Search Documents

It is widely accepted that particles stabilise flotation froths and that stable froths result in improved flotation performance. Predicting the effect of particle addition on froth stability is, however, challenging. Dynamic surface tension measurement using maximum bubble pressure presents an attractive technique to investigate the effect of surfactant and particles at the air-water interface. The range of bubble lifetimes that can be studied (typically 0.1 to 60 s) is analogous to variations in air rate in flotation cells, and the corresponding changes in surface tension give an indication to the diffusion and adsorption rates of particles at the interface. In this paper, we use dynamic surface tension measurements to investigate the effect of particles on bubble surfaces at the microscale and link this to bulk froth stability measurements carried out using a froth column. Using the maximum bubble pressure method, the results show that the addition of particles results in lower surface tension, both at the dynamic (i.e. short) bubble lifetimes and towards equilibrium (i.e. 60 s bubble lifetime). This corresponds with the bulk froth stability measurements, where the three-phase system yielded more stable froths than the surfactant only system. Furthermore, increased particle loading at the air-water interface, whether through higher surfactant concentrations or lower air rates (longer bubble lifetimes), gave lower surface tension and higher froth stability. This demonstrates the link between bubble loading and froth stability. It is proposed that the maximum bubble pressure technique can be used to predict froth stability for two- and three-phase systems, enabling the effect of particle loading to be accounted for and quantified. Moreover, the technique has the potential to allow rapid determination of particle and surfactant diffusion at the air-water interface and prediction of the corresponding effect on bulk froth behaviour.

By J. Wickens

Haile Gold Mine is located near Kershaw, South Carolina, approximately 50 miles south of Charlotte, North Carolina. Gold was first discovered at the site in 1827, and the property has been through several operating periods since. The relatively low grade and refractory nature of the deposit has been a challenge for efficient processing since the start of mining on the property. Early processing techniques included gravity separation and barrel chlorination. The last operation employed heap leaching in 1985 through 1992. After being closed and reclaimed for over 20 years, the property is poised to re-open and produce once again. In this chapter of the Mine?s legacy, flotation and ultra-fine grinding will be employed to achieve economic extraction of gold and silver from the pyrite. This paper briefly reviews some of the mine?s history, the metallurgical testing, the flowsheet and discusses design considerations. KEY WORDS: process plant, flash flotation, leaching, SMD, stirred media detritor

Feb 27, 2013

By John F. Gamble

Paper 1?South African experience with asbestos-related environmental mesothelioma: Is fiber type important? Neil White, Gill Nelson, Jill Murray The purpose of this review was to illustrate the importance of the type of asbestos in environmental mesothelioma. South Africa is a logical place to assess fiber type. The three major types of asbestos (crocidolite, amosite and chrysotile) were mined (all asbestos mining stopped in 2002) in South Africa. The association between asbestos and mesothelioma was discovered in South Africa. The occupational literature indicates high mesotheliomagenic potential for crocidolite, less for amosite and less still for chrysotile. Since South Africa has been a major source of crocidolite, relatively high rates of mesothelioma in the mining population is not surprising. High rates of mesothelioma due to environmental exposure is surprising, except perhaps when the authors? point out potential sources for community exposures (e.g., mine tailings used for road surfacing, golf courses, brick and plaster making; insulation in residential ceilings; children playing on fiber-rich waste rock). The authors? reviewed four studies reporting on mesothelioma cases and their sources of exposure and fiber type. Overall 23% of the known cases were attributed to the environmental (not occupational) exposure and about 90% were due to crocidolite asbestos. The proportion of environmental mesothelioma is considerably higher than in Western Australia where crocidolite is also mined. There the overall rate of environmental mesothelioma is about 6% (and less than 1% from residence in a crocidolite mining area).

Jan 1, 2007

By Morteza Gharouni Nik

Flexible Dilatometer Test (FDT) is one of the in-situ test methods for determining the deformational characteristics of rock masses. In this study, several dilatometer tests have been conducted in different geotechnical phases of site investigations by means of two types of FDTs. The purpose of this paper is comparison of the performance of these two types of dilatometers and analysis of the differences in the results of the tests.

Jan 1, 2008

By Anthony B. Szwilski, Dalip Sarin, Richard D. Begley

This paper will present the results of an analysis of several abandoned coal mine projects and includes field data for over a dozen different reclamation projects recently completed in the state of West Virginia. The analysis was performed with the objective of summarizing and or classification of the environmental consequences with reference to the characteristics of the mining facilities (surface, underground, etc.). The analysis also addressed the itemized cost of remediation with respect to procedures, environmental concerns and time. The results of the analysis are that each abandoned coal mine site in West Virginia have/had many unique features and in most cases include a combination of environmental concerns that complicate comparisons. The study also revealed that the abandoned mine land program for mines abandoned prior to 1977, that is being financed by a tax on the production of coal, has produced many benefits for the state of West Virginia. This grant program administered by the Office of Surface Mining, has resulted in a high quality methodology of remediation that has been successful for many years in greatly minimizing and/or eliminating environmental concerns from abandoned coal mines.

