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By J D. van Wees

Preliminary project evaluation is relevant to the evaluation process of the decision makers (or executives) prior to making the critical business choices. Important to the assessment is an integrated sensitivity, scenario and risk analysis at every stage of a mining project. This should include the evaluation of different options taking into account uncertainties. Construction of interactive financial computer models where each element is functionally integrated into a fully integrated life-cycle allows rapid and automatic study of the sensitivity of each element through changes in the value of an input. The scenario analysis is the effect of changing more than one input at a time, organised through scenarios in a decision tree. Risk analysis is an integrated analysis of the effect of all uncertainties of the parameters, using Monte Carlo simulation. Key to the asset decisions process is that the decision maker is provided with the essential integrated decision information. We have clustered this information into several scenario groups. Within each group, two levels of uncertain information are distinguished: discrete scenarios critical for the decisions; and remaining uncertainty within the scenario (risk analysis) which can be modelled by continuous probability density functions (pdfÆs). For an asset, the relevant scenarios in each group and the associated continuous pdfÆs need to be defined. When the scenario groups and associated pdfÆs have been defined for the asset, the decision process can be started by structuring the different scenario groups in a Scenario Tree. A Scenario Tree contains decision and end nodes. Each end node corresponds to a completely defined mine project or asset model. The calculations for each end node result in a set of stochastic realisations for the reserves, production forecast, cash flow, and profitability indicators (NPV, IRR, DPR). Thus, a deterministic and fully probabilistic multi-commodity analysis tool is provided to investigate the sensitivity and robustness of decisions.

Jan 1, 2003

By J. Kortnik

Mining has always been, and still is, an activity which is vital for the development of mankind. This is because a predominant proportion of industrial products and energy is produced from raw materials that are excavated using mining methods. The need for environmental protection and the close proximity of urban settlements and mines in Slovenia have necessitated ever stricter requirements for the excavation of raw materials and introduction of more environmentally-friendly mining methods. This is achieved by implementing a closed eco-technological cycle of raw material excavation within the scope of mining methods. In surface mines, this means prompt reclamation of the degraded surfaces, and in underground mines the use of methods with minimized impact on the surface and on underground water. In underground mines, mining methods with backfilling installed according to the multi-barrier disposal system are the only ones that allow the possibility of implementing a closed eco-technological cycle of excavating raw materials. Various industrial waste materials are also included in the backfilling material in order to improve its strength properties. Backfilling consisting of several different waste materials is produced in the form of a composite. Before backfilling consisting of waste material composites can even begin to be used in mines, an environmental impact assessment of its suitability for mines needs to be made. In order to make such an assessment, a pressure leaching cell and an open diffusion cell were made, i.e. a pressure leachate test and a sorption test were developed. The two cells and the developed tests will enable the study of the influence of backfilling on the environment if installed in an underground mine. The pressure leachate test performed with the use of the pressure leaching cell simulates leaching from a consolidated backfill during the seeping of underground water into the backfilling material under pressure. The sorption test performed in an open diffusion cell simulates the flow of eluate leached from the backfilling material through the rock/geotechnical barrier. The two tests were developed in such a manner that they are performed either in succession immediately after one another, but they can also be performed separately at a certain time interval. The paper presents an assessment of the suitability of backfilling made of different waste material composites. Keywords: environmental impact assessment, multi-barrier disposal system, waste material composites, pressure leachate test, sorption test, pressure leaching cell, open diffusion cell, eco-technological cycle, mining methods with backfilling.

