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By V. G. Prikhodko, G. I. Sukhinin, I. V. Yarygin, A. V. Fedoseev, S. A. Novopashin

"The first experiments on the vacuum drying of spherical clay sample are presented and the theoretical model of the process is considered. The model is based on the solution of the heat and the moisture transfer equations with the effective thermal conductivity and water diffusion coefficients for wet porous clay-like medium. The time and radial dependence of the temperature and the moisture were calculated for different initial conditions. The results obtained for the time dependence of the moisture content are in good agreement with the experimental results obtained in the initial period, when all the moisture in the sample did not freeze to form an ice crust. INTRODUCTION Capillary-porous materials very often occur in nature and in industry. A porous medium is a solid matrix with voids, or pores, which are continuously connected. These pores are usually filled with fluids or moisture, water vapor and air that can pass through the medium because the voids are interconnected. The void fraction in the solid matrix is referred to as the porosity. Porosity or void fraction is a measure of the void (i.e. ""empty"") spaces in a material, and is a fraction of the volume of voids over the total volume. The moisture content in porous media determines the properties of the porous body, its mechanical and thermo-physical properties, such as density, plasticity, viscoelasticity, swelling, cracking, and so on. Complex processes of heat and mass transfer occur in porous bodies when they are heated or cooled, during drying or freezing (Luikov,1966). The course of these processes depends essentially on the physical-chemical composition of the solid matrix of the porous body, on its fractal dimension, porosity and morphology. The clay and clay minerals are the most important porous materials in the history of the mankind (Mukherjee, 2013). Clay is a very fine grained, unconsolidated rock matter, which is plastic when wet, but becomes hard and stony when heated. It has its origin in natural processes, mostly complex weathering, transported and deposited by sedimentation within geological periods. Clay is composed of silica {SiO2), Alumina (Al2O3) and water (H2O) plus appreciable concentrations of oxides of iron, alkali and alkaline earth, and contains groups of crystalline substances such as quartz, feldspar, and mica. Building materials, bricks, and tiles, pottery, porcelain and faience are made from clay. Clay is used in the food and medical industry, and, not least, in the mining industry as a carrier containing aluminum, silicon and other valuable elements, as well as metals (copper, gold) as constituents, contained in the pores in the form of micro- and nano-particles or grains."

Jan 1, 2018

By Doug Harding

The Niagara Tunnel Project (NTP) is a 10.4 km (6.5 mi) long, 14.4 m (47.5 ft)bored tunnel that will run under the City of Niagara Falls from the Upper Niagara River to the Sir Adam Beck Power Station. The completed project will enhance the capacity of the Sir Adam Beck Power Station by adding 500 m3 (17,657 ft3) of water per second through the tunnel. The paper describes the project in which the world’s largest hard rock TBM at14.4 m (47.5 ft) in diameter is being used to excavate the tunnel. Features of the project include the use of a High Performance (HP) Main Beam TBM, state-of-the-art ground support and tunnel logistics systems. A continuous conveyor is used for muck transport from the TBM to the disposal area. The paper will also discuss the optimization of the TBM system as the tunnel advances through the varying geology. In June 2004 the Ontario Government announced that Ontario Power Generation(OPG) had been given approval to proceed with the third tunnel under the city of Niagara Falls—the first two tunnels were constructed in the 1950s using drill and blast techniques. The third tunnel, appropriately named The Niagara Tunnel Project (NTP), consists of a 10.4 km (6.5 mi) long TBM-bored, concrete-lined tunnel with a finished diameter of 12.5 m (41.1 ft). In August 2005, OPG announced the selection of Strabag AG of Austria, one of the largest construction companies in Europe, as the contractor to build the NTP Project at a price of CAN $600 million. In September 2005, Strabag A.G. selected The Robbins Company of Solon, Ohio to design, manufacture and deliver a new 14.4 m (47.5 ft) diameter High Performance state-of-the-art Main Beam Hard Rock TBM to be used in the excavation of the tunnel. In order to meet the aggressive construction schedule as requested by OPG/Strabag, the TBM needed to be supplied as “ready to bore” within a 12 month period after the contract was awarded to Robbins.

