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By Eric Monrad

Discrete event simulation modeling provides a tool to quantify the throughput capacity of stockyards. Interactions between the main equipment types (trains, dumpers, conveyors, stackers, reclaimers, shiploaders) can be captured, including route blockages, breakdowns, and planned maintenance. Simulation has been successfully used at world-class stockyard facilities to determine current capacity and to identify gains resulting from improvement projects. Recent projects have focused on iron-ore, coal, and soya facilities, but the technology is suitable to be used on any bulk material type.

Jan 1, 2008

By Norman D. Harte, George W. Holl

The development of the most important tool used in Site Testing is reviewed briefly and the application of the information gained is described. The operation of Site Testing and pregrouting of underground excavations is dealt with in detail. Practical experiences (and pitfalls into which the inexperienced might fall) are recorded. But for the application of Site Testing and grouting of shafts, tunnels and other excavations, vast areas of the present goldfields in South Africa would remain unexploitable.

Jan 1, 1981

By R. L. Grayson

The Office for Mine Safety and Health Research, National Institute for Occupational Safety and Health is responsible for providing research leadership in the prevention of mining work-related illness, injury and death. Planning of the NIOSH FY99 research program focused on the comprehensive collection and risk analysis of fatality, injury and illness data according to commodity and mine type. This data, coupled with the mapping of information obtained from stakeholder meetings over several years, provided the basis for prioritizing research needs. Results of the combined analysis were compared to the FY98 program to identify surveillance and research gap areas. The FY98 research program was then assessed according to commodity and mine type and compared with exposure assessments, traumatic fatality rates, injury rates and employment trends in each commodity-mine type combination to gain insight into the potential balance of the future research program. This paper presents the methods, data and results of this planning process.

Jan 1, 2002

By J. N. Adamson

The Alcan Smelter project at Lynemouth on the Northumbrian coast draws cooling water for the power station through shafts and tunnels from the North Sea. The sea at this part of the coast is frequently very rough and even in calm weather the coastal currents are strong. The adjacent coal mine makes use of these currents to disperse colliery waste and discharges into the sea some thirty thousand tons each week. In consequence the sea bed is continuously shifting and the sea is black and turbid. Construction of sea shafts under these conditions presents difficulties as drilling from a floating vessel is hazardous and sea bed activity of divers is greatly hindered by the entire absence of visibility. After considering several alternatives a method of construction was agreed with the Consultants in which the drilling and also the lining of the shaft would be completed in sequence from an eight legged work barge (GEM 126). Each shaft would be drilled to full depth and a steel cylinder, with its ends closed temporarily, would be lowered into the hole and grouted into the formation to form a full-length permanent lining. The bell mouth for each shaft would be constructed in advance to form part of the cylindrical casing. On interception of the shaft by its appropriate tunnel the lower end of the cylindrical casing would be cut away and the internal walling of the shaft installed from below. After completion of construction the shafts and tunnels would be flooded and the bell mouth sealing covers removed by divers.

Jan 1, 1997

By Shamsuz Zaman, Barry Hansen

The major development in the evolution of the conventional subaeration flotation machine has been the steady increase in the size of the individual units. In 1950, large machines were of 1.35 m3 (48 ft3) volume capacity. In 1989 the largest volume capacity operating is 85 m3 (3,000 ft3 ) These improvements have enabled the mining industry to operate successfully in the face of declining ore grades and adverse metal prices. This paper describes the design features and performance characteristics of a number of significant flotation machine designs.

Jan 1, 1989

By Erich U. Petersen

Discussion by Erich U. Petersen Harbuck et al. (1990) present results of research on sulfuric acid leaching of a germanium-gallium ore and shed considerable insight on possible extraction methods for gallium and germanium. However, the presentation does not give sufficient details to evaluate the research, so some of the conclusions may not be as applicable as stated. The objective of this communication is to indicate that relevant and easily obtainable geological and technical information was omitted. Consequently, on this basis, alternative explanations for some of the data are possible. Discussed below are the omission of: • pertinent geological, mineralogical and geochemical literature; • details regarding the determination of germanium concentration in quartz by electron microprobe; and • details on the calculation of the amount of germanium locked in quartz. "These topics are important since the determination of the amount and locus of "unrecoverable, locked germanium" may have an important impact on the economics and methods of germanium extraction and the directions of future research. Harbuck et al. state that "A key to increasing germanium extraction is understanding the mineralogy of the ore." However, only two studies are cited that in some manner describe the mineralogy of the ores. In addition, both of these studies were very preliminary, of limited scope and examined very few

