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By G. C. Presley

Estimated domestic production of pumice and pumicite in 2004 increased about 23 percent since 2003, according to the U. S. Geological Survey (USGS). The USGS estimate of domestic production of 687 kt(757,000 st) for 2003 turned out to be 870 kt (959,000 st)of actual production. The USGS estimated the value of pumice and pumicite sold or used in the United States to be $26 million in 2004, up $4 million from the value in 2003. There was an estimated decrease in the mine, or mill, average price to $24.14/t ($21.90/st) in 2004 from $25.19/t ($22.85/st) in2003.

Jan 1, 2005

By H. Do, R. Yoon

Mineral flotation is effective over a relatively narrow particle size range of approximately 10 to 100 µm. If the upper particle size limit can be increased, however, a run-of-mine ore may be coarse ground, and only the middlings are ground further to achieve required grades. This will result in significant energy savings and increased throughput. In this communication, methods of increasing the upper particle size limit will be discussed on the basis of a flotation model that can predict flotation from both hydrodynamic and surface chemical parameters. An example of increasing flotation recovery by control of a chemistry parameter is given.

Jan 1, 2007

By W. Z. Rogers

U.S. feldspar output sold or used in 2005 was an estimated 760 kt (838,000 st), valued at $44 million free-on-board plant. This was below the 2004 volume and was the second year of decline in a row. Output included flotation concentrates, feldspar content in feldspar-silica mixtures, potash feldspar and aplite. The strong housing market in the United States maintained demand for ceramic tiles, plumbing fixtures and fiberglass insulation requiring feldspar. Shipments of glass containers were about the same as in 2004. Imports of ceramic tiles and plumbing fixtures continued to increase, taking the place of U.S.-produced goods and the feldspar required to make them. For 2005, 80 percent of the ceramic tiles sold and 50 percent of the plumbing fixtures sold in the United States were imported. Since 2000, manufacturing plant closures in the plumbing fixtures industry have reduced the demand for feldspar and feldspar-silica mixtures by 100 kt (110,000 st). Increased demand from the ceramic tile industry has partially offset the lost volume.

Jan 1, 2006

By E. R. Bauer

Previous studies and research efforts have shown that noise-induced hearing loss (NIHL) is a problem in the U.S. mining industry. This is especially true in surface and underground coal and stone mining where large, noisy equipment predominate. Workers in coal preparation and stone processing plants have also been found to be subject to high sound levels that could potentially cause NIHL over prolonged periods of exposure. National Institute for Occupational Safety and Health (NIOSH) researchers have been conducting a cross-sectional survey of equipment noise and worker noise exposures in the mining industry to estimate the potential for NIHL within the mining community. One commodity recently surveyed was the extraction of sand and gravel from surface pits and by river dredging. Little is known about the noise environment and worker exposures in these environments, where processing and mining equipment similar to coal and stone are employed. To address the potential for NIHL in the sand and gravel industry, sound levels on and around the dredges and processing equipment were recorded to identify areas of high noise levels. Full-shift worker dosimetry, in conjunction with task observations, was documented to determine the relationship between exposure and source. This paper presents research examining noise on dredges, in several surface mine sand and gravel operations and in the processing facilities. The locations where workers are likely to be overexposed and were found to be most susceptible to noise overexposures are reported. Results indicate that there are areas on the dredges (crane, suction pumps, and diesel engines) where sound levels greater than 90 dB(A) are present. In addition, crushers and screens used in the processing of the sand and gravel also generate sound levels greater than 90 dB(A). Although no surveyed worker exceeded the Mine Safety and Health Administration (MSHA) Permissible Exposure Level (PEL) of 90 dB(A) TWA8, laborers, mechanics, oilers, helpers, pickers, and greasers are the workers likely to be exposed to hazardous sound levels and thus develop NIHL over time. Knowledge of the equipment noise, area sound levels, and worker dose levels is information that management and employees can use to reduce exposures. Exposures can be reduced in certain areas through administrative controls and through engineering controls applied to the noisiest equipment.

