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Keeping an eye on the future while honoring the past, Frank McAllister, chief executive officer of Stillwater Mining Co., and life member of the National Mining Hall of Fame and Museum, gave the keynote address to a packed house during the 23rd National Mining Hall of Fame and Museum Banquet in Leadville, CO on Sept. 11. McAllister?s company made news just days before the induction ceremony, when it was announced that Stillwater Mining would acquire Marathon PGM Corp. for $118 million (ME, Oct. page 14).

Jan 1, 2010

By P. Bevilacqua, G. Ferrara, M. C. Williams, T. P. Meloy

Tabling is an old environmentally friendly separation unit operation. This paper models shaking tables and explores the action and design of riffles on shaking tables. By reassessing riffle shape and riffle patterns, significant improvements in tabling performance appear feasible. While table sales appear at their nadir, a high-tech environmentally friendly table may have a significant market in the coming decade. Riffles on a shaking table impact particle separation. Particles are affected by riffles and their exit position on the table is dramatically changed, Riffle shape determines how much the riffle will influence a given material. Moreover, riffle patterns influence the concentration of a given material and its exit points on a table. This effect of riffle placement and design is modeled in a spreadsheet. Major performance and separation improvements may he expected by improved table design. Two physical laws of tabling have been derived. These laws aid in the design of sophisticated high-tech tables.

Jan 1, 1995

By A. Frank Alsobrook

DOUG HALBE: Thanks, Terry. And in spite of your introductory comments, I'm going to attempt to continue our hallowed tradition of saying nice things about the speakers. This is really a serious comment now. We, as mineral processing and mill people, don't often talk to people outside our general operating area. One thing that we've tried to do in this operators' symposium is get speakers from various types of plant operations to help illustrate all the things we have in common. Our next speaker is from the industrial minerals area. I think there's a lot to be learned from industrial minerals operations. Some of the people in the last session learned some things about fine grinding in industrial mineral operations. I was a little surprised to see people there grind to 2 microns. Our next speaker is Frank Alsobrook. Frank is another nonmetallurgical engineer. He has a degree in geology, a master's of science from the University of Wisconsin. He's had his own very successful consulting company for a number of years. This is your 11th anniversary, Frank? Very good. He's also the immediate past chair of the industrial minerals division. I think the folks at the speakers' table should be ashamed. You have been so rowdy that Frank chose to sit in the audience. [laughter] We'd like you to come up now, Frank, and tell us some things that you've seen that might be useful to us. INTRODUCTION FRANK ALSOBROOK: The three topics addressed briefly are (1) teamwork and operations modeling, (2) the pitfalls of capital conservatism, and (3) the potential for by-product recovery. Ideas for improvements in these areas are not unique to industrial minerals but apply to metal mining and processing operations, as well. Several additional topics are suggested at the end of the paper.

Jan 1, 1998

By Jon C. Yingling

A control system for reducing peak loads on mine conveyor networks is proposed. The system involves continuous monitoring of flows into the conveyor network and section feeders with variable discharge capability. The control strategy uses differences in material transit times from various production units to the transfer points in the network to forecast load levels that will be intersected by the discharge of the controlled feeders over future time intervals. Feeder setpoint adjustments are made to prevent excessive peaks in the combined flows at the transfer points, while maintaining adequate feeder throughflow to avoid production bottlenecks.

Jan 1, 1992

By R. E. Pennington

My subject this morning is coal liquefaction technology. Actually, coal liquefaction involves a number of technologies in a very complex system. The first slide shows the major components of such a system with arrows to indicate appropriate flows. The components are the facilities for coal feed preparation and handling; the coal hydrogenation or base liquefaction section; facilities for product separation and recovery, and in addition, facilities for the production of hydrogen from coal-based sources. A very rough break- out of the investments involved in these areas is given at the bottom of the slide. Investment is spread about equally among the three areas of operations Another way of looking at it is that the investments in what might be called support facilities are of the same magnitude as the base investment in the hydrogen facilities. Therefore, it is appropriate in a discussion of coal liquefaction technology to treat it as a system composed of a number of technologies. The next slide lists the various functions in the feed preparation section along with an indication of technology status. Storage, crushing, grinding, drying of coal all have been in commercial practice for a number of years. The slurrying and pumping of coal at least in water slurries, is practiced commercially also. The heating of coal slurries in oil to high temperatures under pressure is not in commercial practice and development and testing is going on by a number of people in this area. Some rather complex phenomena occur when coal oil slurries are heated to high temperatures.

