Submitted by Claudinei Pracidelli (cpracide@ipen.br) on 2015-08-12T12:22:44Z No. of bitstreams: 0 / Made available in DSpace on 2015-08-12T12:22:44Z (GMT). No. of bitstreams: 0 / Planejar e gerenciar o desenvolvimento tecnológico são questões estratégicas para as organizações que desejam realizar processos de P&D. A elaboração de Planos Tecnológicos (PT) pode representar um desafio significativo de esforço e planejamento para essas organizações. Os problemas mais comuns são falhas nas previsões dos projetos sejam eles de novos produtos, serviços ou processos. Esse estudo tem por objetivo desenvolver uma metodologia para identificar, classificar e quantificar os fatores denominados alavancadores e desafiadores que possam estar presentes na elaboração do PT. Desenvolveu-se um protocolo para entrevista e coleta de dados em duas fases, aplicado aos envolvidos na elaboração do PT. Na Fase 1 considerou-se a metodologia de construção do PT vigente na unidade de análise. Para Fase 2, considerou-se a metodologia T-Plan na construção do Mapa Tecnológico. Os fatores investigados foram organizados em dimensões (planejamento, desenvolvimento e aplicação) que foram segmentados em variáveis de pesquisa (viabilidade, compromissos, comunicação, direcionadores, priorização, monitoramento, aprendizado, revalidação, aplicação e replicação) e, dependendo dos resultados, eles foram classificados em alavancadores ou desafiadores. O processo de elaboração do PT foi também avaliado com base em dois atributos: qualidade e satisfação. Nas duas fases, ambos foram avaliados segundo a percepção dos entrevistados. Para a Qualidade, a representação foi em 4 quadrantes, para indicar a presença e a formalidade evidenciando a existência da variável da pesquisa. Para a Satisfação foram avaliados estatisticamente considerando o valor médio e desvio padrão entre a condição atual e a desejada. Essa distancia caracterizou as oportunidades das mudanças. A unidade de análise foi o Centro de Célula a Combustível de Hidrogênio - CCCH, um departamento do Instituto de Pesquisa Energéticas e Nucleares do Brasil. A análise da Fase 1 considerou um PT elaborado anteriormente e da Fase 2 foi aplicado a metodologia T-Plan. Nessa segunda fase foi construído o Mapa Tecnológico para os próximos dez anos considerando direcionadores estratégicos, produtos, tecnologias e recursos necessários para realização do protótipo comercial até 2024 e assim viabilizar a inclusão da Célula a Combustível na Matriz Energética Nacional. Com as análises dos resultados das duas fases verificou-se: Fase 1: foram identificados como fatores Desafiadores: Direcionadores e Aplicação; como Fatores Potencial Desafiador: Viabilidade, Priorização, Monitoramento, Aprendizado e Revalidação; como fatores Potencial Alavancador: Replicação e como fatores Alavancadores: Compromisso e Comunicação. Fase 2: todos fatores foram classificados como Alavancadores: Viabilidade, Compromisso, Comunicação, Direcionadores, Priorização, Monitoramento, Aprendizado, Revalidação, Aplicação e Replicação. Concluiu-se que na metodologia T-Plan há uma sensível alteração da avaliação dos fatores Alavancadores e Desafiadores. O Mapa de Rotas Tecnológicas do CCCH, construído na Fase 2 indicou as seguintes rotas tecnológicas: 1) preparação de materiais e principais componentes do módulo; 2) partir da demanda do mercado para chegar aos novos produtos; 3) partir do desenvolvimento das tecnologias para chegar aos novos produtos; 4) desenvolvimento dos materiais para chegar aos produtos e atender aos drivers. Tais resultados sugerem concluir que a aplicação da metodologia do T-Plan não é só viável, mas até recomendável, no âmbito da elaboração de Planos Tecnológicos das Instituições de Pesquisa Pública. / Dissertação (Mestrado em Tecnologia Nuclear) / IPEN/D / Instituto de Pesquisas Energeticas e Nucleares - IPEN-CNEN/SP

