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By W. A. Grell

"The oxygen meter has been in use at MacLeod Cockshutt Gold Mines for over a year, At MacLeod about 200 tons per day of reground concentrate containing roughly 10% pyrrhotite and 20% pyrite is cyanided in four 181 x 18' Dorr agitators. A survey by the Department of Mines showed that oxygen content of some of the agitators was rather low. Experience with our oxygen meter indicates that the oxygen content must at times have been too low for good gold dis solution.We have found that in winter, when pulp temperatures drop to about 50° F, oxygen saturation in the agitators is not difficult to maintain. In summer, however, when pulp temperatures rise to 70or 75°F, the oxygen content will drop very readily. It was found that a high oxygen content can be maintained readily if the pulp is sufficiently dilute. Thus at 50° F, a pulp of specific gravity 1. 75 i.e., about 55% solids, will saturate; but at 70 or 75° F, the specific gravity must be decreased to 1 .45, equivalent to about 40% solids, in order to maintain saturation. Very thick pulps, such as thickener underflows, are noticeably difficult to saturate in the laboratory, and lose their oxygen rapidly.Clear solutions, on the other hand, absorb oxygen readily and hold it. The primary thickener overflow, before agitation, is 100% saturated; after storage of 3 to 4 hours it is still 100% saturated at re clarifier tank. Barren solution after spraying in a launder is 100% saturated.We have not yet attempted to determine what percentage saturation is necessary for good extraction, but it is known that there is a point at which extraction decreases rapidly. So far, the measures required to maintain over 80 or 90% saturation have coincided with measures required to hold the reducing power to the point believed necessary."

Jan 1, 1964

By A. D. McKay

Uranium exploration expenditure in Australia reached a record level of A$220.5 million in 2008, which has subsequently declined to A$185.2 million for the year ended 30 June 2009. Recent discoveries include: Ranger 3 Deeps east of Ranger open pit (Northern Territory), Pepegoona and Yadglin sandstone hosted deposits (South Australia), and Thunderball project (Northern Territory). Australia?s Reasonably Assured Resources recoverable at costs of <US$80/kg U at June 2009 are estimated to be 1,210,000 t U, 4% higher than the estimate for December 2008. The main additions were in the south eastern portion of the Olympic Dam orebody. The Olympic Dam Expansion is based on a large open pit and will increase output to an annual capacity of 19,000 t U3O8; 750,000 t copper; 800,000 ounces gold. The Four Mile in situ recovery project was approved in July 2009. An ion exchange facility is to be constructed at Four Mile and uranium-bearing resins will be transported to the Beverley plant to recover the uranium. Recent developments at Ranger mine, and Honeymoon, Oban and Yeelirrie projects are discussed.

Aug 1, 2010

Polymer electrolyte membrane (PEM) fuel cell has increasingly become the potential choice of zero-emission power source for portable, mobile and stationary co¬generation applications. However, technical barriers need to be overcome before its widespread commercialization; cost reduction and performance improvement including reliability are the two key areas, that can be realized through better cell/stack design and improved understanding of the transport processes occurring inside the individual cells and stacks. In this presentation, we will provide an overview of various cell/stack models that are available in the literature, their strength and weakness, and then present a comprehensive multi-species, multi-phase and multi-dimensional formulation of a single PEM fuel cell, with consistent and systematic formulation for all the regions involved, including the solid bipolar plates, gas flow channels, the electrode backing layers, the catalyst layers and the electrolyte membrane. Such a detailed approach allows us to extract sufficient information to the analysis of a stack of PEM fuel cells. Stack model will be presented that investigates the various stack designs and flow configurations, and the optimal stack design based on the present study will be described. Also some innovative cell/stack designs will be featured.

