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By R. Wisniewski, S. Schafrik

Every underground coal mine in the United States must deploy and operate a wireless communication and electronic tracking system. This paper addresses the reliability and availability of an installed tracking system and the communications infrastructure that supports it. This paper assumes that the tracking system uses the communication system to perform its operation. A particular interest is the requirements for the systems to operate continuously without failure after a mine disaster for 24 hours, and the requirements in the MINER Act for the tracking systems to be “functional, reliable and calculated to be serviceable” and the communications systems “redundancy.” These requirements imply a certain reliability and availability. This paper describes a quantitative way to assess these systems requirements, using tools that are available to and commonly used by the reliability, maintainability and availability community.

Jan 1, 2014

By T. N. Andersen

The history of gold and silver analyses shows an interesting duality. On one hand, classical chemical and instrumental methods have evolved to meet changing needs, but on the other hand, the age-old and somewhat empirical fire assay has remained a popular tool. Inasmuch as gold and silver generally have been present in ores at low concentra¬tions, methods have been challenged by a need for sensitivity and selectivity coupled with reasonable assay time. A progressive increase in the importance of low grade materials as ore sources has led to the need for improved methods. Assays of these materials are required for process control and accounting in operating plants as well as for guiding research and development activities. The analytical response to these needs is evidenced by numerous reviews published through 1977-¬e.g., cf Kolthoff and Elving (1966), Beamish and Van Loon (1966, 1972, and 1977), Young (1971) , Mallett (1970), and Sen Gupta (1973). In this paper we present a brief sketch of the history and status of various gold and silver methods. A more detailed summary of atomic absorption spectroscopy (AAS) is Given, as this method has gained in popularity more than other assay methods. AAS methods currently in use are summarized and discussed briefly. This paper is not meant to be a detailed review, as are the above mentioned publications. Rather, we borrow from those works and more recent papers to report trends in gold and silver analyses (particularly in AAS). Also, we discuss some selected poten¬tial problems, and problems that have been experienced by this laboratory.

Jan 1, 1981

By R. N. Chakravorty

Spontaneous combustion presents a very serious hazard to both safety and economics of mining operations. Notwithstanding considerable research that has been done over the years to present and control spontaneous combustion the risk still exists. Consequently, this problem poses a major challenge to mine safety researchers; new and improved techniques are constantly being developed to deal with this major hazard. This paper reviews the current practices to prevent and control spontaneous combustion in coal mine operations highlighting new developments in this area. Research and development work presently being carried out in Canada to' deal with this problem is also discussed which includes monitoring, inertization and application of biotechnology.

Jan 1, 1988

When I reached Warren after the "de luxe" South American expedition I had little idea what was in store for me. From the large check Thayer had handed me just before I left New York I was pretty sure the future would be good, and that before long it would involve Anaconda. Evidently, Mr. Thayer had left it to Dr. Ricketts and John Greenway to work out the details The next morning Greenway asked me to come to his office and told me that he and Dr. Ricketts had discussed the question and that Anaconda would make me an offer I could not refuse. They proposed to pay me almost $1000 a month, more than twice my current salary. They had agreed that I should stay with Calumet and Arizona for the rest of the year to help with Bisbee development and anything I could to assist with the New Cornelia plans and construction Of course I could not turn down such a flattering offer, as I had about reached the limit of advancement with a much smaller company in anything save a high executive job, and it would be a long time before I could be ready to change from exploration and geology to operating. Greenway and I agreed that I would stay with him for the remaining eight months of 1916 without any particular title but helping in any way I thought would be most useful. Bisbee and Ajo Study It turned out to be a busy half year, in addition to many good times with my Bisbee friends. The Uplift Club did not meet as regularly as in earlier years, but Mason Ross, Jim Lewis, Bill Gohring, Roy Mitchell, Hubert d'Autremont, Arthur Notman, and I did have many "bull sessions" and poker games. I saw much more of Greenway than before and made many trips with him to Ajo and later to the new