Este trabalho apresenta resultados de estudos e caracterizações de Conjuntos Eletrodo/Membrana (MEAs) de Células a Combustível a Membrana Polimérica (PEMFC). Algumas condições de operação de células e diferentes processos de produção de MEA foram investigados. A técnica de Espectroscopia de Impedância Eletroquímica (EIE) (em situ - 0 a 16 A) foi usada \"on-line\" como uma ferramenta de diagnóstico, relativa ao desempenho de célula. As medidas de EIE foram feitas através do Sistema de EIE para células a combustível FC350 (GAMRY), junto a um PC4 Potentiostato/Galvanostato e conectado à carga dinâmica (TDI) para experimentos de EIE \"on-line\" (100 mHz - 10 kHz, dU = 5 mV). MEAs com 25 cm2 de área ativa, usando eletrocatalisadores PtM/C 20 % (M = Ru, Sn ou Ni) fabricados usando o Método de Redução por Álcool (MRA). A tinta catalítica foi diretamente aplicada no Tecido de Carbono (GDL) e este prensado na membrana de Nafion® (105). MEAs usando eletrocatalisadores Pt/C e PtRu/C 20 % da E-TEK foram fabricados para comparação. Todos os cátodos foram confeccionados com Pt/C 20% da E-TEK. Foram fixadas as concentrações de metal nobre em 0,4 mg Pt.cm-2 no anodo e 0,6 mg Pt.cm-2 no catodo (E-TEK). Diagramas de Nyquist dos MEAs com Pt/C e PtRu/C da E-TEK ou PtM/C MRA apresentaram as mesmas resistências de ôhmicas para os MEAs. Este fato pode ser explicado por supressão de aglomerados durante o processo de preparação do MEA ou pela homogeneidade do eletrocatalisador ancorado ao carbono. Também pôde ser observado, a baixas densidades atuais que há uma diferença de desempenho significante entre o eletrocatalisadores da ETEK e os preparados pelo MRA. Os resultados das curvas de polarização confirmaram que PtM/C MRA apresentara um aumento de atividade para as células alimentadas com metanol e etanol. A técnica de EIE se mostrou eficiente para a avaliação do método de preparação dos MEAs e do desempenho da célula, os resultados de EIE mostraram uma coerência na escolha do modelo do circuito elétrico para os MEAs utilizando hidrogênio, metanol e etanol. Esta coerência indica que outras resistências não consideradas no modelo não são relevantes na resistência total dos MEAs. / This work reports results of studies and characterization on Membrane Electrode Assemblies (MEAs) for Proton Exchange Membrane Fuel Cell (PEMFC). Some cell operation conditions and different processes of MEA production were investigated. The Electrochemical Impedance Spectroscopy Technique (EIS) (in situ - 0 to 16 A) was used \"on-line\" as a tool for diagnosis, concerning the cell performance. The EIS measurements were carried out with a FC350 Fuel Cell EIS System (GAMRY), coupled to a PC4 Potentiostat/Galvanostat and connected to the electronic load (TDI) for \"on-line\" EIS experiments (100 mHz - 10 kHz, dU = 5 mV). MEAs with 25 cm2 surface area, using PtM/C 20% (M = Ru, Sn or Ni) electrocatalysts were manufactured using the Alcohol Reduction Process (ARP). The catalytic ink was applied directly into the Carbon Cloth (GDL) and pressed in the NafionR membrane (105). MEAs using Pt/C and PtRu/C 20% from E-TEK electrocatalysts were manufactured by comparison. All the cathodes were sprayed with Pt/C 20% from E-TEK. The noble metal concentrations used were set to 0.4 mg Pt.cm-2 at the anode and 0.6 mg Pt.cm-2 at the cathode (E-TEK). Nyquist diagrams of the MEAs with Pt/C and PtRu/C from E-TEK or PtM/C (M = Ru, Sn or Ni) ARP showed essentially the same ohmic resistances for the MEAs. This fact can be explained by suppression of agglomerates during the MEA preparation process or by the homogeneity of the anchored electrocatalysts at the carbon surface. It could also be observed, at low current densities, that there was a significant performance difference between the electrocatalysts from E-TEK and those prepared with the Alcohol Reduction Process. The polarization curves results confirmed that the PtM/C (M = Ru, Sn or Ni) ARP showed an activity increase for the methanol and ethanol fed cells. The technique of EIE was shown efficient for the evaluation of the method preparation of MEAs and the acting of the cell, the results of EIE showed coherence in the choice of the model the electric circuit for MEAs using hydrogen, methanol and ethanol. This coherence indicates that other resistances no considered in the model are not relevant in the total resistance of MEAs.

