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The use of magnetite as a medium in the wet processing of coal has been used since the early days of dense medium separation. The high magnetic susceptibility and density of magnetite make it an ideal medium to use in wet coal beneficiation because it is relatively easily and successfully recoverable. Owing to the need for more sustainable technologies, Coaltech has been investigating alternative dry processing processes: the Bohou process (developed in China) was identified as a possible feasible option. The Bohou process comprises dry dense medium separation using magnetite as the medium. The recovery and re-use of magnetite are, however, problematic. The aim of this investigation was to determine how efficiently magnetite can be recovered and to identify the factors influencing the magnetite losses during this dry processing. The test work for the project was divided into two phases. The aim of Phase 1 was to identify the magnetite losses to the oversize coal fraction for different moisture conditions of the coal and magnetite. In Phase 2, magnetite and high-titanium magnetite (an alternative source of magnetite) were used to conduct test work to determine which medium could be successfully recovered from fine coal. Magnetite or high-titanium magnetite was mixed with the coal sample as a medium. During Phase 2, the effects of using different screens and different moisture conditions were investigated. For both phases, the samples received were divided into three categories containing different moisture contents: dry coal and dry magnetite, dry coal with wet magnetite (4% to 4.4%), and wet coal (3.5% to 6.5%) with dry magnetite. In Phase 1, the coal samples were screened at 13.2 mm, the oversize mixed with magnetite, and then screened again with a 13.2 mm screen: the magnetite losses were then recorded. For Phase 2, the prepared samples were screened at 3 mm, 13.2 mm, and with a 3 mm high-frequency screen. The undersize was passed through a low-intensity magnetic separator. The recovered magnetite was then passed over a magna chute to recover additional magnetite. ii The results for both phases indicated that the highest recovery of magnetite occurred when dry magnetite and dry coal samples were used. The samples with wet magnetite also gave high recovery, but the samples with wet coal were detrimental to recovery and significant losses were observed. It was found that the magnetite stuck to the surface moisture of the coal. The use of a high-frequency screen improved recovery of the magnetite from the wet coal samples from 45.38% to 74.27%. Recovery from the high-frequency screen for both dry and wet magnetite samples was lower than that achieved with a conventional 3 mm screen. The test results indicated that magnetite can be recovered in the dry beneficiation of coal when the surface moistures of both the coal and magnetite are controlled. Use of a high-frequency screen can improve recoveries only for conditions where the surface moisture of the coal is high. / Dissertation (MSc (Metallurgy))--University of Pretoria, 2021. / CoalTech / Materials Science and Metallurgical Engineering / MSc (Metallurgy) / Unrestricted

Flotation is the separation process most used to recover valuable minerals from sulphide ores. The design of industrial flotation plants is a complex process involving many stages. Current design practice involves performing laboratory scale grinding and batch flotation tests, followed by a circuit design based on the scale-up of the laboratory kinetics and recovery-grade data. A pilot plant is then operated to evaluate the performance of the circuit based on recovery and grade, usually in the configuration of the intended full-scale plant. The circuit design is refined and economically evaluated after which the design of the full-scale plant is performed. A new approach to full-scale flotation plant design has been proposed by the Julius Kruttschnitt Mineral Research Centre and the Mineral Processing Research Unit of the University of Cape Town, as part of the Australian Minerals Industries Research Association (AMIRA) P9 Project. In this new methodology, the effects of the ore on plant performance are decoupled from the circuit effects. The ore properties are characterised by operating the pilot plant in as simple a configuration as possible. The pilot plant units are configured to perform a similar duty (in terms of mineral content and particle size) to the full-scale operation and their response measured. An important factor in the success of the methodology is having a pilot plant that is capable of accurately characterising the ore properties. For this purpose, the Wemco® Floatability Characterisation Test Rig (FCTR) was built. The FCTR is a self-contained, highly instrumented mobile pilot plant designed