Jan 1, 2005

By H. Saari, M. Pates, P. C. Patnaik, A. Merati

Single crystal nickel-base superalloys such as PWA1484 exhibit superior performance compared to conventional superalloys, and are used extensively in turbine blade applications requiring good high temperature properties. The life of these blades is typically limited by cracks and erosion. Due to the high cost of these blades, welding techniques are being considered to weld/repair worn components, extending their useful lives and delaying the need for expensive replacement components. However, the sensitivities for solidification cracking and post weld heat treatment cracking are relatively high in these alloys. Electron beam (EB) welding can deliver concentrated heat sources and has the potential to address these issues. Numerous welding trials and structural tests must be conducted to identify the optimum method and welding parameters. Weldability is studied over a range of material conditions, welding parameters, and directions. The influence of welding parameters on the fusion zone microstructure and resultant weldability is investigated using combination of microscopic examination and micro-hardness testing. This paper summarizes some of the results of a feasibility study conducted to understand the effects of welding parameters on localized microstructural features, cracking sensitivity, and mechanical properties of autogenously EB welded coupons of single crystal PWA1484.

Jan 1, 2004

By K. Yoo

Chalcopyrite is the most abundant copper sulfide mineral, which is normally processed using pyrometallurgical methods (i.e., smelting) to produce copper metal. Smelting has several major disadvantages, such as high gas-handling costs, high capital costs, saturation of sulfuric acid market, and inability to treat low-grade concentrates and to recover some by-products, such as zinc, nickel and cobalt. The development of hydrometallurgical processes for chalcopyrite is desirable to overcome the problems of smelting. Because chalcopyrite is refractory, the leaching rate for chalcopyrite is very low. Therefore, increasing the leaching rate has been extensively investigated, both in sulfate and chloride media, as well as in the presence of bacteria. Chloride leaching processes have shown relatively high leaching rates. The mechanism of the chloride leaching process has been investigated, but the behavior of chalcopyrite leaching in chloride solution is not clear. Therefore, the effect of the solution redox potential on the leaching rate of chalcopyrite in chloride solution was investigated. In the present study, leaching experiments were carried out using 0.1 M chloride solutions and the results indicate that high leaching rates of chalcopyrite can be achieved at relatively low solution redox potentials.

Jan 1, 2007

Falling asleep at the wheel of a moving vehicle is not only dangerous but avoidable. It is implicated in up to 30% of all road fatalities in general and up to 65% of mining incidents involving haulage trucks. These types of crashes normally result in serious injury and/or fatality due to the lack of breaking that occurs. However, when a 300 tonne haul truck has a sleep related crash it is not only the safety of the driver that has a high price but also the commercial impact on the mines? productivity and efficiency. We have been developing our ASTiD technology which stands for the Advisory System for Tired Drivers to seamlessly integrate in to Modular Mining?s Dispatch system to provide real-time early warning fatigue risk management. The benefits being driver shift optimisation, sustained productivity and of course less accidents. By monitoring the drivers alertness levels in real-time using ASTID, the Dispatcher becomes empowered to make critical, management decisions that will ultimately prevent serious injury or loss of life and the driver gets to stop when he needs to and not just when he is supposed to. This paper shows how this integrated solutions works.

May 1, 2011

By M. Gruber-Pretzler

Technical Sn- bronzes tend to form both macrosegregations and microsegrega¬tions during DC-casting due to the particular thermodynamic properties and kinetics of phase transformation. As a result a heterogeneous cast microstructure forms that is some¬times a reason for a decrease in workability. The extent of macrosegregations in DC-casting can effectively be influenced by casting parameters like casting velocity, primary cooling or inlet geometry which in fact change the relative flow between the melt and the forming solid. In order to understand the influence and interaction of the related phenom¬ena, simulation methods are applied. The solidification of the strand as well as the forma¬tion of macrosegregation are simulated with a two phase volume averaging model. The velocity field of the melt flow is explicitly calculated by solving the corresponding mo¬mentum conservation equations. Within the mushy zone the local formation of microseg¬regations in the presence of feeding flow is estimated. The thermodynamics of the Cu-Sn system is accounted for and it is distinguished explicitly between interface and average concentrations. To investigate the influence of feeding flow on the formation of mac-rosegregations, a study has been performed. Based on this result, the phenomena of mac¬rosegregations are described in a detailed discussion.

