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By Margaret Armstrong, Normand Champigny

"In order to define the ore/waste boundaries as finely as possible, mine planners often insist on kriging very small blocks (relative to the spacing of the available sample grades). These kriged estimates for very small blocks are over-smoothed. For several simple sampling patterns the relation between the block size and the variogram range, and the kriging results were studied. Meaningful estimates of individual blocks are obtained when the variogram range is large compared to the block size and the sample spacing. For a variogram range less than half the sample spacing, the kriged block estimates were found to be uncorrelated with the actual grades. The over-smoothed estimates should not be used for calculating recoverable reserves IntroductionNowadays most mining companies know that the geostatistical estimation method, kriging, gives the best estimates of individual block grades. As most mining engineers and geologists are now familiar with the basics of geostatistics, the definitions of the variogram and of kriging will not be repeated here. An appendix containing definitions and mathematical formulae is given at the end of the article for the sake of completeness.Even though it is well known that the kriged estimates for very small blocks are over-smoothed, mine planners who want to define the ore/waste limits as finely as possible (especially for selective underground mines), are often tempted to krige very small blocks. So we ask how small is ""too small""? Clearly ""smallness"" cannot be expressed in yards or metres. It depends on the nature of the orebody under study and this is reflected in the variogram model chosen to describe it.To answer this question, the changes in four key parameters are studied:• the kriging variance,• the variance of the estimated grade,• the slope of the linear regression of the true but unknown grade on its estimated value, and• the coefficient of correlation between the actual grade and the estimate;as a function of the block size and the variogram range. (Definitions of these four parameters are given in the appendix). Ideally the kriging variance should be low while the variance of the estimated grade should be equal to the dispersion variance of the blocks. The slope should be l.0, and so should the correlation coefficient.These four parameters have been calculated for several simple 2-D examples. The effect of using kriged block estimates that are too heavily smoothed are shown, and the dangers of trying to use these estimates for predicting recoverable reserves for small blocks (i.e. selective mining units) are pointed out."

Jan 1, 1989

By Jacques H. Nantel, James F. Archibald

"Frozen tailings material may be required, in the future, to perform the support functions of underground backfill in mines located in zones of permafrost, notably in the high Arctic. To date, no knowledge of physical support parameters of such materials has been obtained in Canada due to the limited mining activity in permafrost regions. It is therefore judged essential that the important physical and mechanical properties relating to frozen tailings material be assessed.Innovative mining methods will be required to cope with the harsh environmental conditions that exist at mining sites in the Canadian Arctic. A preliminary laboratory study, in the absence of field trials at limited Arctic mining sites, has been completed in which the physical and mechanical properties of several types of representative mill tailings mixtures have been investigated. A variety of tests, to determine frozen slurry and pelletized tailings strength properties, moduli of compression, optimum water contents, deformation characteristics and the like, have been conducted.The results of this study will be used to establish guidelines for the suitability of tailings use in such northern mining environments. IntroductionFrozen tailings material has never been used to backfill underground openings in Canadian mines. At present only one Canadian mine, the Polaris Mine situated on Little Cornwallis Island, is investigating the use of frozen backfill. However, the Canadian North covers a large territory and potentially contains a large number of mineral deposits. The understanding of concepts related to mining activities in sub-zero frozen ground is therefore important.The implications of using frozen tailings as underground backfill material are far reaching both from the point of view of mine stability and disposal of tailings in the arctic regions.The strength of frozen materials (soil, backfill, etc.) may take on different meaning depending on the engineering situation. Both the concepts of rupture and excessive deformation need to be considered.The functions usually required to be performed by the backfill material in underground mines may be summarized asfollows:a) working floors; such as in cut-and-fill stopesb) stope wall support; for cut-and-fill and delayed fill stope~c) self-support when backfill is exposed on one face; during pillar recovery phases.For fill functions such as working floors, the short-term response of the frozen fill is the dominant concern. For the other fill functions, the long-term deformation response of the frozen fill, or creep, is of interest."

