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By Francisco Anglade

Dado que la simulación digital es una herramienta auxilar para los ingenieros de procesos -en tanto evalúa la factibilidad de un flowsheet propuesto y predice el efecto de una modificación para un flowsheet existente, su importancia también se extiende también a la evaluación de alternativas para las estrategias de control en los circuitos de la planta. En ese sentido, el presente trabajo señala los beneficios económicos y técnicos obtenidos en la planta San Rafael mediante el empleo de simuladores en los circuitos de molienda, chancado y concentración gravimétrica, los cuales permiten corroborar los cambios efectuados u optimizar los circuitos señalados de forma simple y rápida.

Sep 9, 2007

In this address I look back over the past 40 years of mineral exploration in New Zealand û essentially the period since the Second World War (ie since 1945). It was the period of my personal involvement, and indeed of the personal involvement of a number of you. Luckily it was aperiod of great interest and activity. In the previous 50 years, virtually nothing had happened, and it is kindest to draw a veil over that period. In the very important earlier 40 years (1855 - 1895) the New Zealand gold rush occurred. That must have been a fascinating, rewarding period, which has been thoroughly documented by better historians than myself. I will simply comment firstly that its mineral explorers (gold-prospectors) were very successful indeed, and found most localities of the minerals they sought, in spite of using very different methods from ours of today. Secondly, they were preceeded by one of Maori exploration, which searched for a much restricted list of minerals, but succeeded in finding virtually every locality we know of today. The explorers of both of these early periods were obviously highly successful, but, in the time available, I must restrict myself to the period since 1945. I am currently editing the effective up-dating of Gordon WilliamsÆ 'Economic Geology of New Zealand' (1974). It covers the last 12 years or so. Many of you are contributing to that volume û both as authors and as referees û and I would like to take this opportunity of thanking you all. Although this new volume excludes the energy field, many of us have been involved in it, and I am therefore including energy minerals in this review, as Williams did in 1974.

Jan 1, 1987

Geochemical data on Australian granites and pegmatites, and the mineral components of these rocks, are compared with that obtained in similar studies in the U.S.S.R. and elsewhere.The geochemical character of tin granites and the trace chemistry of their component minerals, particularly biotites, have some significance as ore guides in prospecting for tin.The primary geochemical dispersion of tin can be readily tested both in the laboratory and field by colourimetric methods, after volatilization with ammonium iodide, using modifications of the method described by Wood (1958).Secondary dispersions of tin in residual soils or alluvia can likewise be readly tested by rapid colourimetric methods in the field, but simple hydraulic methods, handling larger sample volumes, give reliable outlines of dispersion patterns.INTRODUCTIONThe search for tin ores, whether lode or placer in type, is usually directed on genetic grounds to country within or adjoining acid intrusives.A long established means of prospecting is to test samples for cassiterite by panning or other hydraulic separation.These methods can be used on crushed lode material or the natural materials from placers.With the advent of new techniques for extraction and for colourimetric analysis for tin (Wood, 1958 and Ross and White, 1961) a means is available for rapid analysis of materials not susceptible to quantitative testing by hydraulic methods because of the fine sizings of cassiterite or the occurrence of tin structurally held in minerals. The new methods thus opened up the field of tin prospecting by extending the search for ore guides to genetically associated rocks and minerals, wall ror-ks of veins and a wider range of superficial deposits.

Jan 1, 1963

By C. P. Kelley, T. J. McKeon

Several recent developments in fine screening technology have been implemented at the DuPont Starke, Florida plant allowing enhanced zircon recoveries while minimizing operator requirements and total operational costs. The total design concept came about through the efforts of engineers at Derrick Corporation (Buffalo, New York), DuPont Titanium Technologies (Starke, Florida) and Roche Mining (Carrara, Australia). The use of the Kelsey Jigs for zircon recoveries from the tailings stream requires two wet sizing functions in order to operate properly. The first wet sizing is required on the initial mineral slurry feed to the Kelsey Jig. This sizing is intended to protect the Kelsey Jigs internal screen basket from plugging with nearsize particles, thereby keeping production rates maximized. The second sizing function is intended to recover properly sized garnet ragging material, which inadvertently ends up in the tailings stream leaving the Kelsey Jig. The unique machine design developed by the three partners in this project incorporated both wet sizing functions (protection and garnet recovery) into a single patented high capacity wet screening machine fitted with patented screen surface technology. This screen surface technology allowed for high capacity slurry handling capabilities at separations as fine as 230 microns while experiencing no nearsize blinding and extremely long screen panel life. The high open area urethane screen surfaces utilized in the application typically last 20 to 30 times longer than stainless steel wire surfaces. The stacked machine design minimized total equipment requirements and screen footprint requirements, and reduced power consumption and overall installation costs.