Jan 1, 1976

By C. D. Anderson

"IntroductionTungsten carbide is a valuable material used in a variety of different applications, including the manufacturing of cutting tools, bearings and as a cost-efficient alternative to industrial diamonds. Both the high hardness value (Mohs 9) and scratch resistance of this material make it a valuable commodity for use in the mining industry.Usually, the production of tungsten carbide is a multistep process involving one or more of the following unit operations: hydrometallurgical digestion, solution purification, crystallization (as ammonium paratungstate), calcination, hydrogen reduction and carbon synthesis. The proposed three-step process eliminates three of these steps (crystallization, calcination and hydrogen reduction) by implementing a combination of hydro/pyrometallurgical techniques. These include alkaline pressure leaching, carbon adsorption and carburization roasting. By eliminating some of the intermediate processing steps, there is potential to reduce energy consumption and decrease overall operating costs.Methods and resultsInitially, alkaline pressure leaching with sodium carbonate (Na2CO3) was employed to selectively leach tungsten, as tungstate (WO4 2-), from an industrial Scheelite (CaWO4) flotation concentrate. Experimental variables included lixiviant (Na2CO3) concentration, temperature and residence time. Experimental constants, based on previous work, were percent solids at 13 wt% and agitation at 400 rpm (Queneau and Strathmore, 1969). Leaching results showed it was possible to extract 97% of the tungsten present. The most favorable conditions for leaching were determined: 2M Na2CO3, temperature of 180° C and a residence time of 30 minutes."

Jan 1, 2015

By D. W. Fuerstenau, P. C. Kapur

A new method is proposed for measuring the grindability of solids and the energy efficiency of grinding mills. The method is based on a similarity law of fracture mechanics for elastic materials in conjunction with the self- preserving character of the size distributions formed when feed particles are comminuted individually in compression. The single-particle grindability index reflects more closely the inherent resistance of a solid to size reduction than the grindability indices currently in vogue. The performance of grinding mills is evaluated in comparison with the single-particle breakage mode, which has the highest energy utilization or efficiency of all mechanical grinding routes. For a given set of stipulations, the performance index of the commonly used ball mill when grinding dolomite is found m he only 21%. compared to 44% for the high-pressure roll mill, a newly-invented energy-efficient mill. The difference is also reflected in the energy consumed per unit mass offines produced when closed-loop grinding circuits are simulated, which shows that the high-pressure roll mill circuit is invariably more energy-efficient than the ball mill circuit, provided the energy input per pass through the mill does not exceed a prescribed limit. Theoretical upper bounds on the yield of the ground product in a desired size range and lower bounds on the energy investment are calculated from the single-particle breakage mode which has, apart from the highest energy utilization efficiency, a minimum dispersion in size of the comminuted particles. Data on theoretical hounds for seven minerals/ores are presented. It is argued that it is unlikely that a grinding mill can be designed and a comminution circuit constructed whose performance exceeds these bench-mark values.

Jan 1, 1995

In this study, numerical simulations of yield pillars employing the finite element method with time-dependent Drucker-Prager material model are conducted. The stress control mechanism of yield pillars on weak floor strata is studied. The development of pillar yield zone, the distribution of pillar stress and the development of failure zone in the weak floor strata are investigated. The study indicates that a properly selected yield pillar size may significantly reduce the peak stress induced in the weak floor strata and effectively control the development of failure zone in the floor.

Jan 1, 1999

By R. H. Grau

The National Institute for Occupational Safety and Health (NIOSH) has conducted research to improve the ventilation of large-opening mines. The research has demonstrated that the ventilation of large-opening mines improves significantly by including ventilation requirements in the mine planning process and implementing some practical techniques during mining. Planning the location of long pillars to reduce the number of crosscuts between intake airways and return airways, positioning auxiliary fans in their proper locations, and establishing ventilation stoppings with minimal leakage all significantly improve the ventilation of large-opening mines. Mine operators that adopt these techniques in the mine ventilation plan will reduce mineworkers? exposure to airborne contaminants.

Jan 1, 2008

By J. A. Ehler

Speed and torque control of standard A.C. induction motors can be accomplished using a variety of devices ranging from mechanical, hydraulic, and electrical. Also, the motor can be specified as an A.C. wound rotor or D.C. motor using the associated controls. Normally, any one of these drive types can be adequately used to provide the torque control necessary to accelerate a conveyor belt system. The selection will depend on the economics, experience, and preference of the designer or end user. These drive types will be presented from a functional and performance viewpoint to assist in the understanding of the available technology.

