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By Brian W. Stump

"Seismic waves from explosions can be used to characterize physical processes in and around the source. The quantification of absolute levels of ground motion is important for minimizing impact on nearby people and structures. We contrast work in characterizing seismic radiation from contained nuclear explosions with ground motions from multiple explosion quarry blasts. A physical basedunderstanding of the explosion source function allows prediction and extrapolation to new environments where experimental data may not exist."

Jan 1, 1990

By R. L. Nyirenda

An investigation of the reducibility of a cassiterite concentrate with charcoal was made in the temperature range of 1123-1373 K. The course of the reaction was monitored by a combination of sample weight loss measurements, product gas analysis, and chemical analysis of the reaction product. It was found that the cassiterite could be best reduced by a combination? of high temperature, reasonably high charcoal proportions, high charge poroslty, and the addition of a small percentage of lime. Analysis of kinetic data obtained from isothermal experiments using theory from the oxidation of carbon by carbon dioxide gave an activation energy value of 255 lci/mole for the consumption of carbon by reaction with cassiterite.

Jan 1, 1990

By Jin Zuomei

The kinetics of dissolution of nickel matte in the presence of manganese dioxide with silver ions was investigated. The catalytic silver ions enchanced the leaching rate up to a factor of 17. The effects of stirring, temperature, particle size, concentrations of Mn02, silver and ferric ions, and the experimental procedures were studied. Solid residues at various levels of nickel extraction were examined by SEM, TEM, electron micoprobe and X-ray diffraction. These results indicated that the dissolution reaction was topochemical and fits a surface reaction control model. The activation energy was calculated to be 39.15 KJ/mol. The leaching rate of Ni3S2 was independent with stirring rate, but the reaction rate constant was inversely proportional to the initial particle diameter. The order of the reaction rate are 0.41, 0.69, 0.33 with respect to Ag+, Mn4+ and Fe'+ con-centration respectively. Thus a kinetic rate equation was developed. Moreover, we propose a mechanism of silver catalyzed leaching of Ni3S2'

Jan 1, 1990

The outlook for suppliers of energy to the expanding economies of the Pacific Basin region is essentially positive, but particularly for exporters of high quality steam coal. This paper argues that economic growth in the Pacific Basin region has exceeded world economic growth for some years and that this will continue to be the case for the next decade at least. It looks briefly at the link between economic growth and energy demand and at the relationship between energy demand and the demand for electricity. Changing preferences in fuel mix for electrical generation in the region are noted and tentative forecasts made about variations in this mix. The pros and cons of various forms of fuel used to generate electricity are considered from the point of view of the consumer. Having concluded that steaming coal in particular is likely to become even more important as a generator of base load electricity, the paper looks at the opportunities this presents for exporters such as Australia, and touches on some factors that could prevent development of those opportunities. This paper will concentrate on electrical energy. For the purposes of this paper, the Pacific Basin refers essentially to Australia, New Zealand and the Asian countries bordering the Western Pacific. As a supplier, Siberia is not included because, although it has great potential, it is thought that problems of climate, infrastructure and political restructuring will delay the realisation of that potential until the next century. Although it deals with the Pacific Basin region, where many countries are industrialising rapidly from a predominantly agricultural base, it looks at the experience of mature industrial DECD economies where their experiences seem relevant.

Jan 1, 1990

The kinetics of cyanide loss were found to be first order under any given set of conditions, allowing rate constants to be easily determined. At room temperature and in the absence of activated carbon, some cyanide is lost by hydrolysis to hydrogen cyanide, but this does not occur to any significant extent at pH values higher than about 10. A higher rate of hydrolysis occurs when air agitation is used. When activated carbon is present, an additional carbon-catalysed oxidation reaction is responsible for a fairly high loss of cyanide. The evidence indicates a reaction mechanism that consumes oxygen and produces cyanate ion. Some of the cyanate thus produced decomposes to form a mixture of ammonia, carbonate, and urea, depending on the solution conditions. Additional cyanide is lost as a result of the adsorption of sodium cyanide by the activated carbon. At high temperatures, an additional hydrolysis reaction, which involves the formation of ammonium formate as an intermediate, occurs an/j is responsible for. a high loss of cyanide, leading ultimately to the formation of ammonia, hydrogen, and carbon dioxide. The presence of activated carbon has no effect on the rate of this reaction.

