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By M. Adnan Goksel

A blast furnace test of approximately 5,000 tons of PelleTech Corporation (PTC) cold bond pellets was successfully run at Kaiser Steel Corporation (Kaiser) Steel Manufacturing Division at Fontana, California. The pellets were produced from mill scale, BOF dust and blast furnace flue dust. A 15 day base period, during which time the metallic burden was 2/3 heat indurated pellets and 1/3 sinter, preceeded the test. During the test period the metallic bur- den was 10% cold bond pellets, 56.7% heat indurated pellets and 33.3% sinter. A 15 day post test base period followed during which the PTC pellets were replaced by conventional pellets. The pellets were produced in the 3.C Semi-works Facility located on Kaiser property. The facility incorporates the Michigan Technological University Hydro-Thermal Agglomerating Process.

Jan 1, 1979

By Stanley W. Ivosevic

Introduction Increasing investor and industrial demand for gold is not being matched by new mine output from traditional sources. This forces the exploitation of alternative natural and industrial resources to supplement traditional sources. A traditional natural resource is either high- to medium-grade ore, of gold or silver with coproduct gold. Or, they are medium- to low-grade base metal ores having byproduct gold. Traditional ores are also frequently extracted at relatively great expense by selective underground mining. Alternative natural resources include low-grade, near surface ores and the products of mining-dumps - and of onsite processing - tailings. Traditional industrial resources are newly mined gold or that obtained from plant sweepings. Their alternative analogues include gold in old scrap and chemical sludges and precipitates, notably those incidental to the electronic industry. These alternative gold resources have several attractions. They are untapped and abundantly available. Having been overlooked by prior metals suppliers, title to many alternative resources is easily acquired. Or, the value of such a resource may go unnoticed until its gold is rendered exploitable by an advance in extractive technology or an other approach. This article addresses the effect of large tonnage, low-grade lode ores on gold supply. Exploiting these ores is rendered commercial by their amenability to bulk mining by modern large-scale mining and metallurgical operations requiring little selectivity. Placer gravels, perhaps the earliest type of gold ore mined, also are bulk minable. But these fall outside the definition of being lode deposits. Most lode bulk mining is from surface open-pit mines. Some, however, is from underground by such large-scale mining techniques as room and pillar, vertical crater retreat, and end slicing. The low-grade gold ore being discussed averages 2.8 g/t (0.082 oz per st). Output How greatly do bulk minable, low-grade resources effect supply? 1982 was a somewhat healthy year for gold mining and exploration in North America in spite of the general depression in the mining industry (Table 1). The wildly fluctuating price of gold bullion had stabilized at an annual aver¬age of $12.08/g ($376 per oz) - (Handy and Harmon base price). Half of the 1.3 kt (43 million oz) of 1982 world gold mined were from South Africa's high-cost, medium-grade, selective underground mines. Of the remaining half, 20%, or about 130 t (4.2 million oz), was mined in North America. This includes Canada and the US - the third and fifth largest gold producers in the world. Of that North American production, more than 62.2 t (2 million oz) of gold, or about 50%, came from bulk mining of gold ores with or without co-product silver. Most of this was in the US, where bulk minable gold-silver lode ore produced nearly 31 t (1 million oz). This amounted to 60% of the nearly 46.6 t (1.5 million oz) produced in the US during 1982. An additional nearly 7.7 t (250,000 oz) of gold were produced as the byproduct of bulk mining of cop¬per ore, for a total of 34 t (1.1 million oz) of gold, or 75% of US gold production by bulk mining. To further illustrate this, US placer, mine dump, and related operations produced an insignificant 4% of US gold output at the time. Exploitation of bulk minable gold deposits is becoming increasingly important worldwide. Most new Australian gold mining announcements are of bulk minable developments. This trend will increase in North American mining as more large tonnage, low-grade operations come onstream in Canada, where much current production is from underground. It will increase with the general climb in Mexican gold mining. And it will grow with expansion of the 12 t/a (400,000 oz per year), gold production of the Dominican Republic. Production Metal price and operating costs make these large tonnage, low-

