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By A. C. Hatton

Doped SrCoO3.8 was found to be a promising material for use as a cathode component in intermediate temperature SOFCs. In this work, strontium cobaltite ceramics doped with 10 mol% to 90 mol% samarium were synthesized using the glycine nitrate process in order to study the electrical conductivity and thermal expansion at temperatures of up to 800°C. As-synthesized powders were deagglomerated, pressed and sintered at temperatures ranging from 1100-1250°C. The effect of temperature and composition on electrical conductivity and thermal expansion are presented and discussed.

Jan 1, 2005

By N. Kubo

Sumitomo Toyo Copper Smelter and Refinery was commenced in 1971, and its production capacity of sulfuric acid was 550tpd at the beginning. In 2001 Toyo Copper Smelter and Refinery projected to expand its copper production capacity to 450,000tpy, and now the project is still in progress. To achieve this expansion project, 4,000tpd of sulfuric acid production capacity is necessary to the acid plant. So as a part of this project, the construction of the new converting and absorbing line and the improvement of the existing converting and absorbing line were carried out from 2001 until 2005. Then the production capacity of these 2 lines has already reached the target, 4,000tpd of sulfuric acid. Moreover, at the design of the new line, we adopted several latest technologies and materials in order to construct the world's leading acid plant. Basing on the operation performance of the new line, we have improved the existing line in 2005. Both of these 2 converting and absorbing lines are working quite well and contribute to big energy saving and excellently stable operation. Cu2007

Jan 1, 2007

By Finch. J. A., C. Perez, J. M. Ortiz, G. Cortes, A. B. Yañiez, F. Coddou, P. Morales, H. Elgueta

A campaign to perform characterization tests in a TankCell®-300 flotation cell installed at Chuquicamata Codelco's concentrator was conducted. The campaign included integrated gas dispersion measurements (gas velocity radial mapping and single point gas holdup and bubble size) and determination of frother concentration. Cell streams were sampled to assess metallurgical performance at the same time. The experimental program was designed to establish the bubble surface area flux operating range and its effect on performance, and the effect of using longer residence times and of a device designed to enhance mixing in the collection zone (FlowBooster(TM)). The gas dispersion results and their relationship to metallurgical performance are discussed.

Jan 1, 2009

By Wei Zhang, Jinhong Zhang

"The adsorption of ethyl xanthate on copper sulfides, i.e., chalcopyrite, chalcocite and bornite, has been studied in situ in aqueous solutions by applying an atomic force microscopy (AFM). AFM images show that xanthate, such as potassium ethyl xanthate (KEX), adsorbs strongly on chalcocite and bornite mainly in the form of insoluble metal xanthate, which binds strongly with the mineral surface without being removed by flushing with ethanol alcohol. This adsorption mechanism is totally different from the one obtained with chalcopyrite/xanthate system, during which oily dixanthogen is the main adsorption product on chalcopyrite surface. The findings obtained from the present AFM study suggest that an AFM image analysis is a powerful tool for the study of the collector’s adsorption on mineral surface and as well the development of novel collector for copper sulfide flotation.INTRODUCTIONIn mining industry, copper sulfide minerals, i.e., chalcopyrite, chalcocite and bornite, are usually separated selectively from non-valuable gangue by froth flotation, which treats the highest throughput and produces the maximum economic outcome of any surface chemistry process. In flotation, collectors are added into the pulp (mixture of water and fine-grained minerals) to selectively adsorb onto the target mineral and render its surface with high hydrophobicity, which is generally beneficial for a strong mineralbubble attachment and thus a high flotation recovery.The adsorption of collector on mineral surface, therefore, is vital for a successful flotation process and it has been studied by applying various surface analysis techniques, such as IR (Infrared Spectroscopy), CV (Cyclic Voltammetry) and XPS (X-ray Photoelectron Spectroscopy). (Poling, 1963; Allison et al., 1972; Mielczarski et al., 1984; Leppinen et al., 1989; Kartio et al., 1996) These studies have revealed a lot of information, such as the reaction, product and mechanism, of the adsorption of chemicals on mineral surface. It is also of great interest to directly get the image of adsorbed collectors on mineral surface changing with pulp chemistry, such as pH, redox potential, ionic strength and chemical’s dosage."

