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By K Schonert, K Eichas

Electrostatic separation of non-conductive materials can be accomplished by triboelectric charging. The efficiency of convential separators becomes worse in the size range below about 100 ¦m. These problems are solved by developing a new double-drum-separator. The investigations have shown the possibility of separating very fine mineral mixtures (eg quartz/calcite) in a strong electric field after tribo-charging in a special dust-feeder. The paper reports about the influence of particle size and field intensity on the separation and deals furthermore with the problem of desagglomeration.

Jan 1, 1993

By Jacque Turgeon, Gontran Foy

"The Mineral Research Centre of the Quebec Department of Energy and Resources has worked extensively on the development of a dry process to extract pure mica flakes from a phlogopite ore. The liberation of mica from the gangue is effected basically by impact crushing, and the ground ore is screened into several fractions, each having a fairly narrow range of grain size. Each sized fraction is then fed to an air separator where heavy grains are separated from light flaky grains. Heavy fractions are returned to hammer mills where gangue minerals are ground finer and blocky mica particles are exfoliated. A second stage of screening is performed and each fraction is sent to an air separator. This sequence is repeated until mica products are virtually free of gangue. These different fractions are then treated in a cage mill in which mica flakes undergo a more orderly exfoliation along cleavage planes. The ground mica is again submitted to a final screening stage, after which each fraction constitutes a final commercial product.This process permits the recovery of about 70% of the mica contained in the ore. The over-all process will be described along with technical details of each unit operation. Recent work on a wet grinding method to produce very fine mica will also be discussed.IntroductionRecords of production of mica in Quebec date back to 1886. Production has been more or less continuous since that time, with peak activity during the war years. Production was interrupted in 1966, but started again in 1972 when Marietta Resources and Laviolette Mining and Metallurgical Corporation started their joint operation in Canton Suzor, northwestern Quebec. Mica deposits of more or less importance exist in different parts of Quebec, of which three have attracted attention in recent years: the Canton Suzor deposit, the Canton Lamy deposit and the Canton Chasseur deposit. The Suzor orebody was first identified by Carl Faesler in 1936, who described the rock as ""brown biotite in flakes half an inch in diameter, with interstitial augite, apatite and feldspar""."

Jan 1, 1982

By C. Butcher

Numerical simulations of straight tube hydroforming of a dual phase steel were performed using both upper and lower bound constitutive models for porous ductile materials. The Gurson model is based upon an upper bound approximation to the material behavior and thus overestimates formability. Conversely, a lower bound solution to Gurson's unit cell geometry was developed by Sun and Wang to provide a conservative estimate of formability. The effect of a compressive axial load (end-feed) on damage development and tube formability is investigated. The resulting upper and lower bound models successfully captured the experimentally determined burst pressure, formability and failure location.

Jan 1, 2010

The modern resource extraction enterprise is a complex capital intensive business operating in a world of constantly evolving social, environmental and economic scrutiny. Investors, government, media and special interest groups expect to see business environmental and social performance respond and deliver increasing corporate responsibility and sustainability.   Thorough interrogation of business performance using a multi-disciplinary due diligence approach presents a more sophisticated review and benefits beyond the traditional compliance/conformance 'audit' style assessment.   Using a due diligence approach allows assessment through a comprehensive lens which examines potential short- and long-term risks including sometimes less tangible environmental and social liabilities, and informs management, investors and regulators of broader business performance. This approach provides information in a form that business can measure performance in a repeatable and enterprise wide sense.   This paper provides an outline of the due diligence process applied in this way, drawing from lessons learnt and industry based experiences in the due diligence process and the benefits and tools that can  be applied in an environmental and social due diligence business performance assessment

Jun 1, 2010

By Reid K. J, Restarick C. J

The breakage and flow characteristics of quartz, ground as a minor constituent with calcite in a continuous wet ball mill, have been determined by carefully controlled grinding tests.A mathematical model, combining the simple functions which describe these characteristics, has been used to predict both steady state and non steady state results.The calculated results are compared with experimental data.

