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The topic of the relationships between energy and particle size has had two very active periods -the first in the early thirties, when the relative merits of Rittinger's and Kick's proposals were vigorously debated; the second in the early fifties, when Bond's Third Theory was published. This second stage has produced several contributions that have provided a clearer picture of energy /size correlations in comminution. Derivations of a general relationship have been made from single-fracture experiments and from the rate of comminution, and both methods arrive at an equation of the type E = AK-11? The constant A in the equation may be regarded as a grindability parameter. In some respects, an understanding of the phenomena associated with comminution is still lacking, and research in this field should therefore be expanded. T HE SEARCH for a relationship between the energy consumed in comminution and the size of the broken product has been long and varied, and many

Jan 1, 1964

By Tom Cooney

A small number of mining contractors worldwide have evolved their businesses to be able to provide a ?total service solution? to their clients. Thiess, an Australian-based international mining service provider, works with numerous clients to tailor delivery methods and commercial arrangements to suit individual projects. The benefits of Thiess? extensive experience is brought to each client and project, whilst business improvement within projects, to the mutual benefit of both the client and Thiess, is a key part of all long term contract relationships. Historically, optimal business outcomes were closely related to the achievement of production and cost performance measures. Whilst these remain fundamental to successful mining businesses, other elements of sustainability are assuming increasing importance. As a large energy user, greenhouse and energy management is becoming an important part of Thiess? business. Thiess is a signatory to Australian government initiatives such as Greenhouse Challenge Plus, and is integrating energy management into its operations and business improvement programs, in many cases to the benefit also of the client. This paper will highlight the benefits that an organisation such as Thiess can bring to a mine owner. Thiess? approach to business improvement and cost reduction, sustainability and energy management, as well as the relationship between these will also be considered. Increasingly, overall mining performance is dependent on the alignment of formally disparate elements.

May 1, 2007

By S. D. Botts, F. Cantuarias

"The Antamina project, owned by BHP Billiton Plc, Mitsubishi Corporation, Noranda Inc., and Teck Cominco Ltd., is a $2.3 billion copper/ zinc project, located in the Ancash Department of Peru. The project consists of an open pit mine, a 70 000 ton per day concentrator, a 302 km long concentrate pipeline, port facilities, a new access road, power line, and town site. The project is designed to produce up to 1.5 Mtpy of copper and zinc concentrates over a 23 year project life, and will be the third largest producer of zinc and the seventh largest producer of copper in the world.This mega project is the largest mining investment in the country and, during its construction stage, was the most important construction project worldwide. On May 28, 2001, Antamina commenced testing operations and four months later, it reached commercial production. Antamina was officially inaugurated on November 14, 2001 by Peruvian president Alejandro Toledo.The construction stage of the project generated 8000 direct jobs, with a peak of 10 000 employees, and 30 000 indirect jobs. The permanent workforce consists of approximately 1650 employees, the vast majority of which are Peruvian Nationals, around 30% of whom came from the region where the deposit is located. Approximately 5600 indirect jobs were generated from the project. Independent sources state that Antamina increased the Peruvian mining exports by 30% (mining exports constitute 50% of Peru’s total exports) and Peruvian GDP by 1% in its first year of full operation in 2002.Since winning the privatization bid for the project in 1996, the company has implemented an approach to community development and environmental protection based on sustainable development principals. Throughout the development of the project, a number of initiatives have been undertaken to ensure full involvement of the local populations in community development activities and the company’s environmental program.Due to its size, difficult logistics, cultural considerations and financial aspects, the project has faced a number of unique challenges in the area of environmental protection and management of community interaction. Antamina has been innovative in its approach to these issues and, as a result, has set new standards in Peru for environmental and community management and sustainable development."

