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By Gerald V. Jergensen, Edward J. Samuel

Slurry system are the principal method for storage and transportation of solids within and between concentration operations In a mineral processing plant. A slurry 1s a mixture of solid particles In water, or a chemical solution, that behaves like a liquid. The design of slurry transportation systems is generally analagous to pumping and piping water, but with a few notable exceptions: • The interaction of particle on particle affects slurry transport. • Particles often interact with the fluid, particularly when chemicals have been added to the system. • Particles have a frustrating tendency to settle from the slurry suspension, especially into locations not considered In the design. • Solids have an affinity for wetted surf aces and tend to wear them away. Slurry transportation systems Include a number of separate components, each requiring special design considerations. A systematic evaluation of each component of a slurry transfer system will help overlooking the small details that could cause operational headaches. Most slurry transport systems include: • A receiving sump or tank that provides for mixing and/or momentary storage of slurry. • A driving force.. by a pump, atmospheric pressure or gravity. • A suitable conduit for transportation.. pipes or launders. • A delivery objective.. another sump or process vessel, or distribution system to several process points. • A control strategy and design to regulate the transfer operation. The design of the slurry transportation system normally evolves through the following steps: • Finalizing the process flowsheet and establishing the weights and volumes to be handled. • Identifying and characterizing the various process fluids and slurries. • Defining critical and minimum transport velocities of fluids. • Selecting a pipe diameter (or dimensions and gradient) and

Jan 1, 1986

By Christopher J. Hall

It has been known for a long time that summing pressure drops and rises due to friction, shock, fans and natural ventilation is incorrect. In fact, lost works and works should be summed. In spite of this, the traditional method of finding a fan/system operating position has been the H/Q Curve. This paper presents (lost) work/m curves, progressing from a single fan moved around the system to include natural ventilation work, and fans in a series, parallel and series/parallel. The solutions obtained graphically are substantiated by dry air thermodynamic solutions, and the traditional solutions are shown to be in error. This method of solving problems is particularly useful when moving fans around the system, and essential in series/parallel and series situations with substantially different fan densities. The dry air analysis is employed because of its simplicity. Real air, with evaporation and condensation, will react somewhat differently, and one should use real densities (i.e.[l + w +w]/va ) when using this method. One source of error when applying this method to real air, although probably not major, will be investigated in a subsequent paper. Friction and shock losses are proportional to the square of the mass rate of flow, leading to the typical parabolic system curve. However, the unbalanced water stuff potential energy term, on a unit mass basis, is substantially independent of the mass rate of flow. It is possible that this could be handled as a negative natural ventilation work.

Jan 1, 1987

Some basic terms used in cost management and accounting include: - Cost. A sacrifice made to acquire goods or services, measured by the price paid. Technically, the sacrifice is called a cost until the benefits from the goods or services have expired, at which time the sacrifice is called an expense. In this text, the terms "cost" and "expense" are used interchangeably. - Revenue. An increase in the value of the firm resulting from the sales of goods and services. - Income. The excess of revenues over costs for a specified period. The term is often used with modifiers to indicate specific quantities on an income statement (e.g., pretax income; net income). - Activity. A measure of production work. Traditionally, physical production volume (tons of ore or units of product) has been used as the measure of activity. Other measures include direct labor hours, equipment operating hours, and quantity of materials or supplies consumed. - Responsibility center. A segment of an organization that is responsible for a specified set of activities. In mining, individual operating divisions can be treated as responsibility centers, known as profit or cost centers. Departments within a division are generally treated as cost centers. - Cost center. A portion of an organization having responsibility for achieving specified levels of cost. - Profit center. A portion of an organization having responsibility for achieving specified levels of profit (revenues and costs).

