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Jan 1, 1966

By Ian Wark

IT has been shown1 that in the absence of heavy metal salts, the nature of the alkali used to promote differential flotation-whether caustic soda, lime or sodium carbonate-is unimportant. The hydroxyl ion is the active depressant upon which differentiation depends, and the pH value determines whether a film of collector forms on any given mineral surface. Even when sodium cyanide is used in conjunction with alkalies, it is the pH value and not the nature of the alkali or its concentration that is important, for upon the pH value alone depends the fraction of the added sodium cyanide that is present as cyanide ion, which is the true depressant. When heavy metal salts become dissolved from partly oxidized ores, or are added intentionally as activators, conditions are different, and metallurgists have found that lime and sodium carbonate do not give identical results, even when added in amounts sufficient to produce the same pH value. In the few instances in which we had attempted to confirm this view, we had failed to do so, for, with nothing to guide us, we had inadvertently chosen solutions that gave contact curves of a "stand-ard type," which correspond to conditions of ready floatability. Now, however, we find that, in the presence of copper salts, and within a restricted range of reagent concentrations, the nature of the anions present is important, and that sodium carbonate does influence the results, apart from the usual effect due to its influence on pH value. With the recognition of this anion effect, and with the control of temperature already introduced,' it appears that the factors of major importance in connection with this set of reagents have been taken into consideration, and that the results obtained and the conclusions drawn from contact tests will be of more immediate value to the operator.

Jan 1, 1939

Keywords: Stellenbosch, university, teaching, research The pyrometallurgical activities at Stellenbosch University are reviewed in this paper. The history of the activities, both in teaching and research, is outlined, as well as some of the perceived research opportunities that the University of Stellenbosch is currently focusing on. The course content, as well as its relationship to other courses in the curriculum, is discussed and the interfaces between the courses are explained to present a holistic picture of the education an engineering graduate receives in process pyrometallurgy.

Jan 1, 2006

By Bernard Porter

Differential thermal analysis measurements were used to characterize a phase diagram for the KF-YF3 system at compositions between 0 and 60 mole-percent YF3, A congruent melting point compound was observed at 3KF?YFs, which melts at 965°±5° C and undergoes solid-state decomposition at 725°±2° C. One peritectic and two eutectic compositions are also defined.

Jan 1, 1969

By McMahon DW, Schapper MA

Hard rock underground mining has been wedded to the drill-blast method of breaking rock. Current practice and technology have focused on greater efficiencies in the blasting and handling of ore, on the basis that thelower costs that come with larger scale operations compensate for the waste dilution associated with the bulk methods. However, it is suggested that new technology is available or is on the horizon that could completely change the shape of hard rock mining in the 21st century. Hard-rock continuous-mining machines, possibly assisted by high pressure water jets, coupled with automated sorting and materials handling systems, could re-orient the miner's focus to winning metal rather than mining tonnes of ore. More continuous mining processes could accelerate the penetration by high technology in the hard rock underground mine, with the potential of greater manpower productivities and lower costs per tonne of metal produced. This new technology will be important in maintaining a competitive supply of metals, given the falling headgrades of the orebodies remaining for development and the increasing market threat from manufactured substitutes.

Jan 1, 1985

By A McCallum, J Abols, G Patrick, G Johansen

The authors challenge the traditional thinking that whole ore cyanidation followed by Carbon in Pulp (CIP) or Carbon in Leach (CIL) should be applied as a standard process in the majority of gold processing flow sheets. The concept of whole ore leaching by using cyanide can result in unnecessary environmental and capital risk. Alternative, currently available technologies can be used to provide the desired level of gold recovery at a much lower installed cost and less impact on the environment. Gravity concentration, alone or in conjunction with flotation, can produce a gold bearing concentrate that can then be fed directly to a batch or continuous intensive cyanidation unit. The In-line Leach Reactor (ILR) is an intensive cyanidation unit developed by Gekko Systems of Australia. Advantages of this technology include significantly reduced capital outlays for greenfield plants or plant upgrades and increased investor returns. Reduction of onsite cyanide and carbon inventories improves plant safety, materials handling and site security. By using direct electrowinning to treat the gold bearing solutions produced by the ILR, the need for a conventional carbon stripping circuit is removed. Potential also exists to increase grind size û saving energy, further reducing capital and operating costs and decreasing the environmental impact of a mill. Detoxification of cyanide before the release of solution to the tailings dam can minimise tailings disposal and containment requirements. When used in the right application the proposed process will have little or no impact on gold recovery and may actually increase recovery for complex ores. Areas applicable to this type of treatment include: plants in environmentally sensitive regions, lower tonnage higher grade deposits, coarse gold deposits, and preg robbing ores û some of which may not currently be economically feasible using standard processes and flow sheets. We have provided two examples of such projects, where an alternative to whole ore leach and CIP or CIL has the potential to deliver these benefits.

