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By A. P. Sasmito

It is well known that underground miners are exposed to one of the most dangerous working environments on earth. As mine delve deeper, the geological factor, mine position and climate condition as well as heat generation from mining machine give rise to the mine operating temperature. This, in turn, has an adverse effect on the environment and thus leads to higher operating costs. Careful estimation and design of air flow rate, spray system, cooling load and additional ventilation auxiliary equipment are of importance to ensure safety, comfort and productivity whilst maintaining low operating cost. A computational fluid dynamics simulation approach is employed to examine underground mine ventilation in a 36 m cul-de-sac of tunnel of coal mine. The model predictions in the turbulent range were validated by comparison with published data. Different turbulence models were tested to select one that yields adequate accuracy and is computationally efficient. Effects of the following parameters are evaluated: tunnel geometry, air flow rate and inlet air temperature. The objective of the simulation is to arrive at an optimal strategy for ventilation and thermal comfort at low cost.

Aug 1, 2013

By Gustavo Angeloci

Artisanal mining is a rudimentary activity that today attracts over 30 million people in virtually all developing countries around the world. As the price of gold has steadily increased over the past decade, 15 million people have become involved in extracting this metal in 55 countries. Individuals have switched to mining from primary industrial sectors such as agriculture to increase their income. These workers generally have little capital, low education levels, and no previous experience in mining. Together with a lack of technical support from governments, these factors lead to disorganized and informal mining activities that generate environmental and social chaos. The absence of technical knowledge and capital has caused a proliferation of Gold Ore Processing Centres (GOPCs) around the world established by local entrepreneurs, who provide a way for miners to process their ores using amalgamation for a fee that is relatively low to non-existent. Gold recovery by the independent miners rarely exceeds 30 % and gold-rich tailings are left at GOPC facilities as a form of payment. GOPCs recover around 90 % of the remaining gold using cyanidation, flotation, and amalgamation, without any compensation paid to the miners. In processing these mercury (Hg)-contaminated tailings, Hg cyanide complexes are produced that are dumped into aquatic environments, leading to rapid bioaccumulation of Hg by fish. In the town of Portovelo, Ecuador, the establishment of partnerships between GOPC entrepreneurs and artisanal miners has proven to be successful in forming legal small-mining companies to create more equity and reduce pollution. About 108 GOPCs operate in Portovelo-Zaruma, with 40 % of these still working illegally without proper regulation and permitting. Over 20 % of these GOPCs continue to use grinding, concentrating and amalgamating of the gold, with 58 % performing cyanidation of tailings and/or gravity concentrates, and 15 % combining flotation with cyanidation. About 94 % of the GOPCs concentrate the ore prior to applying amalgamation, which significantly reduces Hg emissions to the environment. Incorporating flotation has given the operators increased skills in mineral recovery, with the side benefit of producing a copper concentrate as added value. Despite these innovations, mineral recovery is still inefficient, and waste management is a major challenge in creating true sustainability in this sector (technical efficiency together with social and environmental responsibilities). Further organization, training and capacity-building are needed. The principles of Lean Manufacturing Methods ("Just in Time" production and "Automation") are suggested as possible techniques to assist small GOPCs to become sustainable. In this concept, a larger mining company can become associated with artisanal miners in a partnership to provide training and investment for exploitation of small deposits that would be infeasible as a single large operation. As well, an International Training Centre for Artisanal Miners (ITCAM) is being established in Portovelo with collaboration of the Government of Ecuador to further enhance and upgrade mining activities in this region. ITCAM will provide artisanal miners with technical, business and environmental training to become responsible small-scale miners. In building this new capacity, ITCAM intends to create an atmosphere of trust to attract private and corporate investors to become partners with artisanal miners.