Jan 1, 1975

By Robert M. Dreyer

Although lateritic deposits have long been a principal source of bauxite and are becoming an increasingly important source of nickel, the problems in the evaluation of such deposits are not generally understood. In the evaluation of lateritic bauxite and nickel deposits, there are many similarities, but there also. are significant differences. It has long been recognized that laterites with commercial concentrations of trivalent metals represent the ultimate in the intense leaching of tropical soils. Any factors which effect-the rate of soil leaching will effect the form of local lateritic concentrations. Although the most intense leaching generally occurs on somewhat elevated areas of gentle relief where there is a free downward flow of rain water, the- effect of local rock structures in effecting varia¬tions in soil metal concentrations has-not been well understood - primarily because the laterite forms a masking blanket over the rocks from which the laterites were derived. All of the-factors which facilitate downward movement of water may effect greater surficial concentrations of trivalent metals. Such features as zones of fracturing, zones of greater rock permeability, and areas of karst topography may, therefore, be responsible for greater leaching. The variations in rock structures and the vagaries of ground water flow pat¬terns impart, to the laterites, rapid lateral and vertical variations in thickness and metal concentrations. Because of such rapid

Jan 1, 1970

By J. D. Miller

Many factors -- political, environmental and technological -- will determine the extent to which the United States realizes the potential of its vast coal resources. Not the least of these factors is technogical development including mining, processing and transportation. With regard to processing technology, about 50% of the 800x106 tons of coal mined annually in the U.S. is processed in preparation plants. The purpose of the physical separations accomplished in these preparation plants is to remove ash (present as clays and other oxide minerals) and sulfur 'present mostly as pyrite). Coal flotation circuits for such separations are becoming more important in the processing of minus 28 mesh coal. (1,2,3) For example in the U.S. in 1960, 31 flotation plants processed 26,500 tpd; whereas in 1980, there were 80 flotation plants which processed 78,300 tpd. This corresponds to an annual growth in flotation plant capacity of 10 per year during the past two decades. Coal flotation is based on the natural or induced hydrophobicity of coal particles which are separated from hydrophilic ash and sulfur constituents by attachment to air bubbles. The coal particle/air bubble aggregates are collected in a froth phase which is created by the addition of a suitable frother such as MISC. Without exception, such separations are made in a conventional flotation cell, which, in essence, is a stirred tank reactor with a shrouded rotor to shear the air as it passes through a hollow shaft. The dispersed air bubbles (4.0 mm diameter) are stabilized by addition of the frother. Collision of the air bubbles with, and/or precipitation of the air bubbles on, the coal particles results in the formation of coal particle/air bubble aggregates which rise in the gravitational field and are collected in the froth phase developed at the top of the flotation cell. Restraints on successful separation by this conventional flotation technique are particle size and retention time. Generally it is found that effective flotation is only achieved for particle sizes between 10 and 1000 microns. Further, with respect to retention time, it is found that a nominal retention time of at least 2 minutes is required for successful separations. These facts limit the effectiveness of conventional coal flotation. Coal fines may be lost in the reject stream and disposal is frequently a problem. The retention time required for conventional flotation results in large floor space demands which limit the capacity of the plant.

Jan 1, 1981

By W. R. Reed

NIOSH continues to conduct respirable dust control research for surface mine blasthole drilling operations. Research areas have included testing variables (shroud leakage area, drill deck cross-sectional area, shroud height, collector-to-bailing airflow ratio, etc.) that have the most impact on respirable dust control, development of a dust collector inlet hood, development of a dust collector dump point shroud, and testing of a small diameter water separating sub. This paper summarizes the results of the aforementioned research that has been completed. Additionally, past dust control research for drilling operations of both underground and surface mines completed by the U.S. Bureau of Mines, created in 1910 and incorporated into NIOSH in 1997, is reviewed.

