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By Boris Belenky, M M. Graevsky, R I. Semigin, A E. Frantov

"In the mining industry, most of stripping and rock fragmentation is performed by blasting. The academician N.V. Melnikov has projected that blasting methods would be used to crush 20% of soft rocks and 80435% of medium and hard rocks. Thus, the volume of blasting will continue to increase.This is especially true for electrical blasting, since this method has a number of well known advantages, and in some cases (e.g. for underground blasting in coal mines) it is the only acceptable method."

Jan 1, 1995

By J. Martinovic

The large proportion of gangue minerals present in platinum bearing ores in South Africa provides challenges to the flotation and downstream processes. In order to take effective measures to reduce their recovery in flotation, an understanding of the mechanisms and factors influencing their behaviour is needed. Typical gangue minerals are pyroxene, feldspar, quartz, chromite and talc. Of these, talc is a naturally hydrophobic mineral and although it is present in relatively small quantities, it has a disproportionate effect as it has a strong froth stabilizing effect, increasing the recovery of other gangue minerals by entrainment. Talc recovery is effectively reduced with the addition of polymeric depressants. Although the other gangue minerals are assumed to be hydrophilic and their recovery by entrainment is expected to follow the water recovery, there is some evidence that they may be activated by the typical reagent suites used. Reagents such as copper sulphate, added as an activator, and collectors are used to selectively induce hydrophobicity on the sulphides. It has been shown that some of these gangue minerals can be activated. This research work investigates whether inadvertent copper activation is mineral specific and evaluates the mechanisms and factors affecting the reversal of activation with the addition of the depressants using electrokinetic measurements, adsorption and microflotation tests. Results are presented that show that the selected minerals do respond differently and that the reversal of activation is dependent on mineral type, depressant type, dosage and ionic strength of the electrolyte.

Jan 1, 2005

Comparing Energy Efficiency of Multi-Pass High Pressure Grinding Roll (HPGR) Circuits With increased emphasis on reducing costs and carbon emissions in mineral processing, it is becoming essential to employ the most efficient comminution devices and to use them to maximum effect. High pressure grinding rolls (HPGR) are considered highly efficient compared with other devices, however their relative efficiency in multi-HPGR circuits is less well understood. A series of comminution tests was carried out to evaluate three multi-pass HPGR circuits and a jaw crusher-ball mill circuit. Combinations of HPGR units (1.0 m and 0.25 m diameter), jaw crushers and Bond ball mills were used to grind a 32 mm top size porphyry copper feed (BBWI = 12.1) to a product P80 size of about 150 ¦m. Up to three passes of HPGR were used in each circuit, with energy measurement and size analysis at each point in the comminution process. The energy efficiencies of individual comminution stages and of the overall circuits were quantified and evaluated using three different approaches. The operating work index method for comparing comminution energy efficiency underestimated HPGR performance due to the large amount of fines generated. The -75 ¦m efficiency factor and F50/P50 reduction ratio interpolation methods both give a fairer measure because they better take into account the amount of fines generated by HPGR. The results show that the relative comminution efficiencies of the three multi-pass HPGR circuits tested differ by as much as 22%, providing insights as how to best employ HPGR in a comminution circuit. The most energy efficient of the circuits tested was a three-pass HPGR circuit with a 1.0 m diameter roll on the first pass in closed circuit with an 8 mm screen followed by a second and third pass in a 0.25 m roll.

Sep 13, 2010

By U. Richter

Conveyors are a highly effective means of transporting material over long distances. Recently there has been a trend toward long conveyor systems with high capacity single flights. These conveyor systems are an efficient alternative to costly truck fleets. Also with deeper mines, the use of diesel driven trucks becomes more difficult. Another trend is in underground mining, where conveyors are an efficient alternative to drift hoists or dedicated rail systems.

