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By N. A. Abdel-Khalek

An experimental study was carried out to compare the results of laboratory column flotation versus conventional flotation for the cleaning of fine coals of different rank and their oxidized samples as well as discrete size fractions. Surface oxidation caused a significant reduction in the flotation yields achieved with both methods. However, the column flotation produced concentrates? of lower ash content. The recovery -size curve achieved with column was similar in shape to that obtained with conventional cell, with superior results in the region of fine fractions. The influence of some column operating parameters was also discussed.

Jan 1, 1990

By V. F. Hollister

Although it is apparent that porphyry copper deposits may have formed in the Andean orogen from Permian time onward, commercial deposits thus far developed appear to have Cenozoic ages only. Following Chilean useage, the porphyry deposits are divided into either: (a) a stockwork, or (b) a tourmaline breccia model. Stockwork type deposits tend to occur on major strike-slip structures which may be either transcurrent or transverse faults related to plate movements, while the tourmaline breccia type may more frequently form independently of regional faults. Stockwork types may be conjugate fractures that intersect and ramify as a network of veins and veinlets, cutting altered rock, and genetically related to a major regional fault, or in other cases they may reflect the intersection of two large fault structures. Circular fracture patterns may more rarely occur in stockwork deposits in response to a specific intrusive. Tourmaline breccia types are characterized by circular and radial fractures genetically connected in some way with tourmaline breccia pipe development or an intrusive piercement that preceded it. Each structural model contains mineralized intrusive8 which have a close time-space relationship to ore and in each model, mineral paragenesis is similar, regardless of age or location in the plate. Also, each model contains the same type of alterntion halos (phyllic, argillic, prophllitic) as are developed in intru- sive centers in porphyry copper deposits found in North America. The potassic zone is exposed best in the older deposits. Examples of each type of deposit are illustrated, demonstrating the feature evolved.

Jan 1, 1973

By V. M. Johnston

The most abundant fuel resource in the U.S.A. is also the most under-utilized. Proven reserves of bituminous coal, sub-bituminous and lignite constitute from 60% to 90% of our total fossil fuel reserves -- dependent upon the parameters used by the analyst making the estimate. Despite this ample supply, bituminous coal provided only 20% of U. S. energy consumption in 1967 and 1968, this dropping to 17.57 in 1971 and 1972. By 1978, according to my projections, 16.7% of the Nation's mechanical energy will come from bituminous coal. However, our energy needs are growing at such a rate that the 20.6% provided by bituminous in 1967 equalled 480 million tons while the 16.7% of U. S. consumption visualized for 1978 will require nearly 650 million tons. In order to view coal's position with perspective in this developing energy crunch, it is necessary to examine the total energy situation. To this end, I have prepared a couple of tables which you should have before you. I chose this procedure rather than slides because I would need to utilize an entire wall to make the data visible to an audience. Therefore, I refer you to the long sheet entitled "U. S. Energy Consumption - Trillion Btu - 1967-1978." As you can see from the heading, I am confining my treatment of the problem to the intermediate term. In the long run, if we are willing to pay the cost, we can do a lot of things, including the complete conversion of coal into a sulfur-free fuel.

Jan 1, 1973

By Koehler Stout

Stopewall or room closure can be a problem in nining operations. In some mines, wall closure causes ore passes and nanways to collapse when they are enclosed in nine fill. When this phe- nomena occurs, heavy ground and, or, rock bursts frequently happen. Often, ground problems become progressively worse as mining in the stope block progresses toward the upper level. The sill and pillars in the level above may experi ence heavy ground and bursts. Sometimes the conditions get so bad in the stope that it is unsafe to mine the ore, so the stope is abandoned and the ore is lost.

Jan 1, 1980

By W. D. Delahaut

Sampling tests performed at the Paradise Peak Mine compared various blasthole samplers and reverse circulation sampling methods. Statistical analysis of the data indicates that be-low-the-deck bag sampling produced a 24 to 29 percent error when compared to bulk sampling methods. Use of a chip pile wedge sampler reduced error to 17 percent. Reverse circulation sampling upgraded over bulk blasthole sampling by 7 percent for gold and 11 percent for silver. These results indicate that bias sampling conditions exist when small volume bag sampling is employed in production blasthole drilling.

