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By Kristie Tarr

Portland cement is primarily used to solidify backfill in underground mine workings and it represents a major cost in mining operations. CANMET-MMSL has invented an alternative binder technology that does not contain any amount of Portland cement and is made using waste materials, such as development rock and smelter slag. The technology has been successfully tested with many types of base metal and ferrous slag. Research conducted in collaboration with several mining operations in Canada has shown that the CANMET-MMSL binder has considerable potential as a replacement for Portland cement in mine backfill. An integral part of the overall mining operation, backfill is used for two main purposes: safety and environmental remediation. Depending on the mining method used, backfill provides a working surface, stabilizes stope and pillar walls, as well as the surrounding rock mass, and controls caving of stope backs. There are several benefits associated with the replacement of Portland cement in backfill, including reductions in (i) the footprint by placement of slag waste underground, (ii) the environmental effects and long term liability resulting from disposal and containment of slag waste on surface such as acid rock drainage, (iii) GHG as a result of reduced Portland cement usage (the production of 1 ton of Portland cement produces 1 ton of GHG), and (iv) the significant costs associated with reduced Portland cement usage.

Oct 1, 2010

By Jean-Claude LeRoy, Herman Keller

"INTRODUCTIONEROCON's work is the reclamation of mine wastelands. It has had considerable experience in particular in the reclamation of gold mine tailings in the Canadian Shield since the latter part of the sixties when most gold mines were closing down.A typical example is the famous Hollinger Mine in Timmins which produced $566 million worth of metal from 1910 to 1968 and had left behind some 56 million tons of tailings covering about 1,000 acres which were reclaimed on very short order and are now lush meadows of agricultural quality.To date, practically all gold mine tailings have been reclaimed once and for all by establishing a permanent, self-sustaining and maintenance free vegetation cover.RECLAMATION & THE MINING TOWNSThe first appreciation of people in a mining community where the tailings have been revegetated will be noticing one day the elimination of dusty conditions that used to arise formerly on every dry and windy day. In that respect, EROCON encourages not only vegetating the tailings but also the immediate surroundings of the mills and plants themselves at active mines. The elimination of windborne dust will result in an appreciable decrease in maintenance costs of plant and machinery and more pleasant working conditions for all."

Jan 1, 1975

By H. E. Urtubia, C. W. Bailey

"BHP-Billiton’s Minera Escondida Limitada is one of the world’s largest copper producers. It treats a combined 88 million tons of copper ore per year through its two concentrators: Los Colorados and Laguna Seca. Over the past three years, metallurgical sampling has been performed at the Laguna Seca concentrator to calibrate both the JKSimMet and JKSimFloat grinding and flotation simulators. In the past, the calibrated simulators have been used to predict the effect of changes in operating conditions in the grinding and flotation circuits separately. To assist in the development of future processing options, predictions were required of the effect of changing grinding circuit conditions on flotation performance. This was achieved by using an integrated grinding and flotation simulation. The grinding circuit performance was predicted under different operating conditions (such as tonnage rate and product grind size) using JKSimMet, and these results were then used in JKSimFloat to predict the flotation performance for the new grinding circuit product. This combination of the simulators allows both the effects of residence time and grind size on flotation performance to be investigated.This paper presents the first combined grinding and simulation modelling and simulation case study using JKSimMet and JKSimFloat. The modelling and simulation methodologies for the grinding and flotation circuits are discussed along with the circuit simulations that were performed. The simulator predictions are presented in conjunction with independent laboratory results of the new operating conditions. The ability to predict flotation circuit performance based on changes in grinding circuit performance is also discussed. This methodology provides improved predictions of flotation circuit performance when grinding circuit changes (including grinding capacity increases) are made.INTRODUCTIONOver the past decade, the grinding and flotation research groups at the Julius Krutschnitt Minerals Research Centre - JKMRC (Brisbane, Australia), University of Cape Town (Cape Town, South Africa) and McGill University (Montreal, Canada) have been developing a methodology for optimising grinding and flotation plants using actual plant data together with semi-empirical sub-process models. The project is being conducted as part of the Australian Minerals Industry Research Association (AMIRA) P9 Project, titled “The Optimisation of Mineral Processes by Modelling and Simulation”. The project first commenced in 1962 and is currently in its “Nth” phase."