Jan 11, 1984

By R. Robertson

Dense medium cyclones are the preferred means for cleaning 112 in. x 14 Mesh to 28 Mesh (12.7 mm x 1.0 mm to 0.6 mm) raw coal and are becoming a common choice for cleaning raw coal from a nominal top size of 2-1/2 in. to 3 in. (63.5 mm to 76.2 mm) down to 14 Mesh to 28 Mesh (1.0 mm to 0.6 mm). During the last ten years, dense medium cyclone circuitry design has undergone changes which have combined to improve process efficiency. This paper describes these improvements and compares present day design with the design used prior to the mid 1980's. Improvements in the following areas are described: Raw coal desliming, cyclone configuration, drain and rinse applications, dilute medium circuitry, and instrumentation and control.

Jan 1, 1997

By Jr. Chesson

"Phosphate" is a misnomer as often used. The word is increasingly used to refer to any material containing phosphorus - an element essential to any form of life. Phosphate rock, a mineral - fluorapitate - is recovered from Florida's sedimentary deposits in particle sires ranging from 0.1 to 13.0 millimeter. This product of mining, washing, screening, and flotation is commonly called "phosphate". Its phosphorus content, measured and reported as P2O5, varies from 29% to 35%, and is essentially insoluble. "Phosphate" is also used to describe products containing soluble phosphorus obtained from acidulation of phosphate rock with mineral acids; primarily, sulfuric acid. Many miners have nearby chemical plants wherein phosphate rock is converted into upgraded products such as phosphoric acid, superphosohates, and ammonium phosphates with 45% to 70% P205, soluble and suitable for use as fertilizer. The rock and upgraded products are all commonly called "phosphate"; the plants, "phosphate plants' and the producers collectively are known as the "phosphate industry". The public in Central Florida generally loses identification of the individual operators that include major corporations such as IMC. Williams Companies, W.R. Grace, Mobil, Embark, U.S. Steel, Borden, American Cyanamid and others. They all become just a "phosphate company".

Jan 1, 1978

By C. W. Schultz

The distribution of material passing a screen, or a set of screens, is described by the equation [ ] where p = the probability that a single particle will pass the screen on a single presentation k = number of layers of screen cloth n = distance from head of screen expressed as number of screen openings. This model can be used to predict the performance of conventional screening operations (i.e., k = 1) as well as the so-called "statistical screening" operations. Using this technique, in which multiple identical layers of screen cloth are employed, screening can be carried out at a finer size than is possible with conventional techniques with no loss of separation efficiency.

Jan 1, 1969

By James K. Ballard

Leach dumps in Butte are relatively new in comparison with older established dumps in other areas throughout the West. With the exception of one 10 million ton dump, all dumps have been formed on a prepared base. This is necessary because the entire leach dump area overlies an alluvial fill which varies in depth from 100 to 400 feet and through which solution would be lost. Preparation of the leach pad consists of first removing all vegetative material and compacting the exposed surface with rollers. This surface is covered with a 4" layer of minus 1" crushed rock which in turn is roller compacted. A 3" compacted layer of asphalt hot mix is then applied to the crushed rock surface. Final sealing is effected by a 1/4'? coating of catalytically applied hot asphalt. Dump leaching was inaugurated in 1964. First solution applied was wholly made up of mine water pumped to surface through a central pump shaft. Sulfuric acid was added on surface at a surge pond to control pH of the leach solution. Acid addition is necessary not only to benefit the leach dumps, but to prevent the formation of ocher scale within the pipe line distribution system. Mine water pH is on the order of 2.8. The combination of ferrous and ferric iron as well as magnesium and aluminum salts is such that ocher forms at a pH of 2.38. It is therefore mandatory to control pH at 2.0. Dump effluent pH is held at 2.3 or less.