Jan 1, 2016

By Alexandre Desbarats, Michel David

"All optimum pit design studies start from the geological are reserves inventory, the estimated grades of all blocks of potential are within the interpreted limits of the deposit. The actual optimization procedure is then carried out on block valuations based on these estimated grades. Thus, the relevance of any pit design can be seen to depend directly on the ore reserve estimation . To insure a proper pit design, a first step would be to use a geostatistical reserve estimation technique such as kriging, however, this is not enough. A frequently neglected fact is that the blocks of ore estimated during the planning stage of the mine are usually considerably larger than those on which the ore-waste selection will be made at the time of mining. Experience in the exploitation of large low-grade deposits has shown that large blocks, estimated to be are, when mined selectively in smaller blocks, often yield significant amounts of waste material. This phenomenon, known as internal waste, is a function of the variability of the grades, the size of mining unit and the amount of sampling information on which ore-waste decisions are made.In this study, it was proposed to consider the effect of internal waste caused by selective mining, on. pit design, using geostatistical methods to predict the tonnage and grade of recoverable reserves within large blocks.Optimum pits obtained using a block valuation formula taking into account the recoverable reserves within large blocks were compared with optimum pits obtained using a conventional block valuation formula. It was found that the optimum pits obtained by the proposed method had the highest total valuations and thus were, in fact, ""more optimum”. These pits were characterized by greater are tonnages at a lower average grade, the additional ore more than compensating for the drop in grade. It was also found that the consideration of internal waste in pit design could considerably alter pit limits in marginal areas of the deposit.It was concluded that selective mining had a significant, potentially critical, impact on the design of optimum pits especially in the case of large low-grade deposits."

Jan 1, 1984

By Kurt D. Mitchell

"This paper discusses general application for A C variable frequency drives in the mining industry. A review of induction motors characteristics, adjustable frequency controller fundamentals, and three commonly used controllers is presented. General application guidelines for the three different types of controllers; variable voltage input , current source input and pulse width modulated are then reviewed in detail, and an example of the economic benefit of this technology is discussed. IntroductionSoon after static DC variable speed drives were well established in industry, a need for static AC variable speed drives was seen. The first technical papers describing possible systems appeared in the mid-1960s, with commercially available units arriving in the early 1970s. Without exception, static AC drives are substantially more complex than their DC counterparts, but they have some very desirable properties. As compared to DC motors, AC motors are less costly, physically smaller, more reliable, require less maintenance , easily sealed, have good load regulation, are able to run at higher operating voltages, and have little danger of over-speed runaway . These properties are particularly desirable in explosion-proof, submersible or difficult accessibility applications.Variable speed AC drives are now a proven technology. available in packages from Sub-horsepower to hundreds of horsepower, from 115VAC to 4160 VAC. This paper covers the principles of operation of three common types of controllers, application criteria, motor consideration and finally an example of how an AC variable speed drive can pay for itself in terms of energy savings."