Jan 1, 2008

By Georgene Renner, William R. Yernberg, Steve Kral

Agapito Associates (AAI) provides consulting services in geo-engineering, mining engineering and related disciplines. Founded in 1978, the firm operates out of offices in Grand Junction, CO, Golden, CO and Lombard, IL. Members of the staff include mining, civil and geological engineers, physicists, geologists, numerical analysts, computer specialists, instrumentation specialists, plus administration and technical support personnel. AAI has provided consulting and engineering services to mining companies producing base metals, precious metals, coal, potash, trona, limestone, oil shale and salt, and to defense and nuclear-waste disposal industries. AAI also provides services for measuring in situ horizontal stresses using an advanced biaxial overcore stress downhole measurement system developed by Sigra of Australia. Since 1978, AAI has measured in situ stress in copper, oil shale, molybdenum, trona, limestone and coal mines, and in tunnels and concrete structures. Since 1994, the staff has completed 527 overcore stress determinations. AAI has the equipment and personnel for overcoring, sample coring and instrumentation installation in limited access, surface and underground mines. Portable Longyear CP-65 drills, borehole deformation gauges and strain indicators are used for difficult-access overcoring and are permissible for use in gassy mines.

Jan 1, 2006

By S. M. Jasinski

Peat is a natural organic material of botanical origin. Peatlands are situated predominately in shallow wetland areas of the Northern Hemisphere. Commercial deposits are formed from the gradual decomposition of plant matter under anaerobic conditions for about 5,000-years. In 2004, peat was harvested in 16 states. Florida, Michigan and Minnesota accounted for more than 80 percent of the U.S. production. Reed-sedge was the dominant variety of peat harvested in the United States, comprising almost 80 percent of the output. This was followed by humus, hypnum moss and sphagnum moss.

Jan 1, 2005

The Mining Foundation of the Southwest will host its 24th Annual American Mining Hall of Fame Awards Banquet at the Tucson El Conquistador Golf & Tennis Resort in Tucson, AZ on Saturday, Dec. 9. The Mining Foundation of the Southwest is a non-profit organization whose objectives are public education about the mineral industries. It also recognizes outstanding accomplishments in and contributions to the fields of fuel and mineral resources.

Jan 1, 2006

By L. Hoffman, F. Seymour, S. Hoerger

Newmont has a large integrated operation in Northern Nevada with numerous mines, stockpiles, and processing facilities. There are over ninety defined metallurgical ore types and over sixty defined gold recovery process options. To take better advantage of the available synergies, a complete Nevada wide mine plan and process model along with a mixed Integer and Linear Programming optimization tool has been developed and implemented. This system is maintained and operated by a Nevada Planning Group. Standard in-house planning software tools and methods have been implemented at all mine sites. While increasing the effectiveness of planning in Nevada, these changes have allowed a significant reduction in overall Mine Engineering staff.

Jan 1, 1999

By Albert Musschoot

The expanding applications of vibrating feeders for controlling the flow of bulk materials, and their adaptation for processing requirements, have developed considerable interest in stockpiling and reclaim systems. The general design of these units consists of a material transporting trough, or platform, driven by a vibratory force system. Design flexibility and variety is limited only by engineering ingenuity. The basic motion of the vibratory trough, or work member, is a controlled directional linear vibration that produces a material tossing or hopping action. Material travel speeds vary from 0 to about 30 m/min, depending on the combination of frequency, amplitude, and slope vibration angle.

Jan 6, 1981

By Richard Gertsch, Jack Eloranta, Leslie Gertsch

An ongoing research program is characterizing the ore qualities that most affect mine and mill processing of iron. Current practice uses assays of magnetic iron and silica, but additional qualities are needed for advanced process control. If additional qualities can be measured from core, blastholes, or process samples, they can be modeled and controlled similarly. What qualities, other than assays, hinder or facilitate beneficiation at each processing step, and how can they be measured in the mine/mill ore stream? This paper describes preliminary determinations of the effects of ore chemistry, hardness, blasthole drill performance, fragmentation control, and grindability on mill performance.

Jan 1, 2005

By William W. Edgerton

The California Department of Transportation (Caltrans), the Contra Costa Transportation Authority (CCTA), and the Alameda County Congestion Management Agency (Alameda CMA) are involved in a unique partnership on the planning and design of the fourth bore of the Caldecott Tunnel, located on State Route 24 in Alameda and Contra Costa counties. The project will add a two-lane bore north of the existing three bores. The project will alleviate traffic congestion in the non-peak direction. This paper provides background on the existing facility, summarizes the need for the new fourth bore, describes the proposed improvements, sets forth the approach for project delivery, and lists some of the challenges that are expected during construction.

