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By R. L. Summers

The tremendous engineering advances occurring during this past century are very evident within the boundaries of the Anthracite Section of AIME. The Steelton plant of Bethlehem Steel Corporation, located along the Susquehanna River just east of the Commonwealth's capital at Harrisburg, for more than 105 years has experienced a most dynamic life which has paralleled America's industrial growth. (Figure 1) In June 1865, just after the Civil War, a group of men met to organize the Pennsylvania Steel Company. The war had brought into sharp focus the vital importance of the railroads to the country's expansion. Until that time wrought iron rails were used, and the replacing of track after only several months wear had become an almost unbearable cost. The spirit of free, competitive enterprise and the prospects of a lucrative market compelled these men to form that first Pennsylvania Steel Company and to develop better rail products. They issued the following statement: "...our desire to free ourselves from dependence upon a foreign market (has) led to the organization of the Pennsylvania Steel Company, and the parties who have connected themselves with it are determined to produce upon American soil all the principal manufactures of steel that are now, at such a serious cost for freight, commission, insurance, exchange, duty, etc., and often, with so much delay and uncertainty, imported from abroad. (We) are preparing to establish near the consumer, works at which articles of accustomed pattern will be promptly produced, and from the

Jan 1, 1971

By Ronald J. Doll, John Elkin, M. P. Evans

The application of "Alignment Free” right angle shaft mounted drive systems offers improved reliability and reduced costs for surface and underground belt convey- ors. Comparisons to conventional approaches will cover installation, operating, maintenance, and spares inventory cost savings. Various options for belt acceleration and load control on fixed and variable length (booster) belt conveyors will be reviewed for operating performance, reliability, and total cost. Lastly, a case study of a successfully operating installation will be highlighted.

Jan 1, 1996

By Peter Kowalczyk

The acquisition of submarine gravity data using airborne gravity technology is a practical reality. Ocean Floor Geophysics plans to deploy a free-swimming ROV based submarine gravimeter on a commercial basis in early 2009. The submarine instrument is a variant of the well-used GT-1A airborne gravimeter. Airborne gravity surveys are now routine. The primary factor controlling the accuracy of airborne gravimeters is the precision of the GPS measurement of vertical movement of the sensor platform. The gravity measurements along a flight line are the differences between the output of the gravimeter vertical accelerometer and the estimate of the aircraft vertical acceleration using the differential GPS system. The principle difficulty of moving an airborne gravimeter to a free-swimming submarine platform is the necessity to have an accurate real time estimate of the changing elevation and hence changing vertical acceleration of the platform; GPS doesn't work underwater and an accurate estimate of depth fluctuations to the necessary precision is difficult to acquire. It is interesting that the airborne gravity gradiometer technology, which competes with the airborne gravity technology, was first developed as a classified military application for use by missile submarines during the cold war. Gradiometers were developed for this application specifically to avoid this problem. A gradiometer does not require as accurate an estimate of its vertical position to make a useful reading- it measures gravity gradients, not the gravity field itself.

Jan 1, 2008

In the last four years, 2007~2010, 9 out of 24 metal/nonmetal underground mine fatalities were caused by ground fall across United States of America (Mine Safety & Health Administration, MSHA). To reduce or eliminate incidents/accidents caused by ground fall, this paper clarified how to design and select ground support based on different ground conditions, how to use mine ground support standards, what geotechnical engineers and underground operators should do to keep mine production free of ground failures.

Jan 1, 2012

By R. T. Swinderman

This paper discusses how many of the common practices in conveyor specification and design are out of date compared to the current expectations of users for safe, serviceable, reliable, and fugitive material-free conveyance of bulk solids. Ten of the most common mistakes made in the specification and design stages related to user expectations are reviewed along with the cost vs. price implications of those decisions. A general specification and design hierarchy that designers can use to improve conveyor design is included.

Jan 1, 2010

By D. W. Jahn

Road construction in the near future will require contractors to guarantee that a project will remain trouble free for years after the project has been completed. These guarantees will challenge aggregate producers to become technically proficient in judging performance of their products. Testing procedures are described that may be used to predict performance of concrete and asphalt pavements before being committed into a construction project, and may also be used as quality assurance tools during construction to monitor performance as construction proceeds.