Jan 1, 2005

By Tom Treleaven, Andrew Williams

The town of Greenwich, CT, an exclusive suburb of New York City awarded several contracts for the installation of sanitary sewer in the North Mianus section of town. The Valley Road section was the most challenging from a rock excavation standpoint. The cut was up to 14 ft (4.25m), with adjacent utilities [20 in. (500mm) water, 6 in. (150mm) water and 8 in. (200mm) gas] located to within 5 ft. (1.5m) of the proposed sewer trench. Rock types varied but were ultra metamorphic in nature, ranging from quartzites, granite gneiss and various types of migmatities.

Jan 1, 2004

By Torben Edens

Norddeutsche Affinerie?s (NA?s) primary smelter continually increased production in the past decade. The smelter?s concentrate capacity was expanded from 500,000 in 1993 to 1,000,000 t/a dry concentrate in 2000 and the goal of the present upgrade is 1,150,000 t/a. These goals were reached without erecting new equipment in the anode area, but instead by refitting the existing plant. The life-span extension of the casting moulds was absolutely necessary to increase the casting performance from 260,000 to 450,000 t anodes per year on a single casting wheel. Different mould manufacturing processes and alloys were tested in order to find the optimal mould. In the past the moulds were cast directly, now the anode mould is milled into NA copper cakes. Accompanying measures taken were the shortening of maintenance and repair times as well as improvements in the refining furnace equipment.

Jan 1, 2005

By T Hughes

Upward pressure on all mining operations is coming from the triple bottom line. To some extent this is being offset by the rise in mineral prices, but this may or may not continue. The other serious issue facing all companies is the replacement of economic reserves as exploration levels over the past decade continued to decline in line with falling mineral prices. In order to underpin the sustainability of the mining industry it is necessary to continue to reduce cost, reduce the mine environmental footprint, whilst increasing community benefit. At the same time it is imperative that we increase the economic reserves. The highest risk is in adding new mineral discoveries as the strike rate for economic discovery decreases. Gekko Systems Pty Ltd recognises that the most simple and risk averse route to increasing economic reserves is to reduce cut-off grade in the mine, thereby bringing formerly uneconomic reserves into the economic category. We have been developing a new process flow sheet which embodies the triple bottom line and the issue of economic replacement of reserves. This paper describes this flow sheet and presents four examples where this concept is/can be applied to bring about triple bottom line benefits. Sustainability can only be assured if we are the ones in control of our environment, costs and reserves.

Jan 1, 2007

By Ketan H. Trivedi

This paper describes the method of analyses used for the design of temporary and permanent Secant Pile Walls, describes various aspects of construction including, guide walls, sequence of pile installation, plan alignment and verticality tolerance, methods of drilling (auger, wash boring, cased and open holes), lateral bracing for secant piles, cutting of keys in secant pile walls for the connection of permanent floor slabs, sealing of water leaks and waterproofing. The paper concludes with a brief case history of a secant pile wall project recently constructed in New York City.

Jan 1, 2006

By P Atkinson, M P. Simpson, J R. Kyle

BM37 is a bonanza-grade (>30 ppm Au) ore shoot of the Maria Lode of the Karangahake adularia-sericite epithermal deposit in the southern Hauraki Goldfield. Samples from BM37 contain up to weight percent gold. The ore shoot is a vein that pinches and swells, but is typically tens of cm thick, and locally exceeds 0.5 m in true width. Gold occurs as irregular anhedral electrum grains that range up to 300 microns across and contain 38 to 59 wt per cent Au (ave. 52 wt per cent Au). Electrum occurs in sulphide-rich bands in association with pyrite, chalcopyrite, acanthite, galena, sphalerite, and local covellite. Lower grade samples contain local to rare mckinstryite [(Ag, Cu) 2S] and polybasite [(Ag, Cu) 16 (As, Sb) 2S11]. Pyrite from BM37 is nearly stoichiometric; it lacks the As that commonly occurs at up to percent levels in pyrite from other veins in the goldfield. Acanthite also contains low quantities of trace metals, and typically has less than 2.5 per cent Se. The vein shows complex textures. Bonanza grade sulphide-rich ginguro bands form discrete layers adjacent to the vein margins, and occur as breccia fragments encased by later massive to comb quartz with local quartz after platy calcite. Both the breccia fragments and ginguro bands are cross-cut by later quartz veins. Textures thus indicate that formation of the high-grade portions of BM37 resulted from one or more discrete events that differed markedly from the events that formed the bulk of the vein.

