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By Richard Druesedow, Richard Ray

Tests at the VP-5 "C" shaft fan installation of Island Creek Coal's Virginia Pocahontas Mines were performed to determine pressure drop due to the design of the shaft collar and ductwork leading to the fan. Data from the test locations in the shaft, duct and fan indicate significant pressure losses in the system as well as significant turbulence in the flow. Data taken with a 3-D probe in the fan annulus confirmed the importance of using this type of instrument in turbulent flow applications. This data will be later supplemented with data taken after addition of turning vanes in the 45° turn adjacent to the fan inlet.

Jan 1, 1993

By A. Pradakar, J. G. Groppo, J. W. Leonard

All coal transportation systems from the coal face to the final point of use would become more productive if additional tonnages, obtained through improvements to bulk density, could be placed in fixed volume containers such as scoops, shuttle cards, trucks, barges and ships, as well as conveyors. This paper reviews previously reported work where the treatment of coals with small amounts of mining chemicals (0.12 to 0.28 kg/t or 0.25 to 0.56 lbs/st) during lavoratory testing was show to increase loaded coal bulk density by about 15%. The latest bulk density enhancement findings to develop from ongoing research involving underlying chemical and physical theory together with the added use of simple mechanical excitation are discussed.

Jan 1, 1995

The gases transportation and adsorption in the coal are greatly dependent on the pore-crack parameters, such as the porosity, the pore distribution, as well as the number and size of the pores. What?s more, the pore parameters of the coal are always changing with the temperature. However, the pore characteristics and their changes are extremely difficult to quantify. In this case, Fractal Theory provides a good tool to address this issue. Based on this theory, the pore distribution coupled with the size of the pores can be quantitatively described. In this paper, the equation used to calculate the Fractal Dimension of coal pores was deduced and Mercury Porosimetry was employed to test the pores distributions of coal samples at different temperature. The experimental data excellently verified the Fractal characteristics of coal pores. In addition, the experiments also indicate that the Fractal Dimension of the coal pores linearly increases with the temperature.

Jan 1, 2012

By Dean D. Turner

Exploration geochemistry requires computer processing for quick and efficient reduction and interpretation. An easy to use microcomputer based geologic workstation fulfills this need and allows the geologist to independently process geochemical data. Functions necessary for geochemical data processing are: 1)Digitizing; 2)Communications; 3)Data base management; 4)Statistical analysis; 5)Mapping analysis; and 6)General purpose applications (ie: word processing). A geologic workstation that can perform these tasks will yield significant advantages in processing and interpreting geochemical data.

Jan 1, 1987

By B Faulkner, M. Weinecke

In 1997, Sveciala began a program to develop a process to convert waste tires into valuable commodities. A review of numerous approaches revealed shortcomings that were process related or mechanical related, while some of the approaches emphasized he production of low-value products. A market study revealed that a process that could produce a good grade of carbon black would be economically feasible. This paper discusses the laboratory and pilot-plant development and commercial plant design of such a process.

Jan 1, 2002

By P. V. R. Bhaskar Sarma, P. K. Sahoo, G. Roy Chaudhury

A process was developed to treat an ammoniacal leach liquor containing zinc using Di (2-ethyl hexyl) phosphoric acid (D2EHPA) as the extractant. The objective of this work was to develop a process package for the treatment of complex sulfide leach liquors. Zinc extraction could not be carried out directly from the ammoniacal solution in mixer-settler units because of crud formation and low extraction efficiency. After neutralizing the free ammonia with H2SO4, the extraction efficiency was only about 40%, due to the high concentration of (NH4)2SO4. To decrease the (NH4)2SO4 concentration, the free NH3 was steam stripped, and the resultant liquor was subjected to zinc solvent extraction. An extraction efficiency of 98% could be achieved by controlling the equilibrium pH. Stripping studies were also optimized after removing ammonia from the zinc-loaded organic. A continuous 100-hr operation that included extraction, scrubbing and stripping, was carried out successfully.

Jan 1, 1995

By I. Iwasaki, J. N. Orlich

The effect of slurry rheology and ball coating characteristics on the abrasive wear of grinding media and the rate of grinding were studied using -10 mesh quartzite in laboratory marked ball wear tests. Pulp viscosity was found to be closely related with both the thickness and physical characteristics of the coating affecting abrasive wear. The packing density of particles at the ball surface was the primary determinant of wear while the grinding rate was more dependent on viscosity and thus the ball coating thickness. The optimum grinding rate was achieved when the coating thickness was about twice the largest particle size.

