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By J. E. Marshall

"The concept of employing a project management team to coordinate all aspects of the construction of a new resource development has gained wide acceptance. This team can be formed from within the staff of large mining companies or contracted from major engineering firms and consultants. The mandate of the project managers usually terminates on successful startup of the operation. For frontier mineral developments in the Canadian Arctic or in the developing countries, startup and the initial year of operation represents the period in which the project is most vulnerable to technical, political and managerial problems. A complete change of the management team or the retention of the construction project managers and the resulting cost combined with the breakdown of organizational accountability within the operating staff .are unnecessary management problems.Independent project management services provide the commitment necessary to sustain the continuity of management through all project phases. Efficiency and the ability to make decisions quickly are characteristics of the many successful small mining companies. These qualities are necessary in the project management group, which will be responsible for up to 90% of the preproduction costs.Continuous project management in the construction and operational phases of a mineral development are common in the iron ore industry, but remain anomalous in the base metal, energy mineral and industrial mineral fields.The Nanisivik project on Baffin Island in the Canadian Arctic is used to illustrate the advantages of total project management through construction and operation.Total project management has further potential for foreign interests and financial and utility organizations desirous of participating in the Canadian mining industry, but with no direct involvement in the construction or operating management. Participation agreements in the operating phase of a project can be negotiated to have management fees related to both the production and the profits of the enterprise."

Jan 1, 1980

By M. H. Kotze, V. Yahorava

A gold-selective ion exchange resin, containing tributylamine groups, was developed by Mintek for the recovery of gold from cyanide leach solutions. The Dow Chemical Company and, more recently, Purolite commercialized the production of this gold selective resin for use in the gold mining industry, and it is marketed as Dow XZ-91419.00 and Purolite A194 respectively. A novel application of this resin is the selective recovery and separation of AuCl4 - f rom p latinum group metals (PGMs) in chloride and nitrate solutions. The current paper describes potential benefits of this type of resin for selective recovery and upgrading of gold from low grade chloride or nitrate waste streams, and the possibility of gold separation from PGMs during their refining in chloride media.

Jan 1, 2014

By R. Simard

"Conventional exploration strategies identify many mineral deposits as potentially interesting, although only a few of them turn out to be of economic importance. In the context of exploration for sulphide nickel deposits in the Canadian Shield, a decisional model, based on a statistical study of parameters relative to nickel deposits as well as to barren sulphide occurences, has been developed.Because such geophysical variables as gravimetry, aeromagnetism and topography could be related to the relative importance of nickel-bearing deposits, a statistical analysis of 13 such variables was carried out for 98 targets which were considered promising after conventional exploration. Among these 98 targets are36 sulphide nickel deposits in the Canadian Shield and 62 drill-tested non-economic occurrences. The results of this study led to the development of a linear logistic model that permits evaluation, for each of the targets, of the probability of finding a nickel deposit of potential commercial interest. This decisional model can thus complement conventional exploration strategies.RésuméLes stratégies conventionnelles d'exploration définissent un très grand nombre de cibles comportant un inténet minier potentiel dont seules quelques-unes correspondent à des gisements économiquement importants. Dans Ie cadre de l'exploration des dépôts nickélifères du Bouclier Canadien, nous avons défini un modelé de décision fonde sur l'étude statistique de divers paramètres relatifs tant aux gisements d'importance qu'aux cibles dites stériles.Ayant fait l'hypothèse que certaines variables géophysiques (gravimétrie, aéromagnétisme et topographie) peuvent suffire à fournir des indications sur l'importance relative d'un gisement nickélifère, nous avons entrepris l'analyse statistique de 13 variables évaluées sur un échantillon de 98 cibles considérées comme potentiellement intéressantes par les stratégies conventionnelles d'exploration. Ces 98 cibles se composent de 36 dépôt nickélifères d ‘importance recontrés sur tout Ie Bouclier Canadien et de 62 cibles stériles reconnues par forage. Nous avons défini à l'aide de ces données un modèle logistique linéaire. Ce dernier nous permet d'évaluer pour chacune des cibles les chances de trouver un gisement. Ce modèle de décision peut done s'inscrire comme outil complémentaire aux stratégies conventionnelles d ‘exploration."