Aug 1, 2013

By D. L. Cluff

Ventilation Air Methane (VAM) is a high volume low concentration methane source. The capture or use of methane from VAM is challenging, which results in the routine discharge of methane into the atmosphere. Mitigating VAM has the benefits of providing an energy source and reducing the atmospheric Greenhouse Gas (GHG) burden. The GHG radiative forcing effect of methane is 17?23 times as potent as carbon dioxide on a 100-year time horizon. Thus, any reduction in atmospheric methane would be beneficial. The calorific value of methane is 55.5 MJ/Kg; therefore, a 100 m3/s flow with VAM concentrations from 0.1?1% can provide 3.8?38 MW of exploitable power. Strategies to mitigate VAM such as: Thermal Flow Reverse Reactors (TFRR), Catalytic Flow Reverse Reactors (CFRR), Lean Burn and Catalytic Gas Turbines, Biothermica Vamox®, Megtec VOCSIDIZER©, and Vamcat? are briefly reviewed. The review of VAM mitigation technologies reveals disadvantages such as the need to maintain a minimum internal heat capable of oxidizing the methane. This requirement uses all of the available methane up to the point of reaction sustainability and up to half at the highest methane concentration in VAM. Some systems may introduce a pressure drop to the ventilation system, which would impinge on the existing ventilation system design. These impediments necessitate the development of a more amenable technology. In the proposed system, gas turbines (GT), coupled to a combustion chamber with an external fuel supply, assist the combustion of the VAM. The combustion-chamber coupled system provides electricity, while the heat contained in the GT exhaust gases increases the temperature of the VAM, encouraging the development of a flame inside a combustion chamber. The flow from the combustion chamber streams through a primary air/fluid heat exchanger capable of producing steam of a high enough quality to generate electricity using conventional steam turbines. The residual heat after primary extraction, directed through other equipment, provides additional heat based products such as industrial scale dry air, chilling by an absorption chiller or hot water. The overall design of the system is scalable for low to high VAM flows or variations in concentrations and is capable of providing the company or community with heating, chilling, hot water, electricity or motive force as needed by the particular site or community. The Multi-generation system uses heat from three sources to provide clean efficient energy while mitigating the atmospheric emissions of methane. These sources are heat from the GT, often considered waste heat, heat from fuel injected into the igniters and heat from the VAM. The opportunity to collect carbon credits may improve the economics. In order to design a system with this capacity, a detailed analysis of the combustion characteristics of three separate flows is required. VAM is the main airflow, having the highest volumetric effect, while the GT exhaust and the additional fuel added to the hot exhaust flow of the gas turbine are lower flows, but have a higher velocity and temperature. The aim of the modeling undertaken in this work is to establish the combustion dynamics, degree of pre-heating required and the geometry essential to the design of combustion based VAM mitigation multi-generation systems.

Aug 1, 2013

By R J. Holmes

An accurate knowledge of the chemical, mineralogical and physical characteristics of ores and mineral products that are mined, processed and traded is crucial to effective resource utilisation, plant design, process optimisation and finally quality control to ensure that contract specifications are met. However, all too often the responsibility for sampling is entrusted to managers and personnel who do not fully appreciate the significance and importance of collecting representative samples for analysis, and everyone seems satisfied as long as some material is collected and returned to the laboratory for analysis. Furthermore, sample stations incorporated into the design of new plants are often the first casualties when cost cutting exercises commence. This needs to change, because there is little point in accurately analysing samples if they are not representative in the first place. The resultant analyses can be next to meaningless and the effort taken to analyse such samples is to a large extent a waste of time and resources.Ultimately, a poor knowledge of the characteristics of ores and mineral products limits the ability of mining companies to optimise the life of ore resources and plant performance, and failure to meet final product specifications can have disastrous consequences, including price penalties and more seriously loss of sales contracts. It is high time that sampling is given the attention it deserves as the first critical step in the quality measurement chain.CITATION:Holmes, R J, 2013. The importance of sampling in the mineral industry, in Proceedings MetPlant 2013 , pp 34-49 (The Australasian Institute of Mining and Metallurgy: Melbourne).

