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By S. Shankar

Available literature on the effect of re-entrainment on overall airborne dust concentration in mine airways or the fundamental mechanisms of coal dust re-entrainment in mine atmosphere is scant. Therefore, as part of the Respirable Dust Center's ongoing research, a three part study was envisaged: study of the re-entrainment phenomena of anthracite and bituminous coal dust particles in a wind tunnel under the influence of varying air velocities; study of the same in the Lake Lynn Laboratory Mine of the USBM with both airflow and walking by personnel causing re-entrainment; and mathematical modeling and computer simulation of the re-entrainment phenomenon. In this paper, results from the re-entrainment studies in the wind tunnel and the Lake Lynn Laboratory Mine are presented. Further, the results from the wind tunnel studies are compared with the results from in-mine studies conducted at the Lake Lynn Laboratory Mine of the USBM. Comparing the results from the two studies it was observed that increasing air velocity increased the rate of re-entrainment, but increased time of exposure decreased the airborne dust concentration. Compared to same size particles, a mixture of sizes created more airborne dust concentration when re-entrained. It was also observed that contribution of airborne dust concentration due to airflow was negligible compared to the contribution due to walking.

Jan 1, 1995

By J. F. Mack, P. R. Michael, J. M. Shapaka, S. J. Self, M. W. Richmond

"On October 11, 2000, an estimated 306 million gallons of water and coal waste slurry drained from an impoundment in Martin County, eastern Kentucky into an adjacent underground mine. Approximately 230 million gallons of the water and slurry discharged from two underground mine portals and affected over 75 miles of streams in Kentucky and West Virginia. In response to this and several other similar events, the U.S. Office of Surface Mining Reclamation and Enforcement (OSMRE) commissioned an oversight study that evaluates how well state and federal regulatory programs established under the Surface Mining Control and Enforcement Act are ensuring that impoundment operators are minimizing the potential for impoundment-basin breakthroughs. The study focuses on slurry impoundments constructed in the hollows of Appalachia where numerous coal seams and steep topography combine to result in a large number of mined seams intersecting and underlying impounding facilities. Factors under consideration include: (1) full accounting of all mineable coal seams intersecting and underlying the impoundment; (2) identification and accurate location of underground mines close enough to the impoundment to potentially affect its stability; (3) assessment of the stability of coal barriers between the impoundment basin and adjacent mines, and stability of roof rock and pillars in mines subjacent to the structure; (4) determination of the flowability of the impounded slurry when expanding or undermining the facility are being considered; and (5) measures undertaken to reduce breakthrough potential when necessary. The oversight study began in 2012 after program-evaluation criteria were defined in an OSMRE technical position paper. The study is scheduled to be completed in 2017. BACKGROUND The Surface Mining Control and Reclamation Act (SMCRA) authorizes the disposal of coal mine waste by constructing a coarse coal mine waste embankment across a valley and pumping the fine coal mine waste (slurry) into the resulting basin (Figure 1). A concern shared by many engineers, geologists, and mine inspectors familiar with coal mine waste slurry impoundments is related to the common occurrence of underground mine workings adjacent to or beneath the impoundment: the potential for slurry “breakthroughs” into mine works and subsequent breakouts into the surface waterways (Figure 2). On October 11, 2000 a combination of coal refuse slurry and water from the Big Branch impoundment in Martin County, Kentucky broke through into an underground mine and subsequently discharged into the receiving streams. The location of the point of breakthrough, pathways of slurry/water flow within the mine workings, and two points where the liquid exited the mine are shown in Figure 3. An estimated 306 million gallons of water and coal refuse slurry drained from the impoundment into the adjacent underground mine. Approximately 230 million gallons subsequently discharged from the underground mine at two portals."

