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By H. Askari-Nasab, B. Osei, K. Awuah-Offei

The U.S. coal mining industry consumes approximately 142 billion kWh/a of energy. The U.S. Department of Energy estimates that the industry’s annual energy consumption could be reduced by 49%. This constitutes nearly $3.7 billion of potential savings on coal production costs at 5.3¢/kWh of energy. Additionally, with climate change regulation on the horizon, any benefits from energy savings in the near future are compounded by associated reductions in CO2 emissions. Research indicates that operating conditions significantly affect energy efficiency. Modeling and simulation have been shown to be a cheap and reliable means of evaluating the effects of process interactions and operating conditions. The goal of this work was to apply stochastic process simulation to model the energy efficiency of a typical truck-and-shovel mining system and use the model to evaluate production strategies to improve energy efficiency. The research team conducted energy audits of truck-and-shovel overburden removal and used the results to develop regression models describing truck and shovel fuel consumption. The team then built a stochastic simulation model of the truck-and-shovel overburden removal operation and used it to assess a variety of improvement measures by simulation experimentation. Valid fuel consumption models for shovel loading and truck haulage have been formulated, based on the energy audit results. Valid stochastic process models of truck-and-shovel operations have been formulated to study energy efficiency. The following strategies, in decreasing order of impact, provide the most energy savings for truck-and-shovel overburden removal at the mine: (1) shorten haul roads, (2) increase shovel capacity and (3) increase shovel utilization through optimal truck matching. Additional data will be required to adequately describe operator effects on energy efficiency.

Jan 1, 2011

By Daniel J. Dobbels, Eric R. Drooff, James R. Wheeler

Construction of Boston’s C11A1 Section of the Central Artery (I-93)/Tunnel(I-90) Project beneath the existing MBTA Red Line Subway at South Station required excavation to depths in excess of 33.5 m (110 ft) through permeable sand and gravel subject to almost 27.4 m (90 ft) of hydrostatic groundwater pressure. As tacked drift tunnel underpinning system was designed to provide positive support to the active station prior to mainline tunnel construction. As part of this system, a permeation grouting program was developed to facilitate tunnel excavation. This paper describes the design and implementation of the grouting program, in sit testing, and the overall performance of the grouted soil mass.

Jan 1, 1999

By Harry Asche

Tunnels are frequently specified by owners to be designed to a structural code, often a bridge code. In the USA, AASHTO have created a tunnel code, based on structural principles, the AASHTO LRFD Tunnel Design Specification. The Load Resistance Factor Design method (LRFD) described in the AASHTO title is an approximation to the probabilistic design of structures, based on the independence of load and resistance. This methodology is well known to be problematic in geotechnical design, but it is widely used. The paper considers the difficulties of this approach and describes alternative approaches that would result in more appropriate designs for tunnels.

Jun 13, 2021

By C. L. Schneider

The calculation of the liberation spectrum in the product from continuous milling operations is a problem of considerable importance and is difficult to solve because the population balance equation must be integrated in two-dimensional space. Complete solutions require the estimation of a large number of parameters unless a structural model of the ore texture can be used. A very simplified textural model based on the use of the modified Andrews-Mika diagram and the PARGEN simulation of multi-phase particles has been formulated and is used to simulate the behavior of a continuously operating laboratory ball mill. A sensitivity analysis for this mill has been done to show the likely effect of model approximations on the predicted liberation spectrum which will be measured.

Jan 1, 1992

By Y. Guan

The dissolution behavior of copper and gold from their pure state and from Au/Cu alloys in cyanide solutions has been investigated using a rotating disc. Oxygen was used as an oxidant. The effect of the composition of the alloys, stirring speed of the disc, concentration of lixiviants and temperature on the overall dissolution kinetics has been studied. Gold/copper alloys of three compositions were used in this study. The atomic percent of gold in these alloys was 75, 50 and 25, respectively. The dissolution behavior of these three alloys was compared with that of pure gold and of copper under the same chemical conditions. In general, the dissolution of copper and gold from alloys is partially controlled by surface chemical reaction and largely by mass transfer.