Jan 1, 2008

By F. Stanley, A. Noble, G. Luttrell

"The supply chain for coal-fired power stations involve a multi-stage network of mining units, preparation plants, blending facilities and transportation systems. Attempts to optimize the supply chain have historically been difficult due to the lack of communication/coordination between the various groups involved in coal production, transportation and utilization. In light of this issue, a new approach for globally optimizing the coal supply chain called Micro-Price Optimization has been developed to simplify the optimization problem and to provide coal producers with fundamental insight needed to improve the profitability of their operations. This fundamental concept assigns unit values to each particles (or groups of particles) passing through production units. Optimization occurs whenever the maximum tonnage of positive value particles are recovered and passed to market, while the minimum tonnage of negative value particles are recovered. Elements considered by the concept include factors such as target boiler cost/efficiency, waste disposal costs, coal quality parameters, emission penalties, transportation charges, or other quantifiable impact factors. This article reviews the basis for the micro-price concept and provides a detailed industrial case study involving the determination of optimum coal qualities that need to be supplied by mine operators to feed a coal-fired power station. INTRODUCTION The performance of coal preparation plants have long been known to play an important role in determining the overall profitability of mining operations. This significance is due to the fact that the misplacement of just 1 ton/hr of clean coal to reject resulting from poor plant performance can represent nearly $300,000 per year in lost revenues for a mine producing a steam market coal (i.e., 1 ton/hr x $50/ton x 6,000 hr/yr = $300,000/yr). This loss can be even more pronounced, occasionally approaching $1 million per year for each 1 ton/hr of misplaced clean coal, for operations producing high-quality coking coal products sold into the premium metallurgical market (i.e., 1 ton/hr x $150/ton x 6,000 hr/yr = $900,000/yr). Detailed economic studies indicate that improvements in plant yield resulting from increases in organic efficiency have one of the largest overall impacts on mine revenue when compared to other cost centers within the mining operation. One of the first studies to show this important financial impact was reported by Norton-Hambleton Consultants (Norton, 1979). Their study indicated that an unfavorable change in plant efficiency was second only to coal transportation in terms of its impact on profitability, while an unfavorable change in the cost of underground mining was a distance third. This longstanding realization has continued to provide a strong financial incentive for coal producers to optimize the separation efficiency of their coal processing and blending operations."

Jan 1, 2015

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

A comparison of gold, platinum and sulfide ion selective electrodes was made in this investigation for determination of Eh in solutions containing sulfide ions as a model system. The comparison was made in terms of the accuracy of the measured response, response time, pH dependence, and reproducibility of measurement. In addition, the sensitivity of each electrode towards changes in sulfide ion concentration was measured in terms of the change in measured Eh per decade change in concentration of sulfide ions. On the basis of a detailed investigation of the electrode processes occurring at the surface of gold and platinum electrodes, it was postulated that within the pH range investigated these electrodes respond to changes in the hydrosulfide ion, HS-, concentration in solution. In comparison, the sulfide ion selective electrode is known to respond to changes in the sulfide ion, S-, activity in solution. Although the potentials measured with gold and platinum electrodes were mixed potentials, pretreatment procedures can be used to obtain a signal suitable for process control. For control of sulfide ions in flotation pulps, the use of a gold electrode pretreated at 1.0 V with respect to a standard hydrogen electrode is recommended.

Jan 1, 1990

By R. A. Pimentel

Many longwall operators experience difficulty complying with the federal regulation limiting average dust exposure. Others are currently in compliance, but the dust exposure limit keeps then from increasing their production. Spray water is a major means of dust control. Excess water can cause problems in the transportation system and the cleaning plant, and reduces the Btu value of the run of mine coal. Thus, the dust exposure reduction per unit of water sprayed must be maximized. This paper discusses underground tests recently completed as part of a Bureau of Mines research program to determine the effects of variations in spray water flow rate, pressure, proportioning and spray orientation on longwall shearers.

