Search Documents

By B. Mishra, Q. Shi

Numerical simulations have been used to investigate roof fall in the past decades. Comparing to the continuum based methods, the discrete element method has been well recognized for its excellent performance in simulating large strain problems and fracturing processes in the rock mass. However, the discrete element method has its limitations. When simulating a large-scale problem, a large number of particles are required, which consumes significant computational resources. In the present study, a 3D numerical model coupled with the finite-difference method (FDM) and the discreteelement method (DEM) was created to simulate the laminated roof failure in an eastern coal mine in the US. In the FDM-DEM coupled model, the laminated roof of the entry is represented by an assembly of bonded particles using PFC3D. The laminated roof is simulated by adding parallel discontinuities. The discontinuities are given certain stiffness and strength in the model. The ribs, floor, and far-field surrounding rock are represented by continuum zones using FLAC3D. The strength of the discontinuities is varied sequentially and the fracturing of the laminated roof was analyzed with respect to entry advance. The results showed that the laminated roof fractures along the discontinuities while an intact roof fractures in a dome shape. Increasing the strength of discontinuity could enlarge the tensile zone inside the laminated roof and hence change the crack distribution. In addition, the crack quantity in the laminated roof behind the advancing face decreases with the increment of discontinuity strength while this trend is not occurring ahead of the advancing face. The simulation demonstrated that coupled method using PFC3D/FLAC3D can reproduce the laminated roof failure in underground coal mines.

Mar 2, 2022

By W. L. Swager

Tramp (undesirable) elements introduced into iron and steel castings via purchased ferrous scrap are evaluated as to their likely degree of future threat to the quality of castings. Conclusions are based on analysis of literature and on nonmail surveys of foundries, scrap processors, trade and technical associations, and others. The existing tramp-element problem is expected to be persistent, but amenable to improved control by foundries and their suppliers. Four recommendations for action are given.

Jan 1, 1981

By James W. Pennington

MERCURY, also widely known as quicksilver, ranks tenth in quantity in world output of nonferrous metals. However, its unusual and desirable combination of properties- liquid liquidity at ordinary temperatures, high density, uniform volume expansion, electrical conductivity, ability to alloy readily, high surface tension, chemical stability, and toxicity of its compounds -gives mercury an industrial and military importance out of proportion to the small physical size of the production industry. Although mercury has been known and used for over 20 centuries, until the 16th century consumption was small and chiefly in medicine. Since then mercury's applications have paralleled scientific advancements, kind current principal uses of mercury are in electrical apparatus, industrial and control instruments, agriculture, pharmaceuticals, and the electrolytic prepa¬ration of chlorine and caustic soda. Other materials may be substituted for mercury in come applications; yet, for those uses that require mercury's unusual combination of physical and chemical properties, there is no ideal substitute.

Jan 1, 1959

By R. V. Higgins

This report presents computer instructions for calculating the performance of three-phase flow of gas, oil, and water. The calculated results for an illustrative example are presented. The example is the waterflood of a reservoir containing free gas in the reservoir as a result of the partial depletion of the oil by the expansion of the gas initially in solution. The flood pattern for the example is a 5-spot.

Jan 1, 1967

By Harold J. Schock

This paper describes an experimental method for the monitoring of diesel-generated exhaust gas pollutants in a dead-ended drift for the purpose of assessing the effect of control approaches. Experiments were conducted to determine the relative merits of these ventilation configurations: no auxiliary ventilation, induction ventilation at the entrance to the drift, and ventilation of the dead-ended drift with positive displacement tubing. The drift used in this experimental work was approximately 105 ft. (32.0 mf long and slightly downsloping, with an average height and width of 8 ft. (2.4 m) and 28 ft. (8.5 m1 , respectively. The data were gathered for assessing these ventilation methods and for gathering data to support a computer model of the dispersion and mixing processes. For this drift, it was found that ventilation with positive displacement tubing provided the best removal of diesel-generated pollutants. Induction ventilation appeared to be the least effective of the three methods examined. A comparison was also made between personal monitoring and area monitoring. Results of this analysis showed that in regions of high concentration gradients, it was not possible to get good agreement between point sampling and personal monitoring. In well-mixed areas, good agreement between the two methods of monitoring was obtained.

