Search Documents

By Fengyu Ren, Ruslan Puscasu, Kunpeng Yu, Gideon Chitombo, Liangliang Kang

Weak rock mass and poor flow of material can cause excessive ore loss and dilution in sublevel caving. This paper proposes a method to establish design parameters for an inclined deposit within a weak rock mass and evaluates its effectiveness through a case study. In order to solve the problem of low production capacity and poor safety conditions of sublevel caving mining at the Yingfangzi silver mine in China and to ensure a smooth production from the refractory ore body, it is necessary to select appropriate stope structure parameters. Based on random medium theory of gravity flow and the improved equation of ore discharge in random medium, an end wall drawing experiment is carried out to determine the optimum design and flow parameters. It was observed from the experiment that, due to the influence of the randomness of particle movement, there is a mismatch in the flow parameter measurement. The flow characteristics and distribution of the marker particles are different from that of the tested particles resulting in large drawbody shape distortion. The study finds that the flow parameters obtained by the new method are more practical and account for drawpoint width and recommends that the new method for determining the sublevel stope height is used when the drawbody is a non-standard ellipsoid. The outcomes have shown a significant reduction in the dilution and improvement in the recovery rates, and the safety and efficiency of mining have been greatly improved.

By Bijan Taheri, Behrouz Maghsodi, Monireh Heshami, Reza Kohan

A common problem recently encountered with the increase in the rate of input feed at Enrichment Plant 2 of the Sarcheshmeh Copper Complex is the loss of value to the tails, translating to lower recoveries. The feasibility of the direct transfer of part of the high-grade concentrate from rougher stages to an appropriate position along the circuit was studied, and two positions were proposed for direct transfer of the concentrate. One position was the feed flow into cleaner cells, and the other was the feed flow into the recleaner cell. The results indicated that transferring the concentrate from the first unit of the rougher stage to the feed flow into the cleaner cells was feasible, with no limitations, while the second position required the installation of a set of hydrocyclones. It was found that the transfer of concentrate to the proposed positions not only addressed the problem of limited cell capacity, resulting in debottlenecking of the circuit, but also improved metallurgical separation efficiency up to 1.4%.

By Yuting Xue, Taghi Sherizadeh, Mark Van Dyke, Dogukan Guner, Khaled Mohamed

The Coal Pillar Rib Rating (CPRR) technique has been developed to assist in rib support design in underground coal mines. One major challenge of the data collection process is the measurement of coal strengths in the field. Schmidt hammer has been verified as a useful tool to determine coal strength. An alternative approach is to obtain the representative strength of coal mass by determining the coal lithotypes in the field based on the coal brightness profile by experienced geologists or mining engineers. In this paper, image processing techniques have been used to quantify the texture of coal images of different lithotypes with the purpose of classifying coal lithotypes. The coal images were collected from the pillar ribs with exposed surfaces in underground coal mines, and the coal lithotypes were identified when taking the images. The method of Gray-Level Co-Occurrence Matrix (GLCM) was used to analyze the textures of coal images of different lithotypes, and the texture parameters, such as contrast, homogeneity, energy, and entropy, were compared. The results show that the images of coal with different lithotypes have different textures, which can be quantified through the image processing. The results from this study demonstrate the potential of classifying coal lithotypes using rib photos and easing the data collection process of CPRR.

Feb 1, 2024

By J. L. Fuller

Thousands of mine air samples are taken underground each year by MSHA inspection personnel in order to further assure that miners have a safe and healthy environment in which to work. While most air samples are taken with stain tubes, many samples are obtained in evacuated containers and returned to a laboratory for more accurate analysis on a gas chromatograph. In order to enhance the accuracy, reliability and repeatability of the samples taken with evacuated containers, improved procedures have been developed, which are described in this report, for filling two different types of evacuated sample containers using either mechanical or electrical pumps. In those instances, such as when sampling strata gases in drill holes, where mathematical calculations may be required for proper sampling, example calculations are provided. The use of a third type of evacuated container, which is generally restricted to non-specific sampling of the ambient mine atmosphere, is also described.

Jan 1, 1986

By Frederick P. Agterberg

It can be useful to model the mean grade values for a metal in mineral deposits containing that metal as representing the extreme value tail of a lognormal frequency distribution for the concentration values of the metal in rocks of all types. Results for copper and zinc in the Abitibi area of the Canadian Shield are compared to results previously obtained for the Canadian Appalachian Region. The lognormal model is also applied to a set of 162 large gold deposits in the Abitibi area. In the second part of the paper, 1311 large and small gold deposits in the Abitibi area are modelled as discrete events. By means of a newly developed spatial clustering model it is possible to predict the variances of random variables for frequencies of deposits in cells of different sizes.

