Search Documents

By A. Villanueva

The effect of High Pressure Grinding Rolls (HPGR), as a preceding stage to a conventional ball mill circuit at PT Freeport Indonesia?s C1/C2 concentrators, has been studied in terms of downstream grinding efficiency and circuit performance. When milling the product from the HPGR, mill capacity increased by 21% for the same product grind size, when compared to processing similar ore from a conventional crushing circuit. This achievement is a result of several reasons, among them: reduction in feed size (F80), fines generation beyond the proportional reduction in F80, reduction in ore hardness induced by HPGR comminution mechanism, optimization of the recycle system of the HPGR and ball string optimization in the ball mill circuit given the new feed to the mill.

Jan 1, 2012

By P. H. Oliver

The current theory of how explosives fracture rock offers no explanation for the improvements in fragmentation and the reduction of fly rock and back break which occurs when an adequate inter-row delay time is used. Nor does it explain why fragmentation improves with rectangular drill patterns where the hole spacing may be as much as four times the hole burden. A new theory of rock fragmentation is proposed which builds on the existing theory. It offers rational explanations for the many blast effects which the current theory does not address and the need for adequate timing delays between rows. It improves on the design of inter-row delay timing by defining the length of free-blasted face needed in front of a hole when selecting the delay element which will provide an adequate inter-row delay time.

May 1, 2003

By Toshiharu Teranishi

When we apply the Au nanoparticle superlattices to the future nanooptical and nanoelectronic devices, the control of not only the particle size but also the interparticle spacing and symmetry of superlattice are the essential problems to be overcome. First, we developed a novel synthetic procedure to precisely control the particle size of alkanethiol-protected Au nanoparticles in the range from 1.5 to 9.7 nm by the heat-treatment of the small Au nanoparticles in the solid state. Absorption and nonlinear optical properties of alkanethiol-protected Au nanoparticle superlattices were then elucidated. On the other hand, the hexagonal close-packed (hcp) 2D superlattices of small Au nanoparticles with the interparticle spacings from 1.9 to 3.6 nm were successfully prepared by using newly-synthesized ligand for single electron tunneling devices. Finally, various symmetric superlattices, such as chain (2-fold), quasi-honeycomb (3-fold), square (4-fold), etc., of Au nanoparticles could be produced by making use of interligand interactions or some templates.

Oct 1, 2003

By P. H. Oliver

"The current theory of how explosives fracture rock offers no explanation for the improvements in fragmentation and the reduction of fly rock and back break which occurs when an adequate inter-row delay time is used. Nor does it explain why fragmentation improves with rectangular drill patterns where the hole spacing may be as much as four times the hole burden.A new theory of rock fragmentation is proposed which builds on the existing theory. It offers rational explanations for the many blast effects which the current theory does not address and the need for adequate timing delays between rows. It improves on the design of inter-row delay timing by defining the length of free-blasted face needed in front of a hole *Retired from Inco Ltd., Sudbury, Ontario when selecting the delay element which will provide an adequate inter-row delay time."

Jan 1, 2003

By I. R. Muirhead, S. Frimpong

"The mechanization of mining operations in underground coal mines has led to faster cutting rates of coalfaces with increased levels of emission of gaseous and particulate contaminants in the workings. Consequently, the fresh air streams from the main ventilation systems reaching distant workings are often insufficient, ineffective or inadequate and have to be supplemented by auxiliary ventilation systems to create and maintain the required working environments underground. The efficiencies of auxiliary ventilation systems are largely affected by drivers of the system such as the type and capacity of the fan; the type, length, diameter and condition of the ventilation ducting and the distance from the discharge end of the intake ducting to the face. Traditionally, single point measurements of methane gas concentrations using either flame safety lamps or hand-held measuring instruments have been used to assess how safe underground coal workings were. Unfortunately, such occasional measurements of methane gas concentrations do not give an accurate picture of the real gas concentration in the working as they are often taken from the easily accessible locations in working. Continuous monitoring of the methane gas concentration in development headings enables a better assessment of the environmental conditions prevailing there. All variations in the methane concentrations are more easily captured on a continuous monitoring basis than by instantaneous single point measurements. The approach adopted in this work was to continuously monitor the concentration of methane very close to the face and about 60 m outbye in development headings, observe the types of auxiliary ventilation equipment and their sizes being used in the working as well as noting the lengths from the discharge ends of the forcing and exhaust ductings to the face.In this paper, empirical methods are used to calculate the mean efficiencies of the auxiliary ventilation systems in selected development headings in coal mines in North America. This enables the assessment of the effectiveness of the auxiliary ventilation systems and the identification of the system drivers in them. The results show that the efficiencies of the forcing systems ranged from 17.02% to 96.81% while the efficiencies of the overall systems varied from 6.04% to 54.16%. The distance from the discharge end of the intake ducting to the face appeared to be the strongest driver in the performance of the auxiliary ventilation systems studied. It was also noted that when the discharge end of the intake ducting to the face does not exceed 7 m, there were faster purging rates of methane at the face and the efficiencies of the overall auxiliary ventilation system were greater than 50%. These findings are very important in underground coal mining in North America as they will assist to avert calamities, such as the Westray coal mine disaster in 1992 which resulted from the explosion of methane gas, by identifying which components of the ventilation system need special attention to create safe working conditions underground."

