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By Klados. T.

MSC.Software assessed the performance of the drive end and non-drive end bearings on a ball mill using the finite element method. The assessment included the effect of mill and pedestal deformation on the performance of the bearings. Oil film thickness, oil pressure distribution and power requirement were of interest. A solution approach coupling a structural solver to a Reynolds equation solver was specifically developed for the project. Results showed that the deformation of the bearing surfaces had a significant influence on the performance of the bearings. For example, for the non-drive end bearing, the minimum oil film thickness computed for the deformable bearing surfaces was significantly lower than calculated for the non-deformable case. The results also showed that cavitation was likely in both the drive end and non-drive end bearings (severe negative pressures were obtained in both bearings). Other design variations were also assessed, e.g. a case with a modified radial clearance which improved the results.

Jan 1, 2006

By J. F. T. Agapito, C. E. Brechtel, M. E. Adam

Full-scale stopping and simulated over- cast structures were constructed in large opening (30 ft high by 55 ft wide) room and pillar excavations in an oil shale mine. The program was undertaken to develop construction techniques and to generate data on structure costs and leakage rates. Leakage rates were measured using both sulfur hexafluoride tracer gas and "brattice window" methods at varying differential pressures. The measurements were conducted before and after a full-scale face blast to characterize the effects of blasting on leakage, and blast air pressures were measured across the stoppings. The operating performance of different combinations of permanent and temporary stoppings was evaluated by developing an operating model for a two-panel oil shale mine. The operating performance for the different stopping combinations was then compared to the system cost to evaluate the overall performance.

Jan 1, 1987

By J. Hanna, J. Jung

Researchers at The University of Alabama have recently developed a two-step method for the treatment of phosphorus sludge. The process includes the bulk removal of phosphorus by physical separation techniques followed by the remediation of the residual P4 in the sludge using a novel, wet, air-oxidation technique known as "HSAD." Tests made on electric furnace, phosphorus sludge samples have demonstrated that an essentially complete and fast removal of the contained P4 can be achieved by the HSAD wet oxidation treatment. Further studies were made to determine the applicability of the two-step process to sludges of different origins, pretreatments, storage conditions and P4 contents. The present work discusses the mechanisms and factors controlling the HSAD, wet, air-oxidation remediation approach.

Jan 1, 1993

By Michael G. Nelson, Sekhar Bhattacharyya

Between 1974 and 1977, a detailed study of coal pillar strength was conducted by the University of Utah at the Beehive mine in southeastern Utah. This study was funded by the U.S. Bureau of Mines, and included laboratory testing of coal samples, extensive field instrumentation and measurements, and finite element analyses based on the laboratory results. Recently, a similar analysis of the laboratory results and mine design geometry was completed using the LAMODEL program developed by NIOSH. The results of this analysis were close to the data collected in the field. This study allows comparison with the earlier finite-element analysis, and illustrates the utility of the LAMODEL software suite.

Jan 1, 2005

By E. Azrag, A. MacDonald

A hydrogeologic investigation was conducted to predict inflow to underground mine workings and mining-induced hydrologic impacts for a proposed underground mine beneath a lake in northern Canada. Flow and shut-in tests were conducted to determine hydraulic conductivity values and to estimate the hydraulic head. A conceptual hydrogeologic model was developed and incorporated into a numerical ground-water flow model (utilizing MINEDW, a three-dimensional, finite-element code with special attributes designed for mine dewatering). The mining sequence was represented in detail(e.g., driving ramps and drifts, extracting panels, and backfilling mined areas). Due to limited field data, a quantitative assessment of uncertainty was implemented to estimate limits of possible inflows.

Jan 1, 2003

By A. S. Mallicis, Li Xiawoei, P. W. Weiblen, I. Iwasakl

Platinum group metals (PGM) are often found in close association with arsenide and sulfarsenide minerals in copper-nickel bearing gabbroic rocks. Major losses of platinum in flotation have been attributed to the susceptibilities of the arsenic minerals to oxidation and subsequent losses of their recoveries in cleaner flotation stages. The use of a nitrogen atmosphere in grinding and in flotation, the effectiveness of activation for improving their floatabilities, and the role that electrochemical interactions play not only between grinding media and minerals, but also among different minerals, are discussed.

Jan 1, 1989

By W. E. L. Minter

The most important Witwatersrand gold placers occur on extensive unconformity paleosulfaces that were produced during protracted periods of fluvial degradation. The erosional etches on what was generally unlithified sub-strate indicate that low sinuosity erosion patterns prevailed. The transport systems were dominantly braided fluvial with a minor debris-flow component. The placer sediments were non-cohesive sands and gravels. They were evidently transported by fluctuating, yet perennial, discharges across extensive, low relief braid plains, not far from littoral environments. Progress made in understanding heavy mineral transport processes now emphasizes the importance that selective entrainment probably had in producing concentrations. Cognizance that these characteristics are not unique to the Witwatersrand should be taken into account when designing exploration models.