Jan 1, 1986

By E. M. De Souza, A. M. Coode

"Since potash was discovered substantial rock mechanics research has been done to develop the technology needed to cope with the unique conditions in Saskatchewan mines, to assure general mine safety and to assess the problems associated with mining potash at depth.The practical result of this research was the development of multiple entry systems incorporating yielding pillars for access ways and the chevron type layouts for production panels. These developments proved the viability of extracting potash from between 950 m and 1100 m depth using a high degree of mechanization. High extraction ratios could not, however, be achieved using the developed technology.The presence of a competent salt back is critical to mining the potash, and underground practice is governed by the presence of anomalous geological zones. These factors may be associated with the occurrence of brine inflows. One potash mine in Saskatchewan ceased its underground operations and was closed due to flooding of the entire mine. Two other potash mines in Saskatchewan had significant brine inflows. The costs involved in brine pumping, equipment relocation, bulkhead construction, grouting, and in auxiliary operations can run into the tens of millions of dollars.At Central Canada Potash, the use of stress relief and yielding pillars in the design of the mining layouts has resulted in over-all stable underground excavations and safe mining practices. There are two types of production room s, the chevron and the hybrid, which result in a planned block average extraction ratio of 35010. Mining activity has resulted in brine ingresses in two areas, and additional operating costs have been incurred over the years. These mining areas have demonstrated abnormally high closure rates, and rapid back deterioration. A program was established in those two areas to ensure the practice of safe mining procedures.The short-term perspectives inherent in the program included the elimination of all uncertainties associated with the possibility of an increase in brine inflow leading to flooding, the elimination of the abnormal ground behaviour and ground deterioration in the inflow areas, and the reduction of the long-term adverse effects of mining on regional mine stability. The program was also designed to provide means for developing alternative safe mine layouts which would improve the exploitation of potash resources. Details of the extensive work performed during the program are found elsewhere (E. De Souza, 1988).Grouting and salt backfilling are viable techniques to control brine inflows in underground excavations in potash mines. Detailed instrumentation of the backfilled test areas provides information on the long-term behaviour and effectiveness of the grout/backfill system, allowing for rational decisions on the complete abandonment of these mined out areas, thus resulting in considerable operational cost savings.This paper is presented in two parts: the first addressed the problems of diamond drilling , grouting and backfilling in Panel 209 and the second, addresses the problems of instrumentation and rock mechanics."

Jan 1, 1990

By Zia Pirzada

"Time is of the essence" and "Time is money" These are powerful and true statements during a project life cycle and have far-reaching implications on the success and failure of the project Time and progress management is crucial to the project success. Project delays may increase the cost to an unacceptable level and may render the project as economically unfeasible. On the other hand, if the project is completed on time or earlier than as planned, it may generate economic benefits greater than what had been envisioned To take advantage of the financial opportunities and to improve the cash flow as well as Return On Investment (POI), project schedule can be accelerated to complete the project earlier than planned Project schedule acceleration can be achieved by using analytical tools, such as "Schedule Optimization", "Schedule Reduction", "Schedule Compression" or a combination of any of these concepts along with the "Planning for start up". Schedule optimization does not entail any extra cost, however, other acceleration methods, such as Schedule Reduction and Schedule Compression, may require extra expenditures from the owner. Based on the forecasted early start of the revenue stream, the extra expenditure could become a worthwhile venture with a very high rate of return To accelerate the schedule, all aspects of the project should be reviewed with acceleration costs calculated. All risks and opportunities should be evaluated and taken into consideration to determine if the acceleration is feasible and advisable and will provide definite financial advantages Sometimes schedule acceleration may be desired to prevent the company from paying liquidated damages. This is especially true when the project is not expected to complete on the contractual completion date and when the cost of acceleration is less than the liquidated damages that may accrue against the company.

Oct 1, 2010

By E. Wright

"INTRODUCTIONThe Ruttan Mine is located twenty-two km east of Leaf Rapids in northwestern Manitoba. The copper-zinc exhalative massive sulphide deposit is comprised of a series of individual and interconnected en echelon lenses which strike east 20 degrees north and dip south 70 degrees. The mine has been owned and operated by the Hudson Bay Mining & Smelting Company since July 1987. Sherritt Gordon Mines Limited began mining the orebody in 1973 from an open pit, but production has been entirely from underground since 1980. HistoryDuring the progression from open pit to underground mining, it was recognized that manual methods of ore reserve calculation were inadequate for responding to changing metal prices and evaluating alternative mine plans. The mine planning system that was developed is described in the paper, ""Computerization of Ore Reserves and Mine Planning Functions at Ruttan Mine"", presented by B.C.W. Haystead at the 1984CIM Annual General Meeting. At that time, programs for core logging, diamond drill hole plotting, grade interpolation, ore outline digitizing, and reporting had been developed by the Systems Department for use on Sherritt's UNIVAC 1100 mainframe computer. Telecommunications linked terminals at the Ruttan coreshack and office to the UNIVAC in Fort Saskatchewan, Alberta. The same mine planning system was also used at a second property.Operation of the mine planning system was expensive, and it was evident that increased use required a costly upgrading of the UNIVAC in order to maintain an acceptable service level to all users. The system was re-evaluated,' and it was concluded that: core logging was not easily adaptable to a new property, nor flexible enough for exploration; plotting, grade interpolation, and digitizing required considerable manual effort; and that the UNIVAC operating system was difficult to learn.It was recommended that a study should determine if: core logging could be redesigned and/or implemented on a microcomputer; interactive graphics be used to reduce the effort for functions requiring visual interpretation; and the creation of input processors would assist users in setting up parameters for guiding the programs."

