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By Akira Fujisaki

"The oil crisis accelerated the change of non-ferrous metals' demand structure. Maturing societies in developed countries and preference for lighter, thinner and smaller products are eroding the non-ferrous metal industries' growth potential. Inventory-control, stockpiling and developing new demand are measures Japanese smelters have taken to cope with the changing demand.The most effective means for risk management of product demand lies in the cooperation between ore producing countries and metal consuming developed countries to assist developing countries in their efforts to ""take-off"", which in turn will bring about a surge of demand for metals.SummaryThe non-ferrous metal industry in the world is suffering its most serious slump since the war. With some of the markets of the advanced industrialized countries approaching saturation point and economized usage of natural resources and substitution growing, the possibility of a quick recovery of the demand for base metals is dim.To cope with the changing product demand Japanese producers have had recourse to such measures as strict inventory control and stockpiling for the purpose of stabilized imports. They have also tried hard for securing raw materials and promoting new field s of demand but the very core of ""risk management"" has been the diversification of line s of business to bolster and stabilize the foundation of management of the non-ferrous metal industry in Japan.To see the demand for nori-ferrous metals recover from the slump and be put on a path of solid development, we have to wait for the economies of the developing countries to ""take off"" and for its realization the economies of the developed countries must be reactivated with new growth industries playing a leading role, and the transfer of technology and money recycling must be carried out smoothly under an orderly international trade system."

Jan 1, 1983

By K. R. Wood, G. W. McDonald

"The tailings disposal system at Les Mines Selbaie includes dewatering of tailings in a high-capacity thickener, followed by point discharge of the thickened solids to form a stable conical pile. Tailings water drains to ponds formed behind engineered dams, prior to either recycling f or process use or discharge to the environment. Design and economic considerations of the system are discussed. Construction, start-up and operating experiences are also presented.Introduction Les Mines Selbaie is located in the Abitibi region of northwestern Quebec, approximately 700 km north of Toronto and 150km south of James Bay. More locally, the Detour gold mine is 60 km to the west while the Noranda smelter is 220 km to the south.The deposit was discovered as a result of a Questor INPUT Mark VI geophysical survey in 1973, followed by diamond drill programs from 1974 to 1976. Three mineralized zones were delineated and underground exploration was carried out on all three. A production decision for the 'B-zone' copper-gold-silver orebody was made in July 1979. The underground operation started in July 1981, with full production of 1500 t/d being achieved in May 1982.During the planning phase, every effort was made to ensure that the operation would be environmentally sound . The design included the provisions of the then newly proposed provincial environmental guidelines. The tailings disposal system formed the most significant part of the environmental program due to the large volumes of solids and water effluent. In addition, the design allowed for future expansion of the system to accommodate mining of the other zones, thus minimizing future costs and disruptions."

Jan 1, 1986

By F. Barriga-Ordonez, J. A. Finch, L. Calzado, S. R. (Ram) Rao

Sludge, formed by lime treatment of acidic drainage and stored in tailing ponds of the Sudbury region, contains 5-7% Ni, mostly in a mix of hydroxides with Fe (~ 10%), Mg (~ 10%) and Cu (-0.5%), and Ca (-3.5%) as sulphate. Investigations were conducted to recover nickel by a 2-stage process. In the first stage, the sludge was leached with sulphuric acid at pH 3.2. About 90% of the nickel was extracted, producing a solution, which contained mainly nickel (2 g/L) and magnesium (3.7 g/L). In the second stage, nickel was separated by treating with ozone which recovered 99% of the nickel in the Ni(III) oxidation state as -85% pure nickel oxide-hydroxide (NiOOH) precipitate. The oxide settled and filtered readily. A potential use of the product in battery making is suggested. The leach residue contained 0.5% Ni making it less toxic for disposal. Some physical properties of nickel oxy-hydroxide and process parameters including ozone consumption will be discussed.

