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By J. W. Perez

Raw coal will often break intragranularly in either a completely random way or in a differential mode where one species will have a different rate of breakage than another. Locked coal-ash and coal-pyrite particles can also break by the preferential detachment of one species from another along zones of inherent weakness in locked particle assemblages. The mode. cf breakage is largely a function of the nature of the feed, but it is also influenced by the comminution device and the operating variables. Evidence of breakage of particles in the various modes is seen in the crushing of raw coal and middlings particles with a rotary beaker, jaw crusher, rolls, hammer mill and rod mill. Evidence from the literature indicates the detachment mode is often important for coal, ores and metallurgical products. Further confirmation comes from the crushing of a specially prepared 'ore' of sized magnetite in plaster of Paris.

Jan 1, 1988

By Shail J. Butani

In 1986 the Bureau of Mines conducted a probability sample survey, Mining Industry Population Survey, to measure such employee characteristics as occupation; principal equipment operated; work location at the mine; present job, present company, and total mining experience; job-related training during the last 2 years; age; sex; race; and education. The population estimates are necessary to properly analyze the Mine Safety and Health Administration (MSHA) injury (includes illness and fatality data) statistics; that is, to compare and contrast injury rates for various subpopulations in order to identify those groups that are exhibiting higher than average injury rates. This report uses the survey's results to characterize the U.S. nonmetallic mining workforce from March through September 1986. Similar reports have been prepared for the metallic, stone, and sand and gravel mining industries, as well as for the entire metal and nonmetal mining (includes metallic, stone, sand and gravel, and nonmetallic industries) sector and the cool mining sector.

Jan 1, 1988

By Kenneth L. Rubow, Virgil A. Marple

"INTRODUCTION Respirable dust is defined as the dust which penetrates to the alveolated regions of the lungs. Due to the size selective nature of the particle removal mechanisms in the nasal passages and lung airways, criteria defining respirable particles must be a function of the particle size. Three criteria defining respirable particle penetration are shown in Figure 1. These criteria have been defined by the British Medical Research Council (BMRC), the American Conference of Governmental Industrial Hygienists (ACGIH) and German TBF 50-11 (1).The quantity of respirable particles in an aerosol can be measured by use of two-stage samplers. The first stage consists of a particle preclassifier with penetration characteristics corresponding to one of the respirable penetration curves in Figure 1. The large nonrespirable dust particles are removed from the airstream in the preclassifier and the smaller respirable dust particles pass on to some device which can measure their concentration (the respirable dust concentration).Instrumentation for the measurement of respirable coal mine dust has been limited by the severe conditions existing within the coal mine. The conditions of particular importance are the methane atmosphere, high humidity, and the general non-laboratory type environment. The most severe of these conditions is the methane atmosphere since any electronic or electric powered instrumentation must be intrinsically safe to operate in such an atmosphere.In spite of the difficulty of sampling respirable dust within the mines, many instruments have been developed for in mine use. Although these instruments operate under a variety of principles they generally fall within two categories: personal samplers and area samplers.A personal sampler is worn by the mines while he is performing his duties in the mine. These devices are generally small, light weight and require little power so as not to interfere with the miner's ability to work."

Jan 1, 1988

By F. E. Brinckman, G. J. Olson, D. Johnsonbaugh, T. K. Trout

"Microbiological metal recovery is an emerging technology likely to play an increasing role in commercial ore leaching, metal removal from process and waste streams, and perhaps ultimately in processing to yield metal products in specified forms or oxidation states. We are studying the potential for using microorganisms for the recovery of elements important to emerging materials technologies and for which domestic supplies are limited and/or low grade. Examples to be discussed include the bioaccumulation of yttrium and gallium. These elements are important in the production of new superconductor and semiconductor materials. However, limited domestic reserves and technologies for their recovery may cause supply problems. Microbiological processes may offer new techniques for recovery of these and other strategic elements.IntroductionMicroorganisms in ore leachingMicroorganisms assist in the commercial leaching of copper and uranium from low grade ores (1,2) and recently have been shown to have immediate commercial potential for the pretreatment of refractory gold ores to increase the gold-cyanide recovery yield (3). Copper bioleaching is the best known example of biotechnology applied to metal recovery. Copper can be recovered by commercial leaching of huge piles or dumps of low grade sulfidic ores and waste materials, which are not otherwise processable. Microbial activity in the leach dump environment oxidizes metal sulfides to soluble metal sulfates:"