Jan 1, 2004

By Alan A. Campoli

The U.S. Bureau of Mines conducted research to characterize longwall gob loading under bump-prone geologic conditions. Bureau-designed stress meters were installed in the floor rock beneath two longwall panels and coal pillars in the gate road between them. Gob and gate road pillar stress was monitored continuously by a state-of-the-art data acquisition system. The timing of the final destruction of the abutment pillar's load-bearing core was optimal, since the pillar is located between two gob areas and no longer of significant importance for ground control. Maximum stress was observed immediately in front of the longwall face, and this pressure quickly dropped as the face moved past the instruments. The center of the longwall panels regained significant overburden load, while the instruments located less than 100 ft from the edge of the panel showed little or no increase in pressure due to gob reloading.

Jan 1, 2010

By H Arvidson, J Vann

When only wide-spaced drilling is available, for example at concept, prefeasibility and feasibility stages, properly implemented linear estimation (including ordinary kriging) predicts grade tonnage relationships that are over-smoothed compared to final production estimates (and production). Non-linear estimation and conditional simulation are alternative geostatistical approaches that can provide more reliable estimates of the recoverable tonnage and grade from wide-spaced drilling. Non-linear estimation and conditional simulation have been rarely used on iron ore deposits. However, these techniques have had wide application in other commodities such as gold and base metals. Conditional simulation has been used in the iron ore industry (eg Guibal et al, 1997); however, its use here is outlined as a means of generating non-linear estimates, not just its use for variability and drill spacing analysis. As a rule, regardless of commodity, the decision to use non-linear geostatistics will necessitate increased skills and require more time. This decision must therefore be justified in terms of cost-benefit. Such cost-benefit analysis is not straightforward, and to help an approach for determining when linear estimates are inadequate is presented. Recommend in this paper is a well-established non-linear geostatistical approach, the global ædiscrete Gaussian modelÆ (DGM) of change of support, as a tool to establish whether moving from linear to non-linear estimates will materially improve estimate results. Also discussed is the additional use of DGM as a block model validation tool. One specific factor contributing to the lack of application of non-linear geostatistical methods in iron is the added difficulties that arise when conditional simulation and non-linear estimates are required to reproduce the numerous and often important correlations between variables in iron ore deposits. Consequently, presented in the paper is a synoptic review of non-linear estimation and simulation methodologies applicable to correlated variables.

Jan 1, 2007

By Christopher Van Dyke, Knox Van Dyke, Lixin Wu, Jaime Gutierrez

"I. INTRODUCTION(SILICA, THE LUNG, INFLAMMATION, AND FIBROSIS)Inhalation of respirable-size silica (0. I to 5 µm in diameter) deposits the particles in the deep spaces of the Jung where oxygen is exchanged. The resulting pattern of inflammation is substantially different compared to that observed from other inhaled substances such as carbon, polystyrene titanium dioxide etc. 1 Following the inflammatory reaction the body attempts to isolate the damage by walling off the area via fibrosis. 2 The unique nature of the inflammatory response to silica makes it logical to infer that fibrosis is a later-stage manifestation of the initial inflammatory damage. In addition to the inflammation extensive lysis and cellular death particularly to macrophages and neutrophils, can occur, depending on the dose of silica.' The ingestion of significant amounts of silica by macrophages and neutrophils produces an inflammatory sequence which activates the lipoxygenase pathway of arachidonic acid metabolism and produces platelet activating factor (PAF) and leukotrienes (LT).4·5II. CALCIUM IONOPHORE MIMICS SILICA TOXICITY IN VITROPhagocytic cells exposed to silica in vitro produce PAF and LT. This response is reminiscent of phagocytic cells exposed to the calcium ionophore (A23 l 87) in the presence of ionic calcium.6-8 A23 l 87 forms a complex with free ionic calcium which passes through cellular membranes, thus transporting calcium inside the cell. The increased intracellular calcium concentration triggers the production of small amounts of prostaglandins large amounts of LT. PAF and. depending on dose cellular death (see Figure 1 ). Could silica cause LT production and cellular death by a similar mechanism? How could silica - an inert solid - act in a similar fashion as a soluble stimulant? Clearly the negative SiO2 and OH- surface of silica can bind calcium ions9 and therefore could theoretically act as a solid-state ionophore releasing bound calcium inside of cells following phagocytosis."