Jan 1, 2005

By J. M. Skeaff

"The main solution, ore and residue pulp streams in the Rio Algom Quirke I uranium mill at Elliot Lake have been sampled and analyzed for radium-226. Analysis of the ore and leached residues indicates that Ra-226 dissolves and precipitates within the first pachuca tank. A maximum of approximately 0.2% of the Ra-226 in the ore remains in solution during leaching.IntroductionConcern over the acid drainage and radionuclide dissolution problems associated with uranium tailings disposal sites in Canada has prompted investigation into methods for improving current uranium processing practice.Present commercial practice usually involves leaching of the uranium ore with sulphuric acid, ion-exchange separation of the uranyl sulphate complex from the leach liquor and"" precipitation of the uranium as yellowcake. Daughter products of U-238, such as Th-230, Pb-21O and Ra-226 remain with the tailings and undergo long-term dissolution.Table I summarizes the probable behaviour of the radionuclides during milling. The concern here is with Ra-226, because it will deposit in the bones if ingested and is ""thus considered a serious health hazard(1), Similarly, Po-218 and Bi-214, which are daughter products of Rn-222, can be retained in the lungs and are considered to be the principal sources of radiation dosage(2) arising from the inhalation of Rn-222. Previous investigations(3-9l indicate or imply that Ra-226 undergoes redistribution during milling. However, detailed published information on the behaviour of Ra-226 in the uranium milling process appears to be lacking. A knowledge of the behaviour of Ra-226 in uranium mills, particularly during leaching, could lead to improved methods for its control.This paper reports the occurrence of Ra-226 in the Rio Algom mill. The main objectives of the study were to determine (1) the distribution of Ra-226 within the solids, (2) at what point, and how rapidly, redistribution occurs and (3) whether there are high concentrations of Ra-226 in solution."

Jan 1, 1981

By J. W. Smith, J. Van Dusen, A. Papachristodoulou

"As part of a study to evaluate factors affecting tankroom air quality, the mechanism of aerosol generation from bursting bubbles in electrowinning operations has been investigated. Typically 2 to 3 mg/m2.s are produced in zinc tankrooms. Analysis shows that the rate of production of film drops (geometric mean diameter - 2 urn] increases with decreasing bubble size, and that jet droplets (geometric mean diameter - 20 um) are not produced with gas bubble larger than - 4 mm. Both mechanisms of drop formation and current efficiency are affected by surface active agents, with an over-all reduction in emission of up to 60% to 70% being achievable. A source control system which does not adversely affect electrolyte properties is always preferred, and coalescence of all gas bubbles in to a continuous stream of gas at a single point on the electrolyte surface would eliminate aerosol emissions. This objective was the basis for design of a coalescence device which, in laboratory tests, reduced the emission rate by over 95%.The control device fit s over the electrodes in the electrowinning cell and is partially immersed in the electrolyte. A number of changes in the design which resulted in significant improvement in the performance of the device are reported.Field tests have shown that only about 75% of the aerosol below 10 um can be eliminated by coalescence. The remainder (up to 95% of the total) is controlled by coalescence of droplets, by impaction on the exposed collector surface and gravitational settling.The device does not interfere with operation of the tankroom, handles the effect of surges in power during harvesting, and is simple and inexpensive to maintain. IntroductionDuring the electrowinning of metals (such as zinc and copper) gases are evolved along the electrode surface forming small bubbles. The bubbles travel upwards and burst on the electrolyte free surface generating, in this way, small droplets. Because the electrolyte is often highly acidic or contains toxic materials, the whole process can result in the formation of an aerosol in the atmosphere above the electrowinning cells which poses a serious health hazard to workers in the area, and corrodes equipment."

Jan 1, 1988

By Alexander Smith

"The three principal known mineral deposits of the Taku River area lie in the Tulsequah synclinorium. The axis of this north-south trending structure is along Tulsequah River valley; about 6 miles east of the eastern contact of the Coast Range batholith.The one proven mine of the area, the Polaris-Taku, is on the west side of the valley. It is a gold property, the gold occurring in fine needles of arsenopyrite disseminated in carbonatized volcanics. The mine was originally called the Whitewater, and the adjacent area the Whitewater gold belt. During the years 1937 to 1942 gold having a value of $3,284,000 was produced from 313,500 tons of ore milled."