Jan 1, 1986

By A. P. Annan, C. Vaughan, J. L. Davis

"The increase in the price of gold in the last decade has led to a significant increase in placer gold exploration around the world. Placer deposits occur in depressions along ancient river and stream channels. In many instances these channels have been covered with materials from subsequent erosion or glacial activity. Use of high resolution geophysical techniques to map the bedrock and soil strata can improve the probability of finding the placer deposits. The buried bedrock surface is often the factor controlling deposition. Ground probing radar (GPR) and seismic sounding are complementary high resolution techniques which can be used to map bedrock topography and soil stratigraphy. Current radar instrumentation operates best in coarse grained soils. Penetration depths of up to 30 m have been attained, and stratigraphic horizons have been mapped with spatial resolutions of better than 0.5 m. Although its spatial resolution is considerably lower than radar, seismic refraction achieves superior penetration in electrically conductive environments such as clay and silt soils. The seismic refraction method thus proves to be complementary to the radar method. The seismic reflection technique is analogous to the radar method. Current seismic instrumentation and energy sources however, provide limited spatial resolution and do not permit the use of seismic reflection for reflecting horizons lying at depths of less than 20 m to 30 m.This paper discusses the use of both radar and seismic methods for placer exploration. The radar and seismic techniques, the field methods, equipment, and data displays are presented. Field examples illustrate the high resolution mapping capabilities of the techniques. The radar data agree very well with the borehole data, and in fact they sometimes detect subtle soil strata variations associated with changes of permeability that were not initially observed in the borehole logging. The radar method can give a continuous profile of water table and bedrock in sandy soils. Seismic soundings are necessary to differentiate between the bedrock and water table reflections observed by the radar."

Jan 1, 1987

By X. Grant Chen, A. R. Farkoosh, M. Pekguleryuz

Nano-scale Al-(Fe,Mo)-Si dispersoids form during solution treatment in grain interiors (intradendritic regions) of cast Al7Si0.5Cu0.3Mg alloyed with 0.3Mo (wt.%). Unlike the Q-Al5Cu2Mg8Si6 and ?-Al2Cu age-hardening precipitates which coarsen resulting in loss of strength in Al-Si-Cu-Mg alloys, these Mo-containing dispersoids are thermally stable and retain their strengthening effect at elevated temperatures. Consequently, the age-hardened Al7Si0.5Cu0.3Mg0.3Mo (wt.%) exhibits high strength and creep resistance at 300 °C.

Jan 1, 2014

By D. Mills, W. H. S. Lawson

"The need to make repairs is seldom a major consideration in the design, fabrication and installation of major components of electrical generation plants. Repair welding, however, is a fact of life in the electrical generation industry, for restoration of degradation in service, from cavitation of hydraulic turbine runners, to corrosion and fatigue damage in pressure vessels. In making weld repairs to carbon and low-alloy steels, the largest source of trouble is hydrogen embrittlement and related post-weld cracking. Various strategies have been developed to control problems from this source, including post-weld heat treatment, the use of nickel-base alloy filler metals and the temper bead welding technique. Each of these basic strategies is being applied as circumstances require; each strategy must, however, be implemented in a manner that reconciles weldment structure and hardness, degree of restraint and service environment with the consequences of unsatisfactory performance of the repaired component.IntroductionMajor working components of electric generating plants are specified and installed on the basis that, wherever technically and economically feasible, they will retain functional capacity without major repairs for the twenty-five-plus years of normal plant lifetime. Nevertheless, repairs are often required, and welding is usually an essential feature of the work. Remedial welding may be performed to correct design or fabrication errors which become evident only at the time of component installation. The most common causes of requirements for repair involve corrosion, fatigue or related processes which prove more aggressive than expected during service. Increasingly, our planning for future repair requirements is related to continual improvements which are occurring in nondestructive evaluation technology. As components are periodically reinspected during their service life, fabrication induced defects may be revealed for the first time quite late in the life of the component. When this occurs, repair must be considered wherever inaccessibility of a flaw makes it impossible to prove its inactivity. Finally, there are certain components, for instance in hydraulic turbines, which cannot be economically made or used without the expectation of service induced wear. Here, periodic maintenance welding must be regarded as a normal event."