Jan 1, 1990

By O A. Cottrill, G A. Oldfield, S B. Nowell

Host-rock û wallrock major and trace element geochemistry associated with epithermal gold mineralisation in the Hauraki Goldfield of New Zealand is poorly documented, even though rock geochemistry is a recognised tool in exploration. Such responses assist in recognition of the regional scale imprint of fossil hydrothermal activity, and indicate targets for detailed evaluation within these alteration zones.   Recent investigation of gold deposits in the Waihi (Gladstone), Golden Cross (Empire), Thames (Waiotahi) and Coromandel (Tokatea) areas indicate enrichments of Au, As and Sb in the andesitic wallrocks hosting mineralisation. Of the other elements examined, Si, K and Rb are enriched, and Na, Ca, and Sr are depleted at all deposits. These trends are best developed in the vicinity of veining. In deposits with clay alteration dominating (Waiotahi and Tokatea) there is also depletion of Mg, Mn, Zn and Cu. Ba and Cr are variably enriched or depleted within different styles of alteration. Base-metal enrichment in the wallrocks is not a feature of Hauraki deposits.

Jan 1, 1990

By Kenneth L. Rubow, Virgil A. Marple, Bruce K. Cantrell

"In a cooperative study by the University of Minnesota and the U.S. Bureau of Mines, diesel exhaust and mineral dust concentrations have been measured for aerosols generated in the laboratory and in five underground coal mines. Three mines utilized diesel-powered haulage equipment and two used all-electric equipment. Two source apportionment techniques have been applied to differentiate between the mineral dust and diesel exhaust aerosol concentrations measured. The first technique, using a micro-orifice, uniform deposit impactor (MOUDI) for size selective sampling, is based on modeling aerosol size and the premise that the diesel exhaust portion of the aerosol is predominantly submicron and the mineral dust portion is mostly greater that one micrometer in size. The second technique, Chemical Mass Balance (CMB) modeling, was used to referee the analysis of diesel exhaust and mineral dust aerosol concentrations from the size selective sampling results.The MOUDI size distribution data were modeled to obtain parameters describing the fine and course fractions of the sampled aerosol and to estimate the contributions to each mode from both mineral dust and diesel exhaust aerosol sources. The results showed the size distribution of the mixed aerosols exhibited two definite modes with the minimum between the modes occurring at 0.8 µm. Less than 5 pct of the coal mine diesel aerosol was found in the coarse size fraction. CMB analysis confirms the original premise for using aerosol size to separate diesel exhaust and mineral dust aerosol during sampling.Based on the results from the size selective sampling, a personal diesel aerosol sampler has been developed for measuring diesel aerosol mass concentrations. Th.is sampler uses an inertial impactor to size separate the respirable aerosol at 0.8 µm. All material less than 0.8 µm is collected on an after filter for subsequent gravimetric analysis."

Jan 1, 1990

And it takes more than good organisation. You may read or heard this poignant reflection: We tried hard, but it seemed that every time we were beginning to form up in teams we would be reorganised. I was to learn later in life that we tend to meet any new situation by re-organising, and a wonderful method this is for creating the illusion of progress while producing confusion, inefficiency, and demoralisation This was written by the Roman Gaius Petronius in AD65. How much have things changed in nearly 2,000 years? What then does it take besides the fundamentals and good organisation to build a successful career in a successful organisation? I'm prepared to venture a list of what I'll'call Tips for Young Professionals. If you've got what it takes, and apply these, I think that you'll gain a great deal of satisfaction from your career, even if you don't reach the distant target each of you should have in mind now. So settle back in an advice-receiving mode, and please forgive me if I come across as a master of the bleedin' obvious, as Basil once accused his wife Sybil of being in the unforgettable Fawlty Towers.

Jan 1, 1990

By M. Rieber

The potential for the wide-spread commercialization of superconductivity, the disappearance of all resistance to a direct current (D.C.) electric flow, began in 1986-87 with the development by Bednorz and Muller at IBM's Zurich Laboratory of an yttrium -barium -copper oxide conductor which attained zero resistance at 90t:. Although the status of superconductivity is still pre-bench scale, it is useful to forecast its probable effects on the copper industry. I t should not be forgotten that at their inception, the impacts of transistors, semi-conductors, thin films and fiber optics on the electric/electronics sector of this industry, were largely underestimated. Superconductors are not metals, but a class of ceramics. They represent an efficiency increase of one or more orders of magnitude. If their development is to be a boon to the copper industry, rather than a reduction of metal demand through miniaturization or material substitution, vastly expanded copper containing electrical uses must be in prospect. In this paper the projected uses of high temperature superconductivity are examined, followed by the remaining problems to be overcome. Assuming success, a time horizon for maturation is estimated. The penalties for the non-recognition of new markets and material substitution are shown on the basis of past forecasts. Finally, the application of successful superconductivity to the copper industry over the forecast period is estimated.

Jan 1, 1990

By D. G. Chedgy

Environmental improvement efforts are focusing with increasing intensity on pollutants resulting from combustion. The high cost of removing these pollutants at the power station is well documented. Physical coal cleaning has always been and should remain the most economic method of reducing sulfur oxide emission from coal combustion. It is critical in the selection of preparation plant circuitry to consider capital and operating costs, as well as the level of sulfur reduction. This paper describes the technical criteria which must be used for efficient process selection and summarizes the cleaning systems available or in development.