Jan 1, 2007

By A. J. Magerowski

Energy consumption is a main component of operational costs for the comminution of mineral bearing ores. Reduction of energy consumption has continually been addressed by mill operators and equipment manufacturers. Our testing over the last few years strongly indicates that the overall energy needed to comminute a mineral bearing ore can be brought down significantly, if more work is done in the crushing stages of the comminution circuit.This calls for uprating of the conventional crushing equipment into a new generation of crushing equipment to produce finer products. This will result in the emergence of new ideas in the design and application of equipment and corrnninution circuits.

Jan 1, 1986

By L. M. Gould

"Syncrude Canada operates the largest oil sands crude oil production facility in the world and produces over 13% of Canada’s total oil requirements. To achieve this, Syncrude mines the oil sands in open pits, extracts the raw oil known as bitumen from the sand using water-based processes and upgrades it into sweet light crude oil by fluid coking, hydroprocessing, hydrotreating and reblending. The final product, Syncrude Sweet Blend (SSB), is sent by pipeline to three Edmonton area refineries and then to pipeline terminals which ship the SSB to refineries in Canada and the United States.As parts of the Mildred Lake base mine reached their economic life, they were replaced with new facilities at the Aurora Satellite mine. Aurora is situated on Oilsand Leases 10, 12 and 34, 35 km northeast of the Mildred Lake facility (Fig. 1).In 2000, the first hydrotransport low-energy extraction production train started up at Aurora. A second production train is scheduled for start-up in 2003. Open pit mining at Aurora occurs using two hydraulic shovels, two cable shovels, and trucks ranging from 320-ton to 380-ton payload capacities (Fig. 2).Once the oil sands is excavated, the trucks dump the ore into a crusher designed to break up the big lumps of oil sands and rock at peak rates of 11 000 t/hr. The ore is then transferred by conveyor to a surge pile and then to a mixing box which combines the oil sands with hot water. Following bitumen separation in the primary separation vessel, froth is delivered to Mildred Lake for processing via the intersite pipeline (Fig. 3).The goal of this paper is to illustrate how high precision shovel GPS (HPGPS) is being used at the Aurora mine to aid in mine planning. This can be accomplished by first describing the function of the mine planning department, describing the Aurora orebody, and finally explaining how the HPGPS system functions and how it is employed at Aurora.The short range mine planning department ensures a steady supply of ore is delivered to the plant at the desired grade in a sequenced and economical manner. This is done by creating a mine plan that consists of shovel dig locations that require the shovels to mine in a specified area at a specified elevation."

Jan 1, 2002

By J. T. Furey

"A pilot plant study was conducted to evaluate the performance of column flotation in the recovery of gold from a gold/tellurides bearing sulphide ore, and to compare the performance of column flotation to conventional ""mechanically agitated"" flotation.Tests were conducted in a 60 liter glass column with ground flotation feed split from a concurrently operating conventional pilot plant, thus permitting direct comparison between the two processes. During the test program, the effects of wash water rate, gas holdup, froth depth, residence time and flow bias were examined in detail.The ore had an average ""as tested"" feed grade of about 5 g/t gold and 1 % sulphur, with the gold occurring primarily as inclusions of montbragite (Au2Te3) in pyrite, with minor amounts of native gold. Conventional flotation using 60 minutes residence time across four roughing stages recovered about 97% of the gold into concentrates grading about 50 g/t Au. A single stage of column flotation roughing using 25 minutes residence time matched the conventional circuit recovery of 97%, but produced grades of+ 150 g/t Au. INTRODUCTIONColumn flotation is the most significant innovation that has occurred in the mineral processing industry in recent years and has become an important alternative to mechanical flotation. Column flotation has been most widely accepted and applied in cleaning service where it has frequently proven to be superior to mechanically agitated flotation. Roughing in columns has not been ignored, but early testing indicated that columns may not be capable of achieving adequate recovery and, to date, columns have not been seen as serious competitors for mechanical roughers."

