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By Rowan Melrose, Naj. I. Aziz, Arvind Misra

Mathematical models have been developed to simulate longwall heading development systems in Australian Longwall Mines. The models developed consider the effect of non concurrent cutting and supporting systems and concurrent cutting and supporting systems. They also consider the impact of operating parameters on each of these systems. Operating parameters that are considered include pillar dimensions, the use of surge cars, bolting time, shuttle car speed and heading advance per cycle. The effect of these parameters is considered with respect to production rates and also panel advance rates.

Jan 1, 1996

By G. P. Hand

The purpose of this paper is to bring to your attention the various kinds of high performance graphites available today, their characteristics and possible applications. These materials are products of a proprietary high temperature technology developed by Superior Graphite Company. We feel we have only begun to tap the potential of this technology and the utilization of the resulting products. During the course of the paper, we shall investigate high purity, high performance graphites made from raw materials such as mined natural graphites, synthetic graphites and petroleum derivatives. We shall define their characteristics and resulting benefits to current applications, along with applications currently under development. It is our desire to stimulate speculation and development of current high performance graphites and their applications as well as ideas for new high performance products and applications. First, a little background about the process. The technology was developed through a concentrated R&D effort which culminated in 1976 in the construction of a unique furnace capable of continuously processing tonnage quantities of granular carbons at temperatures in excess of 2,500 degrees C. This process is capable of refining various carbonaceous raw materials, including natural graphites, to levels of purity and consistency that were previously unattainable in commercial quantities. Carbon contents in excess of 99.9% are currently being produced on a continuous flow-through basis. Since beginning operation in 1977, this plant, located in Hopkinsville, KY, has been expanded in stages to its present capacity of producing over 45,000 tons of purified graphites and graphitic carbons per year. In addition to the purification process, the technology used allows the introduction of selected elements into the carbon/graphite structure to provide additional benefits. Elements of interest include boron, silicon, copper, iron and rare earths. The characteristics of and applications for some of these products will be discussed later.

Jan 1, 1990

By C. J. Bise

Virtual reality (VR) is a concept in which the human experience of perceiving and interacting with a computer-modeled environment is achieved through the use of sensors and effectors. It is an advanced form of computer graphics. The images are generated based on where the user looks and how the user moves. As personal-computer-based (PC) instruction gains acceptance as an innovative approach to providing safety training, VR can provide a multisensory, rather than merely a multimedia, mode of presentation. New technology continues to be introduced into the mining industry to meet the productivity needs of coal and noncoal producers. There is also an increased need for more innovative training of mine workers. New technology and equipment designs often affect the basic causes of accidents. For example, the development of cabs and canopies for underground coal-mine equipment has reduced the number of accidents related to roof falls and rib rolls. However, safety-training specialists then had to focus on the machines themselves, because the modifications had the potential for causing "pinch-point" accidents. In fact, although the overall physical demands on mine workers have diminished, there has been an escalation in the concerns about trauma from repetitive physical activity. Thus, health-and-safety training specialists have shifted their atten¬tion to the recognition, evaluation and control of workplace hazards (Hancock and Hill, 1995). Recognizing that the spatial relationships of a workplace convey more information about hazards when experienced rather than described, trainers agree that simulation is the method of choice. Unfortunately, until recently, simulation systems were either simple software programs that did not come close to portraying the real experience or were complex hardware systems (such as flight simulators) that did, but at a cost of millions of dollars (Fritz, 1991). However, researchers and training specialists are excited about an emerging approach to work-force education based on virtual reality. VR is also described as cyberspace, immersive simulation, artificial reality, telepresence, virtual environment or virtual world (Meyer and Dunn-Roberts, 1992; Peterson, 1992). It represents a group of concurrent advances in computer and interface technologies. They enable an individual to interact in a multisensory way with a computer-generated environment. To achieve this, a typical VR system incorporates a computer that contains the necessary databases for producing realistic images and audio; a head-mounted display (HMD) or screen for viewing the images; and a three-dimensional controller, joystick or data glove for interacting with the computer-generated environment. If virtual reality is to become an effective tool for the safety training of mine workers, its attributes will have to be measured against other forms of delivery. Accordingly, Carr (1992) listed the following areas in which VR should be considered the method of choice: ? When training mistakes would be costly. ? When the necessary environment cannot be experienced in the real world. ? To build interfaces that are sensible and can be manipulated. ? To make training situations really "real." ?To make perceptible the imperceptible.