Jan 1, 2006

By T. Strong

"Selectively recovering pentlandite from high levels of pyrrhotite presents a technical and operational challenge. The liberation characteristics and also the chemical environment is critical to performing a successful separation. Reviewing the mineralogy to understand the characteristics of the ore and the plant flotation behavior is fundamental to designing a successful improvement program.At Savannah Nickel the challenges presented by a falling nickel price required a rethink of the flowsheet to improve the project economics through improving the concentrate grade and recoveries. Glencore Technology reviewed the plant performance and proposed and tested solutions to improve the grade performance of the concentrator with the support of the plant team. A pilot plant comprising a M20 IsamillTM followed by an L500/1 Jameson Cell was operated on various plant streams. In addition to the pilot plant, flotation surveys and a plant based laboratory program was used to supplement the plant understanding and within two weeks significant improvements were identified and demonstrated. The combination of the pilot operation and the plant based laboratory program was able to quickly demonstrate the improvements and test with equipment that is fully scaleable from pilot plant to full scale.IntroductionPanoramic Resources Limited is a Western Australian mining company formed in 2001 for the purpose of developing the Savannah Nickel Project in the East Kimberley region of Western Australia. Panoramic successfully commissioned the $65 million Savannah Project in late 2004. The process plant at Savannah comprises a single stage crusher, SAG mill, flotation, thickening and filtering stages to produce a bulk nickel, copper, cobalt concentrate. Metallurgical recoveries average 86-89% for nickel, 94-97% for copper and 89-92% for cobalt. The plant was originally designed for a throughput of 750,000 tonnes per annum, but has consistently outperformed the design specifications.Due to low nickel prices the Savannah Nickel mine and processing plant were placed into care and maintenance in May 2016. Prior to suspending production Glencore Technology was engaged to investigate options to improve the concentrate grade. With the discovery of Savannah North in 2014 and the Savannah North Scoping Study demonstrating LoM ~8 years and Mining Inventory of 6.07Mt @ 1.26% Ni, 0.64% Cu and 0.09% Co significant future potential exists. By completing pilot plant studies prior to shutting down, the plant engineering studies can be completed and the plant readied for restart by the time the nickel price improves."

Jan 1, 2017

By Christopher Snee

??care has to be taken that the design is driven by sound geological reasoning and rigorous engineering logic rather than by the very attractive images that appear on the computer screen.??Hoek 1999 Design of a cavern is inextricably linked to the engineering geology of the site. The importance of sound geological reasoning will be illustrated by transportation projects in New York City where there are proposals for at least 11 caverns. These caverns have been the subject of advanced exploration techniques and geological interpretation but even so the raw data falls short of the sophistication of modern numerical methods. This paper will give geological explanations for the engineering characteristics of the rock in New York City which will provide guidance for practitioners when approaching cavern design in New York and elsewhere.

Jan 1, 2008

By Dennis J. Riley

A. This outline addresses what a sub-contractor, or a subsub-contractor should do to get paid in the event the general contractor or building owner files for bankruptcy. B. Negotiating payment terms. Progress payments vs. "pay when paid". How a sub or subsub can avoid financing the contract. C. Court interpretation of "pay when paid" clauses allow postponement not excusal of payment. See, e.g., Seal Tite Corporation v. Ehret. Inc., 589 F. Supp. 701 (D.N.J. 1984) (where the court held that the general contractor could not delay payment indefinitely to the subcontractor in the event of non-payment from the owner); United Plate Glass Co. v. Metal Industries. Inc., 525 A.2d 468 (Commw. Ct. Pa. 1987) (where the court held that payment from owner was not a condition precedent to paying subcontractor but instead a timing mechanism indicating when payment should be made); But see. Straham v. Landis Construction Co., 499 So. 2d 417 (La. App. 4 Cir. 1986) (where the court strictly interpreted the "pay when paid" clause).

Jan 1, 1991

By Eleanor Abshire

THIS PUBLICATION is the third to be prepared as a result of a cooperative project by the Bureau of Ships and the Bureau of Mines for accumulating literature published on zirconium and hafnium. The undertaking also resulted in the establishment of an information center on zirconium and hafnium at the Bureau of Mines station at Albany, Oreg., for the use of research organizations and others. The present bibliography consists of references (with abstracts) to pertinent literature on zirconium. The first publication in this series was Information Circular 7771, Bibliography of Zirconium, published in April 1957. It consists of 969 abstracted reports and 645 U.S. and foreign patents. The second publication, called a supplement to Information Circular 7771, is numbered Information Circular 7830 and consists of 844 abstracted reports and 62 U.S. and foreign patents. It was published in October 1958.