Jan 1, 1990

By Mohammad Noaparast, Babak Fotoohi

"Due to certain advantages in (semi-)Autogenous-Ball mill circuits in most of the high-throughput ore grinding units of mineral processing plants, much attention is paid to optimize the mill performance. Despite the maturity of the grinding mill mechanical design, there had been made less attention to the efficiency of the grinding media in the past. In this research, the possibility of establishing a relationship between liner/lifter wear rate and variations in the composition of the iron ore (from Chadormalu mine) is investigated.Measurements and determination of liner/lifter wear rates and patterns concluded in recognition of critical liner segments exposed to much abrasion during the ore grinding. After metallurgical analysis of liner materials and correlation of wear rate with the ore composition, the homogeneity in the metallurgical microstructure of the alloyed steel (such as the uniform distribution and amounts of the constituent phases) was determined as the most influential factor in the response of the liner/lifter to the variations in the ore composition. Magnetite with greater abrasion index than hematite, in finer particles, is responsible for additional abrasion of liners; hematite with greater work index exists in the mill with larger particle sizes, thus it could produce wear on liner parts with less tolerance to impact as is the situation for martensitic steels.INTRODUCTIONThe mineralization in Chadormalu plutonic iron ore deposit is consisted of mostly magnetite, hematite, martite, apatite, quartz and carbonates. The average composition of the ore is presented in Table 1. In the processing circuit, the gyratory crushed ore reduced to 30 cm would finally be the feed to three similar 32’ semi-autogenous mills in parallel processing lines. The pulp in the mill would have the characteristics mentioned in Table 2. The quality of the mill output has its direct effect on the downstream processes either physically or chemically (e.g. in cycloning or flotation respectively). In order to take advantage of optimum performance for these circuits, a close control of the ore grinding conditions is necessary; because any shortages in throughput, liner/lifter damage or changes in ore composition could bring the unexpected casualties. In this work, it has been attempted to find (possibly) a reasonable relationship between variations in ore characteristics together with liner quality and the amount of wear rate in different liner/lifter segments of a semi-autigenous mill. Liner/lifter segments are supplied by three different domestic steel making companies. The alloy structure of the liners/lifters is made up of pearlitic chromoly steel."

Jan 1, 2005

By Fathi Habashi

"A process is proposed for the treatment of phosphate rock for the recovery of uranium and the lanthanides. The process assures the production of phosphatic fertilizers without polluting the environment with radioactive material.IntroductionWhile many processes for uranium recovery from phosphoric acid produced by the H2S04 route are known and utilised commercially, little is known about uranium recovery from phosphoric acid produced by the HN03 route1. Advantages of the latter route are both the elimination of the gypsum disposal problem, and the possibility of radium disposal in a controlled way2. Further, the lanthanides originally present in the rock can be recovered if the nitric acid route is used; they will be mostly lost in the gypsum produced by the sulphuric acid route3. In the present work a scheme for the recovery of uranium and the lanthanides from phosphate rock without interfering with the normal route for fertiliser production is proposed using HN03 as a leaching agent. Attention was also given to uranium decay products and their separation so that they might not contaminate the fertiliser4. Further, an attempt was made to defluorinate the leach solution in order to upgrade the fertiliser and at the same time recover the fluorine5. Rapid analytical methods for the determination of uranium, radium, and lanthanides in phosphate rock were developed6,7."

