Search Documents

By James R. Oehler

Progress, future challenges, and the continual search for more efficient and rapid methods of excavating underground openings and shafts were main themes at the 1983 Rapid Excavation and Tunneling Conference (RETC) held June 12-16 in Chicago, IL. The event, jointly sponsored by the Society of Mining Engineers, the American Society of Civil Engineers, the Canadian Institute of Mining and Metallurgy, and the Engineering Institute of Canada, offered a diverse program for both civil and mining engineering disciplines. Although all papers given at the three-day conference were noteworthy contributions, and each is included in the conference proceedings currently available from SME, there were a few sessions that had particular mining-related interest. Research, Acceptance Needed for Water-Jet Technology Water-jet-assisted rock excavation is seen by some as a technology moving from the prototype phase to a fully developed, accepted system within the next decade. For an industry that is traditionally fairly slow in accepting significant changes, this development appears especially noteworthy. However, speakers at the water-jet technology session generally agreed that many large US manufacturers are not viewing water-jet-assisted equipment as viable replacements for all-mechanical systems. This, they fear, may mean some US manufacturers will lose a significant share of certain equipment markets to foreign competitors who are moving aggressively ahead in this area. Despite the advantages of increased cutting rates, reduced power requirements, less dust, prolonged bit life, and reduced sparking in many cutting situations, water-jet technology applied to mining is apparently having some acceptance problems in the US. R. J. Evans, professor of industrial engineering at the University of Pittsburgh, noted that there are several perceptual barriers to water-jet coal cutting; such as uncertainties concerning the fu¬ture demand for coal and the reliability of equipment, apprehensions that jet-assisted equipment will make the mine operator dependent on specific types of hard-to-obtain equipment, and fears about accessibility of the equipment for repairs. Evans also said numerous parameters need defining before taking advantage of water-jet-assisted cutting systems in under-ground coal mining in the US. For the cutting head, information must be obtained on optimum bit geometry and spacing, and maximum and minimum torque requirements. For a complete US water-jet cutting system, Evans added, research is needed to establish optimum jet pressures, jet powers, number of jets per bit, and location of jets relative to the bit. One research project making progress towards optimizing parameters for a water-jet-assisted drag bit cutting system for coal mining was described by Levant Ozdemir, director of the Earth Me- .

Jan 8, 1983

By R. L. Murray-Smith, M. E. A. Robertson, M. J. Prosser

The AZTEC is an automated instrument, for the non-destructive analysis of gold ore samples, which uses energy dispersive X-ray fluorescence (XRF), This is achieved by X­ray tube excitation of gold K X-rays. The first production instrument was commissioned at Vaal Reefs Chemical Laboratory (VRCL) in November 1987, followed by two second generation instruments in 1989. AZTECs have also been installed at Western Deep Levels and at Anglo American Research Laboratories (AARL). A further unit is being assembled at Ashanti mine, Ghana. At VRCL the AZTECs are used primarily for the evaluation of mine (stope) samples. Each of the production instruments can routinely analyse 650-700 samples per day, with the aid of a robotic sample transfer system. Various techniques have been evaluated for increasing sample throughput. For example, higher value samples can be counted for a shorter time to obtain the necessary relative precision.

Jan 1, 1991

By Silvia H. M. Grimaldi, Afonso H. Martins

The scope of this experimental work was to study the yttrium extraction and stripping behaviour in a solvent extraction system with mono(2-ethylhexyl)2-ethylhexylphosphonic acid (IONQUEST 801) in a chloride system The study was performed for only one contact between organic and aqueous phases The experiments were carried out according to a factorial design. Due to the statistical analysis and its experimental proof, the optimum conditions for maximum yttrium loading into the organic phase of the extraction stage were 16 minutes for time of contact between phases, 980 rpm of stirring intensity and pH=2.3 for the aqueous phase of the sovent extraction system. The optimized experimental conditions by the statistical approach for the stripping stage were: time of contact between phases equal to 20 minutes, 1050 rpm of stirring intensity and 1.75 M HCI into the stripping aqueous solution.

