Search Documents

By Makarinskym F. M.

"This paper describes mechanical and operating modifications that were and are being made to current on-line flotation cells at Falconbridge Nickel Mines concentrators. Improved metallurgical performance and metal recoveries of some 3·4% over the past ten years are the end result of the modifications made. The paper acknowledges the contribution of operating, technical and maintenance personnel and the Company ""suggestion plan"" program. 1. INTRODUCTIONFalconbrirdge Nickel Mines Limited, incorporated in 1928 is a major product of nickel, copper,coba1t and other metals and minerals. The Canadian Nickel Division operating facilities in the Sudbury Area currently includes seven mines, two concentrators, and a smelter.For many years at all concentrators, improv0mcnts in metal recoveries have been continually under investigation. One area was to improve the flotation cell performance. This paper will deal with mechanical and operating modifications to the cells at the Strathcona and Falconhridge Ni-Cu sulphide concentrators, at the Sudbury Operations.One of the prime means to mineral beneficiation processing has been, and will continue to be, the basic froth flotation cell. The efficient operation of a flotation cell is the key to satisfactory metal selectivity and recovery. The essence of good design is simplicity. Changes to cell design can contribute to a significant improvement in metal recovery.Over the past 10 years, modifications to the flotation cells have contributed to an improvement of some 3-4” in mineral recovery. Providi11g tl1c initiative for improvements include operating, maintenance and technical personnel, as well as the employee suggestions submitted th1·ough the Suggestion Plan Program."

Jan 1, 1982

By Janice Zinck, Ian London

In recent years, the secure supply of critical and technology metals has become increasingly important tomajor industrialized economies that seek to sustain their industrial base and develop advanced technologies, such as clean energy. Canada, with its significant reserves of rare earth element (REE) and other metals, has an opportunity to supply some of the global demand for these materials. However, to transition from promising mineral deposits to marketable products, investment in strategic research and development (R&D) and expertise is needed to address the complex technological challenges around the production, separation and processing of these metals, and to better understand the global market for these key commodities. To this end, in its April 2015 budget, the Government of Canada committed to invest $23M over 5 years to accelerate production of REE and chromite/ferrochrome. The goal of this program, developed in close association with industry, is that Canada contributes a sustainable supply of REE to the global market. The research and development program will provide the technological capacity to establish a Canadian REE industry. This paper will discuss REE R&D advances achieved in the first year of the program in areas of mineral characterization, beneficiation, leaching, separation and environmental management and will highlight the Canadian model of collaboration where industry (e.g. prospective producers, technology companies), government, academia and other stakeholders work closely to ensure that the R&D is targeted, innovative and effectively deployed and commercialized.

Jan 1, 2016

By E. Wusaty

"Fording Coal is a wholly owned subsidiary of Canadian Pacific Limited. The company was founded in 1968 to mine metallurgical coalfor export at the Fording River operations in southeast British Columbia.Today, Fording Coal Limited also operates the Whitewood mine under contract to TransAlta Utilities and the Genesee mine under a joint venture arrangement with Edmonton Power. Both these operations are located just west of Edmonton and produce subbituminous low-sulphur coal which is used for power generation. Fording also owns and operates two industrial mineral mines in the United States and is mining overburden under a lo-year contract with Syncrude Canada at Fort McMurray.As of December 1992, Fording Coal Limited owns and operates the Greenhills mine which was closed due to bankruptcy. This papers deals with the innovations and changes which have been made and those which are currently being implemented to make this operation competitive in the world export coal market. IntroductionOn December 4, 1992, following a tendering process, Fording Coal was awarded 80% controlling interest in the Greenhills mine by Trustee Arthur Andersen Inc. Assets acquired included 100010 of the land and coal leases and 80% of the major joint venture assets including all structures. The remaining 20% is owned by Pohang Steel Canada Ltd., a wholly owned subsidiary of Pohang Iron Steel Co. of Korea. The Greenhills mine had been in continuous operation since 1983 and was finally closed due to bankruptcy of its majority owner on October 31, 1992.A permit to operate the Greenhills mine was issued by the British Columbia government on January 29, 1993, and Fording Coal Limited started mining operations in late February 1993.To return the Greenhills mine to profitability significant changes were required in workforce productivity, mining methods and equipment selection. These mine plan changes are designed to make the Greenhills operation competitive in world markets, provide longterm employment for the company's workforce and ensure that a secure supply of coal is available."