Jan 1, 1979

By A. B. Cecala

Enclosed cabs have been used for many years to isolate workers on mobile equipment in the mining industry for health and safety reasons. These enclosed cabs create a microenvironment for workers where they can be either more protected or more vulnerable to contaminants. Over the past decade, the National Institute for Occupational Safety and Health (NIOSH) has performed substantial research efforts to improve the air quality inside enclosed cabs of both underground and surface mobile mining equipment. In these efforts, NIOSH has partnered with mining companies, original equipment manufacturers (OEMs), and manufacturers of filtrations and pressurizations systems in a synergistic effort to reduce respirable dust and improve the air quality inside these enclosed cabs. Various field studies over this time have shown an array of results ranging from very minor to very significant reductions (protection factor: 3 ? 89) in respirable dust levels inside these enclosed cabs. In addition to and concurrent to the field work, NIOSH also performed a comprehensive laboratory study to evaluate all the factors involved in cab filtration and pressurization systems and identified those factors that were most significant for an effective system. From this comprehensive research effort, the key components for an effective filtration and pressurization system have been identified in an effort to provide the best air quality, thus minimizing the respirable dust exposure, to equipment operators inside of enclosed cabs of mobile mining equipment.

Feb 27, 2013

The 112th Annual National Western Mining Conference (NWMC) hosted by the Colorado Mining Association (CMA) drew some political heavyweights, if by voice only, into the fray of two of the hottest topics that the mining industry is currently facing ? climate change and the new energy economy. A changing political landscape in Colorado, as well as in Washington D.C., has given rise to questions about the economic future of the United States and the mining industry?s role in that future. While there has been a recent push away from traditional energy sources to a ?new energy economy? that is rich in renewable energy sources such as wind and solar, the NWMC?s agenda emphasized the role that minerals will play in new energy technologies. The conference was also full of talks about the industry?s role in reducing the United States? reliance on foreign oil and other mineral commodities. To that end, an impressive lineup of speakers were invited to attend the three-day conference Feb. 8-11, in Denver, CO. Unfortunately, Mother Nature had other plans and three of the four headliners, including Denver?s mayor and Democratic candidate for governor of Colorado, John Hickenlooper, were unable to get to the conference because of a massive blizzard on the East Coast locked them in Washington, D.C. However, with modern technology, a full auditorium heard presentations from Hickenlooper, National Mining Association (NMA) president and chief executive officer Hal Quinn and Glenn Kelly, vice president, government affairs for NMA. Republican candidate for governor of Colorado, Scott McInnis, did speak to the crowd in person.

Jan 4, 2010

By J. E. Lowe

The unique application of a large walking dragline in the mountains of southern West Virginia was developed and implemented by Hobet Mining, Inc. Hobet is an independent operating subsidiary of Ashland Coal and is headquartered at the No. 21 Mine in Boone County, West Virginia, near Danville. Hobet also operates the 07 Mine located in Logan County, West Virginia, near Holden. Both mines are similar in equipment and manpower used; both produce over 2,000,000 tons of clean coal annually. Each site encompasses large, contiguous properties with access to rail service. The larger of the two is the Boone County property; it totals nearly 40,000 acres and has ample reserves. In 1977, Hobet was in the process of constructing a preparation plant (Beth Station) at its 21 Mine site with a capacity for two million tons. One of the first orders of business was to design a mine plan that would provide production for the capacity of the plant. Coal production would come from a more than adequate reserve base using the most economical mining methods available. Hobet looked at different deep and surface mining methods to use in order to develop the property; ultimately, it was determined that the mountaintop removal method with the use of a large dragline was the most economical way to develop reserve. Prior to this time surface mining in mountainous Southern West Virginia was generally done by contour mining and/or augering techniques.

Jan 1, 1993

By B. Tolwinski

Long-Term Open Pit Scheduler or L-TOPS is a new software package for evaluating, planning, and design of open pit mines. L-TOPS transforms geological, economic, and technical information about a mineral deposit into a detailed mining schedule that maximizes economic efficiency without neglecting the practical requirements of mining operations. L-TOPS has been customized for integration with Placer Dome Inc.'s existing in-house resource/reserve optimization software to function as a primary tool for property acquisition studies and for the designing of mines for feasibility studies. This pa-per presents an overview of L-TOPS and reports on its application to Placer Pacific's (Placer Dome's Australian affiliate) Mt. Rawdon project.