Indiana University-Purdue University Indianapolis (IUPUI) / Marc Prensky’s digital natives theory became popular, because it supplied teachers with answer as to why students were unresponsive to their curriculums. In essence, Prensky’s theory asks: what has changed? In most cases, it is not the teachers’ curriculums that have changed, so it has to be something else. Prensky points to digital technologies, because teachers are now having to teach students who never knew a world without digital technologies—Prensky, of course, asserting that this changes the way students think, which naturally transfers over to how they learn. In short, it is the students that have changed due to digital technologies. According to Prensky, students, within the digital natives generation, would value their courses more if teachers utilized digital technologies in their classroom. However, critics of the digital natives theory assert that Prensky has not considered many variables that could have an effect on how students use digital technologies, such as socio-economic factors, gender, education, and geographic location, and ultimately there is no empirical evidence to support the use of digital technologies in Prensky’s pedagogy (see Sue Bennett and Karl Maton, Chris Jones et al., Anoush Margaryan et al., and Neil Selwyn). Although, I mostly agree with the critics evaluations of the digital natives theories, I believe that there are larger economic variables, such as Gee et al.’s new capitalism, that influence how students value digital technologies as well as literacy and learning. This concept was reflected in the survey that I conducted in order to examine how students value W131 in general, the writing done in W131, and writing done in social digital technologies. The survey demonstrated that students do not understand social digital writing to be writing; therefore, utilizing digital technologies in the writing classroom, as Prensky suggest, would not be beneficial, because it would take a great deal of class time for students to come to the understanding that social digital writing is writing. More importantly, the survey indicated that students are highly career motivated, which influences how students value their courses. For students, a course’s value is determined by how applicable it is to students’ career goals. The survey results suggest that while students recognize that first-year composition (FYC) has value, they do not necessarily see it specifically valuable to their primary goals. Although I believe it is important for students to be able to find value in a course, I am not suggesting that FYC should be tailored to cater to students; on the contrary, I believe that the ideal FYC course would acknowledge the values of the field of study that it pertains to, and attempt to demonstrate to students how those values relate to their own. This is ideal—however, by using the Writing about Writing pedagogy, designed by Douglas Downs and Elizabeth Wardle, this kind of value system may be possible. Downs and Wardle’s pedagogy also has the potential to bridge the value systems of the students, and writing studies, because Downs and Wardle’s pedagogy focuses on students gaining a better understanding of writing studies as a field of study, by engaging and exploring texts that represent writing studies’ central beliefs and important works. Through texts that come out of the writing studies discipline students can gain a better understanding of concepts that come out of writing studies, as well as build a bridge between students’ values and the values of the writing studies discipline. Texts such as chapter six (“The Means of Production: Literacy and Stratification as the Twenty-First Century) of Deborah Brandt’s Literacy in American Lives, James Paul Gee’s “The New Literacy Studies and the ‘Social Turn,’” and Harvey Graff’s “The Literacy Myth at Thirty,” offers students a new perspective on the economic climate that effects the job market, as well as provide a meaningful way into writing studies. In this chapter, I will discuss Downs and Wardle’s Writing about Writing pedagogy, how I would implement their pedagogy in a FYC course, and what would be the ideal learning outcomes for this course.

No description available.