Jan 1, 1998

By J. B. Hiskey

INTRODUCTION The extraction of gold and silver from ores, concentrates, and various metallurgical products can be achieved by a number of hydrometallurgical techniques. The solvation properties of alkali cyanide solutions on gold and silver were recognized 200 years ago. A cyanidation process for leaching gold from its ore was patented in 1887 and 1889 by MacArthur and Forrest. The solvent action of thiosulfate on gold and silver was observed over 100 years ago. Recently, several patents have been issued for processes using ammonium thiosulfate as lixiviant for precious metals, Berezowsky, et. al (1978) and Kerley (1981). Tozawa and and coworkers also examined the dissolution of gold in ammoniacal thiosulfate solution. Thiourea leaching of gold and silver initially discussed by Plaksin and Kozhukhova in 1941 but has received only limited attention since that early work. Use of thiourea as an alternative to cyanide was the topic of several papers presented at the 1981 AIME annual meeting In Chicago, Illinois. Hiskey provided a review of the fundamental chemistry of the dissolution of gold and silver in acidic thiourea solutions. Pyper and Hendrix reported on the leaching of a finely disseminated gold ore using thiourea as a lixiviant. The review article(6) previously presented was fairly comprehensive covering Important contributions to the chemistry of thiourea and the processing of gold and silver with acidic thiourea solutions. A search of the technical literature was made to determine recent (since 1981) progress and developments in applying thiourea to the processing of gold and silver. This review reveals that Soviet and Eastern European scientists are continuing to make major contributions to our understanding of thiourea/precious metal systems.

Jan 1, 1984

By R. S. Ondrey, R. A. Haney, T Tomb, R. T. Stoltz, Novakowski D. L. Chiz, E. J. Gerbec, D. J. Atchinson

Although the number of operating longwalls in the United States (approximately 100) has remained relatively constant over the last five years, longwall production levels have significantly increased and in some cases more than doubled. As a result of this production increase, control of respirable dust continues to be a problem. Therefore, the Mine Safety and Health Administration (MSHA), Pittsburgh Health Technology Center, Dust Division, initiated a study to investigate the availability and adequacy of technology for controlling dust on longwall mining operations. The study involved 23 longwall mining operations in three different Coal Mine Safety and Health Districts. Each operation was visited for a full shift. Respirable dust samples were collected on face personnel and at fixed locations along the face. Methods being used to control dust were noted, with special emphasis placed on obtaining quantitative data relative to ventilation, headgate dust controls, cutting drum sprays, external machine sprays and cutting sequence. Attempts were made to correlate dust control practices in place at the time of the visit to dust concentrations measured at the tail and on the tail shearer operator and to the average of all the dust concentration measurements from the occupations sampled. The methods used to control dust were also compared to the gamut of methods known to be available. This paper presents a discussion on the effectiveness of the methods being used to control dust and on the availability of technology for the control of dust on longwall mining operations.

Jan 1, 1991

By Alper Kirmaci, Taghi Sherizadeh, Dogukan Guner, Cameron Mitchel

Brow hazards are a significant concern in coal mine ribs and form when weak coal sloughs out of a rib face and exposes an overhanging block of more competent rock or coal. Of 36 rib failure fatalities in the last two decades, 36% resulted from rib brow failures. This highlights the need to better understand the mechanisms driving brow formations and failures to mitigate this hazard and eliminate potential fatalities. The research team at Missouri S&T worked to enhance the current CPRR system and include the potential for these brow hazards. We employed physical modeling methods to build a scaled model from critical brow cases observed in the field. The dimensions and properties of the models were scaled down by 14.4 times from the field cases. The results of the physical modeling efforts were used to assist in calibrating distinct element numerical models vital to understanding brow formation and failure mechanisms. Subsequently, three physical models were created and tested to provide data on an otherwise impossible-to-capture event at the field scale. The results of these tests provided formed brow dimensions that agree well with those observed at the field scale. The brow dimensions were 1.25 inches deep into the rib, equivalent to 1.5 feet when scaled up. Similarly, the numerical modeling efforts provided good agreement by capturing a brow forming 1.55 inches deep into the rib. The physical model results further validate the applicability of physical modeling efforts for capturing otherwise difficult and dangerous phenomena in a controlled lab setting.

Feb 22, 2026

By A. W. Khair, S. S. Peng

Discussion by J. Parker Gentlemen; Rainy day in Upper Michigan, a good time to catch up on reading. Am doing that, and have a couple of questions concerning the K and P paper on roof problems and supports. I wonder if the authors can enlighten me. The compressive strength of the coal was reported as 4.4 MPa (633 psi) and compressive stresses measured in the coal seam were reported at around 27.6 and 48.2 MPa(4000 and 7000psi ). Can such a soft coal actually contain such a high level of stress? Can it be measured as if the material were elastic, or does the coal behave plastically? Can that stress level be confirmed with hydraulic load cells? And if the coal is so soft, and if it is plastic, why is the stress field not hydrostatic'? The intact roofrock appears to be unusually strong, with compressive strength reported at around 145 MPa (21,000 psi), and some failures were noted as soon as the rock was exposed. Were tests run to find out how that rock responded to the addition of moisture, from sprays or from humid air? Did moisture weaken the rock? Did it cause the rock to expand quickly, thus to induce internal compressive stress? How can the near-vertical cutters, as shown in the photographs, be attributed to primarily horizontal stresses? Did the cutters follow any particular pattern in the development panels, which might be related to a particular stress pattern? For example, did they always appear alongside the stiffest pillar? Or always along the northwest rib? Was there any evidence of the pillars and entries "rotating" under the influence of differential horizontal stresses? How much did the entries and pillars rotate as the longwall face approached and passed? After rooffalls, did the openings assume shapes which would indicate a preferred shape in that stressfield and geology? Did crosscuts always survive without damage, as shown in the sketch?

