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By A. E. Halim, J. F. Brune

The 2006 Sago, Darby, and Aracoma mine disasters in the United States (US) forced the US government to implement the 2006 MINER Act and additional regulations that require all US underground coal mines to install and maintain refuge chambers to manage entrapment emergencies, in particular, fires and explosions. However, there is a debate on whether barricading in refuge chambers is a good strategy to survive such emergencies. Australian coal mines are not required to use refuge chambers and, instead, have adopted a strategy that focuses on instructing and training miners to self-escape to the surface. This paper analyzes merits and problems of using refuge chambers and self-escape to the surface to manage emergencies in fires or explosions in an underground coal mine. The authors found that the use of refuge chambers may not be the best strategy during extensive fires or when multiple explosions happen. In these situations, mine rescuers are unlikely able to extract miners who are sheltered in chambers and conversely, self-escape may save more lives than sheltering. Chances for successful self-escape are further improved by regular, externally assessed training such as Level 1 Emergency Exercises required in the Australian State of Queensland. These exercises put pressure on mine operators to ensure and maintain the effectiveness of their emergency management system.

By Irwan Halim, Stephane Polycarpe, Brian Hann

The Narragansett Bay Commission Phase III CSO Program includes construction of the 11,600-foot long, 30-foot ID, deep rock Pawtucket Tunnel in Rhode Island. This paper provides an overview of the Design Build Project features and highlight some of the important design considerations, features, and innovations, including geologic conditions and related TBM design, and deep shaft and tunnel segment designs. The paper provides the most recent updates on some of the project construction activities including TBM tunnel progress and retrieval schemes, tunnel pump station and deep vertical shaft liner installations, SEM construction, and microtunneling for the longest adit using Fiberglass Reinforced Polymer Mortar pipes.

Jun 23, 2024

By R. E. Lindstrom

The mineral bastnasite is utilized to describe alternate processes for the extraction and separation of the rare-earth elements by solvent extraction. The rare earths can be acid-leached directly or fused with NaOH before acid leaching. Cerium, the major constituent, can be recovered by fractional precipitation, fractional leaching, or solvent extraction with tri-nbutyl phosphate. The latter process is capable of producing 99.5-percent pure CeO2 at 98+ percent recovery. Lanthanum is subsequently recovered by fractional precipitation or solvent extraction with a nitrogen-based extractant. A 20-stage mixer-settler operation with a primary amine extractant results in a 95-percent pure La203 fraction at 96 percent recovery. Europium is amenable to extraction from most of the remaining rare earths with an organophosphate extractant. Selective stripping of the europium, followed by reductive precipitation, produces high-purity Eu203. Another possibility for europium purification involves the differential extraction of europium with an amine followed by a sub- sequent reducing strip. Separation of the remaining elements is more difficult but can be accomplished with amine or quaternary ammonium extracts. Typical separation factors achieved are 3. 8 for praseodymium-neodymium and 10. 5 for neodymium-samarium.

Jan 1, 1967

By M. C. Manderson

Phosphate rock is a naturally occurring mineral which, in upgraded form, is important to both agriculture and industry. Phosphate rock normally must be upgraded before it can be assimilated and used. Most of this upgrading is now carried out by chemical means, largely through the reaction of a strong inorganic acid (primarily sulfuric acid) with the phosphate rock to remove major impurities and to produce soluble phosphate. A less important but yet still commercially significant conversion method involves the thermal reduction of phosphate rock at high temperature in an electric furnace to produce elemental phosphorus. The elemental phosphorus is then converted to usable end products. This conversion route is a more costly method than the chemical route, but it has the advantage of being able to produce chemically pure phosphorus derivatives. On the other hand, the use of phosphate rock for agricultural application-primarily for use as a plant nutrient ingredient for fertilizer -does not require the same level of purity. As a consequence, the chemical method of phosphate rock upgrading is the predominant technique for producing phosphatic fertilizers.