Jan 1, 1994

By R. F. Dawson, A. S. Bagnall, K. Barron

"At Smoky River Coal Limited (SRCL), economic occurrences of structurally thickened coal deposits form attractive surface mining targets. These steeply dipping, structurally complex deposits require that special attention be given to pit wall design and operational practices.Where anchor support is feasible, there is potential for reducing footwall waste requirements and/or increasing coal recovery. SRCL has used rock anchors to support footwall slopes since 1985. This paper outlines design considerations and performance of rock anchor support systems at SRCL.Three case histories are included that illustrate the design process for supporting steeply dipping footwall slopes using rock anchors.IntroductionWestern Canada contains vast reserves of high grade coking coal largely located in two belts within the Rocky Mountain Foothills straddling the Alberta/British Columbia border. There are about one billion tonnes of ""clean"" coking coal reserves (Romaniuk and Naidu, 1986) situated near existing mining infrastructure. Within the reserve areas shown in Figure I, a total of six producers operate 10 large mines linked with ports situated on Canada's west coast. Al! of the producers operate conventional shovel/truck surface pits.Surface mineable reserves within some of the mountain coal mines are located on dip slopes or where the geologic structure has thickened the coal near the surface, creating low strip ratio targets. Footwall slopes in these mines are developed parallel to bedding, thus minimizing waste extraction and preventing undercutting of potentially unstable strata. The base of the mineable coal measures in both north and south regions is marked by massive quartz sandstone units (Torrens Member and Moose Mountain Member) which often form the footwall. Footwalls developed within this basal sandstone unit can attain very high unbenched heights often with little risk of instability. In cases where the footwall is developed on weaker strata above this basal unit, stability considerations control slope height when bedding dips exceed about 30°. In these situations it is desirable to assess the benefits of artificial support to increase the unbenched footwall slope height."

Jan 1, 1995

By R. F. Dawson, A. S. Bagnall, K. Barron

"At Smoky River Coal Limited (SRCL), economic occurrences of structurally thickened coal deposits form attractive surface mining targets. These steeply dipping, structurally complex deposits require that special attention be given to pit wall design and operational practices.Where anchor support is feasible, there is potential for reducing footwall waste requirements and/or increasing coal recovery. SRCL has used rock anchors to support footwall slopes since 1985. This paper outlines design considerations and performance of rock anchor support systems at SRCL.Three case histories are included that illustrate the design process for supporting steeply dipping footwall slopes using rock anchors.IntroductionWestern Canada contains vast reserves of high grade coking coal largely located in two belts within the Rocky Mountain Foothills straddling the Alberta/British Columbia border. There are about one billion tonnes of ""clean"" coking coal reserves (Romaniuk and Naidu, 1986) situated near existing mining infrastructure. Within the reserve areas shown in Figure I, a total of six producers operate 10 large mines linked with ports situated on Canada's west coast. Al! of the producers operate conventional shovel truck surface pits.Surface mineable reserves within some of the mountain coal mines are located on dip slopes or where the geologic structure has thickened the coal near the surface, creating low strip ratio targets. Footwall slopes in these mines are developed parallel to bedding, thus minimizing waste extraction and preventing undercutting of potentially unstable strata. The base of the mineable coal measures in both north and south regions is marked by massive quartz sandstone units (Torrens Member and Moose Mountain Member) which often form the footwall. Footwalls developed within this basal sandstone unit can attain very high unbenched heights often with little risk of instability. In cases where the footwall is developed on weaker strata above this basal unit, stability considerations control slope height when bedding dips exceed about 30°. In these situations it is desirable to assess the benefits of artificial support to increase the unbenched footwall slope height."

