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By Fred N. Kissell, Robert J. Timko

Safe escape from coal mine fires continues to be a concern of the mining industry. The most life-threatening fires occur outby the working sections. Because stoppings always leak some air, an outby fire may in time cause intake escapeways to become contaminated with smoke and toxic gases. Smoke and gas infiltration into intake escapeways can be minimized by raising their air pressure over that of adjacent airways. This can be done by checking off the intake escapeway near the working face. The Bureau of Mines has investigated the use of a parachute stopping as a quick-erect check curtain during mine fires, and the concept has been tested in several mines. In every instance, when a parachute stopping was erected on the section, the intake pressure went up substantially. The pressure-raising effect of the parachute persisted for up to 1200 m (4000 ft) outby. Results indicate that checking off the intake escapeway may serve as a viable way to improve safety during mine fires.

Jan 1, 1991

By Ron Robinson, Trevor Harrison

The planning, installation and commissioning of the first scheme of controlled recirculation of air flow in a section of coal mine in Great Britain is described, together with the proposals for a second installation. The work updates a previous paper (Robinson and Harrison, l986) on the subject. The special problems of ventilating the increasingly distant faces of the undersea mines in the North East Area of the British Coal Corporation are discussed and the alternative solutions stated. The advantages of using a system of controlled recirculation of air are proposed together with the safety features considered necessary. Design and installation details of the recirculation fans and a new booster fan are described.

Jan 1, 1987

By Eugene Honeycutt, David Gallagher, R. E. Melley, Nick Madison

Drummond Co. Inc.'s Shoal Creek Mine slope conveyor is the highest lift, highest horsepower, highest tension conveyor system in North America. The system has a capacity of 4950 t/h (5500 tph), a vertical lift of 360 m (1180 ft) and a total connected power of 6000 kw (8000 hp). The mine will include 2 longwall machines and 5 to 7 development sections. Annual raw production will approach 9 million tly (10 million tpy). This paper describes the early investigation of system capacity, haulage system options, and the final selection of a single flight belt conveyor. It will review the basic system de- sign and equipment selected. Also included will be some highlights of the installation of the conveyor system.

Jan 1, 1996

By William E. Foreman

The results of the electrokinetic study of the activation of quartz by divalent cations showed that the charge reversal was related to the point at which the cation hydrolyzed. The reversal was not due to the presence of solid hydroxide at the surface of the quartz but due to the charged ions in the solutions. The charge reversal for beryllium at a log molar concentration of 1x10-4 was observed at pH 5 and 9. The quartz was positively charged between a pH reading of 5 to 10. Magnesium at the same log molar concentration did not show a charge reversal from pH 2 to 12. The probable cause of the charge reversal was due to the ionized Be3 (OH)3+3 or Mg (OH)+ . Variations in the electrokinetics of quartz were minimized by heating the sample to 300° C.

Jan 1, 1968

By M. W. Ryan

The US Bureau of Mines investigated cold-cutting alternatives to oxyacetylene torch cutting of metal. The alternatives examined were a pneumatic circular saw with an abrasive cutting wheel, a handheld abrasive water-jet cutting tool, an ultrathermic-cutting system, hydraulic punches and cutters, and a pneumatic reciprocating hacksaw. Sparks generated with the pneumatic circular saw or ultrathermic-cutting system were not completely eliminated with the use of water sprays. The water sprays also reduced the cutting rate of the pneumatic circular saw by 70%. The safety and performance of a handheld abrasive water jet cutting system requires additional research. The hydraulic cutters and punches are readily available and do not introduce any hazards. However, they are not comparable in price to the oxyacetylene gas torch and many different attachments would be needed to replace the torch. The pneumatic reciprocating hacksaw, which did not produce any sparks, is an acceptable alternative in terms of cutting rates. However, the price of the saw and blades is not comparable to that of the oxyacetylene gas torch. The results of this study will further the advancement of safe, efficient alternatives to oxyacetylene gas torches, which will improve miner safety.