Jan 1, 1993

By V. Matthews

"INTRODUCTION Typical grinding electrification requirements are defined by high power, constant torque and slow speed. Dual pinion mills also include a need for tight tolerances in torque between the two motors, to avoid overloading any single motor. Standard induction (asynchronous) motors have often been used but only in combination with mechanical gearboxes (reducers), required to reduce process speed to the correct level for mill pinions. The gearbox introduces added system complexity, capital cost, maintenance and energy cost due to mechanical losses. SYNCHRONOUS AND ASYNCHRONOUS MOTORS Elimination of the gearbox requires a motor designed to operate at a very low speed (rpm). Traditionally, mill motor requirements were best served by synchronous motors. The benefits of synchronous motors include- • Higher Efficiency (no conductor losses in rotor) • Very high power at low speed • Flexible Power factor (leading or lagging) • Constant speed (not load dependent) • More accurate speed control Synchronous motor cost is higher due to construction complexity, need for exciter and excitation panel, brushes, brush lifters. Figure 1 represents the equivalent circuit for a synchronous motor.Asynchronous motors, also known as squirrel cage induction motors, are singly excited, per Figure 2, the resulting equivalency circuit is less complex and only in need of a single voltage source.Commonly, a DC voltage supply is connected to the rotor (both physically and electrically) via brushes. The DC voltage enables the production of flux in a single direction. The brushes are connected to rings. The slip rings encircle the rotor but are insulated from the rotor. The slip rings are connected to a rotor winding known as a field winding. On large motors, brushless exciters are often used. A brushless exciter is a small AC generator whose field circuits are mounted on the stator and armature circuits are mounted on the rotor shaft. The exciter generator’s 3-phase output is rectified to DC by a 3-phase rectifier (mounted on the shaft) and fed into the main DC field circuit. It is possible to adjust the field current on the main machine by controlling the small DC field current of the exciter generator (located on the stator). [1] Brushless synchronous motors are often preferred over the traditional brush design but introduce additional complexity to motor construction in the form of additional windings and rectifiers comprising the excitation circuit. It stands to reason that because of the additional complexity, a synchronous motor will be higher in cost than an equally rated asynchronous induction machine."

Jan 1, 2015

By F. N. Kissell, N. I. Jayaraman

Dust scrubbers on continuous miners are steadily gaining in popularity. Recent US Bureau of Mines research on scrubbers is reviewed, with emphasis on development of a new type of water-powered scrubber that can be retrofitted to existing miners; comparison of scrubber effectiveness with blowing and exhaust line ventilation; and improving the quartz dust collection of flooded-bed panels.

Jan 1, 1991

By Steven H. Brown

Ore bodies which were once uneconomical to mine by conventional methods such as tunneling or open pits, have become attractive due to the development of nonconventional techniques, involving considerably less capital expenditure. Technologies such as uranium solution mining or in-situ leaching, have enabled commercial scale mining and milling of relatively small ore pockets of lower grade, and may make a significant contribution to overall U.S. uranium supplies during the next 20 years. Commercial size solution mining production facilities have operated since late 1975. Solution mining involves the pumping of ground water, fortified with oxidizing and complexing agents into an ore body, leaching and solubilizing the uranium in-situ, and then pumping the solutions to the surface where they are fed to a processing plant. Processing involves ion exchange, precipitation, calcining, and packaging operations. This paper presents an overview of the solution mining process and the health physics monitoring programs developed over the last four years at several production facilities as a result of the radiological character of these processes. Although many radiological aspects of the process are similar to that of conventional mills, conventional-type tailings as such are not generated. Some special monitoring considerations are presented which are required due to the manner in which radon gas is evolved in the process and the unique aspects of controlling solution flow patterns underground. An overview of the major aspects of the health physics compliance and monitoring programs that have been developed are discussed.

