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By Elli Nurminen

Keywords: Thermal conductivity of sulphates, flash smelting, heat recovery boiler, flue dust Accretions and build-ups in metallurgical heat recovery boilers decrease the efficiency of the heat transfer and may cause process shut downs. Transient plane source method (Hot Disk) has been applied to measure the thermal conductivities of the Copper Flash Smelting flue dusts. Thermal conductivities of copper, iron and zinc sulphates, and process flue dusts were measured. The results indicate that all the components are effective thermal insulators, having a thermal conductivity of less than 1 W/mK. Decreasing dust layer porosity has an increasing effect on thermal conductivity. Insulating layers on the boiler walls decrease greatly the heat transfer efficiency of the boiler. The gathered information will be used in CFD-modelling of the process, and in the process control.

Jan 1, 2005

By B. K. Parekh, Z. Chen

INTRODUCTION The need for cleaning and recovery of fine (minus 28 mesh or 0.5 mm) coal fraction has increased in recent years. This results from realizing a substantial recovery of ultraclean coal from the waste stream improving overall Btu (heat) recovery, providing extra revenue for the coal industry. Also the potential of using the clean coal so obtained for making coal-water mixture which could replace oil. An additional benefit of recovery clean coal from the waste stream is reducing environmental concern of burning uncleaned coal and in waste disposal. Deashing of coal by physical beneficiation processes is limited by the degree to which ash components are liberated from coal. Conventional processes have been inefficient in terms of Btu recovery, for ultrafine coal. Chemical cleaning methods, which involves leaching of ash material from coal, have provided ultraclean coal at high Btu recoveries, are more costly than the physical cleaning methods. An advanced physical separation technique that appears to address the need discussed above is selective flocculation. This technique which has been successfully utilized in iron ore beneficiation offers the potential of processing fine and ultrafine coal to produce a clean fuel. OBJECTIVES The main objective of the present study is to investigate applicability of selective flocculation technique for recovery of clean coal product from the waste coal slurry supplied by the Peabody Coal co., from their three different coal preparation plants. It is also the objective of the program to conduct preliminary economic study of the selective flocculation process.

Jan 1, 2002

By J Aydin Bilgin, Sedat Esen

This paper describes the ideality of some commercial explosives with the help of the detonation theory and detonation velocity measurement. Ideality of an explosive can be determined by comparing experimentally measured and ideal detonation velocities. A measured detonation velocity at a certain charge diameter markedly lower than the ideal value indicates incomplete reaction and thus non-ideal detonation. Since it is shown that commercial explosives exhibit non-ideal behavior, two-dimensional detonation theory should be used to evaluate the performance of explosives. This theory enables to compute the detonation properties of explosives (detonation velocity, detonation pressure, etc.) as a function of charge diameter and confinement. The use of the one-dimensional detonation theory to compute the detonation properties for commercial explosives has an error associated with it as these calculated properties are independent of charge diameter and confinement. It assumes that shock front is planar. Hence, it is incapable of assessing the ideality of the explosives due to its assumptions. Shock front in real situation is curved in shape but not planar as in one-dimensional detonation theory. In this paper, the non-ideal behavior of some commercial explosives is modeled using EXRINT code based on the steady-state two-dimensional detonation theory firstly. Then the degree of ideality of each explosive found from the code is checked using detonation velocity test results conducted at a quarry. It has been shown that idealities of the tested explosives determined by the code agree well with the field detonation velocity test results.

Jan 1, 1999

Soil erosion is strongly related to soil hydraulic properties. Understanding how surface coal mining impacts those properties is important in developing effective management practices to control erosion during reclamation. Soils from undisturbed areas, roughly graded mine spoil, replaced topsoil before seeding, and revegetated areas at the Rosebud Mine in Eastern Montana were evaluated to determine impacts on soil hydraulic properties. Field and laboratory studies were conducted to determine soil hydraulic properties, including particle-size distribution, organic matter content, and saturated hydraulic conductivity. WEPP simulations and risk analyses were performed on the soil hydraulic property data to determine the impacts of changes on soil erosion. The hydraulic properties of the soils in each representative area have significant differences due to the mining and reclamation practices at the mine. WEPP simulations show that the potential for soil erosion increases due to mining activities disturbing the soil. WEPP simulations also indicate that the potential for erosion may return to pre-mining levels over time with effective revegetation practices.