Jan 1, 2003

By M. L. Trépanier

"Engineering and technical services are supplied by the Engineering Department, located at Thetford Mines, Quebec, approximately 60 miles southwest of Quebec City. The department serves the three operating mines in the Thetford area, the Asbestos Hill mine at Putuniq, Nouveau Quebec, and the Nordenham plant at Nordenham, West Germany. The Engineering Department is responsible for supplying the following services. 1. Administration and coordination of capital projects. 2. Engineering, design and drafting services for in-plant changes or improvements. 3. Preparation of geological plans for mine planning and ore reserves determinations. 4. Short-, medium- and long-term mining plans. 5. Rock mechanics studies and monitoring. 6. Grade control monitoring. 7. Environmental control engineering and construction. Details of the organization and services rendered will be the basis of the paper."

Jan 1, 1976

By Pierre Boileau

Outline ? Who are We? ? Canada?s GHG Emissions 1990 - 2000 ? Emissions from the Petroleum Sector ? Emissions from Petroleum Exports ? Emissions from Manufacturing Industries ? Emissions from Mining and Metallurgy ? Conclusions Greenhouse Gas Division Key Functions: ? National GHG Inventory Report, Emission & Removal Trends Analysis, and Indicator Fact Sheets ? Scientific and Engineering Guidance, Technical Advice, Data Quality Assurance & Quality Control and Methodological/Data Development ? International Negotiations (FCCC) & scientific/technical guidelines (IPCC & ISO) ? Expert Review Teams (ERTs) ? Outreach ? GHG Verification Centre ? Clearinghouse ? Protocol Development

Nov 1, 2002

By K. Scholey, S. Marcuson

As high grade nickel sulphide ores are being depleted and with the continuing challenges experienced in economically processing nickel laterite ores, it is important to investigate technologies that can extract nickel from low grade ultramafic ores which are present in large quantities worldwide. In the Thompson Nickel Belt, there are some hundred million tonnes of mineralization that are potentially amenable to surface mining. Since the original discovery of the Thompson orebody, recovery of nickel from these ultramafic deposits has been an elusive goal. Research and development projects as well as commercial processing have been attempted. In the 2000's as other resources became scarcer, a major drilling, mine evaluation and research project was initiated at Vale. In 2007, Vale Base Metals Technology Development invited Cytec and potential academic partners to participate in an industry-university research consortium with the goal of developing new technologies and methods of processing the ultramafic deposits. Three university professors, J. Finch of McGill, P. Somasundaran of Columbia and R. Pelton of McMaster accepted, each group attacking the problem with a different approach. This paper describes the management of the research consortium and the significance of the results from Vale's perspective. The next four papers in this session will summarize the project and results from the partners' point of view. Vale is pleased to share the experience of the collaborative research and development with the mining industry.

Jan 1, 2011

By Jean-François Lapointe

Many advances have been made concerning the automation of heavy equipment teleoperators such as those found in mining. Complete automation, however, is not achieved yet and the operation of these vehicles still relies on the presence of a human operator. Fortunately, a lot of research has been done in order to improve the performance of these human-machine systems. This paper presents the characteristics of different control modes and input devices used for the control interface of those telemanipulators. We describe the benefits and drawbacks of each particular control interface on the overall system performance, based on a review of research in the field. We conclude with some recommendations and a discussion of future research needs, given the new potential advances offered by virtual environment technology and embedded computing.