Jan 1, 1968

By Jan M. Mutmansky

30.1-THE SCOPE OF SYSTEMS ENGINEERING JAN M. MUTMANSKY JAN M. MUTMANSKY 30.1.1-DEFINITIONS The terms "systems engineering," "systems analysis," and "operations research," common in today's technical literature, often are interchanged because of their similar meanings. However, some differences exist which need explanation. The most convenient way to achieve an understanding of the differences is to start with the definition of a system, namely, a collection of components which interact in a specific manner to accomplish a common objective. Accordingly, a haulage truck, a computer, a missile, a mining company or a nation each may be considered a system. Systems engineering generally can be defined as the conception, planning, design and engineering of any system of interacting elements so that the objective of the system is automatically optimized. Thus, systems engineering normally is con¬cerned with systems not yet activated.',' Systems analysis may be described as a scientific method of making decisions based on a quantitative or other objective evaluation of all action alternatives. It is very similar to systems engineering but usually is not considered to be restricted to problems of design prior to use. While the previous two disciplines are somewhat vague and can encompass a great variety of engineering functions, operations research can be more specifically defined as the application of mathematical models to the problem of optimizing the objective of any predefined system. Systems analysis and systems engineering are closely aligned sciences but opera¬tions research differs in the following ways. First, it generally is associated specifically¬with optimization and mathematical models while the other two often are not. In addition, it, is used predominantly on well-defined problems which can be ex¬pressed in mathematical terms. However, systems engineering or systems analysis may deal with highly complex social or governmental systems which may be ill¬defined and unsolvable by the classical methods of operations research. Finally, systems analysis and engineering always strive to look at the entire system to avoid the problem of suboptimization often necessary in operations research because of the necessity for a mathematical model. Because of his more extensive system, however, the systems engineer often is less able to find the optimal system. In summary, operations research, systems analysis and systems engineering are very similar in purpose but one, operations research, is more mathematical in nature and forms an important part of the other two activities. Other definitions which may be helpful are provided by Griffiths 3 Wilson,4 Falkic 5 Hall,2 Quade and Boucher, 6 and Flagle et al. 1 30.1.2-METHOD AND TECHNIQUES The systems or operations research approach makes use of scientific problem solving. The basic procedure comprises the following general steps: 1. Definition of the problem. 2. Construction of a model of the system. 3. Testing of the model under known conditions.

Jan 1, 1973

By R. R. Rollins

Field data combined with theoretical derivations were used to design a surface mining operation using explosive casting. Calculated casting results varied from 44 to 65% depending on bench height. This model was then applied to field tests at an eastern, contour, coal stripping operation. Results from five experimental casting shots are summarized and compared to conventional mining methods. The overburden material removed by casting ranged from 35 to 65% with an average of 50%. Fragmentation was improved and it was demonstrated that this procedure is economically attractive with a resultant cost savings of $.59/m3 or $5.93/t of clean coal.

Jan 1, 1987

By Kiseong Hyeong

Geochemical characteristics, shapes and surface textures of manganese nodules from two blocks located in the southern (9°N~11°N) (KR5) and northern parts (16°N~17°N) (KR2) of the Clarion-Clipperton fracture zone between 130°W and 133°W were investigated in terms of sediment distribution and metal contents for better understanding of controlling factors of seabed manganese nodule genesis. Two blocks, ~700 km away, are dominated by the nodules with different origins, each of which has distinctive chemical compositions and shapes. KR2 block is dominated by irregular and poly-type nodules of hydrogenetic origin with low Mn/Fe, Cu, and Ni contents and high Fe and Co contents, while KR5 block is dominated by discoidal and ellipsoidal nodules of diagenetic origin with high Mn/Fe, Cu, and Ni contents and low Fe and Co contents. In addition, nodules from two blocks show different surface textures: smooth and transitional in KR2 and dimorphic and rough in KR5. Sediment distribution is also distinctly different in two blocks. The study area consists of three sediment types: Unit 1 ? dark brown mud with an intermediate metal content, Unit 2 - yellowish brown mud with poor metal content, and Unit 3 ? black metalliferous mud. KR2 is characterized by the thick occurrences (<250 cm) of Unit 1 at the surface while Unit 1 distributes thin (<12 cm) in KR5. Higher primary production rate in the southern block proximal to equator and resulting high supply rate of metals to the sediment might be the cause for the dominance of diagenetic nodules in the southern block, but potential controls of different sediment distribution on the nodule genesis can not be excluded. If it is the case, Unit 1 with an intermediate metal content likely has been acting as a sink for metals by precipitating micro-nodules within the sediment column. Within the KR5, the hydrogenetic nodules occur preferentially on the seabed where Unit 3 distributes at shallower depth (<50 cm). Unit 3 has 2 or 3 times higher metal contents than other types of sediments. It might play the same role as Unit 1 in the northern block that prevents the supply of metals to the sediment surface. It also supports the potential effect of sediment distribution on nodule genesis. Keywords: Nodules genesis, Sediment distribution, Supply rate of metals

