Pirólise das cascas de grãos de girassol: um estudo sobre a cinética de reação e sobre os produtos gerados

• Ano de defesa: 2019
• Autor(a) principal: TIBOLA, Fernando Lucas
• Orientador(a): CARDOSO, Cássia Regina
• Tipo de documento: Dissertação
• Tipo de acesso: Acesso aberto
• Idioma: por
• Instituição de defesa: Universidade Federal do Triângulo Mineiro
• Programa de Pós-Graduação: Programa de Pós-Graduação Multicêntrico em Química de Minas Gerais
• Departamento: Instituto de Ciências Exatas, Naturais e Educação - ICENE
• País: Brasil
• Palavras-chave em Português: Casca da semente de girassol.; Energia de ativação.; Pirólise analítica.; Hidropirólise.
• Palavras-chave em Inglês: Sunflower seed husk.; Activation energy.; Analytical pyrolysis.; Hydropyrolysis.
• Área do conhecimento CNPq: Físico-Química
• Link de acesso: http://bdtd.uftm.edu.br/handle/tede/630

The search for renewable sources of energy presents biomass as an alternative for fossil fuels by the use of thermoconversion processes. Sunflower seed husk is a residue derived from the production of sunflower oil and is widely generated in Brazil. The present work aimed to study the pyrolysis reaction for this biomass in nitrogen and hydrogen atmospheres; it also aimed to study the kinetic parameters of sunflower seed husk decomposition using models based on isoconversional, distributed activation energy and parallel and independent reactions. The proximate analysis was performed and the chemical composition of the biomass was determined; considering these results, the value of gross calorific value was estimated. Analysis of conventional micro pyrolysis and hydropyrolysis, at 600 °C, were performed in a CDS 5200 micro pyrolyzer coupled to a gas chromatograph and a mass spectrometer (GC/MS QP 2010 Plus Shimadzu), in order to verify the main pyrolytic products. The thermogravimetric analyses were performed dynamically, using five heating rates; 5, 10, 15, 20 and 25 °C/min. The estimated gross calorific value was 18.54 MJ/kg. The main products identified in the conventional pyrolysis of the sunflower seed husk were: acetic acid and oleic acid; for the hydropyrolysis were: acetic acid, furfural, nonanal and methyl oleate. The products obtained can be used in the food, pharmaceutical, cosmetic and chemical industries, suggesting their high added value. The activation energy values estimated by the isoconversional models ranged from 104.7 to 179.8 kJ/mol. The results of the Miura-Maki model varied between 90.1 kJ/mol and 169.6 kJ/ mol; whereas the distributed activation energy model, with the Gaussian curve, presented result from 153.4 to 157.7 kJ/mol. On the parallel and independent reaction model, it was considered the presence of for three pseudocomponents and the activation energy values ranged from 76.3 kJ/mol to 183.6 kJ/mol. The results indicated that the sunflower seed husk presents similar decomposition parameters as other biomasses. The isoconversional models provided an initial estimate of the activation energy values, however their application were not adequate for high conversion values. For the distributed activation energy models, higher mass conversion values were considered for the calculations. The isoconversional models and distributed activation energy facilitates the comparison of the activation energy values with other biomass, but may not result in a good representation for the biomasss heterogeneity. The model of parallel and independent reactions is more robust and more complex for calculation than the other models, but considers the heterogeneity of the biomass. From this model, it is difficult to compare activation energy values with those of other biomasses. The results obtained in this work can contribute to the management and treatment of the sunflower residue, indicating options for fuel generation and for the production of value-added products.