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By H. Lachmund, R. Bruckhaus

At Dillinger Hüttenwerke/Germany steel production of grades for linepipe applications especially for sour service has a long tradition. The BOF process after replacement of the vessels is optimized by a newly developed lime addition model and variations in lance tip geometry. Equipped with three state-of-the-art VOD tank degassers metallurgical requirements of lowest contents of e. g. sulphur, nitrogen and hydrogen can be achieved. Three continuous casting machines of vertical bending type with solid core even improve already high levels of cleanliness. The vertical part corresponds to the metallurgical length of 12 to 15 m and therefore assures a maximum of cleanliness after solidification before bending. Slab thickness up to 400 mm can be produced with model controlled dynamic soft reduction. The accurate alignments of the casters assure minimized segregation and microporosity. Surface and internal cracks can be avoided by special cooling, bending and straightening strategies.

Jan 1, 2005

By Pablo González, Rodolfo Espinosa, Jose-Luis Noyola, Sergio Cossio

"Minera Penmont, at La Herradura, is a joint venture between Industrias Peñoles, S.A. de C.V., and Newmont Mining Corporation. The mine is located in the northern Mexican state of Sonora. La Herradura consists of an open pit mine with two-stage crushing and heap leaching facility, the gold is recovered from the pregnant solution using the Merrill-Crowe process; production began in July 1998. La Herradura produces about 130,000 gold ounces per year, and treatment capacity is 22,000 tonnes/day. Ore mineralization occurs in a shear zone with quartz and native gold. Gold distribution is quite heterogeneous due to the coarse visible gold, in some coarser particles ranging from 100 to 600 microns.Sampling and assaying protocols where established during exploration and prior to starting up operations, based on nomographs developed from early heterogeneity tests. But, as the coarse gold problem became noticeable, it was necessary to develop new sampling protocols to have an acceptable relative standard deviation to control the fundamental error within ± 15%.An experimental program was developed and conducted on a selected ore block made of 195 blastholes; regular ore grade control procedures were applied to both sets of data to evaluate the difference in results between the protocol established prior to starting up operations (“existing”) and the new protocol (“leaching”). In the “existing” protocol, subsampling is done through riffle splitters, and coning and quartering. Fire assaying is used to estimate the gold content, on a 50 g sample. In the “leaching” protocol a 12,000 g sample was bottle rolled cyanide leached, and the leach residue was assayed on a 50 g sample using fire assaying, and a weighted average total gold content was calculated. Currently, a new alternative method is being evaluated, where sub-sampling is done using rotary splitters, and fire assay on a 50 g sample; in this “rotary sampling” protocol and for comparison purposes, gold assays were also repeated using the “leaching” protocol.Test results were compared in three groups < 0.30 g/t (below cut-off), 0.30 to 0.8 g/t, and >0.8 g/t. Overall. Results show that the protocol established prior to starting up operations underestimates the gold assays. Detailed technical results, alternative options, and their implications are discussed in the paper."

Jan 1, 2003

By J. S. Stachulak

"IntroductionInco Limited operates nine underground mines on the rim of the Sudbury Basin. These operation s are situated near the city of Sudbury, 589 km west of Montreal, and 363 km north of Toronto. The ores are mined primarily for nickel and copper, and the principal minerals are pentlandite, chalcopyrite , and pyrrhotite. Total ore production from underground is in excess of 51 000 tons per day.The total volume of fresh air supplied to the nine mines is six million cu.ft/min. There are 50 main fans in operation at these mines, powered by electric motors totaling 11 200 kW (15 000 hp).The trend in metal mining during recent years towards mechanization and high-tonnage production methods has greatly increased ventilation requirements. The now of air must quickly dilute and carry away diesel exhaust fumes, dust created by mining operations, and the fumes of the explosives used in blasting. Mechanical ventilation is required to obtain the necessary volume and control, as natural ventilation pressures alone are, for the most part, inadequate and unreliable. In the event of a mine fire or other needs, close control of ventilation is essential.There are two unique heating systems presently in operation at Inco: Creighton Natural Heat Exchanger and Stobie Ice Stopes."

