Дисертації з теми "Silicon recycling"

The first part of this master’s thesis contain the history of photovoltaic technology and types of PV cells. Gave a consideration to advantages and disadvantages of solar cells. Compared their effectiveness and important parameters. In the next part described the recycling technology of modules at the end of their lifetime. Described certain recycled materials. At the end of the work described possible improvements to existing technologies used for encapsulating of cell. And wich would improve the recycling process.

Ce travail de thèse porte sur un procédé plasma de purification de silicium pour usages photovoltaïque. Il est appliqué à deux types de matériaux : du silicium d’origine métallurgique et des produits de recyclage des boues de sciage des lingots et des plaquettes de la filière photovoltaïque. Les boues de sciage des plaquettes sont essentiellement constituées de liquide de coupe, de particules de SiC (abrasif), de microparticules de silicium et de microparticules de fer provenant du fil de découpe. Le silicium de ces boues est un silicium de haute pureté, qui est déjà de qualité photovoltaïque. Il peut représenter jusqu’`a 60 % du poids initial du lingot. Le procédé objet du projet comporte une phase de séparation du SiC par centrifugation, suivi d’une phase d’élimination chimique du fer, puis d’un traitement par plasma réactif pour l’élimination du SiC résiduel. Ce travail porte sur cette dernière phase. Un traitement plus complexe que celui initialement prévu a été rendu nécessaire par l’existence dans les boues de sciage de particules de SiC provenant du bris des grains de l’abrasif initial. La séparation du SiC étant incomplète, le traitement par plasma a dû éliminer des quantités beaucoup plus importantes qu’initialement prévu. Cela a nécessité une modification importante du procédé initial, et la mise au point de phase de pré-traitement destiné à rendre exploitable par le plasma le produit issu de la séparation. Ce travail combine études théoriques, modélisations numériques et expérimentation. La modélisation thermodynamique permet de déterminer les meilleures conditions d’élimination des polluants (gaz réactifs adaptés, débits, températures, pressions) tandis que la modélisation du brassage électromagnétique mesure l’efficacité du renouvellement de la surface du bain liquide au cours du traitement
This thesis focuses on a plasma process of purification of silicon for photovoltaic applications. It is applied to two types of materials: metallurgical silicon and recycling products from sawing sludge ingots and from wafers of photovoltaic industry. Platelet sawing sludge consist mainly of cutting fluid, SiC particles (abrasive), silicon microparticles and iron micro-particles from the cutting wire. Silicon sludge is a high-purity silicon, which is already of photovoltaic quality. It can represent 60% of the original weight of the ingot. The present process comprises a SiC phase separation by centrifugation, followed by chemical elimination phase of the iron, then a reactive plasma treatment for removing residual SiC. This work deals with this last phase. A more complex treatment than originally planned was made necessary by the existence in the SiC particles of sawing sludge from the initial breaking of the abrasive grains. Separation of SiC is incomplete, the plasma treatment had to remove much larger quantities than originally planned. This required a significant modification of the original process, and the setting of a pre-treatment phase point intended to make it usable by the product of the plasma separation. This work combines theoretical studies, numerical modeling and experimentation. Thermodynamic modeling to determine the best conditions for the removal of pollutants (adapted reactive gases, flow rates, temperatures, pressures) whereas modeling the electromagnetic measurement brewing efficiency renewing the surface of the liquid bath during treatment

Orientador: Carlos K. Suzuki
Tese (doutorado) - Universidade Estadual de Campinas, Faculdade de Engenharia Mecanica
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Resumo: O Brasil é na atualidade um dos principais produtores de silício para o mundo, sendo que a quantidade de quartzo extraído para a sua produção incluindo o ferro-silício, é da ordem de 2 milhões de toneladas/ano. Para a obtenção do quartzo destinado à redução carbotérmica em silício, nos diversos estágios de extração, britagem, seleção, transporte, e lavagem, cerca de 300.000 toneladas/ano de lascas de quartzo tomam-se rejeitos. Neste trabalho foi desenvolvida uma metodologia ambientalmente correta, denominada "quench-Ieaching" e "crush-leaching", que se utiliza da lixiviação aquosa para a purificação deste material. Os resultados mostram que ocorre uma remoção efetiva de impurezas majoritárias nas lascas de quartzo, tais como, AI, Fe, Na, K, Ca, Mn, ..., dando-lhe uma pureza de 99,9% de SI 'O IND 2'. Uma comparação com diversos insumos de quartzo produzidos no exterior para uso em tecnologia avançada, como para produção de sílica vítrea translucente e "fillers" de "micro-chips", revela que este material purificado com esta tecnologia toma-se de qualidade equivalente ao pó de quartzo internacional
Abstract: Nowadays, Brazil is one of the main silicon metal and iron-silicon producer in the world. But on the other hand, the amount of natural quartz that has been extracted for this purpose is up to 2 milliontons/year. The key-point is the large quantity of rejected quartz lascas, approximately 300,000 tons/year, generated during the various stages of extraction, crushing, selection, transportation, and washing. A new environrnentally mendly purification methodology denominated "quench-Ieaching" and "crush-leaching, that only uses aqueous leaching, has been developed. The result shows an effective elimination of major quartz impurities, such as Al, Fe, Na, K, Ca, Mn, ... , that transforms this rejected material into a 99.9% purity SI 'O IND 2'. The quality of this material is as high as the quartz powder commercially available in the intemational market for use as "fillers" and translucent silica glass raw material for semiconductor industries
Doutorado
Materiais e Processos de Fabricação
Doutor em Engenharia Mecânica

