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By Joseph T. Matoney, Okley B. Bucklen, Claude A. Goode, Philip G. Meikle

INRTODUCTION Annual coal production rose to over 1.03 billion st (931 Mt) in 1990. At the same time the number of mines producing this increased tonnage has decreased over 60% in a 30-year period, from 9230 mines in 1960.1 The great increase in production made possible through continued mechanization requires greatly improved loading facilities just to get coal away from the mine. Also the trend to combine production from more than one mine and cleaning it in a single preparation plant continues. A recent census of US coal preparation plants indicated that 310 plants were in operation.2 In addition to increased loading capacity, storage and blending facilities are more necessary both at the producer and user end. In this climate of rapidly changing technology, any written account is faced with the possibility of obsolescence before its appearance. Thus, this chapter seeks to define the common and current practice in coal loading and storage facilities with the full knowledge that this practice is an ever-moving target. FUNDAMENTALS OF COAL STORAGE Storage of coal is becoming an increasingly important part of coal handling systems at mines, particularly since the advent of the unit-train concept in transportation. In order to take advantage of reduced transportation rates on trainload shipments of coal offered by unit-train movement, operators have found that storage is an economic necessity. In unit-train practice, large predetermined quantities must be loaded in relatively short periods of time, as opposed to conventional practice where coal is loaded at a speed dependent on the production capacity of the mine and/or the cleaning capacity of the preparation plant. Clean coal storage is generally practiced in order to accomplish one, or a combination, of the following objectives: 1. To load out promptly and economically. 2. To facilitate blending in order to even out chemical and physical inconsistencies and to prepare desired products or to attain maximum product uniformity. 3. To store certain sizes whose prices and market demand fluctuate with seasons and to permit shipping in good weather. Coal storage, then, is necessary and desirable, both from production and utilization standpoints. There are, however, several undesirable aspects attendant to the storage of coal, the most important of which are oxidation and spontaneous combustion, changes in properties which may affect utilization of the coal, degradation of coal due to rehandling, and the added cost of handling and storage facilities.

Jan 1, 1991

By Rodolfo V. de la Cruz

The broad front concept is based on the principle that gasification can be achieved more efficiently and completely from a plane broad combustion front in contrast to other geometries obtainable with current methods of gasification. By restricting combustion to a plane broad front, the ideal condition for gasification is achieved. A plane broad combustion front can be developed in coal by initiating and propagating combustion from the walls of an oriented channel and collecting product gases from another similarly oriented channel. Flow will then be directed along the highest permeability of the coal bed, the available cross-sectional area for fluid flow is substantially increased and, more importantly, the increased flow will be uniformly distributed throughout the whole mass of coal. The success of the method is greatly dependent on how well an initial and rigorous permeability survey and associated corrective measures yield a well-characterized coal bed. To maintain uniform reaction rates, the advance of the combustion front is located with pressure- or mass flow-transducers. These sensors are then connected to servo-controlled mufflers for controlling segments of the fire front which are advancing ahead of others. Finally, the development of the concept to overcome problems of roof collapse, reactant and product gas leakages, and water invasion are briefly summarized.

Jan 1, 1976

By Keith Whitworth

The USSR, over the last 20 years, has continued to increase its out-put year by year and it is now almost four times what it was at the end of the Second World War. In 1975, it exceeded 700 million tons of run-oi-mine coal (all ranks) which amounts to over 20 percent of world output. This rapid progress has been due to modernization of the industry, by means of increased mechanization and automation and the development of new machines and systems for underground workings and by the expansion of open-pit workings and the development and implementation of larger earthmoving machines.

Jan 1, 1977

By J. Diao

In order to understand the flotation kinetic behavior of coal and associated mineral matter, a detailed investigation was conducted in a 2-liter Denver flotation cell using three high sulfur coals at three feed sizes, minus 28. 100 and 200 mesh. Subsequently. the flotation products were sieved into different size fractions and analyzed for their ash and pyritic sulfur content in order to delineate the effect of particle size on the rate at which each constituent floats. The results were tested with several different flotation kinetic models and the best model for coal was then chosen. The flotation rate constant and the ultimate recovery calculated from a kinetic model were used to delineate the effect of particle size, collector (dodecane) and frother (MIBC) dosages on the flotation kinetics of coal, ash and pyrite.