Jan 1, 1981

By M. Gauthier, A. C. Brown

"Monometallic zinc mineralization associated with marbles of the Grenville Supergroup in the Mont-Laurier Basin of Quebec is found to be stratiform and to occur (1) within limited zones of dolomitic marble and (2) more precisely along contacts between these marbles and adjacent metaclastic units. Massive sphalerite with accompanying pyrrhotite and pyrite is the prime exploration target, and commonly gives rise to good geochemical anomalies, but generally weak and ambiguous geophysical responses. Disseminated sphalerite in dolomitic marbles may signal proximity to interesting massive mineralization, although, due to weathering, this broadly disseminated mineralization may not be detected easily on outcrops. It is concluded that the western and possibly the eastern margin of the Mont-Laurier Basin constitute favourable areas for continued exploration.IntroductionThe Grenville Supergroup marbles of Ontario, Quebec and New York State host numerous occurrences of zinc mineralization (Fig. I) , several of which have been periodically mined since the beginning of this century (Fig. 2). The Balmat Edwards district of New York is the giant of this depo sit-type, with the production since 1915 of some 20 million tons of ore grading 10% zinc, and acknowledged current reserves of approximately equal tonnage and grade. At present, there is renewed interest in the potential for similar mineralization throughout the Grenville Supergroup, and this paper outlines some of the geological, geochemical and geophysical guidelines that may be employed in the search for new ore. The geologic guidelines are derived especially from lithologic and stratigraphic features which survived intense, multiphase deformation and metamorphism.Although major portions of the extensive Grenville Supergroup hold potential for zinc mineralization, the present study is confined to a known zone of mineralization in the Mont-Laurier Basin of Quebec. Concurrently, we are compiling information on the regional metallogeny of the basin so that our conclusions can be applied to areas of similar Grenville Supergroup host-rocks elsewhere."

Jan 1, 1980

By Y. Prevost, D. Verhelst

"A computer-assisted process control system for the Noranda Process Reactor Wa5 installed at the Home smelter in 1991. Operating as an advisory tool for the furnace operators, and using a flexible oxygen balance as the basic building block of the computer program, the new control system has helped to reduce the variability in the grade of the matte produced by 50% . The smelter is currently operating at a 72% copper matte, with a standard deviation of between 1.0 and 1.3, while treating a wide range of concentrates, secondary materials and scrap. Enhanced process control has allowed for longer reactor campaigns, and improved stability of the converting operation.This paper reviews the feed classification and blending practice used at the smelter, outlines the strategy of the new computer control system, and summarizes the benefits realized since the implementation of the system in early 1990.IntroductionUntil 1989 the Noranda Home smelter operated as a multi furnace smelter, at one time having three hot-charge reverberatory furnaces, and finally operating with one wet-charge reverberatory furnace and one Noranda Process Reactor. In 1989 the final reverberatory furnace was closed and the Reactor became the sole smelting vessel, treating around 750 000 tonnes of concentrate, secondary materials, and scrap per year. At the time of the start-up of theNoranda Reactor in 1973, the vessel was capable of treating 750tonnes per day of a heterogeneous mixture of copper concentrates, fluxes and secondary materials to produce copper in one operation. Through process improvements, and the introduction of additional oxygen in 1982(pannell and Mackey, 1988), the daily tonnage increased to 1800 tonnes by 1988. The operation had also been changed to produce a high-grade matte instead of copper. Figure1 illustrates the main features of the reactor, a cylindrical vessel which is charged at one end and tapped at the other. The matteis subsequently processed through Peirce-Smith converters and anode furnaces before being cast into copper anodes. Figure 2 outlines the progressive increase in the furnace smelting capacity. Over this period the percentage of secondary materials, and scrap feeds also increased to approximately 110 000 tonnes per year, or 15% of the total new feed input (Bedard et al., 1991). Now operating wholly as a custom feed operation, the Home smelter can treat over 2200tonnes per day of new metal-bearing material."

