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By Huaiyang Zhou

"Hydrothermal systems are a major component of the processes that shape the composition and structure of the ocean crust, providing a major pathway for the exchange of heat and elements between the Earth’s crust and oceans, and a locus for prolific biological activity on the seafloor and underlying crust. On the other hand, the structure and composition of hydrothermal systems are the result of complex interactions between heat sources, fluids, wall rocks, tectonic controls and even biological processes.Ultraslow spreading ridges, including the Southwest Indian Ridge and the Gakkel Ridge, are most remarkable end member in plate-boundary structures (Dick et al., 2003), featured with extensive tectonic amagmatic spreading and frequent exposure of peridotite and gabbro. With intensive surveys during the last decades, it was suggested that ultraslow ridges are several times more effective than faster-spreading ridges in sustaining hydrothermal activity. This increased longevity can be attributed to deep mining of heat and even exothermic serpentinisation (Baker et al., 2004).Distinct from faster spreading ridges, one characteristics of hydrothermal mineralization on seafloor in ultraslow spreading ridges, including the active Dragon Flag hydrothermal field at 49.6 degree on the Southwest Indian Ridge, is the abundant and pervasive distribution of lower temperature minerals (such as Fe-silica or silica, Mn (Fe) oxides, sepiolite, pyrite, marcasite, etc.) in the hydrothermal fields. Structures formed by lower temperature activity in active and dead hydrothermal fields can also be identified. High temperature minerals such as chalcopyrite are rare or very limited in hydrothermal chimneys at ultraslow spreading ridges. The distribution of diverse low temperature hydrothermal activity is consistence with the deep heating mechanisms and hydrothermal circulations in the complex framework of ultraslow spreading tectonics. On the other hand, deeper and more extensive mineralization at certain locations along the ultraslow spreading ridges can be reasonably presumed."

Sep 1, 2014

By Thomas C. Ruhe

The Bureau of Mines conducted research to determine the safe operating conditions for using recycled (used) lubricating oil from mining equipment as a partial replacement for diesel fuel to make ANFO-type blasting agents. The use of recycled oil (RO) saves energy, reduces oil imports, and reduces mining costs. Low ambient temperatures may cause these recycled oils to become too viscous for proper absorption by ammonium nitrate (AN) prills and result in poor blast performance, safety hazards, and environmental problems. To help quantify and resolve these issues, viscosity, mixing, and performance tests were conducted at various temperatures. Diesel fuels No. 1 and No. 2 were studied separately and in blends with 25,50, and 75% RO. Good quality ANFO mixes (94-6) were produced with dry absorbent prills and blended fuel (No. 1 diesel plus RO) at temperatures as low as -40° F (-40°C) with 75% No. 1125% RO, and at -20°F (-29°C) with 50/50. Diesel fuel No. 2 also made good mixes as low as -30" F (-34" C) with 75% No. 2/25% RO, and at 0° F(-18° C)with 50/50. Reference detonation velocity tests were conducted in 1.4" (3.6 cm) diameter steel pipe at 70°F (21°C) on No. 1 diesel ANFO (94-6), giving an average value of 9722 ft/s (2964 m/s). Comparison tests showed good ANFO performance at low temperatures. Blended fuel ANFO (75% No. 1/25% RO) mixed, loaded, and tested at -40°F (-40°C), produced an average velocity of 9247 Ws (281 8 m/s). A 50/50 blend gave a velocity of 8083 Ws (2464 ds) at -20°F (-29°C). Based on these results, a practical field method has been developed to help evaluate whether a specific oil blend will mix properly with AN at a low ambient temperature. This method will help to promote the safe and reliable use of RO ANFO at low temperatures, with adequate performance.

