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By K. R. P. Petersen

Paper written on project work carried out in partial fulfilment of M.Sc. Eng.(Metallurgical Engineering) degree The interrelationship between mineral liberation and leaching behaviour of a gold ore is ill defined, mainly due to the complexity of both leaching and mineral liberation. This study presents a neural network approach to modelling the liberation of gold bearing ores. A complete mineralogical analysis of unmilled and milled ores, including gold deportment and gangue content are used as inputs to a self-organizing neural net, which generates order preserving topological maps. The arrangement and shapes of these clusters are coupled to unmilled free gold data to predict gold liberation in milled ores (absolute error: 8.1%). Moreover, the self-organizing maps were diagnostic of the quality of data used, indicating that the relationship between particle size and gangue material content requires further investigation.

Jan 1, 2003

By Jan Svoboda, Toyohisa Fujita

"The current status and history of innovation in magnetic methods of material treatment are reviewed. The milestones and key drivers of innovation are identified, advantages of magnetic separation in comparison to other physical methods of material manipulation are discussed and reasons for failure to live up to its potential and expectations are identified. The future focus in such diverse areas as mineral processing, waste treatment, recycling and biosciences is discussed and the research and development needs are outlined.Our walk through the innovation landscape in magnetic separation illustrates the enormous effort that has been expended over the years to convert a wealth of novel idea into workable techniques. Remarkable progress has been achieved and numerous successful innovations have been introduced into material treatment operations. On the other hand these techniques have experienced their fair share of failures. The reasons for these cover a wide spectrum of risks that accompany any effort to implement new technology."

Jan 1, 2003

By Mitsutaka Hino

The contents of gangue minerals, such as A1203, P205, crystalline water and so forth in the iron ore imported to Japan tend to increase year by year, Though the increments of such gangue contents are approximately 0.1-0.2 mass%, some problems for the blast furnace operation in ironmaking process have already been reported, In order to clarify the mechanism of harmful effect caused by the small increment of gangue minerals, mainly A1203, on the blast furnace operation, the dripping behavior of FetO-CaO-SiO2-AI2O3-MgO slag from the iron funnel, which simulated the micro-porosity in sinter ore, has been observed with the wide range of basicity, Al2O3, FetO and Mgo contents. The effect of MgO on the dripping behavior of slag has been summarized in this paper, It was found that the addition of 2mass% MgO resulted in large increase of hold-up on the most of the conditions. When FetO content was less than 20mass% and the basicity was lower than 0.8, MgO lowered the hold-up even if the slag contained 10mass% Al2O3. Every slag hold-up showed the minimum at the basicity of less than unity on the conditions of constant FetO and A1203 contents. This trend became remarkable when the slag contained 2 mass% MgO.

Jan 1, 2003

This paper presents an initial investigation into the viability of co-kriging the grades of multiple mining cuts in a two dimensional, thin reef scenario. Deposits with gradational mineralized zones, in the perpendicular sense, are not as well served by the use of reef accumulation and thickness as deposits characterized by a sharp distinction between ore and waste rock. South African Bushveld Complex platinum deposits and Witwatersrand gold deposits are examples of this distinction. The calculation of an optimal mining cut is of paramount importance in the mining of Bushveld platinum. Two-dimensional kriging of a constant stoping width mining cut is an effective method for resource calculations once a cut is decided, but this begs the question of how to decide on the cut. Comparison of multiple cuts is used as a way of achieving this decision on many of Anglo Platinum’s operations. Although the kriging of each cut is valid in isolation, occasional negative values occur when incremental grades between overlapping cuts are calculated. Negative incremental grades cannot reflect reality. They are thought to be related to the inability of the method to include the strong continuity in the perpendicular direction demonstrated by the relevant variograms. Co-kriging of related variables has been investigated as a potential means tore impose this inherent order relationship. Various co-kriging options have been investigated. The method has been tested on a real data set from an established platinum operation. One of three types of anomaly has been investigated so far. The results show that co-kriging the mining cut grade as the primary variable, with just one secondary variable, the reef thickness, eliminates most occurrences. Severe anomalies remaining are arguably indicative of population mixing and might be more effectively treated by rezoning the data. Aim—To investigate the viability of co-kriging the grades of multiple mining cuts as a method for resolving anomalies in the estimation of such cuts on Bushveld platinum deposits, with applicability to other thin reef type deposits with a gradational not sharp cut-off between ore and waste in the direction perpendicular to the reef. Keywords: co-kriging, cross variograms, ordinary kriging, platinum, two-dimensional, grade profile

