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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 A. Kosiór

Many remnants of gold exploitation in the Middle Ages were found in the Lower Silesia region. The oldest evidence of such activity was found in the neighborhood of Zloty Stok and comes from the 7th century. Mining of precious and non-precious metal ores has a great relevance in the late Middle Ages when advanced metallurgic technologies were mastered, that allowed to obtain gold, silver, lead, copper, zinc and arsenic from complex ores occurring in the oldest middle part of Sudetes. Historically it concerned the area of the Swidnica Principality and Klodzko County. Experience obtained in Freiberg, which is located close to the Lower Silesia, was used in the development of mining. A high level of mining and metallurgic technology was obtained in the 15th century that caused significant increase of production of the metals mentioned above. Unfortunately, the good time of Lower Silesian mining lasted only up to the 18th century; the notion of preservation of cultural heritage was unknown at that time. The Lower Silesian medieval mines were not in such a fortunate situation as the ?Wieliczka? and ?Bochnia? mines, which are operating to present-day, and which made preservation of the most interesting headings and objects possible. All these objects are now available for visitors. However, in the case of the middle Sudetes it seems that it is often sufficient to localize old shafts and headings on the basis of careful observations and old maps and carry out some earthwork to uncover medieval headings and objects of underground mining activity. They are often preserved in amazingly good state; this also pertains to mining devices. Another issue is of course the permanent preservation of that heritage and its possible availability for re-searchers and tourists. Some success has been achieved in that field (Zloty Stok Gold Mine is a good example), but also problems were encountered in many cases. The Lower Silesian Coal Basin, which has not been exploited for 10 years is an evidence that there is not a holistic conception of mining heritage renovation. Many attractive mining objects disappeared irrecoverably from the mountainous landscape of the Middle Sudetes despite common consciousness of their significance for cultural development of Silesia and other regions.

Jan 1, 2006

By T. D. Arnold

The Barrick Bullfrog underground mine was established as an afterthought to the main open pit. As open pit ore dwindles, the underground mining becomes increasingly more important as an ore source, and to the overall economics of the project. This situation is similar to many other mines, and there is a strong move towards underground mining in the United States today. There are inherent problems in starting and operating underground mines in the shadow of any open pit operation, and at the Bullfrog there were several attempts at productive increases that were both successful and unsuccessful.

Jan 1, 1996

By L. N. Hill

The classifiers on the primary grinding circuit at Cyprus Sierrita have been upgraded from 0.66 m (26 in) diameter hydrocyclones to 0.84 m (33 in) diameter hydrocyclones. This has resulted in a 4.3 % (11 t/h) (12 standard tons/hour) increase in mill throughput while producing a flotation feed which contains 4.8% less +300 micron (48 mesh Tyler screen size) material. This reduction in flotation feed particle size has increased copper (CU) recovery by 0.8 %. Various grinding circuit relationships were evaluated. These relationships include circulating load versus throughput, horizontal versus vertical cyclone configuration, and the effect of cyclone components on performance. We conclude that the improvements achieved are due to a shift in the overflow size distribution created by a cyclone diameter more suited to our operation, and by eliminating the cyclone capacity constraint in the grinding circuit.

Jan 1, 1994

By Olivier Martin

In busy and historic cities, traditional open box metro stations are becoming outrageously difficult, unacceptable for the citizen and uneconomical. Hybrid stations provide an interesting alternative. In-house experience of Gautrain (South Africa), West bay (Qatar), Cairo line 3A (Egypt), and Melbourne (Australia) all aim to reduce disturbance to the city and its inhabitants during construction. Constructed in rock or in deep soil under water table, they take advantages of the latest construction techniques from cement grouting to freezing, and from traditional excavation of cavern to large tunnels constructed by sophisticated tunnel boring machines (TBM). Today, they form the ultimate construction challenge.

