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By Michael H. Leon, John A. Organiscak

Controlling worker dust exposure on longwall mining systems is difficult because the working face area serves as an immediate return during the mining cycle and the amount of airborne dust generated is directly related to production. Since improvements in longwall mining technology have significantly boosted production levels, additional technology is needed to control the airborne respirable dust generated at present and future production levels. One concept to reduce longwall worker's dust exposure is to maintain two splits of air at the face -- a clean intake split in the workers walkway, and a return (dusty) split over the face conveyor. The U. S. Bureau of Mines has recently investigated a concept to overcome the visibility handicap of face partitions by utilizing a permeable polyester mesh. The mesh material was anticipated to provide adequate air-splitting capabilities as long as the pressure differential between the face and worker walkway was minimal. Initial testing of this concept at the Bureau's Lake Lynn Laboratory showed that notable reductions could be achieved with a 1/8 in (3.18 mm) and 1/16 in (1.59 mm) mesh opening size. Dust reductions at 100 ft (30.5 m) and 200 ft (61.0 m) downstream of source were 58 and 36 pct, respectively, for the 1/8 in mesh and 79 and 55 pct, respectively for the 1/16 in mesh. Longwall application of the 1/8 in mesh showed similar results to the Lake Lynn Laboratory tests. A flame retardant mesh was used underground with portable lighting mounted on the shearing machine for face side lighting.

Jan 1, 1993

By C. R. Everly

"The purpose of this paper is to review the most effective methods of reducing chloride transfer and chloride removal in the solution extraction and electrowinning (SX/EW) process. Elevated chlorides in electrolyte have various negative effects including a reduction in current efficiency, increased handling costs at rod plants and smelters, increased anode corrosion, cobalt losses due to increased electrolyte bleed, degradation of HDPE piping, and increased corrosion in the SX/EW plants. Historical controls that Sierrita has used to control chloride transfer, in order of effectiveness, have been chloride gasification at the EW that is directly correlated to amperage and chloride concentration in electrolyte, wash stage bleed and efficiency, width and velocity of aqueous bands, and electrolyte bleeds. Maintaining high bleed rates and high amperage settings has been a challenge with decreasing pregnant leach solution (PLS) grades, so keeping chlorides out of the electrolyte has become imperative. The effectiveness of reducing aqueous entrainment, optimizing wash stage efficiencies, and improving organic quality to reduce the transfer of chlorides to the electrolyte are illustrated in this study. INTRODUCTION The transfer of impurities from PLS feed streams to electrolyte in the Copper Solution Extraction process is a very common problem and is the reason that the wash stage exists in most SX operations. The main impurities affecting the SX process are iron, chloride, nitrate, and manganese. Elevated chlorides in the electrolyte have various negative effects including reduced current efficiency, increased handling costs at rod plants and smelters, increased anode corrosion, increased cobalt losses due to increased electrolyte bleed, degradation of HDPE piping, and increased corrosion in the SX/EW plants. Freeport-McMoRan Sierrita Hydromet is unique in that a high-chloride byproduct stream from the molybdenum process is pumped into the SX raffinate solution pond. This byproduct steam accounts for the majority of chloride introduced to the circuit, and over the years has built up to a point where 4000ppm chloride is consistently in the PLS feed to the SX. Concentrations of chloride over 70 ppm in electrolyte will result in downgraded cathode, so it is important to limit chloride carryover from SX as much as possible. Historically, Sierrita has been able to manage chloride levels with reactive techniques including increasing electrolyte bleeds and rectifier amps. Decreasing copper in PLS has made high amps harder to maintain, and increasing bleed rates have a direct impact on production goals."

