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By B Reid

"Since the commencement of mining operations at the Cowal Gold Operations (CGO) in 2005, reverse circulation (RC) drilling has been the preferred method for grade control (GC) sample collection. This method was selected because it allowed:for multibench drilling (20 m hole depths for two benches of mining) to aid mine planning increased data density for comparison against the wide spaced ore reserve model angled drill holes to intersect perpendicular to the strike and dip of the shallow dipping mineralisation ability to take two metre sample intervals to enhance the understanding of the mineralisation’s short-scale variability and provide the ability to flitch mine.From June 2008 to December 2013, RC GC was performed using a UDR rotary cone splitter. The field duplicate data over the period displayed strong precision, with a correlation coefficient of 0.94 and an average relative per cent difference (RPD) of 21 per cent for gold. Up to 66.1 per cent of field duplicate data greater than 0.1 g/t fell within ±20 per cent RPD. This is within limits of industry best practice. The Mine to Mill reconciliations over the same period showed the estimated GC grade was 7.7 per cent lower than the calculated head grade (CHG).In December 2013, the Progradex sampling system (PGX) was introduced at CGO due to its advertised ability to capture 100 per cent of the drill cuttings for the complete sample interval, inclusive of fines. Analysis of field duplicate data indicates that since the introduction of the PGX, the sample precision has drifted. From January 2014 to February 2016, the correlation coefficient was 0.92 and up to 51.2 per cent of field duplicate data, greater than 0.1 g/t fell within the ±20 per cent RPD. Over the same 26 month period, the Mine to Mill reconciliation improved to one per cent lower than the CHG. Granulometric analysis of the RC samples collected from the PGX indicated the fines material(<212 µm) averaged up to 22 per cent of the samples mass and following assay determination, the fines material represented a weighted average of 31 per cent of the total gold content within the sample.This paper highlights the:importance of the complete capture of all drill cuttings during an RC drill programinfluence of fines material on the sample quality and accuracyimpact sampling of the fines material has on the Mine to Mill reconciliation performancechallenges experienced in commissioning a PGX system.Citation:Reid, B, 2016. A Fine Looking Sample - the Importance of Fines in Grade Control Sampling to Mine to Mill Reconciliation, in Proceedings Ninth AusIMM Open Pit Operators' Conference 2016, pp 28–38 (The Australasian Institute of Mining and Metallurgy: Melbourne)."

Nov 15, 2016

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 R. Ratnagiri, B. Minaie

"In order to expeditiously produce defect-free metallic components in materials processing applications, the relationship between the process parameters and the product properties needs to be well understood while minimizing the production engineering iterations. To achieve this goal, a realistic mathematical formulation of the process should be carried out and an appropriate numerical modeling of various phenomena occurring in such process should be implemented. The materials processing of transforming the molten material into a finished metallic component involves fluid flow and solidification/melting. In the present paper, a finite element based analysis of the fluid flow ·and solidification/melting phenomena in cavities is presented and the various issues in modeling these phenomena are discussed. These transport phenomena play an important role in determining the final characteristics and material properties of the part by affecting the formation of defects and microstructure. A realistic numerical modeling of these phenomena can significantly reduce the rejection rates during the process and can increase the quality of the final product.IntroductionDuring the intelligent materials processing of various metallic components, it is often required to have a thorough knowledge of the behavior of the transport phenomena involved in this process. This is due in large to the coupling that exists between the transport phenomena and the final material properties of the components produced during materials processing. This interrelationship demands that the pertinent transport phenomena in the form of fluid flow and solidification/melting be studied and predicted accurately. In many materials processing applications, the fluid flow is in the form of either a forced convection free surface flow intended to fill a cavity or a natural convection flow resulting from the gravity when the cavity is filled. In either case, the phase change in the form of solidification/melting is also involved in order to complete the process. However, the thermal history during this phase change has a direct impact on the material properties of the final part and the possible defect formation that may be involved. This thermal history itself is dependent on the nature of the fluid flow during the earlier stages of the process. As such, there is a coupling between the fluid flow, phase change, microstructure, and defect formation in the resulting component. It is therefore necessary to analyze these phenomena in order to find optimum methods to produce good quality parts by minimizing the defects that may be generated. Such an analysis can result in the development of appropriate numerical models for the process that can facilitate the economical and timely manufacturing of various components with high consistency. The present paper discusses the issues related to the transport phenomena encountered during materials processing of components engineered largely by using various combination of convective fluid flow and solidification/melting in cavities."