Jan 1, 1999

By H. Janas

In a gas/coal outburst the gas plays an active, driving part. The proneness of coal to outbursts can be determined by means of its gas emission properties, since coal that is liable to outbursts differs from coal with normal gas emission properties in that it liberates its gas from the sorptive bond more quickly. There is a risk of outburst when the flow of metha¬ne originally desorbed by the coal is sufficient to move the loosened coal which has been broken suddenly. The violence of a gas/coal outburst can be evaluated from the distance of projection of the mass of coal. It depends on the gas pressure and on the liability to outburst of the coal at the original centre of the outburst. Both factors are complementary in their effects so that the same work is done in a gas/coal outburst when there is a high gas pressure and low proneness to outburst as when there is a low gas pressure and a higher proneness to outburst. The gas pressure in the coal increases with its gas content. Consequently it is possible to deduce the gas pressure of a coal seam from its gas content. In the Federal Republic of Germany the risk of a gas/coal outburst is thought to exist when the desorbable gas content of the coal reaches or exceeds the value of 9 m3/ton and if the specific limit value of the proneness to outburst is exeeded. The Mine Ventilation Testing Station of the Westfalische Berggewerkschaftskasse has developed a new method for determining the risk of gas outbursts immediately after taking the samples at the coal face (1), (2).

Jan 1, 1980

By Bekta? Uz

Istanbul is the bigest metropolitan city of Turkey with more than 15 millions of population and construction activities are steadly increasing with respect to that increase in population. In this papaer petrographical, physico-mechanical properties of natural aggregate mines from west, (Tekirdag) to East, Izmit (Gebze) 'will be summarized in connection with the concrete production. However the locations suitable for aggregate production in these area as; Paleozoic aged sandstones (Ayazaga, Cendere, Mahmutbey areas), Permb-Carboniferous aged limestones (Cebeciköy area), Triassic limes tones (Ömerli-Gebze areas) and Eosen limestones (Çatalca area), Plio-Quaternary aged volcanic basalts (Tekirdag, Çorlu, Beykoz areas). Plio-quaternary aged, fine grained aggregates within sandy formations are mined in Silivri-Sinekli area, Catalca-Ormanali area, Agacli-Akpinar (Kemerburgaz area) and Sile-Karakiraz-Sahilköy areas. Sandstones mineralogically contain mainly of Quartz+Feldspar and less amount of Mica (biotite+muscovite) rich with slica content and sedimentary origined. Especially limestones are cryptocrystaline textured, unique mineral composed of calcite and secondary have Dolomite ± (Quartz+Albite). Basalts are microlitic textured and contain Olivine+Pyroxene+Plagioclase. Chemically basalts rich with Fe and Mg and also volcanic origined. Sands are fine grained natural aggregates mainly contain semiangled, rounded minerals and rock fragments. Mineralogically have Quartz + Feldspar ± pyroxene+ ambhibole ±garnet and less amount of epidote ± magnetite ± hematite. Different rocks, used in aggregates such as limestones, sandstones-sands and basalts, supply varied concrete strength because of their mineralogical composition and characteristics of textures. Moreover, Basalts (Karatepe area) are good example for the higgest concrete strength (1017-1895 sc; kg/cm2) in our study area because of their clambed mineralogical apperance such as intersertal texture. As the result of extensive field and comparative laboratuary studies, the effect of petrographic, physical, mechanical properties of the aggregates on concrete srtength is extensivelly discussed in this paper.

Jan 1, 2005

By G. Vik, P. Chryssanthakis, S. C. Bandis, L. Haruik, N. Barton, M. Christianson, A. Makurat

