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By Rubén Alvarado

The markets and environmental protection rules are more and more exacting, both of which have determined that copper smelters should look for technological development and global management to ensure their viability and competitivity in the short and long term. The main facilities of the present and future Smelting-Converting Process at Codelco's Caletones Smelter, is based on Teniente Converter reactors with a high operational availability that have reached concentrate processing capacities near 2,000 tpd. These reactors are in operation in most of the smelters in Chile as well as in Zambia, Peru, Mexico and, in ?the near future, in Thailand. Since 1993, the Smelting-Converting process of the Caletones Smelter of Codelco-Chile has been based on one Reverberatory furnace, two Teniente Converters and four Peirce-Smith Converters. These facilities, together with the operation of two Fluidized Bed Dryers, three Slag Cleaning Furnaces, and two Oxygen Plants have allowed the smelter to reach concentrate smelting capacities and copper productions of 1,215 kt/year and 360 kt/year, respectively. This transitional operating scheme, combining together traditional and advanced technological equipment, needs further modernization to successfully face the modern world challenges, especially with relation to the environmental commitment, production costs and wide satisfaction of customers. For this reason, for the period 1997-2000, a Modernization Plan has been worked out. This plan considers an increase of the present throughput, which will permit a significant increase in productivity, as well as finding a definitive solution for meeting the environmental regulations. Among these projects, we can point out the definitive shut down of the Reverberatory Furnace, which is a contaminating piece of equipment of low energetic efficiency. Additionally, it considers the installation of two new Slag Cleaning Furnaces, one additional Oxygen Plant, and the incorporation of two new Sulphuric Acid Plants with a production capacity of 4,500 T/D, that will recover over 92% of the sulphur content, of process off-gases.

Jan 1, 1998

By K Kuganathan

This paper describes a new methodology that can be applied to compare several bench extraction strategies requiring backfill. The method is applicable at the planning or operational stages and can be used to maintain dilution within design parameters and improve the overall economics of bench stoping operations. The parameters influencing bench performance have been empirically rated based on economical, geomechanical, operational and backfill properties. Four different extraction strategies have been considered and rated from most preferred to less preferred using an integrated approach to bench extraction.

Jan 1, 1998

By Cocker J, Urosevic M

Seismic methods have become common for the detection of low-throw faults ahead of underground coal mining. Surface seismic methods cannot theoretically be used where dykes occur, because seismic waves transmit from the surface down to the seams, and reflect back to the surface. Consequently, where sub-vertical structure such as dykes occurs, the surface seismic method fails.The ability of seismic methods to image dykes depends on the geometry used, the dyke thickness and the seismic wave propagation mode in relation to dyke composition and internal structure. Surface seismic methods find it difficult to distinguish between faults/fractures and very thin dykes (1-2m in thickness) when the dyke's thickness is less than the seismic wavelength. Consequently, borehole seismic methods have to be used to detect the presence of such thin dykes.

Jan 1, 1998

By G. Schubert, H. Hoberg

A large number of diverse size reduction machines is currently available for the comminution of waste materials. Equipment selection is determined by the nature of the material to be treated and by its behavior under external mechanical stressing. Accordingly, wastes can be divided into those with elastictbrittle and those with ductile/viscous behavior. The scientific understanding of the comminution of wastes is lagging strongly as compared to that of the grain-shaped mineral raw materials. Only in a few unique cases have the fundamentals of the comminution of ductile or viscous materials been presented. The paper centers on a characterization and systematic analysis of the types of stress fundamental to comminution. On the basis of this discussion an overview is presented of the currently available technologies for the comminution of wastes, with attention centering on those machines designed for materials with ductile or viscous behavior.