May 1, 2001

By Tapiwanashe Chenje, David Hewitt, Peter Radziszewski

"Steel media wear is a major cost component in mineral processing. In the case of existing operating mill, steel media wear prediction can be used to help compare the performance of steel media from different suppliers before completing marked ball tests. It can also be used to investigate how ores from different site of a given mine affect steel media wear. In the case of Greenfield cases, steel media wear prediction can be used to estimate the cost of steel media for a given feasibility study.This paper presents a wear testing and prediction methodology that ties together abrasion wear and corrosion wear testing results through the use of a simplified discrete element charge motion model. The experimentation dimension to this methodology takes samples for steel media, mine site ore and water to determine abrasive and corrosive wear parameters of a given media, ore, water set.The test methodology development is illustrated along with a comparison of wear predictions with observed wear rates in some operating mills. A case study is included that illustrates how this methodology was used to estimate steel media wear performance. The paper closes with a discussion on the use of parts of the experimental methodology to investigate other abrasive wear conditions such as liner wear, paste backfill piping and ore breakage as well as avenues for future test development.INTRODUCTIONThe cost of comminution processes represents a significant part of the overall costs of a mining operation. Grinding media/liner wear alone accounts for 15-25% of the total operating cost. The annual steel grinding media consumption is approximately 2.5 mtpa or 0.3% of total world steel production [Smorgon Steel Group, 2005]. Using an estimated grinding media cost of about US$0.75/kg [Halbe and Smolik, 2002], gives a media cost of over US$1.875 billion per annum. Mining continues to shift towards exploitation of lower grade ores as the higher grades get depleted. These low-grade ores require finer grinding for the liberation of the value minerals, and hence it can be assumed that grinding media consumption will also continue to rise.The Bond abrasion test, dating back to 1963, [Weiss, 1985] is still used to estimate the total mill media wear. This is a purely empirical test based on the ore. From Bond abrasion index tests, it is possible to determine a wear rate using the following function:"

Jan 1, 2009

By R. W. Lawrence

"Biological leaching can be used to enhance the recovery of gold and silver from refractory ores, concentrates and tailings. The method liberates precious metals associated with sulphide minerals such as pyrite and arsenopyrite making them amenable to cyanidation. The chemistry and features of biological preoxidation leaching is discussed. A summary of the results obtained on various ores, concentrates and tailings is presented.INTRODUCTIONRefractory precious metal ores in which gold and silver are finely disseminated in sulphide minerals such as pyrite and arsenopyrite are becoming more important to the mining industry. This is due both to a depletion of simpler, free-milling ores and to a significant increase in the price of gold in recent years. Whereas many ores can be directly cyanided with gold solubilizations over 90% obtained, the refractory ores respond poorly to direct cyanidation and require decomposition of the precious metal-bearing sulphide minerals to increase recoveries.Decomposition of sulphides by oxidation prior to cyanidation can be carried out by several means. The oldest method is roasting which removes unwanted ore constituents by high temperature oxidation and volatilization. In Canada, for example, roasting is used at Giant Yellowknife (Connell and Cross, 1981). Another method gaining increasing acceptance is pressure hydrometallurgy which uses aqueous oxidation conducted at high temperature and pressure. Homestake Mining Company have recently completed construction of a plant incorporating pressure oxidation at their Mclaughlin property in California (Guinivire, 1984)."

Jan 1, 1985

By Norman B. Davis

Introductory Feldspar is one of the most important mineral products consumed by the various branches of the ceramic industry. In the manufacture of table ware, electric porcelain, floor tile, and enamels, it supplies the chief fluxing ingredients necessary to bond the other more or less inert materials together when moulded into desired shape and fired in a kiln. Feldspar is used in the manufacture of bottle glass as a means of introducing alumina in a form easily assimilated. It is also used in certain scouring soaps particularly designed for cleaning enamel and glass surfaces. Feldspar, as it finds its way to the trade, is not a single mineral but is rather a mixture of various proportions of the feldspar silicate series, either in natural intergrowth or blended in the milling process, to produce a desired result. It is often further modified by the presence of quartz in amounts up to 30 per cent. The table on the next page gives typical commercial analyses of feldspar from various sources. Canadian feldspar produced to date has consisted mainly of the high-potash, relatively low-soda, variety, and has enjoyed a good market in the United States for the manufacture of enamels, electric porcelain, and vitrified table-ware. About eighty per cent of the output has been exported to the United States, but, with increased milling facilities in Canada and changes taking place in domestic United States sources of supply, the proportion exported will be reduced next year.