Jan 1, 2003

By Thomas C. Poulter

Abstract The Poulter seismic method of geophysical exploration is an attempt to obtain an increased efficiency in the conversion of the energy of an m~pl06ion into useful energy which has directive properties and which contains a minimum of random frequency and random phase relations. Very little effort has been made in the past to simplify OT even control the uniformity of the seismic energy being introduced into the ground. The Poulter seismic method is also an attempt to improve the signal-to-noise ratio not merely by trying to complete the impartial filtering done by the earth on ,the continuous spectrum of primarily high-frequency energy radiated from a shot point but by applying a frequency control at the point of origin of the seismic wave. The energy from a shot-hole charge is peaked in a frequency which is much higher than will be transmitted through the ground, and its absorption introduces background interference. Only 10 to 20 per cent of the seismic energy of a shot-hole charge .is directed downward in a 90-degree vertical cone, whereas, from a pattern of charges detonated above the surface of the ground, 85 per cent of the seismic energy is included in a 90-degree cone and in some cases it is even confined to as small as a 30-degree cone. This greatly reduces the horizontally distributed energy, thereby producing a marked improvement in the signal-to-noise ratio. The frequency of the signal energy may be peaked in a rather narrow range by the proper application of two or more impulses upon the surface of the ground controlled as to direction, magnitude, and timing. These impulses may be controlled by the reflection shock wave technique, the pressure pulse technique, and the sequence firing technique, using the primary controls as outlined. The information obtained from the study of directivity of seismic energy in a high velocity, uniform material such as the ice on Taku glacier, in the Juneau ice field in Alaska, has been of great assistance in the application of the method to oilfield and mining problems.

Jan 1, 1950

By S. L. Aaroe

"TYRETHANE PRODUCTSTyrethane® is the family brand name which has been adopted by The W. S. Tyler Company of Canada, Limited to identify its polyurethane products. Since we have been manufacturing Woven Wire Cloth for over one hundred years and have been the innovator for most of the product improvements and developments of that industry, it is only natural that our first and primary efforts involve the use of Tyrethane® as a screening medium. The product is ideal for application in the mining industry and other operations where the rate of wear on existing media is exceptionally high.In the event that you have already had some experience with polyurethane it should be poirted cut that there are many grades of the material. The polyurethane used in Tyrethane® Products will be compounded in a variety of chemistries and different heat treatments will be used to develop best mechanical properties to handle specific applications. However Tyrethane® will not be a ""cure all"" but when it is properly applied as a screening medium it will assist by lowering the unit cost for screened materials.Prior to an explanation of the advantages of Tyrethane® let's review the conventional screening media whose applications may be considered as good candidates for replacement by Tyrethane®.1.,Woven Wire Cloth.2.,Perforated metal screens.3.,Rubber faced perforated metal screens.4.,Perforated rubber screens.5.,Cast steel screen segments and weldiments.6.,Profile wire.In most cases a Tyrethane® section is designed for a one for one replacement of the material now being used. It is rarely necessary to modify the screening equipment to enable you to install the Tyrethane® Product although it may be desirable to take some steps to improve the service life of hold down components such as Clamping Strips or Tension Members. Those parts can be encapsulated in polyurethane if necessary.To fabricate the Tyrethane® section we have three basic building blocks. They are: (1) Small molded segments having square or slotted openings, (2) Reinforcing material and (3) the raw liquid polyurethane."

Jan 1, 1976

By Réal Tanguay, Mathieu Piché, Jacques Carignan, Charles Beaudry, André Bonenfant