Jan 1, 1996

By Robert Snow, Francisco Sotillo

Six types of amines were evaluated in the cleaning step of the rougher concentrate for the Crago “Double Float” process in terms of relative selectivity. Selectivity of these amines was ranked based on both batch and locked cycle flotation tests. Two parameters were used for selectivity ranking, the Selectivity Index, SI, and the ratio of insol rejection to the tailings weight percentage, R*. The comparison of the flotation results of the batch tests of the cleaning step of the Crago process for an unsized amine feed generated the following ranking from the most selective to the least selective mine: Quaternary > Primary [ ]Tertiary [ ] Condensate > Ether > Secondary(?).

Jan 1, 2002

By R. K. Devala

In this paper, numerical approximation schemes, for solution of the mass transfer problem in mine ventilation have been developed by using three implicit finite difference schemes. Results from these schemes have been compared with the analytical solution for spatial and time increments, using the concept of Root Mean Square error. For implicit finite difference schemes, in general, the modified central difference scheme is better than the two other schemes at lower velocity. Also, at lower air velocities, implicit schemes underpredicted the concentration values. At higher air velocities, the Crank-Nicholson and Laasonen schemes provided better results than the Modified Central Difference scheme.

Jan 1, 1994

By Mike L. Aziz, Keith D. Ferguson, Glenda Ferris

The Equity Silver mine has been a severe producer of Acid Rock Drainage (ARD) since 1982. The mine was closed in 1994 and a compacted clay cover installed, but ARD continues to be produced. Three permanent employees manage the collection and treatment system at the site. The site still poses a significant environmental risk to the environment and downstream users and requires a high level of diligence. Various stakeholders' perspectives of the risk posed by Equity, and what constitutes acceptable risk, will be examined in this paper from a company operation staff, corporate environmental manager and downstream environmentalist perspective.

Jan 1, 2000

By D. Koch

Bentonites and bentonite containing sealing materials are used since many years for sealing purposes in foundation, dike construction, hydraulic engineering and landfill construction, especially for encapsulation of old waste deposits In the near future compacted bentonites will be important components of multi-barrier systems for dry charge of old mines, for underground disposal of hazardous or radioactive wastes. Because of their exceptional physical, structural and chemical properties, bentonites are offering manifold possibilities to protect the environment against the negative effects of dumping grounds. Often the compliance with legal regulations for waste dumping or the isolation of contaminated areas is possible only by using bentonite containing sealing systems. The essential properties of bentonite, bentonite containing building materials and the different techniques of making horizontal technical base liners and vertical cut-off walls are explained. For horizontal technical base liners the adsorption ability, the ion exchange capacity and the swelling behavior of bentonites are important. For cut-off walls bentonite controls the rheological behavior of the slurry and is responsible for the low permeability of the hardened bentonite-cement-wall. In the multi-barrier systems of repositories for chemical or radioactive wastes compacted bentonites are considered to be favourable sealing and backfilling materials because of their high swelling capacity, their adsorption and ion-exchange ability and their plasticity in water saturated state.

Jan 1, 2005

By C. Patrick, D. Puckett

The feasibility of monitoring the locations and vital statistics of equipment and personnel in surface and underground mining operations has increased with advancements in radio frequency identification (RFID) technology. This paper addresses the use of RFID technology, which is relatively new to the mining industry, to track surface equipment in mine pits, loading points and processing facilities. Specific applications are discussed, including both simplified and complex truck tracking systems and an automatic pit ticket system. This paper concludes with a discussion of the future possibilities of using RFID technology in mining, including monitoring heart and respiration rates, body temperatures and exertion levels; monitoring repetitious movements for the study of work habits; and logging air quality via personnel sensors.