Jan 1, 1977

By Kelvin K. Wu, George H. Gardner

On July 24, 2002, a nonfatal entrapment accident occurred at the Quecreek #1 Mine, Black Wolf Coal Company, when an active mining section inadvertently cut into a flooded abandoned mine. This incident, and the dramatic rescue which ensued, brought national attention to a common problem in the coal mining industry. Since 1995, there have been more than 100 inundations at coal mines in the United States. Unavailable, inaccurate, or incomplete mapping of older abandoned mines is typically responsible. Serious problems associated with accidental discharges of fluid mine waste material (slurry) and water from coal refuse disposal facilities have resulted from similar causes. Recent problems related to the inaccurate location of old abandoned mine works have increased the interest in the use of conventional and emerging drilling and geophysical techniques for detection of air-filled and water-filled cavities. The United States Congress has committed significant funding toward investigating the applicability of these technologies. MSHA actively promotes the use of the best available technology to minimize the significant adverse safety and environmental consequences associated with unplanned breakthroughs and inundations. This paper provides background information and a general summary of the MSHA-sponsored field demonstration projects which are currently in progress. Potential benefits and limitations are discussed. The need for field verification/ground-truthing is emphasized. Under appropriate conditions, geophysical methods can be effectively integrated into a comprehensive field exploration program.

Jan 1, 2005

By W. C. Hirt

Deposits of ferromanganese crust containing cobalt and nickel occur on the seafloor in the Pacific Ocean near the Hawaiian Islands and Johnston Atoll. This paper describes developmental flotation metallurgy to separate crust from its associated substrate gangue. Important variables in ferromanganese crust flotation include reagent type, aeration rate, conditioning time and agitation intensity, pH, temperature, water type, and feed size distribution. Flotation in seawater of minus 600 ~m (-28 mesh) material assaying 6.2% Mn, 0.2% Co, and 0.13% Ni with diesel fuel-crude tall oil-sulfonate collectors produces concentrates assaying 15% Mn, 0.6% Co, and 0.3% Ni with recoveries of 89-95% while removing 62% of the feed weight.

Jan 1, 1990

By E. Zahl, J. Whyatt, H. Lawson

The U.S. Mine Safety and Health Administration (MSHA) issued Program Information Bulletin P09-03 in April 2008, providing formal guidance on using programs that model the redistribution of stress during underground mining of coal. A key part of this guidance is visual observation and mapping of ground conditions. If a correlation between ground conditions and model output can be established, the model is considered to be verified, and can be used to guide mine design in similar ground. A simple scale is recommended for ranking observed roof, rib and floor conditions. This paper discusses optimization and implementation of a ground condition rating scheme in the gateroads of a deep underground longwall coal mine. Roughly 80% of each gateroad length deteriorated in a fairly uniform manner. However, this manner varied between gateroads, as did pillar size. The implementation of a ground condition mapping program, similar to that recommended in PIB P09-03, was successful in characterizing the ground response to mining in gateroads of a longwall coal mine.

Jan 1, 2013

By J. G. Pippenger

The Coteau Properties Company's Freedom Mine is a surface lignite mining operation utilizing large draglines, trucks and shovels, tractor-scrapers, and bulldozers to uncover a single coal seam. In 1989, a work order system was instituted to record data by equipment type, cost, productivity, and distance, and to provide historical information for planning the most efficient and economic use of each equipment type in the mining operation. This report explains how the work order system was initiated, what data is tracked, and how the data is utilized for equipment and project scheduling.

Jan 1, 1994

By Phil W. Welch

At first glance, the similarity between the fine grinding of cement clinker and coarse grinding done in other mineral processing industries may seem remote. However, it is interesting to note that the mill discharge fineness of cement clinker is only 70 to 90% passing 100 mesh and quite comparable to other mineral processing grinds. There is however, a greater dependence of the mill on the air separator in the finish grinding of cement clinker than in other mineral processing industries which explains why a technique to guage the balance between a mill and separator first began in the cement industry. (1) More recently an adaptation of this technique has shown its application to the processing of phosphate rock and is the central topic of this paper. First, an explanation of work done with fine grinding cement circuits seems appropriate together with a few general comments regarding cement. When unground or partially ground cement clinker enters a finish grinding mill, it is subjected to mechanical forces of impact and attrition which gradually reduce it to a range of sizes characteristic of finish cement. That is, a range of approximately 1 to 125 microns. The large proportion of superfine particles relative to the coarse and intermediate size particles is typical of portland cement particle size distribution. It accounts for the workability characteristics of plastic concrete and the early strength development of concrete which is so necessary to its successful use as a construction material. For this reason It is quite evident from quality control tests when a shortage of superfines exists.