The large jointed chalk reservoir situated at 3 km depth in the North sea's Ekofisk field is undergoing major compaction after nearly 15 year of oil and gas production. Approximately 150 km 3 of the overlying sediments, mostly shales, are involved in the subsidence. A maximum central subsidence of nearly 3 meters, and a maximum present rate of 45 cm per year has set in motion numerous studies of the phenomenon. Non-linear finite element (FEM) and non- linear distict element (DEM) analyses of the compaction and large scale subsidence were performed. Consistent differences between the continuum and discontinuum analyses were noted. In the latter, slip on hypothetical bedding planes and sub- vertical or vertical faults was allowed, which possibly gives a more realistic simulation of the real processes of subsidence in such a large body of rock. Laboratory studies of the reservoir joints included roughness measurement, JRC and JCS characterization, direct shear tests while saturated in heated Ekofisk oil, and coupled closure-shear-flow tests with heated oil followed by heated sea water. Discontinuum modelling using Cundall's UDEC was performed on representative jointed assemblies (two sets of steeply dipping conjugate joints) to investigate the effect of a major reduction of pore pressure within the deformable matrix and along each joint. It was found that the large shrinkage deformation of the matrix allowed joint shearing to occur despite the constraint of uniaxial strain. Relative mass bulking due to small but widely distributed joint shear possibly explains the observed maintenance of excellent productivity despite large vertical strains in the reservoir.

Jan 1, 1986

By Robert A. Jankowski, Charles A. Babbitt, Natesa I. Jayaraman

The U. S. Bureau of Mines, through a contract research program with Foster-Miller, Inc., has identified guidelines for the selection of the most effective water spray system and water flow rates for use on continuous mining machines. Specifically, these parameters were modified to obtain maximum dust control with regard to quartz dust exposure and more stringent respirable dust standards due to quartz. A novel water spray system, consisting of flat fan spray nozzles, mounted across the top of the mining machine, along with high flow, flat fan and higher pressure hollow cone nozzles mounted under the boom has been identified and tested. The anti-rollback/underboom spray system minimizes dust rollback while increasing dust knockdown by its unique positioning of spray manifolds and orientation of spray nozzles. Respirable dust suppression characteristics of the system acted in three ways: - by wetting the surface of the broken coal material to prevent dust from becoming airborne; - by controlling the airflow pattern at and near the face to minimize dust rollback to the operator Is control location; and - by dust knockdown, i.e., airborne capture, or scrubbing of airborne dust from the air. During underground trials, the anti-rollback/ underboom spray system reduced dust levels at the operator's position and in the immediate return by 55 and 15 pct, respectively, when compared to a conventional spray system. Quartz dust levels at the operator '8 position were essentially eliminated, while quartz dust levels in the immediate return were reduced by 57 pct. Applying the concepts of this technique throughout the mining industry should reduce the health hazard associated with excessive exposure to respirable quartz dust, as well as allow coal mine operators to comply with the associated, more stringent, respirable dust standards.

Jan 1, 1987

By V. C. Rogers, K. K. Nielson

INTRODUCTION The potential health impact from uranium milling operations is mainly associated with long-term releases of radioactive contaminants from the mill tailings.(1,2) The major mechanisms for mitigating these potential releases focus on increasing the tailings containment with the addition of migration barriers such as thick earthen covers and clay liners. Some limited investigation has also focused on reducing the radionuclide source terms. This alternative approach has some desirable features, but stringent cost requirements are placed upon source removal methods in order for them to be economically favorable. A cost effectiveness evaluation is presented herein, in which costs for containment methods are used to establish maximum cost guidelines for the source removal methods. The 230U decay chain, shown in Figure 1 contains the radioisotopes of major concern, 230Th, 226Ra, 222Rn and its short-lived alpha-emitting daughters, When the uranium is removed in the milling process, these isotopes, which are normally not removed remain in the tailings solids. The general pathways to the environment from uranium mill tailings are depicted in Figure 2. The dominant pathways are radon to the atmosphere and radium and thorium to a groundwater aquifer. The magnitude of the contaminants released into these pathways can be characterized by the following parameters: 1. The 230Th and 226Ra content. 2. The emanating power for radon. The fraction of radon generated that is free to migrate. 3. The leach rates. Source reduction methods seek to reduce the magnitude of any or all of these parameters. In general the dose rates are proportional to the source terms. For radon production the source term is proportional to the product of the radium concentration, R, and the emanating power, E, so that the risk is reduced by the same factor that reduces RE. For example, if the radium content is reduced by 95 percent, but E is increased by a factor of two, then the dose rates are reduced by an order of magnitude. The source term for the groundwater pathway is not as easy to identify. The peak in the radium concentrations in the accessable water body can also