Jan 1, 1995

By W. Z. Choi

A combined size reduction- liberation model of grinding has been developed to predict the product size distribution for both free and locked particles. The model is an extension of the population balance model for size reduction. Locked (or composite) particles have been subdivided into discrete classes of different compositions to obtain more detailed information. The model has been tested on a sphalerite ore from Tennessee. Liberation data have been obtained using an areal scanning technique on microscope images of polished particle mounts.

Jan 1, 1985

By W. K. Fletcher

As part of an ongoing programme on behaviour of heavy minerals In streams, the dispersion of Au as free gold (Day and Fletcher, 1987), Sn in cassiterite (Fletcher et al, 1987) and W in scheelite (Saxby and Fletcher, 1987) have been investigated downstream of mineralization. The studies of Au and W were undertaken, in British Columbia and the Yukon Territory, respectively, in streams that are strongly influenced by spring snowmelt floods. Sn was investigated under tropical rainforest conditions in Peninnsular Malaysia.

Jan 1, 1988

By E. F. Divers

In response to a request from the Mine Safety and Health Administration, the Bureau of Mines has recently completed a respirable dust survey of 18 U.S. coal preparation plants. Of these, three were essentially free of dust problems. Respirable dust exposure of workers in the remaining plants depended on the time spent in the dusty areas. In five of the plants surveyed, Bureau tests showed that in some areas worker exposures could exceed Federal dust limits in less than 2 hours.

Jan 1, 1988

By D. W. Fuerstenau

The flotation behavior of quartz in the presence of alkyl ammonium acetates as a. function of alkyl chain length has been interpreted in terms of hemi-micelle formation at the solid-liquid interface. The van der Waals cohesive free energy that is responsible for hemi-micelle formation has been found from these results to be 1.02 kT per CH group. This 2 is in excellent agreement with literature values obtained from research on the properties of micelles in bulk systems.

Jan 1, 1964

By D. J. MacKinnon

Smooth, compact, dendrite-free, 24-h zinc deposits have been electrowon from zinc chloride electrolyte using a diaphragm cell. The cell consisted of sealed anode compartment con- taining DSA anodes which were separated from an open cathode compartment by Dynel cloth membranes. Fresh electrolyte was fed to the cathode compartment where zinc deposition onto an aluminum cathode was aided by air-sparging. The catholyte passed through the diaphragm into the anode compartment from which chlorine gas and spent anolyte were withdram.