Jan 1, 1975

By C. Strachan

This paper presents an evaluation of tailings dam incidents from the 1994 USCOLD Tailings Dam Committee report. Comparisons are also made with water storage dam incidents from USCOLD reports and recent tailings dam incidents. The evaluation results show that tailings dam incidents are due to a number of factors including overtopping, static and seismic instability, seepage and internal erosion, and foundation conditions, and that no particular type of tailings dam or operational condition is more susceptible to incidents. In addition, the results confirm that tailings dams should be located, designed, operated, and reclaimed with a thorough knowledge of site conditions, mill operation, site monitoring, and tailings characteristics.

Jan 1, 1999

By A. Vien

MOCCA is a Multivariable Optimal Constrained Control Algorithm developed specifically for non-square industrial control applications with practical difficulties such as interactions, time delays, constraints, modelling development, etc. MOCCA consists of an off-line simulation/translation module, for tuning the control parameters, and an on-line module that implements the designed control law. This paper describes an evaluation of MOCCA on the Hemlo grinding circuit which comprises one open circuit ball mill and two closed circuit ball mills in series. In this case a 4x4 unconstrained control problem was considered. The manipulated variables included the fresh ore feed rate and three pump box water additions. The controlled variables were the grinding circuit product particle size and three pump box levels. In this application soft constraints were implemented through control action and control error weighting. The feedforward capability of MOCCA was used to compensate for a measured water flow disturbance to one of the pump boxes. MOCCA performed very well during plant evaluations when compared to the original classical multi-loop control strategy and proved to be quite robust. Perhaps most importantly, the process engineers and plant operators have a high level of comfort both in understanding MOCCA's general operating principles, and with its demonstrated performance.

Jan 1, 1991

By B. G. Kelley

The MIDREX® Direct Reduction Process was developed during the 1960s by the Midland-Ross Corporation, which had pioneered shaft furnace technology and stoichiometric gas reforming for use in processing minerals. In 1969, the first MIDREX® Direct Reduction Plant was built in Portland, OR. Since then, 49 additional modules have been sold in 18 countries. For the last ten years, over 60 percent of the world's direct reduced iron has been produced in MIDREX Plants. During the quarter century since commercialization, many technical improvements have been made, including larger shaft furnaces, in-situ reforming, greater heat recovery, improved catalysts, and hot briquetting. Midrex continues to enhance the technology in the areas of economy-of-scale, energy efficiency, alternate fuels, and raw material flexibility.

Jan 1, 1998

By Jalal Vakili

In designing very large excavated slopes which are becoming increasingly common in both mining and civil engineering projects, the most important decision of the engineer is the selection of a slope angle. The purpose of the geotechnical study of the slope is to ensure reasonable stability of the slope in the most economical way. Because the rock mass composing each slope is unique, there are no standard solutions for slope stability analysis. A practical solution is formulated from the basic geologic data, engineering properties of the rock, geometry of the slope, and ground water observations. Stability analysis consists of analyzing the forces causing and resisting slope failure. There are several methods of slope stability analysis. The limit equilibrium method evaluates the overall stability of the sliding mass just on the verge of slip, using some or all of the three equations of static equilibrium of a plane problem. The stress-strain relationships of the rock mass are not considered. Method of analysis include the assumption of the shape of the slip surface. Peterson (10) introduced the Swedish method of analysis in 1916, which is based on cylindrical sliding surfaces. Fellenius (4) in 1926 extended this method and introduced the method of slices. This method was refined by Bishop (I) in 1955 and later used by Morgenstern and Price (8) in 1965. In many cases layers of extremely soft strata or strata weakened by neutral stress cause failure to take place by translation along plane of weakness instead of by rotation on a circular surface. In this paper, a slope with a horizontal layer of weak meterial is selected for analysis. This is a usual case for open pit lignite mines where lignite seam may be non-cohesive and 'weaker than the overburden rock or a soft clay layer underlies the seam. It is also a common case of rock fill dams supported on a foundation stratum of clay where the strength of the clay layer is less than that of the rock fill. It is shown that utilizing this method, the location of potential failure surface and the value of the minimum factor of safety can be calculated directly and the trial computations of factors of safety for a number of assumed failure surfaces are not necessary.