"Le gisement Isle-Dieu est situé sur le flanc sud de l'anticlinal de Galinée. La stratigraphie locale comprend, de bas en haut, la rhyolite du Groupe du Lac Watson surmontée par le basalte du Groupe de Wabassee. Un horizon repère, siliceux et sulfure, d'origine sédimentaire, appelé ""Tuffite Clef', est présent au sommet du Groupe du Lac Watson et pend à 45° vers le sud.Le gisement Isle-Dieu est constitué par une lentille qui recoupe, en partie, la ""Tuffite Clef"". Elle est séparée en deux trorçons par un dyke de tonalite. Les données obtenues à partir des forages effectues à travers la rhyolite sous-jacente permettent de définir les zonations chimiques et pétrographiques de la cheminée d’altération.Ces transformation minéralogiques et chimiques sont caractérisées par un enrichissement en MgO, Fe2O3, MnO et un appauvrissement en CaO, SiO2 et Na2O. La zonation spatiale de ces altérations permet de mettre en évidence la géométrie et l'extension des conduits hydrothermaux. L'épaisseur maximale des sulfures massifs au sein de la lentille est en étroite relation avec l’importance des zones d'altération. Les patrons de variations chimiques dénotent une orientation préférentielle WNW des conduits hydrothermaux. Les parties les plus altérées et les plus déformées présentent localement de fortes variations positives en Zr, Nb, et terres-rares; ces concentrations sont vraisemblablement imputables a /' enrichissement résultant de la diminution du volume lors de l'altération.L'étude pétrographique montre que la porosité et la perméabilité du milieu ont joué un rôle important dans la circulation des fluides car les roches de la cheminée présentent des phénomènes de dévitrification, de bréchification et de microfracturation très prononces. La nature magnésienne de certaines chlorites et la perméabilité accrue du milieu semblent en accord avec le modelé propose par Roberts et Reardon, ( 1978 )"

Jan 1, 1990

By J. E. Quinn, S. Wolstencrof, K. H. Soldenhoff

Ion Exchange (IX) using Strong Base Anion Exchange (SBA) resins is conventionally used to purify uranium from sulfuric acid pregnant leach solutions (PLS), particularly when uranium grades are relatively low. However, the presence of chloride in the PLS interferes negatively with conventional SBA based IX processes, by reducing the uranium loading on the resin. Chloride can be present in the PLS due to the use of saline bore or seawater in leaching, or chloride containing leach/IX reagents. ANSTO has been examining strategies to combat this problem for several years. ANSTO previously reported that a recently developed high-capacity SBA resin was capable of extracting uranium efficiently from saline leach liquors produced at Boss Resources’ Honeymoon in-situ recovery mine in South Australia. The resin was tested successfully in a 2017 Field Leach Trial carried out onsite in the existing wellfield area. While the piloting was extremely promising, the elution was more challenging, with eluate tenors limited to 2 g/L U3O8 using NaCl. This is due to the resin’s strong affinity for the uranium complex, which makes it difficult to elute efficiently by standard methods. In this paper, we describe a novel elution process developed for strong base resins that significantly improves upon conventional methods. The process, developed by ANSTO, is based upon conversion of the extracted uranyl sulfate species to uranyl carbonate, followed by elution with sodium chloride. The loading and elution process was demonstrated in continuous locked-cycle piloting conducted at ANSTO in 2019. The results were excellent, with eluate tenors of 8–9 g/L U3O8 achieved from Honeymoon PLS containing 50 mg/L U3O8, with very little transfer of impurities. In subsequent test work, the eluate was shown to be amenable to uranium peroxide precipitation. The results represent a huge step forward for the purification of uranium from saline leach liquors.

Jan 1, 2020

By S. Vongpaisal, T. R. Yu

"A set of new blast damage criteria has been developed, with special reference to blasthole mining operations, for assessing damage by incorporating the vibration level, rock properties, site characteristics and the effects of ground support systems. The main objective of this work was to provide a database with reasonable accuracy for use in optimizing blast design, numerical analysis and ground control expert system module development.The new damage criteria allow one to estimate the degree of damage to rock structures in terms of a dimensionless parameter defined as Blast Damage Index (BDI). This allows for the description of blast damage in a unified form, and facilitates the development of codes for numerical modelling to express the degree of blast damage universally. A number of field investigations from several stope production and slot opening blasts at a large underground base metal mine were carried out to verify the developed index. The results show a good correlation between the observed damage and the type of damage predicted from the BDI values.Practical measures are also provided for minimizing blast damage in large underground blasthole mining operations"

