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By L. Zeng, Q. Feng, Z. Qiu, L. Ou, Central South University

It is well-known that the use of nanobubbles can significantly improve the flotation efficiency of ultra-fine particles. However, this is mainly focused on coal and phosphate rock flotation. In the field of nonferrous metal processing, the related research is few. In this paper, a small laboratory mechanical cell associated with a specially-designed nanobubbles generator was used to investigate the effects of nanobubbles on enhancing ultra-fine scheelite flotation. Nanobubbles were created and based on the hydrodynamic cavitation principle through Venturi tubes. Comparative flotation tests were performed using different tubes to evaluate the nanobubbles impact on the ultra-fine scheelite particle flotation recovery. In order to better understand the nanobubbles enhanced ultra-fine scheelite flotation, nanobubbles potential and size distribution were measured. The effect of nanobubbles on the particle aggregation and scheelite particles potential were also studied through the turbidity tests, microscope tests and zeta potential measurements. According to the results, the mean size of nanobubbles was about several hundred nanometers, and the surface of nanobubbles was of highly negative charge in alkaline conditions. The flotation recovery of ultra-fine scheelite particles was increased in the presence of nanobubbles. The zeta potential measurements indicated that the repulsive forces between scheelite particles decreased when nanobubbles existed. Through the turbidity tests and microscope tests, the promotion effect of nanobubbles on particle coagulation could be verified more directly. The existence of nanobubbles in flotation system promotes the particle aggregation, thus increasing particles apparent size and particles capture by bubbles, which may be the fundamental reason why nanobubbles enhance ultra-fine scheelite flotation.

Jan 1, 2016

By S. C. Robinson

"IntroductionALTHOUGH most uranium deposits of the Canadian Shield lie along its western and southern margins, those of the Lake Athabasca region extend easterly along the north shore of the lake and beyond to Charlebois lake. The western end of this belt of deposits, in the vicinity of Goldfields, is 80 miles from the Palaeozoic contact, and its eastern end, at Charlebois lake, is 240 miles from the nearest Palaeozoic rocks.Deposits in this belt may be grouped in four districts, which are, from west to east:(1) The Goldfields district, an area approximately 20 miles square, centred on Beaverlodge lake and extending eastward from St. Joseph's point to Moose channel.(2) A small area in the vicinity of Sucker bay, which is about l0 miles east of Fond du Lac.(3) An area including Middle lake to the northwest shore of Black lake at the Nisto mine.(4) A fairly large area extending northward from the eastern end of Black lake, through Charlebois lake to Spreckley lake.HistoryThe region has stimulated interest in mining circles since the reconnaissance survey of J. B. Tyrrell of the Geological Survey of Canada in l893, who reported concentrations of iron along the north shore of lake Athabasca. The deposits were staked and re-staked up to the early 'twenties' but are too lean to form ore."

Jan 1, 1952

By X. B. Wang, Z. Q. Guo

Slagging coal gasification process became a highlight of coal chemical industry in China during the last decade. Refractory lining's life of slagging gasifiers is one of the most critical factors for a cost-effective operation. The paper introduces current status of coal gasification in China, lining structure of slagging gasifiers and performance of refractory lining. It also summarizes the major factors impacting on refractory wear in slagging coal gasifiers in four Chinese chemical plants, based on ten years of industrial experience. The utilizability is discussed in terms of cost-effectiveness of high chromia refractories and possibility of the alternatives.

Jan 1, 2004

By G. V. Sirianni, G. E. Viens, R. A. Campbell, G. N. Banks

A combination shaft-electric furnace for the smelting of ores and the melting of metallized feed is being developed at the Mines Branch. When iron oxide pellets are smelted in this unit, they are preheated and partially reduced in the shaft before being transferred to the electric furnace where smelting is completed. Also, limestone flux added with the pellets is-preheated and calcined in the shaft. It has been demonstrated that, in smelting iron oxide in this unit, the throughput of the 250-kva electric furnace can be approximately doubled and the amount of electrical energy required can be very significantly reduced when the shaft furnace is operated in conjunction with the electric furnace. These benefits are achieved mainly by utilizing the sensible heat and latent energy contained in the arc furnace off-gases.