Jan 1, 1993

By Robert B. Parsons

"First down and four to go. In the game Of football, this is not a bad position to be in. However, in this game of political football, it means that there is still a long way to go. The government in Ottawa has concluded an important agreement with one producing province, and now has at least four more provinces to deal with-B. c., Saskatchewan, Nova Scotia and Newfoundland.On September 1, 1981, the federal and Alberta governments took a significant step forward in formulating an oil and gas policy for Alberta and the rest of Canada on signing a comprehensive five-year agreement that covers taxes, prices, incentives and other fiscal matters related to the production and marketing of oil and gas.This month, Tax Notes examines the main features of the agreement, and offers some eye-opening observations of what the new accord could mean for the future of the Canadian petroleum sector in particular and Canadian business in general."

Jan 1, 1981

By Scott K. Palm, Neil D. Pearson, Jr. Read

"Uncertainty is an important feature of many investments, but it is especially important for mineral properties. Mine properties often entail large investments and fixed commitments. Managers in the mining industry often view price uncertainty as undesirable, due to the possibility that the price of the mined commodity will fall to a level that prevents the firm from recovering its investment and fixed costs. This paper identifies pitfalls in conventional valuation methods and outlines a new approach to valuation based on option pricing theory and dynamic programming. In the process, it identifies generic strategies for organizing mine production in ways that allow the owner to benefit from the uncertainty in mineral prices. IntroductionRisk is pervasive in the mining industry. The operation and maintenance of a mine may involve high, and unavoidable, fixed costs. A mine owner can only begin to recover these fixed costs if the price of the mined commodity is greater than the incremental cost of production. But the prices of many minerals are extremely volatile. The price volatility of copper has been significantly higher than the price volatility of a typical stock, for example. A mine owner cannot be sure that the price of the mineral product will remain high long enough for the firm to recover its capital and fixed costs.Mine owners are able to minimize their losses during periods when the output price is below the incremental cost of production by temporarily closing operations. During these periods they incur only fixed costs. While shut-downs help minimize losses, the y do not help the firm recover its initial investment. If output prices remain low long enough, the fixed costs and original investment may never be recovered. High fixed costs, therefore, lead to substantial downside risk."

Jan 1, 1986

By John De La Vergne, Morri Medd

"This paper describes the sinking of a circular concrete ventilation shaft through 110feet of water-bearing overburden. The brine circulation freezing method was used to stabilize the walls during excavation. In order to take advantage of the cold winter weather, a custom-built heat exchanger (natural radiator) was installed in place of the standard mechanical refrigeration plant.IntroductionIn the late fall of 1979, Les Mines Selbaie awarded a contract to the firm of 1.S. Redpath Limited to sink a ventilation shaft on its property in northwestern Quebec. The shaft was to be sunk through 110 feet of water-bearing overburden and approximately 90 feet of rock to a final depth of 200 feet below surface. The water table was measured at 16 feet below the surface elevation.After examining the soils report and diamond drill core from the shaft area, Redpath came to the conclusion that freezing was the best way to stabilize the overburden for sinking. LocationThe mine site is 420 statute miles due north of Toronto, just east of the Ontario/Quebec border (Fig. 1). Access to the site is provided by a development road built by the Quebec government from the Matagami/lames Bay Highway. History of Ground Freezing In the Mining IndustryIn 1862, shortly after the development of mechanical refrigeration, a mine shaft was sunk through an artificially frozen water-bearing formation in the United Kingdom. The first application of ground freezing in North America was for a Michigan iron ore shaft in 1888. Since that time, the freezing method has been used to sink hundreds of shafts throughout the world. Its best known application was to sink sixteen shafts through the Blairmore Formation in Saskatchewan.The same method has been used in every case. It involves chilling a calcium chloride brine solution and circulating the brine in concentric pipes, spaced between 3 and 6 feet around the shaft perimeter and usually 4 to 5 feet from the limits of the proposed shaft excavation."

