In this work, compositions containing transparent glass bottles and banana leaves (desiccated and crushed), with different mass fractions (30-50%), were prepared for obtaining cellular materials for thermal insulation purposes. The formulated and prepared compositions were uniaxially pressed (10 MPa) and the compact powders fired between 700 and 850°C for 30 min in order to investigate the effect of the banana leaves on the formation of pores and on the thermal and mechanical properties of the processed glass foams. The results indicated that the obtained glass foams with porosities between 58.5 and 87.5%, compressive strength ranging between 1.17 and 3.50 MPa and thermal conductivity ranging between 0.06 and 0.15 W/mK, are potential candidates to work as thermal insulators with appropriate properties for a specific application.
With the purpose of adding value to the waste of banana crop and rice processing, banana leaves and pseudostem, and rice husk were prepared and characterized through proximate and ultimate chemical analyses, high heating value (HHV), thermogravimetric analysis (TGA) and differential scanning calorimetry (DSC). The prepared waste was then compacted into briquettes in a hydraulic press at 18 MPa for 1 s. The resulting briquettes were characterized through the same analyses used in waste and through mechanical compressive strength. The waste moisture content, between 8 and 15%, were adequate for briquetting and combustion. The briquettes exhibited the maximum energy release under combustion at temperatures that were lower than the waste's. The rice husk and its briquettes had a lower energy release in comparison with the other waste. The HHV of the waste ranged from 15 to 18 MJ/kg. The compaction of the waste resulted in an increase of the HHV for the rice husk and the briquettes presented the highest compressive strength: 19 MPa. From these three waste samples that were studied, the banana leaves presented the best features, properties, and potential for generating energy as briquettes. © 2017 American Institute of Chemical Engineers Environ Prog, 37: 1266–1273, 2018
Resumo Composições contendo dois diferentes tipos de resíduos, vidro de garrafas transparentes, VGT (50-70%), e lodo de estação de tratamento de efluentes, ETE (30-50%), e formador de poros, CaCO3 (2-10%), foram preparadas para a produção de isolantes térmicos para fins estruturais. As matérias-primas das composições formuladas foram, em uma etapa posterior, misturadas, compactadas uniaxialmente a 40 MPa e, após secagem (110 °C/2 h), queimadas entre 750 e 1000 °C com patamares de 15 a 60 min. As matérias-primas e os materiais obtidos foram caracterizados do ponto de vista de suas propriedades químicas, físicas e microestruturais. Os resultados obtidos mostraram que é possível produzir isolantes térmicos, a partir de composições otimizadas contendo 70% de VGT, 30% de lodo de ETE e 5% de CaCO3, queimados entre 750 e 1000 °C/60 min, os quais apresentaram porosidades entre 3 e 62% com condutividades térmicas entre 1,25 e 0,5 W/m.K e com resistência à compressão entre 8,7 e 5,4 MPa. Os materiais obtidos são fortes candidatos em aplicações estruturais tais como painéis para isolamento térmico, os quais requerem uma combinação adequada de condutividade térmica, porosidade e resistência mecânica.
RESUMOResíduos de vidro podem ser reutilizados para o desenvolvimento de materiais alternativos. Uma opção viá-vel são os materiais celulares para isolamentos térmicos já que, apresentando poros isolados, possuem baixa condutividade térmica, baixa densidade aparente e temperaturas de serviço mais altas que a dos materiais isolantes poliméricos. Neste trabalho, foi preparada uma suspensão aquosa com resíduos de vidro previamente moídos, Ágar-ágar (gelificante) e Emustab® (emulsificante), a qual foi adicionada diferentes frações de óleo de soja (50, 70 e 90% em massa). Subsequentemente, foi realizada a emulsificação do óleo vegetal no líquido da suspensão por meio de agitação em misturador mecânico de alto cisalhamento. Corpos de prova cilíndricos foram produzidos via colagem por gelificação e queimados a 700 °C/30 min. Os resultados mostraram que os vidros celulares obtidos apresentaram porosidade entre 74 e 93% com poros bem definidos e distribuídos e baixas condutividades térmicas (0,05 a 0,09 W/m.K). Tais resultados indicam que os materiais obtidos são potenciais candidatos para atuarem como isolantes térmicos, como por exemplo, painéis para revestimentos utilizados na construção civil. Palavras-chave: Emulsões, vidros celulares, resíduos de vidro. ABSTRACTGlass wastes can be reused for the development of alternative materials. A viable option are the cellular materials for thermal insulation since with isolated pores they show low thermal conductivity, low density and service temperatures higher than those of the polymeric insulating materials. In this work an aqueous suspension was prepared with previously milled glass wastes, agar (gelling) and Emustab® (emulsifier), in which different soy oil fractions (50, 70 and 90 wt% ) were added. Subsequently, the emulsification of the vegetable oil was carried out in the liquid suspension by stirring in a mechanical mixer at high shear. Cylindrical samples were produced by gelation slip casting and fired at 700 °C/30 min. The results showed that the obtained cellular glasses had porosity between 74 and 93% with well-defined and distributed pores and low thermal conductivity (0.05 to 0.09 W/mK). These results indicate that the obtained materials are potential candidates to act as thermal insulators, such as panels for coatings used in construction.
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