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By G. T. Lineberry, R. S. Mateer

Often only after years of "technical dormancy" do errors in published literature become apparent and meaningful. To prevent duplication of effort for future generations, the fol¬lowing corrections are offered. These errors were discovered during a recent study in which a computer program for mine hoist rope selection was developed (Lineberry and Mateer, 1988). In order of increasing gravity: Captions for Figs. 3 and 4 are transposed. • Purported to be a more accurate method of rope selection than the process of successive approximation, the direct method assumes linearity between a given rope's minimum breaking strength, T, and unit rope weight, Wv. Because of the sensitive location of the constant, K, in equation (8) for breaking strength, the significance of this nonlinearity is magnified. For a typical 6 x 37 class fiber core wire rope (Wire Rope Corp. of America, 1985), K actually varies from 43,650 to 52,190, depending upon rope diameter. Although the direct solution permits a rapid selection of hoist rope, an indirect (iterative) solution procedure is favored because of its im¬proved accuracy and ease of computerization. • Equation (8) for minimum breaking strength is in error. It should read:

Jan 1, 1989

By Toyohisa Fujita, Mitsuo Mamiya, W. Tai Yen, Hiroki Kogita

Green algae taken from an acidic mine drainage and blue-green algae taken from an alkaline hot spring stream were collected and tested for their ability to recover or remove dilute metal ions. Experimental results demonstrated that unwashed blue-green algae and washed green algae effectively adsorbed base metals ions and eluted them at pH 1. It was also found that washed and dried algae adsorbed precious metal ions more effectively than unwashed algae. For example, the washed and dried blue-green algae was capable of adsorbing 0.31 kg of gold per kg of algae. The gold from tetrachloroaurate solution which was adsorbed on washed blue- green algae was found to change to a metallic state following initial metal binding. In the case of a dilute gold complex solution leached with thiourea, only a small amount of gold could be captured by algae. Further experiments were conducted on components of the algae, such as alginic acid, agar, cellulose and chitin and mixtures of these components, in order to determine their contribution to metal adsorption characteristics. However, a mixture of these two components demonstrated both good adsorption and desorption characteristics indicating an interaction between the individual components.

Jan 1, 1995

By T. Ertekin, R. V. Ramani, W. Sung

The emission of methane in the coal mine working faces has two immediate impacts with regard to coal mine planning. Firstly, at the planning stage, the coal mine ventilation system must be designed such that airflows in the faces keep the concentrations of the gas in faces areas to below one percent. If the concentrations were greater than one percent, the production machine has to be shut down resulting in a loss of productive time. In an extreme case, concentration can reach explosibility limits which may lead to ignitions and explosions. Secondly, in excessively gassy coal seams, several alternatives can be applied to the mine layout configuration, and the mining method to be predicted for the extraction of coal, so as to insure a productive and safe operation. In this study a two-phase, two-dimensional finite-difference model was used to predict the methane emission rates into active mine working area under several methane drainage schemes. The numerical model utilizes a recently developed multi-mechanistic flow theory which describes the flow of methane in an heterogeneous and anisotropic coal seam. Transport of methane in the micropore structure of the coal is described by the Fick's law of dif- fusion under the influence of existing concentration gradient, while flow in the more permeable butt and face cleats (macropore spaces) is formulated by Dar- cy's law under the influence of existing pressure gradient. The desorption of the methane is accounted with the aid of a quasi-steady kinetic sorption model. A series of simulation studies were conducted in a systematic manner by sifting through the parameters associated with the coal seam characteristics and the degasification strategies in order to understand those which most significantly affect the methane emission rates in the face areas during mining. Along these lines, the effects of coal seam properties such as thickness, porosity, permeability, sorption characteristics and scheduling of drainage process against the mining operation have been isolated to understand the role of each individual parameter on the methane emission rates.