Jun 13, 2021

By John Corcoran

INTRODUCTION Content of this Report The 1300m long twin-bore 8.1m diameter Airside Road Tunnels (ART) were excavated beneath the busy taxiways and stands of Heathrow Airport between 2002and 2003. The tunnels were fully completed and handed over to the client for use early in 2005. This paper will describe the purpose of the tunnels, and the measures put in place to minimize the impact of construction on the daily activities involved in running an international airport. Terminal 5 Construction Heathrow Airport is the busiest international airport in the World, with a current capacity of circa 67 million passengers per year, based on existing infrastructure of4 passenger terminals, 1 cargo terminal, 2 runways and 170 aircraft stands. Terminal 5(T5) is being built to increase Heathrow’s passenger capacity by providing the following: 12 additional aircraft stands through redevelopment of the south apron area, in the autumn of 2004 A main terminal building (T5A) and a first satellite (T5B), and 43 additional stands by the spring of 2008, most of which will be able to receive the new generation large aircraft (Airbus A380) A second optional satellite (T5C) by year 2010 A third optional satellite (T5D) by year 2015 The total value of the project is approximately 4.2 billion pounds for the main phase of the works spanning from 2000 to 2007. Purpose of the Airside Road Tunnel The ART has been constructed to support the internal road traffic of the airport between terminals, aircraft stands, runways and taxiways, for passenger buses, service and technical vehicles. The majority of the traffic will be buses transporting passengers between the terminals and their aircraft.

Jan 1, 2005

By Christopher D. Henry

Environmental geologic maps of the Wilcox and Jackson-Yegua lignite belts of the Texas Coastal Plain delineate land areas on the basis of their natural characteristics. Criteria used to define map units include substrate, soil, topography, geologic process, vegetation, and land use. The maps are useful in planning and reclamation of lignite mines and in meeting the requirements of State and Federal surface mining laws. Specific applications include identification of land capability, recharge areas and geometry of aquifers, flood-prone areas, areas that may qualify for prime farmland status, and other areas sensitive to lignite mining.

Jan 1, 1982

By Pascal Deschamps

"INTRODUCTION During the last decades, many underground facilities for the storage of hydrocarbons have been excavated worldwide and the technology is fully mature. Similarly to other underground structures, the initial basic design has to be adapted along with the work progress, in order to cope with the actual site conditions and in particular the geology, hydrogeology and associated rockmass quality. In addition, Client’s or underground Contractor’s constraints (such as resources availability, schedule or cost impact) may vary from design to construction and require last minute adjustments. Engineers are required to introduce flexibility and anticipation of unexpected situations (similar to the above-mentioned) while conceiving large underground facilities. Although most of the cases require only minor adaptations, crucial parts of the facility have sometimes to be considerably modified and reviewed. This article will present four cases evidencing how the design of one of these essential structures - the concrete plug – has been adjusted during site implementation without impairing the initial performances. Hydrodynamic containment The product containment of the unlined caverns discussed here is ensured by the principle of hydrodynamic containment. A permanent water flow is naturally or artificially maintained with an orientation toward the storage cavern and then, neither product-tight membrane nor lining are required. The hydraulic gradient (and the associated water flow lines), being directed from the surrounding mass toward the cavern, prevent from outward migration of the product. If the hydraulic gradient is not sufficient or if the water table is evidencing instability, water can be artificially injected into the rockmass through purpose-built boreholes, drilled from dedicated galleries. This water injection system, called the water curtain, is generally located several tens of meters above the level of the cavern. This principle is illustrated here after."

Jan 1, 2016

By D. M. Muir

Thiosulfate offers a non-toxic alternative to cyanide for processing gold ores. The mechanism of leaching gold using ammoniacal thiosulfate solution is driven by the Cu(II)-Cu(I) redox couple and is complicated by competing ligands such as NH3 and S2O32-. It is shown that an understanding of the copper speciation and sulfur speciation is required to optimise this system. This paper presents Eh-pH and speciation diagrams for varying concentrations of Cu(II), S2O32- and NH3 and discusses the conditions under which various copper and sulfur species are stable.

