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By Don Muraoka

Soda ash, anhydrous sodium carbonate, is produced from underground trona deposits occurring in the Green River Sasin of Southwestern Wyoming. Stauffer Chemical Company of Wyoming, a jointly owned subsidiary of Stauffer Chemical Company and Rocky Mountain Energy Company mines the trona and processes it into high-purity soda ash. Stauffer Wyoming has been in operation since 1962 with a current production capacity of approximately 2.2 million tonnes (2 million short tons) per year of soda ash. The Refinery has five parallel operating trains utilizing the monohydrate process which is a series of chemical processing unit operations described below. Screening and Crushing the Trona The mined trona is brought to the surface in two counterbalancing ore skips. The ore is initially screened with Refinery feed, less than peagravel size material, entering the process while the oversize is conveyed to an outdoor stockpile.

Jan 1, 1984

By Joseph P. Gildner, Michael S. Kucker, Robert A. Robinson

Considerable controversy seems to exist over the extent and nature of information that should be provided in design-build type contracts. Much of this controversy may relate to the types of owners, ranging from private industry to state and federal agencies that are implementing design-build. Philosophies for the development of geotechnical information ranges from no information to a thorough investigation approaching that needed for final design. Several recent projects, such as the Channel Tunnel in Europe, Whittier Tunnel in Alaska, Tren Urbano in Puerto Rico, and Sound Transit in Seattle have taken varying approaches to providing and interpreting geotechnical information for bidders. The pros and cons of these various methods are discussed and assessed.

Jan 1, 2001

By John G. Groppo, Bonnie Webb-Groppo

INTRODUCTION The first portion of this chapter is concerned primarily with the contamination aspects of fine coal cleaning that include both the solids and water discharged as waste products after coal preparation. Topics include characteristics of the water and solids, changes that occur to both of these phases during use and after impoundment, as well as the impact that these changes have on unit operations and the environment. Attention is also given to the formation of acid mine drainage and treatment options that may facilitate reuse of the water. The second part of the chapter analyzes the problem of air contaminants from coal preparation plants including analysis of air pollutants and control methods. An overview of air quality regulations is also presented; most provisions have little or no applicability to coal preparation plant operation but are presented to provide an understanding of end-user constraints. The final part of the chapter emphasizes the long-range problem of refuse disposal and control. An overview of characterization, maintenance, and control of the refuse area is presented, as well as design guidelines. A brief review of stability analysis procedures is also included. PREPARATION PLANT WATER Characteristics of Makeup Water for Coal Preparation There are few specific rules governing the quality of makeup water used in coal preparation processes.'" It is generally accepted, however, that the solid matter content should be less than 5%. The solids concentration in plant makeup water typically varies between 0.25 to 0.9 lb per gal (30 to 110 g/L) and may reach concentrations as high as 1.7 lb per gal (200 g/L). The water used in coal preparation is usually obtained from one or more of the following sources: public supplies, rivers and streams, canals, mine water, and wells. In most cases, water is obtained at the lowest cost including any necessary treatment. A major portion of the recirculated water is clarified by thickeners and settling ponds to remove fine coal and clay particles. Sufficient water is generally available to meet the needs of coal preparation in most areas. It has been estimated that approximately 65 to 70% of the makeup water used in a coal preparation plant comes from surface sources. It is important to note that a variety of substances are commonly found in natural water supplies, whatever the available source may be (Table 11-1). Excessive concentrations of some of those substances can have an affect on plant performance; the effect of specific contaminants on unit operations will be discussed

Jan 1, 1991

By José A. Matar Ibañez

Geologic terranes in Argentina include potential mineralized environments from localized younger Precambrian cratonic outcrops through Paleozoic sequences, generally in the northwest or under younger cover, to the Mes[o] zoic-Cenozoic Andean Systems in western and southern Argentina. Argentina is self sufficient or nearly so in many metallic, nonmetallic, and energy commodities, and exploration in each of these categories is ongoing. Present production of precious metals (silver and gold) is important, and many recent discoveries of base metals, precious metals, alloy metals, and other mineral categories have been made. Economic trends, geologic environments, and commodity types important in actual exploration are described, and it is emphasized that extensive areas showing attractive alteration, geochemical, and geological anomalies, especially of porphyry, cordilleran vein, and epithermal characteristics, remain to be fully evaluated.