Jan 1, 1990

This paper presents a resume of the likely profitable mining areas in New Zealand. It covers the main 'minerals' û gold, coal, oil and gas, ironsands, silica sands, clays, lump silica, perlite, sulphur and limestone. The potential mining projects are depicted on a map of New Zealand together with the associated works involved in hydro-electric and geothermal power development requirement for industries such as aluminium, nickel ferro-silicon or silicon carbide production. The political need for mining development to relieve unemployment and reverse emigration is stressed. A case is made for exploration and development assistance by government in labour re-training, energy supply and transportation, if the tremendous losses through lack of use of human and industrial resources are to be rapidly reduced. These losses are currently estimated at $10 000 000 000 per year. The need for protection of the sanctity of contract and security of tenure of all mining operations is touched on briefly as is the need for a reasonably balanced view on conservation. However, as both of these are more properly covered in papers on the legal and environmental aspects of the mining climate, they are presented here only as they affect the economy of the mining operation. Finally, there is a brief comment on the mining climate in New Zealand relative to Australia and South Pacific mining operations.

Jan 1, 1990

Large GDP increases in the Pacific Rim countries have been accompanied by similarly large increases in demand for oil products. In the case of residual fuels, this demand has been tempered by the substitution of other energy products such as coal or gas. In the region's developing and newly industrialised nations, it has not been possible to make the very large investments in infrastructure which allow other energy sources to be used for transportation. As a result, GDP growth has been mirrored in the demand growth for automotive fuels. Other non-substitutable products such as lubricants have also benefitted by the region's GDP growth.   The combination of a number of years of sustained growth, coupled with increasing quality requirements is now stretching the upgrading capacity of the region's refineries. IT, as seems likely, the region continues to enjoy a high GDP growth rate, then this will be accompanied by increasing reliance on finished products coming out of the Middle East.   The owners of the most simple form of refinery in which crude is simply distilled and the naphtha reformed into petrol will face major capital investments. If they decide not to bear this cost, they will face increasing problems in selling their surplus residual fuel oil at an economic price. Quality will become an increasingly important issue. Not only in the well publicised areas such as unleaded petrol, but also for products such as lubricants which play a major role in the efficiency of modem equipment. Quality of service such as hours of opening, ease of access, and service station facilities will also become increasingly important as the oil companies use these to attract customers and gain brand differentiation.

Jan 1, 1990

By M. Fiset, D. Belley

"To better understand the wear process of various materials that may be used as blades on snow removal equipment, the first step is to evaluate the influence of the load applied and the moving speed on road wear rates of one type of steel and three types of polymers. While the behavior of steel conforms to Archard's law, wear rates of polymers increase to a power of ex of the load applied according to a model implying that the wear of these materials is due to fatigue. The wear rate of some of the polymers varies considerably in terms of speed, unlike the steel. The wear resistance of some of these polymers outclasses the steel tested as long as the speed is not too great. They, therefore, present interesting alternatives for snow removal on more fragile surfaces such as sidewalks and zone made of inter-block slabs.IntroductionSince the dawn of the Industrial Revolution, the massive use of machines has brought with it a number of different problems regarding wear. Snowplowing roads, parking lots and sidewalks is an activity that generates enormous expense in a country such as Canada. To better understand these wear processes and in the hope of stimulating new approaches designed to reduce the costs related to this sector of activity, this paper presents the behaviour of several materials (steel, polymer and rubber) as they wear on an asphalt-fines matrix surface lubricated with water. Also discussed is the effect of various parameters such as the load applied and speed."

Jan 1, 1990

By N. A. Abdel-Khalek

An experimental study was carried out to compare the results of laboratory column flotation versus conventional flotation for the cleaning of fine coals of different rank and their oxidized samples as well as discrete size fractions. Surface oxidation caused a significant reduction in the flotation yields achieved with both methods. However, the column flotation produced concentrates? of lower ash content. The recovery -size curve achieved with column was similar in shape to that obtained with conventional cell, with superior results in the region of fine fractions. The influence of some column operating parameters was also discussed.

Jan 1, 1990

By J. E. Garlanger

Each year, Florida mines approximately 40 million tons of phosphorite, most of which is ultimately converted to various commercial fertilizers. The phosphorite is mined from within the bottom portion of the 40-to 60-ft. thick surficial aquifer, using open pit mining techniques. The ore zone or "matrix" is generally overlain by relatively permeable fine sand to silty and slightly clayey fine sand. The ore itself is highly variable in nature but, in Central Florida, typically consists of less permeable clayey phosphatic sands and sandy clays with stringers of permeable sand. The ore is much more sandy in the north Florida mining area.

