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By Diana Drinkwater

As ore grades decline, ore deposits get harder and mineralogical complexity increases, metallurgical skills are more important than ever to ensure that today?s mining operations are operating efficiently and profitably. Yet specialist undergraduate degree programs have all but disappeared and metallurgical skills training for graduate engineers in the workspace if often haphazard. In response to this situation, specialists at the JK Centre in Queensland, Australia, have put together a professional development program designed to fast-track skills development for early career metallurgical professionals. The program, called ?MetSkill ® ?, is offered as a group training package for young metallurgists in the workplace. It is centred on a meaningful technical investigation negotiated between the JK Centre delivery team and the client company. As well as learning about project management and data collection and analysis, the participants study specialist topics such as comminution, flotation and mineralogy under the tutelage of senior research and consulting professionals. The technical investigation provides an opportunity for immediate practice of these new skills and JK Centre specialists are on hand to provide feedback and support throughout the program. The participants are employed across different operations in Australia and the Asia-Pacific, and although they occasionally come together for group training activities they are often separated by considerable distance. Specialist educational professionals from The University of Queensland have provided an innovative web platform to support collaboration and communication between all participants. This paper will describe the MetSkill ® program in detail, as well as providing a report on its initial roll-out to 2 groups of Australian graduate metallurgists in 2012

Sep 1, 2012

By U. A. Peuker, A. Grohme

"The cost effective and sustainable production of high purity rare earth elements is still challenging. The most commonly used method, known as solvent extraction, is very complex, needs many steps to separate the rare earth ions in a high purity, and causes a lot of environmental problems. An alternative method is the utilization of a separation column filled with adsorbent material. Within the column the desired target substance can be selectively separated out of a multi component mixture in one step. To find out if an adsorption material is suitable for the separation with a column, a characterization of the adsorbent material is necessary. In this paper are described the usage of modified activated carbon (oxygen and phosphorous modification), Di-(2-ethylhexyl) phosphoric acid (D2EHPA) impregnated Amberlite® XAD 7 HP and Lewatit® VPOC 1026 as adsorption materials. Several adsorption isotherms and process conditions are determined to characterize the selectivity between the adsorption materials and different rare earth ions. With these isotherms the mass specific rare earth ion retention for the adsorbent materials can be calculated. In addition to the isotherms the best working parameters are investigated e.g. pH-value and the time for equilibration. Finally, the separation factors between two rare earth elements are determined. The separation factor shows how successful a two element system can be separated."

Jan 1, 2014

By Zhongxue Li, Cuiping Li, Xiaoyun Hu, Yiqing Zhao, Huaying Wang

"Under the auspices of World Federation of Engineering Organizations’ Committee on Engineering and the Environment (WFEO-CEE) and Society for Mining, Metallurgy and Exploration (SME) Task Force on Sustainability and Mining (TFSM), and aimed at helping raise global understanding on and promote capacity building of risk management, this paper presents a framework and prototype of toolbox or knowledge warehouse for facilitating the application of risk analysis, mitigation and management techniques (RAMT) in the mining and minerals sector. The conception, design and implementation of the intended system of knowledge warehouse of risk analysis, mitigation and management techniques (KWoRAMT) are outlined. The system architecture of KWoRAMT is based on a browser/server (B/S) structured platform with web oriented interfaces and composed of data base, knowledge warehouse, searching mechanisms, and risk assessment methodologies. The knowledge sources for KWoRAMT will come from the TFSM expertise and Internet, including laws and regulations, codes of practice, standards, guidelines and best practices. The functions and outcomes of KWoRAMT consist of guided navigations with web links, categorized risk tools, annotated best practices with cases, and integrated risk approaches and solutions based on typical risk methods. Risk categories include those impacting on mine safety, mine occupational health, and mine community environment throughout the whole of mine life cycle from exploration, construction, and exploitation and processing to post-mining closure. Mining associated hazards will be identified and linked by vulnerability onto risk receptors through pathways. Risk management techniques for assessing impacts and consequences of mining induced hazards will be categorized with their pros and cons or strengths and weaknesses. Best practices and significant cases including experiences and lessons with problems, solutions, and recommendations on how solutions would be derived will be illustrated. Integrated risk approaches based upon typical methods will be developed for alternatives and actions."