Jan 1, 1980

By Keith C. Hendrick

"Metal prices are frequently the most critical and least predictable element in determining the profitability of mining operations. Short -term fluctuations can be offset in varying degrees by hedging or other market actions. Such solutions are not practical for the longer term, The paper investigates the nature and extent of metal price risks and evaluates methods to reduce them.IntroductionIt is management's responsibility to improve the odds by managing the-risks by identifying them clearly, assessing them accurately, minimizing them where possible-and, then, timing decision s success fully.In determining the profitability of current operations, preparing forward plan s or developing feasibility studies for new projects or expansions, pr ices are usually the most critical input. Being market determined rather than cost based, they can also be the most unpredictable As a result, commodity prices are frequently the greatest of all risk factors.Nature of Commodity PricesThe cyclical nature of commodity prices is well known. They are stable only when supply is in balance with demand and forecast to remain that way. An imbalance on either side of the equation can lead to a price reaction completely out of proportion to the actual or perceived surplus or shortage.This exaggeration arises through the cumulative effect of market forces. When the market senses an uptrend, consumers buy for the expected increase in activity. They also seek additional quantities for inventory before price s rise. Merchants defer spot sales anticipating higher price s, speculators go along for the same reason, and producers raise prices in response to demand. Events tend to confirm the expectation of each party and strengthen their reaction causing prices to move higher."

Jan 1, 1983

By J. X. Guo, A. Pindred, J. Moore

"Two modified centrifugal flotation cells (CFC), Q2 and Q3 models, have been developed for froth flotation. The operating mechanism of Q2 uses a rotating bowl to create a centrifugal force on the feeding slurry. Froth concentrate is collected on the central top of the cell and tailing is discharged along the top edge of the rotating bowl. The Q3 utilizes a vertical rotating feed pipe to introduce the feed slurry into a stationary flotation column cell. A centrifugal force is also created by a rotating pipe for the feeding slurry. Froth concentrate floats over the cell and tailing discharges through the bottom of the cell. The centrifugal force causes the flotation recovery of fine particles from CFC to be higher than from the conventional cell. The major operating variables of CFC are the rotating speed, air flow rate into feed slurry, and slurry feeding rate etc. Flotation tests have been carried out on synthetic mixtures of galena-silica and chalcopyrite-silica, as well as some natural base metal ore samples. Parallel tests were also conducted on a conventional flotation cell. The comparative test results demonstrated that both Q2 and Q3 have the advantage of higher recovery of finer than 10 µm mineral particles, which are very difficult for the conventional non-centrifugal flotation cell to recover. The grade-recovery curves produced from CFC are equivalent to or better than the conventional flotation cell. There is a potential in the future for the CFC to be employed in slime flotation.1. IntroductionA centrifugal flotation cell (CFC) was originally developed by Clean Earth Technologies [I] to separate oil from water and was subsequently applied in froth flotation. Figure 1 illustrates the design of the original CFC, in which a vertical feeding pipe is attached to the center part of a rotating drum and a stationary shell encloses it to direct the float froth and tailing discharge. The slurry flows down to the bottom of the spinning drum, gets in touch with a screen of air bubbles and then migrates outwards under the effect of centrifugal force. After the mineralized froth enters the rotating cell, it is pushed back to the inner surface. The overflowing froth is collected in the froth launder while the tailing slurry is discharged through orifices along the outer rim of the drum."

