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By Dorothy A. Canter

Three Federal programs exist for identifying significant environmental chemicals, including minerals, that should be tested for toxicological effects. Two programs are mandated by law and can lead to industry-funded studies; they are administered by the Environmental Protection Agency and the Agency for Toxic Substances and Disease Registry, respectively. The third is the National Toxicology Program, a Federally-funded testing initiative. This paper summarizes the three programs, describes their similarities and differences, and discusses their applicability to minerals.

Jan 1, 1991

In order to overcome some of the deficiencies associated with conventional fine coal cleaning methods, a novel process known as microbubble column flotation (MICROCEL?) was developed at Virginia Tech. This article provides an overview of recent commercialization efforts and in-plant testing of this technology. The results of the in-plant test work indicate that the MICROCEL technology offers several advantages for the upgrading of difficult to clean coals. The test data have also been used to develop guidelines for the design of coal flotation columns and to validate existing scale-up procedures.

Jan 1, 1991

By Patrick J. Doig

The NS9 Drop Shaft contract formed part of the Waste Pollution Abatement Program (WPAP) conducted by the Milwaukee Metropolitan Sewerage District (MMSD). The contract involved the construction of two shafts, a deaeration chamber and connecting tunnel, and ancillary facilities. Portions of the construction were located in saturated overburden where dewatering was prohibited. Ground freezing was utilized for temporary support of the excavation. This paper concentrates on the freezing system and the excavation of frozen ground, with particular emphasis on the use of mechanical cutting equipment, including a raiseborer and a roadheader.

Jan 1, 1991

By F. F. Aplan, S. Chander, A. R. Alaboyun

Several aspects of the capture of hydrophobic dust particles by droplets in sprays have been studied. The particle capture depends on several sub-processes involving collision, adhesion and engulfment. The collision events between dust particles and a single droplet were observed with a high speed motion analysis system to determine the influence of a surfactant on the capture process. In the adhesive process it was observed that the dust particles are collected at the surface of the water droplet to produce a rigid film at high dust loadings. In the presence of the surfactant, however, the particles were engulfed inside the droplet keeping a fresh surface on the droplet available for capture of more particles. A theoretical analysis is presented to take into account the role of contact angle on the penetration of particles into droplets. A significant increase in collection efficiency was observed with decrease in droplet size.

Jan 1, 1991

By Louis W. Cope

In the early 1900s, vat leaching was a common process for treating gold ores. It was, however, labor intensive and was abandoned in the 1930s. Technology advances in recent years, though, have caused vat leaching to once again become a viable alternative in precious metal processing. At least three plants have been built. Others are being considered as alternatives to agitation and heap leaching. What is vat leaching? Vat leaching is a process in which ore is crushed and screened to a size of between 6 to 12 mm ( 0.25 to 0.5 in.) This crushed ore is placed in a large, boxlike container where an alkaline-cyanide solution is added and later removed. The process might be likened to indoor, controlled heap leaching. The ore does not require fine grinding in a ball mill. Therefore, capital and operating costs are lower than agitation treatment. But the extra handling causes costs to be slightly higher than heap leaching. If any amount of fines is present, the ore should be agglomerated.

Jan 1, 1991

By D. P. Gold

Major sources and reserves of Cb/Nb, Ta, REE, Y, Sc, Zr, Hf, Cu, apatite and vermiculite may be concentrated in primary and secondary minerals associated with different stages and depths of emplacement in carbonatite complexes and kindred alkalic intrusive rocks. Exploration targets include: apatite and pyrochlore (Nb) in the plutonic and hypabyssal core and ring-dikes: bastnaesite (REE), strontianite, barite and fluorite in hydrothermal veins and cone-sheets (subvolcanic setting): thortveitite (Sc,Y) and vermiculite in metasomatized aureoles (fenites): high grade eluvial deposits of apatite and pyrochlore, and secondary REE, Nb, Ti. and V-minerals in supergene and weathered zones.

