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By Kim A. Lapakko, David A. Antonson, Jon R. Wagner

This study examined the potential of mixing rotary kiln fines (RK fines), a waste product generated when limestone is converted to lime (CaO), with acid producing mine waste to provide 1) short-term mitigation by neutralizing acid produced by iron sulfide oxidation and 2) long-term mitigation by facilitating the passivation of iron sulfide mineral surfaces. Five loadings of RK fines were mixed with 75 g of Duluth Complex rock to produce neutralization potential (NP) added: acid potential (AP) quotients of 0,0.11,0.22,0.66 and 1.1. The mixtures were subjected to wet-dry cycling laboratory testing for 585 weeks. The rock alone produced acidic drainage, with pH decreasing below 4 after about 20 weeks of reaction and ultimately reaching the approximate range of 3.3 to 3.5; sulfate release did not decrease over time. The RK fines elevated pH and inhibited sulfate release for time periods which increased with the mass of RK fines present. The pH of drainage from the 0.11 quotient (NP added1AP) loading decreased below 6.0 after 75 weeks of dissolution and decreased to 3.6 after 117 weeks, at which time the reactor was terminated. The duplicate 0.22 quotient loadings of RK fines decreased below 6.0 after 95 and 170 weeks. The former was terminated after 117 weeks, and the latter reached a minimum pH of 2.8 after 512 weeks. Drainage pH from the 0.66 quotient decreased below 6 after 581 weeks. For the drainages which acidified, the cumulative calcium release prior to pH decreasing below 6.0 was 92 to 103 percent of that initially present as calcium carbonateloxide in the RK fines. The pH of drainage from the 1.1 quotient typically remained above 8.0 throughout the period of record. Sulfate concentrations in the drainages decreased while the neutralizing fraction of the RK fines was present, but increased after this fraction was depleted.

Jan 1, 2000

By R. P. King

INTRODUCTION It is now 21 years since Wiegel and Li published their paper on a random version of Gaudin's model for the mineral liberation phenomenon (Wiegel and Li, 1967). This paper was to revitalise interest in North America in one of the most fascinating, difficult and important problems in the field of theoretical mineral processing. Gaudin had many years previously (Gaudin, 1939) already presented a penetrating analysis of the problem and Wiegel and Li based their analysis very closely on the Gaudin model but they realised that the indeterminate geometrical structure of mineralogical materials demanded that only probabilistic models could provide the necessary quantitative information when working with real materials. They proposed and solved a randomised version of the Gaudin model but retained the essential geometrical simplicity of cubic mineral grains and a cubic fracture pattern. Although their model met with some limited success it was to be superseded in due course. During the 1940's and 1950's the classical field of geometrical probability spawned the mathematical discipline of integral geometry and as early as 1965, Bodziony (1965, a,b) showed that the techniques of integral geometry could accommodate the problems associated with the indeterminate nature of the geometrical mineralogical structure, provided that these were couched in probabilistic terms. In particular he showed that the quantitative description of the comminution process and that of liberation could be decoupled with the resulting economy of effort. This idea has profoundly influenced the course of research in liberation theory and has greatly facilitated its application and the measurement of liberation in a practical way. Bodziony demonstrated also that any theory that required the specification of the mineral "grain

Jan 1, 1989

By B. F. Buie

In South Carolina and Georgia an area about 20 miles wide situated near the inner margin of the Coastal Plain and extending from the vicinity of Columbia, S.C. southwestward about 180 miles to the vicinity of Macon, Georgia is the principal kaolin-producing area of the world. It is especially important as the world's major source of clay used for paper coating. Essentially all of the land known or likely to be productive of quality kaolin in this area is now owned or controlled by producing companies. The least-fully developed portion is that in the vicinity of Wrens, Georgia which has been explored and developed since 1961. For the two decades following the end of world war II, demand for kaolin increased at approximately twice the rate for other industrial minerals. From 1945 to 1965 production increased four-fold. Since 1965 the rate of increase has been less, but the outlook now is that production and demand will double at least once again before the year 2000. A substantial part of this increased demand has come, and will continue to come, from industrial development, especially in the paper industry, outside the United States. The general effect, in addition to a continuing increase in production in the U.S., will be to cause: 1. Intensive research for development of more effective and more economical methods of beneficiation; 2. Concerted research effort to find an economical way of modifying high-viscosity kaolin so that it can be used for paper coating; 3. More active exploration in the U.S. and overseas, especially for deposits to supply the foreign markets; 4. More intensive study of the geological factors responsible for the accumulation of commercial deposits of kaolin; 5. Some modest rise in price, relative to the cost of other industrial minerals. The effect on kaolin producing region of Georgia and South Carolina will be to cause: 1. Working of progressively lower-grade deposits; 2. An increase in the acceptable thickness of overburden; 3. Mining of deposits farther down-dip, the use of which is now inhibited by large volumes of groundwater; 4. Increased threat of invasion of the kaolin in industry's market by substitute materials; 5. A substantial increase in concern over environmental factors; 6. More attention to be paid to the large opportunity offered for mining of silica sand and other co-products.

