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This M.A.Sc. work focuses on the development of a sensor to operate at industrially relevant conditions, directly in autoclaves, to generate accurate online free acidity estimates. The main goal is to obtain accurate (within 5% from titrated) free acid estimates at leach temperature while compensating for various metals in solution at high solid loadings. The electrodeless conductivity sensor and calibration technique that were developed in previous work have been improved upon for operation in slurry systems. The sensor operates at temperature on the basis of induction currents and is suitable for very concentrated solutions containing solid dispersions. Three systems have been investigated: limonitic feeds, limonite-saprolite blends, and a converter slag feed. Up to 40 wt.% solids were tested with investigation carried out from 25°C to 260°C. High quality estimates of acidity were produced for all systems studied, with the average difference between measured and titrated acidities being within 5%.

This M.A.Sc. work focuses on the development of a sensor to operate at industrially relevant conditions, directly in autoclaves, to generate accurate online free acidity estimates. The main goal is to obtain accurate (within 5% from titrated) free acid estimates at leach temperature while compensating for various metals in solution at high solid loadings. The electrodeless conductivity sensor and calibration technique that were developed in previous work have been improved upon for operation in slurry systems. The sensor operates at temperature on the basis of induction currents and is suitable for very concentrated solutions containing solid dispersions. Three systems have been investigated: limonitic feeds, limonite-saprolite blends, and a converter slag feed. Up to 40 wt.% solids were tested with investigation carried out from 25°C to 260°C. High quality estimates of acidity were produced for all systems studied, with the average difference between measured and titrated acidities being within 5%.

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior / This paper presents a study of the characteristics of magnetic materials. The application of this study is the feeding of an electrodeless fluorescent lamp (EFL). This type of lamp is driven by electromagnetic effects and, because of this, the electrodes are eliminated. Thus, the EFL has longer lifetime associated with low lumen depreciation representing an alternative to lighting systems among other discharge lamps. Because of the EFL magnetic characteristics, the operation frequency of this type of system has to be high in order to reduce the size of inductive elements avoiding the shadowing. Thus, the study of different magnetic materials capable of operating under these circumstances is proposed. Experiments were performed in order to obtain material characteristics such as the magnetization curve and the energy losses, and simulations were used to study characteristics not available through practical means. Four different materials are analyzed, the ferrites N87 (from EPCOS) and IP12E (from THORNTON) and amorphous and nanocrystalline alloys. In the ferrites cases, it was possible to carry out practical experiments and prove that they are able to meet the operating needs of EFL. However, it was not possible to acquire toroids alloys, amorphous or nanocrystalline, with the internal diameter required to accommodate the bulb of the EFL therefore, results of simulations are presented for these cores projects. At the end of the work, comparisons are made between the results obtained. / Este trabalho apresenta um estudo das características de materiais magnéticos. A aplicação deste estudo é o acionamento de uma lâmpada fluorescente sem eletrodos (LFSE). O acionamento deste tipo de lâmpada é realizado a partir de efeitos eletromagnéticos, sem a necessidade de eletrodos. Em virtude disso, as LFSE apresentam, dentre as demais lâmpadas de descarga, uma longa vida útil associada a uma baixa depreciação do fluxo luminoso, representando uma alternativa atraente para sistemas de iluminação. Devido as características magnéticas das LFSE, a frequência de operação desse tipo de sistema deve ser elevada, com o objetivo de reduzir o volume dos elementos indutivos, evitando o sombreamento causado pelos mesmos. Com isso, é proposto o estudo de diferentes materiais magnéticos capazes de operar sob estas circunstâncias. Foram realizadas experiências a fim de obter características de materiais, tais como, a curva de magnetização e as perdas de energia, e simulações para estudar características não acessíveis através de meios práticos. Quatro diferentes materiais são analisados, os ferrites N87 (da EPCOS) e IP12E (da THORNTON) e as ligas amorfas e nanocristalinas. No caso dos ferrites foi possível realizar experiências práticas e comprovar que os mesmos são capazes de suprir as necessidades de funcionamento da LFSE. Porém, não foi possível adquirir toroides de ligas, amorfas ou nanocristalinas, com o diâmetro interno necessário para acomodar o bulbo da LFSE, portanto, resultados de simulações são apresentados para os projetos destes núcleos. Ao final do trabalho são realizadas comparações entre os resultados adquiridos.