Jan 1, 2003

By E de N, B H. Usher, F D. I Hodgson

Due to the haphazard application of static tests in South Africa, several methods and interpretations have been followed. This has resulted in confusion amongst practitioners and regulators in the use and validity of these methods. Research was done over a two-year period to define standardised methods and interpretation of results. This included laboratory testing and continuous consultation with all interested parties throughout the country. The research yielded a modified ABA, based on several existing methods. The methodology includes AP determination using hydrogen peroxide, and an analysis of the supernatant by ICP. This has the advantage of not only registering reactive sulfur, but also provides the NAG pH, that enhances the interpretation and QC of the tests. Analysis of the supernatant provides an indication of heavy metal solubilisation, should acid conditions arise. One hundred and seventeen samples were compared to Leco S analyses and provided a good correlation. The Leco values were slightly elevated due to the reporting of total S as opposed to æreactive SÆ. The NP method deviates from the usual methodology, in that H2SO4 is used (to provide a field analogy) and the fact that a 24-hour stabilisation period is allowed before back-titration. The latter modification appears to prevent psuedo-buffering by transient phases. These methods have also been tested for repeatability and prove to be robust. A very simple macro-driven spreadsheet, æABACUSÆ, was also developed. This spreadsheet allows the entry of basic data and provides a detailed interpretation and graphical display of typical ABA data. In cases where drill holes are used, the Pennsylvanian approach of volume calculation can also be done with ABACUS. The results of the research have been distributed to interested parties in South Africa and it is hoped that these methods and their application will find widespread acceptance.

Jan 1, 2003

It is usually the case that the short-term plannerÆs role is occupied by the younger site mining engineer. ThatÆs because mine scheduling is generally seen as a mundane and thankless task. But, short-term planners play an extremely important role in maximising the value of the mining resource, generally the companyÆs biggest asset. A look at any mining operation today will expose the competing drivers behind the operational and strategic plans. Operations are too often faced with pushing short-term constraints. It is the responsibility of the short-term engineer to answer the question of æWhere to next?Æ. In answering this question the young mining engineer is in an environment overflowing with urgency and constraints. Hasty decisions made at this time may have significant adverse consequences to the long-term value of the resource. Long-term strategy must address a broad and expanding number of issues that are generally overlooked by the short-term planner. It takes a holistic, rather than the prescriptive approach of short-term planning to determine the best strategic direction for the operation. To better understand the consequences of decisions made at the operational level short-term planners need better vision of the whole business. The key to improving the mining business is a planning process that integrates the short-term planners role with the overall mining strategy. Future developments in the mine planning process will focus on bridging this ædisconnectÆ between the operational objectives and the long-term goals. Improvements will come from the tools which planning engineerÆs use, and the planning methodology surrounding them. There will be significant hardware improvements to improve the speed with which a short-term planner can evaluate plausible options. Software that maximises the use of the improved hardware will be developed. Complimenting these technological improvements, conceptual methodologies of mine planning will improve to allow strategic planning to be brought within the focus of the short-term planning engineer. In todayÆs mining industry the young mining engineer is embarking on a career where business processes are paramount. This paper discusses the ædisconnectÆ that occurs today between the operational planning and long-term strategy and how this is driving developments in mine planning today.

Jan 1, 2003

By S. O. Choi, C. Park, C. Sunwoo

Two methods of stress measurements have been executed on the surface and underground to con-struct an oil storage cavern using hydro-fracturing and overcoring method. The first measurement has been performed to make a design of the caverns before excavating and the second to confirm the stress state during excavation. Six measurements have been carried out in the hydro-fracturing test at the depths between –17.8 and 54.5m from the sea level and a single measurement in the overcoring test in a single borehole at the depth of –21m from the sea level. The ratios of the maximum horizontal to vertical stress measured using hydro-fracturing and overcoring method are 2.95 and 3.1, respectively. Also, the orientations of the maximum horizontal stress are N53E and N58E. These measurements show that both methods give almost same results and significant horizontal stresses are acting on this cavern. Deux méthodes de mesure de contrainte ont étè exécutées sur la surface de terrain et sous la terre pour construire une cavité de stockage de pétrole en utilisant l’hydro-fracturing et l’overcoring. La première mesure a étè faite pour le plan des cavités avant l’excavation et le seconde pour con-firmer l’état de contrainte durant l’excavation. Six measures ont étè faites dans le teste de l’hydro-fracturing à la profondeur entre –17.8 et 54.5m depuis l’élèvation maritime. Une seule mesure a étè faite dans le teste de l’overcoring dans une seule trou de songdage à la profondeur de –21m. Le ratios de la maximale contrainte horizontale à la contrainte verticale mesure par les deux méthodes sont 2.95 et 3.1, respectivement. Les orientations de la maximale contrainte horizontale sont N53E et N58E. Ce montre que les deux méthodes donnent presque m me résultats et la contrainte im-portante est activée sur ces cavités. Zwei Druckmessungen wurden durchgeführt auf der Erdoberfläche und im Innern von Ölspeicher-kavernen unter vergleichender Anwendung des Hydrofraktionierungs- und des Kernbohrungsver-fahrens. Die erste Messung wurde durchgeführt um einen Plan der Kavernen vor der Herstellung zu erstellen und die zweite um die Druckverhältnisse während der Bohrung zu überprüfen. Sechs Messugnen wurden mit der Hydrofraktionierungsmethode bei einer Tiefe von 17,8m und 54,5m unter dem Meeresspiegel und eine einzige Messung mit der Kernbohrungsmethode in einem Bohr-loch bei einer Tiefe von 21m unter dem Meeresspiegel vorgenommen. Das Verhältnis von maxi-malem horizontalem zu vertikalem Druck bei der Hydrofraktions- und der Kernbohrungsmedthode ist 2,95 bzw. 3,1. Die Bezugspunkte des maximalen horizontalen Drucks in beiden Verfahren sind N53E und N58E.

