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By J. Ramirez-Castro, J. A. Finch

"Galena is the finest component of the product of a closed-circuit grind treating a lead-zinc ore, largely due to preferential recycling of this high-density mineral by the cyclone. For example, at the Pine Point Mines concentrator, for ~ 55% -200 mesh over-all, the galena will be close to 95% -200 mesh. This sliming of the lead can limit recovery, selectivity and dewatering. A proposed circuit modification to reduce the sliming is to incorporate a unit cell. A simulator was constructed to study the No. 3 grinding circuit at Pine Point modified by a unit cell on ball mill discharge (BMD).The simulator used a cumulative size basis rate-of-breakage with plug flow ball mill model, the parameters being obtained by laboratory grinding tests. Flotation and the cyclone models used a cumulative recovery/size matrix. The behaviour of each mineral, galena, sphalerite, pyrite and calcite/dolomite, was simulated. Simulation was adapted to a programmable calculator. A close fit to the existing circuit performance at two tonnages and mineral mixes was established.The simulator showed that the modified circuit could significantly coarsen the Pb grind, from 95% to —50% -200 mesh, depending on recovery, without substantially altering the size of the other minerals. The other principal findings were: compared to laboratory flotation tests on existing circuit BMD, the unit cell concentrate (CONC) will be coarser and markedly lower in grade; relatively low unit cell stage recoveries are desirable, because the cyclone scavenges the tail to give a circuit recovery which is higher than the unit cell stage recovery; unit cell stage recovery should not exceed the cyclone stage recovery, as the latter is the maximum circuit recovery; low unit cell stage recovery helps offset the disadvantage of the high flow at BMD; other high-density minerals will also be scavenged into the CONC, as illustrated by pyrite, making CONC quality difficult to maintain; density control of BMD flotation does not greatly alter feed density to the cyclone or ball mill.Possible plant metallurgy is forecast for a CONC diverted to final lead concentrate."

Jan 1, 1980

By E. Topuz, C. Duan

"INTRODUCTIONOperations research (OR) applications have experienced a substantial growth within the mining industry during the last three decades. The purpose of this paper is to present a summary of the results of a comprehensive survey of the application of various OR techniques to the major mining activities. It is hoped. through this sur vey , that the most widely used OR approaches, the important areas of application, and future trends have been identified.This survey included more than 500 articles published in this field in English since the late 1950s. Most of the relevant literature was found in mining publications, but, in terms of quality and originality, important applications were also found in literature not related to the mining industry. The sources constituted periodicals, proceedings research reports, and a few books. A listing of selected publications from which three or more articles reviewed in this survey appear is given at the end. Operations Research MethodologiesOperations research is concerned with optimal decision making in, and modeling of, deterministic and probabilistic systems that originate in real-life situation s. One basic feature of the OR methodologies is the attempt to optimize certain design parameters, subject to a set of constraints. This distinction has been employed in the survey as a guideline for selection of the techniques covered under the title "" OR methodologies"". The methodologies thus encountered in the literature are listed below. In a few cases, simulation has not been considered because it is not an optimization method per se."

Jan 1, 1989

By Gonzalo Mato, Colin Godwin, G. Ditson

"The mid-Cretaceous Seagull batholith intruded Mississippian sedimentary and volcanic rocks and Jurassic(?) granitic and ultramafic rocks within the Omineca Crystalline Belt in the Yuk on Territory near the British Columbia boundary. Leucoerotic fluorine- and boron-rich granites of the batholith exhibit many textural variations from aplite to pegmatite, but are dominated by a coarse-grained seriate unit and a fine-grained porphyritic unit.Four distinctive tin vein occurrences within and near the batholith are described, the most interesting of which is the MC showing of quartz-calcite-chlorite-cassiterite veins in intensely fractured zones of sedimentary and volcanic rocks. Three other showings occur within the batholith:J) the EC showing of quartz-fluorite-cassiterite-sulphide veins with prominent muscovite-illite alteration;2) the DU showing of quartz-hematite-fluorite-sulphide- sulphide-cassiterite with considerable manganese staining and sericitic alteration; and3) the VAL showing of quartz-tourmaline-cassiterite-fluorite-arsenopyrite veins with little associated alteration.Most cassiterite occurrences are within easterly-trending, vertical structures and all occurrences are thought to represent parts of a single system. These mineralogical and physical variations are apparently related to the distance from the upper contact of the batholith.For the Seagull batholith, Rb-Sr isotopic data give a 100±1.4 Ma isochron age that is concordant with the K-Ar model age from biotite of 101±4 Ma. Initial Sr isotopic ratios for the batholith are high at 0.712, indicating an old, sialic crustal source for this pluton. This initial ratio is similar to values for granitic rocks associated with tungsten deposits in the Yukon Territory. The high initial ratio for Sr, the high Si02 content, the high s/I index, the presence of normative corundum. leucogranitic composition and associated lithophile-tungsten mineralization demonstrate that the Seagull batholith is probably an S-type granitic body. This factor is significant to regional exploration jar tin and tungsten in the Canadian Cordillera."