Jan 1, 1988

By M. S. Klima, B. K. Kim

The use of a 25.4-mm- (1-in.-) diam water-only hydro-cyclone for separating liberated 125 x 25- µm high-density particles from similar-size lower-density (2.65 g/cc quartz particles, as might be used in soil washing applications, was investigated. As expected, cyclone performance was greatly affected by changes in cyclone geometry and operating conditions. A single-stage separation recovered 75% of the magnetite (4.8 g/cc) while rejecting nearly 60% of the quartz. With ferrosilicon (7.0 g/cc) as the heavy component, the recovery improved to 85%. The use of dense medium in a single stage increased both ferrosilicon recovery and quartz rejection to approximately 90% each. In addition, computer simulations of a three-stage circuit were performed. The simulations showed that recoveries approaching 97% with quartz rejections of 95% were possible.

Jan 1, 1999

By Thomas F. Pedersen, J. Jay McNee, Alan J. Martin

Field sampling was conducted in Lake Junin, Peru in order to assess the post-depositional reactivity of the highly contaminated lake sediments. High resolution profiles of dissolved Fe, Mn, SO42- and H2S across the sediment-water interface illustrate that the organic-rich sediments in the main basin become anoxic within several millimetres of the sediment-water interface. These permanently submerged deposits in the main basin serve as a diffusive sink for dissolved Zn and Cu. Conversely, the periodically unsaturated deposits in shallow areas are characterized by the remobilization of Zn and Cu in the deep acidic (pH < 4) pore waters, resulting in the release of these metals to the overlying water column.

Jan 1, 2000

By John C. Heter

The P.W. Gillibrand Company holds 705 placer and lode claims in the Precambrian San Gabriel Anorthosite Complex of the western San Gabriel Mountains. These claims contain large tonnages of ilmenite, magnetite and apatite with anomalous quantities of zirconium (zircon), niobium, vanadium and rare earth elements. Stockpiling of heavy mineral concentrates associated with aggregate mining from alluvial pits has occurred since 1984. The limited reserves of material from these alluvial deposits and their relatively low heavy mineral grades caused Gillibrand Company to initiate an extensive drilling and exploration program to develop the hardrock resources of ilmenite, apatite and magnetite.

Jan 1, 1995

By K. N. Han

The kinetics of gold dissolution in iodide solutions with oxygen in an autoclave was investigated. The leaching process was described by a gas-liquid-solid heterogeneous reaction. The effects of stirring speed, temperature, oxygen partial pressure and lixiviant, concentrations on the overall leaching rate was investigated. It was found that the dissolution of gold could be represented by a heterogeneous chemical reaction. Under the conditions studied, the apparent activation energy ranged from 34.7 to 54.3 kJ/mol. Experimental findings were in good agreement with the kinetic model proposed.

Jan 1, 1998

By Yoginder P. Chugh, K. V. K. Prasad, R. Missavage

This paper presents results of field monitoring and finite element studies to analyze and improve a room-and-pillar retreat mining system. Fie1 d instrumentation was utilized to monitor pi11ar load changes, roof to floor convergence and differential roof strata movement as retreat mining progressed and to determine in-situ horizontal stresses. A two-dimensional finite element model depicting strata behavior at this mine was developed and used to analyze existing and alternate improved mining geometries. The results showed excellent correlation between fie1 d observed and model predicted behavior. Some of the recommended changes in mining geometry based on the study were incorporated in the mining system.

Jan 1, 1986

By Travis S. Wellman, Jon C. Volkwein

The Bureau of Mines conducted a study to assess the impact of a directional water spray system on a unique single inlet dust scrubber on a low profile mining machine. Tests were conducted in a full scale model mine using a Joy 12 CM 10-AA continuous mining machine. Tracer gas was introduced at the face and concentrations of the tracer gas were monitored at the face and in the return. Various parameters included: mining position, depth of cut, brattice setback and combinations of scrubber, directional sprays or symmetrical sprays. Results indicated that either directional or symmetrical water spray configuration improved the ventilation effectiveness of the scrubber by a factor of 2 to 3. Average face ventilation effectiveness (FVE) values for all testing of the scrubber and directional sprays were 0.95, versus 0.37 for a standard 6 m (20-ft) blowing curtain without sprays. No FVE values were less than the standard 6 m (20-ft) blowing results.

Jan 1, 1989

In conjunction with steady increases in production levels, longwall operators have applied greater quantities of ventilating air and spray water in an effort to control respirable dust and/or methane. Air velocities greater than 7.6 m/s (1,500 )fpm) have been measured on longwall faces. Operators have expressed concern over the potential entrainment of respirable dust at these high velocities. The greatest likelihood for entraining dust into the high-velocity airstream may occur as shields are advanced, allowing relatively dry particles to fall from the shield canopy directly into the airstream. Laboratory tests to simulate dust liberation during shield movement were conducted at the Pittsburgh Research Laboratory of NIOSH at velocities ranging from 2.0 to 8.2 m/s (400 to 1,600 fpm). Airborne dust samples were obtained with personal impactors to quantify the size distribution and concentration of the dust entrained at the various air velocities. Statistically significant increases in both total and respirable dust concentrations were measured as test air velocities were increased.