Jan 1, 2007

By Jeffrey D. Smith, William G. Fahrenholtz, Jose M. Soto

Interactions between A356 aluminum (Al-Si alloy) and dense fused silica (FS) riser tubes used for low-pressure casting of aluminum alloys were evaluated using a sessile drop approach. The tubes have a short service life, but cost and thermal shock resistance make them an effective solution. The main problem encountered during use is the reaction of aluminum with silica to form alumina and silicon, which causes failure. Tests have been conducted on as-fired (uncoated) and modified (coated) tubes. Experiments were carried out in a horizontal furnace at 1225°C under argon to minimize the effect of the aluminum oxide on the interactions at the alloy-silica interface. Images of the drop were acquired and contact angle values were estimated for uncoated and coated samples, but no significant differences in the contact angles were observed. Scanning electron microscopy revealed the presence of cracks at the interface between the reaction zone and the unreacted silica. The presence of reaction products (silicon in the reacting alloy and aluminum in a reaction zone between the alloy and the unaffected silica) has been confirmed using energy dispersive spectroscopy. A two layer coating system was found to be effective in reducing penetration of the aluminum alloy.

Jan 1, 2004

By S. C. Bouffard

Barrick&apos;s Zaldivar operation in Chile produces copper by heap leaching, solvent extraction, and electrowinning. The heap consists of a dynamic pad, and its stacking and operating conditions have changed over its 11 years of operation. These changes have included pad re-mining midway through the cycle, tightening of the irrigation drip lines, an increase of the coarseness of the particles, and an increase of the heap height. This paper reviews the heap operating data to understand the effects of these changes on the kinetics and recovery of copper minerals. Field tests demonstrated that neither re-mining nor tightening the irrigation grid added value for both low and high grade oxide and sulfide ores. The P80 of the feed ore was increased by 0.8 mm, which did not reduce the copper recovery of oxide and sulfide ores. The increase of the heap height above 8 m lowered moderately the copper recovery from sulfide minerals, and very slightly the recovery from oxide minerals. Despite the lower recovery, the higher tonnage stacked in the taller heap increased the copper output. Optimizing the chemistry of the agglomeration and feed solution holds more promise for increasing the copper recovery than the above physical changes.

Jan 1, 2007

"Adopted in 2003, theses guidelines are intended to assist the Qualified Person(s) in the planning, supervision, preparation and reporting of mineral resources and mineral reserve estimates. The report is divided into two broad sections “General Guidelines” appropriate for most metals and “Guidelines Specific to Particular Commodities” for potash, industrial minerals, uranium and coal. “These guidelines are reference in the Companion Policy of NI 43-101 with a statement that a qualified person classifying a mineral deposit as a mineral resource or mineral reserve should follow them.”Executive SummaryThe following is a summary, in table format, of the main elements of the Estimation Best Practice Committee's report ""Estimation of Mineral Resource and Mineral Reserve Best Practice Guidelines"". While the summary table is provided for convenience, the Committee recommends that the report be read in its entirety and the table summary not be used as a stand alone document. These guidelines are not intended to be either prescriptive or exhaustive. They do not preclude innovation. Preamble: These guidelines have been prepared by the Canadian Institute of Mining and Metallurgy and Petroleum (CIM) led Estimation Best Practices Committee. They are intended to assist the Qualified Person(s) (QP) in the planning, supervision, preparation and reporting of Mineral Resource and Mineral Reserve (MRMR) estimates. All MRMR estimation work from which public reporting will ensue must be designed and carried out under the direction of a QP in accordance with National Instrument 43-101 (NI 43-101) and related forms. A QP is defined in NI 43-101 as ""an individual who is an engineer or geoscientist with at least five (5) years of experience in mineral exploration, mine development, mine operation, project assessment or any combination of these; has experience relevant to the subject matter of the mineral project and technical report; and is a member in good standing of a professional association"". Disclosure of MRMR estimates is to be made in accordance with industry standard definitions approved by the CIM (the CIM Standards adopted by the CIM Council in August 2002) which have been incorporated by reference into NI 43-101."