Jan 1, 2014

By Bern Klein, Givemore Sakuhuni, Libin Tong

The use of continuous discharge centrifugal concentrators introduced in the early 1990’s for recovery of gold associated with sulphides has introduced a novel application niche for gravity concentration which could not be realized with the low mass yield batch and semi-continuous concentrators. A typical application is scavenging gold associated with sulphides from flotation tails which has potential to increase productivity by reducing gold loss to tailings and lower grinding cost by using a coarser grind. However, the full potential of this technology has not been fully exploited partly due to the lack of reliable small sample procedures to demonstrate applicability. This paper introduces a bench-scale procedure developed to characterize the Knelson Continuous Variable Discharge concentrator (CVD) for scavenging gold from flotation tails. The procedure code named gravity release analysis was derived from standard flotation release analysis. It is a modification of the gravity recoverable gold and gravity amenability test in order to best simulate continuous centrifugal concentration. Based on this iterative procedure, a gravity release index similar to the flotation rate constant, for measuring individual mineral gravity susceptibility for an ore is introduced which can be a useful quantitative measure to both predict application of centrifugal concentration and for plant design. The gravity release analysis procedure was tested on a polymetallic flotation plant tailing at Myra Falls, BC, Canada and results show that it can predict CVD performance. The gravity release index for gold was observed to decrease with each successive cleaner stage showing that the initial stages recover liberated gold whilst successive runs recover gold associated with sulphides and or gangue. The difference in magnitude of the gravity release index for different mineral species shows the species separable by centrifugal concentration.

Jan 1, 2014

By Ari Kokko

Metso has a long history supplying boilers for high ash coal firing. These boilers are based on circulating fluidized bed (CFB) technology. CFB?s biggest benefit is fuel flexibility ? it can burn fuels from high moisture content to high ash content. Metso has delivered tens of CFB boilers burning waste or high ash coal starting on 80?s. Some of the boilers have been in operation twenty years meaning that there is a long term experience from these plants available. This feedback includes boiler performance and maintenance issues of the boiler. Metso is also delivering coal washing plants to improve coal quality, i.e. reducing ash content of the coal. The idea to combine coal washing plant and CFB boiler was made up two years ago in Metso. Up-coming legislation of coal washing and restrictions for washery reject land-filling in India are good drivers for this kind of concept. Pre-study of this kind of concept led to the conclusion that coal washing process can be fine-tuned so that reject?s calorific value is only 1100 kcal/kg and that was set as a target for boiler design. Metso shipped 200 tons of washery reject to its own research center located in Tampere Finland. First a wide range of fuel characterization tests were done in lab-scale and after that one week test run in 4 MW CFB pilot boiler was done. Test run proved that 1100 kcal/kg can be fired without any support fuel with special boiler design. Test run results gave a good set of data regarding combustion efficiency, emission performance and boiler dynamic behaviour when burning this kind of fuel. These results are introduced in this paper. This paper introduces also the CFB boiler concept for washery reject firing including boiler plant, fuel and ash handling systems and flue gas cleaning system. Power plant can be integrated with coal washing plant so that boiler size matches with washing plants c

Sep 1, 2012

By T. Fujita

A high-grade fluorite ore is converted into hydrogen fluoride to produce many kinds of materials containing fluorine. Recently, it is becoming necessary to use low-grade fluorite ore due to the depletion of high grade ore. The low-grade fluorites usually have impurities such as SiO2, P, CaCO3 and arsenic. The most impurities such as SiO2, CaCO3 and P can be removed by using flotation method. However, the removal of arsenic is difficult, and the arsenic contamination decreases the hydrogen fluoride production percentage. The novel technologies for processing low-grade fluorite ore are urgently needed, in order to lower the arsenic concentration to less than 100 mg/kg. In this study, the removal of arsenic from low-grade fluorite ore has been investigated by means of an autogenous grinding using tower mill in sulfuric acid aqueous solution and 0.3 mm zirconia balls in water. The nano grinding in water can prevent the dissolution of 0.3 mm size zirconia balls as grinding media by sulfuric acid solution. Experimental results showed that the arsenic concentration was reduced from 260 mg/kg to 90 mg/kg and CaF2 recovery reached 90% by this process.