Jan 1, 2003

By Ramana G. Reddy

Thermodynamic modeling and experimental study on impurity capacities and their distribution between mattes or metal and slags in smelting, converting and refining of non-ferrous metals was discussed. A brief review on the recent developments in copper smelting and converting is presented. The analysis showed that, copper smelting capacity increased by a factor of 10 since 60's, smelting rate increased by a factor of more than 5 and process fuel equivalent decreased by a factor of 2. A thermodynamic model for prediction of impurities capacities in slags and their distribution in mattes and slags was developed. The impurities capacities (i.e. sulfur and arsenic) of slags were calculated a priori with no adjustable parameters using the Reddy-Blander model. The capacities predictions were made in a wide range of matte and slag compositions, Pso, and temperatures in conditions pertaining to copper and lead industrial slags. The calculated results for sulfide and arsenate capacities are in good agreement with the available experimental and industrial copper and lead industrial slags data. The sulfide and arsenate capacities in copper slags (fayalite, ferrite and olivine) and lead slags are reviewed. The application of RB model predicted ratios of 02 and S2 partial pressures in industrial copper smelting processes are discussed. Application of this model for the prediction of Sb, Bi and other impurity capacities and their distribution ratios in mattes or metal and slags, in industrial smelting and refining processes is discussed.

Jan 1, 2003

By Rennie Kaunda, David Streeter, John Kemeny

This paper describes a field/laboratory study that was conducted in cooperation with a mine in Arizona. The primary purpose of the study was to investigate the effect of blasting energy on the crushability and grindability of the post-blast rock fragments. The crushability and grindability of the rock fragments were evaluated through laboratory comminution tests. A secondary purpose of the study was to investigate different laboratory methods for estimating the comminution properties of the rock fragments. In particular, a number of standard rock mechanics tests were conducted and compared with the comminution test results. Finally, the study was used to evaluate new technologies for estimating insitu rock mass strength and for assessing post-blast fragmentation. To estimate in-situ rock mass strength, the specific energy of drilling (SE) was calculated during blast hole drilling utilizing a continuous drill monitoring system. Post-blast fragmentation was estimated using the Split image processing system. Results from the study support the idea that increases in blast energy can enhance crushing and grinding. Also, several simple rock mechanics tests were found to correlate well with the results from standard comminution tests, which could prove to be useful in practice.

Jan 1, 2003

By B. Zlender

ABSTRACT: The paper presents investigation of carboniferous slates from the Trojane hilly area performed on series of samples of equal material. The results of static loading tests show that carboniferous slate is heterogeneous and yields on slate layers. Where that kind of heterogeneity is distinctive the strength results are essentially lower of commonly tests results. The results of dynamical loading tests show that the slate surfaces have the essential meaning for the stability of the material. When those surfaces are moistened the material become unstable. RÉSUMÉ: L'article présente une épreuve des ardoises carbonifères de la région montagneuse de Trojane sur une série des échantillons des matériaux identiques. Les résultats des tests de charge statique montrent que l'ardoise carbonifère est hétérogène et qu'elle cède sur les couches d'ardoise. Quand l'hétérogénéité est distinctive, les résultats de stabilité sont essentiellement plus bas que les résultats obtenus par des tests ordinaires. Les résultats des tests de charge cyclique montrent que les surfaces d'ardoise sont très importantes pour la stabilité du matériel. Quand ces surfaces sont mouillés, le matériel devient instabile. ZUSAMMENFASSUNG: Der Artikel präsentiert die Forschung von Karbonschiefersteinen im Bereich des Bergland Trojane, ausgeführt durch Serien von Proben aus den gleichen Erdmaterial. Die Resultate der statischen Belastungsprüfungen zeigen, das die Karbonschiefersteine heterogen sind und die Schieferflächen nachlassen. Wo bei dieser Art der Heterogenität die Festigkeitsergebnisse wesentlich niedriger sind als bei gewöhnlichen Testergebnissen. Die Ergebnisse der zyklischen Belastungsprüfungen zeigen das die Schieferflächen eine wesentliche Bedeutung für die Stabilität des Erdmaterials haben. Wen diese Schieferflächen befeuchtet sind, wird das Erdmaterial unstabil.