Jan 1, 2008

By Thomas C. Ruhe

The Bureau of Mines conducted research to determine the safe operating conditions for using recycled (used) lubricating oil from mining equipment as a partial replacement for diesel fuel to make ANFO-type blasting agents. The use of recycled oil (RO) saves energy, reduces oil imports, and reduces mining costs. Low ambient temperatures may cause these recycled oils to become too viscous for proper absorption by ammonium nitrate (AN) prills and result in poor blast performance, safety hazards, and environmental problems. To help quantify and resolve these issues, viscosity, mixing, and performance tests were conducted at various temperatures. Diesel fuels No. 1 and No. 2 were studied separately and in blends with 25,50, and 75% RO. Good quality ANFO mixes (94-6) were produced with dry absorbent prills and blended fuel (No. 1 diesel plus RO) at temperatures as low as -40°F (-40°C) with 75% No. 1/25% RO, and at -20°F (-29°C) with 50/50. Diesel fuel No. 2 also made good mixes as low as -30" F (-34°C) with 75% No. 2/25% RO, and at 0°F (-18°C) with 50/50.

Jan 1, 2008

By J. C. DeSantis

Thin, highly reflective rhodium films with metal compositions greater than 98% (elemental -weight percentage) have been deposited by chemical vapor deposition using Rh(allyl)3 (ally1 = q3-C3H5) in the presence of a hydrogen plasma. Uniform, crystalline films that adhere well to several types of substrates result from depositions at temperatures as low as 150°C. Depositions using H2 (no plasma), or an argon plasma yields material that is amorphous, contains a significant amount (>14%) of residual carbon, and has a dramatically slower growth rate. The composition of these materials does not vary significantly from that of the materials obtained from the in vacuo thermal deposition with Rh(allyl)3.

Jan 1, 1992

By Yuri Yemelianov, Stanislav Balikov, Alexander Epiforov, Andrey Boldyrev, Andrey Bogorodsky

"Test work was carried out using copper gold-bearing flotation concentrate with 6.85%Cu, 14.30%Fe, 20.70%S and 2.34%As. Gold and silver grade in the concentrate is 54.6 g/t and 92 g/t, respectively. Gold and copper are valuable components in the concentrate. Gold is partially associated with pyrite and fahlores. Copper in the concentrate can be found as tennantite (Cu12As4S13). The 71% of gold from the flotation concentrate is recoverable by cyanidation with simultaneous cyanide consumption in the amount of 96 kg/t. The major reason of refractoriness is that gold is fine encapsulated into sulfides and the presence of cyanicide-copper. The concentrate ground as much as 95% minus 10 µm was treated using low-temperature POX at the temperature of 100±5°C, L:S ratio of 5:1 and the process time of 1-5 hours. Residual sulfide sulfur in the cake is 2.28% which is 89% sulfide oxidation. The highest copper recovery to POX solution is 91%. It was found that gold recovery to cyanide solution is 85-94% during alkaline pre-treatment of POX cakes followed by cyanidation. In this case, cyanide and lime consumption is 75-90 kg/t and 120 kg/t, respectively. In order to recover precious metals from POX cakes leaching using sodium sulfite was carried out. Test work was conducted at varied reagent concentration, L:S ratio and leaching time. Gold and silver recovery achieved was 85-95% and 59-63%, respectively."

Jan 1, 2014

By W. de Bruijn

Differential reduction and expansion or shrinkage of hematite under the influence of intimately associated foreign oxides may be a source of stress formation and sinter degradation during blast furnace reduction. To study specific effects, synthetically pre-pared hematite powder evenly doped with 1% by weight of several elements present as oxides, was pressed into tablets and sintered at high temperature prior to reduction. Continuous thermo-gravimetric and dilatometric analyses were per-formed on the sintered tablets as these were being subjected to reduction under simulated blast furnace time/temperature/gas composition conditions up to 1183 K. These findings were coupled with observations on the microstructure of tablets removed from various stages of the reduction process.

Jan 1, 1988

By R. G. Reddy

Reduction of different chromite ores with carbon was studied as a function of C/FeO ratio and temperature in the range 700 °C to 1100 °C by thermogravimetry (TGA) analysis. Powders of chromite ore(-150 mesh) and carbon(-150 mesh) were thoroughly mixed in a desired proportions and were placed in the reaction crucible. The reduction rates of reactions were determined by continuously monitoring the weight loss as a function of time at constant temperature using TGA set up. The analysis of results suggest that FeO present in the chromite ores is reduced to Fe involving gaseous intermediates CO and CO2. The overall rate of FeO reduction is controlled by the oxidation of carbon. A kinetic equation, that of random nucleation, was proposed. The activation energies for the reduction of FeO, present in Roast Movat and Transvaal ores, with carbon were determined to be 55800 and 23000 J/mole, respectively. The results of the present study are compared with the data available in literature. The low activation energy values as determined in this study suggest that the carbon oxidation reaction is catalyzed. It is concluded from the present investigation that the low grade chromite ores can be significantly upgraded to higher value added chromite that can be used as a feed source for economical smelting.

