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By Daniel T. Eyde

The U.S. Geological Survey (USGS) estimates world production of natural zeolites to be 2.7 Mt (3 million st) in 2013. China ranked ?rst with 2 Mt (2.2 million st), followed by the Republic of Korea at 230 kt (253,000 st) and Turkey at 50 kt (55,000 st). Japan?s production is reported to have increased as a result of zeolites, reportedly low grade local mordenites, being used to treat the low-level radioactive contaminants in the areas surrounding the damaged reactors at the Fukushima Daiichi power plant. China and other countries? high-volume, low-value construction applications, which include dimension stone, pozzolans and lightweight aggregate, are also included in production. This means the production data does not accurately indicate the quantities used in high-value added specialty applications. Consumption in the United States, according to USGS estimates, increased slightly, to an estimated 71.3 kt (78,400 st). Domestic uses for natural zeolites were, in decreasing order by tonnage, animal feed, pet litter, cement (primarily down-hole cement applications by the drilling industry), water purification, odor control, waste water cleanup, fungicide or pesticide carrier, gas absorbent, fertilizer carrier, oil absorbent, desiccant, catalyst and aquaculture. The six leading uses accounted for more than 70 percent of the domestic natural zeolite sales tonnage.

"Metallurgical process development in greenfield projects must define the comminution flowsheet and establish the equipment sizes that are required to deliver the project design criteria. These are critical steps that heavily influence the financial performance of the project, requiring a detailed understanding of the ore properties of the project resources and the best practice methods to size comminution machines. This paper reviews current practices for determining the ore characteristics relevant to comminution circuit design. Particular attention is given to the design of sampling and testing programs, and the methods commonly applied to size crushers and mills for conventional size reduction applications in mineral processing. IntroductionMetallurgical process development in greenfield projects requires the selection of a comminution flow sheet and must establish the equipment sizes required to deliver the project design criteria. This necessitates a detailed understanding of the ore properties that define the project resource. For brownfield projects the same objectives may apply for plant expansions, or the project objective may be simply to define the capacity and operating cost of an existing facility for a new ore source. The process development phase in either instance will typically comprise the following key activities:• Geometallurgical classification and sampling of the ore deposit or deposits.• Determination of comminution energy requirements.• Benchmarking similar projects.• Identification of flow sheet options.• Equipment selection and sizing.This paper is concerned specifically with process development testing and will as such focus on the first two activities on the list: sampling and testing of the deposit. The discussion will focus on testwork programs to support the design of comminution circuits commonly in use in mineral processing today, specifically crusher, tumbling mill and stirred mill technologies.It is important that any testwork program is designed giving consideration to the types of flow sheets that are viable for the project, and the data that will need to be generated to support the final equipment sizing. Designing a testwork program to only provide information about one particular type of flow sheet will not allow sufficient information to be generated for a rigorous trade-off analysis of options, and may therefore preclude financial optimization of the project. Testing programs should be designed to collect sufficient data to ensure that any backtracking at a later stage to fill in missing information is minimal."

