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By B. I. Hop

The f10wfield set up by the standard Hydro gas purging unit has been predicted by a numerical model. In addition turbulent trajectories of gas bubbles released from the rotor are predicted. Here the deposition rate of inclusions on the bubble surface is allowed to depend on local conditions. Bubbles passing regions with strong pressure gradients, such as close to the rotor, will experience large slip velocities and large deposition rates. This model can deal with any distribution of bubble sizes and inclusions. The results found from the multidimensional flow predictions are discussed in relation to what can be obtained from a much simpler metallurgical engineering approach. The differences between these two approaches to predict the same process will be discussed. The model predictions are compared to experimental results for removal of SiC-particles from aluminium.

Jan 1, 1996

By L. H. Michaud

A mining company plans to extend its surface coal-mining operations in central Pennsylvania. Although the proposed site contains pyritic material, the results of the acid-base accountings for the site shows an overall Neutralization Potential to Maximum Potential Acidity Ratio (NP:MPA) of 4.26:1 for the entire site. The pyritic material is, however, associated with the lower of the three seams to be mined. If traditional dragline-mining methods are used, this would result in the acidic material being placed at the top of the spoil piles, exposing it to air and water, and therefore to the formation of acid mine drainage (AMD). Further concerns are associated with the fact that the alkaline material is not distributed evenly over the mine site. To prevent the formation of AMD, the company has proposed to mine the area using truck-shovel mining methods. This technique offers a more flexible alternative for cut sequencing and for the selective placement of waste material. Working with the Department of Mineral Engineering at The Pennsylvania State University, amine plan was developed for this site. This plan results in the layering of the alkaline and acidic spoil to achieve an overall net alkalinity in all spoil areas. Therefore, mining this site should not result in the formation of AMD.

Jan 1, 1996

By G. A. Doyle

The quality of water in mine pit lakes depends in part on the physical limnology (Le. stratification, turnover, and development of anoxic conditions with depth) of the lake. Limnologic data collected from four existing pit lakes indicate that pit lakes develop a thermocline, or temperature stratification, in the upper 10m to 30 m of the water column. Two of the pit lakes (26 m and 55 m deep) undergo seasonal turnover of the entire water column, whereas two deeper pit lakes (110 m and 240 m) undergo seasonal turnover of only the upper portion of the water column. In the deeper lakes, seasonal mixing does not extend through the entire water column and a distinct chemocline develops with depth.

Jan 1, 1996

By Bensley C. N

In June 1995, BHP announced that it would build a Hot Briquetted Iron (HBI) plant and associated beneficiation, materials handling and infrastructure facilities at Port Hedland, Western Australia. This plant, the first direct reduction plant in Australia, will convert beneficiated iron ore fines into metallic iron for briquetting into HBI. The reduction plant will be based on the FINMET fluid bed technology jointly developed by Fior de Venezuela and Voest-Alpine Industrienlagenbau. Electric Arc Furnace steelmakers in the Asia Pacific region will be the principal customers for the product. This paper presents an overview of the facilities to be constructed by the project as well as discussing some particular technology and design engineering issues associated with the project.

Jan 1, 1996

By William J. Miles

Bentonite Corporation decided to pursue ISO-9002 Registration for our bentonite production for many reasons. We wanted to improve our current Quality System to encompass all business aspects, not just Quality Assurance. We wanted this system to build supplier/customer confidence and provide our customers with all the services that they needed for their business functions: such as Quality Assurance for their needs; appropriate shipping and delivery; appropriate billing; and appropriate sales, technical and management support of our product. These objectives of our Quality System are addressed by the ISO 9000 clauses and requirements. There were additional reasons and expectations for implementing an ISO 9000 Quality System. ISO 9000 registration would develop and aid international sales since the ISO system is a basic requirement in many parts of the world such as Europe and the Far East. It would bring acceptance of bentonite products by new customers and markets Another objective was to develop better trained employees. We hoped that the ISO Quality System would help us reduce costly non-conformances and reduce overall production and operating costs. We hoped to achieve ISO 900 registration before our major customers required it. For example, our major market is use of bentonite as a binder in foundry mold sand systems. The foundries in North America primarily service the automobile manufacturers who have individual Quality System requirements that are being merged with ISO 9000 Standards. As the foundries addressed the automobile manufacturer?s needs, Bentonite Corporation received numerous inquiries and surveys of our Quality System and its conformance with ISO 9000 Standards. Eventually, ISO 9000 Registration will become a requirement to directly or indirectly service this market.