Jan 1, 1981

By John Reilly

"INTRODUCTION Successful management of megaprojects, meaning delivery within budget, on time and according to expectations, is a fundamental requirement. Many projects have been successful, some have not. This paper reviews megaprojects1, drawn from the author’s projects over the last 50 years, with “lessons-learned” and a summary of recommendations that, if implemented, would improve megaproject management and delivery. Characteristics of these projects are summarized – including outcomes related to key factors such as politics, management, organizational structure, contracting methods, cost estimates, risk and other elements. The projects include the Washington D.C. Metro, Boston Southwest Corridor, LA Metro, Toronto Rapid Transit Expansion Program, BART San Francisco, MARTA Atlanta, London Underground and the Washington State Highway megaprojects – including the SR520 Floating Bridge and the Alaskan Way tunnel. Other projects that illustrate successful, innovative management and contracting methods include the Madrid Metro (low-cost delivery), the Sydney Northside Storage tunnel (outturn cost, alliancing) and the Lake Mead tunnel (working in partnership, risk management). KEY ISSUES A characteristic of megaprojects is that their complexity increases exponentially with size (Reilly 2010, Galloway et al. 2012). These projects are very visible politically, have many stakeholders who must be satisfied and generally span many years and political election cycles. To be successful they must meet expectations, function efficiently, and be delivered under, at or close to budget and schedule. There is a widely-based perception that large, complex projects are always delivered late, over budget and with problems. Specific examples include projects such as Tren Urbano in Puerto Rico – $1.28 billion over initial budget (+133%), the Silver Line Transitway Project in Boston – $286 million over budget (+90%), the London Jubilee Line Transit Project – 2 years late and £1.4 billion (+67%) over budget, the Channel Tunnel Rail Project – £3.7 billion (+80%) over budget, Denmark’s Great Belt Link rail and road link (54% over budget), the 2003 Woodrow Wilson bridge tender in Virginia (72% over estimate) and Boston’s Central Artery Project – several billion (perhaps 100%) over what would have been a realistic initial budget and years late (Reilly 2001c, 2004a; Salvucci 2003)."

Jan 1, 2016

By Eung Ha Cho, Olufemi Olajide

A laboratory study of dense-medium cycloning with Redstone seam coal has been conducted. The investigation was performed using a 203 mm (8 inch) Heyl-Patterson dense-medium cyclone. Two underflow orifices of 31.8 mm (1.25 inch) and 44.5 mm (1.75 inch) in diam were used. The effects of feed pressure and particle size were determined on the cycloning performance. In addition, the cyclone performances with coal-rich and refuse-rich samples were also investigated. The results of the experiments were analyzed using basic hydrodynamic principles. The increase in the feed pressure increases the specific gravity of separation (defined as the specific gravity of a particle which has an equal chance of reporting to either the overflow or underfow) for both underfow orifices. The specific gravity of separation increases as the particle size decreases with the smaller underflow orifice. However, an opposite relationship has been observed with the larger under flow orifice. The separation becomes sharper with the smaller under flow orifice than with the larger underflow orifice especially for fine material. Also, the separation becomes sharper with an increased feed pressure for a coal-rich sample. However, this effect is less significant for a refuse-rich sample. This means that a high feed pressure is required for a coal-rich sample to maintain a good separation. It also means that applying a high feed pressure provides a good separation regardless of the type of feed coal in terms of ash content in the solid.