Jan 1, 1998

TIPS FOR SUCCESSFUL WASTE MANAGEMENT ? WASTE MANAGEMENT PLANS ? Define the question to be asked in waste characterization studies ? Calibrate assessments and designs with field conditions ? Ensure consistent with short, medium and long-term mine plans ? Design robust plans - goalposts and expectations will change ? Fully assess and integrate costs into economic models ? Integrate waste specialists into the feasibility and design teams ? Keep it simple and when you can?t, communicate it in simple terms ? PLAN EXECUTION ? Integrate the waste management plan into daily mine operations ? Identify the critical KPI?s , track them and set clear action triggers ? Know the difference between knowledge and data ?make sure you retain knowledge and document the important Maintain management, engineering and operational focus through the mine life

May 1, 2010

By D. J. Reddish

The paper describes a case study where numerical modelling has been applied to predict potential risks associated with inflows of water in active mine workings from an overlying sandstone aquifer. The objective of the modelling was to predict the development of strata fractures and strains as the longwall panels were extracted and investigate their relationship to an sandstone aquifer. The numerical modelling study also included the investigation of the effect of mining on a fault that existed close to the start position of one of the panels. The potential effects of mining on the fault were undertaken by parametric studies adjusting properties for the fault and the relative position of extractions, which allowed the mine planner to position the panel layout accordingly.

May 1, 2003

By J. Bigu, M. G. Grenier, S. Hardcastle

"This study was undertaken in a belt conveyor drift of an underground hard rock mine. The conveyor transported ore or waste from a crushing operation located upwind from the drift sampling locations. A 250 m section of this drift was selected and several types of measurements were taken. Average respirable concentrations in the drift were 0.43 mg/m3 and 0.19 mg/m3 for total and silica dust, respectively. From the respirable dust concentration profile along the drift, it may be possible to estimate the contribution from extended sources such as dust produced by the belt and return idlers.The airborne dust in the drift had an average mass-median aerodynamic diameter of 4.2 micron. A continuous dust monitor showed that the crushing operation produced fairly high dust concentrations (sometimes greater than 4 mg/m3) over short periods of time.IntroductionAirborne dust in the respirable range is known to be the cause of various forms of lung ailments . In underground mines, respirable dust sources are created at many stages of production. All mining operators are responsible for de signing and establishing means of reducing airborne dust. In some cases, sources of dust are well defined and suppression methods are standard.In the case of interest here, the airborne dust cloud was formed from the contribution from many sources, which may be either discrete or extended. At the experimental site, the discrete or point sources were the crushing operation and the belt conveyor transfer point (tail pulley). These sources may be controlled by proper dust capture and scrubbing systems as well as dilution ventilation. Examples of extended dust sources in the area include dust produced by the re-entrainment of settled particles along the drift. Ventilation air movement and vehicular traffic both contribute to this phenomenon. Dust produced by the conveyor is another example of an extended dust source. Caked deposits on the return strand and idlers as well as the transportation of dry material on the belt, can be major contributors. Proper wetting of roadways and muck as well as proper belt cleaning techniques can help reduce these emissions. The cleaning apparatus, used on the belt where these experiments were conducted, is shown in Figure I. These and other belt cleaning techniques are described in more detail elsewhere."

Jan 1, 1987

By Robert A. Creaser, Iain Mitchell, Robert L. Linnen

Abstract - The Bermuda Zn-Pb showing is hosted by dolomitized Blue Fiord Formation of Devonian age, located east of the Ensorcellement dome on the Grinnell Peninsula of Devon Island. Fluid inclusions in hydrothermal calcite indicate that the mineralization precipitated from low-temperature, highly saline brines. The ?34S compositions of sphalerite, galena, and marcasite range from 16.1‰ to 35.2‰. Consequently, the Bermuda showing is interpreted to be Mississippi Valley-type (MVT) mineralization. The apparent age of mineralization has been determined by the Rb-Sr method from sphalerite separates, and a Late Devonian age of 357 ± 50 Ma (MSWD=65), with an initial 87Sr/86Sr ratio of 0.7083 ± 0.0020 is indicated. This date, within error, is the same as the Polaris deposit. This suggests that the mineralization formed during the Ellesmerian Orogen, although it is also possible that mineralization is associated with extension, related to the opening of the Sverdrup basin. The strontium and sulfur isotopes and fluid inclusion analyses indicate the involvement of a brine that acquired its salinity from interaction with evaporites, lower in the stratigraphic succession. The Polaris mine is the type deposit in the Cornwallis Zn-Pb district and is hosted by the Thumb Mountain Formation. The results of this study are significant because they demonstrate that regional brine movement is more widespread than previously recognized, and that MVT mineralization in the Cornwallis Zn-Pb district is not restricted to the Thumb Mountain Formation.