Jan 1, 1990

By Stuart F. McTavish

Mechanically suitable grinding mills became available to the mining industry in 1908. Since then, mill operators have been searching for the best material and design with which to line the mills. These liner systems had to fulfill several criteria. Most important, they had to last long enough in an operating mill to protect its structure from the abrasive wear of the ore and the grinding media. In addition, they had to be capable of efficiently transferring the energy from the mill to the mill charge in order to facilitate the grinding process. And these liners had to be easy to install and remove. The first liners used were generally made of cast white iron, Hadfield manganese, unalloyed high-carbon steel and composites of steel and concrete or cemented in flint blocks or natural stone. In the early 1920s, pieces of solid rubber truck tires were used as emergency repairs for broken cast metal liners. Thus was rubber first introduced as a mill liner material. The first patent for rubber mill liners was awarded in 1921 to James Denny and Rolla Watson, both of the Coniagas Mine in Cobalt, Ontario, and to Dale Barnum of the Comstock Lode in Virginia City, NV. This original design was covered under US Patent No. 1470597. It had a fabric backed rubber that was bonded to the shell of the mill.

Jan 1, 1990

By B S. Utting, W J. Cowie

The alluvial gold industry of New Zealand is based on the placer deposits in Otago and on the West Coast. Production from these since discovery in the 1850s has been an estimated 480 t (15 Moz) of gold. Annual output has expanded continuously since 1980 and is expected to be over 2 t of gold for 1989. Following a historical review, the characteristics of typical operations, which use hydraulic excavators and mobile trommel units are discussed. Descriptions are then given of alluvial activities in Otago and on the West Coast.

Jan 1, 1990

By M. Leroux, P. Lacombe, S. R. Rao, J. Y. Kim, J. A. Finch, G. Labonté, N. Macminn, M. Ounpuu

"Laboratory investigations on two complex ores, the A1 zone ore from Les Mines Selbaie and the Lyon Lake ore from Mattabi Mines Ltd. (Division of Noranda Minerals), have been carried out to determine some of the main variables in collectorless flotation. In particular, the effect of pulp potential (controlled by gas composition), conditioning time, pH and grinding media have been studied.Chalcopyrite showed the greatest response to collectorless flotation among the four major sulphide minerals present, followed by galena. Flotation of sphalerite was variable from minimal to important depending on the mineralogy and the pre-treatment performed. Appreciable silver recovery was achieved collectorlessly for the Lyon Lake ore while it could not be achieved for the A1 zone ore of Les Mines Selbaie. It appears that the difference between the two ores is related to silver's predominance as tetrahydrite in the Lyon Lake ore while it is as argentite and native silver in the A1 zone ore.The response of the ores to collectorless flotation is strongly dependent on the pulp potential, Ep, and pH. Using different gas compositions and different conditioning times it was found that collectorless flotation occurs when Ep is +195 to +295 mv (vs SHE). The actual on-set potential for collectorless flotation is dependent on the ore. A too high potential or prolonged oxidation leads to a decrease in selectivity. Some other factors were examined, notably the effect of pH and the type of grinding media on the selectivity achieved in the laboratory.Preliminary results from a plant trial at Mattabi Mines Ltd. confirmed that collectorless flotation occurs and that it is preferential for chalcopyrite and to a lesser extent galena. Collectorless flotation was not attempted at Les Mines Selbaie. However, examination of the distribution of collector between the different addition points in the copper circuit suggests that it may be present."

Jan 1, 1990

By S. P. Mathew

The ISASMELT Lead Process is a continuous two stage process for the production of crude lead from concentrate. It is based on the use of a top entry submerged Sirosmelt lance to produce turbulent baths in which high intensity smelting or reduction reactions can occur. The process involves oxidizing the concentrates in the first stage to produce a high lead slag. This slag is tapped continuously and transferred down a launder to a second furnace where it is reduced with coal. Crude lead and discard slag are tapped continuously from this furnace through a single taphole and separated in a conventional forehearth. Process and engineering design work for a commercial scale Lead ISASKELT plant designed to produce 60000 tpa crude lead has been completed. This plant is planned to be operational in 1991.

Jan 1, 1990

By J. A. Sekhar

Solidification processing/casting is increasingly being adopted as the preferred manufacturing technique for the fabrication of net shaped complex geometry components. Modeling of solidification processes is important both for design purposes as well as for understanding the physics of morphological evolution of the solidification microstructure. A fundamental aspect of such modeling involves the precise understanding? of heat transfer through the two phase solid/liquid region. A scheme to do this will be presented where the nonlinearity of the fraction liquid with change in temperature can be incorporated into the numerical calculations. The importance of properly accounting for the non-linear mushy zone will be discussed. Typical processes like squeeze casting and electromagnetic stirring will be discussed to illustrate how precise modeling of the solid/liquid region can aid in the calculation of accurate heat transfer coefficients for these processes.

Jan 1, 1990