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By Zhu Mingshan, Wu Jiang, Xu Yingqin

A mathematical model to simulate spontaneous combustion of coal in goaf was developed. Under the condition of two-dimensional flaw of air through a bed of uniform mixture of coal, gob, stone etc., the model simulates the temperature rise in the air-and-particle system associated with Arrhenius particle surface reaction. The model is developed as a set of coupled non-linear partial differential equations, which include (1)mass conservation equation for oxygen, (2)energy conservation equation for gas, (3)energy conservation for solid, and (4)velocity equation for gas, that are solved numerically. An elaborate parametric analysis is made of effect of leakage air flux and position of source and sink, parameters relating to the coal accumulating character and the kinetic properties of coal on the tendency to spontaneously combust. In addition, the dynamic process of temperature rise within goaf under several conditions is displayed with picture drawn by computer.

Jan 1, 1991

By J. Iannicelli

Kaolin tailings ponds play an important role in reclamation of land and water. Discharges impounded from kaolin plants include oversize fractions consisting of coarse kaolin, mica, quartz as well as magnetically extracted contaminents, acid filtrates, and plant washdown streams. Tailing ponds perform an essential function in sedimentation of particulates, blending and reoxygenation of liquid waste, and neutralization and clarification of discharge water. During the past fifteen years, most kaolin firms have segregated their coarse filler waste to allow for possible reclamation for production of delaminated coating clay. This excess coarse filler fraction constitutes a reserve for future coating clay production.

Jan 1, 1985

By Dan Ifrim

Soft ground tunneling poses major challenges to the underground industry. Most of soft ground tunnels are in highly urbanized areas, often include limited cover, and include a strong trend of increasing diameters. Therefore, soft ground tunneling works can sometimes cause inevitable ground movements and settlements that may lead to damages to adjacent buildings, roads, structures or utilities; many of these being “lifeline” infrastructure assets. Tunneling operations, Tunnel Boring Machine (TBM) advance rates, and face pressure control can significantly increase or decrease such risks, depending on how well the TBM and operational parameters are applied to the ground conditions. Additionally, the risks of impacting existing infrastructure are heightened in many parts of North America because of cobbles and boulders. To date there is no standardized guideline that determines appropriate tunneling rates nor operator’s guidelines, to ensure safe tunnelling in soft ground. The paper analyzes tunneling records from completed soft ground tunnels to determine a relation between ground conditions, tunnel cover, TBM cutters maintenance and TBM advance rates. The records are discussed to draw several mitigation measures to be adopted during tunnelling, to reduce risks of settlements, over excavation or sinkholes.

Jun 13, 2021

By Richard Weinstein, Richard Snoby

There are many advantages to upgrading coal with dry jigging technology. The most obvious is the lack of process water, which eliminates the need for fines dewatering and slurry confinement. Dry jigging eliminates the clean coal moisture penalty associated with wet processing. Particulate emissions are virtually nonexistent due to inclusions of fabric dust collectors on all modern dry jig plants. Because of the environmentally friendly nature of dry jig plants, installation permits are often measured in days, not months. There has also been a fundamental advance in dry jigging efficiency. All of these advantages have renewed the coal industry’s interest in dry jigging. But air jigging is not right for every application. There are limitations due to particle size, particle shape, moisture and near gravity content. This article explores the evolution of dry jigging. It reviews parameters important for determining the suitability of dry jigging. It also compares historical performance data as measured by imperfection, against results from modern dry jigging technology. The article also presents data from modern dry jig installations.

Jan 1, 2007

By David D. Spencer

As in many other areas of the Mexican economy, the legal rules applicable to mining in Mexico have been changing fast. Mexico's mining sector is opening up to levels of international participation that were unforeseeable just a few years ago. Over the last several years, Mexico has made dramatic changes in its trade and investment policies. Many of these changes have their roots in the administrations of Miguel de la Madrid and perhaps even Jose Lopez Portillo. However, the current administration of President Carlos Salinas must be given credit for articulating, advancing, promulgating and implementing these changes. Just a few short years ago, few people believed Mexico would repeal so many of its restrictions on foreign investment and lower its average tariff level from something around 100% to less than 10%, where it is today. NAFTA and mining The North American Free Trade Agreement (NAFTA) is the most comprehensive international expression of Mexico's new policies. Except perhaps for the agreements establishing the European Union, NAFTA is the most detailed trade agreement ever written, consisting of about 2000 pages. The provisions of NAFTA with the greatest relevance to the mining industry include the chapters on investment and government procurement. Many mining companies may also find the temporary work provisions relevant. Finally, no discussion of NAFTA and the mining industry would be complete without some mention of the North American Agreement on Environmental Cooperation, the so-called Environmental Side Agreement.

Jan 1, 1994

By S. L. Bessinger

The need for improved safety and productivity brought about the introduction of longwall mining to the Appalachian coal fields. These same forces continue to drive developments in modern longwall equipment and mining practices. Current initiatives to improve productivity and safety are focused on automation and the effects of scale in equipment design. Longwall roof-supports, shearers and face-conveyors have changed significantly. Panel layouts have evolved to include larger total tonnages and provide for more rapid development of gate-entries. These advancements have improved longwall productivity and new production records are continually being set. Roof supports Reliability is implicit in the quest for automation. It is impossible to automate equipment if it is not reliable. To a large degree, this has been the problem with longwall shield automation efforts. The "electronic control" of shields depends on the proper functioning of electronic equipment, electrohydraulic valves and full-flow service valves onboard every support.