[pt] Esta dissertação apresenta um debate sobre a técnica que aproveita os materiais disponíveis no local. Este debate começa pelo próprio conceito de técnica e pela ideia de progresso técnico, para se esclarecer mais sobre a natureza da técnica que estamos pesquisando. Diferentes movimentos que se relacionam à técnica que estamos pesquisando são apresentados, como a tecnologia apropriada, a permacultura e a arquitetura popular tradicional. O objeto de estudo é a construção em terra crua, bambu e fibras naturais, que são os materiais pesquisados no Laboratório de Investigação em Living Design (LILD). É utilizada a metodologia prática deste laboratório e sua experiência prévia com técnicas que trabalham com estes materiais para dar prosseguimento à investigação. / [en] This dissertation presents a discussion on the technique that uses materials available on site. This discussion begins with the concept of technique and the idea of technical progress, to further clarify the nature of the technique that we are researching. Different movements that relate to the technique that we are researching are presented, such as appropriate technology, permaculture and traditional folk architecture. The object of investigation is buildings with mud, bamboo and natural fibers, which are the materials studied by the Laboratório de Investigação em Living Design (LILD). This study uses the practical methodology of the laboratory and its previous experience with techniques that work with these materials to continue the investigation.

We address the challenge of providing low-cost, universal access of useful information to people in different parts of the globe. We achieve this by following two strategies. First, we focus on the delivery of information through computerized devices and prototype new methods for making that delivery possible in a secure, low-cost, and universal manner. Second, we focus on the use of participatory media, such as blogs, in the context of news related content, and develop methods to recommend useful information that will be of interest to users. To achieve the first goal, we have designed a low-cost wireless system for Internet access in rural areas, and a smartphone-based system for the opportunistic use of WiFi connectivity to reduce the cost of data transfer on multi-NIC mobile devices. Included is a methodology for secure communication using identity based cryptography. For the second goal of identifying useful information, we make use of sociological theories regarding social networks in mass-media to develop a model of how participatory media can offer users effective news-related information. We then use this model to design a recommender system for participatory media content that pushes useful information to people in a personalized fashion. Our algorithms provide an order of magnitude better performance in terms of recommendation accuracy than other state-of-the-art recommender systems. Our work provides some fundamental insights into the design of low-cost communication systems and the provision of useful messages to users in participatory media through a multi-disciplinary approach. The result is a framework that efficiently and effectively delivers information to people in remote corners of the world.

We address the challenge of providing low-cost, universal access of useful information to people in different parts of the globe. We achieve this by following two strategies. First, we focus on the delivery of information through computerized devices and prototype new methods for making that delivery possible in a secure, low-cost, and universal manner. Second, we focus on the use of participatory media, such as blogs, in the context of news related content, and develop methods to recommend useful information that will be of interest to users. To achieve the first goal, we have designed a low-cost wireless system for Internet access in rural areas, and a smartphone-based system for the opportunistic use of WiFi connectivity to reduce the cost of data transfer on multi-NIC mobile devices. Included is a methodology for secure communication using identity based cryptography. For the second goal of identifying useful information, we make use of sociological theories regarding social networks in mass-media to develop a model of how participatory media can offer users effective news-related information. We then use this model to design a recommender system for participatory media content that pushes useful information to people in a personalized fashion. Our algorithms provide an order of magnitude better performance in terms of recommendation accuracy than other state-of-the-art recommender systems. Our work provides some fundamental insights into the design of low-cost communication systems and the provision of useful messages to users in participatory media through a multi-disciplinary approach. The result is a framework that efficiently and effectively delivers information to people in remote corners of the world.