Jan 1, 1996

By C. Ramasamy

The tariff reductions on imports, as a part of on-going liberalisation process in India, has fueled competition within and outside India and has, in turn provided an opportunity to reach global markets. This change calls for quality upgrades and cost-competitiveness without impairing the environment. In this context, gas based processes, contributing to improvement in quality and environment as well as processes where controls are applied when gases inimical to environment are involved, are discussed in a remelt/cast-house scenario. The impact of such processes on fabrication cost of sheet ingot is seen alongwith consumption and cost of materials and compared with a world class standard plant in North America.

Jan 1, 1996

By N. A. Warner

Fundamental studies on the reaction of limestone or dolomite at high temperature with S02 are extended to the realm of large scale primary copper smelting. Whereas flue gas desulfurisation in the electric power utility industry is concerned with S02 concentrations normally less than 0.5 percent, high temperature smelting gases can have S02 levels approaching 100 percent. The reaction involved is very exothermic so proposals are made in this paper for returning the heat generated in sulfur fixation directly back to the copper smelting process. This integration leads to metal production with lower energy requirements than current technology. The anhydrite reaction product can either be disposed of locally with minimum adverse environmental impact or upgraded to a value-added product. It is assumed, of course, that no viable market exists to support sulfuric acid production.

Jan 1, 1996

By Jan Yaozhong

The composition and the possible utilization of Ti bearing blast furnace from a titanomagnetite blast furnace smelter were studied. The slag contained about 20% Ti02 and trace Sc. The mineralogical analysis indicated that Ti in the slag is mainly as perovskite. By means of magnetite separation, the Ti containing phase could not be enriched. An effective hydrometallurgical approach was proposed with sulphuric acid leaching. The method proposed for processing the studied slag renders product Ti02 and SC203. Besides the recovery ofTiO2 and SC2O3' the leaching process yields fine grained residues which can used as additives for making cement.

Jan 1, 1996

By Evangelos Spyridonos, Thomas Frommer, Wolfdietrich Skala, René Prissang

Operational grade modelling is a technique that uses production data to run daily updates of property models. It will enable mining engineers to use property predictions based on the most recently acquired data as support for quality control and decision making. The approach necessitates that the properties of the run- of-mine material can always be attributed to individual mining blocks or charges. The software employed must be highly reliable, because a system failure or the loss of data could seriously affect the mine's quality management. An operational grade modelling system has been developed for the Breitenau magnesite mine. It makes use of the Linear Octree Based Property Modelling system which was conceived and realised at the Free University of Berlin. This paper describes the system design and gives an account of the experiences during the first six months since system start-up.

Jan 1, 1996

Rhyolitic rocks are volumetrically significant in the eastern part of the Coromandel gold province, yet deposits hosted by rhyolite (Kapowai, Broken Hills, Neavesville, Wharekirauponga and Waihi Beach) are generally low grade and subeconomic, especially compared with andesite-hosted deposits. In contrast, rhyolitic volcanic centres in Nevada host a number of economically significant epithermal gold deposits such as Round Mountain, Sleeper and Bullfrog. The Nevada deposits are associated with 27-20 Ma continental arc volcanics dominated by ignimbrites (eg Round Mountain), or younger 17-9 Ma bimodal rhyolite-basalt volcanism related to extensional basin-and-range tectonics (eg Sleeper). The Round Mountain deposit is localised on a caldera boundary fault and the mineralisation was deposited soon after eruption of the host rhyodacitic ignimbrite. In other Nevada deposits, hydrothermal systems are linked to the closing stages of flow-dome complexes and mineralisation is localised along normal faults associated with extensional basin-and-range tectonism. The style and composition of the mineralisation is similar in both the Coromandel and Nevada deposits and consists of sheeted and stockwork quartz veins, containing electrum as the main ore mineral and only minor sulphides (mainly pyrite) Likewise, the vein minerals were deposited from low salinity hydrothermal fluids in the temperature range of 200-270¦C. Both the Neavesville and Round Mountain deposits are geochemically anomalous in molybdenum. The deep oxidation of the Nevada gold deposits, dry climate and low level of competing land uses combine to make it economic to mine and process very low grade ore (0.2 - 2.0 g/t Au) by heap-leaching with cyanide solutions in most areas of Nevada. Although extensive low grade gold mineralisation is known at deposits such as Wharekirauponga and Neavesville, it is sub-economic because of shallow oxidation and land use conditions that are unfavourable for open pit mining and heap leaching.