Jan 1, 1987

By Ing. H. Kellerwessel, Ing. M. Esna-Ashari

This paper refers to the new crushing and grinding process, invented by Professor Schonert (Ref. 1), Clausthal, Germany. The process is known as high pressure particle bed comminution or interparticle crushing. Several papers already describe fundamentals of the process, the equipment used, results of lab size and large scale tests and the first results of commercial operations (Ref. 2 to 7). Of course, we will treat the topic from the perspective of a downstream gold ore upgrading or leaching process. Some recently executed testwork indicates that the process provides special advantages in this field. To describe the process generally, in view of the already existing publications.

Jan 1, 1998

By Peter Kowalczyk

The acquisition of submarine gravity data using airborne gravity technology is a practical reality. Ocean Floor Geophysics plans to deploy a free-swimming ROV based submarine gravimeter on a commercial basis in early 2009. The submarine instrument is a variant of the well-used GT-1A airborne gravimeter. Airborne gravity surveys are now routine. The primary factor controlling the accuracy of airborne gravimeters is the precision of the GPS measurement of vertical movement of the sensor platform. The gravity measurements along a flight line are the differences between the output of the gravimeter vertical accelerometer and the estimate of the aircraft vertical acceleration using the differential GPS system. The principle difficulty of moving an airborne gravimeter to a free-swimming submarine platform is the necessity to have an accurate real time estimate of the changing elevation and hence changing vertical acceleration of the platform; GPS doesn't work underwater and an accurate estimate of depth fluctuations to the necessary precision is difficult to acquire. It is interesting that the airborne gravity gradiometer technology, which competes with the airborne gravity technology, was first developed as a classified military application for use by missile submarines during the cold war. Gradiometers were developed for this application specifically to avoid this problem. A gradiometer does not require as accurate an estimate of its vertical position to make a useful reading- it measures gravity gradients, not the gravity field itself.

Jan 1, 2008

By Turan Uysal, Thierno Saidou Barry, MURAT ERDEMOGLU, Mustafa Birinci

Nonbauxite ores such as aluminum silicate clays and coal fly ashes have been widely considered as potential resources of alumina (Al2O3). The interest focused on these ores is due to their high alumina content. Over the years, in countries where there are little or no bauxite reserves or where the recovery of existing bauxite ores to produce alumina with the Bayer process is not economical, alternative processes have been explored. Among these processes, acid leaching is seen as the most attractive process. In the acid leaching process, heat treatment for thermal activation to destruct the refractory structure of the minerals in the ores is generally recommended as a pretreatment method. Recently, the applicability of high energy ball mills, which are useful for mechanical activation as a pretreatment method before leaching, has attracted much attention. This is a short summary of our previous review [1], giving the details of alumina manufacturing from thermally and mechanically activated clays and coal fly ashes by acid leaching.

