Search Documents

Understanding multiphase particulate systems is essential for the further advancement of mineral processing technology. Characterisation, analysis, and simulation of these complex systems provide a fundamental basis for the development of improved mineral processing technology. One of the more recent tools that can be used to help provide a foundation for improved mineral processing technology is high resolution cone beam X-ray micro computed tomography (CT). During the past ten years point-projection X-ray micro CT systems have been used for 3D visualisation and quantitative analysis of multiphase particulate systems. Analysis of packed particle beds containing as many as 30 000 particles can be accomplished in less than three hours with special software to establish the 3D characteristics of each particle in the population and the spatial organisation of the packed particle bed. Now, due to advances in X-ray optics, the resolution afforded with point-projection micro CT systems has been improved by at least an order of magnitude using a lens-based X-ray micro CT system. The development of software tools for the 3D characterisation, analysis, and simulation of packed particle beds using high resolution X-ray micro tomography (HRXMT) is discussed including examples of application in the areas of comminution (particle damage and preferential grain boundary fracture), exposure/liberation analysis (liberation-limited separation efficiency, including coal washability), and filtration/heap leaching (pore network structure of packed particle beds and simulated flow using the LB method of computational fluid dynamics).

Sep 13, 2010

By Carol Harrison

"Diseñar, implementar y evaluar un proceso de adquisición de tierras y reasentamiento ha sido un reto para los proyectos mineros en el pais, pues es un tema fundamental para el desarrollo del proyecto y reviste al mismo tiempo una alta complejidad en contextos sociales como el nuestro. Asimismo, no existe una reglamentación clara al respecto ni una institucionalidad que permita enmarcar el proceso, que al final resulta en una negociación directa entre dos partes. La presentación profundiza en ejemplos de experiencias de reasentamiento rural, particularmente en la definición y monitoreo de indicadores."

Sep 1, 2017

By A A. Ndiaye, A Galli

In a companion paper on current hedging practices in the mining industry (Armstrong et al, 2009) we showed that contrary to popular belief, mining groups are still using financial derivatives to hedge against foreign exchange risk and interest rate risk, and more recently against adverse changes in energy prices, notably the oil price. This paper presents a case study on a hypothetical gold mine to illustrate the impact that hedging policies could have on its profitability by reducing the downside risk due to adverse changes in the exchange rate and increases in fuel prices. The characteristics of the hypothetical mine have been set to reproduce those of a real gold deposit, the Kisladag mine that is currently being exploited by open pit methods in Turkey. This mine was selected because its feasibility study was available to the public. Geostatistical simulations are used to reproduce the inherent uncertainty on the recoverable reserves û stochastic simulations are used to generate the variability of the other three key sources of uncertainty: the gold price, the cost of energy and the exchange rate. A simple strategy based on straightforward vanilla options (puts and calls) was developed for hedging the last two risks, on the assumption that the company sells its production at the prevailing spot price.

Jan 1, 2009

By Yi Luo, Jian Yang, Hua Jiang

Surface subsidence events induced by underground longwall coal mining operations can cause various disturbances to surface structures ranging from integrity and stability to functionality problems. Highway bridges, as a kind of special road construction that can only tolerate smaller movements and deformations than road pavements, are particularly susceptible to severe influence caused by subsidence-induced ground movements and deformations. However, based on accurate subsidence prediction and correct influence assessments, efficient and effective mitigation and remediation measures can be designed and implemented to ensure the continuous service of bridges, safety of the travelers and smooth mining operations. In this paper, based on the predicted final and dynamic surface movements and deformations, the techniques to assess subsidence influence on the integrity, stability and functionality of bridge structures (e.g., decks, beams, abutments, etc.) are presented. A number of mitigation measures to protect the bridge structures are recommended along with an actual application case.