Jan 1, 2015

By Bryce Sullivan, Cliff Baratta, Ehsan Alavi, Timothy Dobbs, Lisa Mori

"Soil conditioning is one of the main factors in successful application of EPB machines in tunneling projects, which involves changing the characteristics of the ground in order to make it suitable for the tunneling process. Selection of the type of conditioner mainly depends on soil type, properties of the tunnel boring machine, and most importantly geological condition. Proper EPB tunneling and soil conditioning in ground above water table is challenging. This was encountered in Northgate Link Extension Tunneling Project in Seattle, WA. In order to improve the tunneling operation, a novel algae-based encapsulated oil was used as a conditioner and as a result the operation of the TBM was improved significantly. This paper reviews the traditional soil conditioning measures that were adopted in University Link and Northgate Link projects in Seattle, WA and compares the results with results when using the encapsulated oil additive. INTRODUCTION Soil conditioning agents are used in EPB tunneling to transform the excavated soil into a workable paste with the desired hydrological and mechanical properties. Reducing wear, power consumption, friction, adhesion, and improving the face stability and material flow are some of the benefits of using soil conditioners in EPB tunneling. Soil conditioning is performed by injecting foam, polymer, water, and bentonite to the tunnel face, excavation chamber and screw conveyor. Selection of conditioning agent mainly depends on soil type, geological condition (groundwater and soil permeability) and TBM features (injection points, open or closed cutterhead, type of foam generator, etc). The most widely used soil conditioners are foam and polymer and in some cases due to existing conditions, clay dispersion or anti-wear additives are also used (Milligan 2000, Langmaack 2000). Foam. Foam is created by dispersing air in a surfactant solution. A different combination of surfactant type and foam parameters should be used for different soil types. Laboratory tests on virgin soil should be performed to identify the best surfactant and foam parameters for the specific soil type (Langmaack 2000). The foam parameters can be described as follows:"

Jan 1, 2016

By Robert C. Freas, Donald D. Carr, Lawrence F. Rooney

Perhaps no other mineral commodities in this volume have as many uses as limestone and dolomite. These carbonate rocks are the basic building blocks of the construction industry, the material from which aggregate, cement, lime, and building stone are made. Carbonate rocks, and their derived products, are used as aggregates, fluxes, glass raw material, refractories, fillers, reactive agents in sulfur-oxide removal, abrasives, soil conditioners, ingredients in a host of chemical processes, and much more. Although the use of limestone and dolomite goes back before recorded history, new uses and products are continually being found. Carbonate rocks form about 15% of the earth's sedimentary crust and are widely available for exploitation. Found extensively on all continents, they are quarried and mined from formations that range in age from Precambrian to Holocene. Reserves of carbonate rock are large and will last indefinitely, although high-purity deposits may be absent or have limited availability in certain areas. Limestone and dolomite are so useful and so abundant that in 1989 about 798 Mt were produced in the United States. In fact, about 75% of all stone quarried or mined in the United States was carbonate rock. Sand and gravel was the only mineral commodity produced in greater quantity. In this chapter we have sought to provide the general reader an overview of carbonate rocks, their composition, distribution, production, and uses. The literature on the limestone and dolomite resources of the United States and Canada is so vast and diverse that one can easily become mired in print. We tried to list those references that are easily accessible and that provide the economic geologist with a starting point for more intensive study. The table listing selected references on limestone and dolomite resources in Canada and the United States reflects our attempt to be selective rather than exhaustive and to direct the reader to the best sources of detailed information.

Jan 1, 1994

By G. R. O?Neil

The justification for a "ligand- selective' approach to fine mineral beneficiation via flocculation is established initially. Special emphasis is placed upon the need to identify non-selective, interfering and complicating adsorption effects. Specific strategies directed towards the design and synthesis of complementary selective flocculants are detailed using a number of different polymers and chelating agents as examples. In this regard, the affinity of polymer-bound ligands for metallic cations, ligand concentration, possible modes of attachment, the application of spaced-out ligands and other considerations in the preparation of selective flocculants are highlighted.