Jan 1, 1983

By V. S. Gischig, G. Preisig

Hydraulic stimulation of deep reservoirs is an essential procedure for developing engineered/enhanced geothermal systems (EGS), but also in other Geo-energy contexts. The goal is enhancing permeability to such a degree that fluid flow rates within the reservoir are sufficiently high for an economically productive reservoir. Two fracture stimulation mechanisms are distinguished that may occur concurrently during the hydraulic treatment: 1) During hydro-fracturing (HF) new tensile fractures are propagated from the borehole by means of a fluid pressure overcoming the minimal principle stress d3 plus the tensile strength T0 of intact rock. In case of a pre-existing fracture oriented normal to d 3 , the fracture can be opened by exceeding d 3 only. Fluid injection is performed via small packed intervals for creating a stack of hydraulic fractures. 2) During hydro-shearing (HS), over-pressure induces slip along pre-existing fractures that are favourably oriented in the stress field for reactivation in shear. Such stimulation is usually performed in a large packed interval or in an open borehole. Which mechanism occurs predominantly during stimulation depends on the rock mass structure and in-situ stress field, but also on the orientation of discontinuities intersecting the open-hole section and thus being pressurized. Both mechanisms also differ in how they affect fracture permeability. While permeability gained by HS is mostly irreversible due to rearrangement of asperity contacts accompanied with shear dilation, permeability enhanced during HF reduces nearly reversible after pressurization unless proppant is used to ensure permanent apertures. In this contribution, we critically discuss the pros and cons of both mechanisms regarding efficiency of enhancing permeability and the associated hazard of induced earthquakes based on literature review and numerical modelling. We review literature that reports on how much permeability required for productive EGS reservoirs and how much permanent permeability can be gained by stimulation. We also compile information regarding the degree of seismicity induced during HFor HS-dominated stimulation procedures, together with conceptual studies that reveal characteristics of seismicity associated with the two mechanisms. Many observations and models indicate that HF may have a higher tendency of being aseismic, while felt seismic events are usually associated with HS. Further, we present a hydro-mechanically coupled fracture flow model that investigates, if and to what degree the stimulation strategy can be designed such that one of the two mechanisms is evoked and dominates over the other. It shows that HS may dominate in presence of larger persistent fractures nearly optimallyoriented in the stress field, even if HF is attempted in short packed intervals. The model further demonstrates that stress transfer during HS promotes the development of permeability across an anisotropic layer of the stimulated rock instead of a large volume. Hence, the study sheds light onto the feasibility of creating productive EGS reservoirs in crystalline rock at several kilometres depths.

Jan 1, 2015

By Akiyoshi Horiuchi, Manabu Kanno, Shigeki Sato, Taro Aichi

"AKITA ZINC Co., Ltd. (Iijima Zinc Refinery), jointly owned by DOWA METALS & MINING Co., Ltd.(DMM), has used the company’s own hematite process for iron control since the beginning of operations in 1971. The hematite process consists of reductive leaching with SO2 gas and iron removal in autoclaves by high temperature hydrolysis. This process enhances not only zinc recovery but also the recovery of gold, silver, copper, lead and rare metals, which is carried out at another DOWA metallurgical plant. All by-products produced in the hematite process are marketed and sold. This paper presents an overview of the hematite process and the recent process improvements made.INTRODUCTION DMM carries out mining and smelting activities for precious metals, PGMs, rare metals and base metals such as copper, lead and zinc. It owns KOSAKA SMELTING & REFINING, producing copper and lead, and the AKITA ZINC Co., Ltd. (AZC) in Akita Prefecture. DOWA is a specialized smelting company which has established a metallurgical complex for copper, lead and zinc, including a recycling business. AZC was established in 1971 at a production capacity of 72,000 t/y zinc; it is jointly owned by DMM and five other non-ferrous metal companies. AZC has increased its capacity continuously and now produces 210,000 t/y of zinc. Figure 1 shows the changes in zinc production and capacity at AZC."