Jul 15, 2013

By D J. Brake

The underground metalliferous mining industry continues to change under the influence of many factors including, to name a few, new mining techniques and equipment, new approaches to risk management, more stringent safety and health standards, new employment practices and orebodies become deeper and often lower grade. In addition, the same technological revolution and plummeting cost of technology that has brought the GPS, smart phones and digital cameras to the general population is also working its way through the mining industry impacting on communications, automation and process control as well as introducing major efficiency and productivity dividends. However, not all factors are positive including, in particular, the issues of carbon costs and electrical power. This paper explores some of the trends affecting ventilation in hard rock mines, some of the existing and likely future challenges and some of the potential future solutions to these issues.CITATION:Brake, D J, 2013. Ventilation challenges facing the metalliferous sector, in Proceedings The Australian Mine Ventilation Conference , pp 3-12 (The Australasian Institute of Mining and Metallurgy: Melbourne).

Jul 1, 2013

By B Robertson

Over the 40 years that the author has been engaged in the Australian underground coal mining industry, there has been a continuous improvement in safety performance as the sector has grown in size and productivity. The underground environment hosts many hazards with significant risk profiles that are kept in check by effective health and safety management systems that have evolved largely following major underground disasters. Observations are made on the changes observed for specific aspects of the underground coal sector, with particular reference to ventilation issues, and predications are made as to the needs of the future.CITATION:Robertson, B, 2013. Past achievements and future challenges in the underground coal sector, in Proceedings The Australian Mine Ventilation Conference , pp 27-32 (The Australasian Institute of Mining and Metallurgy: Melbourne).

Jul 1, 2013

By William Gleason

The world has seen unprecedented economic changes in recent years, starting with the stock market collapse of 2008 and the great recession that followed. With these changes, the mining industry, like others, has been forced to find ways to adapt to the shifting and sometimes volatile conditions. It has been a bumpy ride that has not been easy. Prices for most commodities have been in a decline in the past several quarters ? albeit still well above the average prices of 10 years ago ? as the costs of production have been on a steady incline for the past 10 years. Adding to the concern was the report in April that China, which had grown at an average pace of 10 percent/year, for the past decade, slowed to less than 8 percent gross domestic product (GDP) growth this year, catching many off guard. Even gold, once the safe haven for investors during rocky times, stumbled in April of this year, losing 7 percent of its value in two days. So what?s an investor to do ? and how can companies still attract financing? For the first time in 10 years, SME, in conjunction with the New York Local Section of SME, attempted to clear the waters of the mining finance sector with a conference focused on ?Current Trends in Mining Finance.? Held at City University of New York, Graduate Center, April 29-30, the two-day conference attracted 148 attendees and was intended for senior executives and mining industry specialists, covering a range of important topics and trends through 17 panels with about 50 speakers. The presentations came from representatives from some of the most influential companies in the mining and financial sectors, including Citi, Nomura, Societe Generale, Caterpillar, Newmont Mining Corp., Ernst & Young, Export Development Canada (EDC), KPMG, HSBC, Tocqueville Asset Management, BNP Paribas, Revett Minerals, Royal Gold, Environ and ERM.

Jul 1, 2013

Editor?s note: Each year, Mining Engineering features an industrial minerals review. Several people put in a fair amount of time in developing the material for this issue, all the while doing their own jobs. Thank you to the industrial minerals annual review editor, to the Industrial Minerals and Aggregates Division technical committee chair and vice-chairs, and to the authors of the individual commodity profiles. Jim Norman, member SME, of Tetra Tech, is the industrial minerals annual review editor. Rajesh Raitani, member SME, of Cytec Industries Inc., is chair of the Industrial Minerals and Aggregates Division?s Technical Committee. The technical Committee vice chairs include: ? Vishal Gupta, member SME, of FlSmidth, Agricultural Materials. ? Candace Trimble, member SME, of Oil- Dri Corporation of America, and Bradley Van Gosen, of the U.S. Geological Survey, ceramics and refractory materials. ? Stanley Krukowski, member SME, of the Oklahoma Geological Survey, chemical raw materials. ? Russell Winn, member SME, of R.E. James Gravel Co., chemical raw materials. ? Justin Zdunczyk, member SME, of Plum Creek, construction materials. ? Jerry Gauntt, member SME, of Golder Associates, fillers and pigments. ? Michael Cheshire, member SME, of Los Alamos National Laboratory, sorbents, filters and process aids. ? Rajesh Raitani, member SME, of Cytec, Industries Inc., specialty minerals. Their help makes possible this June industrial minerals issue. On behalf of ME readers, the editors thank them.

