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By Chris Plackowski, Bruckard. Warren J., Anh V. Nguyen

"Enargite is a significant penalty mineral in the copper industry and its separation from many copper sulfides by flotation is difficult. The separation may be crudely achieved using selective oxidation techniques or through the use of pulp potential control. This paper summarizes our latest contributions to a better understanding of enargite surface electrochemistry and hydrophobicity. Oxidation, roughness, hydrophobicity and species formation on the surface of natural enargite were examined by a novel experimental approach that combines electrochemical techniques, atomic force microscopy, X-ray photoelectron spectroscopy and droplet evaporation tensiometry. It allows for synchronized electrochemical control and examination of the oxidative surface morphology, speciation and hydrophobicity of enargite at pH 4 and pH 10. At low pH, surface layer formations consisting of metal deficient sulfide and elemental sulfur were identified associated with a limited increase in roughness and heterogeneous distribution of surface species produced by initial rapid dissolution of Cu, followed by diffusion limited surface layer deposition. At high pH, a similar diffusive mechanism associated with oxidation products consisting of copper sulfate and hydroxide and a significant increase in surface roughness were established. Receding contact angle measurements showed no significant difference in the contact angle on a surface oxidized at pH 10 and the freshly polished surface. Contact angle increased from 46° on the polished surface to 59° after oxidation at pH 4. Competing effects of hydrophilic copper oxides and hydroxides, and hydrophobic species of elemental sulfur on the mineral surfaces under oxidizing conditions at pH 4, and the change in surface roughness at pH 10, contribute to the changes in enargite hydrophobicity under electrochemically-controlled oxidation conditions. Most likely, both surface species and surface roughness produced by oxidation are critical to the changes in the wettability of enargite and other sulfide minerals."

Jan 1, 2014

By Oliver Bowles

Limestone, including dolomite, is the most widely used of all rocks - nearly 300 million tons annually in the United States alone. It occurs in some form in every State and is produced in thousands of localities. Because of its attractiveness, substantiality, and durability it is employed extensively as a building stone. In crushed and broken form it is used for concrete aggregate and railroad ballast and in highway construction, metallurgy, agriculture, and a host of chemical and industrial processes. This paper proposes to furnish general information on the origin and occurrence of limestone and dolomite, chief production centers, major uses, and methods of quarrying and preparing stone for market. Footnote references will guide the reader to sources of more complete information.

Jan 1, 1956

By J. Burlin Johnson

This report describes an investigation of the relationship between crater dimensions formed in laboratory blasting experiments and the mechanical properties of the material cratered. Scaled field data have been included when available. The results show that tensile strength and possibly other mechanical properties may be useful in predicting maximum crater dimensions.

Jan 1, 1963

By E. H. Burroughs, M. J. Gavin

The references in the following compilation are selected chiefly from the literature of the years 1915-1920 , though a few of the more valuable standard works published before that period have necessarily been included . References to many articles have been omitted purposely , because the material covered by them is duplicated in publications included in the bibliography . It is manifestly impossible for the Bureau of Mines either to recommend or adversely criticize the statements of the various writers , particularly as to cost and profit estimates in articles referring to American shales , but it is hoped that the investigator will use caution in considering such statements , as it is well known that much of the literature on this subject has been published for promotion purposes and is therefore over- enthusiastic . Bearing this fact in mind , the reader should be able to judge for himself the reliability or usefulness of these articles .