Durant la darrera dècada, les nanopartícules de sílice han trobat aplicacions en catàlisi, depuració d’aigua, camps biomèdics, agrícoles i industrials ... per les seves característiques físiques i químiques úniques, com ara una gran superfície, una excel·lent biocompatibilitat, una bona estabilitat tèrmica, mecànica i química, mida i forma de porus regulable, riquesa en grups silanol a la superfície que permeten una fàcil modificació superficial. La nostra recerca en aquesta tesi s’ha centrat en la preparació i caracterització de diversos tipus de nanopartícules de sílice funcionalitzades i la seva aplicació en catàlisi, biomedicina i recuperació d’elements de terres rares. Es van preparar noves nanopartícules de sílice mesoporoses derivades d’amides de prolina-valinol mono i disililades i es van utilitzar com a catalitzadors reciclables per a la reacció aldòlica asimètrica amb elevada activitat i selectivitat. Aquests nanomaterials es poden recuperar i reutilitzar amb èxit fins a sis vegades (capítol 2). Per contra, els nostres esforços en la preparació de nanopartícules d’organosílice reciclables com a catalitzadors quirals o lligands per a la α-trifuorometilació i α-fluorinació enantioselectives de compostos carbonílics no van tenir èxit (capítol 2). Es van preparar una sèrie de nanopartícules d’organosílice mesoporoses periòdiques mixtes que posseïen grups Boc i tert-butil èster com a agents potencials per ultrasons focalitzat d’alta intensitat (High Intensity Focused Ultrasound, HIFU). Es preveia que aquests nanomaterials alliberessin CO2 i / o isobutè del grup COOtBu sensible a la temperatura. Tanmateix, es va trobar que el grup Boc era bastant estable i no es podia eliminar en condicions de HIFU a 80 ºC, requerint l’addició d’àcid. El concepte no deixa de ser prometedor per futurs agents de contrast per a teràpies basades en HIFU (Capítol 3). Medicaments antiinflamatoris no esteroides com l’ibuprofè i el diclofenac es van unir de forma covalent a nanopartícules de sílice a través d’un grup funcional amida per a aplicacions potencials en formulacions tòpiques (pomades i cremes). A més, el recobriment de teixits de cotó amb aquestes nanopartícules de sílice funcionalitzades va proporcionar teixits hidrofòbics per a potencials aplicacions cutànies tòpiques en apòsits destinats a tractar ferides cròniques. El medicament antiinflamatori corresponent s’allibera in situ mitjançant el trencament enzimàtic selectiu de l’enllaç amida en presència de proteases (capítol 4). Es van preparar nanopartícules de sílice mesoporoses amb nucli magnètic funcionalitzades amb fragments de cyclen com a adsorbents nous per a la recuperació específica i selectiva de diferents ions de terres rares (RE) de les aigües residuals (Capítol 5).
Durante la última década, las nanopartículas de sílice han encontrado aplicaciones en catálisis, purificación de agua, campos biomédicos, agrícolas e industriales ... debido a sus características químicas y físicas únicas, tales como alta superficie, excelente biocompatibilidad, buena estabilidad térmica, mecánica y química, tamaño y forma de poro ajustable, superficie enriquecida con grupos silanol que permiten una fácil modificación superficial. Nuestra investigación en esta tesis se ha centrado en la preparación y caracterización de varios tipos de nanopartículas de sílice funcionalizadas novedosas, así como su aplicación en catálisis, biomedicina y recuperación de elementos de tierras raras. Se prepararon nuevas nanopartículas de sílice mesoporosa derivadas de amidas de prolina-valinol mono y disililadas y se usaron como catalizadores reciclables para la reacción aldólica asimétrica con elevada actividad y selectividad. Estos nanomateriales se pueden recuperar con éxito y reutilizar hasta seis veces (Capítulo 2). Por el contrario, nuestros esfuerzos en la preparación de nanopartículas de organosílice reciclables como catalizadores o ligandos quirales para la α-trifuorometilación y α-fluoración enantioselectivas de compuestos carbonílicos no tuvieron éxito (Capítulo 2). Se preparó una serie de nanopartículas de organosilica mesoporosas mixtas periódicas que poseen grupos Boc y éster de terc-butilo como posibles agentes sensibles al ultrasonido focalizado de alta intensidad (High Intensity Focused Ultrasound, HIFU). Se esperaba que estos nanomateriales liberaran CO2 y / o isobuteno del grupo COOtBu sensible a la temperatura. Sin embargo, se encontró que el grupo Boc era bastante estable y no podía eliminarse en condiciones HIFU a 80 ºC, sino que se requería además la adición de ácido. Sin embargo, el concepto es prometedor para futuros agentes de contraste para terapias basadas en HIFU (Capítulo 3). Fármacos antiinflamatorios no esteroideos como ibuprofeno y diclofenaco se unieron de forma covalente a nanopartículas de sílice a través de un grupo funcional amida para su posible aplicación en formulaciones tópicas (pomadas y cremas). Además, el recubrimiento de telas de algodón con estas nanopartículas de sílice funcionalizadas proporcionó telas hidrófobas para posibles aplicaciones cutáneas tópicas en apósitos destinados a tratar heridas crónicas. El fármaco antiinflamatorio correspondiente se libera in situ mediante la escisión enzimática selectiva del enlace amida en presencia de proteasas (Capítulo 4). Se prepararon nanopartículas de sílice mesoporosas con núcleo magnético funcionalizadas con fragmentos de cyclen como adsorbentes novedosos para la recuperación específica y selectiva de diferentes iones de tierras raras (RE) del agua residual (Capítulo 5).
During the last decade, silica nanoparticles have found applications in catalysis, water purification, biomedical, agricultural and industrial fields… due to their unique chemical and physical characteristics, such as high surface area, excellent biocompatibility, good thermal, mechanical and chemical stability, adjustable pore size and shape, enriched surface silanol groups with easy surface modification. Our research in this thesis has been focused on the preparation and characterization of various types of novel functionalized silica nanoparticles, as well as their application in catalysis, biomedicine and rare earth elements recovery. Novel mesoporous silica nanoparticles derived from mono- and bis-silylated proline-valinol amides were prepared and used as recyclable catalysts for the asymmetric aldol reaction with high activity and selectivity. These nanomaterials can be successfully recovered and reused for up to six runs (Chapter 2). Conversely, our efforts in the preparation of recyclable organosilica nanoparticles as chiral catalysts or ligands for the enantioselective α-trifuoromethylation and α-fluorination of carbonyl compounds were not successful (Chapter 2). A series of mixed periodic mesoporous organosilica nanoparticles possessing Boc and tert-butyl ester groups were prepared as potential high intensity focused ultrasound (HIFU) responsive agents. These nanomaterials were expected to release CO2 and/or isobutene from the temperature-sensitive COOtBu group. However, Boc group was found to be quite stable and could not be removed under HIFU conditions at 80 ºC, requiring the addition of acid. The concept is nevertheless promising for future contrast agents for HIFU based therapies (Chapter 3). Non-steroidal anti-inflammatory drugs such as ibuprofen and diclofenac were grafted to silica nanoparticles through an amide functional group for potential application in ointment and cream topical formulations. Furthermore, coating of cotton fabrics with these functionalized silica nanoparticles provided hydrophobic fabrics for potential topical cutaneous applications in dressings intended to treat chronic wounds. The corresponding anti-inflammatory drug is released in situ by the selective enzymatic cleavage of the amide bond in the presence of proteases (Chapter 4). Two functionalized magnetic core-shell mesoporous silica nanoparticles containing cyclen moieties were prepared as novel adsorbents for the specific and selective recovery of different rare earth (REs) ions from wastewater (Chapter 5).

