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By D. McElhinney, J. Winfield, G. Buchan, B. Slaker, A. Iannacchione, T. Minoski, G. Rashed, M. Van Dyke, M. Murphy

"The National Institute for Occupational Safety and Health (NIOSH) has previously established pillar design guidelines for the underground stone mining industry. These guidelines were created from an empirical database of pillar observations and were largely drawn from shallow, flat-lying mining operations. Current trends forecast a great amount of underground stone mines developing under deeper cover, higher seam dips, and more frequent multiple-seam mining configurations than in the past. The complex loading conditions and limited experience in these environments presents a substantial increased risk of ground failure. To investigate these loading conditions, NIOSH has installed a pillar and roof monitoring system at an underground limestone mine in central Pennsylvania. The mine is operating in a seam with dips ranging from 13 to 18 degrees and overburdens ranging from 275 m (900 ft) to 425 m (1,400 ft). Instrumentation installed in an undeveloped pillar and in surrounding strata is currently measuring pillar and roof behavior in response to stress redistribution during excavation. Laser scans are being used to measure ground displacement and changes in conditions associated with local mining conditions and significant geological features. Initial stress measurements show a gradual increase in stress in response to mining, and stress changes that correspond with blasts. The seismic system is operational, with calibration events signaling on each of the 18 sensors. INTRODUCTION Improving mine-wide ground control stability can help reduce the potential for catastrophic failure of underground structures. The National Institute for Occupational Safety and Health (NIOSH) has conducted prior research in stone pillar design and has established fundamental pillar design guidelines for the underground stone mining industry, which resulted in the development of the S-Pillar program (Esterhuizen et al., 2011; Esterhuizen and Murphy, 2015). The data that constitute the S-Pillar program were derived from past mining experience that was almost exclusively drawn from shallow, flat-lying, single-level mining operations1. Stakeholder interactions with NIOSH researchers have indicated that increased numbers of underground stone operations are expected to mine under significantly deeper cover, with greater seam dips, and under multi-level operating conditions (Slaker and Murphy, 2016). The complex loading conditions and limited experience in these challenging environments present a substantial increased risk of ground failure. Inadequate pillar design in these new and challenging environments could result in catastrophic wide-area pillar collapses and an increased safety burden to miners working in the U.S. limestone mining industry. To develop design guidelines and prevent inadequate pillar designs for these challenging environments, NIOSH is currently conducting detailed pillar response investigations at case-study mine sites operating in challenging environments."

Jan 1, 2018

By Tomek Ulatowski

This article discusses four principal areas relevant to financing direct reduction facilities: (1) Lenders' differing requirements with respect to projected cash flows; (2) The impact of leveraging on project viability; (3) The importance of appropriate debt structure; (4) The significance of accurate and complete capital cost estimates. The overall findings emphasize the inseparable connection between the project economics and its financeability, and particularly how direcly intertwined they both are in the project planning.

Jan 1, 1978

By Michael J. Martinson

A powerful methane explosion in the mid-shaft pump station of a main service and ventilation shaft killed several persons on the station; more workers were killed when a mancage travelling down the shaft fell to the shaft bottom under a pile of broken concrete slabs from a brattice wall destroyed by the explosion venting into the shaft and a tangled mass of twisted steelwork from the equipped compartment. The newly-commissioned shaft serves a recent extension of an established mine on the Orange Free State (OFS) goldfield in South Africa. After outlining the circumstances in which the paper was written, and reviewing the nature and extent of the methane hazard in OFS mines, the paper describes the physical layout of the shaft and summarises evidence given by witnesses at the official inquiry concerning events prior to the explosion. No attempt is made to apportion blame for the incident.