Jan 1, 1971

During industrial copper electrowinning, a fraction of the electrolyte becomes entrained with the oxygen gas bubbles that are evolved at the anodes. The fraction of entrained bubbles increases from the bottom of the anode to the top, resulting in a bubble distribution that appears as an inverted wedge between the cathode and anode. Since the bubbles act as insulating spheres, electrolyte resistance increases from the bottom of the electrodes to the top resulting in correspondingly higher local current densities and uneven copper growth along the cathode. To counter-act the inherent tendency toward excessive copper growth near the bottom of the cathodes, the use of tapered anodes was examined. The potential improvement in cathode current distribution was evaluated by comparing the primary current distributions for 2-D computer models of a copper electrowinning cell with plate shaped anodes against one with tapered anodes.

Jan 1, 2007

By A. Hayatdavoudi, K. G. Sawant, F. Boukadi

"In this work, we found that contact between shale and water results in development of micro fractures. Based on results of experiments on Pierre shale, we conclude that appearance of micro fractures begin with saturation of capillaries, ionic and diffusive transport of water into the shale clays and once capillaries are saturated, the cause of micro fracture propagation is the conversion of ionic activity/exchange to excess pressure that did not exist before fracking. Based on these findings, the spread of micro fractures appear to be a time-dependent phenomenon which has not been addressed in the existing macro/micro fracture models.INTRODUCTIONShale has often been involved as a hazard in drilling operations. This hazard can be defined as “destabilization” of shale. When contacted with water-based drilling fluids, some shales readily swell and sometimes, cause the wellbore to cave-in, slough, wash-out, close, and pack-off, impeding the drilling by sticking the drill-pipe. However, once drilling reaches the desired depth or length, the casing is set, cemented, and perforated, and then actually we wish to initiate fractures and destabilize the shale formation, using hydraulic fracturing.Clays constitute a major portion of minerals in shale. These clays contain a large amount of free energy which is the main factor for “slick” water adsorption/absorption. In fact, the reason for using “surfactants” in hydraulic fracturing fluids is to make the penetration of the fluid into the capillaries much easier, thus water meets with less resistance to enter the small capillaries. Also, the result of high capillary suction pressure is due to small Angstrom size capillaries, smaller pores and presence of ions and hydrateable metal atoms. The free energy is thus, related to all the above mentioned and other affects. Capillary pressure, osmotic pressure and other pressures are responsible for creating the micro-fractures in shale, thus, increasing the network of micro-fractures which leads to more gas production. The objective of this study is to evaluate the pressures of the individual ions which are released by the diffusing “slick” water into shale. These pressures would be added to the above mentioned capillary pressure, osmotic pressure, bacterially-induced pressures, chemically-induced reaction pressure, pressure due to exchangeable ion-transport, pressure due to release of free energy of solvation and eventually to the pore pressure as suggested by Terzaghi’s equation."

Jan 1, 2015

By V. Schwinn, P. Fluess, N. Cauderlier, J. Bauer

From a strategic and economic point of view, the development of fine grain high strength steels for long distance pipelines is intensified world wide to satisfy the demand for natural gas in the future.The project related property profiles based on strength, toughness, crack arrest and sometimes resistance against HIC at defined design temperatures require an effective structural refinement using advanced steelmaking and processing in the rolling mill. The microstructure of modern line pipe steels ranges from ferritic pearlitic to ferritic-bainitic and structures where bainite is the dominant component, possibly upgraded by secondary phases. This paper illustrates microstructures and properties of recent orders on line pipe steels both for onshore and offshore application using different processing routes in the plate mill. Examples will be given for SAWL 485 offshore grades, X65 HIC and X70 HIC onshore grades, respectively. Finally, production results of a recent X80 order will be presented.