Jan 1, 1990

By C. Garcia, C. L. Lin

Characterization and analysis of multiphase particles and/or particulate systems (such as the packed particle bed) are of great technological importance for mineral processing applications. In general the performance of these applications depends on the statistical characteristics of particle microstructures, such as composition distribution, surface exposure of mineral grains, pore network structure, etc. For continued technological progress in the field of multiphase particulate processes, the need for quantitative spatial analysis of multiphase particles in three dimensions has increased sign6cantly. Such quantitative information must be accurate enough that the measured values can be used as parameters for simulation models, process design procedures, and control strategies. Modern 3D image-acquisition techniques, such as X-ray microtomography (XMT), offer a unique imaging capability that can produce high-resolution (a few micrometers) three-dimensional images of the internal structure of multiphase particulate samples. These three-dimensional image data present new challenges for image analysis, image processing, and visualization. Furthermore, important issues should focus on how to use the 3D information and derive new insights into the improvement, design, and operation of mineral processing processes. In this paper, utilization of XMT for characterization and analysis of leaching process involving multiphase particulate system is discussed.

Jan 1, 2005

By L. F. Barrett, D. E. Cameron, J. C. Wilson

Exploration by Anaconda Minerals Co. in the Rico area from 1978 through 1983 resulted in dis¬covery of the Silver Creek molybdenum deposit. The drill-indicated resource is 40 Mt (44 million st) of 0.31% Mo, and projections suggest that the deposit may exceed 182 Mt (200 million st). No source intrusion has been intersected by drilling, but its presence is sugested by intramineral silicic alkali-alaskite porphyry dikes observed at the surface and in drill holes. Age dates and fluid inclusion studies indicate that the deposit was formed 5.2 ± 0.2 m.y. ago and that more than 1200 (3937 ft) of cover has since been removed by erosion. The deposit is hosted by Precambrian quartzite and greenstone, and Paleozoic sediments. Three prominent faults intersect in the vicinity of the molybdenum deposit, and one of these, the Last Chance fault, strongly influenced the shape and location of the deposit. The juxtaposition of host rocks across the Last Chance fault reflects significant offset spanning at least three different periods. Wallrock alteration associated with the deposit includes potassic, phyllic, and propylitic zones in noncalcareous rocks and garnet and anhydrite-diopside zones in the carbonates. All +0.2% Mo mineralization is within the potassic and garnet zones. Premineral faults that intersect the deposit contain the only surface molybdenum, tungsten, and fluorine anomalies. Dispersion halos of the indicator elements were defined by drilling in the discovery phase of exploration, and are particularly well-developed in the hanging wall of the Last Chance fault.

Jan 1, 1987

In 1991, most industrialized countries, except for Germany, were in a recession or a period of reduced growth. The US economy, already in recession, suffered from mounting banking system losses and the uncertainty brought about by the Persian Gulf War. However, US and worldwide minerals exploration did not collapse as it did during the mid-1980s. Even though gold and base metal prices declined, prices were still above cash costs for most operations. This allowed the continuation of established exploration programs but sharply limited new initiatives. Exploration 1990-1991 Planned worldwide 1991 exploration expenditures declined by about 8% from 1990 levels, according to a survey of 153 companies by the Metals Economic Group (MEG). Canada was the leading exploration target with 23% of the total, followed by Australia and the US (19% each), South Africa (13%), Latin America (11%) and the South Pacific (7%). The remaining 8% was split evenly between Europe and the rest of Africa. In Latin America, Mexico and Chile are the most attractive countries for exploration. Recognizing the risks involved, the industry has been cautious about ventures in the former Soviet Union. Survey results also showed that while the majors expected to maintain exploration spending, smaller firms were cutting back or actively seeking farm-outs from the majors (personal communication, M. Wegener, MEG).

Jan 1, 1992

By Preusse. Axel

Underground coal mining can cause seismic events. There is currently no way to predict such phenomena reliably, in particular stronger events. That is why, according to the current state of the art, empirical methods are employed in this field. Some assessment criteria, which relate to the geological and mining situation and either stimulate or rather help to avoid seismic events, are presented in this paper. These criteria are examined for a practical mining situation in Germany, with a view to estimate possible seismic events.

