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By P. V. Avotins, I. Djurkovic, D. R. Nagaraj, M. Grunjic, A. Day

"As part of a major reconstruction and expansion of the Majdanpek Copper Mine, an investigation and optimization of the flotation collector regime was undertaken. The flotation response of the major minerals to various reagents and the effect of pulp chemistry was studied from both a fundamental and practical point of view. These studies led to plant trials and the eventual adoption of a modified collector suite which improved both copper and gold recoveries.INTRODUCTIONThe Majdanpek Copper Mine processes 40,000 tons per day of ore containing about 0.43% cu. In addition to copper, the ore also contains recoverable quantities of molybdenite and gold. The mine has been in operation since 1961 and is the largest in Yugoslavia. It is currently undergoing major reconstruction and expansion. The flowsheet of the Majdanpek concentrator is shown on Figure 1.The ore body is variable in composition and changes in mill feed require proper control of operating variables to achieve the optimum metallurgical results. A detailed study including grindability, flotation response, and solid-liquid separation was carried out on several samples of the ore. Flotation response and the choice of reagent chemistry were found to be very important in achieving the highest recoveries of metal values. An automatic reagent control scheme insured that optimum dosages were used in the plant.The flotation collectors used at the present time include sodium isopropyl xanthate (SIPX), AERO 3302 Promoter and AERO 5415 Promoter. The addition of AERO 5415 to the reagent suite is a recent development and was based on the favorable results obtained in the extensive laboratory testing program conducted to establish the optimum reagent combination and dosages. Subsequent plant tests confirmed that AERO 5415 provided significant improvements in copper and gold recoveries. A description of the mineralogy of the Majdanpek ore and details of laboratory and plant metallurgical data are given in this paper. The chemistry of AERO 5415 Promoter and its interaction with minerals relevant to Majdanpek ore are also discussed."

Jan 1, 1992

By L. W. Hamel

"Two 35 foot diameter enviro clear thickeners were tested in series as CCD units from June until October, 1978. Up to shutdown in July, we ran with automatic bed level control via the level probes and underflow pinch valves. Despite extensive efforts, we were unable to eliminate the surges created between the units by the opening and closing of the pinch valves. Early in July, the best rake speed and gap setting were determined. After shutdown, the enviro clears were run by manually controlling the pinch valves. These efforts were successful.A few mechanical problems were encountered while operating the thickeners. New units should incorporate more support for the drive coupling and a rubber feed seal. A few modifications of the instrumentation control scheme will be required before the units can be fully automated. A less sophisticated automatic flocculant addition system will accomplish the desired results. Control of the underflow withdrawal via the pinch valve should be investigated further. Our best results were obtained by keeping the feed volume to the No. 1 enviro clear constant. Surges were controlled by opening or closing both underflow valves proportionately.Capacity of the enviro clears is dependent of many variables. The ore treated during the test program was much finer than that reported on in R & D Project Report 76-02. Conditions were never steady enough to determine best flocculant dosage or addition point(s). The lowest soluble losses were obtained at very high wash rates. The underflow densities drop but the soluble losses also drop. Regression equations were developed in order to assess the effect of the various parameters. Within the range studied, these equations will predict the performance of enviro clear thickeners as CCD units on Elliot Lake ores. Our results show that the enviro clear thickeners are a viable alternative to the conventional CCD thickener."

Jan 1, 1979

By H. Wotruba, L. von Ketelhodt, M. Kowalcyk, C. Kleine, M. Robben

Sensor-based sorting is a financially and technically viable technique that is operating with little or no water and relatively little power consumption. Sensor-based sorting has already proven its operational stability at two gold applications in South Africa. Sensor-based sorting cannot only turn waste dumps and diluted mining blocks into reserves. The implementation can also cause a decrease in specific operating costs of mill and mine when for example replacing selective mining by bulk mining methods with subsequent sorting. Successful installations, operational experience, test work data and flow sheet integration from mine-to-mill underline the impact and potential that sensor-based sorting can have on the gold mining and processing industry.