Jan 1, 1997

By R. J. Sweigard

Fine coal refuse is often pumped, as slurry, into surface impoundments as a means of permanent disposal. As the available volume is filled, the height of the embankments are frequently increased. Many times the additional embankment material is placed upon consolidated fine coal refuse. There has been some concern about the long-term effect of consolidation of this material at or above the liquid limit upon its shear strength. A laboratory investigation was performed using three different types of fine coal slurry taken from Central Appalachian coal preparation plants. The refuse was consolidated in 10-foot plexiglass columns under incremental amounts of surcharge loading. The incremental loads were designed to simulate the effect of increasing the height of a refuse embankment on top of the consolidating coal slurry. After the refuse in the columns had consolidated for several months, the columns were cut apart and triaxial tests were performed on both the consolidated material and unconsolidated material for comparison of their shear strength parameters.

Jan 1, 1997

By H. Tutu

The legacy of gold mining operations continues to affect water quality in the Witwatersrand Basin in South Africa. The acid mine drainage (AMD) emanating from the tailings dumps liberates heavy metals from the ore minerals. The objective of this study was to characterise the geochemical processes that are important in understanding chemical evolution of polluted water in the study area. Analytical results for water samples collected in the catchment of the study area generally showed elevated concentrations of heavy metals in the vicinity of tailings dumps and mining operations and a decrease in the distal. Dams and wetlands, despite their proximity to the tailings dumps, recorded low concentrations of heavy metals and other pollutants. The characterisation of AMD was summarised in a conceptual model in which plots of redox potential versus pH and electrical conductivity versus pH were identified as the most important sub-models that captured the gross physical-chemical characteristics of polluted water and its interaction with the environment.

Jan 1, 2006

By Richard B. Berg

California was a major talc-producing State until the late 1980s when production from the deposits in the Death Valley area ceased because of a number of factors which included pressure to discontinue mining in and around Death Valley National Monument, and health concerns affecting markets for tremolitic talc. The states of Montana and Texas now account for slightly more than half of U.S. talc production. Deposits in an area encompassing southern Death Valley and extending east into the Kingston Range were formed by contact metamorphism of carbonate beds in the Precambrian Crystal Spring Formation next to Precambrian diabase sills. These deposits contain ore ranging from high-purity, fine-grained talc to platy, tremolitic talc with high brightness. Deposits of tremolitic talc and talc schist in the Silver Lake District in San Bernardino County resulted from metamorphism of Precambrian carbonate beds intruded by granitic plutons. Northeast in Esmeralda County, Nevada hydrothermal alteration related to Late Jurassic plutons caused talc replacement of Precambrian to Early Cambrian dolomite. A hydrothermal origin is also indicated for talc deposits in the lnyo Range just north of the Death Valley District where bodies of unusually pure talc occur in Paleozoic lime- stone near Jurassic granitic plutons. Talc is now mined from a deposit in the foothills of the Sierra Nevada Range southeast of Sacramento where quartz-mica schist of the Permian Calaveras Formation has been hydrothermally altered to talc. Replacement of magnesite of the Precambrian Allamoore Formation produced talc deposits mined in the Allamoore District of west Texas. This dark-gray talc of low iron content with carbon- aceous material and dolomite is ideally suited for use in ceramics where it makes a white product when fired. Small bodies of platy light-pink to white talc suitable for use as an extender in paint are also mined in this district. In the Llano District of central Texas talc has replaced impure carbonate rocks and serpentinite. All Montana talc production is from deposits in the southwestern part of the State that formed by Precambrian hydrothermal alteration of dolomitic marble. This alteration produced material with high purity that ranges from very fine-grained, massive talc to coarser grained, foliated talc. Markets include pitch control in paper, paint, cosmetics, ceramics, rubber and plastics. In southwestern and northeastern Oregon, talc has replaced serpentinite in the vicinity of Mesozoic plutons. Soapstone for carving is mined from a southwestern Oregon deposit. Deposits of similar origin occur in central and northwestern Washington.