Jan 1, 1991

By Irina Chernyshova, Erik Larsen, Hanumantha Rao Kota, Vladislav Slabov, Garima Jain

The mining industry faces pressure to provide metals for the green digital shift using sustainable technologies. This study evaluates biosurfactants as collectors for ultrafine and coarser particles of hematite and malachite, aiming to improve the flotation of ultrafine particles.

Jun 1, 2023

By M. Hepokoski, M. Klein

"Mine refuge shelters are designed to protect mine workers from hazardous environmental conditions after a mine disaster, but high temperature and humidity levels inside these shelters may pose a significant safety risk. Due to the safety risks associated with human testing, detailed thermal models of shelters and human occupants have been developed using TAITherm simulation software. These models are used to predict the temperature and humidity within the shelter resulting from metabolic heating, evaporation due to sweat and respiration, moisture and heat from the shelter’s carbon dioxide scrubbing system, and heat transfer within the shelter. A detailed human thermoregulation model simulates the sensible and latent heat generated by the shelter occupants, and predicts the occupant’s body core temperature and moisture lost due to sweating and respiration. This information is used to assess the safety of the shelter. This paper presents the technical details of the human thermal model, validation comparing the human model to human subject test data, and results of a mine shelter analysis. IntroductionPortable mine refuge chambers are used in U.S. coal mines to provide protection to mine workers from hazardous conditions following a traumatic event. Although these shelters are designed to supply clean air and sustenance for up to 96 hours, prolonged exposure to the mine shelter environment itself can pose a substantial risk to human safety. Heat generated by the shelter occupants combined with heat from the carbon dioxide (CO2) scrubbing system can raise the shelter interior temperatures and relative humidity to dangerous levels that can lead to heat stress in humans. Unfortunately, the thermal burden associated with mine shelter exposure is not well characterized due to potential hazards associated with underground human subject testing. In order to assess the thermal burden on people within a mine shelter environment, a detailed thermal model was created to accurately predict the temperatures and humidity levels within the shelter, and the impact of these environmental conditions on human occupants. The model consists of a mobile inflatable tent-type mine shelter with 23 humans, and includes the surrounding mine environment. The thermal simulations were performed using a validated commercial heat transfer prediction computer software. Additionally, a module of the software provided the capability to simultaneously model the thermophysiology of 23 unique humans contained within the mine shelter. The human thermal models accounted for the thermal interaction with the environment and provided a core temperature response prediction that can be used to evaluate survivability in heat stress situations (U.S. Army, 2003). The models can also be used to determine maximum occupancy in order to maintain safe temperature and humidity levels inside the shelter in specific mine environments, to optimize shelter size for maximum heat dissipation, or to simulate active cooling systems."

Jan 5, 2017

By Gary B. Glass

In 1997, 92.3% or 235.7 Mt (259.8 million st) of coal produced in Wyoming came from the Wyodak coal zone in the eastern Powder River coalfield. The mined portions of the zone consist of one to three beds of coal with an aggregate thickness between 15 and 33.5 m (50 and 110 ft). The thickest expression is 61 m (200 ft). The delivered coal from this zone averages 0.33% sulfur, 5.12% ash and 19.98 MJ/kg (8,590 Btu/lb.). This coal zone occurs at or near the top of the Paleocene Fort Union Formation, which is overlain by the Eocene Wasatch Formation. There is also production from two coalbeds in the lower portion of the Wasatch at the southern end of the basin. Production of coalbed methane derived from the Wyodak coal zone is currently an estimated 289 Mm3/a (10.2 billion cu ft/year). This production is occurring west and downdip from the coal mines and is increasing each year.

Jan 1, 1998

By T. W. Camm

Aristotle made the observation that man is a political animal. Engineers often like to think they are above the fray when it comes to organizational politics, but most organizational theorists believe politics is a fundamental dynamic in any group. This paper examines the various ways that people use power within organizations to negotiate the political interactions in the work place.