By J. F. Brune, A. Verma

"Face ignitions in underground coal mines are a major risk for underground mining operations, as they can lead to methane or coal dust explosions. The 2010 disaster at the Upper Big Branch Mine resulted in 29 fatalities due to a methane and coal dust explosion initiated from a face ignition. Much research has been conducted to mitigate face ignition hazards, from water sprays to installing passive and active explosion barriers. Despite the increased use of water sprays in U.S. coal mines, there have been more than 50 documented face ignitions in the U.S. underground coal mines since 2010, indicating that this hazard still prevails. This paper will examine the statistics of face ignitions and gas explosion in U.S. coal mines based on MSHA data. It will study factors contributing to these face ignitions and outline best practices for their prevention based on experience and practices worldwide. INTRODUCTION Methane and coal dust explosions are one of the major causes of coal mine disasters in the U.S. and around the world. Such disasters have resulted in the large number of fatalities and loss of mine infrastructure. The recent explosion at the Soma coal mine in Turkey has caused the death of 301 miners (Mining Turkey, 2014). As documented by U.S. Mine Safety and Health Administration (MSHA, 2015a), the U.S. coal mining industry has also experienced several catastrophic mine explosions with accidents at Upper Big Branch mine, Darby mine, Sago mine and Jim Walter Resources No. 5 mine in the last decade, causing the deaths of almost 60 miners. Every explosion requires a source of ignition, the right amount of fuel and oxygen. In underground coal mines, methane acts as a fuel while ventilation air acts as a source of oxygen. The source of ignition may vary from spontaneous combustion, electrical equipment and switchgear, mechanical heat sources, face ignitions due to friction rock-on-rock or from cutter bits and lightning strikes. Under the right conditions, energy of less than 0.3 mJ is sufficient to ignite methane-air mixtures (James, 2007) that can result in a catastrophic explosion. Much research has been done to mitigate the methane explosion hazard by proper dilution, continuous monitoring of methane and elimination of ignition sources. Historical studies indicate that face ignitions are the major cause of explosion in underground coal mining operations worldwide (Belle, Carey, and Robertson, 2012). Statistics shows that most mine disasters were started from a small face ignition, which turned into a major explosion fueled by additional methane and coal dust (Belle et al., 2012). To investigate face ignition hazards, researchers must study potential ignition sources as well as potential explosive atmospheres near mechanical coal cutting operations. Statistical analysis of U.S. coal mine face ignitions reported by the U.S. Mine Safety and Health Administration (MSHA, 2015b) shows that several factors are responsible for face ignitions."

Jan 1, 2016

By Gregory P. White

A number of private companies and universities have developed computer programs which can be used to simulate surface coal mining by dragline. In this paper, we briefly discuss the concept of computer simulation, compare these computer programs with each other, describe the major changes required to convert these programs to an IBM computer system, and analyze their sensitivity to inaccurate input data. We also present a summary of the required data input for each program, core storage requirements, and output results. Sources for obtaining these programs and their documentation are listed at the end of the paper.

Jan 1, 1983

By B. Waterman, R. Collins, V. R. K. Paruchuri, P. Gonzalez, H. Dijkman

"INTRODUCTION Mining and processing of sulfide ore bodies has the potential to solubilize sulfate. Gypsum in the host rock, as well as oxidation of sulfides during milling and processing can solubilize sulfate. Acid rock drainage (ARD) also has the potential to generate waters high in sulfate. Even after treatment of the ARD with lime, the treated water can have sulfate present in gypsum saturation levels. Most mine-sites reuse sulfate impacted water but as a mine nears closure, reuse options may be limited and water treatment becomes an option. Furthermore, sulfate discharge requirements, particularly for anti-degredation narrative standards, can be very strict. Freeport has investigated many new technologies to economically remove sulfate from these types of water. A Dutch company, Paques B.V. developed one of these technologies and it utilized biological reactors to convert sulfate into elemental sulfur in a 2-step process. In 1992 the first industrial reference of the SULFATEQTM technology was commissioned at the Nystar Budel zinc refinery in the Netherlands. PILOT PLANT TECHNOLOGY AND DESCRIPTION As shown in Figure 1, the plant contains several process steps, which can mainly be divided into the following sections: 1. Anaerobic biological system in which sulfate is reduced to hydrogen sulfide by sulfate reducing bacteria. 2. Aerobic biological system in which hydrogen sulfide is oxidized to elemental sulfur by sulfide oxidizing bacteria. 3. Solid/liquid separation in which sulfur, calcium carbonate and biomass solids are separated and dewatered. Sulfate impacted ground water is pumped to the feed water tank through a plate and frame heat exchanger to maintain the solution temperature around 95°F. A custom mix of micronutrients is dosed to the feed tank. This nutrient mixture provides essential elements for the growth of anaerobic and aerobic biomass. Urea is added to the feed tank and provides the required nitrogen source to the biomasses. The pretreated feed water is pumped into the anaerobic reactor. The reactor works on the gas lift principle. Sulfate reducing bacteria utilize hydrogen gas as electron donors and reduce sulfate to hydrogen sulfide. This reaction increases the alkalinity of the solution. Carbon dioxide gas is added in order to control the pH within working range of the reactor. Due to the low solubility of the hydrogen gas, the anaerobic gas mixture is recycled through the system. The gas mixture recycle also provides the gas lift for mixing within the anaerobic reactor."

