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By G. T. Homce

Most electric motor predictive maintenance methods have drawbacks that limit their effectiveness in the mining environment. The U.S. Bureau of Mines is developing an alternative approach to detect winding insulation breakdown in advance of complete motor failure. In order to evaluate the analysis algorithms necessary for this approach, the USBM has designed and installed a system to monitor 120 electric motors in a coal preparation plant. The computer-based experimental system continuously gathers, stores, and analyzes electrical parameters for each motor. The results are then correlated to data from conventional motor-maintenance methods and in-service failures to determine if the analysis algorithms can detect signs of insulation deterioration and impending failure. This paper describes system design and implementation. At this writing, however, installation is still underway, and field data analysis results are not yet available.

Jan 1, 1994

By Paul L. Bearden

The accumulation, handling, and utilization of sludges formed from wet process phosphoric acid is one of the major problems in the industry. The purpose of this paper is to explain some of the considerations and techniques that can be employed to provide some measure of control over the problem. An acid made from a Central Florida phosphate rock is used to illustrate the effects of one process design approach used to provide one type of control. Other approaches or techniques are discussed on a general basis. In every case, the discussion is purposely limited to conventional dihydrate processing in which phosphoric acid is produced from the filter at a strength of approximately 30% P205 and is subsequently concentrated to higher strengths such as 44 and 54% P205.

Jan 1, 1966

By R. L. Wooten

When discussing what Coal Mine Safety in the future will be, it is important to examine three areas which at present provide significant parameters to the industry. These three areas are: 1) Safety improvements in mining equipment; 2) Labor-management relations; and, 3) The politics of coal mine safety. EQUIPMENT Over the past several decades significant safety improvements have been made in the types of equipment now in use in most operations. Many of these improvements have evolved through mandates from either the U. S. Bureau of Nines, MESA, MSHA; and in some instances, the states. Cabs and canopies are examples of federal mandates while the use of ATRS initially was a state mandate.

Jan 1, 1985

By Werner A. Ruemmele

Eisenhower Memorial Tunnel, called Straight Creek Tunnel during construction is located 60 miles west of Denver, Colorado at 11, 160 ft. elevation. It is 8, 510 feet long, and carries two lanes of 1-70 traffic under the Continental Divide. This paper describes improvements and changes made in construction methods for utilities, concrete lining, ceiling, wall covering and paving to allow maximum offsite fabrication and activity overlap resulting in a one-year faster completion for traffic. The substantial changes proposed on a design-and-construct basis by the contractor and put into effect after State approval were: 1. Substitution of ductile iron and thick-wall P.V. C. pipes for clay pipes allowing placement and operation before hole-thru. 2. Outside pre-assembly of large rebar mats, using a novel tension-splice with cable clamps. 3. Arch concrete placement method modified to make 4, 322 ft. of lining in 10 weeks possible. 4. Safety barriers precast and epoxy coated offsite instead of cast-in-place and tile faced. 5. Prestressed hollow ceiling slabs with porcelainenamel coated steel sheets assembled offsite, instead of in-place glazed tile and in-place cast concrete ceiling. 6. Glazed tile wall panels 8 ft. long by 11 ft. high assembled off site and erected using vacuum pad mounted on special lift. 7. Asphalt paving while other work proceeded, instead of reinforced concrete slab and asphalt overlay. Work started in January 1968, but advance came to a one-year standstill for major structural redesign and negotiations of a new agreement during 1970. Using multiple drift construction followed by top-heading and bench excavation, it then progressed to hole-thru in July 1972. As a result of art 18-month overlap of activities the tunnel was opened for traffic only eight months later in March 1973. Gibbons and Reed Company of Salt Lake City, Utah sponsored the joint Venture of Al Johnson-Gibbons and Reed-Western Paving-Kemper during 1971, 1972, and 1973. The tunnel was the subject of a previous paper delivered at the RETC '72 in Chicago by R. C. Hopper, T. A. Lang, and A. A. Mathews, describing geology, unusually severe structural loading and multiple-drift tunnel excavation.