Jan 1, 2016

By John W. Korczak

The use of geological and grade block models has been standard practice in mine design for many years now, with a wide range of software available for creation and analysis. Although geotechnical parameters are of vital importance to mine planning there is very little in the way of commercially available systems for integrating geotechnical data into the mine planning and design process. Sirovision is a new technology developed by the CSIRO (Commonwealth Scientific and Industrial Research Organization) in Australia for automated, safe and accurate 3D mapping of geological and geotechnical features. Datamine has integrated this capability into its product range so that Sirovision has become an integral part of the day-to-day mapping, mine geology and geological / geotechnical modeling in both open pit and underground mine environments. This is the first integrated underground application of Sirovision from Datamine collaboration with Xstrata Nickel at the Nickel Rim South Project. This paper discusses the role of Sirovision in collecting the raw data required for geological and geotechnical analysis and the interpretation in a quick, safe, auditable and reproducible manner.

May 1, 2009

By G. Gabra

"A process of leaching niobium oxide from pyrochlore concentrate using hydrofluoric acid is described. Variables such as acid concentration, temperature, reaction time, solid/acid ratio, agitation speed and particle size are correlated to the recovery of niobium oxide.The relatively low activation energy (1,86 Kcal/mole) and the dependence of reaction rate on agitation suggest that the process is diffusion controlled. The optimum conditions for extracting niobium oxide from the leach solution, using either methyl isobutyl ketone or tributyl phosphate have been determined.IntroductionMost of the commercial production of niobium and tantalum has been derived from the treatment of columbite - tantalite minerals.In recent years (1960) , pyrochlore mineral has been found to be an alternate source of niobium . This mineral varies widely in composition and contains in addition to the main elements of calcium , sodium and niobium, some tantalum, fluorine, rare earth elements, titanium, alkali an d alkaline earth elements.It is well known that the province of Quebec possesses several pyrochlore niobium deposits totalling approximately 151 million ton s at an average 0.45% niobium oxide(1). One of the deposits, the St-Honor carbonatite, was brought into production by Niobec Inc. in 1976. Flotation o f this material produces a concentrate of about 60% Nb205(2).In view of an expanding niobium market in recent years and the presence of large niobium deposits in the province, a research and development program was initiated at the Centre de Recherches Miner ales to evaluate known processes for the separation of niobium and tantalum from each other as well as their purification . Some work has also been undertaken at the CRM to develop an improved extraction process. T his work will be the subject of further communication s."

Jan 1, 1985

By Simon C. Dominy, Ian M. Platten, Garry F. Johansen, Alwyn E. Annels, Brian W. Cuffley

Abstract - Coarse gold-bearing veins are characterized by high grades that are localized and erratic. Effective sampling of coarse gold-bearing veins is difficult because of the low concentration and erratic nature of the gold particles. Diamond drilling is an effective measure of geological continuity, however, grade distribution can only be reliably obtained from underground development (including close-spaced sampling, bulk sampling, and trial mining). Comparison between surface and underground drilling, underground linear/panel and bulk sampling indicate that drilling and linear/ panel samples generally understate bulk sample grades. Bulk samples are likely to be the closest estimators of true grade. It is unlikely that anything above an Inferred Resource category can be estimated from surface drilling alone, and at best the grade will only be a global estimate. Underground development, in-fill drilling and bulk sampling/trial mining will be required to delineate Indicated and Measured Resources. Closely spaced development and bulk sampling is likely to be the only way to determine Reserves. The resource estimation process must driven by a clear geological model that should attempt to understand both geological and grade continuity. Traditionally, grade interpolation has been undertaken using classical methods, though more recently, computer-based block modelling techniques have been used with some success. Three case histories are presented, documenting the problems of estimating resources in coarse gold-bearing veins and the practical ways in which they were approached.