Jan 1, 1989

By Austin Whillier

INTRODUCTION Use of air-cooling or refrigeration equipment in underground mines is needed when conventional ventila¬tion techniques do not maintain acceptable environ¬mental temperatures in working areas. Because refrig¬eration can be very expensive, it should be implemented only after all possible and practical steps have been taken to eliminate or reduce heat sources in the mine. As an example, to prevent the main ventilation fans from contributing heat to mine air, they should be located in the air return and not in the air intake. It is particularly important to prevent any direct contact between hot water and ventilation air, especially in mines which encounter large flows of hot fissure water. Any water hotter than the prevailing wet-bulb temperature of the ambient air must be removed by pipes located as close as possible to the water source. This hot water must not be allowed free contact with the incoming ventilation air at any time during the water's passage out of the mine. Although insulation of the pipes carrying the hot water is seldom necessary, direct contact between the air and the water must be prevented so the warm water cannot evaporate. REVIEW OF COOLING PRACTICES Spot Coolers vs. Centralized Refrigeration To eliminate a few specific hot places in an otherwise cool mine, it is possible to use devices known as "spot coolers." A typical spot cooler that uses chilled water is shown in Fig. 1. These devices consist of self-contained refrigeration units that are often mounted on rail cars for haulage to hot spots. The cooling capacities of such spot coolers usually are limited to about 100 kW or 30 "refrigeration tons." A refrigeration ton represents a cooling rate that produces 1.0 st of ice in 24 hr; that is a cooling rate of 3.517 kW (200 Btu per min). Typically, the electric-power consumption to drive the compressor motor of the refrigeration plant in mines is 1.0 kW per refrigeration ton, corresponding to a coefficient of per¬formance of about 3.5. The principal difference between spot coolers and centralized refrigeration plants is the method of re¬jecting heat from the refrigeration system. Centralized refrigeration plants always discharge heat into the reject or return airflow of the mine; often that is the primary influence in selecting the location for the underground refrigeration plant. Heat from spot coolers usually is rejected into drain water or into air that is not flowing to the location requiring the cooling. As a result, spot coolers remove heat from troublesome hot spots in the mine, injecting that heat-plus the electrical energy used by the cooling unit itself-into other working areas where the ambient conditions are cooler. In effect, this is "robbing Peter to pay Paul." In deep, extensive mines, spot coolers usually pro¬vide only temporary and, over the long term, expensive solutions to localized cooling problems. Centralized re¬frigeration plants are preferred for such mines, with cooling distributed throughout the mine as required. Fig. 2 illustrates a typical underground centralized re¬frigeration plant. Centralized plants lend themselves to improved maintenance at reduced costs while offering the economy of size. Refrigeration plants of larger unit sizes have considerably lower initial costs than smaller unit sizes. The remainder of this chapter is devoted to large refrigeration plants, with no further consideration of spot coolers. Cost of Refrigeration Total Cost: The total cost of refrigeration amounts to about $200/kW of cooling per year (1981 US $). This total cost breaks down into approximately three equal parts: 1) Financial charges, which include the interest and amortization on the capital cost of the initial installation, and the cost of necessary underground excavations. 2) Operating and maintenance costs which include the cost of the electric power to drive the refrigeration plant's compressors. 3) Distribution costs which include costs for pump¬ing, insulated piping, and air-to-water heat exchangers. The local cost of electric power, the number of operating months per year, and the method of refrigera¬tion distribution all contribute to the actual costs in¬curred in a given application. However, the variations usually are limited to no more than ±30% of the $200/ kW per year total cost figure. Cost Per Ton: Refrigeration cost per ton of mineral production can be calculated if the annual production tonnage from the refrigerated section of the mine is known. In most cases, this cost will be less than $1 .00/t. However, in deep mines with high rock temperatures, such as those found in South Africa, the total cost of refrigeration can increase to several dollars per ton of broken rock. Distribution In deep extensive mines, distributing refrigeration often accounts for about half the total cooling costs. As a result, careful consideration and planning must be

Jan 1, 1982

By A. L. Putz, G. Ladouceur, A. R. Laplante

A laboratory centrifugal concentrator was used to evaluate two gravity circuit configurations treating a flash flotation concentrate at a Canadian gold mill. The Initial circuit consisted of a 76 cm (30 Inch) plant Knelson Concentrator (PKC) for coarse gold removal. Later, a hydroseparator and spiral were Installed, with the hydroseparator underflow feeding the spiral and the spiral tailings plus hydroseparator overfiow reporting to a 51 cm (20 Inch) PKC. Gold recovery In the 76 cm PKC averaged 45%. Gold was recovered consistently In all size fractions greater than 38 µm, where recovery dropped to 22% for the -38 µm material. Changing the circuit to Include the hydroseparator and spiral decreased the Knelson unit recovery to less than 17%. The decrease was attributed to the spiral which recovered much of the free gold ahead of the Knelson and to changes In the mill feed (free gold portions were finer and less abundant). The spiral demonstrated erratic behaviour although It still recovered significant coarse gold (+75 µm) yielding unit recoveries of 18-44%. Although mechanical difficulties were experienced with the 76 cm PKC, Its performance was superior to that of the hydroseparator, spiral and 51 cm PKC configuration. Much of the gold In the ball mill recirculating load was found to be too coarse for significant recovery In the flash flotation cell and should be recovered by gravity from the cyclone underflow or ball mill discharge. The LKC proved to be a successful device to evaluate gravity recoverable gold content. Dilution of test samples with silica further enhanced this methodology.