Jan 1, 1995

By M. G. Premo

The McKinley Mine is located in the northwest New Mexico, in McKinley County, approximately 25 miles from Gallup. The mine is operated by The Pittsburg & Midway Coal Mining Co. (P&M), a wholly owned subsidiary of the Chevron Corporation. P&M is headquartered in Englewood, Colorado. Since the McKinley Mine began operations in 1962 a total of 83,391,000 metric tons of coal have been sold through 1990. The 1991 production was approximately 5.000.000 metric tons. The mine operations are contained on a 109.000 square kilometers lease area of which 44.000 square kilometers are on the Navajo Nation. The present customer base consists of four utilities and one industrial account, all of which are located in Arizona. The utility customers are the Arizona Public Service Co. Cholla Station at Joseph City, The Salt River Project. Coronado Generating Station near Joseph City, and The Tucson Electric Company, Irvington Generating Station in Tucson. The industrial customer is the Stone Container Corporation, Snowflake Paper Mill.

Jan 1, 1992

By John A. Herbst, K. Rajamani

Process improvement is probably the most widespread objective of mineral process plant operators in the late 1980's. An important part of such improvements is dynamic optimization which involves reacting to inevitable plant disturbances in such a way that productivity is maximized at every instant of time. This paper describes the way in which mathematical models can be and have been used in dynamic optimization. Both off-line and on-line model applications are described.

Jan 1, 1989

By E. M. Frizzell

Decisions affecting ground control design require detailed knowledge of roof rock geology. This is especially true when weak roof materials and anomalies create hazardous conditions and. if not properly supported, result in roof falls. The U.S. Bureau of Mines has developed a system to evaluate geological conditions by using a roof drill that will provide an estimate of the compressive strength of the roof rock in real time. Through the use of sensors and a microcomputer on the roof drill critical drilling parameters can be interpreted and analyzed almost instantaneously, making it possible to inform an operator of hazardous roof conditions such as voids and changes in strata during the drilling process. Geotechnical data can be downloaded to a portable semiconductor memory device, which is brought to the surface so that data can be directly accessed with a personal computer for further analysis. Results from field tests are presented.

Jan 1, 1992

By Carl E. Nelson

Shallow epithermal stockworks hosted by maar eruption craters contain over ninety percent of the bulk mineable gold identified to date in the Circum-Caribbean region. Pueblo Viejo (Dominican Republic) and Santa Rosa (Panama) contain combined gold reserves of over 600 tonnes. Bulk mineable gold deposits are also being discovered in and around veins that were formerly mined underground. Bellavista, El Recio and San Martin (Costa Rica) contain combined announced gold reserves of over 50 tonnes. Representative rock suites collected at 8 bulk mineable gold deposits include 291 samples of veins and vein stockworks, hydrothermal eruption breccias, sinter, variably altered host, unaltered host, nearby intrusive rocks and basement. Analyses completed to date show that Circum-Caribbean epithermal ores are enriched in arsenic, mercury and antimony as well as gold and silver. Exploration efforts in the region naturally focus on districts with past production. However, an order of magnitude more bulk mineable gold has been discovered in shallow epithermal stockworks outside of the old bonanza vein camps. Exploration guides include basal island arc volcanic sequences, hydrothermal and hydrovolcanic (maar) eruption breccias, thinly-bedded carbonaceous maar sediments, and hot spring-related silicification and argillic alteration.

Jan 1, 1990

By M. J. Laurila

Elemental analysis of slurry streams using X-ray fluorescence (XRF) has long been employed. However, detector technology has limited the application of XRF devices. Using detector technology employed on NASA's Mars Pathfinder to analyze soil samples, Process Control, Inc. has developed an on-line analyzer to mount on a sampling system. The prototype XRF elemental analyzer was installed at Detroit Edison's Monroe Power Plant in January, 1998 and has been employed to monitor feedstock quality. A slurry system has been developed for flotation control. This paper describes the testing of the analyzer using the new, draft ISO standard for evaluating the performance of on-line analyzers (ISO/DIS 15239).