Jan 1, 1998

By C Li

Removal of gangue minerals from ilmenite concentrates can beaccomplished by relatively low temperature roasting in controlled gasatmospheres to selectively enhance the magnetic separationcharacteristics of the ilmenite. At roasting temperatures below 800¦C the magnetising reactions are often not consistent with phase equilibria considerations. Metastable phases can nucleate and control the roasting products. In weathered ilmenites the phase assemblages and microstructures in the altered ilmenite grains can influence the roasting reactions. In this paper we give an overview of the phase chemistry of chemically weathered ilmenites and of metastable phases formed by low temperature roasting. We also report the results of roast experiments conducted in a neutral gas atmosphere. Major increases in magnetic properties after short roasting times at low temperatures were obtained for a range of ilmenite concentrates. For example heating a secondary ilmenite concentrate from Western Australia for 15 minutes in nitrogen at 600¦C gave an increase in the three kilogauss magnetic fraction from three to 92 wt per cent. The solid state phase changes accompanying the inert atmosphereroasts were characterised by combining elemental analyses withquantitative phase analyses of the ilmenite concentrates and their roast products. It was found that the phase reaction that is principally responsible for the increase in the magnetic properties of weathered ilmenites involves a transformation of disordered ferrous-containing pseudorutile to an ordered ilmenite-hematite solid solution containing typically ten to 35 mole per cent of the hematite component. Examples are given of the application of the inert atmosphere roast to effect separations of ilmenite from gangue minerals.

Jan 1, 2001

By Djona M. Gaballah I.

Selective chlorination of unroasted and roasted spent hydrorefming catalysts was studied between 300 and 600°C using the following gas mixtures : C12+CO, C12+N2 and CI2+air. Such materials contain Co, Ni and Mo compounds supported by alumina and/ or silica. They also contain variable amounts of V compounds, C, S, etc., accumulated during the life time of the catalyst. Direct oxychlorination of the C+S rich sample allows higher extraction rates than those obtained by the carbochlorination of the same roasted one. It seems that the roasting step doesn't favor the economic metals' recovery. Results of the chlorination of C+S poor spent catalysts, in the presence of CO, in the chlorinating gas mixture, or of carbon added to the sample, were comparable. Cobalt and nickel chlorides were .extracted from the chlorination residues by their dissolution with acidified water, whereas molybdenum and vanadium chlorinated compounds were recovered by selective condensation from the vapor phase. The recovery rates of valuable metals as well as the selectivity were higher for the chlorination of spent catalysts than results obtained by the hydrometallurgical processing of the same sample. Results of the scale-up of the oxychlorination of the unroasted sample confirmed those of the laboratory scale. The global recovery rates were about 88 pct of cobalt, 93 pct of molybdenum and 76 pct of vanadium. The carbochlorination was applied to the recovery of W and Ti from Denox catalyst that is a carbon and sulfur free one. Recovery rates higher than 99 pct at temperatures lower than 500 °C could be obtained. This may indicate that the chlorination process can be applied to the treatment of various industrial wastes or by-product containing transition and/or refractory metal compounds A flow - sheet for the pretreatment of these materials is proposed.