Jan 1, 1974

By Gustavo G. Pilger, Jair C. Koppe, João Felipe C. L. Costa

Information for mine planning requires to be close spaced, if compared to the grid used for exploration and resource assessment. The additional samples collected during quasi-mining are frequently located in the same pattern of the original diamond drill holes net but closer spaced. This procedure is not the best in mathematical sense for selecting a location. The impact of an additional information to reduce the uncertainty about the parameter been modelled is not the same everywhere within the deposit. Some locations are more sensitive in reducing the local and global uncertainty than others. This study introduces a methodology to select additional sample locations based on stochastic simulation. The procedure takes into account data variability and their spatial location. Multiple equally probable models representing a geological attribute are generated via geostatistical simulation. These models share basically the same histogram and the same variogram obtained from the original dataset. At each block belonging to the model a value is obtained from the n simulations and their combination allows one to access local variability. Variability is measured using an uncertainty index proposed. This index was used to map zones of high variability. A value extracted from a given simulation is added to the original dataset from a zone identified as erratic in the previous maps. The process of adding samples and simulation is repeated and the benefit of the additional sample is evaluated. The contribution of an extra sample was evaluated locally, globally and in terms of variation in total measured resources. The procedure showed to be robust and theoretically sound, mapping zones where the additional information is most beneficial. A case study using coal seam thickness illustrates the method.

Jan 1, 2002

By V. K. Karra

An improvement in the present day screen sizing methods calls for knowledge on i) how material in the size range: 0.5 x 1.5 times the through-fall opening of the mesh on a deck, splits between the oversize and undersize streams of the deck, and ii) how near-mesh content of the feed affects the screening performance. In the throughput based sizing method given here, this is accomplished through the introduction of a generalized partition curve and a near-mesh factor. A newly developed efficiency factor is employed in addition to the traditional screen sizing factors.

Jan 1, 1979

By Ronald E. Feltman

Most engineering firms engaged in the design and manufacture of milling components and systems have established, through the years, a relatively well defined system design procedure. The process design engineer has at his disposal several alternative approaches to the successful completion of this task. Unfortunately, while these alternatives, at first glance, appear to be rather straight Forward, any attempt to implement them into a fully integrated commuter design program becomes increasingly more complex when one addresses himself to the problem in total. This paper summarizes Kennedy Van Saun's approach to the solution of this problem through a planned system design. Following the problem definition and discussion, a detailed analysis and system design synthesis is presented; the major aim here being to provide a system design which may be programmed and run on a relatively inexpensive computer installation such as the IBM 1130 system currently in use at Kennedy Van Saun. A summary section is also included, which Provides a general outline guide to the program systems design of equipment which, while quite different from milling system functionally, nevertheless lends itself to the approach used in this paper.

Jan 1, 1969

By Mohammad Ranjbar, Zahra Manafi, FAZAELIPOOR MOHAMMAD HASSAN, HAMGHAVANDI MOHAMMAD RANJBAR, Mahin Schaffie

Bioleaching has an increasingly important place among available mining technologies as biological processes have emerged as alternatives for metal recovery, especially for metals like gold and copper. An important disadvantage of bioleaching is the slow reaction rates, with microbial attack times often lasting weeks. Therefore, applicable research is required to improve these rates. From previous research, copper bioleaching has been divided into two specific regimes: (1) surface reaction controlling step and (2) mix of surface reaction and diffusion controlling steps. The presented model, which includes the effects of both these regimes, predicted the results of copper bioleaching recovery with good accuracy.

By N. T. Mirafuente

The device called "Dynastat" which is described in this paper provides in situ borehole measurements of dynamic and static parameters for use in a wide range of design applications. In the dynamic mode, the Oynastat allows measurement of shear and compressional wave velocities. From these velocities in situ dynamic Young's modulus and other dynamic elastic parameters can be calculated. In the static mode, the device allows measurement of load versus deformation from which in situ static Young's modulus can be determined. Information on in situ horizontal stress fields can also be estimated from the load deformation curves. In both mining and civil engineering applications, in situ measurements of material properties are indispensable for accurate evaluation of design problems. Laboratory dynamic and static test measurements in comparison to in situ measurements are often misleading due to difficulties in obtaining undisturbed samples and in accounting for effects of discontinuities, etc., for mass properties. The authors contend that among in situ borehole measurements, the method employed with the Dynastat is the most accurate and detailed technique of measurement. The Dynastat employs the crosshole method of shear and compressional wave velocity measurements and also performs as a borehole jack to obtain load-deformation relationships of materials at exactly the same location at depth in boreholes.