Jan 1, 2003

By Buks Kruger

"After the milling and flotation of the platinum bearing ore, the flotation concentrate is electrically smelted in 6-in-line electric arc furnaces and the resulting furnace matte treated in Peirce Smith converters to remove the iron sulphide. The iron free (less than 1% Fe) converter matte is then granulated and sent to the Base Metals- and Precious Metals Refineries for further processing.During the smelting and converting processes two distinct gas streams are produced.The Peirce Smith converter off gas contains 4% - 9% SO2 which is treated in a conventional Sulphuric Acid Plant to produce sulphuric acid (H2SO4).The electric furnace off gas contains 0.9% SO2 and was (until September 2002) vented through a 91 meter high stack to atmosphere.Off gasses which contain less than 3% SO2 is difficult to handle and quite a few processes had been developed over the years to cope with this gas. A broad spectrum of process suppliers and technology approaches is available and the different technologies can be divided into a few main approaches i.e.Scrubbing of the off gas with an alkaline solution to produce an environmentally friendly and stable waste product which can be discharged onto a tailings dam or permanent landfill site.Physical absorption of the SO2 into a chemical solution to produce high quality chemically pure process chemicals.Catalytic reaction of SO2 with O2 to produce SO3 which is absorbed in water to produce sulphuric acid of less than 90% strength.In October 2002 Impala Platinum commissioned a Sulfacid Plant at its Smelter in Rustenburg which recovers the SO2 from the electric furnace off gasses into a weak sulphuric acid solution.The Sulfacid Plant technology is widely used in the paint pigment industry. This is, however, the first application of the technology on electric furnace off gas.The furnace off gasses contains flue dust which is removed in electrostatic precipitators. The gas exiting the precipitators normally still contains between 40 mg/Nm3 and 60 mg/Nm3 dust and passes through a quench-scrubber before entering the reactors. The quench-scrubber cools the electric furnace offgas down from ± 200 °C to 60 °C and act as a final dust removal stage."

Jan 1, 2003

By A K. Bayer

When the human eye fails in the evaluation of quality parameters in the extraction of minerals the use of laser-induced fluorescence analysis (LIF) can supply more detailed information on the composition of rocks. On the basis of measurements of selected raw materials engineering concepts for the use of this method in the mining industry as an innovative system for horizon control of mining machines will be described and the most important analysis parameters, influencing factors and interference variables are presented.

Jan 1, 2003

By Rex E. Loesby

The marble deposits of Yule Creek were first discovered in the late1870s. Minor quarrying occurred between that discovery and the early 1900s. Major development occurred in 1905, when Channing Meek, with some help from the Rockefellers, raised $3 million to develop the Colorado Yule Marble Quarry. That is $50 million in today’s dollars. Some of the words used to describe the marble deposit were “gigantic, remarkable, flawless and immense.” Boosters proclaimed, “The marble age is here.” Obviously, dreams were big for Marble.

Jan 1, 2003

By Nelson Collao I.

Loss of the organic phase from solvent extraction circuits is a major cost factor for SXEW operations. Recognized sources of loss include evaporation, entrainment, and biological degradation. The mechanisms for both entrainment and evaporative losses are well recognized. Biological degradation of the organic has not been as extensively evaluated as the other mechanisms but is a major source of loss. This paper discusses the impact of biological degradation on an operating plant, potential mechanisms for degradation, conditions under which biodegradation of plant organic can occur and plant conditions that may assist in promoting biodegradation.