Jan 1, 1998

By John Wulff, David A. Stevenson

The rates of solution of copper, nickel, and three copper-nickel alloys in liquid lead were studied at 527° and 727°C under dynamic conditions. The relative velocity at the solid-liquid interface was varied from 8.65 to 125 cm per sec. Analysis of the data for the pure metals indicates that the solution rate is transport corztrolled at lower velocities, but a transition to mixed control occurs at higher velocities, higher temperatures, and higher percent saturation. 1 HE present work concerns the effect of relative velocity at a solid-liquid interface on the dissolution kinetics of pure solid materials in liquid metals. This general problem is of interest in electrode kinetics, in electrolytic processes, and more recently in the field of liquid metal corrosion. Considerable work has been done on dissolution kinetics in aqueous environments because of the obvious importance to electrolytic processes.1,2 In purely metallic systems investigation has been more limited. There are, of course, extensive data from loop tests which are used in an engineering evaluation of liq- uid metal corrosion. Here, however, the dissolution process is complicated by several interdependent processes. In general, one of two factors is considered to be rate limiting in the dissolution process: the transport of material from the solid-liquid interface into the bulk liquid, or an activation process directly at the interface. A number of studies of the dissolution rates of solid metals in liquid metals under static conditions have been published.3- Since the attendant hydrodynamic conditions imposed by thermal gradient convection and concentration gradient convection are difficult to analyze, it is doubtful if a clear interpretation of the experimental findings of these papers in terms of the mechanism involved in the dissolution process can be made. A clearer picture of the dissolution process is provided by

Jan 1, 1962

By John Sakala, Jeyapandian Sasikumar, Sydney Kwalela

The Isasmelt Furnace was commissioned in September 2006 with a concentrates treatment capacity of 850,000 tonnes per annum. However, the converter section became a bottleneck to the high throughput. Over 25% of the Isasmelt Furnace down time was attributed to lack of converter space. Factors that affected converter operations were low tuyere line campaign life (an average of 150 blows), high reverts generation, low conversion rates, and high converter cycle time. As a result of efforts carried out to improve converter operation, the average campaign life has increased to over 250 blows and reverts generation has been reduced from 22% of concentrate treated to 15%. Blister copper conversion rate has increased from 15 tonnes per hour to 19 tonnes per hour and blowing time per cycle has been reduced from 5.7 hours to 4.7 hours.

Jan 1, 2012

In todayÆs evolving and globalised world, mining companies are being pressured to move beyond compliance towards long-term sustainability and sustainable development. Companies are expected to æengageÆ communities and measure the success of these engagements without a clear understanding of æhowÆ to do this. This move, away from compliance, develops more of a focus on sustainability and æcommunityÆ social responsibility rather than corporate social responsibility. This shift leads to the development of world-class projects that provide sustainable development for people, reduce the incidence of costly delays, and promote good global citizenship for companies. The process of æengagingÆ communities in mining project design and development leads to sustainable development, a stronger license to operate, and a reduction in social and political risk. To create this mutually beneficial relationship between communities and companies, communities must be æengagedÆ in the project development and risk assessment processes as early as possible, preferably during the exploration or the concept phases. How to create this æengagementÆ and manage this risk will be discussed.

Jan 1, 2007

By M. M. Tilman

The objectives of this research were to determine the practicability of using cobalt as a means of controlling the amount of ferrite in the micro-structures of semiaustenitic stainless steels, and to determine the effects of reduced ferrite content on mechanical properties of these steels. Cobalt additions of up to 3 weight-percent were made to type 17-7 PH2 (AISI 631) stainless steel. Ferrite contents were determined for alloys in the aged condition, and for alloys quenched from the hot working temperature. Ferrite can be completely eliminated from the microstructure of 17-7 PH stainless steel by additions of cobalt, but complete elimination of the ferrite phase results in lower tensile strength, yield strength, and hardness. Tensile properties, hardness, and impact strength were determined for aged material. A subzero temperature treatment before heattreating was necessary to obtain maximum strength in the alloys containing cobalt. Addition of 2 weight-percent cobalt enhances mechanical properties of 17-7 PH stainless steel.

