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By D. N. Thompson, R. L. Sayer, K. S. Noah

Economical remediation of acid rock drainage (ARD) at secluded high-altitude western ore mines is difficult given the current treatment technology. Several passive-engineered systems that are based on wetland technology were tested in the laboratory with three western ore mine ARDs (Co, Cu and Fe mines) and with a copper leachate effluent. These systems used well-weathered lodgepole pine sawdust as the sole carbon source and mud from a pond at one of the mine sites as the source of sulfate-reducing bacteria (SRB). Simple one-pass flow-through systems removed 44% to 99% of the vari¬ous heavy metals front the Co and Cu mine ARDs and increased the pH from 3 to 7 after 28 days of SRB acclimation with a five-day residence time. Carbohydrate utilization rates were generally low, except for one 437-day run, which consumed 25%, 30% and 21 % of the cellulose, hemicellulose and lignin, respectively. Initial pH, amounts of toxic heavy metals and the degree of predegradation of the sawdust were found to significantly affect both remediation potential and acclimation time. Engineered SRB systems, alone or in combination with other passive technologies, offer promise for the economical remediation of western US ore mine ARDs.

Jan 1, 2000

By R. E. Ray

In an effort to reduce the risks to underground miners of health hazards associated with exposure to high concentrations of diesel particulate matter(dpm), the Mine Safety and Health Administration(MSHA) published proposed rules in 1998 limiting dpm exposure in both underground coal and metal and nonmetal mines. The proposed rule for underground coal mines would require removal of 95% of dpm by mass, while the rule for metal and nonmetal mines would eventually limit total carbon exposure from dpm to 160 micrograms per cubic meter of air over an eight-hour shift. The comment period for both proposed standards ended on July 26, 1999.In this session, representatives from MSHA, the National Institute for Occupational Safety and Health (NIOSH), equipment manufacturers, labor and industry will discuss the impact of the proposed regulations on mine operations and worker health. Questions will be taken from the audience after brief presentations from each panelist. This paper provides a compilation of written summaries of each panelist’s opening presentation.

Jan 1, 2000

By William R. Yernberg

A conference on coalbed and coal mine methane was held March 27 and 28, 2000, in Denver, CO. The conference, organized by the Strategic Resource Institute, was attended by leaders in the coal mining and gas energy industry. The conference focused on the recovery of methane from coal beds as an energy resource and the removal and utilization of coal-mine methane (CMM) related to underground coal mining. The two-day conference discussed methane resources around the world, methods of recovery, methane markets, underground coal mining, health and safety issues and environmental issues related to methane. The consensus among the presenters is that the future looks promising for coal bed methane (CBM) and CMM.

Jan 1, 2000

By M. L. Young, M. S. Klima

Hindered-settling columns are used throughout the minerals industry for both size and density separations. In this study, the performance of a continuous laboratory-scale hindered-settling column was evaluated for various particle systems. The test variables included solids composition, water rate and column height. Column performance was evaluated using partition curves and corresponding performance parameters.

Jan 1, 2000

By T. M. Ruff, W. G. McCoy, M. J. Beus, S. Iverson

Monitoring conveyance position and wire rope load directly from the skip or cage top offers several significant safety and production advantages. The Spokane Research Laboratory of the National Institute for Occupational Safety and Health (NIOSH) developed a shaft conveyance monitoring system (SCMS). This system consists of position and guide-displacement sensors, a maintenance-free battery power supply and a new sensor, which is mounted on the wire rope with a Crosby Clip, to measure hoist-rope tension. A radio data link transmits sensor output to the hoistroom. A state-of-the-art automated hoisting test facility was also constructed to test the concept in a controlled laboratory setting. Field tests in full-size shafts are now underway.

Jan 1, 2000

By Gregory W. Gustina, Terry P. Boyle

Analysis of the structure of the benthic macroinvertebrate community, consisting of the number of taxa and the relative distribution of total numbers, is a routine method of assessing the ecological quality of streams. Various multivariate statistical techniques, which assess the structural variability of the benthic macroinvertebrate community and the relationship of that variability with natural and anthropogenic environmental variables, have utility in separation of the various physical and chemical factors associated with impact. Multivariate methodology, while computationally complex is statistically rigorous and better integrates physical, chemical, and biological data for more synthetic interpretation. Using the multivariate analysis technique, canonical correspondence analysis, we have analyzed a number of sites in the upper Boulder River Basin, Montana to determine which are the important environmental variables associated with variation in community structure. The results of this analysis an integrated with more traditional analysis of community structure and incorporated in a risk analysis for the mediation of abandoned mines and mill sites within the watershed.

