The effect of replacing fine ore by coarse ore on sintering reactions was investigated using an infrared furnace on laboratory scale and sinter pots on pilot plant scale. Five sinter mixes were prepared by changing the percentage coarse ore from 0% to 100% in 25% increments. Coarse ore fraction, sintering temperature, holding time and oxygen partial pressure were selected as sintering parameters, and two-level factorial design was used for identification of parameters that significantly influence the formation of sinter phases. Experimental results showed that the coarse ore fraction has a higher effect on the sintering process compared to those of other parameters. The experiment design also enabled to set these parameters to their optimum values. The porosity of compacted pellets was measured using a helium pycnometer. The replacement of fine ore by coarse ore resulted in a decrease in porosity (increase in packing density) of compacted pellets. The particles are closer to each other in pellets consisting of more coarse particles than fine particles. Laboratory experiments were performed at 1300°C in air, using a high heating rate (15°C/s). The holding time was set to 2.5 minutes. X-ray diffraction (XRD), reflected light microscopy (RLM), scanning electron microscopy (SEM) and energy dispersive spectrometry (EDS) were used to characterize sintering reactions and sinter phases. XRD analysis revealed that sintered pellets consisted of hematite, SFCA, SFCA-I and calcium silicate. The proportions of SFCA slightly increased when the fraction of coarse ore varied from 0% to 25%, but decreased with a further increase in percentage coarse ore. At 25% coarse ore fraction, the porosity of the compacted pellets decreased, resulting in an increase in packing density and sintering rate. More hematite reacted, resulting in the formation of high amounts of SFCA. Above 25% coarse ore fraction, the amount of hematite increased, and the concentrations of columnar SFCA decreased despite a further decrease in porosity. This was attributed to the decrease in reaction surface area for coarse ore, and the short reaction time, which limited the extent of reaction of the coarse particles. The variation of SFCA-I and calcium silicate was not significant under laboratory conditions. Reflected light microscopy and SEM analysis easily identified two major sinter phases: hematite and SFCA. A clear distinction between the different types of SFCA could not be made using EDS analysis. Sinter pot tests were carried out in order to examine the effect of coarse ore fraction on physical and metallurgical properties of sinters. The tumbler and reduction disintegration indexes increased with increasing coarse ore fraction in the sinter bed. This was presumably due to the increase in amounts of hematite and decrease in surface area for reaction. Consequently, the reducibility of sinter decreased as the percentage coarse ore increased. This study has concluded that the presence of 25% coarse ore in the sinter mix led to enhance sintering reactions. The amounts of SFCA increased, and sinter quality was improved. It is recommended that in future work, sintering reactions should further be investigated by also measuring the permeability of the sinter bed and the reaction surface area of solid particles. Copyright / Dissertation (MSc)--University of Pretoria, 2012. / Materials Science and Metallurgical Engineering / unrestricted

O circuito de moagem de Carajás foi originalmente projetado para moagem de sinter feed, obtendose como produto final pellet feed. O processo consiste em etapas de moagem e deslamagem para que se atinjam as especificações de granulometria e área específica. No processo, como um todo, há geração significativa de finos, que são então descartados, acarretando em perdas de material que poderia ser incorporado como produto. O melhor entendimento das características dos vários tipos de minérios, bem como a previsão do desempenho do circuito de moagem em função de tais características permite estabelecer cenários para promover aumentos na recuperação em massa e na produtividade do circuito. O presente trabalho tem por base a caracterização tecnológica dos principais tipos de minério de Carajás e o desenvolvimento de um método para previsão de desempenho do circuito de moagem, em função de tais características. Para o desenvolvimento do método foram realizados ensaios de moagem em bancada e amostragens no circuito industrial. Os resultados dos ensaios de moagem em bancada serviram para definição das condições operacionais em que o ensaio em bancada melhor representou o circuito industrial, denominado ensaio padrão. Os dados obtidos nas amostragens e na caracterização tecnológica serviram de base para a calibração dos modelos matemáticos dos equipamentos de processo. O modelo calibrado constituiu num excelente recurso para previsão de desempenho. O desempenho do circuito de moagem foi avaliado no que se refere à granulometria e área específica dos produtos obtidos. Ainda foram conduzidas simulações pelo ensaio padrão e pelo modelo calibrado integrado do circuito de moagem, que apontam potenciais dos minérios cujo comportamento na moagem era até então desconhecido. Os dois produtos aqui desenvolvidos são, portanto, de aplicação imediata como recursos para previsão de desempenho e melhoria operacional. / Originally designed for sinter feed grinding, the Carajas grinding circuit includes two ball mills in parallel lines in a closed configuration with cyclones. The ground product is further deslimed in hydrocyclone for achieving the final specifications regarding size distribution and surface area. In this process, there is a significant amount of high grade material, not recovered due to overgrind. Ore characterization was here selected for predicting the grinding circuit performance, which in turn was the basis for optimization. The aim of this work is the characterization of the main Carajas ore types as well as the development of a method that includes these characteristics for predicting the grinding circuit performance. Laboratory grinding tests and samplings in the industrial circuit were carried out to predict the grinding circuit performance. The grinding test results were used to set operational conditions in which the laboratory better represented the industrial circuit. Results from industrial sampling and characterization were the basis for fitting the mathematical models. The fitted model was an excellent resource for the prediction of the grinding circuit performance as well as for the grinding test. To assess the grinding performance, products size distribution and surface area were evaluated. Moreover, simulations of the grinding circuit indicated the potential of some ore types. The derived methods were validated as tools for predicting the grinding circuit performance and for operational optimization.