Jan 1, 1988

By William Petruk

A fully automatic image analysis system that consists of a microprobe, an energy dispersive x-ray analyzer, and an image analyzer was developed at CANME:I' to determine mineral behaviour that affects beneficiation. The interlacing between the instruments permits automatic identification and characterization of minerals in samples of unbroken ore pieces and of mill products. Different types of information are obtained for minerals in samples of unbroken ore pieces than in samples of mill products, and are used differently. For unbroken ore pieces size distributions are determined for discrete mineral grains to predict a grind at which they might be liberated, and other measurements are Irade to predict the percentage of mineral that occurs as nonrecoverable grains. For mill products the minerals are analysed to determine percentages that (1) are free, (2) are likely to be recovered in concentrates, (3) are likely to be lost to tailings, and (4) could be liberated with regrinding. The image analysis data for mill products are processed by a mineral-metals balance program to determine the distributions of free and unliberated mineral grains at each point in a concentrator, pilot plant or bench test. For samples containing trace minerals, such as gold, an automatic search technique is used to scan the entire area of the polished section for the trace mineral grains. The identified trace mineral grains are characterized with regard to size, liberation, and other properties.

Jan 1, 1988

By Julius G. Chang

Against the receding background of the October stock market crash and the December overhang of inventories, the economy began with a shaky start in 1988. As 1988 began, the Administration's estimate of real growth for 1988 had just been reduced from 3.5% to 2.4% and economists and other ob-servers were concerned that the expansion that was 5 years old might be near the end and that a recession might be around the corner. The ensuing moderately strong economic activity, however, belied all the negative signals that were evident earlier, and the real GNP continued to grow at an estimated 2.3% annual rate during the first quarter of 1988, extending the ongoing recovery into the sixth year (table 1.). The relatively accommodative policy of the Federal Reserve Board (the discount rate was cut by 0.25% in January), a strong performance by the export sector, and the revival of consumer spending were major forces underlying the economic strength. But as the quarter drew to a close, signs of tight capacity utilizations were apparent in many of the export and capital goods sectors, including textile, chemical, plastic, metal, and machinery. Employment was at a record high level while the unemployment rate was close to a historical low. Prices were rising at a faster pace than those of 1987, and the dollar resumed its slide after a brief recovery in January and February. These factors gave rise to the fears of higher inflation. Long-term interest rates increased, casting a pall over the prospect of a robust growth for the rest of the year.

Jan 1, 1988

Adequate ventilation of coal mine working faces is the single most important technique for controlling respirable dust and methane. Choosing the right technique presents some tough questions. Bureau research has shown that to control respirable dust you must contain the dust near the face, keeping rollback (turbulence) to a minimum. For methane the most effective approach has been to use a blowing brattice or tubing and to create turbulence and disperse the face methane, allowing it to pass over the machine and into the return. It is immediately apparent that the two approaches may counteract one another, thus complicating the decision as to which system may be best for a given situation. At present, Bureau research has developed two successful machine-mounted face ventilation systems to meet these different needs and allow deeper cutting. The fan-powered dust scrubber is designed to control dust primarily associated with blowing face ventilation systems. The spray fan controls methane on exhaust-ventilated sections.

Jan 1, 1988

By Richard A. Winters

In 1987, at the request of the U.S. Bureau of Land Management, the U.S. Bureau of Mines studied the 34,680-acre Lime Canyon Wilderness Study Area (NV-050-231) to evaluate its identified mineral resources. The Wilderness Study Area is in Clark County, NV, about 30 air miles southwest of Mesquite, NV. The area studied contains an estimated 44 million tons of indicated subeconomic resources of gypsum, an inferred subeconimic resource of limestone and dolomite, and occurrences of gold, copper, uranium, and zeolite. The Wilderness Study Area is underlain chiefly by carbonate rocks with lesser amounts of sandstone and shale. Metamorphic, granitic, and volcanic rocks also crop out within the area. Large portions of the area are overlain by alluvium. The Wilderness Study Area is within the Gold Butte mining district. Several gold mines with past production are nearby to the south of the Wilderness Study Area; one mine is reported in operation on a small scale. Several silver-bearing copper and zinc mines with past production are nearby to the east of the Wilderness Study Area