Jan 1, 1982

By R. W. Boyle, W. Dyck

"Scientists throughout the world have observed radioactive disequilibrium in the uranium decay series. Radiometric and fluorometric determinations of U in plants from the Goldfields district and in sediments and rocks from the Beaverlodge district exhibit marked radioactive disequilibrium. The eU/U ratio in plants rooted in mineralized ground shifts from greater than unity to less than unity for those rooted in background soils. A similar shift is observed in the transition from rocks to stream sediments and to lake sediments in the Beaverlodge district.Results of a Rn-Ra-U survey of lake bottoms in the Key Lake district show that anomalous hydromorphic U from U mineralization is parallelled by anomalous Rn, even though there is much less Ra in the lake-bottom sediments than one would expect from the amount of U present. IntroductionDisequilibrium in the U decay series has been studied for many years and is observed in almost all surficial environments. Rosholt (1959) measured U, 234Pa, 23O'fh, 226Ra, 222Rn, and 210Pb in a large number of U ores and outlined six types of situations to explain disequilibrium. Davy (1974) outlines the geological significance of radioactive disequilibrium situations with respect to exploration. Levinson and Coetzee (1978) discuss possible mechanisms by which separations of parent and daughter elements are affected and suggest analytical pitfalls that may be encountered in the use of radiometric techniques when disequilibrium has occurred. Generally, it is the oxyphile and easily complexed parent 238U (with its associated isotopes 235 U and 234U) that is leached from rocks and soils at a faster rate than are the daughters, 230Th, 226Ra, 2loPb, and 206Pb. This mobilized U is adsorbed on sediments in streams and lakes, or enters groundwaters, where it is eventually precipitated under reducing conditions, occasionally in oregrade concentrations. This surface leaching and"

Jan 1, 1980

By Kurt D. Mitchell

"This paper discusses general application for A C variable frequency drives in the mining industry. A review of induction motors characteristics, adjustable frequency controller fundamentals, and three commonly used controllers is presented. General application guidelines for the three different types of controllers; variable voltage input , current source input and pulse width modulated are then reviewed in detail, and an example of the economic benefit of this technology is discussed. IntroductionSoon after static DC variable speed drives were well established in industry, a need for static AC variable speed drives was seen. The first technical papers describing possible systems appeared in the mid-1960s, with commercially available units arriving in the early 1970s. Without exception, static AC drives are substantially more complex than their DC counterparts, but they have some very desirable properties. As compared to DC motors, AC motors are less costly, physically smaller, more reliable, require less maintenance , easily sealed, have good load regulation, are able to run at higher operating voltages, and have little danger of over-speed runaway . These properties are particularly desirable in explosion-proof, submersible or difficult accessibility applications.Variable speed AC drives are now a proven technology. available in packages from Sub-horsepower to hundreds of horsepower, from 115VAC to 4160 VAC. This paper covers the principles of operation of three common types of controllers, application criteria, motor consideration and finally an example of how an AC variable speed drive can pay for itself in terms of energy savings."