Jan 1, 1996

By Michael S. Moats, Alex Luyima, Tomas Oliveira

Some commercial copper electrowinning facilities use Cyquest N-900 (a polyacrylamide) or HydroStar (a modified polysaccharide) to improve the density and smoothness of copper electrodeposits. However, the effects of these additives have not been studied extensively in the open literature. Thus, the electrodeposition of copper at 40 oC from a non-stirred synthetic electrowinning electrolyte (40 g/L Cu2+, 160 g/L H2SO4, and 20 mg/L Cl-) in the presence of various concentrations of either additive was evaluated using cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS). CV results show that neither additive has much effect on the nucleation overpotential of copper electrodeposition on stainless steel. However, Cyquest N-900 polarized the copper deposition reaction upon the return sweep. The EIS data indicates that Cyquest N-900 increases the reaction’s charge transfer resistance and creates a second low frequency loop. HydroStar had minimal effect on the electrochemical data generated by CV or EIS. Thus, the mechanism by which HydroStar affects the copper deposition reaction still needs to be determined.

Jan 1, 2014

By Bahram Samani

The Bafq - Saghand ore belt (metallogenic zone) is the main region, where the major discovered Uranium resources are located. This belt is a unique Upper Precambrian terrane experienced Katanga ? Pan African tectono ? thermal events. The oldest sialic crust was formed during the middle Proterozoic and followed by K-granite intrusions of Lufilian Cycle (850-800 M.Y.).This event caused Tectono ? Magmatic ? Activization (T.M.A) characterized by intracontinental rifting and associated ore formations. This zone was considered as an iron ore belt in 1960s ? 1970s, and U ? Th ? REE belt in 1980s ? 1990s, but by new discovered of U ? Mo (Co, Au, As, Cu) mineralization is assigned as a U - Polymetal zone, hosting the full sequences of iron oxide (Cu, Au, U) ore forming groups. On the basis of detailed investigations this zone is characterized by the following peculiarities: This zone is the vestigial vessel of Gondwana basement, where the oldest granite and the first platform clastic cover is exposed. This zone is marginal part of Precambrian continental crust, consolidated in 1.3-1.0 B.a. The sub mature continental crust experienced Lufilian Orogenic and Katanga ? Pan African Tectono ? Thermal event by intercontinental rifting, and ore mineralizations. The ore forming stages were sequential processes, started by enriched mantle derived metallogeny, and ended by interaction of silanes/ HACONS (derived from outer core) with crust. The magnetite- apatite (REE, Ti) metallogeny developed from alkaline- ultrabasic magmatic differentiation, capable to from Au- Ni- Sulfide intrusive massifs during 850- 800 Ma. Degassing of silanes/HACONS from deeper level, not only caused mantle enrichment, and plume upwelling as a frontal load, but also played the main role to develop regional Si (-Na-K-Mg-Ca-Co3) metasomatism, and formation of U- Th- Ti- REE- (apatite, magnetite) deposits. The latest (583-510 Ma old) felsic magmatism was major IGU from U-Mo (-Co-As-Au-?Cu?) hydrothermal vein- type deposits. The albitite- type U- Ti- REE (Th) mineralization could be formed by interaction of ascending, and descending solutions along the deep- rooted structural conduits.

May 1, 2007

By Schrade F. Radtke

THE law of our present industrial society is the law of the jungle. By this I mean survival of the fittest. I do not refer to man or animal or the development of superior genetic strain. Rather do I refer to one's product, one's process, or one's material of construction. Each must perform in a superior manner or it is doomed to extinction; it must be steadily improved so that it can meet the competition of ether materials, of other equipment, or other processes. We have before us the classic examples of the horse and buggy vs the automo-bile, cf silk vs nylon, of the steam locomotive vs the diesel engine; in each case, a superior product has virtually wiped out its predecessor. Furthermore, a product, process, or piece of equipment is sold on its performance, together with engineering data which define its •characteristics and performance. For the most part, the present day sales-man must deal in terms of engineering performance of his product; he must know competitive materials -their strength and limitations as well N either old fashioned salesmanship, tradition, nor custom could have saved the horse and buggy from extinction; a superior product which has been steadily and con-sistently improved won out, 'and in turn, this change-over caused a dramatic• change in our whole way of life.