Jan 1, 2011

By J. A. Finch

For base metal sulphides, iron rejection starts in mineral processing. This review focuses on the changes in plant practice specifically to improve iron sulphide rejection by controlling contaminant ion effects and discusses selected innovations in mineral processing that can be expected to play a role in iron control. One change to control contaminant ions is size reduction (the use of stage grinding and inert stirred milling) and another is system chemistry (order of reagent addition and exploitation of the flexibility of sulphoxy species). Plant examples illustrate the successes, and indicate that there are several options available. The general innovations consider the new tools for measuring gas dispersion properties and quantifying froth characteristics from images. Examples of their application to improve concentrate quality illustrate the potential. Other innovations adapt geostatistics to model variations in ore flotation response to provide feed forward control and rigorously apply the statistical experimental methodology in plant test work. An example from one concentrator shows that significant improvements to reduce the iron content of concentrates can be achieved by applying these basic principles.

Jan 1, 2006

By G. J. Ackland, K. Saksl, F. Brunke, M. Kohnke, B. Tegner, C. Siemers

The application of titanium alloys is limited to 550°C due to their poor oxidation resistance. It is known that the addition of niobium decelerates the oxidation of titanium alloys whereas elements like vanadium do not improve titanium’s oxidation resistance. The underlying mechanisms are not yet well understood. In the present study, different binary titanium-niobium and titanium-vanadium alloys as well as commercially pure titanium were investigated. Oxidation experiments were carried out at 800°C up to 288 hours followed by metallographic analyses to study the oxide layer morphology as well as the microstructure at the interface. Energy-dispersive X-ray spectroscopy mappings were used to identify possible changes in the distribution of the alloying elements. In addition, micro-focused hard X-ray experiments were performed to layer-wise analyse the phase composition in selected samples. As expected, the niobium containing alloys show a better oxidation performance compared to commercially pure titanium and the titanium-vanadium alloys. The oxide layer consisted of TiO2 and Ti2O3. Depending of the niobium content, a niobium-rich layer developed below the metal-oxide-interface minimising oxygen diffusion into the titanium matrix. Based on these results, the minimal niobium content needed for improved oxidation resistance was identified so that alloys of technical relevance can now be developed.

Jan 1, 2014

By John M. Gordon

DURING and after 1949, various groups of British mining engineers came to the Dominion Coal Company, Limited, at Sydney, N .S., to see at first hand the Dosco MINER ( 1). These visits culminated in 1952 with the ordering of four Dosco Miners by the (British) National Coal Board on an experimental basis through their Experimental Expenditure Funds. Others are now on order. The first machine was delivered in February, 1953, and, after slight alterations to suit the different power supply, the machine was made ready to work. Due mainly to the size of the machine, new rules and regulations governing its operation had to be put into effect and it was not until April, 1954, that the machine was put underground. It started to produce in June of that year. The three others were delivered early in 1955. The authors were sent to England by the Dominion Coal Company to install and demonstrate these machines and to work with the Coal Board engineers to- further interest in the machines in the British coal fields .