Jan 1, 2004

By Tobias Riedel, Peter Ay, University of Applied Sciences, Bianka Bade, Nicole Pausch, Bernhard Gemende, Florian Logsch, Matthias Leiker, Satyanarayana Narra, Claudia Glaser

This study focusses on the production of micro-structured agglomerates with high porosity from iron (III)-hydroxide-containing materials as adsorbent. A fractal-like structure of the agglomerates was created through a two-stage agglomeration process. Developing porous structures was necessary to increase the adsorption capacity. Various materials were used for the agglomeration experiments: i) filter cake (dry matter content 23 to 27 wt.-%); ii) FerroSorp®DGµ, a product which is already being used commercially for various applications in water cleaning. These materials in the pristine state have different characteristics such as dry matter content and particle size distribution. The desired optimised agglomerates can be achieved with the help of additives or binders, respectively. Additionally, the agglomeration process parameters play a vital role. In order to produce agglomerates with high porosity, the process was carried out in two steps. Firstly, FerroSorp®DGµ (d90 < 30 µm) was agglomerated jointly with the aforementioned filter cake in an Eirich intensive mixer (particle size range 125 µm < d90 < 500 µm). The second agglomeration step post drying was carried out in a pelletisation disc or in an Eirich intensive mixer with the addition of polymeric binders (up to particle sizes ranging from 2 to 4 mm). Agglomerates were characterised both in short and long term loading tests using phosphate as model ion. Contact times were less than 10 min, similar to practical application in percolation columns, or more than 7 days, respectively. The results show that the agglomerates produced in the two-stage pelletisation process have more advantageous properties like better accessibility of the active sites obtained by specificly influencing the particle size distribution during the two-stage pelletisation process.

Jan 1, 2016

By J. Etcheverry, E. Seguel, R. Díaz, F. Parada, R. Parra, E. Balladares

A thermodynamic and kinetic model is proposed to explain the formation of bornite, chalcopyrite and magnetite during partial roasting of enargite-containing copper concentrates. The proposed mechanism involves solid-solid-gas and solid-gas reactions between chalcocite, pyrrhotite, gaseous sulfur and oxygen. The formation of bornite could be explained by a two-step reaction: the first one involving the formation of chalcopyrite by a reaction between Cu2S, FeS and gaseous sulfur, followed by a second step in which the newly formed chalcopyrite reacts with additional chalcocite to form bornite. Although thermodynamically the direct formation of bornite is more favorable than that of chalcopyrite, the lower diffusion kinetics of bornite formation could explain the preferential formation of chalcopyrite. If the reaction occurs with stoichiometric chalcocite and pyrrhotite in the presence of gaseous sulfur to form chalcopyrite, no bornite is formed, while for the stoichiometric reaction between chalcopyrite and chalcocite in the absence of sulfur, only bornite is formed. For the formation of magnetite and chalcopyrite the mechanism could involve the partial reaction of chalcocite and pyrrhotite in the presence of oxygen. The proposed model is thermodynamically consistent with the experimental results obtained in laboratory and pilot plant. INTRODUCTION The processing of high-arsenic copper concentrates with over 0.7 wt.-% arsenic by conventional smelting-converting normally require an additional arsenic removal step to reduce arsenic content to levels below 0.2–0.3%. One of these high-arsenic copper concentrates is the one produced by the Ministro Hales Division (DMH) of CODELCO, which has the typical chemical composition shown in Table 1. Enargite (Cu3AsS4), chalcocite (Cu2S) and pyrite (FeS2) are the main mineralogical species present in these concentrates, with over 75 wt.-%, as shown in Table 2. Partial or “neutral” roasting of these concentrates under controlled temperature and partial oxygen pressure conditions at 923–993K (650–720ºC) can remove up to 95% of the arsenic as As2S3 (As4S6), which has a high vapor pressure under these conditions, leaving a calcine with low residual arsenic. In copper concentrates, arsenic is present generally as enargite and arsenopyrite. This compounds as well as others such as pyrite and covelite, decompose readily above 770 K (500ºC), releasing, in addition to gaseous arsenic trisulfide, gaseous sulfur which by oxidizing to SO2 generates most of the heat required by the process.