Jul 1, 2013

Traditional in situ fan flow test methods under accepted standards require determinations to be made of both static pressures and total pressures during testing. This is to determine the resultant velocity pressures, which are vital in the accurate determination of the final fan airflow. These crucial velocity pressure (Vp) determinations are normally determined using simple manometric instrumentation such as an electronic manometer or an inclined liquid filled manometer. There is relatively little noise or fluctuation in the static pressure determinations and they can be quite easily and accurately recorded. There is almost always considerable fluctuation in the velocity pressure determinations though due to the highly turbulent and irregular velocity profile normally found in such in situ installations. This velocity turbulence means that the recording of such data is subject to random human error as the observer tries to average such fluctuations mentally during the observation period. Worse than this, and in the extreme, the recording of such velocity pressure data could actually easily be misreported if, for some reason, persons chose to do so.The author has devised a field method using highly accurate quartz crystal logging barometers to objectively record these velocity pressures. The method eliminates the ability to either mistakenly or intentionally misreport these crucial velocity pressures and is carried out in parallel with the recognised methodology, so result comparisons can be drawn. As such, a far greater level of confidence can be achieved in the final flow performance results than using the traditional more subjective method. Further to this it is difficult and almost impossible to refute the results using this ancillary substantiation method.The accurate determination of fan flows due to the impost of the carbon tax has taken on much more significance given the financial impacts in Australia at this time. The methodology detailed herein can be applied equally for both fan flow compliance testing and the verification of mine airflow data for greenhouse gas emission evaluations.The paper utilises the results of one 24-point pitot traverse to demonstrate the various findings. These include the very wide range of velocity pressures, which were logged at most of the measuring stations. It also illustrates how the method is utilised and compares the results derived from both this method and the more subjective traditional method along with the benefits of logging the velocity pressure results during the testing process.CITATION:Rowland, J A, 2013. Removing some subjectivity from traditional BS 848 and ISO 5802 in situ fan flow tests, in Proceedings The Australian Mine Ventilation Conference , pp 155-162 (The Australasian Institute of Mining and Metallurgy: Melbourne).

Jul 1, 2013

By John Stubbs

Sub-Surface Shaft excavation Mine development Headframes Surface Production facilities Product storage and loading Tailings area Infrastructure Discovery Lodge Utilities Operations complex Port Marine loading Rail unloading and storage

May 1, 2013

By Christine Hansen

?Kiss my Asteroid? Unofficial Title Human life is tied to minerals It?s worth noting that: The living human body consumes minerals. The minerals we take in multivitamins show the close linkage between human beings and mineral resources. Unlike tourism or specialized manufacturing, a human being could not live without mineral consumption. Minerals and their consumption is a tangible part of human life.

May 1, 2013

By Peter Cunningham

General Description of Projects The objective is to streamline data transfer within our Process Control and Business Systems for the purposes of tracking actual production, reducing manual record keeping, improving process control and improving vehicle maintenance. This presentation focuses on two implementations of mobile equipment data acquisition systems which make use of industry standard data models and data transport protocols. Pilots are part of the Mines Technology Roadmap to improve our mining operations ?Enabling technologies and pilot of key systems

May 1, 2013

By L. D. Smith

Net Present Value Impact of Discount Rate The Discounted Cash Flow (DCF) method of valuations is universally used and accepted. The main criticism of the method is that it does not recognize the value of projects long life projects. This can be seen in the preceding graph where the present value of cash flows in later years are small for discount rates over about 10%. This graph covers a project that has a 25 year operating life. It is clear from the low height of the NPV bars at 10% and 15% in the last years of the project that an additional 25 years would add almost no value to total project NPV. As an example of this effect, an colleague undertook the evaluation of a pulp and paper project. The plant could be justified, but it was not possible to justify planting the trees as they took too long to grow and so had not appreciable NPV. The plant had to purchase wood to feed the plant.

