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By J. W. Parkinson

With most of the coal currently mined in the eastern U.S. already requiring cleaning to meet electric utility coal specifications, the question remains how medium- and high-sulfur coal producers will provide the even better quality coal expected to be demanded if pending acid rain legislation is enacted. One emerging approach is to crush the coal to liberate additional ash and sulfur so that better quality coal can be produced at equal yields. This paper discusses how to measure liberation. the premiums the utility market is willing to pay for lower sulfur coal, and a staged middlings crushing scheme that promises the benefits of total raw coal crushing but at lower costs. For some coals, cautious application of liberation concepts may be the only way to produce a product that can be quality and cost competitive in the future utility coal market.

Jan 1, 1988

By N. A. Abdel-Khalek

The objective of this investigation was to compare the results of counter-current flotation column versus conventional flotation cell for the cleaning of a sulphur ore and its discrete size fractions. The tests were carried out using diesel oil as a collector and alcohol as a frother. Generally, flotation column produced concentrates of higher grade. For example, the grade of a rougher concentrate for a given feed obtained with the column increased by 33% higher than that produced with the flotation cell. Such higher grade could not be obtained using conventional cell even after 3 cleaning stages. Moreover, the column gave superior results for flotation of fine and ultrafine particles.

Jan 1, 1991

By R. D. Hagni

Pyrometallurgical products from lime roasting of refractory gold ores, pyrite, and arsenopyrite have been examined for their mineralogy, porosity, permeability, retention of contaminant sulfur and arsenic, and potential effectiveness of gold extraction. Cathodoluminescence microscopy, supplemented by X-ray diffraction and scanning electron microscopy-energy dispersive analysis study, has shown that the products phases have characteristic cathodoluminescence properties as follows: anhydrite (CaS04), deep blue; unreacted portlandite (Ca(OH)2), deep purple; oldhamite (CaS), light yellow to rarely pink or orange; a sulfur-rich, arsenic-poor phase, violet; an arsenic-rich, sulfur-poor phase, non-CL. Within the temperature range examined (400-850°C), hematite exhibits greater porosity and permeability at the intermediate roast temperatures of 600-650°C.

Jan 1, 1993

By V. O. Tenorio, A. M. Sanzana

"INTRODUCTION This report summarizes a research about mines which are transitioning from surface to underground mines. It is a guide to make strategic decision in these increasing amount of mines. Capital and operating costs are linked with major strategic decisions in the exploitation of an ore body. This is the reason to analyze costs related to this transitioning world trend. There are multiple reasons for transitioning from Open-Pit (OP) to Underground (UG) mining. The primary economic incentive for going UG is that the cost per unit of ore from OP mining eventually exceeds that from UG extraction. This is due to the excessive amount of waste that must be extracted when the depth of the pit increases. In addition, the reduced footprint of UG operations contributes to diminish the environmental impact on the surface. Furthermore, it becomes more difficult to find new, easily accessible ore deposits. Then, a cost model helps to guide strategic decisions in the transition from OP-to-UG mines. Objectives • Propose a methodology to guide strategic decisions in the transition from OP to UG mining. • Create an integrated cost model based on existing OP and UG individual cases. • Identify and characterize a group of mines transitioning from OP to UG. • Analyze operating and capital costs of a particular transitioning from OP to UG mine. MAIN CONCEPTS Open Pit Mining (OP) The main decisions in OP mines are: Cut-off grade, Stripping Ratio (SR), equipment size, stockpiling, pushback sequencing and processing capacity. The stripping ratio is measured as the tonnage of waste required to be removed to reach and extract one tonne of ore. The material extracted from an OP exploitation can be classified as waste and ore. This classification depends on the cut-off grade. The cut-off grade indicates the minimum amount of material with economic value in a block. The waste from the mine is going to the waste dump and the ore is going to stockpiles where will be store and then going to the processing plant (leaching or concentrator). The waste of this process is going to the tailing pond big pools. And the product is sell in the market. Another important issue is the mining capacity which is going to define the investment in mining equipment. Underground Mining (UG) The first decision to be made in order to open an underground mine is selecting the mining method. Caving methods are the more productive and have lower operating costs. There are three caving methods: Block Caving (BC), Panel Caving (BC) and Sublevel Caving (BC). The access development could be an horizontal adit or a straight or downspiral decline. A shaft could be used for inclined or vertical access. Other key issues are: equipment capacity, cut-off grade and production sequencing."

