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Master's Dissertation
DOI
10.11606/D.18.2005.tde-30092005-094638
Document
Author
Full name
Cecilia Rocío Morales Leiva
E-mail
Institute/School/College
Knowledge Area
Date of Defense
Published
São Carlos, 2005
Supervisor
Committee
Santos, Antonio Moreira dos (President)
Crnkovic, Paula Cristina Garcia Manoel
Ribeiro, Clovis Augusto
Title in Portuguese
O emprego da termogravimetria na determinação da energia de ativação no processo de combustão de óleos combustíveis
Keywords in Portuguese
combustão
energia de ativação
óleo combustível
termogravimetria
Abstract in Portuguese
Neste trabalho, determinou-se a energia de ativação (Ea) no processo de combustão de três óleos combustíveis cedidos pela Petrobrás–Cenpes e denominados por A, B e C. Empregou-se análise termogravimétrica (TG) utilizando um sistema Shimadzu 51H e, para todas as amostras observaram-se três regiões oxidativas distintas identificadas como, oxidação à baixa temperatura (LTO), depósito de combustível (FD) e oxidação à alta temperatura (HTO). As energias de ativação foram determinadas como uma função do grau de conversão ('alfa') e temperatura na região LTO e utilizando-se dois métodos cinéticos, denominados ASTM E 1641 (Flynn eWall) e Model Free Kinetics de Vyazovkin. Empregaram-se as seguintes razões de aquecimento: 2,5; 5,0; 10,0; 15,0 e 20,0°C por min entre a temperatura ambiente e 600°C. As demais condições experimentais foram: massa da amostra de aproximadamente 20 mg, suporte de amostra de alumínio e gás de arraste ar sintético com vazão de 100 mL/min. Os valores de Ea encontrados foram os mesmos para ambos os métodos cinéticos: 44 ± 7% kJ/mol ('alfa'=0,1 a 0,9) para amostra A. Para a amostra B os valores de Ea foram em média de 48 ± 4% kJ/mol ('alfa'=0,1 a 0,5) e 66 ± 16% kJ/mol ('alfa'=0,5 a 0,9) e, para a amostra C os valores de Ea foram em média de 58 ± 4% kJ/mol ('alfa'=0,1 a 0,5) e 65 ± 5% kJ/mol ('alfa'=0,5 a 0,9). Conclui-se que a Ea pode ser usada como um parâmetro adequado para apontar uma tendência de comportamento e para caracterizar diferentes óleos sob processo de combustão
Title in English
Use of thermogravimetric analysis to determine the activation energy in the combustion process of fuels oils
Keywords in English
activation energy
combustion
fuel oil
thermogravimetry
Abstract in English
In this work activation energies (Ea) in the combustion of three fuels oils were determined through thermogravimetry. The oil samples, here named A, B and C were supplied by Petrobras-Cenpes. The thermogravimetric experiments were performed in a Shimadzu TGA-51H analyzer. In all the combustion experiments three distinct oxidation regions were observed, identified as low temperature oxidation (LTO), fuel deposition (FD) and high temperature oxidation (HTO). Activation energies were determined as a function of conversion degree ('alfa') and temperature for LTO region, following two different procedures, namely Model Free Kinetics and ASTM E 1641. Transient experiments were performed from room temperature up to 600°C, at heating rates of 2.5, 5.0, 10.0, 15.0 and 20.0°C for min. Samples of 20.0 ± 0.5 mg and aluminum crucibles were used. The reacting atmosphere was synthetic air, which was continuously blown over the samples, throughout the analyzer furnace, at a volumetric rate of 100 mL/min. The activation energies resulted equal for both considered methods. For oil A, the activation energy resulted 44 ± 7% kJ/mol ('alfa'=0.1 to 0.9). For oil B it resulted in average 48 ± 4% kJ/mol ('alfa'=0.1 to 0.5) and 66 ± 16% kJ/mol ('alfa'=0.5 to 0.9). For oil C the activation energy resulted 58 ± 3% kJ/mol ('alfa'=0.1 to 0.5) e 65 ± 5% kJ/mol ('alfa'=0.5 to 0.9). It is concluded that the oxidation activation energy is a suitable parameter concerning to point out a tendency of behavior and characterizing different oils under combustion process
 
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Publishing Date
2005-12-16
 
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