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By Robert H. Schutz

This publication lists and describes devices approved jointly by the Secretary of Interior and the Secretary of Health, Education, and Welfare, under the provisions of [§]70.300-1, Part 70, Subchapter 0 of Chapter I, Title 30, Code of Federal Regulations (35 F.R. 5548, April 3, 1970), for use as respiratory protection against respirable pneumoconiosis-producing dusts. Included are type C supplied-air respirators approved under Bureau of Mines Schedule 19R and dust, fume, and mist respirators approved under Bureau of Mines Schedule 21B.

Jan 1, 1971

Proper water and thermal management is essential for obtaining high performance of Proton Exchange Membrane Fuel Cells (PEMFCs). A steady, two-dimensional water and thermal management model was developed, aiming at considering pressure drop, open circuit voltage variation with stack temperature, water vapor effects on membrane conductivity, which made the model physically more reasonable and more suitable for various operating conditions. The model could predict the distributions of a series of important parameters along the flow channel, and thus the effects of various operating and design parameters on the fuel cell performance could be investigated easily by numerical trial-and-error method. The modeling results compared well with the available experimental results from the literatures. The results also showed that the humidification is crucial for the performance of PEMFCs. The model could be a very useful engineering tool for the optimization of PEMFCs.

Jan 1, 2005

By John Hansen

This paper has been written for presentation at the 103rd Annual General Meeting of the Canadian Institute of Mining, Metallurgy, and Petroleum, April 29 to May 02, 2000. The paper addresses blast pattern fragmentation and diggability versus the blasting technique used. RESUME The author is the Vice President for Thunderbird Mining Systems. In this capacity he manages the mine site installation of surface mining mobile equipment monitoring and navigation systems. These systems are onboard instrumentation and software systems designed to: ??measure and log mobile equipments? production and health; and ??direct the equipment operators via onboard displays that show comprehensive maps and engineering instructions. The author is a mining engineering graduate from the Royal School of Mines. His work experience includes front line supervisor and mining engineer for Hudson Bay Mining & Smelting, mining engineer for Teck Corporation, and mining consultant for PriceWaterhouseCoopers.

May 1, 2001

By Mahesh C. Jha

Cyanidation has established itself as the main process for extracting gold from ores in this century. However, many ores exhibit refractoriness to the conventional cyanidation process. The main cause of the refractoriness is generally the presence of carbon, tellurium, and sulfides, particularly those of antimony, arsenic, and iron. The problem is usually solved by either modifying the cyanidation conditions or providing an oxidation pretreatment. This paper presents results from studies that help in understanding the causes of refractoriness of various gold ores. This is followed by a discussion of many processes that have been developed to solve the problem such as intensive cyanidation, pressure cyanidation, carbon-in-leach cyanidation, and pretreatment processes such as roasting, chemical oxidation, autoclave oxidation, and bacterial oxidation.

Jan 1, 1986

By Madhu G. Ranade

A statistically designed pot grate- kiln test program was conducted to determine the agglomeration process variables necessary for increasing the low temperature disintegration resistance (LTD) and reducibility (R40) of magnetite-based Empire acid pellets. The ASTM tumble index and compression strength were to be maintained at an acceptable level. Six process variables, bentonite addition level, preheat time and temperature, firing time and temperature, and cooling rate, were investigated within the constraints of the Empire plant. The bentonite addition level and firing temperature had the largest effect on pellet properties. The results of this program were verified during a pl ant trial. The target firing temperature at the Empire Plant has been decreased for increasing the LTD and R40 of commercially produced Empire pellets