Jan 1, 1972

By Malcolm J. McPherson

The highest recorded loss of life due to the collapse of mine workings occurred at the Coalbrook North Colliery in South Africa on 21st January, 1960. A total of 437 persons died when bord and pillar workings collapsed over an area exceeding one square mile The whole mass of strata from the 470 ft (143 m) deep seam to the surface being affected. Although the Coalbrook disaster was unique in its scale the problem of pillar failure, particularly in old workings, is by no means uncommon nor confined to recent history. Indeed, the collapse of large pillared areas was a regular feature of mining in the north of England in the early part of the nineteenth century. When a section of underground workings collapses, the air under the descending roof is compressed very rapidly. The pressurised air is dissipated subsequently at a rate governed by the leakage paths available. If the collapsing area is small, such as the case of a local fall of roof, then there will be little danger of an air blast. If, however, an extensive area collapses suddenly then the rapid compression of air will give rise to a pressure shock wave that will be transmitted through the remaining workings as an air blast. If worked out areas are connected to current workings via unstopped airways an air blast caused by pillar failure in the old workings will be extremely hazardous to personne1 and may cause extensive damage to equipment, perhaps even reaching to surface plant. At Coalbrook, the air blast blew out a wall in the surface fan house. Areas that are considered liable to sudden collapse may be isolated from current workings by the construction of stoppings. However, such stoppings must be capable of withstanding the 'hammerblow' effect of peak air pressures developed during the collapse. The work described in this paper was undertaken in order to determine the maximum air pressures that stoppings must withstand during a major pillar failure. The result has been a method of establishing peak air pressures that is quick and simple to use. Readers who are concerned primarily with the practical application of the method are advised to turn directly to the last main section of the paper.

Jan 1, 1980

By Stanislaw Wasilewski, Zdzislaw Krzystanek

The CMC-3 new generation system for continuous methane monitoring enables on-line measurement of methane concentration within the range of 0-100% CH4 with a great autonomy of operation. In principle the system has been worked out in the asspect of hazard detection in mines endangered with rock and gas outbursts. But after last crash in the Halemba colliery, according to the recommendation of the after-accident committee, the system was directed to this colliery for operational tests. The paper describes construction and functions of this system and gives some results of tests conducted at the Halemba colliery. The results point out the necessity of using monitoring equipment of continuous operation in mines of high dynamics of methane emission. INTRODUCTION Commonly used in Polish coal mining the methane monitoring systems of CTT/63/46 Up or CMM-20 and CMC-1 type are based on cyclic measurements with 4-minute repetition of measurements. This period has been stated sufficient from viewpoint of methane emission dynamics under normal exploatation. In these systems, automatic switching-off electrical power is performed by the surface station, i.e in case of detecting exceeded concentration value the station generates control pulse signal which actuates the switchng-off devices CRA and IZZO. Such a way of disconnection causes a considerable time delay, up to several minutes, in electric power break at hazardous areas. In the methane monitoring system with the new CMC-3 station, the different phylosophy of operation has been applied. Measurement of methane concentration is performed in a continnous way. In case of exceeding the alarm value, immediate control of the IZZO unit directly by methane monitor follows and consequently energy break without necessity of communicating with the surface station. Alarm values are set directly in methane monitor. The system ensures central powering of underground equipment from the surface, and in case of power failure the methane monitor equipped with battery operates autonomously for about 12 hours. Such an extention of the methane monitor funtionality has been achieved thanks to the use of internal microprocessor controller. The system with the CMC-3 station has been worked out in the aspect of methane hazard detection in mines exposed to gas outbursts. But after last gas explosion, according the desicion of the After-accident Commitee, the system was installed in the Halemba coliery where it underwent operational tests. Besides