Jan 1, 1966

By Jaczkowski B

The lower orebody (LOB) at Chingola Divi- sion of Nchanga Consolidated Copper Mines Limited (NCCM) accounts for approximately 30 per cent of the total copper production for the company. The uniformity of the geology of the orebody lends itself readily to a computer based ore reserve calculation and accounting system. The mining units are physically defined such that a hierarchical type of com- puter file organisation can reflect the existing physical interdependencies. In 1972, a project team consisting of one representative from each of the mine planning, operational research, and computer services departments was formed to investigate and to define the technical mining requirements of the dynamic ore reserve system (DORS). The system was finally implemented in 1975ò

Jan 1, 1977

By M. Wickham

Design of an open pit backfill requires an understanding of highly varied processes including slope stability, hydrogeology, pit lake chemistry, climate, runoff, and mine waste behavior. Dynamic systems modeling (DSM) provides flexibility to the designers of open pit backfill, allowing them to directly integrate many different physical processes and varying levels of complexity. DSM also provides for the efficient application of uncertainty analysis to define a range of possible results, the sensitivity of the results to uncertainties in model inputs, and the value of additional data. This paper presents the results of an analysis using DSM to evaluate a pit backfill design at an Arizona mine. The objective of the partial backfill was to stabilize an active slope that threatened facilities adjacent to the pit. DSM was used, in part, to develop a pit lake water balance model for evaluating the influence of the backfill on the ability of the pit to maintain passive hydraulic containment of groundwater and surface water inflows and for evaluating costs for various backfill scenarios.

Jan 1, 2001

By R. Shen

This paper presents results of a feasibility study of recycling manganese furnace dust generated in production of ferromanganese and silicomanganese at Tasmanian Electrometallurgical Company, Australia. Dried manganese furnace dust contains about 20 wt% of carbon, in average 33.4 wt% of manganese and 1.3 wt% of zinc. Manganese in the dust is in the form of MnO, Mn3O4 and MnCO3; zinc is mainly in the form of ZnO andZnSO4. Analysis of the zinc balance with dust recycling showed that to keep zinc intake at the acceptable level, it should be partly removed from the dust. In the reduction laboratory experiments, zinc oxide was reduced to zinc vapour by tar of the dust. Reduction of zinc oxide started at 800°C and zinc removal rate increased with increasing temperature; removal of zinc was close to completion at 1100oC. Optimal conditions for removing zinc from the dust include temperature in the range 1000-1150°C, inert gas atmosphere and furnace dust fraction in the furnace dust-manganese ore mixture above 60%. In the sintering of manganese ore with addition of manganese dust in the sintering pot, zinc was reoxidised and deposited in the sinter bed. Removal of zinc in the sintering pot tests was in the range 4-17%. Up to 30% zinc removal was achieved from the bottom layer of the sinter bed. It can be concluded that zinc removal will be low during the processing of manganese furnace dust in the sinter plant. The zinc removal rate will be the highest when pelletised manganese furnace dust is added to the bottom layer of the sintering bed.

Jan 1, 2007

By D. Bois, P. Poirier, B. Bussière

Environmental desulphurization is an attractive alternative for the management of acid generating tailings. Bulk sulphide flotation is the most commonly used method to produce desulphurized tailings, as shown from many previous works. This process can reduce the volume of problematic tailings to manage by making a sulphide fraction concentrate. The desulphurized tailings can then be used as construction material for an engineered cover to prevent acid mine drainage. In this paper, the results from different laboratory and pilot scale flotation tests are presented. These results confirm that low sulphide non-acid generating tailings can be produced by froth flotation. It is also demonstrated that sulphide concentrates obtained from desulphurization mixed with the appropriate binders can be used as feed material for paste backfill. From previous work on the evaluation of operating and capital costs of the desulphurization process for different ore types, the use of desulphurization as a tailings management approach was studied for several scenarios. The desulphurization process was then compared with other technologies (underwater disposal, engineered soil cover) currently used to prevent acidic drainage (AD) for a new mining operation. Results show that partial or total desulphurization are technically and economically viable options to manage tailings during mine operation. Mine waste managers should consider desulphurization as an efficient technology.