Jan 1, 1989

By A. G. Matyas, B. Wasmund, R. C. Francki, K. M. Donaldson

"The construction of large. high-power electric furnaces has been an important factor in the growth of electric smelting technology . New developments in the design and operation of electric furnaces have been spurred by the escalating cost of electric power and increasingly stringent environmental constraints. Key areasofprogress include the application of high voltage to enhance furnace productivity; the installation of novel furnace cooling elements and robust binding systems to extend furnace life; development of process schemes to reduce power consumption by preheating and prereduction of the charge; and environmental control improvements for handling fine dusty feedstocks, and for furnace sealing.This paper reviews these developments and outlines a systematic approach for their application in the custom design of new or retrofit electric furnace facilities.IntroductionThe use of electric smelting furnaces has continued to progress during the last decade. Electric furnaces offer high throughput capacity and productivity. In addition, they produce minimum environmental impact, as the furnaces can be readily sealed, and only a small quantity of off-gas is generated. Electric furnaces present the most favourable choice of smelting technology where high process temperatures in excess of about l400°C are required.Their application is burdened by the escalating cost of electric power, hence it is important to seek new opportunities through further technological development. This paper reviews recent developments in the design and operation of high-power electric smelting furnaces, in the following areas:"

Jan 1, 1993

By P. C. Richards

"Future Integrated Gasification Combined Cycle (IGCC) power plants will have superior environmental performance and unmatched efficiency.The Shell Coal Gasification Process (SCGP) is a clean coal technology, which can convert a wide range of coals into clean syngas for high efficiency electricity generation in an IGCC plant. SCGP flexibility has been demonstrated for feeds ranging from bituminous coals to lignites and petroleum coke, and the process is ideally suited for combined cycle power generation, resulting in efficiencies of 42% to 46% (LHV).In the Netherlands, a 250 MWe coal gasification combined cycle plant based on Shell technology is being built by Demkolec, a development partnership of the Dutch Electricity Generating Board (N. V. Sep). The plant is scheduled to start up in 1993. IntroductionBasic ConceptShell's experience with gasification dates back to the 1950s, when the first Shell Gasification Process was commissioned with oil as feedstock. There are now over 140 SGP gasifiers licensed. The experience gained on oil gasification provided a firm theoretical and practical base for the start of coal gasification process development in 1972.At that time, there were serious concerns about the future availability and price of crude oil. Coal gasification (making carbon monoxide and hydrogen by the partial oxidation of coal) was considered to be an important option for refinery applications, because the synthesis gas (syngas) produced can be used as:• a chemical feedstock for making transportation fuels and chemicals;• a source of hydrogen (making use of the water gas shift reaction) for upgrading petroleum products; and• a fuel for heating process streams and/or generating electricity."