Jan 1, 1956

By Tassos Grammatikopoulos, Sarah Prout, William Mercer, C. Gunning

"The Nechalacho rare metal deposit is located in NWT, Canada. Avalon Rare Metals Inc. is now evaluating processing techniques for recovery of REE to be used in the industry. QEMSCANTM analysis coupled with whole rock, REE, Zr and Nb, and electron microprobe analyses were utilized to identify and quantify the mineralogy of the deposit, and define the REE distribution among minerals. QEMSCANTM mineralogy was performed on fifty intact drill samples using EXPLOMINTM that provided textural information for the mineralization; crushed samples were used to determine the variability of the ore and define REE domains, and composite samples to determine the liberation and association of the REE minerals. The sample matrix predominantly consists of biotite, feldspars, quartz, muscovite/clays, minor chlorite and amphibole, magnetite and hematite and carbonates. REE include in decreasing order of abundance allanite (3.6%), monazite (1.5%), synchysite (0.9%), columbite (0.9%), fergusonite (0.6%), bastnaesite (0.4%), and zircon 11.0%. The majority of the HREE are carried by fergusonite and zircon, and the LREE by monazite, allanite, synchysite and bastnaesite. QEMSCANTM mineralogical data is extremely valuable in assessing the mineralogy of the ore. The data have been implemented in defining the mineralogy of the ore body, support metallurgical test work, predict recoveries and grades, and finally calculate reserves of the deposit.INTRODUCTIONAvalon is in the unique position of owning and developing one of the world’s largest rare earth deposits in the Northwest Territories of Canada.The term Rare Earth Elements (REE) is used to describe the 15 lanthanide elements or metals and, more recently, the metals yttrium and scandium, which display similar physical and chemical properties. REE are not particularly rare and have a similar abundance in the earth’s crust to nickel, tin or tungsten. Unlike these better known metals however, the rare earths have little tendency to become concentrated into commercial ore deposits. When they do become concentrated, deposits of REEs usually display enrichment in one of two groups. The most commonly occurring deposits of REEs contain a sub-group of elements referred to as the “light rare earth elements” (LREEs), which include lanthanum, cerium, praseodymium, neodymium, and samarium. Less commonly, deposits of REEs contain the much more valuable sub-group of elements referred to as the “heavy rare earth elements” (HREEs), which include europium, gadolinium, terbium, dysprosium, holmium, erbium, thulium, ytterbium and lutetium. Yttrium and scandium most commonly occur in association with this second HREE sub-group. Generally, LREEs are produced from the mineral bastnaesite, and the HREEs have been produced from the minerals xenotime and monazite. LREEs continue to be produced from bastnaesite, however in the 1980s, China started production of HREEs from unique laterite clay deposits. China now produces approximately 95% of the world’s rare earths."

Jan 1, 2011

"The first SkimAir flash flotation cell was installed in Outokumpu’s Hammaslahti Copper Concentrator in 1982 to prevent overgrinding of soft sulphides in the milling circuit. Since this first installation the popularity of the flash flotation has fluctuated depending on metal market conditions and regional preferences. Units have been installed in many commodities including copper, lead, gold, PGMs, silver and nickel. Though it has been successfully employed in many operations around the world, flash flotation technology is still not well understood by many in the mining industry. This paper will discuss aspects of flash flotation flowsheet development along with some of the metallurgical and engineering considerations required to successfully incorporate flash flotation into new or existing milling circuits. This paper will also try and debunk some of the myths that exist around flash flotation cells and their operation. Case studies of flash flotation implementation will be discussed.IntroductionModern flash flotation technology was developed several decades ago by Outokumpu, with the first commercial installation of this technology being at the Hammaslahti concentrator in Finland in 1982 (Kallioinen & Niitti, 1985). This was a relatively modestly sized SK80 cell producing final grade copper concentrate directly from the flash flotation cell operating in the grinding circuit. Since that time the size and number of flash flotation cells installed globally has grown considerably to the point where today, it is a widely known application of flotation technology for amenable ores. Owing to their long history in developing the technology, Outotec are the market leader with their SkimAir range of flash flotation cells. Though there is a general awareness of flash flotation process in the mineral processing industry, there is a lack of detailed understanding of the process and the benefits it can provide to new and existing operations."

Jan 1, 2017

By Dominic Fragomeni

"The mineral processing industry has had a long history of innovation that is recognized but not often celebrated. These include significant advances in mineral measurement, testing, comminution, mineral separation and process control technologies that have transformed mineral assemblages into ore.This presentation presents some of the major mineral processing innovations and the impact they have had on our industry. As we look to the future, it is critical that we innovate and change. We will explore some examples of the next developments and how they can be catalyzed in the face of risk management, lower metal price cycles, resource constraints, inertia and the challenge of short term value delivery."