Jan 1, 1976

By Eugene P. Pfleider

The mining industry of the World, and particularly of the United States, has made a complete reversal from underground to surface mining methods since the turn of the 20th Century. This has occurred even as average ore grades were decreasing and strip ratios rising. In the early 1900's there were over 100 underground mines producing from the three iron ranges of Minnesota -- today there are hone. Practically all of our coal prior to 1930 was mined underground; today over one-third is from surface operations and that percentage is increasing. Although world mining has hot changed to surface techniques as rapidly as has the U. S. Industry, the shift is escalating and will approach our figures shortly. A comparison of World and U. S. production figures are shown in Table 1, taken from the AIME Surface Mining volume, and the trend rates for the U. S. are depicted in Fig. 1.

Jan 1, 1968

By J. Duran

Mining at Newmont Mining?s Phoenix?s Mine is currently done by surface operation in the Fortitude and Bonanza pits at a combined rate of approximately 100 kt/d (110,000 stpd). A portion of the orebodies targeted by these pits was mined previously by underground mining methods, dating back to the mid-to late-1800s. Most of the underground workings (voids) are located in the west central area of the Bonanza pit. The surface operation requires excavation through voids, and there is a risk of pit floor subsidence that has to be addressed. This article presents a review of the risk mitigation measures that were implemented to reduce risks to people and equipment working in the area.

By J. F. Brune, A. Verma

"Face ignitions in underground coal mines are a major risk for underground mining operations, as they can lead to methane or coal dust explosions. The 2010 disaster at the Upper Big Branch Mine resulted in 29 fatalities due to a methane and coal dust explosion initiated from a face ignition. Much research has been conducted to mitigate face ignition hazards, from water sprays to installing passive and active explosion barriers. Despite the increased use of water sprays in U.S. coal mines, there have been more than 50 documented face ignitions in the U.S. underground coal mines since 2010, indicating that this hazard still prevails. This paper will examine the statistics of face ignitions and gas explosion in U.S. coal mines based on MSHA data. It will study factors contributing to these face ignitions and outline best practices for their prevention based on experience and practices worldwide. INTRODUCTION Methane and coal dust explosions are one of the major causes of coal mine disasters in the U.S. and around the world. Such disasters have resulted in the large number of fatalities and loss of mine infrastructure. The recent explosion at the Soma coal mine in Turkey has caused the death of 301 miners (Mining Turkey, 2014). As documented by U.S. Mine Safety and Health Administration (MSHA, 2015a), the U.S. coal mining industry has also experienced several catastrophic mine explosions with accidents at Upper Big Branch mine, Darby mine, Sago mine and Jim Walter Resources No. 5 mine in the last decade, causing the deaths of almost 60 miners. Every explosion requires a source of ignition, the right amount of fuel and oxygen. In underground coal mines, methane acts as a fuel while ventilation air acts as a source of oxygen. The source of ignition may vary from spontaneous combustion, electrical equipment and switchgear, mechanical heat sources, face ignitions due to friction rock-on-rock or from cutter bits and lightning strikes. Under the right conditions, energy of less than 0.3 mJ is sufficient to ignite methane-air mixtures (James, 2007) that can result in a catastrophic explosion. Much research has been done to mitigate the methane explosion hazard by proper dilution, continuous monitoring of methane and elimination of ignition sources. Historical studies indicate that face ignitions are the major cause of explosion in underground coal mining operations worldwide (Belle, Carey, and Robertson, 2012). Statistics shows that most mine disasters were started from a small face ignition, which turned into a major explosion fueled by additional methane and coal dust (Belle et al., 2012). To investigate face ignition hazards, researchers must study potential ignition sources as well as potential explosive atmospheres near mechanical coal cutting operations. Statistical analysis of U.S. coal mine face ignitions reported by the U.S. Mine Safety and Health Administration (MSHA, 2015b) shows that several factors are responsible for face ignitions."

