Análise da decomposição térmica de palha de cana-de-açúcar em atmosferas inerte e oxidante mediante métodos termoanalíticos

Orientadores: Katia Tannous, Edgardo Olivares GomezTese (doutorado) - Universidade Estadual de Campinas, Faculdade de Engenharia QuímicaResumo: Este trabalho teve por objetivo o estudo cinético da decomposição térmica da palha de cana-de-açúcar (Saccharum officinarum Linnaeus) em atmosferas inerte e oxidante. O diâmetro médio das partículas foi de 0,510 mm obtido entre as peneiras padrão Tyler de número 28 e 35. As características térmicas (base seca) foram obtidas conforme: materiais voláteis=86,6% (ASTM E872¿82), cinzas=3,8% (ASTM E1755¿01) e carbono fixo=9,6% por diferença; e poder calorífico superior de 18,6 MJ/kg obtido mediante bomba calorimétrica. A característica química foi determinada através de um analisador elementar obtendo-se os teores mássicos de carbono=42,8%, hidrogênio=6,2%, nitrogênio=0,3% e o oxigênio=46,9% por diferença em base seca e livre de cinzas. A determinação dos teores de hemicelulose=33% e celulose=40% foi feita mediante a técnica ANKOM A200 baseada no método de Van Soest. O teor de lignina=22% foi determinado aplicando o método de Klason baseado em hidrólise ácida. Os experimentos de decomposição térmica foram realizados em um analisador termogravimétrico (TG) e o fluxo de calor foi medido em um calorímetro diferencial de varredura (DSC), usando nitrogênio e ar sintético como meio reativo. Estas análises foram realizadas utilizando quatro taxas de aquecimento (1,25; 2,5; 5 e 10 °C/min) em nitrogênio e três (2,5; 5 e 10 °C/min) em ar sintético aplicando massas em torno de 3 mg. A análise cinética realizada para as duas atmosferas abrangeu três esquemas de reações: reação global, reações consecutivas, e reações paralelas. A modelagem cinética através do esquema de reação global foi realizada aplicando os métodos isoconversionais de Friedman (nitrogênio) e Vyazovkin (ar sintético). Em atmosfera inerte, obteve-se energia de ativação de 149,7 kJ/mol, fator pré-exponencial de 1,82 x 109 s-1 e modelo de reação de difusão bidimensional. No entanto, em atmosfera oxidante não foi possível modelar a reação através deste esquema de reação. Analisando reações globais de primeira ordem através de modelos de ajuste e considerando 805 cenários diferentes, obtiveram-se correlações entre fator pré-exponencial e energia de ativação, correlacionando a taxa de aquecimento, temperatura e taxa de conversão no pico. O esquema de três reações consecutivas descreveu muito bem os dados experimentais, aplicando reações de primeira ordem obtendo-se energias de ativação de 133, 198 e 56 kJ/mol, e 200, 300 e 100 kJ/mol em atmosfera inerte e oxidante, respectivamente. Os fatores pre-exponenciais de 2×109, 5×103, e 5 s-1 foram obtidos em atmosfera inerte e 2×1016, 3×1028, e 5×104 s-1 em oxidante. A aplicação do esquema de reações paralelas e independentes foi realizada avaliando três reações de primeira ordem em atmosfera inerte e seis em atmosfera oxidante. Os resultados experimentais e teóricos mostraram uma boa concordância, obtendo-se energias de ativação de 142, 212, e 40 kJ/mol em atmosfera inerte e 176, 313, 150, 80, 150, e 100 kJ/mol em oxidante. Os fatores pre-exponenciais obtidos foram em atmosfera inerte 1×1010, 8×1014, e 0,3 s-1, e em oxidante 1×1014, 1×1025, 2×1010, 5×103, 1×108, e 1×104 s-1. Finalmente, o calor de reação em atmosfera inerte foi endotérmico, requerendo energia máxima de 1 MJ/kg