Jan 1, 1998

By Richard H. De Voto

The McDonald Gold Project and two satellite gold deposits near Lincoln, Montana, contain at least 9.9 million ounces of gold and 30 million ounces of silver. The McDonald gold deposit alone contains 7.2 million ounces of gold reserves that can be open-pit mined and processed by cyanide heap leaching at a projected cash operating cost of $190 per ounce. The deposit is predominantly oxidized with no chance of acid production, and can be mined, operated, and reclaimed with minimal permanent environmental disturbance other than the creation of an open pit filled with a fresh-water lake which would support trout. The Seven-Up Pete Joint Venture, the owner of the McDonald Gold Project, commenced permitting of an open-pit, heap-leach operation in November 1994. In 1998, Montana citizens passed an anti-cyanide, open-pit mining initiative, 1-137, which banned any new open-pit gold mine which uses cyanide processing, The Venture has conducted extensive studies, including metallurgical testing of the treatability of McDonald ores with alternative lixiviants, and has determined that all other mining and metallurgical treatment systems are vastly uneconomical in the recovery of gold and silver from the McDonald deposit. Therefore, the Venture's proposed open-pit mining and cyanide heap-leach processing is the only technology that can be applied economically to the McDonald deposit. Further, the analyses convincingly demonstrate that the proposed open-pit, cyanide heap leaching technology results in maximum resource conservation of this valuable and unique deposit and poses far less risk to human health and the environment than any of the alternative technologies.

Jan 1, 1998

By Keith Heasley

As part of the initial investigation and validation of a new boundary-clement formulation for stress modeling in coal mines. the underground stresses and displacements at two multiple-seam coal mines with unique stress problems are modeled and predicted. The new program, LAMODEL, calculates stresses and displacements at the seam level and at requested locations in the overburden or at the surface. Both linear elastic and non-linear seam materials can he used: and surface effects, multiple seams, and multiple mining steps can be simulated. In order to most efficiently use LAMODEL for accurate stress prediction, the program is first calibrated to the site-specific geo-mechanics based on previously observed stress conditions at the mine. For this calibration process. a previously mined area is "stress mapped" by quantifying the observed pillar and strata behavior using a numerical rating system. Then, the site-specific mechanical properties in the model are adjusted to provide the best correlation between the predicted stresses and the observed underground stress rating. Once calibrated, the model is then used to predict future stress problems abead of mining. At the two case study mines, the calibrated models showed good correlation with the observed stresses, and also accurately predicted upcoming high stress areas for preventive action by the mines.

Jan 1, 1998

By C Woodall, G Jardine

The Henty Gold Mine, located in Western Tasmania uses innovative solutions to effectively manage a mining operation in an environmentally sensitive setting and has been presented with several environmental awards. Fill is required as part of the mining method to provide passive ground support, minimise rock exposure and ensure maximum recovery of the small but high-grade orebody. The use of the whole portion of leach residue in the backfill reduces the surface tailing disposal requirements. Therefore, High Density Paste Fill (HDPF) has been selected as the most appropriate fill method to meet these objectives. Additional benefits include the minimisation of excess water from fill and the subsequent need for the collection and treatment of water and slimes. There are minimal equipment requirements during placement, thereby optimising mine resources for production. This paper covers the development of a suitable paste fill system to meet the specific needs of the Henty Gold Mine and the successful commissioning of this system for the first time in Australia.

Jan 1, 1998

By G. G. O. O. Uwadiale, M. A. U. Nwoke

The flotation of Azara barite tailings was investigated using crude rubber nut oil (RNOc), refined rubber nut oil (RNOR) and oleic acid as fatty acid collectors. Chemical characterization of the rubber nut oils indicated high acidity, high saponification values and high iodine indexes, which are indicative of a high fatty acid compositions. The Azara barite tailings analyzed 64.6% BaSO4 by atomic absorption spectrophotometry. Gravity and magnetic separation techniques yielded a BaSO4 concentrate with a grade of 74.8% and a recovery of 92.5%. Barium sulfate grades of 90.0%, 92.8% and 94.8% with recoveries of 80.3%, 85.4% and 86.7% were achieved with collector dosages of 750g/t crude rubber nut oils, refined rubber nut oils and oleic acid, respectively. Hence, rubber nut oils are effective fatty acid collectors for the flotation of barite tailings.