Jan 1, 1985

By L. A. Cornish, I. A. Mwamba, R. A. Couperthwaite

"In previous work by the authors, it was established that additions of 0.2 at.% Ru to an Fe-40 at.% Al alloy improved the corrosion and oxidation resistance of the alloy. The alloy was produced by mechanical alloying and spark plasma sintering and the work showed that nonequilibrium processing was able to significantly refine the grain size of the material. The sintered material had a higher hardness than the as-cast material and the change in grain size did not significantly affect the oxidation and corrosion. In the present research, the mechanically alloyed powder was coated onto a mild steel substrate using cold-spray coating at a gas pressure of 10 bar and a temperature of 500°C. The coatings were found to be 5–10 um thick, although thicknesses of up to 30 um were observed. The coated materials were subjected to oxidation and corrosion tests to determine the effectiveness of the coating in increasing the oxidation and corrosion resistance of mild steel. This was done to determine the effectiveness of cold-spray coating as a technique to coat these mechanically alloyed powders. IntroductionPrevious work conducted by Mintek (Couperthwaite et al., 2013, 2015) investigated the effect of precious metal additions on the structure, oxidation and corrosion properties of an Fe-40 at.% Al (Fe- Al) alloy. Initial work determined that additions of more than 0.5 at.% precious metal did not improve the oxidation and corrosion properties of the materials and in some cases even decreased the resistance to corrosion. Further work identified Pt and Ru as beneficial additions to the FeAl alloy. Four alloys were then produced by mechanical alloying and sintering (FeAl–0.2 at.% Pd, FeAl–0.2 at.% Ru, FeAl–0.5 at.% Ag, FeAl–0.5 at.% Pt). These alloys were all successfully produced by melting and casting and mechanical alloying sintering and it was found that the nonequilibrium processing greatly decreased the grain size of the materials compared to the ascast materials. It was found that the additions of Ru and Pt were still the most beneficial to the oxidation and corrosion properties, with Ru being considered the most beneficial."

Jan 1, 2016

By R. N. Reddy

The Pseudo capacitance of layered type Mn02 electrode material for electrochemical capacitors (EC's) was investigated. MnO2 was synthesized in our laboratory. Mn02 was prepared from heating of KMn04 at 300°C in air. Cyclic Voltammetry (CV) experiments were carried out using three electrode system, Saturated calomel electrode as reference electrode, platinum mesh as a counter electrode, and MnOz composite material mounted in a platinum mesh used as a working electrode. Two kinds of composite working electrode materials were used, one was mixture of MnOz and 25 wt% acetylene black, while the other was MnOz, 25 wt% acetylene black and 25 wt% carbon. All the experiments were carried out at 25OC. A maximum specific capacitance of 130 Fig and 118 Fig were observed at the scan rate of 2 mV/s and 20 mV/s respectively in 1M KC1 for composite electrode made with carbon. Results obtained in this study are compared with that of other electrode materials.

Jan 1, 2002

By L. A. Ruth

Introduction The US Department of Energy's Office of Fossil Energy has begun a new approach for developing the ultra-clean energy plants. This approach will allow the nation to continue to use low-cost fossil fuel feedstocks during the early decades of the 21st century. The new approach is called Vision 21. The overall goal is to effectively eliminate, at competitive costs, environmental concerns associated with the use of fossil fuels for producing electricity and transportation fuels. Vision 21 is based on the following three premises: •The nation will need to rely on fossil fuels for a major share of our energy needs well into the 21st century. •It makes good sense to rely on a diverse mix of energy resources, including coal, gas,

Jan 1, 2003

By S. L. May

The Bureau of Mines has developed several methods for extracting tantalum and columbium (niobium) and the rare-earth compounds from ores and concentrates. A cooperative agreement was made by the Bureau with Porter Bros. Corporation of Idaho to process 200 pounds of its euxenite concentrate by methods that had been developed at the Albany, Oreg., Metallurgy Research Center. The euxenite concentrate was processed to extract and purify the valuable metals by chlorination, solvent extraction, and hydrometallurgical techniques. Chlorination was used to convert the valuable constituents into chlorides and to partly separate them. Solvent extraction techniques were used to separate the tantalum from the columbium. The rare-earth and uranium compounds were purified by hydrometallurgical methods.