Jan 1, 2003

By R. Van Hille, A. E. Lewis

"The precipitation of a selection of metals from both a synthetic and an actual metal-rich effluent was investigated. The experimental aspects of this study were carried out in a two-stage process consisting of a pre-treatment clarifier and a fluidised bed (pellet) reactor. Each unit operation in the two-stage process was investigated separately. The pretreatment clarification stage at pH ˜ 5 resulted in a 99.9% removal of iron and 97.3% removal of aluminium.The pellet reactor was used to precipitate nickel as nickel hydroxy-carbonate from a pure stream and a removal efficiency of 99.6% was achieved. The high local supersaturation at the reagent inlet points caused the formation of a large amount of fines, but these agglomerated onto the pellets up the length of the bed (See Figure 1).For copper precipitated as copper sulphide from a pure stream, a maximum removal efficiency of 92% was achieved. The high local supersaturation at the reagent inlets also caused the formation of a large amount of fines, but the extremely sparingly soluble nature of copper sulphide meant that the fines were not agglomerated up the length of the bed. In Figure 2, the global supersaturation ratio was relatively low, and thus there is little homogeneous nucleation and degree of fines formation. However, the fines occurring after the third sulphide input point (at 30cm from the bottom of the bed) indicate that local supersaturation also plays a critical role in fines formation. It was therefore concluded that, for the copper sulphide case, it is essential to control the supersaturation at the inlet points in order to prevent fines formation altogether, as it is not possible to agglomerate the fines once they exist in the bed."