Jan 1, 2003

By M. J. Bennett

"The Quemont mill is primarily a differential flotation plant in which copper, zinc ·and pyrite concentrates are recovered. Native gold and silver are associated in the form of very small particles with all the minerals contained in the ore: chalcopyrite, sphalerite, pyrite, pyrrhotite and even with the gangue rock.The proportion of the precious metals associated with chalcopyrite is such that the best recoveries we can obtain in our copper flotation concentrate are about 68 percent of the gold and 51 percent of the silver in the ore. In order to improve the total recoveries of precious metals it is necessary for us to float a pyrite concentrate and treat it by cyanidation for the extraction of whatever gold and silver we can obtain in this manner. In spite of the fact that we regrind this concentrate to 75 percent minus 325 mesh, it is difficult to extract much more than half of the gold and silver present in the pyrite concentrate by cyanidation, due to the extremely fine association of the precious metals with the pyrite.In 1963 we produced 86, 853 ounces of gold by flotation alone, and 14, 581 ounces by cyanidation. These amounts are equivalent to 67. 74 percent and 11. 37 percent respectively of the total gold in the mill heads. Comparable figures for silver are 325, 598 ounces by flotation and 99, 448 ounces by cyanidation; and 51.37 percent and 15.69 percent respectively.The total annual value of these metals (ie. $4, 000, 000) qualifies Quemont as a precious metal producer of some note. On the other hand, it is evident that by far the greater proportion of our gold and silver production is contained in copper flotation concentrates. When the income from our copper and zinc values is also considered, the much greater importance of flotation compared with cyanidation in our operation may be appreciated. This explains why most of our work on controls has been carried out in our flotation mill, rather than in our cyanide plant. Some of the controls installed there could, of course, be employed in either type of operation."

Jan 1, 1964

By P. Amelunxen, E. Herrera, L. Hill, J. Vanderbeek

It is well-known that the particle breakage mode that occurs in a semi-autogenous mill is significantly different from that which occurs in a ball mill, enough so to warrant very different lab scale breakage tests and scale-up models. This phenomenon, at the plant scale, leads to changing process constraints depending on the particular properties of the ore. For example, hard or coarse ores might bottleneck the SAG/AG mill throughput, while the ball mills might constrain throughput when milling soft or fine ores. Because the power draw of a ball mill is fairly constant compared to that of a SAG/AG mill, periods of SAG/AG mill bottlenecks lead to increased ball mill circuit specific energy consumption and a finer grinding circuit product size, which together constitute a loss of efficiency of the overall process. Because HPGR circuit throughput is less sensitive to changes in ore hardness, this situation is less common or severe in those circuits. Furthermore, the ball mills are somewhat decoupled from the upstream crushing circuits through the use of surge bins, which also helps to mitigate this effect. As a result, ore hardness variability constitutes a significant cost penalty that should be applied to SAG mill/ball mill/pebble crusher SABC circuits when evaluating the relative economics of different grinding circuit configurations. Nevertheless, the issue is by-and-large ignored, because most current HPGR trade-off studies are based on averaged ore hardness parameters. This paper provides an estimate of the magnitude of this penalty for a typical operation by using Monte Carlo simulation methods and plant data from Freeport-McMoRan’s autogenous, semi-autogenous, and HPGR-based comminution circuits. A case study from an in-house 96K t/d sulphide project is presented to illustrate the concept. It was found that by including variability effects, the trade-off NPV of the HPGR circuit over that of the SAG mill circuit increases to $84 million from negative $33 million, effectively reversing the original decision of selecting a SAG mill circuit for the fixed hardness case.