Jan 1, 2016

Acid mine drainage (AMD) forms when sulfide minerals are exposed to oxidizing conditions in coal and metal mining, highway construction, and other large-scale excavations. Iron sulfides common in coal regions are predominately pyrite and marcasite (FeS2), but other metals may be complexed with sulfides forming chalcopyrite (CuFeS2), covellite (CuS), galena (PbS), and sphalerite (ZnS). Pyrite commonly occurs with these other metal sulfides thereby causing AMD where Cu, Pb, and Zn are mined. Upon exposure to water and oxygen, sulfide minerals oxidize to form acidic, sulfate-rich drainage. Metal concentrations in AMD depend on the type and quantity of sulfide minerals present. The drainage quality emanating from underground mines or backfills of surface mines is dependent on the acid-producing (sulfide) and alkaline (carbonate) minerals contained in the disturbed rock. In general, sulfide-rich and carbonate-poor materials produce acidic drainage. In contrast, alkaline-rich materials, even with significant sulfide concentrations, often produce alkaline conditions in water. Approximately 20,000 km of streams and rivers in the United States are degraded by AMD. About 90% of the AMD reaching streams originates in abandoned surface and deep mines. Since no company or individual claims responsibility for reclaiming abandoned mine lands (AML), no treatment of the AMD occurs and continual contamination of surface and groundwater resources results. The oxidation of iron disulfides and the generation of acidity occur through several reactions (Stumm and Morgan, 1970). The chemical equations can be found in Caruccio and Geidel (2000). If any of the processes represented by the equations were slowed or altogether stopped, the generation of AMD would also slow or cease. The equations show that 1000 Mg of rock containing 1% sulfur, all as pyrite, would yield upon complete reaction 31.25 Mg of acidity. Therefore, 31.25 Mg of 100% CaCO3 would be required to neutralize the acidity. The alkaline content of overburden determines whether there is enough neutralization potential (NP) to counteract the acid produced from pyrite oxidation. Of the many types of alkaline compounds present in rocks, only carbonates and clays occur in sufficient quantity to effectively neutalize AMD. A balance between the acid-producing potential and neutralizing capacity of an overburden sample will indicate the ultimate acidity or alkalinity that might be expected in the material upon complete weathering. Accurate prediction and control of AMD before surface mining require an understanding of three important factors: 1) overburden geochemistry, 2) method and precision of overburden handling and placement in the backfill during reclamation, and 3) the postmining hydrology of the site.

Jan 1, 2002

By Ronald D. Hill

The occurrence of acid mine Drainage (AMD) with coal mining has been well documented. (1) Less documentation is available of its association with other types of mining, e.g., copper, gold, zinc, and sulfur. Yet there are many locations in the western states where acid mine drainage is as great a pollution problem as in Appalachia and in some cases, because of the high copper, zinc, and arsenic concentrations, they present an even more difficult problem. Until a few years ago, it was generally believed that the neutralization of acid mine drainage was uneconomical thus, AMD was allowed to discharge freely into our streams. However, the demand for good water finally dictated that the mining industry be included under pollution laws. In 1964 the Commonwealth of Pennsylvania passed a law requiring that all active mine discharges meet a discharge standard of pH 6-9, iron less than 7 mg/1, and the water must have a net alkalinity. Several other states now require active mines to treat AMD. In all but a few cases, lime neutralization, often in conjunction with aeration, has been the treatment method used. The high cost of lime as compared to limestone and the poor quality sludge, (slow settling, large volumes, and low solids content) has stimulated work in the utilization of limestone. This paper reports on the current state-of-the-art of limestone treatment of AMD.