Jan 1, 2007

By HeeDong Lee, Owen Reedy, Lawrence Matson, Naidu Seetala, Thomas Key

Spark Plasma Sintering (SPS) consolidated ZrB2+SiC composites using nano-powders (around 40 nm) showed smaller grains compared to those using micron size powders and segregation of SiC into islands is minimal but with higher oxidation of ZrB2 to form ZrO2 in nano-composites. Argon-gas purging prior to SPS consolidation at around 2000 °C and 40 MPa of ZrB2+20vol.%SiC nano-powders was used to minimize the oxidation and obtain fine granules with high densification. The densification of the Argon-gas purged nano-composites is higher compared to those consolidated without Argon gas purging. The EDX analysis showed a strong reduction in the oxygen peak for the Argon gas purged composites. The XRD spectra also support this observation with less ZrO2 phase composition in Argon gas purged composites. The Vickers micro-hardness showed slightly lower values for Argon gas purged composites though they have higher densification.

Mar 1, 2017

By R Cox, S Pandey

The coal seam gas (CSG) industry is expanding rapidly in the Surat and Bowen basins. CSG production involves pumping water from the coal seams to release the gas adsorbed to coal particles. The reduction in water pressure in the coal seams will cause some reductions in water pressure in overlying and underlying aquifers because there will always be some interconnectivity between the formations. The Surat Basin is a sub-basin of the Great Artesian Basin, which contains aquifers of high economic, environmental and cultural value. The Condamine Alluvium is also an important water resource, which overlies parts of the eastern margin of the Surat Basin.Under the Queensland (Qld) regulatory framework, an area of intensive CSG development involving multiple CSG operators can be declared to be a cumulative management area. For such areas the Office of Groundwater Impact Assessment develops assessments of future impacts on aquifer water pressures and develops and manages arrangements. The results are published in underground water impact reports.The Surat underground water impact report (QWC, 2012) was approved in December 2012. This paper summarises the place of the report in the Queensland regulatory framework, the content of the report and progress in its implementation.CITATION:Cox, R and Pandey, S, 2013. Managing groundwater impacts in the Surat Basin, in Proceedings Water in Mining 2013 , pp 169-174 (The Australasian Institute of Mining and Metallurgy: Melbourne).

Nov 26, 2013

By D. A. Akinlade, N. L. Richards, D. C. Murray, W. F. Caley

To investigate the effect of adding Ti to a Ni-Cr-Fe powder metallurgy alloy, a thermodynamic software package was used to predict the phase transformations that occurred during thermal processing. Specifically, the effect of adding 3w/o Ti to a 6w/o Al modified ternary Ni-Cr-Fe alloy (the quaternary) was simulated and the phase transformations that might occur in the material on sintering were obtained using the thermodynamic modeling tool. These predictions were subsequently compared with experimental results obtained by X-ray diffraction and metallography. For comparison, selected compacts were prepared containing only the ternary + 3w/o Ti (no Al). Based upon compressibility curves, the optimum pressure for producing the new Ti compacts was 500 MPa vs 600 MPa for the quaternary composition with Ti. In each case, hardness of the base alloy was enhanced by the Ti addition whereas the residual porosity remained relatively constant at about 19%. Finally, although SEM/EDS failed to confirm the presence of Ti in the gamma prime intermetallic, XRD spectra showed a shift in lattice parameter on addition of Ti, suggesting that the intermetallic was of the form Ni3(Al,Ti).