Jan 1, 1931

By J. C. Escobedo, J. M. Almanza, A. Flores, Cortés. D. A.

Secondary aluminum dross, which has been exposed for several years to atmospheric conditions, was characterized using chemical analysis, X-ray diffraction, optical and scanning electronic microscopy, and energy-dispersive spectroscopy. Based on the characterization, a method to purify the solids is presented. This method starts with the washing of the dross in boiling water to eliminate the soluble compounds like Na and K, followed by the physical separation of the metallic aluminum by milling and screening. Finally, an acid lixiviation process is applied using three different acid solutions, HCl, HNO3, and H2SO4. The best results were obtained using HCl. The main insoluble components of the dross after lixiviation were Al, SiO2, and Al2O3. MgAl2O4, AlN, Si, and Na2Al22O3·2H20 species were also found. Based on the alumina content, the solid product could be suitable as a raw material in the manufacture of castable refractories or metal matrix composites.

Jan 1, 2005

By Seppo Lähteenmäki, Pertti Koivistoinen, Jaakko Levanaho

"This paper describes the benefits and disadvantages of fully autogenous grinding when compared to grinding with steel grinding media. The study is a real case study based on a low tonnage, high grade mining project in a remote location in a developing country. The study compares the capital and operating costs of using either SAG mill, Ball mill, Crusher (SABC) or fully autogenous (AG) grinding circuits and produces an economical analysis of the project for both options. The economics have been developed for the overall project, including mining, processing, environmental and the infrastructure as well as for the additional cost of constructing a fully autogenous grinding circuit instead of the original plan of a SAG Mill, Ball Mill circuit.The paper also describes the development of the autogenous grinding circuit at Outokumpu Oy, Pyhäsalmi mine. This experience was used to design the autogenous grinding circuit for the case study. Pyhäsalmi Concentrator has over 30 years of experience in operating autogenous grinding circuits and therefore provides a sound base for the new circuit design.INTRODUCTIONGrinding of ore using steel grinding media is currently the most commonly used method in the mining industry. Autogenous grinding, ore replaces iron media, is also common especially in Europe and Africa. Iron ore industry in North America uses autogenous grinding in primary and/or secondary stages extensively. In gold, copper and other base metal industries, autogenous grinding is not as common, although there are operations where pebble grinding is or has been used in the secondary grinding stage. There are many variations of autogenous grinding in use in the mining industry. These variations include different mill sizes, mill length to diameter ratios, ore lump sizes, screening and pebble crushing configurations."