Jan 1, 1999

By V. R. Manukonda, I. Iwasaki

Selective flocculation of iron ores is extremely sensitive to the type and amount of soluble salts in pulp solutions. Chemical precipitation of alkaline earth ions combined with ultrasonic treatment deactivates their adverse effects without using any environmentally ill-defined reagents. The manner in which ultrasonic treatment affects starch adsorption on hematite, dissolution of quartz, and the selective flocculation process was investigated. Selective flocculation tests were conducted in the presence of up to 400 ppm calcium ion on a quartz-hematite mixture by precipitation as calcium carbonate, and the role that silicate ion generated by ultrasonic treatment plays in achieving the selectivity of separation is discussed.

Jan 1, 1988

By K. V. K. Prasad

Stochastic simulation has been routinely used for performing risk and sensitivity analyses in a variety of fields. The commonly used means of generating the simulations has been the Monte Carlo approach, which usually employs a Simple Random Sampling (SRS) scheme of the variable distributions. This method is prone to sample clustering and requires a large number of samples to represent the distribution faithfully. This can become problematic for simulating complex processes where it is impossible to run an arbitrarily large number of replicate simulations. The Latin Hypercube Sampling (LHS) method uses a stratified sampling approach that assures representation of the input distributions for any given number of samples. In this paper the LHS and SRS approaches are compared, using a petroleum resource estimation example.

Jan 1, 1994

By B. J. Arnold

A coal's size distribution clay content and moisture content can affect its handling behavior. But the combined effects of these properties and the effects of other properties are not known. Research underway at CQ Inc.'s (formerly EPRI's) Coal Quality Development Center (CQDC) and at Iowa State University (ISU) will answer these questions as part of a four year project to develop a coal handleability index for utilities to use when specifying coals. This paper will present preliminary data from the first year of the project, which focused on obtaining data on the chemical and physical properties of carious coals and their measured handling properties. Additionally, size, ash and moisture analyses and shear test data for several coals used at one power plant will be presented along with correlations between these physical and chemical properties and the measured handling properties. These data lead to the conclusion that while moisture content is the most important variable, the amount of -44 µm (-325 mesh) coal fines is a significant factor in determining coal handling behavior.

Jan 1, 1992

By Erich U. Petersen, Robert B. Coleman, William J. Tafuri, Donald M. Hausen, P. R. Taylor, Douglas N. Halbe, D. W. Rodolff

The definition of refractory gold ores and concentrates, including mineralogical characteristics, is reviewed. The chemistry of roasting and process conditions such as feed size, temperature, and time are discussed. A typical metallurgical program for developing a roasting process scheme is presented. The application of various types of furnaces for roasting is described. Requirements for scrubbing off-gases to meet environmental air emission regulations, and general information regarding engineering design parameters for roasting are presented. Roasting is sound technology for processing refractory ores and concentrates, but it is essential that the metallurgy of each ore or concentrate is well defined before commercialization. A fluid-bed roaster is the preferred type of furnace for roasting. Environmental regulations for air emissions must be carefully addressed.

Jan 1, 1990

By F. Djahanguiri

The US Bureau of Mines con¬ducted research on underground stope leaching of metalliferous ores. Leaching underground would minimize the environmental impact of ore processing on the surface and would maximize minable reserves. An important aspect of this process is the minimization of pregnant solution losses and groundwater contamination by leach solutions. Bulkhead design and construction are important issues for solution control and stope-leaching economics. A reinforced-concrete bulkhead was designed, constructed and tested for solution control in an underground mine near Idaho Springs, CO. This paper presents the bulkhead-design methodology and construction procedure.