Jan 1, 2012

By U. Troncoso

Mantoverde is a heap leach-SX-EW operation that was commissioned in December 1995 at a production rate of 42,130 ton of copper per year and 5.4 million ton of ore per year. Copper production has been steadily increased to reach 62,000 ton in 2005. The forecast copper production for 2006 is 60,300 ton for an ore treatment rate of 9.5 million ton. A first dump leach operation was started in 1999 at a production rate of 1,922 ton of copper. A second dump leach operation was started in early 2002 at a production rate of 2,805 ton of copper. Dump leach production will be increased over time to as much as 24,000 ton of copper. Several improvements in the heap leach process have been implemented to cope with the higher ore throughput and copper production. However, the solvent extraction plant has remained unchanged which has resulted in a lower availability of raffinate solution and, as a consequence, in longer leach cycles. Different studies have been undertaken in order to optimize the solution management system at Mantoverde, including column test work aimed to reduce the leach cycle and solvent extraction plant modifications aimed to increase the raffinate solution availability. The test work program and the economical evaluations carried out, as well as the conclusions and recommendations obtained, are discussed in this paper.

Jan 1, 2007

By M. Piard

The scarcity of literature referring to mines in the Rockies has compelled the writer to co-ordinate information and advice taken at the very source. Help was gladly given by active inspectors and mine bosses. Although the field is unimportant at the present time, due to its distance from markets for raw coal, it is quite worthy of the attention it is receiving from two continents; for, with the commercial synthesis of liquid fuels, it would become the largest fuel laboratory in the world, provided, of course, that freight cost drops to a low comparative level. As explained below, there are no obstacles to economical and safe operation under anything like the typical outcrop shown in Figure 1. Although coal dust is probably more dangerous in the Rockies than anywhere else, the damp outcrops afford means of control. The abundant gas may be bled to the open air, and the rigid roof will settle gradually under a wide span of opened outcropping. The Panel Retreating Wall The Measures: Coal measures having an attitude similar to that shown in cross-section in Figure x are characteristic of the active coalfield on the Alberta side of the Rockies, and they are also found on large tracts of undeveloped land west of the divide. The small anticlines, not shown in the cross-section, do not affect the progress of a pillar line, provided their crests are connected to the atmosphere by drainage bore-holes.

Jan 1, 1928

By J. C. Glandus, N. Tessier-Doyen, M. Huger

The Young&apos;s modulus of bi-phased model materials (vitreous matrix containing spherical alumina inclusions) have been determined by two complementary approaches: experimental and analytical. If the matrix and inclusions exhibit close coefficients of thermal expansion, the experimental results lie in the vicinity of the lower bound of the Hashin & Shtrikman&apos;s model. If there is a dilatometric disagreement between the components, untypical behaviors, similar to those obtained for a family of industrial refractory materials, were observed when the temperature varies.

Jan 1, 2004

By Jian Li, V. Y. Gertsman, David C. Katz, M. Elboujdaini

Analysis of stress corrosion cracking (SCC) usually involves high-end analytical tools including scanning electron microscope (SEM) and analytical transmission electron microscope (TEM). In recent years, focused ion beam microscope (FIB) has found many applications in materials science fields. In this study, high-resolution FIB images have shown details of crack morphology and a plan-view TEM specimen containing the selected crack-tip was successfully prepared. The preparation of cross-sectioned samples containing crack tips was of paramount importance for subsequent TEM analyses.