Jan 1, 2009

By R. M. Clowes

LITHOPROBE is a collaborative, multidisciplinary research project that is providing new insights into the tectonic evolution of the North American continent through its work within 10 study areas across Canada. For the mining industry, such results provide a well-constrained regional framework and better understanding of the tectonic processes that lead to the development of ore deposits. In mining camps, seismic-reflection methods have proven effective in imaging shallow to moderately dipping lithologic contacts as well as structural features and, in some cases, have been used for the direct detection of orebodies. Here, short case histories are provided for the Abitibi greenstone belt (VMS deposits) in Quebec and the Thompson nickel belt in Manitoba.

Jan 1, 2002

By J. Georgi

A number of infrastructure projects are on progress all around Greece at the moment. The common propose of these a project is the promotion of quality in: Design, construction and maintenance stages. They also comply with environmental management, which is, a method of organizing and implementing environmental protection measures. The paper includes by special reference on two important modern transport infrastructure projects for the development of Greece and its communication with Europe and the Balkans. Their landscape types and natural vegetation, local climate, geological conditions, altitudes, aspects and soil types vary As a result, upland landscapes in particular, are endangered. Due to the complex of nature of this environment, the development and the landscape design of the projects is a high challenging task. Wherever the nature of the projects requires intervention to the environment, they intend to follow the direct restoration of landscape and method for ecological balance. The implementation of landscape design of infrastructure projects, aims at restoring the landscape affected by construction works, incorporating transport works into the landscape, emphasizing on areas of particular interest (e.g. archaeological sites), while at the same time observing the principles of an efficient operation and safe use of the alignment. Landscape design provides, among others for the protection of slopes against surface erosion and the reinforcement of their stability, the improvement of road functionality, the aesthetic improvement of the landscape, adaptation of the road landscape to the greater environment, visual guidance of the user, screening of lights of the vehicles moving in the opposite direction, the protection against wind etc. The landscape design strategy and landscape applications are specified by special landscape guidelines and specifications that can be considered as part of the sustainable development of a alignment creating a high a esthetic scenery, ensuring the security of transportation and the environmental protection.

Jan 1, 2002

By Victor F. Hollister

Porphyry copper deposits can be categorized into three models for purposes of prospect evaluation: Breccia-pipe, modified Lowell and Guilbert, and diorite models. The modified Lowell and Guilbert model is normally associated with a quartz-bearing intrusive and a potassic, phyllic, argillic, and propylitic alteration sequence. Variations can occur in the alteration zones of this model that range from orthoclase-rich (Kalamazoo, Silver Bell, and Mineral Park) to ortho- clase-deficient (Petaquilla and Bougainville) potassic zones. The unifying features of the model are the presence of a phyllic zone and a quartz-bearing intrusion. The breccia-pipe model (Toquepala) is characterized by structure and alteration related to or controlled by breccia. Where tourmaline occurs in the breccia, the identity of the model is usually clear. However, if tourmaline is not commonly developed in the breccia (La Caridad), the deposit can be misidentified as to model. Porphyry copper deposits associated with quartz-deficient intrusives, whether these are calc-alkalic diorites or alkalic plutons, are characterized by alteration suites distinct from those of the modified Lowell and Guilbert model. These have been generalized as diorite model porphyry deposits. Because alteration and mineralogical development in diorite model deposits is distinct from that of the modified Lowell and Guilbert, ore guides and exploration tactics differ for the two models. The reprint that follows describing the three prospecting models summarizes their features. It is to be emphasized that these are models used in exploration for specific deposit types and are not genetic, tectonic, or geographic models. Porphyry copper deposits can be metamorphosed. Gibralter is an example of a Lowell and Guilbert model deposit that has undergone regional metamorphism.