Jan 1, 1993

By Gary P. Thomason

We have all heard a great deal about how various projects were financed or certain companies were successful in obtaining a bank loan. There are many more projects and companies who fail to get the money they need. At least a portion of these failures, and a large percentage of the frustrations connected with even the successful financings, are a result of not understanding the process of obtaining money. Recent years have seen a proliferation of sources available to finance minerals operations, but let me assure you that these represent only a minor portion of the minerals financing market. The fundamental source of borrowed money to almost all minerals related companies remains the banks. Therefore, understanding the "Loan Approval Process" can easily mean the difference between getting the money or not. In the following pages I hope to provide some insight into what I define as the loan approval process. Having pre-offered my definition, I intend to delineate the various stages of the process and the planning and information I believe should be contained in each. My ultimate goal is to help you think like a banker and, in so doing, stay on top of the process so that you can successfully obtain the funding necessary for your projects.

Jan 1, 1983

By J. M. Beck

Mineral property appraisers engaged in eminent domain actions on properties for which mining is the highest and best use must be fully competent in all phases of mineral resource estimation, mine project development, and mine operations (or retain the requisite competent assistance), as well as educated in eminent domain appraisal (USPAP Competency Rule). Failure to ensure such triggers the issue of appraisal competence and demonstrates a flagrant disregard of the myriad code(s) and guidelines to which the appraiser is subject. The cavalier assertion of some vague, undefined “latitude” in the valuation process does not exonerate the appraiser from a disregard of the USPAP Competency Rule. Lack of independence (i.e., “advocacy”) in mineral property appraisal is the usual result of a weak background in mining and/or appraisal theory. While it is readily apparent to those able to recognize it in reports and testimony, judges and juries cannot be expected to detect or recognize purposefully misleading (or even fraudulent) valuation concepts or testimony. Purposeful deception by the appraiser can lead to specious over-compensation of the property owner (thus victimizing the taxpayer); or, a failure to provide appropriate and just compensation to the property owner – yet, the purpose of an eminent domain proceeding is to leave the property owner no richer or poorer as a result of the taking. This paper highlights some of the deceptive practices encountered in litigation settings and raises issues of competency, professional ethics, and the effectiveness of the inherent enforcement capabilities within those institutions awarding professional certifications. INTRODUCTION The practice of eminent domain mineral property appraisal requires (particularly with respect to undeveloped mineral properties) that the appraiser possess the requisite level of competence in all phases of mineral resource estimation, mine project evaluation, mine development, and mine operation (through closure). To the extent the appraiser lacks such competence, it is incumbent on the appraiser not only to divulge this lack of expertise but also to seek competent assistance in the performance of the appraisal. This competence or expertise can only be obtained through a combination of appropriate and relevant technical education and direct mining industry experience. There exist a number of professional certification and/or credentialing authorities that speak to such competency. In a similar manner, eminent domain mineral property appraisal (as the term implies) also requires that the appraiser possess the requisite level of competence in the practice of eminent domain appraisal. This competence or expertise can only be obtained through appropriate and relevant education, direct knowledge of appraisal theory, particularly as it relates to the concept of eminent domain, and licensure.

Jan 1, 2019

By J. G. Pippenger

The Coteau Properties Company's Freedom Mine is a surface lignite mining operation located near Beulah, North Dakota. Coteau, a wholly owned subsidiary of The North American Coal Corporation, produces more than 13.5 million tonnes per year, ranking it among the largest mines in North America. In 1993, Coteau ranked seventh in terms of annual coal sales, becoming the largest mine outside the Powder River Basin of northeastern Wyoming. However, for the Freedom Mine to stand among these Powder River heavyweights, Coteau over-came several obstacles, including a coal seam with three quarters the heating value and overburden to coal ratios three times higher than the Powder River mines. Coteau's ability to compete has been built around a program of continuous productivity improvement, cost efficiency, and innovation. This report highlights a few of the major improvements implemented in recent years.