Jan 1, 2017

By G. Danha, D. Glasser, D. Hildebrandt, N. Hlabangana

"In this work, we apply a method known as the attainable region (AR) technique in order to optimize the milling and leaching process of a low grade gold ore. No work on the application of the AR optimization technique has been done yet on a joint milling and leaching process. The advantage of the AR approach lies in its ability to simplify the optimization problem, as searching over a defined set for the maximum of an objective function is a fairly standard procedure. The objective function we selected was that of optimizing a linear function of the value of the recovered material minus the cost of both milling and leaching. Using the three variables (milling time, leaching time and recovery), we constructed a 3D plot and used it to obtain all the possible recoveries from the different milling and leaching times. The optimum for our chosen objective was then found by overlaying a contour plot of the objective function on the 3D plot. Our results show that the optimum was obtained at 90 % recovery with a profit value of 600, milling time of 30 minutes and leaching time of 1750 minutes.INTRODUCTIONAfrican countries are facing a general increase in demand for electrical power. In South Africa, the demand is now surpassing the supply from ESKOM, the main electric power provider of the country. This has resulted in load shedding strategies being implemented in many local communities in an attempt by ESKOM to cope with the high demand. A potentially better approach is to propose use of energy efficient technologies in the country’s largest power consuming industry; the mineral processing sector.In mineral processing, milling is the highest consumer of energy. The objective of carrying out milling is not merely to reduce the particle size of the feed material, but also to liberate the constituent minerals that make up an ore. This is done so that valuable minerals can be separated from the gangue, in downstream processes, such as leaching. However, the milling process is generally performed relatively poorly, and at a considerable expense in terms of electrical power utilization. Tomanec and Milovanovic (1994) estimated that milling accounts for more than 50 % of the total power used in the concentration process, but this can rise to as high as 70 % for hard or finely dispersed and inter-grown ores. Apart from being relatively wasteful of energy, the milling process is also inefficient with regard to mineral liberation because of the indiscriminate nature of the grinding force."

Jan 1, 2016

By M. Sturzenegger

This paper documents a field survey using long-range terrestrial digital photogrammetry at the Palabora open-pit mine, South Africa, for multi-scale characterization of rock mass discontinuities. Stereomodels covering the entire mine were generated based on photographs taken from a distance of 1600m across the pit, using a series of f=20-400mm lenses. Details on the methodology used and its accuracy are discussed. Preliminary results on discontinuity orientation, persistence and intensity are presented, highlighting the effect of observation scale. The potential uses of long-range terrestrial digital photogrammetry in open-pit mine and large natural rock slope environments is emphasized. The use of an f=400mm lens from distances larger than 1.5km may represent an important step forward in the geotechnical characterization of inaccessible remote rock faces.

May 1, 2009

By Christoph Broeckmann, Andrew Gardula

"The adoption of high-pressure grinding throughout the cement industry has yielded enormous savings in energy and wear material costs. There are also a number of installations, which are applied in iron ore and kimberlite processing operations. High pressure grinding offers the same potential for energy and media savings, as well as opportunities for improved, downstream metallurgical performance, in hard rock mineral processing. This paper focuses on developments in machine design and wear surface engineering for high-pressure grinding of the hard rock ores in the mineral processing industry.INTRODUCTIONIn the early eighties 3.4 % of the world electric energy was consumed for crushing and grinding operations of minerals and 0.6 % in the ore dressing industry. During that time using a laboratory press Prof. Schönert found that interparticle comminution at high pressure requires remarkably less energy as conventional grinding technologies. In grinding of cement clinker he expected energy savings between 33 and 50 % compared to ball mills [1]. Piston presses are limited in throughput. Thus, the principle of interparticle comminution was adapted by the use of high pressure grinding rolls (HPGR) to a continuous plant process. Figure 1 shows the main components of a roller press: The roller nip of width s is formed between the floating roller (1) and the fixed roller (2). The diameter of the rolls will be denoted with D, the width with B. The total press force F can be adjusted using a hydraulic system with two or four pistons (3). In order to compare machines with different roll geometries the specific pressing force p is introduced:"