Jan 1, 2005

By J. Stumper

The control of the distribution and movement of liquid water is crucial for increased reliability and durability of PEM fuel cells: whereas the proton exchange membrane requires a minimum amount of liquid water for optimum operation, water excess in the GDL will impede reactant gas access to the catalyst layer thereby reducing performance. In order to understand the relationships between water management on one hand and fuel cell performance and durability on the other, Ballard has been developing a number of minimally invasive techniques that can throw light on the role of liquid water for both cell performance and durability. This paper introduces a novel measurement method that can provide information about the amount and distribution of liquid water under operation. It is shown how the MEA Resistance and Electrode Diffusivity (MRED) method can be used to determine i) the amount of liquid water in the fuel cell, ii) the pure ohmic cell resistance and iii) the O2 -diffusivity of the cathode. Furthermore, through a combination of the MRED method with current mapping it is possible to determine spatially resolved MEA resistance profiles.

Jan 1, 2005

By D. Atkinson

"Porphyry molybdenum-tungsten mineralization on the east flank of Hudson Bay Mountain crops out over 5 km2 and is intersected to depths of 2 km. Features such as a hornblende-biotite aureole, mineralogical zoning and dike, vein and fracture geometries within lithologies of the Middle to Lower Jurassic Hazelton Group and Cretaceous Skeena Group reflect an intrusive complex, the Upper Cretaceous to Early Tertiary Hudson Bay Mountain stock which has been intersected by drill holes. The stock is believed to be the mineralizing agent. A southeast-dipping granodiorite sill has been outlined by drilling within the Hazelton Group. Molybdenite and scheelite veins cut all rock types; however, the granodiorite sill hosts a higher density of fine-grained, banded, quartz-molybdenite and pegmatitic quartz-molybdenite veins reflecting a competency contrast between the intrusive sill and other country rock. Due to the relative abundance of these veins, grade is higher within areas of the sill. Above the 15000£ cross-cut 20.6 million tonnes grading 0.401% MoS2 and 0.041% W03 have been defined. During exploration of the deposit sampling procedures had to be adjusted because of the nugget effect attributed to drill intersections of banded and pegmatitic veins.IntroductionMolybdenite was discovered in outcrop at the foot of Kathlyn Glacier on Hudson Bay Mountain and first reported by the Geological Survey of Canada in 1944. The deposit has several names: Hudson Bay Mountain or Glacier Gulch, both after its location, and Yorke-Hardy after the original staker.The deposit is on the east flank of Hudson Bay Mountain, 9 km northwest of Smithers, west-central British Columbia, within NTS area 93L/14 (54° 49' North, 127° 18' West, Fig. 1). Hudson Bay Mountain, on the southern edge of the Bulkley Valley, is a dominant topographical feature reaching 2590 m elevation. Mineralization is partly overlain by the Kathyln Glacier which is visible from Highway 16. Access to the 3100 m of underground development is from a portal at 1066 m elevation on the east slope of Hudson Bay Mountain."

Jan 1, 1995

By P. Wanjara, M. Xiao

During fusion welding of aluminium alloys, the avoidance of defects (such as porosity, oxides, hot cracking, undercutting) as well as the ability to optimize the microstructure-property characteristics in the assembly are critical for the stringent manufacturing specifications in the aerospace industry. In this work, aluminium alloy (AA) 2024 was electron beam welded autogenously as part of a study to determine the influence of parametric conditions on the characteristics of the heat affected and fusion zones to obtain optimal welding conditions. In particular the evolution in the weld geometry, microstructure and mechanical properties were examined as function of the processing conditions, including beam current, beam focus, beam oscillation, linear heat input and welding speed. For optimized parametric conditions, microstructural examination of the joints revealed narrow fusion and heat-affected zones comprising of dendritic structures without the occurrence of defects that enabled a maximized joint efficiency.