Jan 1, 2016

By P. G. Kovalchik

Recent research conducted by NIOSH, Pittsburgh Research Laboratory showed that electrical current levels permitted under present regulations may not limit cable temperatures to less than 90°C in reeled trailing cables. Reeled cables, tightly wrapped with many turns, all carrying current in an enclosed space, can become overheated due to poor heat transfer. This overheating can cause the cable insulation to soften and become easily damaged. The damaged insulation reduces the life of the cable and can lead to shock, electrocution, and mine fires. This paper describes a method of measuring the conductor temperature of mine trailing cables during normal operation. The temperature is measured using a 50/125 micrometer Graded Index Multimode Optical Fiber located in the center of the metallic conductors. Distributed temperature measurements are made using an Optical Time Domain Reflectometer (OTDR). This system is capable of measuring temperature with an accuracy of plus or minus one degree centigrade over a length of 4 km at 1-m intervals. With this unique way of measuring temperature, tests can be conducted simulating actual mine conditions and provide important data to allow MSHA's Approval and Certification Center to develop approval criteria for cyclically rated reeled machines.

Jan 1, 1998

By W. E. Heinrichs, R. W. Davis

Introduction Cross borehole seismic tomography (CBST) is a geophysical technique that allows definition of the distribution of some physical rock property between two boreholes. The method is similar to the computer-assisted tomography (CAT) scans used by the medical industry. This paper describes the method, its applications and the developing trends in its use that interest the mining industry. The idea of using tomography in connection with geophysical methods for measuring rock properties between boreholes has been around for three or four decades. Until the advent of high-speed, large-capacity computers, the necessary calculations were too formidable for production use. Another factor in the development of the technique has been the refinement of a mathematical base to meet the needs of the medical industry. The geophysical applications have benefited from this refinement. An extensive discussion of the basic theory is given in Kak and Slaney (1988). CBST, although widely researched and written about, is still not extensively put to use in mining and engineering projects. Most real world examples in the literature have come from research carried out by government laboratories or by large companies. An exception is the regular use by Prospection Geophysique Francaise (Cottin et al., 1986) in damsite investigations. The Japanese appear to be doing extensive research and testing of CBST's uses in civil engineering projects (Saito et al., 1988). Canada is researching the use of the method in connection with nuclear waste site investigations (Wong et al., 1987). Finland has tested the method in connection with a foundation investigation for a nuclear power plant (Cosma et al., 1984). In the US, the US Bureau of Mines has taken an interest in using CBST as a means to enhance in situ mining operations (Tweeton, 1988). Major oil companies are examining the method as a tool in oil field development (Justice et al., 1989). Description of the method CBST involves placing a series of receivers down one borehole and recording transmissions from an energy source placed successively at a series of positions in another hole. The objective is to generate a dense network of seismic raypaths between the holes. The denser the network of raypaths, the better the features between the boreholes are resolved. Either seismic travel times or sine wave amplitudes are measured by the receivers. Analysis of travel times between boreholes develops a picture of rock velocities between the holes. Analysis of seismic wave amplitudes develops a picture of the distribution of energy transmission characteristics between the holes. These seismic properties can be used to define occurrences of fracture zones, lenticular sequences or other important geologic data not apparent from examination of the borehole logs. When longitudinal (compressional) and transverse (shear) waves are analyzed, the physical properties, such as elastic moduli, can also be mapped. When wave amplitudes are measured, rather extensive corrections to the data are necessary. There is some disagreement among researchers as to the feasibility of making some of the corrections. For this reason, this paper will concentrate primarily on travel time analysis. Wave amplitude analysis will be mentioned occasionally only in passing. This does not mean that amplitude analysis does not provide important data on rock parameters, only that for the present there are limitations on its uses. Vertical seismic profiling (VSP), extensively used in recent years in oil exploration, is similar to CBST. Instead of using two boreholes, however, the VSP method uses an array of seismic sources or detectors down one hole and an array of detectors or sources along the surface radiating outward from the hole. While adequate for determining vertical velocity distributions, the VSP method is not, by itself, suitable for most engineering or mining projects. Computer programs used to analyze the field data make use of the fact that the total travel time or change in signal amplitude between boreholes is described by Dines and Lytle (1979) as: [9k = f Rk f( x,Y) ds (1)] where gk = the total time or attenuation along the kth ray path,