The solar industry is one of the fastest-growing energy industries in the global market. The reason is a combination of the falling prices of modules and inverters and increased conversion to fossil-free energy production. When a photovoltaic module reaches the end of its life it needs to be replaced and discarded, which can create a sustainability problem depending on how this is managed. Today, less than 10% of the global photovoltaic waste is recycled. Only the European Union has implemented photovoltaic waste regulations in the form of the WEEE Directive, which requires that 85% of the waste is collected and at least 80% of waste collected must be prepared for reuse or recycling. This master thesis examines the energy technical, economic, and political conditions for a Swedish photovoltaic recycling plant. This is done through a literary study that is enhanced with calculations of future potential waste volumes and their economic value. As an alternative to a Swedish plant, the energy consumption for transporting waste to existing recycling plants in Europe is evaluated. The photovoltaic technologies included in this work are silicon-based mono-and polycrystalline modules, cadmium tellurium (CdTe) and copper indium gallium selenide (CIGS). Based on the calculations and the literature study, the energy technical conditions are good and not a barrier for a potential facility, the political conditions are deficient, and regulations need further development. The economic conditions constitute the largest barrier as waste volumes are not large enough for a Swedish facility to be economically profitable until 2042. The energy consumption for transport to existing recycling plants in Europe was 22 MJ/module for silicon-based mono-and polycrystalline modules and 10 MJ/module for CdTe modules. Which is a good alternative to a Swedish plant as collection processes and recycling processes are already in place.

The purpose of this work is to find a methodology in order to make possible the recycling of fines (0 - 4 mm) in the Construction and Demolition Waste (CDW) process. At the moment this fraction is a not desired by-product: it has high contaminant content, it has to be separated from the coarse fraction, because of its high water absorption which can affect the properties of the concrete. In fact, in some countries the use of fines recycled aggregates is highly restricted or even banned. This work is placed inside the European project C2CA (from Concrete to Cement and Clean Aggregates) and it has been held in the Faculty of Civil Engineering and Geosciences of the Technical University of Delft, in particular, in the laboratory of Resources And Recycling. This research proposes some procedures in order to close the loop of the entire recycling process. After the classification done by ADR (Advanced Dry Recovery) the two fractions "airknife" and "rotor" (that together constitute the fraction 0 - 4 mm) are inserted in a new machine that works at high temperatures. The temperatures analysed in this research are 600 °C and 750 °C, cause at that temperature it is supposed that the cement bounds become very weak. The final goal is "to clean" the coarse fraction (0,250 - 4 mm) from the cement still attached to the sand and try to concentrate the cement paste in the fraction 0 - 0,250 mm. This new set-up is able to dry the material in very few seconds, divide it into two fractions (the coarse one and the fine one) thanks to the air and increase the amount of fines (0 - 0,250 mm) promoting the attrition between the particles through a vibration device. The coarse fraction is then processed in a ball mill in order to improve the result and reach the final goal. Thanks to the high temperature it is possible to markedly reduce the milling time. The sand 0 - 2 mm, after being heated and milled is used to replace 100% of norm sand in mortar production. The results are very promising: the mortar made with recycled sand reaches an early strength, in fact the increment with respect to the mortar made with norm sand is 20% after three days and 7% after seven days. With this research it has been demonstrated that once the temperature is increased it is possible to obtain a clean coarse fraction (0,250 - 4 mm), free from cement paste that is concentrated in the fine fraction 0 - 0,250 mm. The milling time and the drying time can be largely reduced. The recycled sand shows better performance in terms of mechanical properties with respect to the natural one.

