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By R. Guardia, J. Hoskins, E. Claros, Y. Kamiya, R. Ramirez, J. Dalenz, P. Fernandez, E. Ilgren

Crocidolite is a well known causative agent for mesothelioma. Studies have shown that the pathogenicity of the fiber from different mines varies considerably and it has been postulated the parameter that appears most likely to account for this variation is fiber width. Epidemiological studies have shown that ‘thin’ fibers from mining areas of Western Australia and the Cape Province, in South Africa are associated with a high mesothelioma risk while exposure to ‘thick’ asbestiform amphibole fiber of the same fiber type are associated with little or no mesothelioma risk. This study is concerned with ‘thick’ Bolivian crocidolite but similar findings also probably explain the paucity of mesotheliomas in the Finnish anthophyllite, South African amosite and African Transvaal crocidolite mines. The findings from the present study suggest the incidence of mesothelioma in the three major cities of Bolivia is not significantly elevated above background even though Bolivian crocidolite has been used for the past 60 years commercially and residentially in all three cities. Although some cases of mesothelioma may have been missed due to a failure to reach hospital or a shortened natural lifespan, mesothelioma generally occurs after the age of 50, we cannot tell precisely the extent to which these were confounding. We suggest the most likely explanation for the lack of mesotheliomas despite the large populations at risk from the long and extensive residential and commercial use of crocidolite containing products, is related to an increased fiber width distribution and a concomitant reduction in the ‘Stanton fiber size’ fraction.

Jan 1, 2012

By E. Neumann

With fuel costs unstable but escalating, solid fuels are playing an increasingly larger part in industrial concerns. Coal, petroleum coke and wood are examined from a burner system design viewpoint and from operational experience in kilns, hot gas generators, etc. The burner of today must also handle multi-fuel tasks and allow immediate, painless switching from one fuel to the next as well as the simultaneous burning of two or mope fuels. The paper discusses the principle of burning alternate pulverized fuels as well as the practice both in the United States and around the world.

Jan 1, 1983

By Heiko Schiemann, Christoph Beyer, Thomas Pretz

"Due to multiple experiences in the field of planning and engineering of processing plants for secondary materials the Chair for Processing and Recycling of Solid Waste Materials decided to develop a software tool that supports the engineering and the planning of the basic layout of processing plants for secondary material flows. The detailed description of the material flow and its characteristic parameters is one of the main tasks to be worked out and should be considered as the basis for representative simulation results.The description of the material flow and its characteristic parameters is based on a fraction vector containing 12 material fractions. This is a compromise between a detailed material flow description and a compact and therefore time-extensive calculation model. Each material fraction is characterized by 15 parameters, which can be edited with the help of an easily accessible user-interface. In addition to basic parameters like ignition loss, water content and calorific value more parameters like the material fraction-specific particle-size distribution are contained. Using the model library SimuRec, the processing success and the recovery of complex processing plants for secondary materials can be predicted."

Jan 1, 2003

By Z. Zhang, M. -Y. Liu, X. -G. Chen, F. Breton

"The microstructures of AlSi10Mg foundry alloy in permanent mould (PM) and high pressure vacuum die (HPVD) castings were analyzed and compared. The as-cast microstructures of two castings mainly consisted of eutectic silicon particles, primary Mg2Si and Fe-rich intermetallic phases. The surface layer in HPVD castings, which has a unique feature and different structures, was carefully characterized. The dimension variation of microstructural phases along the cross section in PM samples is less than that in HPVD samples, although the size of microstructural phases in PM samples was much larger than that in HPVD samples. The mechanical properties of PM and HPVD samples were evaluated on as-cast and T6-treated conditions. The tensile properties of HPVD castings are remarkable better than those of PM castings on the as-cast condition. The T6 heat treatment greatly improves the tensile strength of PM castings while it has limited impact on the tensile strength of HPVD castings.INTRODUCTION The AlSi10Mg alloys are widely applied to the high pressure die casting (HPD) and high pressure vacuum die casting (HPVD). In the HPD process, the melt is injected into the die cavity under a high speed (30–50 m/s in the gate velocity for aluminum alloys), and solidified under a high pressure (up to 200 MPa in the cavity) and with a high cooling rate (up to ~103 Ks–1) (Gourlay, Laukli & Dahle, 2007; Ji, Wang, Watson & Fan, 2013). This results in a unique microstructure feature that is different to other casting processes under gravity. One major concern in HPD castings is porosity due to trapped air in the cavity (Ji et al., 2013), which seriously restricts the application of a heat treatment on the improvement of mechanical prosperities because of the formation of blisters on casting surfaces. For the process improvement, the high pressure vacuum die casting was developed in 1980s (Uchida, 2009). In this process, the melt is injected into the die cavity under reduced pressure (vacuum), which greatly reduces gas porosity in castings due to effectively avoiding the trapped air. Consequently, HPVD castings are heat-treatable without the formation of blisters on castings surface during heat treatment. The HPVD process has been widely applied to produce high quality structural castings in recent years attributed to reliable vacuum system development (Uchida, 2009). However, the microstructure features of HPVD castings are not systemically characterized yet."