Jan 1, 1992

By L. B. Sand

Zeolite ores and protores occur in extensive deposits in the western United States. A recent paper1 describes the general geology and mineralogy of these deposits and their geographical distribution. The zeolites are alkali-and silica-rich varieties of mordenite, erionite, chabazite, phillipsite, ferrierite, and clinoptilolite. The zeolites were formed primarily by the alteration of Tertiary pyroclastics and in some cases by the alteration of Tertiary siliceous flows. The altered pyroclastics are of principal economic significance. The volcanic ash and tuff were deposited in restricted basins where saline lakes developed. The pyroclastic layers often are of uniform thickness and macrotexture for miles from the center of the basin and interfinger with detritals toward the edge of the basin. Thus, in addition to unaltered volcanic glass, the gangue minerals in these deposits include some combination of primary minerals in the pyroclastics, alteration products of the glass other than the zeolite of interest, and detrital minerals. The gangue minerals include quartz, cristobalite, tridymite, opal, orthoclase, micro cline, montmorillonite, hornblende, calcite, gypsum, thenardite, and iron oxides. The presence of one or two other zeolites in the layer in some cases also is considered as gangue. There are no quantitative mineralogical descriptions of these deposits in the literature; this: study was undertaken to obtain this information. As the zeolites occur as single crystals, crystal aggregates, zeolite-glass particles and in cemented aggregates, a method of study was chosen which would give the size distribution of the zeolite in these types of association. For this reason dispersion of the rock was achieved with a minimum of grinding action. This excluded those zeolite ores, silicified by hydrothermal altera¬tion which require grinding. A relative index of the ease of disaggregation of the zeolite ores thus is obtained, but the technique does not give absolute size distributions of the zeolite crystals. Samples were selected for analysis which do not necessarily represent the best ore horizon, but do represent a spectrum of zeolite occurrences from significant deposits. They are mordenite, erionite, and phillipsite from Rome, Oregon, clinoptilolite and chabazite from Reese River, Nevada, chabazite (and var. herschelite) from Bowie, Arizona, erionite from Jersey Valley, Nevada, and erionite from Pine Valley, Navada.

Jan 1, 1967

By Edwin S. Smith

One of the many responsibilities of mining engineers and mill superintendents is to provide for the safe and economic disposal of wastes (or tailings) remaining after a mineral has been extracted from an ore. The cost of disposal of these tailings exerts a considerable influence on the minimum grade of ore extracted from the mine. It varies to a great extent with each project and is dependent on many diverse factors, such as the local topographical, meteorolgical, geological and seismological conditions together with the applicable water pollution laws of the area. The process used to extract a mineral from an ore determines the physical characteristics of the tailings and thus is one of the more important factors to be considered when planning disposal facilities. Today's trends .in ore-processing operations complicate the problems of waste disposal: recently developed extraction methods result in the production of finer tailings, the use of lower grade ores produces greater volumes of wastes, while the enhanced land values in the vicinity of industrial plants preclude the former practice of spreading wastes laterally and force the expansion of waste desposits upwards to greater heights. The frequent occurrence of stability problems in waste deposits indicates that many mining organizations may not be employing current soil mechanics concepts and practices. One of the most spectacular, and often most disastrous, types of tailings dike failure is that resulting from liquefaction of the fine particles combined with a breach of the main retaining dike.

Jan 1, 1967

By F. Vallianatos

The main objective of the present investigation is to demonstrate the potential of ERT (Electrical Resistivity Tomography) and HVSR (Horizontal to Vertical Spectral Ratio) methods as geophysical tools for the monitoring of subsurface cavities. The survey sites are located in Akrotirion Peninsula, almost 7 km east of Hania town in Crete Island, Greece. At this site, the surface expression of a known cavity with a diameter of about 25 m is visible. The true geometrical characteristics of the cavity were unknown since there are no boreholes in the area. The focus of this survey was primarily of a qualitative nature and the objective was to determine if ERT and HVSR could be used to identify and map near surface cavities (less than 30 meter in depth) in a limestones kartsic area such as Akrotirion Peninsula. A 2D/3D model of the resistivity distribution is given for the area under investigation. Furthermore, analysis of microtremors data provides a profile of the seismic response of the tectono-karstic voids.

Jan 1, 2006

By H. B. Oblad

Coal/pyrite fines were froth floated in a laboratory cell to examine the rate of pyrite recovery during conventional coal flotation. The effects of collector, particle size and carbon to total sulfur ratio on the kinetics of recovery were investigated. These data coupled with microscopic examination suggest that miniscule amounts of coal that remain attached to the pyrite surface affect the rate of flotation of pyrite.

Jan 1, 1985

By Haydn H. Murray

The area from Ohio on the east, Tennessee on the south, and Minnesota on the west: contains some very unique and useful clay deposits. Included are fireclays and plastic clays in Ohio, Kentucky, Indiana, Illinois, and Missouri; flint clays in Kentucky and Missouri; ball clays in Kentuckv and Tennessee; adsorbent clays (fuller's earth) in Missouri, southern Illinois, and Tennessee; and alluvial clays and shales for structural clay products from every state. Unique kaolin clays are known in Minnesota, Missouri, and southern Illinois and halloy-site localities are known in southern Indiana. The geology, physical properties, and uses or potential uses of these midwestern clays are described.

