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By P. Somasundaran, F. F. Aplan

The Formative Years Douglas Winston Fuerstenau was born December 6, 1928 in Hazel, SD to Edwin Arnold and Hazel Pauline (Karterud) Fuerstenau. His father, of German extraction, was a farmer and, later, a cabinet maker, while his mother, of Norwegian lineage, was a school teacher. His parents are still alive today at ages 91 and 88, respectively. Two younger brothers, Richard and Maurice and a sister, Jean, completed the family. The family first lived near Watertown and later in Lemmon and Mobridge, SD. The 1930's were a difficult period for any family in South Dakota. A decade-long drought made this a part of the dust bowl, which together with a serious infestation of grasshoppers (the locust plague described in The Bible), and the world-wide depression, made living difficult for all. In spite of these privations, Doug has many happy memories of his childhood which can be attributed to the resilience of youth and a strong family structure. He has fond memories of summers spent with his cousins on family farms where the children were introduced to farm chores at an early age. When he was old enough, he worked in a grocery store after school. At the age of 14 he spent the summer hearding 2,000 sheep near Lemmon, SD as his contribution to the war effort in that labor-short period. He remembers well the dust storms of the 1930ts, the destruction at his grandmother's farm by tornado, pulling weeds on the farm, threshing grain with a monstrous steam-driven machine and such pleasant childhood activi- ties as fishing for bullheads, hunting for rabbits, searching for arrowheads in newly plowed fields, and ice skating in the winter. Early in life his parents instilled in him a strong work ethic, a love of learning and the need for a good education. In 1943, the family moved to Rapid City, SD. With a population of 13,000, it was

Jan 1, 1989

By M. Imazu, Ö. Aydan

"A new rock classification, Rock Mass Quality Rating (RMQR) proposed by the authors is briefly explained and its application for the design of tunnels and large underground openings support systems is described in this paper. RMQR is an index to evaluate the state of rock mass. The preliminary support design may be based on the concept to prevent structurally controlled failures of rock mass. RMQR can also evaluate the yielding characteristics of rock masses so that it is possible to design a support system to prevent or control the deformation of surrounding rock through the utilization of the proposed rock mass classification and some analytical and numerical techniques.INTRODUCTIONThe first three authors proposed a new rock classification system named Rock Mass Quality Rating (RMQR) (Aydan et al. 2014). RMQR quantifies the rock mass state, and using the classification system together with intrinsic geo-mechanical properties of intact rock, possible geo-mechanical properties of rock masses can be estimated. The instability modes of underground openings can be structurally controlled because of the orientation of discontinuities in rock mass and the in-situ stress induced (Aydan 1989; Aydan et al. 1993, 1996; Aydan and Genis, 2010). The authors (Aydan and Ulusay, 2013; Aydan, 2016) have also tried to apply this system to the design of a tunnel support system. The authors presented initial guidelines for the RMQR classification system earlier (Aydan and Ulusay, 2013).In this paper, the authors provide further guidelines and establish some criteria for support system design that considers loading conditions and types of underground structure according to RMQR. Guidelines are alsos proposed for selecting the proper size of rockbolts, rock anchors, shotcrete, steel ribs and concrete liner. These guidelines are based on past experiences with various underground structures, theoretical understanding and the anticipated behavior of rock mass under given in-situ stress conditions and excavation techniques. The authors also utilized some databases developed for large underground caverns and tunnels excavated in squeezing or rock-bursting ground conditions."

Jan 1, 2016

By Y. C. Kim

Three rock fracture parameters define three points along empirical cumulative size (of rock fragments) distribution curves at Inspiration copper mine. These parameters are: rock quality designation (RQD), longest piece of intact rock and % of +1 inch. The RQD and the longest piece are actually measured on drill hole cores whereas % of +1 inch is visually estimated on the same cores. These size distribution curves are then utilized in a variety of engineering applications such as; slope instability analysis, blast design, copper recovery prediction from heap leaching, etc. The three rock fracture parameters for two dominant rock types (porphyry and schist) in the pit had to be estimated separately due to different rock fracture characteristics.' Both ordinary kriging (OK) with measured hard data only and soft kriging (SFTK) with hard and soft data were used to estimate each parameter. The cross validation of 100 measured sample values served as the-basis for evaluating the potential benefits of SFTK over OK. Use of subjective information during SFTK required obtaining (prior) probability distributions for all three rock fracture parameters. These distributions were obtained from the typical rock fracture parameters observed in drill hole cores falling inside the geologically interpreted structural domains with varying degrees. of fracture intensity and also through direct mapping along the exposed bench faces. Two different types of soft information were developed for this study; namely, Type "A" and Type "K". The former is based on sample distribution of fracture parameters whereas the latter is based on two step estimation designed to narrow the range of variation observed in data Type "A". The results of the cross validation were analyzed using a linear regression of actual values versus estimated values. The results confirm an improvement on the estimates made by SFTK with hard and. both types of soft data over those produced by OK with hard data only.