Jan 1, 2006

By G. W. H. Norman

"The La Corne molybdenite-bearing veins, discovered in 1915, lie halfway between Amos and Val d'Or near the southwest corner of La Corne township, Abitibi county, Quebec. The Molybdenite Reduction Company, which carried on operations during 1927 to 1930, sank a 200-foot inclined shaft to develop the property and produced about 22 tons of concentrntes from a 30-ton mill during 1929. Hollinger Consolidated Gold Mines, Limited, carried on further underground exploration in 1930. The Molybdenite Corporation of Canada drilled a part of the property in 1938 to 1939 and produced 1 ton of concentrates in 1938. Wartime Metals operated the property from 1942 to July 15, 1945. At this time the mill was enlarged to treat 200 tons daily. Molybdenite Corporation of Canada since July 15th, 1945, have continued the operation of this property and have revised the mill flow-sheet in order to produce both a bismuth and a molybdenite concentrate.The production for the period 1942-1946 is as follows:Total molybdenite production from the mine in the 1942 to 1946 period was about 4,127,400 lb.The La Corne deposit occurs at the northwest contact of a small mass of biotite granite with biotite schist. The form and extent of the biotite granite mass is concealed by a wide sand plain that extends northwest and west from the deposit and overlies bed-rock except in four small outcrop areas. These are spaced 1,000 and 2,000 feet apart along a narrow strip extending 5,000 feet south from the mine. The outcrops suggest that the granite must be at least 1,500 feet wide and 3,000 feet long northeastward. Where exposed in the mine workings the contact dips 70°N.W., but is not a sharply defineable feature due to the presence of numerous granite dykes and tongues in a zone of biotite schist 100 feet wide along the margin of the granite. The biotite schist in the few outcrops that flank the north and south sides of the granite strikes northeast and dips 60° to 70° S.E."

Jan 1, 1954

By J. Cueto, M. Torres, J. Fernandez, J. Nuñez, C. Salgado, G. Zarate

Anglo American has used the extractant M 5640 in all the Divisions, which is an aldoxime modified with TXIB formulation, except in Los Bronces, where an aldoxime modified with tridecanol (TDA) formulation is used. It is a well-known fact that the aldoxime degrades while the modifier does not. With time the aldoxime/modifier ratio decreases significantly depending on the operating conditions of each plant. In order to evaluate the effect of this increasing modifier content in the organic of the plant, especially in the organic losses, a complete metallurgical test work program was started at laboratory and pilot plant scale. Results showed that the addition of aldoxime without modifier does not affect the chemical performance of the organic phase, but there is a significant decrease in the viscosity and density of the organic phase. Based on the results obtained in the metallurgical program, it was decided to run plant scale tests at both SX plants, Mantos Blancos and Mantoverde. In these tests, instead of adding the usual formulation of aldoxime modified with TXIB to maintain the organic inventory, CuPRO MEX™ 3406 which is an aldoxime without modifier is going to be added until the original aldoxime/modifier ratio is reached. The plant tests started in April 2013 at Mantos Blancos and in June 2013 at Mantoverde and will last 18 months. The results obtained at the laboratory and pilot plant scale, together with the preliminary plant test results, are discussed in this paper.

Jan 1, 2014

By G. Itoh, S. Fukasawa

The Al-Zn-Mg alloys have been known to be susceptible to stress corrosion cracking (SCC), which is based on intergranular cracking arisen from hydrogen embrittlement (HE). The mechanism of HE has not been fully understood yet. In order to elucidate the mechanism of HE, we need to investigate the behavior of hydrogen in the alloys. In this paper, behavior of hydrogen in an Al-5.8%Zn-2.4Mg alloy was investigated by means of hydrogen microprint technique, a method to visualize location of hydrogen emission from specimen surface as silver particles. One side of the tensile test pieces was electrolytically polished and then covered with photographic emulsion. Hydrogen was pre-introduced into the test pieces from opposite side by cathodic electrolytic charging for 30min. Then, the test pieces were stretched with continuing the charging. After that, the specimen was fixed, rinsed, dried and observed with a scanning electron microscope. As a result, silver particles were observed on some grain boundaries.