Jan 1, 1992

By P. Semberg, B. Bjorkman, C. Andersson

"In this study, the interaction between magnetite and the additive olivine was studied after oxidation as well as after isothermal reduction at temperatures in the 500º-1,300º C range. In the olivine sample, the forsteritic olivine particles react partly during the oxidation pretreatment to form magnesioferrite and vitreous silica along the particle corona. This breakdown of the olivine particles during oxidation liberates magnesium from the particles, which do not react until temperatures of above 1,150° C in reducing atmosphere. When the hematite in the sample is reduced, and when the temperature is high enough to allow solid-state diffusion at ~800º C, the magnesium of the magnesioferrite redistributes, so that the magnesium concentration approaches the same level throughout the iron oxide structure. For magnetite, this did not occur until 800° C. At 1,000° C, this magnesium reacts further with the silica in the glassy slag phase, which crystallizes into fayalitic olivine. At this temperature, the magnesium has diffused over distances of more than 600 µm from large olivine particles after 2 hrs reduction. From this point, the primary slag phase in the pellet, until melting, is solid fayalite. Upon reduction to metal, the metallization front concentrates the MgO in the remaining wustite, which can lead to MgO levels of up to 10 mole% locally. The melting point of the fayalite is raised from 1,145º C to a melting range of 1,238-1,264º C due to the MgO increase, as estimated based on phase diagrams, which were adapted to the pellets tested. Much of the olivine that remained unaltered in the oxidation process will be encapsulated by iron before the particles begin to dissolve in reducing conditions and, therefore, plays no role in the reduction before final melting of the particles occurs.IntroductionEnvironmental concerns have placed increasing pressure on the CO2-intensive iron and steel industries to further optimize operation toward higher productivity and more efficient use of reducing agents. At the same time, high demand for iron ore has caused new iron ores with lower grades and more complex chemistries to be taken into production. In Scandinavia, the main iron-bearing material is magnetite-based pellets with olivine, which allow operation with very low slag volumes and, hence, lower fuel rate ( Slagnes and Sundqvist Ökvist, 2008; Hallin et al., 1994). Both the MgO and SiO2 of the olivine, as well as the elements of the gangue of the ore, i.e., Si, Mg, Ca, Al and alkali, interact with the iron oxides to give the finished pellet product its final properties in the blast furnace. Tailoring the additive mix to be used for a certain iron ore for optimal product properties, therefore, requires detailed knowledge of the mechanisms by which these elements dissolve and react in the pellet."

Jan 1, 2015

By T. W. Beck, J. A. Organiscak

The U.S. National Institute for Occupational Safety and Health (NIOSH) Office of Mine Safety and Health Research (OMSHR) has recently studied several redirected scrubber discharge configurations in its full-scale continuous miner gallery for both dust and gas control when using an exhaust face ventilation system. Dust and gas measurements around the continuous mining machine in the laboratory showed that the conventional scrubber discharge directed outby the face with a 12.2-m (40-ft) exhaust curtain setback appeared to be one of the better configurations for controlling dust and gas. Redirecting all the air toward the face equally up both sides of the machine increased the dust and gas concentrations around the machine. When all of the air was redirected toward the face on the off-curtain side of the machine, gas accumulations tended to be reduced at the face, at the expense of increased dust levels in the return and on the curtain side of the mining machine. A 6.1-m (20-ft) exhaust curtain setback without the scrubber operating resulted in the lowest dust levels around the continuous mining machine, but this configuration resulted in some of the highest levels of dust in the return and gas on the off-curtain side of the mining face. Two field studies showed some similarities to the laboratory findings, with elevated dust levels at the rear corners of the continuous miner when all of the scrubber exhaust was redirected toward the face either up the off-tubing side or equally up both sides of the mining machine.

