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By G. W. Davies

"IntroductionThe development of British Columbia's northeast coal deposits, represents the single biggest industrial undertaking in British Columbia's history.As a result of this development, several thousand jobs were created, hundreds of millions of dollars in new tax revenue and billions of dollars in new foreign exchange began flowing into Canada.The Northeast Coal Development began in 1981 with the signing of sales contracts to ship a total of 6.5 million tonnes of metallurgical and additional quantities of thermal coal annually to Japan over a 15-year period. The current long-term agreements contain provisions for extension to 20 years.The sales contracts with a group of Japanese steel mills were signed by two Vancouver-based mining companies, Quintette Coal Limited and Teck Corporation. The agreements followed years of exploration and negotiation beginning in 1968.The first shipment of coal from Quintette and Teck's Bullrnoose Mine was transported by BC Rail and Canadian National Railways to the Ridley Island coal port in the fall of 1983."

Jan 1, 1992

By Z. M. Zavodni, C. D. Broadbent

"Major rock slides in open-pit mines are rare, but they can develop in spite of sophisticated slope engineering design practice. Experience has shown that, except under high seismic load conditions, the serious slope instability condition is almost always accompanied by the gradual development of one or more tension cracks behind the slope crest, allowing for time-displacement monitoring. Continuous surface displacement measurements with attendant prompt analyses are usually adequate for the prediction of slope behaviour.This paper describes efforts that have been made to quantify parameters associated with slide movement, and compares the displacement records of several large-scale open-pit porphyry copper mine slope failures. Two principal failure stages are recognized in the typical slope failure leading to total collapse: (a) REGRESSIVE STAGE, during which the failure will re-stabilize if some disturbance external to the rock and structure is removed; and (b) PROGRESSIVE STAGE. during which the failure will gradually displace at an accelerating rate to the point of total collapse unless active control measures are taken. Over-all displacement records in both failure stages are apparently of simple exponential form. with a definite break occurring at the onset-of-failure point.Certain common empirical relationships are suggested for the large-scale slope failures analyzed in this study. Based on plots of displacement rate vs time prior to collapse, a semi quantitative empirical relationship is presented for failure collapse prediction. The comparison of historical slide displacement records furnishes the operating engineer with practical guidelines to estimate the characteristics of future large-scale slope failures."

Jan 1, 1980

By Rachel S. Prudhomme, Michael L. Jeremic

"The consolidation of mine backfill by free zing is a concept which has been under study in the mining engineering laboratories at Laurentian University during the past three years. The proposed underground application of freezing involves the artificial freezing of in-situ backfill by means of a refrigerated brine solution which would be circulated through a circuit off freeze pipes. The most interesting findings to date are: (I) The uniaxial compressive strength off frozen fill is considerably higher than that of cemented fill in a ratio of 20:1 (aggregate to cement), and (2) load deformation characteristics of the frozen fill suggest that a higher ice content results in more brittle failure and that samples which have initially failed can still support up 10 one-half the ultimate load without additional failure.Although at this early stage a derailed economic analysis of the procedure has not been possible, a general evaluation of the costs involved suggests that the method could be competitive with the hydraulic placement of cemented backfill. Results obtained from laboratory investigations indicate that the freezing of backfill is a structurally feasible option .IntroductionGround consolidation by freezing is based on the principle of transformation o f water contained in an aggregate-slurry into ice, which act s as a binding agent between the bulk particles, and which results in the transformation of a granular soil into a ""rock -type"" material. The abrasive nature of the particles enhance s the strength o f the ice by providing internal friction. As a result of this internal friction, the chances of plastic flow of the frozen mass when in a loaded condition are reduced(1). T he strength of a frozen aggregate is al so dependent on the grain shape of the aggregate particles which may or may not promote particle interlocking(2) and on the temperature since, below the freezing point of the water/aggregate mixture, the strength of the frozen mass increase s with decreasing temperatures.In the shaft sinking industry, artificial freezing of loose , unconsolidated soils has been in practice for several decades. Shafts for Saskatchewan 's potash industry have been sun k to depths of 3000 feet by employing artificial freezing to stabilize the Blairmore Formation(3). The common procedure for freezing ground for shaft sinking is summarized as follows(4,5): I) 150 mm diameter bore holes spaced on 1.5 m centres are drilled in a circular pattern with a radius of 1.5 m outside the periphery of the proposed shaft."