Jan 1, 2005

By Mostafa Benzaazoua, Bruno Bussière, Philippe Poirier, Denis Bois

"Environmental desulphurisation is an attractive alternative for the management of acid generating tailings. Non selective froth flotation is the most commonly used method to produce desulphurized tailings, as shown from many previous works (McLaughlin and Stuparyk, 1994; Bussière et al., 1995; 1998; Benzaazoua et al., 2000a,b; 2002). This process can reduce the volume of problematic tailings to manage, by making a sulphide fraction concentrate. The desulphurized tailings can then be used as a moisture retention layer in a cover with capillary barrier effects to prevent acid mine drainage.In this paper, the authors present the results from different laboratory and pilot scale flotation tests which confirm that low sulphide, non-acid generating tailings can be produced by froth flotation. It is also demonstrated that the sulphide concentrates obtained from desulphurisation, when mixed with binders gave good long term results in terms of mechanical behaviour, thus demonstrating that the sulphide fraction can be used for paste backfill material. From previous work (Bussière et al. 1998, 1999) on the evaluation of the operating and capital costs of the desulphurisation process for different ore types, the use of desulphurized tailings to create a dry cover was then studied for several scenarios. The desulphurisation process was compared with other technologies (underwater disposal, engineered soil cover) currently used to prevent acidic drainage (AD) for a new mining operation and the advantages and disadvantages of desulphurisation are presented as well as the costs of this method of AD prevention.INTRODUCTIONThe principal environmental problem of the mining industry today is the generation of acidic drainage (AD) resulting from the natural oxidation of the sulphides in mine tailings. This phenomenon involves the generation of acidity which increase the amounts of toxic metals in the waste water released into the environment by a mine. The environmental impact of the AD has been described in detail in previous work (e.g. Down et Stocks, 1977; Ritcey, 1989; Gray, 1997; Ripley et al., 1996; Aubertin et al., 2002)."

Jan 1, 2004

The principles of geometry and trigonometry are so continuously used by mining engineers for the purpose of accurately and intelligibly recording their measurements, that the writer is prompted to lay the following cursory remarks upon mine surveying before the members of this Institution in the hope of eliciting a free interchange of opinion upon details of this interesting branch of the profession. He proposes to deal with surveying only so far as it concerns the mining engineer, not to intrude upon the domain of the professional surveyor, and, in this instance, to discuss more especially that which may be termed the mechanical, rather than the mathematical side of surveying.In the latter part of the eighteenth century and the beginning of the present one, the usual underground surveying equipment in the English metalliferous mines, consisted of a magnetic needle in a fiat square wooden box of about 9-inch sides, a two-foot rule, a long cord, aud a stool, upon which to place the needle and box. The operator took his bearing by sending his assistant with the end of the cord as far in a straight line as the length of the cord would admit.On its being drawn that he held its end in one hand and placed the side of the compass-box against it with the other, and noted the bearing thus found either by a book entry, or by ticking it off with a piece of chalk on the board the compass lay in. He then measured the cord with a two-foot rule. It is needles to say that with these appliances the accuracy of the results were open to question, and mining surveying was not unduly popular.In the present day, engineers have the advantage of using instruments brought to such a state of perfection, and of employing such an exact system of underground surveying, that inaccurate work must usually be attributed either to lack of care, or lack of ability in the operator.