Jan 1, 2013

By A. Lashgari, V. Kecojevic

This paper presents research on the environmental impact of digging and loading equipment used in surface coal mining. Environmental impact was assessed through the measurement of equipment exhaust and dust emissions, and sound level. In this study, exhaust emission refers to carbon dioxide (CO2), carbon monoxide (CO), nitrogen oxides (NOx), sulfur oxides (SOx) and volatile organic compounds (VOCs). Dust generation refers to fine particles (PM2.5), inhalable particles (PM10) and total suspended particulate matter (TSP). Sound level refers to the sound pressure level at different distances from the equipment. Modeling of the environmental impact of digging and loading equipment was conducted using the Microsoft Visual Studio.NET software package. This research was a part of a broader project involving the development of a software system for the selection of productive, cost-efficient and ecofriendly mining systems, sponsored by the Appalachian Research Initiatives for Environmental Sciences (ARIES). This research may assist mining professionals in quantifying the environmental impact of digging and loading equipment, and developing strategies for reducing the overall impact of such equipment in surface mining.

Jan 1, 2013

By R. Elias

Botswana is a mining-dominated sub-Saharan country. Workforces are characterised by poorly educated operators and front line supervisors, with equipment and management to 1st World standards. Poor communication, ignorance of business objectives, inability to meet targets, and lack of problem-solving capacity are the norm. Training leads to high expectations and is of concern to management as a source of dissatisfaction, despite the long-term benefits higher skills have for mine viability. The aims of a technical training programme are presented with various models and approaches being implemented at operations in Botswana. These are used to construct a series of guidelines for technical training initiatives.

Jan 1, 2000

By J. P. Baur

The sensitivity of radiochemical techniques makes possible the study of the initial stage sulfuric acid leaching kinetics of chalcopyrite and other copper sulfide minerals. High-grade Transvaal chalcopyrite was neutron irradiated in a TRIGA reactor to produce radioisotopes copper-64, iron-59, and sulfur-35. Dissolution rates were measured in the time interval zero to 60 minutes during which time significant anomalies were observed. First, an initial period of rapid dissolution lasting a few minutes; second, an arrest or "plateau" region usually lasting from 6 to 10 minutes; third, a second period of dissolution of lesser rate than the first. The effect of solution variables such as pH, oxygen partial pressure, and ferric ion concentration at different temperatures were measured. The initial rate data were correlated by considering the rapid reaction to be due to the dissolution of surface oxidation products or the formation of an iron depleted surface layer. The data for the second slower reaction have been explained to be due

Jan 1, 1972

By Douglas R. Cook

Our present and future needs for base and previous metals are not satisfied by the present rate of new viable discoveries. This deficiency can be met by increasing the number of competent exploration organizations and by doing a more effective job of prospecting. My principal purpose is to show that new discoveries can be increased by improving the use of exploration techniques in a concept-oriented exploration program. Exploration techniques are defined and classified. The effectiveness of many exploration groups can be improved by better definition of objectives and thorough planning of the exploration program. The role of objectives, planning, and the use of techniques are discussed within the scope of the exploration framework. Common pitfalls in the use of exploration data are identified such as: inconsistency of geologic measurements, negative use of data, indiscriminate use of geo-surveys, collection of irrelevant information, and the unrealistic desire for exploration panaceas. Suggestions for improving the use of techniques include the use of multiple-working hypotheses, improvements in the quality of exploration data, use of geology in the selection, planning and interpretation of geochemical and geophysical surveys, and the recognition of variables and limitations affecting the interpretation of exploration data. The critical role of geologic mapping by Federal and State agencies is mentioned for satisfying the continual exploration demand for better geologic maps and filling many gaps that currently exist. The importance of imaginative and qualified exploration personnel is discussed as well as the maximum utilization of their exploration creativity. The problem of integrating field studies, research and training at universities and research institutions is identified. The need for high-quality research in economic geology is emphasized especially the importance of reducing the steadily increasing gap between basic and applied research.

