leads to bigger air bubbles. The optimum bubble size can be created according to different feed characteristics. This is important in case of feed fluctuations.

Sep 1, 2012

By M. Narasimha

The flow in a hydrocyclone classifier is highly turbulent complex nature of multi-phase structure, which has led designers to rely on empirical mathematical models for predicting the performance. A number of classifying cyclone models have been developed and successfully used in mineral comminution circuit simulators over the past four decades (Plitt, 1976 and Nageswararao, 1978). However, most of the mathematical models currently available to describe hydrocyclone classifier performance are based on single average mineral density component behavior. In industrial comminution circuits, the feed to the cyclone composed of a mixture of particles of varying degrees of liberation and sizes. The behavior of multi-component particles in a hydrocyclone is poorly understood and unaccounted for in most of the mathematical model equations available in the literature. There is evidence from a number of experimental data sets indicating the significant influence of the multi-component particles on measured cyclone performance. A concept for modeling the performance of hydrocyclones based on multi-component behavior is proposed in this paper. A set of semi-empirical model equations for cut-size, sharpness of separation are presented and the corresponding model parameters evaluated from the measured data are given.

Sep 1, 2012

In flotation, particulate materials are separated by controlling the hydrophobicity of the particles using appropriate collectors. In this regard, contact angle (?) is the most important process variable. However, the flotation models used in industry today do not include ? as a parameter. As result, flotation circuits are designed based on the first-order flotation rate constants (k) determined from laboratory experiments. A problem with this approach is that laboratory experiments usually give substantially higher k values than achievable in full-scale operations, which makes it difficult to use the model for plant design. In the present work, we have developed a model from first principles using both surface chemistry and hydrodynamic parameters, such as ?, ?-potentials, surface tension (?), particle size, energy dissipation rate, etc. The basic approach is similar to the one developed previously for bubble-particle interactions under laminar flow conditions (Yoon and Mao, J. Colloid and Interface Science, 181, 61, 1996) except that the model parameters have been modified by considering the turbulence in a flotation cell. In addition, the model describes the recovery processes in froth phase, including bubble-coarsening due to coalescence. Based on this model, we have developed a computer simulator (FlotSim) that can be used to design flotation circuits from the mineralogical (or liberation) data on the feed and the hydrodynamic characteristics of a flotation machine. Since the model is dynamic, it can also be used for process control. Further, the simulator has predictive capacity as it is based on a first-principles model. The model-based simulator has been validated in a carefully controlled bench-scale flotation experiments. Keywords: flotation kinetics, flotation model, contact angle,?-potential, size-by-size recovery, liberation, DLVO theory

Sep 1, 2012

By Venkata S. Buddhiraju

Pelletization of iron ores involves balling on a rotating disc to produce wet pellets and induration of wet pellets on a moving grate to produce fired pellets. The quality of pellets produced and the productivity of the pelletization process depend strongly on the characteristics of the feed to the pelletization disc, especially the particle size distribution and the moisture content. The upstream processes involved in the preparation of pelletization feed include grinding, thickening and filtration of the iron ore slurry. The focus of the present work is the closed circuit wet grinding of iron ores. The circuit consists of a primary ball mill, a regrind mill and a hydrocyclone. A population balance model was developed to predict the grinding kinetics and an empirical model was fitted for the separation of fine particles from the coarse particles in the hydrocyclone. Batch grinding kinetics experiments were performed on a laboratory scale ball mill to obtain the ore breakage parameters which were subsequently used for the simulation of the industrial mills. The models were customized for the industrial operations and the effects of different process variables like feed flow rate, water flow rate, etc., on the size distribution of product from the grinding circuit were studied. Additionally, different circuit configurations were simulated to determine operating conditions that could result in the desirable product particle size distribution. The results of simulation were in close agreement with plant observations and the new circuits explored through simulation have helped in identifying potential opportunities for process optimization and control

Sep 1, 2012

By Arkady Senchenko

At present, there are different traditional and modern methods for ore grindability evaluation. The correct and rational approach to sampling, testing methods and mill sizing enables one to design a workable technology. This paper contains TOMS institute experience in different grinding indices determination over the last 7 years (SAG Design Test, BWi, CWi, RWi, and other). Mill sizing examples and circuits modeling for the projects in Russia and Kazakhstan are considered. Keywords: ore grindability, SAG Design Test

Sep 1, 2012