Jan 1, 2015

By R. Burnette

Gold has been mined from a variety of deposit types that range in age from Archaean to Recent. The large variability in the geological settings of the gold deposits implies transport and concentration of gold by magnetic, hydrothermal and sedimentary processes. The factors that control the concentration of gold at certain sites and the grade estimation thereof remain major topics of debate. Due to the complex nature of the Witwatersrand Basin a mineralogical study, including mineralogical, petrographic and geochemical investigation was launched on TauTona Mine in order to characterize the various reef facies. The aim of the investigation was to determine if a correlation could be found between macroscopic characteristics of the reef, hanging wall and footwall, and the microscopic nature of the ore (especially gold grade). Petrograpgic and mineralogical results indicate that a correlation exist between gold, detrital and hydrothermal sulphides, uraninite, carbon, detrital heavyminerals and phyllosilicates. No correlation exist between gold and Mg, Fe or S. It appears that clast supported reef is of higher wade than matrix supported, but more work is suggested. No correlation exists between reef thickness and grade. The reef samples had the lowest phyllosilicate content compared to the hanging wall and footwall samples with pyrophyllite the most dominant. All of the correlations diagrams showed significant scatter and suggests a multi- factorial mineralization model. Gold distribution is also controlled by sedimentary features and thus it is not possible to select a single model for the formation and distribution of gold. It is evident that both sedimentary and hydrothermal factors influenced the mineralization and gold distribution on TauTona mine. It is thus essential that all related theories be incorporated in the development of a grade prediction model.

Jan 1, 2011

By Derrin A. Auerswald, Jacolien P. Wyethe, Nanne M. \/egter

Base and precious metal refineries often produce effluent solution and slurry streams containing between 50 mg/L and several grams per liter of base metals. Metals have historically been precipitated from these streams with lime to produce effluent streams at pH values between 8 and 9. This effluent treatment process generally does not remove alkali and alkali-earth metals or halides efficiently and with more stringent environmental legislation, more sophisticated effluent treatment plants must be considered which could for example incorporate sulphate removal with ultra-filtration, or the SavminTM process, followed by reverse osmosis for the removal of halides. The flowrates of effluents are often high and if base metals can be recovered before neutralization, the revenue generated from this stream can reduce the cost to produce clean water significantly, and in the case where high concentrations are disposed of, result in a profitable operation. As an add-on to an existing the plant the recovered metal is upgraded and recycled to the plant, but the production of a saleable metal can also be considered. Technology selection for metal recovery depends on the composition and flowrate of the effluent, but could incorporate resin-in¬pulp or other ion-exchange technology; precipitation as sulphides, hydroxides or carbonates; or solvent extraction. This paper describes, as a case study, the technology selection process and uses data from Zincor. Zincor is a division of Exxaro Base Metals (Pty) Limited, a subsidiary of Exxaro Resources Limited.

Jan 1, 2011

By M. A. Hardie

"CASES and mixtures of them are so common and so much a part of everyday existence that they become so taken for granted that their individual characteristics and idiosyncrasies rarely become of curiosity to others than those involved in tl1eir production, processing, treatment, transportation, and for utilization. The use of the most common and universal mixture of gases -air -is begun at birth by ail living creatures and their discontinuation of its use terminates existence. Modern man rides on air in his tires, rides through it for high-speed transportation, and uses it for his comfort in the heating and air conditioning of his domicile. It is neither the aim nor the in-tent, in the next few moments, to provide a panacea for even a portion of the problems inherent in the gas industry nor to delve deeply into any particular facet of its diversities. The purpose is primarily to touch upon some of the peculiarities and generally to consider approaches to employ in the pursuit of solutions."