Jan 1, 1962

Permian coal seams from the Tomago Coal Measures in the Northern Coalfield, New South Wales, were analysed petrographically and reflectance measurements made for each. Vitrite contents were moderate to high for most of the coals but for two they were very low.The mineral-matter contents were low to moderate by Australian standards. Different profiles of a particular seam could be correlated by petrographic methods.Standard seam profiles were drawn up and from these an idealized Tomago seam sequence was compiled. All the coals were of high-volatile bituminous rank. Their carbon contents, but not thcir reflectances, varied significantly with the quantity of vitrinite present.

Jan 1, 1968

By Thierry Bernard, Guy Gagnon

Blasting at very close proximity to urban areas is typically a situation where both local communities and mining stakeholders get nervous. The context becomes logically even more tensed when the blasting operations have to be performed above an old underground mine. When mitigating subsidence risks requires firing the largest possible shots, the nuisance control (flyrock, vibration, and noise) required by local and national regulations, contrarily urge for being more conservative.

Jan 1, 2014

By Pengfu Tan

Xstrata Copper at Mount Isa in Australia has operated one copper Isasmelt furnace and four P-S converters. The phenomena of foaming occur in above 10% of converter operations. A thermodynamic model of copper P-S converter and a viscosity model of converter slag have been developed to simulate the slag blow and copper blow. The model predicts the chemistry and viscosity of copper skims during copper blow. The effects of oxygen potential, charge of dirty materials, slag carry-over, under-blowing, over-blowing, and temperature on the foaming and viscosity of copper skims have been discussed. Some improvements of the industrial operations have been presented.

Jan 1, 2006

By Anthony Iannacchione

Coal mine bursts have represented a major hazard for U.S. mining operations for more than 90 years. During this time, many prevention controls have been developed and tested. This paper reviews 11 prevention control techniques. Although coal mine bursts are not common events in most underground coal mines, their occurrence almost always requires a change in mining practice. Over the many years of dealing with these hazards, specialized requirements for layouts and novel extraction sequences have been developed on a site specific basis. The keys to mitigating risks are to properly assess the coal burst hazards and to possess the knowledge and skills to prevent or remediate their occurrence.

Jan 1, 2008

By Wade Edward Speer

The Hiddenite District of Alexander County, NC has produced some of the world?s finest large emeralds since the first one was discovered 134 years ago. In fact, North America?s largest emeralds come from the district, making this one of the continent?s most unique gem deposits. In addition to emeralds, the Hiddenite District is also famous as the discovery site for the rare spodumene mineral hiddenite, first identified in 1881. Nowhere else in the world do these two minerals naturally occur together. The emeralds are a unique color variety of beryl (Al2Be3Si6O18) with trace amounts of Cr+3 and V+3 substituting for Al+3. The hiddenite (LiAlSi2O6) crystals also exhibit emerald green color due to traces of chromium. Consisting of three large deposits and numerous prospects, the district encompasses an area of 10 km2 (4 sq miles) centered on the small town of Hiddenite. Operations at the Adams, Ellis and North American Emerald Mines properties have been productive at irregular intervals since the 1880s. Currently, only the North American Emerald Mines property is being mined on a regular basis. Recent activity there has exposed a 3-hm2 (7.4-acre) pit with depths of 25 m (82 ft) that provides the best exposures of unweathered bedrock seen in the district in more than 120 years. Although no official records exist, public and private data indicate that the production of the entire Hiddenite District from 1880 to 2007 is about 70,000 carats of emerald and 20,000 carats of hiddenite. The bulk of the emeralds came from the North American Emerald Mine property (NAEM, formerly known as the Rist Mine) where sustained mining replaced the previous sporadic prospecting in 2000.