Jan 1, 2008

By R. J. Kline

Most accidents are the result of risk taking. They can happen anywhere. Our coal industry categorizes accidents by type, occupation, commodity, age, every way you can imagine. We now know, how many were injured and when, for all the different types of accidents. We have ask ourselves many times, why are we having accidents, how can we stop the accidents and fatals in our industry? Present numbers and projections do not show that this will happen. Serious accidents can result in fatalities. Fatal accident can be prevented, and the coal industry can achieve zero fatalities. How soon this happens, depends on a great number of factors. I will discuss accidents and reasons for us having accidents in an attempt to get to the root causes. The historical perspective will be touched on, and the risk and analysis of accidents will be probed.

Jan 1, 2000

By T. J. Nelson

Natural aggregates, primarily stone, sand and gravel, are recovered from widespread, naturally occurring mineral deposits and processed for use primarily in the construction industry. They are mined, crushed, sorted by size, and sold loose or in concrete products to build roads, houses, buildings and other structures. Smaller quantities are used in agriculture, cement manufacture, and chemical and metallurgical processes. The growth of cities, their buildings and the highways that connect them have created demand for enormous quantities of aggregates. Consumption has now reached 9 t (10 st) per person and continues to grow faster than population. The aggregates industry is the largest mining industry in the United States in terms of production by weight, by volume and by number of active operations. About 80 percent of the concrete pavement and more than 90 percent of the asphalt pavement is composed of aggregates.

Jan 1, 2006

By E. Fahrenkrog, D. Sbartaro, E. N. Cifuentes

An intelligent supervisor using expert system tools and applied to a crushing plant has been developed with a structure based on a model of a human operator. It consists of a knowledge base containing a qualitative model of the process and a rules base with the heuristic logic used by an operator when supervising a plant. The simulation results obtained show the potential of this type of system to supervise the automatic operation of a plant. There has been very significant development in artificial intelligence over the last two decades. Within this development, two approaches can be distinguished, (Winston, 1984). The "model approach," in which the main objective is to understand and model the be¬havior of living systems. The second approach is the "engineering approach." Here, systems capable of performing tasks usually requiring human intelligence are created. As part of this latter approach, knowledge engineering and its main achievement, expert systems, have been developed. Expert systems arose from the need to incorporate the abilities of a human expert in solving realistic problems in which the conventional approach has great difficulties. The first successful applications of expert systems were in medical diagnosis, geophysics, and fault detection. However, since 1971, when Fu (1971; defined intelligent control as the inter action of artificial intelligence and automatic control, some significant developments in the use of artificial intelligence tools for process control have been achieved (Astrom, 1986; Pinto 1988; Fahrenkrog, 1988; and Porter 1987). The modern control theory has made important advances. And, although successful in some applications, it has failed to cope with the practicalities of many industrial processes. As a result, the automatic operation of a plant has been confined to a small region around a normal operating point and to periods without any great disturbance. One of the main reasons for this is the lack of accurate and structured knowledge of the processes involved. Despite this, operators applying their knowledge, experience, and a little intuition, often obtain good results controlling the plant in such situations. Considering the above, the next obvious step is to include similar reasoning capacities in a computational system. The development of such an expert supervisory system prototype applied to a mineral crushing plant is presented. Problem description The problem is to conceive a control system with the ability to handle quali-

Jan 1, 1989

By J. Chilton

The fact that methane ignitions continue to occur at the mining face indicates that monitoring with machine-mounted methanometers does not always indicate the presence of high methane concentrations. Methane concentrations at the face change quickly due to changes in airflow. By measuring these changes in airflow, it may be possible to predict changes in face methane levels more quickly. Currently there are no techniques or instruments to accurately measure airflow inby the mouth of the ventilation curtain or tubing. Tests conducted in the NIOSH ventilation test gallery compare the data provided by one-, two-, and three-axis ultrasonic anemometers. The effects of changes in airflow direction and turbulence on instrument readings are discussed, and guidelines are given for selecting the type of instruments to be used for monitoring airflow near the mining face.