Jan 1, 2005

By L. Parthasarathy, S. K. Pan, M. P. Srivastava

"Total iron ore reserves in India, as reported by the Indian Bureau of mines, are 23.6 billion tons. Hematite iron ore reserves constitute about 45 % of the total reserve. If we go by the National Steel Policy-2005 projections, India’s supply of hematite iron ore would not last more than 40 years. Laboratory investigations were carried out for the development of a process flow sheet for treating low grade as well as Banded Hematite Quartzite (BHQ) iron ore. The purpose of these investigations was to aim for better resource utilization.Beneficiation studies were conducted on samples of low grade and siliceous iron ore from the Dalli mines, a captive mine of the Bhilai Steel Plant and BHQ ore from Southern states of India. The process flowsheet, developed for upgrading of low grade iron ore, incorporates wet screening of the ore at 0.5 mm, followed by grinding of the +0.5 mm fraction to below 0.5 mm. The whole –0.5 mm fraction, after grinding, was treated in a conventional hydro-cyclone and stub cyclone followed by treatment in Wet High Intensity Magnetic Separator (WHIMS). This resulted in a concentrate product having >66% Fe content from a feed containing 55.5% Fe with an iron recovery of 48 %. The process flowsheet developed for treating BHQ ore in the laboratory resulted in an increase in iron grade in the concentrate from 43.4 to 61.3 Fe % with a yield of 51.7 % .INTRODUCTIONThe classification of Indian iron ore resources have been made compatible with United Nations Framework Classification (UNFC), which is more scientific and has been adopted in most countries in the world. Iron ore reserves and resources estimated using the UNFC classification system, as of April 01,2000 are about 12,906 million tons of hematite ore and 10,628 million tons of magnetite ore. The Indian Bureau of Mines (IBM) has given a breakdown of these reserves by designation as either lumps or fines of hematite iron ore (Table 1). The percentage of the reserves reported lumps and fines are 42 and 34% of the total reserves respectively. High grade iron ore is less than 10% of the total reserve."

Jan 1, 2008

By Fathi Habashi

"Crushing and grinding of ores and their beneficiation by washing away gangue minerals has been practiced since ancient times. Primitive crushing was done by hand pounding the ore with a hard stone then by using metallic hammers. The mortar and pestle was mechanized using a lever and when the size of operations increased in the middle ages, the stamp mill was introduced. The grindstone played an important role in grinding of ores. Panning for gold and hand sorting of minerals were two old methods of separation, now gave way to modern techniques. Flotation started in the middle of the nineteenth century by using oils to collect the mineral particles and float them on the surface of the aqueous slurry. It was only in the 1920s when it was discovered that organic compounds were affective floating agents. Textbooks written by distinguished engineers such as Rittinger, Rickard, Pryor, Taggart, Richards, Gaudin, and others contributed to the recognition of this field as a new discipline to be taught in Universities. INTRODUCTIONThe ancient Egyptians knew already that it would be easier to melt an earth rich in gold particles than another which is poor. As a result all efforts were made to enrich the gold by washing away the light gangue minerals (Figure 1). Another ancient method for enriching gold particles from a river stream was by means of fleece, hence the Greek myth of the “golden fleece”. The present day Georgia was known in ancient times as Colchis and was a center for gold working. It was known to the ancient Greek as the land of Golden Fleece. The use of special cloth to catch gold particles was also described by Agricola in his 1555 book De Re Metallica (Figure 2)."

Jan 1, 2009

By S. Frimpong

Hydraulic shovels are widely used for primary production in surface mining operations. Variability in material diggability, unstructured mining environments and limited space and operator inefficiency affect the performance of these shovel excavators. Dynamic models of the hydraulic shovels are essential for understanding and improving machine performance. This paper contributes to this subject area by advancing hydraulic shovel kinematics and dynamics using the modified Newton-Euler method. A virtual simulator is developed to simulate the hydraulic shovel performance in the ADAMS environment. The simulator is validated with data on shovel geometry and the physical and mechanical properties of a formation in a surface mining environment. The results indicate that a shorter digging time increases the shovel operating power requirements, and that the required peak power increases by 100% when the digging time reduces by 50%. Simulation results also show that a shallow trajectory facilitates the digging process, with 50% reduction in peak power requirements compared to a deep one. This simulator provides a powerful tool for performance monitoring, excavation process designs and structural optimization of hydraulic excavators. This work also forms the basis for developing comprehensive simulator models for automated shovel operations in constrained mining environments.