Jan 1, 1970

By R. Spring

Artificial intelligence, and especially expert systems, are currently receiving considerable attention. Of interest to the control engineer is the utilization of these tools for real-time process control applications. To evaluate this technology, a real-time expert control system was implemented in one of the grinding circuits at Brenda Mines Ltd. The performance of this micro computer based expert system compared satisfactorily to the proven supervisory control system currently in use. The study confirmed the expectations that expert systems have potential for real-time, supervisory control of mineral processing operations.

Jan 1, 1989

By Tyler A. Dawson, Ryan P. Butler, Timothy Gualandri, Jason R. Edberg

"In the early 1920’s, the City of Tulsa, Oklahoma constructed an approximately 8,238-foot long tunnel, the Tiawah Tunnel, through bedrock. Voids behind the concrete tunnel liner were detected via probe drilling in early 2000 as part of an interior visual condition assessment. In 2012 and 2015, conditions along the entire tunnel were efficiently assessed through geophysical investigation using ground penetrating radar (GPR) along the inner tunnel crown and at various select locations within the tunnel. Fifty-seven (57) potential voids, extending up to 19 inches in depth and 12 feet in width, were detected with 1,000 MHz GPR and confirmed through probe drilling with approximately 80% accuracy. GPR proved to be an efficient and reliable technology for void detection behind concrete tunnel lining. This paper highlights the geophysical investigation and how geophysical efforts were combined with other investigation efforts to definitively determine the presence of voids outside of the tunnel lining.INTRODUCTION The city of Tulsa, Oklahoma has a population of about 400,000 people. The original source of water for the city was the Arkansas River. The first pumping operation provided untreated water to homes and businesses in 1904. The residents of Tulsa found this water to be unacceptable due to the high levels of salt and gypsum present. As the city grew, land and storage/treatment facilities were acquired in order to obtain and distribute a more suitable raw water. The raw water needs for the city are currently satisfied by transport and treatment of about 100 million gallons per day (MGD) of water from surface water sources. Water is transported many miles from Spavinaw/Eucha and Oologah lakes to Yahola Lake and the Lynn Lane Reservoir (totaling over 3-billion gallon capacity). From here, the raw water is treated and transported to the various customers (City of Tulsa 2015). The Tulsa Metropolitan Utility Authority (TMUA) is responsible for the operation and maintenance of the raw water transport system."

Jan 1, 2016

By R. C. Keaney

The metals industry is in complete chaos with mines being shut down, profits becoming non-existent, and continual losses to imports from other countries. Yet the raw material supplier to the glass industry has many opportunities to grow and to produce profits. Fortunately, the cost of most glass raw materials are low enough that competition from imports is not anywhere as critical as it is in the metal industries, such as copper, aluminum, lead, and others. But the glass raw material supplier must develop new products, both chemically and physically, to effectively compete in the future. The purpose of this paper is to point out generally where these opportunities exist and to suggest how they may be further developed. As the glass industry looks for energy saving materials, they look once again towards finer materials. A glass furnace is now approximately 40% efficient. Glass engineers are constantly striving for energy savings and it is well known that finer materials melt easier so that the manufacturer can operate his furnace either at lower temperatures for the same production or he can produce more material at the same temperature. The old 20 mesh sand specification is no longer sacred and as the mesh size for sand changes so do the specifications for all other raw materials used in the melting process. Highly instrumented glass furnaces can now measure quite accurately the energy needs to produce glass and can also measure the energy loss in each furnace. Glass technologists desire today a sand with a top size of 40 mesh while some would like to have the top at 60 mesh. This becomes more difficult to accomplish as a raw material supplier without .grinding. As you well know, grinding develops fines. Yet the same technologists will tell us that we can have nothing passing a 140 mesh screen. Therefore, we must develop processes which allows us to produce a finer screen size without increasing the amount of fines passing through the 140 mesh screen. To counteract this, different and changing industries are now demanding much finer products so possibly there will be markets for the fines which are currently separated out of the products. Methods that are practical and low cost must be found to develop different products with different screen specifications. What works for sand can be carried over to the other raw materials used in melting. Among the answers to finer products, of course, are pellets. Aglomeration or pelletizing has been looked at in the past and will be looked at in the future. Considerable work has been done in the glass container industry on this and must be carried out more extensively. By using aglomerated material or pellets, the glass producer will gain the benefits of melting fine materials without suffering from handling or dust problems. Pelletizing, particularly where using basic glass melting materials such as burned lime or sodium silicate, will not only produce a good pellets but will add desirable minerals to the glass batch.