Jan 1, 2016

By S. D. Rosenthal

"This article will share my ‘shift in career direction’ journey from corporate mine engineer, with 31 years of mining various commodities with a wide range of responsibilities in a variety of countries, to the world of academia. There are times in one’s career that a change is required, albeit perhaps not as drastic of a change as moving to teaching. This paper will share how the transition arose, the decision to make the change, the challenges of the first year in academia and the journey within academia going into the second year.As a graduate of the Montana College of Mineral Science and Technology (Montana Tech) with a B.S. mining engineering degree in May of 1982, my first job with Utah International in the Farmington, NM area took me back to my home state of New Mexico. Some of you will remember that the early 1980s was not a period of prolific opportunities for mining engineers, given low commodity prices, especially for copper (for example, Anaconda Co. had been taken over by Arco and was in the midst of closing down its Butte operations). Coal was good and the learning opportunities abounded with Utah (which became BHP and then BHP Billiton).Gold was taking off in the mid to late 1980s thanks to use of cyanide and heap leaching technology improvements, coupled with deregulation of the gold price, so I ventured off to work in the gold industry with a (then) junior Canadian company called Barrick at a new acquisition of theirs known as Goldstrike. That same gold surge was causing a shortage of iron ore mining engineers in Australia. So after a few years in Nevada, I uprooted the family and left for a little town in the Pilbara of West Australia, known as Newman, to work in the iron ore industry with BHP Iron Ore. An initial short overseas posting turned into six plus years before transferring to BHP’s Indonesian steam coal mines in Kalimantan on the island of Borneo. BHP was going through a rough period following some ill-fated projects (Magma Copper purchase, Beanup and HBI) and was reviewing assets and staffing, so internal opportunities became scarce. Employees were encouraged to “leave the company and find work elsewhere.” So, off I went to Argentina to try copper mining in the Andes with Minera Alumbrera. This short stint in South America was followed by a move to another mining town, Morenci, AZ, and a posting with Phelps Dodge (now Freeport- McMoRan). After 12-plus years without living close to snow, we moved to the Denver, CO area in a new position with Newmont Mining Corp. Along the way I became a professional engineer (Nevada) and completed a masters in project engineering and management. After 11 years with Newmont, I moved to Butte, MT where I accepted a position as assistant professor of mining engineering."

Jan 1, 2015

By C. L. Wilsey, K. M. Oakes, W. J. Reich, M. J. Protani

The time frame required to complete the National Environmental Policy Act (NEPA) process for a new mine or the expansion of an existing mine can range from nine to 24 months, or even longer. The time frame will vary depending on whether an environmental assessment (EA) or an environmental impact statement (EIS) will be completed Completing properly designed baseline studies to collect natural resource data to support the EA or EIS prior to the start of the NEPA process can shorten this time frame. In this paper, a two-year natural resource baseline study by Homestake Mining for the Ruby Hill Mine, Eureka County, NV, is used as a case study to describe how a properly designed and executed natural resource baseline study streamlined the NEPA process.

Jan 1, 2003

By Roger Storry, Donald Bruce, Arnaud Hochart

"INTRODUCTIONThe Port of Miami Tunnel (POMT), designed and constructed by Bouygues Civil Works Florida between 2009 and 2014, was a Public Private Partnership between the Miami Access Tunnel Concessionaire, Florida Department of Transport, Miami-Dade County and the City of Miami. The project comprises dual 11.3m internal diameter, 1.27km long, twin lane road tunnels running between Watson and Dodge islands and under the main shipping channel in Biscayne Bay (Figure 1).The POMT was a unique project which embodied many technical firsts and involved the first large diameter tunnels constructed through Florida’s challenging sedimentary carbonate strata. At the outset, a comprehensive ground investigation was performed, using both conventional and less conventional investigation techniques, to characterise the highly heterogeneous ground conditions.The findings of the investigation had a major impact on the tunnelling methods, triggering a series of mitigation works to ensure that the tunnels could be excavated safely and effectively. The mitigations included modifications to the already designed Tunnel Boring Machine (TBM), to facilitate an innovative excavation process, and a unique grouting campaign (Storry et. al. 2013a). The project was completed and opened to traffic in August, 2014 and has significantly alleviated traffic congestion in Downtown Miami.GEOLOGICAL CONTEXTThe geological conditions at the project site consist of carbonate sediments which can be divided into distinct geologic units; the Miami Limestone Formation (Layers S3, S4), the Fort Thompson Formation (Layer S5), the Anastasia Formation (Layer S6), the Key Largo Formation (Layer S7) and the Tamiami Formation (Layer S8). Multiple changes in sea level over a relatively short geologic time scale have resulted in a heterogeneous profile consisting of interbedded sedimentary rocks and sediments, which vary widely, both vertically and laterally (Figure 2)."

