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By Jue Kou, Lei Yu, Bern Klein, Lusheng Zhou, Chunbao Sun, Genzhuang Li, Reem Roufail, Amit Kumar

Magnetic liners can improve the performance of ball mills by increasing grinding efficiency, extending service life, and reducing maintenance costs. Despite their importance, the fundamental understanding and the quantitative investigation on the effects of the magnetic liners has not been addressed in the literature. This paper addresses this gap by studying charge motion, and how the use of a magnetic liner affects the breakage mechanism of the mill, using discrete element method (DEM) modeling and the Hertz-Mindlin contact model with relative velocity dependent (RVD) rolling friction. Charge motion was modeled under different mill speeds. Compared to conventional steel and rubber liners, the charge motion in the magnetic liner mill was predominantly cascading. Quantitative analysis of the energy dissipation within the mill was conducted to investigate mill breakage. Regardless of speed, over 50% of the total energy dissipation in the magnetic liner mill was in the form of abrasion and attrition. The results highlighted the appeal of magnetic liners in secondary and regrinding application, where abrasion and attrition are considered more efficient in the fine material breakage, and where impact is ideally minimized to reduce mill wear. A number of experiments were conducted to assess the effect of different model parameters on the performance of the magnetic liner mill. The highest abrasion/attrition intensity was observed with high values of the model parameters namely the restitution coefficient, static friction coefficient, and rolling friction coefficient.

Jun 12, 2019

By Jue Kou, Lei Yu, Bern Klein, Lusheng Zhou, Chunbao Sun, Genzhuang Li, Reem Roufail, Amit Kumar

Magnetic liners can improve the performance of ball mills by increasing grinding efficiency, extending service life, and reducing maintenance costs. Despite their importance, the fundamental understanding and the quantitative investigation on the effects of the magnetic liners has not been addressed in the literature. This paper addresses this gap by studying charge motion, and how the use of a magnetic liner affects the breakage mechanism of the mill, using discrete element method (DEM) modeling and the Hertz-Mindlin contact model with relative velocity dependent (RVD) rolling friction. Charge motion was modeled under different mill speeds. Compared to conventional steel and rubber liners, the charge motion in the magnetic liner mill was predominantly cascading. Quantitative analysis of the energy dissipation within the mill was conducted to investigate mill breakage. Regardless of speed, over 50% of the total energy dissipation in the magnetic liner mill was in the form of abrasion and attrition. The results highlighted the appeal of magnetic liners in secondary and regrinding application, where abrasion and attrition are considered more efficient in the fine material breakage, and where impact is ideally minimized to reduce mill wear. A number of experiments were conducted to assess the effect of different model parameters on the performance of the magnetic liner mill. The highest abrasion/attrition intensity was observed with high values of the model parameters namely the restitution coefficient, static friction coefficient, and rolling friction coefficient.

By Axel Preusse

Underground coal mining can cause seismic events. There is currently no way to predict such phenomena reliably, in particular stronger events. That is why, according to the current state of the art, empirical methods are employed in this field. Some assessment criteria, which relate to the geological and mining situation and either stimulate or rather help to avoid seismic events, are presented in this paper. These criteria are examined for a practical mining situation in Germany, with a view to estimate possible seismic events.

Jan 1, 2009

By S Speed, N Corlis, A Goldstone, G N. Browne, M Fitzpatrick

In 2005, Solid Energy New Zealand Limited obtained non-notified consent for the disposal of 1Mt of coal ash at the Rotowaro minesite, forming part of a coal supply agreement with the Huntly Power Station. A non-notified resource consent was sought which necessitated that environmental effects be shown to be æless than minorÆ, and resulted from robust science and a pragmatic approach to design. As part of the assessment of environmental effects, there was a need to understand the effects of boron concentrations on aquatic organisms (ie algae, plankton, plants and invertebrates) in the receiving environment. Boron is a naturally occurring element that is found in the form of borates in the oceans, sedimentary rocks, coal, shale, and in some soils but Waikato coals and ashes have particularly high boron content. Boron is an essential micronutrient for higher plants with interspecies differences in the levels required for optimum growth. As aspects of the ANZECC (2000) derived boron limits are based on toxicity of aquatic algae and plants to boron it was important to assess these components in the environment. The effects on the receiving environment of the Awaroa Stream were assessed using predicted water chemistry and comparing actual boron concentrations in a comprehensive and multifaceted reference-condition approach of catchment ecological indicators. In addition a toxicological-based assessment of boron and a re-calculation of the ANZECC trigger levels were undertaken and applied to the ecological indicators. The reference-condition approach revealed that habitat and overall water quality attributes at and between sites was more influential in determining the aquatic biotic communities than boron concentrations alone. There was no evidence of any gradient of changes in ecological indicators with changing boron concentrations, nor evidence of any residual effect of high historic boron concentrations on the aquatic biota.