Jan 1, 1995

By T. Carageorgos

The removal of arsenic from process streams as ferric arsenate compounds is being practised by mining industries. Therefore, the solubility and stability of these solids is of considerable importance to the mining plants that have to keep the environment free from pollutants. There is some information on the solubility of the ferric arsenate compounds, mainly on scorodite, obtained from synthetic solution. However, there is not so much work on ferric arsenate compounds formed at high temperatures (175 - 230°C) during the leaching process. In the present work, the solubility of the ferric arsenate compounds formed during acidic pressure oxidation of arsenopyrite is presented. The results of the solubility tests showed that the ferric arsenate compounds formed at high temperatures (200 - 230°C) and high pressures (1034 - 1551 kPa 0,) released arsenic into solution in amounts less than 1.2 ppm and iron in amounts no higher than 1.0 ppm. So, they seem to be potential compounds for arsenic and iron disposal.

Jan 1, 1998

By Larry D. Wayland

Almost 100 sedimentation ponds were conceptually designed for a large surface mining study area in northeast Texas. An approximate procedure was developed to economically estimate construction quantities in order to predict surface water control costs. This procedure utilized site-specific empirical relationships developed from detailed analyses on a representative number of proposed sedimentation ponds. Use of these equations provided earthwork volumes, and spillway pipe lengths. The procedure developed for this study is presented along with the results of a verification analysis.

Jan 1, 1983

By Morley H. Mathewson

The unprecedented demand for capital investment in the mining industry today has intensified management's interest in every known technique which will help to reduce operating costs and increase production. One proven approach leading to the accomplishment of this objective is well known in the mining industry and is gaining added prestige, particularly where keen competitive conditions exist. This approach is in the area of incentives applied to mining productivity. An investigation of many incentive plans now in use throughout the mining industry revealed a predominant number of conventional type plans, Most of these plans are designed to reward the hourly-paid employee on the basis of percent over and above a standard hourly or daily ton rate, By contrast, this search failed to divulge any incentive plan solely and independently developed for production management employees. This does not mean that such plans in the mining industry are nonexistnet, but it does indicate that production management incentive systems are scarce or are being kept under wraps.

Jan 1, 1960

By Robert Marks, Enrico Dal Negro, Richard Schulkins

"In July 2012 construction started on the Grosvenor project, a five million tonne per annum underground longwall mine planned for Moranbah in Central Queensland. Grosvenor is located immediately to the south of the existing Moranbah North mine which has been in operation since 1998. EPBM technology is being used for the first time in Australia for excavation of a coal drift. The TBM was used to build two drifts on the project, one for the coal conveyor which will transport to surface, and another for people and equipment to access the underground once the mine’s operational (as shown in figure 1). The TBM will pass beneath a steel archway roof that has been installed at the drift’s entrance and begin drilling into the ground to build the seven metre diameter tunnel, descending at an angle of one in eight until it reaches the depth of the coal seam approximately 160 metres below.INTRODUCTION AND BACKGROUND The first TBM used in a coal mine was in 1962, a Wohlmyer, in Westerholt, Germany. A further 75 km of tunnels were excavated in coalmines within Germany between 1971 to 1983. This paper will review the Grosvenor Mine project (Grosvenor) owned by Anglo American Metallurgical Coal (Met Coal) includes the construction of a new underground coal mine and surface facilities on the northern boundary of the town of Moranbah in the Central Queensland Bowen Basin coal precinct. The contract to undertake the underground development works was awarded to Redpath in 2012. The scope of the Grosvenor Project was to construct temporary office and workshop facilities, install 2 portal arches, backfill boxcuts and infrastructure, excavate by EPBM method 967 m of 1:6 gradient Conveyor Drift and 1,258 m of 1:8 gradient Transport Drift, development of 2,520 m of pit bottom area roadways and development of 10,550 m of the first longwall tailgate. In the following figures 2 and 3, is possible to see the aerial view of the job-site."