Jan 1, 1995

By W. A. Grell

"The oxygen meter has been in use at MacLeod Cockshutt Gold Mines for over a year, At MacLeod about 200 tons per day of reground concentrate containing roughly 10% pyrrhotite and 20% pyrite is cyanided in four 181 x 18' Dorr agitators. A survey by the Department of Mines showed that oxygen content of some of the agitators was rather low. Experience with our oxygen meter indicates that the oxygen content must at times have been too low for good gold dis solution.We have found that in winter, when pulp temperatures drop to about 50° F, oxygen saturation in the agitators is not difficult to maintain. In summer, however, when pulp temperatures rise to 70or 75°F, the oxygen content will drop very readily. It was found that a high oxygen content can be maintained readily if the pulp is sufficiently dilute. Thus at 50° F, a pulp of specific gravity 1. 75 i.e., about 55% solids, will saturate; but at 70 or 75° F, the specific gravity must be decreased to 1 .45, equivalent to about 40% solids, in order to maintain saturation. Very thick pulps, such as thickener underflows, are noticeably difficult to saturate in the laboratory, and lose their oxygen rapidly.Clear solutions, on the other hand, absorb oxygen readily and hold it. The primary thickener overflow, before agitation, is 100% saturated; after storage of 3 to 4 hours it is still 100% saturated at re clarifier tank. Barren solution after spraying in a launder is 100% saturated.We have not yet attempted to determine what percentage saturation is necessary for good extraction, but it is known that there is a point at which extraction decreases rapidly. So far, the measures required to maintain over 80 or 90% saturation have coincided with measures required to hold the reducing power to the point believed necessary."

Jan 1, 1964

By Ken Musgrave

"What Most Effective Management Does?It must satisfy the demands, of three groups of people: owners, employees and the public.OwnersOwners want profitable operations that will pay them a return on their investment, plus operations managed for long life. Many owners are also concerned with employee's well being and their company's public image.EmployeesJob security and a good income are probably still the most important demands, however, as time goes by, employees are also demanding more involvement in safety issues, working conditions, and even how work is done.The PublicThe public requires acceptable environmental standards, as well as enjoying the prosperity supplied by a successful operation.How are Mines Managed?Most mines are managed very traditionally. The basic credo is that the managers make the decisions, and the hourly, and junior salaried employees do what they are told. Clearly this is the extreme case, epitomized by the long service shift boss who might say ""It took twenty-years to become a shift boss, and no miner is going to tell me what to do"" .There are some exceptions, two notable ones being Campbell-Chibougamau, and T.G.S. (now Kidd Creek Mines) which, in very different circumstances, decided on a more participative style.Campbell-Chibougamau, having closed down due to unprofitable operations, reopened, using a team structure with working leaders, and a system for sharing gains against cost targets with employees. Although the system has some problems, and development miners are bonused conventionally, this has been a basically successful program.Texasgulf Sulphur, a company with a history of non-union operations, and a participative management style, made a corporate decision to operate their Kidd Creek Mine in the same way. The orebody was rich enough to allow them the luxury to do this, but they have never had a strike, so perhaps they have more than saved the cost of the benefits and salaries they needed to pay. They also reward employees with a stock distribution scheme based on service and earnings."

Jan 1, 1985

By P. Amelunxen, E. Herrera, L. Hill, J. Vanderbeek

It is well-known that the particle breakage mode that occurs in a semi-autogenous mill is significantly different from that which occurs in a ball mill, enough so to warrant very different lab scale breakage tests and scale-up models. This phenomenon, at the plant scale, leads to changing process constraints depending on the particular properties of the ore. For example, hard or coarse ores might bottleneck the SAG/AG mill throughput, while the ball mills might constrain throughput when milling soft or fine ores. Because the power draw of a ball mill is fairly constant compared to that of a SAG/AG mill, periods of SAG/AG mill bottlenecks lead to increased ball mill circuit specific energy consumption and a finer grinding circuit product size, which together constitute a loss of efficiency of the overall process. Because HPGR circuit throughput is less sensitive to changes in ore hardness, this situation is less common or severe in those circuits. Furthermore, the ball mills are somewhat decoupled from the upstream crushing circuits through the use of surge bins, which also helps to mitigate this effect. As a result, ore hardness variability constitutes a significant cost penalty that should be applied to SAG mill/ball mill/pebble crusher SABC circuits when evaluating the relative economics of different grinding circuit configurations. Nevertheless, the issue is by-and-large ignored, because most current HPGR trade-off studies are based on averaged ore hardness parameters. This paper provides an estimate of the magnitude of this penalty for a typical operation by using Monte Carlo simulation methods and plant data from Freeport-McMoRan’s autogenous, semi-autogenous, and HPGR-based comminution circuits. A case study from an in-house 96K t/d sulphide project is presented to illustrate the concept. It was found that by including variability effects, the trade-off NPV of the HPGR circuit over that of the SAG mill circuit increases to $84 million from negative $33 million, effectively reversing the original decision of selecting a SAG mill circuit for the fixed hardness case.