Jan 1, 1997

By Christoph Mueller

Mining operations today are characterized by a high degree of mechanization and single machine automation. However, their potential for cost cuttings and increase of productivity in the future is quite limited. Enabled by newest IT and networking technology, the operation of underground mines more and more can be seen from a process related point of view: Standardized Ethernet and Wireless LAN are the basis for a seamless and unified communication backbones providing an integrated infrastructure for data, telephony and video. All the components are available as off-the-shelf devices leading to an excellent cost efficiency. Basing on this standardized infrastructure, the equipment is able to become part of the infrastructure. To enable machines to be integrated smoothly into IT networks, the machine also has to have enhanced networking capabilities. This results in a new system architecture for the on board machine electronics separating real time control from IT and networking level functionality which can be implemented by a Machine Server. This machine server communicates with all kinds of above ground systems using mainly standardized formats like html or the IREDES standard. This information is made available mainly in 3D mine visualization tools. The paper explains this technology and shows implementations by two working examples.

May 1, 2006

By George H. Hope, Steve Ciccone

"The Red Dog Mine is both the largest known zinc reserve and the largest zinc producer in the world. The mine started in 1989, and by 1999 had increased production from approximately 300,000 tonnes per year (t/yr) of zinc concentrate to in excess of 900,000 t/yr. The VIP Mill Optimization Project further increased zinc concentrate production to 1.1M t/yr while improving both product quality and zinc recovery. The Mill Optimization project also addressed a number of issues related to risk reduction: power generation capacity, water treatment capacity and concentrate thickening. The project was faced with numerous challenges, the most daunting of which was the schedule. This US$105M project was executed, from conception to completion, inside of two years. Less than nine months elapsed from concept to delivery of materials and equipment to site. The project also faced a 100-day ice-free shipping window, the challenges of construction in an Arctic environment, and an extremely tight labour market for qualified craft personnel. These challenges were successfully addressed with several innovative approaches to project execution, including an Alliance contracting arrangement between the owner, engineer and contractor; full integration of the team; construction of modules in Anchorage; and fast-track engineering, procurement and construction.INTRODUCTIONThe Red Dog Mine, which began operations in 1989, is located above the Arctic Circle in Northwest Alaska, approximately 145 km north of Kotzebue (Figure 1). An 80-km road connects the mine site to the DeLong Mountain Transportation System (DMTS) port site. Red Dog is the largest known zinc deposit in the world, with known reserves totalling 94.5M tonnes, and is the largest zinc producer with a concentrate production rate of more than 1.1M t/yr.Open-pit mining is by typical drill, blast and load operation using moderately sized mining equipment. Ore is processed through conventional crushing, grinding, and flotation to produce separate lead and zinc concentrates. Filtered zinc and lead concentrates are trucked year-round to the DMTS port site, where they are stored in two A-frame buildings, 330 and 440 m long. A lightering barge system is used to transfer concentrate from the shallow water load-out to deep-sea vessels anchored approximately two miles offshore. Shipping is limited to a 100-day, ice-free window beginning in early July."

Jan 1, 2003

By J. P. Caulfield

THE Hudson Bay Mining and Smelting Company's underground mine at Flin Flon, Manitoba, has in the past been serviced by two working shafts-the North Main shaft, and the No. 3 shaft. The North Main shaft is used to hoist the total production from under-ground, and handles the greater part of the mine supplies and crews. The shaft is five-compartment design, rectangular in cross-section, and is equipped entirely with steel shaft sets from the surface to the finished depth of 2,210 feet. Hoisting equipment in the surface plant will not permit the North Main shaft to be extended below its present finished depth. The No. 3 shaft, located approximately 2,300 feet from the North Main shaft, is used primarily as a ventilation shaft, and for hoisting lower-level development waste to the 390 level, where this material is used as mine fill. The No. 3 shaft is of standard rectangular design, timbered with 8-in. by 8-in. creosoted fir sets, hung on 6-foot centres. From the surface to the 1,430 level, the No. 3 shaft consists of three 5 ft. by 5 ft. compartments, and below this level to the completed depth of 2,300 feet, the shaft is increased to four compartments. To service the mine and to expedite development below the 2,210 level, a one and one-half compartment winze was sunk from the 2,210 level to a depth of 766 feet, or approxima tel y the 3,000 level.

