Triboelectrostatic separation is a physical separation technique that is based on surface electronic property differences among minerals to achieve a separation. Minerals have different surface conductivities and electron affinities. They are charged differently in quantity and/or polarity after a tribocharging process. Particles with different surface charges move discretely under external electric field produce a separation. Electrostatic separation is a dry mineral processing method that does not require any water or chemical reagents. It can greatly simplify the processing circuit and reduce operating cost. Additionally, problems caused by water in conventional wet mineral processing such as water freezing, dewatering, water pollution and water treatment are eliminated. Electrostatic separation has great potential as a fine particle separator (i.e. < 1mm) in industrial minerals processing application, especially in arid areas where water supply is limited. In the current study, particle tribocharging kinetics was evaluated using a model system comprised of copper, pure coal, silica and ceramic. The results of the tribocharging process were recorded and analyzed using an oscilloscope and a signal processing technique. Charge exchange, charge separation and charge relaxation corresponding to tribocharging processes were studied using the generated pulsing signals. The signals provided a method to quantify the charge penetration into the conductor bulk during tribocharging. A new method to measure the particle surface charge using the pulsing was proposed and assessed, which was extremely useful for subtle surface charge measurements which effectively eliminated environmental noise. The interactive forces at the contacting interface, relative displacement, material electronic properties and ambient relative humidity were found to impact particle surface charge. The silica surface sites are 69 times more chargeable than the coal surface, which provides a fundamental explanation for upgrading that is achievable for silica-rich coal using triboelectrostatic separation. The influences of operating and environmental parameters were quantified and compared using an environment controlled chamber. Energy consumption at the interface was found to be positively correlated with the particle charge. Relative humidity has dual effects on the particle tribocharging, excessively low or high humidity levels do not favor particle tribocharging. Finally, a semi-empirical mathematical model of particle tribocharging was developed from the basic tribocharging compression model utilizing the parametric experiment study results. The model provides a more accurate method to predict particle surface charge under exact tribocharging conditions. A novel rotary triboelectrostatic separator (RTS) using the tribocharging mechanism was tested for upgrading fine coal. The particle size influencing the RTS tribocharging and separation process is investigated. A practical method to quantify the particle charging distribution was developed based on the direct particle charge measurement and a Gaussian distribution assumption. The smaller particles were found to have a higher average surface charge and wider surface charge distribution, which provided an opportunity to separate the high grade and the low grade coal particles. However, particles that are too small have weak particle-charger tribocharging effect that reduces particle tribocharging efficiency. The particle separation process was analyzed considering the exact experimental hydrodynamic separating conditions. Smaller particles were found to be more sensitive to the airflow that used to transport the particles as a result of the effect on residence time in the separation chamber. A method combining mathematical and statistical analysis was proposed to theoretically predict RTS separation efficiency based on the particle charging conditions and particle separation conditions. The particle horizontal displacement probability distribution was ultimately derived from this method. The model predictions indicate that a wider horizontal displacement distribution provides improved separation efficiency for the RTS unit. The theoretical analysis indicates that a particle size range between 0.105 and 0.21 mm has widest horizontal displacement distribution and thus represents an optimum particle size range which is in agreement with experimental results. The influences of the RTS operating parameters on separation performance achieved on a pure coal-silica mixture were investigated using a parametric study. The optimum operating conditions were identified. Using the optimum conditions, a five-stage separation process was conducted using the RTS unit to obtain the necessary data for the development of an ideal performance curve. Two stages of RTS separation were found to generate good quality clean coal with acceptable recovery. Particle tribocharging tests were performed using pure coal, pure silica and the coal-silica mixture as model feed materials. The test result found that mixing the pure coal with the sand reduced the particle charge distribution of the coal while increasing the charge distribution of the pure silica particle. The finding explains the inability to produce clean coal products containing ultra-low ash contents. However, the rejection of silica to the tailings stream is very high. The RTS upgrading of low-ash coal sample was tried using experiment design method, which revealed that feed rate was the most significant while the applied charger voltage and the injection air rate were the least significant in regards to product quality. Feed mass flow rate and the co-flow air rate have a significant interactive effect. Considering the theoretical findings, the impact of high feed rates is due to the negative effect on particle tribocharging efficiency resulting from an increase in the particle-particle surface charge relaxation. Under the optimum test conditions, an ultraclean coal was produced with an ash content of 3.85±0.08% with a combustible recovery of 62.97±1.11% using the RTS unit.