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Tese (Doutoramento)
IPEN/T
Instituto de Pesquisas Energeticas e Nucleares - IPEN-CNEN/SP

Thesis (Ph. D.)--Chemical and Biomolecular Engineering, Georgia Institute of Technology, 2005.
Jones, Christopher, Committee Chair ; Eckert, Charles, Committee Member ; Schork, Joseph, Committee Member ; Weck, Marcus, Committee Member ; Zhang, John, Committee Member. Includes bibliographical references.

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Coordenação de Aperfeiçoamento de Pessoal de Nível Superior
The silica refractory is nowadays one of the most used linings in the world due to its excellent cost/benefit ratio. The silica sand is available in abundance in the market for use as a raw material for production of ordinary applications refractories, and this does not encourage the search for new usages of its wastes. However, in some industrial sectors where the natural raw materials are used, it has been noticed an increased difficulty to find materials with adequate purity grades to its applications. Furthermore, most of the productive sector is looking for alternatives to reduce the generation of industrial wastes that must be disposed in specific landfills. In this study one aimed to evaluate the potential use of a waste from the synthesis of SiO2 refractory for the application with Alkaline Sodium Silicate and Silica Refractory Paste. This paste is utilized as lining for Ingots and Pouring Ladles in the Foundry Process. This proposal is supported by the demand of Tupy S/A to recover that waste. This company is totally committed to the environment care of your productive processes, always aiming the reduction of wastes generation and its discard. In this proposal it was considered an initial processing stage to partially remove the excess iron present in the wastes that is deleterious to the silica lining. The refractories were produced making waste additions up to 100% in weight. The obtained refractories characterizations, as well as each process step efficiency evaluation, were done through techniques like thermal analysis, X-ray diffraction analysis, grain size distribution curves and ambient temperature compression strength measurements. The results showed good performance with the addition of silica waste, especially a significant increase in ambient temperature compression strength; provided by incorporation of the waste with higher amount of grain small, medium and large. The economic viability of the economy is considerable and preservation of raw materials, conventional silica sand, and the reuse of waste silica mix, avoiding disposal at a landfill.
O refratário de sílica é hoje um dos revestimentos mais utilizados no mundo pelo seu excelente custo/benefício. A areia de sílica como matéria prima para a obtenção de refratários de uso convencional está disponível no mercado em abundância, o que não incentiva a busca por alternativas para a reutilização de seus resíduos. Entretanto, em diversos setores industriais onde matérias primas naturais são utilizadas tem notado o aumento na dificuldade de obtenção de materiais com grau de pureza adequado a suas aplicações. Além disso, todo o setor produtivo tem buscado por alternativas para redução da geração de resíduos industriais a serem descartados em aterros específicos. O presente trabalho busca avaliar o potencial do uso de um resíduo refratário na síntese de refratário de SiO2 para aplicação com Massa Refratária de Silica e Silicato de Sódio Alcalino (MRSNA) para revestimentos de lingoteiras e panelas de vazamento utilizados no processo de Fundição. Esta proposta está baseada na necessidade da reutilização desse resíduo pela empresa Tupy S. A. Esta empresa tem como premissa a constante preocupação ambiental nos seus processos produtivos, buscando sempre a redução da geração de resíduos ou descarte destes. Para o desenvolvimento desta proposta foi considerada inicialmente uma etapa de beneficiamento para a remoção parcial do excesso de ferro presente no resíduo que é um contaminante para o revestimento de sílica. Os refratários foram produzidos considerados adições de resíduos em teores em peso de resíduo de até 100%. Para a caracterização dos refratários obtidos, assim como para avaliação da eficiência das diferentes etapas de processamento foram utilizadas ferramentas como análise térmica, difratometria de raios-X, construção de curvas de distruibuição granulométrica e medidas de resistência à compressão a tempertura ambiente. Os resultados mostraram um bom desempenho com a adição do resíduo de sílica, especialmente um aumento significativo na resistência à compressão à temperatura ambiente; proporcionado por uma curva de distribuição granulométrica heterogênea (grãos pequenos, médios e grandes). A viabilidade econômica é considerável pela economia e preservação da matéria prima, areia de sílica convencional, e pela reutilização do resíduo de sílica mix, evitando o seu descarte em aterro industrial.

Despite the growing interest in heterogeneous polymerization catalysis, the majority of the polymerization catalysts used industrially are single-use entities that are left in the polymer product. Recoverable and recyclable polymerization catalysts have not reached the industrial utility of single-use catalysts because the catalyst and product separation have not become economical. The successful development of recyclable transition metal polymerization catalysts must take a rational design approach, hence academic and industrial researchers need to further expand the fundamental science and engineering of recyclable polymerization catalysis to gain an understanding of critical parameters that allow for the design of economically viable, recoverable solid polymerization catalysts. Unfortunately, the rapid development of Atom Transfer Radical Polymerization over the past 10 years has not resulted in its wide spread industrial practice. Numerous reports regarding the immobilization of transition metal ATRP catalysts, in attempts to increase its applicability, have extended the fundamentals of recyclable polymerization catalysis. However, for industrial viability, more research is required in the area of how the catalyst complex immobilization methodology and support structure affect the catalyst polymerization performance, regeneration, and recyclability. A comprehensive rational catalyst design approach of silica-immobilized ATRP catalyst was undertaken to answer these questions and are discussed here.