Persistent poverty, social and economic inequalities are some of the challenges in the process of national development efforts targeted in the United Nations Millennium Development Goals (MDGs). Yet in South Africa, poverty, hunger, social and economic inequalities are still on the increase especially among poor rural to urban migrants. Because of severe poverty in rural areas, large populations of rural poor migrate to urban areas in search of better life. However, the growing energy needs in the urban areas where these people settle and their use of inefficient energy technologies negatively impact on the balance of environmental resources on which their socio-economic development depends. Efficient, affordable and environmental friendly technologies are therefore vital for improving the livelihood conditions and protecting the much needed environmental resources of the country. On the contrary, current practices presently dominating energy provision issues in South Africa are insufficient to solve the problems of socio-economic inequalities, especially for the increasing urban poor population. In addition, they are also failing to protect the environment and natural resources. Electrification of poor urban and peri-urban areas by both grid and off-grid systems through the top-down development practice is doing very little to change the socio-economic conditions of the poor section of the population in the country. Likewise, the provision of modern energy through public sector agencies such as Eskom is inadequate and inappropriate for the rapidly expanding urban and peri-urban poor areas in the country. One major reason that hinders provision of such services to the overcrowded consumer population in these areas is the massive capital investment required and inability to pay electricity bills by urban poor households. Against the above background, this study examined the use of improved wood stoves in two peri-urban areas (Umsilinga and Isnathing) in Pietermaritzburg, South Africa as an alternative modern energy technology on how they would socio-economically benefit the peri-urban poor. It looked at the following: The efficiency of four improved wood stoves (Yamampera, Simunye, Household Rocket and Vesto) in comparison with the three stone open fire, The impact of the efficient burning of the four improved stoves, Factors influencing consumers in choosing a specific energy technology to use, The effectiveness of the improved wood stoves placed in 24 peri-urban households and observed for the specified period, and Additional potentials of such stoves to other prospective users. The key finding of this research is that the use of these improved wood stoves could play a pivital role in household economic growth and improving livelihoods. Participants ranked smokeless burning, low selling price, fuelwood saving and light weight of the stoves as priority preferences for using these stoves. Speed of cooking and less constant attention to the fire were also ranked as important preferences. From women participants view point, the low selling price of the stoves and their considerable fuel saving would reduce strain on the household investment capital, household indoor pollution and tedious work of women’s fuelwood collection. Low investment costs in acquiring the stoves would encourage women’s participation as entrepreneurs in modern energy technologies. However, results from focused group discussions and observations of usage of stoves that were placed in 24 homes showed that the incorporation of consumer preferences in the design of improved wood stoves would be key. This would enable stoves to adequately meet the energy needs of targeted users and be used frequently as an alternative energy solution by both urban and peri-urban poor who are currently lacking electricity and suffering from energy poverty. / Thesis (M.Soc.Sc.)-University of KwaZulu-Natal, Pietermarizburg, 2009.

As tecnologias e a sociedade atual demandam novas competências dos professores. Portanto, a formação inicial desses profissionais é fundamental para que os futuros professores possam integrar as Tecnologias de Informação e Comunicação (TIC), de maneira criativa e inovadora, às suas práticas pedagógicas para potencializar o processo ensino-aprendizagem. Em consequência, as maneiras como os professores formadores se apropriam das TIC para essa formação são de grande importância. O objetivo geral do estudo foi analisar como os professores formadores do Conselho de Formação em Educação (CFE) no Uruguai se apropriam das TIC para a formação de futuros professores. A revisão da literatura aborda conceitos e questões inerentes à apropriação das tecnologias pelos professores: mudanças necessárias na formação de professores; o conceito de apropriação da tecnologia pelos professores, que abrange como os professores adquirem conhecimentos para utilizar as TIC como recursos pedagógicos; os significados que eles constroem sobre a sua importância no processo de ensino-aprendizagem e os usos que eles dão a elas; os aspectos que favorecem ou dificultam os processos de transformação para a inovação com as tecnologias; as discussões sobre a formação inicial para a utilização das TIC como recurso pedagógico; o contexto da formação de professores no Uruguai e as políticas relacionadas às tecnologias. A pesquisa foi qualitativa de natureza interpretativa. O estudo foi realizado em um centro de formação de professores no Uruguai. A técnica de coleta de dados foi a entrevista individual semiestruturada. Os participantes do estudo foram 16 professores que ministram as disciplinas de didática nos diferentes cursos de formação de professores. A amostra foi intencional por critérios. Os principais resultados do estudo foram: a utilização das TIC mantendo metodologias tradicionais com novas ferramentas e a dificuldade de aproveitar as vantagens que as TIC proporcionam para transformar as metodologias de ensino. Entre as dificuldades estão: a falta de conhecimentos sobre como utilizar as TIC como recurso pedagógico; a predominância da individualidade na busca de conhecimentos sobre como integrar as TIC nas aulas e atividades e a necessidade de preparar os formadores em relação às TIC para que possam formar os futuros professores mediante o exemplo. / Technologies and today's society require new competences from teachers. Therefore, teacher training is essential for future teachers to be able to integrate Information and Communication Technologies (ICT) creatively and innovatively into their pedagogical practices to enhance the teaching-learning process. As a consequence, the ways in which teacher trainers appropriate ICT for this training is of great importance. The general objective of this study was to analyze how training teachers of the Education Training Council (CFE) in Uruguay appropriate ICT for the training processes of future teachers. The literature review contemplates concepts and issues inherent to teachers' appropriation of technologies: changes in technological competences needed for teaching, the concept of technology appropriation by teachers, which includes how teachers acquire knowledge to use ICT as pedagogical resources, the meanings they construct about their importance in the teaching-learning process and the uses they give to them; aspects that promote or make it difficult to innovate with technologies; discussions on teacher training for the use of ICT as a pedagogical resource; the context of teacher education and technology education policies in Uruguay. The methodological approach was qualitative. The study was conducted with sixteen teachers at a teacher training center in Uruguay. The technique of data collection was the semi-structured interview. The sample was intentional by criteria. The main results of the study were: the use of ICT maintaining traditional methodologies with new tools; the difficulty of taking advantage of the benefits of ICT to transform teaching methodologies. Among the difficulties were: the lack of knowledge on how to use ICT as pedagogical resources; the predominance of individuality in the search for knowledge on how to integrate ICT; the need to prepare teachers to use ICT to train future teachers by example.