Jan 1, 2003

By C. Tan, C. Detournay

Wellbore stability is a major concern for drilling in naturally fractured formations. The infiltration of drilling mud into the fractures is a factor, which may compromise wellbore integrity due to the loss of strength experienced by the fractures. The reduction in the fracture frictional and cohesive properties is attributed to weakening of the infill materials and lubrication of fracture asperities by the mud filtrate. One way to investigate the influence of mud infiltration on wellbore stability in fractured formations is to use a numerical modeling approach. A requirement for the numerical model is the ability to predict the region of mud infiltration. This paper describes a numerical technique to model the extent of mud infiltration for application in coupled fluid-mechanical simulations in densely fractured rock masses using the computer code, UDEC. Several factors are considered including fracture pattern, in-situ stresses, reduction in joint frictional angle and cohesion, viscosity of the mud filtrate and fracture plugging. Results of numerical simulations are presented to illustrate the technique and show the influence of these factors on the extent of mud infiltration. Un des problèmes importants posés par le forage en milieu fissuré saturé, est celui du maintient de la stabilité du puit. L’infiltration de boue de forage dans le massif peut avoir pour effet de réduire les propriétés frictionnelles et cohésives des fractures et de compromettre ainsi la stabilité du puit de forage. Le radoucissement des propriétés des fractures est attribué à la dégradation du materiau de remplissage et au pouvoir lubrifiant des boues. L’analyse numérique offre un moyen d’investiguer l’influence jouée par l’infiltration de boue sur la stabilité du puit. Un des critères de sélection du modèle numérique sera son pouvoir de prédiction du domaine d’infiltration de boue. Cet article décrit une technique numérique permettant de modéliser l’infiltration de boue de forage dans le cadre de simulations hydro-mécaniques, en milieu à haute densité de fractures, effectuées avec le logiciel de calcul UDEC. Parmis les facteurs tenus en compte, on trouvera la nature du réseau de fractures, les contraintes in-situ, le radoucissement en friction et cohésion des joints, la viscosité de la boue et le bourrage des fractures. Des résultats de simulations sont présentés pour illustrer la technique et montrer l’influence de ces facteurs sur la taille du domaine d’infiltration de boue. Bohrlochstabilität ist ein wichtiger Aspekt für das Bohren in geklüfteten Gebirgsformationen. Das Eindringen der Bohrlochstützflüssigkeit in die Klüfte kann die Bohrlochintegrität wegen des Verlustes der Festigkeit des Kluftsystems gefährden. Die Reduktion der Reibung und kohäsiven Eigenschaften ist der Schwächung der Kluftfüllung und der Schmierwirkung der eingerungenen Stützflüssigkeit in Bezug auf die Kluft-Asperities geschuldet. Numerische Berechnungen sind ein Weg zur Untersuchung des Einflusses der Infiltration der Bohrlochstützflüssigkeit auf die Bohrlochstabilität in geklüfteten Gebirgsformationen. Eine Voraussetzung für numerische Modelle ist die Fähigkeit den Bereich der Infiltration der Stützflüssigkeit zu prognostizieren. Diese Publikation beschreibt ein numerisches Verfahren, um die Reichweite der Infiltration von Stützflüssigkeiten mittels fluid-mechanisch gekoppelter Simulationen im engständig geklüfteten Gebirge mit dem Programm UDEC zu modellieren. Verschiedene Faktoren, wie Kluftmuster, Gebirgsspannungszustand, Reduktion von Kluftreibungswinkel- und kohäsion, Viskosität der Stützflüssigkeit und Rissabdichtung wurden untersucht. Ergebnisse numerischer Simulationen werden präsentiert, um die Vorgehensweise zu illu

Jan 1, 2003

By Isabel Lázaro

A detailed study has been undertaken into the electrochemistry of the leaching of chalcopyrite in acidic solutions containing ferric ions. Mixed potential measurements have shown that the maximum potential achievable on a chalcopyrite disk in a ferric sulfate medium lies within the so-called passive or prewave region in the anodic behavior of chalcopyrite. The very low current densities due to the anodic oxidation of chalcopyrite at potentials in the region of the mixed potential has made studies of the initial stages of dissolution difficult. However a careful rotating ring-disk electrode (RRDE) study has enabled data to be obtained for the stoichiometry of the initial dissolution reaction to be obtained. Thus, in addition to the detection of soluble iron and copper as products in this potential region, a soluble sulfur species has also been detected. A comparison of the experimental with the expected collection efficiencies of the products on the ring has revealed that this soluble sulfur species is likely to be thiosulfate. The characteristic transient anodic behaviour of chalcopyrite in this potential region has been interpreted in terms of a rate limiting solid-state diffusion process. Thus, extrapolated rates based on reported measured solid-state diffusion coefficients for the mineral at elevated temperatures have been shown to be consistent with the potentiostatic current-time transients. Furthermore, comparative studies of the anodic characteristics of the copper sulfide minerals covellite and bornite has confirmed their greater reactivity in this potential region. The results of this investigation have been combined with a parallel study of the non-oxidative behaviour of chalcopyrite in order to derive a model for the dissolution process which is consistent with other published studies of the electrochemistry and dissolution of the mineral.

Jan 1, 2003

By N. Panteleeva, E. Konoplev, I. Michailova, S. Titkov, T. Gurkova, T. Chumakova, Sylvinit Co.