Jan 1, 2000

By Syd S. Peng

Mountaintop removal (MTR) mining started in West Virginia nearly 30 years ago. This surface mining method can extract multiple coal seams as thin as a few inches in whole and minimum rock dilution in very steep mountainous terrain. MTR is highly efficient, even if coal seams are in close proximity and small in a real extent. Consequently, MTR has been widely used in the Central Appalachian coalfield (mainly Kentucky, Tennessee, Virginia and West Virginia) with great success. In that respect, there has been no demand for research and little scientific research has been performed to investigate its impact on the surrounding area. During the past two years, however, the debate over MTR mining has grown quickly and has become very intense. This article describes chronologically issues raised by various parties, legal actions, impacts on mining permit applications and research projects developed to address the issues.

Jan 1, 2000

By J. D. Miller, D. M. Catarious, F. L. Stanley

The quality of cleaned products from coal preparation plants is often variable due to natural fluctuations in the washability characteristics of the plant feed. To combat this problem, many modern plants have installed on-line analyzers that provide feedback for the real-time control of product quality via the adjustment of circuit cutpoints. Unfortunately, optimization studies show that this approach may actually lead to increased losses of saleable coal. This paper discusses the problems associated with the real-time manipulation of circuit cutpoints and suggests alternative modes of operation that are better suited for plant optimization. A case study involving an eastern U.S. coal plant has been used to compare the economic impacts of these different approaches for plantwide control.

Jan 1, 2000

By Y. Luo, S. S. Peng

This paper presents some results obtained from research on long-term subsidence over and near chain pillar systems - the area available to long-term subsidence in longwall operations. Although the long-term subsidence for most longwall operations is insignificant, it does exist in some cases. In the cases that showed significant long-term subsidence, it was found that the development process could be expressed by an exponential decaying function. The stability factor of the chain pillar system and the potential for long-term subsidence are the two most important factors that control the magnitude and development characteristics of the long-term subsidence process.

Jan 1, 2000

By William R. Yernberg

The current state of the copper industry was the topic of discussion at the Copper 99 — Cobre 99conference held Oct. 10 to 13, 1999, in Phoenix, AZ. More than 700 copper-industry engineers, executives, consultants, academics, vendors and other interested parties attended. This successful and well-organized conference was the fourth in a series of international conferences devoted to the mineral processing and extractive metallurgy of copper. The 1999 meeting marked the first time that the conference was held in the United States. The meeting was co-organized by the Minerals, Metals and Materials Society (TMS); the Chilean Institute of Mining Engineers (IIMCH) and the Metallurgical Society of the Canadian Institute of Mining, Metallurgy & Petroleum(CIM). The meeting was also sponsored by The Society for Mining, Metallurgy and Exploration Inc.

Jan 1, 2000

By Lynn B. Hales, Randy A. Ynchausti

Because of the high economic value associated with small improvements in the operating performance of mineral processing plants, innovations in instrumentation, stabilization and expert control systems have been an ever-present part of the landscape in plants throughout the world since the I 960s. Expert control systems are computer programs that continuously monitor plant conditions; contain "expert knowledge" concerning the process, equipment and operational knowledge; and make timely recommendations for new process set points or even directly change the process set points to achieve desired management goals. Early rudimentary expert control systems first appeared in the early 1970s. They have grown from small, experimental but ambitious projects in which single unit operations were controlled to plant-wide systems that include technologies used in the U.S. space shuttle program. Experiences and results of applying these systems throughout the world will be explained discussed and analyzed. Typical results will be outlined and the use of expert control in the future will be projected.