Jan 1, 2019

"In flotation research, relatively little attention has been paid to understanding particle-bubble detachment phenomena compared with attachment processes. With CFD models now incorporating attachment/detachment kinetics, it is important to obtain more accurate formulations for detachment probability. The formula most often used is due to Bloom and Heindel (2002) who proposed that the rate of detachment would equal the product of detachment frequency, as previously estimated by other authors, and probability of destabilization, as estimated previously by Schulze. These two factors both account for the balance between stabilization and destabilization forces, so the product accounts for this effect twice. An integrated procedure has been followed to estimate the overall detachment rate by re-analysing the process. In this analysis, detachment rate is calculated as the frequency of eddy-aggregate interactions (or “collisions”) sufficiently energetic to cause detachment. The Bond number analysis of Schulze has been incorporated into the turbulence frequency analysis of previous authors in an integrated way. The new formulation has essentially the same type of dependencies as the previous model, but gives a lower detachment frequency. Detachment frequency has been calculated using the new formula for conditions relevant to an industrial flotation cell. INTRODUCTIONIt is well known that the effectiveness of froth flotation for separating different minerals is limited to the particle size range of approximately 10–100 mm (Trahar & Warren, 1976; Trahar, 1981). Fine particles tend to follow fluid streamlines around bubbles limiting the likelihood of bubble–particle collision, while coarse particles can be more easily detached from bubbles before collection can be achieved.Phenomenological models have been developed to quantify the physico-chemical aspects of flotation in order to better understand factors affecting these limitations, and to suggest ways of broadening the window of feasible flotation. Koh and Schwarz (2008) have incorporated these models into computational fluid dynamics (CFD) models of flotation cells, which have then been used for design and scale-up purposes (Schwarz et al., 2015). The models are based on dividing the process of bubble–particle interaction into three subprocesses: collision, adhesion and detachment. Of these, the hydrodynamics of bubble–particle collision and the probability of adhesion have been studied most extensively, while the dynamics of detachment have received relatively little attention from investigators."

Jan 1, 2016

By Alan E. Gallie

FOR many years the Witwatersrand has been the leading gold mining r camp in the world and, to a Canadian mining student, could not fail to be of overwhelming interest. The vast scale upon which the operations are conducted, the enormous production accomplished, and the perfection of the operative technique, have all so forcibly impressed themselves on his memory that it is difficult to select any one feature as more outstanding than another. For the purposes of this paper, however, the author has selected the very first feature of mine operation with which he came in contact, namely, shaft sinking, as it reflects, quite as well as any other, the spirit of mining in South Africa. Early mining in Johannesburg was by open cuts or trenches, dug along the outcrops of the reefs. The ore was thrown from bench to bench to the surface. As the depth increased, rock was hoisted by bullocks. In 1887, the first shafts were sunk and true underground work began. At the same time, boreholes were put down to test the continuity of the reefs at depth. The first was at the Village Main reef. It cut the South reef at 517 feet and the Main reef leader at 581 feet. The Main reef leader assayed eleven penny-weights. Subsequent boreholes proved the reefs down to thousands of feet. Many companies secured deep-level claims as a direct result of the information obtained from the early holes. These companies then held land on which there was no readily available ore. In order to get to their pay rock, vertical shafts through the upper strata were necessary. Shareholders were impatient, and shafts had to be sunk as speedily as possible. The old methods of shaft sinking were investigated, new methods developed, and soon all records were being broken. In the last thirty-five years, the record has been slowly advanced, and last summer it was again broken to stand at 430 feet in a 31-day month. During the period from 1915 to 1935 inclusive, in the Witwatersrand district, 96 miles of shafts were sunk. Today, with the advance in the price of gold and the increase in the mining area, there are over twenty-five major shaft-sinking operations being carried on.