Jan 1, 1991

By H. Rozovsky

This paper deals with the large iron ore concentrating plant owned by the Iron Ore Company of Canada. The plant is part of the Carol Project, which is being developed in the Wabush area of western Labrador. The mining and milling operations were officially opened in July of this year. The handling of fine material has always been considered a serious operational problem. The crushing, grinding and sizing of 50,000 tons of iron ore per day, in a dry state, could present sizeable problems in maintenance and orderliness. The operation, as a whole, embraces many recent developments in the iron ore industry. Mining operations include the latest techniques of jet piercing and blasting. Primary crushing involves a single crusher, which handles the complete production. Grinding of the ore includes the latest concepts of dry autogenous grinding in air-swept mills. The actual concentration of the ore is per-formed, in the wet state, by the use of spiral concentrators, with provision for possible flotation or magnetic separation, if required. The upgraded concentrates are either stored or pelletized, prior to shipment by rail to Seven Islands.

Jan 1, 1962

By D. Murray

A 2-hectare uranium tailings area has been reclaimed. The exposed tailings of 1.4 hectares were capped with glacial till and vegetated with grasses and legumes. The water running through the tailings was diverted around the tailings in a line ditch and treated with sodium hydroxide and barium chloride. Difficulties occurred in placing the till capping because of the low bearing strength and the uneven surface of the tailings. This led to varying thicknesses of till and the need for manual labour in some areas. Total reclamation costs were $32,200, with vegetation establishment costs at $13,700 per hectare. This report provides a record of work for use in assessing the long-term suitability of these treatments.

Jan 1, 1979

By John Starkey

"During the period June 2007 to March 2007, John Starkey of Starkey & Associates (Starkey) worked in Russia for High River Gold, supervising the engineering design work that was being done at the IRGIREDMET Research Institute, in Irkutsk Russia. The work entailed moving the Newmont No. 4 mill from Elko, Nevada to Berezitovy, a mine site north and west of the city of Skovorodino, in the Amur Region of Siberia. This was a grass roots project and required construction of all phases of the infrastructure and process facilities that are associated with a 5000 t/d open pit mine and CIP mill.During the course of this engineering design exercise, many aspects of doing business in Russia were encountered, with regard to laws, norms, and business practices. This paper discusses many of these findings. Also by living in Irkutsk, many observations on Russian life and social customs were made and these merit discussion from a general interest point of view.Prior to going to Russia, another engineering and ore testing firm (TOMS) had approached Starkey to find out if Starkey could assist them in upgrading their SAG ore testing procedures to Western standards in order to offer their clients turnkey projects, that included reliable SAG and AG grinding. TOMS was aware that Starkey had invented the SPI test but did not know that the SAGDesign test had by then been fully developed and was being offered commercially as the most accurate way in the world to design new grinding mills. They were also unaware that this new testing method had been patented by Outokumpu (now Outotec) and that this method allowed them access to a design method, through Starkey, that would lead to a manufacturer’s guarantee (by Outotec) of throughput and grind for any new semi-autogenous or autogenous grinding circuit, with or without ball mills.When Starkey started working at IRGIREDMET in June 2005, they also made a request to add a design method for SAG mills that would be considered acceptable to Western clients. From these requests, presentations were made in Russian to both institutes and each decided to join the SAGDesign Consulting Group as satellite members and buy a SAGDesign test mill to use with their Bond Ball Mill Work Index mills, to provide SAGDesign testing services. To complete the service, contracts have been put in place for Starkey to use these results to design new grinding equipment and to train engineers at TOMS and IRGIREDMET how to do this work.Starkey also undertook to train engineers at both labs to go into the field and to take the samples for SAGDesign testing programs. It is here where the SAGDesign testing service upgrades other grinding test programs because the samples to be used for design are professionally chosen, and the results will be much more likely to produce a satisfactory design. Starkey is a mining engineer and is uniquely qualified to do this task. This and the SAGDesign test are the key components that lead Outotec to offer a performance guarantee for mills designed by Starkey."