Jan 1, 2008

By M. Fig, A. Juganda, M. Zurhorst, J. Brune, C. Strebinger, G. Bogin

"Understanding the airflow patterns in and around the longwall panel can help to identify poorly ventilated areas that may be prone to methane accumulation. Ventilation network modeling provides quick simulation time, and flexibility in adjusting airway parameters and ventilation controls. Such modeling is effective for analyzing linear ventilation networks in underground mines, but cannot compute flows in caved areas of hard rock mines or longwall gobs. The use of Computational Fluid Dynamics (CFD) enables a more detailed investigation of the interaction between the airflows in these caved areas but requires much longer computational times, designing complex meshes and determination of a variety of modeling parameters. Airway friction factors and ventilation controls are simple to implement in a network model but can be difficult to model and adjust in CFD. This paper will focus on using mine ventilation network simulation to identify and analyze key parameters that are affecting airflow distribution in and around the longwall panels, prior to more detailed analysis with CFD modeling, using the example of a longwall coal mine. INTRODUCTION In longwall coal mine ventilation systems common in the U.S., the main purpose of bleeder ventilation is to dilute methane gas and prevent the formation of explosive gas mixtures in the caved, poorly ventilated gob areas and adjacent mine workings. In longwall operation, these critical areas include the development headings inby the longwall face, and the gob. Methane-air explosions in these areas may be ignited by spontaneous combustion, rock-on-rock friction and other sources. Although rare, ignitions due to rock-on-rock friction caused by roof falls caving into the longwall gob are possible and were suspected in the Willow Creek mine explosions in 1998 and 2000 (Elkins et al., 2001; McKinney et al., 2001). Rock-on-rock frictional ignitions are difficult to prevent, as they occur in inaccessible areas. Therefore, rendering the gob area inert is essential to prevent the formation of explosive mixtures. Research by Gilmore et al. (2015) and Brune et al. (2015) has shown that gob inertization can be a difficult or impossible when using bleeder systems, since the flow of gases through the gob depends on the gob permeability and the amount of fresh air leaking from the face and the immediate roof caving conditions cannot be controlled by the mine operator. Having the ability to predict the location where explosive gas zones (EGZs) form inside the gob will be helpful for designing the best ventilation setup to minimize explosion and fire risks."