Feb 27, 2013

By A. M. Gaudin

THE purpose of ore dressing is to separate the rough ore into one or several valuable concentrates and a discarded tailing. The first step is to crush the ore so that the resulting particles may be individually valuable or worthless. The next step generally has to be a sizing operation, because the property by which concentration is effected depends on the size of the in-dividual mineral particles as well as on their physical properties. These two effects may cancel each other if a preliminary sizing is not resorted to. Sizing is accomplished by screening or classifying. Screening depends almost solely on the dimensions of the particles; classifying depends also on the specific gravity of the particles and the viscosity of the settling medium in which the classifying operation is conducted. Classification, therefore, is to a certain extent a con-centrating operation as well as a sizing operation. Before the days of concentration by flotation, the available screens were mechanically poor. As a result classification was employed for sizing in the range. of comparatively coarse sands (table feeds). In recent years, the advent of stage-grinding to flotation size has brought about the development of good screens, which are more economical than classifiers down to about 20, -mesh. With decreasing size at which separation is to be made, screens become increasingly uneconomical, while classifiers become increasingly economical. The line of demarcation between the respective fields of screening .and classification is, therefore, fairly sharp. With the development of processes of concentrating finely comminuted ore, the need for classifiers or other sizing devices operating so as to make efficiently a split at a very fine size has become increasingly apparent. Such classifiers might be termed de-slimers, from the fact that they separate a material having a slimy ap-pearance from one having the characteristics of a sand. Sizing-tests are carried on by means of testing sieves, the finest of which have apertures of about 1/500 of an inch. The 200-mesh sieve, which has an average open-ing of 0.0029 linear inches is generally considered the limit of practical test-sizing. As a result, little is known of minus 200-mesh material and the advantages of classifying concentrator feeds within the minus 200-mesh range has been overlooked. An extension of the -present sieve scale beyond the 200-mesh screen is given in Table 1.

Jan 2, 1927

By Michael S. Wieland

Charge malfunction problems result from rather universal damage mechanisms and are widespread throughout surface and underground delay blasting. Recent refinements in instrumentation technology reveal a range of charge performance difficulties, not just outright misfires. This report focuses on the U.S. Bureau of Mines research regarding desensitization and malfunction of delay detonators and cap-sensitive explosives, utilized in underground coal mining. Delay blasting generates tremendous shock waves and rifting forces that fracture and heave the surrounding stratum. The shock waves from charge explosions propagate outward in all directions through the coal, impacting neighboring charges with later delays. The impact phenomena have debilitating effects, causing degrees of reduced charge performance ranging from misfires or weak detonations to out-ofsequence detonations. Impaired charges react poorly. fracture less coal, and produce fumes with higher toxicity. Coal-mine, underwater, and simulator tests were conducted to m3re thoroughly understand the shock-wave and rift-compression damage mechanisms. Recently the U.S. Bureau of Mines partially resolved the malfunction problem by demonstrating the feasibility of formulating a rugged explosive, which could pass the requisite tests for certifying an underground coal-mine explosive. The charge formulation was not certified only because it lost initiation sensitivity too quickly from natural aging and had to be rebatched to finish the testing.

Jan 1, 1994

By P. Klaus

"KfW IPEX-Bank is the commercial arm of KfW Bankengruppe, responsible for international project and export finance.KfW was one of the first banks in Germany to promulgate environmental guidelines for its commercial business activities. These guidelines were first made public in 2000 and updated for the second time in 2004. They now include specific reference not only to environmental but also to social concerns. The guidelines specify the procedures to be followed in assessing credit risks related to environmental or social hazards.The bank considers sustainability as an interdependent framework of economic, ecological and social factors. In its efforts to contribute to sustainable development worldwide the bank uses its influence as far as possible to improve a project’s performance if such improvement is deemed necessary."

Jan 1, 2005

Laboratory testwork was carried out on an overall orebody composite, of 2.9 per cent Cu and 4.2 per cent Zn, prepared from drill core taken from the Currawong fine-grained, copper-zinc massive sulphide deposit near Benambra in Victoria. While 90 per cent of the copper was readily recovered in a concentrate of 20 per cent Cu, after grinding to 95 per cent passing 38 microns, zinc responded poorly to conventional flowsheet/reagent regimes. Experience elsewhere with the use of reverse cleaning, to separate pyrite from sphalerite, led to a series of tests in which better (but still modest)metallurgical results were obtained. The best result was a zinc recovery of 55 per cent in a concentrate of 50.5 per cent Zn. The major loss of zinc occurred in the reverse cleaning stage where the unit recovery of zinc was similar to pilot plant results achieved at Mount Isa Mines on similar feedstock. Diagnostic mineralogy suggested that an overall zinc recovery of 70 per cent was probably the practical upper limit, at a 50 per cent Zn grade.