Jan 1, 1983

By R. J. Matetic

The impact of longwall mining on the local hydrological regime has become an important environmental focal point. Unfortunately, only a few studies have addressed the timing and range of well fluid level fluctuations and the associated ground movement. Furthermore, even fewer studies have determined the influence of longwall mining on water quality. The U.S. Bureau of Mines is providing insight into this environmental concern through a program of field case studies. One such study was conducted in Cambria County, PA where five observation water wells were drilled above two adjacent longwall panels. In this study, three wells were completed as nested piezometers and the remaining two served as producing wells. The piezometers were positioned along a line oriented subparallel to the longwall face and were located at the centerline of each panel and over the intervening chain pillars. The piezometers were designed to monitor fluid level fluctuations in both shallow and deep water-bearing zones. Slug tests were conducted before and after mining to characterize changes in hydraulic conductivity of the respective water-bearing zones. Pressure transducers and data loggers were installed to provide continuous fluid level fluctuation data as mining developed through the study area. The producing wells were drilled to provide water quality information. One well was located directly above the centerline of a panel and the other was positioned over the panel's set-up rooms. The wells were designed to simulate domestic use and were produced daily, for four hour intervals, throughout the study. Samples of the produced water were collected before and after mining progressed through the area. In addition, an array of monuments was installed near the study wells and was periodically surveyed to characterize mining-induced surface deformations. This study shows that: a) the observed changes in ground water chemistry did not affect the potability of the water; b) short-term major water level fluctuations occur at the approximate time of undermining; and c) water level recovery begins before the process of subsidence is complete.

Jan 1, 1986

By M. A. Candia

Stability analyses were performed on the La Libertad, Nicaragua existing tailings embankment in order to determine the conditions for the minimum buttressing required for stability of the dam as a short term measure. Two critical sections, shown in Figure 1, were investigated under static, drained and undrained conditions for existing and modified geometries. The existing geometries reflect the "as built" topography of the dam, and the modified geometries reflect the implementation of a toe berm to buttress the slope. For these geometries drained and undrained conditions as well as different elevations of the toe berm were evaluated against a factor of safety.

Jan 1, 1996

An insufficient hydrologic data base exists for most large and small coal basins in Alaska owing to the lack of need in the past to collect data. The runoff process is insufficiently understood which is complicated by specifically northern phenomenon, and the lack of understanding of hydrologic relationships in permafrost environment. This paper presents an understanding of the hydrologic effects of frozen ground and presents methods by which the influence of surface mining upon the hydrologic balance can be analyzed.

Jan 1, 1988

By T. M. Plouf, G. A. Lang

INTRODUCTION The finding or acquisition of ore bodies containing 200,000 opt gold and greater is becoming more difficult. There are more investors and small heap leach operators who have or can raise the capital to make the investments in the large ore bodies. Echo Bay Mines' approach has been to regionally develop small ore bodies, two or three in the same geographic location, which when considered together contain over 200,000 opt gold. CONCEPT The "world class" ore body syndrome, which many large gold producing companies maintain, can restrict company growth if the finding or acquisition of these large ore bodies is not forthcoming. Another approach has been taken by Echo Bay Mines. The concept is to regionally develop two or three small ore bodies suitable for processing with portable equipment. The systematic scheduling of mining, processing with a single flexible processing plant using the same management/ operator team can reduce your overall investment. The initial selection of mining and crushing equipment suitable for sun11 open pit operations is essential. A very viable option in the mining sequence is to use contract mining/crushing/screening/agglomerating and stacking. This option also lowers your initial capital investment and increases the flexibility in mining as you move from one mining operation to another. LOCATION AND SEQUENCING One single small ore body of itself is not attractive enough for the large producer. The recovery of the initial capital investment, although very rapid, does not make a viable project. The only alternative is to find two or more small ore bodies close enough geographically to each other so that the same management/operator team can be used to run the operations as each is put into operation. Echo Bay Mines has regionally located several ore bodies ranging in recoverable ounces up to 100,000 oz. These small separate ore bodies, located within a 30-mile radius of each other, for planning purposes have been considered as one single ore body. The first small ore body has the initial burden to recover the capital invested in the office, laboratory, power plant and processing plant. Other capital investments such as water supply, access and haul road, fencing, septic system, pads and ponds are reoccurring at each mine site. The first small ore body must recover the initial capital investment in the movable structures as well as the reoccurring capital investment in the fixed structures very rapidly. A total capital recovery time of 6 to 9 months should be used as an economic decision point for both choosing which small ore body should be processed first, and what the plant design capability should be. The sequencing of the small mines is very critical. All the fixed structures mentioned above must be installed at the second mine site before the first mine has been mined out. The ideal sequencing will allow for only one month between shutdown of the first small mine and production from the second. SPECIFIC OPERATION Echo Bay Mines has completed the construction of the Illipah Mine located in White Pine County, Nevada, with this small mine sequence approach. The Illipah Mine is a 40,000 ounce recoverable gold ore body. This ore body met all the necessary requirements. The Illipah project could support the capital investment in the movable structures which will