to develop and validate the new flotation plant design methodology. The aims of this thesis were to propose, develop and validate a methodology for using the FCTR to design industrial flotation plants. The hypothesis was that full-scale flotation plant design could be accurately performed using the P9 flotation model and modelling and scale-up methodologies, in conjunction with the FCTR. Test work was performed in three main areas: calibration of the ore characteristics and model parameters for the flotation model currently used by the AMIRA P9 Project; validation of the flotation model and modelling methodology; and prediction of full-scale plant performance using parameters determined on the FCTR. The ore floatability characteristics were calibrated using four FCTR circuits of increasing complexity. The ore floatability characteristics were determined for various models derived from data from one, two, three and four calibration circuits. Validation of the flotation model and modelling methodology was performed using three validation methods: internal validity tests, parameter sensitivity tests and predictive validation. From the internal validity tests, some of the models did not meet the validation criteria. The parameter sensitivity tests used Monte Carlo simulations to determine the sensitivity of the regressed model parameters. The tests produced small differences in the values determined from the models and the average values from the Monte Carlo simulations. The floatability characteristics appeared to be stable and unique. Predictive validation was performed using five FCTR circuits, different in configuration to the calibration circuits. The predictive validation was performed using the floatability characteristics determined from each of the calibration models, in conjunction with estimates of the model parameters. Overall, the predictions of the circuit performance were accurate and within experimental standard deviations for most streams in the circuits. The predictions of the key parameters of pentlandite and chalcopyrite recovery were accurate, especially for the final concentrate. The prediction of pyrrhotite recovery produced the largest errors. The prediction of pyrrhotite recovery appeared to be dependent on the addition of depressant to the cleaner and recleaner circuits of the circuit to be predicted. When the depressant addition rates were significantly different from those used in the calibration circuits, the prediction of pyrrhotite recovery was inaccurate. These errors were however reduced when experimental water recovery values were used. The extensive and robust validation of the flotation model and modelling methodology has shown that the flotation model and modelling methodology are valid under certain conditions. This test work represents the first comprehensive validation of the flotation model and modelling methodology incorporating changes in circuit configuration. Using the proposed modelling and scale-up methodology in conjunction with the FCTR, the metallurgical performance of three industrial flotation circuits were predicted. The predicted results were then compared to the experimentally determined results around the industrial circuits. In each case, a scale-up factor between the ore floatability characteristics determined on the FCTR, and the full-scale floatability characteristics, was required to achieve an accurate prediction. The scale-up factor ranged from 0.17 to 0.97 for the case studies investigated. In light of the results from each stage of test work, the proposed flotation plant design methodology was refined. With this methodology and the continual development of techniques for the measurement and prediction of the P9 flotation model parameters, accurate industrial plant design using the FCTR will become possible. With the addition of other unit operations, such as comminution, into the flowsheet, this methodology will eventually lead to the achievement of the ultimate goal of accurate plant design of green-field sites.

Flotation is the separation process most used to recover valuable minerals from sulphide ores. The design of industrial flotation plants is a complex process involving many stages. Current design practice involves performing laboratory scale grinding and batch flotation tests, followed by a circuit design based on the scale-up of the laboratory kinetics and recovery-grade data. A pilot plant is then operated to evaluate the performance of the circuit based on recovery and grade, usually in the configuration of the intended full-scale plant. The circuit design is refined and economically evaluated after which the design of the full-scale plant is performed. A new approach to full-scale flotation plant design has been proposed by the Julius Kruttschnitt Mineral Research Centre and the Mineral Processing