Feb 27, 2013

By M. L. Sharrah

Communication about the energy problem has come at us in great profusion during the last couple of years--reports, speeches, editorials, advertisements--and events. Events such as the Arab embargo on oil exports which vividly demonstrated the world's dependence on oil, a finite and nonrenewable resource. And the three-fold increase in the price of oil which provides a constant reminder of the political and economic implications of dependence on foreign oil. A distinction among countries exists today which was almost inconsequential two years ago--the oil exporting nations and the oil consuming nations. The only rational way for the consuming countries to lessen the political and economic clout of the OPEC group is to reduce their dependence on oil. The United States is capable of playing a significant part in such a move for several reasons.

Jan 1, 1975

By Jey K. Jeyapalan

A characteristic common to most tailings dam failures caused by earthquakes or excessive rain storm is that the tailings tend to liquefy and flow for substantial distances as a viscous fluid, with the potential for extensive damage to property and life. Failures of El Cobre, Chile (1965), Mochikoshi, Japan (1978), Aberfan, Wales (19661, Buffalo Creek, West Virginia (1972) are examples of such catastrophic incidents. In these four incidents more than 400 lives were lost, and the loss of property was approximately $200 million. In order to be able to assess the potential for damage in case of such a failure, it is necessary to predict the possible extent of flow slide movement. This paper discusses simple procedures for performing such analyses. Also, in order to illustrate the use of these analysis procedures in tailings dam design, two case histories are analyzed.

Jan 1, 1982

By Brij M. Moudgil

Flotation of fine and coarse coal after multistage addition of the frother was found to yield coal fractions with significantly lower ash content as compared to the feed. It was observed that the lowest ash content, specific gravity and reactivity of coal was associated with finer size fractions. Ignition and combustion characteristics of different coal fractions were evaluated using a differential thermal analyzer (DTA) with calorimeter attachment. It is suggested that in the ignition stage, the removal of mineral matter affects the reactivity through the physical changes brought about by the ash removal. In the char combustion stage the mineral matter seems to influence the reactivity through the catalytic activity of surface concentrations of metal ions, ratio of combustible/incombustible material, internal pore structure and roughness.

Jan 1, 1984

By Robert R. Dorfler

AMPS[. has completed a rationed grinding ball test in a 2.93 m x 2.93 m ball mill at Climax Molybdenum Company. The test consisted of purging the ball distribution formed by charging 100%, 76 mm carbon steel balls with a distribution formed by charging 50% 76 mm and 20% 51 mm alloy steel balls. The resulting change in ball surface area yielded improvements in both tons ground and fineness of grind with a significant reduction in total ball consumption. This paper summarizes preliminary studies leading to the plant test, grinding efficiency results, and future plans to optimize the ball charge.

Jan 1, 1981

By Walter H. Schwedes

Ore grinding mills are really just slowly rotating barrels, but barrels that are growing in size so fast that the application of electric drives for them is rapidly approaching a technology like that for wind tunnels or pumped storage drives. This application is particularly worthy of care because some 40% of the 75 megawatts of power used by a large copper ore concentrator, or some 60% of the 200 megawatts supplied to a large iron ore concentrator, are for grinding. These ore plants are located where the ore is, not where a utility happens to be. So, the challenge is not only to choose a drive and .power transmission for reasonable cost, high performance, reliability and minimum maintenance, but to afford the interface between mill drive and power distribution and source systems to minimize the whole ore plant's monthly power bill, or costs of self generation. Conclusions can be reached in optimizing a drive selection only for each particular ore plant's set of parameters, but by identifying the criteria for selection and then weighting each type of drive per criteria, yardsticks for final choice become apparent. This is the purpose of this paper. Grinding action takes place inside the barrel, where the ore charge is ground with the aid of balls, or mill length rods, or large chunks of ore as in autogenous grinding.