Feb 24, 1997

By Peter B. Dowden, Robert A. Robinson

Boulders, frequently found in tunnels excavated through soils, can pose major problems for full face TBMs in terms of slowing or halting the tunnel advance, cutter damage, and abrasive wear. The paper aims to consider the problem as a whole, from the geological characteristics of boulder sites, to the appropriate physical design of theTBM, and its operation in boulder-laden soils. In addition, visualization of boulders and other subsurface obstructions by seismic methods and ground penetrating radar are reviewed. The paper will assist the construction planner in assessing the risks and preparing appropriate specifications.

Jan 1, 2001

By B. A. Hillman

Silicon is the second most abundant element on earth, exceeded only by oxygen. Silicon dioxide forms a crystalline structure of repeating SiO2 molecules which form characteristically hard, durable crystals. As a result, crystalline silica is Ubiquitous in the crustal rocks, sediments and the mineral products derived from mining. An examination of the history of studies that identify silica as a human and animal carcinogen is presented in the context of the development of a public health policy in California. The implications for the cost of conducting aggregate and other mining operations in the state are discussed.

Jan 1, 1992

By Brooke T. Mossman

Asbestos fibers are highly fibrous silicate fibers that are distinguished by having a large aspect (length to diameter) ratio and are crystallized in an asbestiform habit that causes them to separate into very thin fibers or fibrils. These fibers are distinct from nonasbestiform cleavage fragments and may appear as thick, short fibers which break along cleavage planes without the high strength and flexibility of asbestiform fibers. Since cleavage fragments of respirable dimensions have generally proven nonpathogenic in animal studies, little data exists on assessing well-characterized preparations of cleavage fragments in in vitro models. The available studies show that cleavage fragments are less bioreactive and cytotoxic than asbestiform fibers. © 2007 Elsevier Inc. All rights reserved. Keywords: Asbestiform; Cleavage; Fibers; Fibrous

Jan 1, 2007

By Steve Kral

Improved metals and other commodity prices have caused the mining industry to open new mines, re-evaluate development opportunities at potential mines and increase production at existing ones. This sense of renewed optimism is being seen at operations and development projects around the world. Except in the United States. The regulatory structure there has not allowed the domestic industry to share much in mining’s resurgence. It can still take up to 10 years to permit a new mine. And, while Clinton-era regulations regarding mill sites have been put on hold, existing mines that wish to expand operations still face significant regulatory and environmental hurdles. But things may begin to improve in the United States.

Jan 1, 2005

By Derrick Chambers, George Kevin Chapin, M. Shawn Boltz

Seismic monitoring is one of the few noninvasive technologies with the potential to provide sub-surface geomechanical information to operators of large open-pit mines. Although passive seismic data has been used to refine emerging failure geometries and provide advance indication of surface deformations in the literature, doing so reliably in an operational context is much more difficult. This is due in part to difficulties in estimating and interpreting source locations and parameters in complex, low-stress open-pit environments. Additionally, the high costs associated with implementing, operating, and maintaining deep borehole seismic networks, which are most commonly used to monitor large open pits, can be difficult to justify, especially if monitoring benefits are not readily apparent. In this study, we explore the use of a near-surface nodal seismic deployment, which is commonly used in oil and gas exploration, for monitoring open-pit mining-related seismicity on a short-term basis. A deployment of 18 geophones was conducted on the surface in and around the Bingham Canyon Mine, a large open-pit mine near Salt Lake City, Utah, USA, where we find the small seismic array can detect and locate a variety of mining-related seismic sources, even with an extremely simplified velocity model. We outline the process of creating an idealized velocity model, developing a local magnitude scale, and interpreting the observed seismicity. Of note, we analyze a sequence of mining-induced events associated with a known structure on the south pit wall. We conclude with discussion on how surface-based deployments may be used to augment, or in some cases supplant, borehole seismic networks at large open-pit mines depending on monitoring requirements and objectives.

Apr 26, 2022

By Cathleen J. Webb, Arden D. Davis

The Homestake Gold Mine at Lead, South Dakota, has been proposed as the host site for the Deep Underground Science and Engineering Laboratory. The laboratory will house neutrino experiments in mine workings at the 7400-foot depth, as well as research in geomicrobiology, rock mechanics, and ground-water flow. Initial plans for the laboratory were developed in 2000 after Homestake Mining Company announced the closing of the underground gold mine. Homestake’s owner, Barrick Gold Corporation, had agreed to donate the mine for a laboratory if it could be protected from environmental liability. That initial agreement was delayed, and Barrick turned off the mine’s pumps in 2003, allowing lower levels of workings to begin to flood with water. In early 2004, the Governor of South Dakota signed an agreement with Barrick that would indemnify the company and eventually transfer ownership of the mine to a state laboratory authority. South Dakota’s governor also announced plans to ask the state legislature for funds to help in the initial construction of the laboratory. A consortium of scientists from several states is currently preparing a detailed laboratory proposal for the National Science Foundation.