Jan 1, 1995

By Danqing Xu, A. W. Khair

This paper presents an analysis of mechanism of secondary fragmentation and respirable dust generation due to regrinding. In continuous miners, the recovered coal and uncleaned coal from the previous cutting cycle have to be transported through the circumference of the cutting drum, subjecting the coal to regrinding. Such regrinding comminutes the coal material utilizing kinetic energy, thus creating a great amount of respirable dust. The mechanism of a single particle subjected to regrinding is analyzed. A mathematical model is developed to describe regrinding in field conditions. The important factors influencing the comminution process are discussed in detail. Utilizing three types of coal seams, laboratory experiments are being carried out with an Automated Rotary Coal Cutting Simulator (ARCCS) to quantitatively evaluate the effects of some particular parameters, such as cutting velocity, depth of sump and properties of coal material, on breakage and on the amount of respirable dust generated. An orthogonal fractional factorial experimental arrangement is used to optimize experimental design. Preliminary experimental results are presented.

Jan 1, 1991

By Dennis A. Giardino, Leonard C. Marraccini

This paper surveys noise levels, noise exposure patterns, and frequency spectra found in the mining environment; the effects of mining noise on the working population; and the quantification of hearing loss in the coal mining industry. Federal mining noise regulations and the present state of the industry, with respect to noise control technology, are discussed. Examples of proven noise controls for mining are included along with measured noise reductions.

Jan 1, 1986

By Osvaldo A. Bascur

Standards and technology for bringing information to the desktop have greatly evolved in recent years. The benefits to be realized depend on how these new tools are embraced at the performer level. A key operating challenge is to ensure cooperative effort is geared towards the most efficient achievement of identified operating and corporate objectives. Presentation, application and database layers are emerging in successful client/server applications, the three-tier architecture.

Jan 1, 1996

By William F. Daly, William H. Hansmire

Installation of initial tunnel support is often the most uncertain element of work in the design of, and a contractor bidding on, construction of a rock tunnel. The risks the construction contractor and owner assume are delineated to a great extent in the technical specifications portion of the contract documents. It is intended that this paper identify current practices for specifying initial tunnel support and the impacts each case has on the assignment of risks associated with providing the initial tunnel support. Examples of recently completed tunnel designs are given.

Jan 1, 1985

By Murray W. Hitzman

Two great revolutions in mining occurred during the 20th century. The first took place almost 100 years ago (1903-1905) with Daniel Jackling’s experiment in the economies of scale for large-scale mining at Bingham Canyon. Jackling’s ideas changed the focus of base metal exploration toward lower-grade, high-tonnage deposits. The second revolution was the impact of environmental and social concerns on mining. It started near the end of the 20th century and is still under way. This article speculates on the effects of this second revolution on the future of mineral exploration.

Jan 1, 2005

By W. T. Plummer

• The SuperBowl is a fluidized bed, semi-continuous, enhanced gravity separator for gravity gold recovery. The market for this type of equipment has, until recently, been dominated by a single supplier. Many mineral processors have encouraged the SuperBowl designers to develop competitive equipment for obvious reasons. • The primary beneficiary of competition in this field will be the mineral processing community because legitimate competition fosters continuous improvement in product and price.

Jan 1, 1996

By Michael J. Taylor

Introduction A prime goal in the design and operation of uranium milling waste or tailing disposal systems is to mitigate adverse effects of tailing liquid on the adjacent groundwater. Adverse effects are often defined as modifying the groundwater quality in such a manner as to have detrimental health effects on downstream users. To accomplish this goal, the following three types of systems are employed with regard to the seepage and groundwater aspects of waste disposal: Type I Systems Seepage is allowed to occur unabated from the tailing disposal facility. Detrimental radionuclides and chemical elements are prevented from causing adverse downstream effects by natural purification actions in the subgrade geologic materials and the near zone groundwater. Monitoring is required to assure the predicted natural purification is occurring. The consequences of seepage loss is minimal since the m be predicted with current investigation and analytical techniques and can be evaluated as to effectiveness during operations. Type II Systems Seepage is partially retained in a waste impoundment or leakage from a designed retention system is anticipated. Natural purification is relied on for controlling migration of detrimental radionuclides or chemical elements, or contingency planning is employed to collect and return the tailing liquid to the impoundment. Installation efforts and concern for escape of tailing liquid are greater than for Type I systems, but extra precautions to preclude all seepage are not implemented. Monitoring is required to detect leakage and/or assure the natural purification of escaping tailing fluid. The consequence for accidential excusions are moderate, and will be excessive only if massive system failure occurs. Type III Systems Seepage is totally restricted by a costly system constructed and operated with extra care. Natural

Jan 1, 1980

By Henry A. Russell

During the last ten years Parsons Brinckerhoff has become a leader in the area of tunnel rehabilitation. A significant part of any tunnel rehabilitation program is the control of groundwater infiltration into the structure. This leakage over time, causes deterioration of the structures, and creates numerous operational problems for the tunnel operator. This paper will address current procedures for identification, documentation, and recommendations of repair methods for the control of groundwater infiltration in rail and highway tunnels.