Jan 1, 1960

By B. H. Kim

It is hypothesized that the standard approach adopted to characterize the ground and to determine the rock strength properties at depth are flawed and generally tend to underestimate the rock strength and possibly the stiffness, particularly when the rock mass is characterized as massive to moderately jointed or blocky to very blocky. It is therefore necessary to conclusively established that the hypothesis, that the rock strength in highly confined rocks is greater than generally anticipated, is actually valid and generally applicable, and then to develop new procedures to establish rock parameters that can be reliably used for the design of deep excavation.

May 1, 2009

By D. Hatfield

"Flotation plants typically aim to maximise recovery at or above a target grade. As the ore from the mine varies, operators increase or decrease the mass pull in different flotation banks by adjusting air and level set points in order to achieve target concentrate grade. A methodology has been developed to maximise overall recovery at target grade by determining the optimal mass pull for each bank. However, the approach of targeting equal grade for each ore type in the deposit leads to sub-optimal overall recovery. This is because some ore types sacrifice a large amount of recovery to reach target grade while others easily achieve target grade and can be processed at higher than target grade for little or no loss in recovery. Processing different ore types at different grades and blending the concentrates therefore gives a higher overall recovery.This paper presents a case study where an 80 year production forecast was made for a large Chilean copper concentrator in feasibility stage. A circuit model was created using SGS’s Integrated Geometallurgical Simulator (IGS) for the different ore types to be processed. The model was calibrated from standard rougher flotation tests (MFT), cleaner tests and from the results of plant surveys of similar operations. The pull rates for each bank in the circuit were determined to achieve an optimal graderecovery curve for each ore type. These curves were combined at different concentrate grades for each ore type to obtain the mathematically optimal overall recovery at target grade. The paper shows a methodology for obtaining an optimal combination of operating conditions for each ore type to maximise overall recovery at a set combined concentrate grade."

Jan 1, 2013

By Chris Carr

This paper describes the process employed and the work undertaken to enable the surrender of the mine permit relating to the two tailings deposits at the abandoned Red Mountain Mine site near Rossland, BC. The first phase of the work undertaken was to provide urgent remedial work for protection of the environment, primarily through rehabilitation or replacement of surface water drainage systems. The second phase was to up-grade the water management systems to the appropriate level given their consequences of failure. The final phase of work is to ensure long term geotechnical stability of the facilities to the same level of risk. Establishment of a sustaining fund will facilitate long term monitoring and maintenance of the facilities.

May 1, 2002

By S. Banisi, J. Marois, A. R. Laplante

"This paper compares the behaviour of gold and ore in the grinding circuit of Hemlo Gold Ltd. Particular attention is given to grinding kinetics, classification behaviour, and liberation. For grinding kinetics, laboratory grinding of gold flakes and silica, 840-1200 um in size (14/20 mesh), was also performed to provide a standard for comparison and to study in a controlled environment the mechanisms of breakage, folding, smearing and impacting.Grinding kinetics were characterized at laboratory scale with breakage and selection functions. The breakage function showed that 75% of gold disappearing from the 840-1200 um class reported to the 600-840 um; this figure is much higher than for silica ( 46%) or most other minerals, and implies that comparatively fewer fine fragments are produced from the breakage of gold flakes, on account of gold's malleability. The selection function of silica was four times that of gold. At plant scale, the ratio of the selection function of ore and gold increased from 6 for at 50-100 um to 20 at 500-1000 um.Observation of original flakes and their fragments with the scanning electron microscope showed that the main mechanism of ""grinding"" from the 840-1200 um to the 600-840 um class was folding rather than actual breakage. This was confirmed by a measure of individual flake weight. The postulated breakage cycle is that relatively globular flakes become increasingly serrated through grinding; they can then regain their original shape through folding and reflattening into cylindrical and spherical shapes, as the majority does; however, some fragments will at this point undergo actual breakage. Photographic evidence is presented to support the proposed mechanisms.Smearing of gold unto silica was observed when silica was ground after a gold, and embedding of silica into gold flakes when gold was ground after a silica. Both mechanisms occur whenever gold and harder minerals are jointly ground, and result in ""unliberation"" of gold. It is postulated that smearing of gold onto other minerals plays an important role in explaining how gravity recovery can increase overall gold metallurgy, especially when used ahead of flotation.Classification of gold in the primary hydrocyclones takes place at a much finer cut-size than ore, 20 vs. 57 um. This and the slower grinding kinetics result in high gold circulating loads in the primary loop, 6700%, and a gold content in the primary cyclone underflow (PCUF) is twenty four times that of the ore. The gold size distribution for primary cyclone overflow is much finer than that of the ore, although they are essentially similar in the PCUF.Liberation, or more accurately ""gravity recoverability"", was assessed with a 7.5 cm (3"") Knelson concentrator. It varied between the thirties for the primary mill discharge and two cyclone overflows, to highs of 89 to 92% for the PCUF and secondary mill discharge, 89 and 92%, respectfully."