Jan 1, 1997

By S. Frimpong, N. Demirel

Overburden excavation is an integral component of the surface mine production chain. The walking dragline is the most economic production equipment for overburden excavation in strip mining. Draglines are capital intensive, and thus, investments in multiple units severely impact the economic viability of projects. The use of few dragline units results in highly concentrated production focus, which must be efficiently managed to derive the potential economic benefits. Efficient use of draglines requires a thorough knowledge of the powered functions, the 3D rotational and translational motions and machine-formation interactions within the operating environment. Dragline kinematics and dynamics are required to understand and characterize machine performance and efficiency. In order to sustain the high productivity in difficult operating conditions, the dynamics of the dragline must be modeled and analyzed based on comprehensive kinematics. This paper investigates the planar kinematics of the front-end assembly and its interactions with the formation during excavation using the “Vector Loop Analysis” formulation with comprehensive simulation modeling in MATLAB Simulink. The kinematic models are used to examine the translational, rotational and angular displacement, velocity and acceleration components of the dragline front-end assembly along defined bucket trajectories during excavation. The results are the precursors for comprehensive modeling to examine the load deformation, torque requirements and dragline stress loading profiles for improving machine health and longevity.

Jan 1, 2006

By W. S. Fyfe, R. J. Puddephatt, S. Zhou

Gold is easily mobilized at temperatures within range 600-11OO°C by gases such as Cl2, CO, H2S, in gas mixtures, at low pressures. Such gases are relevant to conditions of granulite facies metaomorphism in environments of magma underplating. These observations suggest an efficient mechanism for moving gold to the upper crust during major thermal events. The efficiency of precipitation of gold at lower temperatures is related to available mineral surfaces and pyrite appears to be an excellent substrate for gold precipitation.

Jan 1, 1989

By Henrique Garcia Pereira

In a large scale mining project, the global feasibility study must take into account the interdependence of three sub systems: the geological subsystem, represented by the orebody model; the technological subsystem, consisting .of mining and ore dressing models; and the economic subsystem, including the selling price of final product, production costs and investments. In cases where the ore is heterogeneous, the interdependence between geological and technological subsystems may be assessed by a Data Analysis technique such as Correspondence Analysis (CA). This technique was applied by David and Dagbert (1975) on examples of data from geochemistry and geology. In the approach used in this paper, CA is used to create the basic framework for defining different types of ore. The final definitions of ore types take into account the mi¬ning method and the results of applying beneficiation processes to the ore.

Jan 1, 1982

By F. T. Paleari, J. A. Finch

Radial gas holdup profiles were measured in a 50-cm-diam, 400-cm-high flotation column using a multi-cell-conductivity probe. Three bubble-generation systems, including a system with up to eight vertical filter-cloth spargers, a system with three horizontal filter-cloth spargers and a system with three (horizontal) Cominco-type spargers, were examined. The variables investigated were the number of spargers, the symmetry of their arrangement and the height above the spargers. Batch water containing up to 20 ppm frother was used. Generally, the profiles tended to be uniform (flat) with some profiles exhibiting a slight "wavy" pattern. The vertical sparger arrangement proved to be the most difficult in which to achieve a profile symmetry. The horizontal spargers gave uniform profiles at right angles to their length but gave decreasing gas holdup along their length. The Cominco-type spargers gave slightly less scatter in the data. Switching off selected spargers to simulate a malfunction did not produce strong asymmetry in the profiles.

Jan 1, 1995

As discussed previously, total cost is the sum of the direct materials, direct labor, and production overhead costs. The assignment of direct materials and direct labor costs to individual activities is generally straightforward. The assignment of overhead often is not. Overhead costs frequently contain allocations that only approximate the demand the activity has made o; the overhead resources. The inaccuracy of the overhead calculation can create erroneous production cost information and lead to suboptimal management of the operation. This problem is particularly acute when determining the production cost of individual products in multiproduct firms. Pricing, process management, and product mix decisions are especially susceptible to errors in product costing. The problem of properly determining production cost is complicated by the fact that few if any alternative methods exist to identify the inaccuracies in overhead allocation. To avoid errors, some firms simply ignore overhead costs in their product cost calculations, particularly those resulting from marketing and distribution of the final product.

Jan 1, 1999