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By A. B. Szwilski

The mineability and coal processing costs are influenced largely by the structural and physical properties of the coal seam. The mining process involves coal cutting, pillar support, crushing, and floating. A correlation between the rank, ash content, and coal strength/stiffness is discussed. The coefficient of variability of rebound tests on the face of various coal seams are compared with those of laboratory compressive strength tests by other investigators.

Jan 1, 1988

By F. F. Aplan

The material known as coal has a highly variable composition. As a consequence, coals show a great variation in their physical and chemical properties as a function of coal rank. The situation is further complicated because the preparation engineer must deal with raw coal, as mined. This is an assemblage of coal, upwards of 30% mineral matter and, typically, several percent pyrite. The kind and amount of the mineral constituents is also highly variable from source to source. A knowledge of coal rank and source location, and the kind and amount of associated impurities, is the first step in evaluating the response of a raw coal to preparation procedures. The raw coal must first be characterized before information from one source can be extrapolated to that of another.

Jan 1, 1988

By T. G. Bobick

Task analyses were conducted by the Bureau of Mines at four underground low-seam coal mines to evaluate their supply-handling systems and for use in subsequent design of laboratory simulation experiments. Items were tracked (by videotaping) from delivery to the surface storage areas to their final destinations underground. Of particular interest were those tasks that required manual handling of supplies or equipment. Analysis of the videotapes revealed that the miners handled materials while stooped over a total of 37.8 pct of the time, 31.5 pct while on both knees and 9.5 pct while kneeling on one knee. These working postures impose considerable stress on the lumbar spine and may be implicated in the high number of back injuries in this work population. This paper also discusses various mechanical-assist devices developed by the Bureau and successfully evaluated in the underground workplace. These devices can be used to minimize the manual effort and the corresponding risk of injury associated with handling supplies and equipment components in low-seam coal mines.

Jan 1, 1988

By Kelly F. Bailey

The issue of regulating non-asbestiform varieties of the amphiboles actinolite, tremo1ite, and anthophyllite to the same degree as asbestos has been studied in detail by the National Stone Association. The ramifications of such a regulation, and the over simplistic regulatory definition of a fiber, are enormous not only for the aggregate industry and its users, but also for the nation. Evaluation of the health, geological, mineralogical, technical, economic and legal issues do not support an "asbestos-like" regulation of non-asbestiform minerals. The adverse consequences of regulating non-asbestiform varieties of actinolite, tremolite and anthophyllite like asbestos would be magnified many times if a similar standard for generic mineral fibers were promulgated.

Jan 1, 1988

By J. K. Ahlness

The US Bureau of Mines investigated technologies for determining the integrity of in situ leach mining wells. A self-contained trailer-mounted well integrity testing system (WITS) was designed and built to enable rapid testing of well casings for leaks as required by environmental regulations. The WITS utilizes two inflatable packers to seal off the entire casing length or any portion thereof. Water pressure is built between the packers to the desired test pressure, and the presence or absence of casing leaks is determined by monitoring the pressure drop between the packers. A winch and steel cable are used to run the packers in and out of the well. The WITS underwent an industry field test at the Irigaray in situ uranium leaching mine near Buffalo, WY. A total of 37 wells with an average depth of 69 m (225 ft) were tested at an average rate of four wells per eight-hour shift with a two-person operating crew. This represents a 75% time savings and an 83% labor savings compared to the rigid-pipe method previously used at the mine, with which a three-person crew tested an average of one well per shift.

Jan 1, 1988

By W. Petruk, D. B. Sikka

Lithium-bearing lepidolites from three deposits in the province of Goias, Brazil, were investigated to determine whether there is a correlution between the lithium content of the mineral and the color of lepidolite and associated tourmaline. Such a correlation can be a useful guide to field geologists for outlining high-grade lithium ore zones. It was found that mauve-pink lepidolite associated with pink tour-maline, and brownish lepidolite associated with black tourmaline have high lithium contents, but that the color of lepidolite is not due to lithium. The pink color of lepidolite and tourmaline is likely due to Mn3+, and the brownish tint of lepidolite and black color of tourmaline to Fe3+. Lepidolites appear to be lithium- rich when the lepidolite and associated tourmaline contain relatively high amounts of Mn3+ and/or Fe3+.

Jan 1, 1988

Separation of dolomite from Florida phosphates was achieved by first conditioning the feed with fatty acid at pH 10 followed by reconditioning at pH 4 or below, before flotation. Observed selectivity of this two stage conditioning process was attributed to the amount as well as changes in the nature of the adsorbed collector species upon reconditioning. In this paper, bench scale flotation results of optimizing the major process parameters, such as reconditioning pH and collector dosage, for upgrading natural high dolomitic phosphate samples from Florida are discussed.