Jan 1, 2015

By W. Burger

In underground mines worldwide, a large number of short and small diameter slot holes need to be excavated. Herrenknecht has developed and built a new boxholeboring machine based on the well-proven Microtunnellingpipe jacking technology. The innovative Boxhole Boring Machine significantly increases work safety and requires only minimal drift dimensions. The high and consistent production rates that can be achieved result in enormous time savings compared to conventional drill and blast excavations. GENERAL ASPECTS In gold, copper and ore mines ventilation shafts are required to prepare block caving operations, to discharge ore onto the transportation level and to provide evacuation shafts. A high level of occupational safety and efficiency is the main objective when drilling vertical or inclined shafts. The faster and more safely shafts can be constructed, the earlier the actual production in the mine can start or be continued. Mechanized or conventional methods (drill&blast) that have been used to date only partially meet the required safety standards and fail to provide the requested production rates.

Jan 1, 2012

By M. A. Cristovici

The possibility of using surfactants as wetting agents for the suppression of sulphide ore dust has been investigated. Numerous surfactants were examined to determine their characteristics and to investigate their ability to improve the wetting of the sulphide ore dust. However, the surfactants selected as suitable dust suppressors proved to have a negative effect on the flotation of the ore contaminated with such reagents. A method was developed to eliminate the detrimental influence of dust-suppressing surfactants. It consisted of surfactants adsorption on activated carbon and separation of loaded carbon prior to flotation. The technique is simple and requires minimal changes in the plant flowsheet.

Jan 1, 1990

By B. Berhe, R. D. Lawrence, J. Hinzer

"The fortunes of mining companies and their implied value are tied to cycles - both economic and commodity – within which they operate. Hence the determination of appropriate future metal prices is one of the most critical factors faced by mineral valuators especially for advanced projects. Price, and hence revenue, is usually the most sensitive input to the valuation model. Empirical studies of past forecasts show that the success rate for commodity price forecasting is very poor. This paper explores various approaches and comments on their strengths and weaknesses. We conclude that careful evaluation of long-term metal prices is a key element and is hardly a luxury that can be left to simple averages or rules of thumb. INTRODUCTION Discounted Cash Flow (""DCF"") analysis, is well suited for the valuation of advanced mineral development assets, for which there are identified mineral resources and some form of economic assessment (Pre-Feasibility or Feasibility Study). The DCF method is also the most commonly used method for determining value for such assets. It provides a means of relating the magnitude of expected future cash flows from profits (or losses) to the magnitude of the initial cash flow (investment) needed for capital expenditures to purchase or to develop an asset for commercial production. The method proves useful in making investment decisions as it allows for the quantification of the Net Present Value (“NPV”), as well as the Internal Rate of Return (IRR) and Payback Period on initial investment capital. Valuation by its very nature is a forward-looking exercise. The DCF method attempts to estimate the NPV of expected future cash flows, by selecting factors that will likely affect future cash flow based on informed analysis. One of the most critical and sensitive factors is the determination of appropriate future commodity prices. “The variables that have the greatest impact on a DCF evaluation are the reserves, the metal prices, and the discount rate.”1 The determination of future commodity prices for valuation purpose or during M&A negotiations is a hotly contested issue. There are a number of analysts, institutions and specialized commercial data suppliers that provide both short and long-term commodities price forecasts. Also, the use of an aggregated mean for all available forecasts, or consensus forecasted prices for valuation purposes is not uncommon. The methods used in making forecasts for each forecaster may vary and in many cases may not be publically disclosed. Nonetheless, the aggregated mean of all forecasted commodity prices of reputed institutions is usually taken to “represent the market’s view of likely future commodity prices.”"