Während die Wasserdissoziation mit der Hilfe von Gleichstrom (Wasser-Elektrolyse) einen gut untersuchten Prozess darstellt, war der Mechanismus der Wasserdissoziation durch Einwirkung hochfrequenter (HF) elektromagnetischer Felder als relativ neues Phänomen noch nicht vollständig aufgeklärt. Für die Realisierung der Wasserdissoziation in HF-Feldern mit einer Frequenz von 13,56 MHz wurde in dieser Arbeit ein neuartiger experimenteller Aufbau verwendet, dessen Kernstück aus einem sich zwischen zwei parallelen Elektroden befindlichen Glasreaktor, der über eine Durchmesserverjüngung verfügte, bestand. Dieser Aufbau ermöglichte die Untersuchung der wässrigen Elektrolytlösung in den drei Phasen Erwärmung, Blasenbildung und Entladung mit Gasbildung. Die messbare Gasbildungsrate wurde als ein Maß für die Intensität der Wasserdissoziation gewählt. Ihre Abhängigkeit von der HF-Spannung, der HF-Leistung, der Art des Elektrolyten, der Konzentration des Elektrolyten und dem geometrischen Aufbau des Reaktors wurden untersucht. Bei vielen Elektrolyten bestand das produzierte Gas vollständig aus Wasserstoff und Sauerstoff im molaren Verhältnis von 2 zu 1 sowie aus Wasserdampf. Für einige Elektrolyte wurden davon abweichende Verhalten hinsichtlich der Stöchiometrie beobachtet. Das im Zusammenhang mit der Wasserdissoziation emittierte Licht wurde spektroskopisch untersucht. Es konnten angeregte OH-, H- und O-Radikale nachgewiesen werden. Dieser Befund legt nahe, dass die Wasserdissoziation durch die Wechselwirkung von hochenergetischen Elektronen mit Wassermolekülen verursacht wird. Der Versuchsaufbau ermöglichte also die Ausbildung eines nicht-thermischen Plasmas in der Gasphase im Bereich der Reaktorverjüngung. Mit Hilfe von Simulationsrechnungen konnte der Verlauf des elektrischen Feldes in Abhängigkeit von der Elektrolytkonzentration für den gewählten Versuchsaufbau modelliert werden. Das Erreichen der für die Initiierung von selbsterhaltenden Entladungen in Wasserdampf notwendigen Feldstärke von 2,6 MV/m wurde durch die Modellierung verifiziert. Modellrechnungen stehen im Einklang mit dem vorgeschlagenen Mechanismus der HF-Wasserdissoziation. Des Weiteren wurde das Anwendungspotenzial der Radikalbildung für den Abbau von Modellschadstoffen wie Perfluoroktansäure (PFOA) untersucht. Der Abbau perfluorierter Verbindungen, der bisher durch eine wenig effiziente thermische Totaloxidation erreicht werden kann, konnte mit dem Plasmaprozess erfolgreich demonstriert werden.

This paper presents the design and development of an electronic ballasts family obtained through the use of the integration technique of converters for feeding the electrodeless fluorescents lamps (EFL). This type of lamp is driven by electromagnetic effects and because of this the electrodes are eliminated. Thus, the EFL has longer lifetime associated with low lumen depreciation representing an alternative to lighting systems among other discharge lamps. It is necessary to develop an electrical model capable of describing the behavior of the lamp in order to design electronic circuits to provide a good operation. In this work, the developed model includes not only, the lamp static behavior at different operating points, but also the magnetic losses involved. Because of the EFL magnetic characteristics, the operation frequency of this type of system has to be high in order to reduce the size of inductive elements avoiding the glare. Due to this, it is proposed a set of electronic systems for feeding the lamp in an efficient way. The systems are studied to establish relationships regarding the behavior and limitations imposed by them. This work also presents the power control delivered to the lamp. Finally, experimental results are presented in order to validate the developed project. / Este trabalho apresenta o projeto e o desenvolvimento de uma família de reatores eletrônicos obtidos através da técnica de integração de conversores estáticos, aplicados à alimentação de lâmpadas fluorescentes sem eletrodos (LFSE). O acionamento deste tipo de lâmpada é realizado a partir de efeitos eletromagnéticos, sem a necessidade de eletrodos. Em virtude disso, as LFSE apresentam, dentre as demais lâmpadas de descarga, uma longa vida útil associada a uma baixa depreciação do fluxo luminoso, representando uma alternativa atraente para sistemas de iluminação. Visando obter circuitos eletrônicos capazes de proporcionar o funcionamento satisfatório da LFSE, faz-se necessário o desenvolvimento de um modelo elétrico capaz de descrever o comportamento da mesma. Tal modelo desenvolvido nesse trabalho contempla, não só o comportamento estático da lâmpada em diferentes pontos de operação, como também suas perdas magnéticas envolvidas. Em virtude das características magnéticas das LFSE, a frequência de operação desse tipo de sistema deve ser elevada, com o objetivo de reduzir o volume dos elementos indutivos, evitando o sombreamento causado pelos mesmos. Com isso, propõem-se um conjunto de sistemas eletrônicos capazes de realizar o acionamento eficiente da lâmpada. O estudo de tais sistemas tem por finalidade estabelecer relações e comparações quanto ao comportamento e as limitações impostas pelos mesmos. Neste trabalho, o controle da potência entregue a lâmpada também foi analisado. No final, os resultados experimentais são apresentados no intuito de validar o projeto desenvolvido.