Jan 1, 2000

By J. H. Canterford

The nickel industry in Australia has followed the general pattern apparent in many other regions - lots of ups and downs, successes and failures, but always plenty of challenges. Some of these can be attributed to local geographical and infrastructure factors, others to a healthy mix of corporate good luck and management countered by decisions that, in retrospect, were less than optimum. The roles of several entrepreneurs have certainly added plenty of spice! In terms of processing technologies, there was an initial heavy reliance on the use of "off the shelf' commercially proven processes such as ammonia leaching of concentrates and mattes, and flash smelting. Over the past decade there has been an increasing dominance of plant modifications and process technologies that have been developed "in house" in order to enhance project economics and exploit lower grade and more complex resources. This presentation provides an overview of the past 40 years of the major developments in the Australian nickel industry and concludes with some guesses as to where we will be in another decade or so.

Jan 1, 2005

By Mark Freberg

"IntroductionThis chapter is intended to provide information on the operation and maintenance of several pieces of equipment used in heavy media separation. Most heavy media separation circuits, particularly those involving bath separators can be considered as high maintenance areas. Because of this the efficient operation and maintenance of these circuits is very important if the cost per ton of material treated is to be kept to an acceptable level.Heavy media separation (HMS), is a process used to separate particles of different specific gravities. Under laboratory conditions the ideal way to separate two types of particles which have different specific gravities is to suspend them in a heavy liquid which has a specific gravity between those of the two types of particles. Those particles with the lower specific gravities will float on top of the liquid while the higher specific gravity material will sink to the bottom. Given enough time and a sufficient volume of heavy liquid this process will be essentially insensitive to the sizes of the particles involved.Heavy media separation circuits make use of the same principles described above. The material to be treated is introduced into a mixture of finely ground solids, called media, and water which takes the place of the heavy liquid; the mixture of solids and water is known as medium. The separating force can be either gravity or centrifugal force. The type of solids used as media varies but it is usually a high specific gravity material such as magnetite, galena or ferrosilicon.Heavy media separation is used extensively in the cleaning of coal and to a lesser extent as a preconcentration step in base metal and iron ore operations."

Jan 1, 1989

By S. Banisi, J. Marois, A. R. Laplante

"This paper compares the behaviour of gold and ore in the grinding circuit of Hemlo Mines Ltd. Particular attention is given to grinding kinetics, classification behaviour, and liberation. For grinding kinetics, laboratory grinding of gold flakes and silica, 840 µm to 1200 µm in size (14/20 mesh), was also performed to provide a standard for comparison and to study in a controlled environment the mechanisms of breakage, folding , smearing and impacting.Grinding kinetics were characterized at laboratory scale with breakage and selection functions. The breakage function showed that 75% of gold disappearing from the 840 µm to 1200 µm class reported to the 600 µm to 840 µm; this figure is much higher than for silica (46%) or most other minerals, and implies that comparatively fewer fine fragments are produced from the breakage of gold flakes, on account of gold's malleability. The selection function of silica was four times that of gold. At plant scale, the ratio of the selection function of ore and gold increased from 6 for at 50 urn to JOO pm to 20 at 500 um to 1000µm.Observation of original flakes and their fragments with the scanning electron microscope showed that the main mechanism of ""grinding"" from the 840 µm to 1200 µm to the 600 µm to 840 µm class was folding rather than actual breakage. This was confirmed by a measure of individual flake weight. The postulated breakage cycle is that relatively globular flakes become increasingly serrated through grinding; they can then regain their original shape through folding and reflattening into cylindrical and spherical shapes, as the majority does; however, some fragments will at this point undergo actual breakage. Photograhic evidence is presented to support the proposed mechanisms.Smearing of gold unto silica was observed when silica was ground after a gold, and embedding of silica into gold flakes when gold was ground after a silica. Both mechanisms occur whenever gold and harder minerals are jointly ground, and result in ""unliberation"" of gold. It is postulated that smearing of gold onto other minerals plays an important role in explaining how gravity recovery can increase over-all gold metallurgy, especially when used ahead of flotation.Classification of gold in the primary hydro cyclones takes place at a much finer cut-size than ore, 20 µm vs 57 µm. This and the slower grinding kinetics result in high gold circulating loads in the primary loop, 6700%, and a gold content in the primary cyclone underflow (PCUF) is twenty-four times that of the ore. The gold size distribution for primary cyclone overflow is much finer than that of the ore, although they are essentially similar in the PCUF.Liberation, or more accurately ""gravity recoverability"", was assessed with a 7.5 cm (3 in.) Knelson concentrator. It varied between the thirties for the primary mill discharge and two cyclone overflows, to highs of 89% and 92% for the PCUF and secondary mill discharge."