Jan 1, 1996

By M. L. Harris

Explosions in underground mines and surface facilities such as processing plants are caused by confined accumulations of combustible dust and/or flammable gas mixed with air in the presence of an ignition source. Underground explosions can be prevented by minimizing methane concentrations through methane drainage and ventilation, by adding sufficient rock dust to inert the coal dust, and by eliminating ignition sources. The effectiveness of rock dust in arresting explosion propagation was proven by experiment and practice (1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11). The precise mechanism by which rock dust (generally pulverized limestone dust) quenches flame has not been fully explained, but is believed to be absorption of thermal energy from the heated gases and absorption of radiant energy, which reduces the preheating of unburned coal particles ahead of the flame front. One measurable aspect of explosibility is incombustible content. In order to determine whether enough rock dust is applied, 30 CFR1 § 75.403, Maintenance of Incombustible Content of Rock Dust, requires at least 80% incombustible content on the roof, ribs, and floor of underground coal mines. 30 CFR § 75.403-1 further defines the incombustible content as follows: ?Moisture contained in the combined coal dust, rock dust and other dusts shall be considered as a part of the incombustible content of such mixture.? In order to determine the incombustible content of the mine dust, samples of deposited dust from specified areas in a mine must be collected, analyzed, and then compared with the minimum standard of 80%. The traditional low temperature ashing (LTA) approach to determine if a coal and rock dust mixture is compliant with the inerting requirement consumes the coal dust and considers the remaining material to be inert. Compliance with the law is then determined by comparing the measured percentage of inert material of the representative band sample with the pre-established requirement of 80%. The incombustible content of the sample includes rock dust, the amount of moisture as received at the lab, and the inherent ash in the coal. The LTA method is not itself a direct measure of explosibility but is a surrogate that calculates a single parameter associated with large-scale Bruceton Experimental Mine (BEM) explosion test results conducted with dry rock dust. This method assumes a homogenous mixture with no layering of rock dust and coal dust. Float coal dust is a serious explosion hazard if it accumulates on top of the rock dust and is not mixed with the rock dust (12). Mitchell and Nagy (13) studied the effectiveness of water as an inerting agent for the coal dust explosion hazard. The study emphasized that surface water evaporates readily from dusts. Thus, in a passageway where the dust is wet, changes in weather or the ventilation system could dry the dust and make it unsafe in a relatively short period of time. Where adequate rock dust has been applied, this drying effect is not a factor. However, if the mine depends upon the moisture content as part of the incombustible content, fluctuations in the dust surface moisture within a mine can render moisture content an ineffective and inconsistent measure of safety. Additionally, if sufficient moisture is absorbed and subsequently relinquished by rock dust, a cake can form and render the rock dust ineffectual. The trend has long been recognized that mine explosions occur primarily during the winter season when the humidity is low for long periods of time (14, 15, 16). In light of this trend and due to the potential variability of the moisture content of the dust, it may not be prudent to include variable surface moisture in the total incombustible content of the sample. Instead, surface moisture should be viewed as an additional safety measure as long as the rock dust is dispersible. However, moisture limits the ability of the rock dust to disperse and can significantly reduce its capacity to effectively inert propagating explosions (2, 13, 17, 18, 19, 20, 21, 22). Given the methods by which the as-received moisture and incombustible content are determined, dust samples from the 2010 MSHA database were assessed to determine the variability of the moisture content throughout a year and how often the measured as-received moisture might have affected the dust explosibility determination if removed. The findings were then verified by observation in laboratory studies and within the NIOSH OMSHR Safety Research Coal Mine (SRCM).

Feb 23, 2014

Mine managers need better information to locate new opportunities and then to assess the effect of their decisions. We are developing the Intelligent Decision Support System (IDSS) and its two major modules, the Pattern Recognition System (PRS) and the Knowledge Representation Subsystem (KRS) to automatically provide the information from monitoring system sensors. This paper focuses on the KRS Algorithms that extract key information from lists of time study type event sequences. Because a static system cannot operate effectively in a dynamic mining environment, we are prototyping an index based technique that allows the system to adapt itself to this dynamic environment.

Jan 1, 1990

By M. K. McCarter

A unique telemetry system was developed to monitor potentially unstable natural slopes above a residential area. Continuous interpretation of data transmitted from remote movement-sensitive devices and immediate communication of signficant changes to emergency personnel were made possible by a readily available "home" computer. Even though the computer based system was originally developed for a non- mining application, it could be used with little or no modification to monitor ground control instrumentation in open pit and underground situations.