Jan 1, 2007

By R. A. Reiley

Introduction Democratic countries are founded on the principle that all citizens have the right to participate in policy setting and decision-making processes. Citizen participation is especially evident in environmental issues and policies. In the United States, there are currently over 10,000 environmental organizations and new ones are being formed each year. Many of these organizations are formed on a watershed basis and are particularly concerned about the impact mining has on the environment. While the environmental issues vary from area to area, most concerns center around mining impacts related to subsidence, water pollution, and water diversion. Citizens have a number of avenues for participating in lawmaking that affects the mining industry. Some of these avenues include participation in litigation and citizen ballot initiatives. In addition, there are less formal methods of participation that include attending public meetings, commenting on agency rules or lobbying on specific legislation. The intent of this article is outline the various public participations mechanisms, highlight the latest legal developments that have affected mining industry through citizen participation, and briefly discuss emerging issues.

Jan 1, 2001

By V. Svalbonas, M. Fresko

The present versions of the Welding Codes, such as BS7608, have long been known to be compatible with hand computations of membrane and bending stress, rather than detailed finite element solutions. However, in the last five years, in the mining industry, this incompatibility has been largely ignored, and the code interpretations have been pushed into the realms of ground welds, residual stresses, and even flaw growth. Such techniques have to be recognized as extrapolations not necessarily sanctioned by the original code documents. The safety of such extrapolations, as they are related to grinding mill fatigue design, is investigated herein.

Jan 1, 2002

By Shawn Collins

BACKGROUND The history of the Pine Point Mine is a rich one. This property once boasted one of the largest and most profitable lead-zinc mines in Canada's long and storied mining history. The Pine Point mine used open pit technology to extract the ore, but they faced several challenges. In addition to logistics problems with haul distances and metal prices, the mine faced the challenge of a large in flow of water from the Great Slave Lake. Eventually, the Pine Point Mine was closed leaving behind a large deposit of lead-zinc ore. Following the closing of the Pint Point Mine, Tamerlane Ventures Inc. acquired this property which includes approximately 70 million tonnes of lead-zinc reserves. The initial phase of this project will concentrate on the R-190 deposit as a test site to prove their new approach for extracting the ore. The R-190 reserve is believed to have approximately 1,014,000 million tonnes of high grade ore varying from 5% to 52% combined lead-zinc. Once the pilot project proves the approach is valid, the process will be repeated in approximately 33 other ore bodies on the property. This paper is written to discuss the design process to determine the most effective means of placing production and service equipment in the same shaft. Currently the design work and the mining scheme is complete, but lead-zinc pricing has prevented Tamerlane Ventures Inc. from moving forward with the project.

By P. C. Thakur

In Part I of this paper, it was established that the width of longwall faces in highly gassy mines is primarily limited by the volume of air reaching the tail-end of the face. The ventilation air reaching the tail-end of the face should be not only enough to keep methane concentrations below the statutory limits (generally 1 percent) but also enough to prevent any gas layering. The air volume leaking from the longwall face into the gob should also be able to push the explosive methane-air mixture away from the gob area immediately behind the longwall face where active roof-fall is taking place (typically 30-45 m). The second group of variables that also controls the width of the longwall panel consists of (a) the rate of advance, (b) bleeder air quantities, (c) specific methane emissions for the gob area and, (d) efficiency and cost of gob gas capture. This paper will discuss the second group of variables and its impact on the optimum width of longwall faces in highly gassy coal mines.

Jan 1, 2009

By H. Akbari

Ordinary portland cement (OPC) is the key pozzalonic component of the concrete mix widely used as a construction material worldwide. B illions of tons of OPC are used in the construction industry each year. However, calcinations of limestone and silica that produce OPC also produce almost an equal amount of C O2 during the cement manufacturing process. Thus, OPC production accounts for nearly 7% of all anthropogenic C O2 emissions each year. The main objective of this study was to develop a geopolymer-based composite to be used as a substitute for OPC in concrete application to significantly lower the carbon footprint of the construction industry. A waste material produced during the coal combustion process was used as the main raw material for the geopolymer-based composite. It was mostly the nonmetallic content of the F-type fly ash produced from the combustion of bituminous coal. The authors envisioned extracting some of the valuable metal oxides from fly ash prior to using the major nonmetallic portion of the fly ash for geopolymer concrete application. The results obtained from this study showed that the compressive strength of geopolymer concrete compares favorably with that of conventional concrete prepared using OPC.

Dec 1, 2013