Jan 1, 1988

By Gary F. Meenan

Continuous pi lot scale dewatering tests compared the performance of the vacuum disc filter with that of the screen bowl and the solid bowl centrifuges. The test results allow the a priori prediction of plant product moisture based on the feed particle size. This information is useful for selecting the best dewatering device for a given size material and for optimizing the dewatering performance of existing plant installations. Quantitative information was gathered on the ability of filter aids to improve the filtration rate of fine coal slurries. A polymeric flocculant and oil were added to the disc filter feed material at various dosage levels. Both filter aids increased the disc filter output. For the coal tested, the flocculant filter aid achieved higher filtration rates at a lower cost.

Jan 1, 1988

By P. Maraboutis

Iron removal by precipitation as jarosite from Fe-Ni-Co sulfate solutions, (synthetic or real, resulting from laterites leaching) has been investigated. Precipitation was carried out at 95 C, and at an initial pH 1.6, which was either kept constant with CaCO3 or Li2CO3 additions, or left to drift with the evolution of the reaction to lower values. The precipitation of K-, NH4- and Na- jarosite was initially examined using synthetic solutions. In all cases, hydronium ions were incorporated into the precipitate as well. Residual iron in solution was lower (0.2-1 g/1) and equilibrium was achieved faster (within 4-8 h) when precipitating K¬jarosite at constant pH, using CaCO3 for neutralization. Nickel and cobalt losses were small. Na- jarosite precipitation was also studied from real solutions with high initial iron content, under constant pH=1.5, controlled with CaCO3 additions, and it was shown that low residual iron concentration in solution (0.3-0.5 g/1) can be achieved again, with relatively small nickel and cobalt losses. The thickening and filtration characteristics of the precipitates were excellent in all cases examined.

Jan 1, 1988

Jan 1, 1988

By W. P. Tassie

"The location of Quintette Coal Limited's pit and geologic nature of the dedicated reserves combine to introduce a number of factors which can adversely affect waste dump stability. These factors include steep terrain, variable material type and particle size, and precipitation. This paper describes the solutions to related waste dump problems. A brief geotechnical review of the waste dumps is given and Quintette's operational strategies during periods of dump stability and instability are discussed. Despite best efforts, failures occasionally occur and discussion is included on Quintette's success at bringing failed dumps safely back into use. IntroductionQuintette Coal Limited (QCL) property is situated on the east slope of the Rocky Mountains near Tumbler Ridge, approximately 120 km southwest of Dawson Creek, British Columbia. This surface mine is located on mountainous terrain and is subject to climatic extremes of wind, precipitation and temperature.QCL has a current annual production of 4.75 million tonnes of metallurgical coal with a stripping ratio of 7: 1. This correctly implies the extraction of over 33 million bank cubic metres (BCM) of waste which is placed on numerous waste dumps at various locations adjacent to the pit.There are three active pits - Mesa, Wolverine, and Shikano (Fig. 1). Shikano is a newly developed pit located near the plant site. It is not subject to the unique dump management problems prevalent at the Mesa and Wolverine pits, therefore the Shikano waste dumps will not be discussed . The dumps for the Mesa and Wolverine pits, however, have been technically and operationally challenging since shortly after mining began in 1983. Their characteristics, associated site specifics and management, therefore, are the subject of this paper.Waste dump locations for the Mesa and Wolverine pits are shown in Figures 2 and 3 as is the relative waste distribution . Each sub-pit is connected to a principal waste dump in reasonable proximity and to an alternate dump should disposal of waste be necessary at that location. The waste dumps are constructed from the top elevations initially to coincide with subpit development. In the initial years (1-7) waste dump heights will be up to 250 m, then, as the mine matures (8-20 years), waste dump maximum heights will continuously decrease to coincide with lower bench elevations"

Jan 1, 1988

By Donald R. Alvic

For electric utilities serving the aluminum smelter industry in the United States, sulfur oxide (SOx) abatement legislation could bring about increases in the costs of generating electricity. This paper documents the method and assumptions used in estimating these increases, and the contains the results of the estimation. 1.2 SMELTER INFORMATION The smelters used in this study were identified by the Bureau of Mines (BOM) and are listed in Table 1.1. Also included in Table 1.1 are the electric utilities that serve these smelters. Compliance costs were estimated for these utilities. Some of the utilities are unique in the way that the information is handled or in the way the utility is operated; these are discussed below. 1.2.1 Big Rivers and Associated Co-ops, Data for Big Rivers and Associated Co-ops were gathered by George Mason University (GMU) students for BON and are included in this study.