Jan 1, 2016

"The National Mining Hall of Fame and Museum (NMHFM) announced the class of 2019 National Mining Hall of Fame inductees. This year’s inductees, selected by the National Mining Hall of Fame’s Board of Governors, represent exceptional financial acumen in assembling several operations that formed the basis of a successful American mining company; conception and development of equipment which contributed to improved efficiency and mine safety; and unrelenting advocacy for the U.S. mining industry and its workers. These individuals, selected for being determined, forward-thinking innovators, doers and leaders have propelled the industry toward vastly improved safety and social responsibility.The Prazen Living Legend of Mining Award, named for renowned mining artist Gary Prazen, will also be presented at the ceremony. This award recognizes an individual or organization for significant and sustained commitment to educating the public about the relationship of mining to our everyday lives through educational materials, programming, and outreach.2019 National Mining Hall of Fame inducteesFrank Calandra, Jr. has devoted more than 50 years to the mining industry and he is an icon in ground control technology for the mining, tunneling and civil construction industries.From the ground up, his passion, sweat equity and shrewd business acumen have grown Frank Calandra, Inc. (FCI) and Jennmar from a single plant in Pennsylvania to a world-class enterprise with 25 plants employing thousands globally. As evidenced by Calandra’s more than 20 patents on ground control devices (not to mention the additional 80 patents his companies hold), his innovation and commitment to safety have made underground mining safer and more efficient. In the late 1970s and early 1980s, Calandra was instrumental in upgrading American Society for Testing and Materials (ASTM) standards in roof control for both state and federal regulations. Through his work with industry associations such as the National Mining Association, National Coal Council and Center for Energy and Economic Development, among others, Calandra has contributed his time, expertise and financial support to ensure a balanced political and regulatory climate for mining. Calandra is an inductee of the West Virginia Coal Hall of Fame."

Aug 1, 2019

By A. Eftimie, M. Stanley

The World Bank Group (WBG) believes that extractive industries can make significant contribution to sustainable development and poverty reduction, providing that environmental, social, and corporate governance issues are properly managed. The WBG recognizes that stakeholders have legitimate concerns about the impact of extractive industries, and management proposals are built around the central theme that investments and policy advice in the extractive industries should lead to poverty reduction. To help governments create appropriate policy and regulatory frameworks, this paper focuses on the linkages between overarching policies and laws and the management / governance of extractive industries at the local communities. It encourages the use of new instruments designed to help ensure that local communities benefit from extractive industries.

Jan 1, 2005

By R. Sellaro, E. Sarver

It has long been understood that extended occupational exposures to respirable mine dusts can lead to chronic lung disease. In underground coal mines, coal workers pneumoconiosis (CWP) and silicosis are major concerns. While many efforts have been made with the aim of understanding the mass-based concentrations and silica contents of respirable dusts under a variety of mining conditions, little research has been completed in characterizing dust at the individual particle level (by composition, size and shape). This study employed scanning electron microscopy with energy dispersive x-ray (SEM-EDX) to analyze dust samples collected from an underground coal mine in Central Appalachia. The results indicated that particle characteristics can vary widely between locations, though many trends might be explained based on knowledge of mining conditions. A continuous personal dust monitor (CPDM) was also used during the collection of some samples to determine respirable dust concentrations, which were compared against estimated concentrations based on the particle-level analysis.

Jan 1, 2014

By J. L. Thompson

The combustion of pulverized coal is a century-old practice. Many people have investigated coal dust and the residual fly ash particles that re-main after combustion. But the combustion process and fly ash formation mechanism are not under-stood. Working at our Maysville, Kentucky lime plant, the Dravo Lime Company Research team has collected samples of partially burned coal dust from the flame of a pulverized coal burner. Specimens were placed in a scanning electron microscope (SEM) equipped with an energy dispersive spectrometer (EDS). Microscopic examination of the particles, together with a large collection of micrographs of lime dust fused to fly ash particles, now make it possible to theorize as to how combustion advances through a piece of coal dust. Coal is a physical mixture of carbon-based compounds interspersed with bits of ash-forming materials, primarily alumina-silicate compounds. The alumina-silicate materials are commonly in angular nodules measuring 100 A to 700 A across their major dimension. It would appear that if the coal particle is in a well mixed gas stream, combustion starts at the surface and advances radially toward the particle center. With poor gas mixing, it is common that combustion moves from one end of a particle and advances on a broad front almost normal to some axis. In either case the combustion process and ash-forming mechanism are the same. As combustion occurs the carbon-based compounds oxidize in a highly exothermic reaction. Heat from the re-action melts the alumina-silicate nodules causing them to flow together and coalesce into an open sponge-like structure. As melting continues surface tension of the liquid and free surface energy causes the sponge-like structure to simplify into fewer, larger pores. Most likely the lighter molecular weight hydro-carbons burn before the heavier species. This means that as the melting ash structure is metamorphosing to a single large pore, there continues to be out-gasing throughout the structure due to combustion. Surface tension will form a spherical piece of fly ash if the ash material is liquid for a sufficient period of time. Out-gasing from combustion of the heavier hydro-carbons will provide internal gas pressure to keep the particle spherical until it freezes.