Jan 1, 1989

By John W. Wilson

Every operation connected with the working of a deep-level mine has, to a greater or lesser extent, a direct bearing on the costs of production, and hence, profitability of the mine. If adequate mine planning is not done in the early stages in the life of a mine, considerable expenditure can result from the cost of maintaining mine service tunnels, production delays in stopes caused by poor strata control, distortion of fittings in hoisting shafts, rockbursts and so on. In fact, the optimum profitability of a deep-level, hard-rock mine can only be achieved if the layout of the shaft systems, ore passes, tunnels, stoping areas and other underground excavations are designed to withstand or accommodate the rock stress conditions that will be created by mining operations. In South Africa where the deepest mines in the world are located, access to the underground workings of most deep-level gold mines is via vertical shaft systems and a network of tunnels connecting the shaft systems to the stoping areas. In current practice, there are two basic methods of extracting the gold-bearing reef,* namely, the scattered stoping method and the longwall stoping method. The choice of the stoping method is governed largely by the anticipated gold distribution and payability of the reef in the area, the geological conditions, the degree and complexity of faulting and dyke intrusions, the depth at which the gold-bearing reef is to be mined and the inclination and width of the reef. The longwall system was first introduced at the East 717 Rand Proprietary Mines Limited in 1942 in an effort to combat the rockburst hazard which appeared to increase with increase in depth. This mining method became standard practice on that mine for stoping operations 700 ft. below the surface. Since that date, several deep mines on the Central Rand, East Rand and West Wits gold mining areas have adopted this method.

Jan 1, 1977

By R. C. Babcock

Exploration for mineral deposits in the western United States is increasing annually, and the data generated by this effort are increasingly complex, diverse, and abundant. It is obvious that to make full use of this data base, which is both private and public, the technology of the computer must be involved. To lay out the framework for discussion of the particular uses of computers in all steps of exploration, this chapter will discuss the various approaches to the reconnaissance program which might be considered, the types of data to be acquired, the interpretation of these data, and the generation of recommendations based on this interpretation. Where possible, some of those areas where computer technology is now used will be pointed out. The discussion will cover the extent to which the computer is now utilized in those areas or where it should be brought into the program to aid in these activities. However, this chapter will not present an exhaustive evaluation of this technology, but will stress the exploration job and its requirements, so that subsequent discussion of the technology itself can be placed in perspective.

Jan 1, 1979

By Samuel B. Romberger

During the formation of most epithermal precious metal deposits geochemical changes can be characterized by the introduction of large amounts of silica, minor amounts of sulfur, and trace quantities of gold, silver, and other metals. During the same process, large amounts of alkalis and alkaline earth elements, such as sodium and calcium, and sometimes aluminum are removed from the rocks. In deposits hosted by carbonate sedimentary rocks large amounts of carbonate may be removed before or during the silicification process. Small amounts of iron may be introduced by the mineralizing solutions, however, in most epithermal deposits this may be a relatively immobile component and is locally derived. The results of these changes are deposits consisting of up to 90 to 95 percent silica as quartz veins, breccias, silicified host rocks, and jasperoids containing a few percent sulfides, mostly pyrite, and a few parts per million gold and silver. Other minerals commonly but not always present are barite, arsenic, antimony, or mercury sulfides, and tellurides. Often gold shows a spatial, and therefore an apparent genetic, relationship to pyrite in primary ores. Alteration and gangue assemblages sometimes include sericite and/or adularia, and parts of the deposits may contain alunite and/or clay minerals. Even though the value of these deposits usually lies in their gold content, silver is usually present in larger quantities than gold (Romberger, 1990). Based on these general characteristics observed in a large number of epithermal deposits, together with processes occurring in active geothermal areas to which they are often genetically linked (Henley, 1985), a model is proposed whereby deposition occurs along a subhorizontal zone separating environments of contrasting chemistries. The upper environment is characterized by oxygenated acid waters and the deeper environment by a reducing near neutral aqueous system. The model describes the chemical changes occurring as a result of mixing and/or boiling within this zone. It builds upon the physical models proposed by Romberger (1988a) for disseminated gold deposits and Bonham (1988; 1989) for volcanic rockhosted deposits.