Jan 1, 2016

By S. R. Brown

A number of relatively recent factors associated with the design of new metallurgical processing plants have made the effective training of operators a requirement for a successful start-up. Some of these factors include large capital investment in a minimum of processing lines, highly complex process control systems, and stringent regulations on plant effluent, to name a few. More than ever, operating mistakes during the start-up phase can lead to substantial delays in achieving design production, as well as problems with government authorities if permit limits are exceeded. The only way to assure your return on plant investment is to ensure new plant operators have the knowledge to properly run the plant from the outset. A comprehensive set of operating manuals specifically targeted for plant operators and foreman, written by experienced operating personnel, is the only effective way to provide the necessary information for start-up-related training.

Jan 1, 1995

By C. Rodriguez, T. BoBo

Comminution, being the energy intensive part of a mining operation receives much scrutiny by cost controllers, CEO’s, investors and others as the mining industry goes “back to basics” to reverse the decline in productivity which occurred during the mining super cycle. Blasting is the first and lowest cost per ton stage in the comminution value chain. The basic principle that effective blast design can optimize fragmentation from the Run of Mine (ROM) ore muck pile to improve productivity through digging, loading and crushing to grinding and increase mine site profits has been well documented. Benefits of controlling fragmentation in the blast include reduced wear on equipment, faster loading, increased truck loads while detecting oversize rocks at the muck pile can reduce the frequency of a blocked primary crusher. A second basic principle is a measure of particle size distribution (PSD) at each unit operation in the comminution cycle allows engineers to manage blast design to produce fragmentation in the ROM ore most suitable to optimize downstream unit processes to improve mine site productivity and profits. Split-Online® systems have measured PSD of rocks on conveyors from the primary crusher to the SAG mill for over 20 years. Split-Engineering partnered with various mining companies to develop Split-ShovelCam® to automatically measure fragmentation from shovels and excavators working the ROM muck pile. This paper takes the reader “Back to Basics” by discussing the use of real time fragmentation analysis at the muck pile as an important parameter to optimize energy factors required for each blast. Case studies are given. INTRODUCTION The basics of mining are: • Explore for and find economic resources of valuable minerals • Mine rocks containing valuable minerals using blasting • Crush and grind rocks to liberate valuable minerals (comminution) • Recover valuable minerals for sale Comminution is an energy intensive process which accounts for a major proportion of mine site costs. Effective blasting can improve comminution and deliver significant reductions to mine site unit costs, (CEEC, 2016). Engineers, scientists, builders and even philosophers have long promoted the phrase “measure to manage”; the premise being “you can’t improve what you don’t measure”. Blast Engineers measure fragmentation in ROM ore for feedback to manage energy input in the design of blast patterns to optimize the ROM product size for downstream operations, whether they be for ROM Leach or feed into the primary crusher.

Jan 1, 2019

By Bernard P, Lhoumaud E, Gunzburger Y, Conin M, De Santis F, Kinscher J

Seismic repeaters are commonly observed in natural fault zones dominated by slow aseismic motion. The corresponding seismic signal, characterized by highly similar wave forms, is usually interpreted as the repeating ruptures of locked asperities on fault planes (“patches of higher roughness”), loaded by a-seismically slipping areas (“creeping areas”) (Chen & Lapusta 2009; Bourouis & Bernard 2007). Only very few occurrences of seismic repeaters have been reported in underground mines, where these phenomena are rather unexpected since the stress state and the seismic wave propagation continuously evolve with the advancing excavation front (Kinscher et al., 2020). A recent study based on a local seismic network installed in the underground mine of Garpenberg, Sweden, has shown that seismic repeaters and multiplets represent the main part of the total released seismic energy (magnitude of seismic events: -2 < M <1, on moment magnitude scale), with some seismic families being active during several months to years. It is suggested that repeaters are linked to aseismic slip on pre-existing talc-filled fractures, induced by the excavation, and loading of asperities. These results imply that part of redistribution of stresses in the mine is due to aseismic slip, which might explain the observed distant and delayed seismicity.