Jan 1, 2000

By A. Karzhau, B. Aldamzharov, Y. Tussupbekov

"This case study produced for the metal mine operating in Kazakhstan, which has ventilation controlled manually and working continuously at maximum speed to keep air flowing through each part of the mine 24 hours a day. The mine auxiliary ventilation has been designed with the maximum length of ducting systems with extra air volumes to compensate for potential leakage. The mine provided auxiliary ventilation to all production stopes even to those, which for various operating reasons become temporarily inactive. However, mine safety has to consider risks associated with the deficit of fresh air for mine gases dilution and removal. The mine needs additional investments for re-designing ventilation network and therefore needs to estimate financial risks associated with it. The aim of this study is to conduct risk analysis for ventilation network optimisation processes at the operational metal mine in Kazakhstan. Mine ventilation surveys were undertaken for validation of the computerised ventilation model. The mine ventilation network modelling has been undertaken to be compliant with Kazakhstan mining regulations. Results of the mine ventilation optimisation processes were analysed in terms of financial risks for investments into reconstruction of the ventilation shafts, extension of the ventilation network, variable speed fans and automated regulators. Savings were resulted from improving ventilation system efficiency by reduce airflow in areas without mining activity and redistributing existing ventilation capacity. Based on savings derived from the optimised ventilation network an additional NPV has been received. Stochastic modelling use Monte Carlo simulation producing representation of possible outcomes for the additional NPV considering electricity pricing as a major variability. As result probability distribution for the optimised ventilation network demonstrates the additional NPV in a range of 1.6 - 2.2 million US$ in the corresponding defined value of 90%. Moreover, there is only 5% chance that the additional NPV to be less than 1.5 million US$. Conducted risk analysis for ventilation network optimisation processes gives considerations on volume of investments into the mine ventilation system.INTRODUCTIONCosts for mine ventilation are typically increasing when mines expand to deep levels. Some underground mines in Kazakhstan still use continuously operating fans at its maximum capacity. This is not helping to save energy and costs that are in many cases very significant. This case study produced for the metal mine operating in Kazakhstan, which has ventilation controlled manually and working continuously at maximum speed to keep air flowing through each part of a mine 24 hours a day. The mine auxiliary ventilation has been designed with maximum length of ducting systems and extra air volumes to compensate for potential leakage. The mine provided auxiliary ventilation to all production stopes even to those, which for various operating reasons become temporarily inactive. However, mine safety has to consider risks associated with the deficit of fresh air for mine gases dilution and removal from the mine workings (Sabanov, 2019). The mine needs additional investments for re-designing ventilation networks and therefore need to estimate financial risks associated with it. The aim of this study is to conduct risk analysis for ventilation networks optimisation processes at the operational mine in Kazakhstan. Mine ventilation surveys for validation of the computerised ventilation model have been undertaken"

Jan 1, 2019

By Júlio C. Lúcio

Consider the case of a mining company with N investment opportunities in projects of different commodities. The problem is: since the company has limitation of capital, equipments, technical staffs, etc, what is the best portfolio of production projects in order to maximize expectations from shareholders? In the no-longer past, the traditional method for the selection of portfolio of projects was the rank-an-cut method. But, this does not properly account for the risk to which the company is exposed. The Markowitz?s Mean-Variance is an advance because the risk of the NPV can be estimated at the level of the company or even division of the corporation. The final product of the Markowitz?s model is the efficient frontier, in which, the manager can clearly understand the maximum return from existing assets and the associated risk level - but this model does not recommend which one is the best portfolio. In this paper we present a model to select the best portfolio considering not only economic indicators, but also requirements of production, constraint in investments, etc. We show that if investors are diversified, managers should select projects with highest return, regardless of risk. However, in practice, if bonuses of managers are tied to their performance, the choice for portfolio with lower return and risk can happen. Numerical application considering typical portfolio of large mining company is used as example.

May 1, 2009

"This paper describes some of the methods and equipment used for fine milling of minerals, and gives particular attention to the Vibro Energy system.In addition, the paper describes a specific application in the gold mining industry. This is the 200 tpd plant built by Anglo American Corporation at the President Brand Mine in South Africa in 1985, now a division of Freegold. This plant treats a gold bearing pyrite flotation concentrate which is finely ground to 15 microns prior to cyanidation and carbon-in-pulp (CIP). l .0 INTRODUCTIONFree milling gold ores are those that yield acceptable dissolution and recovery of the gold following grinding to what can be described as normal fineness, frequently between 50% and 90% passing 74 microns.Increasingly, gold metallurgists are faced with ores that are refractory. The traditiona1 treatment route for refractory gal d ores and concentrates has been by roasting, but for environmental reasons this is becoming less acceptable, or in some areas of the world, totally unacceptable. New methods of treating refractory gold ores are being developed and applied in practice. These new methods include pressure and biological oxidation. Higher gold liberation can also be attained by increasing the fineness of grind, although with conventional systems there are economic limits to this.In flowsheet development and test programs on new deposits, a standard procedure is to establish the relationship between the grind and subsequent go 1 d extraction. The normal situation is that gold extraction increases as the ore, or concentrate, is ground finer. Typically, this relationship is as shown in Fig. l, where the incremental additional extraction is very small once an optimum, or economic, grind has been achieved. This generally app1ies whether the material is free milling or refractory. The limits to grinding are set by the type of equipment which is commonly in use, usually ball mills. These mills have the obvious advantage of high capacity, however, they are increasingly inefficient as finer grinds are required. In general, ball mills are used to reduce ore to some agreed percentage passing 74, or possibly 53 microns."