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Dissertacao (Mestrado)
IPEN/D
Instituto de Pesquisas Energeticas e Nucleares - IPEN/CNEN-SP

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The chemical recycling of polyolefins has been the focus of increasing attention owing potential application as a fuel and as source chemicals. The use of plastic waste contributes to the solution of pollution problems.The use of catalysts can enhance the thermal degradation of synthetic polymers, which may be avaliated by Themogravimetry (TG) and mass spectrometry (MS) combined techniques. This work aims to propose alternatives to the chemistry recycling of low-density polyethylene (LDPE) on mesoporous silica type SBA-15 and AlSBA-15.The mesoporous materials type SBA-15 and AlSBA-15 were synthesized through the hydrothermal method starting from TEOS, pseudobohemite, cloridric acid HCl and water. As structure template was used Pluronic P123. The syntheses were accomplished during the period of three days. The best calcination conditions for removal of the organic template (P123) were optimized by thermal analysis (TG/DTG) and through analyses of Xray diffraction (XRD), infrared spectroscopy (FT-IR), nitrogen adsorption and scanning electron microscopy (SEM) was verified that as much the hydrothermal synthesis method as the calcination by TG were promising for the production of mesoporous materials with high degree of hexagonal ordination. The general analysis of the method of Analog Scan was performed at 10oC/min to 500 oC to avoid deterioration of capillary with very high temperatures. Thus, with the results, we observed signs mass/charge more evident and, using the MID method, was obtained curve of evolution of these signals. The addition of catalysis produced a decrease in temperature of polymer degradation proportional to the acidity of the catalyst. The results showed that the mesoporous materials contributed to the formation of compounds of lower molecular weight and higher value in the process of catalytic degradation of LDPE, representing an alternative to chemical recycling of solid waste
A reciclagem qu?mica de poliolefinas tem sido foco de crescente aten??o, devido ao seu uso potencial como combust?vel e como fonte de produtos qu?micos. O aproveitamento de res?duos pl?sticos contribui para a solu??o dos problemas de polui??o. O uso de catalisadores adequados pode facilitar a degrada??o t?rmica de pol?meros sint?ticos, que pode ser avaliada por termogravimetria e espectrometria de massas. Este trabalho teve como objetivo avaliar uma alternativa de reciclagem qu?mica de polietileno de baixa densidade (PEBD) sobre s?lica mesoporosa tipo SBA-15 e AlSBA-15 utilizando termogravimetria e espectrometria de massas.Os materiais mesoporosos tipo SBA-15 e AlSBA- 15 foram sintetizados atrav?s do m?todo hidrot?rmico partindo de tetraetilortosilicato TEOS, pseudobohemita, ?cido clor?drico - HCl e ?gua destilada. Como direcionador estrutural foi utilizado Pluronic P123 (copol?mero tribloco). As s?nteses foram realizadas durante um per?odo de tr?s dias. As melhores condi??es de calcina??o para remo??o do direcionador org?nico (P123) foram otimizadas por an?lise t?rmica (TG/DTG) e atrav?s de an?lises por difra??o de raios X (DRX), espectroscopia na regi?o do infravermelho (FTIR), adsor??o de nitrog?nio e microscopia eletr?nica de varredura (MEV) se verificou que tanto o m?todo de s?ntese hidrot?rmico, como tamb?m as condi??es de calcina??o baseadas nos estudos cin?ticos por termogravimetria (TG) foram promissores ? produ??o de materiais mesoporosos com alto grau de ordena??o hexagonal. Os estudos de decomposi??o e evolu??o de gases foram realizados em uma termobalan?a acoplada a um espectr?metro de massas. A an?lise geral das amostras com o m?todo de Scan Analog foi realizada a 10?C/min at? 500?C para n?o deteriorar o capilar com temperaturas muito altas. Assim, com os resultados foi poss?vel observar os sinais massa-carga mais evidentes e, empregando o m?todo MID, foi obtida a curva de evolu??o desses sinais. A adi??o de catalisadores produziu uma diminui??o na temperatura de degrada??o do pol?mero proporcional ? acidez do catalisador. Os resultados obtidos, mostraram que os materiais mesoporosos contribu?ram para a forma??o de compostos de menor massa molecular e maior valor agregado no processo de degra??o catal?tica do PEBD, representando uma alternativa de reciclagem qu?mica destes res?duos s?lidos

Le but général de ce travail fut de quantifier la silice biogène (BSiO2) dans les sédiments du continuum de l'Escaut (estuaire – zone côtière), ainsi que son taux de recyclage - rétention. Le coefficient de diffusion moléculaire de la DSi a été déterminé pour différentes valeurs de température et deux salinités et une relation empirique reliant le coefficient de diffusion à la température et à la viscosité de la solution a été établie. La distribution longitudinale de la BSiO2 dans les sédiments de surface, ainsi que les profils verticaux de BSiO2 et de silice dissoute ont été déterminés durant différentes saisons en 2004 et 2005. Les flux de DSi ont été également estimés via des expériences d’incubations et par modélisation des profiles verticaux de DSi. Des expériences de dissolution des sédiments ont permis de déterminer (via modélisation) les constantes cinétiques de vitesse de la BSiO2 et une première évaluation du taux de recyclage de la BSiO2 (5 – 70%). Sur base des calculs à partir des profiles de DSi dans l’eau interstitielle, le taux de recyclage de la BSiO2 varie entre 8 et 92% dans l’estuaire, ce qui correspond à une rétention moyenne de la BSiO2 supérieure à 60%, et souligne ainsi l'efficacité du filtre estuarien par rapport à la silice. En revanche, le recyclage de BSiO2 dans la zone côtière apparaît comme très intensif, avec des valeurs souvent supérieures à 40%. Ces résultats montrent l'importance d'inclure les estuaires dans le calcul des budgets globaux de Si. / The general objective of this study was to quantify the BSiO2 in the sediments of the Scheldt continuum, together with its recycling and retention in this area. First an empirical relation linking the diffusion coefficient of DSi to temperature and salinity was determined, via diffusion experiments. The longitudinal BSiO2 distribution in surface sediments and the vertical BSiO2 and DSi profiles in sediment cores where then measured during 2 years and different seasons, together with other parameters characterizing pore waters, such as alkalinity, pH, sulphate… DSi fluxes were also estimated either directly through whole core incubations measurements or via modelling of interstitial water profiles. BSiO2 dissolution experiments allowed the evaluation of the kinetic rate constants also through modelling of the results, and gave preliminary information over the BSiO2 recycling rates (5 – 70%). The recycling rate as obtained from pore water profiles vary between 8 and 92%, with an average value of about 32%, which highlights the importance of the estuarine filter for silica. Recycling is much more intense in the coastal area, with values up to 40%, which we explain by higher salinity and higher sediment permeability. The different experiments and results also indicated that secondary mineral precipitation might be and important process affecting BSiO2 in the Scheldt sediments.