Jan 1, 1990

By Karel SPIRKO

The one-dimensional mathematical model of unsteady-state heat conduction through semi-infinite homogeneous and isotropic airway walls with convective heat and moisture transfer between their wet or dry naked surfaces and mine air with time variable temperature and humidity has been developed on the basis of introduction of acceptable simplifications of description of heat and moisture transfer between rock mass and mine air. The analytical solutions for computation of the temperature distribution and surface temperature of the airway walls and floor and for calculation of water vapour pressure near the wet surfaces at given time are obtained by means of the model presented. The presented solutions are derived for general conditions and they could be easily adapted to the actual ones. Results of the model represent basis for balancing heat and moisture transfer between mine air and its surrounding in deep mines under time variable temperature and humidity of the air and enable us to solve complicated dynamic changes of mine air temperature and humidity in an airway system by relatively simple mathematical tools. INTRODUCTION The importance of unfavourable influences and the costs of condition arrangements increases with mine depth. Precision demands on the methods which predict the environmental condition changes and by which it is possible to optimize condition arragements are still increasing. Environmental conditions in deep mines are determined especially by flow velocity, barometric pressure, temperature, and humidity of mine air. Therefore new and more exact mathematical models of mine air flow through airway system and those of heat and moisture transfer between mine air and individual important sources of heat and moisture are developed. The paper presented deals with description and solution of problems of heat and moisture transfer between mine air and airway walls as the rock mass is one of the important heat and moisture sources in deep mines. There are several different approaches to the problem. In some models the moisture transfer between mine air and airway walls is not considered at all. In other models the moisture transfer is described only by certain empirical coefficients. Simultaneous heat and moisture transfer is described seldom. This paper tries to describe in a simple way simultaneous convective heat- and mass-transfer processes taking place on wet naked surface of airway walls by means of corresponding

Jan 1, 1993

By Zhongxue Li, Baolu Zhou, Yiqing Zhao

"Rare earth elements (REEs) are a kind of new materials which have excellent optical, electrical and magnetic properties, and they play an important role in the development of high technology and green energy industries. With abundant reserves and a wide range of REE type, rare earth industry has a rapid development in China in recent years. However, environmental issues associated with REE exploitation have severely restricted the sustainable development of rare earth industry in China. At present, literatures on the externalities of REE exploitation are very limited, especially in China. This paper builds an evaluation model based on life cycle evaluation to estimate the external costs of REE exploitation at Bayan Obo. The results show that the external costs for producing one metric tonne of rare earth oxides (REO) in Bayan Obo was CNY 34739 in 2013, the external costs of waste gas, waste water, radioactive substance, REE resource depletion, and land occupation are CNY 14945, 12515, 1400, 3199, and 2680, respectively. Waste gas and water constitute about 79% of the total external costs. The internalization of the external costs would reduce the financial profit of Northern Rare Earth (Group) by 18%. This study has taken into account only those externalities whose market values can be estimated, and therefore the external costs of REE exploitation in Bayan Obo is likely to be underestimated. The results fill the gap in literature and provide further understanding on the external cost of REE exploitation.Introduction / Background Along with increasing concern about environmental pollution problems caused by the usage of fossil fuel and the shortage of fossil energy, a transition has occurred where development has moved toward green and renewable energy sources with less pollutant emissions (Stegen 2015). Rare earth elements (REE) are a group of important raw materials for these trends since they have unique magnetic, electronic and optical properties, and thus make them widely used in making high-performance magnets and energy saving lamps (U.S. DOE 2010). In addition, REE are crucial for manufacturing of widespread high-tech applications in medical, defense and electronic industries. Many countries have made medium-term and long-term plans for the development of their REE industries, and the annual growth rate of global REE demand is expected to increase by 6% by 2020, and reach about 170,000 metric tons of rare earth oxides (REO) by 2020 (Rollat et al 2016)."