Jan 1, 1968

By Klaus Detert

Fifteen and 18 pct Ni maraging steel and several binavy and ternary alloys of the iron-rich corner of the Fe-Co-Ni system have been studied. After annealing in the austenite range, these alloys were deformed slightly by cold rolling and subsequently aged. Compavison of experimental measurements at various processing stages indicates that small degrees of deforn~ation (5 to 10 pct reduction in thickness) do not influence hardness and strength or the aging kinetics. Electrical resistivity and ductility are somewhat redu]ced and the coercive force is substantially lower when compared to identical samples which were not deformed. The results are explained in terms of retained austenite which transforms into martensite with the small amount of deformation. RECENTLY there has been increasing interest in maraging steel for applications in electric power generators requiring a high ratio of power to weight.' Fifteen pct Ni maraging steel has been investigated to evaluate its properties and performance for application as high-strength magnetic rotor steel,' and a thorough investigation of the precipitation and transformation processes in this alloy has been conducted in this laboratory.3 The influence of deformation, which preceded the aging treatment, was also studied. It was found that a small deformation in the order of 5 pct has a rather striking effect in reducing the coercive force. Other interesting effects on the properties caused by such deformation have led to the more detailed studies reported herein. EXPERIMENTAL METHOD The methods used to produce the samples from 15 pct Ni maraging steel have been described elsewhere.3 The general procedure of hot forging and cold rolling to sheet has been followed. The composition is included in Table I which also contains the composition of the 18 pct Ni maraging steel grade 250 studied. More data about the material and the processing of the 18 pct Ni maraging steel have been recently reported.4 The experimental alloys of binary and ternary Fe-Ni-Co alloys were made by levitation melting in an argon atmosphere and casting into rod-shaped ingots 7 mm thick weighing 20 g. From these ingots 25-mm-long rods were machined to study the phase transformation by a dilatometer. These rods were then cold-rolled to strips, 2.4 mm thick. Annealing for austenitizing was done in tube furnaces in an argon or helium atmosphere followed by cooling in the water-cooled portion of the tube. Aging was done in a salt bath containing a neutral blend of Alkali nitrates and nitrites. Vickers hardness was measured using a load of 50 kg for 15 sec. Tensile tests were carried out on a hard beam tensile tester at a strain rate of 5 X lo-' per sec using flat samples with a gage length of 37.5 mm and a cross section of 1.25 by 6.25 mm. Estimated sensitivity was 5 K x strain and 0.35 kg per sq mm stress. Magnetic saturation was determined on small cylindrical samples, 2.5 mm in length and diameter, by measuring the force exerted by the gradient of a magnetic field of 1000 oe per cm in a mean field of 11,500 oe. The measured values could be reproduced within *1 pct. Coercive force was measured by a precision-type magnetic field probe in a magnetic coil as described by Foerster.5 The magnetizing field was 1300 oe. The samples were 5 cm long, 1 cm wide, and 2.4 mm thick. he coercive force was measured to within +0.1 oe. Electrical resistivity was measured by using a potentiometer on flat strips with a gage length of 100 mm and a cross section of 2.5 by 0.5 mm. The accuracy of the measurement was 0.1 pct but the reproducibility of the measured specific resistivity among different samples was in the order of 1 pct. The method used to prepare the samples for electron transmission has been reported elsewhere.3 RESULTS Fig. 1 shows the influence of deformation after annealing on the resistivity, hardness, and coercivity. The samples were annealed for 30 min at 1000"C,

Jan 1, 1968

By C. R. Daly, D. Biswas

This study presents the development of a simplified artificial neural network (ANN) for the characterization of rock mass with a simultaneous display of its output in a three-dimensional interactive environment as well as in the form of a text document. The system was developed using JAVA object-oriented language, virtual-reality modeling language (VRML) and JavaScript, and it runs on the Internet. The user can walk through a three-dimensional virtual roadway, checking the underground rock mass behavior and, consequently, can design a support system. The system first characterizes the rock mass with the help of a neural network and recommends a suitable support system for the particular geomining condition. The system then represents its output in a three-dimensional environment. The neural network developed in this system was trained with 261 data sets, and its performance was evaluated with five case histories. The evaluation results showed that the network could identify the rock category and support system adaptively. The average error for the support load was 2.7%. Among the five case histories, two were represented in a three-dimensional environment. The output obtained from the overall system compared favorably with the existing underground conditions.