Jan 1, 2008

"The content of production reports has its origins in raw measurements taken in harsh production environments. The ensuing measurement/estimation errors always affect reproducibility such that, regardless of the fact that they are balanced through statistical data reconciliation, reported numbers are simply the most probable values of inferred probability distributions. This has important implications for how metal recoveries should be monitored and reported. Indeed, in a context where many process optimisation activities are based on small improvements in recovery, there should be no doubt that inadequate handling of measurement/estimation errors can easily exaggerate or mask actual changes in process performance. However, estimates of the reproducibility of reported metal recoveries are rarely reported to plant management. This situation persists despite the fact that a code compliant metal accounting system must inform management about business risks related to metal accounting. To this extent, this paper focuses on the continuous management of reproducibility level of metal recoveries in compliance with the best practices. Sensitivity analysis of primary and secondary metal accounting models is performed to show the resulting probability distributions for metal recoveries. Some guidelines are given for designing and managing metal accounting systems capable of achieving and sustaining predefined levels for the reproducibility of metal recoveries.INTRODUCTIONEach and every mineral processing plant produces daily, weekly and monthly production reports in which metal balances for payable and penalty elements are presented. While such production reports are usually consulted in offices, underlying raw measurements are taken in harsh production environments where mechanical vibrations, humidity, corrosion and dust, to name a few, disturb measurement procedures. It is thus no surprise that several authors (Francois-Bongarcon & Gy, 2002; Gaylard, Randolph, & Wortley, 2014; Holmes, 2010; Spangenberg & Minnitt, 2014) have reported pervasive issues related to mass/sampling measurements in the context of mineral processing."

Jan 1, 2016

By Micheal Mayhew

"This presentation will provide information and facts on the drilling and blasting within a frozen shaft using a full face methodology. The Author will briefly discuss the history of the sinking of a frozen shaft in Saskatchewan, the challenges faced, and the solutions delivered. The case study will include a discussion describing the series of events that led to the decision to adopt a full face blasting methodology. The case study will describe key elements such as the drilling pattern, hole size and depth, explosive products and blast vibration monitoring systems. INTRODUCTION During the shaft sinking process at a project in Saskatchewan, it was recommended that a drill & blast benching method be utilized. Following an evaluation of the site, the geological conditions proved amenable to a ground freezing system that would stabilize the rock formations and prevent inflows of water into the shaft (Table 1).The shaft sinking process required that the ground surrounding the proposed shaft be frozen by drilling several near vertical freeze holes radially at a specified distance from the edge of the proposed shaft excavation. This would allow for the circulation of a chilled brine solution down the freeze holes. The circulation is achieved by means of stainless steel pipes encased within each other to provide a delivery and return conduit for the brine (Figure 1). As a result of this periphery freezing, the ground within the shaft excavation is also predominately frozen.The finished internal diameter of the shaft was 5.5 meters with varying overall excavation diameters to facilitate different liner designs used for various rock formations. For the most part, the fully unsupported/unfinished excavated diameter of the shaft varied from 6.9 meters to 8.5 meters depending on the zone excavated. The challenge was that the proposed drill and blast excavation method posed a significant risk due to the potential to damage the freeze wall and pipes during blasting. The decision was made to commence the excavation through mechanical excavation (i.e. chip and cut) methods then change to a drill and blast method utilizing a split benching design. Through this process, the team encountered five main challenges: 1. Sub-horizontal geological structures and slips that affected blasting performance and sometimes resulted in a sloping surface to the top of the bench; 2. Confined working area for the crews and equipment due to a limited work area as a result of utilizing the split (half) bench drill and blast methodology; 3. Mechanical chipping and cutting of the one-meter buffer zone to the final shaft diameter; 4. Crews working on extremely slippery uneven frozen rock and ice surfaces, which affected safety and efficiency; 5. Establishing a blast vibration monitoring system to determine if the drilling and blasting of the full shaft excavation diameter were acceptable."