Jan 1, 1985

By R. P. Mahant

"Extensive pilot plant investigations were conducted both on partial roasting an d electric furnace smelting from September 1973 to August 1975.The objectives of the pilot plant investigations were:(I ) to confirm the application of available process technology to treatment of Falconbridge concentrate.(2) to examine partial roasting variables.(3) to investigate electric furnace smelting of roaster calcines .(4) to develop process design and operating parameters for a commercial plant.This part of the paper will cover the following topics:Partial Roasting InvestigationsPilot Electric Furnace InvestigationsPartial Roasting InvestigationsThe specific objectives were to:1. establish process variables for maximum oxygen efficiency and bed fluidi ation.2. determine the product distribution between the roaster and the various gas cleaning stages.3. produce a mass and thermal balance."

Jan 1, 1984

By J. Bigu, M. G. Grenier, S. Hardcastle

"This study was undertaken in a belt conveyor drift of an underground hard rock mine. The conveyor transported ore or waste from a crushing operation located upwind from the drift sampling locations. A 250 m section of this drift was selected and several types of measurements were taken. Average respirable concentrations in the drift were 0.43 mg/m3 and 0.19 mg/m3 for total and silica dust, respectively. From the respirable dust concentration profile along the drift, it may be possible to estimate the contribution from extended sources such as dust produced by the belt and return idlers.The airborne dust in the drift had an average mass-median aerodynamic diameter of 4.2 micron. A continuous dust monitor showed that the crushing operation produced fairly high dust concentrations (sometimes greater than 4 mg/m3) over short periods of time.IntroductionAirborne dust in the respirable range is known to be the cause of various forms of lung ailments . In underground mines, respirable dust sources are created at many stages of production. All mining operators are responsible for de signing and establishing means of reducing airborne dust. In some cases, sources of dust are well defined and suppression methods are standard.In the case of interest here, the airborne dust cloud was formed from the contribution from many sources, which may be either discrete or extended. At the experimental site, the discrete or point sources were the crushing operation and the belt conveyor transfer point (tail pulley). These sources may be controlled by proper dust capture and scrubbing systems as well as dilution ventilation. Examples of extended dust sources in the area include dust produced by the re-entrainment of settled particles along the drift. Ventilation air movement and vehicular traffic both contribute to this phenomenon. Dust produced by the conveyor is another example of an extended dust source. Caked deposits on the return strand and idlers as well as the transportation of dry material on the belt, can be major contributors. Proper wetting of roadways and muck as well as proper belt cleaning techniques can help reduce these emissions. The cleaning apparatus, used on the belt where these experiments were conducted, is shown in Figure I. These and other belt cleaning techniques are described in more detail elsewhere."

Jan 1, 1987

By F. J. Munn

"Since 1976, Cardinal River Coal s Ltd. has completed mining in eight pits. In each of these pits, at least one wall has failed, none by design, although not totally unexpected, yet there was no loss of production nor risk to personnel or equipment. Cardinal River Coals Ltd. has been successful in implementing a program to cope with failures and now feels justified in adopting more optimistic design parameters.The wall control program at Cardinal River Coals Ltd. is based on the premise that the walls are going to fail, monitoring is to confirm when. The program consists of monitoring slope movements and piezometric levels as well as structural mapping and visual inspections. In case of excessive movement, the frequency and intensity of the monitoring is increased. If a failure is impending, suitable remedial action is undertaken such as cutting down the crest, building up the toe, depressurization of the wall, artificial support, or a combination of the above. If remedial action is not possible, monitoring permits operations to continue up to near the time of failure.At the design stage, the emphasis is on identifying the potential failure mechanisms and the con sequences of failure. Once the potential failure mechanisms are identified, a monitoring system can usually be employed to give sufficient response time, and providing the consequence of failure is not severe and/ or remedial action can be taken to arrest the movements, then it is practical to mine pit slope s which have a higher probability of failure."