Jan 1, 2010

By John C. Cook

A 1-year program of exploratory research, to determine the feasibility of radar exploration in advance of coal mining, has been completed. Advance detection of obstructions including faults, clay veins, abandoned wells, and pyritic concretions would improve the safety and efficiency of mining. Initial calculations based on laboratory tests of the RF electrical properties of bituminous coals indicated feasibility; radar waves at frequencies below 100 MHz should be detectable through tens to hundreds of meters of coal and be well-reflected by clay, pyrite and metal obstructions. Using a proprietary, experimental, VHF short-pulse "mining radar" system, two cycles of field testing and equipment improvement were completed. Measurements were made in three bituminous coal mines, a quarry, and a salt mine. Comparisons were made with ground-penetrating radar equipment developed by others for salt dome exploration and for military tunnel detection. The proprietary mining radar equipment and techniques used were found to be the most effective known for coal exploration, but further improvements are needed; one major problem in all systems is interfering clutter signals arising in the equipment and from mine room reverberations through leakage coupling of the antennas to the air. Nevertheless, several practical goals have been achieved: excellent radar reflections were received and identified through up to 30 feet of coal; reflections from a wet, abandoned drill hole were identified by their polarization property and detected at distances up to 272 feet, and mine-wall reflections were detected at distances up to 735 feet (both through salt); propagation through and reflections from large vertical clay veins in coal were demonstrated; experimental results agree reasonably well with theory. The results and experience gained during the project affirm the feasibility of the method. They also provide a firm basis for the development of a practical radar technology for exploration in advance of mining. No Subject Inventions, as defined in the contract, were made in the course of this work.

Jan 1, 1971

By Jérôme Girard, Shiu Kam, Sue Longo

"Historically, tailings management in a northern climate has involved the deposition of tailings into the Tailings Management Area (TMA) as conventional slurry. This type of system is obviously viable but presents challenges that are difficult to manage as circumstances change over the life of mine. These issues can include:? Increases in mill throughput, and? Life of the TMA for the life of mine.This case study will present how thickened, high-density, non-segregating tailings are used as an alternative to conventional slurry disposal to achieve greater storage capacity and enhanced environmental performance for a gold tailings facility in a northern climate. This paper will focus on how this change in deposition strategy accommodated the increased throughput of the mill and the increased life of mine. Specifically, the paper will discuss the addition and integration of new processes to the exiting mill system to accommodate the tailings management issues. It will highlight the challenges from laboratory testing to pre-feasibility to the engineered design of the thickened tailings system implemented at Musselwhite Mine.BACKGROUNDGoldcorp Canada’s Musselwhite Mine, in Northwestern Ontario (120 km north of Pickle Lake), is an underground gold mining operation that began production in 1997. The current mill throughput is about 4000 tpd (1.4 Mtpa). Gold extraction is based on a CIP process with cyanide destruction.The existing tailings management area (TMA) is located about 2 km southwest of the mill complex. The TMA is contained by high ground to the north and to the west and flanged by a moraine ridge along the south side. A number of dams have been constructed along this ridge. The dams were first built in 1996 and subsequently raised in 2000 and again in 2005. Excess tailings pond water is discharged to a polishing pond then released to the environment via a wetland.The TMA was originally designed to contain 13.7 Mt of tailings under a ponded surface for closure. The water cover was to inhibit adverse long-term environmental effects because the tailings contain pyrrhotite and other sulphide-bearing minerals that are potentially acid generating. The design was modified during Stage 3 Construction in 2005 to expand the storage capacity to 17.3 Mt (Golder, 2005). As of end of 2009, over 16 Mt of tailings had been deposited in the TMA. The slurried tailings were historically deposited at 50% solids."

Jan 1, 2011

By R. L. Grant

The Bureau of Mines applied automatic computational methods to analyze the degree of correlation between sound transmission and atmospheric conditions. Statistical analysis of data collected over a 5-month period indicated that the following weather variables, listed in order of decreasing importance) have a significant effect on the transmission of sound in the atmosphere: 1. Wind velocity and wind direction. Winds in the direction of travel of the sound wave increase the sound intensity and duration. 2. Barometric pressure. High pressures are related to low sound intensities and durations. 3. Atmospheric temperature. High temperatures are related to low sound intensities and durations. Inversion of the atmospheric temperature did not appear to affect sound transmission under the conditions of this study.