Jan 1, 1995

By C. S. Barrett, O. R. Trautz

PREVIOUS investigations have shown that lithium is body-centered cubic from near its melting point to the temperature of liquid air1,2,3 Nevertheless there was an incentive to search again for a transformation at low temperatures: C. Zener4,5 has remarked that the low value of the elastic modulus (11 - C12)/2 of body-centered cubic metals and alloys implies a rapid increase in free energy with decreasing temperature, which would favor the occurrence of a transformation; also the shear movement to which this modulus applies is one that can transform a body-centered cubic structure into a slightly distorted face-centered cubic structure. It was confirmed that lithium does not transform spontaneously at liquid nitrogen temperature, but it was found that a transformation can be induced at this temperature by cold working the metal,6 and at slightly lower temperatures a different transformation occurs spontaneously. Transformations were also found in solid solutions of magnesium in lithium. THE NATURE OF THE TRANSFORMATIONS Before presenting a detailed treatment of the technique used and the specific data obtained, it would be well to give a brief survey of the general characteristics of the transformations. A new crystal structure begins to form spontaneously in a specimen when it is cooled below a critical temperature. In lithium the structure appears to be close-packed hexagonal; in the Li-Mg alloys most of the diffraction lines (but not all) are near those for hexagonal lithium. The transformation proceeds as the temperature is lowered and soon stops if the temperature is held constant or raised. The course of the transformation on cooling is indicated by the curve at the lower left of Fig I. This curve is drawn in stepped fashion because the transformation goes by discrete steps with audible clicks. Because of the similarity to the decomposition of austenite into martensite in steels, it seems appropriate to designate the beginning of the spontaneous transformation on cooling as the Ms point. On heating to room temperature after the low temperature treatment only the usual BCC structure is found. On heating, the low temperature modification begins to disappear at a temperature which will be designated as Ac. The transformation on heating is halted when the rise in temperature is halted. The temperature must be raised 40 to 50°C above Ac before the reversion is complete-an interval which is sensitive to the rate of heating and to the time of holding at temperatures above Ac. This behavior on heating thus has similarities also to the formation of martensite in the cooling of steels.

Jan 1, 1948

By H. B. Pulsifer

ONE of the most common basic open-hearth furnace products is a simple carbon steel with a carbon range from 0.05 to 0.15 per cent. The material is widely used for sheets, tubes, bars, wire and the innumerable special objects of secondary fabrication. The properties of the material vary over wide ranges, depending on the more exact composition and details of manufacture or treatment that affect its structure. The present paper is a review of those properties and structures that have been found by studying this steel as used in the cap screw industry. At first glance this might be thought a narrow application of the steel, but, since the industry uses the material in the cold-worked, annealed and heat-treated conditions, the title of the paper may be excused for its comprehensiveness. Yet, in studying the wide ranges of properties and structures that preclude a more specific title, there can be no suggestion of completeness or finality. Even a summary of a few years' work is no more than a preliminary survey of a field that will be fertile in scientific data and industrial products for many years to come. An outline of the structures will be given first, then a list of the previous contributions that are at hand and finally some details of the work and related problems, especially concerning this low-carbon steel in the surface-hardened condition.

Jan 1, 1931

By S. W. Evans, G. Pienaar

Weldable steel plate with a good combination of strength and toughness is currently produced from 0,12 to 0,28 per cent carbon low-alloy steel heat-treated by roller quenching and tempering. Alternatively, steel plate of the same strength can be produced at a lower production cost by the use of very-low-carbon steel (0,03 to 0,08 per cent carbon) processed by in-line quenching without tempering. This paper reports the results of experimental work on these steels, and compares them with the properties of conventional steel. On thinner sections, it was found that the properties of the experimental steels compare favourably with those of conventional grades.

Jan 1, 1989

By J. Langwaldt

Ammonium-nitrate is a main component in blasting agents and dissolved ammonium residues may be discharged with mine water. The European Union aims to reach a good state of the water quality and recommends ammonium content below 0.5 mg/L for drinking water. Natural zeolites adsorb ammonium from water. In this work, the removal of low-concentration ammonium by commercial natural zeolites was studied in continuous tests. Natural zeolites made up between 83% and 95% of the mineral composition. The major zeolite minerals were chabazite and clinoptiolites and minor amounts of erionite and mordenite were as well present. The five natural zeolite samples, 500~710 µm, were conditioned to obtain zeolites in the Na-form. Ammonium adsorption onto natural zeolites depends mainly on the zeolite mineral type. The chabazite containing zeolite was superior over the four clinoptiolite samples for the removal of low concentrations of ammonium from water (pH of 7.5, flow 5 mL/min, room temperature). The adsorption capacity of chabazite was 48.3 mg NH4+/g zeolites, i.e. 73% of the theoretical exchange capacity 69 mg NH4+/g, during duration over 107 days and almost 6700 bed volumes exchanged. The four tested clinoptiolites had an ad-sorption capacity of 15.7mg to 25.0 mg NH4+/g zeolites. The natural zeolites were rapidly regenerated by an alkaline sodium chloride solution fed to the columns.