Jan 1, 1992

By Harry H. Peek

Artesian pressures of unusual magnitude occur in the deeper aquifer units beneath a considerable part of southeastern North Carolina and extend into South Carolina. The high pressures were first observed in 1968 in wells near Wilmington that were drilled to "basement" rock and which were screened between depths of about 260 to 300 m (meters). The pressure was recognized by Peek and Heath1 as an anomalous geo-pressure and unrelated to recharge conditions in the region. Since 1973, much new information has been obtained on hydro-geologic conditions in the area and a preliminary report on the deep artesian pressures was published in 1975.2 Most of the basic information has been obtained from groundwater research stations constructed by the Groundwater Section of the North Carolina Department of Natural and Economic Resources as a part of Ground-water studies in the Coastal Plain Region. These stations consist of an exploratory well drilled to basement rock with wells completed in each principal aquifer unit to provide data on aquifer characterestics, water levels and water quality.

Jan 1, 1977

By M. R. Moon

The mine fire at Wilberg Mine in 1984 reached the surface resulting in the failure of the vertical ledge forming the roof and entrance for three main intake portals. The fallen material was covered with a concrete cap to seal the air from the mine. As the mine was recovered and ventilation pressure was placed on seals on the perimeter of the fire area, the concrete capped rubble proved ineffective. Due to the steep and rugged terrain and the inaccessibility to the portals from underground, horizontal holes were drilled into the portal entries and three seals were placed remotely. The seals in conjunction with pressure balancing the seals around the perimeter of the fire area resulted -in the control of the mine fire.

Jan 1, 1993

By R. J. Miller

The current National commitment to expanding the human presence into the solar system will clearly require major facilities in Earth orbit or possibly on the moon. Such facilities will need large amounts of materials for structural modules, life support, propulsion, and shielding. The heavy transportation costs in fuel required to lift materials from the Earth's surface make a terrestrial-based space system inherently inefficient. A more cost-effective approach would be to provide as much of the required materials as possible from other bodies in space not having the high cost of Earth launch. This paper identifies potential targets for space-based resource utilization, constraints on exploitation, and relative benefits of various sources.

Jan 1, 1992

By A. E. Isaacson

Researchers at the Bureau of Mines, U.S. Department of the Interior, developed and tested equipment to measure corrosion rates on a commercial-scale mill. Bench-scale experiments were also designed for duplicating ore grinding conditions closely enough that realistic rate determinations can be made in laboratory tests. Rates measured in a laboratory system compared favorably with those measured in the field. Cast steel was found to have corrosion rates in a copper mill and laboratory test cell of 22 and 21 mpy, respectively. Corrosion was found to account for less than 5 pct of the total grinding media wear in the operations studied.

Jan 1, 1989

By Josef J. Schwegel

The first vertical shaft lime kiln operating according to the parallel-flow regenerative principle was developed and built in the nineteen-fifties by Schmid-Hofer in Austria. Upon proving this concept of calcining or "burning" limestone to be very energy efficient for the production of good quality lime, Maerz Ofenbau AG of Zurich, Switzerland was in 1965 licensed for the design detailing and construction of these kilns. The first regenerative shaft type lime kiln outside of Austria was built in 1966 and through close co-operation with customers and their operating personnel, the advanced technical developments of today's kiln designs were accomplished. At present approximately 190 kilns of this type in capacities ranging from 60 to 700 short tons per day have been built or are under construction throughout the world in highly industrialized as well as less developed countries.

Jan 1, 1981

By Chi-shing Wang

The U.S. Bureau of Mines has been developing the mechanical roof pulling technique as a method for evaluating the effectiveness and the comparative advantages and disadvantages of various roof bolting systems, based on the characteristic responses of bolted nine roofs to a prescribed external loading system. Preliminary experiments were conducted in the Bureau's Safety Research Coal Mine using a 12-foot and a 16-foot-span test rig. The experiments have proved the capability of the test rigs and suggested the viability of the test method. This paper summarizes the test concept and the experimental results.