Jan 1, 1954

By F. Urekar, R. B. Pankhurst

"Air spaces and air gaps in an explosives column are known to allow greater distribution and cushioning of explosive energy from the rock mass. This energy distribution is enhanced if the explosives ' gases can be confined in the borehole for as long as possible by plugging and stemming above the air space.Power Plug is an inflatable plug which can seal a borehole at any point to separate the stemming from an air gap and explosive toe load.IntroductionThis paper will discussion-going work by C-I -L Inc. and operators of two open pit mines to study the results of using Power Plugs:I. Pit wall stability - the authors have found the Power Plug effective for wall control blasting in open pit mines.2. Selective mining of coal seams - the authors work shows the Power Plug allows mining selective coal seams by predrilling underseam waste wedges.Pit Wall StabilityWall stability in an open pit mine is essential for safety. Good wall stability can be achieved with wall control blasting techniques which cushion the effect s of the explosives charge by decoupling the charges from the borehole wall. The usual method of decoupling a charge in a large-diameter rotary borehole is to load the explosives in tubes (Fig .I) . We now believe the air deck system is effective in sea ling a borehole above the explosive charge to create an air deck within the borehole which will cushion the blast.In a linear decoupled charge, an air annulus surrounds the explosives charge and cushions the effects of detonation genera ted gases on the pit wall. In an air deck, i.e. with the hole plugged at the collar, the gases genera ted by an explosive toe load are sealed in the empty borehole column. After a period of time, these trapped gases produce radial cracking between holes along the entire length of the borehole.It is common practice to employ de coupled explosive charge columns in the borehole to limit blast damage to surrounding rock. The exact mechanism of energy transfer in such blasts, however, is not well understood. Interruption of the continuous explosive column in a borehole by means of stemming, or air decks, may also be viewed as another form of decoupled blast. Decoupling of the explosive charge from the borehole wall affects both explosive energy release and explosion pressure developed in the borehole."

Jan 1, 1988

By Robert B. Parsons

"While it might seem like heresy to suggest that ""taxation"" can be a source of financing, never the less some generous tax rules can considerably enhance the tax savings pertaining to a particular expenditure or project. A basic tax knowledge, and careful tax planning, can optimize government participation in a project. INTRODUCTIONIn trying to identify sources of financing for a project, ""government"" as a source of funding is normally thought of in terms of government grants, loan guarantees, interest rate buy downs, property tax waivers, hydro subsidies, and so on. Generally, such concessions are somewhat difficult to obtain, especially in the current period of apparent fiscal restraint. One source of government funding which should not be overlooked is the income tax regime, and, at the provincial level, the various provincial mining tax regimes.While the taxpayer would not normally view a tax system as a potential source of government financing, nevertheless various federal and provincial rules applicable to the mining industry can offer attractive tax deductions - and tax savings - with respect to particular expenditures. In fact, it is not unusual for a civil servant to refer to a tax deduction as a tax ""subsidy"". For example, in the right circumstances, the cost of a smelter expansion in New Brunswick would cost the operator only 31 cents on the dollar, with the federal and provincial governments paying for the other 69 cents by foregoing tax revenues (Table I). In a sense, such tax savings could be compared to a government grant equal to 69% of project costs. Of course, not every project expenditure will generate that degree of government funding. The fact of the matter is that the percentages of tax savings attached to different expenditures cover a wide range, depending on a complex mix of factors. The point to understand is that the tax rules can offer some valuable savings, even after tax reform, and that a basic knowledge of the tax rules can yield some fruitful rewards."

Jan 1, 1989

By Richard C. Corson

"Modern microprocessor systems make it possible to use several variables to anticipate changes in the process and to react with responses before upsets can be magnified by the process or by control action.Through tighter control, ""insurance"" can be eliminated from process set points without affecting product quality. In actual operation with a traveling grate furnace this control philosophy has produced savings of up to 20% in fuel consumption and 8% in fan power usage while producing a more consistent quality product.IntroductionA straight grate indurator, or pelletizing machine, consists of a continuo us moving train of pallets on which a feed stream of unfired, ""green"" pellets is deposited on a hearth layer o f fired pellets. This bed moves through several zones in the furnace where it is dried, preheated, fired and cooled by streams of gases which are pulled or blown through the bed by a series o f large process fan s. Control systems for straight grate plants are designed to maintain gas flow through the machine to ensure that sufficient time and heat are available to raise the temperature of the entire green bed to 1300°C where hematite bonding take s place.For the pas t two year s a new approach to control systems using microprocessor-based instrumentation has been designed and tested in an existing plant with a straight grate indurating furnace processing magnetite ore. The purpose of the test was to determine the most efficient operating setpoints for all levels of production above fifty per cent of design capacity. Through a combination of feed forward control, variable setpoints and additional loops, significant savings have been realized. Thus far the project has taught us much about control systems design and operation, energy utilization, and the process itself."