The intention of the study was to find the preferred medium of communication and the preferred language for the dissemination of Human Immunodeficiency Virus/Acquired Immune Deficiency Syndrome (HIV/AIDS) information among the unskilled employees of Kumba Iron Ore mining company, with an assumption that disseminating of appropriate information can influence positive behaviour change with respect to the HIV/AIDS disease. In this study company and clinic workshops came up as the most preferred media for receiving HIV/AIDS information and English came up as the most preferred language for all the media types except radio where Tswana-Sotho came up as the most preferred language. It also came up clearly in the findings that most women do not like to discuss HIV/AIDS issues with friends or relatives / Dissertation (MIT)--University of Pretoria, 2012. / Information Science / Unrestricted

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This study attempts to provide detailed analysis of materials gathered from various sources and to an orderly presentation of facts and figures regarding railway construction in China.

Ore specimens from the cupriferous zone of the basal Nonesuch shale at the White Pine Mine were analysed for sulphur isotopes, carbon and sulphide contents and boron. The results of the analyses were discussed in relation to a biogenic-syngenetic mineralization process for the ore body. A model, based on the δS³⁴sulphide frequency distribution, was developed to determine the δS³⁴ sulphate value of the lower Nonesuch paleoenvironment. A transmitted light microscopic examination of chlorite was undertaken in order to present a more complete picture of this proposed source for copper in the cupriferous zone of the Nonesuch shale. / Thesis / Master of Science (MSc)

Banded iron formations (BIFs) are iron oxide- and silica-rich chemical sedimentary rocks and the principal source of high-grade (HG) iron ore. Magnetic survey methods are commonly applied in the exploration for BIF-hosted iron ore deposits but the interpretation of total magnetic intensity (TMI) data is often complicated by the presence of strong remanent magnetization and anisotropy of magnetic susceptibility (AMS). This study evaluated a tri-axial fluxgate vector magnetometer system for ground-based high-resolution mapping of BIF-hosted HG iron ore deposits at a 16 ha site near Mary River, Baffin Island. Magnetometer orientation was measured using a MEMS (Micro Electro-Mechanical System) accelerometer and dual D-GPS receivers. 12-oriented block samples were collected for analysis of rock magnetic properties and supplemented with outcrop measurements using a hand-held susceptibility probe. The large (3 Gauss) dynamic range of the tri-axial vector magnetometer permitted mapping of HG magnetite ore zones, with TMI in excess of 400,000 nT. A 20 m-wide W-E trending HG zone and a narrow (<10 m) BIF zone were identified in RMV maps with distinctive dipole signatures. Within the HG zone a northwest-southeast oriented magnetic fabric was defined by linear magnetic lows that offset the strike of the HG ore zone and were interpreted as brittle faults or shear zones. The RMV orientation indicated the presence of strong bedding parallel magnetization, while its signal amplitude showed a wide variation between ore types and provided basis for ore grade differentiation. Paleomagnetic measurements revealed high Q ratios for hematite ores and strong AMS for BIF. The results from Mary River demonstrate that remanence and AMS effects are important in BIF-hosted iron ores and cannot be neglected in magnetic interpretation and inversion modelling of magnetic source bodies. / Thesis / Master of Science (MSc)

<p> Sulphur isotope data from coexisting sulphides and sulphates from the 120m level of the Shangtancen ore body of the Taolin Pb-Zn ore deposit have been used to estimate the temperatures of sulphur mineral precipitation. The data indicate that sulphide was the dominant species in solution at both high and low temperatures. The data also show that the 𝛿34S value of total sulphur in solution was close to zero at high temperatures, but had low negative values (about -6.7‰) at low temperatures. This is interpreted in terms of the effects of mineral precipitation on the isotopic 34 composition of the solution. The decrease of the 𝛿34S value of the total sulphur with decreasing temperature was brought about because the removal from the system, by precipitation, of isotopically heavy sulphate exceeded the removal from the system, by precipitation, of isotopically light sulphide.</p> / Thesis / Bachelor of Science (BSc)

<p> The McBean Mine is a small gold producer located along the Larder Lake Break. Ore from the open pit consists of massive and gneissic syenite. The highest go I d grades come from highly carbonitized syenitic rocks with abundant fine grained, euhedral pyrite. Petrographic observation shows gold to be found as inclusions in pyrite, platings on pyrite and as free grains in the gangue. XRD analyses show the major carbonate type to be dolomite. In addition to dolomite, minor amounts of calcite are found in auriferous syenitic rocks. SEM microscopy shows carbonate composition to vary with rock types and grain location. Geochemical studies show a high intensity of carbonate alteration and the association of gold with tungsten and uranium. Auriferous syenites were determined to have elevated HREE element abundances compared with unaltered syenite. The mine is therefore characterized by extensive hydrothermal carbonate alteration related to the Larder Lake Break. </p> / Thesis / Bachelor of Science (BSc)