Jan 1, 2019

By J. P. Jylhä, A. Jokilaakso

The Outotec Flash Smelting process is widely used in primary copper production. A layer of slag on top of matte (copper–iron sulphide melt) creates a barrier through which matte droplets descend. Droplets of different sizes settle through the layer at different rates, which increases possibility of copper losses as smaller matte droplets may be removed with the slag. In this work CFD-DEM (computational fluid dynamics – discrete element method) coupling was used to simulate matte droplets settling through the slag during slag tapping. Discrete droplets and slag flow were simulated with DEM and CFD, respectively. This new approach enables tracking and solving movement and interactions of individual droplets. User-defined models were created to take coalescence and reaction kinetics into account. Coalescence created larger droplets, while the reactions decreased droplet size and increased its density. Drag caused funnelling effect, which pulled droplets towards the centre line of the descending cluster. This research is the only study known by the present authors in modelling liquid-liquid systems with the CFD-DEM coupling. Simulating coalescence and chemical reactions for discrete droplets enables more realistic simulations. However, CFD- DEM simulations are computationally resource intensive already without additional models, so a full scale industrial settler modelling still waits for further increase in computer performance. INTRODUCTION Flash smelting is a method used in copper and nickel production. In the flash smelting process, oxidation of sulphides in a concentrate is used to release energy needed to smelt the feed. In the process, copper matte is formed. Matte has copper content in the range of 55 – 70% (Sridhar, Toguri, & Simeonov, 1997), the rest is mainly sulphur and iron but has still many other impurities (Taskinen, Seppälä, Laulumaa, & Poijärvi, 2001). Oxidized iron forms iron-silicate slag while SO2 is collected for acid production (Davenport & Partelpoeg, 2015). The Outotec flash smelting furnace (FSF) can be divided in four major component: concentrate burner, reaction shaft, settler and uptake. Concentrate, flux and oxygen enriched air are injected into the reactor through the concentrate burner. The mixture then reacts in the reaction shaft forming matte and slag, which are collected in the settler, while off-gases flow out of the reactor through uptake for heat and dust recovery, and SO2 collection for H2SO4 production. The matte and slag form separate layers due to immiscibility and density difference. Raw material feed is continuous, but the matte and the slag are tapped periodically. A flash smelting furnace is depicted in Figure 1.

Jan 1, 2019

Despite the claims of energy efficiency and the considerable development that has gone into dramatically extending rolls? life and facilitating rolls? change-out, in the six years since the last SAG conference, only a few HPGR operations have entered the realm of mineral processing. Risk barriers to the take-up of new equipment or processes are: a massive increase in materials handling issues as well as in the number of pieces of equipment required, low total circuit potential energy savings, and similar or higher capital costs. An alternative route is to make use of the complementary strengths of the HPGR and SAG in hybrid circuits. Minimising materials handling issues, providing an ideal balanced feed to the AG or SAG mill, and improving controllability through shifting grinding load as the RoM feed changes, are all potential major advantages to this approach. Conceptual circuit layouts, based on real measured ore and equipment data, are presented here to illustrate the potential production upside, the reduction in operating costs and the reduction in the physical and energy footprints.

Jan 1, 2012

By J. F. Perreault, J. Paraszczak

"The profitability of an underground mine depends to a great extent on the production cost.Random equipment failures and their consequences have significant influence on the total operating cost of a mining system. Having this in mind, a reliability study has been initiated for loadhaul- dump machines in an underground mine. The main purpose of this study is to identify the critical machine subsystems, determine their failure pattern and help work out an effective maintenance strategy. In the first part of this study, the failure data of diesel powered LHDs, gathered during an I8-month period have been analyzed. For the purpose of the analysis, the machines have been treated as systems comprising seven subsystems connected in series. The most critical subsystems, i.e. electrical and hydraulic, were further investigated, and analyzed by graphical and analytical methods. Different failure distribution models were applied and discussed. Basic Defmitions and ConceptsIn order to avoid confusion, several terms used in this paper are defined below, as compiled by O&apos;Connor (1991). The acronymsBS and MIL-STD stand respectively for: British Standard and US Military Standard.Failure: the termination of the ability of an item to perform a required function (after BS 4778).Time Between Failures (TBF): the length of time between two consecutive failures.Observed Mean Time Between Failures (MTBF): For a stated period in the life of an item, the mean value of the length of time between consecutive failures computed as a ratio of the cumulative observed time to the number of failures under stated conditions (after BS 4778).Maintenance, Corrective: The actions performed, as a result of failure, to restore an item to a specified condition (after MIL-STD-721 B).Maintenance, Preventive: The actions performed in attempt to retain an item in a specified condition by providing systematic inspection, detection and prevention of incipient failure (after MIL-STD-721B)."