Jan 1, 1981

By V. C. Rogers, K. K. Nielson

INTRODUCTION An evaluation of the radiological health risks from uranium mining and milling requires the determination of several key parameters. As shown in Figure 1, the first step is the estimation of the radioactive source term. The radionuclides in the ore consist of the 238U decay series nuclides shown in Figure 2, the 235U series nuclides, and 40K. The 238U decay series isotopes dominate the source term, with the 235U series isotopes causing less concern and 40K remaining at background levels. [ ] Specifically, the risks from uranium mining and milling are mainly associated with 230Th, 226Ra, 222Rn, and its short-lived daughters. These radioisotopes are mainly alpha-particle emitters; hence, some dispersion mechanism is necessary to bring them into intimate contact with man so that they can be inhaled or ingested For water pathways, the leaching of the isotopes from [ ] the solid ore or tailings provides a measure of the amount of contaminant initially available to the environment. For the air pathway, dust-creation mechanisms such as blasting, crushing or general resuspension processes dominate for 226Ra and 230Th. However, 222Rn, being a chemically inert gas generated from the decay of 226Ra, can migrate through the ore, overburden and tailings over considerable distances. As shown in Figure 1, the next step in the pathway to man is environmental dilution and delay. For the water transport mechanism, the delay in the isotopes reaching an accessible water supply may be considerable (several thousand years or more), but for airborne nuclides the dispersion in the atmosphere is rapid and constitutes the main mitigating factor. Considerable ventilation is provided in underground mines to dilute and remove radon and its daughters in order to keep their concentrations low and thereby minimize their inhalation by miners. The rate of uptake by both the workers and the general public is often difficult to ascertain. It involves breathing rates, rates of water consumption and other poorly-defined parameters. The final steps are the risk estimators used to predict doses and cancer rates from the inhaled radon daughters and ingested or inhaled radium. Many

Jan 1, 1981

By Joseph Cervik

Methane drainage methods can be broadly classified as surface or underground. Surface methods make use of vertical and slant holes. The underground method discussed in the present paper involves horizontal drilling from shaft bottoms and from locations along the periphery of mines. Every foot of hole drilled in coal from under- ground locations is productive and gas flows increase as hole length increases. Therefore, underground techniques have a great potential for producing large-volume flows of methane. Pumps to dewater the horizontal holes are not necessary because gas pressure forces the water out of the hole. Methane can be recovered through the use of a simple and inexpensive gas-water separator. Hydraulic fracturing, which has been used successfully to stimulate gas flows from vertical holes, has not proved practical in the case of horizontal holes.

Jan 1, 1980

By S. Saklar, i. Bayraktar

The effect of the feed size distribution on the kinetic parameters in pyrite flotation was studied. The kinetic parameters of the particular sizes were determined as a function of whether other particle sizes were present. From the data, a relation between the pyrite flotation rate and the particle size distributions was obtained. It was shown that the flotation rate constant (k) is a function of the size modulus (dt) of the Gates-Gaudin-Schuhmann distribution, and its variation may be expressed as k = a • exp(b . d,) for either individual size fractions or composite feed. Parameters a and b are dependent on the particle size distribution of the feed. Specifically, parameter a increases linearly as the distribution becomes coarser. The above relationship was also tested under conditions in which the collector (KAX) dosage was varied from 130 to 278 g/t. It was shown that the established relation was not dependent on the collector dosage.

Jan 1, 2002

By K. Terhaar, K. Prisbrey

The objective was to determine operating protocols for a lead and silver column flotation cleaner being considered for installation at Sunshine Precious Metals Inc. 's Kellogg mill in Northern Idaho. In this column, tetrahedrite and galena were floated, and pyrite and other gangue minerals, including siderite and silica, were depressed. The procedure was to develop a dynamic simulation using a linear transfer function approach. The transfer function related cause-and-effect variables such as the influence of collector and depressant dosages on recovery and grades. Bench-scale flotation tests followed by pilot column testing provided the data used to develop a linear transfer function. The transfer function was derived using a spreadsheet. This model was applied to simulate how the flotation column could be made to respond to disturbances in feed grade. The results were that xanthate, zinc sulfate and sodium cyanide were found to be suitable controls for grade and recovery. Simulations showed the best sequence of manipulations of these reagents, and these sequences are useful for future operator training. The conclusion was that linear transfer functions were able to simulate lead and silver recovery, develop scenarios for operator training and provide a foundation for future on-line control.