Sep 1, 1921

By Marco Lombard, Paulus Kapolo, Christopher J. Greet

"The conversion of a concentrator from one grinding media type to another is a major undertaking in terms of both financial and technical risk. So, a strategy of completing sufficient laboratory and field tests to mitigate this risk, and give the operation confidence that advancing to plant trial will give a high probability for success.The objectives of this paper are twofold: to provide the reader with a strategy for mitigating risk prior to undertaking a plant trial; and to provide a statistical basis for analysing plant trial data. That is, when employing an electrochemically inert grinding media in the primary grinding circuit it is possible to change the pulp chemistry of the system and improve the metallurgical response of the ore.This paper tracks the changes in pulp chemistry and metallurgical performance of Rosh Pinah Zinc Corporation’s silver/lead/zinc concentrator as the primary ball mill was converted from forged steel grinding media to high chrome grinding media. The changed in metallurgical performance are correlated to the shift in pulp chemistry.INTRODUCTIONTheoryBruckard et al (2011) recently published an article describe the effect of the grinding environment on the flotation of copper sulphides. While this paper confined its discussion to copper sulphides the arguments presented apply equally to other sulphide mineral systems. Broadly, these studies indicate that most sulphide minerals are more noble than the grinding media used during comminution. Therefore, the sulphide minerals are cathodic with respect to the forged steel grinding media, and the following reactions apply:Cathode (sulphide mineral): ½O2 + H2O + 2e- ? 2OH- (1)Anode (grinding media): Fe ? Fe2+ + 2e- (2)A galvanic couple between the grinding media and the sulphide mineral(s) exists, which increases the corrosion rate of the forged steel media. The corrosion products of the grinding media, iron oxy-hydroxide species, invariably precipitate on to the surfaces of the sulphide minerals thereby affecting their floatability (Johnson, 2002).The application of more electrochemically inert grinding media to “real” ore systems at an industrial level to improve metallurgical performance has not gained universal acceptance. The aim of this paper is to provide a protocol for conducting laboratory and plant test work that clearly demonstrate that metallurgical benefits are not only possible, but measureable, by way of example. In this case, the work conducted at Rosh Pinah Zinc Corporation in Namibia is described."

Jan 1, 2013

Senior staff representatives of the Bureau of Mines and the National Institute for Occupational Safety and Health (NIOSH) met in Washington on September 6, 1972, to review and evaluate their cooperative accomplishments to date and to consider the planning and conduct of future coordinated activities. The six presentations given at this joint staff seminar are published here for the benefit of those concerned with the problems of coal mine health, and especially those with responsibilities in administering the Coal Mine Health and Safety Act of 1969.

Jan 1, 1972

By Patterson J. H

An infra-red absorption study has been made of crocidolite, country rock. and associated host rocks from Wittenoom Gorge. The spectrum of the country rock is appreciably different from those of crocidolite and the magnetite-rich host rocks which are closely similar. A process to separate crocidolite-bearing ore from country rock based on infra-red emission is therefore possible in theory.

Jan 1, 1966

The Australian metallurgical processing industry has shown great innovation and progressiveness over the past ten years. During the same period, exploration activity, particularly by Australian companies, has increased substantially in Indonesia. Following feasibility studies, the decision was made to establish a metallurgical laboratory and design facility in Indonesia. An Indonesian partner was selected, and legal and corporate matters were determined. The laboratory was established but proved far more difficult than a similar undertaking in Australia. Australian and Indonesian staff were recruited and training programs, including training of Indonesian staff in Australia, were implemented. Difficulties of operating in Indonesia included: ò language difficulties ò _ local pace of life ò culture ò communications. Rewards of the decision to establish the means to present the technology to Indonesia have included: ò a contribution to Australia's export of technology. ò an opportunity to expand Normet's client base. ò the opportunity to learn aspects of a foreign culture. ò the means to establish a sound long term investment. This export of technology from the Australian mining industry to Indonesia is an example of the initiatives and capabilities shown by the Australian mining service industry.

Jan 1, 1989

1. Domestic Production and Use: In 1979, 12 companies operated 32 primary aluminum reduction plants, with 3 firms accounting for 64% of production. Washington, Oregon and Montana accounted for 32% of the total production; Gulf Coast States 20%; other Northern States 32%; and other Southern States 16%. Based on published producer prices output of primary metal in 1979 was valued at over $6 billion. Aluminum consumption by 25,000 firms was centered in the East Central United States. Of aluminum consuming industries in 1979, building accounted for about 24%; packaging 23%; transportation 22%; electrical 11%; consumer durables 8%; and other uses, 12%.

Jan 1, 1980

By John B. Gayle

[The coking time exerts a Considerable influence on the throughout of a coke oven, and for this reason a large number of papers dealing with the relation between coking tine and the different operating variables have been published. Although all of the factors known to ink influence the coking time have been studied, agreement leas not boon reached on several questions, 3/4/ and it appears worthwhile to evaluate any data that become available during investigations of the carbonizing properties of various oafs and coat blends, this report, therefore, includes a Study of the relation between coking lime and flue temperature and represents the second phase of overall investigation ion of factors influencing the coking time in slot-type ovens.]