Research Unit of the University of Cape Town, as part of the Australian Minerals Industries Research Association (AMIRA) P9 Project. In this new methodology, the effects of the ore on plant performance are decoupled from the circuit effects. The ore properties are characterised by operating the pilot plant in as simple a configuration as possible. The pilot plant units are configured to perform a similar duty (in terms of mineral content and particle size) to the full-scale operation and their response measured. An important factor in the success of the methodology is having a pilot plant that is capable of accurately characterising the ore properties. For this purpose, the Wemco® Floatability Characterisation Test Rig (FCTR) was built. The FCTR is a self-contained, highly instrumented mobile pilot plant designed to develop and validate the new flotation plant design methodology. The aims of this thesis were to propose, develop and validate a methodology for using the FCTR to design industrial flotation plants. The hypothesis was that full-scale flotation plant design could be accurately performed using the P9 flotation model and modelling and scale-up methodologies, in conjunction with the FCTR. Test work was performed in three main areas: calibration of the ore characteristics and model parameters for the flotation model currently used by the AMIRA P9 Project; validation of the flotation model and modelling methodology; and prediction of full-scale plant performance using parameters determined on the FCTR. The ore floatability characteristics were calibrated using four FCTR circuits of increasing complexity. The ore floatability characteristics were determined for various models derived from data from one, two, three and four calibration circuits. Validation of the flotation model and modelling methodology was performed using three validation methods: internal validity tests, parameter sensitivity tests and predictive validation. From the internal validity tests, some of the models did not meet the validation criteria. The parameter sensitivity tests used Monte Carlo simulations to determine the sensitivity of the regressed model parameters. The tests produced small differences in the values determined from the models and the average values from the Monte Carlo simulations. The floatability characteristics appeared to be stable and unique. Predictive validation was performed using five FCTR circuits, different in configuration to the calibration circuits. The predictive validation was performed using the floatability characteristics determined from each of the calibration models, in conjunction with estimates of the model parameters. Overall, the predictions of the circuit performance were accurate and within experimental standard deviations for most streams in the circuits. The predictions of the key parameters of pentlandite and chalcopyrite recovery were accurate, especially for the final concentrate. The prediction of pyrrhotite recovery produced the largest errors. The prediction of pyrrhotite recovery appeared to be dependent on the addition of depressant to the cleaner and recleaner circuits of the circuit to be predicted. When the depressant addition rates were significantly different from those used in the calibration circuits, the prediction of pyrrhotite recovery was inaccurate. These errors were however reduced when experimental water recovery values were used. The extensive and robust validation of the flotation model and modelling methodology has shown that the flotation model and modelling methodology are valid under certain conditions. This test work represents the first comprehensive validation of the flotation model and modelling methodology incorporating changes in circuit configuration. Using the proposed modelling and scale-up methodology in conjunction with the FCTR, the metallurgical performance of three industrial flotation circuits were predicted. The predicted results were then compared to the experimentally determined results around the industrial circuits. In each case, a scale-up factor between the ore floatability characteristics determined on the FCTR, and the full-scale floatability characteristics, was required to achieve an accurate prediction. The scale-up factor ranged from 0.17 to 0.97 for the case studies investigated. In light of the results from each stage of test work, the proposed flotation plant design methodology was refined. With this methodology and the continual development of techniques for the measurement and prediction of the P9 flotation model parameters, accurate industrial plant design using the FCTR will become possible. With the addition of other unit operations, such as comminution, into the flowsheet, this methodology will eventually lead to the achievement of the ultimate goal of accurate plant design of green-field sites.