By J. B. Forrester

In the operation of the coal mines in Utah few adverse conditions confront us. Physical conditions for the economical extraction of the coal are as near perfect as it is possible for them to be. Still several obstacles are encountered to keep up our interest and prevent us from getting in a rut. Of these I shall speak only of Burning, Wants, and Sluffing of Ribs. Should one travel the outcrop from Ivy Creek in Emery county to the Utah-Colorado line, there would be one outstanding feature indelible impressed upon one's mind. That feature is the omnipresent indications of burning in place. Viewing the eastern escarpment of the Wasatch Plateau from a distance, many splotches of dark red are plainly seen always lying above the coal floor. This stratum is a felspathic sandstone, appearing as a white line running the full length of the above escarpment and about midway between the floor of the valley and the top of the plateau. The coal bearing complex consists of shales, sandstones and coal. This complex varies from two hundred to eleven hundred feet in thickness. The number of coal seams are exceedingly variable. As a rule the argilutites form the bulk of this complex. This material is baked by the burning of the coal and the iron present is oxidized to the ferric state, coloring the shale to a dark red. This baked material forms a shingle tales that in places cover the entire complex. It is natural to expect that the most extensive burning is in the canyons facing to the south and east and on the south slopes of the ridges running to the east or west. Such, indeed, is the case. Still in this arid region many crop fires have existed upon the north slopes, especially in those canyons that face to the east. In fact today, instances are not rare where grassy north slopes, heavily timbered with balsam and fir that have attained a diameter of 14 to 24 inches, are found growing upon the disintegrated baked shingle and later development proves that the coal has been burned at least 500 feet back from the outcrop. Still these conditions are not normal. In this arid climate the south and east exposures are steep and barren, except for the scrub pine, cedar, mahogany and kindred semixerophytes. Bunch grass is also a lover of such exposures. There is very little soil found in such places; it is either blown away as fast as formed or washed away by the rare torrential rains, or the rapidly melting snow. Thus we see that the physical conditions are favorable for the starting and maintainence of outcrop fires. This brings us to the probable origin of this phenomenon. There are four probable ways' that such fires, could be started, namely:

Jan 1, 1921

By N. Kinoshita, Y. Inada

The authors have proposed and discussed storage of low temperature materials such as LNG, LPG and frozen food in rock caverns. In this case, as the rock mass around the caverns will receive effects of low temperature, it is necessary to consider the thermal behavior and the stability of caverns. In this study, strength and deformation characteristics obtained by the uniaxial tension test and the compression test at low temperatures were discussed. Using the results, temperature and stress distribution around caverns when LNG was stored, were analyzed. Then thermal behavior of the rock mass around caverns was discussed. Die Autoren haben Lagerung von Niedertemperatur-Materialien wie LNG, LPG und tiefgefrorenen Nahrungsmitteln in Felskavernen vorgeschlagen und diskutiert. Da in diesem Fall die Felsmasse um die Kavernen den Effekten der niedrigen Temperatur ausgesetzt ist, ist es erforderlich, das Thermalverhalten und die Stabilität der Kavernen zu berücksichtigen. In dieser Untersuchung wurden Stärke-und Deformationseigenschaften, die durch ein-axialen Spannungstest und Kompressionstest bei niedrigen Temperaturen erhalten wurden, diskutiert. Mit diesen Ergebnissen wurden Temperatur- und Stressverteilung um die Kavernen bei Lagerung von LNG analysiert. Dann wurde das Thermalverhalten der Felsmasse in der Umgebung der Kavernen diskutiert. Les auteurs proposent et discutent l'entreposage de matériaux à basse température, tels que le GNL, le GPL et des aliments congelés, dans des cavités rocheuses. Comme, dans ce cas, la masse rocheuse entourant la cavité subit les effets des basses températures, il est nécesaire d'étudier le comportement thermique et la stabilité des cavités. Dans cette étude, les auteurs discutent des caractéristiques de résistance et de déformation, obtenues par essai de tension uniaxial et essai de compression à basse température. En se servant des résultats, ils analysent la répartition de la température et des pressions autour des cavités, lors du stockage de GNL. Ils discutent ensuite le comportement thermique de la masse rocheuse autour des cavités.