Jan 1, 1980

By R. J. Pindred

Discussion by R.J. Pindred In his paper, Davis presents an overview of risk. He also introduces the Capital Asset Processing Model (CAPM) as a foundation for selecting the appropriate discount rate for a mining project. While applying portfolio theory is more defensible than the ad hoc adjustment of discount rates, the CAPM is not a panacea. CAPM shortcomings [The CAPM, as Davis stated, is expressed in the equation: ri=rf+pi4) where ri is the project discount rate rf is the risk free interest rate (3i is the project beta, and 0 is the market risk premium (rm - rf)] Application of the CAPM is more difficult than Davis indicates. Valuation is prospective, while the CAPM parameters are historical. Beta is determined from a regression analysis of historical data, while the beta needed for valuation is the expected beta. Betas are known to be unstable and the regressions that generate them often have low explanatory power. The difficulty of estimating a "project" beta must also be considered. Thus, the beta that is used in the CAPM will be based on the analyst's judgment. Like Cavender's discount rate, this judgment can lead to different project NPVs. Subjectivity in valuation cannot be avoided by a mechanical application of the CAPM. The risk-free rate, which Davis identifies as a short-term real rate of 4%, is also subject to scrutiny. A mining project is not a short-term investment and no single risk-free rate is appropriate for all of the cash flows. The hypothetical mine discussed in Cavender's paper is a six-year project. One might argue for the application of a risk-free rate from the Treasury yield curve at the duration of the project (in a bond-duration sense). This, too, is inappropriate. The risk-free rate should be matched to the timing of the cash flow. These rates can be determined by calculating the implied forward rates from the yield curve using a procedure known as "bootstrapping." It is likely that each of the project's cash flows would be discounted at a different rate. Commodity prices Davis criticizes the "ad hoc adjustment to the discount rate." Yet, in his discussion of the value of stochastic simulation, he suggests that the gold price be modeled as a "random walk, with or without a trend." This is essentially an arbitrary modeling of price risk. Consider that a liquid market in gold futures exists. The futures' price curve, which is closely related to the market's estimate of future spot gold prices, should be used to provide inputs to the model. This is especially true of a relatively short six-year project. Alternatively, as Davis correctly points out, a risk-averse investor can sell the commodity short to hedge price risk. Is it any more correct, in the portfolio sense, to account for price risk at all ?? References Cavender, B., 1992, "Determination of the optimum lifetime of a mining project using discounted cash flow and option pricing techniques," Mining Engineering, Vol. 44, No. 10, pp.1262-1268 Fabozzi, F.J., 1993, Bond Markets, Analysis and Strategies, Second Edition, Prentice Hall, Inc. Higgins, R.C., 1992, Analysis for Financial Management, Third Edition, Richard D. Irwin, Inc. Solnik, B., 1991, International Investments, Second Edition, Addison Wesley Reply by G.A. Davis Pindred discusses two issues related to my paper, the shortcomings of the Capital Asset Pricing Model (CAPM) and which commodity price values to use in the valuation exercise. Even though these topics are not directly related to the use or misuse of Monte Carlo simulation, they are important points to take into consideration in valuation exercises. Since I do not appear to have addressed these issues satisfactorily in my original paper, I will comment on each here. Pindred agrees with me that applying portfolio theory, and specifically the CAPM, to the selection of project discount rates is more defensible than ad hoc methods. But he then points out that the application of the CAPM to project valuation is more difficult that I indicate. It is true that the CAPM is a difficult tool for project valuation in general,. But the application of the CAPM to mining projects is one of the easiest I can think of. The biggest problem with using the CAPM for project valuation is coming up with an expected project beta. I suggest a project beta for gold projects of 0.45. The "true" value might be 0.35, 0.55 or whatever. Pindred correctly notes that the selection of the appropriate project beta is based

Jan 1, 1996

By Stuart Lister

"When MacLean Engineering chairman and founder Don MacLean got the first question from a minesite about the possibility of addressing ventilation limits through incremental fleet electrification, he was intrigued. It was back in 2015, and the MacLean scissor bolter was already diesel-electric (jumbo trailing cable), so it made sense to him that if they could engineer a battery drive system for the unit’s tramming cycle, they would have the inaugural electric vehicle (EV) MacLean unit.At that time, there were not any entirely diesel-free hard rock mines in existence on the planet, and that remains the case to this day — although the Borden project in northern Ontario is progressing toward that goal (see page 33). This meant there was essentially zero market demand for battery electric vehicles as well as a complete lack of battery technology to address the battery electrification of heavy haulage. Heavy haulage is the part of a typical mine’s mobile fleet with the largest footprint when it comes to diesel particulate emissions, greenhouse gases and wasted energy in the form of heat.Three years later — the wave of battery electrification that is currently picking up speed across the mining industry promises to hit full swing by the early 2020s when a slew of new build, diesel-free mines will start construction. But this movement toward emissions-free mobile fleets is not a completely new phenomenon. Instead, it is an updating of mining technology from a previous generation. What is going on now is the re-electrification of mining. Up until the 1960s, early generations of battery technology (lead acid) and electric locomotive systems were the norm for material and ore haulage in Canada and elsewhere.The thought of a coming paradigm change in mining was particularly pertinent to Don MacLean back in 2015, as he had been part of the era that ushered in the first generation of rubber-tire diesel equipment, when he was a divisional foreman with Inco in Sudbury in the 1970s. He was part of the operating team that was tasked to build a rail loop on one extraction level of the mine. At that time, events on the ground overtook the project, as diesel-powered mobile equipment became a viable option. Once the first diesel scoop was introduced at Creighton #3 shaft, it was clear what the power, haulage capacity and mobility could do for operations and that era of electric rail haulage underground was effectively over."