Jan 1, 1996

By Richard S. Dennis

Acid recovery employs ion exchange (I-X) resin as separation media for inorganic acids from dissolved metallic salts by physical adsorption and without the use of chemicals. This technology has been used for years on spent etching and plating liquors to recover acid for reuse in the bath and to reduce waste acid neutralization costs. It is also used for electrolyte treatment to facilitate valuable metal recovery via acidity reduction. TETRA's ccrxr'" I-X contactor has been used successfully for acid separation from its metallic salt counterpart in a simple, continuous operating mode using strong base anion resins. Efficient separation is enhanced by acid reconcentration to nearly its original strength or as high as 14-20%. Continuous treatment also recovers heat to the tankhouse or bath and improves metal quality due to consistent acid quality. Conventional fixed bed ion exchange (I-X) systems are impractical for acid recovery because of complex control design and large resin inventories needed to process very low liquid-to-resin treatment ratios associated with strong acid concentrations.

Jan 1, 1996

By Abishev D. N, Balakirev V. F, Davydov G. I

The problem of recovery of cobalt products from poorly oxidised nickel ores (Kempirsaisk deposit) and pyrite concentrates with a low content of cobalt (Sokolovsk-Sarbaisky deposit) has not been solved to the present time in Kazakstan. The balance reserves of nickel ore of the Kempirsaisky deposit make up more than 35 million tons with a nickel content of 1.13 per cent and cobalt content of 0.05 per cent; besides there are 110 millions tons of out-balance ores (Anon, 1995). In a tailing dump of Sokolovsk-Sarbaisk Mining and Productional Association more than 320 million tons of tailings of wet magnetic separation have accumulated, which contain 7.2 per cent of sulphur, 0.022 per cent of cobalt, 0.012 per cent of nickel, 0.094 per cent of copper, 0.079 per cent of zinc, 16.45 per cent of iron, and from which a high quality pyrite concentrate car) he separated through flotation, containing 48 - 50 per cent of sulphur, 44.15 per cent of iron, 0.141 per cent of cobalt, 0.07 per cent of nickel, and 0.10 per cent of copper. The well-known technological flow charts for cobalt and nickel recovery from the tailings of sulphide-magnetite ores dressing (to give pyrite concentrate) and from oxidised nickel ores, are not profitable at the existing prices for metals, but are not worthless and require significant capital investments for the realisation of their value. The flow chart `sulphate roasting - leaching - solution processing' is used widely for combined processing of cobalt-containing pyrite ores and concentrates.

Jan 1, 1996

By Jr. Matthews

The Candelaria copper-gold deposit is located in Region m of Chile, 805 kilometers north of the capital, Santiago. Candelaria was discovered in 1987, following a six month exploration program. In late 1986, induced polarization (IP) surveys outlined an anomalously high response within the area of interest. The first test hole bad three intersections totaling 49 meters, with an average grade of 1.97% copper. Drilling eventually outlined approximately 390 million tonnes, grading 1.09010 copper and 0.26 grams/tonne gold. Production began in early 1995 and is estimated at 120,000 tonnes copper and 80,000 ounces gold annually.

Jan 1, 1996

By Roma T. Dec

Many industrial wastes may require preliminary processing to change their particle size, density, surface properties or flowability to become more suitable for treatment and recycle. This can be achieved by pressure agglomeration using roll presses. In the following paper an overview of various roll press processing methods like briquetting, compacting, compacting-granulating or densification is presented together with basics of process and equipment design. The emphasis is focused on major factors influencing compaction process and responsible for pressure build up and final product quality. Finally, two examples of roll press application for briquetting of steel plant wastes and compaction of alumina base catalyst tailings are introduced.

Jan 1, 1996

By Richard A. McIvor

"All mine shaft conveyances in Canada and most of the United States that are supported by a single hoist rope or attachment point and used for transporting persons are required by regulation to be equipped with safety catches and mechanisms. These safety mechanisms, commonly called safety dogs, are designed to stop and hold a free falling conveyance, with a full personnel load, in the event of a hoist rope or attachment component failure. The conveyance’s safety mechanism must be tested under dynamic conditions before it is used to transport personnel. This paper will discuss free-fall testing and it’s results on conveyance free-fall tests performed in the test tower at INCO Limited, Sudbury, Ontario.Topics covered will be free-fall tests on various wood types such as B.C. fir, Karri wood and Trusjoist MacMillan Limited Parallamwood (PSL), comparison of deceleration rates versus free-fall velocity and the influence of safety dog tooth design on deceleration rates."