Jan 1, 1993

By Kegomoditswe Koitsiwe, Tsuyoshi Adachi

"This paper characterizes quarterly LME copper price fundamentals from 1995 to 2011 by analyzing the transformation of the market mechanism based on structural change perspective. Using chow test for structural change based on the least square multiple regression, we divide the price fluctuation into: Stable price period (1995Q3-1999Q2), Low stable price period (1999Q3 – 2003Q3) and Price fluctuation period (2003Q4 – 2011Q2). The results show the existence of structural breaks disproves the investigation of the full sample period as a whole. In different structural breakpoints the main drivers of copper prices changes and their impact are significantly different. Moreover, the paper examines the role of speculation in copper price fluctuations.Introduction The rise in commodities price volatility and financial and economic crisis have led to questions over the organisation of futures and physical commodities markets. Spikes in commodity prices and volatility have coincided with a surge in financial speculators in the commodity markets inspiring a polarised and hotly debate among academics and practitioners about the role of investors in the development of physical markets. In his seminal work Kaldor (1939) focused primarily on whether speculative activity in the futures markets reduces the variance of commodity spot prices. Yet, part of the literature finds that the introduction of futures contracts destabilizes the spot market. IMF (2006) studied commodities boom and its causes concluding that there is little support for the hypothesis that speculative activity affects either price levels over the long run or price swings in the short-run. The impact of speculative activity on commodity prices remains a highly contentious topic. Other market analysts take the view that the supply and demand for physical commodities remain the major determinants of market trends (Krugman 2008). It is the aim of this study to contribute to the literature by examining the drivers of copper price changes from a structural change perspective. In this context we are attempting to answer to: What are the main drivers leading to copper price fluctuations? Are these factors having the same effect in different periods or not? It is meaningful to understand drivers of copper prices and thereby, their fluctuations because it will help developing countries depending on copper export to anticipate market situation and avoid bad economic development challenges that can result from price fluctuations. Moreover, this can ensure sustainable mineral supply."

Jan 1, 2017

By William H. Sutherland

INTRODUCTION Coal workers' pneumoconiosis and sili- cosis are only two of several diseases which are rlassed as pneumoconiosis. These are respiratory diseases caused by dusts which are inhaled and accumulated in the lungs. The individual particles of dust cannot be seen by the human eye. They are so small that they escape the natural cleansing mechanism of the nose and air passages and make their way down to the terminal air sacs of the lung where they injure the cells and cause the formation of scar tissue. Consequently, if there is exposure to high concentrations of dust over a period of time - usually, a number of years - the amount of scar tissue increases and begins to impair breathing. As a result, the miner develops shortness of breath, coughing and wheezing ad-if exposure continues - this progresses to permanent disability and frequently to death. Death is often due to pulmonary heart disease, the effect of stress on the heart 2s it tries to compensate for the weakened lungs. Specifically, silicosis is an occupational lung disease caused by the accumulation of free silica (quartz) in the lungs. Silicosis is considered the most important form of pneumoconiosis, not only because of its seriousness as a respiratory crippler, but also because of the large number of workers who risk contracting it in a variety of occupations. Quartz is one of the most common substances of the earth's crust, estimated at about 60 percent. Silicosis has been found in coal, metal and granite miners, as well as in other workers, such as sandblasters and pottery makers. Silicosis is also known to predispose the lung to tuberculosis and to increase the chances that a worker will contract chronic bronchitis and emphysema. The seriousness of silicosis was tragically brought to public attention about 50 years ago. During 1932-34, workers were involved in digging a tunnel through rock at Gauley Bridge, West Virginia. While their exposure time was relatively short, they developed silicosis because of the high concentrations of quartz. By 1936, 476 workers had died of silicosis and about 1500 were believed to have the disease (Washington Post, 1982). It is difficult to tell how many coal miners have silicosis. Because x-rays and breathing function tests do not show the difference the type of pneumoconiosis is generally diagnosed by the miner's work history. For example, if a worker

Jan 1, 1986

By Houston Kempton, Tim Dyhr, Andy Davis, Mark Bloom, Connie Travers, Dave Atkins, Jeff Deen