Jan 1, 1999

By P. Todd, K. Dever, P. S. Mills, A. A. Campoli

Resin bolt performance is dependent on the size of the resin annulus, the difference between the hole and bolt radii. The vast majority of the millions of resin roof bolts installed each year in the United States employ an annulus of 0.125 or 0.188 inches. Short encapsulation pull tests with resin annuluses of 0.125 and 0.095 inch resisted an average of 2.25tons per grouted inch, with no significant variation. Resin loses to simulated fractures increased as annulus size decreased, with a minimum loss of35% and a maximum loss of 60% associated with0.188 and 0.095 inch annuluses, respectively.

Jan 1, 2000

By Byron T. Darnton

Gravity concentration at the Pegasus Gold/Montana Tunnels Mine, near Helena, MT, began in June 1991 when a coarse-gold-scalping circuit was commissioned. It processes a small portion of the ball-mill circulating load to reduce the risk of gold particles that are too coarse to float from advancing to flotation. The circuit also cost-effectively enhances overall gold recovery and payable gold ounces. This gravity circuit has been a major success. Since the circuit was commissioned, throughput has increased 30%. Several modifications and improvements were made during the last three years that allowed the gravity circuit to keep pace with the higher tonnage. The overall approach to gravity concentration at Montana Tunnels has always been to optimize production rather than maximize the gold ounces produced. This philosophy has now yielded a circuit expansion and relocation project. It will allow for an estimated 50% increase in gravity gold production, while significantly reducing the unit costs of production.

Jan 1, 1995

Alluvial gold was found in the Terawhiti area, West of Wellington, in the 1850s. This led to the discovery of reef gold. Periods of minor 'gold fever', company flotations, and mining activity occured between 1869 - 1973, 1881 - 1986, and in the late 1880s, with one final company active in 1911 - 1914. 1n the early 1980s, further field work was carried out. No viable mining operations resulted from any of this activity.

Jan 1, 1993

New ZealandÆs share of global greenhouse gas emissions, at about one fifth of one per cent, is very small. But the profile of those emissions is unique among OECD countries; more than half come from methane and nitrous oxide associated with livestock agriculture. Consequently, fulfilling its obligations under the Kyoto Protocol is potentially quite onerous for New Zealand.In this paper we use a single region, static general equilibrium model to assess the implications for New Zealand of various climate change policy options. The energy and agriculture sectors are modeled in a detailed manner to enable realistic simulations to be carried out.Choosing an optimal set of policies is made more difficult by the fact that New Zealand relies heavily on emission intensive sectors for much of its export earnings. For example, one emission intensive sector alone, dairy, accounts for over 20 per cent of all merchandise exports. Avoiding carbon leakage is therefore an important consideration in selecting appropriate greenhouse policies.Our analysis shows the degree of sectoral adjustment required is substantial. In addition, the total costs depend on the uncertain level of variables such as the global carbon price and the level of afforestation activities in New Zealand, ie the rate of new forest planting.

Jan 1, 2002

Six pioneers of the American mining industry will be inducted into the National Mining Hall of Fame on Saturday, Sept. 13, at the Museum Convention Center in Leadville, CO. The 16th annual Mining Hall of Fame induction banquet will begin with a reception and open house at 5:30p.m., followed by the dinner and program at 7 p.m. The six inductees include James M. Gerstley, the only living member, and George O. Argall, Jr.; John F. “Leadville Johnny” Campion; Charles R. Nailler; Edwin N. Pennebaker and Russell L. Wood.

Jan 1, 2003

By Peter Moser, Frank Chiapetta, Sacha Diaj, Florian Bauer

Good toe breakage and a flat working bench after blasting are important parameters to achieve a high productivity during material loading and reduce the necessity for secondary blasting. Good toe breakage requires a proper burden – side spacing design and a suitable sub-drilling. With unfavourable jointed rock mass conditions the use of horizontal bottom holes still can be found as common work practice even that this is associated to high risks.

Jan 1, 2009

By J. H. Potgieter

The method used to assess the reactivity of lime was evaluated to gauge it usefulness as a quality control tool. The effect of particle sizes, different lime and water masses for a fixed s:l ratio and the same for various s:l ratios on the reactivity values obtained, were investigated. An attempt to introduce the amount of grit produced during the slaking reaction as an additional measure of limeís quality and reactivity, proved to be unsuccessful. It was also found that the relative amount of lime slaked during the different tests was independent of the reactivity value of the lime. The investigation confirmed the usefulness of the accepted test procedure as are liable method to measure the reactivity of lime, despite various reservations expressed from a theoretical point of view.