Jan 1, 1986

By M. Ghiani, P. Carbini, R. Ciccu, C. Del Fà

"This paper is concerned with the problems inherent in the efficient and economical processing of the fine fractions of a coal from the Sulcis basin (Sardinia, Italy) whose characteristics are typical of low-rank coals occurring in the Mediterranean region. Three different techniques, based upon surface properties, are examined. Flotation can be very efficient from both a technical and economic point of view, provided care is taken in the modulation of the flotation pulp. Interesting results have been obtained with oil agglomeration and this method could be economically feasible. Finally, electrical separation has proven a viable technique, although it entails preliminary drying.Besides discussing the problems encountered in the experimental research, some significant results of general validity are also given. They demonstrate that cleaned products can be obtained with fairly interesting recoveries, thus opening the way to advanced research aimed at setting up the most suitable technique for industrial application. IntroductionAs a result of the oil crisis, which caused a major upset in world energy supplies, the last ten years have seen a revolution in the energy policies adopted.In particular, the status of coal, which seemed destined to decline in view of the availability of liquid fuel, has had to be re-examined. The need to meet energy demands under improved reliability conditions and controlled prices through a broader and more flexible diversification of sources of supply has evoked, especially in highly industrialized countries, a renewed interest in coal. The result has been a consistent increase in demand and production as well as investments in new mines and the reinforcement of the infrastructure.This turn of events has also lead to a re-evaluation of young low-rank coals, hitherto considered uneconomical and thus neglected, because of their low heat value. In fact these coals, which have a high ash content, may also be relatively highly contaminated with sulphur. The above drawbacks, which still today preclude the widespread use of these coals, are bound to create even greater problems in the future as increasingly restrictive environmental control imposes, without exception, recourse to cleaner fuels."

Jan 1, 1986

By J. M. Beeckmans, S. G. Butcher, M. Goransson

"The counter-current fluidized cascade is a novel and potentially efficient pneumatic gravity separation device. Data are presented on over 150 runs of cleaning Alberta thermal coals, covering several size ranges. The coarser sizes of coal were processed in admixture with a fluidizing medium consisting of 0.5-by 0.1-mm hematite (or magnetite) and limestone particles. The partition curves for coal particles larger than about 3 mm, mixed with fluidizing medium, showed that the sharpness of separation achievable with the cascade approaches that of wet heavy medium processes, whereas with particles in the size range of 3 by 0.6 mm the sharpness of separation was comparable to that of a Baum jig. Useful cleaning was also achieved with particles smaller than 0.6 mm , Throughput rates of up to 11 tonnes per metre width of cascade per hour were achieved, with no indication of a deterioration in performance.IntroductionPneumatic coal beneficiation has steadily lost ground vis-a-vis hydraulic beneficiation during the past quarter century, primarily because of the sharper separations achievable with the latter methods. Nevertheless, there are certain inherent advantages of pneumatic separation methods which would give them an advantage in the market place were it possible to increase their efficiency to be technically competitive with those of hydraulic processes. These advantages are a dry product, resulting in a higher calorific value per ton, and avoidance of the problems associated with treatment and storage of process waste waters. Also, although it may be necessary to dry the raw coal prior to pneumatic processing, the dry rejects produced constitute an ideal fuel for a fluidized-bed combustor, which could provide heat both for drying the coal and for other purposes."

Jan 1, 1982

By Tim J. Carew, Dennis C. Martin

"One approach to stabilization of rock slopes is to place a buttress at the toe of the slope to provide additional resisting forces and increase the length and strength properties along the failure surface. This paper describes the rock mechanics and mine planning aspects of incorporating a buttress of intact rock in the lower part of the slope as part of the slope design for the south wall of the final pit at Cassiar Mine. Stability analysis techniques and results are described. Analyses results have indicated that, in order to maintain steep over-all slopes in the final pit, a buttress of intact rock shoud be incorporated into the lower section of the slope until late in mine life. The effect of the buttress is to flatten the slope and reduce the slope height thereby improving slope stability. The mining plans would be such that the buttress would be mined out during the last four months of mining when the consequences of instability would be least severe.IntroductionThe concept of using a buttress to stabilize slopes has been used in mining and civil engineering construction in may locations (Richards and Stimpson, 1977). Most buttresses involve placement of coarse rock fill timber cribs or other material as a load at the toe of an already unstable slope to provide forces which resist failure by counteracting driving forces and increasing the length and strength of the failure path.This paper describes the geotechnical and mine planning aspects of incorporating a buttress of intact rock in the design of the south wall of Cassiar Mine. The effect of an intact rock buttress is to flatten the slope and reduce the slope height, thereby improving slope stability. No actual construction is required other than normal excavation of the slope. The ""mine plans would be such that the buttress would be mined out at the end of mine life when the impact of instability would be less severe and additional ore might possibly be recovered from the slopes. Mining of the buttress could induce instability at the very end of mine life at a time when maximum ore extraction has been achieved."