Made available in DSpace on 2015-03-26T12:27:13Z (GMT). No. of bitstreams: 1 texto completo.pdf: 1212927 bytes, checksum: 7adf068a0a8f76b2fa586b434a9e3c65 (MD5) Previous issue date: 2006-03-20 / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior / The EFC bleaching with the current technologies, based on the chlorine dioxide use represents the second greatest cost in the eucalyptus kraft pulp bleaching (US$ 25-30/t), being the wood the first (US$ 40-80/t). On the other hand, the bleaching reagents offer, typically chlorine dioxide, has been a limiting factor for the production increase in many old industrial units since the units capacity generating this reagent can only be increased by its complete substitution. Besides, the bleaching effluent with the chlorine dioxide is of difficult re-circulation in the chemical recovery. Pulp bleaching alternative technologies, which minimize the use of chlorine dioxide are, therefore, very welcome. The focus of the investigations searching for alternative reagents have been based on the pulp pre-bleaching, i.e., in the two stages of the bleaching sequence, aiming at using less chlorine dioxide and lower the number of kappa pulp that follows the bleaching phase. The practical industrial experience in Brazil shows that the kappa number, after the wood cooking and delignification with oxygen, varies from 9 to 11. The subsequent pulp bleaching with this level of kappa number requires from 33 to 44kg of active chlorine per pulp ton, that is, about 4kg of chlorine per kappa number unit. Therefore, the main objective of this study was to investigate alternatives, which allowed, not only the specific chlorine dioxide consume reduction but also, and mainly, the kappa pulp number reduction that follows to the bleaching phase. Such alternatives included: (1) increase in the delignification efficiency with oxygen by the use of additives and optimization of the operational variables; (2) substitution of the acid stage and/or first de-oxidation stage by a peroxide acid catalyzed with molybdenum salts (PMo) or other salts; (3) industrial evaluation of the PMo stage in a PMoZDP sequence; and (4) NaOH substitution by Mg(OH)2 in the P and Ep stages of the AZDP, a/(Ze)DP and D*(Ep)D bleaching sequences. These objectives accomplishments resulted in the four chapters of this work. The MgSO4 use in the oxygen delignification and the application of the most severe alkali conditions (25kg/t) and of the temperature (115oC) allow the kappa pulp number reduction to values of 9,0, thus reducing the bleaching cost by the Oa/(Ze)DP sequence, without pulp quality loss. The substitution of the sequence AZDP acid stage by the peroxide acetic stage (produced from the glucose pentacetate), also reduced the kappa of the bleaching start, with the bleaching time reduction. The peroxide acid catalyzed with molybdenum (PMo) use in substitution of the acid stage (A) reduced substantially the kappa of the bleaching start, having also reduced the bleaching total cost by the AZDP sequence in R$2,13/t of pulp. Such results were confirmed in a trial mill in a 1200t/day plant without pulp quality loss and the bleaching effluent. The best conditions to operate the PMo stage were: temperature 90-95OC; pH 3,5; 2 hours; 0,1kg/t molybdenum and; 5kg/t hydrogen peroxide. The principal effect of the kappa reduction observed in the PMo stage occurred through the hexenuronic acid removal from the pulp. That the substitution of 25% of the sodium hydroxide and 100% of magnesium sulphate used in the Ep stage by the Mg(OH)2 was demonstrated to be possible without significant damage to the viscosity and brightness