Jan 1, 2002

By Todd R. Taubert, Kenneth L. Bickel

The U.S. Bureau of Mines (USBM) pioneered the development of disposable filters for reducing diesel particulate emissions from permissible mining machines. The USBM is now evaluating filter media that can withstand the high exhaust temperatures on nonpermissible machines. The goal of the evaluation is to find an inexpensive medium that can be cleaned or disposed of after use, and will reduce particulate emissions by 50 % or more. This report summarizes the results from screening tests of a lava rock and woven fiberglass filter media. The lava rock media exhibited low collection efficiencies, but with very low increases in exhaust back pressure. Preliminary results indicate a collection efficiency exceeding 80 % for the woven fiber media. Testing of both media is continuing.

Jan 1, 1995

By L. J. Laughlin

The majority of non-drive conveyor pulleys use rotating shafts, and typical idler rolls use non-rotating shafts, even though both products are used to support and guide the conveyor belt and its load. This paper will explore and compare the requirements for rotating and non-rotating shaft designs and the impact of that design on the product. Additionally, it will explore how the “roller” bearing types (deep groove ball, tapered, or spherical) affect these designs.

Jan 1, 2003

By M. Karmis, C. Haycocks

Geographic Information Systems (GIS) are becoming a more commonly used tool for resource estimation as they provide not only a database management platform, but also the graphical capabilities to visualize resource characteristics. Interpolation methods used commonly in these resource studies do not typically provide a quantitative answer to the question: "How accurate is the estimate?" By comparing localized measurements at several locations to the interpolated thickness distribution used in a resource estimate, a quantitative analysis of accuracy can be obtained. The technique is demonstrated with a case study from Central Appalachia.

Jan 1, 1999

By James P. Rider, Charles D. Taylor, Edward D. Thimons

Research was conducted to investigate how ventilation of a mining face is affected when scrubber flow is greater or less than intake flow. Tests were conducted in a full-scale surface test gallery built to simulate a mining entry with a continuous mining ma- chine at the face. Methane gas was released at constant flow at the mining face. Gas measurements taken at six locations near the face were used to evaluate how well the face was being ventilated. Increasing scrubber flow resulted in lower methane levels even when scrubber flow was much greater than intake flow.

Jan 1, 1997

By R. Todd Swinderman

Impact cradles are installed below the belt in conveyor loading zones to cushion the forces from material loading. In this paper, the author will discuss the need for and then explain the new CEMA standard for engineering of impact cradles. He will review the engineering theory and work through an example to demonstrate the assumptions used in the standard do not inappropriately affect the CEMA rating system.

Jan 1, 2002

By Kalyan K. Bhattacharyya

A systematic slope design for open-pit mines has become a reality only in recent years. Advances in the science of rock mechanics, coupled with extensive use of computers, have enabled the numerical solution of slope design problems which were not previously amenable to analytical or numerical solution. This slope stability study was performed for the UJV-SB open-pit uranium mine of the Getty Oil Co., located in the Shirley Basin area, Wyoming. The purpose of the study was to determine the appropriate slope angles for a starter pit. The data generated during the mining of the starter pit would test the initial design and suggest appropriate modification in the design for future mining in the project area. There had been a history of slope failures in the open-pit uranium mines in the area due to the low competency of the overburden materials and adverse hydrological conditions.

Jan 1, 1979

By Bruce T. Stanley

Though most porphyry-molybdenum deposits lend themselves to various reserve estimating techniques, still there must exist the constant effort to not merely obtain an estimate but rather to obtain the best estimate. To answer the challenge of a complete ore reserve estimation, one must attack the problem with the purpose of obtaining the results closest to reality. What we wish to determine is simple: metric tons (short tons), grade, and kilograms (pounds) of molybdenum contained. In order to effectively accomplish this task, further consideration must be given to the ease of using the information obtained and its inherent reliability. The only known method for ore reserve estimation that supplies the needed results along with its distribution and a measure of confidence provided by sound mathematical backup is geostatistics. The following review is an example of geostatistical application of an ore reserve estimate at the AMAX Henderson mine demonstrating technique, viability, and usefulness of results.

Jan 1, 1979