Jan 1, 2000

By A. Pinches, R. Winby, P. J. van Staden, M. K. Rhodes, P. C. Miller

This paper is a progress report on the commercialization of using bioleaching for base-metal concentrates. The paper focuses on bioleach processes for recovering copper from chalcopyrite and nickel/cobalt from pentlandite/pyrrhotite. Data is discussed from pilot-plant trials in which an overall recovery >95% was obtained for the bioleaching of copper from chalcopyrite. The pilot plant was operated in closed circuit with solvent extraction and electrowinning circuits for final metal recovery. For the bioleaching of nickel and cobalt from pentlandite/pyrrhotite, an overall recovery of 97% was achieved. Precipitation routines were used to produce a final nickel/cobalt product. The pilot plants were capable of treating a few kilograms of concentrate per day. Prominent features in the design of a 1-t/day (1.1-stpd) copper-bioleach demonstration plant for the treatment of chalcopyrite concentrate are discussed. The plant, which is now under design, will be constructed and operated based on the results obtained from the laboratory pilot-plant campaigns. Issues of scale-up for the demonstration plant, together with integration into upstream and downstream processing, are also addressed. Independently derived capital and operating costs are presented for a possible commercial plant. These cost studies indicate the principle economic issues in considering the application of bioleaching to the extraction of base metals. The benefits of bioleaching complex concentrates that are not amenable to physical beneficiation and economic treatment by conventional smelting are highlighted. Issues, such as the environmental aspects, that illustrate the benefits of bioleach technology are given.

Jan 1, 2000

By Courtney Black, Paul F. Ziemkiewicz, Eberhard Werner, Matthew Daly, Joseph J. Donovan, Jeff Frazier

Injection of alkaline waste-lime slurry was performed at a West Virginia surface coal mine site, to attempt neutralization of acid springs by an alkaline recharge method. Deep trenching (>5 m) using an excavator yielded the most effective injection into the aquifer. Water from two springs, 90 m from the deep trench, showed 70%-80% reduction in acidity in response to injection. Neutralization persisted >170 days after treatment, with pH between 5.1-5.7 and metal acidity from 25-60 mg/L. A minor fraction of lime introduced was consumed. The sustained neutralization is attributed to reaction of acid water with subsurface lime, entrained below the wafer table by macropore infiltration. Characteristics of groundwater transport are critical in determining recharge structure location.

Jan 1, 2000

By J. Wagner, P. Eger, G. Melchert

In 1991, LTV Steel Mining decided to close an open-pit taconite mine in northeastern Minnesota using a passive-treatment approach consisting of limiting infiltration into the stockpiles and wetland treatment to remove metals. More than 50 Aft (55 million st) of sulfide-containing waste had been stockpiled adjacent to the mine during its 30 years of operation. Drainage from the stockpiles contained elevated levels of copper, nickel, cobalt and zinc. Nickel is the major trace metal in the drainages. Before the closure, the annual median concentrations ranged from 1.5 to 50 mg/L. Copper, cobalt and zinc are also present but they are generally less than 5% of the nickel values. Median pH levels range from 5 to 7.5, but most of the stockpile drainages have pH levels greater than 6.5. Based on the chemical composition of each stockpile, a cover material was selected. The higher the potential that a stockpile had to produce acid drainage, the lower the permeability of the capping material required Covers ranged from overburden soil removed at the mine to a flexible plastic liner. Predictions of the reduction in infiltration ranged from 40% for the native soil to more than 90% for the plastic liner. Five constructed wetlands have been installed since 1992. They have removed 60% to 90% of the nickel in the drainages. Total capital costs for all the infiltration reduction and wetlands exceeded $6.5 million, but maintenance costs are less than 1 % of those for an active treatment plant. Because mine-drainage problems can continue for more than 100 years, the lower annual operating costs should pay for the construction of the wetland-treatment systems within seven years.

Jan 1, 2000

By S. K. Kawatra, S. J. Ripke

Finely disseminated iron ores compose much of today's reserves. After removing the silicate gangue, the resulting fine iron oxide concentrates require pelletization with a binder to enable transportation and reduction. Binders can be used more efficiently if their binding mechanisms can be completely understood. Typically, bentonite clay is needed as a binder to improve the strength of the pellets. Bentonite is an effective binder at a relatively low cost, but costs could be reduced further by replacing bentonite with even lower-cost binders, such as high-carbon Fly-Ash Based Binder (FBB). In this study, it was found that bentonite binds by a physical mechanism, while FBB binds by a chemical mechanism. These mechanisms were determined to be incompatible. Partial replacement of either binder with the other reduced dry magnetite pellet compressive strengths below the industrially acceptable value of 22.2 newtons (5 lbf). Activators and accelerators that activated the fly-ash deactivated the bentonite. The incompatibility of these two binders is explained.