Flotation is the separation process most used to recover valuable minerals from sulphide ores. The design of industrial flotation plants is a complex process involving many stages. Current design practice involves performing laboratory scale grinding and batch flotation tests, followed by a circuit design based on the scale-up of the laboratory kinetics and recovery-grade data. A pilot plant is then operated to evaluate the performance of the circuit based on recovery and grade, usually in the configuration of the intended full-scale plant. The circuit design is refined and economically evaluated after which the design of the full-scale plant is performed. A new approach to full-scale flotation plant design has been proposed by the Julius Kruttschnitt Mineral Research Centre and the Mineral Processing Research Unit of the University of Cape Town, as part of the Australian Minerals Industries Research Association (AMIRA) P9 Project. In this new methodology, the effects of the ore on plant performance are decoupled from the circuit effects. The ore properties are characterised by operating the pilot plant in as simple a configuration as possible. The pilot plant units are configured to perform a similar duty (in terms of mineral content and particle size) to the full-scale operation and their response measured. An important factor in the success of the methodology is having a pilot plant that is capable of accurately characterising the ore properties. For this purpose, the Wemco® Floatability Characterisation Test Rig (FCTR) was built. The FCTR is a self-contained, highly instrumented mobile pilot plant designed to develop and validate the new flotation plant design methodology. The aims of this thesis were to propose, develop and validate a methodology for using the FCTR to design industrial flotation plants. The hypothesis was that full-scale flotation plant design could be accurately performed using the P9 flotation model and modelling and scale-up methodologies, in conjunction with the FCTR. Test work was performed in three main areas: calibration of the ore characteristics and model parameters for the flotation model currently used by the AMIRA P9 Project; validation of the flotation model and modelling methodology; and prediction of full-scale plant performance using parameters determined on the FCTR. The ore floatability characteristics were calibrated using four FCTR circuits of increasing complexity. The ore floatability characteristics were determined for various models derived from data from one, two, three and four calibration circuits. Validation of the flotation model and modelling methodology was performed using three validation methods: internal validity tests, parameter sensitivity tests and predictive validation. From the internal validity tests, some of the models did not meet the validation criteria. The parameter sensitivity tests used Monte Carlo simulations to determine the sensitivity of the regressed model parameters. The tests produced small differences in the values determined from the models and the average values from the Monte Carlo simulations. The floatability characteristics appeared to be stable and unique. Predictive validation was performed using five FCTR circuits, different in configuration to the calibration circuits. The predictive validation was performed using the floatability characteristics determined from each of the calibration models, in conjunction with estimates of the model parameters. Overall, the predictions of the circuit performance were accurate and within experimental standard deviations for most streams in the circuits. The predictions of the key parameters of pentlandite and chalcopyrite recovery were accurate, especially for the final concentrate. The prediction of pyrrhotite recovery produced the largest errors. The prediction of pyrrhotite recovery appeared to be dependent on the addition of depressant to the cleaner and recleaner circuits of the circuit to be predicted. When the depressant addition rates were significantly different from those used in the calibration circuits, the prediction of pyrrhotite recovery was inaccurate. These errors were however reduced when experimental water recovery values were used. The extensive and robust validation of the flotation model and modelling methodology has shown that the flotation model and modelling methodology are valid under certain conditions. This test work represents the first comprehensive validation of the flotation model and modelling methodology incorporating changes in circuit configuration. Using the proposed modelling and scale-up methodology in conjunction with the FCTR, the metallurgical performance of three industrial flotation circuits were predicted. The predicted results were then compared to the experimentally determined results around the industrial circuits. In each case, a scale-up factor between the ore floatability characteristics determined on the FCTR, and the full-scale floatability characteristics, was required to achieve an accurate prediction. The scale-up factor ranged from 0.17 to 0.97 for the case studies investigated. In light of the results from each stage of test work, the proposed flotation plant design methodology was refined. With this methodology and the continual development of techniques for the measurement and prediction of the P9 flotation model parameters, accurate industrial plant design using the FCTR will become possible. With the addition of other unit operations, such as comminution, into the flowsheet, this methodology will eventually lead to the achievement of the ultimate goal of accurate plant design of green-field sites.