Jan 1, 2012

In attempting the predict coal cleat orientation in the subsurface for effective methane degasification of the coal beds in the Warrior coal field of Alabama, approximately 150 rock joint orientations and 45 coal cleat orientations were measured in each of 37 7 ½ minute quadrangles in Tuscaloosa, Walker, Jefferson, Fayette, Winston, Blount, and Bibb Counties. Data from these surface locations, and coal cleat data from eight underground mines was corrected for magnetic declination and titled beds rotated to the horizontal where necessary and plotted on rose diagrams for comparative analysis. Data collected on each joint and cleat consisted of attitude, quality, type, spacing, persistence, lithology, bedding thickness, surface texture, and filling. File data and published and unpublished reports from the State Survey and the State Mine Inspector's Office were re-viewed. Twenty-seven mining companies, most of which supplied information pertinant to the project were also contacted. The information obtained consisted of crop line information structure, and underground mine outlines, all of which were put on 7 ½ -minute topographic quadrangles. LANDSAT-1 imagery and Skylab photography were compared to dominant joint and cleat trends in the study area. Detailed results can be found in an open-file report entitled "Fracture Analyses in a Selected Area of the Warrior Coal Field, Alabama." A master's thesis entitled "The Relationship Between Surface Joints and Subsurface Structure in a Selected Area of the Warrior Coal Field" is being prepared to illustrate the relation-ship of the fracture system to the structure in the Warrior coal field. A proposal has been submitted for research on a project entitled "Rock Fracture Systems and Their Affects on the Extraction of Fossil Fuels in the Warrior Basin, Alabama"

Jan 1, 1976

By S. Dicarlo

"In late 1985, B-zone ore was first processed through the Eldor Mines mill at Rabbit Lake. Extensive modifications had been completed in order to mill this ore. In-plant process development was initiated to tune up the new circuits and concentrated on leaching, solvent extraction, impurity and uranium precipitation and tailing and effluent treatment. This process development effort and the results are described.INTRODUCTIONEldor Mines, a division of Eldorado Resources Limited, operates the Rabbit lake mine-mill complex at Collins Bay on the western shore of Wollaston Lake in northeastern Saskatchewan.The first orebody was discovered in 1968 by Gulf Minerals Canada Limited below a small body of water named Rabbit Lake. Ore from the Rabbit Lake (RL) deposit was first processed through the new mill in June, 1975, with depletion scheduled over the next ten years. Continued exploration in the area led to the discovery of four orebodies in the vicinity of Collins Bay: A-zone (1971), B-zone (1977), D-zone (1978) and Eagle Point (1980). Collins Bay is about ten kilometres from the mill facility.In 1982, Gulf Minerals was acquired by Eldorado Nuclear Ltd., who continued the development effort to bring the B-zone deposit into production. The RL pit was mined out in May, 1984 with stockpiled ore providing mill feed until startup on B-zone ore, which was scheduled for November, 1985."

Jan 1, 1988

By R. J. Kendall

As we enter the new millennium, the South African mining industry has to ensure that it becomes more competitive if it is to survive in the ever more demanding global environment. Traditionally, mechanization in narrow stopes has been limited to the use of scraper winches, and numerous mechanization attempts have been restricted to pilot projects operated on an extremely limited scale (with varying degrees of success). The benefits of hydropower are well documented, and Northam Platinum has shown these benefits to be achievable on a mine-wide basis. However, the equipment originally developed for hydropower systems has followed the traditional labour-intensive approach commonly used in deep level narrow stoping operations. The problems experienced with the hydropower system are discussed and the rationale for developing alternate technologies is explored. The hydropower system has shown to be a versatile powering medium which can be harnessed for a diversity of uses. It (hydropower) enables the mining engineer to change traditional paradigms and to design an entirely new approach for optimizing the mining operation based on explosive techniques. The system developed for Northam consists of the following: ?Purpose-built stope drill rig operated off the hydropower system with special features to ensure accurate drilling patterns throughout the length of the blast hole ?Purpose-built high rate cleaning system for rapid transfer of fractured ore to the stope orepass ?Redesigned stope layout to facilitate in-stope water control and to recover fines from the run-off water ?Purpose-built drill rig for rapid establishment of reef raises and advanced strike gullies ?Purpose-built drill rig for flat end development. On both types of development end rig, emphasis is placed on ensuring accurate drilling patterns throughout the length of the hole to maximize linear advance per blast. The paper discusses the implementation of the Northam system on a large scale as well as current initiatives to further improve on the efficiencies of mining operations. It concludes by emphasizing that mechanized hydropowered stope technologies are in their infancy and thus offer unlimited scope in progressing beyond today?s paradigms to present as yet unthought of solutions for optimizing deep level ore extraction.