Jan 1, 1994

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 V. K. Risinggård, M. Sparta

We report on the development of a finite-element method model for a pilot furnace for the production of manganese alloys. The model is a multiphysics model that addresses material flow, electrical conditions, heat transfer, and physical and chemical transformations. It is capable of studying both quasi-steady and transient states in time-dependent simulations. The model includes common charge materials and fluxes and can simulate production of both ferromanganese and silicomanganese alloys with acid and basic slags, as well as changing charge compositions. The model output provides access to the material distribution in the furnace during furnace runs, temperature profiles, current paths, energy balances, and alloy and slag production rates and compositions.

Apr 16, 2024

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

By Russell Frith

A review of published literature reveals case histories whereby the entire periphery of a coal pillar has “burst” out as a single event during first workings, the associated energy and material release causing significant damage to adjacent roadways and any equipment/infrastructure located within said roadways. Such events are distinct from coal burst events during first workings such as that at the Austar Mine in 2014, or those linked to overburden bumps related to either horizontal stress-driven slip along major faults and/or thick, massive strata units in the overburden or floor of the coal seam.

By Stephen Mansfield

Analysing how accurately a blast design is implemented is one of the cornerstones of a successful operation, and critical for mine optimisation. This paper presents a concept that involves the collection and analysis of data for the five stages through which a blast transitions, from budget through to implementation.

Feb 1, 2020

By T. L. Joseph

A DEMAND for specialized knowledge has directed engineering curricula towards competency in some particular field or occupation. Preparation for life in a broad sense of completeness has received little consideration. Ways and means are needed for weaving some of the threads of liberal education into the fabric of engineering education. Any effort to develop a humanistic-social stem of engineering education will depend largely upon the content of the courses and the type of instruction offered. Many of the courses in college curricula are intended to lay a foundation for more advanced courses to be taken later by those. who specialize in some particular field. Students in other fields lack the background necessary to take the advanced courses and have too much detailed information, soon forgotten, forced upon them if they pursue the foundation courses. To develop a humanistic-social stem for engineering education existing catalogue courses selected should follow some general plan aimed towards broad educational objectives. Courses packed with detailed factual information are necessary for the stu-

Jan 1, 1947

By Ken Musgrave

"A program is described that helps managers and supervisors control maintenance more effectively. Work- order generation, preventive maintenance, repair parts inventory, planning and scheduling, reporting, analyzing costs, printing purchase orders and other functions are covered. Flexibility often permits integration with other programs such as payroll, cost accounting and materials management.The Role of MaintenanceMaintenance provides a service to allow the rest of the operation to do its job effectively. Its success should not be measured by maintenance cost alone, but also by its effectiveness in reducing downtime and maximizing production. It can make sense to spend more maintenance dollars if this results in an even greater contribution from increased production.The Cost of MaintenanceIn mining companies, maintenance costs can be as much as half of operating costs. Maintenance has generally not been given the management attention that an expenditure of this magnitude deserves."

Jan 1, 1986

By Geoffrey Purcell

Improvements which have been made in commericial flotation systems during the past fifty years have resulted more from trial and error methods in the mill than from research in the laboratory. Research has often provided explanations of why mill changes have improved the metallurgical process. Hopefully, in the next fifty years, changes in mill flowsheets will come about, primarily, as a result of research work. However, since minerals, in their infinite variety, cannot be reduced to a standard state, research on commercial ores will have only a local utility, and research on pure minerals will have little commercial application. What will emerge from research on pure systems are mechanisms of adsorption, and this in turn may throw some light on the very much more complex adsorption processes taking place in the pulps of commercial ores. Quartz, without a doubt, has been the subject of more research effort than any other mineral, but we are still a long way from completely understanding its behavior in flo¬tation. Hematite and calcite have received considerably less attention. Ores containing a mixture of all three minerals, however, are commercially important, and the iron deposits in Alabama have been extensively studied by the United States Bureau of Mines (1). The literature reveals no reports of research on synthetic mixtures of all three.