Jan 1, 1978

By W. L. Freyberger

In many papers concerned with fundamentals of the froth flotation process, authors have considered the contents of a flotation cell to be comprised of two immiscible phases, the froth and the pulp. I (Of course, each of these phases is in turn made up of several solid phases plus air and water.) This generalized concept of the flotation system can be extended by considering the cell contents to include two phases: an extracting phase, the air bubbles plus the collector, which removes a selected mineral component from the second phase, the ore pulp. Thus, there is an analogy between a flotation system on the one hand, and chemical extracting systems, such a solvent extraction system or a leaching system, on the other hand. Such extracting systems may be operated in cocurrent or countercurrent fashion. This paper includes first a brief discussion on the general nature of cocurrent and countercurrent operation as applied to froth flotation, and then presents the experimental results of flotation of a specular hematite ore by each method, using a tall oil fatty acid as collector. Cocurrent Flotation A conventional flotation circuit involving roughing, scavenging, and cleaning flotation is illustrated schematically in Figure 1. In such a circuit the col¬lector, or extractant, and new feed ore enter together at the head of the rougher circuit, and flow cocurrently to the scavenger circuit where more collector is added. According to this practice, sufficient collector is added to the head of the rougher (and scavenger) so that the final tailings are of low enough grade to be discarded. Since the flow of collector and ore is cocurrent, the process consists of single stage contact between the extracting phase and the ore pulp. If the scavenger concentrate is recycled to the head of rougher, the overall circuit has some of the characteristics of countercurrent flow. In such a case part of the extractant (collector) is added at the discharge end of the circuit, and may

Jan 1, 1971

The Pogo Mine, near Delta Junction, Alaska is a new 2500 STPD gold operation. The control system of the mine and milling operations are a hybrid of DCS (Distributed Control System) control and PLC (Programming Logic Controller) control. A DeltaV DCS system serves as the main control and operation platform while the PLCs operate a multitude of vendor specific packages. The communication backbone of the DCS system is a hybrid of star and ring fiber optic topology, which provides reliability and flexibility. The communication between the DCS and PLCs is typically facilitated by serial communication. This communication insures the integrity of the whole control system.

Jan 1, 2008

By Jacek B. Stypulkowski

This paper discusses the challenges faced by the design team of the under-river crossings of electric transmission feeders in New York City, a densely populated urban area. The under-river crossing of a 345 kV feeder was initially designed as Horizontal Directional Drilling (HDD), but was redesigned as a utility tunnel because of site con¬straints on both sides of the river. Multiple studies addressed location, available tech-nologies and costs. Multiple soil investigation phases addressed design aspects of HDD, as well as tunneling. Contractual issues varied from a design build alternative with Geotechnical Data Report (GDR) to design tender approach with GDR & Geotechnical Baseline Report (GBR).

By R. J. Baumgartner

Sustainability issues are from rising interest and importance for the mineral industry worldwide. In order to bring them into management processes and to improve decision processes, economic, ecological and social aspects of products, services or technologies have to be assessed. In this paper, the concept of integrated sustainability assessment is presented. Each aspect is assessed with quantitative or qualitative methods. The results of these ecological, social and economic sub-assessments are integrated by the means of Fuzzy Logic in order to regard preferences of decision maker and circumstances of decision situation. An example demonstrates the application of this new instrument.