Jan 1, 2012

By A. B. Szwilski

The paper outlines the factors taken into account for the selection of steel arch supports. The results are based on experience using the long wall system of coal mining where roadway closure can be extreme. Results of tests on scale-model steel arches and full-scale yield elements are also presented.

Jan 1, 1979

By T. Crivits, I. Bellemans, K. Verbeken

In the metallurgical industry, furnace cooling is often employed to enhance furnace lifetime. Hence, the pyrometallurgical phase comes in close contact with a non-air coolant. The proximity of the pyrometallurgical phases to the coolants may lead to dangerous situations. In case of a breach of the cooling circuit, the contact between a hot and a cold liquid may cause a vapour explosion. The outcome of this vapour explosion includes a pressure wave which could result in damage to the furnace, bodily injuries or even casualties. To prevent such dramatic events, the origin of vapour explosions is currently being studied in more detail. For this purpose, OpenFOAM was used to perform Computational Fluid Dynamics (CFD) simulations. In a first step, simulations were run to get a better idea of the influence of the compressibility on the simulations. The obtained results help in getting a better insight on the need of computational power, and possible numerical errors using compressible or incompressible solvers in future simulations. In a second step, systems without vapour explosions were simulated and compared to experimental results with mercury and aluminum. INTRODUCTION Humanity started using metals for tools around the Chalcolitic (~7400 cal BC), when copper was melted in small furnaces (Radivojevic, Rehren, Farid, Pernicka, & Camurcouglu, 2017). Nowadays, metallurgy has grown into a major industry and it has become impossible to imagine society without metals. In the pyrometallurgical industry, coolants (low temperature liquids, for example water) and pyrometallurgical phases (high temperature liquids, such as slags, mattes and alloys) are typically present in close proximity of each other. The interaction between these two phases can have catastrophic consequences (Tveit et al., 2008; Ferguson & Zsamboky, 2017). A vapour explosion may occur as the consequence of the rapid evaporation and expansion of the coolant. Whereas the volume of a gas increases linearly with the temperature (approximately a factor four by heating from 100°C to 1300°C), a simple calculation of the ratio of the two specific volumes shows that evaporation causes the volume of water to increase by a factor of 1700 at 100°C and ambient pressure (Table 1 and equation (1)), a number that was also found in literature (George, Nexhip, George-Kennedy, Foster, & Walton, 2006). The volume change occurs so fast that it resembles an explosion, hence the name vapour explosion. Such an explosion at industrial scale can cause economical losses, bodily injuries or even fatalities.

Jan 1, 2019

By Magdy Ibrahim

Detailed as-built project schedules are necessary to close out construction projects, benchmarking, forecasting, dispute resolution, and improving cost estimates of future projects. Manual procedures for developments of as-built documentation is time consuming, involves numerous interfaces and human interventions. This paper presents computational framework that encompasses automated site data acquisition and generates schedule updates utilizing commercially available project scheduling software. The work is carried out collaboratively with a Hydro Quebec team. The site data is captured employing mobile computing using iPad® type computers and Wi-Fi. The information is directly compiled in a centralized database server. The synchronization tool is a bi-directional application and is used on servers to communicate with iPad® computers deployed onsite. The captured data is stored in Microsoft SQL® relation database that consists of 63 entities. Computer software application has been developed in Microsoft Visual Basic® (vb.net) environment for extracting the collected site data, linking the database to the as planned schedule, and generating the actual, also known as as-built schedule. The development can be utilized in automated progress reporting, evaluating future bids, generating master schedules and a wide range of efficient EVM applications.