Jan 1, 1980

By James A. Martin

Evaluation and subsequent development of a quarry in east-central Missouri was based on a general but brief examination of outcrops and core from five (5) test holes. Neither core, outcrops, nor existing quarries in the general area gave any indication of potential major problems. In the third year of operation large areas of collapse rubble, consisting of green shale and large blocks of limestone and sandstone, were encountered. Their size and random distribution resulted in both blasting and quality control problems. By the fourth year of operation, production costs became prohibitive and the site was abandoned. Prior to dismantling the plant a geologic investigation, which included shallow seismic and resistivity surveys, was made of the unmined portion of the lease. The collapse dolines appear to be related to structure and predate development of the modern topography. Surface indications of these features are few. The seismic profiles were especially helpful in plotting their distribution. Geologic relationships and seismic data developed at this site are being related to similar suspect areas in Missouri and have been useful in their evaluation.

Jan 1, 1970

By D. A. Karvonen

Although the economy in the Province of Saskatchewan has historically been agriculturally oriented, a major new source of wealth has been realized through natural resources such as petroleum and natural gas, coal and uranium and since the 1960's - potash. Potash or potassium chloride, in the form in which it is presently produced in Saskatchewan is used primarily as fertilizer, a source of potassium, one of three essential elements required for healthy plant growth with about 5 percent of production sold to the chemical industry for use in such products as soap and liquid detergent, glass and ceramics, textiles and some pharmaceuticals. Saskatchewan is estimated to have approximately 40 percent of known world potash reserves and its ten active mines account for some 25% of annual world production. The development of this resource was recognized to be important to the development of Saskathcewan. In an effort to guarantee a fair and lasting economic benefit to the Province of Saskatchewan the Potash Corporation of Saskatchewan (PCS) was created on February 4, 1975 through an Order-in-Council under the Crown Corporation's Act and later on April 1, 1976, the Potash Corporation Act provided for its continuation. PCS was given the mandate to acquire ownership of a significant portion of the potash mining capacity in Saskatchewan and to establish an organization capable of operating the facilities, marketing the product and conducting all of the other activities necessary for a successful corporation competing in the world potash industry.

Jan 1, 1983

By L. D. Cruz

In Exxon's Los Bronces Expansion Project in Chile, a stochastic simulation is performed to resolve the complex decision problem of matching the mine to mill system capacities from both technical and economic standpoints. The unique combination of weather conditions at the mine and the 30-km belt conveyor network for ore transport to the mill necessitates this analysis in the planning phase to optimize the design capacity of the sys tem. Appropriate statistical distributions of major equipment performance, snow storm duration, power outage, etc, ate developed from actual mine local records and manufacturers specifications. The interactions of operational constraints including ore storage capacities, number and sizes of individual equipment, ore variations, and mine and mill production rates are studied more realistically than in a traditional planning approach. Details of the computer modeling and typical results of simulation studies are discussed.

Jan 1, 1981

By Salim Akhtar

The operation of a mineral processing plant with a complex flowsheet is represented by a mathematical operator. Such a representation permits a quantitative evaluation and monitoring of the separation processes in different sections of a processing plant, and gives an overall separation efficiency of the plant.

Jan 1, 1973

By R. L. Miller

The potential for recovery of enriched uranium from spent nuclear fuel which has been consolidated into a nuclear waste form was explored in the studies reported here. The waste form of interest is iron-enriched basalt (IEB)--a silicate-based, fused-cast ceramic. IEB samples were prepared containing fuel assembly materials that simulate the core debris of Three Mile Island Unit II;1,2 the nominal composition of the consolidated waste form is given in Table 1. Ore Types The IEB samples, or man-made uranium ores (MMUO), are in two different mineralogical forms. Each MU0 was made by melting the constituent materials and holding at about 1500°C for 1 h. The MMUOs were then heat treated to control crystallization and crystal growth and then cooled to room temperature.

Jan 1, 1983

By Byron M. Jones

The use of computers in system analysis is well established. Analog computers have been used for this purpose since about 1940. As the power of digital computers increased and their cost decreased, much of the analysis formerly done by analog computers has been diverted to digital computers. The mathematical foundation for system analysis was laid between the years 1700 and 1900. In the 1930?s, telephone repeater amplifiers were designed using systems analysis techniques. From 1940 to 1960 systems were analyzed using either direct simulation or LaPlace transforms. Since 1960 analytical methods have been expanded to include linear vector space theory. All of these methods are being used to analyze the dynamic behavior of mining machinery.