Jan 1, 1985

By R. F. Engler

"IntroductionThe Coal Branch region of west-central Alberta has been the focal point for unprecedented exploration and development activities over the past ten years prompted by the renewed markets for high-quality thermal coal. Although mines were developed and operated extensively throughout the region from 1910 until 1960, information relating to the detailed stratigraphy of the coal measures and their areal distribution tended to be localized to individual mine sites. Continuity along trend was impaired by a paucity of outcrop restricting geologic mapping to stream bank and roadside exposures. Recent studies and subsequent publications by Jerzykiewicz and McLean of the Geological Survey of Canada (1978, 1980) have established a detailed sedimentological model and defined the stratigraphic nomenclature for the region . The term Coalspur Beds has been adopted to describe the coal-bearing sequence between the overlying Paskapoo Formation and underlying Brazeau Formation. Complete sections of the Coalspur Beds have been compiled from sub-surface borehole data and published by Manalta Coal Ltd ., Dentherm Resources Ltd. and Luscar Stereo Ltd. This paper is an attempt to correlate this information on a regional basis to illustrate trends within the Coalspur Beds."

Jan 1, 1986

By T. P. Kostek

"Historically, gear pumps and motors have been popular in the mining industry because of their competitive cost, simple yet rugged construction, ease of rebuild, and relative long life and insensitivity to contamination. However, with the ever increasing ""popularity"" of fire-resistant hydraulic fluids, both users and manufacturers of gear equipment must make special considerations to enable the equipment to continue giving satisfactory performance even with the water-containing fluids.The paper discusses 60-40 invert emulsions and waterglycolsIntroductionMuch information has been published on the specific characteristics of the various types of fire-resistant hydraulic fluids. Fluid manufacturers' literature and other publications have dealt with such specifics as fire resistivity, seal compatibility and wear rate characteristics. Gear pumps and motors have been, and will continue to be, applied successfully in hydraulic systems employing both the ""invert"" emulsions (60-40) and water-glycols as the hydraulic fluid.Because most external spur gear equipment has been designed to function with petroleum oil as the fluid medium, certain guidelines must be followed to ensure satisfactory service life. FluidsThere are a number of different types of fluids which fall in the category of"" fire-resistant"" , the most common'being phosphate esters, water-in-oil emulsions, oil-in-water emulsions and water-glycols. The two in most prevalent use today as hydraulic fluids are the water-in-oil emulsions and the water glycols"