By D Kotzen

Online cyanide analysers have been successfully used to control free cyanide in the gold/silver leach process for over 15 years. Use of such analysers leads to cyanide savings and improvement in recoveries. Plants with leach cyanide analysers show both lower and more consistent cyanide levels in tailings. Cyanide code compliance requires meeting residual cyanide targets in tailings. Monitoring and logging of the residual cyanide in plant tailings and effluent is required. Meeting targets may require cyanide recovery/destruction processes to be implemented. The operating cost of destroying cyanide is often the same order of magnitude as the cyanidation cost. Various cyanide destruction and/or recovery processes are reviewed. Choice of a process consistent with the environmental and operational requirements is illustrated. Online weak acid dissociable cyanide (CNWAD) analysers have recently been developed and introduced on gold plants. The application of a WAD 1000 online CNWAD analyser at a large gold plant is presented. The analyser ensures code compliance, reduces cyanide destruction process operating costs and forms a historical record of CNWAD values in tailings.

Jan 1, 2007

The area between Merrygoen and Digilah is located on a structural high that separates the Sydney Basin from the Great Artesian Basin, and hence the stratigraphic succession of younger rocks overlying the basement is relatively thin. The stratigraphy is briefly described and it is shown that fluvial sedimentation prevailed from Upper Permian through to Middle Jurassic times. Flint clays occur in the Permian, Triassic and Jurassic but only those in the Jurassic appear to have commercial value at present. The chemical, mineralogical, and physical properties of the flint clays are discussed.

Jan 1, 1973

By Christopher M. St. John, Tony F. Zahrah

Empirical and numerical methods are the two extremes of the tools available for the seismic design of subsurface excavations and underground structures. Both have their limitations: when relying on purely empirical methods directly relevant experience may be scant; site data may be insufficient to justify a comprehensive dynamic analysis. The primary purpose of this paper is to review the analytical tools available to the design engineer of subsurface excavations and underground structures. Particular attention is devoted to simplifed models that appear to be applicable in many practical cases.

Jan 1, 1985

By Arash Khosravifar, Matt Steffan

An expansion of the City of Klamath Falls Wastewater Treatment plant required geotechnical seismic hazard evaluations and deep foundation design. The site is located on the shore of Lake Ewauna and is underlain by diatom rich lake deposits. Diatomaceous soils exhibit unique engineering properties that are not well understood. Cyclic Direct Simple Shear (CDSS) testing was performed on three undisturbed samples to evaluate cyclic and post-cyclic properties of the diatomaceous soils. Results from the CDSS testing indicated that the soils would not liquefy in the classical sense, though cyclic softening behavior was observed. The CDSS results were used to develop a Cyclic Resistance Ratio curve for the diatomaceous soil to compare with clean sand liquefaction curves. Seismic lateral pile capacities were developed using two approaches. One approach used conventional p-multipliers for liquefied soil and modified them to reflect expected excess pore pressure ratios. The other approach applied residual strength and fifty percent strain values from post-cyclic monotonic shear testing. A lateral spread hazard zone was identified along the Lake shoreline and reduced, seismic lateral pile capacities were recommended. The objective of this paper is to report the seismic design considerations for this project in a unique geologic and seismic setting. INTRODUCTION The engineering properties of diatomaceous soils have rarely been studied and the cyclic behavior under seismic loading is generally unknown. Some of the critical geotechnical uncertainties of diatomaceous behavior include potential for large consolidation settlement, influence of irrecoverable strains due to diatom particle crushing, shear strength (peak and residual), and cyclic properties. This paper presents results of cyclic shear testing, seismic evaluations and seismic lateral pile design in diatomaceous soils performed for the expansion of a waste water treatment plant in the city of Klamath Falls, Oregon, site of the largest recorded earthquake in Oregon’s history. The expansion consisted of adding six new facilities at the existing Plant including influent pump station (IPS) and headworks, aeration basin, tertiary treatment, and other buildings. The IPS/headworks and aeration basin will be founded approximately 15 feet below ground. The other buildings will be founded at grade. The existing facilities are supported by timber piles that penetrate the surficial diatomaceous soils and terminate on a hard underlying deposit. Figure 1 shows the site plan and proposed additions.