Jan 1, 1986

By R. L. Loofbourow

R. L. LOOFBOUROW 26.1-WATER FLOW, USE, EFFECTS, CONTROL Sec. 4 discusses ground water as a mineral resource. This section deals wits its control. 26.1.1-IMPORTANCE Flows of water have an important effect on the cost and progress of many deep excavations. The existence of water limits the methods which can be used in some and presents hazards in others. Lowering the water table may reduce the flow of springs and wells, with legal liability. Some mine water is used directly, some must he treated before discharge, and some contains dissolved solids which can be recovered profitably. Loss of life, property and production from flooding is grim, yet scores of mines have worked safely for generations under ground-water reservoirs, lakes and even the sea. The need for better control of mine water is measured by the severity of recent floodings, concern with the quality of the effluent, and direct and indirect costs of working wet ground. There are improvements in freezing in shaft sinking. pumps and their controls, treatment of mine water before it is pumped, bulkhead construction and certain efforts to reduce inflow. 26.1.2-PUMPING COST VS. COST OF WET WORK Direct operating and capital costs of pumping are more evident than indirect items, such as provision of extra standby power and maintenance facilities, The total of all these items is the cost of pumping water from an excavation. This is only a part of the extra cost of working wet as compared to dry ground. Less productive methods, less efficient equipment and more expensive explosives may have to he used in wet work. Wet rock plugs certain equipment. Maintenance is higher and labor less efficient. The cost of any means of keeping work drier should he weighed against the higher cost of working wet. The true difference in the cost of working wet ground, compared with dry, probably is known at only a few places (see checklist of cost items. Sec. 26.4.13). An extreme comparison of mining wet and dry ore is available from Ambrosia Lake, N.M. (Fig. 26-1). Between 1963 and 1967, a wet and a dry mine were worked by the same company under conditions otherwise comparable. Average operating cost at the wet mine, pumping 1,600 to 1,800 gpm. was $16.06 per ton of ore. The comparable figure for the dry mine was $7.50. Principal differences included the fact that the wet mine was worked from drainage levels below the, ore with rail haulage, the dry mine in the ore with off-track equipment loading and hauling to the shaft. In the wet mine, ore packed in chutes, cars and skips and froze in surface bins, stockpiles and trucks. Wet-mine costs included drilling drain holes, building and maintaining ditches and pumping water containing abrasive solids.

Jan 1, 1973

By S. Lin

Fan stall is a notorious phenomenon with axial-flow fans. When multiple fans of this type serve a ventilation system, their mutual impacts are very complicated and not well understood. Results from laboratory experiments indicated that the immediate consequence of a fan working across its stall zone (i.e., the pronounced trough on the fan characteristic curve) is that some branches in the system may suffer abrupt and even drastic changes in air quantity and pressure. The quantity range of the fan that causes the abrupt change is called an unstable operating range. The corresponding quantity range of a branch is called a non-achievable quantity range of the branch because any quantity within this range cannot be achieved without changing some parameters of the ventilation system (e.g., branch resistances). These concepts are introduced based on the test results from tubing networks to bring attention to these important characteristics of ventilation systems.

Jan 1, 1996

By Byron C. Hardinge, Michael Sokaski, Paul F. Sands, W. Loring III Mc Morris, David J. Akers

INTRODUCTION In the early days of coarse-coal cleaning by the dense-medium process in Europe, loess was one of the materials used for medium solids. Newly developed cyclones were used to reclaim and thicken the loess suspension. On occasion, when the cyclone thickener at the Maurits mine in the Netherlands plugged, the overflow was found to be filled with clean coal free of impurity. From this observation stemmed the concept of the cyclone as a cleaning device. Development took place during World War II in the laboratory of the Dutch State Mines under the direction of M. G. Driessen. A 15-tph (13.6 t/h) pilot plant was in operation in the laboratory by 1945, when, in September, Driessen made the first public disclosure of the process in a paper presented to the Institute of Fuel in London.51 In April 1945, operation of this pilot plant was observed by H. F. Yancey, who was so impressed with the potential of the cyclone process that, on his return to the United States, a research program on the cyclone was immediately started by the US Bureau of Mines (USBM). This work led to an AIME paper in 1946 in which the first details of cyclone operation on American coals were made available.52 Commercial adoption of the cyclone proceeded in Europe, initially in the Netherlands, Germany, and France. In the United States, where coal is less costly and most of the coals are easy to clean and respond well to simpler cleaning processes, the first cyclone plant was not built until 1961.53 THEORY Before discussing the theory of a dense-medium cyclone, a brief description may be helpful to some readers who are not familiar with its basic operation. In a typical dense-medium cyclone, illustrated in Fig.7-51 a mixture of medium and raw coal enters tangentially near the top of the cylindrical section, thus forming a strong vortical flow. The refuse moves along the wall of the cyclone and is discharged through the underflow orifice. The washed coal moves toward the longitudinal axis of the cyclone and passes through the overflow orifice, or vortex finder, to the overflow chamber. Washed coal is discharged from this chamber, usually through a tangential outlet.