Jan 1, 1991

By M. A. T. Cocquerel, J. G. Eacott

"Simulation techniques may be used to optimize existing processes and plant operations, and in plant design at the engineering study stage of a project . This paper describes the latter application, using a computer, to optimize the concentrate stockpile requirements of a modern copper smelter.A large open-pit mining operation is envisaged and it is assumed that copper concentrate is smelted in two flash furnaces. The proposed mining plan gives rise to metaffurgical considerations in smelting which dictate that concentrate blending is carried out in the early years of operation in order to eliminate wide variations in the grade of concentrate charged to the furnaces . Stockpiling facilities are therefore necessary for blending purposes and also to provide a strategic reserve of concentrate to ensure continuity of concentrator and smelting operations.The objective of the study is to determine the optimum size of concentrate stockpile required to take account of both metaffurgical and strategic considerations. Two separate simulation models are developed to achieve this objective. The first model is used to determine the minimum size of stockpile necessary for blending purposes to smooth out variations in concentrate grade between 15 - 60% Cu, with associated 34 6% Fe, respectively, and ensure that the concentrate fed to the furnaces does not faff below 12% Fe, which is considered a minimum for good smeltability.The second simulation model covers a projected three-year operating period and indicates the maximum size of stockpile which is likely to develop during scheduled and unscheduled shutdown periods in the concentrator and smelter.Covered storage volume and conveying facilities for the optimum size of concentrate stockpile can be designed based on the results generated by the simulation models."

Jan 1, 1980

By J. Sliwinski, J. Oliveira

"The application of geometallurgy and corresponding sample selection can take on several formats within industry. Current practice can range from a strictly geostatistical approach to one in which geological and metallurgical parameters are used in combination to create a representative sample selection strategy. The stage of a project and the level of information available at the time of sampling influences the methodology used to create a representative sample.A geometallurgical study of Carpathian Gold’s Rovina Valley Project in Romania is used to demonstrate a sample selection strategy that integrates geological, mineralogical and metallurgical data to maximize the relevance of the geometallurgical unit definitions. This approach, practiced by Xstrata Process Support for its’ clients, ensures that the results of the metallurgical program can be interpreted in the context of these units.INTRODUCTIONGeometallurgy is a cross disciplinary approach in which metallurgical performance of an ore is linked to intrinsic geological and mineralogical characteristics. The objective of a geometallurgical study is to characterize the range of metallurgical performance of an orebody. This allows the geoscientist or metallurgist to create a robust flowsheet able to treat the full range in variability and to develop production strategies to maximize financial performance. The standard approach is to individually sample and test a series of ore types or geometallurgical units. Several different approaches are used in industry to define what constitutes geometallurgical units and how to sample them.One current methodology is the use of multivariate statistics. Geochemical data along with available geological data are used to define multiple variability domains (Williams, 2004; Walters, 2009). There are risks associated with this methodology since the extent of the data set itself may not support a purely statistical approach at the time that metallurgical units need to be defined. The assay suite collected by exploration programs is often limited to pay metals while metallurgical performance is often affected by ore gangue components. Furthermore, in many cases metallurgical scoping and pre-feasibility studies take place prior to the availability of extensive geochemical data sets. Purely statistical methods can produce multiple populations which require extensive sampling, testing and validation prior to consolidation into a reasonable number of composites for metallurgical testing. Methodologies are therefore required that allow representative sampling and testing of consolidated geometallurgical composites to occur at various phases throughout the development of a mining project."