Jan 1, 1984

By Robert S. Foote

The U.S. Energy Research and Development Administration (ERDA) is currently conducting a national program to survey for uranium the conterminous United States and Alaska by 1980 using airborne and surface techniques. This paper discusses the techniques used and some of the results of airborne surveys conducted to date by Geodata International, Inc. Airborne gamma radiation and the earth's magnetic field data are measured to provide data leading to regions potentially more favorable for the exploration and discovery of uranium ore. High-sensitivity radiometric and magnetic field data have been gathered from an aircraft with an average surface altitude of 400 feet (Figure 1). Under most conditions, data are usable up to an aircraft surface elevation of about 1250 feet where limitations will be discussed. Results of data analysis under GJO-1632, GJ0-1644, GJO-1654 and GJO-1663 will be discussed.

Jan 1, 1976

By Ronald S. Tanaka

In the planning stages for a dozen years, the 9.11 mile long Mount Macdonald Tunnel is the focal point of the $600 million dollar Rogers Pass Project. The paper will discuss the construction of the tunnel that is being carried out from both ends. The eastern portion contractor has used a tunnel boring machine to excavate the upper part of the tunnel and at the west end contractor selected the conventional drill and blast method. A ventilation shaft located near the mid point is the main part of a ventilation system unique in the Western Hemisphere.

Jan 1, 1987

By I. Longson

As a longwall coalface advances a caved goaf or waste region is left behind. Air flow takes place through this permeable goaf due to the pressure differentials existing across it and en route this leakage air picks up both heat and moisture. A marked deterioration in climatic conditions occurs in the face area at all points downstream of where this leakage air rejoins the main air-stream. This goaf heat source can make a very significant contribution, typically 30-40% to the rate of total heat pickup on an advancing UK longwall coalface with a VST of 40°C and hence on the climatic conditions that prevail at the return end and in the return gate of the face. The magnitude of the rate of heat collection from the goaf depends on a number of factors but it has been established that it is particularly influenced by the prevailing virgin rock temperature and the total flow rate of the leakage air. This paper proposes a model for the goaf based on a packed bed analogy and other assumptions required in order to evaluate the rate of heat pickup are identified. The outlet condition of the leakage air predicted by the model have been shown to correlate with underground measurements taken for a range of different production patterns with the face cutter at various locations on the face. The sensitivity of these predictions to variations in the input data has been tested and is commented on. At this stage of the development the capabilities and predictive limitations of the model are discussed. Further areas of investigation are suggested in order to improve the predictive ability and to extend the versatility of the model.

Jan 1, 1989

By Stephen Njoloma, William Bracken, Harald Cordes, Ivan Hee

"DC Water’s First Street Tunnel (FST) is part of the $2.6 billion Clean Rivers Project designed to reduce the occurrence of combined sewer overflows into local waterways. Due to flood events in the Bloomingdale and LeDroit Park neighborhoods, the FST Project was accelerated by DC Water to mitigate future flooding by boosting storage capacity and thus relieving the undersized combined sewers.The FST Project was finalized in 2016 as a collaborative effort between DC Water, its consulting team consisting of Greeley & Hansen and McMillen Jacobs Associates, and the design-build team of Skanska, Jay Dee Contractors (SKJD) with WSP Parsons Brinckerhoff as the designer.Scope of project. The FST Project (Fig. 1) included four primary shaft sites, a large 6 m (20 ft) internal diameter, 823- m (2,700-ft) long bored tunnel and three adit connections from the off-line shafts to the large-diameter tunnel. The adits which vary in size and length, are the subject of this article. The Channing Street site (Fig. 2) was established as the main site for an Earth pressure balance tunnel boring machine (TBM) and included a 49-m (160-ft) deep shaft with slurry wall support of excavation and 20-m (65-ft) internal diameter final cast-in-place permanent concrete liner. The construction sites at Adams Street, V Street and Thomas Street each consisted of off-line shaft structures tied to near-surface sewer diversion chambers and ventilation facilities. These three off-line shafts were connected to the large bored TBM tunnel via adit tunnels. Each of the three adits had a portion or the entire length excavated by sequential excavation method (SEM) in frozen ground.The Adams Street adit (Fig. 3) was constructed in two phases. The first phase is the 23-m (75-ft) long and 5-m (16-ft) diameter section immediately outside the drop shaft which also serves as the deaeration chamber and was excavated by SEM. The second phase which is 91 m (300 ft) long and 3 m (10 ft) in diameter was excavated by Micro TBM (MTBM) launched from within the permanently lined deaeration chamber. MTBM excavation commenced toward a reception chamber that was excavated by SEM from the previously bored FST TBM tunnel. This SEM excavation had a 5 m (17 ft) diameter and a length of 4.5 m (15 ft)"