Jan 1, 1992

In addition to capital and operating costs, the accurate estimation of ore reserves is a key component to the successful outcome of any feasibility study. In recent years, there have been many project failures caused by the improper estimation of ore reserves. The accurate estimation of an ore reserve relies heavily on an understanding of the geology and the underlying assumptions unique to the estimation techniques being used. These assumptions are reviewed, and the shortcomings of the estimation techniques and their possible impact on a given project's economics are discussed. The latest developments in geostatistics in overcoming existing reserve-estimation problems are presented.

Jan 1, 1998

By E. S. Peterson, M. K. Harrup, K. A. Dolbeare, J. E. Wey

Efficient methods for removal of copper from heap leach solutions without mobile organic phases are a current mining industry need. To satisfy this need a selective, high-capacity, durable solid material is required. The INEEL has developed a set of materials based upon current solvent extraction chelates that provide selective copper concentration in the presence of high concentrations of iron. In contrast to conventional solvent extractions, our strategy anchors the chelators to a non-polymeric solid substrate through the use of a custom designed linker molecule. The fundamental synthetic routes to these materials have already been established and attachment to the solid surfaces achieved in an efficient manner. Our continuing research is focused on the optimization of the synthetic pathways to these solid materials and the evaluation of their copper capturing capabilities.

Jan 1, 2002

By T. J. McKeon

Gravity separators such as spirals are commonly used in multistage cleaning and scavenging circuits to improve the quality and recovery of concentrates produced in the industrial minerals industry. Unfortunately, field surveys suggest that many industrial operations are poorly configured in terms of equipment layout. This shortcoming can often be attributed to a failure by engineers to make use of fundamental process engineering tools for circuit design. One of the most important of these is linear circuit analysis. This powerful tool makes it possible to mathematically compare the relative efficiency of circuit configurations in advance of experimental testing. This article provides a basic review of the linear circuit analysis concept and discusses some of the key insights it provides for the layout of multistage circuits. An industrial case study is provided to show the tremendous impact that this process engineering tool can have on the design of multistage spiral circuits in a heavy mineral wet plant.

Feb 1, 2012

By Peter N. Calder

There is little doubt that the stability of both highwalls and spoil piles is essential to efficient strip mining. Accurate determination of the appropriate geotechnical parameters will pay dividends during mining, but only if the mine operation closely follows the engineering plans which have incorporated These factors. Productivity is invariably higher in mines where failure of highwalls and spoil piles does not occur. This is the result of the reduced rehandle and better working conditions found in stable mines. Control of the waste piles and highwalls also leads to better coal recover since failures can result in the burial of uncovered coal, which is then lost to mining. Safety is an important consideration. The importance of providing a safe working place for employees and of protecting costly mining equipment is hard to overemphasize. For miners, working in areas where instability exists, the degree of hazard involved in their occupation is increased particularly where night operations are involved. It is true, too, that there have been many cases where loading equipment has been buried and severely damaged by failures.

Jan 1, 1980

By Robert F. Droullard

The U. S. Bureau of Mines (USBM) has investigated instrumentation and methods for measuring exposure to radon daughters in underground mine atmospheres. Both personal and area monitors have been studied through in-house and contract research. A field study in uranium mines identified some reliability problems that required additional work for the personal dosimeter systems. Improved versions of continuous working level detectors have been developed and tested for use as area monitors in underground mines. Test results for the personal and area monitors were satisfactory for underground mine applications.