Jan 1, 2003

By F. T. Cawood

Inauguration of the new political dispensation in South Africa in 1994 initiated a dynamic shift in the ownership, management and development of the country’s affluent mineral heritage. The process of substituting the old South African regime with a new equitable system, started soon after the 1994 election of the African National Congress (ANC) to parliament. The Congress’ Freedom Charter revealed the intent of the new dispensation when it called for radical transformation of mineral development. However, since 1955 there have been important changes affecting the rules of mineral development. These are: •Firstly, a drastic change in politics ushered in by negotiation, a spirit of reconciliation and a desire to settle disputes peacefully •Secondly, the globalization of the South African mining industry in tandem with the opening of domestic mineral resources to foreign capitalists; and •Thirdly, the introduction of sustainable development as a holistic approach to mineral development in order to replace traditional narrow-minded environmental management. Each of these significantly shaped the new mineral investment environment of South Africa. This paper represents a summary of the historical developments leading to the current Mineral and Petroleum Resources Development Act No. 28 of 2002, its Regulations, the much-publicised Broad-Based Socio-Economic Empowerment Charter and its associated Scorecard.

Jan 1, 2003

By G W. Wilson, M Aubertin

A desulfurised tailings cover was installed at the Detour Lake Mine in Ontario, Canada, to reduce oxygen penetration into the underlying sulfidic tailings. The cover ranges from one to 1.5 m in thickness and was intended to maintain high water saturation to reduce oxygen diffusion and consume oxygen by oxidation of the residual sulfide minerals. The tailings impoundment was instrumented to measure climatic parameters, water levels and water content profiles within the tailings and single-layer cover. One year of monitoring data was collected. Additional tailings samples were obtained for geotechnical and geochemical characterisation. The average grain size of the cover material was found to be coarser than the underlying tailings. Monitoring also indicated that air entry values of the cover material were lower than the tailings. Numerical modelling was conducted on the cover to predict water content profiles under varying climate conditions together with the depth of oxygen penetration and diffusive oxygen fluxes. Estimates of the diffusion coefficient and kinetic oxidation rates from field data compared well with values obtained by laboratory measurements. Numerical simulations indicate water saturations of less than 85 per cent can be expected under varying climate conditions. Predicted oxygen flux rates through the desulfurised cover over tailings with high acid potential indicate low flux rates reaching these tailings due to either consumption of oxygen by residual sulfur within the cover or saturation of the underlying tailings.

Jan 1, 2003

By J Andrina, D Richards

The Grasberg is a large copper and gold open pit mine operated by PT Freeport Indonesia and located in the high equatorial mountains of Papua Province, Indonesia. The climate is alpine/sub-alpine with little seasonal variation in temperature and rainfall. The annual precipitation varies from about 3000 to 5000 mm over short distances around the Grasberg, but in general, an average daily precipitation of 10 mm per day applies and leaching of the overburden is continuous throughout the year. Mining commenced in 1988, and almost all of the overburden mined up to 2003 was potentially acid forming. The current acid drainage from this overburden is being collected and treated. From 2004 to the end of the Grasberg pit operation in 2014, approximately 70 per cent of the overburden will be potentially acid forming and 30 per cent limestone. A program of laboratory leach columns, field test pads and an instrumented full-scale dump was developed with the objective of defining scale up factors to quantify the acid and metal leaching rates and to evaluate the stockpile geochemistry and control options. The results of an ongoing seven year program have demonstrated feasible scale up between laboratory columns, field test pads and the trial dump in relation to material geochemistry and ARD evolution trends at Grasberg. The potentially acid forming waste types are highly reactive and maximum acid generation rate occurs within two to three years and that maximum copper release occurs within one to two years of exposure. The results also show that the net acid generation (NAG) test provides a good estimate for the potential acid load from overburden types. The chemistry, temperature and oxygen data from the trial dump suggest that oxidation and acid generation is occurring throughout the dump but at a decreasing mass rate with increasing distance from the toe of the dump. It is apparent that convection and/or advection are important mechanisms for the transport of oxygen into and within the dump. Key results and findings of the investigations carried out are presented and the implications of the findings for long-term ARD management at the Grasberg mine are outlined.