Jan 1, 1991

By Jorgen Elbrond

In a stream of ore in an underground mine or in a beneficiation plant bins are installed between machines or machine system. When the upstream machine is stopped the downstream machine can continue operation for a while and vice versa. The paper describes a procedure for calculating the total capacity of a system consisting of two machines with an intermediary bin as a function of the bin's live volume and of the installed machine capacities and their production variations, which are defined. Extensions to several machines in parallel and in series are shown as well as practical examples.

Jan 1, 1982

By George P. Tateosian

Merchants perform a number of functions in the copper market. As a major distribution arm of the copper industry, they secure scrap and other copper bearing materials for processing into usable refined shapes. These are ultimately sold to fabricators. Merchants ' hedging and arbitrage activities help keep values in proper relationship from product to product or region to region. Through these switching and trading operations, they optimize the flow of copper from mine to consumer. And finally, merchants act as a repository for copper units during times of surplus and a stockpile from which to draw during tines of shortage.

Jan 1, 1979

By Kenneth P. Katen

Though the use of continuous mining machines consolidated the operations of cutting, drilling, blasting, and loading in one machine that would theoretically provide uninterrupted production, it was soon realized that the face haulage and roof support operations remained as major impediments to continuous production. The ability to provide not only continuous cutting and loading, but also continuous haulage and roof support (see Fig. I), was the basis for the introduction of mechanized longwall systems in this country from Europe in 1951. The early systems employed friction props for roof support, but were to become obsolete shortly after introduction of the first hydraulically powered, self-advancing supports in 1960. Since then, use of the longwall technique has grown to the point where it is currently providing more than 5% of the annual output of underground coal mines in the United States. The shortwall system had its origin in Australia, but was first introduced into this country in 1962 following the development of powered roof supports. It, too, provides for continuous cutting, loading, and roof support (see Fig. 2), but has not experienced the widespread popularity of longwall due to its inherent inability to easily provide for continuous haulage. While there are in the neighborhood of 100 longwall systems currently in operation in this country, there are only a handful of short- wall operations providing production of slightly more than 907 184.7 t/a (1,000,000 stpy) Both of these systems provide uninterrupted roof support for face operations by means of hydraulically powered steel roof supports. In each case, the coal removal consists of open-end cuts made from the narrow end of a large rectangular pillar (panel) which has been blocked out by continuous miners developing entries around its perimeter. However, this is the extent of the similarities between the two systems. It is hoped [ ] that the information presented in this chapter will enable the reader to better understand the two mechanical systems and the mining concepts involved in their employment.

Jan 1, 1981

By Giovanni Barla

The stress-relief method for the determination of the ground stress tensor is a common procedure in rock mechanics. In particular, the method of applying gauges to the end of a borehole is a well-established technique. Investigations, both experimental and theoretical, indicate that large discrepancies can exist in the determination of the ground stress tensor when the rock substance is not the ideal elastically isotropic material assumed for the reduction of data. The purpose of this paper is to extend the analysis of strain gauges applied to the end of a borehole to rock material more closely approximate to an orthotropic substance.