of the pulp bleached by the D*(Ep)D sequence / O branqueamento ECF com as tecnologias atuais, à base de dióxido de cloro representa o segundo maior custo de produção de polpa kraft branqueada de eucalipto (US$ 25-30/t), sendo a madeira o primeiro (US$ 40-80/t). Por outro lado, a oferta de reagentes de branqueamento, tipicamente dióxido de cloro, tem sido fator limitante para o aumento da produção de muitas unidades industriais antigas, já que a capacidade de unidades geradoras desse reagente só pode ser aumentada pela sua completa substituição. Além disso, o efluente do branqueamento com dióxido de cloro é de difícil recirculação no sistema de recuperação química da fábrica. Tecnologias alternativas de branqueamento de polpa que minimizem o uso de dióxido de cloro são, portanto, muito bem-vindas. O foco das investigações em busca de reagentes alternativos tem sido na fase de pré-branqueamento da polpa, i.e., nos dois primeiros estágios da seqüência de branqueamento, visando a utilizar menos dióxido de cloro e baixar o número kappa da polpa que segue para a fase de alvejamento. A experiência prática industrial no Brasil demonstra que o número kappa da polpa, após cozimento da madeira e deslignificação com oxigênio, varia de 9 a 11. O branqueamento subseqüente da polpa com esse nível de número kappa requer de 36 a 44kg de cloro ativo por tonelada de polpa, ou seja, cerca de 4kg de cloro ativo por unidade de número kappa. Portanto, o principal objetivo deste estudo foi investigar alternativas que permitissem não só reduzir o consumo específico de dióxido de cloro, mas, principalmente, reduzir o número kappa da polpa que segue para a fase de alvejamento Tais alternativas incluíram: (1) aumento da eficiência de deslignificação com oxigênio pelo uso de aditivos e otimização de variáveis operacionais; (2) substituição do estágio ácido e/ou primeiro estágio de dioxidação por um estágio de peróxido ácido catalisado com sais de molibdênio (PMo) ou outros sais; (3) avaliação industrial do estágio PMo numa seqüência PMoZDP; e (4) substituição do NaOH por Mg(OH)2 nos estágios P e Ep das seqüências de branqueamento AZDP, a/(Ze)DP e D*(Ep)D. O cumprimento desses objetivos resultou nos quatro capítulos deste trabalho. Foi concluído que o uso do MgSO4 na deslignificação com oxigênio associados à aplicação de condições mais severas de álcali (25kg/t) e temperatura (115ºC) permitem reduzir o número kappa da polpa para valores abaixo de 9,0, diminuindo o custo do branqueamento pela seqüência Oa/(Ze)DP, sem prejuízo para a qualidade da polpa. A substituição do estágio ácido da seqüência AZDP, pelo estágio de peroxiacético (produzido a partir do pentacetato de glicose), também reduziu o kappa de entrada do alvejamento. A utilização do estágio de peróxido ácido catalisado com molibdênio (PMo) em substituição ao estágio ácido (A) reduziu o kappa de entrada do alvejamento substancialmente, tendo reduzido também o custo total do branqueamento pela seqüência AZDP em R$2,13/t de polpa. Tais resultados foram confirmados em teste industrial numa planta de 1200t/dia, sem prejuízo para a qualidade da polpa e do efluente de branqueamento. As melhores condições para operar o estágio PMo foram: temperatura 90-95ºC; pH 3,5; 2 horas; 0,1kg/t molibdênio; e 5kg/t peróxido de hidrogênio. O principal efeito da redução do kappa observado no estágio PMo ocorreu pela remoção de ácidos hexenourônicos da polpa. Foi demonstrado ser possível substituir 25% do hidróxido de sódio e 100% do sulfato de magnésio utilizados no estágio Ep pelo Mg(OH)2, sem danos significativos para a viscosidade e alvura da polpa branqueada pela seqüência D*(Ep)D