Jan 1, 1956

By Z. H. Xu

Flotation as a versatile multiphase separation technology has been practiced for more than 100 years in coal and mineral processing. Although effective over a wide particle size range, flotation for mineral separation has been largely understood as an art rather than a science, treating the flotation system as a black box. With rapid progresses in microscopic technologies coupled with high speed video recording and imaging analysis, ingénue design of visualization systems has made it possible to understand fundamentals of flotation by visualization. In this presentation, the state of the art where visualization plays a key role in advancing our fundamental knowledge of flotation will be reviewed. The areas to be covered include characterization of bubbles (shape, size, velocity and sol-ids loading) in a running flotation system, either column or mechanical cell, bubble-solid attachment, hydrodynamic cavitation in fine particle aggregation and flotation, froth imaging, particle-particle interactions by zeta potential distribution measurements, and heterogeneous gas nucleation by atomic force microscope imaging. With these capabilities, critical roles, good or bad, of ore proper-ties, solution chemistry, slurry hydrodynamics, and operation variables in flotation systems as applied to mineral, coal and oil sands processing were clearly elucidated.

Jan 1, 2014

By Horace C. Porter

Much has been written of the changes undergone by coal in storage and the deterioration of coal through exposure to the weather. In order to obtain definite information for the benefit of the Government departments and of all who store coal in large quantities, a series of tests was begun in the fall of 1909 under the supervision of J. A. Holmes, then chief technologist of the United States Geological Survey, and was continued by the Bureau of Mines after its establishment in 1910. The tests were confined to determinations of the loss in heating value of the coals and did not include a study of other deterioration; for example, in coking quality or the yield of by-products in coking. The Bureau of Yards and Docks of the Navy Department cooperated in tests of New River (W. Va.) coal, a variety largely used by the Navy. A preliminary report presenting a brief account of the early results of these tests has been published by the Bureau of Mines as Technical Paper 16.a The detailed report is presented in this bulletin, which gives a full account of the tests and the analytical data covering a period of five years' storage. Data of somewhat similar experiments for shorter periods with gas coal from the Pittsburgh bed, with Pocahontas coal on the Isthmus of Panama, and with Sheridan, Wyo., subbituminous coal, which is used for railroad and other purposes in the West, are included.

Jan 1, 1917

By Yunhua Gan, Xiaowen Chen, Meilong Hu, Haige Li, Yang Tong

Ethanol is a kind of renewable fuel, which can be produced from biomass and applied in many energy areas, such as motorcar. The combustion of ethanol in meso-scale is facing great challenges, such as great heat loss, poor stability, and low combustion efficiency. Electro-spraying technique is an effective method to atomize liquid ethanol due to its great advantage of monodisperse and uniform characteristics. In present study, electro-spraying was applied in liquid meso-scale combustor to produce very small droplet diameter and uniform droplet distribution. Experiments were carried out based on nozzle-ring-mesh electrode structure using pure liquid ethanol as fuel. Electro-spraying characteristics were measured by Phase Doppler Anemometer (PDA) under different nozzle voltages, ring electrode voltages, flow rates, and steel mesh positions. The results may be helpful to the design of new meso-scale electro-spraying combustor using renewable liquid fuel.