Jan 1, 2014

By D. A. Sloan

THE Young Davidson mine is of particular interest because of the extremely low costs and also because of the novel method devised for pillar recovery. The outstanding feature of the mining system is its simplicity and regularity. The successful operation of this property was de-finitely assured by the rise in price of gold in 1934. The mine is situated in the southeastern part of Powell township, about forty-five miles southeast of Timmins, Ontario. The local town, two miles distant, in Matachewan, which is twenty-five miles northwest of Elk Lake, the terminus of a branch line of the Temiskaming and Northern Ontario railway. Mining is confined to one of a group of five claims. The ore occurs in a body of syen.ite porphyry which is intruded along a contact of Timiskaming conglomerates with Keewatin altered ruffs and greenstones. This intrusion extends in a north-easterly direction from Davidson creek for 3,300 feet, of which length 700 feet lies within the Matachewan Consolidated property. The maximum width of the mass is 700 feet; it tapers off as it extends east-ward. The Orebody.-The syenite porphyry is of three types, probably all differentiates of the same magma, but only one of them is gold bearing. This is a cherry-red, coarsely crystalline type which forms the central part of the mass. It is more brittle and more fractured than the others, and consequently has allowed easier access to the gold-bearing solutions. The gold has been brought in by a branching system of quartz veins and along minute fractures. It is mainly in the form of very fine 'free' gold, but also occurs in pyrite, which is the chief metallic mineral.

Jan 1, 1942

By Marco Silva

Underground mines are complex environments that require continuous control and monitoring actions in order to have a safe and efficient operation. At Nexa, the goal of achieving "zero harm" promotes the constant search for in its operational processes. Currently, there are manual activities that reduce the agility and precision when working with information from inside the mine, using mostly radio communication and management by sight of badges as an operational standard. This project was born in the context of increasing the operational safety of underground mines, bringing gains to the entire process involving the underground.

Sep 29, 2023

By Nagel, Theodore

USE of oxygen in metallurgical operations was investigated by a committee of unusually able engineers more than ten years ago. A record of their work appeared under the title "The Use of Oxygen or Oxygenated Air in Metallurgical and Allied Processes," Serial 2502, Report of Investigations, U. S. Bureau of Mines. Shortly thereafter the A.I.M.E. published "Use of Oxygenated Air in Metallurgical Operations," based on a symposium at the New York meeting, February 1, 924. Quoting from the Bureau of Mines report In view of the many recent developments in oxygen manufacture, and considering the increasing cost and decreasing quality of our raw materials, the Bureau of Mines has taken the matter of the application of oxygen or oxygenated air to the metallurgical centers for consideration and has appointed an advisory committee to study the problem.

Jan 1, 1935

By C. E. Rodgers

WHEN I was asked to prepare, for presentation at the 1938 Annual Meeting of the Institute, some data concerning low-discharge grinding at the Sylvanite mill, it seemed entirely reasonable to expect to have at my disposal the results of at least four full months' operation after the last unit, as then proposed, was installed. Delays in delivery of equipment, nevertheless, shortened the interval, as will be shown herein. In submitting the data contained in this discussion, I wish distinctly to state that the intention is not to claim that final conclusions can be reached at this time concerning our operation. Test periods, in certain instances at least, have been too short for this purpose, although some, where so stated, have been extended through March and April. It is hoped, however, that an advantageous trend in practice can be shown and that the experience related may be of interest to others who are now operating, or who are considering the operation of, low-discharge grinding mills. In the plant under review, four mills are in use: one primary and three secondary. Present mill capacity (grinding, as shown by screen test, about 99 per cent through-200-mesh and approximately 88 to 89 per cent minus-325-mesh with infrasizer giving about 90 per cent of the latter) averages about 525 tons per day. A brief description of each unit will be given and comments will also be made relating to operation. This will be followed by certain test data from which, in conclusion, operating results are summarized.