Jan 1, 2002

By R. Larry Grayson

A survey of 1250 surface and underground coal mines across the United States was made according to a stratified sampling technique based on national coal districts. A total of 171 responses (13.7% response rate) have been returned and summarized, giving a picture of computer usage in the coal industry. Overall, 63.5% of the respondents use computers, but the percent varied from 100% for large mines to only 44.1% for small mines. As expected, a proliferation of microcomputers has pervaded the industry. Importantly, in spite of the high usage of computers in the industry, sophisticated engineering applications have not yet burgeoned.

Jan 1, 1989

By Nigel Pearson, Malcolm J. McPherson

In the Grasberg Mine, a series of orepasses of diameter 2 to 4m are being constructed, each one to carry as much as 10,000 tlhour of copper- and gold-bearing ore through single stage vertical drops of over 500m. At the base of each orepass, the fragmented rock falls into an orebin of diameter 1 Om and 100m deep. Long before the planned tonnages were reached on the early orepasses, a problem arose that was both serious and intriguing. Pressurization of air in the orebins caused by the falling rock reached such levels that when the feed to the top of an orpass was interrupted, a massive surge of air ascended rapidly and produced a dangerous backblast accompanied by dust; grit and rock fragments from the top of the orepass. Backblasts lasted for about one minute and were not only hazardous to the health and safety of personnel but also required time-consuming clean-up operations. The paper describes the aerodynamic analyses that were con- ducted in order to understand fully the mechanisms involved in the phenomenum, and the development of a procedure that al- lows the effects of falling material to be incorporated into existing ventilation network software.

Jan 1, 1997

By J. P. Golightly

The nickeliferous laterites of Soroako are described in their setting in the huge Cretaceous ultramafic complexes of central Sulawesi, Indonesia. The ore bodies occur on spurs, ridges and hill flanks beneath remnants of extensive erosional surfaces. Weathering pro- files that have developed on unserpentinized harzburgite and on strongly serpentinized lherzolites show distinctive laterite structures, mineralogy and chemistry. The former are unique to the Soroako area and permit an unusual degree of upgrading by rejection of unserpentinized peridotite boulders. A mass balance calculated for a selection of profiles indicates that in situ leaching of a column of peridotite 20-50 meters thick has taken place with only minor lateral migration of nickel in solution.

Jan 1, 1979

By Pedro Marques Bernardo, Carlos Dinis da Gama

This paper presents a methodology for design and simulation of underground ventilation networks, based on the analysis of real situations, followed by the careful interpretation of the obtained results in order to implement their optimization. The method involves two basic steps: the construction of a complete ventilation data base for the mine, upon a series of care- fully previous surveying studies in order to determine the values of its ventilation parameters, and the simulation of relevant situations for the ventilation system optimisation. A simulation model, modified after the Hardy Cross method, allows the testing of various mechanical means located at different points of the network, aiming to determine the technical-economical feasibility of each solution. These simulations obey the directions of air flow in each point of the mine, as determined by the directions of the natural ventilation flow established in the data base that represents the network. The methodology was validated upon studies developed in ventilation network of the Panasqueira Mine (Portugal), in two situations: regular production (mechanical ventilation) and care- maintenance (natural ventilation).

Jan 1, 1997

By B. Denby

Recent advances in virtual reality (VR) have resulted in major opportunities for improving the safety training of mine workers, supervisors and managers. VR has the potential to expose mine personnel to hazardous situations in a safe, highly visual and interactive manner. Customized simulations of mine layouts, dynamic operations and mine environment can be set up, and mine personnel can be allowed to move around the virtual mine, making decisions at key points. The consequences of both correct and incorrect decisions can be immediately fed back to the trainee.

Jan 1, 2000

By C. F. Meyer

The recirculation of mine air in an underground colliery, has always been regarded as a hazardous practice in South African collieries. The Mines and Works Act and Regulations states that fresh air, flowing Into an underground section, must flow out directly into the return airways after being utilized once in the section. One of the largest producing underground collieries in South Africa, Initiated a project on controlled recirculation with the permission of the South African Government Mining Engineer. The project involves the recirculation of 65 m3/s of air inside a ventilation district which serves a total of six production areas. The aim of the project was to increase the airflow to the sections without altering the existing ventilation system. Tracer gas studies were carried out to determine the actual distribution of the recirculated air to the individual areas. The results showed that an effective 54,18 m3/s of the recirculated 65 m3/s reaches the sections. This gives an air utilization figure of 83,4 per cent. Dust surveys were also carried out as part of the project to determine the effect of the recirculation of the return air on airborne dust levels. The results showed that the dust levels remained constant in the main intake and return airways and that no hazardous situation was being created. The project proved to be successful and showed that controlled recirculation can be executed and used as a solution for the supply of air to sections without endangering any lives.

Jan 1, 1993