Jan 1, 1969

By J. D. Patsey, G. T. Lineberry

Introduction A computer program was developed for analyzing drum-type hoists before modifying an existing system or designing a new one. Its use permits the preliminary evaluation of a system before seeking technical assistance from mine hoist designers and manufacturers. The user-friendly program accepts a variety of data and analyzes hoisting systems for any balance state. The program can be used to calculate skip capacity to yield a desired production rate, solve for drum face width, select a permissible wire rope, estimate total horsepower of the hoist plant, and estimate annual power cost. Whether required for a large mining complex or for a relatively small operation, a hoisting system must be carefully designed to ensure the efficient, reliable, and safe flow of material. Because shaft sinking and hoist installation can total between 2.5% and 3% of the cost of opening a deep mine, proper hoist selection is critical. Today's mining engineer has at his disposal the most powerful design and analytical aid ever, the micro- computer. There is, unfortunately, limited software for the study of hoisting systems, unlike that for other materials handling equipment (Manula and Albert, 1980; Prelaz et al., 1964; Bucklen, 1969; Thompson, 1985). HOIST reduces a time-consuming set of calculations to a concise package of interrelated subprograms. A literature review revealed no common-user pro- grams to analyze hoisting systems, although at least four major hoist designers/manufacturers/installers have their own in-house programs. To provide a tool with which the mining engineer could preliminarily analyze a materials hoisting system or could check the calculations of a hoist contractor, a computer program was developed. HOIST was written in BASIC for the IBM-PC for ease of program adaptation and to en- courage field use on compatible systems. Details of program development are omitted, since the basic principles of hoisting analyses are relatively straightforward, simple, and readily accepted (Har- mon, 1973; Nordberg, n.d.; Adler, 1957). Program features, intended usage, and benefits of the com- puterized solution are emphasized over theory development and mathematical rigor. Background The mine hoist system that is selected and installed at a mine is the "lifeline" of that mine, with installations lasting 20 years or more. Thorough study is warranted to ensure that productivity demands are met at a minimum cost per ton. The increased cost of a large, powerful, high-speed hoist must be offset by increased production to justify its selection. To optimize this tradeoff, an extensive hoisting analysis should be performed. The analyses to properly size the skip (or cage ) , the drum, and the hoist drive are conducive to computerization, permitting rapid evaluation of changeable operating and design parameters, such as velocity, acceleration, state of balance, and productivity demand. The program is particularly useful in conducting sensitivity trials, such as investigation into the effect of change of productivity on skip capacity and on horsepower of the hoist drive. HOIST is currently limited to the study of drum-type hoists with cylindrical drum(s). However, only minor changes to the program would permit analysis of friction hoists and conical drum configurations. Model development and testing The program is based on accepted equations and physical relationships. Examples of manual calculations formed the basis for decision points and program branching. Data is input in the order that it would be needed if the problems were solved manually. The choices are arranged likewise. HOIST was developed in sections, with manual solutions performed to check program logic. The testing became more rigorous as sections were completed. Output from one section becomes input for following sections, as appropriate. The simplified flow diagram of HOIST is given in Fig. 1.

Jan 1, 1988

By Richard Klimpel

A common problem in mineral processing and chemical engineering is the need to estimate flow rates and/or weight ratios involved with engineering operations for which it is inherently difficult to directly measure stream weights. Simple examples of this situation include stream separators (a classifier operating on a particle flow) and stream mixers (the mixing of new feed and circulating load in a ball mill circuit). Often in these types of operations, it is possible to sample the streams involved to get approximate component analyses (e.g. size distributions of solid streams, chemical composition of chemical streams). In this paper various formulae are developed which can be used to estimate stream flow rates or weight ratios given information on the stream components. The type and level of experimental error present in the stream component analyses does have an important bearing on the numerical values (and reliability) of the weight ratios calculated by the various formulae. A simple but theoretically sound method is shown for selecting appropriate estimation formulae for any given engineering operation. The derived formulae are applied to sets of experimental classification data for illustration purposes.

Jan 1, 1979

By Bruno A. Fichna

Longwall mining offers low cost potential for coal with high capital investment. As opposed to two shifts-per-day operation in most long- walls, Saarberg Mines in Germany increase utilization of capital by operating their longwalls around the clock. Differentiation between capital and operating costs, corrective maintenance versus preventive maintenance, improved roof conditions, and economical life of equipment was investigated. A surprisingly high degree of improvement was attained. Capital costs at Saarberg longwall coal mines have been reduced through a step-by-step research and trial program. This reduction was particularly influenced by the high performance pilot longwalls at the Ensdorf mine. The following presentation shows data and figures of those longwalls. End results were 40% reduction in capital costs, which could contribute favorably to investment decisions in the coal industry in a supply side economics environment.

Jan 1, 1982

By Floyd M. Thorman

Gypsum is the crystalline chemical compound CaS04?2H20. A close chemical relation - and frequently occurring with Gypsum ? is Anhydrite which is Cask. Gypsun has wide commercial use because relatively simple heat processing reduces it to Plaster of Paris. While Anhydrite can be converted to Gypsum and thence to Plaster of Paris, the procedure is not simple and is quite costly. Anhydrite, however does have use in the agricultural field and in the Portland Cement industry. Occurrence of Gypsum in the earth structure is usually near or at the surface. Most underground mining is at 60 to 100 feet although one mine in southwest Virginia reaches a depth of 1300 feet. Gypsum is one of our softest minerals, rating only 2.0 on the Mohs scale of hardness. Specific gravity is 2.3 to 2.4. It is soluble in water but only slightly so. Interestingly, it is more soluble in cold water than in hot. For example, one part Gypsum dissolves in 370 parts water at 106° Fahrenheit while at 212°F. the water requirement is 452 parts. Compressive strength of massive Gypsum runs about 3000 lbs. per square inch. Color ranges from grey and brownish-grey to white.