Jan 1, 2018

By R. E. Brewer

Pilot scale flotation tests were conducted with a l?ft-diam column at the Barrick Resources (USA) Mercur mine, Tooele County, UT, to scavenge unleached (0.01 to 0.018 oz/st) gold values from the tailings of a carbon-in-leach (CIL) circuit. The optimal recovery was 35 pct of the unamenable-to-leaching gold, at a grade of 0.353 ounces of gold per short ton, using a mixture of dithiophosphate, xanthate, and diesel fuel as a collector. This was achieved by floating approximately 1.6 wt pet of the CIL tailings. The gold values are believed to be contained in arsenic-bearing minerals, attrited carbon, and carbonaceous material in the ore. Redox potentials were measured with a gold electrode during the conditioning stage prior to flotation. The correlation between flotation recovery and redox potential values could be used to control reagent additions. Treatment of a previously leached and weathered tailings material, averaging about 0.055 ounces of gold per short ton, was also investigated. The tailings were first water leached at approximately 60? C, and the water-leached tailings, containing approximately 0.03 ounces of gold per short ton, were then fed to the column flotation unit. The effects of pH' and sodium sulfide addition on gold flotation recovery and redox potentials were examined. Maximum gold flotation recovery, 36 pct, was achieved at pH 8,5 with a sodium sulfide addition of 0.18 Ib/st. Overall gold recovery by leaching and flotation was in the range of 70 to 80 pet.

Jan 1, 1989

By Robin Schott

The blast furnace process is the most important process to produce pig iron. The necessary process energy is mainly covered by coke. But the production of coke is connected with CO2-emissions and high costs. A significant measure to reduce the coke rate and with it the CO2-emissions plus costs is pulverized coal injection (PCI) through the tuyeres into the blast furnace. A further increase to substitute coke by coal can be achieved by using the Oxycoal+ technology. This article compares and shows the cost effectiveness and the decrease of CO2-emissions with the help of simplified energy balances for the only coke operation of the blast furnace, the operation using pulverized coal injection and the operation using the Oxycoal+ technology.

Aug 17, 2017

By H. J. McQueen

Friction stir welding (FSW) generates complex microstructures in the nugget and thermomechamically affected zones (TMAZ) that have led to diverse explanations. However, consideration as an extension of microstructure development in piercing/extrusion can lead to a better understanding of flow patterns and microstructures during FSW. Furthermore, the intense strains in the nugget/TMAZ can be interpreted by comparison with ultra-high strains in torsion that exhibit dynamic recovery as extending into regions with high angle boundaries strongly serrated with spacing near the subgrain size defined by the high temperature. The subgrain diameter and extrusion pressure have been shown to be dependent on the Zener-Hollomon parameter Z (=t exp(Q/RT), Q activation energy, R gas constant) combining temperature T and strain rate E in the same mariner as for torsion and compression. Moreover, such tests exhibited steady state stress os above a certain strain Es (rising as Z increases) in which T, , subgrain diameter and dislocation spacing remain constant. Due to the subgrain boundaries (SGB, low angle <5°, i.e.,LAB), continually rearranging by migration, decomposition and reformation, the subgrains remain equiaxed in elongating grains, whose boundaries (GB) become serrated as they migrate to absorb SGB. As confirmed by straining in torsion at constant T and Z. , more subgrains bordering the greater GB area have several high-angle facets (HAB) ; these small cellular regions with a mixture of HAB and LAB facets are designated HAB-subgrains. As serrations in neighboring grain boundaries impinge, the grains pinch off becoming shorter; this occurs at higher strains as subgrain size decreases with rising Z. The pinching-off makes the neighbors thicker so the grains never become thinner than about two subgrain diameters. In conjunction with such geometric dynamic recrystallization (gDRX), GB&apos;s undergo a net migration into grains with denser substructure, enlarging those with larger subgrains. Consequently a better name has been proposed: grain dimensioning dynamic recovery (gDRV).