Jan 1, 1980

By I. Tinto

"IntroductionEnvironmental pollution problems, caused by gases or effluents, by high noise levels or from air borne dust, are placing increasing demands of the operators, from statutory authorities, and from the general public, to adopt more stringent dust control measures. This requires that a successful plant dust control program be an integral part of any plant operation. While a successful environmental program is a key factor in maintaining productivity and good labour relations, anticipation of future environmental regulations during the plant design phase can avoid the high cost of plant upgrading, or dealing with pulmonary conditions in the work force in subsequent years.Particulate removal, conventionally called dust collection, involves the removal of coarse- and fine-particulates from the airstream. Although generally limited to that required for contro!Hng plant generated air emissions, particulate control equipment also has a wide application for air cleaning and filtration inside the plant, as well as for recovery of usable products.In the late 1950s and early 1960s the public became more concerned with the problems of air pollution. This increasing concern was stirred by an awareness of the extremes to which water pollution had progressed in many of the rivers and lakes, by increasing perception of air pollution as detected by visible smog and harsh chemical odors, by the alarming rate of increase of smog plagued cities and communities, and by specific incidents where ill health could be traced to specific episodes of air pollution. Particle size is perhaps the most important single factor affecting particulate control. Large particles (over 5 microns) constitute the major mass fraction of most sources of emission and economical control equipment dqes exist for their efficient control. However, while these larger particles frequently represent the source of soiling and unsightly smoke plumes, they are not a major health problem as they tend to settle relatively quickly, are more easily scrubbed from the atmosphere by rain, and are not able to penetrate the respiratory system. By far the most important form of particulate air pollution is the fine particulate, (below 3 microns) which is harmful to the pulmonary system. The adverse effects caused by this particulate matter on human health are for the most part related to injury to the surfaces of the respiratory system. Particulate material in the respiratory tract may produce injury itself, or it may act in conjunction with gases, altering their sites or their modes of action. A combination of particulates and gases may produce an effect that is greater than the sum of the effects caused by either individually (i.e. synergistic effect)."

Jan 1, 1989

By W. R. Reed, S. Klima, J. Driscoll, T. W. Beck

"Tests were conducted to determine properties of 4 foam agents for their potential use in longwall mining dust control. Foam has been tried in underground mining in the past for dust control and is currently being reconsidered for use in underground coal longwall operations in order to help those operations comply with MSHA’s lower coal mine respirable dust standard (1.5 mg/m3). Foams were generated using two different methods. One method used compressed air and water pressure to generate foam, while the other method used a low pressure air generated by a blower and water pressure using a NIOSH developed foam generator. Foam property tests comprising of a bottle shake test, foam expansion ratio, and water drainage were used to classify foams. The bottle shake tests determined that the lowest concentration of foam agent to be used was approximately 1.5%. Compressed air generated foams tended to have low expansion ratios (10-19) with high water drainage. Blower air generated foams had higher foam expansion ratios (30-60) with lower water drainage. Foams produced within these ranges of expansion ratios are stable and potentially suitable for dust control. The different foam agents produce foams with different material properties. Results of testing eliminated two foam agents for future testing because they had poor expansion ratios. The remaining two foam agents, while having different foam properties, seem to have properties adequate for dust control. These material property tests can be used to classify foams for their potential use in longwall mining dust control. INTRODUCTION About one-half of U.S. underground coal is produced by longwall mining. This technique allows for mining high volumes of coal, producing significant amounts of coal mine dust. This can lead to the overexposures to longwall miners and possibly occupational respiratory diseases black lung and silicosis, which have no cure and can be disabling or fatal. The only method to avoid these occupational illnesses is through elimination of exposure to respirable coal mine dust and crystalline silica (quartz). The current occupational exposure limit for respirable coal mine dust is 1.5 mg/m3 during each shift that a miner is exposed in the active workings of the mine or in mine facilities [1]. When respirable quartz is present, the mine must maintain an average concentration at or below 0.1 mg/m3. If the mine exceeds the 0.1 mg/m3 respirable quartz dust concentration, then the applicable respirable dust standard is reduced, calculated as 10 divided by the percent quartz present [2]. Respirable dust samples collected by U.S. Mine Safety and Health Administration inspectors for the five-year period from 2010 to 2014 found that 5.6% (53 of 943 respirable coal mine dust samples) of the longwall operators on the tailgate side exceeded the coal mine dust standard, and 4.3% (76 of 1768 samples) of the jacksetters exceeded the standard. If silica is present, the reduced standard is implemented, meaning that 11.4% (36 of 316 respirable coal mine samples analyzed for dust) of the jacksetters exceeded the reduced standard. Only 3.8% (18 of 478 samples) of the longwall operators on the tailgate side exceeded the reduced standard [3]. Had the 1.5 mg/m3 standard been in effect during this period, non-compliant samples would have been much higher. For example, over 15% of the samples collected at the tailgate shearer operator occupation exceeded the lower standard."