Sep 1, 2012

By Graeme Jameson

"In current flotation circuits it is customary to grind the whole of the mill feed to an initial size, which is determined by the liberation characteristics of the ore, and the ability of the flotation machines to float the fully liberated particles. Usually, the product of the primary mill will be ground further in a ball mill, to improve the liberation of the values and hence the product grade, before passing to rougher flotation cells. The final grind size is ore-dependent, and is a balance of factors including the relation between surface liberation and grind size, the grain size of the valuable particles within the host rock, and the feed grade. The P80 for the feed to flotation may be as high as 300 µm for free-milling copper ores, and as low as 53 µm for finely disseminated complex ores. The grinding of the feed ore requires considerable input of energy. The rate of replacement of wear components such as mill liners and media, is proportional to the energy input. The costs of these two factors - energy and wear - are usually comparable and together they form the major part of the running costs of a concentrator, and indeed, of the whole mining operation. The energy required increases as the final grind size decreases. This talk will focus on the reduction of milling costs that could be achieved, using a fluidized bed flotation technology that can give high recoveries at coarse particle sizes. A number of different circuit designs will be presented, using the new technology. Calculations show that reductions in the running costs of a mine and associated concentrator of the order of ten to twenty percent could be achieved."

Jan 1, 2014

By Nani Pajunen, Kari Heiskanen

"Products filling our societal needs, like communication and transportation needs, are becoming more sophisticated and efficient. The cost has been an increased complexity of material combinations. The same trend is also seen in investment goods. As an example, different crusher types have almost doubled the power to weight ratio in a relatively short time while producing even higher crushing rations. This has been possible by high performance materials and advanced designs. Another example is new hybrid materials in prefabricated high-strength steel structures in construction with the aim to lighten the products and obtain energy savings in the use phase e.g. in transportation. This development in general has made the end of life phase obscure. Recycling is often understood as the first phase of the material cycle. This has been supported by the material centric point of view. When, say indium, has been collected and mechanically treated to a concentrated fraction, it is assumed as recycled. This is not the case. The same applies to special steel alloys where one tends to lose some of the alloying elements to slag or even into the gas phase in the melting and refining stage, not in the earlier steps of recycling. At present there is no clear understanding of recycling of hybrid materials and no clear willingness to create new functional recycling systems. As the EU directives and most of legislation worldwide are based on the material centric thinking and implemented even on total mass recovery basis there is neither legislative incentive nor very strong economic incentives to work out the problem. In our research, we focus on industrial design towards sustainability from a product centric point of view from product collection to final metallurgical steps. It is vital, in the design phase of product, to understand the effects of decisions on recyclability to a saleable raw material. Main goal of our work is to create the fortunate circumstances in supply chain - to pass the barriers and find the effective and fruitful drivers - for reasonable use of raw materials and recycling co-operation with industry. The boundary conditions in the work are extractive metallurgical performance and the economic viability of all the steps. It can be shown from our work that small design alterations may have a large impact on the recyclability. The earlier the decisions are made in the product life chain the more positive impact they will have. It can also be shown, that a strong processing and metallurgical industry is vital to any meaningful recycling of the modern EoL products. Finally, it is also question of the individuals and values: supply and demand. Are you ready to take up the gauntlet: demand recyclable products."

Jan 1, 2014

By Dave Deglon

The Western Cape Mineral Processing Facility (WCMPF) is a collaborative educational initiative between the Departments of Chemical Engineering of the University of Cape Town, the University of Stellenbosch and the Cape Technikon. The WCMPF was established in 1989 with the aim of improving mineral processing education in the Western Cape. Since its inception the WCMPF has had a number of successes in this area, especially in improving the quality of mineral processing practical training. In addition, the WCMPF has played an important role in promoting liaison and interaction between tertiary educational institutions teaching mineral processing in the Western Cape. Over the past decade the WCMPF has played a key role in the education of over five hundred mineral processing graduates and diplomates. This paper presents an overview of the activities of the WCMPF and attempts to encapsulate the ‘lessons learned’ from over a decade of successful functioning as a collaborative educational initiative in mineral processing.

