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Previous issue date: 2006-12-18 / Naphthenic lubricating oils are used in transformers with the purpose of promoting electrical
insulation and dissipating heat. The working temperature range of these oils typically lies
between 60?C and 90?C and their useful life is 40 years in average. In that temperature range,
the oils are decomposed during operation, whereby a small fraction of polar compounds are
formed. The presence of these compounds may induce failure and loss of physical, chemical
and electrical properties of the oil, thus impairing the transformer operation. By removing
these contaminants, one allows the oxidized insulating oil to be reused without damaging the
equipment. In view of this, an investigation on the use of surfactants and microemulsions as
extracting agents, and modified diatomite as adsorbent, has been proprosed in this work
aiming to remove polar substances detected in oxidized transformer oils. The extraction was
carried out by a simple-contact technique at room temperature. The system under examination
was stirred for about 10 minutes, after which it was allowed to settle at 25?C until complete
phase separation. In another experimental approach, adsorption equilibrium data were
obtained by using a batch system operating at temperatures of 60, 80 and 100?C. Analytical
techniques involving determination of the Total Acidity Number (TAN) and infrared
spectrophotometry have been employed when monitoring the decomposition and recovery
processes of the oils. The acquired results indicated that the microemulsion extraction system
comprising Triton? X114 as surfactant proved to be more effective in removing polar
compounds, with a decrease in TAN index from 0.19 to 0.01 mg KOH/g, which is consistent
with the limits established for new transformer oils (maximal TAN = 0.03 mg KOH/g). In the
adsorption studies, the best adsorption capacity values were as high as 0.1606 meq.g/g during
conventional adsoprtion procedures using natural bauxite, and as high as 0.016 meq.g/g for
the system diatomite/Tensiofix? 8426. Comparatively in this case, a negative effect could be
observed on the adsorption phenomenon due to microemulsion impregnation on the surface of
the diatomite / ?leos lubrificantes naft?nicos s?o usados em transformadores tem com a finalidade de promover um isolamento el?trico e agir como fonte dissipadora de calor. A temperatura de
trabalho destes ?leos est? entre 60 a 90?C e sua vida ?til ? de em m?dia 40 anos. Nesta temperatura, durante o servi?o, ocorre a degrada??o do ?leo, onde uma pequena fra??o de
compostos polares ? formada. A presen?a desta fra??o pode provocar falhas e a perda das propriedades f?sicas, qu?micas e el?tricas do ?leo, impossibilitando o uso do transformador. A
remo??o destes compostos permite que o ?leo isolante oxidado possa ser novamente utilizado, sem causar preju?zo ao equipamento. Nestes contexto, este trabalho prop?e-se a investigar a utiliza??o de tensoativos e microemuls?es, como extratantes, e a diatomita modificada, como adsorvente, na remo??o dos compostos polares existentes nos ?leos oxidados de transformador. A extra??o foi realizada pelo m?todo de contato simples ? temperatura ambiente. O sistema em estudo foi agitado por cerca de 10 minutos, em seguida mantido em repouso ? 25?C at? completa separa??o das fases. Por outro lado, os dados de equil?brio de
adsor??o foram obtidos utilizando um sistema em batelada para as temperaturas de 60, 80 e 100oC. As t?cnicas anal?ticas de IAT (?ndice de Acidez Total) e espectrofotometria no infravermelho foram utilizadas no acompanhamento dos processos de degrada??o e
recupera??o dos ?leos degradados. Os resultados obtidos indicam que o sistema de extra??o por microemuls?o utilizando triton X114 mostrou-se ser o m?todo mais eficiente na remo??o dos compostos polares, com redu??o no ?ndice de acidez total (IAT) de 0,19 para 0,01 mg KOH/g. Este valor se encontra dentro dos limites especificados para um ?leo de
transformador novo (IAT m?ximo = 0,03 mg KOH/g). Nos estudos de adsor??o, os maiores valores de capacidade de adsor??o foram de 0,1606 meq.g/g na adsor??o convencional usando bauxita natural e de 0,016 meq.g/g para o sistema diatomita/tensiofix 8426. Comparativamente, neste caso, observou-se um forte efeito negativo apresentado sobre o
fen?meno adsortivo devido ao processo de impregna??o com microemuls?o
| Identifer | oai:union.ndltd.org:IBICT/oai:repositorio.ufrn.br:123456789/15869 |
| Date | 18 December 2006 |
| Creators | Silva, Ana Cristina Morais da |
| Contributors | CPF:11933615320, http://lattes.cnpq.br/1433426629868073, Ara?jo, Rinaldo dos Santos, CPF:31548857300, http://lattes.cnpq.br/8579051478703901, Leite, Ricardo Henrique de Lima, CPF:52264343400, http://lattes.cnpq.br/3801476460958779, Barros Neto, Eduardo Lins de, CPF:59545844434, http://buscatextual.cnpq.br/buscatextual/visualizacv.do?id=K4798645D3, Moura, Maria Carlenise Paiva de Alencar, CPF:21414130368, http://buscatextual.cnpq.br/buscatextual/visualizacv.do?id=K4702157Y9, Dantas, Tereza Neuma de Castro, Cavalcante Jr, Celio Loureiro |
| Publisher | Universidade Federal do Rio Grande do Norte, Programa de P?s-Gradua??o em Engenharia Qu?mica, UFRN, BR, Pesquisa e Desenvolvimento de Tecnologias Regionais |
| Source Sets | IBICT Brazilian ETDs |
| Language | Portuguese |
| Detected Language | English |
| Type | info:eu-repo/semantics/publishedVersion, info:eu-repo/semantics/doctoralThesis |
| Format | application/pdf |
| Source | reponame:Repositório Institucional da UFRN, instname:Universidade Federal do Rio Grande do Norte, instacron:UFRN |
| Rights | info:eu-repo/semantics/openAccess |
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