"INTRODUCTIONFlotation of mineral particles by cationic surfactants – namely alkyl amines and their derivatives – is finding ever growing application in processing of various ores and in quality refinement of the benefication end products, iron concentrates for example. In the recent years application of cationic collectors - alkylmorpholines - enabled the development of new highly efficient procedure of water-soluble mineral processing, being also the one with low energy consumption. This procedure is a reverse flotation of carnallite from bay salts of salt-pans and from carnallite ores.The efficiency of cationic SAS influence depends upon colloid-chemical state of the collector in flotation liquid phase, especially if the latter comprises mineral salts. Availability of clayey impurities or slime particles of iron oxide in cation flotation feed, which actively sorb the cationic collector, deteriorate considerably the cation flotation performances. In Halurgy Institute the investigations of cation flotation under potash and carnallite ore processing have been carried out, and new reagent modes, enhancing cationic surfactants sorption at mineral particles, have been developed. Application of new reagents enables one to decrease considerably the consumption of expensive cationic collectors and to enhance the floatability of coarse mineral particles."

Jan 1, 2003

By Karl J. C. Harries

"1.1. WHAT ARE AGREEMENTS AND HOW ARE THEY FORMED?In order to have an agreement, at common law, there must be an offer, acceptance of that offer, and consideration passing between the parties. In addition, the material terms (i.e. the basics or substance) of the agreement must be discernible, preferably by means of documentation. Although these concepts may appear simple and straightforward, the law relating to them is voluminous and complex. Some brief comments are worthwhile.• Offer/acceptance: Both offer and acceptance should be in writing, but they need not be. The actions, conversations, and/or correspondence of the parties may constitute either or both of them. Notwithstanding, the local law or practice of a jurisdiction will impose some specific requirements for certain types of agreements. If these requirements are not met, the agreement may be unenforceable. For example, Ontario’s Mining Act requires transfers of unpatented mining claims to be evidenced in writing and recorded.1• Consideration: Consideration is usually thought of as being money, but it can be virtually anything, even “the premises” (i.e. the mutual covenants or promises contained in the agreement itself). In addition, if one party, relying upon the offer of another, does something to his detriment, then the doing of the act can be considered to be an acceptance of the offer and, under the legal concept of “detrimental reliance”, can also be consideration. Whether or not detrimental reliance exists will depend upon the circumstances of each case.2• Material terms: The requirement that the material terms of an agreement must be discernible does not mean that all of the terms of an agreement must be documented or even have been considered, just the basic or material ones. In addition, it will be up to a judge to decide what is material – not necessarily the parties. In order to establish the material terms, a Court may look at all relevant documentation and may hear oral evidence. It will resist “writing the agreement”"

Jan 1, 2003

By D. J. Adams, W. K. Rymon-Lipinski

Rock engineering plays a crucial role in contributing to sustainable development in South African mining. A framework for this has been created through legislation and structures to encourage the mining industry to have a long and prosperous future. However, rock engineering input is an essential element to achieving success. The most accessible deposits have been mined in South Africa and although large reserves still remain, many of these are difficult to access and will require excellent rock engineering knowledge and skill in the future. This is borne out by the fact that more than 50 % of fatal accidents are related to rock engineering issues. Many of these may be addressed with rock engineering solutions which are not beyond current rock engineering technology. A reduction in fatalities and injuries contributes to a sustainable mining industry.

Jan 1, 2003

By Dave Deglon

"The Western Cape Mineral Processing Facility (WCMPF) is a collaborative educational initiative between the Departments of Chemical Engineering of the University of Cape Town, the University of Stellenbosch and the Cape Technikon. The primary objective of the WCMPF is to facilitate the education, development and graduation of suitably qualified engineering graduates and diplomates for the mining industry. The WCMPF consists of academics and Technical Officers in the Departments of Chemical Engineering of the three tertiary institutions. The Technical Officers are usually metallurgists, with several years of industrial experience. The main objective of the Technical Officers is to improve the practical education of mineral processing students. In addition, the Technical Officers are responsible for organising an annual mineral processing student field trip for students from all three tertiary educational institutions. In recent years the WCMPF has embarked on a number of additional initiatives aimed at improving the quality of mineral processing education. These include the development of several new pilot plant practicals, an initiative in pyrometallurgy, the introduction of novel ‘end to end’ or ‘integrated’ practicals and the use of mineral processing simulation packages to complement the practical training.The WCMPF has been functioning for well over a decade and, by virtue of this, might be considered a successful collaborative educational initiative. The WCMPF has played a key role in the education of over five hundred mineral processing graduates and diplomates. During this time period, the WCMPF has gained a body of internal knowledge which might be of benefit to other educational institutions, viz."