Jan 1, 2016

By Allen Pratt, Guy Deschênes, Mike Fulton, Hai Guo

Calaverite is a gold telluride species, with the composition, AuTe2. Calaverite is usually characterized by an exceedingly slow dissolution rate in a cyanide solution. Cyanidation of a slurry containing synthetic calaverite (P90 of 10 microns) was studied to determine the leaching kinetics and surface reactions. Alkalinity, dissolved oxygen, lead nitrate and sulphide minerals (pyrite and chalcopyrite) were among the parameters evaluated. The reaction products at the surface of calaverite were documented using X-ray photoelectron spectroscopy. High lime concentration with lead nitrate and injection of oxygen produced the fastest leaching rates. New gold leaching mechanisms were identified which appeared to be related to the parameters selected.

Jan 1, 2005

By Paul L. Boni

Trona, Na3(CO3)(HCO3) ? 2H20, is mined in quantity from saline facies of the Eocene Green River Formation of southwestern Wyoming. The Green River deposits are the world's largest known resource of natural sodium carbonates. An estimated 127 billion tons of trona ore are known to occur in beds exceeding 4 ft in thickness (Wiig and others, 1995). Twenty-five trona beds, exceeding 3 ft in thickness, and covering at least 100 mil have been identified. The beds are numbered sequentially in ascending stratigraphic order. Trona beds underlie more than 850 mil (bed 17) and are up to 37 ft thick (bed 1) (Culbertson, 1966). Five underground mines, operating in beds 17, 19, 20, 24, and 25, process trona to produce soda ash (sodium carbonate). A total of 11,837,703 short tons of soda ash were produced from 17.1 million tons of trona ore in 1997 (Kostick and Clark, 1998). A detailed study of trona bed 17, using techniques of petrography and X-ray diffraction, has been undertaken in the Solvay trona mine, near Green River, Wyoming. A continuous, vertical-channel sample was taken from near the production shaft for this study. At this location, bed 17 is 12.6 ft thick and includes several stratigraphic markers that are easily correlated throughout the mine and in surrounding drill cores. Bed 17 in this area averages 90% trona through its entire thickness (Wiig and others, 1995) and 95-100% trona in the lower two-thirds of the bed. Mineral impurities include water-insoluble dolomite, quartz, pyrite, clays, and other minerals and partially water-soluble northupite and shortite. Northupite, Na3Mg(CO3)2C1, contributes to chloride contamination in the soda-ash product and is concentrated in the upper one-third of bed 17, which is left behind as roof rock. Northupite has two modes of occurrence: (1) as bedded strata with dolomite, chert, clay, and shortite and (2) between primary trona crystals in trona spar. Petrographic and mineralogic data indicate that this section of bed 17 was deposited subaqueously during its early and late history and may have undergone periods of deposition in a subaerial or marshy environment. Stratigraphic data indicate that trona accumulated at an annual rate of 2-4 in. per year. During trona deposition, dolomite, CaMg(C03)2, precipitated in parting layers when new water entered the lake, freshening supplies of calcium and magnesium. The lack of clay minerals in the trona facies suggests water input may be by means of springs, as opposed to overland flow. Clay occurrences in thicker dolomitic partings within the trona facies indicate periods of episodic overland flow, possibly resulting from storms in the surrounding basin.

Jan 1, 1999

By Jay Jones, William D. Rech

The Henderson Mine developed a water treatment system in 1985 to meet the NPDES requirements for its mine water discharge. Unacceptable levels of Zinc and Manganese formed the basis for the design and operation of the treatment system. Since initial start up, this system has reliably removed metals from the mine water and facilitated low cost compliance with water standards. The potential addition of a bio- monitoring requirement to the NPDES Permit in 1990 has added a second dimension to the metals removal process. This paper will review the history of Henderson's success at developing a low capital treatment system for metals removal and the anticipated effects of bio-monitoring upon this system based upon preliminary bio-monitoring screening.