Jan 1, 1941

By J. Miettunen

"The lining of a grinding mill has an important role in creating the conditions for the grinding process. The main purpose of the lining is to transfer the energy taken by the mill motor to the contents of a mill. The power draw curve of the mill, if measured with sufficiently short intervals, describes how well the lining works in lifting and mixing the material to be ground.The power draw curve can also be used for determining the volumetric filling of a mill. This new measuring technique was developed at the Pyhasalmi concentrator in 1989-90. The measuring device with its PC-connections offers an excellent tool for controlling volumetric mill filling, for maximizing throughput and for research purpose (e.g. process studies, mill linings design).The paper describes the new method and the results achieved at Outokumpu's concentrators.INTRODUCTIONVarious methods have been developed for measuring mill load; weighing, noise, etc. Weighing is one of the most reliable methods but installing the sensor to existing mills is often difficult. Besides the load measurement does not indicate the volumetric filling if the specific gravity of the mill feed fluctuates. Noise measurement has often failed with its sensitivity to various disturbance sources.As known, the power draw measurement is one of the most accurate measurements in grinding circuits and therefore it has been utilized in sophisticated control, e.g. in power peak seeking algorithms for maintaining maximum grinding efficiency.About 10 years ago power oscillation measurement was developed at Pyhasalmi concentrator. In this method the amplitude of the oscillation caused by the lifters was measured. The oscillation amplitude and the mill filling has quite a good correlation and together with the power draw measurement it could be used for maximizing mill throughput (Koivistoinen and Miettunen, 1989). The main difficulties in this method were that the dependence between mill filling and the amplitude is unlinear and that the dependence also is individual for each mill.The method developed during 1989-90 is also based on the power oscillation but on its phase shift. In principle level of the material in a mill is measured. The method has been successfully used for maximizing throughput at Pyhasalmi and Enonkoski concentrators and at Harjavalta slag concentrator."

Jan 1, 1991

By L. Betteridge, A. Marks

"An OK 300 cu. ft. Skim - Air cell was installed at the HBM&S concentrator in Flin Flon in 1987. Since that time, 3 additional OK Skim - Air cells have been installed in HBM&S concentrators. The cell treats a coarse 70% solids slurry with a residence time of 2.5 minutes. The product from the cell (a unit cell type application) is a final grade copper concentrate with high precious metal values. Since its installation, the cell has improved gold recovery by 10 - 15%. Process variables such as circulating load, pH, froth depth, feed size, and reagent additions all have an effect on the operation of the cell. Maintenance on the cell has been minimal. Initial operating problems involving level control have been significantly reduced and operations are now relatively trouble free. Although very successful at Flin Flon, site specific operating circumstances will determine the suitability of this cell. INTRODUCTIONHudson Bay Mining and Smelting operates four concentrators in Northern Manitoba. Three treat copper-zinc ores, the fourth mills a copper-nickel ore. The Flin Flan concentrator operates two circuits in parallel which treat copper and zinc ores from the Trout Lake and Callinan mines. Both circuits in the Flin Flan mill have Skim-Air cells integrated into the grinding circuits.The Trout Lake cell was installed first and had a payback period of a few months. Required modifications to the cell were made to enhance its performance. These included changing the discharge valve size, tuning the level controller, and installing an insert into the rubber valve sleeve to increase its wear life. The payback period on the Callinan cell was significantly reduced because these modifications were completed prior to its installation.The cells produce a final grade copper concentrate and since their installation gold and silver recoveries to the final copper concentrate have increased significantly. Operating parameters such as coarseness of cell feed dictate the metal recoveries and froth depth determines the selectivity of the cell and therefore the grade of the concentrate.The Skim-Air cell can be suitable in applications where a final product is generated. However, when a bulk concentrate, which requires further separation, is produced, the coarseness of the product may not make it amenable to conventional flotation.The Flin Flan mills Skim-Air cells have worked exceptionally well with little maintenance required."