Jan 1, 1967

By A. G. Roach

MILLING of Nova Scotia gold ores began in 1862 with arrastras and wooden stamps and has progressed to heavier stamps followed by tables and other forms of concentration for the recovery of the sulphides. Chlorination and cyanide leaching of the concentrates has been practised, and in 1936 the combined amalgamation and all-sliming cyanidation plant of Seal Harbor Gold Mines was built. It has since been found that it is not necessary to cyanide the full tonnage and now only the concentrates are being so treated. From his experience in this enterprise, the writer presents the accompanying flow-sheet and supporting comments. While he has not the temerity to maintain that it is the best or only flow-sheet for Nova Scotia gold ores, he feels that it warrants thoughtful consideration by members of the milling fraternity of the Province. THE ORE The gold in Nova Scotia ores occurs both free and intimately associated with sulphides-chiefly arsenopyrite. Much of the free gold is quite coarse and crystalline. This is especially true when it occurs in white quartz. When in the slate, it is usually in thin plates and scales, frequently coated and discoloured. The values bound up in the sulphides are not amenable to amalgamation and must be recovered by other methods-concentration, followed by smelting or fine grinding and cyanidation. While high freight and treatment charges apply on concentrates shipped from the Province to smelters, a considerable quantity has been so disposed of in the past. However, it is hoped that a customs cyanidation plant will soon become available to producers of these auriferous concentrates in Nova Scotia.

Jan 1, 1938

Operating CIP/CIL gold recovery plants in the arid regions of Western Australia face unique challenges due to water and ore quality issues. The presence of cations of Mg, Fe and Cu metals in water supplies and leached sulphide ores can have considerable effect on plant consumption of lime and cyanide, due to pH buffering and complexation effects. Reagent costs are critical to many of these operations. In this paper, computational modelling is used to analyse a number of process options to mitigate such issues. This requires careful consideration of the chemistry of the process system, and the ability to predict accurately the response of speciation and precipitation reactions to changing process conditions. The Mg-Fe-Cu-CN-H20 system is specifically modelled in this application. The Gibbs Free Energy Minimisation thermodynamic framework has been selected to model equilibrium phenomena. Furthermore, this approach has been extended to the process flowsheet level, incorporating multiple unit operations and recycle streams in a steady-state mass balance model. The Gibbs equilibrium composition module of HSC Chemistry software has been successfully integrated into the commercial flowsheeting package SysCAD. Consideration of the Gibbs Energy Minimisation capabilities of other flowsheeting packages has also been given. This approach has been successful in simulating the aqueous process chemistry typical of such plants. It has resulted in a predictive capability where equilibrium states respond appropriately to process changes. Potential cost savings may be identified by examining alternative process conditions to minimise overall reagent consumption.This methodology may be extended to other hydrometallurgical plants where issues of solution ideality, temperature and other equilibrium processes are sufficiently understood.

Jan 1, 2005

By Z. Lin, M. Isac, R. I. L. Guthrie

The kinetic and thermodynamic efficiencies of chromium recovery from the slag in an AOD process during the slag de-oxidation period with ferrosilicon is a complex process affected by slag basicity, temperature, the dissolution kinetics of the reducing agents, and intermixing of the slag/metal/alloy addition phases within the vessel. The present work focused on a study and simulation of the fluid dynamics and mixing behaviour of ferrosilicon additions in the AOD process for the production of stainless steel. In order to visualize the mixing behaviour, a two dimensional slice model of an AOD vessel was first built and filled with ZnCl2solution and then covered with silicone oil in order to represent the bulk liquid steel and slag phases, respectively. The injection of argon/oxygen process gases was simulated using air or helium. Particle trajectories and intermixing of the phases was monitored with a high-speed camera. To simulate the 75FeSi additions, glass spheres were used. A three-dimensional version of the AOD model was then constructed in order to confirm the adequacy of the slice model. Similar particle mixing behaviour was observed. Both models demonstrated that the ascending gas/liquid plume created two asymmetric mixing zones: a smaller rapidly re-circulating mixing zone adjacent to the side-wall locating the tuyere(s), and a larger mixing zone in the main part of the vessel. The process efficiency during the reduction period is governed by the thermal behaviour of ferroalloy as well as the mixing efficiency in the main large mixing zone. To enhance the recovery efficiency for chromium, small Fe-Si particles are suggested, given their wide distribution within the slag phase, and their large interfacial areas and rapid melting times for Cr2O3reduction from the slag. Keywords; modelling, ferrosilicon, chromium oxidation, AOD steelmaking.