Doctorat en Sciences
info:eu-repo/semantics/nonPublished

Concrete as a building material is subject to continuous innovation and thanks to advanced technology and quantum of research, its properties are still improved. It is logical that the more concrete we produce, the more waste it arises. The volume of this waste can not be stored in landfills endlessly, nowadays most of the waste economies in the world are trying to recycle concrete rubble. The recycling is not such a problem, the technology has been long verified but the quality of the recycled concrete aggregate is unquestionably one of the primary assumption which leads to accomplish required properties of concrete. In fact, the recycling process is „crushing“ the concrete into particles with an effort to eliminate the cement paste on the surface of the aggregate. An ideal solution would be create a resistant and firm coating that would adhere perfectly to the cement matrix. This diploma thesis is focused on the properties of recycled concrete aggregate and methods of improvement and optimization of the concrete mix composition.

碩士
大葉大學
環境工程學系碩士班
96
In this study, a hydrometallurgical method is adopted to recover the valuable resources of silicon and copper (Cu) from copper containing scrap silicon wafer. The collected scrap wafer contains 0.52% Cu and has a density of 2.395 g/cm3, water content of 0.103％ and ash content of 100.2％.This study reveals that an optimum leaching condition of 1N H2SO4, 200 times H2O2, 700C, 20g/50ml and 4 hours can obtain a Cu leaching recovery of 98.6%. The Cu contained in this leaching solution can either be 100% crystallized as a marketable CuSO4．5H2O by heating at 700C for two hours and crystallization at 27 0C for 12 hours, or be 100% replaced as a marketable Cu powder by adding the fine iron powder. The solid obtained from the first optimum leaching which contains 0.01% Cu was subjected to a same optimum leaching condition to recover all the remaining Cu. The Cu contained in this second leaching solution can be 100% recovered as Cu powder by adding fine iron powder. The solid obtained from second optimum leaching is proofed to be a 100% purity of silicon by the analysis of EDS and XRD.

碩士
國立臺北科技大學
資源工程研究所
100
Silicon ingot cut wafer produce abundant silicon sawing waste during the sawing process. If it can be recycled, it can reach the purpose of environmental protection and the reduction of cost. In order to promote the post application value of silicon and silicon carbide, the removal of metal impurities is essential when recycling silicon sawing waste. The experimental results show that silicon and silicon carbide can be separated by using centrifugation. When recycling of silicon sawing waste was performed by using the centrifugation in a magnetic field, the iron can be removed from silicon powders by the ratio of waste to solvent is 3/7. In addition, this study show that H2SO4 aqueous solution could react with the waste rapidly and remove most of metal. The residual iron in the silicon powder could reach 28.83ppm. If the sawing waste was pretreated by use of scrubber, the residual iron could reach 25.99ppm.The analysis of chemical kinetics show that the reaction order for metal oxidation in sulfuric acid is higher than that in hydrochloric acid, citric acid or nitric acid, meaning that the reaction in sulfuric acid is more sensitive to the concentration of hydrogen ion. The reaction of citric acid to metal oxidation has the lowest activation energy. The reaction of nitric acid to metal oxidation has the highest activation energy. The research shows that a ultrasonic cleaner removed most iron in a short period of time. However, in a long period of time, the effectiveness of removing iron by using a stirrer is better than using a shaker or an ultrasonic cleaner. In this research, we separated silicon and silicon carbide and removed iron impurities from the cutting waste successfully by using the centrifugation in a magnetic field. By acid treatment, we can reduce iron impurities to less than 100ppm. Because the concentration of acid is low, it can prevent damage to the environment, and it can realize the target of simplifying the process and reducing cost.

碩士
國立中央大學
國際永續發展碩士在職專班
106
The goal of this thesis is to assess the economic feasibility of a recycling facility for crystalline silicon based PV modules. Two cases are described in this study, the first one is the building up and operating a recycling facility located in the north region of Italy and the second one is located in the north region of Honduras. This thesis utilizes an economic model called the discounted cash flows in order to assess the economic feasibility of the recycling facilities. A sensitivity analysis was applied in order to identify the range of parameters values within which a project can remain economical viable. The sensitivity analysis was applied to the critical values that affect the viability of the project (Investment, collection, process and conferred cost, as well to the prices of the material chosen to be recycled). The discounted cash flow method results shows for the first case the unprofitability of the recycling plant located in Italy in the entire scenarios including the sensitivity analysis. In the other hand the results from the economic method for the second case, described the profitability of the recycling plant located in Honduras, revenues are obtained in the fourth year of operation. The results of the sensitivity analysis for the second case confirm the feasibility of the project obtaining revenues from the facility in the third year as the best scenario