Jan 1, 1995

By Peter A. Spencer

Much criticism has been levelled at bacterial oxidation over the quantities of air required for successful operation. Examination of the oxidation reactions and the assumptions concerning oxygen transfer made in the literature (1) indicate that the aeration requirements can be much less than those beirig suggested. Observations made on a large scale pilot test have confirmed reasonable aeration levels in extended site operation over a six month period. These aeration levels have implications for the engineering design and the power needed for aeration and agitation. Thus, these parameters effect both capital and operating costs as well as influencing the complexity of the design and normal operation. A number of companies have developed bacterial oxidation cultures intended for commercial ·expl oi tat.ion ( 2, 3, 4). Most of these cultures have been based on Thiobacillus and operate at temperatures between 30°c and 40°c. This temperature range limits their application in hotter regions unless means for both heating and cooling are provided in the design. Thiobacil!us cultures are also reported as not able to oxidize arsenic (III), which may limit the application of these cultures to successfully treat arsenopyritic ores and concentrates (5). BacTech (Australia) Pty Ltd has developed a culture which operates at temperatures above 4o0 c and which has been tested in a large site based continuous pilot plant at up to 55°c over a six month period. The culture showed resistance to high levels of soluble arsenic, allowing the arsenic to be retained in solution for control led precipitation and disposal. Data for. the arsenic precipitates indicated that these waste solids were relatively stable and, under the correct circumstances, were suitable for disposal into tailings dams without causing environmental problems.

Jan 1, 1990

Various computer packages are now available for balancing data obtained from complex concentration plants. It is well established that the filtered data generated by these programs are statistically better than the raw data. However the degree of improvement as well as the accuracy of the estimated variables depend strongly on the propagation of measurement errors through the estimation algorithm. Therefore, for the subsequent use of the filtered data, their confidence intervals are as important as the data themselves. Variance of filtered variables have been derived in a very general way for any arbitrary flowsheet and when data originate from various sources such as flowrates, chemical assays, particle size distributions and pulp percentages of solids. The theoretical formulae are incorporated in the BILMAT package for mass balance calculation and illustrated on various flowsheets involving grinding, classification and flotation. The validity of the proposed method is discussed by a comparison to a Monte Carlo approach, for a simple processing circuit.

Jan 1, 1986

By Fathi Habashi

At the Duisburger Kupferhütte plant in Germany, pyrite cinder is collected from the sulfuric acid manufacturers in that country and processed to recover the nonferrous metals contained in the cinder, before charging it to the blast furnace for iron recovery. A typical analysis of the cinder is given in Table 9-1. The pyrite cinder is mixed with NaCl and treated continuously in a multiple hearth furnace. The evolved gases are scrubbed with water to form a weak acid which is used for the leaching process. Each batch requires about 2 days for leaching. The concentrated leaching solution obtained in the first 15 to 20 hr is sent for copper recovery, while that subsequently obtained, being poor ill metal content, is recycled. The residue, called purple ore, now a high-grade iron ore (61-63 % Fe); is sintered and delivered to the blast furnace.

Jan 1, 1970

By Lynton S. Land

Representative collections of recent dolomites, and of samples concentrated by leaching-out of coexisting magnesian calcites, provide grounds for appraisal of the compositions and cation ordering in recent dolomitized sediments. Unit cell volumes for near-stoichiometric compositions exceed those of ordered dolomite and increase as the departures from regular cation order became more pronounced. Infrared absorption maxima of disordered examples occur at perceptibly lower frequencies. Stable isotope ratios indicate that best ordered examples formed in highly saline environments. Present observations are qualitatively reconciled with data from synthetic products described by other authors.

Jan 1, 1972

By Emil O. Frind, David W. Blowes, K. Ulrich Mayer

The multicomponent reactive transport model MIN3P can be used to simulate the evolution of pore water, pore gas, and the mineralogical composition in mine waste environments. The model is formulated for variably-saturated conditions, considers transport of dissolved and gaseous species, and describes geochemical reactions based on a partial equilibrium formulation. Reaction processes included are complexation, oxidation-reduction, ion-exchange, mineral dissolution-precipitation and gas exsolution- dissolution reactions. An example application, describing the generation of acid mine drainage and subsequent reactive transport for a ID-vertical profile in a tailings impoundment near Elliot Lake, Ontario, is provided.

Jan 1, 2000

By James Sheridan

Risk can generally be defined as the possibility or chance of a loss corresponding to uncertainty. Analysis is the process for examining the components and relationships of a complex system in order to determine the impacts of its variables. Risk analysis is therefore a course of action taken to analyze multiple variables of a system that is subject to speculative outcome. When risk analysis is applied to mine development, it becomes the means for assessing and measuring those parameters that contribute to economic viability. Mining can be a risky business. It is composed of an assortment of factors that contribute to its financial outcome. Of these factors, the most consequential output is the net present value (NPV). Applying risk analysis in mine development can identify those factors having the most significant impacts and applying limits to those impacts. Mathematical computer modeling using Monte Carlo techniques is available and can be customized to suit specific mine development ventures. Essentially, those parameters that are not fixed values can have input variability. Rationally deduced engineering estimates should be the basis for determining the initial values applied as inputs in the models. Risk analysis therefore provides the user a means to identify, rationalize and assess the risks in mine development in an informed, calculated, and unbiased format for making economic decisions.