Jan 1, 1987

By E. W. Hawk

The power generation industry may be required to reduce CO, emissions if regulations related to global climate change are enacted. Coal-fired generation, which emits 82% of the power sector CO2, would be a likely target for CO2 reduction. Compliance with the Kyoto protocol will require a 30% reduction from the projected year 2012 emission level even with moderate load growth. This paper describes an analysis of power industry CO2 reduction options and their costs to assess how a generator would make compliance decisions under a mandatory CO2 emissions reduction program. Carbon sequestration, fuel switching and new plant construction are considered.

Jan 1, 1999

By R. J. McGregor, Deepak Malhotra

Engineers frequently encounter situations where decisions that are counterintuitive to the logically trained engineering mind are made because of other influences, whether they be financial, social, cultural, or environmental. Such influences can overrule the "logical" decision-making process. The aim of this book is to explore some of the nontechnical issues, which most engineers don't learn about in school, that can have a major impact in the mining industry. This chapter gives a brief overview of this volume and introduces the topics that will be addressed.

Jan 1, 2001

By Simon J. McDonald

In late 2007 Neptune Minerals Plc. commissioned Genesis - a leading consultancy and engineering company affiliated to the Technip group - to undertake a Seafloor Mining Conceptual Study for mining of Seafloor Massive Sulphides (?SMS?) in Neptune?s New Zealand licenses. A key deliverable of the study was information to de-risk the perception of SMS mining for investors the minerals, and that deep-sea mining of SMS material is technically feasible, commercially viable and can safely be managed as a sustainable marine resource industry. The aim of the study, completed in April 2008, was to evaluate alternative existing marine technologies for seafloor mining, ore lifting, dewatering and surface offtake, considering the following parameters: ? Efficiency; ? Reliability; ? Safety; ? Environmental impact; and ? Cost

Jan 1, 2008

By J. Harrison Daniel

More stringent dust standards, because of quartz in coal, have become a major compliance problem for the coal industry. Reducing quartz levels has become the major focus of the Bureau of Mines dust control research program. Results to date have identified hath the sources of quartz and prospective control technology. Control techniques are being developed for both room-and-pillar and longwall mining underground operations. Techniques include changes in face ventilation, mining cycle modifications, and better roof bolting dust control.

Jan 1, 1985

By Sarah Vest, Richard Sherman, Leo Martin

In 1988 a major exploration program was undertaken to determine the characteristics of the rock and soil for a 7.6 m diameter sea outfall tunnel beneath Boston Harbor out into Massachusetts Bay. The diffuser discharge location had been mandated by the EPA to a 10 sq. km area of seafloor connected to the proposed Deer Island Treatment Facility by a 14.5 km tunnel corridor. Geophysical surveys, deep rock borings, and laboratory testing, provided the information for the conceptual design. The program identified the range in material types and parameters to prove feasibility of a TBM driven tunnel and to locate the optimum alignment and depth.