May 1, 2013

By Stephen Mullowney

Outline ? Setting the stage ? Deal activity ? Q1 2013 update ? Key deal sectors ? Deals by geography ? Outlook for 2013 Key Observations 2012 ? Major retreat in M&A activity ? Glencore-Xstrata deal dwarfs all other deals ? Gold & copper dominate deal activity

May 1, 2013

The Forestry Reclamation Approach (FRA) specifies that the upper 1.22 m of material on the reclaimed surface should be left as uncompacted as possible to facilitate tree root growth. One of the main concerns about applying the FRA to steep slopes is that the upper 1.22 m of material could cause the reclaimed slopes to be unstable. Successful application of FRA on flat and rolling surfaces precipitated this investigation. Details of a field investigation conducted at a steep-slope mine are available in an earlier publication (Kumar and Sweigard, 2011). A total of 70 survey monuments were driven into the slope in a regular pattern to monitor slope movement. Quarterly surveys of the monuments were done to quantify any type of mass movement either horizontally or vertically. The methodology proposed for slope movement was verified using numerical models. Analytical models based on limit equilibrium technique and numerical models based on the finite element method were developed for slope stability analysis. The limit equilibrium analysis was done using Geo-Slope software following the Simplified Bishop Method. The finite element (FEM) numerical model was developed using the Plaxis computer program following the strength reduction technique. Two kinds of slope stability analysis were performed: first with the top 1.22 m of loose material and second without top loose material. Finally, the field investigation results were compared with stability analysis results. Both of these approaches showed that application of the FRA on steep slopes is not causing any significant instability problems that would not exist otherwise for overly steepened slopes. Keywords: Forestry reclamation approach, steep slope, slope movement, factor of safety

Feb 27, 2013

By E. A. Schmidt

The Thompson Creek molybdenum deposit is located in the Bayhorse mining district about 20 air miles southwest from Challis, Idaho. Cyprus Mines Corporation began exploration on the property in 1968, and at present is in the pre-production stripping phase. Molybdenum mineralization is contained in a late Cretaceous (88 m.y.), composite, biotite granodiorite-quartz monzonite intrusive complex. The complex intruded carbonaceous argillites, causing local silicification and hornfelsing of the sedimentary rocks. The main portion of the orebody is unconformably overlain by up to 1000 ft of Challis volcanic rocks (49 m.y.). Surface mineralization and related rock alteration can be recognized over a 2500- x 8000-ft area extending northwesterly from the discovery outcrop. Molybdenite occurs in a network of subparallel quartz-biotite-muscovite-orthoclase veins and veinlets within the intrusive rocks. The zone of +0.020/0 Mo mineralization outlines a steeply dipping tabular configuration in the main orebody and gradually changes into a hood-shaped configuration along strike to the northwest. The overall grade [ ] of the deposit is controlled by the abundance of the quartz- molybdenite veins and veinlets in the intrusive rock. Very little disseminated mineralization is present, and no economic mineralization occurs in the argillaceous sedimentary rocks. Muscovite, biotite, and orthoclase/microcline define three alteration zones that conform with the overall zone of mineralization. The upper alteration zone contains dominantly muscovite and sericite associated with quartz veins. The central zone contains coarse biotite and locally orthoclase and microcline. Molybdenite is most abundant within this zone. The lower zone contains thin envelopes of orthoclase/microcline around quartz veins. Based on about 313,000 ft of drilling and 8592 ft of underground development work, computer-derived ore reserve calculations indicate 200 million tons averaging 0.1 1% Mo at a 0.050/0 Mo cutoff grade with a waste to ore stripping ratio of about 3:l.