Jan 1, 2018

By Timothy P. Smirnoff

Sustaining the region?s mobility needs, achieving projected economic growth, and maintain Midtown Manhattan as a center of regional, national and global importance has led to continued investment in commuter rail and transit infrastructure in New York City and resulted in design and construction of large underground caverns. The current plans for stations in Manhattan include New York Penn Station Expansion (NYPSE) caverns for Trans Hudson Express (THE) Tunnel Project for New Jersey Transit (NJ Transit) and the Port Authority of New York and New Jersey (PANYNJ), Metropolitan Transportation Authority Capital Construction Long Island Railroad (MTACC/LIRR) twin caverns for East Side Access (ESA) Project, and station caverns of the No. 7 Line Subway Extension Project and Second Avenue Subway Project for Metropolitan Transportation Authority Capital Construction/New York City Transit (MTACC/NYCT). This paper provides a general overview of these large caverns now in design or construction in Manhattan, the area?s geologic setting, the geotechnical factors considered and approaches commonly applied for cavern design.

By Charlie Yates, Max Ramey, Kurt Nielsen, Michael Hardy

The Yankee Gulch sodium minerals project (YGP) is a solution mining project operated by American Soda. The mine operates on a federal lease administered by the U.S. Bureau of Land Management (BLM). Commercial operations began in November2000. In 1964, Irv Nielsen discovered nahcolite mineralization where the YGP pilot plant is now located near the Piceance Creek in Rio Blanco County, Colorado (Nielsen, 1969).Development of the project accelerated after Williams Corp., of Tulsa, OK, joined with American Alkali in1996 to form American Soda. Pilot testing by American Soda led to commercial permitting, plant design, construction and startup. Figure 1 shows the location of the Yankee Gulch leases and the location of the upper and lower plant sites.

Jan 1, 2003

By D. B. Felsher

"Lakeshore Gold’s Bell Creek Mill is located in Timmins, Ontario. The mill has been in operation since 2009 and has undergone several small expansions since then. In 2012 - 2013 the first major mill expansion was commissioned raising the mill capacity from 2,000tpd to 3,150tpd. This was done through the installation of a new ROM ore truck dumping facility, jaw crusher, ore storage dome, SAG mill, leach tank, CIL tank, and electrowinning cell. This paper will cover the equipment installed to raise the tonnage as well as the commissioning of the new equipment including problems encountered and how these problems were solved.IntroductionLake Shore Gold acquired the Bell Creek Mill, along with the Bell Creek Mine, from the Porcupine Gold Mines Joint Venture, a joint venture between Goldcorp Canada Ltd. and Kinross Gold Corporation, in December 2007.The Bell Creek mill, which processed ore from the Bell Creek Mine has consistently achieved recoveries of over 95%, is a conventional gold mill circuit, involving crushing and two stage ball mill grinding, gravity and leaching, followed by Carbon-In-Pulp (CIP) process for gold recovery. The facility had been placed on care and maintenance in 2002. At the beginning of 2009, the mill had been refurbished with an initial capacity of 800 tonnes per day and was subsequently refurbished to a capacity of 1,500 tonnes per day near the end of the third quarter of that year. The Mill was then expanded in 2010 to a capacity of 2,000 tonnes per day.In late 2011, the Company commenced a 50% expansion of its milling facility, from a processing capacity of 2,000 tonnes per day to 3,150 tonnes per day. Phase 1 of the expansion, which mainly involved enhancements to the solution circuit (“back end”) and increased the mill’s capacity to 2,500 tonnes per day, was completed at the end of 2012. Commissioning of Phase 2 of the expansion, to a capacity of 3,150 tonnes per day, commenced at the end of July 2013."