Jan 1, 1973

By William D. Mayercheck

Beginning in 1974, the Bureau of Mines, U.S. Department of the Interior, sponsored R & D efforts related to further development and use of continuous face haulage in underground coal mines (Cowan, 1975). The U.S. Department of Energy continued this effort as of October 1977. This paper represents an update of an article previously published in Mining Engineering magazine (Mayercheck, 1979). Development progress is summarized for a variety of prototype systems or components now being built, surface tested, or tried underground.

Jan 1, 1981

By Lawrence W. Teufel

Knowledge of in situ stress and natural fracture distribution at depth improves our ability to stimulate and produce low permeability reservoirs. The focus of this study is three closely spaced, 2.5 km deep vertical wells in the Piceance Basin of Colorado. The wells were completed through the tight lenticular and blanket gas sands of the Mesaverde Group. In situ stress directions and magnitudes were determined from hydraulic fracture tests and anelastic strain recovery measurements of oriented core. The distribution, orientation, and characteristics of natural fractures in the subsurface were determined from detailed observations of over 1300 m of core, of which 400 m was oriented. Stress measurements clearly show that horizontal stresses are strongly influenced by lithology. In a sandstone/shale sequence at a depth of about 2.0 km in situ stresses in sandstone formations are anisotropic, with the average ratios of the minimum and maximum horizontal stresses to the overburden stress being 0.82 and 0.96, respectively. In sharp contrast bounding shale formations are lithostatic. This stress contrast between sandstones and bounding shale formations could act as a barrier to hydraulic fracture propagation during stimulation and impede vertical fracture growth. Natural calcite-filled fractures are present in over 7 percent of the core, with several horizons having a much higher frequency of fractures. Fractures are found primarily in sandstone. The fractures have a strong preferred orientation of N 1060E[+]110, which is aligned with the maximum horizontal stress and direction of hydraulic fracture propagation. The interaction between a well developed fracture fabric and anisotropic stresses in sandstone formations produces a permeability anisotropy, with the maximum permeability aligned with the fracture fabric and maximum horizontal stress.

Jan 1, 1986

By Robert A. Irvine

Traditionally, cost effective gains in the capacity of material handling systems were a result of increases in equipment size. In general, the use of maximum capacity components in a system optimizes the production "costs per ton." The trend-"Bigger is Better" will continue in material handling equipment. Since it is rare for plant operators to lament an over abundance of screening capacity, one can safely predict that vibrating screens will follow this trend. Large Vibrating Screens - The Challenge Large vibrating screens represent a unique challenge for Manufacturers, Plant Designers, and Plant Operators. The inherent mode of operation for vibrating screens is self-destructive. More often than Manufacturers admit, Designers plan for, or Operators staff for, a vibrating screen succeeds and self-destructs. This is a problem. It can magnify with larger vibrating screens.

Jan 1, 1983

By M. Robb, S. J. Bate, M. Boisvert

The never-ending quest for gold-bearing ore deposits is a primary industry in Canada, employing people of widely differing expertise. The exploration models for gold deposits are generally geologically complex and the targets have relatively small cross-sectional areas. These problems are compounded in Canada by the minimal outcrop exposure in most mineral provinces and the high percentage of water-covered areas. Naturally the chances of successfully delineating an economic gold deposit are very much greater if all parties involved can act as a team of explorationists constantly confemng amongst themselves particularly as the applicable disciplines generally overlap and complement each other. Three case histories (see Figure 1) are presented to illustrate this philosophy with emphasis placed on the role of the geophysicist in translating the exploration model as defined by the geologist into physically measurable parameters and identifying target areas with similar characteristics. The Conwest-Miminiska property in Ontario is a grassroots exploration play. Additional ore reserves needed to be delineated on the Salmita property in the Northwest Territories. At Laura Lake, near Chapais, Quebec geophysical methods were employed to trace thin high-grade mineral intersections under deep overburden and severe cultural interference.

Jan 1, 1989

By D. A. Saint Don, M. Prueher, S. Barnwell

With the current changes in technology, multiple methods are now available for aggregate resource identification. From Sonic to Coring, Reverse Circulation to Percussive, there are many choices to make regarding drilling technology. The discussion will outline the methods above with focus on aggregate investigation and highlight the new technologies that will make a difference in your search.

Jan 1, 2004