Jan 1, 1959

By G Morgan, C Kemp

In December 2010, a trial of borehole radar technology was conducted to test the usefulness of the technique in better refining the position and geometry of narrow vein orebodies away from the primary data sources of drilling and mapping of development excavations. This paper summarises the reasons why the technique was applied, describes the testing methods selected and summarises the outcomes of the trial.Poor reconciliations of recovered metal from a section of an orebody at Jundee mine site, Western Australia, led to an investigation that identified insufficient understanding of the geometry of a narrow vein orebody as a potential cause. This orebody was situated between mapped development excavations and away from surrounding drill holes. Borehole radar was identified as a possible technique that could supply information on vein location and continuity away from other data sources allowing more accurate orebody modelling and subsequent stope optimisation.A borehole radar instrument (10 - 100 MHz frequency) was inserted into pairs of purpose-drilled boreholes on either side of relatively well-constrained mineralisation and the radar reflection data was collected. This process was repeated in five locations across the mine to represent the most common geological settings, lithologies and orebody varieties encountered at Jundee to determine the suitability of applying the technique in each of these settings. Collected, processed and interpreted radar data was compared to other geology data collected independently for verification and interpretation.Conclusions drawn from the analysis were that the technique could effectively determine the following features of the mineralised veins in the majority of test environments: geometry of veins, magnitude of offsets where structures intersect and orientations of planar structures with short strike length. The technique was very useful in selecting the appropriate structural interpretation where available data could lead to multiple, equally likely, interpretations.CITATION:Kemp, C and Morgan, G, 2012. Using borehole radar to refine orebody interpretations in a narrow vein gold deposit, in Proceedings Narrow Vein Mining 2012 , pp 121-130 (The Australasian Institute of Mining and Metallurgy: Melbourne).

Mar 26, 2012

By J Ledgerwood

Namakwa Sands is a mineral processing company based on the West Coast of South Africa and is solely owned by Exxaro Resources Limited. Mineral ore is mined and processed, concentrated and both chemical and mechanically upgraded before being sent for electrostatic and magnetic separation units. The final high value mineral products report as Zircon, Rutile and Ilmenite.The recovery of non-magnetic material is largely dependent upon a number of factors, including but not limited to dew point, ambient temperature, feed rate, mineral size distribution, specific gravity and mineral content in head feed. One important limiting factor to recovery in typical dry mill operations is the particle size distribution of the feed. Variance in the particle size has catastrophic consequences for recovery. This is the reason for this study. Until recently large variances in non-magnetic production were viewed to be a function of machine operation. This view was later rejected with the feed size distribution determined as the major driver of low recoveries, for Namakwa Sands orebody 50 per cent variance in particle size distribution can be noticed within one day. This is because of the successive mining blending techniques employed.The predicament is that the two modes were so closely placed together that recovery of a single mode is almost impossible without the consequence of greatly reducing recovery. The second mode was found at 125 µm while the first was at 90 µm. Interestingly, for the mentioned feed type a cumulative size distribution of a unimodal feed type is almost exactly the same as for a bimodal size distribution. Thus a plot of cumulative size distribution will show no difference due to the modes being so close together. This is the reason why this phenomenon was not noticed before.The study also found that, using an high tension roll (HTR) or rare earth roll, a fine stream with a single mode at 90 µm versus a coarse stream with a single mode at 150 µm would yield completely different results interms of yields. Larger conductive particles are thrown from the roll while small particles loose charge faster (entrainment). Results in terms of the bimodal size distribution show that even though 25 per cent of the feed type is greater than 150 µm the yields followed a similar pattern to that of the coarse particles rather than that of the majority (75 per cent) fine particles. This confirms what was published by M Ziemski and P N Holtham in 2005 on charge decay rates; they mentioned that particle bed effects played a major role in recovery.