Jan 1, 2015

By J. A. Kost

A survey of 80 coal producers was conducted to determine the extent and scope of respirable dust control research for underground coal mines and the current methods employed to control respirable dust. Results of the survey showed that proper face ventilation and an adequate water spray system are sufficient to comply with mandatory standards in room and pillar mining. Difficulties still exist with longwall equipment, auger miners and buring machines. In these cases, known dust control techniques are not sufficient to obtain compliance. Present state-of-the-art face ventilation and water systems were discussed in addition to the sampling program.

Jan 1, 1980

Copper waste dump leaching is growing in importance because of the.large tonnages (up to 250,000 ton/day) of low grade waste rock available from open cut mining of copper deposits and proof that controlled leaching of copper from such dumps can be profitable.Overburden or waste rock, ranging in size from large boulders to fines, is dumped as cheaply as possible on sloping sites. Copper is leached from the dumps by applying up to 12,000 gal/min of leach solution (a combination of spent solution from cementation and make-up water) to the top of the dumps by various techniques.Efliuent from the dumps is sent to a cementation plant for copper recovery.Factors which may be controlled, either directly or indirectly, to give a controlled copper content in the dump efliuent (usually 1-2 g/l.) are the cycle of operations (i.e. the alternate wetting and drying periods), thevolume of solution applied to the dump, pH, Fe2+ and Fe3+ content or redox potential, oxygen content, bacteria and their necessary nutrients, and temperature.Dissolution of oxide copper minerals appears to be mainly a function of acid concentration. Copper sulphide minerals need oxidation for dissolution to occur and this is accomplished by a combination of oxygen,ferric ion, and bacteria. Oxidation of pyrite, oxidation of Fe2+ to Fe3 +, and hydrolysis of Fe3+ are of some importance in leaching practice. The presence of gangue carbonate minerals is detrimental.Physical factors connected with penetration of solution into large rocks are important and the treatment of an individual dump usually extends over a period of many years. Recovery of copper from solution is usually achieved by cementation with iron (usually in the form of crumpled cans) but the use of sponge iron is becoming more important. Iron consumption varies from 1 to 4 lbiron per pound of copper. Preconcentration of the copper in the efliuent solution by solvent extraction followed by electrolysis may become a useful method.Application of dump leaching techniques to metals other than copper depends on finding an economic method of recovering the metal from solution...

Jan 1, 1967

By Franciszek Letowski

"Recovery of precious metals associated with a sulphidic matrix has an important economic effect on complex sulphide ore treatment. Because a significant portion of the silver and gold associated with pyrite are rejected to tailings during the selective flotation of pyritic Zn-Pb-Cu ore, other ore processing routes have been investigated.Direct leaching of the ore with ferric sulphate solution followed by separation of different components of the solid suspension by flotation was applied. Such a process allows for: production of zinc sulphate solution; transformation of galena PbS to insoluble lead sulphate PbS04 and its accumulation in a non-floatable fraction together with precipitated geothite FeOOH and other insoluble gangue minerals; separation of sulphur and non-decomposed sulphides in the floatable fraction.Laboratory research carried out on the ore samples from an Alaskan pyritic deposit from the Delta region indicates that gold and silver are mostly concentrated in the floatable fraction.Total recovery of zinc from the ore attains 96.5% to 98.5% after ferric sulphate leaching. About 85% of copper was extracted from the ore during the ferric sulphate and subsequent ferric chloride leaching, and about 6% of the copper remained in the non-floatable fraction and mixed fraction during the leaching-flotation step. Extraction of lead from the nonfloatable fraction during leaching with calcium chloride solution attained 98% to 99%. Extraction of silver from the floatable fraction during leaching with ferric chloride solution reached 98%. Extraction of gold from the floatable fraction during cyanide or thiourea leaching reached 71% to 89%. The results of the laboratory research are presented."