Jan 1, 1985

By Mahiyar Nasarwanji, Jonathan K. Hrica, Jonisha P. Pollard, Lydia M. Kocher, Brianna M. Eiter

Within the metal/nonmetal mining sector, fall-related incidents account for a large proportion of fatal and non-fatal injuries. However, the events and contributing factors leading up to these incidents have not been fully investigated. To help provide a clearer picture of these factors, an analysis of imminent danger orders issued by the Mine Safety and Health Administration (MSHA) between 2010 and 2017 at both surface and underground metal/nonmetal mine sites revealed that most orders are associated with fall risks. Of these cases, 84% involved the workers not using fall protection, fall protection not being provided, or the improper use of fall protection. Fall risks for workers most frequently occurred when standing on mobile equipment, performing maintenance and repairs on plant equipment, or working near highwalls. In most cases, a single, basic, corrective action (e.g., using fall protection) would have allowed workers to perform the task safely. Overall, these findings suggest that a systematic approach is needed to identify, eliminate, and prevent imminent danger situations. Furthermore, to protect mineworkers from falls from height, frequently performed tasks requiring fall protection should be redesigned to eliminate the reliance on personal fall protection.

Remote sensing methods have been used to evaluate vegetative growth patterns for many applications, though relatively little work has focused on tracking mine reclamation progress. For coal mines in Central Appalachia, reclamation approaches that include production of biofuel feedstocks are increasingly attractive, as these may yield significant post-mining land values and contribute to carbon-neutral energy supplies. To optimize productivity, the influence of reclamation parameters must be well understood ? which necessitates tracking biomass production over long time periods. Satellite-based estimations may offer low-cost alternatives to conventional biomass appraisals, and also the potential to provide critical input for carbon accounting at varied spatial scales. In this paper, we use biomass production experimental plots on reclaimed mine sites established by the Powell River Project (PRP) for a comparative study between satellite measurements of Normalized Difference Vegetation Index and inventory estimates of biomass under a variety of conditions. The PRP is a unique public-private partnership in the coalfields of southwestern Virginia dedicated to enhancing beneficial use and environmental protection of mined lands.

Feb 27, 2013

By L. A. Ruth

Vision 21 is a government/industry/academia cost-shared partnership to develop the technology basis for integrated energy plants that will, early in the 21stcentury, result in the deployment of ultra-clean plants that produce electricity and “opportunity” products. Vision 21 plants will use fossil fuel feed-stocks in combination with other domestic resources, e.g., biomass, municipal waste, and petroleum coke. Opportunity products could include transportation fuels, steam, high-value chemicals, synthesis gas, and hydrogen. Performance targets for Vision 21 plants, example plant configurations, and the key technologies that will be needed are described.

Jan 1, 2000

By Douglas G. Hubert

To put coal in its proper perspective as a source of energy for electric power production, we must first compare it to other energy sources. A report of the Atomic Industrial Forum dated February 1958 records a number of authoritative though widely varying predictions. The most optimistic of these states that by 1968 there will be a total U.S. capacity of about 6000 megawatts of nuclear power, if growth continues at the present rate. Other sources indicate over 200,000 megawatts of total electrical capacity in utility plants by 1968. This is only 3% nuclear. Therefore, 97% of our total power production will be from non-nuclear energy. Fig. 1 shows the distribution of energy sources of electric utility product- ion in the U.S. as reported by the Federal Power Commission in 1954. Note that less than one quarter of the total is hydro and about one half of the total is coal. For 1957, the Edison Electric Institute reports that of the total steam- electric generation in the U. S., 68.6% was by coal, 7.9% was by oil and 23.5% was by gas. This is an increase for coal and a decrease for oil and gas in those three years. Thus we can conclude that two-thirds of the steam-electric power in the U. S. is now generated by coal. Fig. 2 shows the major markets for coal for 1947 vs 1957. The greatest in- crease has been in the electric utility market, where it has more than doubled in the ten years. One-third of the total coal produced goes to the utilities which now represent coal?s major market. Utilities used 160 million tons of coal in 1957, and the estimated quantity for 1967 is 275 million tons, and for 1977 is 525 million tons. It is predicted that 85% of steam-electric power will be generated by coal in 1975.

Jan 1, 1959

By J. V. Thompson

The Powderhorn complex as a source of perovskite (calcium titanate) containing about 1.5% rare earths has been examined in several recent feasibility studies. Much promising exploration and process research has been done in recent years. This paper is presented with cautious optimism and with the acknowledgment that there may be some technical and economic areas yet to be explored. The Powderhorn carbonatite and alkalic stock in Gunnison County, Colorado, lies about 203 airlines km southwest of Denver at an elevation of 2450 to 2750 m (see Figures land 2). All of the mineable ore bodies are owned by Buttes Resources Company of Houston, Texas.