Jan 1, 2017

By Z. Y. Liu

A local additional potential model (LAPM) was developed to illustrate the role of strain rate in stress corrosion cracking (SCC) of pipelines. According to LAPM, both density and mobility of the local active spots on the steel surface, i.e., dislocation emergence points, increase linearly with strain rate. Generation of such active spots introduces an additional negative potential locally, affecting the electrochemical reaction and, consequently, the susceptibility of the steel to SCC. Electrochemical corrosion measurements, slow strain rate tests and electrochemical hydrogen permeation test were combined to demonstrate the validity of LAPM to illustrate pipeline SCC in an acidic soil solution. It is found that a maximum of the SCC susceptibility occurs at strain rate of 10-6 s1, which is associated with an enhanced hydrogen evolution due to the local additional potential (LAP) effect.

Jan 1, 2010

By J. G. Pippenger

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

Jan 1, 1995

By C. Ek

In bismuth metallurgy, low-copper high-sodium mattes are by-produced. Different charges containing mixtures- of crude mattes, oxidized matte, and/or copper sulfide concentrate and/or copper silicate ore have been smelted to give a rich matte and a disposable slag, then converted to obtain blister copper with high recovery and a rich slag to be recycled.

Jan 1, 1983

By A. Jennings, J. Cornet, P. Perrone

Controlling long overland conveyors with multiple drive stations is a complex problem. The methods for controlling these belts in a steady state are well-covered in existing literature, but a discussion of starting and stopping strategies is absent. This paper outlines different control strategies for starting, stopping and running conveyors with multiple drive stations. To illustrate the benefits of applying the methods described in this paper, the authors show how their adoption corrected many of the control system problems at Essroc Cement’s overland conveyor, which features three drive stations separated from each other by long lengths of continuous conveyor belt.

Jan 1, 2013

By William C. Smith

Roof support, an important aspect of ground control, involves maintaining roof competency to ensure a safe and efficient mining environment. Wide variability in rock quality and stress distributions requires a systematic approach to roof support design that satisfies specific goals. The success of past roof sup-port in reducing the incidence of roof falls has been primarily attributed to safer roof bolting practices. However, roof falls continue to be the number one occupational hazard in underground coal mines. This U.S. Bureau of Mines report presents a general overview of roof bolting and other roof support methods used in the United States. Characteristics of bad roof and associated roof failure theories are briefly presented as background to roof support. Methods of detecting and monitoring roof behavior and/or bolt performance provide essential feedback on roof support requirements. A discussion follows on roof bolt design that assimilates roof and support parameters into useful equations or nomographs to help decide what bolt types to use and how they should be installed under different roof conditions.

Jan 1, 1993

The organisers of this function have suggested that this presentation should accomplish the following broad goals:set the technical tone for the conference to follow, implying some discussion of the æstate-of-the-artÆ of reserve estimation; and raise some current and common problems or deficiencies in our art in order to be thought provoking. As an engineer it is always easier to raise problems than to solve them with state-of-the-art. Consequently, I have had to limit the extensive list of problems that could have been discussed within this presentation. In regard to the state-of-the-art, this presentation will not be an esoteric discussion of the latest statistical estimation processes, although I intend to challenge those with skills in that area to address some of the thought provoking issues later on. The subtitle of the paper was established after reading an excerpt from æLife on the MississippiÆ by the American humorist Mark Twain in which Twain observed that the Mississippi River had become shorter during his working period on the River due to natural cut-offs and man made channels. Projecting into the future, he calculated that by now, Cairo, Missouri and New Orleans, Louisiana would become a single city with one mayor (the two cities are still separated by some 500 air miles). As a moral to this story Mark Twain observed that one can obtain: æwholesale returns of conjecture out of such a trifling investment of factÆ.