Jan 1, 1988

By Leslie E. Apodaca

INTRODTUCTION The use of spiral concentrators for processing fine coal particles is an old idea that has recently gained acceptance in the 11.S. coal industry. It was not onti1 the Australian Minerals Industry developed a spiral concentrator specifically for separating coal from ash in the latter 1970's and early 1980's that spiral concentrators were seriously considered as viable equipment for processing fine coal. The Wright Coal Spiral was introduced in 1980, the Mineral Deposits Limited Mark 10 Coal Spiral was introduced in 1982, and the Vickers Wyong Coal Spiral was introduced in the latter part of 1984. Each spiral design was different and utilized constant profile troughs, constant pitch troughs, compound profile troughs, and various splitter arrangements. Mineral Deposits Limited has combined the best features of the compound profile trough and constant pitch trough with critically-placed splitters to develop the MDL LD4 spiral concentrator which is a truly efficient coal washing spiral. This spiral concentrator was introduced into the U.S. Coal Industry in 1987. Recently, Mineral Engineering Technology of the United Kingdom and Multotec of South Africa have introduced their own coal spiral designs. Spiral concentrators were first installed in fine coal processing circuits in the Australian, South African, and Canadian Coal Industries in the early 1980's and in the U.S. Coal Industry in 1985. SPIRAL CONCENTRATOR SEPARATION PROCESS The separation process that occurs within the spiral concentrator trough is very complex, as it is a combination of three gravity separation processes. When the coal slurry first enters the spiral trough, each coal and ash particle and the water is subjected to centrifugal forces. These forces cause the water, light coal particles, fine heavy ash particles, and medium middlings particles to the outer vertical portion of the spiral trough. The coarse ash particles and the coarse middling particles remain on the inside of the spiral trough. The center or transitional area of the trough contains a mixture of middlings particles and near-gravity material that is present in the slurry, as shown in Figure 1. At the same time the coal and ash particles are suhjected to centrifugal forces, the trough design (both profile and pitch) causes the particles to be subjected to flowing film and stratified bed separations. The combination of these three separations, whose efficiency is dictated by the spiral troogh design, will effect the separation of the lighter coal particles from the heavier ash and middlings particles. As the slurry flows down the spiral, the profile and pitch design of the trough will counteract the centrifugal forces on the fine, heavy ash particles and fine middlings particles and cause them to migrate from the vertical portion of the trough to the center or inner portion of the trough. At the same time, any heavy particles trapped in the transitional area of the trough will be forced to migrate to the inner edge of the trough and any coal particles will be forced to migrate to the outer edge of the trough. SPIRAL SPLI'TTEP ARRANGEMENT The critical placement of splitters along the inner edge of the trough for removal of the heavy ash particles as the slurry flows down the trough further enhances the separation of the coal particles. At the bottom of the spiral trough are product splitters arranged to make a final separation of the slurry stream into clean coal, middlings, and refuse products.

Jan 1, 1988

By S. K. Kawatra, T. C. Eisele

"Recent advances in microbiology have made the application of biotechnology to metallurgical processes possible. Hydrometallurgy stands to gain the cost from the use of microorganisms, as they are useful for both dissolution aids and for removing metals from solution. The development of genetic engineering techniques promises to greatly increase the importance of bioprocessing of metals and minerals by the year 2000.In this paper, the basic effects of microorganisms on metallurgical processes are reviewed, and the applications which are currently either in use or near being used are presented. Representative data collected at Michigan Technological University is also given.IntroductionMany hydrometallurgical operations exist which are thermodynamically possible, but which are industrially impractical due to slow kinetics, high reagent costs, or the need for a highly corrosive environment. However, recent discoveries in microbiology indicate that in many cases these difficulties can be reduced greatly by the action of bacteria and other microorganisms (1-8).A major advantage of using living organisms in hydrometallurgy is that once the culture is established the microorganisms produce their own reagents either from the material being processed or from low-cost nutrient supplements. They thus allow extremely complex chemical reactions to be carried out at reasonable cost. The major drawback of using microorganisms is their inability to tolerate extremely high temperatures, excessive concentrations of toxic metals, or very highly acidic, alkaline, or corrosive conditions. However, the complex reactions which bacteria make possible frequently eliminate the need for such extreme conditions. Also, in recent years a number of organisms have been isolated from such exotic environments as hot springs and deep-ocean vents which can tolerate temperatures higher than was previously thought possible for any organism, and can catalyze a number of metallurgically important reactions (8)."