Jan 1, 2013

By Tom Demorest

SMART is an association of mining companies that meet regularly to coordinate the technology development needed by the mining industry. Since 1995, the member companies and institutions have directed research and influenced the manufacturers and suppliers to improve surface mining technology and services. SMART actively supports learning seminars, collaborative research projects, and user groups. Members of SMART include some of the major surface mining companies in North America and Australia. These companies have recognized the value that collaboration can bring to the needs of individual organizations as well as the global mining industry.

May 1, 2009

By George Hope, Brigitte Lacouture

"The Red Dog Mine has increased mill throughput for most years since startup. Although flotation equipment has been added over the last 10 years, the Red Dog metallurgical performance has been restricted by a lack of adequate flotation capacity. Two reduced tonnage trials conducted in 1997 as well as numerous SAG relines have consistently indicated the potential to significantly increase both zinc concentrate recovery and grade with additional flotation capacity. Late in 1999, a new circuit was designed with increased flotation capacity while simplifylng the current circuit, providing for three stages of dilution cleaning, and creating a retreat section. The purpose of the retreat section is to target the more complex particles and allow the chemical environment to be fine tuned for improved iron depression. In total, twentyone (21) Outokumpu OK50 mechanical flotation cells and four (4) 3.66m dia. column cells will be added to the current flotation circuit. The VIP (Value Improvement Program) Mill Optimization project is also addressing thickening, water treatment and power issues and has a total budget of $US105 M. Startup of equipment will be phased in to minimize the impact on current operations and is expected to be complete by the end of Q3-2001.INTRODUCTIONRed Dog Operations started production in November 1989. The mine is located above the arctic circle in northwest Alaska. It is linked by an 80 km road to a port-site facility where the concentrate is stored. Concentrate is shipped to markets throughout the world during the one hundred (100) days of open seas. Typical of sedimentary exhalative deposits, the metallurgy proved to be challenging and coupled with many mechanical shortcomings, the initial few years were very difficult. The start-up issues were slowly resolved and in 1998, a major grinding expansion, the PRI (Production Rate Increase) project, was completed. The project was designed to allow a 40% increase over the 1995 throughput. In 2000 mill throughput was 3,050,000 tonnes to produce a total of 960,000 and 140,000 dry tonnes of zinc and lead concentrates respectively, making Red Dog the largest zinc concentrate producer in the world. To address a shortage of flotation capacity remaining from the PRI grinding expansion, a project designated as the VIP (Value Improvement Program) Mill Optimization project was initiated. The mill optimization project is targeted to produce 1,100,000 tonnes of zinc concentrate at 56% zinc grade and 87% zinc recovery. The project will add twenty-one (21) Outokumpu OK50 (50m3) flotation cells, four (4) 3.66mO column cells and address water treatment, thickening and power generation capacities."

Jan 1, 2002

By M. Maldonado

This work details the application of a decentralized control strategy to a pilot flotation column working with a two-phase system (water-air). The process is represented by a multivariable system composed of three inputs and three outputs. The selected control variables are the froth depth, the air hold-up and the bias rate, whereas the corresponding manipulated variables are the set-points of the local flow controllers of tailings, air and wash water. All controlled variables are estimated using electrical conductivity based techniques. In particular, the results of a new method for estimating the bias rate, based on the measurement of the volumetric fraction of wash water under the interface, is presented. This method reduces the coupling problem associated to the bias estimation as a difference between feed and tailing water rates. Moreover, the nominal system transfer matrix can be represented by an upper triangular matrix, in such a way that the closed-loop system stability reduces to the stability of the independent control loops. The experimental results show that the closed-loop system performance, particularly that of the bias rate loop, is strongly dependent on the air flow rate, reaching in some cases the saturation point of the controller.

Jan 1, 2007