Jan 1, 1980

By L. A. Wolff

"Second only to profitability (but not always), productivity is the most sought after measurement for any operation. Whether it is in mining, manufacturing, construction, etc. managers always strive to know how productive various plants are. Even the Federal Government publishes, on a monthly basis, the nation's factory productivity.Just what is productivity and how is it measured? This is an important topic that needs definition. There could be as many definitions as there are people who use it. In the mining industry, the problems of defining productivity would be analogous to the definition of equipment availability. Each mine uses its own definition to suit its needs. Webster's Dictionary primary definition for productivity is ""the quality or state of being productive,"" with productive defined as ""yielding or furnishing results"". This is a definition open to a broad spectrum of interpretation. A discussion of how productivity is currently used in the mining industry and an introduction to a potentially different approach to its measurement and meaning is outlined in this paper.Defining ProductivityTypically, mining companies track several productivity measurements. These are partial measurements and can include the following: tons per specific equipment class per hour, tons per man-hour, and tons per shift. None of these, however, track the over -all performance of an operation, that is, a unit of output per unit of input.For a mining operation, output can be defined as the ore for mill processing. Input includes the required components of production to get to the first step of processing.The Wesbter's Dictionary definition exposes a major fault with the popular conception of productivity. The critical issue of accountability is not addressed. Anyone can produce, but how effectively and efficiently are resources used? Quantifying an inclusive measurement is difficult. Statistics referring to an increase in productivity are often published. For example, the statement, ""gold productivity has increased by 10%"" has many potentially dangerous interpretations. One must ask, what does this statistic really mean? Did gold companies produce 10%” more gold? Were less manpower or equipment required to produce an equivalent amount of gold? Did ore grades increase resulting in more ounces of gold produced, etc. Obviously, production and productivity can have similar implied applications and meanings, but also two different, distinct meanings.To mitigate a problem like this, a standard needs to be developed within the mining industry. Because of varying ore grade, changing waste to ore ratios, different mining methods, etc. all of which have a direct impact on mining, development of a standard is difficult. Kendrick(1) discusses the use of Total Factor Productivity as a productivity measurement. Summarized, the total factor productivity measure is an indication of the change in efficiency in the use of basic labour and capital factors associated with an operation.This measurement has little meaning when calculated at a given point in time. It should be an on-going calculation, tracking an operation over a period of time, to evaluate trends. These trends can be used to determine if an operation's productivity is what it should be, and alert management to potential problems before they become major and adversely affect an operation."

Jan 1, 1990

By Todd S. Harris

"IntroductionThe western region of North America has long been considered a dynamic market supporting such diversified industries as lumber, agriculture, cement, and electronics. In recent years however, the region has also been the focus of a great deal of activity in the extender and filler mineral s business from companies seeking to position themselves to take advantage of the large demand for these materials both here and abroad.Extender and Filler MineralsExtender and filler mineral s include 15different products used in numerous end uses. The nine most important extenders and fillers are listed in Table I. These products range in price from under $50 a ton to over $4,000 a ton and basically represent the following three different types of minerals:Particulate products-Calcium carbonate; Kaolin; Silica.Platy minerals-Talc (Montana, Canada); Mica.Fibrous minerals-Talc (California, Eastern U.S .A.);Wollastonite.What distinguishes these products from other industrial minerals? For one thing, an important feature of extender and filler minerals is that they are used primarily in such consumer non-durable good s as paper, paint, plastics, sealants, and rubber which traditionally do not react as violently to swings in the economic cycle. In addition, these minerals are sold principally on key physical properties, usually brightness, particle size and shape, oil absorption, and hardness. As part of the physical minerals segment of industrial minerals, extenders and fillers are traditionally the most stable group and typically the most profitable. Studies by C.H. Kline over the past decade on extender and filler minerals has revealed historic average profitability (expressed as a percentage on sales) nearly double that of most other industrial mineral s.The demand for these minerals in the western region (Fig. 1), closely follow s the areas of greatest population concentration. These markets include pulp and paper, mainly in the Pacific Northwest, and paint, around Los Angeles and San Fran cisco. Other significant markets for extender and filler minerals in western North America include joint cements, carpet backing, and plastics, mainly PVC pipe."