Jan 1, 2007

By C. P. Mishra

The Bureau of Mines investigated the availability of mercury from 22 deposits in market economy countries. The 15 significant deposits evaluated have demonstrated resources of approximately 25 million metric tons of ore containing 5.3 million flasks of mercury and account for more than 85 pct of the demonstrated resources for market economy countries. Using data gathered as part of its Minerals Availability Program, the Bureau determined the mercury production potential of each deposit. At a January 1984 mercury market price of $300 per flask, the deposits evaluated could economically produce an estimated 2.5 million flasks of mercury from six mines operating at the time of this study; no mercury is available at this price from nonproducing operations. At $600 per flask, approximately 4.5 million flasks of mercury are available. For production costs up to $300 per flask, operating mines could supply mercury at the current production rate of 114,000 flasks per year until 1988, when the amount of mercury available from these deposits would decrease. This decline could be offset by the development of resources currently reported at the identified level (17 million flasks) at much higher production costs.

Jan 1, 1985

By Mike Lewis

"Descending several stories down a metal staircase into a shaft spanning a quarter city block -- soon to become Roosevelt Light Rail Station in Seattle, WA -- visitors are greeted with four perfectly round, precast concrete-lined horizontal holes leading deep into the earth. The sound of water trickling out from a small drainage trough can be heard over the faint echoes of construction within. Upon entering, the light is dim, but the air is clear with barely a dust particle flowing through the sunbeams. This type of air quality is only accomplished with diligent controls, and JCM Northlink, the company in charge of building the Northgate Link Extension Project, is taking those measures seriously.Commissioned by Sound Transit, JCM is a joint venture of three companies: Jay Dee Contractors, Frank Coluccio Construction Co. and Michels Corp. The tunnels JCM constructed are intended to provide fast, reliable underground rail service, as well as relieve one of the region’s most congested traffic areas. The $440 million project will connect the Northgate, Roosevelt and University District neighborhoods north of Seattle to the downtown corridor and SeaTac airport further south.The scope of this project includes excavation for two light rail stations, boring of two parallel 5 km- (3.3-mile) long light rail tunnels in six runs and the construction of 23 cross passages. Begun in 2014, Sound Transit estimates that crews excavated more than 382,000 m3 (500,000 cu yds) of soil and installed 7,352 precast concrete tunnel liner rings during the shaft construction and boring phase. Now that tunnel boring is complete, JCM is in the process of constructing the cross passages, which act as maintenance areas and escape routes for passengers. Throughout the entire process, the company has utilized atomized mist to control particle emissions.“Our dust control needs change at every phase of the project and don’t go away until the project is fully complete,” said a JCM safety representative. “We found that different dust suppression technologies were needed at different intervals, but atomized mist seemed to fulfill our needs at every step.”"

Jan 9, 2017

By Ben C. McLellan, Philip J. Bangerter, Andrew Murphy, Glen D. Corder, Damien Giurco

Sustainability now forms a critical part of metallurgical plant design. In addition to compliance with requirements and corporate principles, design engineers must also consider how community and societal responses to the metallurgical industry affect the way they design and build plants. Three broad areas to consider are: the design engineer’s contribution to sustainability through the design process and the relationship to the social license to operate (SLO)—the unwritten license communities give companies to safely and responsibly operate the plant and equitably share benefits; the realization of sustainability goals through methodologies emerging in the design activities; and the integration of design frameworks into a contemporary project design context and its investment objectives. This chapter explores sustainability in metallurgical plant design in the context of SLO, design tools and frameworks, and community and societal influences.