Jan 1, 2000

By AIME AIME

In the present number of Mining and Metallurgy, issued on the fiftieth anniversary of the founding of the Institute, it appears appropriate to chronicle a few of the interesting incidents respecting its early life. We are fortunate in being able to cull the following notes from unpublished manuscripts of Doctor Raymond and Doctor Drinker, than whom no other members could have written with greater exactness and fidelity. THE seventh decade of the 19th century may be said to have marked an. era in the history of the world. Industrially and .commercially it was marked by the wide application and utilization of discoveries already made, which came to their full effect at this period in steamships, railways, telegraph and cable lines; the standardization of parts in machines, from watches to locomotives; the use of 'dynamite, antiseptic surgery, the open-hearth steel process, the compressed-air rock-drill, the electric generator, and the Gatling gun. Through the opening of the Suez canal in 1870 the maritime trade of the world was revolutionized, sailing vessels were supplanted by steamers, while ocean cables and ocean "tramps" brought about far more rapid movement of commerce than had before been experienced. Politically, this period was marked by the sudden birth of the German empire and the beginning of that intensive internal development of the national resources of that empire in preparation for colonial extension and war, the amazing result of which has been made evident by the recent world conflict. In the United States, the significance of this decade was peculiarly important. The re-admission to the union of Virginia, Mississippi, Texas and Georgia in

Jan 1, 1921

By N Anderson

The world-class Golden Mile gold deposit in the Eastern Goldfields of Western Australia is part of the Kalgoorlie Consolidated Gold Mines (KCGM) operation, which is wholly owned by Northern Star Resources Limited. Current mining operations across the Golden Mile is dominated by the large Fimiston Open Pit, which is over 4 km long, 1 km wide and 600 m deep. It is part of a larger mineralised system that stretches over 8 km and includes the Mt Charlotte Underground Mine, which is also operated by KCGM, as well as numerous historical open pit and underground mines. This mineralised system has been continuously mined for over 125 years and is set to continue well into the future. The Golden Mile deposit is in the Norseman Wiluna Greenstone Belt which is made up of a series of mafic volcanic and sedimentary rocks that have been structurally deformed and intruded by granitic rocks. There are two main styles of mineralisation across the Golden Mile. Firstly, the Fimiston style, which consists of shear hosted Golden Mile lodes with abundant sulfides and tellurides and secondly, the Charlotte style that comprises younger stockwork veins. Fimiston style mineralisation is the primary style of mineralisation within the Fimiston Open Pit. Historically, in excess of 3500 m of underground development and over 755 stopes were mined prior to the consolidation of the area and the commencement of Fimiston Open Pit operation. Old underground workings, known as voids, are either empty or backfilled and extend to more than 1.2 km below surface. Although they are a routine part of mining operations at KCGM, voids pose a significant challenge for the geology team in terms of planning and executing exploration and grade control drilling, geological modelling, grade and tonnage estimation, drill and blast design and execution, marking up ore block designs, mining, and reconciliation. This paper will discuss the various challenges faced by the geology team due to the presence of voids, solutions used to overcome some of these challenges and the results of these activities.

Mar 22, 2022

By J. A. Ehler

Speed and torque control of standard A.C. induction motors can be accomplished using a variety of devices ranging from mechanical, hydraulic, and electrical. Also, the motor can be specified as an A.C. wound rotor or D.C. motor using the associated controls. Normally, any one of these drive types can be adequately used to provide the torque control necessary to accelerate a conveyor belt system. The selection will depend on the economics, experience, and preference of the designer or end user. These drive types will be presented from a functional and performance viewpoint to assist in the understanding of the available technology.

Jan 1, 1998

By Todd Minoski, Matthew McElhinney, Morgan Sears, Craig Compton

In an effort to advance the science underlying ground control engineering, researchers with the National Institute for Occupational Safety and Health (NIOSH) are frequently involved in field studies at collaborating mines. Often, these field studies involve visiting the mine site, instrumentation installation, and data acquisition. Each of these aspects involve potential risks to NIOSH employees. As an organization whose mission it is to promote the health and safety of mine workers, the health and safety of our workforce is paramount. This paper provides documentation of the best practices followed by NIOSH employees who are tasked with visiting and conducting work at underground and surface mines. This includes Mine Safety and Health Administration (MSHA) approved training, mine site specific training, and hazards associated with all aspects of mining that could be encountered by the employee. Additionally, this paper details best practices associated specifically with instrumentation installation including the mitigation of hazards associated with the proper equipment handling, drilling, and the mine environment. The information showcased in this paper can be used as considerations for industry practitioners such as mine operators, consultants, and academic researchers engaged in the installation of instrumentation in the field. Furthermore, the best practices detailed in this paper can be used as a foundation for agreements made between mine operators and researchers to ensure safety procedures will be followed while on mine property. This will result in enhanced safety of both researchers involved in field studies as well as mine employees tasked with assisting and accompanying those researchers.