INTRODUCTION Historical mining activities in the Robinson Mining District, in the Egan Range of east-central Nevada (White Pine County), resulted in five open pits (Veteran, Tripp, Liberty, Ruth, and Kimbley Pits), several large mine-waste dumps, and numerous underground workings developed for copper, zinc, gold, lead-silver, and manganese (Figure 1). Groundwater percolating downward through the copper sulfide ores produced a blanket-like supergene zone enriched in copper, which has been one of the primary objectives of mining since the early part of this century. To obtain permits for future operation, an EIS was conducted that evaluated future pit- lake chemistry, groundwater quantity and quality issues, transport of water and solutes subjacent to a proposed tailings impoundment, and the potential for waste dump acidification. AREA HYDROGEOLOGY The mine area is on a ridgeline draining to the Steptoe Valley to the east and to the White River Valley to the West. Precipitation in the Robinson Mining District ranges from a low of 15 cm (6 in.) per year in the valley to more than 50 cm (20 in.) per year in the surrounding mountains. Evapotranspiration exceeds precipitation, leading to a net loss of water from the basin as either surface flow or underflow to the north at Currie, Nevada (Eakin et al. 1967). The White River Valley, which lies to the south and west of the mine area, includes approximately 4,200 km2 (1,620 mi2) of the upper part of the Colorado River Basin. This valley is 112 km (70 mi) long, 32-48 km (20-30 mi) wide, and like Steptoe Valley, evaporation and transpiration exceed precipitation (Maxey and Eakin 1949). The local groundwater flow system in the Robinson Mining District and the proposed mine area is dominated by two main components: (1) a groundwater mound or high between the Ruth Pit and Murry Springs, and (2) a shallow groundwater flow divide that follows the ridge crest south of Ruth, which contains the Veteran and Tripp pits. Besides the alluvium, the main hydrostratigraphic units controlling groundwater flow are limestones, shales, and sandstones, along with the intrusive quartz monzonite stocks. Based on the piezometric surface measured in October 1993, three distinct groundwater regions were identified. In the Giroux Wash area, an apparent fault runs between WCC-G1 and WCC-

Jan 1, 1995

By R. D. Hamilton, W. J. Miles

In 1987, the International Agency for Research on Cancer designated crystalline silica as a 2A probable carcinogen. As a result, crystalline silica is regulated under the Hazard Communication Standard as a probable carcinogen at a concentration of 0.1% or greater in the workplace. Crystalline silica will be listed as "reasonably anticipated to be a carcinogen" by the National Toxicological Program. This designation of crystalline silica as a probable carcinogen has created major issues for the mineral and chemical producer, including labeling, hazard communications, marketing a material with potential hazard exposure, and potential liability. The State of California also regulates crystalline silica under Proposition 65 in products as a carcinogen, based upon the IARC determination that it is a probable carcinogen. More federal and state regulations are anticipated as a result of the IARC classification of crystalline silica and its subsequent federal regulation. Respirable crystalline silica has been regulated as a hazardous dust for many years by OSHA. This regulation was initiated to prevent silicosis, another occupational disease. OSHA has established monitoring devices for determining the concentration of airborne respirable silica in order to measure exposure to this substance. The accurate determination of the crystalline silica content is critical to dealing with these health risks and regulations. In the past, crystalline silica was considered to be safe and, because of its ubiquitous nature, little effort was made to determine or quantify its presence in most materials. The Hazard Communication Standard requires that a1l products containing 0.1% or greater crystalline silica must be properly labeled for this material and its hazard. Unfortunately, the 0.1% threshold was not chosen on the basis of established analytical capabilities for crystalline silica, but results from general limits for potentially carcinogenic chemicals and substances. Numerous methods have been developed for the determination of crystalline silica in a variety of products. However, these methods are not generally applicable since they must be specific for silica in any of its crystalline states and not just for total silica content. Chemical tests for silica are not difficult and quite accurate at the 0.1% level; however, in addition to its crystalline phases, it occurs in amorphous phases and in a wide variety of crystalline and amorphous silicates. In general, there is little correlation between total silica content and crystalline silica.

Jan 1, 1991

By Qiong Wu, Li Guo, Qinghua Gu

BP neural network is a multilayer feedforward network trained by error back-propagation algorithm, which is one of the most widely used neural network models. However, BP neural network has exposed more and more shortcomings and deficiencies with the expansion of the application scope. In the prediction of ore quantity, BP neural network has the characteristics of slow convergence and easy to fall into local minimum point. In order to obtain the global optimal solution, and to improve the defects of BP neural network, this paper proposes combination optimization algorithm of genetic algorithm (GA) and BP neural network to improve the speed and accuracy of forecasting the main design flow chart and the analysis of the sort distinguish algorithm are offered, and then some problem in the design and debugging of the algorithm are discussed. On this basis, the GA-BP neural network model is constructed and applied to optimize the initial weights and threshold value of BP neural network. This model choices the floating point coding method to encode the connection weights and thresholds, and divides subjects into several populations. Through the introduction of selection, mutation, crossover, initial weight and other operators, making operational synergies between the various groups. This study selects 30 geological units, 8 quantitative variables (Pb, Zn, Cu, Mo, Si, Ni, Co, V) and 12 qualitative variables to carry out empirical analysis. Then the simulation of the algorithm is carried out in MATLAB and the parameters are analysed. By normalizing the input samples, 22 groups of observation data are used as the training data for prediction, and the latter 8 groups of observation data are used as the test data to be verified. The results show that when the ore quantity characteristics are not very significant, the model will produce prediction bias. But the improvement of the algorithm increases the efficiency of the function approach capacity of BP neural network and conquer the BP neural network system’s instability. It provides an auxiliary guide for ore prediction, which have higher reference value.