em 350 °C, e em atmosfera oxidante foi completamente exotérmico liberando até 8 MJ/kgAbstract: The aim of this work was the kinetic study of the thermal decomposition of sugarcane straw (Saccharum officinarum Linnaeus) in inert and oxidative atmospheres. The mean diameter of particles was 0.510 mm obtained between the Tyler standard sieves number 28 and 35. The thermal characteristics (dry base) were determined according to: volatile matter content = 86.6% (ASTM E872-82), ash content=3.8% (ASTM E1755-01) and fixed carbon content =9.6% by difference, and higher heating values of 18.6 MJ/kg obtained with a bomb calorimeter. The chemical characteristic were determined through an elemental analyzer, obtaining in dry and ash free basis carbon=42.8%-m, hydrogen=6.2%-m, nitrogen=0.3%-m and oxygen=46.9%-m by difference. The sample chemical composition was hemicellulose=33% and cellulose=40% determined by the application of the ANKOM A200 technique, based on the Van Soest's method. The lignin content=22% was obtained applying the Klason¿s method based on acid hydrolysis. The thermal decomposition experiments were carried out in a thermogravimetric analyzer (TG) and the heat flux was measured in a differential scanning calorimeter (DSC), using nitrogen and synthetic air atmospheres, respectively. These analyses were carried out using four heating rates (1.25, 2.5, 5, and 10 °C/min) in nitrogen, and three (2.5, 5, and 10 °C/min) in synthetic air applying sample mass around 3 mg. The kinetic analysis in both atmospheres covered three reaction schemes: global reaction, consecutive reactions, and parallel reactions. In the global reaction analysis were applied the isoconversional methods of Friedman (nitrogen) and Vyazovkin (synthetic air). In inert atmosphere, was obtained activation energy of 149.7 kJ/mol, pre-exponential factor of 1,82 x 109 s-1, and reaction model of bi-dimensional diffusion. However, in oxidative atmosphere, it was not possible to modeling the reaction through this reaction scheme. Analyzing first order global reactions through fitting models and considering 805 different scenarios, were obtained correlations between pre-exponential factor and activation energy, correlating the heating rate, peak temperature, and peak conversion rate. The three consecutive first order reactions scheme represented the experimental data obtaining activation energies of 133, 198, and 56 kJ/mol in inert atmosphere, and 200, 300, and 100 kJ/mol in oxidative atmosphere. The pre-exponential factors correspondent were 2×109, 5×103, and 5 s-1 in inert atmosphere and 2×1016, 3×1028, and 5×104 s-1 were oxidative atmosphere. The kinetic modeling through the independent parallel reactions scheme was carried out evaluating three and six first order reactions in inert and oxidative atmosphere, respectively. The experimental and theoretical results showed a good agreement obtaining activation energies of 142, 212, and 40 kJ/mol in inert atmosphere, and 176, 313, 150, 80, 150, and 100 kJ/mol in oxidative atmosphere. The pre-exponential factors were 1×1010, 8×1014, and 0,3 s-1 in inert atmosphere and 1×1014, 1×1025, 2×1010, 5×103, 1×108, and 1×104 s-1 in oxidative atmosphere. Finally, the heat of reaction in inert atmosphere was endothermic requiring maximum energy of 1 MJ/kg at 350ºC, and in oxidative atmosphere, it was completely exothermic releasing 8 MJ/kgDoutoradoDesenvolvimento de Processos QuímicosDoutor em Engenharia Química33003017034P8CAPE