Feb 1, 2024

By Z. Botha

Sheryl Sandberg, the COO of Facebook, published a book titled 'Lean In', where she invites women to sit at the table. In summary, to 'sit at the table' entails not only embracing opportunity, but to actively seek out opportunities in leadership positions. Sandberg points out that, unfortunately, apart from institutional obstacles, a woman's own perceived limitations have a negative impact on her leadership ambitions. To create an environment where diversity will flourish, where everyone has a seat at the table and everyone has a voice, safety must be established first. To establish safety within a diverse team, there is power in relationships and connections. This study will first and foremost review theories in literature as to why diversity and inclusion are so important and the value that diversity brings to our industry. The study also recommends a few focus areas for improving diversity and inclusion in the industry.

Sep 1, 2022

By Éder Domingos Oliveira, Carlos Antonio Morais, Ruberlan Gomes Silva

The objective of this study is to assess the impact of different reagents, such as limestone, lime, magnesium oxide, and sodium hydroxide, in experiments carried out in the single purification step and in two consecutive purification steps by raising the pH of a rare earth sulfuric liquor with the aim to remove or reduce the impurity concentrations in the rare earth sulfuric liquor. The choice for the best purification condition was made based on the minimum loss of rare earth elements (REEs), reagent consumption, and residue generation. The exploratory experiments show that it takes place in the two consecutive purification steps, the first one consists in dosing the limestone pulp until it reaches a pH of 3.5 followed by an addition of a lime pulp reaching a pH of 5.0. Under this condition, the results were a total removal of Fe3+, PO4 3− , and Th4+ ions and a reduction of 99%, 87%, and 37% w/w in the Al3+, UO2 2+, and SO4 2− concentrations, respectively, in the purified rare earth liquor. Furthermore, the lowest REE losses (8.3% w/w) and reagent consumption (4.3 kg/m3 ) and also a low residue generation (7.5 kg/m3 ) were observed in this condition. Despite reaching similar results regarding impurity removal, the experiments done with the addition of limestone, lime, magnesium oxide pulps, and sodium hydroxide solution in the single purification step, where the pH was raised to 5.0, presented higher REE losses (64.9%, 42.5%, 44.8%, and 60.9% w/w, respectively) and a higher residue generation (43.2, 25.1, 11.1, and 13.6 kg/m3 , respectively). This occurred due to the co-precipitation of salts containing rare earth elements in their composition. The experiments conducted with limestone, lime, and MgO resulted in a higher consumption of reagents, while the same result was observed when NaOH was used (4.3 kg/m3 ). In the experiments carried out with the addition of magnesium oxide and sodium hydroxide, the respective purified rare earth liquors presented a high concentration of magnesium, sulfate, or sodium, which could impact the quality of the marketable rare earth salts, whereas the salts obtained under the best condition observed in this study seem to be amenable for use as raw material in an attempt to obtain rare earth products with an acceptable chemical quality.

By J. P. W. Bennie, A. de Jong, G. M. Denton

Mintek together with Middelburg Steel & Alloys, developed the DC arc furnace process for the production of ferroalloys with the expressed objective of smelting ore fines (<1mm) without the need for agglomeration. In the case of ferrochrome production, the DC arc furnace, being a semi-open bath operation, loses radiant energy directly from the bath to the furnace roof and sidewalls above the melt. This energy loss is reflected in a higher electrical energy usage per ton of alloy than for a submerged-arc operation smelting lumpy ores or sintered pellets. The difference increases still further when pre-heated sintered pellet feed is used in a submerged-arc operation. This shortcoming of the DC arc furnace can however be overcome by preheating the feed to the furnace in a fluidized bed or flash reactor fuelled by cold furnace off-gas. In addition to fluidization and preheating testwork, various preheating flowsheets with associated mass and energy balances have been developed and compared from a techno-economic viewpoint. The three major advantages identified were: a) fluidized beds can preheat ores and fluxes up to 950°C without sticking and defluidizing, b) the open bath DC arc furnace does not require expensive coke or char to maintain the burden porosity and, c) the capital cost associated with the milling, pelletising and sintering plant falls away since ore fines are used directly.

Jan 1, 2004