Jan 1, 2003

By Q. Zhang

This paper, by studying the surface properties of pure dolomite minerals separated from representative marine sedimentary rare earth-bearing phosphate ores in Zhijin, Guizhou, aims to study the effect of different anions on the ? potential of dolomite. The research findings showed that the dolomite mineral had a point of zero charge (PZC) at pH 6.5, and the PZC shifted towards lower pH values with addition of anion SiO32- and PO43-. However, addition of anion CO32- and F- resulted in higher PZC values. Keywords: dolomite, ? potential, PZC, anion

Sep 1, 2012

By David Newton, Christian O’Keefe, Robert Maron, Jerin Russell, Paul Rothman, Dylan Cirulis

"The presence of unwanted coarse material in flotation feed streams negatively impacts both recovery and throughput of concentrator plants. The detection of this coarse material is a long-standing problem in mineral processing that has been poorly addressed by existing instrumentation systems. This problem has been overcome by the development of two new systems that detect in real-time the presence of coarse material in the overflow stream of individual hydrocyclones. They both use sensors mounted to the overflow pipe of the hydrocyclone and provide a robust and maintenance-free system measurement that enables corrective actions through operator intervention or automatic control strategies. One system is non-invasive and detects very coarse material 6mm or greater in size. The other system uses a wetted sensor and detects coarse material down to a lower size limit of approximately 100 um. Both systems have been commercially deployed. The systems will be described in detail. Validation data and typical plant data will be shown"

Jan 1, 2014

By M. Bhartia

India is the 5th largest producer of steel in the world and is slated to produce more than 180 Mt by 2020. Expectedly about 50 % of this would be through the Blast furnace route and the rest through Sponge iron / DRI route. Considering that there will not be any major change in iron making technology by that time, the Blast operation would require lump ore (10-40mm) with around 64% Fe grade and sinter fines (<10mm) with 60% Fe (min) as its feed. DRI process would need calibrated ore of size 5-18 mm as the most suitable size of feed. It is also expected that of the total requirement of ore for the DRI route a significant part would be DRI pellets. In India, there is considerable debate going on regarding the technology to be adopted for the processing of iron ore and there is a lack of clear consensus. The above scenario indicates that the processing requirement of iron ore in the country would involve both washing technology as well as beneficiation technology. CDE Asia Ltd is in the forefront of iron ore processing in the country and the experience gained by the company over the last few years of functioning has led the company to believe that route to be adopted depends on the end product requirement and the starting grade of the feed. Keeping in mind the nature of the feed required for the Blast furnace & DRI operation; it is obvious that good washing technology would be highly beneficial to the iron ore industry. Depending on the grade of ore available the limits of washing will be decided and equipment for lump ore beneficiation such as jigs could be incorporated into the washing circuit. Scrubbing of ore either before washing or selectively scrubbing the lumps could be necessary. Very low grade ore and jig rejects would be required to be totally ground and beneficiated for the production of pellet feed in order to utilize the iron ore resources entirely. Another source of ore for pelletisation would be slimes generated from the washing process as well as the huge quantities already available in the tailings dams in the operating mines. Deslimimg and magnetic route of beneficiation could release at 30-40% of the Fe locked up in these tailings ponds/dams. The paper describes the concept with examples from operating plants and proposes how the adoption could be engineered through test work and proper plan of integration. Keywords: washing, beneficiation, iron ore, lumps, sinter fines, pellets, jigs, screens, evowash, nanowash, thickeners, log washers, drum scrubbers

Sep 1, 2012

By F. Q. Dong

According to the principle that should be originated from nature, compatible with nature, used in nature and back to nature and based on conception of designing of eco-material, the author combined the ideas of material, environment, zoology and healthy. Properties of natural mineral materials were used to produce micro-aggregate elements by bionic method, so its components and function could accord with living environment. Eco-mineral functional materials which can adjust, purify and optimize the microclimate were reviewed. The authors pointed out the multifunction, com-pounding, the compound characteristics and integration regularities of micro-aggregates. It was the first time in the world to put forward the ?gene? technique or ?material chip? technique of manufacturing function micro-aggregates and eco-function elementary materials. The results of this re-search supported by the national ?863? Hi-tech Project, mainly including the high-efficient air purifying mineral compound material indoor, the clay elementary antibacterial materials, the masonry cement/coating/putty/compound with preventing radon radiation, environmental friendly composite functional coatings, mosquito repellent and healthcare material and zeolite-based energy-saving composite materials, were introduced. Finally, the foreground of mineral materials in the field of future advanced eco-friendly materials was also discussed.