Jan 1, 2002

By Richard Komarek

When limestone (Ca03) is calcined in rotary kilns to produce quicklime (CaO), it is not unusual for 10% to 20% of the stone to abrade and emerge from the kiln as quicklime fines (-6.3 mm or -0.25 in.). While there are various industrial processes that can use fines, handling and shipping is tricky and dangerous. Due to the highly caustic nature of quicklime, airborne dust easily bums eyes and skin. On the other hand, money has already been invested in mining (or buying) the raw material and in the equipment and energy needed for calcining. Discarding the fines will not only waste that investment, but add even more cost in transportation and possibly dumping charges. So the question becomes, how can fines best be turned into a revenue-generating asset? Some plants convert leftover quick-lime fines into calcium hydroxide - Ca(OH)2, also known as hydrated or water-slaked lime - for sale into agricultural applications. For farm uses, hydrated lime fines are preferred over quicklime because they are easier to handle. And they are favored over raw limestone fines for their higher concentration of calcium and greater solubil¬ity. From the producer's viewpoint, quicklime fines are ideal for this use because they go through hydration faster than the larger chunks of quicklime. Those larger chunks, or "pebble lime," are more readily salable and more easily handled, for such uses as steel, copper, aluminum and magnesium production, water waste treatment, chemical, paper, glassmaking and flue gas desulfurization in coal- fired boilers.

Jan 1, 1993

By A. E. Prokop, J. P. Rider

Previous research on continuous mining operations has shown that significant interactions exist between dust-control parameter application and the resulting respirable dust levels. However, simply increasing the level of the controls does not guarantee a reduction in respirable dust levels. Full-scale laboratory tests are being conducted to provide information to longwall operators that would assist them in selecting control parameters to reduce dust levels for mine-specific conditions. The interactions between face air velocity, shearer water quantity, drum water spray pressure, external water spray pressure and spray system design were evaluated in a simulated 2.13-m (7 ft) coal seam for two cutting directions. Locations around and downwind of the shearer were monitored to evaluate relative changes in respirable dust levels as a function of each control parameter.

Jan 1, 2003

By Michael J. Martinson, John R. Larsen, J. Warren Andrews

Measurements reported in the paper were recorded in an active Green River, Wyoming, trona mine, partly as a teaching exercise and partly to provide the mine in question with additional input data for its ventilation network program. Measurements were made: - in representative three-entry intake airways in room and pillar sub-mains; - between the lower portion of a vertical down-cast hoisting shaft and the start of an intake airway system established in a room and pillar main; - in a representative downcast section of a divided vertical shaft, and of the collar entrance loss at the top of the same compartment. Pressure differences were measured with manometers and trailing hoses, air flowrates with calibrated anemometers, and barometric pressures and wet-and dry-bulb temperatures were recorded for density determinations. Where possible, results are quoted as Atkinson friction factors, and relevant measurements are recorded in some detail to show the magnitude of fluctuations in observed pressure differences.

Jan 1, 1987

By Y. M. Jiang, D. W. Park, S. M. Lee

A vast majority of longwall operations in the US use shield-type hydraulic supports to provide ground control along the longwall face. The three-dimensional, finite-element technique combined with a progressive failure approach was utilized to simulate interaction between shields and surrounding strata and determine various loading conditions. In addition, a separate finite-element model of the shield structure was made to study responses of each longwall shield to the different loading conditions. Shield responses under various loading conditions and the shield characteristics, such as shield stiffness, the ability of resisting horizontal forces, and the effect of shield height, were studied based on the results from finite-element analyses. The results can provide the basis of effective shield design and be used for evaluation of the shield performance. It is suggested that a technique incorporating the finite-element method be developed to evaluate real-time shield performance for the purpose of effective ground control.

Jan 1, 1993

By L. M. Chan, D. H. Carlson, J. H. Johnson

This paper discusses laboratory evaluation of a tailpipe emissions measurement apparatus (EMA) developed by Michigan Technological University (MTU) under contract to the Bureau of Mines. The apparatus dilutes diesel exhaust and measures the concentrations of diesel particulate matter (DPM), CO, C02, NO and NO2 at known dilution ratios. The EMA was evaluated by side-by-side comparison of its measurements with those by laboratory grade instruments. During the preliminary laboratory evaluation concentrations of DPM, CO and CO2 were measured. The concentrations of CO and CO2 measured by the EMA were usually within ±14 pct of laboratory-measured values for CO and ±20 pct for CO2. EMA DPM concentrations correlated well (r = 0.96) with the laboratory values, but were 29 pct lower on average. The CO and C02 differences were observed to be related to the method of calculating the EMAs' dilution ratio and the difference in DPM concentrations is attributed to thermophoretic and/or condensation losses related to the EMA's unheated sample probe. Preliminery analysis of data obtained with a heated sampling probe and modifications in the sampling procedures have indicated reduced variability in DPM and in the calculated dilution ratios.