Jan 1, 1968

By William J. Cavanaugh

In 1967, Lone Star Industries, Incorporated, established a program to carry out the necessary Research and Development work to bring the Snyder Process to commercial application. The purpose of this paper, is to present the detailed metallurgical results gathered in comparing the Snyder Process of Comminution to conventional grinding techniques for the milling and beneficiation of certain ores and other materials. The ore primarily dealt with in this paper is a fine-grained magnetite ore, containing approximately 23% acid-soluble iron, from the Lake St. Joseph ore body of Steep Rock Iron Mines, Ltd., (Canada). This particular example was selected for presentation in this paper because extensive comparative results with conventional methods of grinding were available. Also briefly described in the paper are the comminution of other ores and materials such as porphyry copper ore and alumina.

Jan 1, 1973

By Taeyong Lee, Cole Bales, Matt Fowler, John Horne

Mitchell Point Tunnel near Hood River, Oregon is one of the more unique segments of the Historic Columbia River Highway and State Trail being constructed through the Columbia River Gorge. This 650-foot bike/pedestrian tunnel set to open in 2024 is being delivered by FHWA in partnership with Oregon DOT, Oregon State Parks, and the U.S. Forest Service. Primarily driven using drill & blast excavation methods through basalt, the shotcrete and dowel-supported tunnel features masonry portals and ve window adits that provide illumination and views of the river similar to the original highway tunnel of many vistas built in 1915 that was removed in 1966 to make way for Interstate 84. This paper summarizes the planning, design, and construction.

Jun 23, 2024

By N. B. Prenn

Many recent projects have been developed and mined based upon imaginary reserves. Imaginary or "geo-fantasy" reserves have cost many companies millions of dollars. The significant and varied technological advances in the mining arena have done little to curb reserve calculation problems. These advances may have served to increase the prevalence of reserve problems by putting more tools in the hands of personnel not properly trained or experienced in reserve estimation. This paper will discuss potential problems related to calculating reserves, which include: SAMPLING ERRORS -obtaining a representative sample. -Decay analysis of wet RC drilling -Bias introduced by sample preparation. -Assay bias; Coarse gold. -Specific gravity samples. GEOLOGICAL ERRORS -structural boundary definition. -Separation of high grade and low grade zones. -Incorrect continuity assumptions MODELING ERRORS -Too much influence of high grade samples. -Improper method of calculation. -Assumed range of influence. -Errors in the data. ENGINEERING ERRORS -Inaccurate assumptions. -Inadequate metallurgical testing. -Designed bottlenecks.

Jan 1, 1992

By Jr. Zink

An economic and operational evaluation of the unrecovered metal, physical conditions, and chemical environment in a leach pad should be made prior to decommissioning. This evaluation will help determine the possibility and method of secondary and/or enhanced metal recovery and the method(s) to be used for detoxification and heap closure. The evaluation requires quantitative sample collection in a locally variable, yet grossly homogenous material. An assessment of a valley fill heap leach pad was made using a technique borrowed from placer technology called sonic drilling. The sonic drilling technique produced very satisfactory core recovery and sample quality. At this site, drilling results demonstrated that the method of heap construction produced expected features after extensive long term leaching. Rather than a uniformly homogenous pile of metallurgically depleted crushed ore, an assemblage of solution channels, un-oxidized sections, unleached areas, and compaction due to various factors, were found. These conditions are thought to represent a normal, rather than unique, situation for a valley fill heap leach. The lack of this information can have a significant impact on the economics and methods of heap re-handling and ultimate closure.

Jan 1, 1992

By Yuexin Han, Yanjun Li, Peng Gao, Yongsheng Sun, Qiang Zhang

The non-isothermal magnetization roasting process and isothermal magnetization roasting process of siderite ore were investigated using thermogravimetric (TG) analysis and a real-time infrared gas analyzer. X-ray diffraction (XRD) and scanning electron microscopy (SEM) with energy dispersive spectroscopy (EDS) were used to analyze the characteristics of samples. The results showed that the decomposition degree and decomposition rate of siderite ore were vitally affected by heating rate and roasting temperature. It was determined that A1 reaction model (f(α) = 1 − α) and A3/2 reaction model (f(α) = (3/2)(1 − α)[−ln(1 − α)]1/2) were the most probable mechanism function of the non-isothermal decomposition process and isothermal decomposition process, respectively. The phase transformation and decomposition mechanism during the roasting process were evaluated. Siderite decomposed in the process of magnetization roasting, released CO and CO2, and transformed into strongly magnetic magnetite. The SEM images highlighted that as the decomposition progressed, the structure of roasted samples was destroyed, and an increasing number of cracks and pores emerged on the surface, which is advantageous to the following grinding process.