Jan 1, 2004

By K. Muehlenbachs, J. U. Stemler

"Abstract - The Boston deposit is a recently discovered Archean lode-gold deposit located approximately 700 km northeast of Yellowknife, in the southern portion of the Hope Bay volcanic belt. Primary H2O-CO2-NaCl fluid inclusions associated with gold mineralization at Boston are of low salinity (4.6 ± 1.4 eq. wt.% NaCl, n = 182) and contain pure CO2. Homogenization temperatures of liquid-phase inclusions average 270° ± 33°C (n = 141), but some fluid inclusion assemblages contain coexisting liquid- and vapor-phase inclusions that homogenize near critical conditions, suggesting phase separation. In these groups, liquid-phase inclusions homogenized at 299° ± 25°C (n = 24), and vapor-phase inclusions homogenized at 338° ± 28°C (n = 18). These temperatures overlap within error, and a median temperature of ~320°C is taken as representative of trapping conditions within the veins. An approximate pressure of 2-3 kbar was estimated from fluid inclusion isochores at this temperature. Stable isotopic compositions of carbonate minerals from the mineralized zones range from -4.7‰ to -3.1‰ in d13C, and from 11.2‰ to 12.8‰ in d18O; quartz ranges from d18O = 12.8‰ to 14.9‰; and pyrite ranges from d34S = 2.1‰ to 3.5‰. The d18OH2O, d13CCO2, and d34SH2S values of the fluid calculated from these minerals at 320°C are 6‰-9‰, -2.4‰ ± 0.6‰, and 1.5‰ ± 0.5‰, respectively, and are intermediate between metamorphic and magmatic compositions. A unique source for the fluids cannot, therefore, be constrained from these data. Petrographic and geochemical data for the Boston deposit are consistent with data from other Archean lode-gold deposits worldwide, implying that the Boston deposit formed in a similar environment and from similar types of fluids. These results suggest that the Hope Bay volcanic belt may represent a major new mesothermal gold belt in this part of Nunavut. Sommaire - Le gîte Boston a été récemment découvert à environ 700 km au nord-est de Yellowknife dans la partie sud de la ceinture volcanique de Hope Bay, il s’agit d’un gîte d’or filonien d’âge Archéen. Les inclusions fluides primaires de H2O-CO2-NaCl associées à la minéralisation aurifère du gîte Boston présentent une faible salinité (4.6 ± 1.4 eq. pds.% NaCl, n = 182) et contiennent du CO2 pur. La température d’homogénéisation des inclusions à phase liquide est en moyenne de 270° ± 33°C (n = 141), mais certains assemblages d’inclusions contiennent des phases liquides et gazeuses coexistantes qui s’homogénéisent dans des conditions quasi critiques, suggérant qu’elles résultent d’une séparation de phase. Dans ces groupes, les inclusions de phase liquide s’homogénéisent à 299° ± 25°C (n = 24) et les inclusions de phase gazeuse s’homogénéisent à 338° ± 28°C (n = 18). Ces températures se recoupent à l’intérieur des limites de l'erreur de mesure, et nous considérons qu’une température médiane de ~320°C est représentative des conditions de piégeage dans ces veines. Les isochores permettent d’estimer une pression d’environ 2-3 kbar à cette température. La composition des isotopes stables des carbonates dans les zones minéralisées s’étend de -4.7‰ to -3.1‰ pour d13C et pour de 11.2‰ à 12.8‰ pour d18O; les valeurs de d18O pour le quartz varient de 12.8‰ à 14.9; et les valeurs de d34S dans la pyrite vont de 2.1‰ à 3.5‰. Les valeurs de d18OH2O, d13CCO2, et d34SH2S du fluide calculé à partir de ces minéraux à une température de 320°C est de 6-9‰, -2.4‰ ± 0.6‰, et 1.5‰ ± 0.5‰ respectivement, reflétant des conditions intermédiaires entre des compositions métamorphiques et magmatiques. Il n’est donc pas possible d’identifier une source unique pour ces fluides à partir de ces données. Les données pétrographiques et géochimiques du gîte Boston sont similaires à celles d’autres gîtes d’or filoniens ailleurs dans le monde, ce qui implique que le gîte Boston s’est formé dans un environnement similaire à partir des mêmes types de fluides. Ces résultats suggèrent que la ceinture volcanique de Hope"

Jan 1, 2006

By Pandey H. D.