Jan 1, 1991

By Stewart R. Wallace

In the spring of 1959 while visiting the offices of the US Geological Survey (USGS) in the Denver Federal Center, I had a chance encounter with Paul Theobold, a former but, at that time, casual associate. Paul mentioned to me the results of his work on stream sediment geochemistry (Theobold and Thompson, 1959). Using panned concentrates, Theobold and Thompson had discovered a tungsten anomaly in Clear Creek and followed it upstream to its source on Woods Creek, a small tributary to the West Fork of Clear Creek. The specific source was a debris cone about 0.8 km (0.5 mile) upstream from the mine yard at the Urad molybdenite deposit. Because of the genetic and zonal association of tungsten and molybdenum at Climax, I found this very interesting. Accordingly, I related this information to Robert Henderson, general manager of western operations for Climax, and asked his permission to do some follow-up work. He, in turn, telephoned Frank Coolbaugh, the president of Amax, telling him of my interest and saying that, "Climax would take care of it." On my first visit to Urad, my companions (Dave Jonson, Bruce MacKenzie, and Dick Baker) and I were confronted by a "Cousin Jack" caretaker who made up for his diminutive stature by a "pistolover" that hung down almost to his knee and by a watchdog that was one-half wolf and one-half mean sled dog. We retreated discretely to Clear Creek and then climbed up the "back" side of Red Mountain by separate routes, across the ridge crest, and part of the way down the "front" side, sampling as we went. Although much of the ground was covered with snow, we found lots of puzzling but friendly looking rocks and the geochemical results were interesting. A geologic map of central Colorado showing the location of the Urad-Henderson and Climax deposits is shown in Fig. I.

Jan 1, 1991

By Tony Szwilski

Indonesia has enormous mineral resources. Its population of more than 180 million people inhabit most of the more than 13,000 islands. The country is becoming a significant economic power in Southeast Asia. Indonesia is the largest Muslim country in the world. Java, its largest island, is the most densely populated area. The country's diversity is its strength. However, as only an estimated 16 million inhabitants speak bahasa Indonesia as the first language, communication problems endure. Although burdened with large debts, Indonesia has been able to service the debts better than most developing nations. This has given it high credibility and, with increasing frequency, creditor nations compete to provide Indonesia loans with the most the most favorable financial terms. Recent rising prices of petroleum crude has further improved Indonesia's economic status. It maintains a policy of stable oil prices that it promotes in OPEC, of which it is an influential member. As a result, Indonesia is becoming increasingly attractive to foreign investors. The South East Consortium for International Development (SECID) is made up of 34 universities in the southeastern US and Indonesian partners Lembaga Afiliasi Penelitian dan Industri (LAPI) of the Institute of Technology in Bandung, West Java. SECID bid successfully against international competition to develop new academic programs and campus for the Sriwijaya University UNSRI) in Palembang, South Sumara. Funding for the project was provided by the government of Indonesia through a loan from the Asian Development Bank (ADB). There are 47 public universities

Jan 1, 1991

By C. Hendricks

This paper is based upon field studies conducted in a western Canadian open pit coal mine. This work has involved the adaptation of microprocessor-based instrumentation to monitor various operating parameters on-board blasthole drills and mining shovels. A review of instrumentation and monitoring methodology will first be presented. Based upon experience from field-based studies, the paper will subsequently focus on the application of monitoring technology within the framework of an integrated Equipment Monitoring System. Such a system will permit the real-time performance evaluation of key equipment involved in surface mille production.

Jan 1, 1991

By J. W. Leonard, D. A. Newman

Discussion by N. Standish and P.N. Standish Leonard and Newman (1989) describe concepts and plans of their forthcoming project designed to increase the bulk density of broken coal at various stages of its production and handling. This is an excellent idea and something that will certainly be useful to the coal mining industry worldwide. The authors seek to achieve bulk density increase by "reducing oreliminating, through chemical additives and engineering design, particle voidage and enhance particle consolidation trickling between the point of breakage (at the face) and loading (in the shuttle car) to increase coal bulk density and productivity." In the paper, they present some supporting results of bulk density versus moisture, with or without oil addition, from the steel industry research. Unfortunately, the paper contains many misconceptions and half-truths that detract from an otherwise excellent objective of the project of increasing bulk density by reducing particle voidage-"the bottom line evaluator." Correct. Theory Definitions Coal bulk density is the ratio of the mass of a collection of discrete particles to the volume that it occupies (ASA, 1980). There can be no possible argument about this definition. Mass and volume are readily measured both in laboratory and large scale installations. So, to obtain the bulk density, one simply divides the measured mass by the measured volume. It is here that we come unstuck as everybody who has ever had to reconcile book values with the measured stock tonnages knows. Where does the problem originate? Almost invariably in a too casual a reading of the above definition and the words "a collection of discrete particles." The word collection means "a number of objects collected or gathered together, viewed as a whole" (The Oxford English Dictionary, 1989). If one knows the bulk density of a pile of coal viewed as a whole,

Jan 1, 1991

By P. L. Webster, S. D. Thompson

Sevim and Wang (1988a) have presented a model for designing haulage systems in underground coal mines. The authors contend that their model uses a heuristic algorithm to optimize various haulage system parameters. In reality, it would be nearly impossible to optimize a haulage system, because mining plans are uncertain and often change with respect to time. Therefore, haulage system design poses both a stochastic and a dynamic design problem, and its optimization appears to be well beyond the scope of heuristic algorithms. In regard to the authors' design model and its practical significance, a number of additional issues warrant further discussion and clarification. These issues include: l) their model's alleged advantage over simulation models, 2) the correctness of their belt network design, 3) the correctness of their bunker design, 4) the necessity of their proposed bunker clearance policies, 5) the correctness of their shaft-bottom bin design, and 6) the