Análisis cinético de la descomposición térmica de biomasas aplicando un esquema de reacciones paralelas independientes

The aim of this work was the kinetic analysis of the thermal decomposition of four Brazilian lignocellulosic biomasses: caixeta wood (Tabebuia cassinoides Lam.), rice husk (Oryza sativa L.), sugarcane bagasse and straw (Saccharum officinarum L.). The thermal decomposition experiments were carried out in a thermogravimetric analyzer using a heating rate of 10 °C/min. The kinetic analysis of the biomass thermal decomposition was carried out applying a scheme of three independent parallel reactions. The results showed that the model was in agreement with the experimental data, and the activation energies obtained were between 118-130 kJ/kmol, 200-215 kJ/kmol, and 100-150 kJ/kmol, for hemicelulose, cellulose and lignin modeled reactions, respectively. Also, were determined linear correlations between the logarithm of the pre-exponential factor and activation energy for each reaction evaluated, and tested in the biomasses analyzed. Finally, was concluded that the correlations obtained could be used for the determination of the kinetic parameters of the thermal decomposition of several biomasses, contributing to the modeling process by reducing the time invested in the iteration process.    El objetivo de este trabajo fue el análisis cinético de la descomposición térmica de cuatro biomasas lignocelulosicas procedentes de Brasil: madera de caixeta (Tabebuia cassinoides Lam.), cascarilla de arroz (Oryza sativa L.), bagazo y residuo de corte de la caña de azúcar (Saccharum officinarum L.). Los experimentos de descomposición térmica fueron llevados a cabo en un analizador termogravimétrico, utilizando tasas de calentamiento de 10 °C/min. El análisis cinético de la descomposición térmica de las biomasas fue realizado aplicando un esquema de tres reacciones paralelas independientes. Los resultados mostraron que el modelo se ajustó muy bien a los datos experimentales, y las energías de activación estuvieron entre 118-130 kJ/kmol, 200-215 kJ/kmol, y 100-150 kJ/kmol, para las reacciones modeladas de la hemicelulosa, celulosa, y lignina, respectivamente. También, fueron determinadas correlaciones entre el logaritmo del factor pre-exponencial y la energía de activación para cada reacción evaluada, y probadas con cada una de las biomasas analizadas. Finalmente, fue concluido que las correlaciones obtenidas pueden ser utilizadas para la obtención de los parámetros cinéticos de la descomposición térmica de diversas biomasas, contribuyendo con el proceso de modelado a través de la reducción del tiempo que se invierte en el proceso iterativo

Análisis cinético de la descomposición térmica de biomasas aplicando un esquema de reacciones paralelas independientes

The aim of this work was the kinetic analysis of the thermal decomposition of four Brazilian lignocellulosic biomasses: caixeta wood (Tabebuia cassinoides Lam.), rice husk (Oryza sativa L.), sugarcane bagasse and straw (Saccharum officinarum L.). The thermal decomposition experiments were carried out in a thermogravimetric analyzer using a heating rate of 10 °C/min. The kinetic analysis of the biomass thermal decomposition was carried out applying a scheme of three independent parallel reactions. The results showed that the model was in agreement with the experimental data, and the activation energies obtained were between 118-130 kJ/kmol, 200-215 kJ/kmol, and 100-150 kJ/kmol, for hemicelulose, cellulose and lignin modeled reactions, respectively. Also, were determined linear correlations between the logarithm of the pre-exponential factor and activation energy for each reaction evaluated, and tested in the biomasses analyzed. Finally, was concluded that the correlations obtained could be used for the determination of the kinetic parameters of the thermal decomposition of several biomasses, contributing to the modeling process by reducing the time invested in the iteration process.    El objetivo de este trabajo fue el análisis cinético de la descomposición térmica de cuatro biomasas lignocelulosicas procedentes de Brasil: madera de caixeta (Tabebuia cassinoides Lam.), cascarilla de arroz (Oryza sativa L.), bagazo y residuo de corte de la caña de azúcar (Saccharum officinarum L.). Los experimentos de descomposición térmica fueron llevados a cabo en un analizador termogravimétrico, utilizando tasas de calentamiento de 10 °C/min. El análisis cinético de la descomposición térmica de las biomasas fue realizado aplicando un esquema de tres reacciones paralelas independientes. Los resultados mostraron que el modelo se ajustó muy bien a los datos experimentales, y las energías de activación estuvieron entre 118-130 kJ/kmol, 200-215 kJ/kmol, y 100-150 kJ/kmol, para las reacciones modeladas de la hemicelulosa, celulosa, y lignina, respectivamente. También, fueron determinadas correlaciones entre el logaritmo del factor pre-exponencial y la energía de activación para cada reacción evaluada, y probadas con cada una de las biomasas analizadas. Finalmente, fue concluido que las correlaciones obtenidas pueden ser utilizadas para la obtención de los parámetros cinéticos de la descomposición térmica de diversas biomasas, contribuyendo con el proceso de modelado a través de la reducción del tiempo que se invierte en el proceso iterativo

Kinetic analysis of biomass thermal decomposition applying a scheme of independent parallel reactions