Jan 1, 1991

By A. J. S. Spearing, T. Kostecki, D. Benton

The use of paste backfill in room-and-pillar coal mines in the United States needs to be fully investigated. This paper discusses a series of physical tests that were conducted to examine the support benefits of theoretical paste backfill regimens in Illinois Basin room-and-pillar coal mines, which necessarily included consideration of weak floor conditions. The series of tests included those simulating strong floor conditions, weak floor conditions, under-confined scenarios, and testing of actual coal-based paste backfill samples. The testing indicated that a paste backfill regimen utilizing a minimum backfill strength of 22 psi at a minimum fill height of 50% of pillar height could significantly increase the longterm stability of coal pillars in the Illinois Basin. Considering typical coal wash plant recoveries, 50% fill would be feasible.

Jan 1, 2014

By M. Mathiba

High CO2 fluxes associated with reclaimed coal mine spoils pose an environmental hazard where such sites are used for building. CO2 concentrations in excess of 25% have been reported in homes constructed on or down gradient of such spoils. The objective of this study was to investigate the effect of a mitigation trench used at one mine site on CO2 fluxes across the trench using chamber?based trace gas measurement. LI8100 automated CO2 flux system was used to measure CO2 fluxes from 32 sample points located across a deep mitigation trench on June 8 and 9. The maximum recorded fluxes were 7.29 and 8.18 µmol/m2/s, with averages of 4.15 and 5.50 µmol/m2/s, up and down-dip respectively. These preliminary results show CO2 flux is higher up-hill than down-hill at 95% significant level. This work shows that flux measurement can be used to investigate CO2 migration on reclaimed mine land. Further work is necessary to allow geostatistical modeling of the spatial variability of CO2 fluxes over reclaimed coal mine spoils. Knowledge gained would assist mining practitioners and regulators in reclamation planning for envisaged post-mining land uses.

Jan 1, 2010

By Alfred W. Hefferan

A longwall face conveyor system serves the primary function as all material handling systems; i.e., to transport material between the source and its destination. However, the conveyor system must provide many other functions as opposed to the traditional belt conveyor system. In this paper, we will attempt to contrast the longwall face conveyor system with a belt conveyor system. In addition, the unique problems encountered along with the solutions to these problems will be covered. Table 1 lists the characteristics required of each conveyor system. The table demonstrates the contrast in the two systems. Both must be designed specifically to encounter its unique problems. The balance of this paper will explain how the longwall face conveyor is designed to address its requirements.

Jan 1, 2000

By B. Rao Pothini, Julio H. Thaler, W. L. Finlay

The White Pine room-and-pillar mine started in 1955 from a suboutcrop, down gentle dips, and with a competent sandstone roof. As mining depths increased, extraction decreased 1% every 35 feet. Moreover, roofs became shaly and less competent, and regions of high fault and joint densities, sometimes with and some- times without high lateral stresses, increased the tendencies towards roof falls. Instinctive reactions towards narrower openings did not alleviate the problem. Careful consideration of rock mechanics principles culminated in the development of two variants to the conventional room-and-pillar mining system based on the concept of stress relief through load deflection. The two systems-EquiAdvance Cave, and PressureArch Panel Mining-are complementary. The objective of the former system is to provide relief from lateral stresses through advance caving and in the process also to achieve higher extraction at depth. Where surface subsidence cannot be allowed, the alternative PressureArch Panel concept is utilized to provide stress relief and moderately high extraction ratio. Both systems have been under trial for over three years and, together, produced over three million tons of copper ore. These two systems, and their production test results to date, are described.