Mar 1, 2017

By M. Rudolph, A. van Hall, G. Öktem, S. G. Özkan, A. Hassanzadeh

Despite the four-decade study on ultrasound’s (US) impact on mineral’s floatabilities, there is still not clarity regarding its role in mineral surface wettability. For this purpose, the present investigation endeavours ……the hydrophobicity and floatability characteristics of a chalcopyrite-pyrite-quartz (Cp- Py-Qtz) system in the presence and absence of an ultrasonic pre-treatment. The ultrasonic process was carried out by a sonopuls at a constant frequency of 20 kHz with an adjustable power level from 30 to 200 W. Initially, the impact of sonication time (15, 30, 45, 60 and 90 s as well as 10, 20 and 30 min) and power magnitude (30, 60, 90, 120 and 180 W) were evaluated while the dissolved oxygen, temperature, conductivity and pH were also monitored. Collector-less micro-flotation tests were carried out on the non-pre-treated and the US pre-treated samples at 60 W and 15 s. The samples’ hydrophobicities were determined by the drop shape analysis approach. The dissolved-oxygen level was varied using a mini bench pressurised water reactor to study the effect of O2(aq) concentration on the chalcopyrite and pyrite wettability characteristics. The results showed that the minerals’ hydrophilicities were relatively more sensitive to the sonication’s time than its power that resulted in reducing all three minerals’ hydrophobicities. In addition, it was found that the dissolved-oxygen content and creation of sub-micron sized bubbles led to an improvement on chalcopyrite and pyrite hydrophobicities. Finally, we proved that the Cp’s floatability increased and Qtz’s recovery reduced while being subjected to the ultrasonic irradiation (15 s at 60 W); however, Py’s recovery remained constant. This conclusion confirmed the possibility of a selective separation in ultrasound-assisted copper ore flotation. We recommend that further advanced investigations be conducted, using an X-ray photoelectron spectroscopy (XPS) and atomic force microscopy (AFM) to thoroughly understand the surface modifications induced by the ultrasonication

Jan 1, 2020

By William J. Campbell

The purpose of this investigation by the Federal Bureau of Mines was to design and construct a fluorescent X-ray spectrograph for dynamic rate studies of selective oxidation in molten metals and to establish basic principles for interpretation of data obtained by this method. An X-ray spectrograph was constructed in which the sample holder is a resistance wound furnace; it was operated up to 800° C. in oxidizing atmospheres. No difficulties were experienced with the cooling or heating systems nor with the protective layer of mica around the X-ray tube window, even though the oxidizing surface of the metal is only 0.5 inch from the X-ray tube window, Means are provided for heating under controlled atmospheres for selected time? temperature cycles.

Jan 1, 1961

By Nikkam Suresh

Dense medium cyclones have been in use for washing coarse and small coals for more than 50 years. There have been modifications in its design and today these units have become indispensable for washing of Indian coals possessing difficult washing characteristics. About 53 percent of the Indian coals (coking and non-coking) are being washed in jigs, about 38 per cent are washed in dense medium cyclones while the remaining 9 per cent is treated in other units like Barrel Washers, Heavy Media Baths and Drum Separators etc. The present paper deals with the attempts made for design of industrial Dense Medium Cyclones for enhanced coal recovery. Two industrial units of 500 mm diameter and 650 mm diameter were designed with their washing capacities being 200 m3/hr and 350 m3/hr, respectively. The results of the pilot tests conducted on 500 mm cyclone treating very high Near Gravity Material coals crushed to -3.0+0.5 mm gave an ash reduction of up to 19.5 percent with the new design i.e., from a feed ash of 34.5 percent to 15.06 percent in clean coal with an appreciable yield of 45 percent in one stage.

Sep 1, 2012

By E. D. Gardner

This paper is one of a series on milling methods being published by the United States Bureau of Mines. Atlanta is in Elmore County, Idaho, about 80 miles from the railroad at Mountain Home, Idaho. The concentrator is at an elevation of, 6,000 feet and located in a timbered, well-watered region of relatively heavy snowfall. The snow, however, does not seriously affect local operations. The track road to Mountain Home, which passes over a mountain range, is closed each winter from about November 1 to June 15. During this period concentrates are stored and bullion is shipped by airplane. Power is generated by a Diesel engine and by an auxiliary hydroelectric plant. Gold is the principal metal produced; the or also contains an able quantity of silver.