Jan 1, 1988

By D. J. Miller

Environmental considerations are extremely important in planning and carrying out mergers, acquisitions and real estate transfers. It is not inconceivable that potential or actual environmental liabilities could exceed the targeted company's net worth or the book value of the real estate of interest. It is therefore essential that an environmental due diligence investigation (DDI) be performed to quantify environmental liabilities before sales, mergers or acquisitions. This paper will discuss general procedures used in environmental due diligence investigations. The emphasis will be placed on mergers and acquisitions. It should be pointed out that the procedures discussed in this paper are general and must be modified to fit each particular merger or acquisition under consideration.

Jan 1, 1988

By H. Habenicht, E. Urschitz

Three mining methods for full extraction in flat coal seams - i.e., longwall (L W), shortwall (SW), and rib pillar extraction (RPE) - are com- pared with each other in view of the introduction of a mechanized, self-advancing roof support. Features are shown according to which RPE appears most attractive under certain conditions. In this presentation, the mining methods are outlined and discussed. The new support (Alpine Breaker Line Support, ABLS) is described, and its employment is explained. A trial operation in RPE using the ABLS has been conducted successfully in a South African coal mine. The results and improvements are stated.

Jan 1, 1988

By A. C. Kunkie, C. J. Marshall

Highly delaminated muscovite mica products (WG-1 and WG-2) have been developed by J.M. Huber Corp. The micas are characterized as a 325-mesh product having high brightness and very narrow particle size distribution. At 40% loading in polypropylene, WG-1 mica provides substantial improvement in tensile modulus and equal tensile strength to unfilled polymer; in high-density poly- ethylene (HDPE), WG-1 provides four times the tensile modulus and a 50% increase in tensile strength over unfilled polymer. Surface modification of the water-ground mica (SM ™) provides substantial improvement in tensile strength over untreated mica at greater than 20% loading in polypropylene; in HDPE, tensile strength is twice that of unfilled polymer.

Jan 1, 1988

By K. A. Eriksson

Over 25 years ago, SKEGA pioneered the use of rubber linings in grinding mills and rubber is today widely accepted and almost standard material chosen for Regrind -and Secondary Mills. There are, however, only a few Primary Mills in operation with "solid" rubber linings because available materials and designs are often not cost efficient in comparison with steel alloys on a cost per ton basis and/or downtime for liner replacement would be too high.

Jan 1, 1988

By R. N. Chakravorty

Spontaneous combustion presents a very serious hazard to both safety and economics of mining operations. Notwithstanding considerable research that has been done over the years to present and control spontaneous combustion the risk still exists. Consequently, this problem poses a major challenge to mine safety researchers; new and improved techniques are constantly being developed to deal with this major hazard. This paper reviews the current practices to prevent and control spontaneous combustion in coal mine operations highlighting new developments in this area. Research and development work presently being carried out in Canada to' deal with this problem is also discussed which includes monitoring, inertization and application of biotechnology.

Jan 1, 1988

By K. Rajamani, L. B. Hales

Much of the process control effort in the mineral industry uses proportional-integral-derivative controllers that require periodic retuning. Retuning hundreds of controllers typically employed in a single plant is a formidable task for the control engineer. Adaptive controllers offer an alternative to this problem, since they are designed to tune themselves. Four schemes of adaptive control-gain scheduling, model reference adaptive control, self-tuning regulator, and optimal adaptive controllers-are discussed with process examples. The control of a ball mill circuit with a multivariable self-tuning regulator is illustrated. This controller encompasses the advantages of the other three controllers and is applicable for a wide range of process variability.

Jan 1, 1988

By Byron V. Knelson

Although the concept of centrifugal recovery has been around in one form or another for many years, it has not been until recent times that it has become clearly understood and properly put into perspective. Simplistic in theory, it is when one begins to examine the variables involved that the true complexities of this matter begin to emerge. In creating an enhanced g force concentrator, there are many aspects both positive and negative that are encountered. Many conditions that are inherent to all conventional 1 g concentrators do not apply to centrifugal concentrators and therefore very few cm factors exist between them. In developing this technology, virtually all principles were proven by method of trial and error. Among the topics discussed are the effect of g force enhancement on particulate behavior with respect to size and shape, density, enrichment, fluidization, and the "teeter principle". In addition, we will discuss the physical effects of g force enhancement with respect to manufacturing in the areas of abrasion, bearings, and vibration. In discussing the recovery parameters of centrifugal concentrators we will draw direct comparisons to various other recovery methods, outlining the conditions most favorable to their application.