Jan 1, 2017

By E. D. Attanasi

The US mining industry finished the traumatic 1980s with a strong economic performance. Worldwide economic growth and capital spending led to tight metal markets. So, 1989 metals prices were generally higher than average 1988 prices. Financial markets' volatility resulted from US junk bond defaults, heavy US savings and loan losses and effects on the US budget deficit, higher energy prices, and the seemingly intractable problems of some debtor countries. Moreover, the events in Eastern Europe promise fundamental changes in the world economic system for the 1990s. US mining companies that survived the decade had weathered economic changes that, at one point, reduced industry employment by 40%, drove oil companies to divest or liquidate recently acquired mineral subsidiaries, and led to substantial write-offs of reserves. Canadian and other international minerals firms experienced similar industry upheavels. The forced modernization and capacity rationalization produced an internationally competitive US industry. For example, even though 1989 US copper production was 27% greater than in 1980, industry employment was less than half the 1980 level. The steel industry and other minerals industries showed similar productivity improvements.

Jan 1, 1990

By William E. Wallace, Michael J. Keane

This review summarizes three sets of ongoing studies which we are performing in collaboration with a number of researchers associated with the Dept. of Interior - Generic Mineral Technology Center for the Study of Respirable Dusts, concerning surfactant-particle interactions studied using this surrogate surfactant. These topics are: (A) the suppression of mineral particle cytotoxic potential by DPL adsorption and the persistence of this effect under conditions of enzymatic digestion; (B) surfactant suppression of organic particle cytotoxicity by DPL adsorption and the effect on subsequent expression of genotoxic potential; (C) potential effects of surfactant on heterogeneous structured complex respirable particles. The references list some of our reports which can provide additional information on these studies. Further, those reports provide references to the literature of the field and to the works of others on these topics. Deep lung airspaces, the pulmonary alveoli and respiratory bronchioles, are coated with a hypophase which is rich in surfactant biomolecules secreted by the alveolar type II epithelial cells. The surfactant is known to be critical to maintaining stable low surface tensions on the inner surfaces of the alveoli by forming a surfactant layer on the airliquid interface of the alveolar hypophase. Upon deposition in the acinar regions of the lung a respired particle's initial contact will be with this surfactant coating over pulmonary tissue. A primary component of this surfactant is the phospholipid diacyl glycerophosphorylcholine, commonly called lecithin. A surface layer of dipalmitoly lecithin on saline will act much as full pulmonary surfactant in decreasing surface tension and producing a hysteresis in surface tension behavior with surface area. We have used dipalmitoyl glycerophosphorylcholine, or dipalmitoyl lecithin (DPL), a major component of that surfactant, dispersed in physiologic saline as a surrogate for studying interactions of both mineral and organic respirable particles with pulmonary surfactant and consequent effects on particle toxic behavior. A. DUST CYTOTOXICITY AND LECITHIN SURFACTANT ADSORPTION Respirable quartz and kaolin clay particles are found to be comparably cytotoxic in a number of in vitro bioassays including lavaged rat pulmonary macrophage release of cytosolic and lysosomal enzymes, and red blood cell hemolysis as a measure of dust membranolytic potential. These direct and prompt cytotoxic activities do not account for the distinctly greater potential for quartz to induce pulmonary disease. When respirable quartz and kaolin are incubated with a dispersion of DPL in saline at 37C it is found that the prompt cytotoxicity of both dusts is fully suppressed as measured in vitro by pulmonary macrophage release of lactate dehydrogenase, beta-N-