Jan 1, 1991

By C. Guo, R. J. Chalaturnyk, M. MacKinnon, J. D. Scott

The Mildred Lake Settling Basin (MLSB) is the largest disposal site for mature fine tailings (MFT) at the Syncrude Canada Ltd. oil sands plant. Over the past years (since 1996), there has been a marked change in the densification behaviour of MFT in the MLSB. Methane-producing microorganisms, known as methanogens, have become very active, and large amounts of biogas (mainly methane) have been produced. Continued field monitoring of the MLSB has provided convincing evidence of the rapid densification process (rapid water drainage from the tailings) at the area with intense microbial activity. This rapid densification has caused pumping challenges in the transfer of fine tailings from the Mildred Lake Settling Basin for the creation of composite tailings. It may also have potential positive effects in accelerating the reclamation of the oil sands fine tailings. A field and laboratory research program was carried out to study the mechanism leading to the rapid densification phenomenon. A review and discussion of the research program is given and some results from the field investigations and small-scale column tests are presented in this paper.

Jan 1, 2007

By Julie Culverhouse, Dennis Grimm, Kieran Harding, Jean-Francois Boulanger

"Agrium’s Canadian Phosphate Business (CPB) is comprised of Kapuskasing Phosphate Operations (KPO) in Northern Ontario, Canada’s only operating phosphate mine, and Redwater Phosphate Operations (RPO) in Alberta, which manufactures the fertilizer from KPO’s concentrate.Production from KPO’s South Pit commenced in 2009 and introduced contaminant problems: high aluminium from crandallite and kaolinite clays. These issues caused a drastic decrease in P2O5 recovery and throughput in both plants. KPO attempted to reduce Al clays by means of aggressive desliming. Meanwhile RPO experienced high amounts of dissolved metals in their feed that are detrimental to fertilizer production.This paper covers the mineralogy of the problem, its impact on contaminant separation at KPO, on RPO’s process and on Agrium’s Canadian Phosphate Business as a whole.Potential solutions to the problem are discussed and analysed, including a process change to deslime high aluminium streams more aggressively and high grade ore flotation, which is atypical at KPO. The latter is a demonstration of the value of communication between the concentrator and the client, as KPO accepted a recovery loss and increased production costs in order to increase overall CPB profits. General lessons learned are discussed, followed by a section on ore blending.INTRODUCTIONAlthough the existence of the Kapuskasing phosphate deposit has been known since the 1970s, it’s only since 1999 that Agrium has been operating the Kapuskasing Phosphate Operations (KPO). The mine consists of three major pits (Center, North and South) from which a mining contractor hauls the apatite ore to the Agrium concentrator. The beneficiation plant processes the ore, separating contaminants such as Fe, Mg and Al which are detrimental to its client, Agrium’s Redwater Phosphate Operations (RPO). The KPO concentrate is finally thickened, filtered and dried before being shipped by rail to RPO.At the Redwater plant, the KPO concentrate is added to a sulfuric acid solution in an attack tank, to create a phosphoric acid solution and gypsum:"

Jan 1, 2011

By Andrew Bamber

The introduction of pre-concentration technology into the underground narrow-vein mining scenario has the potential to change the entire economics of utilizing bulk-mining methods in these situations. An idealized integrated underground mining and processing system, comprising elements of bulk mining, underground preconcentration and backfill systems is presented. Through simulation and a systems engineering approach, the implications of enabling the utilization of bulk mining methods in a narrow vein deposit through the adoption of this technology is considered. Parameters considered include orebody characteristics, ore mineralogy, grade, metal value, mining rate and cost.