Jan 1, 1988

By M. G. Ayat, J. W. Leonard

Introduction Coal preparation plants are continuously losing clean coal in their refuse and contaminating their clean coal product with impurities. This is due to the lack of a system by which the immediate efficiency of the cleaning operation can be determined at any given time. Moreover, the advantage of developing tagging/ tracing techniques would be a reduction in the time and money spent in evaluating the performance of advanced cleaning techniques. Currently, conventional sampling and testing, on-line analyses, and computer information systems are the major tools with which engineers analyze and control the efficiency of processing plants. Conventional sampling and testing is an effective analysis technique but it is slow. On-line analysis provides information on quality parameters rapidly, but these parameters do not provide all of the necessary information. The use of tagged particles in coal preparation plants may provide the necessary link between diagnosis and the application of computers to process control. In this work, a novel technique that uses tagged particles to generate partition data is presented (Leonard et al., 1982). Individually prepared tagged particles are added to the feed and detected in the product or refuse port of specific gravity based processes. Providing that a computer can interpret the output of a detection device and trace particles with predetermined physical properties through the coal preparation plant and that the trace particles actually represent desired raw material, sufficient partition data can be provided for computer analyses and control of processing efficiency. Coal tagging technique The use of tagged particles in coal preparation operations are in the early stages of development. Though there is a brief history of particle tracing in the mineral processing industry (Gardner et al., 1986; Foreman and Amundson, 1976; Poston et al., 1962), the concept has not yet been applied to the analysis and control of processing plant operations. Several methods for tagging coal particles have been identified. These include magnetic, radioactive, and fluorescent techniques. As far as the magnetic tagging of coal particles is concerned, a method has been developed to manufacture synthetic magnetic particles of various sizes and specific gravities. Ideally the synthetic particles would have identical size and density as the coal particles being separated.

Jan 1, 1988

By H. Schubert

The flotation of sylvite and also some accessory minerals is performed in brines containing very high electrolyte concentrations. Under these circumstances the mechanims of collector adsorption exhibit some characteristics which will be discussed by significant examples: - flotation separation of sylvite and halite with n-alkylammonium salts and n-alkyl sulfates - flotation separation of kieserite and anhydrite with acylamino carboxylic acids - flotation of halite by collectors which are adsorbed by hydrogen bond formation.

Jan 1, 1988

By R. Callaway

The Comprehensive Environmental Response, Compensation, and Liability Act of 1980 (?CERCLA?), as amended by the Superfund Amendments and Reauthorization Act of 1986 ("SARA?) establishes a comprehensive Federal regulatory program for addressing environmental and public health risks posed by releases of hazardous substances into the environment from a wide variety of industrial and other sources. The statute is primarily administered by the United States Environmental Protection Agency ("EPA"). The applicability of CERCLA to the mining, milling, and smelting industries (hereinafter referred to as the ?mining industry?) has been upheld by the courts and recently affirmed by Congress. The purpose of this article is to briefly outline the scope of CERCLA as it applies to the mining industry, the scope of EPA's activities pertaining to the mining industry under CERCLA, the types of remedies which may be pursued by EPA, and the liability scheme of CERCLA as it applies to corporate entities, managers, and shareholders involved with the mining industry. Natural resource damage claims, State cooperative agreements, and other State-related issues will not be discussed.

Jan 1, 1988

By A. S. Ibrado

The adsorption of silver on activated carbon from cyanide solutions was studied as a function of concentration, ionic strength and pH. In cyanide solutions, silver exists mainly as the linear Ag(CN)2 complex and adsorbs on activated carbon following the Freundlich isotherm. The uptake and rate of adsorption increase with the addition of KC1 and KNO3 but changes only slightly with pH. In contrast, the adsorption of Cu(I), Zn(II), Cd(II), and Hg(II) shows marked changes with pH, closely following the predominance profiles of their neutral and singly-charged cyano complexes. Clearly, multicharged negative complexes are repelled by the negatively-charged carbon surface. This sensitivity of activated carbon to the charge of the adsorbing species indicates that silver adsorbs as an anion, not chemically bound to the co-adsorbing counterions. For the same reason, activated carbon is selective to metals that form neutral and Singly-charged cyano complexes, namely gold and silver.

Jan 1, 1988

By D. L. Kuck

Water ice pillars far underground mine roof support can be frozen and/or maintained and/or melted on demand. The system to do this consists of a refrigeration brine chiller, brine circulation system and disposable plastic containers. Fusion expansion, resilience to dynamic loads, plastic deformation under stress, and non-contamination of coal or ore are unique properties of ice. Lower labor and material costs are economic advantages of ice far mine structural support. Ice brattices can become ice pillars on retreat. For safety, ice pillars can be placed (by remote control, if necessary) in hazardous sites without human entry.

Jan 1, 1988

By R. N. Torbin

Foster-Miller has recently developed a new concept.for a highly specialized shaft lining system. This innovative shaft lining system uses a continuous slipforming placement technique. lining the shaft from the bottom up such as in a raised bored shaft. Although this part is not unique, the concept is designed to use polyurethane foam instead of concrete for the liner material. Furthermore, the concept is designed to attain rates of advance of 30 m/hr. The polyurethane foam liner is designed to be thinner (100 mm) than a conventional concrete liner (300 mm). It will eliminate the high cost associated with the erection and operation of an on-site concrete batch plant. The system will be designed to be operated remotely, requiring few personnel for its operation. This system (or parts of it) may be appropriate where fast construction speed is required or where a jointless liner is needed.

Jan 1, 1988