Apr 26, 2022

By William W. Edgerton

Establishing geotechnical baselines on soft ground projects that require the use of closed-face tunnel boring machines (TBMs) is difficult. It is hard to see the face when mining and the excavated material is combined and mixed, all of which makes baseline quantifications challenging. In an attempt to meet underlying objectives of minimizing bidder contingencies, allocating or sharing risks and paying for conditions only if they occur, nongeotechnical baselines (i.e., functional baselines) have been developed. These have been used on the District of Columbia Water and Sewer Authority?s Clean Rivers (DCCR) Blue Plains Tunnel (BPT) project. This article examines the development of such functional baselines and how they were implemented on the BPT project.

Jan 1, 2012

By Robert Sturk, Knut O. Halvorsen

"INTRODUCTION AND BACKGROUND The world needs visionary people to break new ground and bring development forward. The human race has an inherent power and lust to explore and push borders, but also to connect and bring people together. Transport of people and goods has through history been a key factor to develop societies and increase collaboration between people and regions. Today, in the era of globalization, efficient transport systems are still vital for further development. Often, ideas of bold projects, like long bridges or tunnels, have been raised long before those projects are realized and actually built. This shows that visions must gradually be transformed into feasible business cases and sustainable political solutions. In some cases also technological development is necessary to make visions come true. Isambard Kingdom Brunel, indeed a visionary engineer, completed the oldest underwater tunnel in the world when the Thames Tunnel in London was opened in 1843. This tunnel is still in operation and now part of London’s rail transport system. Another milestone for the tunnelling industry was passed when the 54 km long Seikan tunnel in Japan was opened in 1988 after more than 15 years of construction. This tunnel is presently the world’s longest railway tunnel. Together with the 50.5 km long Channel tunnel between the UK and France, which has the longest undersea portion 37.9 km, they constitute examples of pioneering engineering projects that bring the industry forward. In 2016, the Gotthard Base Tunnel will be opened and then becomes the longest railway tunnel in the world with its 57.1 km. The trend is obvious that tunnels throughout the world are getting longer and longer. The Brenner Basis Tunnel presently under construction will yet again break the record being 64 km long. Presently, a number of even longer tunnels are planned and under design, some of these also have very long subsea portions, e.g. Bohai Straight Tunnel (123 km), Irish Sea Tunnel (around 100 km) and the Helsinki – Tallin fixed link (approximately 90 km). Northern Europe sees an increasing demand on efficient transport corridors to meet the growth of freight transportation between the Scandinavian Peninsula and central-Eastern Europe. Sustainable solutions will be required, and a shift from road/maritime transports to rail is imperative. Consequently, this paper describes yet another visionary project, a fixed railway link between Sweden and Germany, the Shortcut, to enhance traffic between these regions and to make it greener. It is true that this project still requires some work from politicians, economists and engineers to be realized, however, building a 100 km long tunnel under the Baltic Sea may become reality sooner than we think."

Jan 1, 2016

By Yves Boissonnas, Marco Bettelini

"INTRODUCTION AND OBJECTIVES The operational safety of long and very long rail tunnels represents a key issue in all development stages, including design, construction, commissioning and operation. The spectrum of potential threats is very broad and challenging. These issues can only be mastered by means of a proper combination of a number of safety measures at various levels. This paper focuses on the specific safety issues and the extremely challenging conditions characterizing very long and deep tunnels. They include a significantly increased risk during operation that the incident train cannot exit the tunnel by its own means, long self-rescue and rescue distances, the presence of a number of trains, possibly mixed traffic as well as significant thermal issues. Amberg Engineering is strongly involved in the design and construction of most long and very long rail tunnels in Europe, including in particular the Gotthard Base Tunnel (GBT), Lyon-Turin Base Tunnel (LTF) and the Brenner Base Tunnel (BBT). The combined experience arising from these tunnels forms an invaluable body of expertise, which is summarized in this paper. The focus is on shared issues with practical relevant examples and project-specific solutions. Special attention will be devoted to the 57 km long Gotthard Base Tunnel, which will be operational by mid-2016 and will be the longest infrastructure tunnel worldwide. VERY LONG TUNNELS IN EUROPE Overview From the point of view of safety, tunnels in excess of about 20 km exhibit a significantly increased risk that incident trains could stop within the tunnel. This is related to the European Technical Specifications for Interoperability (TSI) on rolling stock, to be discussed in the chapter on rescue stations. This paper will specifically focus on the following longest tunnels in construction or operation, listed in Table 1."