Jan 1, 1988

By A. Johnson

When are SMART transmitters the smartest choice? To answer this question requires a closer look at SMART transmitter technology. It is necessary to understand this technology in order to recognize how it can best be utilized to give the greatest value for the application. And, once the decision to buy transmitters has been made, it becomes a question of whose SMART transmitter to buy. For, although the under-lying technology is similar, the differences that exist in how the technology has been implemented can make a dramatic difference in the end result. What prudent users of SMART technology do is to analyze their needs by application before making their buying decision.

Jan 1, 1988

By J. W. Leonard

Since the interpolation of exploratory data 1 can be no better than sampling procedures, a series of field experiments were conducted in an effort to determine whether hand-cut channel or core washability determinations best represent continuous miner produced run of mine coal. By obtaining a core drilled to within a few feet of channels taken from an underground face and then overmining both locations; core, channels and run-of-mine coal allocations were obtained from a common sample and all allocations were subjected to identical washability determinations. In order to compare results, basic rules2,3 previously anticipated and later published by the writer were employed. The first rule states that "For any full seam washability determination, the sulfur versus ash function for increasing cumulative specific gravity float coal fractions is linear". The second rule states that "For any full seam washability determination, the recovery versus ash function for increasing cumulative specific gravity float coal fractions is logarithmic".

Jan 1, 1988

By D. A. Lee

The selection of control system equipment for a mineral plant is based on several criteria, including opera tor interface, supervisory capabilities, ease of maintenance, ease of programming and configuration, compatibility with auxiliary control equipment, and total cost. The paper discusses the technical evaluation procedure with respect to control system equipment available today.

Jan 1, 1988

By J. Dean Warner

In 1984 and 1985, as part of its critical and strategic minerals studies, the Bureau of Mines investigated lode and placer tin occurrences near Rocky Mountain (Lime Peak), in east-central Alaska. The lode occurrences consist of mineralogically complex, generally fault-controlled veins, and contain an average of approximately 0.05 pct Sn, as cassiterite. Beneficiation testing of two bulk samples of the vein material produced concentrates containing 65 and 59 pct of the total tin values at grades of 0.35 and 13.9 pct, respectively. Although as much as 30 million short tons (MMst) of mineralized rock containing up to 20 MMlb Sn may be present, the grade of these occurrences is too low to be considered economic at this time. Trace amounts of cassiterite were also identified in surface samples of glacial out-wash gravels collected along North Fork Preacher Creek, which partially drains the area of tin lode deposits near Lime Peak. Low tin grades in the samples do not account for the former erosion of a large volume of lode tin mineralization from near Lime Peak; higher tin grades may be present in gravels closer to bedrock.

Jan 1, 1988

By M. C. van Blerck

Since its introduction in 1956, the capital allowance has been increased and its scope widened. At present the allowance is 10% in respect of two categories of gold mine (post-1973 and other deep level mines) and 6% in respect of natural oil mines. The allowance is a significant incentive encouraging the development of new mines, to the benefit of both the fiscus and the South African economy as a whole. A strong case can be made for increasing the amount and the scope of the allowance. The Margo Report recommendation that the allowance should possibly be replaced with a system of direct grants is, in theory, neutral. However, practical difficulties exist with cash grants and there is concern with the implications elsewhere in the Margo Report that the capital allowance is excessive and that, as a consequence, such direct grants will represent an effective reduction in this incentive. I believe that the best course of action would be the retention (and enhancement) of the capital allowance and the expansion of its scope.

Jan 1, 1988