Jan 1, 1986

By J. G. Whellock, R. J. Phillips, J. W. Matousek, P. J. Marcantonio

"Stillwater Mining Company (SMC), a partnership of Chevron Resources and Manville Corporation, produces a copper-nickel, platinum-palladium flotation concentrate at its Nye, Montana mine. The concentrate is then toll processed in Europe. Recognizing the economic advantage of treating the concentrates at the mine site and of retaining this strategic resource in the United States, the Company commissioned Tolltreck International Limited and International Process Research Corporation to conduct pilot scale smelting tests with a flowsheet that would maximize metal recoveries while satisfying the environmental requirements of operations at Stillwater.Primary smelting was conducted in a single phase, 50 k W, submerged-arc, electric furnace. Refining the product mattes to copper-nickel ""white-metal""; containing approximately 2% iron, was accomplished in a Tolltreck, IV-litre, top blown rotary converter. Over-all platinum and palladium recoveries were approximately 99%; copper and nickel recoveries averaged 94%. INTRODUCTION(l-4)Stillwater Mining Company (SMC) a partnership of Chevron Resources and Manville, operates a copper-nickel, platinum palladium mine and concentrator at Nye, Montana, located in the valley of the Stillwater River, approximately, 100 km southwest of Billings. It is North America's only primary producer of these precious metals. The Stillwater area was mined for chrome ore during World War U and the Korean War, but it was not until 1961 that attention was drawn to the similarities between the Stillwater Complex and the Bushveld Complex of South Africa with its deposits of platinum group metals.A concentrated search for platinum was begun by Manville Corporation in 1967. Its presence, together with palladium, in mineable quantities was confirmed in the period 1976-1978, and the first partnership to develop the deposits was formed by Manville and Chevron in 1979. Anaconda joined the group in 1983, and in 1985 its share was purchased by Lac Minerals. In 1988 the interests of Lac Minerals were purchased by Chevron and Manville.The decision to develop the mine and build a concentrator was made in 1986. Construction began in the fall of that year, and the first concentrate was produced six months later, in March 1987. Underground mining is done in a two-shift, five day- week operation. Since startup, the concentrator has operated on a 24 hour/day, 7 day/week schedule, treating an average of 635 tonnes of ore per day and producing approximately 10 tonnes of concentrate."

Jan 1, 1989

By J. S. Scott

"The Quemont property comprises 640 acres lying directly north of and adjoining the Noranda (Horne) mine. During 1926 to 1928, United Verde Extension Mining Corporation sank a shaft 235 feet and did 3,000 feet of development work on the 215-foot level. Between 1929 and 1930, Quemonr Mining Corporation deepened the shaft to 926 feet, and did further lateral work and drilling on the 500- and 900-foot levels. This work was confined to an area close to the south boundary and met with little encouragement.Following a period of idleness a magnetic survey was made in the winter of 1944, followed in the summer of the same year by some 6,000 feet of drilling. The first successful hole was drilled in February, 1945, from the ice of Osisko lake.To the time of writing, 131,000 feet of drilling, surface and underground,have indicated a large tonnage of gold-silver-copper-zinc ore, and although some knowledge of the geology and structure is emerging, it is too early to draw definite conclusions. The following brief description deals only with those structural features that are reasonably well indicated."

Jan 1, 1954

By James J. Scott

"In the two years since their introduction, Friction Rock Stabilizershave replaced40 per cent of the previously used fixtures in the metal and non-metal mines in the United States. The Friction Rock Stabilizer, or ""Split Set "" , is a mechanical rock stabilizing system which uses friction to prevent rock movement . The Split Set is a tapered, rolled, steel tube that is slotted along its length. As it is driven into a drilled hole smaller than its diameter, it compresses, pre-loading the surrounding rock. This paper discusses the uses and acceptance of the friction rock stabilizer in mines in the United States. IntroductionFriction Rock Stabilizers, commonly called Split Set™· Stabilizers, have been under development by the author and Ingersoll-Rand Company since early 1973. Five years of intensive laboratory and field testing led to their introduction to the metal mines in the United States in the fall of 1976. Actual sales started in February of 1977and, to date, over five million units have been marketed to metal mines. The present rate of usage is near 3 V2 million units per year, which is approximately 50070 of all roof fixtures used in the United States metal mining industry,Richard Hoppe, senior editor of Engineering & Mining Journal. , in an article in the February 1979 issue entitled ""Winning the Battle Against Bad Ground"", said: ""In hardrock mining operations in the western U.S., particularly underground uranium mines where exceedingly difficult ground is common, no roof support system has been accepted more quickly than the Split Set friction bolt invented by Dr. James J . Scott and developed by Ingersoll-Rand Co."" This paper describes how Friction Rock Stabilizers function and presents technical data to show the uniqueness of such systems."