Jan 1, 2005

By Veerendra Singh, NILAMADHABA SAHU, ARIJIT BISWAS

Manganese alloys are important raw materials for steelmaking. However, selective mining of high-grade manganese ore resources has resulted in a scarcity of these high-grade Mn ores (Mn: >42; Mn/Fe: >5). The present research work is carried out to explore a new smelting reduction process to produce high-Mn/Fe syntheticMn ore from low-grade ferruginous manganese ores. Representative samples of low-grade ores (Mn: 25–30%; Mn/Fe: ~1) were collected and smelting reduction studies were carried out using variable smelting power (20–30 kWh), carbon rate (10–20% of ore) and slag basicity (0.1–0.3) to produce high-MnO slag and manganese pig iron. Studies have shown that different-grade high-MnO slags (MnO: 38.57–58.24%; Mn/Fe: >15) and manganese pigs (Mn: 5.16–24%) can be produced at optimum process conditions. The high-MnO slag can be used as synthetic ore for the ferroalloy production process. The developed process is capable to effectively segregate the iron and manganese in the metal and slag, respectively. The optimum Mn and Fe separation (>95%) was achieved by smelting of 10 kg Mn ore batch in a 50-kVA electric arc furnace using 30 kWh smelting power and 0.16 kg of coke. The slag basicity was maintained at 0.3 and the optimum slag SiO2 was ~30%. The studies indicated that the upgrading of low-grade ferruginous manganese ores is a promising solution for achieving high-Mn/Fe-ratio synthetic ores for ferroalloy production. It can help the manganese alloy industry to overcome challenges associated with the scarcity of high-Mn/Fe-ratio Mn ores and efficient utilization of low-grade resources.

Aug 3, 2020

One of the most important parameters in mine ventilation planning is the friction factor (K). Accurate values of friction factors are critical especially when carrying out mine ventilation simulations. No computer simulation of a mine ventilation network is meaningful if the airway resistances are not accurately estimated (when planning a new mine) or measured (for an existing mine). However, in the first case not many reliable values of friction factors exist in the international literature. This paper presents the results of a research project carried out in the province of Quebec where ventilation friction factors were measured in all underground metal mines. These friction factors are statistically analyzed and tabulated. A friction factor database was created that also includes the friction factors measured in the past by other people. This database can help the mine engineer to accurately estimate ventilation friction factors according to the specific conditions. This database offers several values of friction factors typical for hard rock mine conditions typical of modern underground metal mines.

Jan 1, 2009

By I. K. Gilmore

Texasgulf Inc. currently operates an open pit phosphate mine in the central coastal plain of North Carolina. The area of phosphate deposition lies within the Aurora Phosphate district which consists of an embayment which is in the center of the Neogene phosphate deposition. A variety of solid and liquid fertilizer products are produced at the Texasgulf complex. One of these products is known as North Carolina Natural Phosphate (NCNP). New potential for use of unacidulated natural phosphate, now exists in regions with acid soils due to the discovery of the findings from recent research, cost advantages, and moves to reduce chemical inputs.

Jan 1, 1995

By B. Schimm

Mining of material without blasting and / or selectively becomes more and more important for high quality ROM-products. Surface Miners have been developed especially for this purpose. The cutting technology of these machines has been improved, so that harder material as well as wet and sticky materials can be cut with better results now. Especially the cutting drum design and more precise drum manufacturing process now allow production and equal tool wear over a long period. The better knowledge of rock parameters influencing the cuttability and cutting results allow higher production, less cutting tool wear and therefore reduced production costs.

Jan 1, 1999

By T. Peter Philip, Erich U. Petersen, William J. Tafuri, Donald M. Hausen, Douglas N. Halbe