Jan 1, 2017

By M. K. McCarter

INTRODUCTION Mining activity and basic geometry of open pit mines represent major obstacles in geotechnical mapping. Mining creates a constantly changing topographic base which may require corresponding updates of field sheets before mapping can proceed. The rapid pace of mining operations may also threaten removal of important geologic and engineering features before adequate base maps and surveyed control can be established. Maintaining such control during the mapping process is yet another complication. In addition, basic geometry yields nearly vertical outcrops. Access required for direct observation and measurement, essential to conventional plane table or Brunton techniques, may be impossible on such surfaces. Also, nearly vertical surfaces appear fore- shortened in plan view. This reduction in area provides little room for recording geotechnical detail. The difficulties encountered in open pit mapping can be substantially reduced by utilizing a modified form of plane table photogrammetry. This technique employs photographs taken from the ground as the base upon which details are recorded. The information is later transferred to plan maps using the plane table principal of location by intersection (Davis and Foote, 1953). Any change in topography can be accommodated by simply taking additional photographs. Proper spatial representation in plan view can be determined later when updated maps and surveyed control are available. In addition, horizontal photographs from the ground portray vertical surfaces as they are normally viewed thus providing maximum area for recording details. Any detail which can be identified on the photograph can be located correctly even though the actual feature is physically inaccessible. The technique presented in this paper was developed by the author for special applications at Kennecott's Bingham operation in 1970. The procedure was rapidly adopted for general use and has proven to be a practical tool for detailed investigation of potentially unstable areas (Zavodni and McCarter, 1976) and routine geological mapping (Richardson, 1975). Major advantages, other than those mentioned above, include: The speed and accuracy are greater than for conventional plane table or Brunton methods. The photo- graph represents a view from a station at some distance from the area being mapped. This vantage point allows evaluation of possible continuity of structures from one level to another which may not be evident at close range. The photographic base provides a permanent record of the topography at the time

Jan 1, 1977

By B. Farshadi, B. Asi, M. J. Habibian

"In this paper, the most significant environmental aspects that are identified in the Taft Copper Project (TCP) are the quality and quantity of water, pollution of the existing watercourses and post-mining land use, matters such as air and noise pollution are deemed to be of less significance. Analysis has been performed for Do Nothing Alternative, Pre-stripping Phase, Mining Phase, Closure and After-use Phases. Analysis of the environmental assessment of TCP was carried out in three stages. In the first stage, the general negative and positive aspects of the project were identified. In the second stage the intensity, magnitude and significance of the environmental impacts of the project were identified. The third stage is related to the final conclusions of the assessment team and the relevant reasoning. A modified Leopold Matrix was adopted for evaluating the significance and magnitude of the environmental impacts. For this project, the matrix was modified to allow the assessor to take account of negative and positive numbers."

Jan 1, 2011

By Daniel Hodouin, Claude Bazin, Sami Makni

SCOTT COULTER: Thanks, Eric. Thank you all for coming. Our first speaker today is Claude Bazin. Claude received a degree in metallurgical engineering in 1980 from Laval University in Quebec. He worked for a short time in a mineral processing plant and then returned to Laval to complete graduate studies in the field of process modeling and control. He obtained his master's degree in 1983 and his Ph.D. in 1990. In 1987 he joined Brunswick Mining, New Brunswick, as research metallurgist and subsequently process control engineer. In 1990 he joined Helzfield Mines, New Brunswick, as senior metallurgist. In 1991 he accepted a position of professor at the department of mining and metallurgy at Laval University, a position he is still holding. He's a member of the CIM, TMS, and the Society for Mining, Metallurgy, and Exploration. Claude's topic today is "On-Line Material Balance for Flotation Plants." INTRODUCTION CLAUDE BAZIN: During the last two decades, the on-stream analyzer (OSA) has gained the stat& of key instrument for the control of flotation plants. The OSA is currently used in almost every sulphide flotation plant (Leroux and Franklin 1994), and its application to oxide mineral flotation plants is increasing. The OSA assays are sent to the flotation operators via an operator console or to control loops of various degrees of complexity (McKee 1991) implemented in a distributed control system (DCS). Operators and/or controllers take control actions based on these assays to ensure an adequate operation of the plant. Although this application pays off very rapidly for the purchase of the OSA, one could ask, "Could we get more from the OSA?" Some plants reported the use of OSA measurements for process optimization (McKee 1991). The optimization strategy is based upon economic indices calculated from metal recovery using the 2-product formula (Wills 1992, p. 124). The 2-product formula is sensitive to measurement errors in the assays and can lead to considerable scatter in the calculated indices (Hodouin et al. 1993). Least squares algorithms provide a robust alternative to filter out measurement errors (Spring 1992). This paper presents some applications of a recursive least squares algorithm that provides real-time estimates of the mass flow rates within a flotation plant using OSA and mass flow rate measurements.