Jan 1, 1987

By George A. Mealey

Caving mining methods that are based on a planned caving of rock above and/or at times surrounding the material being mined can be classified in three broad categories: longwall mining, sublevel caving, and block caving. Each of the three methods involves a distinct technology as well as art of operation. Each requires a relatively large, regular, and predictable ore body. As a rule, the effect of mining results in some form of impact or change on the surface. Operationally, underground caving methods are characterized by high productivity as well as a high percentage of extraction of the mineral being mined. A key element for the productivity of this form of mining is the ability to standardize the various elements of work taking place underground. Therefore, work-men may perform a specialized role rather than function as all-around miners. Further, the nature of the mining methods lend them to a high level of mechanization. Operations and manpower can be centralized into a relatively small area where supervision can be concentrated and therefore be more effective. Productivity as well as safety benefits thereby. The caving method is unique in that the exploitation openings are deliberately destroyed by the process of mining. Rock mechanics principles focus on the ensurance and the propagation of the cave as well as the continuance of the mine openings designed to extract the broken ore. As a rule, production operations are designed to maintain a steady, continuous flow of ore from the extraction areas. This steady flow rather than an intermittent flow tends to promote good caving action as well as reduce hangups.

Jan 1, 2008

By H. Arima, T. Fujita, W. Yen

The copper catalyzed gold oxidation and reduction mechanisms in ammonium thiosulfate solution were investigated by Eh-pH diagram based on the optimum reagent combination for 60 mass% -75 µm silicate ore at 16g/t Au with the maximum gold extraction of 92% and the minimum ammonium thiosulfate consumption of 23 kg/t-ore for 24 hour’s leaching at ambient temperature. The gold recovery by cementation was nearly 100% by Zn and Al powders at Metal/Au mass ratio of 30, and around 95% by Cu powder at Cu/Au+ mass ratio of 50. In order to oxidize the gold efficiently with the less thiosulfate consumption, the stable region of [Cu(NH3)4]2+ should be as wide as possible in the region, where [Cu(S2O3)2]3- was more stable than [Cu(NH3)2]+. In order to reduce gold from the pregnant solution with the less metal powder’s (Zn, Cu, Al) consumption, the stable region of [Cu(S2O3)2]3- should be wider than [Cu(NH3)2]+ on copper precipitation. Zinc powder may recover gold more efficiently than copper powder with the similar trend on the effect of ammonia, copper and thiosulfate. However, the large amount of copper will be co-precipitated along with gold since the stability of zinc ammine and thiosulfate complexes are higher than that of copper’s. Aluminium may reduce gold efficiently at higher thiosulfate concentration and pH. These results were confirmed and compared with the optimum reagent combination for finer grind sample at 100 mass% -75 µm, which is the optimum ore size for the standard cyanidation at 1.0 g/ l NaCN to obtain about 95% gold extraction. The optimum reagent combination was concluded as 0.5 mol/l NH4OH, 0.0001 mol/l CuSO4*5H2O and 0.05 mol/l (NH4)2S2O3 with the result of 94% gold extraction and 3kg/t-ore of ammonium thiosulfate consumption. Gold and copper stabilities were well agreed with the result of coarser grind ore thermodynamically. The lower reagent combination will reduce gold oxidation power, but significantly minimize the reagent consumption. From this pregnant solution, nearly 100% of gold was successfully recovered by zinc precipitation at Zn/Au+ mass ratio of 30. Aluminium and copper precipitations resulted in less than 40% of gold recovery at Metal/Gold mass ratio of 30. The reagent consumption cost on this lower reagent combination followed by zinc precipitation was $1.6/t-ore, while the cyanidation was $3.1/t-ore. Thiosulfate oxidation mechanism indicated the similarity to Belousov-Zhabotinsky reaction.

Jan 1, 2002

In today?s high tech world, systems are getting bigger, faster, better. To remain at the leading edge, in any business, depends on accurate but flexible design thereby allowing operational managers to provide alternatives to improve their operations. The ultimate goal is to deliver to plan, with optimum economics. Mining is no different, with falling prices and escalating costs, improved margins become the focal objective. There are many ways to achieve this, ranging from operational efficiency improvements through production scenarios to planning initiatives. Of all, planning usually receives the least attention, yet it is the area of most influence on the NPV of the reserve. With computer technology, numerous concepts and iterations are possible thereby closing the gap between optimal and actual design. This paper discusses the application of the split shell design at the De Beers Venetia open pit in South Africa.