Jan 1, 2003

By Donald H. Mullen, Walter R. Storms

"INTRODUCTION The Copper Flat area of the Central mining district, Grant County, N. Mex., has been visited by numerous engineers 4/ of the Bureau of Mines and geologists 5/ of the Federal Geological Survey. In December 1944 the Bureau. 6/ proposed that geophysical work be done in that area in order to locate favorable sites for future company exploratory and development work. This geo-physical work was begun early in 1945 but never fully completed because of insufficient funds. The engineers who made the survey recommended that more work be done, especially to locate the bottom of the Copper Flat laccolith by resistivity-depth surveys. All known minable zinc-lead ore bodies had been found above this laccolith in the Copper Flat mine, but it was thought that other minable ore deposits should occur in favorable limestones beneath it. The geophysicists also recommended core drilling beneath the laccolith.In the summer of 1946, following some mapping by S. G. Lasky of the Federal Geological Survey, funds were appropriated for a Bureau of Mines project in the Copper Flat area. The project was completed in June 1947. 8/"

Apr 1, 1948

By Jack M. Jodrey, Neil D. O’Donnell, R. A. Metz

Bituminous sands of the Lower Cretaceous McMurray Formation in northern Alberta constitute the ore for the surface mining operation at Syncrude Canada Ltd. These sediments represent a complex succession of fluvial, estuarine and marine depositional environments. Grade prediction is realized through a combination of geological interpretation, computer modeling, and reference to past mining experience. Accurate forecasts of feed grade permit reliable predictions of volumes for removal to meet budgeted synthetic crude oil production. This planning facilitates efficient allocation of mining equipment and resources. The feed grade to the Extraction Plant is monitored at various points along the delivery system.

Jan 1, 1992

By Charles D. Litton

An overview of state-of-the-art technology in fire detectors is presented by the Bureau of Mines regarding their use in the mining industry. Detectors are categorized according to the characteristics of a fire to which they respond. Operating principles of the various detectors, their application, and the advantages and disadvantages of each are discussed.

Jan 1, 1979

By M. Olper

Commercial copper plants utilising current best technology are tending towards ever increasing scale, the concentrate requirements of which cannot be serviced by a single mine. In such cases, raw materials are often sourced from different mines, which are often far away from the production plant and usually with very different ore compositions. These plants tend to use the traditional thermal processing steps of smelting, converting to blister, anode refining and casting to produce copper anodes that are then refined in a sulphate electrorefining operation. These thermal steps are in some cases troublesome and require the recycling of considerable quantities of material. A new process was developed taking advantage of the latest developments of the first thermal step of the classic loop, the smelting of copper concentrate to high grade matte or white metal using the well known AUSMELT Top Submerged Lancing Technology. The white metal and/or high grade matte product is converted directly to copper cathode and elemental sulphur using the ECUPREX technology. This approach provides an alternative to the traditional thermal steps of conversion to blister, thermal refining and anode casting, which, especially at small scale, can be expensive and problematic in terms of technical and environmental concerns. At first evaluation, this new process can be operated at low capacities, thereby, changing the traditional approach to copper production. Instead of taking the concentrate to the copper production plant, the copper production plant is taken close to the mine with some significant economic and technical advantages.

Jan 1, 2007

By C. Poon

For slope stability, knowledge of major and minor discontinuity sets that form the rock mass fabric is paramount for pit slope designs. Due to the increased awareness of health and safety in mining projects, efforts have been made to limit structural mapping in order to minimize the risk to personnel associated with approaching potentially unstable areas. Recognizing the importance of such safety precautions, Golder Associates Ltd. is applying a combination of techniques including 3D photogrammetry, conventional mapping and drilling with core orientation to enhance structural data collection. Photogrammetry uses digital photographs to produce a virtual model of a rock mass surface. The application of these techniques will be exemplified through an expansion design of an existing open pit. A comparison of stereonets obtained using these techniques showed some agreements, but also highlighted limitations of each method. The application of photogrammetry was found to be very useful in complementing the other existing techniques.

May 1, 2009