Jan 1, 2018

By Robert L. Sundeen, Richard V. Wenberg

INTRODUCTION Shotcrete can be defined as spray-applied concrete with a maximum size aggregate in excess of 9.5 mm (0.375 in.). The concept evolved from guniting, which uses smaller aggregate and generally produces concrete with poorer physical properties. The larger aggregate used in shotcrete requires less water in the mix, while offering larger bonding surfaces, thus imparting greater tensile and compressive strengths. TYPES OF MACHINES Two basic designs of shotcrete machines in general use are the wet or prehydrated zero slump and low slump type, and the dry or nozzle hydrated machines. Fig. 1 shows a typical zero-slump machine in a con¬figuration commonly used for small-volume require¬ments. The prehydrated zero-slump machine mixes exactly proportioned batches in a sealed pressurized chamber. "Slugs" of hydrated shotcrete mix and com¬pressed air are sent through a distribution hose to the nozzle where the wet mix emerges as a spray. The spray is directed onto the rock surface by the nozzle operator. The low-slump machine is similar, except that a thick slurry mix of aggregate is delivered throughout the distribution hose to the nozzle. Fig. 2 shows a typical low-slump shotcrete machine used in moderate-volume applications. The nozzle-hydrated shotcrete machine accepts a premixed "dry" (4 to 6% moisture) batch of aggregate and cement. A constant feed of this mix is directed by compressed air through the distribution hose to the nozzle. At the nozzle, water for hydration is introduced into the emerging spray. The hydrated mixture is di¬rected onto the rock surface by the nozzle operator. Fig. 3 shows a typical dry-mix machine. The major difference between the two basic machine designs is the consistency of the shotcrete quality. Pre¬hydrated machines have high degrees of consistency and produce high-strength concrete, resulting from their ability to produce exact mixtures of zero or low-slump concrete within the machine. Nozzle-hydrated machines tend to produce poorer quality concrete because of the difficulty in controlling the water content at the nozzle. Water input essentially is an art. As such it is not precise, and the shotcrete produced is of variable quality. MATERIALS HANDLING Materials handling presents a problem to either type of shotcrete machine. At times considerable quantities

Jan 1, 1982

By Christopher J. Hall

It has been known for a long time that summing pressure drops and rises due to friction, shock, fans and natural ventilation is incorrect. In fact, lost works and works should be summed. In spite of this, the traditional method of finding a fan/system operating position has been the H/Q Curve. This paper presents (lost) work/m curves, progressing from a single fan moved around the system to include natural ventilation work, and fans in a series, parallel and series/parallel. The solutions obtained graphically are substantiated by dry air thermodynamic solutions, and the traditional solutions are shown to be in error. This method of solving problems is particularly useful when moving fans around the system, and essential in series/parallel and series situations with substantially different fan densities. The dry air analysis is employed because of its simplicity. Real air, with evaporation and condensation, will react somewhat differently, and one should use real densities (i.e.[l + w +w]/va ) when using this method. One source of error when applying this method to real air, although probably not major, will be investigated in a subsequent paper. Friction and shock losses are proportional to the square of the mass rate of flow, leading to the typical parabolic system curve. However, the unbalanced water stuff potential energy term, on a unit mass basis, is substantially independent of the mass rate of flow. It is possible that this could be handled as a negative natural ventilation work.

Jan 1, 1987

By Eoin Murphy, Stephen Beauchamp, Steven Cowell

"INTRODUCTION Electrification of the heavily trafficked Manchester to Preston route by Network Rail required the rehabilitation of the Victorian era Farnworth Tunnels to accommodate 21st century high speed trains. Network Rail, J. Murphy and Sons Ltd (JMS) and OTB Engineering Ltd (OTB) collaborated closely to complete these works in close proximity to heritage infrastructure whilst maintaining a rail service on the route. This significant challenge has been mastered by a combination of detailed investigation, complex modelling, robust design, extensive monitoring, ground treatment, secant piling, sprayed concrete, steel arches and segmental lining techniques. Investigation of the “Down” Tunnel found deformation and cracking of the lining and this was reconstructed during 11 weekend possessions. The “Up” Tunnel was filled with low strength concrete and a 9m diameter open face shield was used to construct an 8m diameter segmental lined tunnel during a 23 week blockade whilst traffic was maintained in the “Down” Tunnel. ELECTRIFICATION OF THE RAILWAY The Farnworth Tunnel project is part of the UK wide £1bn Railway Upgrade Plan to provide improvements throughout the rail network which includes the Manchester to Preston route. The project also supports the UK Government commitment to build a “Northern Powerhouse” by improving links that bind northern England together and which will help it release its full potential with a more balanced, healthier economy. The majority of the current UK rail network infrastructure resulted from the rapid growth of the railways in the mid to late 19th century which means that most of the existing tunnels are over 120 years old. Over the centuries the introduction of larger rolling stock has reduced the original clearances provided in tunnels. The electrification of a route requires that any over-line structures provide clearance for Overhead Line Equipment (OLE), new rolling stock and to meet modern standards. As part of Network Rail’s current electrification programme a further 36 tunnels have been identified on routes requiring electrification. Not of all these Victorian structures will require alterations to provide OLE clearance but the condition of the existing tunnels and modern fire / waterproofing requirements may ultimately dictate the need for rehabilitation."