Espirais concentradoras têm sido largamente empregadas no beneficiamento de finos de carvão no Brasil. O objetivo geral deste trabalho foi estudar do beneficiamento de carvão em uma espiral, avaliando a eficiência do beneficiamento do carvão da Camada Barro Branco e caracterizando seus produtos. Ênfase foi dada ao rejeito, avaliando as possibilidades de aproveitamento do material e o seu potencial de geração de acidez. A metodologia do trabalho incluiu a caracterização da alimentação e dos produtos de uma espiral em termos de análise imediata e enxofre; estudo da lavabilidade do carvão de alimentação; avaliação da eficiência do beneficiamento e a caracterização do rejeito em termos ambientais. Em valores médios, a alimentação das espirais apresenta um teor de cinzas de 67,5%, um teor de enxofre de 5,2% e um poder calorífico superior de 2377 cal/g. O concentrado apresentou um teor de cinzas de 50,5%, um teor de enxofre de 1,7% e um poder calorífico superior de 3978 cal/g; enquanto que o rejeito um teor de cinzas 78,2%, um teor de enxofre de 7,5% e um poder calorífico superior de 1364 cal/g. A recuperação mássica de concentrado é de aproximadamente 40%. O concentrado atende as especificações da termoelétrica em relação ao teor de enxofre e matéria volátil, mas não atende as especificações de cinzas e poder calorífico. O concentrado das espirais consegue destinação uma vez que é misturado a carvões de melhor qualidade produzidos pela mesma ou outras mineradoras. Quanto a lavabilidade, na densidade de corte de 2,0, o valor do NGM foi de 15%, caracterizando o material como moderadamente difícil ou de difícil separação. A eficiência do beneficiamento na espiral é baixa. O valor do Desvio Provável Médio (EPM), Imperfeição (I) e a Área de Erro foram, respectivamente, de 0,30, 0,30 e 178,13 cm2. Esses parâmetros apontam que o equipamento não apresenta uma boa precisão de separação. O rejeito de carvão descartado da espiral apresenta um NNP de – 209 kg CaCO3/t, indicando um alto potencial de geração de drenagem ácida. Deve-se somar a isso a baixa granulometria (entre 0,1 e 2,0 mm) e a alta área superficial (41 m2/g) do material, que propiciará taxas mais altas de geração de acidez que o rejeito grosso. Analisando os dados, as espirais, mesmo com a baixa precisão, estão exercendo sua função de forma satisfatória para a empresa no sentido de produção de um carvão energético com teor de S aceitável. / Spiral concentrators have been widely used to process coal fines in Brazil. The aim of this work was to study coal beneficiation in a spiral, evaluating its performance for the “Barro Branco” seam. Emphasis was given to the waste material, evaluating a potential use and the acid generation. The methodology of this project included the characterization of the feed and the products of the spiral in terms of immediate analysis, washability curve of coal, and the equipment efficiency in terms of Tromp Curve. The feed material has an ash content of 67.5%, a sulfur content of 5.2%, and a gross calorific value of 2377 cal/g. The concentrate showed an ash content of 50.5%, a sulfur content of 1.7% and gross calorific value of 3978 cal/g; while the reject one had an ash content of 78.2%, a sulfur content of 7.5%, and a gross calorific value of 1364 cal/g. The recovery of the concentrated weight is approximately 40%. The concentrated meets the thermal specifications related to sulfur content and volatile matter, but it does not meet the specifications of ashes and calorific values. So, it is mixed with coals of better quality to attend the thermoelectric standards. Concerning the wash ability, in the cut density of 2.0, the NGM was 15%, characterizing the material as moderately difficult or difficult to separate. Analyzing the Tromp Curve, the value of the deviation probable medium (EPM), Imperfection (I) and the Error Area were, respectively, 0.30, 0.30 and 178.13 cm2. These parameters indicate that the equipment does not show a good precision of separation. The rejected material on the spiral showed a NNP of - 209 kg CaCO3/t, indicating a high potential for acid drainage generation. It should be considered that the material presented a fine particle size (0.1 to 2.0 mm) and a high surface area (41 m2/g), which certainly will provide high pyrite oxidations rates. Analyzing the data as a whole, spirals, even with the low precision, is exercising their function to provide an energetic coal with an acceptable sulphur content, leaving no doubt about its applicability.