The paper describes a fluidised bed ion exchange method for simultaneous removal of phenols and cyanide from the effluent. Use of an eluant enables regeneration of the resin in the continuous operation mode. The breakthrough experiments conducted both on the laboratory scale and on a pilot plant scale have shown that while the level of phenol can be brought down from 462 ppm to about 6 ppm, the free cyanide is almost totally removed. An examination of data indicates that the method can serve the twin objectives of pollution control and phenolic compounds recovery.

Jan 1, 1992

By James P. Kimball

AMONG the curious results of the recent advance of prices in the iron trade of the United States, one of them at least is to be regarded as of great importance. I allude to the utilization of mill cinder as a cheap and almost costless substitute for high-priced iron ores in many blast furnaces, situated within easy reach of such raw material. It has been, with but few exceptions, the practice in this country, based upon tradition rather than upon authority or European precedents, to waste this material on 'account of its high proportion of silicic and phosphoric acids, although known to contain more iron than most ores, and although also known to be sometimes applied to the blast furnace in greater or less quantities without serious detriment to the iron for specific purposes. While in use to a limited extent in the Hocking Valley and Hanging Rock iron regions of Ohio for several years, its use in Western Pennsylvania has only become general of late, under the exigencies of high prices and a short supply of ore. Especially has mill cinder largely entered into the stock of furnaces attached to rolling mills in and about Pittsburgh. Under such circumstances the cinder pig has been paddled on the premises, and the malleable iron produced has been unexpectedly good. Cautiously as at first mill cinder has been applied, it is evident that the temptation to use it freely is a strong one whenever the commercial rates for high-class ores are out of proportion to the general conditions of the iron trade, as sometimes happens in this country, especially as the free use of it is apparently justified by the quality of the iron produced from this cheap and abundant material. Indeed the consumption of cinder pig has., not been wholly confined to mills using up the production of furnaces belonging to the same plant. One furnace at least on the Ohio, at Covington, for several' months has been making foundry pig from "all cinder." The iron has gone into the general trade. It is probable that malleable iron of good quality can he made from the poorest cinder pig, but with what degree of economy will

Jan 1, 1881

By Glenn Kosick, Roger Amelunxen, Glenn Dobby

"The variability in flotation response within an orebody is often a significant problem to address during the design phase of a flotation circuit. In addition, for existing operating plants, the reasons for such a variability need to be clearly understood and accounted for if plant performance is to be optimized. MinnovEX Technologies, in collaboration with major mining companies, is developing methodologies and tools to address the issue of variability in ore characteristics (such as ore hardness and flotation response). The tool is used for design and scale-up of flotation circuits from lab flotation data, and for prediction of recovery and final concentrate grades throughout the mine block model for any given circuit design.INTRODUCTIOTNH: EI SSUEB EINGA DDRESSEDThis paper describes the current development of a methodology and software tool for improved flotation plant design and enhanced prediction of froth flotation performance in an operating plant. The need for this tool is attributed to two primary factors: variability of flotation response properties throughout an orebody and related difficulties with scaleup from laboratory tests. Consider these in more detail.It is well recognized that separation performance via froth flotation will vary significantly within a single mineral deposit. This has been enhanced through the wide application of SAG milling. Throughput with SAG mills is more susceptible to ore hardness changes than is the case with crushing-rod-ball circuits; it is not uncommon to see SAG mill throughput to vary by up to 100% on a regular basis, e.g. 1000 tph to 2000 tph.The implication of this on laboratory testing for prediction of metallurgical performance is as follows: it is unlikely that either the plant grind (size distribution) feeding froth flotation or the flotation residence time will be known at the time of laboratory testing for a given block of ore. Hence, the grind used for the laboratory test is not likely to be that which actually occurs once the ore is processed, and the laboratory retention time may not represent the plant conditions."

Jan 1, 2002

By E. J. Maunders

This paper describes briefly a computerised model of the South African electricity system which has been developed jointly by the Atomic Energy Board and the Electricity Supply Commission. The results of an analysis of this system have been subjected to a fairly extensive sensitivity analysis which reveals that up to the year 1990 between 680 and 700 million tons of coal will be required for electric power generation, together with between 7 000 and 10 000 tons of uranium. This result is fairly insensitive to data variations, but the prediction of a cumulative requirement up to the year 2000, of between 1 300 and 1 800 million tons of coal and 25000 to 70000 tons of uranium, proves to be very data-sensitive.