Jan 1, 1967

By Dave Bulled

"This paper describes the design of an SABC grinding circuit using CEET technology applied to grindability data produced from testing 100 samples and distributed across the blocks of a mine plan using a geostatistical approach. The data distribution required the identification of the location of the sample points and a geological plan of the 130 million ton Ruby Creek orebody together with a mine plan of about 11000 blocks to be mined during the proposed 18 year life of the mine. The mill design was then made with consideration for the estimated hardness of each block in terms of both SAG and Ball milling with allowance for annual periods when the ore is harder to grind. Operating specifications were selected to achieve an optimum of capital and operating costs through use of the CEET program. The geostatistics assigned the statistical error that arises from having a limited amount of sample testing data to the hardness estimate of each block of ore in the mine plan. The final design could then include a quantification of risk and determination of safety factors based on the accuracy of block hardness estimates and CEET model fitting.INTRODUCTIONThe traditional approach to plant design involves the extensive testing of a single large composite sample or a small number of composite samples that are reputed to represent the ore body. It is accepted that the tests used can accurately measure in the laboratory the grindability of the sample by a process representing that to be used in the plant. The size of equipment required to achieve a specified throughput and product size is then calculated from one of a variety of models that have been developed by metallurgists over years of trial and error. Since these tests and models are tried and tested, they are accepted as reasonably precise; however during the operation of the resulting plant the design is sometimes found to be inadequate. It is then suspected that the flaw in the design process lies in the samples not being sufficiently representative of the ore body, since using only a single or small number of composite samples does not recognize the variability of the hardness of the ore, nor does it allow for the lack of precision in the hardness value used in the design.This paper outlines a design procedure suited to an orebody that is described by a geostatistical analysis of a reasonably large number of small samples of drill core. The analysis required the identification of the location of the sample points and a geological plan of the orebody, together with a mine plan of the blocks to be mined during the proposed life of the mine. The mill design was then made using the estimated hardness of each individual block with an allowance for annual fluctuations in the grindability of the ore. The geostatistical analysis assigned a statistical error to the hardness estimates of blocks and of each production year such that the final design included risk estimates and safety factors based on the possible errors that arise from having a limited amount of sample data (Kosick et al. 2002)."

Jan 1, 2007

By V. M. Mankov, O. V. Zamyatin

"Fine free gold at a size of minus 250-100 µm can be effectively recovered from mineral materials (buried clay placers, saprolites, gold-bearing aggregates, technogenic sands etc.), or MM, using some developed and implemented in practice cost-effective basic technological schemes of MM processing at every stage: exploration, main concentration processes, upgrading of gravity concentrates etc. Such technologies are based on mineral materials composition, different content of fine gold mass fractions, and include improved two-stage sluicing technology, jigging technology, advanced technology and integrated technology. The main operation principle of the given technologies is gravity concentration. They provide recovery of fine gold of any size from MM, including gold finer than 100 µm, using concentration systems and plants with a capacity of 1-2 and up to 100-200 m3 per hour. Selection of a cost-effective technology depends on its technical and economic viability regarding to mineral material composition, optimum performance and concentration rate. The developed technologies of mineral materials concentration establish a balance between technological, technical and economic factors, and ensure profitable development of deposits containing free gold and characterized by a complex composition of concentrating material. Free gold recovery with these systems increases by 2.0-2.5 times for gold particles at a size of minus 250+100 µm and 10-30 times for gold particles of minus 100 µm, compared to conventional sluicing systems. The Irgiredmet Institute has developed and supplies primary concentrate washing machines for upgrading gravity concentrates of up to 100 mm in size, with a capacity of 1.0-5.0 m3/h, fitted with various production equipment including pyro- and hydrometallurgical systems. Additionally, the Irgiredmet Institute develops and manufactures systems of mechanized processing of geological and technological samples (UOMP; registered design certificate No.27505, Russia) designed for complete recovery of free gold in the process of geological samples handling and decreasing of a human factor influence. A system includes a package of technologically associated disintegration, classification and concentration equipment with some “know-how” elements that provide effective recovery of fine gold at the exploration stage. A number of Irgiredmet’s patented technologies and systems (patents of the Russian Federation) have no equivalents in the field of mineral processing and provide designing of technologically practical and cost-effective flowsheets that offer higher recovery of gold of different sizes (fine gold), at every stage of processing of mineral materials including basic concentration processes, upgrading and exploration etc."