Espirais concentradoras têm sido largamente empregadas no beneficiamento de finos de carvão no Brasil. O objetivo geral deste trabalho foi estudar do beneficiamento de carvão em uma espiral, avaliando a eficiência do beneficiamento do carvão da Camada Barro Branco e caracterizando seus produtos. Ênfase foi dada ao rejeito, avaliando as possibilidades de aproveitamento do material e o seu potencial de geração de acidez. A metodologia do trabalho incluiu a caracterização da alimentação e dos produtos de uma espiral em termos de análise imediata e enxofre; estudo da lavabilidade do carvão de alimentação; avaliação da eficiência do beneficiamento e a caracterização do rejeito em termos ambientais. Em valores médios, a alimentação das espirais apresenta um teor de cinzas de 67,5%, um teor de enxofre de 5,2% e um poder calorífico superior de 2377 cal/g. O concentrado apresentou um teor de cinzas de 50,5%, um teor de enxofre de 1,7% e um poder calorífico superior de 3978 cal/g; enquanto que o rejeito um teor de cinzas 78,2%, um teor de enxofre de 7,5% e um poder calorífico superior de 1364 cal/g. A recuperação mássica de concentrado é de aproximadamente 40%. O concentrado atende as especificações da termoelétrica em relação ao teor de enxofre e matéria volátil, mas não atende as especificações de cinzas e poder calorífico. O concentrado das espirais consegue destinação uma vez que é misturado a carvões de melhor qualidade produzidos pela mesma ou outras mineradoras. Quanto a lavabilidade, na densidade de corte de 2,0, o valor do NGM foi de 15%, caracterizando o material como moderadamente difícil ou de difícil separação. A eficiência do beneficiamento na espiral é baixa. O valor do Desvio Provável Médio (EPM), Imperfeição (I) e a Área de Erro foram, respectivamente, de 0,30, 0,30 e 178,13 cm2. Esses parâmetros apontam que o equipamento não apresenta uma boa precisão de separação. O rejeito de carvão descartado da espiral apresenta um NNP de – 209 kg CaCO3/t, indicando um alto potencial de geração de drenagem ácida. Deve-se somar a isso a baixa granulometria (entre 0,1 e 2,0 mm) e a alta área superficial (41 m2/g) do material, que propiciará taxas mais altas de geração de acidez que o rejeito grosso. Analisando os dados, as espirais, mesmo com a baixa precisão, estão exercendo sua função de forma satisfatória para a empresa no sentido de produção de um carvão energético com teor de S aceitável. / Spiral concentrators have been widely used to process coal fines in Brazil. The aim of this work was to study coal beneficiation in a spiral, evaluating its performance for the “Barro Branco” seam. Emphasis was given to the waste material, evaluating a potential use and the acid generation. The methodology of this project included the characterization of the feed and the products of the spiral in terms of immediate analysis, washability curve of coal, and the equipment efficiency in terms of Tromp Curve. The feed material has an ash content of 67.5%, a sulfur content of 5.2%, and a gross calorific value of 2377 cal/g. The concentrate showed an ash content of 50.5%, a sulfur content of 1.7% and gross calorific value of 3978 cal/g; while the reject one had an ash content of 78.2%, a sulfur content of 7.5%, and a gross calorific value of 1364 cal/g. The recovery of the concentrated weight is approximately 40%. The concentrated meets the thermal specifications related to sulfur content and volatile matter, but it does not meet the specifications of ashes and calorific values. So, it is mixed with coals of better quality to attend the thermoelectric standards. Concerning the wash ability, in the cut density of 2.0, the NGM was 15%, characterizing the material as moderately difficult or difficult to separate. Analyzing the Tromp Curve, the value of the deviation probable medium (EPM), Imperfection (I) and the Error Area were, respectively, 0.30, 0.30 and 178.13 cm2. These parameters indicate that the equipment does not show a good precision of separation. The rejected material on the spiral showed a NNP of - 209 kg CaCO3/t, indicating a high potential for acid drainage generation. It should be considered that the material presented a fine particle size (0.1 to 2.0 mm) and a high surface area (41 m2/g), which certainly will provide high pyrite oxidations rates. Analyzing the data as a whole, spirals, even with the low precision, is exercising their function to provide an energetic coal with an acceptable sulphur content, leaving no doubt about its applicability.