Jan 1, 1981

By Young C. Kim

Because of the tremendous technological advances achieved in recent years in microcomputers, it is not only technically feasible but also economically viable to develop an automatic truck dispatching system using a microcomputer. Such an effort was initiated by the Department of mining and Geological Engineering, University of Arizona in the summer of 1983. Up to date results and experiences prove that today's microcomputers can be economically employed for such a system to be used at small to medium scale open-pit mines. An IBM/XT microcomputer with 10 MB harddisk storage, together with automatic sensing capability of truck movements at several key locations in the pit, formed the core of this system. System software is written primarily in MICROSOFT FORTRAN with supporting subroutines in MACRO assembly language. The software is designed to automatically monitor truck movement throughout the pit, to make heuristic assignments based on expected shovel availability and truck travel times, and to record production statistics. It is currently dimensioned to handle 50 trucks, 10 shovels, 10 dump sites and 3 material types. Due to the lack of funds to purchase the necessary communications hardware, the work related to the automatic sensing of truck movements has not been performed to date. Otherwise, the automatic truck dispatching-system is fully operational on a realtime mode.

Jan 1, 1984

By Robert B. Fulton

The objective of this chapter is to discuss the interrelationship between industrial minerals and chemical manufacturing. It is intended to supplement rather than duplicate the commodity chapters. Particular emphasis is given to the pertinent chemical element and to market factors. Condensing this broad subject into a few pages of this handbook permits treating only the most important elements derived from industrial minerals. Hydrocarbons, which quantitatively dominate as raw materials for the chemical industry, are omitted, as are the metallic elements and the minerals covered in other "use" chapters such as phosphorous, potassium, and nitrogen for fertilizers, and titanium dioxide for pigments. The remaining six elements of major importance are: boron, bromine, chlorine, fluorine, sodium, and sulfur. These elements are treated individually under separate headings. [Table 1] affords an overview of the main industrial minerals, the chemical products derived from them, and end uses of the products. Salt brines have particular importance as raw material sources for the chemical industry. Table 2 is a chart of the chemical compounds derived from four types of brines: (1) Owens Lake-type brines, which are sources of boron and sodium compounds; (2) Midland-type brines, from which bromine, iodine, and chlorides of calcium, magnesium, potassium, and sodium are derived; (3) Searles Lake-type brines, yielding boron, bromine, lithium, magnesium, potassium, and sodium compounds; and (4) Silver Peak- type brines, produced mainly for lithium. MARKET ATTRIBUTES Some of the important market traits common to industrial minerals used by the chemical industry are: 1. They are international commodities, such as fluorspar and sulfur, which largely move to foreign consumers. 2. Grade, and freedom from deleterious elements are important factors affecting their usability in chemical processes. An example is salt (NaCl) used in electrolysis where ultrapure evaporated salt is required to meet rigid specifications. 3. Purified products take on the characteristics of specialty items and command a distinctly higher price than the basic commodity from which they are derived. 4. In practically all cases, chemical users require some sort of cleaning or beneficiation of the naturally-occurring mineral to bring it to specification, and individual specifications may vary from user to user for essentially the same use. 5. In some instances it is necessary to strike a balance between what the vendor can supply and what the buyer requires, with the result that specifications have to be eased to afford the needed materials in marginal cases. 6. Because they tend to be bulk commodities, low cost for handling and transportation are important and such costs may limit the area from which a chemical user can draw his supply. 7. Shipments are usually in bulk and frequently in multiple-car, full-trainload or full-shipload lots to reduce transport costs, which in turn may require large terminal investment facilities. 8. Purchases are generally by contract of one year or longer term, with spot buying playing only a minor role. 9. Contract prices are usually fixed in short term commitments, but may vary according to assay, with premiums and penalties for content above or below the norm; however, general practice is for specifications to be fixed in the contract with minimums being set for the desired material and maximums for undesired elements. In longer term contracts, prices are often escalated on labor, fuel, and other vendor processing costs. 10. Suppliers of individual commodities to the chemical industry tend to be limited in number and are generally medium- to large-size producers that supply a few major consumers. 11. The bulk of the mineral volume is for basic chemical uses, sulfur suppliers to sulfuric acid producers and fluorspar for hydrofluoric acid producers being typical examples. These basic chemical products then are used for the production of other products. 12. Shortage of a supply of adequate quality leads consumers to seek substitutes. In the case of fluorspar, much work is being done on recovery of fluorine from phosphate rock. Success in the form of fluorosilicic acid and/or hydrofluoric acid production could, in time, affect the hydrofluoric acid chemical industry. 13. Markets tend to be characterized by cycles of shortage followed by oversupply, with attendant wide price fluctuations. 14. Baniers to trade can have an adverse effect on the necessary movement of industrial minerals used by the chemical industry in international trade. Antidumping laws, quotas, and tariffs can disrupt or dislocate normal markets. 15. Chemical industry consumers may back-integrate for security of supply or for favorable economics, sometimes by joint ownership and often with experienced mining partners.

Jan 1, 1994