Jan 1, 2009

By D. Rahal

All ores have an economic optimum particle size (Wills and Napier-Munn, 2006). This optimum value is often a compromise between the need to achieve adequate liberation for the efficient separation and recovery of valuable minerals and the energy consumed by the crushing and grinding process. It has been recognized for nearly three decades that grinding is the most expensive and least efficient stage in mineral processing (El-shall and Somasundaran, 1984). At that time it was estimated that grinding consumed between 25 and 70% of the total power required in mineral processing. This recognition drove the development of new stirred mill fine grinding technology in the 1990s (Jankovic et.al, 2003; Enderle et. al., 1997; Massey, 2008). These milling technologies have a reduced energy consumption compared to traditional fine grinding using ball mills. In the ?coarser? fine grinding applications this improvement is approximately 30%. The benefits increase to above 50% in ultrafine grinding applications (Lichter and Davey, 2006). Despite these gains, the US Department of Energy reported that an additional energy savings of up to 37% is possible in the minerals industry. They identified continuing research and development and implementing best practices in both grinding and materials handling as the primary avenues for the additional reduction (BCS, 2007).

Jan 1, 2011

By S. Lolon

Spontaneous combustion in underground coal mines has become a serious problem particularly in the caved area (gob). Recent statistic has shown that approximately 17% of total 87 underground coal mine fires in the United States are attributed to spontaneous combustion (De Rosa, 2004). Spontaneous combustion results from a self-heating process in exothermic conditions. The accumulated heat, if not removed, is conducive to the rapid increase of temperature and may result in mine fires or explosions. It is well accepted that the interaction between oxygen and coal substances is the main cause for spontaneous combustion, while other factors such as pyrite, moisture, and bacteria play a secondary role to the self-heating of coal. Therefore, only coal oxidation is considered in this study. Coal oxidation occurs as coal comes into contact with air. This process involves complex phenomena in terms of heat transfer, chemical surface absorption, and energy balance related to inherent properties of coal (Wang et al., 2003). For simulation purpose, overall reactions can be simplified as suggested by Mitchell (1990): C + O2 CO2 + heat [65°- 94°C] (1) CO2 + C 2CO + heat [100°- 150°C] (2) Stoichiometric reactions (1) and (2) show that 2.66 grams of oxygen are required to oxidize 1.0 gram of carbon. Once the temperature exceeds 100°C, the reaction has little chance to stop. The crucial step in reducing spontaneous combustion risk is locating the ignition point of spontaneous combustion (hot spot). This information is useful in the effort of developing a preventive method effectively. In this study, this was conducted based on the best gathered information: ventilation surveys conducted in an existing longwall mine located in the western US; the laboratory experiments performed on a physical gob model; and the CFD models to investigate the flow behavior in the gob, the oxidation of coal, and heat transfer phenomena. The hot spot location is determined as a function of oxygen concentration and gob temperature. The critical values are the following: 5% (by volume) for oxygen and 100°C for gob temperature. CHARACTERISTICS OF GOB MATERIAL AND MODELS Permeability Concept Permeability is one of the key parameters in any study dealing with porous medium. This is determined by particle size and the ratio of void volume to the total volume (porosity) of porous medium. This relationship is known as the Carman-Kozeny equation (Scheidegger, 1957) and is given mathematically as [ ] where k* = theoretical specific permeability, m2 dm = the mean particle size, m n = porosity However, permeability tests with various particle sizes were carried out at the University of Utah?s ventilation model (Figure 1) to verify this relationship. These tests indicated a necessity to modify this theoretical relationship. A factor of 0.898 was obtained to make up the different between theoretical permeability and the experimental one. The modified version of (3) is given by: [ ] This equation is used to determine permeability of the simulated mine gob throughout the study. [ ] Mine Gob Material The gob is represented by zones filled with material of given size distribution. For physical measurements and CFD simulations, the material used were crushed rock and coal. Due to compaction, three different characteristics of gob material were used in the model: unconsolidated, semiconsolidated, and consolidated. In the real condition, the largest coal-rock particles are more likely to be located in the area behind the shields. This material is freshly broken and unconsolidated. The size of these broken particles is based on a study carried out by analyzing images taken from the area behind the shields in three coal mines in the United States (Pappas and Mark, 1993). The results have shown that the mean size of materials behind the shields is about 1.22 m. The permeability associated with this size was then obtained from (4) and permeability tests. This was 4.68 x10-7 m2. For semiconsolidated and consolidated zones, due to the lack of experimental data, these were determined through CFD simulations. These simulations were designed by assigning a permeability of 3.15 x 10-8 m2 for consolidated zone and 7.98 x 10-9 m2 to the other zone. The airflow pattern in the gob assigned with given permeabilities was expected to follow the experimental distribution (Brunner, 1985). The mean particle sizes for the semi-consolidated and consolidated zones were 0.02 and 0.006 m, respectively; smaller than those of the unconsolidated zone. Figure 2 shows the 3D view of permeability changes in the gob.

Jan 1, 2009