Jan 1, 1982

By G. P. Hand

The graphite industry as a whole has gone through many changes over the years. Most of the graphite used in major applications since the turn of the century were basic natural or electrode by-product synthetic materials, processed using simple crushing, screening, or grinding techniques. In the mid 1970's new thermal technology was developed which changed the face of the .graphite industry, and opened up a panacea of new products and capabilities. Materials produced through this new technology have helped revolutionize new products and processes in industries including automotive, batteries, fuel cells, electronics, iron, lubricants and steel. This paper outlines the continued improvements in those industries as well as the as well as the outlook for new technology in this rapidly changing area.

Jan 1, 1997

By H. B. Charmbury

The acid mine drainage problem in Pennsylvania is of continuing and growing interest to the coal mining industry, the state government and the citizenry at large. Approximately one-third of the total volume of mine drainage presently polluting the streams of the Commonwealth originates from active coal operations and two-thirds come from ?abandoned mine discharges.? For this reason the Pennsylvania Department of Mines and Mineral Industries has mounted a significant research and action program seeking solutions to this two-fold problem. The Coal Research Board of the Department has sponsored a wide variety of research projects in an effort to study the treatment of acidic and highly ferruginous mine waters. A review of the published literature on the treatment of mine waters indicated that many laboratory and theoretical studies had been undertaken on various aspects of the coal mine drainage problem, but little applied, developmental, or engineering study had been undertaken. In January of 1964 the Board commenced a rigorous program using state and industry funds in an effort to find a ?least cost? solution or solutions to this vexing problem.

Jan 1, 1967

By F. E. du Plessis, P. De Waal

Through the development of innovative in-line mineral quantification sensors, the possibility has arisen to apply modern control theory to implement automatic process control for electrostatic high tension (“HT”) roll separators. A pilot-scale set-up was constructed to enable continuous tests to be carried out. A typical dry mill feed was continuously pre-heated and separated with a modern lab scale HT roll machine. The mineralogy as well as mass-flow of the non-conductor stream was quantified in-line, and the combined streams were re-circulated in an endless loop by a combination of vibration feeders and a bucket elevator. A fractional factorial experiment was executed to determine the most significant control parameters of the HT roll separator. Then a multi-input, multi-output dynamic model of the HT electrostatic separator was extracted by the application of standard system identification techniques for automatic control. The most important control variable to ensure a stable product grade could be identified. This allowed a robust single-input, single-output controller to be implemented. The process variable and set-point was mineral grade and the control variable was electrode voltage. Roll speed was manually adjusted while the mineral grade was kept on set-point by the control system. The roll speed, where maximum mass flow and therefore maximum yield was produced on-grade, could therefore be rapidly determined. Atmosphere humidity and ore temperature served as disturbances. Some other adjustable parameters were kept constant during the experiments, namely feed mineralogy, splitter settings and feed rate. Delivery of maximum yield, with a controlled grade, can improve production while reducing the burden of complex manual tuning. Manual tuning previously involved coping with multiple parameters with uncertain cross coupling influences on the end result. Even the end result was typically only known after completion of mineral assays. Automatic grade stabilisation and yield optimisation for a HT roll separator bank requires in-line measurement of mineralogy and mass flow, as well as the implementation of a robust process control system.

Jan 1, 2005

By Thomas P. Meloy

The understanding, quantification and use of locked particles. Specifically discussed is the use of Textural Transforms (Meloy, 1991) for the implementation of the Interfacial Area Conservation hypothesis (Meloy, 1984); the quantification of the locked particles as a function of fragment to inclusion size ratio; and the selection of set points.

Jan 1, 1991

By P. O. Ripley

Into this tumultuous twentieth century, every second, two new babies are born. This is 5,412 per hour, and 130,000 per day. Relentlessly, consistently, alarmingly, they add to the more than three billion human beings who already inhabit the earth. Every tick of tier clock brings with it a problem child, the problem of another mouth to feed, another body to clothe, another human being for whom to provide. On the other hand, medical science has achieved a postponement of death, considerably past the period of a few years ago. Thus, life expectancy has been increased and world population has increased accordingly. Darwin (4) writing in 1962, suggests "It is curious how long the world is taking to perceive that we are living in what is a fantastically abnormal period of history, and one which must inevitably end soon, The first warning note of a possible population explosion was given by Malthus in 1799". He suggested that population increases geometrical while production increases only arithmetically and that soon we would not be able to feed the rapidly increasing population.