碩士
大葉大學
機械與自動化工程學系
98
The goal of this research is to study the recycling processes for the amorphous type wasted silicon dioxide crucible, which exist high purity. If we can retrieve this high purity wasted crucible with simple processing, it should have many other uses in industries. First, smash the silicon dioxide crucible and pickling it. Followed with the hydrothermal treated to grow the α-quartz crystal. We found that larger amount of sodium element will containment the quartz crystal during the treatment. Therefore, adequate purification processes will be needed to remove the sodium. During the processing, the morphology, crystalline pattern and impurity content of treated powder will be examed by using SEM, XRD and ICP-OES analyzer. From the experimental result showed that with different hydrothermal temperature and solution concentration will reveal quite different results. If the concentration of solution is too dilute which will not precipitate any crystalline particle. In general, with increasing the concentration of solution or temperature, not only the average particle size and their distribution range will increase, but the loss of products will also raise. Therefore, under the consideration of cost, diameter and crystalline intensity, three sets of hydrothermal parameter were suggested to obtain the best results, which are 200℃-1.7M、220℃-0.5M and 220℃-1.0M. According to exist the problem of sodium containment, using the equipment of lifting furnace, tubular furnace and vacuum melting furnace will show different purification result. Using the lifting furnace, the α-quartz will transform to the cristobalite structure, and the effect of reduce the sodium content is unobvious. On the process by vacuum melting furnace, α-quartz also have the same transformation phenomena, and the crystalline intensity drops apparently at high temperature. However, the sodium content reduces obviously by this vacuum process. On the process by tubular furnace, the powder can maintain the crystalline pattern and intensity of α-quartz, and the sodium content can reduce substantially. Based on the experimental result, we suggested that using 0.5 M NaOH solution and hydrothermal treated at 220℃ should obtain the best recrystallization result. Following treated with the purification process of tubular furnace at 1010℃ which can maintain the α-quartz and obvious reduce the sodium content; or use vacuum melting furnace with lower reaction temperature and shorter treating time, should receive the similar results.

博士
國立臺北科技大學
工程學院工程科技博士班
105
In a country producing silicon wafer, an important policy of waste reduction is to recycle the resource from silicon ingot sawing waste. In addition to metals impurities, a large amount of reusable Si, SiC and glycol solution are found in the sawing waste. Effective recycling of silicon sawing waste and innovative applications must improve the circular economic value of the wafer manufacturing system. First of all, this study adopted gravity settling or centrifugation to recover glycol solution and analyzed the feasibility of recycling technologies. The experimental results show that adding different solvents is related to the quality of final recycled glycol solution. In quantification of Si and SiC, several ways to describe the composition of Si and SiC were compared. In addition, acid treatment was applied to remove metal impurities from silicon sawing waste. The effects of acidic species, concentration and ratio of solid to liquid on Fe dissolution and the dissolution kinetics were investigated. Moreover, the vertical sedimentation system was utilized to separate Si and SiC. The difference between the experimental results and theoretical calculation was discussed. Furthermore, an idea about the potential of hydrogen energy generation from silicon and the applications of silicate produced from Si-water reaction were presented. First, the influence of particle size, alkali solution concentration, and reaction temperature were studied and its kinetic mechanism for Si-water reaction was proposed. On the one hand, the silicate solution was used to prepare an adsorbent and to remove nickel ions from wastewater. Analysis of experimental data indicated that the pseudo-second order kinetics and Langmuir model could well describe the adsorption process. On the other hand, the silicate solution was used to prepare gelled electrolytes by sulfuric acid titrating and to apply on the lead redox reaction. In summary, this study are included that the Si and SiC quantitation, techniques regarding solid-liquid, solid-solid separation, metal removal, hydrogen production from silicon and applications of silicate solution. After solid-liquid separation, high-quality glycol solution was obtained; the metal impurities can be dissolved and removed by acids. Using sedimentation, the Si-rich or SiC-rich powders were obtained. The recovered Si could apply to hydrogen evolution, and then the silicate solution or high-purity SiC were reused. Simple, low-cost recycling processes and strategies encourage companies to adopt them and this study benefits the analysis, reduction, reuse and zero-emission of silicon sawing waste.

碩士
國立交通大學
工學院永續環境科技學程
101
This study evaluate the physical recycle mechanism of waste cutting oil . The waste cutting oil is composed of DEG as the base chemical, the results show that filter-press (build-in 1 ml filter cloth) and horizontal decanter (interval rotating speed of 1,400 rpm) are good pre-working machines. After liquid has been pre-heated up to 70℃, the viscosity can be reduced. And ultra-filter device with mud-guide system for final recovery treatment is feasible. The clean recycled oil after proper treatment contained near 0% of solid content. The GC-Mass spectrum analyses reclaimed that the oil presented high similarity to that of the new oil, there is no chemical disruptor after heating. The combination of filter-press, horizontal decanter, heating system and ultra-filter device can prove to be a good long-term recycling which retrieved 52% average recycling rate of waste cutting oil.

碩士
國立屏東科技大學
材料工程研究所
105
In this study, we effectively reused recycling SiC powders which are came from cutting waste oil in the electronics industry. The main purpose is to make recycling SiC powders as high temperature substrates. Waste oil mainly contains silicon mud which includes the silicon carbide, silicon and silicon oxide. If silicon mud can be reused effectively, the treatment cost should be decreased, and environment impacting should be also reduced. High temperature sintering substrate is made by recycling SiC powders, then coating a layer of yttrium stabilized zirconia on the surface. In the experiment, the powders self-grinding were carried out in order to reduce the particle size and the acute angle. After self-grinding, SiC powders were successfully made into a substrate. The SiC disc was sintered at a high temperature from 1400 °C to 1550 °C. The specimens were analyzed such as phase evolution, microstructure, component, thermal expansion rate etc. The SiO2 was coated by sol-gel method as middle layer.We used spin coating to coat the SiO2 sol-gel, spin coating speed is 500 rpm, 1000 rpm, 1500 rpm and 2000 rpm. The middle layer’s heat treatment temperature is 1050 °C, 1200 °C and 1350 °C. The Y-ZrO2 layer was coated on the SiC substrates. SiO2 middle layer was successfully to improve the mismatch between ZrO2 coatings and SiC substrates. In this study, ZrO2 was also sprayed on SiC by using plasma spraying. We compared the difference between the plasma spraying and the spraying.

