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Abstract(s)
Numa sociedade simultaneamente dependente de energia e consciente dos efeitos nefastos dos combustíveis fósseis, urge a necessidade de encontrar fontes renováveis e com baixo impacto ambiental.
Estudou-se a produção de biocombustíveis por pirólise de resíduos alimentares como cascas de batata e de frutas, cascas de frutos secos e borras de café e chá. Para melhorar a qualidade da fracção líquida obtida (bio-óleo) recorreu-se ao uso de catalisadores. Realizaram-se ensaios de pirólise catalisada na presença de carbonatos alcalinos (sódio, lítio e cálcio). Usaram-se ainda desperdícios da indústria de pedras ornamentais, pó de mármore e calcário e da indústria de extração da bauxite bem como um catalisador desactivado duma unidade industrial de FCC.
A biomassa recolhida foi lavada, seca e reduzida a pó num triturador com laminas de aço e caracterizada por termogravimetria (N2), para simular o processo de pirólise. As amostras mostraram velocidades máximas de decomposição térmica em torno dos 400ºC, sendo essa a temperatura seleccionada para os ensaios de pirólise. Os termogramas permitiram uma análise semi-quantitativa da composição das biomassas (humidade, lenhocelulósicos, amidos e óleos).
Os ensaios de pirólise em reactor de leito fixo mostraram produções de bio-óleo inferiores a 40% (massa), com rendimentos superiores para as biomassas com maiores teores em açucares como as cascas de batatas. Estas biomassas conduzem a bio-gás com teores superiores em alcanos de maior cadeia carbonada (C4). Nas condições testadas os carbonatos alcalinos comportam-se como promotores de processos de gaseificação enquanto os resíduos da extração da bauxite, com caracter ácido, promovem a formação de compostos aromáticos (fracção líquida).
Os bio-óleos produzidos foram caracterizados por espectroscopia do infravermelho para a identificação dos grupos funcionais presentes (alcanos, ácidos carboxílicos, ésteres, aromáticos e fenóis). A fracção volátil dos bio-óleos foi avaliada por destilação simulada por termogravimetria. O bio-char produzido foi caracterizado por análise termogravimétrica em atmosfera oxidante.
In a society that is both energy dependent and aware of the harmful effects of fossil fuels, it is crucial to find renewable energy sources with low environmental impact. The biofuels production by pyrolysis of alimentary wastes was carried out using collected residues such as potato and fruits peels, nutshells and tea and coffee grounds. To improve the quality of the liquid fraction (biooil) the pyrolysis was conducted in the presence of alkali carbonate catalysts (Na, Li and Ca). Wastes from ornamental stones industry (marble and limestone) and from bauxite extraction were also used as catalysts, along with a spent catalyst from a FCC unit. The collected biomasses were washed and dried (except nutshells) and reduced to powder in a steel blade grinder. The biomasses were characterized by thermogravimetry in an inert atmosphere to simulate the pyrolysis process. All samples showed maximum thermal decomposition rates around 400ºC and, this temperature was selected for the pyrolysis tests. The thermograms allowed a semi-quantitave analysis of biomass composition (moisture, lignocellulosic, starch and oils). Pyrolysis tests in a fixed bed reactor showed biooil yields below 40% (mass) with higher yields for biomasses with higher contents in sugars such as potato peel. These biomasses lead to biogas with higher contents in alkanes with larger carbon chain (C4). In the tested conditions, alkaline carbonates behave as gasification promoters while acid bauxite residues promote the formation of aromatic compounds (liquid fraction). The produced bio-oils were chracterized by infrared spectrocospy to identify the functional groups (alkanes, carboxylic acids, esters, aromatics and phenols). The bio-oils volatile fraction was assessed by simulated destilation by thermogravimetry. The bio-char produced was characterized by thermogravimetric analysis in an oxidizing atmosphere.
In a society that is both energy dependent and aware of the harmful effects of fossil fuels, it is crucial to find renewable energy sources with low environmental impact. The biofuels production by pyrolysis of alimentary wastes was carried out using collected residues such as potato and fruits peels, nutshells and tea and coffee grounds. To improve the quality of the liquid fraction (biooil) the pyrolysis was conducted in the presence of alkali carbonate catalysts (Na, Li and Ca). Wastes from ornamental stones industry (marble and limestone) and from bauxite extraction were also used as catalysts, along with a spent catalyst from a FCC unit. The collected biomasses were washed and dried (except nutshells) and reduced to powder in a steel blade grinder. The biomasses were characterized by thermogravimetry in an inert atmosphere to simulate the pyrolysis process. All samples showed maximum thermal decomposition rates around 400ºC and, this temperature was selected for the pyrolysis tests. The thermograms allowed a semi-quantitave analysis of biomass composition (moisture, lignocellulosic, starch and oils). Pyrolysis tests in a fixed bed reactor showed biooil yields below 40% (mass) with higher yields for biomasses with higher contents in sugars such as potato peel. These biomasses lead to biogas with higher contents in alkanes with larger carbon chain (C4). In the tested conditions, alkaline carbonates behave as gasification promoters while acid bauxite residues promote the formation of aromatic compounds (liquid fraction). The produced bio-oils were chracterized by infrared spectrocospy to identify the functional groups (alkanes, carboxylic acids, esters, aromatics and phenols). The bio-oils volatile fraction was assessed by simulated destilation by thermogravimetry. The bio-char produced was characterized by thermogravimetric analysis in an oxidizing atmosphere.
Description
Trabalho final de mestrado para obtenção do grau de mestre em Engenharia Química
Keywords
energia renovável renewable energy biomassa biomass resíduos alimentares alimentary wastes pirólise pyrolysis termogravimetria thermogravimetry catalisadores catalysts
Citation
JESUS, Nicole Alexandra Leitão de - Biomassas alternativas para a produção de bio-óleo por pirólise catalisada. Lisboa: Instituto Superior de Engenharia de Lisboa, 2017. Dissertação de mestrado.
Publisher
Instituto Superior de Engenharia de Lisboa