Jan 1, 1994

"SART technology is a useful tool for improving the economics of gold recovery from certain types of complex gold ores. SART liberates cyanide consumed by base metals such as copper, zinc and nickel, and enables the newly freed cyanide to be recycled to precious metals leaching while producing high-grade base metal sulphide concentrates for sale. The benefits of SART include the reduction in cyanide consumption, avoidance of cyanide destruction costs, minimization of risks of environmental non-compliance due to residues of cyanide destruction reporting to mine effluents, and generation of extra revenue from the sale of base metal concentrates. Concerns with SART typically include uncertainties around capital and operating costs and proper integration of SART into the overall metallurgical flowsheet. This paper presents two case studies addressing these concerns. The first involves actual costs of the full scale SART integrated into a gold heap leach operation and treating up to 500 m3/hr of leach solution at a mine in Mexico. The second involves field pilot testing and a preliminary cost estimate for integrating SART into a silver mine in Peru using Merrill Crowe.INTRODUCTION One of the current trends in the gold industry globally is the increasing importance of complex polymetallic gold deposits as discoveries of large Carlin type gold deposits become increasingly rare (Sceresini, 2005). The presence of cyanide soluble copper and zinc in complex gold deposits necessitates changes in traditional gold extraction metallurgical flowsheets. One of the tools available to the industry to help deal with interferences of cyanide-soluble base metals in gold extraction is the SART (sulphidization-acidification-recycling-thickening) process. SART breaks the weak acid dissociable (WAD) base metal-cyanide complexes, precipitates the metals as high-grade sulphide concentrates and makes the freed cyanide available for recycle. Although SART is a commercially available technology, it is still relatively new to the industry. Fewer than ten (10) full scale plants have been constructed in the past couple of decades. Some of these SART plants are small, most are located at remote sites, and the majority have not operated on a continuous basis. This has resulted in a general lack of information in the industry about the true costs, operability and metallurgical performance of SART. BQE Water has been involved in the design, construction, commissioning and operation of large scale SART plants in Mexico, Turkey and Chile and has conducted field testing programs as part of the technical assessment of SART integration into various metallurgical circuits. Having built and operated numerous plants utilizing selective sulphide precipitation of heavy metals, BQE Water has gained unique insight into the design and control of the sulphidization stage of SART to minimize costs and ensure high efficiency in cyanide recovery."

Jan 1, 2017

By C. A. Clark

The Chagres Smelter is located 80 kilometres north of Santiago - Chile, in the middle of an agricultural valley which is also one of the poorest districts in the country. This condition sets the main focus for the smelter&apos;s Corporate Social Responsibility (CSR) programmes, which ultimately aim at building self sustainable social and economic capital in accordance with the local capacities. With the help of Anglo American&apos;s SEAT (Socio Economic Assessment Toolbox), a corporately developed instrument designed to help the operations understand the needs of the communities and the impacts of those operations, the Chagres Smelter implemented several programmes, such as the CETTA (Experimental and Applied Technology Transfer Centre) programme. This project started in 2003, and consists of creating a centre for the transfer of sustainable techniques and skills for the small agricultural and livestock producers that live in the rural areas near the Chagres Smelter. Its main impacts are: Improved production quality (goat cheese and bee honey) and access to relevant markets, improved training and self-sustainability levels of producers, enhanced socio-economic level of the District&apos;s inhabitants by improving their income earning opportunities and technical knowledge, creation and promotion of a local brand as a symbol of quality products from the valley and a positive environmental impact of good breeding and native flora protection practices in the area. Other relevant social programmes are the &apos;Environmental Strivers&apos;, which created a recycling centre in the community; and the &apos;Beautiful Valley" project, which provides management knowledge and skills to local youngsters and leaders who can contribute to finding solutions for local environmental needs.

Jan 1, 2007

By Dennis Z. F. Mraz

"Because rock salt and pot ash formations contain particles capable of elastic deformation, the material has usually been compared with various rheological models containing elastic elements. Extensive laboratory testing of salt and potash samples resulted in various theoretical conclusions based on conditions quite different from those in a deep mine. It is felt that sufficient data have now been collected from underground measurements and observations to demonstrate the inelastic behaviour of salt masses in a deep mine. The conditions in deep salt strata can be defined as near hydrostatic, because the acting pressures are very high compared to the negligible elastic limit of the salt. The pressure field and creep around the single opening is a function of its shape, size and age. The same factors, together with extraction, determine the behaviour of the mining a rea. The application of the correct analytical method in mine design can significantly improve the excavation techniques and predetermine the long-term behaviour of openings."