Jan 1, 1980

By M. K. Walter

"The underground operations of Kidd Creek Mines uses an average of 450 U.S. gpm water during regular operations, and discharges an average of 800 U.S. gpm through consecutive staged pumping lifts of 1200f t.Water is used as a flushing medium for the drilling operations and as a dust suppressant for drawpoint mucking. The water retains an average of 5% suspended solids by weight which is removed underground before being pumped to the surface. This paper outlines the treatment of the mine water for the removal of suspended solids which are chemically treated to settle out as a sludge product of 60% solids by weight. This process reduces the sludge handling operation by 50%. The sludge is systematically disposed into the ore passes.IntroductionThe Kidd Creek minesite, located 27 km north of Timmins, Ontario, produces 4.5 million tonne s of copper, lead, zinc and silver ores annually from its No. I and No.2 underground mining operations. Both mines use a sublevel blasthole stoping method of extraction.Water from the underground operation passes through a series of surface settling ponds, where it is treated to remove heavy metal ions from solution. A blend of the pond effluent with fresh water from Kidd Creek, supply the underground with water at an average rate of 450 U.S. gpm. Water flows from the production zones through coarse sumps and into a main pumping station. There are five main pumping stations underground, three in No. I Mine and two in the No.2 Mine.The No. 2 Mine pumping stations are located on the 4800 level and the 3600 level. All water below the 3600 level to the shaft bottom is controlled from the 4800 pumping station. The water from the 4800 pumping section is combined with water from the remaining levels of the No.2 Mine at the 3600 pumping station. Water from the 3600 pumping station is pumped to the 2400 pumping station in No. I Mine.The No. I Mine pumping stations are located on 2800, 2400, and 1200 levels. All water below the 2400 level to the shaft bottom is controlled through the 2800 pumping station. This water is pumped to the 2400 pumping station. The 2400 pumping station also controls the water below 1600level to 2400 level."

Jan 1, 1988

By Y. Wang

In this paper, the tribological and electrochemical corrosion properties of Al2O3/polymer nanocomposite coatings were studied using a micro-hardness test, a single-pass scratch test, an abrasive-wear test, and finally an electrochemical technique such as potentiodynamic polarization measurement, The coatings containing Al2O3 nanoparticles showed improvement in scratch and abrasive resistance compared with polymer coatings; this improvement is attributed to the dispersion hardening of Al2O3 nanoparticles in polymer coatings, Corrosion test results showed that the embedded Al2O3 nanoparticles in the polymer matrix do not sacrifice the corrosion resistance of the polymer itself.

Jan 1, 2005

By Michael J. Sapko, Ellsworth R. Spencer, Frank J. Perzak

"The fire resistance of several mine conveyor belts is evaluated using a new belt-flammability apparatus developed by the U.S. Bureau of Mines. The test apparatus, experimental details and a calculated flammability index (FI) are described.The FI values are useful for ranking the fir e resistance of mine conveyor belts. Values are determined using parameters readily measured with thermocouples, high-temperature flow probes and a methane-oxygen torch, all of which are components of the Bureau's new test apparatus. The FI varies directly with the flame-spread rate and the rate of heat release during burning and varies inversely with the critical (minimum) ignitor energy output.The fire-resistance ranking of nine different belt types using this moderately scaled apparatus is compared with available full-scale data on belt fires. This comparison shows that the ranking based on the FI is consistent with the full-scale data.IntroductionFull-scale fire hazard evaluations of mine conveyor belts are not easily related to the properties usually measured in small-scale flammability tests. The inadequacy of small-scale belt fire tests has been demonstrated in works by Mitchell, Warner and Reinke.Mitchell and Warner showed that certain neoprene (NP) and polyvinyl chloride (PVC) belts, which had been approved by the Code of Federal Regulations 30 CFR 18.65, were nevertheless capable of propagating flame over their entire length when full-scale fire conditions were simulated. Comparable results were also observed by Reinke at the Tremonia experimental mine in Dortmund, West Germany, where all belts burned in full-scale tests even though they passed the small-scale tests. Only by reducing the severity of the full-scale test could these fire-resistant belts be grouped on a pass-fail basis."