Jan 1, 2003

By Y. P. Chugh

During late 2010, a scientifically founded water spray system was developed for continuous miners (CM) (Patent Pending) that reduces respirable dust exposure for miner operator by about 30%. It includes engineered sprays around the cutting drum, outer bit-ring sprays, chassis sprays and side cutter boom sprays. About 3.6 ? 4.5m (12-15 ft) behind these sprays is additional sprays that spatially cover the area between the CM chassis and the mine roof and ribs. The spray system uses approximately the same volume of water as currently used on CMs with similar operating pressures. An Illinois mine decided to implement these concepts on a CM during rebuild stage. Dust control performance of the rebuilt CM was evaluated using gravimetric sampling and real-time monitoring using multiple personal dust monitors (PDMs). The average results based on about 105 cuts show about 30% and 20% reduction in dust exposure for the miner operator, and the haulage unit operator. Visibility in the mining areas was also significantly improved. The coal company has already decided to implement the system on all their CMs.

Jan 1, 2012

By S. J. Schatzel

Longwall coal mine operators in the US are required to ventilate multi-panel longwall districts but may have little or no knowledge about what happens to the ventilation air between the inlet evaluation points (IEPs), bleeder evaluation points (BEPs), and bleeder fans. The effectiveness of bleeder performance can directly influence the ability of a ventilation system to remove and dilute coal bed methane emissions. Consequently, the performance of coal mine bleeders is an important aspect of underground worker safety. U.S. coal mining stakeholders have acknowledged their belief that the T- junction split at the longwall face tailgate corner is very important in controlling the distribution of ventilation air. The percentage of air directed inby towards the bleeders and bleeder fan and outby to the submains is often not well-defined and can vary over the life of a longwall panel. To obtain direct measurements of bleeder performance, a tracer gas, sulfur hexafluoride (SF6), was released into the intake air stream along the panline of active longwall panels and in the bleeder/gob ventilation air inlets of an inactive panel. Tracer gas sampling was conducted underground using tube bundles attached to permissible vacuum pumps in the gateroads, former gateroads, and bleeders. Surface tracer gas monitoring was also conducted from operating gob boreholes and from bleeder fans. Testing was performed on multiple longwall panels which included various phases of longwall development and variable path lengths of ventilation air transport to bleeder fan installations. The applied methodology defines and describes coal bed gas pathways, rates, and volumes of movement at the bleeder/gob interfaces, and indicates flow rates for air/gas mixtures within these gobs. These findings are reported for three stages of longwall extraction using direct field-based measurements. Changes in the T-junction ventilation air distribution over the life of a longwall panel and its variable effect on panel ventilation airflow are discussed. These findings will assess the effectiveness of commonly applied ventilation strategies for improving air distribution and ventilation controls to meet statutory requirements and to achieve the desired ventilation patterns through multiple phases of longwall panel extraction.

Jan 1, 2011

By Nancy Estrada, Jane Nowell, Cathy Jennings, Debra Yniguez, Carol Lavery, Kristin Harrer