Jan 1, 1986

By G. H. Blackwell, A. J. Sinclair

"The main components of a ""PC” -based mineral inventory system are described in a sequence common to many real reserve/ resource estimation projects and in the practical context of problems and decision-making typically encountered in such studies. Some components are designed particuarly to improve the geostatistical instructional capability of the package. An important part of this approach involves the use of widely available software for data manipulation and evaluation in the design of a mineral inventory study progressing to mine design and feasibility. A variety of more or- less fixed routines written in high level languages provide acceptable computational speeds on a personal computer. These critical segments are linked by simple, short, compiled Basic programs easily adjustable to various data configurations and needs. IntroductionGeostatistical mineral inventory estimation has progressed greatly since its slow dissemination during the 1960s. The mining industry generally has accepted the benefits of the technique, notably the quantification of grade and geology, an indication of error in grade estimation, and of the mined volume / grade variance relationship (Clark, 1979, Isaacs and Srivastava, 1989).Acceptance has been slowed, first by complexities of geostatistical theory and second by a bewildering variety of computer systems and applications programs. Continuing improvements in education will facilitate a better understanding of the underlying theory.The purpose of this paper is to describe, in a practical context, the development of a geostatistical-based approach to reserve/resource estimation. The approach integrates various existing commercial software packages with a wide selection of programs developed by the authors for personal computers which estimate mineral inventories and educate users in the techniques applied; that is, the QMIN system.It is hoped that the approach presented here will convince mining and geological engineers concerned with resource estimation, of the soundness of geostatistical methods and its broad potential to their problems."

Jan 1, 1992

By K. Swedburg, M. Samuels

"The expansion of the concentrator at New Gold’s New Afton copper-gold mine in British Columbia, Canada, completed in 2015, included an increase in the required retention time of the cleaning circuit. On site pilot testing of a Woodgrove Staged Flotation Reactor (SFR) had shown that a high grade copper concentrate would be produced with excellent recovery. The SFR was selected rather than conventional tank cell technology based on the much smaller footprint (which rendered a separate and expensive building extension unnecessary), high concentrate grades demonstrated in testing, and the lower energy requirement. Three SFRs, each capable of taking a nominal feed of 700 cubic meters per hour were installed and commissioned 10 months after the receipt of order. The SFRs operate in series and all of the cells produce a final concentrate typically grading 32% Cu, while the overall SFR stage recovery averages 55%. The tailings from the SFRs are treated in the original conventional three-stage cleaner circuit where the remaining values are recovered in a concentrate grading 28% Cu. Design production was achieved within days of the initial start-up of the SFR circuit.INTRODUCTIONThe New Afton concentrator, located near Kamloops, British Columbia, Canada processes a copper-gold ore with a designed head grade of 0.96% Cu, 0.72 g/tonne Au, and 2.22 g/t Ag.The New Afton Mine is a block cave mining operation. Ore is undercut from the bottom up and removed at the extraction level from a grid of draw points. Ore is trammed to the ore passes by underground loader and dropped to a haulage level for transport by trucks to the gyratory crusher. From the crusher, the ore is conveyed to the mill via a 4.5 kilometre long conveyor system. Block caving was chosen for the New Afton deposit because the underground infrastructure could be built below the historical open pit of the Afton Mine (a previous operation of Teck Resources) and this method is favorable to large-scale low-cost mining.The New Afton deposit is a copper-gold, alkalic porphyry system. Hypogene mineralization is characterized by discontinuous copper sulphide veinlets and disseminations, principally chalcopyrite and minor bornite, along with pyrite as the second most dominant sulphide. Gold particles vary in size from 5 µm to 40 µm and occur as native gold and electrum, associated mostly with the chalcopyrite grains and never with the pyrite. In some instances, a second alteration phase has resulted in the copper sulphides being replaced by tennantite-tetrahedrite locally and along faults that transect the mineralized body. The design head grade of arsenic is 244 PPM, although the presence of tennantite is inconsistent and can vary from trace levels to 15% of the total copper. No arsenopyrite is present in the hypogene ores. Supergene mineralization, consisting of native copper with accessory chalcocite occurs in minor amounts along faults and highly oxidized near-surface portions of the deposit."