Jan 1, 2006

By X. L. Huang

This paper deals with the experimental and theoretic study of the contact pressure beneath the deep foundation of Beijing International Hotel, The experiments have been carried out in project and in model footing 6.6m2. The result of measurements shows the contact pressure at the edge is greater than that at the center. The theoretic analysis on the base of elastic theorey is in good agreement with the test if the proposed assumption used.

Jan 1, 2010

By Edwin E. Maust

In response to the ever- increasing demand for high temperature materials, the Bureau of Mines instituted a program for the study and development of superrefractories, One of the major tools obtained for use in this research was an image furnace of the double-paraboloidal mirror type. Although extensive theoretical analyses of solar furnace performance may be found in the literature, comparable detailed information on the double-paraboloidal-mirror image furnace has been nonexistent. This report presents an analysis based on an investigation undertaken to ascertain the limitations and characteristics of the furnace so that it can be used most effectively. The quantitative determination of the energy available at the image, the control of this energy by mans of a 60-inch iris diaphragm, and its variation with position and time relative to the heat source used have all been dealt with in detail. The quantitative results were obtained using a specially designed waterflow calorimeter and these measurements, in conjunction with the theoretical analysis, are used to present a fairly complete description of the furnace and its capabilities.

Jan 1, 1962

By R F. G Phelps, C J. S Sangster, G S. C

Narrow vein metalliferous mining in the UK has a long history, but there are only two small gold operations at present (Clogau and Gwynfynydd). Four further gold properties are at various stages of evaluation (Calliachar, Cononish, Curraghinalt and Maestryfer). The South Crofty tin mine closed earlier in the year. Narrow veins are exploited underground and are challenging to evaluate because of their geologically variable nature. They are generally less than 3 m wide, discordant, of variable dip (

Jan 1, 1998

By Z. Xiao, A. R. Laplante

"The recovery of gold by gravity from grinding circuits differs from virtually all other gravity recovery approaches in that stage (or unit) recoveries are low, typically 1 to 5%, but overall recoveries are generally in the 25 to 60% range, because individual gold particles are presented many times to the primary recovery unit. Full-scale recovery is difficult to predict from benchscale tests. Further, maximizing metallurgical recovery is generally not the primary objective, because of the more efficient downstream recovery circuit (flotation or cyanidation). In this paper, a new concept, the gravity recovery effort, is presented to assist in the design and optimization of gold gravity circuits. It is defined as the product of the circulating load treated by the primary gravity unit, the recovery of this unit, and the gold room recovery. Predicted gold recovery is linked to the recovery effort, the size distribution of gravity recoverable gold (GRG), the dimensionless retention time in the mill and the partition curve of GRG. A case study of economic optimization of the gravity recovery effort is presented. INTRODUCTIONPredicting gold gravity recovery from grinding circuits has always been a hit-and-miss exercise. The problem can be traced to the highly variable gravity recoverable gold (GRG) content of ores, high GRG circulating load, fraction of the circulating load treated, and performance of primary gravity recovery and gold room. Typical values, highs and lows are shown in Table 1."

Jan 1, 2001

The presence of gold or tin in a particular place in payable quantities may be suspected from geological and prospE;cting reports. It behoves the engineer by judiciously spaced boreholes or pits to establish whether the place is exploitable with profit, and it is the purpose of this paper to set out the ways in which this is done. The various types of deposit to be considered occur in Malaya, Thafland and Borneo, in which countries the writer spent four years in estimating alluvials.The methods described were used in actual practice both by the writer and previous engineers for the same company. The subsequent exploitation of the alluvials evaluated by the methods given below shows that the recovery was as good as, and sometimes higher than, expected. No claims are made to the originality of the methods, but it is 'felt that they may be new to some engineers and< interesting to others contemplating alluvial testing.