Jan 1, 1993

By Vicki Seppala

Phelps Dodge Mining Company operates some of the world’s largest open pit mines. Safely mining in these deep pits requires the commitment to a proactive integrated slope management process. The slope management process also includes the continued look for improved slope design, construction, and maintenance of slope faces. This paper discusses integration of such technology as electronic programmable detonators, 3D imaging using ground-based LiDAR scans, and reflectorless slope monitoring systems in a slope management program.

Jan 1, 2005

By Peter Joralemon

I want to limit my remarks to epigenetic ore deposits, but do not necessarily subscribe to the classic theories of hydrothermal ore deposition. I will consider an epigenetic deposit as a primary deposit in which the economic minerals have been introduced subsequent to the formation of the enclosing rock, regardless of the source. Past ore discoveries have been made to a great extent by prospecting techniques that have remained relatively constant over the last many decades. In many cases the discoveries have been enlarged or enhanced with the use of technical tools such as geophysics, but theoretical geology, which should serve as a foundation for exploration, has shown little progress of practical importance since the turn of the century.

Jan 1, 1967

By G. Thorsen

An alternative way to the normal practice of precipitation of jarosite, goethite, or hematite for removal of iron from zinc sulphate process liquors/ is to employ the techniques of solvent extraction. The process presented avoids the addition of any external alkali for the extraction of iron by integrating the leaching and solvent extraction steps in a hydrometallurgical zinc plant. By starting the leaching of zinc from the solid zinc calcine material with an organic solution of an acid liquid cation exchanger, the organic phase is loaded with the organic zinc salt from the direct reaction with zinc oxide. The residue from the organic leaching is transferred to a hot acid leach circuit where the remaining zinc oxide and the zinc ferrites will dissolve form¬ing an aqueous sulphate solution of zinc and iron. In the subsequent solvent extraction of iron from this aqueous leach solution, iron is exchanged with zinc from the organic phase. The commercial carboxylic acid Versatic 10 (Shell) is highly efficient for this integrated process of leaching and solvent extraction. The resulting iron-loaded organic phase is heated to 150-200 C in the presence of water whereby the iron will be directly precipitated from the organic phase as iron oxide of high purity and the regenerated organic acid is recycled to the organic leaching step for reloading with zinc.

Jan 1, 1980

By John P. Mahaffey

Thank you Mr. Chairman, Ladies and Gentlemen of SME-AIM? for this opportunity to talk to you about, one of the most interesting and challenging facets of our mining industry. Because the need was then -we built in 1964 what is still today, one of the most sophisticated AC mining machine simulators for this or any industry. It simulated the electrical controls and circuits of an AC shuttle car. The student activated the controls on the main console, which represented the elementary control and power circuits. Its accompanying slide-tape program, student manual and worksheets provided our customers with an effective and highly motivational means to teach their face mechanics: 1. practical AC circuit and motor theory 2. print reading 3. troubleshooting techniques Nearly 10,000 men have put in over 100,000 manhours of training on the AC panel and its DC counterpart. The DC panel was modeled after the 14BU10 Loader. The success of these larger panels pointed out the need in our industry for an orangized, basic electrical program designed around mining machinery components & circuits. But probably more importantly, they brought to light the tremendous thirst for upgrading by our industry's employees. We then turned our attention to developing programs around very basic panels. The resulting programs were designed also to assure maximum student involvement.

Jan 1, 1975

By J. B. Platt

Many utility fuel choices 1990-95 defied expectations, with utility decisions and coal market developments ever more closely linked. The Central Appalachian coal boom never occurred; clean-enough coal was developed in the hard-hit Midwest; Colorado-Utah coal surged; Pittsburgh seam production strengthened; utilities embraced Powder River Basin coal; and emission allowance prices collapsed. Competition drove productivity gains, but the future is not a simple repeat. Phase 2 brings fewer viable compliance options. Mega-railroad pricing has become a key risk factor --will this be countermanded by merging utilities and power market competition? Revenue losses from vintage contracts are problematic. Uncertainty also plagues natural gas, in spite of unanimity across major forecasts, since recent experience has been so heavily influenced by the gas bubble.

Jan 1, 1997

By James K. Kindig

Solvent extraction as a method of purifying and concentrating metal values from solution has become a standard hydrometallurgical operation for recovery of both uranium and vanadium, and within the past two years it has been put into operation in a commercial plant for recovery of copper from leach solutions. In this first full scale solvent extraction plant for recovery of copper operated by Ranchers Exploration and Development Corporation near Miami, Arizona, a kerosene solution of an organic compound, LIX-64® is used to selectively extract the copper from the dilute acidic copper sulfate leach liquor obtained from heap leach operations. The copper is back extracted from the solvent into a stripping solution which is fed to an electrolysis circuit producing cathode copper for sale.

Jan 1, 1970