Jan 1, 2018

By Kah Lert

"The Red Mountain porphyry molybdenum deposit is situated in the Big Salmon Range, approximately 80 km east-northeast of Whitehorse, Yukon.Red Mountain is underlain by Paleozoic, argillaceous sedimentary rocks of the Yukon Cataclastic Complex, which have been intruded by a multi-phase mid-Cretaceous stock.Mineraliwtion, quartz stockwork, metal zonation, and an alteration assemblage characteristic of a porphyry molybdenum system have been superimposed on quartz monzonite porphyry and adjacent homfelsed sedimentary rocks. A later, barren and pyritic quartzeye diorite porphyry body and related dikes have dissected the quartz monzonite porphyry, homfelsed sedimentary rocks and associated molybdenite mineralization.Drill-indicated geological reserves of molybdenum mineralization outlined consist of 187 270 000 tonnes grading 0.167% MoS2.IntroductionLocationThe Red Mountain porphyry molybdenum deposit is located at 60°59'N, 133°44'W (NTS 105 C), approximately 80 km east-northeast of Whitehorse, Yukon. The property is situated within the rugged Big Salmon Range, 15 km east of the north-northwest-trending Teslin River. Red Mountain, at an elevation of 1702 m, consists of relatively steep, talus covered slopes with prominent gossanous bluffs marking the southeast flank. Relief on the property is 700 m, with tree-line at an elevation of 1450 m to 1500 m (Fig. 1)."

Jan 1, 1995

By Edward H. Robie

OF the current Adirondack iron mine development, the Benson Mines operation of the Tones and Laughlin Ore Co. (Jones & Laughlin Steel Corp. wholly owned subsidiary) is the last to go into operation. Following an active construction program in 1943, the mine. concentrator and sintering plant were scheduled to enter production in the fall. This description therefore cannot include any operating data, and details of equipment and flowsheet have not as yet been released.

Jan 1, 1943

By Raymond Sandiford, Taehyun Moon

"In 2012, Superstorm Sandy (Sandy) caused extensive flooding in many of the tunnels in New York City. The inundation resulted in two distinct stress changes to the tunnel structures. The first stress change was water pressure on the inside face of the tunnel lining. The second condition related to the change in buoyancy of the tunnels. In areas where the tunnels were supported on rock and an adjoining area supported on soft soil, overstress issues arose. Numerical analyses were performed to assess the structural impacts of the tunnel water inundation; especially stress changes due to internal pressure as well as changes resulting from the buoyancy effects. The paper will discuss the assessment process and its results; it will demonstrate that the change in internal pressure were of little consequence, however the change in buoyancy resulted in significant increases in bolt stresses. INTRODUCTION Superstorm Sandy caused tens of billions of dollars in damage in the NYC metropolitan area. It also caused significant disruption to the transportation system by flooding most of the under river tunnels servicing Manhattan from the outer boroughs and New Jersey. The rehabilitation of the tunnels was of paramount importance to the restoration of the NY and NJ economies. With this rapid restoration, it was essential to determine whether the flooding of these tunnels caused damage to tunnel structures. A series of analyses were undertaken to ascertain whether the change in the stress conditions and buoyancy of the tunnels, due to the flooding, was significant enough to cause damage or over-stressing of the tunnel components. The effects of this unforeseen loading condition was a concern to the agencies operating these tunnels and were thus analyzed to ascertain if there were any adverse impacts. This was a concern because the majority of under river tunnels in NYC was built earlier in the century and constructed using bolted cast-iron lining segments. The cast iron, although quite strong in compression, is much less so in tension. Also, after nearly a century of use, the bolts connecting these segments together have under gone varying degrees of corrosion. The stress changes in both the liner segments and the supporting bolts were estimated for conservative ground support conditions to provide confidence that the flooding had not caused permanent damage."