Jan 1, 1998

By Jorge Lanza

SUMMARY La Granja copper deposit, in terms of volume, is among the five largest deposits in the world and represents reserves of three thousand million tones. The field consists of a 40 m. thick layer of copper lying over the secondary ore and further down the primary copper. The flotation process has indicated a recovery rate of 88 to 90 percent and concentrates of 27 to 32 percent of copper. The acid leaching process of low grade ore produces financially acceptable results. To carry out the project, it is necessary to build long distance pipelines and a port. Both the Feasibility Study and the Environmental Impact Study on the project have been approved by the Peruvian government. INTRODUCTION La Granja is located in the district of Querecoto, province of Chota, in the department of Cajamarca, in the Northwest of the country (Figure 1). Geographically it is situated on the eastern slopes of the Andean mountains at an altitude of 2,000 to 2,700 m.a.s.1. (Figure 1). The site is an 8 hour car ride from the city of Chiclayo, capital of the department. The first 60 km. are over a paved road and the remaining distance is over a narrow hard dirt road. The copper porphyry of La Granja was discovered between 1969 to 1971 during some geochemical prospecting activities carried out by the State mining institution, Ingeomin (currently Ingemmet). From 1978 to 1982, Ingemmet continued with its geochemical and geophysical studies supported by a German technical assistance program. A total of 19 bore- holes were drilled (5,814 m.) and a 90 m. long tunnel made. This study calculated reserves of 175 million MT. In 1993, Minero Peru drew up a technical-financial study based on the above studies and proposed a 12 year extraction operating program: 20,000 MT daily using the leaching process, followed by 13 years of operation using the flotation process with the same daily volumes. In 1994, Cambior Inc. won an international auction in order to carry on further exploration work and to have a purchasing option. Since that date the company

Jan 1, 1998

By S. O. Yuan, R. L. Grayson

As a followup to a USBM-sponsored research project, the authors utilized the knowledge-base structure and system concepts from a Sun Sparcstation-based worker-scheduling system of the mine-management support system to develop a PC-based application. The new software adopts the nested-window concept to facilitate data collection and modification on personnel, including their availability and work priorities during a shift. The system can optimally allocate manpower on a work shift and can delineate supervisory training responsibilities. The various components of the software, including enhancements made to the original system, are described in detail.

Jan 1, 1998

Production of refined zinc (99.95 per cent) at the minesite without increasing greenhouse gas emissions is considered. As an example, exploitation of the full reserve of the McArthur River orebody is proposed, using the existing concentrator, whilst introducing radically innovative smelting technology. Bulk flotation of all the sulphide minerals is followed by smelting in a melt circulation reactor with tonnage oxygen. By smelting the high-energy pyritic concentrate and reacting the evolved sulphur dioxide with near-mine dolomite, a large amount of electricity can be generated. This is enough to supply all the requirements for the smelter itself, an air separation plant and a facility for compressing and liquefying carbon dioxide. Carbon dioxide is disposed of off-shore for enhanced oil recovery or by other means. The reacted dolomite fixes sulphur as an inert and environmentally acceptable solid residue. Treatment by these means leads to virtually zero gas emission smelting. The paper concludes with a vision for the future in which expansion of zinc smelting capacity is seen to be definitely needed.

Jan 1, 1998

By Yanmin Wang, Eric Forssberg

This paper presents recent experimental results in wet ultra-fine grinding and classification of industrial minerals carbonates and kaolin clays using a stirred ball mill and a high performance centrifuge. The studies have been focused on the effect of beads (size, density and load) on the grinding efficiency. The use of chemical additives for the control of slurry rheology in the stirred ball milling is presented. The role of pre-crushing with a high-pressure roller mill on subsequent ultra-fine grinding is discussed for energy saving and size reduction. The use of a disc-stack nozzle centrifuge for ultra-fine classification duties at high solids contents is presented.

Jan 1, 1998

By R M. Smart, A T. Harrison

Backfill systems using unconventional cementitious binders have been successfully used in relatively deep and hard rock tabular mines for longwall, scattered stoping and shaft pillar removals. Two unconventional cementitious systems are discussed: A ground granulated blast furnace slag (GGBS) with an activator containing lime. This has been used with a total tailings æstableÆ slurry at a relatively low dosage of less than seven per cent, by mass, based on dry solids. The room and pillar stopes supported with this fill were up to 20 m high and the tailings were relatively high in pyrite. A GGBS binder plus a silicate based activator and gelling agent that virtually eliminated all water drainage (and hence post filling shrinkage). The system used a slurry, but the addition of the activator created a final placed product that had the behaviour of a paste. The system has been successfully used for almost ten years in the following applications: stoping widths (mining heights) above 1.6 m; and shaft pillar removals in seismically active areas at the end of the life of the shafts. This paper discusses the technical merits and costs of the systems and compares them to other fill systems (including true paste systems). the acceleration (normally g, 9.81m/sec2) is increased to a significantly larger (but generally unmeasured and unknown) value, as shown in Figure 1.