Jan 1, 2016

By R. T. Richins

Coeur d&apos;Alene Mines Corporation (CDE) is a precious metals mining company. The company&apos;s three mining operations are located In Nevada and Idaho. Collectively, these mines (Rochester in Nevada, and the Galena and Coeur In Idaho) produced about 61,000 ounces of gold and more than 7.5 million ounces of silver in 1991. The company is currently planning the development of two major properties; the Fachinal gold-silver project in Chile and the Kensington gold project near Juneau, Alaska. Fachinal and Kensington hold encouraging potential to significantly expand CDE&apos;s gold production during this decade. The permitting process for these two distinctly contrasting environmental settings, project design requirements and regulatory/political circumstances provide the basis for a comparative analysis of licensing and permitting requirements, timeliness of the permitting process and costs in the U.S. and Chile.

Jan 1, 1993

By Z. Henderson, J. Saylor, L. R. Mendoza

"Diesel particulate Matter (DPM) is a byproduct of fuel combustion in diesel engines. It is classified as a carcinogen, with associated respiratory and cardiovascular health effects. The composition, size, and concentration of DPM is dependent on factors such as engine type, loading and fuel composition. Though a number of DPM abatement and control strategies currently exist, particularly in underground mining environments, occupational exposures remain a serious health concern. As a novel abatement approach, DPM scavenging by fine water or “fog” droplets has been proposed and a laboratory set-up has been built to test the efficacy on engine exhaust. Here, we describe a series of tests that varied engine load, system flow rate and fog drop number density. While none of these factors had overwhelming effects on the results within the ranges tested, the improvement in DPM mass removal attributed to the fog treatment was about 45% on average in comparison to no treatment. INTRODUCTION Diesel engines have seen widespread use for well over a century due to their relatively high thermal efficiency and fuel economy1. More recently, however, adverse health risks of diesel exhaust have become increasingly clear. Many of these risks are associated with the physical and chemical properties of exhaust components1–3. The term diesel particulate matter (DPM) is used to refer to the solid components of diesel exhaust, which are a mixture of elemental and organic carbon (EC and OC) and minor constituents including sulfates and metal ash3. The OC fraction of DPM results from unburned fuel and lube oil, whereas EC or soot is formed during the combustion of locally rich regions within the fuel. DPM is classified as a carcinogen6,7 and epidemiological studies have demonstrated a positive correlation between long-term exposure to DPM and other combustion-related fine particulate and increased cardiovascular and pulmonary diseases8,9. Diesel engines operate in relative fuel rich/oxygen lean conditions and are characterized by relatively high emissions of particulate as compared to spark-ignition engines2,3,10. Typically, these emissions range from 107 – 109 particles/cc and cover two primary size ranges: the nuclei mode where particles have diameters less than about <50 nm, and the accumulation mode where diameters are from about 50-10,000 nm. Most OC resides in the nuclei mode as semi-volatile compounds, while most EC is in the accumulation mode3. The physical and chemical properties of DPM vary with the type of engine, fuel (e.g., petro- vs. bio-diesel) and operating conditions such as loading (i.e., a function of torque and rotational speed)2,3,9,11,12. Loading is a particularly important factor with respect to DPM toxicity9,13,14, and on the effectiveness of after-treatment technologies2,3,15. Engine load alone can affect the EC/OC ratio, and the size distribution and number density of DPM. For diesel engines, the load is roughly proportional to the equivalence ratio3, defined as the actual fuel/air ratio over the stoichiometric fuel/air ratio for complete combustion. Light loads generally favor the formation of OC and small particles. As load is increased the volatiles are oxidized leading to larger soot particles (i.e., EC), but lower total number density of DPM. With further loading, the formation of soot offsets the decrease in volatiles, resulting in increased DPM mean size and number density3."