Jan 1, 2015

By C. Landolt

Inco&apos;s Copper Cliff Smelter Complex produces some 11 5,000 tonnes per year of nickel and 120,000 tonnes per year of copper. The Smelter flowsheet has changed a number of times over the years. The most recent changes were effected in the mid-1980&apos;s in response to new realities in metal markets and heightened awareness about the workplace environment. By 1994, the flowsheet will undergo yet another metamorphosis as part of Inco&apos;s SO2 Abatement Program. The paper discusses the improvements implemented during the 1980&apos;s and projects the processing in the Smelter through 1994.

Jan 1, 1993

This publication summarizes the in-house and contract research projects programmed for fiscal year 1984 by the Bureau of Mines under its Conservation and Development activity. The document provides a mechanism for interested parties to gain insight into projects of the Bureau&apos;s Conservation and Development research program. The objective of the Conservation and Development Program is to provide the technological advances needed to stimulate the mining of domestic deposits containing critical, strategic, and other essential minerals in compliance with existing regulations and at costs sufficiently low to be competitive in world markets. Research efforts are directed toward improving the fundamental understanding of processes and procedures involved in the production of minerals. The overall goals will be accomplished by investigating alternative mining methods to increase domestic production of critical and strategic minerals from low-grade deposits; expanding the technology for the economic and efficient extraction of minerals consistent with cost-effective compliance with environmental regulations; and advancing the technologies needed to insure an adequate supply of coal.

Jan 1, 1984

By Xiang Ma, Halvor Dalaker, Kai Tang, Stefan Andersson

Silicon carbide (SiC) is one of the most important non-oxide ceramic materials for many industrial applications and is mainly synthesized by carbothermic reduction of silicon oxide by coke above 2200°C. Replacing natural gas (mostly methane, CH4) for coke in SiC synthesis could considerably reduce energy consumption and CO2-emissions owing to higher carbon activity of CH4 at lower temperature. The generally accepted reaction mechanism is that SiC is synthesized through gaseous intermediate silicon monoxide, SiO. In the present study, the reaction mechanism for the SiO and CH4 gaseous mixture has been examined using atomic scale modelling. Molecular dynamics (MD) using a reactive force field (ReaxFF) has been utilized to examine the initial stages of reactions involving a gas mixture of SiO and CH4 and surfaces of SiC. The MD results revealed some interesting SiC formation mechanisms. The reaction energies of the critical intermediate species were also estimated by density functional theory (DFT) calculations and the implications for the force field parameters used in ReaxFF was discussed.

Jan 1, 2015

By Sidney Katell

The present report, a continuation of the series of Bibliography of Investment and Operating Costs for Chemical and Petroleum Plants, is concerned with articles published from January 1958 through December 1958. The periods covered in previous reports are as follows: January 1930 - August 1948 I. C. 7516 September 1948 - June 1952 I. C. 7705 July 1952 - June 1954 1. C. 7751 July 1954 - December 1956 I. C. 7847 January 1957 - December 1957 I. C. The following sources were used to obtain the references to and the abstracts of the published articles included in this report: 1. Bureau of Mines Information Circulars. 2. Bureau of Mines Reports of Investigations. 3. Chemical Engineering. 4. Chemical Engineering Progress. 5. Coal Age. 6. Coal Utilization. 7. Cost Engineering. 8. Industrial and Engineering Chemistry. 9. Nucleonics. 10. Oil and Gas Journal. 11. Petroleum Engineering. 12. Petroleum Refiner. 13. World Oil.

Jan 1, 1959

By Mark Colwell

This paper summarizes the results of a research project whose goal was to provide the Australian coal industry with a longwall installation roadway (faceroad) design methodology that could be utilized by suitably qualified colliery personnel. This goal was achieved in 2012 and the design methodology (and software package) is referred to as Analysis and Design of Faceroad Roof Support (ADFRS). The intended benefits to underground operations, in the provision of this information and resource, are a safer and more productive workplace.

The key issue which determines the use of imaging for explosives and mining research is the question - `What information will I gain by using imaging technology?&apos; This paper will address that question from the point of view of a researcher and cameraman working in industrial imaging and photography. The paper will establish a common set of reference standards for high speed imaging and photography which researchers can apply when deciding which type of imaging technology is appropriate. It will present an overview of current image analysis technologies and practices in use across a range of appropriate scientific fields and draw lines of commonality of approach between these fields and the field of explosives and mining analysis and research. Further to this, the paper will examine the different technologies from an image quality reference point, ease of operation, cost, and reliability parameters. Finally this paper will present an argument for the hybridisation of established and new technologies which could provide a more beneficial approach to the use of imaging as a tool of research and analysis in the explosives and mining industries. This will include a novel approach to high speed filming and analysis in the field which should deliver high quality images in a time frame which is more appropriate to urgent action and solutions.