Jan 1, 1988

By André van Wageningen

Long-term mine scheduling is one of the most difficult optimization problems. The problem is said to be NP-complete in that the best possible solution cannot be found any quicker than checking all possible permutations and combinations. Although a number of techniques have been used in the past, many include significant simplifications or fail to produce acceptable results within the required timeframe. Genetic Algorithms (GAs) are among the most promising optimisation techniques within operations research. They are based on natural selection and evolution of solutions to complex problems. They have been known to quickly converge within a few percent of the optimal solution by examining only a fraction of the solution search space. The GA itself contains very little problem specific information and as such, has been linked to a discrete-event simulation (DES). The DES feeds information regarding the feasibility and quality of the solutions back to the GA during the optimisation process. In this paper, GAs and DES are described and the coupling of the two methods is outlined. The GA coupled DES is then used to ?optimise? a problem and the results are discussed.

May 1, 2004

By M. Helinski

In the authors? experience inappropriate water management in hydraulic fill masses has been the root cause of most barricade failures. Inappropriate water management can lead to high water pressures, reduced effective stresses and increased barricade stresses (Kuganathan 2002). In addition the high hydraulic conductivity and non-plastic nature of most hydraulic fills makes susceptibility to piping failure (Cowling et al. 1987) a high possibility in many hydraulic backfills where a static water head is available. In order to avert both of these failure mechanisms it is essential to control the elevation of the phreatic surface within the fill mass. This is usually achieved through campaigned filling and resting periods. The duration of filling and resting periods are often estimated using some form of stope drainage simulator. Due to the random nature of many characteristics that influence the fill mass hydraulic conductivity, simulation of hydraulic fill drainage can be difficult. The high consequences of inaccurate phreatic surface estimates combined with the high variability in drainage properties often results in operators taking a conservative approach to this modelling. This conservative approach can lead to significant delays in the filling cycle which can have a major impact on the productivity of many hydraulic fill operations and can often results in an unnecessary movement towards capital intensive paste fill systems. This paper presents a water management technique which combines a simplified drainage model with in-situ monitoring to provide a rational approach to water management. With an accurate drainage model filling operations can be carried out at optimum efficiency without compromising safety. The implementation of this strategy has lead to a significant increase in filling rates at a number of Australian filling operations. A brief case study from one of these sites has been presented.

May 1, 2007

By A. A. Beland, R. J. Dawson, S. Shewchuk

"Shovel buckets, scraper blades, dipper teeth, mine car wheels and hammermills are examples of equipment which require routine maintenance due to abrasion. Service life can be extended by the use 0/hard/acing and buildup materials. Mining and milling applications are described and field welding procedures discussed.A high-stress abrasion test used to select hard/acing and buildup materials/or hammers in a hammermill is described in detail. Field tests of the selected alloys confirmed their performance, and maintenance records showed a significant saving in down time and cost.The relationship between the abrasion resistance of the alloys and their hardness, work hardening, composition and microstructure is summarized. IntroductionLarge volumes of ore are handled daily by the mining industry. The abrasive nature of most ores results in extensive wear to both handling and processing equipment. If such wear is neglected it may cause lost production time and also, in extreme cases, require the complete replacement of expensive equipment. The well-planned maintenance of components subject to abrasive wear by means of buildup materials and hard facing can result in substantial economic benefits. Such benefits can , however, only be realized through the correct choice of welding process, consumables and deposition methods available to maintenance personnel. Hardfacing MethodsHardfacing is applied by a variety of methods; the three most widely used being arc welding, oxyfuel gas and thermal spraying. Table 1 summarizes the major processes used within each method. Filler metals in the form of rod, wire or powder are necessary to fulfill the individual requirements of each process. The filler rods are available in the cast form or, in the case of ductile metals or alloys, as wrought rod or tube. All types are supplied bare or flux covered. Wire is supplied in two forms, drawn flux cored and drawn solid. Powder filler metals are available in many metals or alloys; they may be simple mechanical mixtures or prefused and atomized alloys made to a specific size range and shape for optimum results for each applicable process."

Jan 1, 1980