Jan 1, 1983

By J. G. Schofield, R. C. Francki, K. M. Donaldson, F. E. Ham

"Developments in pyrometallurgical technology have led to larger furnaces operating under more intense process conditions. In order to maintain the reliability of these furnaces, which are frequently single-line units, the design of the refractories, cooling systems and bindings has become more critical. Traditional thermal and chemical requirements for the refractory to resist slag attack must still be carefully determined. The larger, modem furnaces have placed a new emphasis on the structural properties of the refractories as well as their thermal properties to suit the extensive cooling systems. Based on operating experience, supported by computer models, the refractories and bindings are designed to work together to accommodate the thermal expansions and contractions in order to minimize permanent furnace growth and the risks of leaks. IntroductionElectric furnaces are used extensively in smelting copper and nickel ores and concentrates. Laterite nickel ores and high-magnesia copper, nickel and platinum sulphide concentrates are smelted virtually exclusively in electric furnaces to accommodate the high melting point of the slags produced. Although a number of smelting processes using oxygen-enriched and/or preheated air have been developed to replace reverberatory furnace smelting of conventional copper and copper-nickel concentrates, (lnco, Noranda, Outokumpu, Mitsubishi) electric matte furnaces remain a strong process alternative for these concentrates, either as the primary smelting vessel or for cleaning the slags produced from these processes.The development of large, high-powered furnaces has been an important factor in the growth of electric smelting technology, as evidenced by the list of operating matte and ferronickel furnaces shown in Table I. Because the compressive forces required to maintain a tight, leak-free furnace increase with furnace dimensions, the selection and design of the furnace refractories, cooling systems and bindings require increased attention."

Jan 1, 1993

By P. J. Urso

"This paper discusses the mining problems encountered at the Fording River coal mine to date, and how they have been solved. All of the production now comes from surface mining, but underground hydraulic mining is planned and briefly described. Other facets of the operation, including markets, equipment and personnel, are covered. IntroductionFording Coal Limited was formed in 1968 to mine and market metallurgical coal resources held by the company in the East Kootenay region of southeastern British Columbia. The company, at its Fording River operations, holds approximately 48,000 acres of coal lands, having an estimated 2.0 to 3.0 billion long tons of metallurgical coal in place. (Although not a point for further discuss ion in this paper, the company also holds approximately 1.0 million acres of mineral rights. These consist primarily of coal in Alberta, potash and coal in Saskatchewan, and minor industrial mineral holdings of limestone, salt and bentonite in the three western provinces.)Fording Coal is owned 60% by Canadian Pacific Investments Ltd. and 40% by Cominco Ltd. Inasmuch as Cominco itself is owned approximately 54% by CPI, it is seen that the effective CPI ownership of Fording is about 82%. The company, originally staffed and managed by Cominco, has been independent since January, 1978, with its own board of directors, management, staff and employees.The company's head office is in Calgary, Alberta. The Fording River operations are located approximately 45 miles north of the Crowsnest Pass, near the Alberta/British Columbia boundary, only 95 air miles and 200 road miles from Calgary.A contract was signed in 1969 with the Japanese steel mills to provide 45 million long tons of metallurgical coal over IS years, commencing in 1972 at an annual rate of 3 million long tons per year. Despite some start- up difficulties, the mine and plant facilities achieved their rated capacities in 1975, producing and shipping at the 3-million-Iong-ton level. The coal specifications are shown in Table I."

Jan 1, 1980

By T. V. Lord

Minerals containing uranium have been successfully pre-concentrated by flotation at Queen's University, Kingston. In particular, uraninite, uranothorite, euxenite, and fergusonite, have responded to flotation to yield grades of 0.2 to 6.0 .per cent U .o. with recoveries of 85 to 98 per cent, from heads analysing approximately 0.10 per cent U3Os. Of the ten or so radioactive samples examined to date, two distinct groups were recognizable, firstly, those samples in which uranium was the sole constituent of economic interest, and, secondly, those in which Columbium (with minor amount of tantalum) was present in addition to uranium. For the purpose of this paper, the results of investigation on two samples of each of the above groups have been selected as typical.