Jan 1, 1998

By Peter W. Scott

Feldspars have major uses in glass manufacture and in ceramic products. About 6 million metric tons (6.6 million short tons) are used annually. Feldspars are desirable because of their high aluminum and alkali contents. Na feldspars are favored for glass, while K feldspar is often preferred in the pottery and tile industries. Economic deposits occur in a variety of geological environments. Most are in granites or granite-like bodies, pegmatites being a common source worldwide. Alkali granites, particularly those some- times called alaskites, are mined directly as a source of feldspar and associated minerals. Some other igneous bodies, such as aplites, rhyolites, and partly altered granites (for example china stone) provide alternative feldspar-rich products. Nepheline syenites and phonolites are other sources of feldspar and contain higher amounts of alkalis. Feldspar-rich (arkosic) sediments derived from the weathering of pegmatites and granites are widely extracted and processed for use in ceramics. The present study reviewed the various sources of feldspars throughout the world. Data on the quality of products has been taken from literature, and samples have been obtained from a large number of producers. The mineralogy and chemistry of the samples has been determined and, as far as possible, have been related to the geology of the source area. Feldspar products show a wide range of chemical and mineralogical compositions. Some are pure Na feldspar (albite), others are made up entirely of K feldspar (microline and orthoclase), but many are mixtures of Na and K feldspars. Significant quantities of quartz are often present, and many products contain mica and kaolinite. Fe203 con- tents are very low, typically less than 0.1 percent. Detailed mineralogical studies show that four groups of products can be recognized on the basis of feldspar mineralogy. These are albite, albite with microcline, microcline with orthoclase, and orthoclase with albite. Products containing microcline and orthoclase together are mostly sedimentary in origin. Those with albite only, or albite with microcline have a pegmatitic or granite origin. Those containing orthoclase as the dominant K feldspar are derived from aplites or rhyolites. There does not appear to be any relationship between the feldspar mineralogy and the quartz content. Peraluminous S- type granites and pelite-dominated high-grade metamorphic rocks, in which there is a significant volatile component, are likely to be the most important feldspar sources. Partial kaolinization of feldspar-containing rocks often improves minability, decreases crushing costs, reduces iron content, and increases the K2O/Na2O ratio.

Jan 1, 2001

By K. V. Raj, A. T. Weakley, A. L. Miller, D. A. Parks

Diesel particulate matter (DPM) is a common and well-known health hazard in the mining environment. The current approved method for monitoring both the organic and elemental carbon (OC, EC) portions of DPM is a laboratory method with a turnaround time of approximately one week. In order to evaluate exposure levels and take corrective action before overexposures occur, a portable real-time device capable of quantifying both OC and EC is needed. To that end, researchers from the National Institute for Occupational Safety and Health (NIOSH) designed and tested a device based on narrow bandpass optical filters that is capable of targeting infrared absorbance bands associated with DPM. Five optical bandpass filters were chosen based on previous work quantifying DPM using Fourier-transform infrared (FT-IR) spectrometry. The resulting device, referred to as a filtometer, is optimized to exclusively determine DPM and could serve as a cost-effective, field-portable alternative to laboratory-grade FT-IR analysis and instrumentation. The performance of the filtometer was investigated by calibrating FT-IR data from DPM (dependent variable) to the filtometer spectra (predictor variables) using a partial leastsquares (PLS) and ordinary least squares (OLS) approach. The square of the correlation coefficient and root-mean-square error of cross validation m