Jan 1, 1995

By K. Whiting

In October 1993, the first two of a series of full scale passive biological treatment cells were constructed to treat mine drainage from the Burleigh Mine (located approximately 48 km west of Denver, Colorado in the Clear Creek/Central City Superfund Site). The two cells are each 19-21 m long, 10.7 m wide and 1.2 m deep. Each cell contains approximately 216 cubic meters of substrate (composted manure) and is designed to treat 60 L/min of mine flow. One cell is designed as an upflow reactor and the other cell is designed as a downflow reactor. The differences in flow hydraulics and treatment efficiencies will be tested in these two cell for approximately nine months before the remaining cells are built to treat all the discharge. The substrate material was selected based on a series of bench scale tests. During the tests, the amount of metals removed was determined. The design flow rate was based on a sulfide generation rate of 400 nanomoles of sulfide generated per cubic centimeter of substrate per day. Metal removal results for the first three months of operation of the two cells will be presented and compared to results of bench and pilot studies at other sites.

Jan 1, 1994

By Piyush K. Dutta

This report describes the design, development and manufacture of production stoper drills and results of their field tests, it is shown that underground stoper drill noise level can be reduced from 118 dBA to below 100 dBA by using these pneumatic drills. The design concept of these drills is a radical departure from the standard valved rifle bar type drill machine design to a drill featuring a valveless independent rotation system, use of an integral muffler and a shroud tube. Six drills were manufactured in a standard commercial drill manufacturing setup and organization. The design and production technology proved that commercially viable quiet drills can be made available for mine use.

Jan 1, 1983

By T.R. Stacey

Physical testing of rock support for rockbursting conditions has been carried out for over 40 years. A review of this testing shows that it has been mostly component based, rather than actually testing support systems. Further, it is concluded that none of the testing is truly representative of rockburst loading in a similitude sense. Similitude conditions are not achievable, mainly because the real conditions in a rockburst event, such as seismic source location and magnitude, wave frequencies, amplitudes, and interactions, are not all known. Because such information is not available, and because the results of all testing carried out to date have not been able to define, for support design purposes, the capacity of support systems, ongoing physical testing of rockburst support systems is essential. It is essential that the test should simulate, or actually take place in, a supported rock excavation. A rock support system is a combination of individual support components that work together to retain and contain the rock. In doing this, the components are subjected to loading by the rock and to interactive loading between one component and another. It is necessary to prove the capacity of such rockburst support systems by subjecting them to severe loading, as in direct blasting. The direct blasting approach, pioneered more than 40 years ago, probably still provides the greatest validity as a significant test of rockburst support capabilities, even though it does not simulate a rockburst. Direct blast testing of rockburst support systems in a surface environment, such as in a quarry or on exposed rock cutting surfaces, could represent a practical development of the approach, facilitating the execution and monitoring of tests.

Jan 1, 2012

By John A. Organiscak

Enclosed cabs are a primary means of reducing equipment operators? silica dust exposure at surface mines. The National Institute of Occupational Safety and Health recently performed a laboratory study to evaluate which factors on an enclosed-cab filtration system are most significant. The various factors evaluated were intake filter efficiency, intake air leakage, intake filter loading, wind infiltration, use of a recirculation filter, and the use of an intake pressurization fan. The result of this laboratory testing has shown that the two most important factors for an effective filtration system on an enclosed cab were the efficiency of the intake filter and the use of a recirculation filter. A higher-efficiency intake filter considerably increased the quality of the intake air that was delivered into the enclosed cab. It also was determined that air leakage around the intake filter notice-ably reduced its air cleaning effectiveness. The second key factor is the use of a recirculation filter, which was shown to improve the air quality in the enclosed cab by six to 12.7 times more than the intake filter alone. The reason for the significant improvement was that the cab air was constantly drawn through the recirculation filter, thus continually filtering the dust out of the air.

Jan 1, 2010