Jan 1, 1994

By F. L. Pellet, S. Maiolino

"The determination of rock bolt contribution to reinforced joint shear strength is still a challenge, especially for assessing reinforced rock mass stability. For this purpose, several experimental studies have been performed during the last decades, mostly on small scale rock joint and bolt specimens. However, to accurately assess the rock bolt contribution, scale effect has to be accounted for. For this reason full scale lab tests are required as an alternative to in situ tests for which boundary conditions are more difficult to control.In this paper the results of an experimental program carried out with a large shear box, dedicated to test bolts in full scale conditions is presented. Different rock bolt diameters and different rock bolts inclination with respect to the shear plane were tested Experimental results were satisfactorily compared with an analytical model which is able to compute the contribution of the rock bolt to the shear strength of the joint as well the associated displacement of the joint. These conclusions allows us to validate the model in order to help the designer of reinforced rock engineering structures, such as slope or underground openings, to precise the optimum installation of rock bolts. INTRODUCTIONFully grouted rock bolts are commonly used for rock masses reinforcement to ensure the stability of rock slopes and underground cavities. For this purpose, the determination of rock bolt contribution to reinforced joint shear strength is of the utmost importance. During the last decades, several experimental studies have been performed to investigate the behavior of bolted rock joint. For obvious reasons, almost all the experiments were achieved on small scale bolted rock joint specimens (Bjurström, 1974; Azuar, 1977; Dight, 1983; Egger & Fernandes, 1983; Schubert, 1984; Spang & Egger, 1990; Egger & Zabuski, 1991). These studies made it possible to assess the influence of different parameters such as the bolt’s diameter, the number of bolts, the angle between the bolt and the joint, the nature of the rock, the friction and the dilatation angle of the joint. However, to accurately assess the rock bolt contribution, scale effect has to be accounted for (Vallier et al., 2010). For this reason full scale lab tests have been performed as an alternative to in situ test for which boundary conditions are more difficult to control."

Jan 1, 2015

By T. Lamb, T. Aston

"The Gays River Mine is located within a complex hydrological regime and underground mining environment. Early in the mine history, the operation was' affected by an inability to control mine water inflows. More recently, the reopened mine operation had been unable to maintain consistent drainage of groundwater to the mine workings and sustain low groundwater levels.In 1992, a series of investigations were completed, which in part Were funded under the Canada-Nova Scotia Mineral Development Agreement. The studies undertaken included: hydrochemical and drainhole well screen assessments, an air photo study of sinkhole features, numerical modelling studies and a major piezometer installation and overburden soil study. The results indicate that the water draining to the underground workings is comprised of two distinct components: precipitation over the drawdown cone catchment area and seepage from the nearby Gays River. In addition, a third ""balance"" component was' also found, which represents uncertainties in the areal extent of the drawdown cone and river seepage components.After outlining the history of the groundwater problems experienced at the Gays River Mine, this paper examines the various studies undertaken during 1991-1992 and concludes that control of groundwater levels in the mine area is achievable. A number of recommendations are also proposed for future study ."

Jan 1, 1993

By Stanley G. Butcher

Predictions of coal cleaning plant performance from the washability data are traditionally used at the conceptual design stage of a coal preparation plant to confirm process selection. The development of computer programs which simulate the operation of a plant facilitates the optimization of product yield and quality, and ultimately proceeds. It is shown that the optimum is sensitive to changes in mine operations and market price structure. A computerized review of operations is thus recommended as an on-going activity .

Jan 1, 1979

By Lynn C. Fister

"Coal is rapidly becoming a major alternative to oil. According to the World Coal Study Final Report, total world coal trade could approach one billion tons annually by the year 2000. To facilitate the increased production and export market potential of the coal producing countries, advancements must be made to improve the transportation systems. Coal slurry pipeline systems could play a significant role in achieving these market forecasts.There are three major components to a coal slurry system the preparation plant, the pipeline and the dewatering plant. The experience and expertise gained from the Consolidation Coal Company system in Ohio, the Black Mesa system in Arizona and ETSI's Coal Evaluation Plant demonstrate that slurry pipeline technology is proven and available to meet the coal transport challenge.The costs of transporting coal by slurry pipeline can offer significant savings, as about 70 per cent of its costs are fixed. The reverse is true for railroads, where 75 to 80 per cent of the costs vary with inflation. All forms of transport-rail, barge and pipeline-will be required to move the massive volumes of coal. Coal slurry systems can provide a viable transport alternative.IntroductionThe importance of coal as a major alternative to oil is now well known and accepted throughout the world. Increasing oil prices over the last eight years have had a serious effect on national economics, particularly in those countries that are heavily dependent on oil. Coal can replace oil as the principal fuel source which could support world economic growth over the next two decades. This is the main conclusion of the World Coal Study (WOCOL) Final Report, published in May 1980.The product of that report was a result of considerable deliberation by key industry leader s and energy experts. The underlying message of the World Coal Study is that our energy and economic problems can be faced with confidence if coal use doubles by the early 1990s and triples by 2000, and if steam coal trade expand s considerably."