Jan 1, 1991

By Victor F. Hollister

This section describes two exploration models currently used in the search for porphyry exploration deposits: the hood and the vertical cylinder. Each has alternate names within industry and in the literature. The hood is also known as the Climax or Henderson and the vertical cylinder has also been called the Mt. Pleasant model. The paper by Hollister (1978, abstract herewith) refers to the vertical cylinder as the zoned model in reference to the horizontal sulfide and silicate zonation evident in and peripheral to the vertical cylinder of molybdenite mineralization. The distinct ore body geometry in each model type necessitates differing drilling and exploration strategies. Drilling for a hood shape is clearly different from drilling for a vertical cylinder type target. The paper by Wallace et al. (1968, abstract herewith) on multiple intrusion and mineralization at Climax, CO, well describes the hood model. That description is supplemented by the paper by Wallace et al. (1978, abstract with Chap. 37) on the geology of the Urad and Henderson deposits. The paper by Hollister (1978, abstract herewith) describes the vertical cylinder model.

Jan 1, 1991

By C. A. F. Pinto

In the present work compared flotation kinetics of apatite with four different collectors was established. Sodium oleate and rice bra~ oil were used to represent conventional collectors. The new collectors included a sulfosuccinate and a sulfosuccinamate. It was observed that the collection ability of each reagent was very dependent upon the mineral size ranges. The results-were analyzed in terms of size-by-size recovery curves. Flotation rates were also very dependent on size ranges of the mineral particles. One of the new collectors displayed higher flotation rates for coarser particles than the other reagents tested. Synergetic effects were also apparent when a conventional collector was mixed to a new collector.

Jan 1, 1991

By F. A. Aplan, Richard R. Klimpel

This article discusses the role of mathematical optimization techniques as applied to the design and analysis of particulate processing plants. The emphasis will be placed on the macro engineering view of integrated multiple operation plants such as those that typically involve stages of size reduction, sol id-sol id separation, solids storage, chemical reactions involving sol ids, sol ids disposal, etc. The macro engineering view is chiefly concerned with balancing and optimizing the bigger picture of how various unit operations interact technical and economically with each other in an approximate sense rather than how a specific unit operation can be technically described and optimized in detail (micro engineering.)

Jan 1, 1991

By Ernest L. Ohle

Since the first recorded discovery of lead in southeast Missouri near Fredericktown about 1720, knowledge of the deposits has advanced in spurts as a result of outlying discoveries: 1864 Bonne Terre 1890 Flat River, Desloge, Leadwood 1948 Indian Creek 1955 Viburnum The original discoveries at Bonne Terre consisted of residual galena in clay, similar to that in the previous finds at Fredericktown. Occurrences in solid dolomite were not noted until mining of the clay pits exposed the walls of the weathered depressions. The St. Joseph Lead Co. had been established to conduct the operations and it was J. Wyman Jones, first president of St. Joe, who at that time brought about the first of the technological advances that were to occur in the district. He proposed use of the newly invented diamond drill to explore the bedrock showings, after observing the machines in the Vermont Marble Belt.

Jan 1, 1991

By Jan Visman, James W. Parkinson

GENERAL INTRODUCTION Sample collection, preparation and analysis are all steps in a single process designed to provide information about a much larger amount of material than the sample itself. For example, information about the ash content of a unit train load of coal may be derived from a single, relatively small sample of perhaps a few hundred pounds (liters) extracted from the entire shipment. These three steps can be thought of as links in a chain, allowing the simple analogy that the strength of the chain, or, in other words, the value of the information is only as strong as the weakest link. Sample collection, discussed in Part 1 of this chapter, is critical because analytical procedures can do no more than reveal the characteristics of the sample presented to the laboratory. If that sample does not properly represent the population to be characterized, neither will the analysis of that sample. Sample preparation is also a critical part of the chain. Any change in the nature of a sample between the time it is collected and the time it is analyzed will appear to reflect the nature of the population. For example, sample preparation procedures that allow air to partially dry the coal sample before reaching the laboratory will cause the sample analysis to indicate a lower moisture content than the sample originally had. Other changes can be more subtle. Second only to moisture loss, oxidation reactions generally cause the greatest problems. Oxidation of a coal sample can alter surface properties, changing flotation response. In extreme cases, combustion parameters, such as caking or agglomerating properties or mineral composition, such as pyrite content, can change. Water samples can also be altered by oxidation. For example, ferrous iron can oxidize to ferric iron, possibly changing water quality parameters such as pH. Sample analysis, the subject of Part 2 of this chapter, is the final link in the chain. Obviously, no laboratory procedure can correct for problems created by improper sample collection and preparation. At the same time, poor analytical techniques will create incorrect information about the total amount of coal from which the sample was extracted (the population) in the same manner as improper sample collection and preparation. The key to gaining correct information about the population is to view these three steps as parts of a single process. Following proper techniques through only one or two steps of the process will not produce accurate information.