博士
國立臺灣大學
化學工程學研究所
96
Solar photovoltaic (PV) energy will shortly be in great demand, since it is inexhaustible and cleaner than any conventional energy resources. The global PV production was over 2.6 GW in 2006 alone, out of which, the majority was the silicon wafer-based solar cells. Because the fast growing PV market is mainly based on crystalline silicon, the lack of silicon raw materials in recent years is becoming a critical issue. The exponential growth of the solar cell industry has driven up the price of silicon several times and the shortage of silicon has been a serious issue since 2003. So far, most of solar grade silicon (SoG-Si) is from the Siemens process, which is energy intensive and high cost. Therefore, cheaper routes for producing SoG-Si are being developed in the PV industries, but the progress in slow. The price of raw silicon has increased almost ten times for the past five years. Therefore, seeking a feasible and low-cost route for producing SoG-Si is important for the PV industry. On the other hand, because there is about 40% kerf silicon loss during slicing processing, the recycle of the silicon from the cutting slurry could save the raw material used significantly. However, the attempt has not yet been succeeded so far. In this thesis, we developed a novel approach to recover SoG-Si from the Si/SiC mixture obtained from the cutting slurry waste. Herein a detailed discussion of the processes involved in the whole recycle research is reported. The average resistivity and minority carrier lifetime of the grown crystals from recycled silicon were found to be about 0.7 Ω-cm and 1.02 μs, respectively, which were close to the original sawing silicon ingots. Solar cells using multi-crystalline wafers of recovered silicon were fabricated and the best energy conversion efficiency (12.6%) was comparable to the ones from the high-purity silicon (13.2%). The yield of recycle process is about 20% and the cost (32 $/kg) is much lower than the right now price of solar grade silicon. Multi-crystalline silicon (mc-Si) grown by the directional solidification method has attracted world wide attention as a solar cell material because of its low production cost and high throughput. However, the efficiency of mc-Si solar cells is usually lower than single-crystalline silicon solar cells because of the presence of variety of defects such as randomly oriented grain boundaries, dislocations, inclusions and oxides, in large concentration. These defects act as recombination center for light generated electrons and holes and therefore are harmful for the solar cell performance. Recently, grain boundaries have been shown to have different characteristics under different orientations. For example, the Σ3 boundary is a well-known inactive boundary as it does not act as recombination center. Therefore, in order to improve the efficiency of mc-Si based solar cells, efforts have been directed towards growth of mc-Si with highly oriented grains. In fact, controlling the cooling speed during initial stage of solidification induces dendrite growth along the crucible bottom wall which is responsible for growth of large grains with Σ3 grain boundary. In this thesis, we report a novel method to control the grain orientation by using cooling spots at the bottom of the crucible. The cooling spots induce locally larger radial thermal gradients to enhance dendritic growth, but not limited to the size of the crucible. Studies have been carried out for laboratory scale, and some preliminary results have been obtained from an industrial scale experiment. The minority carrier lifetime measurements and electron back scattering pattern analysis in the grown crystals have been carried out to assess the effect of using cooling spot.

Using recycled concrete aggregate (RCA) as a replacement for natural aggregate in new concrete is a promising way to increase the overall sustainability of new concrete. This has been hindered, however, by a general perception that RCA is a sub-standard material due to the lack of technical guidance, specifically related to long-term durability, on incorporating RCA into new concrete. The goal of this research project was to determine whether current testing methods could be used to assess the potential alkali-silica reactivity of concrete incorporating RCA. The test methods investigated were ASTM C1260 and ASTM C1567 for assessing natural aggregate susceptibility to alkali-silica reactivity (ASR), and the ability of supplementary cementitious materials (SCMs) to mitigate ASR, respectively. Seven different RCA sources were investigated. It was determined that ASTM C1260 was effective in detecting reactivity but expansion varied based on RCA processing. Depending on the aggregate type and the extent of processing, up to a 100% increase in expansion was observed. Replicate testing was performed at four university laboratories to evaluate repeatability and consistency of results. The authors recommend modification to the mixing and aggregate preparation procedures, when testing the reactivity of RCA using ASTM C 1260. This study also investigated the efficacy of replacing portland cement with supplementary cementitious materials (SCMs), known to mitigate alkali-silica reaction (ASR) in concrete with virgin aggregates, to control ASR in concrete incorporating reactive RCA. The SCMs investigated as part of this study included: fly ash (class F), silica fume, and metakaolin. The results of modified alkali-silica reactivity tests, ASTM C1260 and ASTM C1567 (AMBT), are presented for two different recycled concrete aggregates when using 100% portland cement, binary blends of portland cement and fly ash, and ternary blends of portland cement, fly ash and metakaolin or silica fume. The results indicate that SCMs can effectively mitigate ASR in concrete made with RCA. A 40% replacement of portland cement with class F fly ash was able to reduce expansions to below 0.10% in the AMBT for concrete containing 100% of a highly reactive recycled concrete aggregate. A ternary blend, however, of portland cement with a class F fly ash and metakaolin was most effective for both RCAs tested in this study. Higher levels of mitigation may be required for some RCAs, compared to the level required to mitigate ASR in concrete made with their original natural aggregates, depending on the age and composition of the RCA.
Graduation date: 2012