Jan 1, 2013

By Robert Hopler

Your petitioner further alleges that at various times, to wit, from 1872 until June 30, 1895, during the existence of the combination and conspiracy in restraint of trade among the various States herein- before described, there were organized under the laws of various of the several States of the Union various corporations having for their object the manufacture and shipment and sale of a high explosive commonly known as dynamite, which said explosive is commonly used for the same purposes as those for which blasting powder is used;

Jan 1, 2013

By G. W. Sparkes

The use of CR-39 plastic polymer as a solid state nuclear track detector in the textural analysis of radioactive minerals in geological samples was first described by I.R Basham in 1981. CR-39 autoradiographs provide a detailed, high-resolution image of the in situ distribution of the radioactive minerals within geological samples on both the macroscopic and microscopic scales. This technique is an inexpensive and effective means of obtaining detailed textural information that provides insight into the style of mineralization, its relationship to primary and secondary structures in the host rock, and its association with particular geological features or mineral phases. Although this technique does not provide any information on the identity of the minerals responsible for the radioactivity, the resultant autoradiographs can be used to select regions for further detailed analysis such as petrography, microprobe analysis, or SEM imaging. This paper summarizes the procedure and outlines the appropriate time and materials required for both the exposure and etching of the CR-39 with respect to the intensity of the radioactivity emitted by the geological samples.

Jan 1, 2013

By Mitchell L. Spencer, Viswanathan Panchanathan

"Bonded magnets are important category in permanent magnets. They are made by one of the following processes: compression bonding, injection molding, extrusion, calendering. An overview of the various bonded magnet processes and properties of products made with different magnet materials along with their applications are discussed. The main emphasis will be on the use of bonded NdFeB and ferrite magnets.IntroductionBonded magnets are a major growth area in permanent magnets. Bonded magnets are made by any one of the following processes: Compression bonding; Injection Molding; Extrusion and Calendering [1,2]. Compression and injection molded magnets are rigid magnets. Materials used in calendering process produce flexible magnets. Only the extrusion process makes both rigid and flexible magnets. The binders used for the bonded magnets vary depending on the processes. Thermoset, thermo-plastic and elastomeric binders are respectively used in compression, injection and the calendering process. Extrusion molding uses elastomers or thermo-plastic materials. The most co=on magnetic materials, Ferrite, SmCo, Alnico and NdFeB can be used in any of the above processes either alone or in combination as hybrid magnets. Another material that has been developed for co=ercial application is SmFeN. Making the material has been challenging and it is being used in niche market applications in limited quantitiesIn the extrusion process, a highly loaded compound is used to produce strip or sheet and is continuously extruded through a die. In calendering the granulated compound is rolled to produce a continuous wide sheet. In the compression bonding process a uniaxial pressing force is used. These magnets have higher loading compared to injection molded magnets. In injection molding the material is forced into a mold cavity and has lower loading compared to compression molded magnets [2,3]. Most of the flexible magnets are made using extrusion and calendering processes and the most co=on magnet material is inexpensive ferrite. Flexible magnets have been made using rare earth materials, but on a very limited basis.The major advantages of magnets processed by extrusion and calendering are as follows: inexpensive tooling, automation; practically any 2D geometry; fast production rates; no chipping or breaking; a wide range of properties; on-line magnetization; easy to convert (e.g. cut, punch or shape).Compression bonded magnets are inexpensive to manufacture. They have higher magnetic properties compared to injection molded magnets; however lower than their sintered counterparts. The magnet shape is restricted to simple geometries and they require careful handling. Their isotropic nature allows complex magnetizing patterns."

Jan 1, 2013

ABSTRACT The SART (sulphidization, acidification, recycle, and thickening) process is an effective way to separate copper and cyanide in the waste stream of gold processing plants using cyanidation. Factorial experimentation has been conducted to create models of copper recovery, cyanide recovery, acid addition, and oxidation/reduction potential during SART. Economic analysis of the resultant models showed that SART is best operated with a sulphide-to-copper molar ratio of approximately 0.56, pH of 4, and a minimized cyanide-to-copper molar ratio. The experiments also showed th0at residence time can have drastic impacts on SART performance.

Jan 1, 2013