Jan 1, 1973

By A. Torkian

Process water from production of concentrates in Meydook copper sulfide mine is transferred to the 8.3 million m3 tailings dam and a water retention pond after initial thickening. Elevated concentrations of heavy metals, sulfate, and TDS and decrease in pH as well as seepage into the aquifers have been the concern of the regulatory agencies since the start of activities. In this paper the results of a 6-month monitoring program from 4 wells are presented. The wells were located approximately 1.5 km from downstream of tailing dam (0.4 km from water retention pond) as well as upstream background well (2.28 km from water retention pond and 1.27 km from tailings dam). The objective was to study possible effect of accumulated tailings on the groundwater resources. Water levels in sampled wells were on average between 20 and 40 m. Results showed high levels of lead (5 ppb), copper (0.17-0.46 ppm) and selenium (73.1- 29.1 ppb). High levels of selenium and lead were partly due to natural geological settings of the area with high levels present in unaffected soils in the vicinity including water wells of villages upstream of mining operations. High copper levels were attributed to both mining operations as well as deposition from particulate air deposition onto the soil and transport to ground water by rain.

Aug 1, 2013

By Shek N. Lau, Nicola Samman

"Enclosed gear cases on board heavy mining equipment have traditionally been lubricated with regular heavy duty gear oils. However, equipment manufacturers, have recommended the use of an ISO-1000 gear oil for this application to ensure adequate lubricant film strength, especially at the higher end of the working temperature range. The majority of these ISO-1000 gear oils are based either on residual/asphaltic oil or synthetics, primarily higher viscosity polyalphaolefins. Although the performance of these lubricants has been satisfactory, they suffered other shortcomings that equipment users have lived with over the years.The major requirement at the user’s mine was to provide lubrication for the shovel Hoist gear case. Within such a gear case design, the gears and the roller bearings, that have different lubrication requirements, are lubricated with the same lubricant. Several lubricants were used, light gear oils as well as the recommended ISO-1000 heavy gear oils. On the one hand, the lighter oils performed adequately for the lubrication of the bearings that formed part of the enclosed gear system. These lighter oils did not perform as well for the lubrication of the gears due to their lower viscosities, resulting in shorter gear servicelives.On the other hand, the ISO-1000 gear oils performed well for the lubrication of the gears, but were too viscous to creep into the bearing elements to lubricate them adequately, especially during the cold northern Canadian winters. This resulted in catastrophic bearing failures and secondary damages to the gears.The challenge, then, was to formulate a lubricant which met the 1000 cSt at 40°C viscosity requirement as stipulated by the equipment manufacturer, while satisfactorily lubricating the bearings at the full working temperature range. This was achieved by the development of a semi-fluid grease lubricant, which has proven in field trials to give adequate performance in this application for the lubrication of both the bearings and gears down to -40°C.This product met the equipment manufacturer’s performance criteria and resolved, to a large extent, leakage of the lubricant through seals experienced with the use of conventional and synthetic gear oils.Although the main performance criteria of the fluid was its capability to lubricate the “Hoist” gear case, it was also used during the field trial in other gear cases on board the shovel to test its full capabilities.This unusual alternative lubricant was field tested and evaluated for more than two years. Based on this assessment, the product was reformulated to improve its fluidity, slumpability and the settling of debris/wear metals to the bottom of the gear cases. This reformulated softer grade, a semi-fluid grease, has been performing satisfactorily for more than eight months and is still undergoing longer term assessment."