Jan 1, 1974

By Steven A. Savage

Agrico Chemical Company, as we presently know it, is the result of the coming together of several different fertilizer operations. The Williams Companies, our parent organization, first entered the fertilizer business in 1971, when it acquired the fertilizer operations of the Gulf Oil Company. This gave us, among other things, the manufacturing facility at Donaldsonville, Louisiana. In 1972, The Williams Companies acquired Agrico Chemical Company from Continental Oil Company, bringing in a manufacturing facility and phosphate mines at Pierce Florida. Our Florida Mines are in the region commonly known as the Bone Valley Region of Florida. The majority of the phosphate fertilizer produced in the United States utilizes rock mined in this region. The Donaldsonville Plant was originally built in 1967-68 on the site of the old Faustina Plantation at an approximate cost of $80,000,000. (This plant is commonly referred to as our Faustina Plant.) Until such time as Agrico was acquired from Continental Oil, the Donaldsonville Facility was solely used to upgrade phosphoric acid into finished granular products.

Jan 1, 1986

By Z. Rogovin

A Knowledge of the amount of time the material spends in a continuous mill in a closed-grinding-circuit is essential for circuit performance analysis and scale-up design. A convenient method for acquiring this information involves the use of tracers in residence-time-distribution (RTD) experiments. In a typical wet process the RTD measurements are usually done by injecting a pulse tracer into the mill inlet and detecting it in the circuit exit. In this article a simple to use mathematical method for the calculation of the closed circuit material residence time in the mill is developed. Using this method there are no restrictions on the location of the tracer injection or detection points. Any convenient location in the closed circuit can be chosen without affecting the simplicity of the method. This method also enables the calculation of the degree of mixing in the mill. The use of this method for the analysis of impulse response data obtained from several commercial grinding circuits is presented.

Jan 1, 1986

By S. F. Diehl

Suites of monomineralic sulfide and carbonate minerals, as well as mine-waste composite samples, were analyzed using chemical and microanalytical techniques to understand behavior and bioavailability of mine waste elements such as Cu, Fe, Pb, or Zn. Petrographic, scanning electron microscopy (SEM), and laser-ablation inductively-coupled mass spectrometry (LA-ICP-MS) studies of mineralogical residence sites of trace elements are important because trace elements affect the chemical and physical behavior of minerals. Leachate solutions show that chalcopyrite, bornite, azurite, malachite, and galena are host to the trace elements Ag, Al, As, Cd, Co, Cr, Mn, Ni, Pb, and Zn. SEM studies reveal whether these trace elements occur within mineral inclusions or are substituted within lattice structures. SEM analysis reveals mineral phases not identified by X-ray diffraction (XRD), such as inclusions of sphalerite and cobaltite(?) within chalcopyrite.

Jan 1, 2010

By J. Oliver, J. Cleason

"With maintenance costs rising and an increasing demand for higher production, the use of sealed spherical roller bearings can reduce maintenance costs while providing increased production uptime. The sealed spherical bearing has increased bearing life by slowing the ingress of contamination. This paper will describe how contamination and bearing wear is reduced by reviewing case histories from coal and metal mines that improved their production by decreasing downtime using sealed spherical roller bearings. INTRODUCTION The spherical roller bearing (SRB) is a robust rolling element bearing that can accommodate high radial loads, low to moderate axial loads, and misalignment with no loss in carrying capacity. (i.e. Figure 1) Because of these characteristics, it is a favorite in mining applications and many other heavy industry applications. Primary applications are the various pulleys on conveyors. Coal and hard rock mines have hundreds of miles of conveyor lines and countless head, tail, drive, and idler pulleys. Maintaining the bearings on these pulleys and replacing bearings that have failed can be a huge expense to a mine in components, labor and downtime. Ideally, the bearings are replaced when the pulley is changed out according to the maintenance cycle, about every 4 years. Reality, however, causes the bearings to be changed out every year, or sooner. These premature bearing replacements can cause production shut downs for as long as 8 hours. Conveyor pulleys have been targeted at many mines as the single biggest maintenance pain point.The primary reason for replacing conveyor bearings is internal wear from fine, solid particle and water ingress through the bearing housing seals. (i.e. Figures 2 & 3) Traditionally, the bearing is mounted in a split pillow block housing (SAF, FSAF, SDAF or SNL are typical industry styles) with only labyrinth seals (LER/LOR) for protection against the ingress of contaminants. The bearings are lubricated with grease. A common way to extend the MTBR is to purge the bearing system with large quantities of grease to flush out the contaminants. If the bearing, and thus the housing seals are not frequently purged with grease, fine solid contaminants enter the housing and bearing through the labyrinth cavities."