Jan 1, 1991

By W. A. Hustrulid

Introduction A problem that has faced mining engineers and mining geologists for many years is how to best explore a particular prospect so that the basic decision as to whether the material present is ore or only high-grade rock can be made with some confidence. It is obvious that one could not begin a large scale mining program on the basis of tests made on a few hand samples. On the other hand, one could not be 100 percent certain as to the average grade or tonnage before beginning development, as this would require the orebody to be mined out in the sampling process. The basic objectives of the exploration program can be stated as (1) to reduce mining risk; (2) to lessen the cost of development; and (3) to increase the profits of mining. The exploration program should be terminated when these objectives are no longer being met. The construction of tunnels is a specific mining operation. In the exploration program one should gather the data needed to determine (1) the type of excavation technique(s) to be used; and (2) the rate of advance that might be expected. As in the evaluation of an orebody, with the data collected it should be possible to estimate mining costs and project life. Unfortunately, at the present time, it is not possible to do this at least when dealing with medium to hard rock types. The reason for this, it is felt, is basically the inability to identify what specific rock mass properties are of use in tunnel design and to specify how these may be obtained in an exploration program. In short, the exploration program should be designed to give information regarding both the volume (length) and 'grade' (in

Jan 1, 1997

By K. Norrena, E. Magri

An important problem in mine operations is the classification of material as waste, low-grade stockpile and ore. This classification must often be made with blasthole data that are widely spaced and that have sampling errors. Geostatistical-simulation techniques combined with basic economic principles allow a procedure for classification that maximizes the expected profit. Geostatistical-simulation methods (Gaussian, indicator or annealing-based) allow the integration of hard and soft data in the creation of alternative, equally probable realizations of the mineral grades. At each location, for each realization one calculates the "profit" if the block were to be classified as ore or waste. The optimal classification is the one that maximizes expected profit (a maximum profit selec¬tion or MPS procedure). In this paper, the authors discuss the theoretical justification of the method and implementation details. The use of blasthole data from different types of mineral deposits, that is, different levels of continuity, are considered. The authors also show the efficacy of the procedure with different levels of sampling error. The increased revenue due to the MPS procedure and improved sampling is shown. The paper shows the geostatistical-simulation procedure and the uncertainty in block grades that result from incomplete and imperfect sampling. The optimal classification is presented. Optimal block classifications are transferred to realizable dig limits by hand-drawing polygonal boundaries. The results of the proposed method are compared to classification based on kriging. Limitations and areas of future work are identified.

Jan 1, 2000

By J. H. Calder, J. C. Hower

Three lithotypes of Phalen coal from Cape Breton County, Nova Scotia, Canada, were subjected to a modified Hardgrove grindability index (HGI) test. The testing scheme differed from conventional (ASTM D-409) Hardgrove testing by, in one case, repeating the test three times prior to removing the -200-mesh fine coal from the Hardgrove mill, and, in a second test, removing fines after each of three successive Hardgrove tests. Only the first stage of the latter testing scheme actually conforms to the standard HGI test. All processed samples were analyzed petrographically by a combined maceral/microlithotype analysis. The increase in the percentage of coal ground to -200 mesh increases through the 60- to 180-mesh fractions for each of the lithotypes for the following two apparent reasons. First, with progressive grinding, more of the oversize material is close to 200 mesh (75 µm), creating a "pool" of particles ready to be ground to -200 mesh, and, second, the removal of fines from the system at each step eases the grinding at the successive step. The fines retained system shows the influence of buffering of further grinding by the particles retained in the grinding mill. The Phalen lithotypes and the series of Central Appalachian coals, evaluated previously by Hower and Wild (1994), differ in that an increase in vitrite and a decrease in trimacerite is observed in successive -200-mesh fractions in two of the Phalen lithotypes. This is the opposite of the trend observed in the slightly lower-rank Central Appalachian coals.

Jan 1, 1998