Jan 1, 2001

By Jay F. Colinet

Coal workers’ pneumoconiosis (CWP), commonly known as black lung, is caused by the inhalation of respirable coal mine dust and is a disabling and potentially fatal lung disease with no cure. Historically, CWP has taken a tremendous human and financial toll on the U.S. coal mining industry. Recent health surveillance data indicate that CWP continues to occur at elevated levels. Respirable coal dust exposure must be controlled to prevent the development of CWP. The Pittsburgh Mining Research Division of the U.S. National Institute for Occupational Safety and Health (NIOSH) conducts laboratory and mine-site research to identify control technologies that can be used to successfully reduce respirable dust levels. Various technologies, using multiple methods of control, can be applied to reduce dust levels. An overview of CWP’s impact and a general methodology for controlling respirable dust in underground coal mines are discussed in this paper.

Despite the current economic downturn that is now decimating iron ore production, Minnesota?s mining operators remain optimistic about the long-term prospects for the industry. Reflecting this optimism, the development of several new mining projects continues in the state. The future of mining in Minnesota was the featured topic at the combined 82nd Annual Minnesota Section of SME Meeting and 70th Annual University of Minnesota Mining Symposium. More than 500 mining industry professionals, including engineers, executives, mining managers and equipment suppliers from the around the world, attended the meeting, which was held April 14 and 15, 2009, in Duluth, MN. The combined meeting featured a keynote session with three distinguished speakers plus a panel discussion by representatives from several of Minnesota?s taconite producers. The keynote speakers were Curtis Clark, president and chief operating officer, Behr Dolbear, who gave a presentation on the ?State of the Mining Industry.? Phil Newman, chief operating officer, CRU Strategies, spoke about challenges facing the mining industry and James A. Skurla, acting director, Bureau of Business and Economic Research, Labovitz School of Business and Economics, University of Minnesota Duluth, discussed the importance of mining to northeastern Minnesota?s economy. The taconite producers panel discussion included Jonathan Holmes, vice president and operations manager, ArcelorMittal; Ed Latendresse, vice president and general manger, Hibbing Taconite; John Tuomi, vice president operations services, United Taconite and Mike Mliner, vice president and general manager, Northshore Mining. The mangers provided updates on their respective operation The meeting included concurrent technical papers sessions on mining, processing, environmental and nonferrous mining. The sessions included technical papers that provided information on the status of a number of new mining projects in the state. The conference also offered a SME short course titled ?The basics of iron mining.? A tradeshow that featured about 100 companies and organizations offering products and services to Minnesota?s mining industry ran in conjunction to the conference. It was estimated that more than 900 people, including conference registrants and special invited guests of the vendors, attended the tradeshow opening reception. This was the largest trade show in many years. The Minnesota Section of SME also held its annual business meeting during the conference.

Jan 1, 2009

By W. H. Langer

At the start of the 20th century Denver?s population was 203,795. Most streets were unpaved. Buildings were constructed of wood frame or masonry. Transport was by horse-drawn-wagon or rail. Statewide, aggregate consumption was less than 0.25 metric tons per person per year. One hundred years later Denver had a population of 2,365,345. Today Denver is a major metropolitan area at the crossroads of two interstates, home to a new international airport, and in the process of expanding its light rail transit system. The skyline is punctuated with skyscrapers. The urban center is surrounded with edge cities. These changes required huge amounts of aggregate. Statewide, aggregate consumption increased 50 fold to over 13 metric tons per person per year. Denver has a large potential supply of aggregate, but sand and gravel quality decreases downstream from the mountain front and potential sources of crushed stone occur in areas prized for their scenic beauty. These issues, along with urban encroachment and citizen opposition, have complicated aggregate development and have paved a new path for future aggregate development including sustainable resource management and reclamation techniques.