Jan 1, 2001

Jan 1, 2004

The epithermal Au-Ag deposits of the Hauraki Goldfield have formed in the convergent plate margin setting of the Coromandel Volcanic Zone (CVZ). The deposits form as siliceous lodes in the upper parts of geothermal systems associated with andesitic and rhyolitic volcanism. Two types of low sulphidation epithermal mineralisation are recognised in these volcanic terranes. Vein deposits within the rhyolitic terrane in the east and south of the CVZ (Whitianga Province) are typified by Chalcedonic Silica-Adularia-Illite type mineralisation. The veins are hosted by both rhyolite-dacite volcanic rocks and the underlying andesitic basement. The mineralisation formed by episodic violent decompressional boiling of deeply circulating meteoric water, with some magmatic fluid contribution; this boiling was associated with hydraulic fracturing and hydrothermal eruptions in geothermal systems where the piezometric surface of the deep geothermal reservoir lay near-surface. Such episodic boiling provides chalcedonic veining, banding and brecciation textures, adularia stability, bladed calcite, and extreme loss of H2S gas from the fluid to cause major gold deposition.   Crystalline Quartz-Illite-(Adularia-Kaolinite) type mineralisation is widespread in the andesitic terrane forming the northern and western portions of the CVZ (Kuaotunu Province). There is a spatial association with weak mineralisation of the high sulphidation (Vuggy Silica-Alunite-Kaolinite-Illite) epithermal type and porphyry eu-Au type. Crystalline Quartz mineralisation is probably formed by the mixing of shallow acidic groundwaters with the ascending deep geothermal fluid in geothermal systems beneath andesitic stratovolcanoes. The piezometric surface to the deep geothermal reservoir in these systems is likely to lie at considerable depth, with acidic gases rising from the geothermal reservoir condensing within the overlying vadose zone. The cooling effect, oxidation and pH decrease accompanying mixing apparently overcomes the dilution effect, and results in quartz deposition, illite (and locally kaolinite) alteration, and precipitation of gold. A high level of base-metal sulphide precipitation also enhances gold deposition. Violent boiling of the mixing fluids may occur at local structural dilation sites, producing high grade "bonanza" gold mineralisation.

Jan 1, 1991

By M J. Kongas, K M. Saloheimo

This paper presents the art of on-stream particle size and elemental analysis used at iron ore concentrators, followed by the results and experiences from several sites.Online particle size analysis is rather common at medium- to large-sized concentrators. Online X-ray fluorescence (XRF) elemental analysis, however, is only used in some iron ore concentrators, while it is a routine practice in base metal concentrator plants. Online XRF analysis is applicable for process monitoring and control down to four to five per cent silica by measuring Fe assays accurately. With lower silica content, direct measurement of silica and other light elements is required. Some light element analysers that are based on the prompt gamma neutron activation analysis (PGNAA) method have been developed, but they have not performed up to expectations with slurry analysis. Other methods have been tried though these have not been used beyond prototype installations. Operating online light element slurry analyser installations are not common in iron ore applications.There is an economic incentive to mine lower and variable grade iron ore resources, which require concentration and removal of several impurities to produce high-quality concentrates for pellet production. Monitoring such operations by on-stream analysis has significant economic benefits, and there is a need to develop a dependable slurry online analyser for Si, Al, Mg and other light elements. The latest developments in slurry on-stream light element analysis are described.CITATION:Kongas, M J and Saloheimo, K M, 2013. Online slurry analysis for process control and monitoring at iron ore concentrators, in Proceedings Iron Ore 2013 , pp 303-308 (The Australasian Institute of Mining and Metallurgy: Melbourne).

Aug 12, 2013