Jan 1, 1991

By K. Hanumantha Rao, K. S. E. Forssberg, A. Vidyadhar

Using pure albite and quartz minerals, the separation of albite from quartz using mixed cationic/anionic reagent schemes is assessed through Hallimond flotation, zeta potential and diffuse reflectance FTIR studies. The reagent schemes are tested in bench-scale flotation for the separation of albite from Greek Stefania feldspar ore. The single mineral flotation tests showed the feasibility of selective albite flotation from quartz at around pH 2 using a mixture of cationic diamine and anionic sulfonate collectors or a combined cationic-anionic collector of diamine-dioleate. In contrast to the selective flotation response of albite at pH 2, where albite is slightly negatively charged and quartz possess zero charge, the zeta potential and FTIR studies elucidate similar adsorption behavior of mixed collectors on both of the minerals. The infrared spectra not only showed the co-adsorption of anionic sulfonate or oleate with diamine on the surface but also showed that the diamine adsorption increases with the presence of anionic collector. The intrusion of anionic collector in between adjacent surface alkyl ammonium ions decreases electrostatic head-head repulsion, thereby increasing the diamine adsorption by increasing the hydrophobic tail-tail bonds. The discrepancy in the flotation and adsorption results at pH 2 is attributed to the coarse and fine size particles employed in these studies, respectively. The comparable adsorption on fine particles of albite and quartz at pH 2 is explained by the interaction of ammonium ions on silanol groups by hydrogen bonding besides electrostatic interactions. The bench-scale flotation results indeed showed that selective albite flotation takes place only after desliming the feed material. An albite concentrate exceeding 10% (by weight) Na20 is produced from a material containing about 6.5% (by weight) Na20, where an albite product of more than 9% (by weight) Na20 is considered to be valuable. Key words: Flotation, Adsorption, Zeta-potential, FTIR

Jan 1, 2003

By Steven J. Luzik

Introduction From 1973 through 1986, a total of 12 fires involving oil-flooded rotary screw compressors (OFRSC) were reported to the Mine Safety and Health Administration (MSHA). Most of these incidents were attributed to faulty or by-passed safeguards, or improper maintenance. The cause of a fire in an OFRSC is unique when compared to other types of compressors. A compressor inspection checklist is provided here that can be referenced when conducting regularly scheduled maintenance operations. This checklist and a well-planned program of periodic training and maintenance should help minimize the probability of fires and explosions in OFRSC's. Operation A rotary screw compressor operates on the principle of positive displacement of air. Compressed air in this type of compressor is produced by the meshing of two helical rotors, or screws, as they rotate within a steel housing called a stator. The male rotor normally has four lobes and is driven either directly or indirectly - through a gear assembly - by a motor. It intermeshes with a female rotor having six cavities. Figure 1 explains the compression mechanism: (1) Atmospheric air is drawn into the stator by the suction action of the two rapidly rotating rotors. (2) As the rotors rotate past the intake port, air is trapped in the stator and in the cavities between the rotors. (3) Further movement of the rotors causes an increased reduction in volume, compressing the entrapped air. (4) Compressed air is expelled at the discharge port in the bottom of the stator at a pressure and quantity determined by the particular compressor rotor design parameters, such as length, diameter, and speed. Radial bearings on the male and female rotors compensate for radial loading on the shaft and position the rotors within the stator. Thrust bearings on the discharge end of the compressor prevent rotor misalignment due to thrust developed during the compression cycle. This design prevents the male and female rotors from making contact with each other or the stator. A clearance of 0.07 to 0.1 mm (0.003 to 0.005 in.) exists between the two rotors and the stator. For this reason, there is virtually no wear on the rotors or stator, and the unit is relatively maintenance-free. Oil is injected into the compressor and serves to cool, seal, and lubricate. When air is compressed from atmospheric pressure to some higher discharge pressure, a specific amount of heat is produced. This heat is sometimes referred to as the adiabatic heat of compression. It is partially removed by injecting oil into the compression chamber. Premachined strips - a raised surface on the male rotor and a

Jan 9, 1988

By Harold A. Taylor

The first use of graphite is lost in the mists of time. It was used by primitive man to make drawings on the walls of caves and by the Egyptians to decorate pottery. As early as 1400 AD graphite crucibles were being made in the Haffnerzell District of Bavaria. Through the Middle Ages graphite was confused with other minerals, especially galena and molybdenite. Two common names that are still being used for the mineral are plumbago, meaning lead-silver, and black lead. The latter name implied that graphite is either composed of lead or at least contains a large percentage of it. Gessner is credited with having recognized it as a separate mineral in 1565, but its composition was not determined until 1779, when Scheele demonstrated that graphite oxidized to carbon dioxide, thus proving its carbon constitution. In 1789, Werner named it graphite from the Greek word graphein, meaning to write. The United States has long relied on foreign countries for its graphite supplies. This reliance has been due more to the lack of suitable domestic graphites than to any particular preference for buying minerals overseas. Sri Lankan graphites were imported as early as 1820, and Madagascar graphites have been imported since the properties on that island were opened up about a hundred years later. Mexico has long supplied the United States with most of its requirements for amorphous graphite.