Jan 1, 1942

By R. E. Mclvor

This is an update of an original dissertation on this topic by Lavallee, McIvor and Stolovitch (1992). A step-by-step, technical procedure used to measure and improve the performance of plant grinding circuits was adapted into a training program. ?Systematic Design of Instruction? was applied to: ? Determine if training was a suitable way to deliver this new technology; ? Define the technical content of the program; ? Select program specifications based on learner and context characteristics; ? Design, create and test prototypes of the training modules; and, ? Establish a process for plant implementation. The training program covers numerous skills that are extremely valuable for plant personnel, not only in the grinding area, but also for many other parts of the plant. This paper describes how new skills are brought into the workplace through designed instruction can be an effective alternative to hiring during severe skilled labor shortages.

Jan 1, 2008

By J. A. L. Napier

It has been established that significant time-dependent stope convergence may occur over time periods of hours and days in certain hard-rock gold and platinum mines. The source of this time-dependent behaviour appears to be associated with both pre-existing discontinuities and with mining-induced fractures that form near the stope face. These induced fractures may be associated with blasting processes and may also be formed in response to high stress concentrations in the unmined regions immediately ahead of the stope face. In shallower platinum mining operations, time-dependent behaviour is, however, observed to be much less marked unless some form of specific mining-induced fracturing occurs. One particular case of considerable interest is the time-dependent behaviour that is found to be associated with the formation and deployment of crush pillars. The purpose of the paper is to present a simple limit-equilibrium computational model of this behaviour that is sensitive to both the formation sequence and the size of planned crush pillars in a mine layout. This model provides a useful means to optimize the sizing of crush pillars, and at the same time may be used to identify potentially hazardous circumstances in which pillars may not crush in a stable manner.

Jan 1, 2012

By Craig C. Johnson

The purpose of this effort was to investigate the feasibility of employing a piezoelectric transducer for seismic communications applications in mine environments. The transducer, a government furnished device incorporated a high Q, spring-mass resonator to load the air side of the piezoelectric crystal. The resonant frequency was seismic load dependent and fell in the range of 300 to 340 Hz. The effort included a mathematical analysis of the transducer, with corroborative laboratory tests, together with actual communications experiments performed first in an open-formation limestone quarry and finally in an operating iron mine. This work showed that the transducer could be coupled efficiently to hard, competent rock media with power conversion efficiencies of 70 to 80 percent (electrical to mechanical) in typical installations. In the iron mine, when radiating peak power was about 30 W (acoustical) in a gated pulse mode, signals were received at a distance of 760 ft through a massive rhyolite porphyry formation. This represents a 15% radiation efficiency with an input of 200 watts. Despite the high ambient noise level due to operating mine machinery, a signal-to-noise ratio of about 20 dB was achieved using a very narrow band filter to process the received signal, and a data rate of about two pulses/sec was demonstrated.

Jan 1, 1972

By Chris Mark

Successful longwall mining requires a stable tailgate entry. Gate entry performance is influenced by a number of geotechnical and design factors, including: - Pillar size and pillar loading; - Roof quality; - Floor quality; - Entry width; and, - Artificial support (primary and secondary). This paper describes a comprehensive, practical, design methodology, based on statistical analysis of a nationwide data base of longwall ground control experience. Geotechnical surveys were conducted at 44 U.S. longwall mines, and underground observations of site geology, entry conditions, and support design were recorded at each mine. The observations were combined with discussions with mine personnel to identify 69 longwall gate entry designs as satisfactory, unsatisfactory, or borderline. Only conventional longwall designs, in which the pillars are expected to carry the full abutment loads, were included in the data base. Designs which employed yield pillars only were excluded. The case histories were characterized using five descriptive parameters. Pillar design was described by the Analysis of Longwall Pillar Stability Factor (ALPS SF). A major new contribution is the Coal Mine Roof Rating (CMRR), a rock mass classification system that quantifies the structural competence of bolted mine roof. Other quantitative measures were developed for primary support, secondary support, and entry width. Multivariate statistical analyses indicated that in 84% of the case histories the tailgate performance could be correctly predicted using just ALPS and the CMRR. Most of the misclassified cases fell within a very narrow borderline region. The analyses also confirmed that primary support and gate entry width are essential elements in successful gate entry design. The relative importance of the floor and of secondary support could not be determined from the data. Based on these results, a simple equation was developed to guide the design of longwall pillars and gate entries: ALPS SF,, = 1.76 - 0.014 CMRR Where: ALPS SF, = ALPS SF suggested for design. Guidelines for entry width and primary support density, as related to the CMRR, are also provided.