Jan 1, 2017

By Robert M. Cox

A thorough geological engineering investigation is required before surface lands overlying abandoned underground mines can be safely recommended as building sites. The major problems confronting the geological engineer are assembling accurate geologic and mining information and developing an accurate rock mechanics model of the situation. A successful investigation requires a combination of technical expertise in rock mechanics and engineering geology tempered with practical engineering judgment. The results of a good study are not always favorable to the prospective builder.

Jan 1, 1975

By R. E. Gundersen

I have to express my surprise and must send a note of warning concerning the use of polyurethane foam as described in a paper by R.N. Torbin and R.F. Kovar, entitled "Innovative Shaft Lining Method," published in your February 1989 edition. In September, 1986, 177 miners lost their lives when they were exposed to fumes downwind from a fire in a tunnel lined with polyurethane foam. Whilst polyurethane exhibits reasonable fire retardent properties in small-scale tests, mass use in a tubular configuration, exacerbated by the furnace effect of cross-radiation, can lead to a rapid, uncontrollable conflagration.

Jan 1, 1990

By C. A. Moseley, M. B. Kahle

The Gulf Coast Region has been the center of extensive lignite exploration and development activity in the past 10 years. Currently, 27.2 Mt (30 million st) of lignite are mined annually, the majority of which is uncovered by large walking draglines. Projections indicate that production could reach 125 Mt (138 million st) by 1990. As mining moves to deeper depths, removal of overburden becomes the decisive factor in mine planning and cost. The geology of a region plays a key role in the selection of an overburden removal system. While alternate stripping methods must be analyzed to determine the most economical and operationally sound method, so far bucketwheel excavator systems seem to be the best method for removing large volumes of soft, unconsolidated material that is found at projected mining depths in the Gulf Coast region. Geology of Gulf Coast Lignites Extent Distribution of the principal tertiary lignite-bearing deposits in the Gulf Coast Lignite province extend from the Texas-Mexico border to the Alabama-Georgia state line (Fig. 1). The lignite-bearing strata includes portions of eight states: Texas, Louisiana, Arkansas, Missouri, Kentucky, Tennessee, Mississippi, and Alabama. Lignites occur primarily in the Wilcox, Claiborne, and Jackson groups in the Gulf Coast. The uppermost strata of the Midway group in Mississippi and Alabama also contain significant lignite resources. Reserves Commercial lignite seams in the Gulf Coast Lignite province range from 0.6-3 m (2-10 ft) in thickness. The estimated lignite resources throughout the Gulf Coast in seams greater than 0.9 m (3 ft) in thickness and up to 61 m (200 ft) in depth currently are estimated at 32 Gt (35 billion st). Table 1 shows these resources by state. Quality Lignite quality can vary within individual mining areas and seams. However, trends in quality occur because of the depositional environment, age, and west-to-east geographical location. Better quality lignites occur in the Wilcox group in Texas and Louisiana. Poorer quality lignites occur in the northern regions of the Wilcox group and those of the geologically younger Claiborne and Jackson groups. Environmental Conditions Gulf Coast province environmental conditions are ideal for successful mine reclamation. The lignite occurs in flat to moderately rolling terrain, a topography easily reproduced from the spoil dumps or spoil rows developed during the mining operation. High to moderate rainfall facilitates rapid revegetation. Evidence from current mine reclamation programs and ongoing test plot studies indicate that mined lands can be reclaimed to reach premining productivities. Sometimes productivities are even greater than that of premining conditions. Existing Mining Methods Present Mines & Production There are seven active mines in the Gulf Coast province, all located in Texas (Fig. 2). Lignite