Jan 1, 1935

By J. -M. Lalancette, D. Lemieux, C. Chouinard

"A gold bearing concentrate containing 107 g/T of gold, 9.3% copper and 706 ppm of mercury was processed at the demonstration scale for the extraction of gold and copper using a cyanide free process. The concentrate was generated through flotation to upgrade the gold and copper grade, but also showed contamination with mercury. This concentrate was submitted to the DST process demonstration plant. The concentrate was first oxidized using a fluidized bed to produce a calcine. The mercury was volatilized during the oxidation stage with an efficiency higher than 98%. The mercury was condensed and removed from the sulfuric acid using a thiosulphate process. Copper was extracted from the calcine as copper sulphate using diluted sulfuric acid. The solid remaining after acid leaching was submitted to the DST chlorination process for gold extraction. Under optimized conditions, a gold extraction of 97.3% was achieved in the chlorination reactor. Gold was recovered from the pregnant brine by precipitation on silica using a DST proprietary process.INTRODUCTION Dundee Sustainable Technologies Inc. (DST) offers proprietary metallurgical processes for the treatment of material from the mining industry. DST processes enable the extraction of precious metals and for the removal and stabilization of contaminants, such as arsenic, from ores and concentrates. DST provides environmentally-friendly, viable and efficient processes, capable of handling complex and refractory ores which cannot be processed with conventional approaches due to metallurgical issues or environmental considerations. Several mining jurisdictions around the world have banned or restricted the use of cyanide. DST has developed a closed loop chlorination process as an alternative to the conventional cyanidation process for the extraction of precious metals from minerals. The tailings from the process are inert from toxic substances such as cyanide and organic compounds, are sulphide depleted which means they do not generate acid, and thus, meet and/or exceed environmental norms. The process has demonstrated excellent gold recoveries within a fraction of the time needed for cyanidation to obtain similar results. Moreover, the closed loop process does not generate any liquid effluent and does not consume much water: it only requires a water make-up to compensate for moisture leaving with the tailings and by-products, and seawater may be used. The improved environmental footprint of the DST process has been certified by the Environment Technology Validation program (ETV) which provides an independent evaluation of the performance claims of innovative technologies."

Jan 1, 2017

By Diogo R. Prado, José Aurélio M. da Luz

Drying operation can have a major importance in a mineral processing undertaking. The proper sizing of dryers can ensure the specified dewatering level without energy wastage. However, often the sizing of fluidized bed is done disregarding the actual residence time distribution (RTD) of the particles inside the reactor. In this case it is usual to adopt the average residence time as a design criterion. In this work, we have quantified the effect of residence time distribution on drying, ensuring that a previously adopted fraction of the particles remains inside the reactor for the required time lapse needed for drying. Design criteria such as particulate flow rate and drying time, taking into account the statistical distribution of residence time was studied, matching the thermodynamic and fluid dynamic aspects of the drying process. Experimental tests carried out have confirmed the RTD for a teetering bed as the same for a canonical ideal mixing system. Although the fluidized bed volume using the proposed formulation was higher than that found for the average time based procedure, the efficiency gain in drying has proven advantageous.

Jan 1, 2014

By Rodrigo Estay Huidobro, Andrés Martinoli, Claudia Pavez-Orrego

The effects of induced seismicity caused by mining activities are one of the main problems that the mining industry faces. Although it has been documented by countries with a great mining tradition (United States, Canada, Australia and Chile) for over a century, the problem has been intensified throughout the years due to the greater depths that mineral extraction reaches, where the stress levels and environmental conditions increase the possibility of a rockburst occurrence. Seismic events inside the mine cause important losses of human lives and infrastructure damage. To deal with this problem it is necessary to implement several kinds of safety protocols. For example, seismic indicators allow to identify, through the analysis of a set of seismic parameters -magnitude, energy, time, decay rate, among others-, periods of time when a seismic event of considerable magnitude is most likely to occur. The objective of this work is to use the frictional energy generated by a microearthquake inside the mine as a seismic indicator, linking it with the occurrence of large magnitude seismic events which are outer the background activity. Thus, we seek to determine the set of seismic parameters which allow the best performance of the frictional energy/heat indicator. In the present study, we considered magnitude, frictional energy, and time as seismic parameters to study the efficiency of the proposed indicator. The optimal set of parameters was determined using two different methodologies: accumulated thermal energy and alert bands. The Piece Skill Score and the Accuracy indexes were used to evaluate each set of parameters. Both approaches show a high rate of true positive and true negative hits. Furthermore, it was concluded that both methods show complementary results in terms of the detection of critical events (Mw > 3.0).

Apr 26, 2022