Jan 1, 2004

By J. D. Bateman, A. S. Dadson

"The Giant claims are on the west side of Yellowknife bay about 1 ½ miles north of the settlement of Yellowknife. They were staked in 1935 by prospectors in the employ of Burwash Yellowknife Gold Mines, Limited, and were transferred to Giant Yellowknife Gold Mines, Limited, in 1937, on the incorporation of that Company. During the period 1936 to 1940 a number of surface discoveries were investigated by trenching, test pitting, and diamond drilling. A shallow inclined shaft was sunk on the Brock zone, a system of narrow and irregular quartz veins, and some 75 tons of high-grade ore was mined and shipped to the Trail smelter. In 1943 management control was acquired by Frobisher Exploration Company, Limited. An intensive campaign of diamond drilling was commenced in January 1944 and carried on continuously for 2 years. This drilling indicated the presence of substantial gold orebodies lying within well-developed shear zones. Two shafts, 1 ¼ miles apart, were sunk during 1946 and underground development started on two of the orebodies.The claims are underlain largely by rocks of the Yellowknife greenstone belt, which extends from the shore of Great Slave lake along the west side of Yell ow knife bay and northward . The most conspicuous structural features are the steeply dipping late faults. The chief of these is the West Bay, which bisects the greenstone belt at an acute angle and crosses the southern part of the Giant group. At the 'big bend' near the west boundary of the claims there is a remarkably sudden change in the strike of the fault, from about 12° N.W. to about 3° N.E. The apparent horizontal displacement along this fault is of the order of 3 miles, with the east side moved relatively north. There are also a large number of lesser faults with apparent horizontal displacements of a few feet up to l,70J feet for the Townsite fault. Most of these faults trend north to northwest. Surface examination indicates that, at least for most of them, the movement corresponds to that along the West Bay fault, that is, the east side moved relatively north. According to the available evidence, all or most•of the movem:nt along the West Bay fault and along the lesser faults was post-ore. Late diabase dyk:s that cut through ore-bearing shear zones, with chilled margins in contact with the mineralized material, are apparently displaced to the same extent as earlier geological markers. ( see Frontispiece. )"

Jan 1, 1954

By R. M. Kalanchey

The application of pressure oxidation processes to copper feed materials has gained increased exposure in recent years and some of these processes have made commercial inroads, although rather limited to date. Among the hydrometallurgical processes with significant commercial potential, Dynatec&apos;s copper pressure leaching process has been applied to arsenic-bearing copper materials and has shown, through a number of batch and continuous test programs, that pressure oxidation is a technically feasible option for the recovery of copper with coincident sequestration of arsenic in an environmentally benign residue.

Jan 1, 2007

By D. Kim

Kennecott operates one of the largest and most modern copper refineries in the world at Magna, Utah, USA. The inputs to the refinery are anodes produced at Kennecott Smelter, which has extremely high contents of lead and bismuth. In order to minimize undesired effects in the electrolytic refining process, unwanted impurities, especially bismuth, must be controlled. This paper describes the process development of practicing state-of-the-art quality control and presents the pilot test results of using the MRT Technology for Bi production.

Jan 1, 2007

By Brent Robertson

Failure to meet quality objectives during the execution of any industrial project has lasting negative impacts on facility life cycle performance. Cost overruns, schedule delays, and rework are characteristics of project quality issues that arise during the project. Commissioning and start-up problems, low production, production bottlenecks, breakdowns and the necessity for operational work-arounds are characteristics of project quality issues that appear after project completion. Risks such as production facility downtime, shortened equipment life, and potential HSE violations must be clearly identified and addressed during project planning phases. Appropriate Quality Assurance (QA) and Quality Control (QC) focus must be placed on identified high-risk areas. In order to be effective, quality systems must be flexible, non-confrontational, consistent, and adaptable to projects of any size ? from capital mega-projects to small maintenance projects. All project participants must be aligned in how they are approaching quality and the difference between QA and QC must be clear to everyone on the project. Emphasis must be placed on QA activities to minimize project cost, reduce rework, manage change, and reduce the production facility operational risk. QA is focused on the work processes used to generate the design and confirming that the processes are present and being followed. Issues in the work processes guarantee that the output drawings and specifications will be less than optimal. The identification and monitoring of quality-critical processes provides a focus for QA activities. QC activities are then used to generate proof that the project was implemented correctly and become a key part of the turnover.

Nov 1, 2011