Scarcely a month goes by that I or someone else at Newmont Mining or Newmont Gold isn't asked to give a talk on the topic I was asked to discuss today. Investors, financial analysts, geologists, metallurgists, even our government--everybody wants to know what the future holds for gold mining. Well, you're not going to get exactly what you asked for. Today, I'm prepared to focus primarily not on what the future will bring to us, but rather on what the future will demand from us. More than that, I cannot undertake because it isn't within my scope to predict how wise and resourceful everyone in our industry will be in the future. What our future will hold, as I see it, will depend on our--and our colleagues'-- responses to these very real demands. Three critical issues stand out in my mind as to what the future will demand of us in the gold mining industry. And these demands will be for: 1. The very greatest of technical expertise and innovation. 2. The highest order of environmental sensitivity and timely accommodation. 3. Planning, planning and more planning. All of these flow inexorably today from the traditional objective of any mining company--or any company in any business, and that is, to make money. Nothing as I see it, should be undertaken by a geologist, metallurgist or even an environmental department, unless the exercises will enhance profits; and nothing may be ignored which can have consequent damage to the bottom line. Thus, the three issues I've listed for you subordinate themselves to the objective of making money, although at least in the environmental area, it might seem to some that we can only incur additional costs without even a dollar-for-dollar return. I hope to disabuse you today of any such out-of-date notion. Let's tackle the first issue-- Technical Expertise and Innovation. Newmont Gold Company this year is celebrating its 25th anniversary of successful and profitable operations on the Carlin Trend. Carlin in 1961, which is when exploration began on the "Trend" by Newmont, actually may share a lot of similarities with Carlin today. They didn't then know where the gold was and, if they found it, they had one hell of a challenge mining and processing ore at a profit because gold was selling at only $35 an ounce. Today, we know where the current reserves are. But we don't know where our future reserves lie. Furthermore, we don't know exactly how we're going to mine them, and, as everyone here knows too well, we don't know what the optimum metallurgical treatment is, even if we can find and mine them. And all that despite the abundant level of modern experience and skills within the current generation of mining companies, and the fact that, even taking inflation into account, gold sells at a higher price today than in 1965 when Carlin began operations. But, of course, I'm telling you what you already know.

Jan 1, 1990

By Jaroslav Briancin, Katarína Gáborová, María Florencia Márquez-Zavalía, Marcela Achimovičová, Ol’ga Šestinová, Pavel Škácha

Naumannite (Ag,Se), a silver selenide mineral, was first discovered in 1828. This study investigates the structure, morphology, chemical composition, and leaching kinetics of naumannite. Mechanical activation in a planetary ball mill increased its specific surface area, enhancing the leaching rate of silver in nitric acid (HNO3). The study found that mechanical activation significantly improves silver recovery.

Jul 1, 2023

By M. Kehnemuyi

The U.S. Department of Energy is charged, by federal law, with the responsibility for developing and implementing programs for long- term storage and terminal disposal of high- level radioactive wastes from both commercial and defense nuclear operations. Approximately 288,000 cubic meters of defense high-level wastes are currently in storage at the government's Hanford Reservation in the State of Washington, the Savannah River Plant in South Carolina, and the Idaho Chemical Processing Plant in Idaho (U.S. Department of Energy, 1980a). High-level wastes from commercial nuclear power production are stored in water pools or basins at various power plant sites. At the end of 1980, approximately 7.460 metric tons of uranium, contained within 28,300 fuel assemblies was in storage at various reactor basins. Although the present inventory of defense wastes are many times larger in volume and in total level of radioactivity than the commercial wastes, in the future, the latter will constitute a substantial quantity of wastes that will have to be disposed of. The present electric generating capactiy of nuclear power plants in the United States is 56.5 Gigawatts-electric (GWe). The amount of spent fuel that would be discharged and accumulated by the year 2000 from these operating reactors would be 38,000 metric tons. With a projected growth of the nuclear industry to 180 GWe in the year 2000, the amount of spent fuel accumulated at the turn of the century could reach 89,000 metric tons of uranium or approximately 318,000 assemblies. In any case, whether one postulates a no growth pattern or one where nuclear power provides its share in the country's electric generating capacity in the next two decades, a means for safe and environmentally accept- able disposal of high-level nuclear wastes must be found. Storage of commercial wastes in water basins, either at reactor (AR) sites or at away from reactor (AFR) sites, and storage of reprocessed defense wastes in surface or near surface tanks is a temporary solution and is not an alternative for permanent disposal.

Jan 1, 1981