Jan 1, 2016

By Basilio Giurgola, Federico Bonaiuti, Norbert Fuegenschuh

The North East Boundary Tunnel (NEBT) project in Washington, D.C. requires design and construction of several SEM adits which have to be built between lateral shafts and the NEBT-TBM Tunnel. The paper describes ground improvements, the actual excavation, and also the final lining works. Schedule and sequencing restrictions provided some unique challenges which had to be considered when designing and constructing these mostly short, but essential portions of the project

Dec 1, 2022

By J. Herhold, S. Plaum

The focus within the economical optimization of projects, which are conducted underground, shifts more and more towards the conduction of construction work underground. Underground operations can be defined in a wide range of various projects, from underground mining tasks to the construction of engineering structures. Within these projects the conduction of construction work cannot only be defined as absolutely necessary, but sometimes also as optimizing for underground processes (e. g. installation of workshops underground to support the mining processes). Even though the conduction of underground construction might cause positive outcomes concerning the productivity, it also tends to be challenging due to local (sub-surface) conditions and influences. To minimize the risk of failure and sudden events within in the conduction of construction work underground, the tool “work preparation” shall be used. Under the given constraints, such as local influences, expected construction work and set time frame, the conduction of the construction work will be planned in advance by consideration of the construction logistics as well as the selection of a fitted construction technique. PROBLEM DEFINITION Economic Challenges - Raw Material Extraction Enterprises in the construction, mining and raw material extraction industries are increasingly under the pressure to perform economically to sustain their position on the global market. Profitability, efficiency and productivity are the basic conditions to be an active participant on the global market as well as a business partner and contractor for mining and construction projects or projects related to the extraction of raw materials. The completion of large-scale as well as common construction projects above ground has been under the pressure to minimize costs and time whilst maximizing the potential outcome, in the meanings of quality and economic gain, for more than a decade now. Whereas the construction industry has to fight the competition on the market with efficient project outcomes, the mining industry has to find ways to perform efficiently to further conduct the extraction of decreasing raw material deposits. The ongoing exploitation of existing raw material deposits to satisfy the constantly increasing raw material demands world-wide, led to the predicament that economically mineable deposits have decreased dramatically. Even tough mineral deposits do still exist on a global level, near-surface deposits decrease rapidly. Therefore, the extraction of raw materials within mining operations will be relocated further away from the surface in greater depths. With the growing distance from the surface to the mineral deposit, the extraction costs will increase many times over. With that in mind, the extraction costs will increase whilst the economic efficiency will decrease. The extraction of certain deposits will no longer be profitable with the common approach. To further extract raw materials efficiently even in greater depth, companies have to change their practice in different ways. That leads to the fact, if the deposits are in the depths, where the extraction processes won´t be economically, other (support) processes have to be in order to guaranty an economical corporate process itself. This precept will divert the focus from the actual mining process to support processes, where potential for optimization still can be found, as shown in figure 1.

Jan 1, 2019

By Sean Hunter

Artificial Intelligence has a long history but is currently coming strongly into focus with new advancements. This leads to questions many people are asking: what exactly is AI, how can it be used effectively in mining operations, and what foundation is required to make AI implementations successful? In mining, many AI applications exist, from drill pattern optimization to predictive maintenance. However, many implementations struggle due to data integration challenges. Mining operations generate large amounts of data from many sources, such as fleet management systems, drill sensors, process control systems, and laboratory results. Unfortunately, this data often exists in silos where it’s difficult to get it out, making AI applications unable to leverage it. Worse still, tools that use AI don’t always provide their data back to the system, creating even further data silos. All these problems make it hard to take advantage of the data at the mine, slowing down and reducing the effectiveness of AI. This paper presents a comprehensive approach to organizing mining data using an AI-ready knowledge graph system. We will first explore the evolution of AI in mining, from early expert systems to modern machine learning applications. Then, we will detail how a knowledge graph can integrate business context, operational data, and AI models into a cohesive system that enables more effective AI implementations across mining operations. The proposed method has been developed considering both the unique data challenges faced by the mining industry, while also considering best practices learned from the AI field at large. By following this approach, it’s possible to better utilize existing data, getting higher quality and more complete results faster, and in a way that’s reusable and composable.