Jan 1, 1966

By J. Kretschmann

"By the end of the 1950s, the German hard coal mining industry produced 150 million tons of hard coal per year in 170 collieries with 600,000 employees. At that time, 70% of the primary energy demand of the Federal Republic of Germany was covered by domestic coal. However, due to coal mining becoming an increasingly globalized business and the oil and gas industry producing with lower costs, the German domestic hard coal industry stood constantly under restructur-ing pressure. The industry declined until the end of its life cycle. In 2007, a political understanding was arranged to phase out German hard coal mining in a socially acceptable manner by the end of 2018. This decision required a new strategy for the coal mining industry. Being strictly finalized, the German hard coal mining industry has to be prepared for the post-mining era. To create a sustainable development strategy, the long-term impacts of coal mining activities in Germany concerning the environmental, economic and social dimensions will be analyzed systematically and forward-looking. The regional and social responsibility during the closing process and for the post-mining era will be emphasized. High technical standards in environmental protec-tion and post-mining technologies, as well as long term experiences in the development of former mine sites to create new jobs are significant from an international point of view. The traditionally constructive social partnership between employers, union, and employees has enabled long-term stable adaption processes and avoided social friction. The sustainability strategy of the German hard coal mining industry can be regarded as a role model for other mining countries and regions facing similar transition challenges. INTRODUCTION Principally, mining is a finite business that reaches its end if the deposits are depleted or the raw materials can no longer be mined in an economically profitable way. However, the impact of mining is po-tentially an infinite one – at least if you measure it at a human time scale. Mining always means interfering with geological and ecological structures that cannot be reversed to their original condition. In general, the mining cycle (Figure 1) can be divided into three phases: 1. The exploration phase, in which the deposit is investigated to determine its technical and economic profitability. The period of these undertakings is relatively short and can lead to the launch of mining operations. 2. What follows is the actual mining phase which usually lasts for a long time and ends latest when all deposits are fully depleted. This lifespan may be shortened if the economic conditions (production cost or market price) deteriorate. Nevertheless, mining may be resumed if those conditions become favorable once more (examples are silver mining in Germany or rare earths mining in the USA). 3. The longest phase, however, is the post-mining phase as the human interference into geology and nature is usually inten-sive and irreversible. Mining can lead to consequences which have a permanently adverse impact on people and the environment; therefore, they have to be managed as best we can (1)."

Jan 1, 2017

By H. Walqui, S. K. Kawatra, C. H. N. Jeltema, T. C. Eisele

"The literature contains many cases where the shape of hydrocyclone efficiency curves vary from the ideal “S” shape. These often appear as changes in slope, or inflections. These inflections can be divided into two categories: “coarse” inflections, which are caused by differences in the density of the minerals being separated, and “fine” inflections, for which there are a number of competing hypotheses concerning their cause. The existing literature addresses either the fine inflection or the coarse inflection, but no studies have reported both types of inflection occurring at once in a single hydrocyclone test. This paper presents hydrocyclone results from both in-plant studies and laboratory experiments that show both coarse and fine inflections. The industrial significance of both types of inflections is discussed. Hydrocyclone efficiency curves show the probability of any given particle reporting to the hydrocyclone underflow as a function of its size. Selectivity functions, S(d), are used to represent the fraction of the feed material in size fraction “d” that reports to the hydrocyclone underflow. Plotting this selectivity function against particle size leads to the standard S-shaped efficiency curve shown in Fig. 1. In the “uncorrected” curve, the tail of the curve does not go through 0%, because a portion of the solids are bypassing classification. This happens as a result of their being carried along by the water, and is most important for the finest particles. The curve can be “corrected” based on the fraction of the feed water that reports to the underflow, represented by the bypass fraction, Rf. The corrected curve then normally passes through 0%, as shown in Fig. 1.The act of correcting the curve shifts the value of the d50 size, which is the size that has an equal probability of reporting to either the overflow or to the underflow. Correcting the curve to account for the bypass fraction makes it easier to compare cyclone performance under conditions that cause the quantity of water in the underflow to change, but that do not alter the actual corrected cut size (d50c).The corrected efficiency curve can be expressed closely by equations such as Plitt (1976):"

Jan 1, 2015