Jan 1, 2003

By Karl J. C. Harries

13.1. RIGHT TO RECEIVE ROYALTY CONTRACTUAL ONLY1

Jan 1, 2003

By M .. Hori, H. Onishi, Y. Goda

The split-lining structure was newly developed for the air-tight lining of the underground compressed air storage cavern. This structure consists of separated reinforced concrete (RC) segments and air-tight membrane. It is most important for the Compressed Air Energy Storage Gas Turbine (CAES-G/T) system to develop the economical lining. In order to verify the applicability of split-lining structure, CAES-G/T pilot plant was constructed and operated for 6 months. We confirmed the practical usefulness and safety of this system through the operation. This paper presents the mechanical behaviour of surrounding rock mass and the lining structure observed through the operation of CAES-G/T pilot plant. Nous avons mis au point une structure de revêtement modulaire pour le revêtement des cavernes souterraines hermétiques à pression. Ce revêtement est composé de segments de béton armé et de membranes hermétiques. Il était très important, pour le CAES-G/T (Compressed Air Energy Storage Gas Turbine), de développer un revêtement économique. Afin de vérifier l’aptitude d’application de notre revêtement modulaire, nous avons construit un système pilote CAES-G/T et nous avons effectué des essais de fonctionnement pendant six mois. Ces essais nous ont permis de confirmer l’utilité et la sécurité du système. A travers le présent rapport, nous rendons compte de la structure de ce nouveau type de revêtement et du comportement mécanique de la masse rocheuse environnante que nous avons pu observer au cours desdits essais. Als luftdichter Druckbehälter wurde eine gegliederte Belagsstruktur für tief unterirdisch liegende Felshöhlungen entwickelt. Diese Struktur ist aus Stahlbetonabdeckung und luftdichter Plane aufgebaut. Bei der Entwicklung des Pressluftgasturbinen – Stromerzeugungssystems (CAES-G/T) war es die wichtigste Aufgabe, einen wirtschaftlichen Belag zu entwickeln. Deswegen wurde zum Nachweis der Effektivität der gegliederten Belagsstruktur eine Pilotanlage errichtet und 6 Monate lang betrieben. Durch den Betrieb konnten wir die Praktikabilität und Sicherheit des Systems bestätigen. Dieser Aufsatz ist ein Bericht über das Verhalten der durch Betrieb der CAES-G/T Pilotanlage beobachteten Belagsstruktur und umliegenden Felsmasse.

Jan 1, 2003

By Seong-Jong Kim

The formation behavior and corrosion characteristics of anodic oxide films on pure Mg and Mg-AI alloys were investigated focusing on the effects of anodizing potential, Al content, temperature and NaOH concentration. Pure Mg and Mg-AI alloys were anodized for 10 min at 3, 10, 40, and 80 V in NaOH solutions. Mg(OH)2 was generated by an active dissolution reaction at the surface of the specimen and the product was affected by temperature while MgO generation increased with NaOH concentration. Moreover, the current density after anodizing for 10 min at a constant potential decreased with increasing AI content in Mg-AI alloys,

Jan 1, 2003

By Glasswell K. Nkonde, Fredrick Chileshe, Steven Simukanga

Improving food security by increasing crop output is a primary objective for most countries in the sub- Saharan region. Most soils in the region are deficient in phosphorus an important nutrient after nitrogen in plant growth. Phosphates are therefore used together with nitrogen and potassium based fertilizers in improving crop production. Zambia like many other countries in the sub-Saharan region imports phosphate fertilizers for use by its farmers. However, indigenous phosphate deposits of igneous origin exist in Zambia of which the main ones are Chilembwe in Petauke district, Mumbwa sugarloaf in Mumbwa district, and Nkombwa Hill in Isoka district. If commercially exploited, these deposits could become a ready source of inexpensive phosphate for the local farming communities in the country. Previous research has shown that partially acidulated phosphate rock (PAPR) produced using Chilembwe phosphate rock is just as agronomically effective as the imported superphosphate fertilizers on food crops in most of the Zambian soils. PAPR is produced by reacting finely ground phosphate rock with only a fraction (usually 50%) of the stoichiometric quantity of the sulphuric acid required to fully convert the apatite in the rock to monocalcium phosphate thus making the process cheaper in terms of acid consumption than the poduction of single superphosphate where the apatite in the rock has to be fully converted to monocalcium phophate. The factors that affect the percentage of available P2O5 in the PAPR produced include particle size of phosphate rock, degree of acidulation, concentration of acid, process temperature profile, residence time and drying temperature. These factors were studied in a 25kg/hr PAPR pilot-plant in the School of Mines at the University of Zambia using Chilembwe phosphate rock. The PAPR pilot-plant consisted of a rotary drum granulator as the main reactor, a rotary drum dryer and a triple deck vibrating screen. Ground phosphate rock was reacted with sulphuric acid and water in the granulator to form a granular product which entered the drier. The dry product was screened into three size fractions. The 1 – 4 mm size fraction was the final product whilst the –1mm size fraction was recycled. The +4mm size fraction was sent to a crusher while the crushed PAPR was sent back to the screens.