Jan 1, 2000

Diesel Particulate Matter (DPM) is considered carcinogenic after prolonged exposure. With increasing use of diesel-powered mining equipment in underground mines, miner?s exposure to DPM has been increasing. Most studies on the issue has been DPM control measures with few studies on diesel exhaust propagation patterns after leaving the tailpipes. This study uses computational fluid dynamics (CFD) to investigate the airflow pattern in an underground metal/nonmetal mine for a single heading. Several high DPM concentration areas are identified in the study and common practices for compliance are suggested. Airflow and DPM distribution are compared between blowing and exhausting face ventilation systems. Suggestions are also provided for the protection of miners in the face area.

Jan 1, 2009

By Scott Ellenbecker

Soon New York City will have a new train station. A tunnel project is under construction to extend Line 7 to a new station that is located near the Jacob K. Javits Con-vention Center. This is also part of the Hudson Yards redevelopment project that is intended to aid redevelop-ment of the west side of Midtown Manhattan around the Long Island Railroad?s Caemmerer Railyard. The station, or ?cavern? as it?s called by those excavating it, will be the portal for that growth. In the city, public transportation means high-rise residential proper-ties will have better access to the business district, and those outside the area will have greater access to event facilities ? two factors that are critical for development investment.

Jan 3, 2010

By R. Rampersadh

Paper written on project work carried out in partial fulfilment of B Eng (Metallurgical Engineering) degree Steel was sampled after calcium treatment, to follow changes in inclusion composition during the processing of alumium-killed steel into continuously-cast billets, at Mittal Vereeniging. There is some shift in the distribution of inclusion compositions towards alumina, as the liquid steel moves from the ladle to the tundish. This shift may reflect some reoxidation. However, the effect on inclusion modification is small, since only a small fraction of the tundish oxide inclusions is fully solid?which agrees with the plant observation that these heats cast without clogging. Magnesium oxide in the inclusions contributes to liquid formation, substantially increasing the range of lime: alumina ratios over which the inclusions are partially or fully liquid.

Jan 1, 2006

By B. C. Alberts

Planning the use of South Africa's energy resources, especially coal, is of the utmost importance. The State and the mining industry require reliable official estimates of the economically mineable coal reserves for planning purposes. An overview of al the previous reserve estimates is given, with specific attention to the two most recent estimates-those of Petrick and De Jager. The differences between these two estimates are highlighted. The following important aspects are discussed: . the need to update the information regarding South Africa's mineable coal reserves, . the necessity of understanding and agreement between the coal-mining industry and the State department responsible for updating the coal-reserve data, and . the importance of the specific assumptions used in the updating of the data. A downward adjustment of mineable reserve figures is proposed, and the factors that influence the meaningful exploitation of the coal reserves are discussed. A recommendation is made as to how the Waterberg coal reserve should be exploited, and it is concluded that the Soutpansberg Coalfield cannot be exploited economically in the foreseeable future. An evaluation of the status of the coal-export trade is made and compared with the assumptions and targets set at the start of the coal-exportation scheme. The comparison shows the extent to which the exploitation of the coal reserves is being negatively influenced by the current market situation. Recommendations are made regarding planning for the coal-export market, and the aspects that have to be taken into account to keep South Africa in the export market are identified. Reference is made to the fact that the present unrestrained wage and salary adjustments, which show a total disregard of South Africa's poor productivity record, require serious thought and speedy rectification if the country is to survive in the export market. A salary and wage strategy must be developed to suit the specific needs of the Republic of South Africa.