Oct 5, 2011

By R H. Hallam

The Mattagami mining district encompasses a favour-?able belt of folded Keewatin-type rocks, with intercalated sediments and intrusives of late Keewatin age. This environment has been subjected to periods of basic and acidic intrusion. The orebodies lie within the fold structure and are associated with faulting and shearing of considerable magnitude. The No. 1 orebody contains 60 to 70 per cent massive sulphides. The minerals, in their order of abundance, are generally: pyrite, sphalerite, pyrrhotite, magnetite and chalcopyrite. It is evident that the broad geological structure of the district is amenable to ore deposition. There are two ? prominent linear expressions which comprise this broad structure. Both strike directions lie at the edge of, or are related to, a complex gabbro-anorthosite-peridotite zone. The fact that eleven of the ore zones discovered to date coincide with the broad structure indicates its over-all importance. It is estimated that the production from Mattagami Lake Mines will be in the range of 600 to 700 tons of zinc concentrate and 70 tons of copper concentrate per day.

Jan 1, 1964

By Brad McBain

Agenda ? Accurassay Laboratories and Automation ? History and experience ? Features and benefits of automation in the lab ? Tata Steel Minerals Canada (TSMC) Iron Ore Laboratory ? State-of-the art systems and design ? The integration of fusion systems and XRF units ? Meeting deliverables: quality, reliability, safety

Aug 1, 2013

By Silas C. Nichols, Jennifer E. Nicks

"Limit states design (LSD), or load and resistance factor design (LRFD), is a method to account for the uncertainty in loads and resistance through a reliability calibration that requires all applicable limit states (strength, service and extreme) to be checked during foundation design. LRFD has been in use internationally for several decades; however it wasn’t until recently that engineers working on highway projects were required to use the method for the design of highway bridges and other appurtenances. Although the bridge community has been using a form of limit states design for structural components since the early 1970s, the design of foundations for bridges, walls and other geotechnical features had long been performed using allowable stress design (ASD), whereby all uncertainty in loads and material resistance is combined in a single factor of safety. While the move to LRFD was viewed as a more rational approach for the design of bridges and structures, the transition to its use for geotechnical engineering has been met by many with confusion and difficulties in application. This article will revisit the history of transition from ASD to LRFD for geotechnical engineering, summarize the status of the transition and issues with its use, and briefly discuss some emerging research opportunities for improving and advancing the design platform.Background and HistoryUntil about a decade ago, foundations and substructures for bridges were traditionally designed using ASD, while the superstructure was designed using load factor design (LFD), a precursor to LRFD that incorporated factored design loads but no risk assessment. This combination led to uncertain and incompatible safety margins in design for the various bridge components. In 1986, the American Association of State Highway Transportation Officials (AASHTO) Subcommittee on Bridges and Structures (SCOBS) concluded that the standard bridge specifications in use at the time for U.S. transportation projects had significant inconsistencies and gaps, wasn’t up to date with emerging technology and that the development of new specifications was warranted. The proposed solution by the subcommittee was to transition to a more coherent method of design where applicable failure and serviceability conditions could be evaluated considering the uncertainties associated with loads and resistance."