Jan 1, 1972

By D. Shaver, M. N. Badonie, J. Newcomer, V. T. McLemore, E. Owen

Rare earth elements and critical minerals have recently become of great economic interest because of their necessity for many new technologies and recent geopolitical unrest affecting the supply and import of resources. The San Juan and Raton basins in northern New Mexico are two structural coal basins that contain elevated concentrations of rare earth elements and critical minerals. These two New Mexican coal basins will be assessed geochemically and petrographically to identify vectors of the rare earth element and critical mineral enrichment. Coalbeds, coal seams, overlying, and underlying rock units will be sampled and characterized to determine any economic viability. Historic data will be compiled into a new and comprehensive coal geochemical database, which will grow with new analyses, and serve as the dataset for this project; this coal resource database will be made available to the public.

Feb 1, 2023

By P. M. Pettit

Hydrologic investigations at Gold Quarry began in 1989 and continued through 1991. Hydro-stratigraphic units include Tertiary sedimentary rocks, Paleozoic siltstones and carbonates. These units display complex and variable aquifer parameters as a function of faulting and hydrothermal alteration, creating compartmentalized hydrologic domains. Testing has included step-tests, spinner production logs and constant discharge tests. Two Three-Dimensional Finite Element Models have been developed, one for optimizing the pit dewatering system and the second for predicting regional impacts of dewatering. Aquifer testing and long term pumping have been used to calibrate both Finite Element Models.

Jan 1, 1992

By V. R. Degner

The minerals industry trend toward very flotation machines, exceeding 10 m3, began in the late 1960's and responds to the continuing desire to achieve better plant economics through improved plant floor-space utilization, power requirements, and operational /maintenance manpower heeds. In general, as process design tonnage increases, the benefits of the larger flotation machine becomes more evident. The development of the larger flotation machine can be distingushed from earlier, smaller, machines in demanding a rational "scale-up" procedure to guide the basic design, thereby producing a machine prototype capable of satisfactory-operational evaluation at minimum cost. Proven flotation machine "hydrodynamic" scale-up consideration, successfully applied in the development of both the WEMCO No. 164 (28.3 m3) and No. 190 (42.5 m3) machine will be reviewed, and the resulting economic benefits of large flotation machines in high tonnage applications will be summarized.

Jan 1, 1985

By W. Hitchcock

To enable the analysis of stability for a mine feasibility study a variety of geotechnical engineering parameters need to be obtained. At the early stage of a project it is usual for those responsible for the study to require a wide spatial distribution of RC holes in order to define a resource at the lowest possible cost. By the time a geotechnical study has commenced drilling priorities have usually switched to improving the definition of a resource, by drilling with diamond coring methods in the central area of the main orebody. The usual timing for geotechnical data collection is therefore after a wide distribution of holes have been drilled but which contain little geotechnical information. Conventional methods employed usually involve estimation methods, including book values and examination of disturbed core, or expensive additional drilling. With downhole geophysical methods we can economically take advantage of existing holes to obtain continuous values for density, defect orientation and ranking, elastic modulus values, unconfined compressive strength estimates and fracture frequency. This paper presents the results of a geophysical study and discusses the advantages and potential pitfalls of the method as compared to conventional methods of data collection.

Jan 1, 1999

By James L. Kelley

The Twin Buttes Mine, one of the more recently developed large copper mines in the United States, is in the Pima Mining District about 25 miles south of Tucson (Figure 1). Other copper producing mines in the district are the Esperanza-Sierrita mining operations, five miles to the southwest and the Pima and Mission Mines, seven miles to the north. Copper metal production from the Pima District in 1974 totaled 276,728 tons and the Twin Buttes Mine's share was 46,473 tons or about 17%.' The district's copper production was 31% of Arizona State's production and nearly 17% of the production from the United states in 1974. The Pima District thus ranks as one of the major copper producing areas in this country.

Jan 1, 1976

By T. W. Martin

The use of conveyors in large, open pit mines and their drawbacks are discussed. Technological developments such as long distance conveyors capable of handling large rocks are explored. The development and testing by the Bureau of Mines of a prototype crib and cable conveyor for handling large rocks are discussed, and possible modifications of the concept for a production model are examined.

Jan 1, 1984