Jan 1, 1937

By Staff

Introduction The Hedley mine, perhaps better known as- the Nickel Plate mine, is one of the outstanding properties of southern British Columbia. Discovered in 1898 by Woollison and Arundell, prospectors, the property was bonded in 1899 to M. K. Rodgers for the Marcus Daly Estate, of Butte, and development was started the same year. From the high grade of the ore outcrop, and its colour, due to oxidation of the arsenopyrite, it was not difficult to open up and trace the showing. The Nickel Plate ore-shoot, which apparently had been easy to follow on surface, was more difficult to trace underground. In 1903, prospecting on an adjoining property, the Sunnyside, showed commercial ore at surface, but it was only after two years&apos; work that the ore-body was defined and shipments started. From this property, $1,200,000 have been taken out. Prospecting was also carried on on the IXL, Climax, Copper Cliff, Mound, Bulldog, Exchange, Silver Plate, Gold Plate, and other properties, all of which had surface showings, but up to date only the Nickel Plate, Iron Duke, Morning, and Sunnyside have produced commercial ore. In 1904, the Bulldog looked like a very promising mine, but it failed to make good. In 1905, the Sunnyside No. 1 was in the limelight, but it also failed to make the grade. In 1906, an outcrop on the Sunnyside No. 3 looked interesting. Subsequent work. on this claim produced $840,000, and at the same time ore which yielded $400,000 was mined from the Sunnyside No. 4. In 1908, the Nickel Plate ore-body entered a lean zone and, as the diamond drill failed to give satisfactory results, the Daly Estate, after making a profit of $1,151,000, sold the property to the Hedley Gold Mining Company, Limited, for $760,000, retaining, however, a large interest.

Jan 1, 1929

By G. R. Heffernan

"In the early 1970ssteelmakers worldwide were looking forward to many years of expansion and profitability. Huge government investments in Europe, the United Kingdom, Japan, Brazil, and Venezuela were committed in anticipation of growing market s based on long-term OECD forecasts. In 1973 the first OPEC oil shock occurred. Steel demand shrank. Restructuring became the buzz word of the day as billions of dollars in taxpayers&apos; money was poured into eliminating excess capacity and labour. In the United States, where government help was not available, inefficient companies went bankrupt; capacity was cut to 100 million tons from 155 million tons. The industry throughout the industrialized world shrank. By 1979the world economy seemed back on track and a modest degree of optimism could be detected in the international steel fraternity. Then came the second oil shock. By 1982 the industry was in the midst of another shakeout. More bankruptcies, more rationalization, and fewer jobs resulted. In Canada some well-known companies came close to the brink as low prices and high interest rates took their toll. In the light of the turmoil in the steel market over the past 20 years an attempt to forecast the trends through to 2001 is intimidating.However, there are good reasons to be optimistic today about both markets and technology.An economic super power is emerging in western Europe as 1992 draws near. The creation of a single market of 320 million well educated and economically ambitious people has major positive implications for steel demand. The mega projects of the channel tunnel, a European network of high speed railways, and the London docklands are the forerunners of greater things. Still to come is another $200 to $300 billion by the year 2001 in identifiable major projects for highways, railways, airports, water and sewage systems. Add to that the demands of an increasingly affluent population for automobiles, appliances and housing. On top of all that place large increasing demands for electric power and you have a potential beyond anything seen during the 1970s and 1980s. In 1988 the EEC steel industry operated at 90% and in 1989 at 92% of effective capacity. A surge in spot prices indicated that 92% was close to the ceiling. This pace moderated in early 1990 but any slack will probably be taken up rather quickly."