Jan 1, 1982

By Wenbin Zhang, George W. Poling

"Prior or simultaneous addition of ammonium sulphate can, not only enhance the activating effect of hydrosulphide ions on xanthate flotation of malachite but it can also eliminate possible detrimental or depressing effects of excess residual hydrosulphide . Use of relatively inexpensive ammonium sulphate appears to reduce the consumption of the much more expensive sulphidizing agent for optimal flotation recovery INTRODUCTIONOxidized copper minerals float poorly with conventional thiol-type collectors. This is believed to be due to the nonadherent character of the collector coating, which is readily re- moved by particle abrasion. Rosas and Polingr reported emulsion flotation seemed capable of resisting abrasion during the flotation of non-sulphide copper ores. It appears that the most common flotation technique for oxidized copper minerals comprises sulphidization with Na .S and subsequent treatment by sulphydryl collector. The principles of this method are available . Malghan recently reviewed the studies on the role of sodium sulphide in the flotation of oxidized copper, lead and zinc minerals.It is well known that in the sulphidized flotation of malachite, the activation process depends strongly on the concentration of the sulphidizing agent, i.e., insufficient sulphide gives poor recoveries because of inadequate sulphidization; excessive sulphide also causes poor recoveries due to the depressive effect of the residual hydro-sulphide ions in solution. A major difficulty in sulphidization, especially with a varying feed nature, is to establish and maintain the optimum sulphide concentration in solution. In plant practice, vigorous control of sodium sulphide is required and stepwise addition of the reagent is recommended to improve the efficiency of the process. Soto and Laskowskim have found that malachite, depressed by an excess of sulphide ions, can restore its floatability if air or oxygen is introduced to the pulp. They attributed this to the oxidation of the HS - ions on the surface of the mineral. Jones and Woodcockuvi showed that a sulphide ion selective electrode could be used to optimize the conditions (e.g . amount of hydrosulphide, sulphidization time, flotation time) more readily and precisely than existing methods in the flotation of oxidized copper ores."

Jan 1, 1989

By M. M. Papic

"This paper describes the Sasol coal liquefaction process, as used in South Africa. It covers coal supply, coal gasification, gas purification, Fischer-Tropsch synthesis, the major utility systems involved and the economics of the process.IntroductionThe Sasol coal liquefaction process is based on Fischer-Tropsch synthesis of liquid fuels from carbon monoxide and hydrogen, which are in turn obtained by gasification of coal with steam and oxygen. The process is shown schematically in Figure I.The first step in the process is coal preparation, in which the coal is crushed and screened to a 3-50 mm size for gasification on one side and to -3 mm size for steam and power production on the other. Oxygen needed for coal gasificatoin is produced in the air separation plant.Coal is gasified under pressure by steam and oxygen in the Lurgi gasification plant, where raw, impure gas is produced . The raw gas is first washed in a scrubber with a circulating gas liquor, heat is then recovered from it in a waste heat recovery boiler and the gas is further cooled for purification. Water-insoluble materials (tar oils) in the gas liquor are separated from aqueous solution and sent to tar refining for the recovery of tar products. The aqueous portion of the gas liquor goes to a Phenosolvan solvent extraction process, where phenols and ammonia are recovered. Water then proceeds to the effluent treatment plant.The scrubbed and cooled raw gas goes to a Rectisol gas purification plant, where all components other than hydrogen, carbon monoxide and methane are removed as completely as possible by absorption in refrigerated methanol. The acid gases (CO2, H2S) stripped from the methanol in the Rectisol unit are processed in a Stretford plant for recovery of sulphur. Regenerated methanol is returned to the process. The purified synthesis gas is passed to the fluidized-bed Synthol reactors, where Fischer-Tropsch synthesis reactions take place.The synthesis products are recovered in a product recovery unit as separate streams of decant oil containing higher-molecular- weight hydrocarbons, light oil comprised of lower-molecular- weight species, the aqueous stream containing water solubles, a C3/C4 stream, a C2 stream , a methane stream and a hydrogen-rich stream. Most of the hydrogen is recycled to the Synthol reactors; a major portion of the methane is reformed to hydrogen and carbon monoxide for recycle; the C2 fraction goes to an ethylene plant; and liquid streams proceed to the product refinery.The product refinery is used to upgrade and purify the Synthol products to specification fuels and chemicals.Sasol l, the first coal liquefaction plant in South Africa , was built in 1955. It is still operating and has a product output of about half a million tonnes per year. The Sasol II plant is in a commissioning stage and will be in full operation in 1981. It is about five times the size of Sasoll. It uses over 12 million tonnes of coal and produces more than 2 million tonnes of saleable products annually (1,2,3). The Sasol llI plant, which is a mirror image of Sasol II, is under construction and scheduled for completion in 1983."