Jan 1, 1991

By John Hughes

1. De Beers, Diamonds and Canada 1.1. De Beers was founded long ago (1888, the same time that Canada became a country) in a rural mining village in South Africa. Today, we employ 22,000 people across 19 countries and have 14 mines including open pits, shafts, beach-sands and seabed. 1.2. Last year our sales were US$5.7 billion and our total production amounted to 47 million carats which means a 40% global market share. For the Kyoto buffs in the audience, the company consumes 66 million cubic metres of water per annum, 210 million litres of hydrocarbon fuel and 1,600 GWh of electricity. Stats are good, but aren?t as expressive as a movie. This one is 2 minutes long, which is quicker than I could elaborate. (Video 1 - 2 minutes) 2. De Beers in Botswana is the leading source of diamonds 2.1 Today Botswana is the Jewell in the Crown. There are three big open pits that enjoy economies of scale that make them the lowest cost producers. Last year 60 million tonnes of overburden and 30 million tonnes of ore were moved in Botswana alone. Botswana produced 31 million carats, compared to 14 million carats in South Africa and 2 million very high quality carats inn Namibia. 3. Diamond Mines provide feedstock? ?.to jewellery stores

Apr 1, 2005

By G. R. C. Pacheco, D. M. Fonseca, R. Neuböck, G. E. Gonçalves, W. Moulin-Silva

Degradation by sulfur gases is an important lining wear mechanism in the copper industry. SO2/SO3 gases infiltrate into the pores of the basic refractory bricks, combine with their raw materials through expansive reactions and significantly modify the bricks’ structure. This study presents a comparison of the corrosion resistance against sulfur attack of different magnesia-based refractories using a simple, low-cost and quantitative method. Recipes containing sintered MgO grains showed lower resistance to corrosion by sulfur oxides compared to basic grades containing fused grains. Chromium corundum grades were used as a reference and showed very good resistance to this corrosion mechanism under the test conditions. The novel test provided relevant results that agree with what is commonly observed during operation and in previous post-mortem studies. This tool could be very useful in selecting refractory grades for the copper industry and predicting their performance. INTRODUCTION Oxidation of matte sulfides during copper production leads to the formation of sulfur oxides, which infiltrate into the pores of the refractory lining and react with the basic oxides below 1000°C to form magnesium and calcium sulfates. This reaction is accompanied by an expressive volume increase, consequent densification of the refractory microstructure and weakening of the brick bond (Malfliet et al., 2013). Thus, corrosion by SO2/SO3 is an important wear mechanism in the non-ferrous industry and the resistance to this compound should be considered when defining refractories for this application. Previous studies on this matter include expensive and complex testing methods involving pressurized SO2 gas cylinders in order to investigate the corrosion resistance of MgO-containing materials by sulfur oxides (Gerle & Podwórny et al., 2016; Fotoyi & Eric, 2011; Fotoyi, 2009; Podwórny & Piotrowski et al., 2008). The current study was based on a test developed by Pacheco & Fonseca (2018) to assess alkali infiltration and aims to provide an evaluation method of the corrosion resistance of refractories by SO2/SO3 in a simple and quantitative manner. This novel test is useful to compare the corrosion resistance of different refractory recipes and properly select the grades that should be employed in the non-ferrous industry. A case study is provided to illustrate the damage caused by sulfur oxides in refractory linings.

Jan 1, 2019

By L. S. Jen

Canadian copper, nickel, zinc, lead and molybdenum mines are characterized by the mining of ores from which more than one metal is recovered. During the 1980s, approximately 15% of the gold, 25% of the zinc, 30% of the copper, 55% of the molybdenum, 80% of the silver and 90% of the lead produced from Canadian mines were produced as co-products and by-products of base metal mining operations. This trend is not expected to change significantly in the near future. The presence of co-products and by-products affects the level of production and the level of revenue from base metal mines in several ways: (I) in general, production of one base metal cannot be expanded or cut back without affecting the amount of production of another metal;(2) the commercial success of certain base metal mining operations depends on the substantial bonus revenues from co-products and by-products; (3) the quality and economic viability of many ore deposits are significantly improved by the presence of co-products and by-products; and (4) while coproduction is critical to the survival of some mines, bonus revenue from by-products can also be life saving to others during economic downturns. For these reasons, deposits with significant co-product or by-product values are likely to continue to be significant targets for exploration and for acquisition.