Jan 1, 1990

By A. Navarra, Norman Toro, T. Marín, Fernando Ayala

The quantitative techniques to evaluate the enhancement of a particular unit operation should consider the corresponding changes to the adjacent unit operations. For example, the expansion of off gas handling capacity should consider the corresponding changes in converter cycle times, matte grade, and other operational parameters, that can provide the optimal system-wide benefit. In general, the upgrading of smelter equipment is risky due to the size of capital investment, as well as any unforeseen impacts on rest of the operations. However, this risk can be mitigated by applying the principles of Front End Loading (FEL) in the formulation of multiphase re-engineering projects. The initial phases of engineering are relatively inexpensive, and determine whether or not to pursue the subsequent phases that are comparatively more expensive. Each phase of engineering depends on increasingly detailed descriptions regarding the critical phenomena that can effect design decisions; the increasing levels of detail may result from numerical simulations, as well as laboratory and plant trials. The quantitative framework should be sufficiently flexible to accommodate these increasing levels of detail, regardless of the particular phenomena, so that it may evolve throughout the project. The current article describes the combined usage of mass balancing, thermochemistry and multiphysics, in the development of discrete event simulation (DES) and finite differences (FD). The incorporation of finite differences into a DES framework depends on adaptive time-stepping, to determine threshold-crossing times, e.g. when the matte temperature surpasses a critical level that necessitates the addition of cold charge. The hybridization of DES and FD is appropriate for multiphase smelter development projects, as it supports semi-continuous material flows, operational policies and scheduling, as well as unexpected events and trends, in increasing levels of detail. This type of framework will support the installation and tuning of modern control systems, including state-of-the art sensors and machine learning algorithms.

Jan 1, 2019

By J. Drenda

The model for methane removal from the workings directly behind an advancing longwall as presented in this paper may be used for U-ventilated cross or length-wise systems of longwall advance, starting from the boundaries of the extraction field. In mines with high methane concentrations, Uventilated longwall extraction from the boundary of the extraction field produces a methane risk. The risk is manifested by a higher methane concentration at the end of the longwall, upper gate and incline. The methane in increasing concentrations, which is emitted mainly from the workings with caved areas, appears towards the end of the longwall and in the upper gate. The graphical model of the longwall provided includes both the workspace of the longwall and the caved area. Based upon a model of the rock distribution in the cave, a ventilation model comprising two standard air splits and large number of crosswise air splits has been constructed. Simulations indicate that if the shearer is not present in the longwall, the air distribution in the caved area is symmetrical. The presence of the shearer, both at the bottom and the top of the longwall, causes an asymmetrical air distribution in the cave, that is the asymmetrical flows in the goaf and longwall workspace and in the inflows and outflow between those regions. This phenomenon causes an increase in methane concentration at the end of the wall and at the upper gate. The methane removal method proposed for workings with a caved area directly behind the advancing U-ventilated longwall, starting from the boundary of the field, consists of the removal of methane-air mixtures from the caved area with the boom pipes. These booms may be of several meters long and may be extended if necessary. The insertion of the boom pipes into the cave towards the end of the longwall and connecting them with the general methane removal system creates negative pressure causing a change in the depression field, which is the aerodynamic potential field in the goaf area around the ends of the boom pipes. This will promote the extraction of the methane-air mixture from voids and the goaf cracks, and the area from which methane is being extracted may extend to the side of the cave. This is a positive phenomenon, which could result in the methane flow from the goaf into the airflow in the longwall workspace decreasing or even stopping. A reduction in the methane flow into the longwall workspace with extractions booms will be advantageous for the production continuity. Based on the floor load model for the rocks in the cave and the methane-removal boom load model, the value of the force required to move the boom behind the advancing wall has been calculated. Strength calculations for the pipe were performed using a finite elements method. The analysis results, as well as the comparison of the pipe material effort to the strength parameters of steel, which can serve as piping material (for the assumed load conditions), lead to a belief that the proposed boom construction satisfies the strength requirements.