Jan 1, 1987

By J. Noll

Many underground metal/nonmetal mines are using enclosed cabs on mining equipment to reduce the exposure of miners to diesel particulate matter (DPM). However, some enclosed cab systems may not be meeting their expected efficiency in capturing DPM, which could be a result of inappropriate filter use, cab leaks, or insufficient pressurization. NIOSH investigated several types of filters for reducing DPM to determine which type had the best capture efficiency. The laboratory results indicated that a MERV 8 (Minimum Efficiency Reporting Value, as defined by the American Society of Heating, Refrigerating and Air- Conditioning Engineers) filter captured about 50 percent of the DPM, a MERV 16 filter collected 96-98 percent of the DPM, and two HEPA (high efficiency particulate air) grade filters captured over 99 percent of the DPM. NIOSH also performed a field study to measure the efficiency of two cabs at a limestone mine. The cab filtration systems of a loader and haul truck were found to be over 90 percent effective in removing DPM except under certain operating conditions when the efficiency was as low as 41 percent. Evidence seems to suggest that these conditions were when a window was open in the cab.

Jan 1, 2011

By Y. Wang, E. Forssberg, A. Johansson, B. Chan

A super-conducting high gradient magnetic separator with matrix vibration in dry separation mode is a powder purification device, which has been used to remove weakly magnetic impure particles from fine calcite powders below 53 µm in this study. A fundamental question concerned is the evolution of the matrix clogging under gas-solids loads. This paper presents the improvement of the separation selectivity using a method of mechanically based vibration on the matrix in the separator. The functions of the matrix vibration are discussed. The results indicated that the mechanically based vibration on the matrix within a high intensity magnetic field while a feed was introduced in an air stream, was found to be effective for the dry purification of fine powder materials.

Jan 1, 2001

By W. Petruk

Imaging is a fundamental requirement when characterizing minerals, ores and related products. Images are used for presentation, texture analysis, characterization, image analysis, identification, etc. The image mode that is utilized is dependent upon the application, mineral properties and available instruments. Different instruments produce images that display different features; in order of increasing complexity they are: hand specimens, a non-polarizing microscope, polarizing optical microscope, scanning electron microscope (SEM), low vacuum SEM, microprobe, secondary ion mass spectrometer, staining, cathodoluminescence, tomography and others. Image analysis uses images produced with either an optical microscope or a SEM, but the SEM images are superior in this application.

Jan 1, 2001

By Farrukh M. Mazhar, Philippe P. Martin

Electrical Vertical Sounding (EVS) profiling has proven to be a valuable tool to set the alignment and guide the design of a 17 km-long, 4.7m diameter water-conveyance tunnel in the Peruvian Andes at an altitude of 4,260 m. EVS profiling helped determine where to locate boreholes, and reduce the amount of drilling to 1,200 m of vertical and inclined boreholes. EVS profiling allowed the designer to identify and verify by drilling the existence of zones with difficult tunneling conditions that were avoided by realigning the tunnel. The rock quality was checked by drilling and a combined scheme of excavation by TBM and conventional drill and blast technique was developed for the final design.