Jan 1, 2015

By K. T. Aust

It is proposed that the intergranular corrosion of austenitic stainless steels is associated with the presence of continuous grain houndary paths of either second phase, or solute segregate resulting from solute-vacancy interactions. Experimental observations of structural changes and crrosion behavior of different types of austenitic stainless steel provide support for this poposal. On the basis of this model, it is shown that the intergranular -corrosion susceptibility of austenitic stainless steels in nitric-dic hromate solution may be substantially reduced either by suitable heat treatments or by impurity control. AUSTENITIC stainless steels, such as Type 304, generally have excellent corrosion resistant properties when properly solution heat-treated and used at temperatures where carbide precipitation is slow. However, several corrosion environments have been found which produce intergranular corrosion of solu-tion-treated stainless steels, that is, those steels with no detectable carbide precipitation.''2 Of the various corrosion environments, the most widely used test solution has been the boiling nitric-dichromate solution. In these acid solutions, stainless steels have been found to be susceptible to intergranular attack despite the addition of carbide-forming elements such as titanium or columbium, or despite lowering of the carbon content or use of high-temperature solution treatments. Studies of the electrochemical mechanism of corrosion attack have been made by several worke1s3'4 who found that oxidizing ions such as crt6 depolarize the cathodic reactions and consequently raise the open-circuit potential of stainless steel immersed in nitric acids. As a result of this, the anodic reaction is accelerated. The reason for the localization of anodic activity at the grain boundaries, and resulting intergranular corrosion, has not been conclusively determined. Several workers, e.g., Streicher,3 and Coriou et al.,4 have suggested that the strain energy associated with grain boundaries provides the driving force for the accelerated intergranular corrosion. This argument would predict that alloys of high purity would still be susceptible to intergranular attack. However, work by chaudron5 and by ArmijO,6 has shown that high-purity alloys are immune to attack, in disagreement with this argument. An alternative suggestion is that chemical concentration differences exist between grains and grain boundaries, that is, impurity segregation at boundaries, and that these chemical differences provide the driving force for localized attack. It is this impurity segregation which can lead to accelerated dissolution of grain boundaries when the alloy is exposed to a suitable corrodant. This mechanism would predict the immunity of high-purity alloys to inter-granular attack, which is in agreement with experi-mental observations. In the present paper, some recent studies on inter-granular corrosion of austenitic stainless steels which were conducted by coworkers and myself will be re-tibility A simple model will be described in which it is proposed that the intergranular corrosion of aus-tenitic stainless steel is associated with the presence of continuous grain boundary paths of either second phase or solute-segregated regions.* On the basis of this model, it is suggested that the intergranular corrosion rate can be markedly reduced by the formation of a discontinuous second phase at the grain boundaries if the discontinuous second phase incorporates the major part of the segregating solute, drained from the grain boundary region. Results are presented of corrosion tests and electron microscopic studies of different types of austenitic stainless steel after various heat treatments which provide experimental support for this model. Finally, a solute clustering mechanism, based on a solute-vacancy interaction, is shown to be consistent with the results obtained for inter-granular corrosion of solution-treated austenitic stainless steels. EXPERIMENTAL Corrosion tests using weight loss measurements were made on sheet specimens, which were lightly electropolished, washed, and immersed in boiling (115°C) 5 N HN03 containing 4 g crt+6 per liter added as potassium dichromate. Studies in which the inter-granular penetration depth was measured both by electrical resistance and metallographic methods have shown an empirical correlation between the rate of intergranular penetration and the weight loss per unit time for identically treated specimens of stainless steel." As a result, although all the corrosion data reported here are in terms of simple weight loss measurements, these data are considered to reflect primarily the rate of intergranular dissolution. Fig. 1 shows a typical result of intergranular attack of a solution-treated Type 304 stainless steel after 4 hr in a boiling nitric-dichromate solution. The wide grain boundary grooving at the surface, and the attack at incoherent twin boundaries, are evident; very little corrosion attack is seen at the coherent twin boundaries. INTERGRANULAR CORROSION MODEL

Jan 1, 1970

By W. A. Thatcher

Nearly three years of experience in Spanish Honduras has placed the writer in possession of many facts concerning its resources which may be of interest to the Institute. According to the most trustworthy surveys, Honduras is bounded on the north and east by the Caribbean Sea; southeasterly by the river Segovia (or Wanks), which flows into the Caribbean at a point called Cabo Gracias a Dios (Cape Thanks be to God), long famous as the favorite hiding-place of the celebrated pirate, Morgan ; southwardly by a corner of San Salvador, the Bay of Fonseca, and the Republic of Nicaragua; Guatemala and San Salvador form tile western boundary. It is one of the five republics composing Central America, has a population of about 310,000 and an area of 150,000 square miles, lying between the 13th and 16th degrees of N. latitude, extending from north to south 200 miles, between the Atlantic and Pacific, and 400 miles from east to west, between Guatemala and Cape Gracias a Dios. It is composed of 13 States or Departments, under one common law. The principal resources are valuable woods, hides, rubber, tobacco, coffee, fruit, cattle, silver and gold. It is of the mineral resources of the country that I will speak, calling attention to the most noted mines, and their relative position to Tegucigalpa, the capital. The introduction of foreign capital into the country dates back about eleven years, and to-day there are at least twenty-five well organized companies.