Jan 1, 2000

By D. W. Park

The Longwall Strata-Control and Maintenance System (LoSCo-MS) is a software and data-communication system developed at the University of Alabama. This system integrates real-time shield monitoring, data presentation, analysis and the forecasting of forthcoming events. The main objective of this system is to provide stability information on longwall panels, including excessive shield load, low setting pressure, leg leakage, poor shield performance and imminent maintenance problems. Analyses of various mining and geological parameters were also performed to determine past and present roof characteristics and to forecast roof loading patterns for the following mining cycles, the next periodic weighting, etc. A local coal mine in the Warrior Coal Basin has adopted this system to provide daily evaluation of ground stability and maintenance problems in their longwall panels. Two years of experience with this system is covered in this paper.

Jan 1, 2000

By G. Gillet

The conventional magnetic separators used in the mineral industry are equipped with traditional magnetic circuits or with permanent magnets (rare earth). However, when processing minerals with low magnetic susceptibilities or minerals of very small particle size, these separators are inefficient. In addition, a conventional magnetic circuit consumes considerable amounts of electricity to generate a relatively low magnetic field (~2 Tesla). The equipment is also heavy and bulky. Only a separator having a superconducting sole-noid can contribute in solving most of the problems, and only such a separator can produce high magnetic fields with low energy consumption. New developments and the experience acquired in using these superconducting magnets have resulted in new uses for magnetic separation, especially in the environmental area. This paper presents and describes a separation system that uses superconducting magnets that are completely automated and able to treat raw materials (concentration or purification) or liquid industrial effluents containing heavy metals in solution. Several industrial sectors, including the surface treatment, petroleum and chemical industries, are generating effluents containing heavy metal ions. The main metal ions found in such effluents include zinc, copper and vanadium. The purification of such effluents by magnetic separation is performed by adding a certain proportion of iron salts. The treated effluent passes through a superconducting separator where the flocs are retained in a matrix of steel wires. The efficiency of supraconducting high-gradient magnetic separation (HGMS) by this method exceeds 95%. Mineral separation and industrial-waste purification results are presented.

Jan 1, 2000

By E. K. H. Goh

A reliability-based engineering design approach for the effective design of reshaped spoil dumps was developed with the aim of obtaining structurally reliable spoil dumps at optimum reshaping costs. The aim was also to satisfy environmental erosion standards and community expectations. This approach encompasses the linking up of three major components: erosion appraisal of spoil dump designs, reliability-based engineering design of spoil dumps and costing of spoil dump reshaping practices. This paper addresses the application of the reliability-based engineering- design approach to the assessment of spoil dump designs for erosion control. Included are various types of erosion prediction models and reliability-based engineering-design analytical techniques. Also included is a case study that demonstrates the application of this approach.

Jan 1, 2000

By M. S. Vernon, J. J. Kellar, W. M. Cross, R. M. Winter, F. J. Johnson, A. G. Pommer

Three substrates (MgO crystal, CaF2 crystal and Mg plate) were used to construct thin layers of Mg(OH)2. Various routes were used to modify these substrates, including surface hydration and sol-gel coating. In each case, it was found (by using Fourier transform infrared spectroscopy) that thin layers of Mg(OH)2 could be produced. In the case of hydrated layers, the surface morphology of the Mg(OH)2 resembles the bulk platelet shape of precipitated Mg(OH)2.

Jan 1, 2000

By B. Cavender

Mining managers trying to rapidly reduce production costs tend to implement a traditional set of top-down managerial practices: layoffs of employees, renegotiation of supplier contracts, cancellation of employee training, restrictions on travel, reductions in office supplies, and so forth. While these practices do reduce costs, the benefit is often limited in both magnitude and duration, and the workforce is usually left demoralized. Successful cost-cutters take a different approach. They make the continuous reduction of costs a priority for all members of the organization, whether managers or workers. The culture of these firms emphasizes the commitment, voluntarily given, of individuals and work groups to this goal. Cost cutting practices often reject all of the traditional methods mentioned above, but are far more numerous, innovative, and successful. This culture of cost reduction is the result of a set of leadership competencies that establish direction for the organization, align the organization’s various constituencies with this direction, and motivate and inspire the organization. Dramatic cost reduction then becomes a routine task rather than a heroic achievement.

Jan 1, 2000