Jan 1, 1990

By John L. Bolles

The Phelps Dodge Corporation's Morenci Concentrator includes facilities for coarse crushing, fine crushing, grinding, flotation, tailing, disposal, concentrate filtering, and drying. The Morenci Concentrator daily throughput is in excess of 60, 000 tons. The ore milled is mainly a medium-hard monzonite porphyry in which the principal sulfide minerals are chalcocite and pyrite. The ore is transported by rail from the Open Pit Mine to the primary crushing plant located at the concentrator site. Ore is side-dumped from 80¬ton railroad cars into a sixty-inch gyratory crusher. The ore is then conveyed to a. 12, 000 ton coarse ore storage bin. Fine crushing is accomplished by four parallel lines of conventionally stacked crushers in open circuit. Each unit consists of one seven-foot standard cone followed by two seven-foot shortheads. Ti% product of the fine crushing plant is distributed by two tripper cars across a fine ore storage bin. The crushed ore is then fed by variable speed belt feeders into thirty parallel, single stage, closed circuit grinding units. Each of the 30 grinding units consists of one 6' x 23' conditioning drum, one 10' x 10' ha l mill and two 54" duplex spiral classifiers as principal equipment. The dry ore is fed into the conditioning drum with water to dilute the ore to a slurry of approximately 78% solids by weight. An aqueous solution of ammonium sulfide is also added to the conditioning drum. The ammonium sulfide primarily acts as a sulfidizing agent. The ore slurry containing the naturally occurring sulfide copper minerals and the sulfidized copper minerals discharges into the feed scoop box of the ball mill, where milk of lime, collector and-.dilution water are added. The ball mill product slurry is gravity fed: to the classifier pool where water is added to obtain the desired classifier overflow product

Jan 1, 1977

By J. García, B. Arango, F. Calderón, O. J. Restrepo-Baena, A. Carreno, L. Rojas-Mendoza, J. Pérez, E. Bedoya

"Tungsten extraction is a subject of global interest due to is properties. These properties, such as its high melting point, have contributed to the development of metallurgical extraction processes that can be adapted to the particular chemical composition and mineralogy of the ore. In Colombia there is a research deficit in tungsten related areas, and especially with regard to its extractive metallurgy. In this study the physical, chemical and mineralogical characterization of a sample were performed. Subsequently, crushing and grinding were employed to reduce the material to a more convenient size, making it suitable for further concentration and metallurgical processes. Through physical concentration techniques it was obtained a concentrated ranging between 60 -70 % of WO3 content.INTRODUCTION Tungsten is a metal of great economic importance due to its excellent properties such as high density and extraordinary melting point 3422°C), which is indeed the highest of all the elements. Tungsten is primarily used in metal alloys, manufacture of special steels, coatings and catalysts; products of interest to both international and national industry. However; given that the use and economic value is determined by the percentage of tungsten in the mineral, particle size and chemical associations, it becomes essential to properly characterize the mineral to further define possible metallurgical extraction routes. The metallurgical processes for minerals enriched in tungsten may vary depending on location and the genesis of the ore body, which means that for each ore a particular set of operating conditions must be determined. This is important since process standardization can lead to misuse of the mineral resource. However, in Colombia there is a research deficit as it relates to minerals enriched in tungsten and to its extractive metallurgy. Then, there is a need to conduct studies that can lead to a better understanding of the ore, and to develop extraction processes for the metal of interest. EXPERIMENTAL A state of the art review was made in order to gain insights of the tungsten metallurgical process. Comminution was necessary with the aim to reduce the sample size; therefore the sample was taken into crushing and grinding stages. Concentration techniques such as magnetic separation, gravity and / or electrostatic were also applied. Physical, chemical and mineralogical characterization were performed by using polished sections, grain size determination, X-Ray Fluorescence (XRF) and X-ray diffraction (XRD) techniques."

Jan 1, 2015

By D. F. Malott

The Michigan Department of State Highways makes extensive use of geophysics for subsurface surveying which would be applicable for uses in other fields. Examples of resistivity surveys are given which include a proposed large volume excavation with suggestions for land use after excavation, subsurface evaluation for engineering design, and a subsurface survey for land appraisal. An example of a combined refraction seismic and resistivity survey is shown where the resistivity is used for outlining the unconsolidated soils, while the seismic method Is used to outline bedrock and to evaluate it for rippability. A refraction seismic survey at the bottom of bridge caissons for evaluation of bedrock uniformity and a relative aid In assessing rock strength is reported.

Jan 1, 1968