Jan 1, 1998

By K B. Quast

Changes in feed size distribution can have significant effects in rod mill grinding. The product sizing resulting from wet batch milling of a tin ore showed little influence on fines production after truncating the feed at either the coarse or fine end. The addition of fine material caused a less amount of fines to be produced and a possible increase in grinding at coarse sizes, although this is complicated by the changing feed size distribution. The changes in feed size distribution caused no tendency for preferential grinding of the cassiterite.

Jan 1, 1998

By Martin Brueggemann

In 1993, the El Paso Smelter began operation of the first commercial CONTOP copper smelting furnace. The CONTOP process was chosen for the plant modernization due to its low capital cost and the ease that it could be incorporated into a 100 year old existing smelter. After four years of operation, CONTOP has proved itself to be a reliable copper smelting technology. This paper will discuss a brief start-up history, current operation, and future modifications and improvements.

Jan 1, 1998

Western Deep Levels, a seismically active deep level gold mine, started placing backfill in their narrow tabular workings as part of the regional support strategy in 1986. Over the years the percentage of working places being backfilled has been gradually increasing. At the end of 1995 the support efficiency and the labour productiveness relating to support installation were scrutinised to determine if resources were being optimised. Owing to financial, safety and productivity constraints it was decided to redesign stope support to be less labour intensive, safer and provide an integrated stope support system. This new integrated system will thus combine the previously used temporary, permanent and back area support consisting of mechanical props, hydraulic props and backfill respectively. Backfill previously formed an integral part of the regional support in conjunction with strike stabilising pillars. To design the integrated support system the backfill placement quality has to be exceptionally good and placement must be done as close as possible to the working face. The backfill to face distance was reduced by 30 per cent and in some areas by more than 50 per cent with an increase of square metres filled to increase the effect of the backfill even more. This paper addresses the design and successful implementation of an integrated stope support system based on the optimisation of backfill to the extent where installation of mechanical and hydraulic jacks could be eliminated.

Jan 1, 1998

By Paykan Safe

This paper reviews various process off-gas cooling options available for sulfide smelting processes. Advantages and disadvantages of each, system are discussed along with the selection criteria for a reliable and cost effective :system. Various systems are presented to demonstrate typical process parameters for smelter off-gas handling systems and to outline operating difficulties associated with each system:

Jan 1, 1998

By E. Topuz, M. J. McPherson, I. M. Konduri

Theoretical investigations and laboratory experiments demonstrated that there is a great potential for the use of jet fan ventilation in mines. This paper summarizes research that consisted of laboratory-scale model tests, full-scale mine model tests and underground coal mine entry tests. The laboratory model used water as a fluid medium and simulated a typical 25-m- (82-ft-) long heading having a 1.5 x 6-m (4.9 x 19.7 ft) cross section. The effects of various nozzle positions and designs were investigated by using still photography. It was also found that the use of jets in combination with line curtains enhanced the overall ventilating effect in the model entry. Flow measurements in the full-scale mine model and in the coal mine entry were conducted to evaluate the effectiveness of the jet fan. It was concluded that the designed jet fan ventilation system was an effective means of ventilating blind airways.

Jan 1, 1998

By E. Oshima

In May 1991, a New Mitsubishi Continuous Copper Smelter Line started operation at Naoshima. Recently, it has been continuing steady operation and one and a half year campaign life has been achieved. In 1996, new records of on line time, the amount of copper concentrate treated and copper anode production were achieved. 1t proves the superiority of the process with respect to pollution control, energy efficiency, flexibility and easiness of the operation and over all economy including off gas handling cost. Furthermore, .plans are underway to prolong the campaign life for two years and to improve the process efficiency. This paper describes recent operation, improvements, and a future capability study.

Jan 1, 1998

By Tuula Mäkinen

One of the latest applications of the Outokumpu Flash Smelting Technology is the direct smelting ,of nickel concentrates to metallised low-iron nickel mattes. Compared to the conventional nickel smelting, the new DON process needs a lower number of smelting vessels resulting in considerable economic and environmental benefits. Fundamentals of smelting nickel concentrates in one stage to low-iron mattes are presented. Properties of nickel. smelting slags with an emphasis of the slag fluidity at high MgO-levels are also discussed. Conditions prevailing in DON mattes at high oxidation degrees are presented as well as their influence on the behaviour of such mattes in the settler and on tapping the furnace. Distributions of elements in the direct smelting are presented and compared with the conventional process. A further comparison is made with pilot-plant data and the industrial scale.

Jan 1, 1998