Jan 1, 2002

A new system for granting access to mineral rights is proposed in the recently released White Paper, ?A Minerals and Mining Policy for South Africa?. Official policy states that ?Government?s long-term objective is for all mineral rights to vest in the State for the benefit of and on behalf of all the people of South Africa?. In order to achieve this objective, government is presently investigating the feasibility of imposing a financial or tax-related disincentive to holding mineral rights. The paper aims to present the pros and cons and to examine the alternatives which will cause minimal disruption to the minerals industry in the period during which mineral rights are transferred to the State. South Africa is a country whose economic and political history is embedded in the development of its mineral resources and has inherited a system which cannot simply be wished away. Hasty or radical decisions will compound the problem, rather than provide a lasting and widely acceptable solution. Mineral rights ownership and its impact on access to mineral deposits are discussed. Taxation as a possible economic disincentive is also evaluated. Finally, the value of mineral resource related information as a prerequisite to mineral policy decisions and as an alternative to mineral rights taxation is emphasized.

Jan 1, 1999

By H. Simonsen

Risk assessment consists of a search for the answers to: ?What can happen? ?How likely it is that it can happen? ?What are the consequences if it does happen? Perhaps the most important aim of risk analysis is to predict the likelihood that a planned profit will be achieved over a given period of time. A typical risk model employed for this purpose includes a stochastic connection between the dependent variable of an expression that describes a process and independent variables represented as random quantities. The output will be a probabilistic distribution. The uncertainties in a planned mining operation include: ?Commodity market characteristics, particularly price ?Ore reserves and mineralogical composition ?Mining method ?Process performance ?Capital and operating costs ?Schedule duration ?Economic environment effects. The processes employed in the probabilistic estimation of a project?s outcome include both Monte Carlo simulations and simulations where variable correlation is considered important. The risk model, once developed and tested, provides a framework for a rational approach to risk analysis and the testing of alternatives.

Jan 1, 1999

By J. Bongardt

Ecologically acceptable techniques are described for the handling of waste materials from the fabrication industry. New production methods and the recycling of sludges from grinding and other waste materials are suggested.

Jan 1, 1997

By J. S. Harington

Our purpose is to record and to explain the widely changing numbers of the huge total of black workers on the gold mines of South Africa over the century from 1896 to 1996. These men were recruited from up to twenty territories, and their contributions are examined. The major areas providing labour over this long period have been Lesotho, the former Transkei within South Africa and Mozambique. From 1989 to 1996, for instance, these three areas accounted for over sixty per cent of the total labour force (tlf). Our principal Figure 1 shows the tlf fluctuating through time to reach a peak of 480 000 in 1988. Irregular falls are also documented with the most serious in 1995 to 180 000. Based on this graph we consider the political, economic, sociological and historical reasons behind these changing employment opportunities. These have included external world-scale events such as war or depression, as well as internal changes of national economy and policy. We show the importance for numbers employed of the discovery of gold in the Orange Free State in 1946, the influence generally of the ?Winds of Change? and the firm maintenance by the State of law and order. Varying gold production costs and profitability against high tax rates, allied with increasing wages and a lack of development capital, have led in the last decade to employment falling by fifty per cent, despite an actually higher value of gold output. Finally, this analysis considers the role of the migrant labour system as it affects, and is affected by, conditions in the gold mining industry, with special reference to its less than humane consequences in the numerically dominant territories of Lesotho and Transkei.

Jan 1, 2004

By G. G. Campbell

Bureau of Mines research to develop an in situ retorting recovery method for oil shale has involved field testing of fracturing techniques for creating fluid-flow paths in impermeable oil shale. Electrolinking, hydraulic fracturing without and with sand propping, and explosive fracturing with a liquid explosive were tested in a 25-ft-square, five-spot pattern. These wells were drilled into oil shale at 50-to 88-ft depths near Rock Springs, Wyo. Results of the fracturing tests were evaluated by injecting air into a test well and measuring flow rates and flow profiles in adjacent test wells before and after each test. To identify points of air entry (location of fractures) in wells, flow profiles were determined by use of inflatable packers and by continuous logging with an airflow probe developed during the fracturing program. Electrolinking and hydraulic fracturing without sand propping were relatively ineffective; hydraulic fracturing with sand propping created horizontal fractures with desirable flow capacity; and fracture flow capacity was significantly increased by detonation of nitro-glycerin displaced in the natural and hydraulically induced fracture systems.

Jan 1, 1970