Jan 1, 2016

By M. A. Schimmelpfennig, A. D. S. Gillies

M.J. McPherson Having worked on the thermodynamics of air/liquid-water mixtures passing through the surface fans of deep mines, I find this paper of great interest and congratulate the authors on producing it. There are two matters, however, deserving discussion. First, the authors have described the classical theory of fog formation with fogging occurring at "supersaturation." In fact, the process of fog formation begins well below 100% humidity. The more strongly hygroscopic nuclei in the atmosphere will attract water molecules and begin to grow at a relative humidity perhaps as low as 70%. The process is a dynamic one with both condensation and evaporation taking place throughout the mixture on microscopic liquid surfaces. As saturation is approached, the rate of condensation accelerates rapidly producing the familiar reduction in visibility. Hygroscopic nuclei are present in all natural atmospheres and under the appropriate conditions of pressure and temperature, will produce clean fogs. However, if the air is polluted by particulates from combustion or other processes then the resultant coagulation with growing liquid particles may produce dense (and sometimes photochemical) smogs. It is this process that is likely to occur in underground mines when moist air is cooled below dew point. Second, the authors have summarized very well the individual measures that might alleviate the problem. In particular, I agree that neither heating nor refrigerating the air, by themselves, provides a satisfactory solution. However, there is a combination of these that provides a neat and effective control of fog formation. This involves a small, self-contained refrigeration unit within a duct but without the usual external heat rejection facility. The air is cooled below dew point and, hence, dehumidified on passing over the cold evaporator coils. The heat from the condenser is rejected back into the air downstream from the water eliminator, as shown in Fig. 1. The duct configuration can be designed to create good mixing at the outlet. I have used a climatic simulation program to illustrate the effect, assuming a 500-m (1,640 ft) long airway of cross section 60 m2 (645 sq ft), an airflow of 9 m3/s (318 cu ft per sec), inlet conditions of 19/19.25°C (66/67°F) wet bulb/dry bulb temperatures, a virgin rock temperature of 17°C (63°F) and typical rock thermal properties for a hard-rock mine. I have also assumed that 10% of the rock surface is wet. Figure 2 shows the variation in temperatures along the airway if no measures are taken. The relative humidity remains close to 100% and condensation will occur throughout the length of the airway. Before any such installation is designed, the exercise must, of course, be repeated for each location with accurate data. However, this example demonstrates the potential of the system. The idea is not new - the principle is sometimes used in air-conditioning plants for buildings. Figure 3 shows the effect of removing 30 kw of heat by evaporator coils sited 40 m (131 ft) along the airway and rejecting that heat (plus another 10 kw of compressor and fan power) into the air at 60 m (197 ft). Condensate water is produced, at a rate of 0.45 L/min (0.12 gpm). The result of this sequential cooling/dehumidification/heating process is to separate the wet and dry bulb temperatures along the length of the airway. The relative humidity increases from 80% at the duct outlet to 92% at 500 m (1,640 ft). The airway is maintained free from fog.

Jan 11, 1983

By B. M. Eiter, J. Hrica, D. R. Willmer

"Mineworkers are routinely tasked with making critically important decisions about whether or not a hazard presents an imminent danger. Researchers from the U.S. National Institute for Occupational Safety and Health collected formative data to investigate mine safety professional perspectives on workplace examinations, which revealed a potential gap in how mineworkers are assessing risk. During interviews, participants revealed not having a systematic methodology for mineworkers to use to determine if a hazard is considered imminent danger. In this paper, we identify and describe three distinct categories of imminent danger complexity and discuss potential steps that could lead to improved identification of imminent danger situations. Finally, we identify potential practices to incorporate into risk management efforts, including feedback, communication and specialized training, to increase awareness of imminent danger situations. IntroductionIn recent years, the metal and nonmetal mining sector, as categorized by the U.S. Mine Safety and Health Administration (MSHA), experienced an increase in the number of fatalities occurring at mine sites. From 2013 to 2015, 69 mineworkers were fatally injured, twice the number of fatalities in each of the previous two years (MSHA, 2015a). As a way to address this increase, MSHA issued its P15- IV-01 program policy letter, suggesting that “miners would benefit from rigorous workplace examinations conducted by experienced and trained examiners” (MSHA, 2015b). The goal of these examinations is to find hazards in the field and mitigate them before they cause injury or death to mineworkers. While it is important to identify all hazards in the workplace, it is critically important to identify those hazards that are considered imminent danger because they require an immediate response to avoid a severe or even fatal injury."