Mar 26, 2021

By David P. Kimball, Dalva L. Moellenberg

On May 21, 1990, EPA released its Strawman II draft program for mining wastes. It proposes to expand RCRA regulation of mining operations to include materials other than wastes. Strawman I1 would establish strict standards for the states to follow, rather than technical guidance. It proposes to establish performance standards; design criteria; monitoring requirements; and corrective action, closure, post-closure, and financial assurance requirements. It suggests "pollution prevention" concepts for mining operations. This paper explores the Strawman II proposals, particularly the technical criteria, and addresses several of the important concerns raised by industry.

Jan 1, 1991

By B. K. Slone

The depth at which it becomes more economical to use slope access as opposed to box-cut access for near-surface coal reserves, termed "transition depth," can be established for a given coal property by considering cost estimates for those parameters that determine respective access method. Fourteen parameters that influence access cost were identified and ranges determined. A Transition Depth Formula was developed to permit determination of the better method of accessing a reserve, given such information as highwall slope, road width, total bench width, pit dimensions, road grade, belt component costs, pumping costs, and cost of overburden removal and reclamation. In most cases, in Appalachia, studies indicate that the transition depth ranges between 20 and 30 m.

Jan 1, 1998

By W. C. Hellyer

The Granduc ore body is located beneath glacial terrain on the borders of British Columbia and Alaska, some 600 miles from Vancouver and 30 miles from Tidewater at Stewart, B. C. The concentrator and attendant facilities are located in wilderness country at an elevation of 2500 feet. The average annual snowfall is 65 feet. Surface facilities and ore body are linked by a 10 mile railroad haulage tunnel. This copper property has been developed by Granduc Operating Company on behalf of Newmont Mining Corporation and American Smelting and Refining Co. First production started in November, 1970. In August, 1966, Granduc Operating Company awarded an engineering and construction management contract to McKee-Swan Wooster, a joint venture of A. G. McKee of Canada and Swan Wooster Engineering Company Limited, to design a concentrator to treat approximately 7000 tons of ore per day. The isolated location of the Granduc ore body indicated comparatively high freight rates on consumable items of concentrator supplies such as reagents, grinding media, etc. A firm flowsheet for the flotation of the Granduc ores having been developed by the Danbury laboratory of Newmont Exploration Limited, attention was devoted to means of reducing operating costs. One obvious method was to reduce or eliminate the costs of steel grinding media by employing some form of autogenous grinding. two pilot plant operations were carried out at the facilities of Lakefield Research of Canada Limited, in which autogenous grinding of Granduc ores was investigated. The results of these investigations led to the selection

Jan 1, 1972

By Weibai Hu

The flotation separation of wolframite from fluorite and quartz is investigated with chelating agents and neutral oil as synergic collectors. Test results indicated that a-nitroso-ß-naphthol has a strong collectivity for wolframite and selectivity against fluorite and quartz. The 8-hydroxyquinoline has collectivity and selectivity also. They both have a better activity than sodium oleate. However, the cupferron is slightly inferior. The synergism of chelating agents and neutral oil looks promising, especially for fine wolframite particles. The activation effect of Fe2+ and Ca2+ ions on separation of wolframite from fluorite and quartz is slight. The UV absorb-spectra measurements showed that the adsorption of chelating agent on wolframite is multilayer, and flotation behavior is related to chemisorption. The chelating agent which bonds to Fe and Mn sits on the wolframite surface, and the reaction between Mn2+ ion with collector is more significant. The essentials affecting reagent activities are the bonding factor and the hydrophobic factor. These factors are discussed by structure-activity relationship theory. The synergism of neutral oil is a secondary collector likely to lengthen the hydrocarbon chain of chelating agents.

Jan 1, 1985