Jan 1, 1991

The research deals with the study of the quality indicators in the productive process and its use for the consuming market, for two types of ores: industrial sand and crushed stone. Companies who represent the profile of the São Paulo producing market in its respective modalities well produce the selected cases. The development of the studies have to be, for the application of consistent methodological models of the fundamentals of the Engineering of Quality, especially how much to the statistical control of processes and its trustworthiness, of form that the results of the research can serve as referential in the boarding for other generic cases of the mineral industry.

Jan 1, 2003

By Lyda W. Hersloff

As decommissioning of various radioactively contaminated facilities begins, the question of appropriate residual surface contamination becomes an issue. Surface contamination can result in exposure to people via inhalation, ingestion, and external radiation exposure, There is therefore the potential of exposure to workers involved in the dismantling of a facility as well as members of the general public acquiring salvageable equipment, tools, and building materials. The levels established as acceptable for unrestricted use by national and international organizations vary by as much as an order of magnitude for certain radioactive materials. The calculated doses associated with some acceptable contamination levels can be significant. The principle of ALARA, as low as reasonably achievable, is therefore a necessary element in establishing surface contamination levels for a specific site. Some components in evaluating site specific surface contamination levels for unrestricted use, especially removable contamination, include evaluations of the historical use of a facility, the mixtures of radioactive materials a&sociated with surface contamination, and resuspension factors for various materials.

Jan 1, 1991

By Andrew P. W. Briggs, Corale L. Brierley

A considerable economic and technical knowledge base has been amassed with the successful and sustained operation of commercial minerals bioleaching/biooxidation plants to extract copper from chalcocite ore and enhance precious metal recovery from sulfidic refractory ores and concentrates. Economic evaluation ofbio-processing must consider the value of the ore, the sulfide-sulfur requiring oxidation to achieve significant metal recovery, the time required for the biological process and, in the case of precious metal feed-stocks, the down-stream reagent consumption. Of these considerations oxygen requirement for the biologically-catalyzed oxidation of sulfide minerals is the prevailing determinant in the capital and operating costs of aerated, stirred-tank reactors for processing concentrates and bio-heaps for processing ores. Oxygen requirement is dictated by the amount of sulfide-sulfur requiring oxidation to achieve desired metal recovery. The testwork program to evaluate a project for application of biooxidation/bioleaching must be designed to insure that factors critical to economic assessment are fully quantified.

Jan 1, 1997

By Peter M. Turcic

A Mine Safety and Health Administration (MSHA), National Institute for Occupational Safety and Health (NIOSH) and Bureau of Mines (BOM) interagency task group was established to assess the health and safety implications of the use of diesel-powered equipment in underground coal mines. The objective of the group was to conduct an assessment to identify areas of concern, to evaluate the adequacy of existing methods for addressing the identified concerns, and to recommend agency approaches for addressing inadequacies. The interagency group concluded its work in April 1986 and presented a report to the Assistant Secretary for Mine Safety and Health. The report included the conclusions reached by a group and recommendations for regulatory action by MSHA. This paper will present the methods and approaches used by the interagency task group and will discuss the findings, conclusions and recommendations of the group. The paper will attempt to meld together the technical and policy aspects of the issues involved with diesel equipment in coal mining.

Jan 1, 1987

By William E. Little, William R. Sharp, Edward R. Kennedy

Cost o f mechanical tunneling requires the knowledge of many machine/rock parameters such as rock types, machine power, penetration rate, cutter life, maintenance schedule, etc. Capital investment, labor requirements, and project scheduling will all play an important role in defining the economics of the overall project. Knowledge of the cost sensitivity of different project parameters will improve the overall success of any particular tunneling project if this information is incorporated into an effective management plan. Through the use of an interactive graphic computer program written for a microcomputer, one has the ability to quickly evaluate relative costs for a variety of parameters for either an existing project or for a proposed site.

Jan 1, 1983

By J. Koinig, K. Mussger, St. Reischl

Jet grouting is a viable supplementary measure for NATM tunneling in special softground conditions. In particular it is used as a type of forepoling to maintain face stability and to provide initial support for large openings until the shotcrete lining reaches sufficient strength. For this purpose cement grout is injected under high pressure through horizontal pipes outside of the tunnel perimeter and thoroughly mixed with the soil producing 1 to 3-foot diameter cylindrical beams. Excavation of the tunnel then proceeds beneath this umbrella of 40 to 50 foot long beams. Design and construction experiences from recent projects are presented for tunnels diameters between 30 and 50 feet in fill and alluvial and colluvial deposits.

Jan 1, 1987