Jan 1, 2014

By S. K. Sharma, R. Markandeya, G. Venkateswara

"In this study, a three level Box- Behnken factorial design combined with Response surface methodology (RSM) for modeling of process parameters of Multi Gravity Separator (MGS) for recovery Iron values from sub grade iron ore, Deposit No. 5, Bailadila complex has been developed. The three significant operational parameters of MGS, Drum rotational speed (RPM), Drum inclination (degrees) and quantity of wash water (LPM) were considered in the experimental work. Other parameters like feed percent solids, shake frequency and shake amplitude were maintained constant. The ‘as received’ sub grade iron ore sample is admixture of lump and fines and chemically assayed 40.80% Fe, 40.90% SiO2, 0.24% Al2O3 and 0.22% Loss on Ignition (LOI). The obtained results were evaluated with the Box-Behnken factorial design, RSM and also Quadratic programming(QP). Second order response functions were produced for Fe in terms of grade (%) and recovery (%) of the concentrate fraction. Taking advantage of QP, it was observed that maximum grade of 62.21% Fe achieved at an inclination of 4.3degrees, 2.7LPM of wash water and at a drum speed of 198 RPM. Similarly a maximum Fe recovery of 65.37% weight can be achieved at 4.3degrees inclination, 2.6LPM wash water and at a rotational speed of 212 RPM Predicted values of responses obtained using model equations were in good agreement with the experimental values. The influence of the process variables of the multi gravity separator concentrator on grade and recovery of concentrate fraction were presented and discussed."

Jan 1, 2014

By Sunil Tripathy, Y. Rama, Srinivasulu. A., Amit Ranjan

Process improvements in an operating plant are always challenging. Mineral beneficiation plants based on gravity concentration techniques need continuous evaluation and monitoring of its processes for getting maximum recovery and better grades. But, in an operating plant it is very difficult to control all the parameters due to numerous reasons such as unsteady operation, fluctuation in the quality of run-off-mine ore, overall flow rate etc. For better understanding of the beneficiation circuit, it is necessary to evaluate the critical operating parameters which affect the performance in terms of grade, recovery and throughput including losses of valuable materials into tailing. Accurate data collection and proper data interpretation followed by making necessary change which is implementable in an operating plant play very critical role in performance of the circuit. In case of gravity operated beneficiation circuits of chrome ores where the quality of the feed and physical parameters varies continuously, the operators are required to modify the critical operating process parameters on continuous basis which is very difficult and tiresome. There are many causes of the data variability, including both error (sampling and assay), and real variation in performance due to changes in ore mineralogy, operating conditions and other factors. In this article, attempts made to evaluate the performance of ultra-fine beneficiation circuit in terms of silica reduction in the concentrate of chrome ore beneficiation plant (COB), India are discussed. The approach adopted and practical problems encountered during the study were also discussed. Results obtained from plant audit based on the above methodology has shown that SiO2 content in the concentrate can be reduced to <4%.