Jan 1, 2005

By G. Budge

In the extractive industry the term ‘continuous improvement’ (CI) usually means procurement of the latest state of the art equipment. This is generally perceived as the only way to add further value to the supply chain, with the driving philosophy of increased tonnage to dilute operational costs. However, not all market places can facilitate this approach. RJB lives in a fiercely competitive market and has targeted the standard efficiency drivers of rationalisation and stock management with a vengeance; and also operate CMMS (Computer Maintenance Management System), RCM (Routine Condition Monitoring)and CBM (Condition Based Maintenance) methodologies. Ultimately though, these systems are only as good as the people who operate and manage them and to add further value without procurement, people must be re-introduced back into the operation. Through TPM (Total Productive Mining), that is what RJB have set out to do.

Jan 1, 2001

By Jorge Ferrero, Andreas Raedle, Uhland Konrad, Michael Dutton, Keivan Pak Iman, Walter Trisi

Strabag, in partnership with Arup, is constructing the Advance Tunnel for the Scarborough Subway Extension (ATSSE); a project by Metrolinx and Infrastructure Ontario (Sponsors). The 10.7 m internal diameter single bore tunnel represents a significant departure from the traditional arrangement of twin subway tunnels in North America. ATSSE is the first-time steel fibers are used to solely reinforce a tunnel of this size in Eastern Canada. This paper discusses the challenges with design and acceptance of SFRC segments and the state-of-the-art numerical models employed to check the joint performance. The advance procurement approach for TBM and PCTL’s procurement to accelerate the project schedule is also presented.

Jun 13, 2023

By S. K. Singh, P. R. Sheorey

To meet increasing demand of coal, underground mining is largely being replaced by the exploitation at deeper horizons and with greater complexities. The exploitation-proposition may be below not-to-be-disturbed surface properties or below water-bodies, posing a constant threat of inundation. Also, the mounting pressures to limit the adverse impacts on the environment bring the extraction-undertaking to face more challenges. An understanding of subsidence-mechanism and a rational quantification of subsidence parameters is a requisite herein. This paper presents such pragmatic quantification, validated at mine-sites in India. In comparison, better productivity, conservation and safety is ensured in this approach.

Jan 1, 1999

By L. Yuan, J. H. Rowland, D. Bahrami, R. Thomas

Blasting is the main method of production in many non-coal underground mining operations and produces multiple toxic gases as a result. The Mine Safety and Health Administration (MSHA) requires mine operators to measure the level of toxic gases in mines as frequently as necessary to ensure they are below regulatory safety limits. The current practice uses portable gas monitors to check the concentrations of toxic gases after a fixed post-blast time. This paper studies the application of a gas monitoring system in the return entry of a limestone mine to determine a safe re-entry time. The National Institute for Occupational Safety and Health (NIOSH) conducted such a monitoring program in a limestone mine from September 2016 through May 2018. NIOSH/PMRD (Pittsburgh Mining Research Division) is endeavoring to develop workplace solutions to improve detection of and reduce the risk of hazardous conditions. This study showed that the use of gas monitoring in the return air can be a useful tool at the mine operator’s disposal to detect and reduce the risk of hazardous conditions and also to reliably estimate the re-entry time.

By P. Zhang

Previous studies have shown that separation of clay minerals from non-clay minerals is the key to economic recovery of the phosphate from the waste phosphatic clays (slime) which represent about 20- 300/0 of the phosphate mined. Small hydrocyclones of different sizes (4" and 6") were tested for sizing the slime at +10 microns in order to remove most of the clay minerals. The effect of design variables and operating parameters were evaluated. Multi-stage cycloning and the effect of dispersant were also investigated. Chemical and mineralogical analyses of different size fractions of both the underflow and overflow samples indicated satisfactorily separation efficiency.