Jan 1, 1945

By K. Sakai, M. Miyaue, T. Aoki, T. Tani, S. Tanaka, N. Kudo

In the planning stage of a tunnel, due to limited technology in the geological survey and the financial restriction, tunnel supports are often designed from unsatisfactory information, and the tunnel construction is started. Therefore, "Information-oriented construction" is carried out in the construction stage, in which the design is rationally verified and modified by observations/measurements. Moreover, the ground conditions ahead of a tunnel face must be predicted for efficient and safe tunnel construction. The authors have examined effective prediction methods to the ground conditions ahead of a tunnel face under construction of mountain tunnels (Aoki et al., 2010) in view of the established method (Schubert et al., 1995). Though the prediction method of Schubert requires the displacement in the direction of tunnel axis, it is difficult to obtain its accurate data by the electronic distance meter. Then, we have proposed a method that uses tilt sensors installed at the tunnel crown near the face to obtain the slight tilting information. To measure inclination of the tunnel crown, this inclinometer was originally developed as a daily control measurement, such that the geological condition and its possible change behind the face could be detected early, and a steady advance and construction safety could be ensured. This paper describes the method of forward prediction mechanism and advantages of this suggested method. It then presents the typical results of a field verification test at a tunnel under construction and an example of evaluation of the ground conditions ahead of the face based on the 3D numerical analysis in three types of condition changes of ground deformation moduli.

Jan 1, 2015

By R. R. Stone

"This paper will examine the role of debt and equity in project financing and will illustrate the impact on the return to the project sponsor of each type. Conventional debt sources will be examined, as will product purchaser advances, foreign export-import bank loans and lease financing. The paper will review guarantees, charges against the project, dividend restrictions and other commitments. It will also discuss various features of sales contracts and the degree to which they can assist in securing financing. IntroductionThe cost of bringing new mining projects on stream is escalating significantly more rapidly than general rates of inflation. Reasons for this include the higher costs of safeguarding the environment and ensuring the health and safety of workers. The need to develop properties in more remote areas is also a significant factor. These higher costs have not been matched by increases in metal prices, making the task of financing these projects ever more difficult. At the same time, the imagination of borrowers and lenders seems boundless, and innovative schemes for financing projects are constantly being unveiled.It is probably safe to say that no two projects have ever been financed in precisely the same way and the number of financing options for any project is limited only by the imagination of the sponsors themselves. The objectives of the project sponsor represent the most important factor in determining the scope of possible financial arrangements. For example, the sponsor may wish to maximize over-all company leverage by isolating each of its projects in separate companies. In so doing, it hopes to facilitate more ventures than would otherwise be the case. These objectives point toward true project financing. Additional objectives may be to develop a number of its properties by joint venture and to reduce the amount of debt on the sponsor's balance sheet. Those sponsors whose objectives include minimizing over-all financing costs will wish to increase the number of financial options and, as a result, will not be so concerned with effecting true project financing. This approach may also provide ""greater certainty that tax benefits are utilized quickly."

Jan 1, 1980

By Z. Gostynski

The paper is a historical cross-section through a 28-year period of operation of the direct-to-blister Flash Smelting Furnace in the KGHM Glogów Copper Plant. It presents the origin of the furnace as well as the path of numerous changes and modifications both in technology and process introduced in the furnace in response to the production and cost-reduction challenges. The authors provide justification of the statement that continuous improvement of the "Polish" Flash Smelting Furnace has ranked it among the most modem smelting units in the world.