Während die Wasserdissoziation mit der Hilfe von Gleichstrom (Wasser-Elektrolyse) einen gut untersuchten Prozess darstellt, war der Mechanismus der Wasserdissoziation durch Einwirkung hochfrequenter (HF) elektromagnetischer Felder als relativ neues Phänomen noch nicht vollständig aufgeklärt. Für die Realisierung der Wasserdissoziation in HF-Feldern mit einer Frequenz von 13,56 MHz wurde in dieser Arbeit ein neuartiger experimenteller Aufbau verwendet, dessen Kernstück aus einem sich zwischen zwei parallelen Elektroden befindlichen Glasreaktor, der über eine Durchmesserverjüngung verfügte, bestand. Dieser Aufbau ermöglichte die Untersuchung der wässrigen Elektrolytlösung in den drei Phasen Erwärmung, Blasenbildung und Entladung mit Gasbildung. Die messbare Gasbildungsrate wurde als ein Maß für die Intensität der Wasserdissoziation gewählt. Ihre Abhängigkeit von der HF-Spannung, der HF-Leistung, der Art des Elektrolyten, der Konzentration des Elektrolyten und dem geometrischen Aufbau des Reaktors wurden untersucht. Bei vielen Elektrolyten bestand das produzierte Gas vollständig aus Wasserstoff und Sauerstoff im molaren Verhältnis von 2 zu 1 sowie aus Wasserdampf. Für einige Elektrolyte wurden davon abweichende Verhalten hinsichtlich der Stöchiometrie beobachtet. Das im Zusammenhang mit der Wasserdissoziation emittierte Licht wurde spektroskopisch untersucht. Es konnten angeregte OH-, H- und O-Radikale nachgewiesen werden. Dieser Befund legt nahe, dass die Wasserdissoziation durch die Wechselwirkung von hochenergetischen Elektronen mit Wassermolekülen verursacht wird. Der Versuchsaufbau ermöglichte also die Ausbildung eines nicht-thermischen Plasmas in der Gasphase im Bereich der Reaktorverjüngung. Mit Hilfe von Simulationsrechnungen konnte der Verlauf des elektrischen Feldes in Abhängigkeit von der Elektrolytkonzentration für den gewählten Versuchsaufbau modelliert werden. Das Erreichen der für die Initiierung von selbsterhaltenden Entladungen in Wasserdampf notwendigen Feldstärke von 2,6 MV/m wurde durch die Modellierung verifiziert. Modellrechnungen stehen im Einklang mit dem vorgeschlagenen Mechanismus der HF-Wasserdissoziation. Des Weiteren wurde das Anwendungspotenzial der Radikalbildung für den Abbau von Modellschadstoffen wie Perfluoroktansäure (PFOA) untersucht. Der Abbau perfluorierter Verbindungen, der bisher durch eine wenig effiziente thermische Totaloxidation erreicht werden kann, konnte mit dem Plasmaprozess erfolgreich demonstriert werden.

The electrodeless plasma discharge is typically driven by radio frequency (RF) power supply within the range (0.2 &iexcl / 40 MHz). The applied power is coupled into the plasma inductively called inductively coupled plasma (ICP). RF ICP technique has achieved significance importance in a diversity of research and industrial applications for over the last threes decades. It is still required to undertake both theoretical and experimental research. In this work, RF ICP technique is applied on the torch modeling in 2D. Based on extended electromagnetic vector potential representation, an axisymmetric model in 2D is proposed for the calculations of the electromagnetic fields in an RF ICP torch. The influence of axial vector potential is included to the vector potential formulations. This is achieved by imposing a helical current carrying wire configuration. The corresponding governing equations are solved numerically by applying finite element method (FEM) using commercial partial differential equation solver (Flex PDE3). Based on this model, the plasma behavior and properties are examined in terms of plasma parameters. Besides, a comparative iii analysis is made between proposed model called helical configuration and the one currently available in the literature called circular configuration. This study shows relatively little difference between temperature fields predicted by two models. However, significant difference is observed between corresponding flows and electromagnetic fields. Especially, tangential flow which is observed in helical configuration vanishes in circular configuration. The proposed model offers an effective means of accounting for the variations of the helical coil geometry on the flow and temperature fields and achieving a better representation of the electromagnetic fields in the discharge. Finally, it is concluded that minimum number of turns (n = 2) yields significant difference between two models whereas, maximum allowable number of turns yield no distinctions on the results of two models in terms of azimuthally applied current. However, axial effect of current still exists but very small with respect to the result obtained with minimum number of turns.