Jan 1, 2003

By Tamara F. Kondrateva, Evgenia E. Savari, Galina V. Sedelnikova, Rauf Y. Aslanukov, RAS (INMI), Grigori I. Karavaiko

"The investigation is dedicated to study of biohydrometallurgical processing of refractory gold-arsenic concentrate with the large content of pyrrhotite. Sulfide concentrate of chemical constituents: 75g/t Au, 4,7g/t Ag, 6,3% As, 29,3% S, 2,3% Sb, 0,5% ? (organic) and of mineral composition, %: 11,8 arsenopyrite, 39 pyrrhotite, 12 pyrite, 2,9 antimonite and the rest – aluminosilicates, carbonates and quartz, was studied. The recovery of gold from concentrate by cyanidation is 51,2%. The rest of gold is embedded as finegraded segregation in sulfides.Sulfide oxidation process study is described. Bacterial oxidation was executed on a pilot laboratory unit using combined autotrophic bacterium: A. thiooxidans , A. ferrooxidans, Leptospirillum ferrooxidans and sulfobacillus thermosulfidooxidation, pH=1,5-2,2, t=28-32?C, oxidation time 120 hours. Pyrrhotite is the least stable sulfide mineral with electrode potential 0,45V versus arsenopyrite (0,55 V) and pyrite (0,55-0,6 V) and is oxidated primarily. Pyrrhotite oxidation is followed by large amount of elemental sulphur, which has a bad influence on cyanidation.It’s established that the rate of arsenopyrite (for the first 48 hours) from concentrate containing 39% pyrrhotite is 2-3 times as less as the rate of arsenopyrite bio-oxidation from concentrate without pyrrhotite. The arsenopyrite bio-oxidation is accelerated only after the elemental sulfur was oxidized by bacterium A. thiooxidans and elemental sulfur percentage was reduced from 6,8 to 3,9%. The bacterium concentration is increased from 2,5x107 to 2,5x109 cells/ml. Almost full oxidation of arsenopyrite (98%) and pyrrhotite (98- 99%) is finished in 120 hours. We have studied two pretreatment methods for elimination sulfur content influence on cyanidation: aeration in lime and electrochemical treatment. Such an operation enables to have supplemental oxidation of elemental sulfur and other oxygen and cyanide absorbants before cyanidation. After treatment the content of elemental sulfur was decreased from 3,9 to 2,2%, gold recovery from 90 to 96% and cyanide consumption from 16,2 to 7,2 kg/t decreases. The content of toxical rhodonite-ions in liquid phase of pulp and disinfection reagents consumption were decreased as result of elemental sulfur content in bio-oxidated product reduction."

Jan 1, 2003

By Åke Saudström

An EAF dust sample generated in a scrap based steel mill was treated by a combination of hydro- and pyrometallurgial techniques. The EAF dust contained mainly ferritic spinels forming solid solution phases according to the general chemical formula (MnxZnyFe1-x-y)Fe2O4 and other oxide phases such as ZuO. CaO and Ca2Fe2O5. The EAF dust was first treated by hydrochloric acid leaching at p8=3 which dissolved 63% of the zinc. The pyrometallurgical treatment of the leaching residue was studied using an induction heating system to simulate some important operations of EAF smelting of the residue in combination with steelmaking. The leaching residue was mixed with carbon powder to obtain a mixture with 52.1% ZnFe2O4 and 175% carbon. The mixture, scrap, and slag former were charged together in a crucible and heated to attain a melt temperature around 1650°C. The effects of different amounts of mixture on the zinc balance and iron recovery were examined. Based on the test results, suggestions are made for the EAF recycling procedure of the leaching residue.