Jan 1, 2014

By A. I. Arol

Bentonite is an important industrial mineral with very wide application areas. Its unique colloidal, swelling, thickening and adsorption properties make it a useful agent in drilling, metal casting, and iron ore pelletizing, environmental, food, cosmetics, pharmaceuticals and many more industries. Because of its swelling property, bentonite suspensions can only be prepared at rather low solid coentrations, i.e. 8-10%. In order to process bentonite in slurries with high solid content, it was thought that a non-polar organic solvent, instead of water, can be used. Not only large amounts of bentonite can be dispersed in organic solvents but also the solvents may be regenerated. The bentonite obtained through such a process must either equal or better properties than those of untreated bentonite. In this study, the effect of organic solvents such as acetone, methyl-ethyl ketone and n-haxane on the main properties of bentonite, such as water adsorption and rheology, was investigated. It was found that bentonite can be dispersed in the mentioned organics in large quantities with no loss of quality. Keywords: bentonite, montmorillonite, water adsorption, industrial minerals

Sep 1, 2012

By H. Breuer

Mineral processing is characterized by a constant adaptation to changing raw materials and market conditions. It is the link between the mined raw material and a marketable product. As a lot of high grade reserves are exploited, a steady deterioration of raw material quality can be observed. At the same time, the customers´ requirements for product purity and consistent quality increase. Indian iron ores are characteristically friable in nature that results in generation of sizeable quantity of fines (0-10mm) every year during various stages of mining and processing in the country with grade varying from 50-60% Fe(T) and are high in silica/alumina (Al2O3 5-8%). The fines generated cannot be directly used for iron making (blast furnace/DRI units) in the country due its physical and chemical properties; therefore, large portion of it gets exported or dumped. Value addition to iron ore fines through various activities such as beneficiation & palletization is the need of the hour, which will not only be economically beneficial to the mining sector in the long run but also generate value addition & employment opportunities. Incentives may be given for adopting latest technologies for direct use of fines in iron making by agglomeration of fines in the form of Pellets and Sinters, as fines forms considerable part of iron ore resources. Due to selective mining, although the iron content of the ore is high but the alumina(Al2O3) content in iron ore is also significantly high which demands for beneficiation as high alumina will create problem during iron making like higher fuel consumption, poor quality of slag produced, reduced productivity of B.F. all mineral has been engaged in hematite iron ore beneficiation with its gravity and magnetic separators since the mid-nineties. The delivery of jigs started for the upgrading of iron ore for its utilization in a Direct Reduction Plant in Australia. Since then, various other installations with jigs for lumps and fines as well as upstream separators for fines are in operation in Brazil, Australia, India and South Africa. Low grade run of mine and/or dump ores are being processed with alljig®-, allflux®- and gaustec®-WHIMS as the core equipment. The article describes the technology in use, the characteristics of various iron ores and the product qualities achieved. The data presented shows the specific advantages of jig application on iron ore upgrading due to the possible high gravity cuts and the easy and low cost operation. The allflux®- technology provides the big advantage of high capacities and a two-step process, both in a single unit. The gaustec®-wet high intensity magnetic separators offer high capacity in combination with unsurpassed process flexibility. Keywords: iron ore, gravity separation, jig, upstream classifier, wet high intensity magnetic separation (whims), pelletization, sinteringMineral processing is characterized by a constant adaptation to changing raw materials and market conditions. It is the link between the mined raw material and a marketable product. As a lot of high grade reserves are exploited, a steady deterioration of raw material quality can be observed. At the same time, the customers´ requirements for product purity and consistent quality increase. Indian iron ores are characteristically friable in nature that results in generation of sizeable quantity of fines (0-10mm) every year during various stages of mining and processing in the country with grade varying from 50-60% Fe(T) and are high in silica/alumina (Al2O3 5-8%). The fines generated cannot be directly used for iron making (blast furnace/DRI units) in the country due its physical and chemical properties; therefore, large portion of it gets exported or dumped. Value addition to iron ore fines through various activities such as beneficiation & palletization is the need of the hour, which will not only be economically beneficial to the mining sector in the long run but also generate value addition & employment opportunities. Incentives may be given for adopting latest technologies for direct use of fines in iron making by agglomeration of fines in the form of Pellets and Sinters, as fines forms considerable part of iron ore resources. Due to selective mining, although the iron content of the ore is high but the alumina(Al2O3) content in iron ore is also significantly high which demands for beneficiation as high alumina will create problem during iron making like higher fuel consumption, poor quality of slag produced, reduced productivity of B.F. all mineral has been engaged in hematite iron ore beneficiation with its gravity and magnetic separators since the mid-nineties. The delivery of jigs started for the upgrading of iron ore for its utilization in a Direct Reduction Plant in Australia. Since then, various other installations with jigs for lumps and fines as well as upstream separators for fines are in operation in Brazil, Australia, India and South Africa. Low grade run of mine and/or dump ores are being processed with alljig®-, allflux®- and gaustec®-WHIMS as the core equipment. The article describes the technology in use, the characteristics of various iron ores and the product qualities achieved. The data presented shows the specific advantages of jig application on iron ore upgrading due to the possible high gravity cuts and the easy and low cost operation. The allflux®- technology provides the big advantage of high capacities and a two-step process, both in a single unit. The gaustec®-wet high intensity magnetic separators offer high capacity in combination with unsurpassed process flexibility. Keywords: iron ore, gravity separation, jig, upstream classifier, wet high intensity magnetic separation (whims), pelletization, sintering