Jan 1, 2003

By Dennis R. Dolinar

The National Institute for Occupational Safety and Health?s Pittsburgh Research Laboratory conducted a full-scale test of a composite polyurethane-aggregate seal in a hydrostatic chamber at the Lake Lynn Experimental Mine. This composite seal consisted of a polyurethane and limestone aggregate core that was formed between two concrete block walls. In the hydro-static chamber test, water is used to pressurize the seal. During the test, the maximum average water pressure the seal was able to withstand was 18.9 psi. Further, the seal began to yield at an average water pressure of only 17 psi. At the time of the test, the minimum seal design requirement was 20 psi under 30 CFR4 75.335 (2005). Therefore, based on this test, the seal did not meet the regulatory minimum design requirement. Uniaxial compressive tests conducted on samples from the polyurethane-aggregate core revealed that both the compressive strength and the elastic modulus of the material were much less than that for polyurethane only with a density of 10.0?12.0 lb/ft3. The significant reduction in the strength and stiffness of the polyurethane-aggregate mixture results from the formation of a soft polyurethane foam around each piece of aggregate. The formation of the soft foam seems to be caused by residual moisture from the aggregate. The moisture also caused the density of the polyurethane in the polyurethane-aggregate mixture to be less than the design requirements. The lower density of the polyurethane in the mixture, along with the formation of zones of pure polyurethane only, resulted in the overall seal density being less than the design requirements. During seal construction, steps were taken to control the moisture, but were not successful. An analysis of the seal failure showed that the calculated shear stresses at failure and the estimated shear strength of the polyurethane-aggregate mixture are fairly close. This suggests that the strength properties of the polyurethane-aggregate mixture along with a weak zone of poorly bonded aggregate controlled the maximum pressure the seal could withstand. At the time of the seal testing, the minimum design requirement was 20 psi, as specified at 30 CFR 75.335 (2005). New emergency temporary standards for seal designs were promulgated on May 22, 2007, with a minimum requirement of 50 psi under specified conditions. However, it will be shown that the evaluation of the polyurethane seal performance as designed to meet the older 20-psi criterion can be relevant to the design requirements under the new standards.

Jan 1, 2008

By Gunnar Persson

The borehole pressure/time history of blasting practice is simulated in a twin pendulum apparatus, where the expanding shotfiring gases force two steel slab swingers apart. A pilot installation built at SveDeFo is described. The relevant factors, that govern the use of this test method as a means of classifying explosives with respect to their toxic fume potential, are described.

Jan 1, 1996

This three-part report provides the results of an industrial engineering study that assessed the safety and efficiency of underground ore handling in U.S. metal mines. One of the primary findings of the study was the improvement needed in controlling muck size in the are handling stream. Oversize ore is causing much additional labor, creating work stoppages, and is a principal cause of accidents in metal mines. The specific objectives of the Present Systems Study were to determine and evaluate the productivity of existing ore handling systems in a representative group of underground metal mines, to relate the available historical accident record statistics of these selected mines to the specific operations in the overall ore handling operations, and to highlight the potential areas of improvement for each mine on the basis of productivity and associated hazardous index for each operation.

Jan 1, 1974

By I. E. Odom

The physiocemical properties and industrial uses of the clay mineral montmorillonite are reviewed. Montmorillonite is the most abundant species of the smectite clay mineral group and is the predominant mineral composing bentonite deposits. The crystal structure, chemical composition, exchangeable ion type, and small crystal size are responsible for several unique properties, including a large chemically active surface area, a high cation exchange capacity and interlamellar surfaces having unsual hydration characteristics. The type of exchangeable ion Na, Ca and/or Mg has a major influence on industrial and chemical uses of montmorillonite because of their hydration characteristcs. Natural occurrences of Na montmorillonite in commercial quantities are geographically limited, but Ca-Mg montmorillonite deposits are known world wide. Foundry, well drilling, pelletizing and civil engineering constitute the major uses of montmorillonite, but the total array of uses of montmorillonite exceeds that of any other mineral.

Jan 1, 1986

By S. Rolseth, J. Thonstad

The traditional electrolyte for aluminium electrolysis is based on molten cryolite (Na3AlF6), acting as solvent for the raw material, alumina (Al2O3). Over the years there has been a trend to increase the content of excess aluminium fluoride (AlF3) to the cryolite-based electrolyte, in order to enhance the current efficiency of the process. In most cases one has ended up at 11?13 wt% excess AlF3because higher contents makes it difficult to control the heat balance of the process. This problem may be overcome if sensors are developed that will allow online control of electrolyte temperature and composition, and we may then see a surge towards still higher AlF3contents. In the development of new anode materials to replace the carbon anode with inert, oxygen-evolving anodes, focus is on anode corrosion, and a low electrolyte temperature is then highly desirable. While the conventional process operates at around 960°C, electrolyte temperatures as low as 750°C are being tested. This is achieved by having large excess contents of AlF3(40 wt%). The consequences of using such electrolyte compositions are discussed.

Jan 1, 2004