Jan 1, 2015

By L. Meier, M. Dennis, J. Schieffer, K. Murray

"INTRODUCTION Contrary to popular belief, Arizona State Trust land is not public land. All uses of the land must benefit the Trust, a fact that is considered with the review of each application received for sale, lease, or permit. This includes applications for activities ranging from commercial development to recreation. In 1863, the Territory of Arizona was established by an act of Congress. This act reserved sections 16 and 36 in each township to be held in trust for the benefit of the common schools. Later, the Enabling Act of 1910 allowed the Territory of Arizona to prepare for statehood. This act reserved the additional sections 2 and 32 of each township for the common schools and granted another 2,350,000 acres to be held in trust for other beneficiaries. In all, Congress granted the State of Arizona almost 11 million acres. The State was to manage those lands and maximize revenue for 13 separate beneficiaries. To meet this mandate, the State established the Arizona State Land Department (ASLD) in 1915. During fiscal year 2015, the ASLD contributed $136 million to the permanent fund, bringing the total value to over $5.1 billion, through the sale and leasing of the land and natural products which includes minerals. The current inventory of State Trust lands includes 9.2 million acres representing about 12.7% of the State.The ASLD Minerals Section manages the exploration, development, and leasing of mineral products on State Trust land. We are not a regulatory agency, but a department guided by our fiduciary responsibilities to the Trust. Our mineral programs include: Exploration Permits, Mineral Leases, Mineral Material Leases, Geothermal Leases, Oil & Gas Leases, and Special Land Use Permits. INDUSTRIAL MINERALS ON ARIZONA STATE TRUST LAND Industrial minerals fall under the category of either Mineral or Mineral Materials Leases. Common industrial minerals found on Arizona State Trust land include potash, limestone, gypsum, salt, specialty clays, zeolites, crushed stone, and sand and gravel."

Jan 1, 2016

By J. L. Francke

This paper describes the practices and methods used in a study of Time Domain Reflectometry (TDR) as an inexpensive deformation monitoring tool in underground excavations at the Waste Isolation Pilot Plant (WIPP). The WIPP is being developed near Carlsbad, New Mexico, for the disposal of transuranic nuclear wastes in bedded salt 655 m (2 150 ft) below the surface. Data collected from WIPP geomechanical monitoring are used to characterize conditions, confirm design assumptions, and understand and predict the performance of the deep salt excavation. The geomechanical monitoring program encompasses numerous geomechanical monitoring techniques ranging from inspection of observation boreholes to advanced radar surveys. In 1989 TDR was introduced as a monitoring tool with the installation of 12.7 mm (0.5 in) diameter TDR cables in the underground excavations. In 1993, a new TDR system was installed in a separate location. Based on experience with the previous installation, enhancements were implemented into the new TDR system that: 1.) extended the period of performance by increasing cable diameter to 22.2 mm (0.875 in), 2.) increased accuracy in locating areas of deformation by aligning cables with nearby observation boreholes, and 3.) improved data acquisition and analyses using a standard laptop computer, eliminating the chart recorder previously used. In summary, the results of a correlation between the TDR signatures to nearby observation boreholes and geomechanical instrumentation will be presented.

Jan 1, 1996

By P. J. Best

Due to its low mine production costs, competitive rail rates and low sulfur content, the Southern Powder River Basin (SPRB) now commands 30 percent of the U.S. utility coal market. In 1996, production exceeded 260 million tons, a growth of 110 million tons since 1989 and 15 million tons over 1995. Continued growth is expected as the second phase of the Clean Air Act Amendments (CAAA) looms. This growth will be the greatest in the southern part of the basin, where coal quality is higher. This article is an overview of supply and demand issues affecting markets for SPRB coal. It reviews the current markets for SPRB coal and addresses future prospects for market expansion.

Jan 1, 1998

By L. Bloom

In 1996, lack of confidence in assaying methods and sample handling affected companies as diverse as Bre-X and Timbuktu. Both share prices and the ability to raise financing are impacted when the quality of assay data is suspect. Overseas projects are subject to enhanced scrutiny when local facilities are used that are unfamiliar to brokers, financing agencies and banks. Quality control systems can be -implemented but there are associated costs. These costs should reflect the risk to the mining company, investors and financiers and the size of the proposed investment. In this regard, assay control call is considered a form of insurance to enhance the value of an exploration or mining project.

Jan 1, 1997