Sep 1, 2012

By William Conger, Greg Schick

Grinding media consumption is a major cost variable in industrial mineral comminution circuits. Specifically, industrial SAG media consumption results from a combination of surface abrasion wear, media breakage, surface spalling and rejection size from the mill. Three main consumption rates; weight of media consumed per time, per kWh and per weight of ore ground are defined and compared. Recent industrial data has provided an opportunity to relate consumption in terms of weight of media consumed to weight of ore ground (g/tonne) and weight of media consumed per kWh of energy consumed (g/kWh) with SAG specific grinding energy consumed (kWh/tonne). Using relationships developed from this data it is possible to project SAG media consumption in future mineral comminution circuits.

Jan 1, 2014

Sedimentary deposits such as sandstone are formed by the aggregation of cemented sand grains. Phosphates and laterite present similar aggregation of mineral grains. Grains and cement have different mineralogy and chemical characteristics. During size reduction through crushing or coarse grinding, the rocks are crumbled. Mineral grains and cement are then liberated, and the produced size distribution reflects their ?natural size distribution?. Mathematical modelling of these concomitant effects of crumbling and mineral liberation necessitates a specific material description and the adaptation of the commonly used theories of breakage kinetics and population balance. The coarse particles are mainly agglomerates made of mineral grains and cement particles whereas the fine particles are grains and cement with a natural grain size distribution. The population balance between the different particle size and particle types during size reduction takes into account the breakage rate and the progeny size distribution. The breakage rate can be described by a simple probability function or by a first order kinetics whereas the progeny size distribution is described by a breakage matrix. The model proposed here considers that the agglomerates will produce other agglomerated particles, liberated grains and cement particles; the two latter having their natural size distribution. The liberated grains and cement particles are subject to size reduction and follow the most commonly used theory of breakage. The present paper describes the theoretical approach of the concomitant crumbling and liberation effects. The application to a mathematical model for the cone crusher is presented. The advantage of such approach is then demonstrated through a simulation study for the optimisation of a crushing plant. Keywords: mineral liberation, modelling, crushing, sedimentary ore

Sep 1, 2012

By R. Bugueño, W. Calderón, G. Montes-Atenas

From the point of view of industrial performance of metal extraction, the efficiency of a column leaching operation depends strongly on the leaching agent and the ore properties such as mineral composition, mineral liberation and particle size distribution. One aspect that has become particularly important is how the leaching solution flows through the porous structure which contains the valuable minerals. It is known that the output flow rate of leaching solution depends mainly on factors of the input flow, environmental condition and porous bed properties. The latter factor is often evaluated and reported under saturated conditions but in practical leaching systems unsaturated conditions are dominant. This investigation has the purpose of determining the residence time of the leaching solution in columns with different diameters under unsaturated conditions by using experimental data and numerical simulations. Laboratory leach test were performed using isothermal jacketed columns with top cap to reduce the evaporation. The simulations were performed using the software SVFlux® which incorporates material properties such as Soil Water Characteristic Curve (SWCC) and Unsaturated Hydraulic Conductivity. Preliminary results indicate a non-linear asymptotic behavior of the saturation rate with respect to the operation time. Results from numerical simulations show the same non-linear behavior and a considerable delay between input and output flows. Further analysis concerning with the effect of transpiration and evaporation mechanisms is discussed.

Jan 1, 2014