Jan 1, 1993

By Sherwin F. Kelly

One of the most succinct and illuminating perspectives of the field of geophysical exploration to appear in recent years is an article by E. A. Eckhardt, in the magazine Geophysics for October 1949. Although his review covers the year 1948, many of the data presented are apropos to a review of 1949, and form a pertinent background for a consideration of current progress. He presents charts of the world-wide distribution of gravimeter and seismograph activity in oil exploration, which show that surveys in the United States accounted for practically 68%; of all gravity work and 80%; of all seismic activity. Canada ranked second, with a proportion of roughly 6%, in each case; South America accounted for about the same percentage of seismic work, and double that amount for gravity surveys. Within the United States, Texas and Louisiana were the scenes of the greatest activity, both claiming about 60% of all surveys by each method.

Jan 1, 1950

By A. J. Terrones

THE classical papers on contact metasomatic deposits by Lindgren on the Clifton-Morenci district,' by Barrell on Marysville, Mont.,' and by Gold-schmitt on the Oslo district, Norway,' laid the foundation for understanding of the importance of separating the metamorphic process from the subsequent metasomatic stage. Knopf' made a big step forward by recognizing that sulfide ore minerals are invariably younger than silicates and by further stressing the importance of structural control" in ore finding. Some years later Harrison Schmitt" fought the idea that contact metasomatic deposits are erratic, irregular, bunchy, economically marginal, and of small size, concluding that these descriptions have little factual basis. He emphasized the importance of detail mapping and careful geological study as fundamental requirements for a better understanding of these deposits. This article presents a comparative description of the structural features at the Magistral, Antamina, Morococha, Vilca, Ferrobamba, Katanga (Quibio), Tintaya, and Huarca contact deposits (Fig. 1). Further, it will describe how these structural features controlled the emplacement of the intrusives, their shape, distribution of metamorphic and metasomatic halos, and sulfide deposition in post-skarn structural channelways. Finally, the modifications introduced by a superimposed hydrothermal stage recognized at some localities will be discussed. Primary exploration and careful sampling of recognized structural targets were instrumental in outlining the copper ore potential at the Antamina and Tintaya districts, thus proving the benefits and reward of careful geological examinations in this type of deposit. The Magistral District: This district lies in the Province of Pallasca, Department of Ancash, in northern Peru, at 8o 16' S and 77" 47' W. High to medium grade copper orebodies in garnetite, bordering a quartz monzonite stock, are exposed at the bottom of a glaciated valley in the western slope of the Andes at 4250 m (14,000 ft)* elevation.

Jan 1, 1959

By E. R. Spencer, D. R. Babich, L. A. Alcorn, A. K. Smith

Noise is one of the most pervasive health hazards in mining. A compilation of Mine Safety and Health Administration (MSHA) noise survey data for fiscal year 1990 shows that approximately 40% of the total samples taken for longwall occupations exceeded the Permissible Exposure Limit (PEL) of 100% (Gigliotti et al., 1991). To effectively determine worker noise exposures on longwall coal mining systems, it is necessary to provide accurate baseline measurements for these mining systems. This research was designed to develop measurement methods and test procedures for identifying noise sources that are major contributors to the underground noise exposure of longwall coal mining system workers. The measurement system that was used to analyze the noise sources around a stageloader used stationary dosimeters in a documented repeatable pattern to record the sound pressure and dose levels. A time-motion study of the cutting cycle and stageloader operator’s work cycle was done to correlate the sound levels at measurement locations and the resulting operator’s daily dose with significant noise events. Results from the underground measurements show that the highest sound levels recorded were at the stageloader discharge segment and tailpiece controls, where sound levels remained about the same throughout the test.

By R. W. Stahl

An emergency is defined as an unforeseen combination of circumstances that calls for immediate action. When applied to a coal mine, an emergency may call for prompt removal of the men to the surface through travelways other than the haulageway or intake airways, which are generally contaminated with irrespirable air as a result of an explosion or fire. Therefore, maintenance of adequate and travelable escapeways from all working areas of a mine is vitally important insurance against disaster. Several mine disasters could have been avoided if well-defined escape routes had been provided and made known to all mine employees. Such occurrences, unnecessary as they generally are, unfairly indict the industry when only a small segment thereof is involved. As a result of a rather recent disaster, which might not have happened if good escape routes had been provided, the Bureau of Mines decided to delve into the escape procedure to determine (1) what is being done in the industry and (2) what might be done at reasonable cost.