Jan 1, 2009

By J. J. K. Daemen

Mining Engineering education is in trouble, if not in crisis. The most visible signs are the decrease in the number of programs that offer the degree, and the continued difficulties in attracting students to the discipline. Unless these trends are reversed, the future of the profession is uncertain, at best. Remedies have been proposed, and some are drastic. They range from consolidating mining engineering education into one or two national schools, to cooperative regional programs, to distance education programs, and to proposals to limit mining engineering to a graduate degree or specialization only. These alternatives deserve serious attention and merit discussion. I hope that one alternative that will remain on the table is the classical and traditional “School of Mines”. A reasonable number of such schools are needed to provide the educational diversity and the critical mass to maintain accreditation and professional registration for their graduates. Most importantly, such an approach is most likely to assure the continued existence of mining engineering as a profession. It also provides the best educational framework to teach mining engineers. However, such Schools are vulnerable, highly susceptible to university budget pressures, and probably can survive only with strong external support.

Jan 1, 2004

By Paul D. Tomlingson

A new sense of urgency permeates the mining industry concerning maintenance. Mining's continuous process environment demands around-the-clock maintenance support. And profitability conscious mining operations require that production targets be met on time - and economically. These goals require nothing less than an effective maintenance program. In turn, the effectiveness of the maintenance program depends on quality information: easily procured, complete, timely, accurate, and properly used. Information picture is changing Some of the fully integrated, mainframe maintenance information pro¬grams of better days remain. Their upkeep and cost of operation, though, is becoming more difficult to justify. Some operations, faced with production cutbacks a few years ago, downscaled and found they liked it. Now, during an upswing, these operations question the need for the more elaborate, administrative-heavy programs they used to operate. Package programs are not taking their place. Too often, the packages are vague and generic. Some vendors claim that if their offerings work in a hospital complex, they must work in an underground mine. That is not so. Maintenance information in the mining industry is different. The situation has changed There are now smaller, self-contained maintenance groups whose information needs are different. These include an electrical crew in a smelter, an underground mobile equipment shop, or a remote service shop between several distant operating pits. These working environments have changed the character of the information needed as well as the methods for obtaining and using it. Operations-maintenance link In coming back from a downturn, operations people realize that their ability to meet production targets hinges on reliable equipment and avoidance of downtime. They have become familiar with the need to use maintenance services effectively. They also want quality maintenance information. When coupled with the sense of urgency about maintenance, a business-like working environment emerges that has significant new differences in both work control and information. Work control impact Work control has been streamlined to improve communications. Supporting information has been streamlined as well. • Verbal orders are the rule rather than the exception to quickly bring a multi-craft crew to the flotation section or a pit crew to a disabled haulage truck. • Written work requests and work order forms are seldom used, or even needed. Rather, electronic work control logs permit operations to request work, maintenance to acknowledge it, get ready, and do it - quickly, without delay. • Routine servicing is triggered by operating hour accumulation (mobile equipment) or tons of throughput (fixed equipment). Operations is now taking the initiative in delivering mobile equip¬ment to the "bad order line," or switching to a bypass conveyor. Operations wants immediate follow-up reports on equipment condition.

Jan 1, 1989

By Richard J. Lewandowski

Corrosion and product contamination have been difficult problems for extractive metallurgy industries in the U.S. because of the highly active chemicals used. During the past twelve years, other industries, particularly the chemical and paper segments, began to combat this problem with some degree of success using newer materials of construction, including reinforced plastics. These materials are made by combining a corrosion resistant thermosetting resin with a glass fiber reinforcing material and are used to con¬struct hoods, stacks, blowers, tanks, towers, pipe, and equipment of the most complex configurations. For service in contact with aggressive chemicals, the equipment is most often fabricated with the bisphenol-A fumarate polyester resins because of their resistance to corrosive attack. Data from both laboratory work and case histories of field applications are presented-for many common chemicals found in extractive processes. Information is also presented concerning design standards and recommended construction procedures

Jan 1, 1970

By J. P. McCluskey

The effects of air quality regulations passed in the last few years have been felt in a more pervasive way by the electric utility industry than by perhaps any other industry. I'm referring especially to those regulations dealing with the control of air emissions from stationary sources, and those specifying the quality of fuel used. Particularly, I would like to describe some of the effects that these regulations have had on the Commonwealth Edison Company. To put the subject into perspective, a brief descrip¬tion of the company will be presented first. Then, a historical outline of some of the efforts at control of electric generating station emissions will be described. Following this will be an indication of the Company's response to early State and local regulations prompted by the growing pressure for stringent envi¬ronmental control. Finally, the Company's plans to achieve com¬pliance with the most recent, Federally approved, State of Illinois regulations will be summarized.