Jan 1, 1994

By R. N. Chakravorty

It is well established that coal can react with oxygen in air at ambient temperature and as a result heat is produced. If the heat is not fully dissipated the temperature of the coal mass will increase, thereby enhancing the rate of oxidation with a greater production of heat. If this phenomena continues, the coal mass can ignite under favourable heat accumulation conditions. A number of mine fires are caused each year due to this phenomena, commonly known as spontaneous combustion. The early detection of spontaneous combustion is of prime importance to mining engineers since any fire which could be detected at an early stage may save the mine from considerable damage and subsequent loss of production. Obviously, there is no single general criteria by which one can assess whether the under- ground mining of a coal seam will result in liability to spontaneous combustion. This has made it imperative to develop systems for the early detection of heating and to follow its development. In recent years considerable advances have been made in the design and development of methods for the early detection of spontaneous combustion. The Mining Research Laboratories (CANMET) is presently investigating the problem of spontaneous combustion in coal mines with Kaiser Resources Ltd. at their hydraulic mine at Sparwood, B.C. on a co-operative basis, and some of the work was described earlier in the Canadian Institute of Mining & Metallurgy Bulletin (1,Z). This paper summarizes and updates the work done by CANMET on the detection of spontaneous combustion in coal mines.

Jan 1, 1980

By J. B. Gwiazda

Introduction Thick seams constitute a considerable portion of Polish coal reserves. In producing mines and those under construction, the reserves where the height is more than 4.5 m (15 ft) total about 24v0 of all the hard coal reserves. The reserves that are under urban and industrial areas can be extracted using stowing methods for surface protection. About 50v0 of thick seam reserves can be extracted by caving methods. Thick seam mining methods Thick seams are usually extracted by multilift methods. There are some methods of thick seam mining that generally can be divided into caving and stowing methods. The stowing method is more expensive, but must be used when mining to protect surface features. The more known methods of thick seam mining include: • extraction of thick seam in ascending order with stowing; • thick seam mining in descending order with consolidated stowing; • thick seam mining with gob consolidation; • thick seam mining in descending order with roof caving; • sublevel caving thick seam mining system; and • thick seam mining system using an artificial roof. • Thick seam mining with introduction of an artificial roof The most advantageous method of thick seam mining is the method using an artificial roof. The artificial roof usually consists of wire mesh. Such wire mesh must be durable and must prevent small rock fragments from passing through. The mesh is usually made of steel properly protected against corrosion. The artificial roof is placed on the coal floor of the top slice (Fig. 1). Caving rock falls on the artificial roof and is thus separated from the coal. The next slice is extracted under the artificial roof. The producing face of the next slice must progress within 10 m (33 ft) behind the front of the first slice. As the second producing face progresses, the wire mesh moves down on the coal floor and may be used as an artificial roof for the next slice. Thus, one artificial roof allows the extraction of several consecutive slices. Application of the artificial roof allows for clean extraction and reduces coal losses. It also eliminates the hazard of spontaneous combustion. Introduction of the artificial roof has been limited due to a lack of artificial roof laying equipment. Manual laying of wire mesh is a labor-intensive operation, and it delays face progress, resulting in poor productivity. To eliminate these problems, artificial roof laying equipment was designed at the Polish Central Mining Institute. The support and the method of laying operation is covered by a patent. Artificial roof laying powered support To extract thick seams using an artificial roof; four-leg shield supports with lemniscate linkage were developed (Fig. 2). This shield is used in the first top

Jan 1, 1988

By Earl Cook

Introduction Men like physical power because it gives control over nature and over other men. Physical power comes in two common forms: explosive and non-explosive. In both forms, the most powerful devices yet invented make use of nuclear energy: on the one hand, the hydrogen or fusion bomb, and, on the other hand, a nuclear power plant. For some nations, nuclear power offers a measure of independence not otherwise available in a time of diminishing and unevenly allocated fossil fuels. Consequently, it has great attraction. Unfortunately, the application of nuclear energy (especially fission energy) to either explosive or electrical power entails a singular risk, that of injury from ionizing radiation, both natural and induced; this risk is found in all stages of the nuclear-fuel cycle, from mining of fissionable materials to the disposal of wastes produced in the "burning" of nuclear fuels. The health costs of nuclear power were not fully assessed in the early stages of the development of nuclear technology and some of them were not properly guarded against, either in the USA, which led the world into the nuclear age, or in Canada, which followed an independent path. What I shall do in this paper is to sketch the history of nuclear regulation in our two countries, to point out what I consider similarities and differences, and to suggest that regulatory history, as perceived by a concerned public, has a great deal to do with what is possible today and probable tomorrow, in other words, with public acceptance or rejection of the nuclear option. The U.S. situation As we sow, so shall we reap. In the USA, further expansion of the nuclearpower industry has been almost stymied by government actions that reflect mounting public concern. There is no national storage facility for spent reactor fuel and it has been decided not to reprocess it; consequently, existing power plants are about to choke on their own wastes. Since the Three Mile Island accident, no new nuclear plants have received operating licenses, although several are ready to start up. The uncertainty of future government action has caused the abandonment of plans for a number of new nuclear plants. In addition, many research projects related to medicine and agriculture, which produce low-level radioactive wastes, are about to be shut down for lack of licensed disposal facilities. Some would maintain that this situation has come about because of the low benefit-to-cost