Jan 1, 2016

By Brad Wells, Wayne Bull, Wayne Dickinson

"Antiscalants were evaluated for control of calcium carbonate (CaCO3) in gold processing applications. Under severely supersaturated conditions, 100 percent inhibition was achieved with 30 ppm antiscalant. Laboratory and field testing established that an antiscalant could both inhibit scale buildup and remove an estimated 0.5 kg/m2 per annum of pre-existing scale. A program was developed to control CaCO3 at a gold mill experiencing severe scale buildup. Annual accumulation of as much as 3 cm of scale in process piping was reduced to unmeasureable levels when 10 ppm antiscalant was applied. No scale-related upsets in mill operation occurred during a five-month trial period.INTRODUCTION Inorganic mineral scale is a crystalline deposit that forms when dissolved mineral constituents exceed the solubility of the respective mineral phase. Formation of mineral scale adversely affects a wide range of industries and is of particular interest in mining and metals processing. Scale affects numerous stages of metal extraction processes. Restricted flow in piping, nozzles, valves, screens, pumps and other components used to transport mineral slurries, metal concentrates, and tailings as well as scale in millwater and thickener overflow circuits are primary concerns (Alfano & Boffardi, 1994). Heap leaching, comminuation, flotation, vat leaching, carbon adsorption, and heat exchangers as well as oxidation steps used in processing sulfidic ores are among key unit operations that may be adversely affected (Simmons & Gathje, 2003). Antiscalant chemicals are designed to prevent formation and growth of mineral scales such as CaCO3. These chemicals, which include two primary classes – phosphonates and anionic carboxylate polymers and copolymers - are added to the gold processing stream at low parts-per-million (ppm) concentrations to interfere with nucleation and growth of scale forming crystals and to disperse fine particulate material. Application points may be located throughout the gold extraction process. Evaluation of the performance of antiscalants plays a critical role in determining the best product for a specific application. Performance evaluations include laboratory testing, pilot scale studies, in-plant trials, and ongoing performance monitoring during mill operation."

Jan 1, 2014

By S Grant, S Emeric, P Baker, E Jones, D Clark

As we strive for a sustainable and resilient future, repurposing assets has become a top priority. In Australia alone, we have a significant number of mineral projects in the pipeline, extensive existing operations, and over 50 000 legacy sites. Collectively, this presents a unique opportunity to be a world leader in mine rehabilitation. Complex stakeholder landscapes, inflexible policies, aged regulatory frameworks, technical uncertainties and increasing liabilities are all barriers hindering effective transition of legacy assets. The impetus for change is further catalysed by shifting consumer preferences, workforces in flux and regional Australians questioning what the transition means for their local community. We need innovative approaches to take a leading role in the industry and support global efforts more broadly. Co-designing an ambitious, shared vision spanning projects, operations and legacy assets with all key parties is a fundamental step to unlock and realise maximum societal, environmental, economic and reputational value. Serious play and gamification can further enhance this visioning process.