Jan 1, 1991

By Simon D. Handelsman

Technical co-operation activities of the Department of Technical Co-operation for Development of the United Nations Secretariat have included the introduction of electronic data processing techniques in mineral sector projects for several years; computers have been provided to countries in Africa, Asia and Latin America. Advisory services are provided to interested developing countries at their request concerning applications for various uses in mineral sector activities. They include advice on appropriate hardware and software depending upon the requirements of the particular Government. The Department's activities in this area are described. The input from a Group of Experts on this subject convened by the United Nations, and their conclusions and recommendations, are also discussed.

Jan 1, 1986

By Donald Leroux

For the last few years, the grinding model first proposed by Andrews and Mika (1975) has regained attention from the scientific community. Though sophisticated identification algorithms have been developed, the number of its parameters that have to be estimated remains huge. Most of these constants (often more than 90%) are for the breakage function. This paper describes a new method for reducing efficiently the number of the breakage function parameters of the Andrews-Mika grinding model. It makes use of second-order statistics and of a stereostochastic model for liberation (for instance, BooKing).

Jan 1, 1992

By Andrew M. Garvie, William W. Plotnikoff, Eugenia Y. Kuo

Water infiltrating the surface of waste rock dumps transports pollutants into the environment. Lysimeters have been used to quantify the infiltration rate. To date their design has been guided by modeling under steady-state conditions. Recently a two-dimensional finite element code has been developed to model the response of lysimeters to time-dependent infiltration rates. It was used to investigate the response of lysimeters installed in a waste rock dump and subject to a monsoonal rainfall pattern. The results are presented and compared with field data.

Jan 1, 2000

By D. Leppert

Large deposits of natural zeolites may provide cost-effective alternatives for treatment of soil and water contaminated ) with heavy metals and radionuclides. Research on the Bikini atoll demonstrated that addition of clinoptilolite to the soil significantly reduces cesium uptake by plants. Re- search on the potential use of zeolites in soils at Bunker Hill, ID indicated only minor benefits at very high contamination levels vs. US Bureau of Mines (USBM) work on the use of zeolites for treatment of mine waste waters emphasized problems with natural waters that previous studies have not addressed. High levels of competing calcium in natural waters significantly decrease the effectiveness of zeolites for heavy metal sorption and may limit the usefulness in these applications.

Jan 1, 1991

By W. Allen Dupree, Charles D. Campbell

A field investigation was conducted by the Ventilation Division, Pittsburgh Health Technology Center (PHTC), Mine Safety and Health Administration (MSHA) to evaluate the effectiveness of a blowing face ventilation system utilizing a water sprayfan system and a single inlet flooded bed dust collector (scrubber) in controlling methane liberation in the face area while mining at brattice distances up to 12.2 meters (40 feet) from the face. The rated capacity of the scrubber was 117 m3/s (4,145 cfm) of air. Results from the investigation indicated a methane dilution capacity of 0.57 m3/s (20 cfm) with the air quantity behind the line brattice averaging 138.7 m3/s (4,900 cfm).

Jan 1, 1991

By L. M. English

A basic model was developed to help assess methane control needs for the longwall mining of coal in gassy areas. Rather than depending on reservoir and rock mechanical theories, it uses an empirically determined gas emission rate as an input, and it operates on the assumption that, within a specific region and zone, gas emissions will be relatively equivalent for uniform incremental volumes of gob created by mining. The computer program divides longwall panels into segments, keeps track of the face advance and generates emission rates and volumes for both the entire panel and for individual zones within the panel by summing values for all undermined segments. This model can aid in the determina¬tion of the number, size and location of vertical wells or other methane-control applications that are needed for gob gas control.

Jan 1, 2000

By G. D. Trump, F. L. Stanley

Spirals have become one of the most popular methods for treating fine coal. Unfortunately, spirals tend to produce an undesirably high specific gravity cut point and often misplace significant amounts of coal and/or rock. In the present study, a process-engineering tool known as linear circuit analysis was used to identify problems with traditional spiral circuits and to suggest alternative configurations. These analyses indicate that a modified rougher-cleaner circuit incorporating a middlings recycle stream offers the best option for improving performance while maintaining a reasonable circulating load. In light of this finding, a full-scale test circuit was installed and evaluated at an existing preparation plant. Data obtained from the plant tests indicate that the new spiral circuit can simultaneously reduce the cut point and improve separation efficiency. Preliminary economic analysis show that the new circuit provides an attractive payback on capital investment.