Mar 2, 2022

By Nelson R. Shaffer

Glamorous, burgeoning biotechnology and mundane industrial minerals would at first glance seem to share little in common, but in truth, modern biotechnology depends on many minerals. Biotechnical processes also can be used in industrial mineral extraction and processing. Biotechnology is broadly defined as the application of biological organisms, systems, or processes to manufacturing and service industries. Genetic engineering has reinvigorated one of mankind's oldest sciences, biotechnology, into a booming business. Many modern processes depend on microorganisms cultivated under very stringent conditions in bioreactors. Minerals from carbonate, sulfate, chloride, nitrate, phosphate, and silicate families are used to provide essential nutrients and to regulate growth conditions (such as pH) in order to assure optimal growth of organisms. Certain cells or enzymes perform better when immobilized upon or within solids, and minerals are often used to immobilize cells, especially in continuous process. Minerals are also used extensively in separating and purifying products of biotechnology. Diatomite, zeolites, and silica are especially useful in purification processes. Industrial minerals also are commonly used to clean up large volumes of process water that must be treated. Biotechnology can be employed in exploration, extraction, and processing of geologic materials and in reducing mining or other environmental problems through bioremediation. Microbes have been shown to solubilize certain elements and so promote extraction of heavy metals, phosphate, aluminum, potassium, and even rare earth elements. In a related technique, unwanted materials such as pyrite impurities can be leached microbially to produce cleaner products in sand and clay industries. Microbial actions can modify surface characteristics and so enhance certain ceramic properties. Certain organisms can accumulate useful elements from dilute sources; others can transform unusable chemical species to more useful forms. Deterioration of stone, concrete, and even glass or brick, can be accelerated by microorganisms. Control of such biodeterioration could improve long-term performance of industrial mineral products. Microbial processes have shown promise in improving several mine-related problems. Certain bacteria help remove clays from phosphate slimes and other suspensions. Others are used to degrade cyanide or other organic chemicals such as floatation aids. Cells immobilized on clays have been especially efficacious in bioremediation. Biotechnology industries, like the industrial minerals industries, encompass huge ranges of materials and processes. Costs of products from these industries range from pennies to thousands of dollars per unit, and their products are vital for maintaining modern life styles. Many biotechnical processes depend upon industrial minerals and certain biological processes can be harnessed to do useful tasks in the minerals field. The interplay of industrial minerals and biotechnology is important today, and as biotechnology advances, its interaction with the industrial minerals industry can only increase.

Jan 1, 1995

By Leslie E. Apodaca

INTRODTUCTION The use of spiral concentrators for processing fine coal particles is an old idea that has recently gained acceptance in the 11.S. coal industry. It was not onti1 the Australian Minerals Industry developed a spiral concentrator specifically for separating coal from ash in the latter 1970's and early 1980's that spiral concentrators were seriously considered as viable equipment for processing fine coal. The Wright Coal Spiral was introduced in 1980, the Mineral Deposits Limited Mark 10 Coal Spiral was introduced in 1982, and the Vickers Wyong Coal Spiral was introduced in the latter part of 1984. Each spiral design was different and utilized constant profile troughs, constant pitch troughs, compound profile troughs, and various splitter arrangements. Mineral Deposits Limited has combined the best features of the compound profile trough and constant pitch trough with critically-placed splitters to develop the MDL LD4 spiral concentrator which is a truly efficient coal washing spiral. This spiral concentrator was introduced into the U.S. Coal Industry in 1987. Recently, Mineral Engineering Technology of the United Kingdom and Multotec of South Africa have introduced their own coal spiral designs. Spiral concentrators were first installed in fine coal processing circuits in the Australian, South African, and Canadian Coal Industries in the early 1980's and in the U.S. Coal Industry in 1985. SPIRAL CONCENTRATOR SEPARATION PROCESS The separation process that occurs within the spiral concentrator trough is very complex, as it is a combination of three gravity separation processes. When the coal slurry first enters the spiral trough, each coal and ash particle and the water is subjected to centrifugal forces. These forces cause the water, light coal particles, fine heavy ash particles, and medium middlings particles to the outer vertical portion of the spiral trough. The coarse ash particles and the coarse middling particles remain on the inside of the spiral trough. The center or transitional area of the trough contains a mixture of middlings particles and near-gravity material that is present in the slurry, as shown in Figure 1. At the same time the coal and ash particles are suhjected to centrifugal forces, the trough design (both profile and pitch) causes the particles to be subjected to flowing film and stratified bed separations. The combination of these three separations, whose efficiency is dictated by the spiral troogh design, will effect the separation of the lighter coal particles from the heavier ash and middlings particles. As the slurry flows down the spiral, the profile and pitch design of the trough will counteract the centrifugal forces on the fine, heavy ash particles and fine middlings particles and cause them to migrate from the vertical portion of the trough to the center or inner portion of the trough. At the same time, any heavy particles trapped in the transitional area of the trough will be forced to migrate to the inner edge of the trough and any coal particles will be forced to migrate to the outer edge of the trough. SPIRAL SPLI'TTEP ARRANGEMENT The critical placement of splitters along the inner edge of the trough for removal of the heavy ash particles as the slurry flows down the trough further enhances the separation of the coal particles. At the bottom of the spiral trough are product splitters arranged to make a final separation of the slurry stream into clean coal, middlings, and refuse products.