Jan 1, 1892

The dust exposure of the longwall shearer operator is usually determined by his position relative to the cutting drums. The dust generated during cutting may travel up-wind, against the primary airflow, and be carried out into the walkway where it can contaminate the intake air for as much as 10 feet outby the shearer operator's controls. Thus, both head and tail drum operators are exposed to un-acceptably high levels of air-borne respirable dust. One Solution The latest generation of long-wall shearers has features that make the use of radio remote or umbilical (hard wire) remote control relatively easy to implement. Remote control can enable shearer operators to control machines from positions that are less dusty than normal control stations. With either type, the head-drum operator can now control the shearer from a position up to 20 feet on the intake-air side of the shearer, while the tail-drum operator's station is now located across from the head drum.

Jan 1, 1984

By James O. Glanville

Ice frozen from a dilute chemical solution is mechanically weaker than ice frozen from pure water. This phenomenon is the basis of a practical method for reducing the strength of a mass of frozen coal. If a chemical additive is applied to moist coal, prior to its shipment during freezing weather, the resulting frozen coal can be more easily broken than in the absence of the chemical additive. This greatly expedites the unloading and handling of coal during winter. There has been considerable research into the nature and mechanical strength of ice frozen from various solutions. The literature relating to this process has been reviewed as has the literature relating to the chemical treatment of coal and mineral particulates. Some important articles are discussed and speculations are made about the nature of the ice-weakening process. A laboratory evaluation of the effects of chemical additives on the mechanical strength of ice and frozen coal has been made. An apparatus designed for this purpose is described, and some results obtained with it are discussed.

Jan 1, 1980

By Luke Clarkson, David Williams

The intent of this paper is to provide overview context to allow broader understanding of conventional tailings dam failure mechanisms. The research leverages global knowledge, experience, and data collection and interpretation for the safe and controlled management of the geotechnical stability of a tailings storage facility. The motivation for this review is to facilitate transparent access to tailings dam background and understanding. This paper addresses the core understanding of geotechnical failure mechanisms, and how these eventuate to instability and failure of tailings dam structures. This research focuses on foundation failure, internal erosion and piping, overtopping, seepage, seismicity, and slope instability and provides insight into what factors contribute to failure, how failure progresses due to such failure, anticipating and monitoring for the aforementioned failure modes, and designing to mitigate their risk.

Feb 15, 2021

By Wallace W. Key

Problems of marketing industrial minerals to chemical manufacturers are manifold. In addition to the difficulty of establishing demarcation lines between "crude" and "processed" industrial (nonmetallic) minerals, and "industrial mineral compounds" further uncertainty exists because some chemical manufacturers do not talk the same language as the industrial mineral producer. For example, paint technologists use "rutile" and "anatase" to describe highly refined chemical compounds. The earth scientists use these terms to describe naturally occurring minerals. Further, marketing research problems are intensified because of the overlapping data of the Standard Industrial Classifications (SIC) groups, and the inexactness of "Chemical Industry," "Chemical and Allied Products Industries," and "Chemical Process Industries," which are widely variable in meaning but are often used interchangeably. Bureau of Mines information Circular 8244, "Minerals for Chemical Manufacturing," was the out¬growth of an attempt to unravel some of the problems caused by overlap of statistical data compared with actual industry practices. Using this study as a base, specific industrial mineral applications of some important sub-industry groups were analyzed for the; California chemical industry. Differences between local and national practices were compared. Practices usually differed, depending on cost and availability of alternate minerals, climate, idiosyncrasies, local regulations, and other conditions. Bureau of Mines Information Circular 8260, "Mineral Fillers for the California Pesticides Industry," is the first such analysis of, a sub-industry group. Other such studies are underway. Obtaining national data is easy, but to be able to compile meaningful information which can be revealed on a regional and State basis generally is difficult and often impossible. This paper will briefly emphasize some of the industrial mineral problems encountered, and bring out the needs and benefits being derived through the continued cooperation of authoritative officials concerned with supply and consumption of industrial minerals in government and industry.

Jan 1, 1965