Jan 1, 1999

By Arpad E. Torma

The electrochemical behavior of a zinc sulfide concentrate during the microbiological leaching was investigated using ZnS-carbon paste electrodes and a cyclic voltametric technique. The effects of Zn2 [ ] , Fe2+, Fe3+ and Cu2+ on the cathodic and anodic currents associated with zinc sulfide leaching in presence and absence of microorganisms, were assessed. The semiconductor nature of zinc sulfide was discussed in terms of ability of microorganisms to obtain their metabolic energy (through removal of electrons) from this high energy gap substrate. The intermediate electrochemical reactions involved in the ZnS leaching were described.

Jan 1, 1989

By J. A. Nelen, R. B. Cook

Panned stream-sediment, geochemistry-based gold exploration in those parts of the southeastern Piedmont proximal to the Fall Line must take into account potential contamination from basal fluvial sediments of the Coastal Plain. Anomalies attributable to the incorporation of placer gold of Coastal Plain origin into modern Piedmont drainages have been identified in portions of Lee, Macon, and Tallapoosa Counties, AL, and Baldwin and Hancock Counties, GA. Identification and interpretation of such multicyclic anomalies must be based on knowledge of the local maximum Cretaceous transgression, paleotopography, modern and paleofluvial system dynamics, and fineness trends and Au-Ag zoning in gold grains.

Jan 1, 1990

By R. C. Ford

The advent of solvent extraction-electrowinning (SX-EW) technology for recovery of copper from low grade oxide ores has extended the operational lives of many historic mines in the western United States, and made many other orebodies economically viable worldwide. Many of these operations are mature and face closure within the next decade, depending on market conditions. Closure of a large copper heap leach operation has not been undertaken, and differs in some important chemical respects from closure of gold leach pads. Challenges for closure include prediction of solution chemistry and draindown characteristics, determining the benefit of cover placement in semi-arid climates and evaluation of solution management strategies once the economics of copper recovery are no longer favorable. This paper discusses issues pertinent to copper heap closure in semi-arid and arid climates, and strategies for their management.

Jan 1, 2000

By M. Niinae, Y. Nakahiro, T. Wakamatsu

In some cases, the extraction and separation efficiency of metals with a combined extractant are better than those with either extractant alone. However, the extraction and separation efficiency of metals with a combined extractant are not always better than those with either extractant alone. As part of the fundamental studies on the extraction and separation of metals with combined extractants, the extraction and separation efficiency of Au and Fe(III) added as an oxidizer in the leaching of Au from a sulphuric acid solution containing thiourea, and the extraction and separation efficiency of Nd and Sm from hydrochloric acid and sulphuric acid solutions were examined. The combined extractants for Au and Fe(III) were di(2-ethylhexyl) phosphosphoric acid (D2EHPA)/tri-n-butyl phosphate (TBP), D2EHPA/trioctyl phosphine oxide (TOPO). tri-n-octylamine (TOA)/TBP and TOA/TOPO, and those for Nd and Sm were D2EHPA/TOA. D2EHPA/TOPO. 2-ethylhexylphosphonic acid mono-2-ethylhexyl ester (EHPNA)/TOA and EHPNA/TOPO

Jan 1, 1994

By Thomas F. Pedersen, J. Jay McNee, Alan J. Martin

Field sampling was conducted in Lake Junin, Peru in order to assess the post-depositional reactivity of the highly contaminated lake sediments. High resolution profiles of dissolved Fe, Mn, SO42- and H2S across the sediment-water interface illustrate that the organic-rich sediments in the main basin become anoxic within several millimetres of the sediment-water interface. These permanently submerged deposits in the main basin serve as a diffusive sink for dissolved Zn and Cu. Conversely, the periodically unsaturated deposits in shallow areas are characterized by the remobilization of Zn and Cu in the deep acidic (pH < 4) pore waters, resulting in the release of these metals to the overlying water column.

Jan 1, 2000

By Natesa Jayaraman, Jon C. Volkwein, Edward D. Thimons

The Bureau of Mines has studied the impact of shuttle car movement on face ventilation. Real-time measurements of air velocity, methane gas, and respirable dust were recorded and compared with a time study of face shuttle car movement. Work was conducted in a blowing face ventilation section where a scrubber-equipped mining machine operated. Air velocities decreased by an average of 35% as the shuttle car entered the face, restricting air flow, and increased by an average of 35% as the shuttle car pulled away from the face, drawing with it additional air. Return air methane levels follow the face air flow volumes, decreasing as air volume increases. The surge of air created as the shuttle car leaves the face helps to dilute methane. Respirable dust levels, however, were found to increase as the air flow increased and decreased the scrubber capture efficiency.

Jan 1, 1989