Jan 1, 1988

By Y. Luo, S. S. Peng, C. T. Holland

Introduction A well-designed mining plan is one that minimizes cost and mining induced problems and maximizes recovery of the coal reserve. To minimize the negative effects on surface structures caused by ground subsidence due to underground mining activities, two kinds of practices are commonly employed by mine operators. One is the support technique, which leaves an area of coal unmined or partially mined beneath the structure to be supported. The other is the protection technique, which protects the structure when it is subsiding with the ground by taking advantage of the ground subsidence process (Luo et al., 1992). In designing the supporting technique, the only currently available method in the US is the one stated in the Pennsylvania Underground Coal Mining Rules (1985). However, the size of the support area designed by this method will be excessively large and result in a wasteful use of coal reserves when the overburden depth is more than 350 ft. A more scientific method is proposed in this paper for designing the support area. This method is based on a large amount of subsidence data collected throughout a number of major US coal fields and the authors' experience with monitoring and protecting surface structures that have been undermined by longwall panels. It considers the critical deformation indices that a structure can tolerate, and depth and height of underground extraction. A support area designed by this new method will not only assure the safety of the structure to be supported but will also maximize the extraction of the coal reserve. Design of support area using the Pennsylvania rules The Pennsylvania Underground Coal Mining Rules (1985) state that no underground mining activity should be permitted beneath structures where the overburden depth is less than 100 ft. An exception to these rules is provided for mine related openings that provide access to the surface for such as entries, shafts, boreholes and site-specific variances for entry development. If the overburden depth is greater than 100 ft, the mine operators should utilize either of the following: •Extraction techniques that provide for planned subsidence in a predictable and controlled manner, or •Support techniques designed to prevent subsidence damages to features identified as: •Public buildings and non-commercial structures [ ] customarily used by the public, including churches, schools and hospitals • Dwellings, cemeteries, municipal public service operations and municipal utilities in place on April 27,1966 •Impoundments and other water bodies with a storage capacity of 20 acre-ft or more • Aquifers, perennial streams and water bodies that serve as a significant source for a public water supply system, and •Coal refuse disposal areas. The support techniques require that a support area be left beneath the surface structure or feature to be protected (Fig.1). The support area should consist of coal pillars, with their size and pattern being such that their bearing strength is maximized. The total coal extraction within the support area should be limited to a maximum of 50%. The support area should be rectangular in shape and determined by projecting a line at a 15° angle from the surface to the coal seam with an offset distance of 15 ft from all sides of the structure. For a

Jan 1, 1994

By H. M. Ray

The discovery of the New Lead Belt in the mid-'50s began a search for mill design criteria that is continuously updated. The opportunity to design, construct, and operate four new mills in the span of 20 years provided fertile areas for new concepts. The central theme for design parameters encompassed simplicity, functional, and economic consideration. Ore characteristics for each plant remained relatively constant, providing stable criteria for grinding circuits. Bond index nominally 10-12. Flotation circuit parameters were based upon power application with 10-20% excess capacity built-in to protect recovery. Newer equipment exhibits greater power application efficiency lowering horsepower requirements per ton. Instrumentation was installed to stabilize circuits, protect equipment, and improve products. With ever increasing requirements of higher quality products, environmental considerations, and operating cost pressures, the upgrading of operating procedures is in a constant state of flux. Installation of more efficient equipment, chemical processing, or any other technique would be considered as feasible. Current practice is for St. Joe to design and engineer in-house its own plant design. The exception being detailing of structural steel. It is felt that familiarity with past design criteria serves as a valuable foundation to incorporate changes. Also, direct contact with operator provides specific data, and feedback for constructive criticism that is utilized for defining and correcting problems. The results are in reality an operator's plant with the benefit of advancing technology that meets the demands for improved products without sacrificing the economies of throughput or recovery.