Aug 2, 2023

By Katherine Hynard, Colin Eustace

Suboptimal decisions introduced during the mine planning process are generally a consequence of both a myopic view of planning objectives as well as time and resources available to convert longer-term plans into execution plans. Erosion of strategic mine plan value in conversion to execution plans is likely to amount to billions of dollars each year. When integrated with operations data feeds, simulation and optimization tools can be used to preserve the value in the strategic mine plan. Optimization models are capable of both automating production of execution plans and improving performance. This reduces the manual burden of revising plans while improving alignment with long-term production objectives. Simulation models can also support the process of developing effective execution plans by providing forward visibility of mine operations performance. They can also be used to test the robustness of optimized execution plans and response to operational variability and disturbances.

May 1, 2025

By N. Arbiter

During the first four decades of flotation practice, close to 200 machine designs were patented, although only about a score were ever used commercially. By the end of that period, the rigors of use had resulted in obsolescence of most pneumatic cells, with a few mechanical cells dominating the field. After World War II, newer designs began to appear but most were modifications in varying degrees of older designs with special features added. Of the dozen or so most recent developments, almost all are pneumatic, relying on compressed air instead of impellers for motive power, although in several cases pumps supplement compressors. Table 1 lists a few of the more fully documented new cells, with their significant characteristics, along with similar characteristics of a widely used mechanical cell. New designs in general are emphasizing: bubble size control; in several cases, methods for delivering feed directly to the froth; methods for introducing and dispersing air through nozzles, eductors, packed beds, or permeable walls; and variable cell volumes, relative to capacities, ranging from very small, with less than a second of retention time, to the largest, with retention times of over 20 min. An important question is the extent to which any of the newer designs are based on locating weaknesses in current mechanical cell designs and then using these as a starting point for innovations. In the present study, the key subprocesses which must take place in a cell are outlined; mechanical cells are analyzed to establish where weaknesses may exist; and then alternative subprocesses are considered which could effect improvements. COMPONENTS FOR CELL DESIGN It is assumed that mineral surface chemistry has been modified as necessary to provide optimum potential floatability. While the cell process may affect this to a degree, cell design is primarily concerned with actualizing the existing potential floatability. The cell design problem is to provide more effectively for the following: 1) Dispersion of air to obtain an optimum bubble size distribution at an optimum ratio of air volume to feed volume. 2) A hydraulic environment which permits most effective contact of potentially floatable particles with bubbles: [Table I - Cell Comparisons* Cell Type Mechanical Column Deister Miller ASH No. of units Multiple Single Single Single Retention time min.10/20 17/27 3.8 ca. is Capacities mt/m3s 0.022/0.066 0.066/0.20 0.11 10.4 st/ft3d 1/3 0.3//0.9 m5.0 469 Air hold-up % 15/20 20 n.a. 50/80 Air escape velocity m/s 0.015/0.0200.020/0.025 n.a. n.a. ft/m 3/4 4/5 n.a. n.a. * References: Mechanical (Harris, 1976,1985), (Bassarear, 1985); Column (Travis, et al. 1987); Deister (Zipperian and Christophersen, 1985); ASH (Air-Sparged Hydrocyclone) (Miller 1989).]

Jan 1, 1989

By J. Lobel, M. Bourassa, J. A. Kozinski, B. Peng

Non-isothermal kinetics studies of the reduction phenomenon of electric arc furnace (EAF) dust generated in stainless steelmaking have been carried out. The dust was mixed with carbon as a reducing agent and dolomite as a binder to form pellets. A Thermo-Gravimetric Analyzer (TGA) was used to determine the weight loss of pellets heated at an average rate of 40 K/min. up to a temperature of 1500°C. The degree of metal reduction was calculated by considering the pellet weight loss, and evaporation of moisture, dust, zinc and lead at high temperature. The reduction process was divided into three different steps. The first covers the 300°C to 760°C temperature range (from 7 to 18 min.), the second step ranges between 760°C and 980°C (18 to 24 min.), and the third covers temperatures above 980°C. Each step is characterized by different chemical reactions. Non-isothermal reduction kinetics equations were set up to describe each step. The kinetics parameters such as apparent activation energies and frequency factors were established. It was found that the first step was chemically controlled, while the second step was diffusion-controlled. Reduction behaviour in the third step was strongly dependent on the initial carbon content in the pellet. Chromium oxide (CrO) could only be reduced in this last step. High temperatures and higher initial carbon content favoured the reduction of CrO.