Jan 1, 1996

By James Pirie

"The major Archean gold deposits in the Red Lake greenstone belt, which have produced over 374 million grams of gold since 1930, occur near the top of the lower komatiitic to tholeiitic mafic to ultramafic metavolcanic sequence. The upper calc-alkalic mafic to felsic rocks form three discrete and separate ediftces overlymg this lower sequence.The gold deposits are classified according to their stratigraphic or lithologic associations into:1) mafic-volcanic-hosted deposits;2) felsic-intrusive-hosted deposits; and3) stratabound deposits.Group 1 and to a lesser extent Group 2 deposits occur within zones of alteration several square kilometres in extent. The nature of this pervasive alteration can be characterized by comparison of petrochemical data from the altered rocks and their fresher equivalents some distance away. The altered rocks have substantial addition of SiO2> CO2, K2O, As and Sb and subtraction of Na20, CaO, MgO and total Fe. Cr, Ni, Co and Zr appear to have been relatively immobile. Hydrothermal alteration and gold deposition probably accompanied early fumarolic activity and continued during subsequent deformation the metavolcanic sequence, with gold eventually being mobtltzed and concentrated into major vein structures to form the present orebodies. The smaller Group 2 deposits formed by emplacement of felsic intrusions into already altered, anomalously gold-bearing mafic metavolcanics, with the heat from the intrusions setting up parasitic hydrothermal systems which mobilized the gold and deposited it along with minor sulphides in fractures in the cooling intrusions."

Jan 1, 1982

By M. I. Kalashnikova, Y. M. Shneerson, E. E. Zhmarin, Y. V. Degtiarev, E. M. Vigdorchik

Separation of a magnetic fraction from nickel concentrate following matte flotation, and its treatment in a separate circuit enable reduces precious metals losses. The magnetic fraction is treated in two stages of oxidative leaching: atmospheric and pressure leaching. A study of the atmospheric stage, using mathematical modelling, is described in this paper. The mathematical model and experimental data were used to carry out industrial process calculations. The model enabled extrapolation of the results of batch laboratory test to industrial-scale continuous processing and the selection of optimal process conditions and large-scale equipment. In December 2004, commercial oxidative leaching tests were performed on the magnetic fraction at the Severonickel Plant (Monchegorsk, Russia). A comparative analysis of the mathematical modelling results and the actual process parameters is presented.

Jan 1, 2005

By T. W. Sullivan

"This paper explores the history of AC static variable frequency control drive systems on open cast mining machinery, in particular electric mining shovels and electric walking draglines, over the past ten years. It critiques the peformance of these drive systems from a productivity and operating cost standpoint and evaluates the over-all success of the original design concepts as they were envisaged in the 1970s. The paper details the state-of-the-art as it exists today as well as design improvements contemplated for the immediate future.IntroductionConsidering the fact that the very first successful application of an alternating current electrical distribution system occurred at the Gold King gold mine near Ames, Colorado, U.S.A., in the year 1891, it seems somewhat ironic that almost 100 years later, AC excavator drive systems are just now becoming commonplace in the mining industry.If one were to read the biography of Lucien L. Nunn, the first person to successfully install a commercially viable alternating current power distribution system, one would quickly visualize a parallelism between his fight to achieve acceptance of his new lower cost technology and that of those commissioned with the belief that AC static variable frequency control drive systems are not only a better performing, lower cost drive system for mining excavators today, but moreover, the drive systems of the future in our industry.This paper will deal with the evolution and incorporation of AC static drive systems on open cast mining excavators. It will trace the history of the development of these drive systems in the mining industry, the current state-of-the-art concerning these systems, and what the future holds for these excavators in our industry."

Jan 1, 1990

By V. Coffin, T. Cienski

"(Figure 1) Reagentized pulp enters into the column at about 1/4 of the distance from the top. Inside the column it meets with a downward flowing stream of water and with an upward flowing mass of air bubbles. Flotation takes place in this counter current system while at the same time fine gangue particles are washed off the froth before it reaches the overflow lip at the top of the column. The main operating features of the column flotation are as follows:a) No moving parts. Solids are kept in suspention not by an agitating action of a propeller but by settling down against the rising air bubbles.b) Wash water. Spray pipes are installed a few inches below the froth surface and deliver required volume of water. The purpose of this water is twofold:(i) it keeps in balance the flow of material through the column and(ii) it washes rising froth in the froth layer as well as removes unwanted fines attached to the bubbles at the lower flotation section. As a result the concentrate produced is of higher purity than in the conventional flotation. Column is characterized by very high up-grading. However, even temporary disruption of wash water supply results in a drastic drop of concentrate grate.c) Flow balance. (Figure 2) For the correct operation volume of the underflow (tail) is larger than that of the feed. The difference is made up by the wash water. This difference called bias is predetermined and ranges from some 4 to 15 USGPM depending on the size of the unit and process requirements."

Jan 1, 1981