Aug 1, 2013

"Cobalt refining at Vale Canada (previously known as Inco) has been associated with Ni production. Because certain compounds of both metals carry risks for adverse health endpoints by inhalation exposure, it is critical to understand the aerosol concentrations of specific substances and the metallurgical processes through which they enter the air. Vale Canada has therefore decided to describe the histories of its Ni-related operations and to report industrial hygiene measurements when available. This paper describes electrolytic Co operations carried out at Port Colborne, Ontario (1954–1966), and provides aerosol measurements (1995–2008) for current Co electrowinning operations.RÉSUMÉ L’affinage du cobalt chez Vale Canada (anciennement Inco) a été associé à la production de nickel. Puisque certains composés de ces deux métaux comportent des risques d’effets néfastes pour la santé par exposition à l’inhalation, il est essentiel de comprendre les concentrations en aérosol des substances spécifiques ainsi que les procédés métallurgiques par lesquels ils entrent dans l’air. Vale Canada a donc décidé de décrire les historiques de ses opérations liées au nickel et de divulguer les mesures d’hygiène industrielle lorsqu’elles sont disponibles. Le présent article décrit les opérations électrolytiques effectuées sur le Co à Port Colborne, Ontario (1954–1966), et fournit des mesures de la teneur en aérosol (1995–2008) pour l’extraction électrolytique actuelle du Co."

Jan 1, 2015

By D. J. Sapsford

This paper details results from laboratory simulation of an innovative underground bioleaching process. The underground reactors are periodic flushed with recycled leachate to remove uranium that accumulates within the reactor water. This leaching cycle has been recreated within the laboratory. This study examines the influence of varying cycle protocol on uranium leaching. Protocol variants examined include variation of flushing frequency, flush volume, leachate recycle, nutrient solution (NPK) addition to reactors and Fe(III) sulphate addition to reactors. The presented data highlight the dramatic improvements in uranium recovery that might be achievable by varying the operating protocol for the actual underground reactors.

Aug 1, 2010

By M. Timberlake, A. J. Jonaitis

"The DENVER Tube Press is a simple, high pressure (1500 PSI (100 bar)) filtration unit, developed for processing difficult-to-dewater materials and to produce a handleable filter cake and clear filtrate product.Lab and Pilot testwork conducted in Australia on coal fines (55-70% -35 micron (400 mesh)) have shown that total moisture contents of less than 20% are consistently achieved in the final cake products from the Tube Press.currently, these coal super fines are sent to waste due to uneconomical mechanical dewatering methods, which were only able to reduce total moisture levels in excess of 30%. Calculated, throughput rates for the 500 series Tube Press exceeded 1700 kg/hr (3750 lbs/hr). Feed solids concentration requirements are between 45 and 50% to achieve these results.INTRODUCTIONThe DENVER Tube Press is an automatic membrane high pressure filter press, which operates at hydraulic water pressures up to 1500 PSI (100 bar). The Tube Press was developed in the late 1960's by Charlestown Engineering, st. Austell, Cornwall, England, formerly a division of English China Clays, Ltd., to address more effective methods of moisture reduction of micron-size china clays. The Tube Press reduced moisture sufficiently to produce a hard surface-dry, handleable cake and clear filtrate discharge, which was recycled into the process. This development work was conducted using a 200 Series Tube Press (200 mm diameter x 2500 mm long filter surface)."

Jan 1, 1993

By T. W. Cavers

The Dwight-Lloyd sintering machine was the answer to the flue-dust problem of the copper blast-furnace smelter. Then came concentration by flotation, which threatened to eliminate the blast furnace from the smelting field altogether, and again the sintering process solved the problem. As is well known, the sintering process is dual in its function; it expels sulphur from the charge and it converts a powdery material into nodules or chunks that hold together. The charge is ignited on top just as it passes over the edge of the first suction box, and the oxygen of the air that is drawn downward through the charge breaks up the sulphide and oxidizes about fifty percent of the sulphur. The heat produced by this reaction in the upper stratum of the charge ignites that lying immediately below, and, when the pallett has travelled the full length of the machine, the tire has reached the graces and the fine concentrate has changed its characteristics by being partially fused and has become a more or less solid mass. When the Granby Company was smelting its ore as mined, one small D-L machine was adequate for the treatment of the flue dust, but as soon as the policy of smelting the concentrate was adopted, it became necessary to add two large machines to the sintering plant. The three sintering units, of which two are 42 in. by 396 in. and the other 42 in . by 264 in. in hearth area, have a combined capacity of from 370 to 450 tons (dry) of charge per day. The capacity varies directly as the hearth area. The sinter produced is about 88 per cent of the dry charge, or 325 to 400 tons per day. The sintered fines returned for resintering average between 30 and 35 per cent of the charge, but this is not as great a disadvantage as might appear, since the addition of hot fines improves the burning qualities of the mixture. From 50 to 54 per cent of the sulphur is eliminated in the sintering operation.