Jan 3, 2018

By P. M. Pettit

Hydrologic investigations at Gold Quarry began in 1989 and continued through 1991. Hydro-stratigraphic units include Tertiary sedimentary rocks, Paleozoic siltstones and carbonates. These units display complex and variable aquifer parameters as a function of faulting and hydrothermal alteration, creating compartmentalized hydrologic domains. Testing has included step-tests, spinner production logs and constant discharge tests. Two Three-Dimensional Finite Element Models have been developed, one for optimizing the pit dewatering system and the second for predicting regional impacts of dewatering. Aquifer testing and long term pumping have been used to calibrate both Finite Element Models.

Jan 1, 1992

By E. L. Piper

Natural graphite has been known for many centuries, having first been reported as a distinct mineral form by Gessner in 1565. At that time, graphite was used extensively as pencil "lead" because of the ease with which it marks paper. It is a black, unctuous material found as flakes, lumps, or needles in scattered locations throughout the world. The less crystalline, or "amorphous", natural graphites are thought to have been formed from coal under conditions of high temperature and pressure. The more crystalline varieties, such as those mined in Ceylon, probably were precipitated from molten solutions or were pyrolyzed from gaseous carbon compounds. Recognition of the good thermal and electrical conductivity of graphite, together with its highly refractory nature, led to an increasing number of appli¬cations for this material. Clay and pitch bonded natural graphite has been used in crucibles, refractories, foundry facings, and other high-temperature appli¬cations. These forms constitute the most important current uses for natural graphite in the United States. Other products containing natural graphite include batteries, lubricants, pencils, brake linings, etc.

Jan 1, 1973

By Cleland N. Conwell

The term "tender tundra" is a myth---a well-developed myth, but contrary to the fact. Any area that supports herbivores must have a plant base to supply food, In Alaska, herds of caribou migrate and live north of the Arctic Circle. And, if there is enough growth in the moss and lichens and arctic grass to support a caribou herd, the "tender tundra" can heal after it has been disturbed by mining. Another myth is that Alaska is an ice box. Actually, many areas In the state---particularly the Interior---have a high agricultural potential. Nevertheless, the fact remains: whether it is reclaimed by advancing the productivity from forest to agriculture or is allowed to remain a wild-life habitat, Alaskan land will revegetate. Reseeding speeds reclamation, but left to nature, native species will reclaim the land whether it was disturbed by forest fires, roads, villages, or mining. In fact, it is impossible to find many of the old gold mining camps.

Jan 1, 1975

By Edward J. Hasenohr

Geochemical studies were under- taken in the Breckenridge mining district to test the effectiveness of soil and rock-chip samples in high- lighting known mineralization in the district, and in locating sites of possible porphyry-type mineralization, if such mineralization is present in the area. Soil sampling can be done more quickly and more cheaply, but it does not provide a direct site- specific sample of mineralized rock. In well-developed soils, supergene effects may mask and/or displace primary hypogene effects; and even in places where the soils are poorly- developed, as in the Breckenridge district, the masking effects may be felt. Soil anomalies, if present, likely will be of lower amplitude and more diffuse (widespread) than corresponding rock-chip anomalies. On the other hand, detailed rock-chip surveys are more time-consuming and expensive, even though they yield direct geologic information in addition to the chemical data. The goals of the combined soil and rock-chip programs were (1) to com- pare the data from the two; and (2) test the effectiveness in identifying significant chemical anomalies with respect to the geology of the district, as it is presently understood.

Jan 1, 1982