Jan 8, 1983

By J. J. Daniels

Advances in borehole geophysical research for mineral assaying and remote detection of mineralization away from the borehole are cited. Nuclear activation measurement research has provided accurate in situ assays of economic metals with neutron-gamma activation, using a high resolution intrinsic-germanium detector. Although nuclear activation analysis is the present "best hope" for obtaining in situ assays for some elements, gamma-gamma and magnetic susceptibility measurements can provide accurate assays for lead-zinc and magnetite, respectively. Borehole optical spectroscopy and X-ray fluorescence are being investigated as possible in situ assaying techniques for some minerals. More laboratory and field calibration research is needed before non-linear complex resistivity (NLCR) can be routinely used as a quantitative assaying tool. Field tests have shown that variations in the local geologic environment can affect the quantitative accuracy of assay values from downhole NLCR measurements. Deeply penetrating borehole geophysical methods are increasingly being used for mineral exploration as drilling costs and exploration have increased. Borehole electrical measurements have been shown to be useful for detecting conductive ore bodies that are not intersected by a drill hole. Hole-to-surface resistivity and surface-to-hole time-domain electromagnetics are demonstrated to be particularly effective for defining mineralized zones in a massive sulfide environment. Borehole gravity meters and three-component magnetometers have been developed and should prove useful for defining geologic anomalies away from the drill hole.

Jan 1, 1987

By M. A. Reyes, J. Bickson, J. R. Srednicki

Federal laws mandate the presence of refuge alternatives (RAs) in underground coal mines and provide guidelines for harmful gas removal. After an explosion, harmful gases can follow survivors into an RA and can reach a deadly concentration. Investigators from the National Institute for Occupational Safety and Health (NIOSH) tested 12 ventilation system configurations (VSCs) to purge sulfur hexafluoride (SF6) tracer gas from a built-in-place (BIP) RA in the Experimental Mine in Bruceton, PA. Using a borehole air supply, tests were conducted with airflows of 750 and 1,000 standard cubic feet per minute (SCFM). Excluding a VSC where the air inlet was 1.98 m (78 in) from the air outlet, the results show that the time to purge the SF6 concentration from 1,000 parts per million (ppm) to 25 ppm ranged from 26 to 29 minutes for an airflow of 750 SCFM and ranged from 18 to 23 minutes for an airflow 1,000 SCFM. Mines can use this information to reduce purge time in case of a mine disaster and determine which VSC to avoid. INTRODUCTION After a fire or an explosion in an underground mine, the concentration of carbon monoxide can reach a fatal level. In a mine disaster, the main goal is to escape. However, if miners cannot escape, they have to migrate to a location to find refuge and, if possible, communication, and a borehole source for a fresh air supply. To ensure survival of the miners, Federal laws mandate the presence of a refuge alternative (RA) within 304.5 m (1,000 ft) of the nearest mining face. In addition, Code of Federal Regulations Title 30 CFR Section 7 sets the guidelines for personnel tracking, RAs, and the removal of noxious gases in underground coal mines (Mineral Resources, 30 CFR, 2014). Federal regulations define an RA as a protected, secure space with an isolated atmosphere and integrated components (Mineral Resources, 30 CFR, 2014). There are three types of RAs: portable metal RAs, portable tent-type RAs, and built-in-place (BIP) RAs. A BIP RA is constructed using masonry or other stoppings to create an isolated space in a mined-out area. Blast doors are installed in one or both of the stoppings for the miners to enter the RA. Furthermore, RAs must provide the following components: breathable air, food, water, air monitoring, and harmful gas removal. Federal regulations have emphasized the mandate for breathable air and harmful gas removal in the following words: “Purging or other effective procedures shall be provided for the airlock to dilute the carbon monoxide concentration to 25 ppm” (Mineral Resources, 30 CFR, 2014). The purpose of the mine ventilation system is to provide a sufficient quantity of air to the underground mine workings, to dilute methane and other contaminants, to maintain a suitable working environment, and to prevent accidents from happening (Cheng and Wei, 2014). In addition, the organic nature of coal amplifies risks from poisonous gases, explosions, and fires (Engström et al., 2018). If an underground coal mine ventilation system fails after an explosion, the concentration of toxic gases, most notably carbon monoxide, will increase. Carbon monoxide is dangerous because it creates tissue hypoxia by binding to hemoglobin (Özmen and Aksoy, 2015).

Jan 1, 2019