Jan 1, 1999

By H. J. Chen, Y. Luo, S. S. Peng

Surface subsidence resulting from underground coal mining can cause problems for buried pipelines. In this paper, a technique for assessing the level of stress on a subsidence-affected pipeline is introduced. The main contributors to the stress are identified, and mitigation techniques for reducing the stress are proposed. The proposed mitigation techniques were then successfully tested.

Jan 1, 1998

By Palmer C. Sweet

By-products from mining and processing plants and coal-fired power plants are being utilized more as valuable resources in Virginia. Mining-related by- products are divided into two categories: those generated from mineral extraction and beneficiation, and those generated from mineral processing or from industrial plants. Materials from both categories are produced in Virginia, where by-products have been exploited for various uses in the past and/or present. These materials include coal- combustion products (fly ash and bottom ash), lime-kiln dust, flue-gas-desulfurization residue, rock fines, magnetite, Cold Spring clay (kaolin), Austinville tailings, soapstone rock, and calcium-carbonate paste. Some of these by-products have never been utilized, although several ideas have been investigated over the years.

Jan 1, 1999

By Paul F. Richardson

Liquids containing suspended solids are encountered in most mineral processing applications. Solids levels cover a very wide range, from ppm levels in cooling water systems to slurries containing greater than 70% solids. When the aqueous phase is recycled or further processed, a solid/liquid separation process is used. Chemical additives used to carry out this process are called coagulants and flocculants. In other cases, one seeks to control or modify the properties of the suspension. Dispersants are chemicals used to aid in suspending solids in a liquid as well as to control the properties of the resulting suspension. Dispersants find a range of uses in mining and mineral processing such as scale control, filter aids, flotation aids, and slurry viscosity modification. Materials used as dispersants include inorganic salts, alkalies, organic surfactants, and polyelectrolytes. This paper discusses the use of dispersants in mineral processing, with an emphasis on control of slurry viscosity. The mechanism of dispersion and factors that affect the choice of dispersant will be discussed.

Jan 1, 1986

By Sam H. Patterson

The advances in knowledge of world bauxite resources in the last few decades include contributions to the geology of deposits, discovery of large resources, shifts in availability, and changes in. the industry in response to political and economic pressure. Improvements in the understanding of geology have resulted from the larger numbers of geologists working on bauxite and better exchanges of information. The large deposits discovered are mainly the laterite type in tropical regions. These discoveries have led to major increases in bauxite resource estimates as well as to shifts in bauxite availability and in the ranking of producing nations. Changes resulting from political, environmental, and economic pressures have resulted in increased costs of bauxite and in renewed interest in potential nonbauxite sources of aluminum. Aluminum is produced from nonbauxite raw materials only in the U.S.S.R.; however, research on extraction processes or investigations of nonbauxite alumina resources has taken place in several countries.

Jan 1, 1984

By M. J. Sanzotti

This paper examines the potential for controlling longwall-induced subsidence by pneumatically backstowing the void created by mining with waste rock, and having the process scheduled as a unit operation of the mining activity. Based on a review of background literature, interviews with representatives of various mining companies, public-interest groups, and state and federal regulatory agencies, a hypothetical case-study evaluation of pneumatic stowing in a southwestern Pennsylvania mine site was conducted. The study indicated that current stowing technology cannot keep pace with the production potential of U.S. longwall systems. Further, at the case-study mine site, concomitant stowing would reduce subsidence by only 50% of that incurred during full longwall caving, the longwall coal production rate would decrease from 4000 tons per shift in the non-stowing case to 1500 tons in the stowing case, and a preliminary cost analysis reveals that pneumatic stowing would add $5.25 to $10.50 to the operating cost of producing a ton of coal at the case-study site.

Jan 1, 1995

By Natarajan K. A.

During sulphide ore grinding, electrochemical interactions between grinding medium and the minerals play a significant role in bringing out enhanced ball wear on the one hand and alter the surface property of the ground minerals on the other. The role of the flotation reagents added simultaneously during grinding with respect to ball wear as well as flotation is yet to be established. Electrochemical measurements such as rest potential, combination potential and galvanic current between sulphide mineral and ball material couples have been carried out in the presence and absence of flotation reagents to understand the nature of electrochemical interactions between ball material and sulphide mineral. Electrochemical mechanisms and models have been proposed to explain the role played by the flotation reagents during different binary, ternary and quaternary interactions with respect to ball wear during grinding.