Jan 1, 1982

By B. MohammadSadeghi, S. Bakhshivash, M. Haghshenas, F. Rahimi

"Spring-Back/Forward in sheet metals is defined as recovery of elastic strain upon unloading in a deformed sheet specimen. Since this phenomenon can cause alternation in the dimensions of a part, leading to irrecoverable compensations, the operative parameters need to be investigated, thoroughly. To assess spring-forward and effective bending parameters, V-shaped bending dies are the most commonly used experimental approach. In the present research, the effect of bending angle and punch tip radius on the spring-forward behavior of an Al-Mg-Si alloy sheet specimen is studied. To this end, a V-shaped die with four bending angles (i.e. 30°, 45°, 60°, and 90°) was designed and fabricated. Specimens with thickness of 2 mm were cut with dimensions of 50 mm×10 mm. Results show that by increasing the bending angle, the spring-forward angle decreases. In addition, smaller punch tip radiuses lead to further spring-forward. The effect of these parameters on the amount of spring-forward angle, strain distribution and homogeneity along sheet thickness was assessed using finite element analysis (FEA). Simulation results show that as the bending angle increases, the strain is developed more homogenously. Finally, micro-hardness test was used to study the effect of strain hardening caused by bending operation on strength evolution. Results show higher hardness trends for the zones in which the maximum plastic strain occurs.INTRODUCTIONPrecise production plays a significant role in the durability of a part. When it comes to sheet metal forming, this issue should be taken into account as an important factor. In order to predict the alternations, bending dies with special geometric parameters (i.e. V-shaped, U-shaped and L-shaped dies) are commonly used (Wagoner, Lim, & Lee, 2013)."

Jan 1, 2016

By Philippe Monier, Frank C. Basham

"This paper outlines the scope and applications of 'COALMOD', the British Columbia Ministry of Energy, Mines and Petroleum Resources' computerized financial simulation model for coal mining developments. After a description of the computer system and language of implementation, the logic and scope of current model sub-routines are presented. This is followed by a presentation of examples on the current applications of the model to public policy evaluation, including benefit-cost analysis, fiscal analysis and evaluation of the effects of public infrastructure investments made in support of mining projects.IntroductionThis presentation has been developed in response to a number of requests from coal mining companies and various public agencies who have indicated interest in understanding our application of contemporary analytical techniques to public policy in the coal sector. In particular, the subject of this paper is an explanation of COALMOD. a mnemonic given to a computerized, mine-specific, financial simulation model which is assisting the Government of British Columbia in evaluations of new coal projects, assessment of public sector investments made in support of these projects and. more generally, measurement of the financial effects of current or proposed government policies, and factors outside immediate government control such as coal prices and transportation costs."

Jan 1, 1981

By L. D. Smith

"Those who submit competing proposals for projects seek to present senior management with complete and fully supported material that will not fail under questioning. Hopefully, misleading notions and omissions will have been minimized and there will have been testing of the assumptions regarding the economic, social and political environments.A capital project evaluation team can do management and itself a service by including a sound approach to the impact of inflation (and its twin problem, interest) on a project and a great disservice with an inappropriate approach to inflation.InflationHandled deftly, inflation can alter a project evaluation to show almost any result the handler desires. It must be a constant source of frustration for design people and cost estimators to spend weeks perfecting the technical aspects of a project in order to minimize costs, only to have all of their efforts set awash in a sea of financial and economic assumptions that submerge all of the detail. In all of this, inflation is perhaps the largest offender, with inflation criteria often being brought to bear at the last minute, almost as an afterthought. Perhaps this tardiness reflects the difficulty of the subject and the belief that senior management will take its own approach to the problems of inflation. Such a belief is unfair to senior management, for it is entitled to not being misled by omission. It is entitled to the full use of the skills of the evaluating team, including reasonable assumptions of the impact of inflation.Working in a consulting context, one has the opportunity to participate in the evaluation of a large number of projects."