Pilots of the MH-60S helicopter are exposed to continuous whole body vibration (WBV). Pilot fatigue is a growing operational concern due to the increased frequency of extended durations of missions (6-8+hours) in support of Operations Iraqi Freedom and Enduring Freedom. Endurance aspects of the currently used rotary wing seating systems were not optimized for the longer missions and wide range of pilot anthropometric measurements, which is now typical of naval aviation. The current seating systems were designed primarily to meet crashworthiness requirements, not for the wide range of pilot anthropometry or to mitigate WBV. Albeit, an issue, pilot fatigue and reduced mission effectiveness are also critical concerns. Current Hazard Reports indicated that pain in pilots’ legs and backs begin two to four hours into the flight and increase with time. Mission readiness also decreases with an increase in flight duration due to the constant distraction of pilots shifting in their seats while trying to get comfortable. Froom, et al [2] reported a dose-response relationship between the length of military helicopter flights and back discomfort. He also concluded that this pain is typically dull, over the lower back, and its prevalence and intensity are dependent on the total flight hours of exposure. Methods This study evaluated WBV produced in the pilot seating systems onboard the MH-60S. The purpose of the study was to test and compare the effectiveness of two different seat cushions, the current seat cushion versus an anti-vibration seat cushion. Both seat cushions were measured for acceleration levels averaged over five-minute intervals using a triaxial seat pad accelerometer. The recordings were completed for a 3-hour straight and level flight. A frequency analysis from 0-80 hertz (Hz) was conducted on all acceleration measurements to determine the dominant axis and frequency of the pilots’ vibration exposure. The results were then compared to the applicable Threshold Limit Values (TLVs) established by the American Conference of Governmental Industrial Hygienists (ACGIH) [1] and the International Organization for Standardization (ISO) 2631.1 [3] to determine the MH-60S pilots’ permissible exposure time for both seat cushions. Results The results of the study showed that for both seat cushions the vibration levels of the z-axis at 16 Hz had the shortest allowable exposure duration, according to the ACGIH TLVs. In the z-axis at 16 Hz, the MH-60S’s current seat cushion’s acceleration levels indicated an exposure time limit of approximately 6 hours, while the anti-vibration seat cushion’s acceleration levels pierced the 8-hour exposure time limit curve. This is shown in the graph below.

Jan 6, 2006

By J. C. Vreugdenburg, B. A. Dippenaar, J. Muller, T. L. de Vries

Iron ore fines are agglomerated to produce sinter, which is an important feed material for blast furnaces worldwide. A model of the iron ore sintering process has been developed with the objective of being representative of the sinter pot test, the standard laboratory process in which the behaviour of specific sinter feed mixtures is evaluated. The model aims to predict sinter quality, including chemical quality and physical strength, as well as key sinter process performance parameters such as production rate and fuel consumption rate. The model uses the finite difference method (FDM) to solve heat and mass distributions within the sinter pot over the height and time dimensions. This model can further be used for establishing empirical relationships between modelled parameters and measured sinter properties. Inputs into the model include the feed material physical properties, chemical compositions, and boundary conditions. Submodels describe relationships between applied pressure differential and gas flow rate through the bed of granulated fine ore particles, combustion of carbonaceous material, calcination of fluxes, evaporation and condensation of water, and melting and solidification. The model was applied to typical sinter test conditions to illustrate the results predicted, and to test sensitivities to parameters such as feed void fraction, feed coke percentage, and the fraction of combustion heat transferred to the gas phase. A model validation and improvement study should follow, ensuring sinter test results are free from experimental errors by conducting repeated tests.

Jan 1, 2015

By W. A. Gericke, B. Olmstead, I. Mc Dougall, C. F. R. Smith

A finite element model was generated of a Søderberg electrode in a ferromanganese smelter. In this model, the casing and fins were modelled explicitly, and temperature-dependent material properties were included. A two-stage analysis procedure was used, the first part being a coupled thermal-electrical analysis using an applied DC current. As the casing material was non-magnetic, the DC current was deemed sufficiently accurate for this initial analysis. The proximity effect was not considered. Thermal boundary conditions based on assumed temperature distributions in the furnace were applied. Calculated temperatures agreed well with measured values. The joule heat calculated in this step was applied as a load to a coupled thermalstress analysis. The model was applied to a comparative study of alternative materials for the casing and fins. A number of different combinations of materials for the casing and fins were evaluated in a comparative study. The position of the baking zone was used as the criterion for evaluating the potential of each material combination. Based on this analysis, some material combinations were discarded as being entirely unsuitable, whilst the two most suitable combinations will be tested experimentally in the furnace. The stress analysis was performed on the most suitable option. The practical advantage of this analysis was that a number of what-if scenarios could be evaluated and discarded prior to embarking on expensive experimental work, thus limiting the amount of experimental effort required. A mathematical model allows for the comparison of options under controlled conditions, where parameters of interest can be varied individually, with all other parameters remaining the same, a condition which is difficult to achieve in an operating furnace.