Jan 1, 1992

By L. C. Kitchener, K. Vollenwyoer

"This paper describes the development of an automated, 70-ton capacity, underground electric trolley truck at Inco Ltd. The purpose of the project is to provide a high capacity and high productivity haulage system to suit continuous loader applications in existing mining horizons where conveyor belt application is not immediately practical. IntroductionWith the start o f a program by Inco in mid-1983 to develop a continuous loader for bulk mining of our hardrock orebodies, the need for a rapid ore transportation system was recognized to match the increased extraction rates planned. Two methods were investigated, truck haulage and conveyor belt. As a result, a conveyor belt system has since been designed and installed with a continuous loader at Stobie Mine and an electric truck has been designed, fabricated and assembled, with shop testing underway. This paper deal s with the latter project. BackgroundMany existing mining horizons which could utilize continuous loaders do not have the straight runs required for conveyor belts. In these situations, truck haulage would be the only alternative of the other transportation methods that would be practical. In order to match the high productivity potential of the continuous loader, however, a more efficient trucking system is required than would be available with conventional diesel powered trucks or with electric truck designs commercially available, or under development. A higher capacity truck and an automated operation is necessary so that the application of additional units to suit increasing haulage distances matches loader output without reducing over-all productivity because of the need for additional operators.A first effort to work with a major electrical manufacturer was unsuccessful and resulted in a project delay of almost one year. In November 1984, an investigation into the concept was reinstigated with UTDC, and an agreement to start design was reached in April 1985."

Jan 1, 1988

By Li. L.

Backfilling has become a popular solution in underground mines around the world. It reduces environmental impact of mining industry and improves ground stability. In most cases, backfill has a high water content so that it can be delivered by pipes from a backfill plant on ground surface to underground stopes. Upon deposition in the stope, the backfill tends to consolidate under its own weight, leading to a generation of excess pore-water pressure. To avoid excessive pressure and protect the backfill barricade installed at the base of the stope, the backfilling of the stopes is usually divided into two stages: plug pour and backfill body pour. The interruption of backfilling operation is undesirable as it slowdowns the mining productivity, and sometimes causes pipe clogging, leading to unexpected increase in manpower cost and further reduction in mining productivity. The backfilling interruption time may be reduced, even eliminated if the drainage of backfilled stopes is sufficiently improved. This paper presents an application of wick drains, a material commonly used in civil engineering, to mine backfilled stopes to help accelerating the drainage. A protocol is proposed for installing the wick drains in a mine stope to be backfilled. Numerical simulations were made, showing that the drainage of the backfill can significantly be improved by the introduction of wick drains. The application of wick drains in mine backfill can thus be considered as a promising technique and merits deeper and more detailed investigation.

Aug 1, 2013

By G. D. Just

"Extensive mechanization of underground mining operations, improvements in blasting technology and the development of simulation models for systems evaluation has now made it feasible to optimize rock fragmentation and materials handling operations. Methods of achieving these objectives are described in this paper, with particular emphasis on the need to obtain precise field data measurements. Techniques are illustrated with reference to the sub-level open stoping system of mine production. IntroductionThe primary objective to be achieved in any mining system is to deliver a specified grade of ore to the mineral processing plant at a planned delivery rate and at the minimum total mining cost. Design and management of such a system is complicated by the large number of unit operations and the often unknown inter- relationships between the different unit processes. This particularly applies in underground mines, where planning restrictions and unit costs are much greater than in comparable tonnage sur face mining operations. These difficulties can often be resolved by the application of judgment based on extensive experience, but the costly trial -and-error methods required for new technology discourage innovation.Most modern medium- and large-scale mines are now extensively mechanized. Consequently, the performance of each unit operation by individual items of equipment should be predictable for a given set of conditions. An essential prerequisite is that quantitative performance data are available from field measurements. Such information can then be used to optimize the design and management of the complete mining system to achieve the minimum tot al mining cost. One of the most significant factors influencing all unit costs is the degree of rock fragmentation. The importance of this variable is indicated by the fact that opt imization of rock fragmentation implies minimization of tot al mining system costs."