Jan 1, 1991

By T. Gouri Charan, G. V. Rao

A spherical agglomeration process for the separation of scheelite fines of less than 30 µm in very low concentration of 0.04% WO3 in a binary mixture with quartz fines of less than 30 pm has been described. A concentrate containing 14% WO, with more than 90% recoveries could be achieved by means of anionic sodium sulfo succinate collector at pH 3.5 and also with commonly used anionic sodium oleate at pH 10.5 as per the conceptual flowsheet suggested. Such a process is envisaged as commercial potential for the recovery of fine-grained scheelite present in the tailings of gold plants as found in India.

Jan 1, 1991

By W. E. L. Minter

The most important Witwatersrand gold placers occur on extensive unconformity paleosulfaces that were produced during protracted periods of fluvial degradation. The erosional etches on what was generally unlithified sub-strate indicate that low sinuosity erosion patterns prevailed. The transport systems were dominantly braided fluvial with a minor debris-flow component. The placer sediments were non-cohesive sands and gravels. They were evidently transported by fluctuating, yet perennial, discharges across extensive, low relief braid plains, not far from littoral environments. Progress made in understanding heavy mineral transport processes now emphasizes the importance that selective entrainment probably had in producing concentrations. Cognizance that these characteristics are not unique to the Witwatersrand should be taken into account when designing exploration models.

Jan 1, 1991

By Joseph Matoney, B. K. Parekh

INTRODUCTION The term "dewatering" refers to removal of water from coal. Water associated with coal can be categorized as "free or surface" and "inherent or chemically bound" moisture.' The free moisture is found on the surface of coal, in capillaries and small spaces between two or more particles. The inherent or chemically bound water is found in the interior of the coal and as part of coal structure. A significant amount of free moisture can be removed by mechanical dewatering techniques. However, inherent moisture can only be removed by applying energy intensive techniques, e.g., direct or indirect heating. Moisture in the coal offsets some of the benefits of coal cleaning. Extra water in clean coal adds to extra cost in transportation, heat lost during vaporization, and plugging of chutes. From a utility perspective, a 1 % increase in moisture can offset a 4.5% decrease in ash.2 Mechanical dewatering can be classified into two major process categories according to the principles involved, namely, 1. Sedimentation-liquid is constrained and particles move freely. 2. Filtration-particles are constrained by a medium and the liquid flows through. Each of the process categories is composed of various separation techniques shown in Fig. Equipment currently being used by the mechanical dewatering of coal of varying size ranges and final moisture content is illustrated in Fig. 8-2. This figure indicates that sizes larger than 13/, in. (37.5 mm) present no particular dewatering problem. Shaker screens of the very crudest types and designs are capable of producing these sizes at low surface moistures. High-speed vibrators are used for the intermediate sizes and can be used for smaller sizes down to 0.02 in. (0.5 mm) if high moistures (15% surface moisture or greater) can be tolerated in the product. Usually, however, the vibrator is not used below 3/, to 3/, in. (9.5 to 6.3 mm) because of the moisture associated with these fine sizes. At this level, centrifugal force is usually employed to aid dewatering. Centrifuges of various types and designs are used practically

Jan 1, 1991

By Kousik Sinha

The advantage of using a clean coal as a feedstock in a direct liquefaction plant is improved performance of the plant by several factors e.g., increased throughput of coal; reduced wear and tear of valves, pipes, and pumps; increased liquid yields, etc. This paper examines the technical feasibility for cleaning Illinois #6 coal as a feedstock to a direct coal liquefaction plant via selective agglomeration using a coal-derived heavy distillate, Wilsonville V-1074 as agglomerant. Effects of addition of Kerosene or coal-derived Naphtha as conditioner, coal particle size, slurry pH, oil to coal ratio, and operating temperature on ash reduction and clean coal weight recovery have been studied. Results show that about 70% of the ash can be removed from this coal and the clean coal weight recovery over 85% can be achieved by using this technique with suitable selection of coal particle size, slurry pH, mixing intensity and oil to coal ratio.

Jan 1, 1991