Jan 1, 1973

By L. Clark

Despite near-record commodity prices, the mining industry continues to search for ways to maintain profits in these times of steadily increasing energy prices and steadily decreasing grades. The pressure is still on today’s miners to continuously improve their operations because they know that one day prices too will drop. Some, however, have seized the opportunity to employ systematic methods to reduce costs and increase the efficiency of their workforce and equipment. As a result, closer attention is being paid to scheduling and the value that could be added by defining the extraction sequence that maximizes the net present value [NPV] of a project. This paper will discuss the challenges faced by Newmont Mining Corporation [Newmont] at its operations and the application of sophisticated software tools and methods in its search of solutions to this problem.

Jan 1, 2007

By Jennifer King, Julius Strid, Steve Brandon

The Upper Hidden Basin Diversion (UHBD) tunnel was driven approximately 1.2 miles by the drill-and-blast method primarily through massive granite bedrock geology for the Kodiak Electric Association, Inc. (KEA) in Kodiak, Alaska. The tunnel was driven from both portals with a constant 11-ft straight-leg horseshoe cross-section. The design and construction of the tunnel was driven by logistics and weather conditions due to its remote location and the rugged terrain of the project setting. This paper will discuss the successful completion of a challenging project over a ve-year period from preliminary planning through the design and construction phases.

Jun 23, 2024

By M. J. Hannan

Considerable interest has arisen in developing analytical methods suitable for measuring resource commodity substitution patterns. some of this work has applied the Translog method to estimate actual elasticities of substitution. Recent examples incl.uae Privolos and Dunietz (1987), Kopp and Smith (1983), and Moroney and Trapani (1983). Another method, one which has received attention earlier in the work of Fisher and Pry (1970), is that of the logistic or diffusion function. We believe that the latter method has properties suitable for analyzing current problems of material substitution. The present study thus evaluates this method in its original logistic form as well as an extended version incorporating additional explanatory influences. The analysis is applied to copper/aluminum substitution and iron ore beneficiation. Substitution for copper by aluminum is examined in the building wire and cable, and magnet wire end-use markets. For iron ore, the substitution of pellets for sinter is considered for the U. S. market.

Jan 1, 1990

By M. J. Gula

In the solvent extraction -electrowinning recovery of copper from oxide or sulfide ores there is a continuous transfer of iron and other impurities from the primary leach solution to the copper electrowinning electrolyte via chemical transfer or mechanical entrainment. Iron is the principal impurity that has to be controlled in the electrolyte by a "bleeding" of the electrowinning solution. This bleeding transfers copper and sulfuric acid back to the primary leach circuit along with the iron. Copper is recovered via the solvent extraction process and generally the sulfuric acid is used as a reagent in leaching. Unfortunately, cobalt, which is added to the electrowinning solution to modify the anodic process, is irreversibly lost through the bleeding operation. This cobalt loss represents a significant operating cost to SX-EW copper producers. DiphonixTM ion exchange resin contains diphosphonic acid and sulfonic acid functional groups on a polystyrene-divinyl benzene matrix. This resin has been found to strongly and selectively extract ferric ion from copper sulfate -sulfuric acid solutions containing cobalt. Thus, an ion exchange process using DiphonixTM resin for the control of iron has been developed to replace the conventional bleed stream process. The new process minimizes the loss of cobalt from the electrowinning circuit and strips the iron into a sulfate based solution suitable for leach solution makeup. In addition, this process can effect a lowering of the total iron concentration in the electrolyte circuit with an associated increase in current efficiency. In this paper, data on the loading and elution of iron are presented. Laboratory and pilot scale data will be discussed along with information on process design and comparative economics.

Jan 1, 1996