Jan 1, 1977

By Alan J. Reed

The Afton copper-gold mine is located in the southern interior of British Columbia, 16 km (10 miles) west of Kamloops and 257 km (160 miles) northeast of Vancouver. 'An aerial view of the property in 1976 is shown in Fig. 1. The Afton copper-gold ore body [27 Mt (30 million tons)] of open pit ore with a grade of 1.0% copper, 0.46 g/t (0.01 6 oz per ton) gold, and 4.1 g/t (0.12 oz per ton) silver, occurs within the Triassic Iron Mask pluton adjacent to its faulted contact with Tertiary rocks. The geological setting of the Afton ore body is described by Carr and Reed (1976). Rocks of the Paleozoic, Mesozoic, and Cenozoic eras outcrop in the vicinity of Kamloops, but the unit with the greatest economic significance is the Upper Triassic Nicola volcanic group and its subvolcanic dioritic intrusion, the Iron Mask pluton. The Afton ore body occurs at the northwesternextremity of the Iron Mask pluton immediately south of a deep graben structure that developed in post-Triassic time (Coast Mountains orogeny) and which was the focus of vigorous sedimentation and volcansim in Tertiary times. The Iron Mask pluton is a lenticular composite intrusion approximately 14.5 km (9 miles) in length in a northwesterly direction. The petrography of the Iron Mask pluton ranges from picrite and serpentinite to latite porphyry. Outcrops of individual petrographic units are generally elongate in a northwesterly direction parallel to the axis of the pluton. The Iron Mask pluton represents the moderately slowly cooled core of an oceanic fissure volcano which built up an island flanked by shallow-water sediments including reef knolls and which, during its later stages, intruded its own volcanic pile.

Jan 1, 1991

By Salvatore] [Parand

Deep well disposal is a much used and abused term which is the panacea for wastewater disposal in some minds and creates near hysteria in others. It can be the answer to a difficult waste disposal problem, or if improperly employed, can create more problems than it solves. My purpose in this presentation is to focus on the value and limitations of deep well disposal as expressed by New York State's experience and policies. To he sure, I feel a place for such practices docs exist if adequate safeguards are utilized. I shall give a broad brush approach to New York's legislative, geologic and operational concerns and speak briefly on some case histories. I shall not delve deeply into the technological details since I am not an expert in mining exploration or well drilling.

Jan 1, 1973

By Armin C. Supp

Since 1975, about a dozen high capacity flotation plants have been installed in the Ruhr district. Depending on the size of the preparation plants, the design capacity of the flotation section is between 100 - 150 t/h. The flotation units generally comprise rougher and cleaner stages in which 5 to 6 or 4 to 5 agitators respectively are arranged in line. The unit volume allocated to each agitator is up to 16 m3. The type of flotation machines, the design of these plants and their instrumen¬tation and control equipment are described in detail. The run of mine coal in the Ruhr district is characterized by a wide variety of the volatile matter. Generally, a distinction must be made between coals with more than 30 - 35% V.M., which are preferably used in power station, and coal with lower V.M. content, which are preferably used as coke-oven feed. The difference between these coals in respect to grain-size distribution, ash cotent and flotation properties will also be described in detail.

Jan 1, 1985

By A. Peppas

Perlite is a naturally occurring siliceous rock, which can be expanded from four to twenty times its original volume when heated at a temperature close to its softening point. The expanded perlite is characterized by increased sound and thermal insulating properties. However, the conventionally expanded perlite products have high porosity and low mechanical properties that limit the range of their applications in the construction and chemical industry. The present work aims at the development of new closed porous microcellular material from perlite with enhanced mechanical and physical properties to be applied in new applications, like joint compounds, functional fillers for special paint types, special blasters and mortars, artificial marble. For the production of these new materials a vertical electrically heated furnace with six different heating zones and controlled gradient temperature profile was used. The effect of major process parameters, like temperature and air flow, on the quality of the produced materials was studied using Greek perlite from Milos Island. The quality of the new products was evaluated in terms of their bulk density, compression strength, water and oil absorption, surface area and pore volume. The experimental results show that the produced materials are characterised by improved mechanical and physical properties compared to the conventionally expanded perlite products.

Jan 1, 2006