Jan 1, 1986

By R. K. Young

Producing a sound plant design for a major project requires hundreds of engineers and many drawings. Economical accomplishment of this task is based upon careful and orderly organization of the design team so that at all times there is a complete and workable staff but at no time a surplus of costly talent. This paper will describe the various stages in the development of plant design which normally follow the laboratory and pilot plant investigations discussed in other papers today. An outline of the procedures used in the assembling of a project design group, within an established engineering organization will be presented. Actual procedures may vary according to the size and character of the plant, the special requirements of the owner, and the make-up of the engineering organization performing the design, but most of the points covered will be found to be basic to any plant design project.

Jan 1, 1960

By B. Caines

Much of the mining industry in North America is in a crisis state. Host producers are operating at production levels well below capacity, some have been merged or sold, while others have been mothballed or closed permanently. For many of us still operating, the future is uncertain. Despite the many cutbacks and closures, there is still an abundant supply of minerals in the world market and there is almost no hope for any relief on price pressures on most mineral commodities in the near future. The Iron Ore Company of Canada (IOC)operates an iron ore mine, a concentrator and a pellet plant known as the Carol Project located in Labrador City, Newfoundland. This concentrator and the pellet plant have the annual capacity to produce 20 million and 10 million tons respectfully. A company owned and operated railway links this operation with the dock terminal facilities in Sept Iles, Quebec.

Jan 1, 1987

By R. C. Gilmore, S. A. Lolon, G. E. Bogin, S. A. Saki, J. F. Brune, J. W. Grubb

"Gob ventilation boreholes (GVBs) are widely used in underground coal mines for longwall gob degasification purposes. GVBs are often drilled within 10 to 30 m above the top of the coal bed into the fractured zone, completed with 20 cm (8 in.) diameter casing and 60 m of slotted pipe at the bottom. The purpose of this completion strategy is to create a pressure sink to capture the emissions before they can enter into the underground workplace. For GVBs to work effectively, they must be drilled close enough to the working areas to capture methane from the fractured zone while the setting depth must be kept above the caved zone to minimize the amount of ventilation air that is drawn into the GVBs. Well completion parameters are important for creating safe working conditions. In this paper, computational fluid dynamics (CFD) studies will be presented to analyze the effect of different practices for GVBs completion parameters for methane extraction, formation of explosive gas zones in the gob and methane concentrations at the longwall face and tailgate. Authors have identified the optimum completion parameters for GVBs, which can maximize the benefit and minimize fire and explosion risk. INTRODUCTION Coal mines may be considered gassy based on the presence of CH4. Gas from the mined coalbed or from rider seams above or below the mined coalbed can migrate into the gob and then potentially move towards the working areas. In longwall coal mines with high methane emissions, sufficient ventilation and additional methane control measures are usually required to reduce the methane concentration in working areas to below statutory levels. Several techniques or combinations of techniques are available to control the methane hazard. These may include mine face ventilation to dilute methane, coal bed degasification, nitrogen injection into the gob to render a methane atmosphere inert and the use of gob ventilation boreholes (GVBs). Longwall face ventilation and dilution alone can only handle methane emissions up to a certain amount. When methane emissions exceed the face ventilation capacity, additional control measures are required. Drilling horizontal or vertical methane drainage holes into the coal seams as well as gob ventilation boreholes from the surface into the gob area to extract methane are common practices. GVBs are usually drilled from the surface above the longwall panel ahead of mining. When the face moves outby the GVBs and the gob begins to form, methane production starts from the boreholes. It is important to control the performance of GVBs to maintain a safe working environment in the mine. The performance of GVBs depends on multiple factors, including borehole location, length and diameter of slotted casing, setting depth of casing above the coal seam being mined, wellhead vacuum pressure, and permeability of caved-fractured zones."

Jan 1, 2016