Jan 1, 2005

By R. J. Balfour, T. L. Papucciyan

"INTRODUCTIONCapital Cost considerations are basic to feasibility in the achievement of success for Mineral Processing Projects as much as or more than in many other industries. Capital cost is an important factor ae it 1R the unit of measurement for process engineering economic decisions. As a result of ever increasing complexity, alternatives of process and remoteness of site, there is an ever increasing emphasis on accurate estimating and the attendant cost control systems in the international market of today for the Mineral Industry where initial plant costs are becoming a more important factor than operating costs. An undervaluation means trouble ahead. An over-cautious assessment may bring an unnecessary abandonment of a project. Consequently, the ultimate cost must be predicted early and accurately and must be controlled to this parameter during the design and construction phases. Cost Est!~ mating is one of a variety of project management tools used to assist in planning and achieving the optimum balance between Quality, Cost and Time, the eternal triangle of evaluation, namely obtaining a project of acceptable quality at minimum cost and on time. In order to attain these established objectives, proper planning, organizing, coordinating, monitoring, adjusting and controlling the design, procurement and construction elements of the project are essential.This project management approach based upon the principle of a Task Force under single management, comprising a complete service organization, requires a substantial number of qualified individuals specialized in their own field and capable of working together as a team to perform their various functions effectively. The Task Force is supported by their chiefs of discipline and performs in accordance with established procedures and standards under the leadership of a Project Manager.General Engineering Company Limited with the backing of the full resources of Surveyer, Nenniger & Chenevert and its total staff of approximately 1,0009 offers the complete project management service to the Mineral Processing Industry of North America and the rest of the world. As mine sites become more remote and difficult of access, the need for an experienced team of specialists who work under the Task Force principle, with well established standards and procedures becomes even more important. Our long history of successful pro1ecta in this field has been our training ground for the fulfillment of this need."

Jan 1, 1972

"In mining operations, it is widely accepted that strategies to drive operational goals must revolve around improving plant availability, reliability and process efficiency. In this paper, an integrated solution framework for reducing process variability, increasing process efficiencies and maximizing plant availability and reliability is discussed within the context of a typical milling circuit. The framework exploits a real-time analysis “gap” evident in production operations that prevents timeous identification of equipment and process failures. This is achieved by leveraging predictive analytics for equipment health monitoring, control loop monitoring and advanced regulatory control solutions towards enhanced process performance, improved asset management and regulatory compliance. The framework provides for early and actionable warnings on equipment and process degradation using real-time operational data.INTRODUCTION The changing landscape of gold mining and processing presents many challenges that threaten sustainability of existing (marginal) operations as well as deter investment in new projects. As existing “shallow” ore resources become depleted, mining operations are increasingly treating low-grade ores with complex and randomly variable mineralogical characteristics. For example, in South Africa, historically one of the major gold producers, the average grade of ore treated has been decreasing from averages above 4.5 – 5 g/t to current grades averaging less than 3 g/t within a decade (Chamber of Mines, 2012). Moreover, lower tonnages are being treated as a result of the narrowing of the available resource base. Also, the regulatory framework has tightened over the years due to heightened concerns on the safety, health and environmental impacts of mining and related activities."