Jan 1, 2003

By J. A. Finch, T. Weber

"Bubble size in flotation is strongly influenced by frother concentration in the pulp liquor. There is no accepted method of judging the dosage and thus how effectively frother is being distributed to control bubble size is not known. This will hamper certain plant test work where constant bubble size (e.g., when comparing reagents) is implicit. Bubble size is not easy to measure in plant and gas holdup is suggested as a surrogate in the development of a proposed “meter” to estimate frother concentration. The meter is calibrated to enable frother concentration to be estimated on samples drawn from any location in the flotation circuit. The meter and its calibration are described.As general background the action of frothers in reducing bubble size by retarding coalescence is discussed and the bubble generation systems for which the effect will be important are considered.INTRODUCTIONBubble size is an important variable in flotation. The flotation rate constant k has been related to mean bubble size Db by k % Db -n with n ranging up to 2 (Ahmed and Jameson, 1989) and even 3 (Yoon, 1993). Recent work has introduced k % Sb, the bubble surface area flux, given by Sb = 6 Jg / Db (where Jg is the superficial gas velocity or volumetric gas rate per unit cell cross-sectional area), i.e., n = 1 (Gorain et al., 1998). Regardless of the exact value of n, the significance of bubble size in flotation remains. In many plant trials it will be implicit that bubble size has not changed and attention will focus on other process variables. The measurement of bubble size, or a surrogate, would be useful addition to any test work.The size of the bubbles is influenced by several variables, gas rate, gas injection system (e.g., impeller design and rotation speed in a mechanical cell) and pulp composition (chemicals added, percent solids), but the most important is frother concentration (Harris, 1976). The frother functions by retarding coalescence (see appendix), which acts to preserve the small bubbles generated in the pulp (and permits a stable froth to form on top of the pulp). The measurement of bubble size is thus related to measuring frother concentration. The distribution of frother and whether sufficient (to control bubble size) is reaching the intended parts of the circuit then become important considerations. At present there is no simple way to judge frother concentration in a plant. In this communication we introduce a possible methodology, a “frother concentration meter”."

Jan 1, 2003

By Ximing Yuan, Yongsheng Xu, Hongjie Li

A study of a static demolition agent that can be used underwater has been carried out. A new type of granulated static demolition agent with rapid reaction has been tested in several hundred experiments. It can be used conveniently and simply in the field. It demonstrates a fast reaction rate with high expansion pressures. The important characteristic of the new type of granulated static demolition agent is the ability to function underwater. It will destroy rock and the other brittle material without flyrock, vibration, shock wave, toxic gas or noise. The reaction rate can be controlled within 30-60 minutes. It is difficult to use these products when the reaction rate is less than 30 minutes and it is less efficient when the reaction rate is longer than 60 minutes. The reaction rate is slightly increased after the material is kept in storage for two years. A new type of the hydraulic device that is used to measure the expansion pressure of solid materials has been designed. The expansion pressure of the granulated static demolition agent has been tested with the device. It is shows that the expansion pressure of the granulated static demolition agent can get to 80~120MPa in 60 minutes. Also included is a discussion of the thermodynamics of the static demolition agent.

Jan 1, 2003