Jan 1, 2001

By T. Chikande

"Falls of ground pose costly hazards to personnel and equipment and thus measures should be taken to prevent them. This study endeavours to improve the support systems used in geotechnically poor ground at a Zimbabwean platinum mine by analysing the status quo and recommending an effective support system. Various techniques were used to determine the quality of ground conditions, predict the rock mass behaviour, and to identify the appropriate rockbolt type. An analysis of the current ground control methods and their limitations was also undertaken.The results showed that the current support system and mining practices in poor ground need to be modified to improve safety and productivity. Stoping overbreak is influenced by poor ground conditions and the explosives currently used. The use of emulsion is recommended to replace ANFO. Redesigning of pillars is also recommended in poor ground conditions. An evaluation of the current roofbolt system indicated an opportunity for improvement. With new insight on the performance of the shorter length roofbolts currently in use, a new support system was recommended taking into consideration cost-benefit analysis. Barring down using pinch bars in poor ground was seen as a risky and time-consuming exercise, hence the use of mechanical scalers is recommended to achieve zero harm and to meet production targets. Smoothwall blasting is recommended in poor ground to minimize excavation damage. Other recommendations include the use of hydrological surveys to determine groundwater levels and implement corrective measures. Both empirical and numerical modelling approaches need to be utilized in determining the optimum support. IntroductionThe presence of geological discontinuities such as faults and joints weakens the rock mass. Adequate support is critical in achieving zero harm in underground mines. This paper reviews the current support systems used in poor ground conditions at a Zimbabwean platinum mine. The area of research is located on the Great Dyke of Zimbabwe. The mine exploits platinum group elements (PGEs) and base metals. It is shallow, having a maximum depth of less than 300 m. The Great Dyke is the second largest reserve of PGEs, following the South African Bushveld Complex (Oberthur et al., 2012). It is a linear layered intrusion that extends for about 550 km with a maximum width of 11 km (Prendergast, 1989). The generalized section of the Great Dyke is almost like a trumpet, comprising layers that dip towards the centre. The reef exploited at the mine, the Mineralised Sulphide Zone (MSZ), is located in the pyroxenite layer, which is hosted in the ultramafic sequence. The MSZ is a uniform layer about 2– 3.5 m thick, dipping at around 10–14° from surface outcrop towards the axis of the basin, and located between bronzite and websterite horizons. The visible disseminated sulphide mineralization shows a typical and consistent vertical distribution of platinum group metal (PGM) and base metal values. The research was undertaken to review the current support systems used in geotechnically poor ground conditions in a bid to improve both safety and productivity."

Jan 1, 2016

By J. C. Stankus

To protect mine personnel and moving equipment at underground roof fall areas, mine operators typically install steel sets, which are covered with wooden blocks and backfilled with an expanding type cement material. In large roof falls, the cost of void backfilling becomes prohibitively high causing some mines to leave the voids open. However, the durability of wood over time and the capability of the steel set and wood lagging to resist falling rock are unknown. This has caused concerns for the Mine Safety and Health Administration (MSHA) and ground control engineers. During past two years, Keystone Mining Services, LLC designed and developed various impact-resistant steel set designs that were approved by MSHA and installed in various underground fall rehabilitations. This paper presents the patent pending impact-resistant steel set design methodology, including (1) steel set design per AISC national standard, (2) design, development, and laboratory testing of a water proof composite impact resistant lagging panel, and (3) impact resistant steel set design based on Law of Conservation of Energy. Two underground cases will be included detailing the application of the system.

Jan 1, 2011