Jan 1, 1981

By Neil Schofield

"The estimation of recoverable ore reserves for feasibility in precious metal deposits such as Pine Creek must account not only f or the extreme variability of the ore grade but also for the complexity of the geology. Compatible models f or both must be adopted. Further, very selective mining demands reserve estimates be based on small selection units whose individual grades cannot be estimated reliably from the exploration drilling data.Multigaussian kriging is one method based on a multivariate normal model for estimating recoverable reserves under such conditions. In this paper, a non-mathematical description of the multigaussian model is presented together with its application to the Pine Creek Gold Deposit. The results, when compared to the first year of production, are encouraging for the model but not without surprises.Together, Part 1 and Part 2 of this study combine a detailed and geologically conditioned variogram analysis with an appropriate estimation method for a highly variable low-grade gold deposit. This and other studies of gold deposits familiar to the author show convincingly both that while the appropriate geostatistical skills and techniques are necessary to tackle the question of reserves, equally important but often discounted is the need for an appropriate and compatible geological model. IntroductionThe Pine Creek gold mineralization is associated with saddle reefs, and quartz and quartz- sulphide veining within the Enterprise Anti cline. The anticlinal structure is complex and, prior to mining, the mineralization was considered to be mainly strata controlled. Grades vary up to 160 grams in l .5rn core samples with coefficients of variation in excess of three.The estimation of the recoverable reserves for such a depo sit must account for both the geological complexity and the extreme variability of the gold grade.Part 1 of this work presented the geological model for the deposit and summary statistics 0 f the gold data. A detailed structural and variogram analysis considered both gold grades and the normal score (or gaussian transform) of these gold grades for different composite sizes."

Jan 1, 1988

By G. J. Desroches

"In order to improve zinc plant productivity, areas of low efficiency were identified. As a result, solution purification was improved, additional dust precipitator capacity was made available and a new zinc casting plant was installed. The effects of these and other changes are discussed and the expenditure and benefits reviewed. HistoryThe operation of the Flin Flon metallurgical complex including an electrolytic zinc plant commenced in October 1930. The design of the zinc plant was based on that of the Commonwealth Mining and Smelting Company at Trail, British Columbia, the Anaconda Great Falls Montana Plant and the Electrolytic Zinc Company plant at Risdon, Tasmania.The plant began with a design capacity of 60 tons per day and currently produces 255 tons per day. Since plant start-up, approximately 3.5 million ton s of zinc metal have been produced, most of it exceeding special high-grade specifications.IntroductionThe facility incorporates the basic process steps of roasting, leaching, purification, electrowinning and casting. Figure I details the flowsheet. During the late 1970s, management recognized that in order for the zinc plant to continue operating, it was necessary to introduce cost-effective practices.Study groups, consisting of design engineers and operations personnel, were formed to investigate the details of plant revisions.The objectives were to improve productivity by reducing manual labour, reducing energy usage, increasing zinc recovery, increasing metal output and reducing costs.This paper details the changes made during the period 1979to 1986 and shows how these changes have affected the productivity and economics of the zinc plant operation."

Jan 1, 1988