Jan 10, 2018

By Kwangmin Kim, Taehee Lee, Minkyu Kim, JUNHYEOK PARK

Mine tailings storage facilities (TSFs) can be a significant source of fine, respirable dust. About 25 percent of the mass fraction of tailings from a hard-rock mine consists of particles of a respirable size (smaller than 10 μm) [1]. This dust poses concerns, especially for nearby communities, because of its detrimental impact on respiratory health. Respirable tailings dust, primarily composed of quartz or free silica (SiO2), may cause silicosis, chronic pulmonary disease, bronchitis, collagen vascular diseases, and chronic granulomatous infections [2]. 

By M. Niec

Lignite deposits in Poland occur within clastic Tertiary series at the depth suitable for opencast mining. Aboundant aquifers with the good quality waters that should be protected against contamination or depletion often accompany them. Landscape and underground water protection are the main regional environ-mental factors that limit the possibility of exploration and mining; presented on map of lignite bearing series distribution allow to delimit areas "free" for exploration and mining and areas where some limitations can be met up to no admittance of any industrial activity.

Jan 1, 1994

By Frederick W. Bauer

The potential worldwide "market" for metallurgical bauxite is about 94 million MT. The high degree of concentration of the alumina sector, combined with the high percentage of long-term contractual relationships, results in a small spot market with an illdefined price structure. Further segmentation occurs based on bauxite quality and alumina plant design. The potential 'free" market is estimated to be about 18 million MT that represent the requirements of nonintegrated alumina producers. It, too, is covered almost entirely by multi-year supply contracts.

Jan 1, 1984

By J-P Franzidis, M. C. Harris

Increasing costs, falling grades and a low gold price have caused severe problems for many of South Africa's gold mines. The need to maximise efficiency is extremely urgent. This paper describes the use of column flotation cell s to scavenge significant quantities of additional gold from flotation plant residues; in particular, very fine particles of free gold not recovered by conventional flotation. Experimental gold- specific collectors enhanced gold recovery significantly. The paper also reports the results of other plant trials, carried out on a variety of ores.

Jan 1, 1991

By Steve Lloyd, Mary Anne Antonioli, Byron Darnton

The Pegasus Gold/Montana Tunnels Mine is a high­tonnage, low-grade, base and precious metal operation in Jefferson City, Montana. Gold heads are typically 0.02 opt with the dominant gold mineral being a native metal electrum quite rich in silver. Early research and development indicated the ore to be amenable to gravity concentration at a 10 to 14 mesh grind. Although full flow gravity preconcentration was considered as a flowsheet alternative, flotation was chosen as the main recovery process due to its apparent lower cost for capital and operating. At this early juncture, the option or concept of recovering coarse free gold by gravity was deemed unnecessary or irrelevant. The intermittent loss of free gold has been observed in the flotation tailing since mill start up. A comprehensive research program was initiated in 1990 to identify the magnitude of this loss and investigate alternatives for its recovery. Batch and pilot plant testing has ultimately led to a permanent gravity circuit being installed at the cyclone underflow. The circuit is designed to scalp out the liberated coarse gold contained in the ball mill circulating load. The final flowsheet consists of: a pinched sluice to upgrade cyclone underflow; a Tyler doubledeck screen to remove over­size from sluice concentrate; Knelson concentrators for roughing and cleaning of screen undersize; an Eriez wet drum separator to remove tramp metal from Knelson concentrate; a Sweco screen to size Knelson cleaner concentrate for tabling; and a Wilfley table to produce final concentrate for direct melting.

Jan 1, 1992

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 Ronald R. Bauer

Wollastonite is a little known industrial mineral of the silicate group. The largest and purest known deposit in the free world is being mined and beneficiated in Millsboro, New York by NYCO, A Division of Processed Minerals Incorporated. The associated garnet and diopside are separated from the wollastonite using dry high intensity magnetic separators. Beneficiated wollastonite is used extensively as an additive and filler in the ceramic, paint, refractory, and wallboard industries. Wollastonite acts as a functional filler due to its unique chemistry and physical acicularity.

Jan 1, 1982