Jan 1, 1980

By R. W. Thompkins

"PREFACEPart 1 of this paper, published in the September issue, covered the occurrence of uranium, radiation from uranium ores, the uranium series, radioactive theory, radioactive equilibrium and application to the radon series, the working level, the theory of emanation and diffusion, transport by thermal diffusion of radon emanating from porous rocks, and definitions.This Part 2, which follows, deals with radiation theory applied to uranium ores, other radon migration factors, factors affecting the radon gas release rate, the measurement of radon gas emanation rates, the tunnel concept, variation of emanation rate with grade and estimating radioactivity from grade analysis.The series will conclude with Part 3, in the November issue, which will discuss the techniques for controlling radiation and provide some example calculations.10.0. Radiation Theory Applied to Uranium Ores10.0.1. The processes of diffusion transport of radon gas, through rock from the fundamental physics is a function o f the radon gas concentration in the interstitial pore spaces and the distance from the surface. Expressed by Fick's first law of diffusion, it is expressed: [ ]10.0.2. The maximum concentration is a function of the emanating power (ß), thus the above equation may be expressed: [ ]10.1. The Effect of Porosity10.1.1. If a constant emanating power is assumed (ß), a family of curves can be obtained for concentrations at varying distances and rock porosities. The curves as originally plotted assumed a constant emanating power of 5 x 10-4 pico curies/litre/sec and show the maximum expected concentrations in the pores in pico curies per litre. Because these concentrations are proportioned to the emanating power, this set of curves can be structured to show the fraction of maximum concentrations possible at various porosities of the rock.10.1.2. Notice that at 10, 20 and 30% porosities a 5-cm sample (hand-sized and drill-sized pieces) has no practical increase in pore concentration. Thus, by measuring the emanating power of hand-sized pieces of ore, the actual radon gas production into any pile of broken ore could be estimated readily."

Jan 1, 1982

By T. Güyagüler, U. Y. Önder

"This study investigated the psychrometric properties of ventilating air in GAL coal mines. Related measurements were done in underground openings and have been arranged as input data for computer programs prepared for ventilation network and psychrometric analysis.Results obtained from network analysis have been used for psychrometric analysis of ventilating air. Changes in heat and moisture content of air in two major path s between entry and discharge of ventilating air have been investigated. Psychrometric processes occurring in the mine were determined and are shown graphically in Figures 1 and 2. Special attention has been given to determine the changes in psychrometric properties and processes involved in the faces. Results are outlined in this paper.IntroductionThe psychrometric properties of mine air are important factors to mine productivity and efficiency. Therefore, psychrometric analysis should be made for all underground mines; any undesired situation observe d could be corrected by taking the necessary precautions.The analyses were done as a case study for GAL mines, the only mechanized lignite coal mine in Turkey. In this mine, workable reserve is about 300 million tons of coal and yearly planned production is 2.2 million tons. Production is continuing from a coal measure-bed having two coal seams with average thicknesses of 1.52 m and 1.72 m respectively. A 0.85 m shale band exists between these two seams.Two full y-mechanized faces, approximately 220 m long, usually work simultaneously. All measurements, including mine gases and air velocity, are done by sensors connected to a control room by a monitoring system.In the analysis, a line diagram is utilized to described the mine on which every junction and branch is numbered."

Jan 1, 1992

By D. M. Maijer, S. L. Cockcroft, A. B. Phillion, P. Fan, C. Reilly, H. Khadivinassab

A combined experimental / numerical approach is proposed to investigate the bulk transfer of solute due to liquid metal feeding during shape casting of aluminum alloy A356 (Al-7Si-0.3Mg). A dumbbell-shaped experimental casting geometry has been developed, which promotes solute redistribution due to liquid metal feeding. The redistribution of solute in trial castings is evaluated based on the area fraction of eutectic phases. In the numerical model, silicon species segregation during solidification are calculated assuming the Scheil approximation, and are coupled with macro-scale solute transport due to Darcy flow in the mushy zone and feeding flow. The model has been implemented within the commercial CFD software, FLUENT, which simultaneously solves the thermal, fluid flow fields and species segregation on the macro-scale. The experimental and numerical results are compared and contrasted to examine the effects of liquid metal feeding in this casting.

Jan 1, 2014