Jan 1, 1974

By L. J. Jansen

Techniques utilized to incorporate geological data in computer modeling and ore reserve estimation have undergone considerable evolution during the past fifteen years. Computer analysis and evaluation of two precious metal deposits are presented as examples of innovative computer techniques developed at Asarco. The first is a gold deposit occurring in a steeply dipping Pre-Cambrian greenstone sequence. The second is a manto-like manganiferous silver deposit occurring in a relatively flat sequence of Late-Paleozoic sediments. In both deposits, four sub-horizontal zones of geological influence are evaluated.

Jan 1, 1985

By Allan M. Johnson

The Sherwood Mine is being monitored to determine the nature and extent of changes in the mine and its environs which result from the closing and the cessation of pumping. Of particular interest was the possibility of piping-induced subsidence occurring as the mine flooded. Previous experience in the district indicated that this possibility was very real. A monitoring system, including acoustic sensors, extensometers, surface subsidence monuments, and ground water observation wells was installed in July 1978, just prior to the mine closing. Late in 1979, three piping-induced subsidence events occurred. The monitored data, and related laboratory studies are being applied to a quantitative description of piping-induced subsidence.

Jan 1, 1980

By W. C. Carter

In mid 1978 Inland Cement Industries Ltd. brought on-line their new one million megagram (Mg) per year cement plant at Tilbury Island, Delta, British Columbia. The Plant--Its Philosophy of Design The design of this plant began in 1974, at the beginning of the rapid rise in petroleum costs later referred to as the "energy crisis". The trend in fuel costs was clear, so one of the basic criteria for the selection of process equipment was high thermal efficiency. Throughout the process of selection of materials handling and process equipment, energy consumption was a factor in decisions. A second factor which influenced the design of the plant was its location on navigable water. The plant is designed to make maximum use of this means of transport to minimize transportation costs. All raw materials (and some fuel) are received by water, and a major portion of the cement and clinker is sent out by barge. Extensive modern dock and material handling facilities were provided to accomplish the shipping and receiving functions. A plant meeting stringent environmental regulations was the third major factor which formed the basis for design. To meet this requirement, all storage facilities had to be covered, 53 bag type dust collectors were applied throughout the plant, and materials handling equipment was designed to minimize dust and spillage.

Jan 1, 1979

By M. Girardeau, J. Blondin, M. Nomine

It is well known that surface moisture and fine content have a strong influence on coal handle- ability. It is known as well that these two criteria are not sufficient to classify coals. It seems that certain types of coals are intrinsically difficult to handle, the reason being still not well understood. For these coals, moisture and fine content are aggravating factors and have to be strictly controlled in order to avoid handling problems (sticking, arching in hoppers.. .). CERCHAR has undertaken research aimed at identifying the role of intrinsic characteristics of coal with regard to handling properties. Two of them have been identified as particularly relevant : the clay content and the "colloidal particle" content. Two simple tests commonly used for soils characterisation, but never used so far for coal, have been applied to characterise a wide range of coals. The derived classification has been compared with an empirical classification based on dry screening tests. DRY SCREENING EXPERIMENTS Dry screening at a relatively low screen aperture (e.g. 6 mm) may be considered as a good tool for assessing the handleability of wet fine coals. Difficult to handle coals always lead to rapid plugging of the screen whilst easy to handle coals can be screened without difficulties. A wide range of coals has been selected with various ash, moisture and fine content. Their characteristics are given in table 1. The experimental set-up consists of a 2 t.p.h vibrating screen equipped with two automatic re- cording balances collecting respectively oversize and undersize material. Provided that the feeding rate is accurately controlled, good reproducibility in the percentage passing as a function of time is obtained. Figure 1 gives examples of different types of relations that were obtained. - LMC coal exhibits a behaviour that is characteristic of easy to handle coals : % passing remains constant in the course of the screening operation. - B coal behaves slightly differently. One observe first a rapid decrease in the flow passing through the screen and then a stabilization. Hand- ling properties can be considered as intermediately - The curve relative to LHB coal is characteristic of a very difficult to handle coal that blinds the screen almost immediately. It is necessary to point out the fact that the classification derived from screening experiments is a global one, including not only intrinsic factors but also external factors such as fines and moisture content. The role of surface moisture is in particular very important and variations in this parameter may upset the empirical classification

Jan 1, 1988

By Craig M. Sams

Matching mill? drives to mill power draws is a relatively new practice with the introduction of variable speed drive arrangements. Semi-autogenous grinding (SAG) mills are the focus of this paper as ball and rod mill characteristics are easily charted as charge loading and speed change. In addition, a look at types of drives available in the market and mechanical ratings is outlined to match the specifics of each drive.

Jan 1, 1991