Jan 1, 1977

By R. S. Kramer

A bulk compositional chemical analysis often provides incomplete information to help the mineral processor when faced with the problem of removing troublesome contaminants in low concentrations. Michigan Tech has developed a unique approach for addressing this problem. A combination of Scanning Electron Microscopy (SEM), Energy Dispersive Spectroscopy (EDS), and image analysis was successfully used to characterize the species responsible for phosphorus contamination of less than . 05 weight percent in iron ore. An automated routine acquired the chemical signature of each particle on a back scattered electron image. The few particles containing phosphorus were identified from the hundreds of particles examined, and the phosphate phases present were easily characterized.

Jan 1, 1993

By G. E. Wasson

Consolidation Coal Co. tested the agglomeration of fine coal using a laboratory pellet mill. The principal operating variables examined were feed coal moisture, coal size distribution, and additives to the feed coal. The moisture of the feed coal was found to be critical to both the pellet mill operability and the product strength. Coals, with feed moistures too high to pelletize, could be pelletized if mixed with lime or a water absorbent material. The addition of dry starch binder improved the product strength.

Jan 1, 1991

By Stephen W. Lambert

One of the primary interests of the United States Department of Energy's Mine Planning Division is to fully develop avenues of technical research which potentially offer positive effects on coal mine productivity. One such area of research involves the removal of methane gas from unmined portions of coalbeds through vertical wells drilled from surface locations. As coalbed methane content is reduced, less gas is available for flow into the mine, and consequently ventilation requirements are decreased and/or coal extraction rates increase. Another attractive aspect of the vertical borehole drainage method is that it presents an opportunity to recover and utilize significant quantities of methane gas, which would otherwise be wasted to the atmosphere. The viability of removing gas from the Mary Lee coalbed using stimulated vertical boreholes was first suggested by Elder and Deul as a result of a United States Bureau of Mines' drilling project conducted from 1971 to 1974 (4). Other United States Bureau of Mines' studies forecasted that degasification would eventually be necessary in the Mary Lee coalbed because most new or expanding mine development would take place at depths exceeding 1 000 feet (305 meters), where the methane problem would be severe (3) (13). In 1975 a large-scaled drilling program was designed in order to supply industry's anticipated need for a degasification technology in the Warrior coal basin, Alabama. The results of this government/industry sponsored effort were to be specifically applicable to the Mary Lee coalbed, the most extensive and economically important deep minable coal present in the area. Major technical objectives of this program are twofold: (1) to measure the effects of various well completion designs, particularly hydraulic stimulation, on mining and (2) to determine the effects of well spacing on gas drainage rates. A cooperative agreement was established with United States Steel Corporation in late 1975 and field work began shortly thereafter in the proximity of a newly developing mine near Oak Grove, Alabama. Government responsibility for this program was transferred from the United States Bureau of Mines to the United States Department of Energy in October 1977. To date, as a result of this program, twenty-one wells have been completed into the Mary Lee coalbed at the Oak Grove site. Seventeen of these wells were drilled on an experimental grid pattern located two miles from the active mine. These grid wells are primarily being used to generate data necessary to determine the effects of well spacing on gas drainage rates and will also provide a large amount of information regarding the long-term effects of degasification on mining. The four remaining wells (designated Ton through TW4) were placed near the mine so that the full effects of completion could be studied within the short time required for underground interception. Results gathered from the first two test wells (TW1 and TW2) have been reported in detail (10) and indicated that several improvements were necessary to increase gas drainage rates. Hydraulic stimulation was one of the most important aspects of well design that required improvement. Nitrogen-charged foam stimulation treatment was used at TW3 and TW4 instead of the gelled-fluid type stimulation used at the first two near-mine test wells.

Jan 1, 1980