A utilização de polímeros tem crescido de maneira significativa em diversos setores da indústria, substituindo materiais como madeira, metais, vidros, entre outros. Entretanto, a constante geração de resíduos poliméricos pós-consumo e seu descarte, tem gerado problemas ao meio ambiente, pois grande parte desses materiais ainda é disposta em aterros sanitários. Assim, a reciclagem de polímeros tem se mostrado uma alternativa mais econômica e ambientalmente correta, já que contribui para minimizar o consumo de recursos finitos, como o petróleo, além de reduzir a emissão de gases tóxicos nos processos de produção e decomposição. No processo de reciclagem, a separação dos polímeros em seus diferentes tipos é uma das etapas mais importantes, pois devido às diferenças nas propriedades químicas e físicas desses materiais, quando misturados e processados, geram produtos finais de baixa qualidade. No Brasil, o método de separação mais utilizado é o de separação manual, porém apresenta grandes desvantagens devido às condições insalubres às quais o trabalhador é submetido e devido a erros de natureza humana cometidos durante o processo. Desta maneira, o objetivo deste trabalho foi estudar diferentes métodos de separação de resíduos poliméricos, dando ênfase na separação triboeletrostática, além de determinar limites de contaminação entre poli (tereftalato de etileno) (PET) e polietileno de alta densidade (PEAD) no produto final reciclado. Foi desenvolvido um dispositivo para separação triboeletrostática de polímeros, o qual se mostrou efetivo na separação de misturas de poli(cloreto de vinila) (PVC)/PET, PVC/acrilonitrila-butadieno-estireno (ABS) e ABS/PEAD, atingindo porcentagens de recuperação maiores que 80% e grau de pureza acima de 90%. No estudo da contaminação entre PET e PEAD, com base na morfologia e propriedades mecânicas apresentadas pelas blendas avaliadas, foi determinado o limite de 3% de contaminação de PET no PEAD, porém não foi possível determinar um limite para a contaminação de PEAD no PET, pois mesmo em pequenas concentrações do contaminante, as blendas apresentaram comportamento instável nos ensaios mecânicos realizados, devido às suas características morfológicas. / The use of polymers has increased significantly in several industrial sectors, replacing materials such as wood, metals, glass, etc. However, the constant generation of plastic wastes and their disposal generate environmental problems, because most of them are disposed to landfill. Thus, polymer recycling seems to be the most economical and environmentally friend alternative, since it contributes to minimize the consumption of non-renewable resources, as petroleum, also reducing the toxic gases emission generated during the production and decomposition processes. The polymer separation in their different types is one of the most important stages of the recycling process, because due to the diferences in their chemical and physical properties, when they are mixed and processed, low quality products are produced. In Brazil, manual separation is the most used method, but it presents great disadvantages, due to the unheathy conditions that the workers are subjected to and the possibility of human errors during the process. The aim of this work was to study different polymer separation methods, emphasizing the triboelectrostatic separation, besides determining contamination limits between polyterephthalate ethylene (PET) and high density polyethylene (HDPE) in the final recycled product. A device for triboelectrostatic separation of polymers was developed, which was effective in the separation of polyvinyl chloride (PVC) / PET, PVC / acrylonitrile-butadiene-styrene (ABS) and ABS / HDPE blends, reaching percentages of recovery greater than 80% and purity above 90%. Contamination between PET and HDPE was evaluated, based on the morphology and mechanical properties presented by the blends prepared. The limit of 3% of PET contamination in the HDPE was determined, but it was not possible to determine the limit for the contamination of HDPE in PET, because even in small concentrations of the contaminant, the blends presented unstable behavior in the mechanical tests performed, due to the morphological characteristics of the blends produced.