Feb 1, 2025

By L. Evrard, M. Van Camp, J. Y. Yen, R. G. Reddy, D. Mantha

Viscosities of two industrial lead blast furnace slags have been experimentally determined as functions of composition and temperature. A Brookfield viscometer with alumina rods and crucibles were used. Experiments were carried out between 1200 and 1573 K in an argon atmosphere with up to 5% addition of FeO, MgO, and SiO2 to the slags. Results showed that 1) the viscosities of two slags decreased with increase in temperature; 2) addition of FeO decreased the slag viscosities; and 3) addition of MgO and SiO2 increased the slag viscosities. Use of the above slag compositions with the addition of FeO is recommended for successful lead smelter operation.

Jan 1, 2005

By T. R. Ellis

Regulation of mineral property valuation methodology by governments and others is due to frauds, condemnation and takings, banking industry problems, and litigation. Definitions of "reserves," "resources," and "qualified person" continue to evolve, along with guidelines to the data and disclosure required to support valuations. A less recognized but vital issue relates to the regulatory acceptability of alternatives to the comparable sales method. Comparable sales generally work well for surface real estate, and sometimes for precious metal deposits, but not at all for most industrial mineral properties. Alternative methods, such as net present value, or a geoscience rating system, often provide better valuations. Yet US regulations dictate comparable sales as the preferred method. The task of convincing regulators of the inapplicability of comparable sales to mineral properties, particularly those lacking reserves, may be as important as the valuation itself.

Jan 1, 1999

By Mohamed Gamal, Bill Zietlow

"In oil fields that have been depleted with conventional surface oil wells but still contain significant reserves, an extraction alternative that has been constructed recently consists of a drilling gallery below the oil-bearing formation at the bottom of a 1,200-ft deep shaft where upward sloping wells are being drilled to allow oil collection by gravity. The gallery is 92-ft diameter with a flat ceiling supported by rock bolts and shotcrete structurally connected to the shaft liner, which doubles as a large tension support element. A special excavation sequence was implemented for the gallery to maximize arching in the stress above the large diameter gallery. The gallery was located in competent sandstone, constructed with sequential excavation methods, and designed with a 3D finite element model. Special consideration was given to optimizing the gallery location to take advantage of the geology for construction and support while giving good positioning to the well drilling equipment. BACKGROUND Brierley Associates was contracted to provide both design and construction management services for an approximately 1,165-ft deep, 18-ft excavated diameter vertical shaft that opens to a 92-ft diameter flat roof gallery. The geotechnical data for the site was based on information available from literature and from data obtained during core drilling and from in-situ testing in a 1250-ft deep borehole. Wire line coring was conducted using a HQ, 10-ft long core barrel with a mud-rotary drilling method through sedimentary bedrock. The geometry of the shaft and the bottom gallery is shown in Figure 1(a). GEOLOGIC SETTING AND STRUCTURAL GEOLOGY The stratigraphy at the site includes a series of interbedded marine limestone, shale, claystone, siltstone, sandstone, and chert units. Limestone and shale are the predominant lithologies in the upper approximately 675 ft, while the lower portion contains five distinct sandstone units and more abundant shale, claystone, siltstone, and coal than the upper zone. A cherty sandstone at a depth of 1,130 below ground surface (bgs) was encountered. At a depth of about 1,000 ft to 1,116 ft bgs, a non-marine sandstone unit was encountered. This sandstone is the hydrocarbon bearing layer. Joints and fractures observed in the limestone had dips ranging from 0 to 90 deg. from horizontal with joint and fracture surfaces that ranged from planar to irregular and smooth to rough. Several, near vertical shear planes with slickensides were observed with surfaces that were generally smooth and planar. RQD values for the limestone ranged from 0 to 100 percent but in general were good to excellent."