Jan 1, 1962

For years traditional optical microscopic techniques have been used successfully to carry out mineralogical studies on processing products. Essential information could be obtained by supplementing microscopic data with X-ray powder diffraction data, chemical analyses, etc. However, most of the time the mineralogists working on plant related issues, would supply qualitative information to the metallurgists, due to quantification not being possible in the available time. Since the late-80s, the use of semi-automated to automated techniques for mineral quantification has impacted positively on the use of mineralogy for optimising processing plants. Rustenburg Platinum Mines (now Anglo Platinum) were the first mining company to purchase a Qem*Sem in 1987. With the success achieved in quantifying the minerals in the concentrator streams of the Rustenburg Platinum operations, a second instrument was purchased soon after. These instruments have proven invaluable tools in understanding the flotation behaviour of the sulfide and gangue minerals in the various reefs of the Bushveld. Restrictions in the resolution of these earlier instruments, as well as the time involved in searching for and correctly identifying the fine-grained platinum-group minerals (PGM), meant that these investigations focused on the deportment of the more abundant base metal sulfides, rather than on the actual PGM. The Mineral Liberation Analyser (MLA), which became available in the late 1990s, was well suited to detect and analyse minerals occurring in trace amounts such as the PGM. Anglo Platinum was the first mining company to purchase such an instrument and now has fourteen systems operating at the AR Crown Mines site. One of the applications of these systems involves the study of feeds, concentrates and tailings from the various concentrators on a monthly basis. These routine investigations provide information on a variety of mineralogical parameters, including liberation, association, and grain size. Results are used to emphasise areas for improvement, and specifically underline those areas where improvements will have the most impact on recovery. After new or different technologies have been implemented, mineralogical characterisation of the different process streams is an essential component in the assessment of the impact of these changes on flotation performance. In addition, the knowledge is databased for future reference to draw trends across the various concentrators around the Bushveld complex, and is also used for comparative studies when plants experience high losses to tailings. Due to the success of these investigations the question was posed whether it was possible to obtain data on a daily basis, as compositing samples could hide the impact of daily events. Although the instruments currently used are suitable for a research environment, these are not ideal for mine-site implementation. For that reason Anglo Platinum, together with FEI embarked on a development program to develop a system that can be implemented on-site to measure the important mineralogical characteristics on a daily basis. Important requirements for such a system include time-to-data, ease of use and regular quality control. Highlighting some results from concentrator studies, the presentation will review the progress on the development of automated mineralogical techniques for fast, automated mineral measurements. This is an abstract only. No full paper was prepared for this abstract.

Sep 13, 2010

A pilot steel ladle injection facility designed to assist in the production of high quality steels suitable for use in pipelines has been built and commissioned at the Basic Oxygen Steelmaking (BOS) plant at Port Kembla Works.The plant design and the injection procedure are described.The performance of the unit and some metallurgical results are discussed in terms of the addition to the steel ladle of various quantities of calcium silicide and a lime based material. The effects of these additions on sulphur content and inclusion morphology and hence on steel ductility are also presented. The influence of ladle lining on desulphurisation is illustrated.On the basis of the experience gathered in the pilot plant a permanent and more sophisticated injection facility has been designed.

Jan 1, 1983

By W. W. Agey

The Bureau of Mines examined and tested the rhodonite deposits of the Silverton lead-zinc district, San Juan County, Colo., as a possible source of domestic manganese. Exploration and development work by several mining companies and preliminary reconnaissance of the area by Bureau of Mines engineers indicated the presence of extensive manganese resources in the form of rhodonite. This report summarizes the results of laboratory beneficiation tests made on samples of different type and grade material obtained from surface and underground exposures of seven veins in the district. Surface and underground examinations revealed the presence of several prominent veins that could be traced up to 2 miles for a single vein along the surface. The principal veins average about 50 feet in width and apparently carry rhodonite to considerable depth. Underground samples were taken from the Sunnyside, Silver Queen, Washington, Independence, and Scotia veins. Samples also were taken from surface exposures of the Sunnyside Extension and Hidden Treasure veins.

Jan 1, 1962