Jan 1, 1938

By King R. L

Low-enthalpy geothermal groundwater resources occur at relatively shallow depths in the Upper Cretaceous/1'ertiary sedimentary sequence in the on-shore Gippsland Basin. The main stratigraphic unit containing hot groundwater is the Latrobe Group. Groundwater temperatures in the range 30 to 70¦C have been recorded from depths between 500 and 1000 m. The hottest groundwater is in the Latrobe Valley and Lake Wellington depressions. Geothermal gradients in these areas range from less than 2¦C/100 m to over 10¦C/100 m (compared to a world average of about 3¦C/100 m). A number of theories have been advanced to explain the geothermal anomalies including exothermic reaction such as oxidation of coal, mixing with deeper, hotter groundwater and high geothermal fluxes along fault zones. Variations in geothermal gradients can also result from type and thickness (and hence thermal conductivities) of the sedimentary pile, depth to consolidated basement rocks, and influence of groundwater flow patterns including proximity to recharge zones. The hot groundwater in the Gippsland Basin has substantial potential as a source of energy for direct heat applications such as process heating, space and water heating for buildings, and agricultural and aquaculture. Geothermal energy has a number of environmental advantages over traditional sources of energy. It is clean, safe, causes minimal land disturbances and in most cases is naturally renewable.

Jan 1, 1992

By B Clements, R Dunne, J Dioses, S Hart

In April 2003 plant upgrades in the æLow GradeÆ Cadia Hill circuit were undertaken in order to improve concentrate quality and metal recoveries from the flotation circuit. The major changes involved: circuit reconfiguration to allow all concentrates to be reground to less than 38 ¦m prior to final cleaning; increasing ball charge in the regrind mill to fully utilise all of the installed power; desliming of the cleaner scavenger concentrate to improve the circuit water balance; and the inclusion of a gravity concentrator in the regrind circuit to recover more free gold to bullion.Once the flotation circuit had stabilised under the new operating conditions concentrate launder modifications and increased froth crowding on the scavenger flotation cells permitted the introduction of stronger collectors without compromising concentrate quality or circuit stability.Twelve months on, the copper concentrate grade has increased by two per cent and metal recoveries increased by three per cent and seven per cent for copper and gold respectively. The project capital outlay of approximately $2.0 million has been repaid in less than three months. This paper will review the project from the design, construction and commissioning perspective as well as the subsequent debottlenecking exercise that was required to eventually yield the full benefits of this upgrade.

Jan 1, 2005

By Jan E. Nesset, Phillip J. Mackey, Joo Y. Kim, Giovanni Di Prisco, André R. Laplante

Understanding the appropriate gold recovery to associate with copper recovery when assessing laboratory testing on porphyry deposits is often complicated by several factors including variable and/or complex mineralogy, and the variability contributed by the low Au content of the various flotation products. As a result, gold recovery is often underestimated and the value contributed by the gold to project economics is less than it should be, a problem that could influence overall project viability. Typically, for these types of deposits, the gold recovery is found to be lower than the copper recovery. In this unique project, having the objective of seeking a better understanding of gold recovery relative to copper recovery, mill feed samples from a selection of six operating world-class Cu-Au low-grade deposits were collected along with the mill metallurgical results for the corresponding sample periods. The samples were subjected to laboratory flotation tests, as well as the Laplante gravity recoverable gold (GRG) test, mineralogical assessment and cyanidation leaching. The aim was to better understand the copper and gold recovery relationship, the links between laboratory and plant flotation performance, the influence of mineralogical differences, and the potential for enhancing gold recovery by gravity recovery techniques. A new correlation of copper and gold recoveries based on the results is presented in the paper. The results showed that the link between copper and gold recoveries established in the best laboratory tests were maintained in the plant results, and further, that the potential for improving Au recovery by gravity or flash flotation methods is directly proportional to the amount of gold greater than 75 microns.

Jan 1, 2005