Jan 1, 1934

By K. Wongpreedee

Recovery and recrystallization of Au wire can degrade strength and alter conductivity properties during exposure to elevated temperature. Au Deformation Processed Metal Metal Composites (Au DMMC's) are being developed for electronic applications requiring high conductivity and high strength. This paper discusses the relationships between microstructure, strength, and resistivity of Au DMMC's. It also presents the results of a recent study on the elevated temperature stability of Au DMMC's of several compositions. Au-7 vol %Ag, Au-14 vol %Ag, and Au-vol 7%Pt DMMC samples were prepared by a powder metallurgy technique. All specimens were processed into wire by extrusion, swaging, and drawing. The smallest final diameter of these wires was 120 ?m. Thermal stability was analyzed by electrical resistivity measurements to determine the relation between transformation rates and time at elevated temperature. The extensive deformation used to produce these composites reshaped the initially equi-axed powder into filaments that are 30 to 100 nm in diameter and 16 to 180 mm in length. The small filament diameter confers high strength on the composite. The high conductivity can be explained by electrons flowing parallel to the filamentary microstructure aligned with the wire axis. Using the Avrami and Arrhenius equation relationships, it is possible to predict the times and temperatures needed to achieve various degrees of homogenization. The Au DMMC's were found to have good thermal stability compared to conventional coldworked Au interconnection wires. Although these composites will revert to solid solutions if exposed to high temperatures for prolonged time periods, their relative stability is sufficient to allow them to maintain their twophase microstructure during the anticipated lifetime temperature profiles of many products.

Oct 1, 2003

By J. C. Salas, A. Weishaupt, J. A. Guzman

The origins of the electrorefining process date back to 1869, when the first ER cathodes were produced at Pembrey, South Wales. By the time that Pembrey was closing, Chuquicamata tank house was under construction, initiating in 1915 a long history of electrolytic cathodes production. Initially electrowon cathodes and later electrorefined cathodes were produced. During the history of Chuquicamata tank house, there have been several challenges associated with the quality demanded for electrolytic copper. Among them, the transformation from electrowinning to electrorefining in 1952, the onset of the direct commercialization of ER cathodes and the phase out of wire bars in the 80s, several technological changes including the implementation of permanent cathodes, and certainly the constant increase in complexity of the anodes refined. This paper explores the manner in which Chuquicamata has addressed these challenges and examines its links to process characteristics, which have been necessary to maintain a product quality according to market requirements and a brand, “CCC”, that is widely recognized worldwide. INTRODUCTION Located in the north of Chile, in the Atacama Desert, Chuquicamata is an open pit copper mine that for many years has played a relevant role in the global and local mining industry. Known from prehispanic times, the Chuquicamata deposit was initially developed between 1912 and 1915 by the Chile Exploration Company, the operating company of the Chile Copper Company controlled by the Guggenheim Brothers in the USA (Yeatman, 1916). Officially inaugurated on May 18th, 1915, by the President of Chile who pressed a button in Santiago sending a telegraph signal to the power generation plant specially built in Tocopilla, 1500 km north. It signaled the beginning of generating energy, sending it to Chuquicamata, another 140 km east (“El mineral de Chuquicamata”, 1915), marking the beginning of its industrial operation.

Jan 1, 2019

By A. Fyson, M. P. Smith, Margarete Kalin

"Drums containing 0.07 m3 of pyritic waste rock from a zinc/copper mine, with and without Natural Phosphate Rock (NPR) additions (40 kg/t waste rock) were set up outdoors. The effluent chemistry has been monitored over a period of 709 days. In the presence of NPR, the cumulative acidity discharged from 7 out of 8 drums was 80 % less than that discharged from drums without NPR. Mixing NPR throughout the drums was more effective in reducing acidity than placement of the NPR in a layer in the drum. NPR treatment was more effective for 'fresh' waste rock than for material which had weathered for more than 4 years. It is concluded that application of NPR to pyritic waste rock could greatly reduce acidity generated.IntroductionWaste rock dumps are significant sources of acid, generated by the oxidation of sulphides. Oxygen and water supply are oxidation rate-controlling factors, and oxygen supply is the reaction-limiting component. If secondary minerals can be formed on the surface of the rocks, pyrite oxidation and therefore acid generation may be reduced or inhibited. Neutralizing agents such as limestone do not prevent the oxidation of pyrite but treat the resultant acid mine drainage (AMD) or acid rock drainage (ARD).Meek et al. (1991) determined in pilot scale experiments that apatite mixed with tailings was more cost effective than liming or use of PVC liners to reduce oxygen and water penetration into the tailings. Phosphate is not acting as a neutralising agent but it creates a chemical condition on pyritic surfaces which prevents reactions of the oxidising agents. Precipitation of principally iron phosphates physically isolates the pyrite surfaces from further oxidation (Ziemkiewicz 1990; Evangelou 1994). The chemistry of the phosphate effects has been described by Spotts and Dollhopf (1990). Secondary mineral formation was evident in the leach pile at Gibraltar when leaching was impaired (Scott, 1991) indicating a link between oxidation and the mineral-formation process. This paper reports on effluent characteristics when waste rock is generating acid in the presence of NPR."