Jan 9, 2018

By F. Alsobrook

Coleman Quartz Inc. has a long history as the sole U.S. producer of lascas for the cultured quartz growing industry based on its unique deposits in Arkansas. Since 1989 the company has also been producing metallurgical grade silica for the ferrosilicon industry from a deposit of unusually pure Arkansas novaculite. This paper chronicles Coleman's trans-formation of an abandoned railroad ballast quarry into a generator of $1.5 million in annual sales to a nontraditional novaculite market. Potential additional applications for this high quality silica rock will also be mentioned.

Jan 1, 1992

By Alena Johnson

"Much of the copper being produced today uses heap leaching, where pure metal is extracted from the ore with a chemical process rather than smelting. This technique is deployed extensively in major copper producing areas including Chile, Peru and the southwestern United States.Copper ore is excavated from the ground, crushed and then spread in uniform layers on a pad. A slow trickle of sulfuric acid is distributed over the pile, where it percolates to the bottom and a collection point. The acid leaches out the copper, along with other minerals, which can be extracted chemically. This process can be used at large sites producing 100 kt/a (110,000 stpy) and greater.Production on a massive scaleProduction at heap-leach sites is continuous and can operate on an enormous scale. The ore is fed into a crusher to break down the large pieces, and then it moves into an agglomerator to capture the fines and create more uniform particles. While in the agglomerator, the ore is mixed with acid for the first time, helping it to bind the fines into larger particles and starting the leaching process. The treated ore moves by conveyors to a stacker designed to spread it uniformly on the pad.The size of the operation comes into perspective by considering a typical pad measures 1.6-km (1-mile) long and 0.8-km (0.5-miles) wide. Working day after day, the stacker creates individual piles or modules on the pad, each 122 x 61 m (400 by 200 ft) and 3 m (10 ft) deep. When one module is filled, it moves across the pad to the next, filling the area in one continuous pile. A completed row of modules spanning the width of the pad is a cell. Once the entire pad is covered, the process begins again laying down another 3-m (10-ft) layer, and it continues until the entire pad reaches its height limit which can be several hundred feet.Once a new module is completed, technicians lay a network of plastic pipes over the surface in a pattern similar to agricultural drip irrigation installations. The diluted sulfuric acid, called raffinate, is pumped through the pipes so it can be distributed over the module, allowing the acid to soak through the ore and leach out copper as it percolates to the bottom. At the same time, approximately 35 to 45 percent of the acid is consumed by dissolving the calcite carrying the metal in the process. The raffinate reaching the bottom is now characterized as pregnant-leach solution (PLS) since it carries the copper the company is seeking to recover."

Jan 10, 2018

By H. M. Park

Risk is a major factor in all mining activities, arising from many internal and external variables. The authors? research has resulted in a systematic method for the quantification of risk in mining projects (Park, 2012), and this research is being presented in a series of papers. The first paper (Park and Nelson, 2013a) identified the variables associated with risk in mining projects, and their effects and was published in the October issue of Mining Engineering magazine. The second (Park and Nelson, 2013b) discussed methods of assessing the overall risk associated with those variables (published at www.me.smenet.org), and presented a statistical model based on a survey of 31 experts. This paper will present an evaluation of the statistical model, using data from previous mining investment decisions in which the authors have been involved.

Oct 1, 2013

By Byron C. Hardinge, Michael Sokaski, Paul F. Sands, W. Loring III Mc Morris, David J. Akers