Jan 1, 2016

By Charles Tkaczuk

Key issues ? Process control is a corporate function implemented locally. ? Security and documentation is mandatory requiring standard practices. ? Publish and communicate activities (do not re-invent the wheel). ? Payback metric system for all projects. ? Partnering with vendors based on experience, expertise and joint R&D. ? Focus on phased process control projects and distribution of costs. ? Integration of services and functions. ? Application of global standards. ? Big picture application thinking.

Apr 1, 2005

By C. W. Hancher, B. D. Patton, W. W. Pitt

"There are a number of nitrate-containing wastewater sources, as concentrated as 30 wt % NO3 and as large as 2000 m3/day, in the nuclear fuel cycle. The biological reduction of nitrate in waste water to gaseous nitrogen, accompanied by the oxidation of a nutrient carbon source to gaseous carbon dioxide, is an ecologically sound and cost-effective method of nitrate waste disposal. These nitrate-containing wastewater sources can be successfully biologically denitrified to meet discharge standards in the range of 10 to 20 g N(NO3-)/m3 by the use of a fluidized bed bioreactor. The denitrification bacteria are a mixed culture derived from garden soil; the major strain is Pseudomonas. In the fluidized-bed bioreactor, the bacteria are allowed to attach to 0.25- to 0.50-mm-diam. coal fluidization particles, which are then fluidized by the upward flow of influent wastewater. Maintaining the bacteria-to-coal weight ratio at approximately 1:10 results in a bioreactor bacteria loading of greater than 20,000 g/m3,This paper describes the results of a bio denitrification R&D program based on the use of fluidized bioreactors capable of operating at nitrate levels of up to 7000 g/m3 and achieving denitrification rates as high as 80 g N(N03-) per day per litre of empty bioreactor volume. IntroductionThe discharge of wastewater containing nitrate at concentrations greater than stipulated by the Environmental Protection Agency (EPA) creates an environmental hazard and constitutes a civil and/ or criminal legal liability.(I.2) At present, we have three options: (1) recycle and reuse of nitrate streams the total economic and technical balance should be Closely examined; (2) use of an alternative acid, which may pose an entirely different set of problems ; or (3) disposal of nonreusable nitrate sources by an environmentally acceptable procedure."

Jan 1, 1980

By Jae-Chun Lee, Sadia Ilyas

We investigate the technical feasibility of bioleaching of metals from low grade sulphidic ore. Experiments were conducted with an adapted consortium of Sulfobacillus thermosulfidooxidans and Thermoplasm acidophilum in batch bioreactors (1.5 L), small columns (10 kg ore load, 8 % S0 sludge) and large columns (80 kg ore load, 12 % S0 sludge). Approximately 83 % Ni, 85 % Cu, 55 % Fe and 81 % Zn was leached out in batch mode while 93 % Ni, 89 % Zn, 81 % Cu and 65 % Fe was leached out in column reactors. Bioleaching potential improved by acid pre-leaching, adaptation of microbial consortium and periodic bleeding of effluents.

Jan 1, 2014