Jan 1, 2003

By T. Negeri

The simultaneous use of two or more families of collectors can sometimes improve one or more key flotation performance indicators, especially if the ore under consideration contains several minerals bearing the same metal. The maximum amount of collectors that can be used is limited by the need to maintain a high concentrate grade and selectivity. Therefore, when more than one collector is required, an experimental design that allows variations of both the proportions and the amounts with respect to other process factors has to be selected to find the optimum dosage. This type of design is known as "process factors in mixture amount experiment". It is a powerful design suitable for discovering the existence and evaluating the magnitude of the interactive effects between various flotation parameters. This paper elaborates the principles on which such a design is based, and demonstrates its usefulness with a case study.

Jan 1, 2003

By V. K. Paruchuri, J. D. Miller, J. Nalaskowski

An understanding of forces responsible for the stability of dispersions of colloidal particles when interacting with each other in aqueous solutions is of great interest academically and industrially. When water-soluble polymers are adsorbed onto colloidal particles, various effects on the stability of their suspensions can be expected ranging from steric stabilization to bridging flocculation. The possibility of detailed characterization of such systems using direct measurements of interaction forces between particles can help in further improvement of existing technologies of solid-liquid separation. An atomic force microscope (AFM) colloidal probe was used to measure the interaction forces between a silica sphere and a silica substrate in the presence of water-soluble polymers. Poly(ethlene oxide) (PEO) with three different molecular weights (7,000, 43,000, and 63,000), each with a very narrow molecular weight distribution, were used in this study. The interaction forces measured with the AFM over an extended time scale are discussed in terms of the adsorption kinetics measured through in-situ FTIR/IRS measurements.

Jan 1, 2003

The oxidation of zinc vapour plays a very important part in the operation of the Imperial Smelting Process. The kinetics of the reoxidation of zinc vapour by carbon dioxide and water vapour onto quartz and zinc oxide substrates is qualitatively understood and this pertains to the conditions found as the gases are being transferred from the furnace to the splash condenser. However, re-oxidation also occurs in the shaft of the furnace where the solid substrates are sinter and metallurgical coke. It was found that there was a threefold increase in the rate of oxidation on sinter, compared to quartz and a 30 to 300 increase in rate on the coke. This was attributed to the high surface area offered by these materials.

Jan 1, 2003

By T. H. Yang, K. K. Lee, Z. Z. Liang, C. A. Tang, L. C. Li, Y. Tsui, L. G. Tham

Abstract: A series of numerical tests of hydraulic fracturing in heterogeneous rocks were performed to investigate the influence of pore pressure magnitude and gradient on initiation and propagation of tensile fractures. The numerical tests were run with a Rock Failure Process Analysis code, F-RFPA2D, incorporated with a Flow-Stress-Damage coupling model (FSD). To investigate the influence of pore pressure magnitude on fracture behaviour, “pinch-off” breaking tests, originally employed by Bridgeman to investigate the effective stress law for tensile fracture in a uniform pore pressure field, were numerically modelled. In another numerical test, a double-notched sample, with fluid pressure in one notch while keeping the other one open to the atmosphere, is numerically extended to investigate how the fluid flow direction or the pore pressure gradient will influence the fracture behaviour. The simulation results show that fracture is strongly influenced by both pore pressure magnitude and pore pressure gradient. Keywords: seepage mechanics; heterogeneous; pore pressure; numerical simulation; failure process ZUSAMMENFASSUNG: Um den Einfluss der Wasserdruckgroesse der Oeffnung und der Porisitaet auf den Bruchentstanden und Verbreiten der Tension von Gebirgen zu beurteilen, wurde viele nummerische Pruefungen auf den hydraulischen Bruch in dem Gebirgen aufgenommen. Diese Pruefungen wurden mittels der Analyse- Software F-RFPA2D und Flow-stress-Damage Coupling model ( FSD) durchgefuehrt. Um den Einfluess der Wasserdruckgroesse der Oeffnung auf den Bruch zu beurteilen, wurden auch Bruchpruefung und nummerische Analogexperimenten gemacht, und dadurch wurde die ganze Phase der Bruchentstanden und Verbreiten wiedergezeigt, und die Ergebnissen ergeben sich, dass die Wasserdruckgroesse der Oeffnung und der Porisitaet sehr viel auf den Bruchentstanden und Verbreiten der Tension von Gebirgen beeinfluessen. Schluesselwoerter: Durchlaessigkeit , ungeleichmaessig, Wasserdruck der Oeffnung, nummerische Analog, Zerstoerungspahse Résumé : Une série de simulations numériques a été ménée pour analyser l’influence de la grandeur de la pression de pore et du gradient sur la naissance et la propagation des fractures de tensions par le biais de la simulation numérique des fractures hydroliques dans des rochers hétérogènes . Le logiciel F-RFPA (Rock Failure Process Analysis code ) intégrant FSD ( Flow-Stress-Damage coupling model ) y a été employé. Les résultats des simultations montrent tout le processus de la naissance et de la propagation des fractures sous la pression de pore. Ces résultats nous ont permis de constater que la grandeur de la pression de pore et le gradient exercent une influence importante sur la naissance des fractures dans les rochers et sur leur mode de propagation . Mots de clé : le mécanisme de transfusion ; l’hétéogénéité ; la pression de pore ; la simultation numérique ; le processus destructif