Jan 1, 1995

By R. J. McLeod

"Grinding at Giant Yellowknife is done in two stages. The first stage consists of two ball mills in closed circuit will: mechanical classifiers, the classifier overflow goes to flotation. The tailings from this flotation circuit are separated into slime and sand portions, the slimes go to an additional flotation circuit while the sand portion goes to the secondary grinding mills.Milltronic automatic sound control units were installed on each of the two primary ball mills and put into operation September 3, 1966. After about two months adjustments to the control units the operators were taken off the grinding circuit on November 1, 1966. The operators duties were taken over by the automatic control units while miscellaneous work was taken over by the helpers in the mill. The labour saving by the installation is approximately $2250.00 per month.After a short period of operation it was apparent there was a slight change in grind. The screen analysis of the primary classifier overflows for the period May to August 1966 averaged 62.23% minus 200 mesh while for the period September to December 1966 averaged 62.0% minus 200 mesh. This is a slight coarsening of the grind. The change in the primary grind has manifested itself also in the screen analysis of the final grind. Before automation the final grind was 80% minus 200 mesh, while after automation it was 7 5% minus 200 mesh. A change of grind was also noted in the flotation concentrates. Before automation the screen analysis of the concentrates was 35% plus 200 mesh and 50% minus 3 25 mesh. A ft er automation it was 35% plus 200 mesh and 47 .5% minus 325 mesh. In other words the grind got coarser or perhaps we should say there was less overgrinding. Another significant change took place in the assays of the slime and sand portion of the primary flotation tailings. It was usual under manual control for the slime portion to assay higher in gold than the sand portion. The reverse is now true."

Jan 1, 1967

By Samantha A. Beeson, Colin Poole

"A selective flocculation-floe flotation technique is already in use in the Canadian potash industry for the removal of water-insoluble slimes, but the process is currently limited in its application and reagent consumption is high. The work described in this paper details investigations into the separation of sylvite and halite from water-insoluble slimes by selective flocculation utilising other commercially available polymers.Preliminary flocculation performance tests were undertaken on pure sylvite, halite and water-insoluble minerals to establish the importance of a number of experimental parameters. The data from these single mineral tests was then used to establish optimum parameters for the separation of sylvite and halite from a synthetic mixture similar in composition to a typical potash ore. Under optimum conditions, separation was achieved with high recoveries using dispersant and flocculant dosages significantly lower than those currently used in plant practice.IntroductionAlthough solar evaporation and solution mining are used in some operations, most potash is extracted by conventional underground techniques and is then processed by froth flotation, in order to separate the valuable sylvite (KCI) from halite (NaCl) and water-insoluble gangue minerals. Flotation is usually preceded by a desliming stage to remove water-insoluble fines, but this also results in high potash losses and affects process brine requirements. To overcome these problems, one plant operated by Cominco in Saskatchewan uses a selective flocculation -floe flotation process (Banks, 1979/1980), in which a polyacrylamide flocculant is added to produce floes of water-insoluble material with minimal incorporation of halides. A collector is then added to render the floes hydrophobic and suitable for removal by froth flotation.A number of workers have also investigated the use of selective flocculation in potash processing, but these too have been concerned with developments in the removal of water-insoluble slimes (Williams, 1960; Brogiotti et al, 1974; Chan et al, 1986; Thompson et al, 1979; etc.). This paper provides results of novel investigations into the selective flocculation of sylvite and halite from water-insoluble minerals and discusses the possible mechanisms involved."

Jan 1, 1995