Jan 1, 1990

By K. M. Ed

AN explosive is a solid or liquid substance which, when fired by some means, changes into a gaseous product occupying a volume very much greater than its original volume. The great speed at which this change takes place causes the explosive to exert a sudden blow on adjacent material. It is this action which is effective in blasting operations when the explosive, confined in a shot-hole, is fired. All explosives are similar in one respect, in that the change into the gaseous state is accompanied by the production of hot gases or flame. This results from the rapid combustion of the solid or liquid ingredients. Ex-plosives differ greatly, however, in the speed at which the reaction takes place. Black blasting powder, for instance, reacts comparatively slowly, hence the flame persists for an appreciable length of time. High explosives, on the other hand, react much more quickly; consequently, the flame is of much shorter duration. In 'closed-light' or 'gaseous' coal mines, the use of ordinary explosives is generally prohibited, due to their inherent ability to ignite gas or coal-dust by reason of the flame which they produce when fired. For instance, black blasting powder, which produces a flame of long duration, is not ordinarily considered safe to use in such mines; neither are ordinary dynamites, as their flames, while shorter than that of black blasting powder are, nevertheless, of sufficient temperature and duration to cause ignition of fire-damp or coal-dust. For this reason, specially formulated high explosives, called 'permitted' explosives, should invariably be used in such mines.

Jan 1, 1940

By K. van Netten, T. P. Ernst

"Froth flotation has been used successfully for about a century in the beneficiation of both coal and mineral particles. With the on-going trend towards lower feed grades, however, there is a need to transform this technology in ways that can deliver ultrafast separations, with strong selectivity, and recovery, covering a broader size range. It should be recognised that the hydrophobic effect, with its highly selective and long-range interactions, will most likely underpin any new technology. We identified the separation of the concentrate from the tailings as the rate determining step of conventional flotation technology. This limitation was then addressed by developing a novel flotation technology, insuring the formation of a concentrate that could be separated more rapidly from the tailings. We introduced a novel binder medium, a highly concentrated water in oil emulsion, to act as the focal point for hydrophobic adhesion, effectively replacing the air bubbles used in conventional flotation. The hydrophobic particles adhere to and become embedded within the binder, forming saturated agglomerates that float upwards. Moreover, by forming these large and resilient agglomerates, the product can be quickly dewatered over a screen and separated almost immediately from the tailings. Remarkably, this new binder permits residence times in the order of a few seconds under batch conditions. This paper examines the performance of the technology as a function of the oil wt% added to the slurry. The paper also examines the performance of the technology as a function of the particle size, showing a decline as the particle size exceeds 0.50 mm.INTRODUCTIONFroth flotation involves the collision and adhesion of hydrophobic particles to rising air bubbles, the carrying of those particles from the bubbly-pulp zone into a froth zone, and subsequent drainage and migration of the pulp to achieve the final concentrate (Wills, 2006). Within a Jameson Cell the feed slurry and air bubbles are brought into intense contact within the active area of the downcomer, achieving rapid kinetics of hydrophobic particle adhesion to the air bubbles (Harbort et al., 1994). However, once the bubble laden product and tailings emerge from the downcomer there is the need for separation of the concentrate from the tailings, an inherently slower process. In other devices such as mechanical cells the initial kinetics of particle adhesion are far slower, relying on the turbulent eddies throughout the cell, while in a column the kinetics rely upon an even slower process of bubble interception with suspended and settling particles (Gorain, 2007). However, in all cases the driving force for segregating the bubbles from the tailings, and the drainage of the froth are inherently the same. We do note, however, recent advances by Galvin and co-workers in achieving so-called Fast Flotation, utilizing a system of inclined channels to dramatically increase the segregation rate of bubbles from the tailings, permitting much higher gas and feed fluxes to be applied, achieving up to a ten-fold throughput advantage (Dickinson et al., 2014). Any further improvement within the existing flotation paradigm would require the introduction of centrifugal forces, but this would also require the formation of much finer bubbles than is typically used given the tendency of relatively large bubbles to reach a limiting slip velocity due to deformations and increased drag. Across all flotation devices we argue the rate determining step remains the segregation of the bubbles from the tailings."

Jan 1, 2016