Jan 1, 2007

By Jacques H. Nantel, James F. Archibald

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

Jan 1, 1986

By C. J. Rockingham

"A comparative study of sulphide textures has been carried out on samples from four Archean copper-zinc massive base metal sulphide deposits: Kidd Creek, Ontario; Lake Dufault -Norbec, Quebec; Hood River-41, N. W. T.; and Geco, Ontario. These deposits have undergone metamorphic recrystallization under a range of conditions, and results of this study indicate that certain sulphide textures may be used as qualitative indicators of metamorphic grade, whereas other cannot.The sulphide textures of most value in this regard are sulphide grain sizes, which increase with increasing metamorphic grade, and the presence or absence of sedimentary/diagenetic textures, which are destroyed at the lower amphibolite facies of metamorphism. Chalcopyrite and pyrrhotite intergrowths in sphalerite increase in size, in degree of coalescence and in the ratio of unmixed pyrrhotite to chalcopyrite inclusions with increasing metamorphic rank. With increased metamorphic grade, the pyrrhotite intergrowths change from rounded inclusions on grain boundaries to rod-like shapes along sphalerite twin planes. There is also a general increase in the relative proportion of pyrrhotite in the deposits. Textures that appear to have little value as indicators of metamorphic grade are sulphide deformation textures, and triple junction point angles and their standard deviations, which show little variation from the lower greenschist to the upper amphibolite facies of metamorphism. The presence or absence of myrmekite-like magnetite also has little value in determining the relative metamorphic history of these deposits, as it is a product of local contact metamorphism."

Jan 1, 1980

By J. Lebl, S. Bharti, D. J. Cornett

"This paper presents the design and application of blasthole mining to an area at Strathcona Mine previously employing post pillar cut-and-fill. Extensive mining in the area had led to gradually deteriorating ground conditions and post pillar stoping was no longer considered acceptable. Alternative methods had to be investigated.Conventional methods for mining in poor ground were rejected because of the high cost. Blasthole mining was selected because iI offered good productivity and safety with acceptable costs. The design of this approach involved field investigations and the use of numerical modelling to simulate the different blasthole options and their impact on ground stability. The blasthole design incorporated reinforcement with cablebolts, use of a radio-controlled remote LHD unit, large-diameter holes, blast design and wall control. Potentially unstable areas were outlined during mining with ground monitoring instruments and the results used to modify mining plans during the production phase.IntroductionIn underground metal mines there is a need to improve safety and productivity and lower mining costs in order to maintain reasonable rates of return on investment. This requires the application of good engineering design to both mine planning and ground control in order to optimize production and costs and to forecast potential problems during mining. The task becomes more important when extensive mining leads to gradually deteriorating ground conditions, making existing mining methods and techniques no longer acceptable from a safety point of view. Alternative mining methods must, however, be sufficiently productive to ensure profitability. This paper presents an example of the engineering design and operating approach used by Falconbridge in dealing with such a situation at Strathcona Mine."

Jan 1, 1983

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

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

Jan 1, 1986

By Andrew L. Mular, Robert P. Edwards

"The operation of flotation circuits is often regarded as a combination of art and science. Expert systems offer a method by which the art may be captured and supervisory control of flotation circuits fully realized. Operating knowledge, the art, can be consistently employed to enhance regulatory control through the judicious application of an expert system. Using an expert system, a supervisory control routine was developed, and success- fully implemented, in the copper flotation circuit at Brenda Mines Ltd.The expert system ran in conjunction with regulatory PI controllers on a personal computer. The expert system received assays via an on-stream analyzer and adjusted regulatory loop set points as required in real-time. From its commissioning in November, 1989, to the end of the mine 's operation in June, 1990, it was enthusiastically embraced by the operators and attained operating levels superior to those achievable manually.IntroductionExpert system (ES) software springs from research into artificial intelligence and is currently making significant inroads into business and industry. ES proponents make many attractive claims; they are a means of capturing the knowledge of experts and they can be programmed by non-programmers. To date, most uses of this software in the process industry are in off-line applications, meaning that the applications are not tied directly to operating (on-line) environments. Moreover, in on-line environments, they are typically employed as advisors and only suggest changes. Human operators are required to close-the-loop to the process. Yet, an ES should be applicable to operating environments and, if the claims of the proponents are valid, should also be better than existing tools. As an intelligent controller an ES must use the knowledge of experienced operators, apply it directly to a process and do this without the intervention of human operators. On-line applications have been successfully employed in the closed loop control of SAG circuits (Herbst et al., 1989) and flotation circuits (Hales, 1989). Harris and Kosick (1988)detail an implementation for flotation control at the Polaris Mine."

Jan 1, 1992