INTRODUCTION In the early days of coarse-coal cleaning by the dense-medium process in Europe, loess was one of the materials used for medium solids. Newly developed cyclones were used to reclaim and thicken the loess suspension. On occasion, when the cyclone thickener at the Maurits mine in the Netherlands plugged, the overflow was found to be filled with clean coal free of impurity. From this observation stemmed the concept of the cyclone as a cleaning device. Development took place during World War II in the laboratory of the Dutch State Mines under the direction of M. G. Driessen. A 15-tph (13.6 t/h) pilot plant was in operation in the laboratory by 1945, when, in September, Driessen made the first public disclosure of the process in a paper presented to the Institute of Fuel in London.51 In April 1945, operation of this pilot plant was observed by H. F. Yancey, who was so impressed with the potential of the cyclone process that, on his return to the United States, a research program on the cyclone was immediately started by the US Bureau of Mines (USBM). This work led to an AIME paper in 1946 in which the first details of cyclone operation on American coals were made available.52 Commercial adoption of the cyclone proceeded in Europe, initially in the Netherlands, Germany, and France. In the United States, where coal is less costly and most of the coals are easy to clean and respond well to simpler cleaning processes, the first cyclone plant was not built until 1961.53 THEORY Before discussing the theory of a dense-medium cyclone, a brief description may be helpful to some readers who are not familiar with its basic operation. In a typical dense-medium cyclone, illustrated in Fig.7-51 a mixture of medium and raw coal enters tangentially near the top of the cylindrical section, thus forming a strong vortical flow. The refuse moves along the wall of the cyclone and is discharged through the underflow orifice. The washed coal moves toward the longitudinal axis of the cyclone and passes through the overflow orifice, or vortex finder, to the overflow chamber. Washed coal is discharged from this chamber, usually through a tangential outlet.

Jan 1, 1991

By T. M. Storer

Much has been written and many discussions held on the virtues (and evils?) of a Company-owned motor fleet. Almost invariably these dialogues take a generalized form and thereby lose something since the individual circumstances, geography and philosophy - particularly in diverse industries, is never quite the same. In considering the nature of my remarks today, I felt a departure from the general approach might be in order, and in lieu of that, will attempt to present a concise picture of how we in the Lehigh Portland Cement Company view this problem and the steps we have taken in our efforts to solve it. At the outset a word may be in order about the Lehigh Company itself, what we do, and the problems that confront us specifically as well as the cement industry at large. We are primarily a manufacturer of portland cement operating 10 plants with a total annual capacity of about 23,000,000 barrels. We market this material in 30 states, shipping both from the plants directly as well as through a system of 18 distribution terminals. About 150,000 truckloads of cement are shipped to customers each year.

Jan 1, 1969

By C. E. Chapin

The Hansen orebody is a large (1 2 million kg U3O8, 0.08% U3O8 average grade) sandstone-type uranium deposit in the Eocene Echo Park Formation of central Colorado. The deposit occurs in carbonaceous braided-stream sandstones that are part of a wet-alluvial-fan complex that prograded eastward across a narrow strike-slip basin. The Echo Park basin is one of a series of basins that formed along the east side of the Colorado Plateau as it was translated northward during the Eocene culmination of the Laramide orogeny. The valleys of east- and southeast- flowing perennial streams, whose courses were transected by the subsiding Echo Park basin, were filled with permeable volcanic and sedimentary rocks during construction of the Oligocene Thirtynine Mile volcanic field. These paleovalleys funneled large volumes of uranium-bearing ground waters through the braided-stream facies of the wet alluvial fan. Uplift of a basement horst downfan from the Hansen orebody reduced transmissivity and helped maintain a reducing environment in the Hansen area; this later became an important factor in preservation of the Hansen orebody. The horst also deflected uranium- bearing ground waters upward into the Oligocene Tallahassee Creek Conglomerate where they formed the Picnic Tree orebody (1.1 million kg U3O8, 0.09% U3O8 average grade) in an altered ash-fall tuff that is essentially barren above the Hansen orebody. Several potential source rocks for uranium are present and range in age from Proterozoic quartz monzonites of Silver Plume age to lower and upper Oligocene ash-flow and ash-fall tuffs. Uranium may have been contributed to the Hansen orebody several times from different sources. Uranium and thorium analyses of ash-flow tuffs indicate that ample uranium was released during cooling and ground-water leaching to form several Hansen orebodies. The host sandstones are conspicuously altered, and their initial high permeability has been greatly reduced by precipitation of intergranular cements, especially clays and opal C-T. The alteration and cementation mineral assemblages and the chemical composition of stagnant ground waters recovered from pump tests indicate that uranium deposition occurred under alkaline, reducing conditions preceded and/or accompanied by bacterial production of framboidal pyrite.

Jan 1, 2013