Jan 1, 1980

By Brenda J. Morrison

Anything to do with radioactive waste disposal in these days is regarded in a very negative light and with the thought that no possible good could come of anything connected with it. However, it should be remembered that the Austrian government's disposal of some tailings from the Joachimsthal mines resulted in what was probably the most important scientific discovery of this century. In 1898 the Austrian government agreed to give a Polish research assistant working at the School of Physics in Paris one ton of tailings to enable her to carry on her research. Her meagre stipend and the lack of a research grant did not allow her to purchase the ore which was relatively expensive. The uranium oxide in it being used to colour the famous Czechoslovakian glassware. As we all know, from this ton of ore Marie Curie by her own physical labours extracted one gram of radium. When she started this research she was pregnant with her first child. Nothing of course was known at the time about the biological effects of radiation. Very shortly, of course, the acute effects such as skin burns were observed but it was some years before the chronic effects were noted. It is impossible to estimate to what cumulative amount of radiation that Marie, Pierre and their daughter Irene were exposed but it must have been enormous and it took its toll. Marie complained for many years of fatigue and exhaustion and at one point she was seriously ill with some kidney problem which was probably due to toxic effects of ingestion of uranium. She lived until she was 67, however, and died of leukemia. Her eldest child, Irene, who carried on her work, did not live as long; she died of leukemia at 57. The other daughter, Eve, related how her mother and she went on a skiing holiday not many years before her death, and how her mother at this time would swim 300 meters at a stretch. (Curie, 1937). This suppleness of limb could have been due to the anti-inflammatory action of radiation. Even today, patients in France with certain types of rheumatic conditions are treated with injections of radium, where other anti-inflammatory drugs such as aspirin or cortisone have not worked. (Bertrand, Legras and Martin). All this anecdotal information is just to point out that it is an ill wind that blows no good. The risks connected with uranium waste disposal and tailings piles are

Jan 1, 1980

By James A. Brierley

The author has known Professor Wadsworth since the 1960s, when interest in the application of microbial technology for metallurgical processes was beginning its rapid rise. The development of bioleaching and mineral biooxidation was advanced, in part, by Wadsworth's belief in the potential for its application, as well as by his numerous contributions to the understanding of the fundamentals of hydro-metallurgy. Wadsworth is recognized for fostering research and development of the field and adding credibility to microbiological-based metallurgical processes, now often referred to as biohydrometallurgy. This Wadsworth Award is recognition of the field of biohy-drometallurgy. It is an honor to serve as a representative for all those individuals involved in research and commercial development of this technology. Modern commercial application of biohydromctallurgy began with the bioleaching of copper from submarginal-grade. run-of-mine material. Kennecott Copper successfully developed this process in the 1950s at the Bingham Canyon Mine in Utah. Other mining operations around the world followed Kennecott's lead. Today, dump bioleaching remains a very low-cost process for scavenging copper from rock that cannot be economically processed by any other method. Despite the commercial success of dump bioleaching, little effort has been made to enhance the micro Biological component of this leach process. Expansion of biohydro metallurgy into recovery of other metals did not occur until the mid-1980s, when the first commercial plant for the pretreatment of refractory gold-bearing concentrate was commissioned at the Fairview operation in south Africa. Now, processes for copper bioleaching and refractory gold pretreatment are engineered specifically to promote the activity of the microorganisms. This paper reviews the current state of commercial applications of biohydrometallurgy. It examines potential future developments and portrays the role of the microbiologist in facilitating continued growth and commercial acceptance of the technology. The commercia1 examples in this paper illustrate the expansion of microbial processing in the mining industry during the last 20 years. Copper bioleaching Early commercial applications of bioleach technology involved processing submarginal-grade, copper- bearing, run-of- mine rock in dumps. Recent applications of the technology use engineered bioleach heaps. Currently. all of these operations are in the Southern Hemi-

Jan 1, 2000