Jan 1, 1992

By V. N. Kolesnikov

The gold-silver deposits of the northern Primorye region are located in the eastern part of the East Sikhote-Alin volcanic belt, where the belt overlaps the Kema island-arc terrain of the Aptian-Albian age. There have been four deposits and numerous mineralization points found in the NE-trending Kema metallogenic belt that is about 1000 km long and 100 km wide. The known mineralization is of epithermal type, controlled by faults, and concentrated in quartz, quartz-fluorite-adularia, and, less commonly, sulfide-quartz vein systems hosted by the Upper Cretaceous-Lower Tertiary volcanic rocks. The vein systems extend for hundreds meters along strike, varying from tens centimeters to 50-60 meters in width. They are surrounded by wide zones of low-temperature hydrothermal alteration containing some gold-silver mineralization for which the commercial value was not studied during the early exploration. The ore bodies contain from 1 to 50-80 ppm of Au and from 1 to 1000 ppm of Ag. Gold is native, associated with quartz, and represented by particles from tens of microns to 1 mm in size. Silver occurs in native form as a constituent of argentite, pyrargyrite, stephanite, and other sulfosalts. The test work carried out for three vein systems 20 years ago showed that gold might be easily and almost completely recovered from the ore by cyanide treatment. The paper describes the geology and mineralogy of the deposits, Salut and Primorskoye, that are the most studied properties of the Kema belt. It also presents the data available on disseminated gold-silver mineralization in stockworks, altered explosive breccias, and wide zones of low-temperature hydrothermal alteration. This mineralization should be explored for possible exploitation as large open-pit, heap-leach deposits.

Jan 1, 1998

By M. G. Karfakis

Grouting has been used in underground mining for more than twenty years. Chemical grouting is often used as a remedial measure when the implemented ground control program is unable to completely prevent structural failures or when there is a need for preventing a structural member from unraveling. Utilization of the polyurethane grout currently being used is restricted by its limited range of physical and mechanical properties that restrict its utilization. To overcome some of the drawbacks of polyurethane, research has been conducted on a newly developed polyester based grout. The polyester resin, identified by Sandvik as StrataGrip, provides a number of features, including variable gel times and much reduced chemical hazard. Equally important are the mechanical properties of the product. The strength and deformability of any chemical grout must be compatible with the intended purpose of grouting and the expected deformation of the rock that is to be grouted. Assessment of the mechanical properties of polyester grout is the focus of this work. Field experiences and laboratory research have defined the properties of an effective grouting material. Experimental results indicate that the polyester grout meets or exceeds the recommended properties for many injection applications. Furthermore, the results suggest that the ability to adjust mechanical properties via resin formulation has the potential to expand the applicability of chemical grouting in ground control.

Jan 1, 1997

By J. Herbst, H. B. Treweek, V. R. Degner, G. Poling

Current mineral industry trends toward handling the high tonnages of lower grade ore and tailings retreat lead to a continuing need for large volume flotation cells. The benefits which accompany the larger cell flotation circuit include reduced capital cost, less mill floor space, reduced operational complexity, and less maintenance, provided the metallurgical performance and solids suspension capability of the cell are not compromised. This study reviews development considerations pertinent to large mechanical air induction type flotation cells from the standpoint of cell internal hydrodynamic characteristics and metallurgical performance. While the importance of process related factors such as chemical usage, pH control, solids size and loading, and circuit arrangement cannot be denied, this study will emphasize the relationship of cell size (volume), mechanism geometry (impeller diameter), and mechanism operating conditions (rotor speed and submergence), to air transfer, liquid circulation, liquid "rise velocity" and mechanism power draw. Specific hydraulic performance maps for large capacity 300 and 500 cu ft flotation cells will be reviewed in terms of the relationship between the operational variables and the air and liquid flow conditions within the cell. Metallurgical results, obtained under plant operating conditions for 300 and 500 cu ft cells, are included to illustrate the metallurgical performance similarity of flotation cells which follow hydrodynamic scale-up criteria set forth in this investigation.

Jan 1, 1976