Espirais concentradoras têm sido largamente empregadas no beneficiamento de finos de carvão no Brasil. O objetivo geral deste trabalho foi estudar do beneficiamento de carvão em uma espiral, avaliando a eficiência do beneficiamento do carvão da Camada Barro Branco e caracterizando seus produtos. Ênfase foi dada ao rejeito, avaliando as possibilidades de aproveitamento do material e o seu potencial de geração de acidez. A metodologia do trabalho incluiu a caracterização da alimentação e dos produtos de uma espiral em termos de análise imediata e enxofre; estudo da lavabilidade do carvão de alimentação; avaliação da eficiência do beneficiamento e a caracterização do rejeito em termos ambientais. Em valores médios, a alimentação das espirais apresenta um teor de cinzas de 67,5%, um teor de enxofre de 5,2% e um poder calorífico superior de 2377 cal/g. O concentrado apresentou um teor de cinzas de 50,5%, um teor de enxofre de 1,7% e um poder calorífico superior de 3978 cal/g; enquanto que o rejeito um teor de cinzas 78,2%, um teor de enxofre de 7,5% e um poder calorífico superior de 1364 cal/g. A recuperação mássica de concentrado é de aproximadamente 40%. O concentrado atende as especificações da termoelétrica em relação ao teor de enxofre e matéria volátil, mas não atende as especificações de cinzas e poder calorífico. O concentrado das espirais consegue destinação uma vez que é misturado a carvões de melhor qualidade produzidos pela mesma ou outras mineradoras. Quanto a lavabilidade, na densidade de corte de 2,0, o valor do NGM foi de 15%, caracterizando o material como moderadamente difícil ou de difícil separação. A eficiência do beneficiamento na espiral é baixa. O valor do Desvio Provável Médio (EPM), Imperfeição (I) e a Área de Erro foram, respectivamente, de 0,30, 0,30 e 178,13 cm2. Esses parâmetros apontam que o equipamento não apresenta uma boa precisão de separação. O rejeito de carvão descartado da espiral apresenta um NNP de – 209 kg CaCO3/t, indicando um alto potencial de geração de drenagem ácida. Deve-se somar a isso a baixa granulometria (entre 0,1 e 2,0 mm) e a alta área superficial (41 m2/g) do material, que propiciará taxas mais altas de geração de acidez que o rejeito grosso. Analisando os dados, as espirais, mesmo com a baixa precisão, estão exercendo sua função de forma satisfatória para a empresa no sentido de produção de um carvão energético com teor de S aceitável. / Spiral concentrators have been widely used to process coal fines in Brazil. The aim of this work was to study coal beneficiation in a spiral, evaluating its performance for the “Barro Branco” seam. Emphasis was given to the waste material, evaluating a potential use and the acid generation. The methodology of this project included the characterization of the feed and the products of the spiral in terms of immediate analysis, washability curve of coal, and the equipment efficiency in terms of Tromp Curve. The feed material has an ash content of 67.5%, a sulfur content of 5.2%, and a gross calorific value of 2377 cal/g. The concentrate showed an ash content of 50.5%, a sulfur content of 1.7% and gross calorific value of 3978 cal/g; while the reject one had an ash content of 78.2%, a sulfur content of 7.5%, and a gross calorific value of 1364 cal/g. The recovery of the concentrated weight is approximately 40%. The concentrated meets the thermal specifications related to sulfur content and volatile matter, but it does not meet the specifications of ashes and calorific values. So, it is mixed with coals of better quality to attend the thermoelectric standards. Concerning the wash ability, in the cut density of 2.0, the NGM was 15%, characterizing the material as moderately difficult or difficult to separate. Analyzing the Tromp Curve, the value of the deviation probable medium (EPM), Imperfection (I) and the Error Area were, respectively, 0.30, 0.30 and 178.13 cm2. These parameters indicate that the equipment does not show a good precision of separation. The rejected material on the spiral showed a NNP of - 209 kg CaCO3/t, indicating a high potential for acid drainage generation. It should be considered that the material presented a fine particle size (0.1 to 2.0 mm) and a high surface area (41 m2/g), which certainly will provide high pyrite oxidations rates. Analyzing the data as a whole, spirals, even with the low precision, is exercising their function to provide an energetic coal with an acceptable sulphur content, leaving no doubt about its applicability.