A utilização de polímeros tem crescido de maneira significativa em diversos setores da indústria, substituindo materiais como madeira, metais, vidros, entre outros. Entretanto, a constante geração de resíduos poliméricos pós-consumo e seu descarte, tem gerado problemas ao meio ambiente, pois grande parte desses materiais ainda é disposta em aterros sanitários. Assim, a reciclagem de polímeros tem se mostrado uma alternativa mais econômica e ambientalmente correta, já que contribui para minimizar o consumo de recursos finitos, como o petróleo, além de reduzir a emissão de gases tóxicos nos processos de produção e decomposição. No processo de reciclagem, a separação dos polímeros em seus diferentes tipos é uma das etapas mais importantes, pois devido às diferenças nas propriedades químicas e físicas desses materiais, quando misturados e processados, geram produtos finais de baixa qualidade. No Brasil, o método de separação mais utilizado é o de separação manual, porém apresenta grandes desvantagens devido às condições insalubres às quais o trabalhador é submetido e devido a erros de natureza humana cometidos durante o processo. Desta maneira, o objetivo deste trabalho foi estudar diferentes métodos de separação de resíduos poliméricos, dando ênfase na separação triboeletrostática, além de determinar limites de contaminação entre poli (tereftalato de etileno) (PET) e polietileno de alta densidade (PEAD) no produto final reciclado. Foi desenvolvido um dispositivo para separação triboeletrostática de polímeros, o qual se mostrou efetivo na separação de misturas de poli(cloreto de vinila) (PVC)/PET, PVC/acrilonitrila-butadieno-estireno (ABS) e ABS/PEAD, atingindo porcentagens de recuperação maiores que 80% e grau de pureza acima de 90%. No estudo da contaminação entre PET e PEAD, com base na morfologia e propriedades mecânicas apresentadas pelas blendas avaliadas, foi determinado o limite de 3% de contaminação de PET no PEAD, porém não foi possível determinar um limite para a contaminação de PEAD no PET, pois mesmo em pequenas concentrações do contaminante, as blendas apresentaram comportamento instável nos ensaios mecânicos realizados, devido às suas características morfológicas. / The use of polymers has increased significantly in several industrial sectors, replacing materials such as wood, metals, glass, etc. However, the constant generation of plastic wastes and their disposal generate environmental problems, because most of them are disposed to landfill. Thus, polymer recycling seems to be the most economical and environmentally friend alternative, since it contributes to minimize the consumption of non-renewable resources, as petroleum, also reducing the toxic gases emission generated during the production and decomposition processes. The polymer separation in their different types is one of the most important stages of the recycling process, because due to the diferences in their chemical and physical properties, when they are mixed and processed, low quality products are produced. In Brazil, manual separation is the most used method, but it presents great disadvantages, due to the unheathy conditions that the workers are subjected to and the possibility of human errors during the process. The aim of this work was to study different polymer separation methods, emphasizing the triboelectrostatic separation, besides determining contamination limits between polyterephthalate ethylene (PET) and high density polyethylene (HDPE) in the final recycled product. A device for triboelectrostatic separation of polymers was developed, which was effective in the separation of polyvinyl chloride (PVC) / PET, PVC / acrylonitrile-butadiene-styrene (ABS) and ABS / HDPE blends, reaching percentages of recovery greater than 80% and purity above 90%. Contamination between PET and HDPE was evaluated, based on the morphology and mechanical properties presented by the blends prepared. The limit of 3% of PET contamination in the HDPE was determined, but it was not possible to determine the limit for the contamination of HDPE in PET, because even in small concentrations of the contaminant, the blends presented unstable behavior in the mechanical tests performed, due to the morphological characteristics of the blends produced.