Jan 1, 1991

By W. F. Quirk

The Missouri-Oklahoma tripoli district was discovered and first mined in 1869 near Seneca, Missouri. Tripoli is a microcrystalline form of high-purity silica that is porous, light- weight, and friable and is derived from a parent siliceous sedimentary rock from which soluble minerals have been leached. Tripoli deposits, 2 to 20 feet thick, occur in cherty limestones of Mississippian age beneath 2 to 10 feet of overburden. They are mined in open pits up to 9 acres in size. The color of tripoli is white, but it also commonly is light pink or red where stained by red iron oxides and clays. Ground tripoli is used commercially as an abrasive or in buffing and polishing compounds and is prized for such physical characteristics as its abrasiveness, porosity, permeability, absorption, and specific gravity.

Jan 1, 1978

By Robert J. Mac Kinnon

A moving grid finite element model for the analysis of transients in a rock mass surrounding an underground coal conversion cavity is presented. Major model components are outlined, including a special element formulated to account for internal discontinuities. A numerical example is described.

Jan 1, 1986

By J. Launay

In order to control and dispatch the sewage water coming from 3 tunnels toward 2 downstream sewage tunnels, a large cavern has been excavated in a suburb of PARIS. Located at a depth of 47,00 m, it has been excavated using the NATM procedure through swelling clay, weathered sandstone, and marl and chalk. It is 16,50 m high, 12,40 m wide and 60, 00 m long, with an elliptical cross-section and its two ends are egg-shapped. The final lining of the cavern is composed of 30 to 40 cm of shotcrete, steel ribs and passive anchor bars. The excavation stages and related movements were surveyed by extensometers, pressure cells and convergence devices. The design, method of construction of the cavern and the results of the measurements made are commented.

Jan 1, 1989

By W. L. Chen

In the United States hydraulic cyclones have been used for thickening, classification and cleaning in coal preparation plants for many years. The cleaning cyclones presently in use are based on using a "heavy medium", such as a fine magnetite and water pulp. The latest addition to cleaning cyclones is the one which uses ?water only?, or simply called "Hydrocyclone". Just as was the heavy medium cyclone, the hydrocyclones were originated in the Netherlands (1, 2). Plants using hydrocyclones were built in Europe (3) and test plants were erected in Canada (4, 5, 6) and India (7). Roberts and Schaefer Company has built four plants using hydrocyclone circuits. One additional plant is in the process of construction.

Jan 1, 1965

By B. F. Westfall

Throughout the 1960's and 1970's world trade grew rapidly, reaching a peak of USS1.8 trillion in 1980. Since then the world recession of the early 1980's shrunk trade to about US$1.6 trillion. The reduced cash flow to developing economies made it difficult to service their huge international debts, Nowadays lenders are reluctant to grant Third World countries additional credit. The shortage of export financing, plus trade barriers set up by developed countries, is further inhibiting international trade. Therefore, countries are turning to new and creative alternatives to financing imports of consumer as well as of investment goods. Non-cash transactions, including different forms of countertrade, are rapidly growing alternatives to traditional trade financing patterns. In 1983 about 30% of international trade, or close to US$600 bill ion, were presumably done by non-cash transactions, up from barely 2% in 1976. By year 2000, half the world trade is likely to be conducted on basis of barter. As of mid-1984 some 88 nations used countertrade regularly and Governments of at least 15 Latin American countries had arranged or mandated commercial countertrade.

Jan 1, 1986

By K. N. Han, M. C. Fuerstenau, T. B. Onlin

An investigation of the removal of finely divided silica, coal, and alumina particles less than 20,µm in size has been carried out using liquid fluidized and packed beds. The bed particles used included 48x100, 100x150, and 150>200-mesh silica, corundum, and ilmenite particles. Important variables examined included surface charge, flow rate, pH and amount of bed particles. Surface charge has been identified as the most important variable in this system. Van der Waals force also assumes a very important role in the recovery of fine particles in fluidized and packed beds. In addition to interaction between large and fine particles, interaction between fine particles themselves assumes an important role in the overall recovery.

Jan 1, 1987