Beneficiation of fine coal (+500 μm –2000 μm) is a worldwide problem in the mining industry, especially dry beneficiation of fine coal. Coal beneficiation can be divided primarily into two methods, namely wet- and dry beneficiation. Wet beneficiation methods are utilized more in today‘s industry because of the sharp separation efficiency that can be achieved. These processes include wet jigging, dense medium cyclones, spiral beneficiation etc. Due to the lack of a sufficient water supply in some regions around the world including South Africa, dry beneficiation methods are becoming more popular. Recent mechanized mining methods caused the fraction of fines from coal mines to increase over the years. However, due to old inefficient technologies, coal fines contained in slurry ponds could not be beneficiated and had to be discarded. One new dry beneficiation technology that has been used and researched extensively is the fluidized dense medium bed (FDMB) technology. The purpose of this study is to determine whether fine coal can be successfully beneficiated with a FDMB. It also has to be determined whether adding magnetite and introducing a jigging (pulse) motion to the air feed will increase the separation efficiency of the fluidization process. Witbank seam 4 and a Waterberg coal was used in experiments during this study. A coarse (+1180 μm –2000 μm), fine (+500 μm –1180 μm) and a mix of the two samples were prepared and tested. It was found that adding magnetite to the feed of the fluidized bed did not increase the separation efficiency. However, previous studies indicated the opposite results with regards to magnetite addition. The difference in results obtained could be prescribed to the ultrafine nature of the magnetite and the small coal particles size range used. If the presence of fine particles in the bed increases, the stability of fluidization decreases. In turn, the separation efficiency of the process decreases. Subjecting the feed air flow to a pulsating motion did not have a significant effect on separation. Good results were still obtained with jigging experiments, although not better than with normal fluidization. Stratification of coal particles according to quality was evident by the results obtained during experiments. The quality of coal increases from the bottom to the top of the bed. Overall the fluidized bed, in the absence of magnetite, was found to be a sufficient de-ashing process and further research on this technology could be very beneficial to the coal industry. / MIng (Chemical Engineering), North-West University, Potchefstroom Campus, 2014

Beneficiation of fine coal (+500 μm –2000 μm) is a worldwide problem in the mining industry, especially dry beneficiation of fine coal. Coal beneficiation can be divided primarily into two methods, namely wet- and dry beneficiation. Wet beneficiation methods are utilized more in today‘s industry because of the sharp separation efficiency that can be achieved. These processes include wet jigging, dense medium cyclones, spiral beneficiation etc. Due to the lack of a sufficient water supply in some regions around the world including South Africa, dry beneficiation methods are becoming more popular. Recent mechanized mining methods caused the fraction of fines from coal mines to increase over the years. However, due to old inefficient technologies, coal fines contained in slurry ponds could not be beneficiated and had to be discarded. One new dry beneficiation technology that has been used and researched extensively is the fluidized dense medium bed (FDMB) technology. The purpose of this study is to determine whether fine coal can be successfully beneficiated with a FDMB. It also has to be determined whether adding magnetite and introducing a jigging (pulse) motion to the air feed will increase the separation efficiency of the fluidization process. Witbank seam 4 and a Waterberg coal was used in experiments during this study. A coarse (+1180 μm –2000 μm), fine (+500 μm –1180 μm) and a mix of the two samples were prepared and tested. It was found that adding magnetite to the feed of the fluidized bed did not increase the separation efficiency. However, previous studies indicated the opposite results with regards to magnetite addition. The difference in results obtained could be prescribed to the ultrafine nature of the magnetite and the small coal particles size range used. If the presence of fine particles in the bed increases, the stability of fluidization decreases. In turn, the separation efficiency of the process decreases. Subjecting the feed air flow to a pulsating motion did not have a significant effect on separation. Good results were still obtained with jigging experiments, although not better than with normal fluidization. Stratification of coal particles according to quality was evident by the results obtained during experiments. The quality of coal increases from the bottom to the top of the bed. Overall the fluidized bed, in the absence of magnetite, was found to be a sufficient de-ashing process and further research on this technology could be very beneficial to the coal industry. / MIng (Chemical Engineering), North-West University, Potchefstroom Campus, 2014