Jan 1, 2016

By Jerry M. Riggsbee, John H. Weber

INTRODUCTION The Washington Metro is a 98 mile rapid transit system that will serve the District of Columbia, southern Maryland, and northern Virginia. The construction work herein described relates to Section B-1 of this system. The contract for this work was awarded by the Owner, The Washington Metropolitan Area Transit Authority, to a joint venture doing business under the name of Ball-Shea-Norair. The partners in this venture were Gordon H. Ball, Inc., Danville, California; J. F. Shea Company, Inc., Walnut Creek, California; and Norair Engineering Corporation, Washington, D. C. The bid price for the project was $33,741,524 with a contract duration of 910 calendar days. Notice to proceed was issued January 5, 1970. The present modified price for the work is $36,866,000 with completion anticipated in July 1974. (About 1,638 days elapsed time.) The work to be done consisted essentially of construction of 3,490 linear feet of cut-and-cover track with side platform, and 600 ft cut-and-cover arch shaped subway stations. Stations are located in Judiciary Square and Eighth & G Street, N. W., areas. Decking of excavation in street areas, maintenance of traffic and utilities, vent and fan shafts, underpinning of court buildings in Judiciary Square and the Smithsonian National Portrait Building, and an electrical substation were included in the contract. Stations were constructed of cast-in-place concrete.

Jan 1, 1974

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.&apos;" 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 Purnima A. Shivdasan

The fluorspar deposits at Okorusu, Namibia are closely related to an alkaline igneous ring complex of late Cretaceous age (125±7 Ma). The fluorite ores consist of relatively fine-grained purple replacement fluorite and subsequent coarser grained purple and green vug-filling fluorite crystals. Homogenization temperature measurements for 38 primary fluid inclusions shows that main stage purple to green fluorite crystals were deposited over a temperature range from 166°C to 144°C, and minor late yellow fluorite was deposited at lower temperatures from 132°C to 128&apos;C. Homogenization and freezing temperatures measured for 18 primary fluid inclusions shows that the fluorite-depositing fluids were less saline than MVT ore fluids and overlap the lower temperature range of fluids that deposited epithermal ore deposits. Mining in two open pits (A and B) at Okorusu has gradually provided exposures which reveal that the fluorite orebodies have been emplaced primarily by the preferential replacement of carbonatites. Evidence for the replacement of carbonatite includes: 1) replacement remnants of carbonatite within the fluorite ores, 2) goethite pseudomorphs after the carbonatite minerals, pyroxene, pyrrhotite, and magnetite that are disseminated in the fluorite ores, 3) partial replacement by fluorite of a titaniferous magnetite rimmed carbonatite dike in the A pit, and 4) partial replacement by fluorite of a large sill-like carbonatite body in the B pit. Electron microprobe analyses of minerals in unreplaced portions of the carbonatites show that their mineralogy consists of titaniferous magnetite, diopside pyroxene, apatite, biotite, and calcite. Magnetite contains 6.97% to 10.46% Ti02, averages 8.44% Ti02, and has an average V203 content of 0.35%. At high magnifications under the SEM, the magnetite shows abundant fine ulvöspinel exsolution lamellae arranged in a cloth texture. Apatite contains moderately high fluorine contents that range 3.21 to 5.0% and average 4.2%, and apatite crystals range in total rare earth oxides from 1.7% to 2.61%. Pyroxenes in the carbonatites are iron-rich diopside, and they contrast to pyroxenes in the fenites that are aegirine-augite. All of the microprobe analyses for mica crystals in the carbonatites give biotite compositions. The fluorite ores also have replaced marble locally in the A pit, especially along the A band in the B pit, and dominantly in the orebody proposed for the new C pit. Carbonatite and marble were preferentially replaced by fluorite because the calcite was readily soluble in the presence of the fluorite-depositing fluids and the dissolution of calcite provided calcium for the formation of fluorite.

Jan 1, 2005