Jan 1, 1998

By Malcolm Ross

The Reserve Mining Co., in the processing of taconite iron ore quarried from the Peter Mitchell Pit, deposited the finely crushed waste rock into Lake Superior near Silver Bay Minnesota. In the early 1970s The U.S. Environmental Protection agency filed a lawsuit against Reserve Mining Co., asking the court to force the company to stop dumping into the lake. On April 20, 1974, after a lengthy court battle, the U.S. District Court concluded that the Reserve Mining discharge into Lake Superior violated federal and state pollution laws and thus ordered Reserve Mining Co., to halt the lake disposal of taconite tailings. At the time many feared that some of the mineral particles contained in the tailings (alleged to be asbestos or asbestos-like) would cause human health problems. This Conference was thus convened to readdress the problem of the mineral content of the Biwabik Iron Formation and to whether any minerals contained in the ore could cause human disease. The four papers given in this session address the nature of the mineral particles in the taconite rock, the definition of the term ??asbestos?? and the history of the legal controversy over the possible health effects of certain mineral particles contained in the Biwabik iron range ores. Paper 1?Geology of the Biwabik Iron Formation and Duluth Complex Mark A. Jirsa, James D. Miller, Jr., G.B. Morey The Biwabik Iron Formation was a principal source of ore for the American steel industry during the 20th Century. The unaltered iron deposits, called taconite, contain approximately 30% iron and 50% SiO2. About 75% of the iron in taconite resides in the mineral magnetite, the remainder is largely in iron carbonate and several iron-silicate minerals.

Jan 1, 2007

By I. M. Ahmed, R. S. Hassan, M. I. Aly

Extraction and separation of La, Sm and Dy ions from acidic sulfate-phosphate solutions was investigated using a cation exchange extractant, bis(2,4,4-trimethylpentyl) phosphinic acid, CYANEX 272, in kerosene. The influence of shaking time, equilibrium pH, extractant, sulfate and phosphate ion concentrations, diluent type and temperature was studied. The extraction was found to be pH-dependent, and increasing the phosphate ion concentration inhibited the extraction which was found to be endothermic. The stoichiometry of the extracted metal species was found to be MOH.H2OHSO4H2A.A2. Aliphatic diluents were found to enhance the extraction compared to aromatic diluents. The results showed that there was a separation mode between the metal ions when varying the hydrogen ion and sulfate ion concentrations, under the used experimental conditions. The investigated process was used for the recovery of La, Sm and Dy from the acid solution resulting from the leaching of low-grade monazite.

By Verya Nasri

The use of a single tunnel boring machine (TBM) tunnel of approximately 12 to 13 m (40 ft to 43 ft) diameter for transit systems to house both light rail or subway tracks in a stacked configuration is an advanced concept that allows significant savings in construction cost and time while reducing, to a large extent, the negative effects on the environment. This solution, similar to the recently completed Barcelona Metro Line 9, integrates station platforms, train storages, crossovers, bypass tracks, ancillary areas and utility corridors inside a single tunnel. Each of the underground stations consist of a cut-and-cover entrance structure and ventilation shafts, that also serve as emergency exits. The excavations for the station structures and shafts can be done on one side of the street with nominal impact on traffic and utilities.

Jan 1, 2010

1. Paper1?Identification and enumeration of asbestos fibers in the mining environment: mission and modification to the federal asbestos standard Arthur M. Langer Asbestos-related disease is increased with cumulative exposure (the concentration of asbestos in the air and duration of exposure). The maximum duration is assumed to be a working lifetime so federal agencies control cumulative exposure by limiting the airborne concentration of asbestos fibers equal to or greater than 5 lm in length. Air samples are collected in the environment of interest by entraining the airborne particulates including fibers on membrane filters and then counting the number of fibers using phase-contrast light microscopy. In addition to length, the fibers must have a length to width ratio of at least 3 to 1. This ratio is also referred to as the aspect ratio. Some counting strategies placed an upper limit on the fiber width restricting the counting to respirable fibers. Airborne asbestos is controlled by monitoring a sub-population of the airborne asbestos. No asbestos fibers shorter than 5 lm or fibers of any length having widths less than the resolution of the light optical method are counted. In the non-occupational environment, the Environmental Protection Agency requires the use of analytical transmission electron microscopy and fibers and counting fibers with lengths of 0.5 lm or greater and aspect ratios of 5 to 1 or greater are counted. The permissible exposure limit for asbestos has been reduced by more than 120-fold since 1969, when the standard was 12 fiber/ml and the current monitoring methodology was developed. The manufacturing and mining worksites are regulated by two different federal agencies and the asbestos exposure limit was higher in the mining environment until recently (Mine Safety and Health Administration 30 CFR Part 56, 57, and 7, Federal Registry, February 29, 2008). Currently the permissible exposure limit (PEL) is the same in both types of workplace and it is 0.1 fibers per milliliter (fiber/ml) over an 8-h shift as a time-weighted average (TWA). A milliliter (ml) is equivalent to a cubic centimeter (cc) and sometimes this standard is reported as 0.1 f/cc. As the phase-contrast methodology was used to monitor lower exposures and environments, other fibrous mineral particulates were incorrectly characterized as asbestos. These occurred in talc deposits and taconite ores from the Eastern Mesabi Range.

Jan 1, 2008