Jan 1, 2004

By Thomas Barczak

Roof support systems are designed for roof control to prevent unplanned falls. It sounds logical and has been the conventional thinking in support design since supports were first installed. In order to determine which support system should be used or which would be the most effective, the degree of control provided by the support system must be known. This question embodies the concept of a ground response curve, which is a measure of support control by assessment of the convergence in the mine entry as a function of the support capacity. In this National Institute for Occupational Safety and Health (NIOSH) study to optimize standing roof support design, ground response curves were developed for longwall tailgate conditions from numerical models of Pittsburgh Coal Seam geology. The models were calibrated against tailgate convergence measurements that were made in two Pittsburgh Coal Seam mines as the depth of cover varied during the panel extraction. Ground response curves were developed for four loading conditions: (1) development, (2) side abutment, (3) front abutment near the longwall face, and (4) full extraction inby the face. In general, the tailgate convergence and required support capacity increase through each of these loading stages. It was concluded that prior to failure of the rock mass, the support system regardless of its capacity has relatively little impact on tailgate convergence. Recognizing that the support cannot prevent much of the (pre-failure) convergence that is occurring is an important part of support design. Supports that exhibit high loading stiffness but cannot sustain that loading through a displacement compatible with the ground response curve will not provide adequate roof control because they can fail prematurely. The required capacity depends on the loading plus yielding characteristics of the support and the amount of rock failure that has occurred. The loading plus yielding character establishes where the support loading intersects the ground response curve. Design criterion for support capacity based on the identifying the onset of strain-soften rock response leading to ?damaged roof? is proposed as a foundation for assessing support design requirements. The capacity without accounting for the loading and yielding character of one support should not be used to assess the capacity requirement of an alternative support design, particularly when the loading and yielding characteristics are significantly different. A sensitivity study was made to evaluate the impact of mining height and overburden depth. As expected, the results show that convergence increases with increase in mining height and increase in overburden depth. Some specific support examples are also analyzed. Although this is a first step and the two-dimensional numerical models have limitations, these initial studies provide valuable insight into the control provided by the roof support system and will ultimately lead to optimizing support design based on specific mine site conditions.

Jan 1, 2008

By James A. Finch, Jason S. Doucet, Cesar O. Gomez

"Exercising control over the physical environment of flotation as a step towards process optimization is the driving force for characterizing gas dispersion in flotation cells, a subject of considerable research and still not fully understood. From an operational standpoint, however, there are just a few variables that can be manipulated to manage gas dispersion on a cell-to-cell basis, the most important being gas rate (superficial gas velocity Jg). Measurements in eight plants demonstrate there is often no strategy for distribution of gas to cells in a bank, i.e., there is no particular Jg profile. Two exercises where Jg profiles were set allowed metallurgical performance to be manipulated and an optimum Jg profile to be selected. To facilitate setting Jg profiles, a multi-unit device based on McGill Jg sensor technology is introduced. Possible directions for gas dispersion management are discussed.INTRODUCTIONThe earliest patents regarding the flotation process ignored the importance of air and in certain cases, steps were taken to eliminate bubbles from the system (Nelson and Smit, 2005). Rickard (1916) described a keen metallurgist who observed better than expected performance and hypothesized that entrained air was enhancing the process. Within a few years of this observation, the basic concept of modern froth flotation was developed whereby air is dispersed into slurry to induce bubble particle contact.As research into flotation advanced, the link between performance and the flow-rate of air entering the cell was established. In the first volume of the International Journal of Mineral Processing, Harris (1974) described the importance of airflow-rate and derived parameters such as the superficial gas velocity (then called the superficial airflow velocity) as being important parameters for cell design and scale-up. Mehrotra and Kapur (1974) presented research suggesting that the rate of flotation was strongly correlated to the aeration rate. McKee et al. (1976) continued to demonstrate the importance of airflow-rate linking it to the entrainment rate of hydrophilic gangue material."

Jan 1, 2006