Jan 1, 2003

By Gülay Bulut, Mustafa Özer, Yunus Emre Benkli, Olgaç Kangal, Istanbul Technical University, Mustafa Tarkan

"Zeolites are naturally occurring as hydrated aluminosilicate minerals. They belong to the class of minerals known as “tectosilicates” and are related to the common minerals feldspar and quartz. Seven natural zeolites that occur in large, commercially exploitable deposits, are: clinoptilolite, chabazite, mordenite, phillipsite, erionite, analcite, and ferrierite. Among them, clinoptilolite is the most abundant one and is not the best known, but is one of the more useful natural zeolite. Clinoptilolite [(Na3K3) (Al6Si30O72) 24 H2O] is very closely related to heulandite and is currently being considered for disuse it self as it may just be a variety of heulandite. It differs from heulandite significantly only in its enrichment in potassium and slightly more silica and it is argued that a separate mineral is not needed.There are large zeolite deposits in western part of Turkey. The sample used in this study was taken from the Gördes region of these deposits. Screen, chemical, XRD and mineralogical analyses were used to determine properties of the natural zeolite sample used in this work.According to the size distribution of the sample, it is found that the zeolite sample used in this study is below 1 mm in size and almost 80% of it is below 0.5 mm. X-Ray Diffraction (XRD) and mineralogical analyses show that the natural zeolite is found to be in the forms of clinoptilolite and heulandite. Clinoptilolite forms as a devitrification product of volcanic glass in tuffs. Quartz, clay minerals, orthoclase, plagioclase, biotite, seruzite-muskovite and epidote were observed as impurities. XRD analysis also shows that the sample contains approximately 58-60% clinoptilolite, 5% quartz, 5% feldspar, 10% smectite, 5- 10% illite and mica and remaining volcanic tuffs. Several types of mineral processing methods were performed in order to remove impurities from the natural zeolite sample to produce high purity zeolite. Gravity separation methods such as shaking table and superpanner were carried out for separating heavy minerals, while high intensity dry magnetic separation was used for discarding magnetic minerals."

Jan 1, 2003

By Jon Kellar, William Cross, Eric Swanson, John Starkovich

Zirconium tungstate (ZrW2O8) is a unique material with a negative coefficient of thermal expansion. In order to fully utilize this material as a filler, a surface treatment needs to be developed to better improve the wetting and dispersion capabilities of the filler. This paper describes an initial study to characterize the filler as well as investigate fatty acid and silane surface treatments for eventual compounding with thermosetting matrices. It was found that ZrW20, has a point-of- zero charge between pH 2.7-3.0, and that both fatty acid and organofunctional silane treatments appear to be viable surface treatments for this unique filler.

Jan 1, 2003