Jan 1, 1959

By C. C. Walden, D. W. Duncan, P. C. Trussell

Thiobacillus ferrooxidans released copper from -400-mesh chalcopyrite at a rate of 54 mg/I/hr. Any flotation chemicals remaining on the concentrate did not inhibit the leach rate. Zinc rougher tailings were also leachable. With bacteria, 75 per cent of the zinc and 68 per cent of the copper came into solution. In the sterile controls, only 16 per cent of the zinc and 10 per cent of the copper were released; 100 per cent of the copper and 36 per cent of the zinc were leached from pyrite cinders through the action of bacteria, and 17 per cent of the copper and 10 per cent of the zinc were solubilized in the sterile controls. Less than 0.027 per cent of ~he iron came into solution. The majority of the copper in a converter slag was acid-soluble, but a reverberatory slag responded to microbiological leaching. About 62 per cent of the copper came into solution, compared to 12 per cent in the sterile control. The various factors influencing the rate and extent of microbiological leaching are discussed.

Jan 1, 1966

By E. S. Moore

Introduction The geology of the Sudbury nickel field has been studied extensively, but there are few reports dealing with the structure of the interior of the basin. It was not until the Treadwell-Yukon zinc-lead deposits were discovered that attention was strongly directed toward the large-scale faulting that has split the basin parallel to its long axis. This faulting has been responsible for the , ore deposits in the basin and it may be regarded in many ways as the most important geological event, next to the intrusion and differentiation of the nickel eruptive sheet, that has occurred in the Sudbury region. The early reports on the nickel region by Bell, and Barlow, were chiefly concerned with the nickel-copper ores and with the formations of the region. Coleman was the first geologist to map the nickel eruptive as a continuous sheet around the belt and to emphasize its basin character. On the map accompanying his later report, he shows an important offset in the nickel eruptive at its southwest end, where the large fault cuts this portion of the basin, but the fault was not traced into its interior, as little detailed work was clone in the basin at that time. No ore-bodies had been developed outside of the nickel-copper deposits associated with the norite when the map was prepared, and attention was mostly concentrated on the nickel eruptive. Coleman did, however, map and name the various formations found within the basin and, in general, his delineation of these has remained the standard for prospectors and other workers in the field until the present day.

Jan 1, 1930

By M. Nakai, G. Itoh, R. Yamada, A. Kurumada

In order elucidate the mechanism for poorer fatigue properties of 7000 series aluminum alloys than those of 2000 series alloys, the effect of the test environment on the fatigue crack growth of the two series alloys was investigated, considering the relationship to hydrogen embrittlement. Two 7075-type and four 2024-type alloys were T6-tempered and T4-tempered respectively, and subjected to fatigue crack growth tests in moist and dry environments. When tested in moist air, fraction of intergranular crack path was higher in the 7075-type alloy with coarse equi-axed grains than in the 2024-type alloy with similar microstructure. This was in accord with the larger crack growth rate in the 7075-type alloy. Both the intergranular crack path fraction and the crack growth rate were decreased by changing the environment to the flow of nitrogen gas. Thus, the large fatigue crack growth rate of the 7075-type alloy is attributable to hydrogen embrittlement.

Jan 1, 2015

By D. Rylander

The operation of Quarry and Aggregate sites are similar to factory production, since it contains sequential production processes, tasks and activities to produce the output product. Compared to the plant though, the quarry processes are generally not synchronized and controlled towards the overall throughput of the site in real time. Some quarries control parts of the production but do generally not utilize real-time technologies for the whole site and all its activities. This fact indicates a general improvement potential in increased productivity at quarry sites, but also unsolved challenges for the same reason. The main contribution of this paper is the presentation of a Lean based method for how to describe the processes to identify control improvement potential within a site. The aim of the identified improvements is to increase overall site productivity by optimizing site, fleet and machine utilization towards the overall throughput, and minimizing operational expenses and inventories. Further the paper exemplifies the method?s usability with field studies at operational quarry plants successfully identifying and quantifying potential wastes and improvements. In addition the identified productivity improvements based on increased control and automation indicate challenges and needs in wireless communication and sensing technologies.

Aug 1, 2013