Jan 1, 1996

By T. K. Mukherjee, C. K. Gupta

"The importance of the processing of secondary resources such as solid industrial wastes and liquid effluents as well as byroducts for the recovery of the associated metal values hardly needs any elaboration. Such processing contributes in no small measure towards the augmentation of the availability and the supply position of resources. As an added benefit, it leads to a reduction in environmental pollution caused by the undesirable waste materials. As some typical examples of secondary resources in the Indian scenario, mention can be made of spent catalysts, metal/alloy scrap, ash, consumed batteries, flue dust, slag, sludge and slime, pickling solutions, spent acids, plating rinse solutions, spent etchants, waste water from synthetic fibre manufacture and from tanneries etc .. These wastes constitute a source of a variety of non ferrous metals. In the processing of secondary resources like these, the techniques of hydrometallurgy such as solvent extraction playa pivotal role.This paper outlines the efforts made to use solvent extraction to recover (1) base metals such as copper, zinc, nickel and cobalt from a number of secondary resources like cake, and sludge (2) refractory metals like molybdenum and vanadium from sulphidic byproducts and spent catalyst and (3) nuclear metal like uranium from phosphoric acid. In the case of base metals, process flowsheet involving the use of acidic extractants such as DEHPA and PC88A have been optimised. The problem of iron removal from the leach liquor, which influences the metal recovery process significantly, has drawn a special emphasis. In the case of refractory metals, basic extractants like Alarnine 336 has been pressed into service to produce kilogramme quantities of pure salts of molybdenum and vanadium. Finally, the paper gives a brief account of plant experience in recovering uranium from phosphoric acid, using a solvent system comosed of DEHPA and TOPO."

Jan 1, 1996

By Ray Y. Lin, Randall A. Blue

"Joining of silicon carbide with infrared using a mixture of Si-30wt.%C as the brazing material has been investigated. Joining was performed at a temperature of 1500 °C in a flowing argon atmosphere for processing times ranging from 5 to 60 seconds. The joining filler materials include thin film silicon obtained by thinning down silicon wafers to about 70 /!m and graphite powder of a 15 /!m average particle size. Joint strengths were determined with a specially designed shear-in-compression jig for testing shear strengths of brittle materials. Cross section examinations of the joined specimens with optical microscopy, scanning electron microscopy and transmission electron microscopy have shown that all joints are essentially void free with excellent wetting between the base SiC and the brazing material. Silicon carbide in the B form has been identified as the reaction product in the joining zone with a transmission electron microscope (TEM) and selected area diffiaction (SAD) analysis. At 1500 °C with a joining time of 60 seconds, the joint has consisted of primarily SiC. With such a high SiC content in the joint, the joint strength is comparable to those by other joining techniques, such as diffusion bonding, as reported in the literature. A kinetic model for the formation of SiC from liquid silicon and carbon is proposed to explain the observed joint microstructural evolution.IntroductionSilicon carbide is of great interest for high temperature structural applications because of its excellent high temperature strength, wear resistance and anticorrosive characteristics [1]. Even though the interest in SiC is high, the use of the material has been limited by the high cost and difficulties involved in forming components of complicated shapes [2]. It is these limitations that necessitate the development of effective joining techniques that are cost effective and able to provide strong joints."

Jan 1, 1996

By Brian Balmforth

Solvent extraction has been applied successfully to the recovery of a range of metals from a variety of process streams. Particular benefits are derived from the use of new highly selective extractants. These will be exemplified by case studies including the recovery of zinc from sulfate and chloride media using ZENECA's new extractants which show a very high selectivity over iron and the recovery of antimony and bismuth from copper refinery electrolytes using ZENECA's strong and selective extractant DS5834. The conclusions are drawn that solvent extraction is a cost effective technology for metal recovery and recycling, even when used to treat relatively small volume/low concentration process streams, and that it can provide the essential enabling components of a larger system for waste minimisation programmes.

Jan 1, 1996

By H. R. Thompson

The Grant Town Power Plant is a nominal 80 MW (net) Waste Coal-Fired Electric Generating Plant which is located in northern West Virginia, approximately 15 miles southwest of Morgantown. The Steam Generator consists of two (2) Pyro-Power Circulating Fluidized-Bed Boilers (CFB), each rated at 400 000 lbs/hour @ 1,350 psig. Main Steam. The Turbine Generator is a single GEC Ahlstrom unit rated at 95 MW gross and 80 MW net. The Plant began commercial generation during April, 1993. The facility is owned by American Bituminous Power Partners, L.P. (AmBit), and operated by Mission Operations and Maintenance, Inc.

Jan 1, 1996

By Keith M. Axler

This report addresses issues specific to the generation of hydrogen fluoride via reaction of calcium fluoride with sulfuric acid. This process has been established on a commercial scale and is under consideration for treatment of calcium fluoride residues from uranium processing. Magnesium fluoride slags are also available as a product of uranium processing. The technique of using sulfuric acid for the production of hydrogen fluoride from magnesium fluoride is also under consideration as a residue processing scheme. In the current study, thermodynamic modeling was used to investigate these chemical processing systems. The results presented herein reveal information relevant to the selection of processing temperatures and conditions. Details include predicted effects in system composition based on operating temperatures for both the calcium fluoride and the magnesium fluoride systems.

Jan 1, 1996