Jan 1, 2014

By E. M. Shemang, C. E. Suh, L. Mbinkar, University of Yaounde

"Two iron deposits within the Precambrian mineral belt of Cameroon are described in detail for the first time: the Archean Metzimevin replacement iron deposit enclosed in Fe-enriched itabirite, and the Proterozoic granite-hosted, shear zone-related Mayo Binka magnetite deposit. In the Metzimevin de¬posit, quartz is corroded and microplaty hematite overprints martite-textured hematite. The Mayo Binka massive magnetite veins show evidence of deformation in magnetite (fracturing and microbrecciation) and in overgrowths of specular hematite (mechanical twinning and undulating extinction). The magnetite is partially replaced by hematite (martitization) and goethite. Ores from both deposits have >88% total Fe2O3 and low contents of contaminants such as SiO2, Al2O3, MgO, CaO, P2O5, and TiO2. They are also poor in Cu, Pb, Zn, V, Cr, and Ni. The Metzimevin massive hematite is characterized by an accentuated light rare earth element depletion relative to the Fe-enriched itabirite. It is suggested that the Metzimevin iron deposit is the result of hypogene leaching of gangue minerals from, and further hematitization of, an itabirite protore. Although the genesis of the Mayo Binka massive magnetite is unclear, it is spatially related to Neoproterozoic granitic rocks. The data allow some comparison of these little known, but pot¬entially economic iron deposits, with some of the world’s better investigated deposits, and are useful to the exploration efforts for iron ore currently underway in Cameroon and the Central African subregion.Deux gisements de fer de la ceinture minérale Précambrienne du Cameroun sont ici décrits en détail pour la première fois : le gisement de fer Archéen de Metzimevin formé par remplacement et encaissé par des itabirites enrichies en Fe, et le gisement de magnétite Protérozoïque de Mayo Binka as¬socié au cisaillement dans un granite. Au gisement de Metzimevin, le quartz est corrodé et de l’hématite en microplaquettes se développe au dépends de l’hématite a texture martitique. Les veines de magné¬tite massive de Mayo Binka présentent des évidences de déformation dans la magnétite (fracturation et microbréchification) et dans les surcroissances d’hématite spéculaire (Macles tectoniques et extinction ondulante). La magnétite est partiellement remplacée par l’hématite (martitisation) et par la goethite. Le minerai des deux gisements contient >88% de Fe2O3 total et un faible contenu en contaminants tels que SiO2, Al2O3, MgO, CaO, P2O5, et TiO2. Il est également pauvre en Cu, en Pb, en Zn, en V, en Cr et en Ni. L’hématite massive de Metzimevin est caractérisée par un appauvrissement relatif en terres rares légères relativement à l’itabirite enrichie en Fe. Il est suggéré que le gisement de fer de Metzimevin résulte du les¬sivage hypogène des minéraux de la gangue ainsi que de l’hématitisation poussée d’une préconcentration de fer dans l’itabirite. Bien que la genèse de la magnétite massive de Mayo Binka demeure obscure, elle est spatialement associée aux roches granitiques Néoprotérozoiques. Ces données permettent de comparer ces gisements de fer peu connus et potentiellement économiques avec certains des gisements mondiale¬ment mieux connus, aidant ainsi les efforts d’exploration présentement en cours en Afrique de l’ouest et au Cameroun."

Jan 1, 2008

By Charlie Graham, Helen Shang, Ashley Scott, Andrew Hall

"Approaches to Energy Recovery• Upgrading for electricity generation - steam turbines• Direct extraction- process improvement or space heating- support medium for animal or plant growth– fish or microalgae• Heat pumps- space heating/coolingWater Energy Grades• High (150+ °C) - electricity Generation• Medium (26 to 121 °C) - direct extraction• Low (5 to 18 °Celsius)- use of heat pump is required• Temperatures between zones will depend on circumstances for best use."

Jan 1, 2012

By K. C. Corin, Z. G. Song, J. G. Wiese

In the present investigation flotation was used as a diagnostic to understand the effects of changes to the media during the grinding stage. The observations from flotation for different media are discussed in terms of particle size distribution, water recovery, solid recovery and valuable mineral recovery. The chemical parameters; pH, redox potential (Eh) and dissolved oxygen (DO) levels were measured. A Base Metal Sulphide (BMS) ore was ground under media of different shapes and compositions to determine the effect of different rod/ball material on the flotation performance of the ore. For a given grind (D80 = 75 µm), media shape had no effect on flotation performance of a BMS ore. Different grinding media had significant effect on slurry chemical properties and flotation performance. Mild steel rods (RMMS) produced the highest solids recovery, nickel and pyrrhotite (Po) recovery, with the highest ethylenediaminetetraacetic acid (EDTA) extractable iron and the lowest DO level. Chrome steel balls and stainless steel rods produced the lowest metal recovery, EDTA extractable iron and the highest DO level. A complementary study was conducted to investigate the effect of using different grinding media compositions, viz, ceramic, forged steel, 15% chrome steel, stainless steel and a mixture of stainless steel and 15% chrome steel (50:50) balls were investigated using a Platinum Group Mineral (PGM), UG2 ore. Grinding products of five different media produced the same solids and water recovery, but the grades and recoveries of Platinum Group Elements (PGE) and chromite were different. Grinding products of ceramic media showed the best flotation performance, with the highest PGE recovery and the lowest Cr2O3 recovery. While grinding products of stainless steel balls (SS) produced the lowest PGE recovery and highest Cr2O3 grade and recovery in the concentrates.

Jan 1, 2016