Aug 1, 2013

By Guichao Wang, Geoffrey M. Evans, Graeme J. Jameson

"In this paper we present a new method for studying the detachment of particles from bubbles in a rotating turbulent eddy. The eddy is formed in a wall cavity in a two-dimensional water tunnel with transparent walls. When water flows through the tunnel, a vortical flow field develops in the cavity. The properties of the eddy can be modulated by changing the free-stream velocity of the water in the tunnel. Bubbles are pre-loaded with one or more particles in a fluidized bed flotation device located beneath the vortex cavity. Loaded bubbles are released one at a time into the cavity, and the motion of the bubbleparticle aggregate is studied using a high-speed video camera. The diameters of the particles and the bubbles, and the number of particles initially attached to the bubble, can be varied. The trajectories taken by the bubbles are quite complicated. In some cases, the bubble moves to the centre of the eddy, and particles rotate around its axis. If the rotational speed is sufficient, particles may detach due to centrifugal force. However, other modes were observed, including inertial detachment due to rapid changes in direction of the surface of the bubble, because of changes in trajectory of the bubble as a whole, or because of pulsations and oscillations of the bubble surface. Clusters of bubbles held together by particles were seen to form and reform. In the traditional explanation for the detachment of particles in flotation cells, it is assumed that particles detach from bubbles rotating in an eddy due to centrifugal force (Schulze, 1977). Although the conditions assumed in Schulze's theory may exist, it is only one of a range of phenomena that can lead to the detachment of particles from bubbles in a turbulent vortex.INTRODUCTIONThe recovery of particles by flotation methods is dependent on the particle size. The recovery in the existing flotation machines reaches a peak for particle size, typically in the range of 20 to 100 µm. This size range varies as a function of the particle’s properties (type and composites). For coarser particles, the recovery drops very quickly (Gaudin, Groh & Henderson, 1931; Jowett, 1980). If the upper size limit can be increased for flotation, dramatic savings in the grinding energy can be achieved."

Jan 1, 2016

By Jianzhong Liu

Based on the characteristics of overburden rock strata movement, surface ground subsidence and casing deformation and failure, a tension-shear combination failure model of surface borehole was set up. The main controlling factors of the mining-induced deformation and failure of surface borehole were researched with this failure model and the limit analysis method. The mining methods and geology conditions mechanics action mechanism to surface borehole and its time ?space evaluation rule was found. The surface borehole deformation and fracture rule were advanced. It provides theoretical support to optimizing layout, structure type, security measure and local casing protection of surface borehole.

Aug 1, 2013

By G. Begin

"The expansion undertaken at Selbaie in 1985 necessitated an adaptation and expansion of the equipment maintenance system. This paper relates briefly the stages of transformation of the maintenance administrative structures, work methods and tools. The maintenance in a mechanized mine requires an expenditure level in the order of 20% of the total operating cost of the enterprise. Thus, the maintenance organization was modified to apply more computerized planning and follow-up, and the role of preventative maintenance was further advanced.IntroductionAs far as maintenance is concerned at Selbaie, the scenario described herein is a resume of the current situation. Although positive results have been obtained, this outline is in no way a detailed account of a fail-proof maintenance system.Once zone A-I was put into production, the expansion the mine experienced in 1985 had a direct impact on the equipment maintenance system. As centralized as it was in the beginning, the system is now partially decentralized.The over-all changes to the maintenance department demonstrate the flexibility required by organizations in new situations. In spite of the exceptional results obtained before the expansion, it became evident that both the maintenance and production sectors would have to be combined. In doing so, a more appropriate coordination of maintenance work could be obtained and the maintenance staff would obtain a more detailed knowledge of the equipment in each sector. In addition, by keeping the general and specialized departments centralized, it was possible to offset the negative effect s of a decentralized system, namely too much manpower."

Jan 1, 1990