Oct 1, 2004

By S. Banisi, M Nesari, J. A. Finch, N. Nobari, H. Javani

"The flotation circuit of the Sarcheshmeh copper mine, which processes 40,000 t/d of ore at 0.9% Cu, consists of rougher, cleaning and recleaning stages. Mechanical flotation cells are used in all stages. To investigate the amenability of flotation columns in the plant especially for cleaning and recleaning stages, a column was designed, constructed, and installed at the Sarcheshmeh pilot plant. The pilot plant, which has an identical circuit configuration compared to the plant, can process up to 2 t/h of ore. The overall rate constant of the ore along with the target recovery of 94% were used to size the column. A 26 cm by 550 cm column with two filter cloth spargers and a submerged froth washing system using perforated tubes was constructed. To detect the interface level a 180 cm conductivity probe consisting of 1.5 cm diameter ring electrodes was installed. The tailings flowrate controlled by a variable speed pump was used as the main control variable. The initial testing program revealed that the optimum superficial gas and wash water flowrate were 1.5 and 0.3 cds, respectively. It was observed that the cleaning stage grade when using the column could increase by 2-3% at constant overall copper recovery.IntroductionThe Sarcheshmeh copper ore body which may rank as third or fourth largest in the world contains 1 billion tomes averaging 0.90 % copper and 0.03 % molybdenum. It is in located south-east Iran and has been processing 40,000 t/d of ore since 1982. After three stages of crushing, the ore with a F80 of 12.7 mm is fed to 8 parallel ball mills in closed circuit with cyclones to produce a product 70% finer than 75 microns. The concentrate of the first stage of flotation is reground and the tailings constitutes the main component of the plant final tailings. A concentrate with an average grade of 31% Cu (chalcopyrite and chalcocite) is obtained after cleaning and re-cleaning stages in mechanical cells. Total recovery of the plant varies between 83-87 % depending on ore type and operating conditions."

Jan 1, 2000

By D. J. Kemp

The 20th century saw changes in the mining and metallurgical industry not only technically but also in social and environmental expectations. As projects continue to become larger their visibility raises concerns among many groups. For mining companies, transparency, openness, and early engagement of all parties are fundamental to assure success. An equally important task is to anticipate the standards that will be required to meet society’s expectations in the 21st century.

Jan 1, 2005

By Derek J. Cyr

Climate has an immense impact on the properties of Athabasca oil sands and the ease or difficulty with which it is excavated and extracted. During the winter months, exposed oil sands surfaces freeze. When hydraulic and electric shovels used in the various operations in the Fort McMurray area excavate the benches, large frozen lumps are created. These lumps are either destined for a lump dump where increased costs are incurred due to rehandle, or they are sent to the primary crushers where they can cause significant downtimes by jamming the crusher. The crusher down time can sometimes be in the order of hours of lost production. Studies on data from two consecutive winters at Syncrude Canada?s North Mine show a high correlation between climate and the generation of frozen oil sands lumps. Temperature, ground cover, traffic, bench exposure time, oil sands grade and moisture content all contribute to this problem. A 1D frost penetration model was used to predict the depth of frost expected in oil sands and the corresponding likelihood of frozen oil sands lumps. To combat the challenge of frozen lump generation, a number of proactive and reactive measures can be taken: artificial snow, shallow ponds, scheduling, blasting or ripping.

May 1, 2004

By H. U. Ross

"INTRODUCTION Extensive studies have been carried on pure gold to determine the various factors that affect its dissolution in alkaline cyanide solutions. With the extension of milling to refractory ores more intensive investigations on the effect of impurities in the ore on the dissolution kinetics are needed. The present work describes experiments carried on refractory flotation tailings with the object to determine how the recovery of gold could be increased. The effect of arsenic and antimony in the ore and the excessive use of lime are discussed. Control of cyanide losses is also dealt with.MECHANISM OF THE GOLD DISSOLUTION REACTION In aqueous cyanide solutions, gold is believed to be dissolved by one of the following reactions:4Au + 8NaCN + O2 + 2H20 = 4NaAu (CN)2 + 4NaOH (1)2Au + 4NaCN + 2 + 2H20 = 2NaAu (CN)2 + 2NaOH + H202 (2)2Au + 4NaCN + H202 = 2NaAu (CN)2 + 2NaOH (3) The first of these, known as the Elsner Equation is supported by )4 3,2,1(several authors while others(5,6) support reactions 2 and 3 known as the Bodlander Equations. According to Habashi(7), the overall reaction for the dissolution process is as shown in equation 2. Most of the workers agree that hydrogen peroxide is produced in the course of the reaction."

Jan 1, 1973