El objetivo de este trabajo fue el análisis cinético de la descomposición térmica de cuatro biomasas lignocelulosicas procedentes de Brasil: madera de caixeta (Tabebuia cassinoides Lam.), cascarilla de arroz (Oryza sativa L.), bagazo y residuo de corte de la caña de azúcar (Saccharum officinarum L.). Los experimentos de descomposición térmica fueron llevados a cabo en un analizador termogravimétrico, utilizando tasas de calentamiento de 10 °C/min. El análisis cinético de la descomposición térmica de las biomasas fue realizado aplicando un esquema de tres reacciones paralelas independientes. Los resultados mostraron que el modelo se ajustó muy bien a los datos experimentales, y las energías de activación estuvieron entre 118-130 kJ/kmol, 200-215 kJ/kmol, y 100-150 kJ/kmol, para las reacciones modeladas de la hemicelulosa, celulosa, y lignina, respectivamente. También, fueron determinadas correlaciones entre el logaritmo del factor pre-exponencial y la energía de activación para cada reacción evaluada, y probadas con cada una de las biomasas analizadas. Finalmente, fue concluido que las correlaciones obtenidas pueden ser utilizadas para la obtención de los parámetros cinéticos de la descomposición térmica de diversas biomasas, contribuyendo con el proceso de modelado a través de la reducción del tiempo que se invierte en el proceso iterativo.The aim of this work was the kinetic analysis of the thermal decomposition of four Brazilian lignocellulosic biomasses: caixeta wood (Tabebuia cassinoides Lam.), rice husk (Oryza sativa L.), sugarcane bagasse and straw (Saccharum officinarum L.). The thermal decomposition experiments were carried out in a thermogravimetric analyzer using a heating rate of 10 °C/min. The kinetic analysis of the biomass thermal decomposition was carried out applying a scheme of three independent parallel reactions. The results showed that the model was in agreement with the experimental data, and the activation energies obtained were between 118-130 kJ/kmol, 200-215 kJ/kmol, and 100-150 kJ/kmol, for hemicelulose, cellulose and lignin modeled reactions, respectively. Also, were determined linear correlations between the logarithm of the pre-exponential factor and activation energy for each reaction evaluated, and tested in the biomasses analyzed. Finally, was concluded that the correlations obtained could be used for the determination of the kinetic parameters of the thermal decomposition of several biomasses, contributing to the modeling process by reducing the time invested in the iteration process.   &nbsp

Biomass combustion modeling using openFOAM: development of a simple computational model and study of the combustion performance of Lippia origanoides bagasse

Combustion is the most commonly used technology to produce energy from biomass; nevertheless, there are still thermal efficiency problems in current biomass combustion furnaces and a lack of knowledge about the properties of residual biomasses that could be used as fuels. Aiming to contribute to knowledge of the potential of residual biomass for energy generation, this work reports on the implementation of a 2D computational model to study the combustion performance of several solid biomass fuels, and its application in the analysis of Lippia origanoides bagasse combustion. The model uses an Eulerian–Lagrangian approach; in the continuous phase, governing equations are solved, and in the dispersed phase, particles are tracked and the mass, momentum, species and energy transfer between the phases are calculated. The model was validated against experimental data from a combustor fueled by three biomasses: wood pellets, olive stone and almond shell. The results show deviations of less than 13%, with few exceptions, which indicates a good degree of agreement with experimental measurements compared with those reported by other studies on the subject. Furthermore, it was found that the stems of Lippia origanoides bagasse show similar performance to that of other biomass used as solid fuel, while the leaves present lower performance.Minciencias, Ministerio de Educación Nacional, Ministerio de Industria, Comercio y Turismo e ICETEX, Colombia | Ref. RC-FP44842-212-201

Análisis cinético de la descomposición térmica de biomasas aplicando un esquema de reacciones paralelas independientes

The aim of this work was the kinetic analysis of the thermal decomposition of four Brazilian lignocellulosic biomasses: caixeta wood (Tabebuia cassinoides Lam.), rice husk (Oryza sativa L.), sugarcane bagasse and straw (Saccharum officinarum L.). The thermal decomposition experiments were carried out in a thermogravimetric analyzer using a heating rate of 10 °C/min. The kinetic analysis of the biomass thermal decomposition was carried out applying a scheme of three independent parallel reactions. The results showed that the model was in agreement with the experimental data, and the activation energies obtained were between 118-130 kJ/kmol, 200-215 kJ/kmol, and 100-150 kJ/kmol, for hemicelulose, cellulose and lignin modeled reactions, respectively. Also, were determined linear correlations between the logarithm of the pre-exponential factor and activation energy for each reaction evaluated, and tested in the biomasses analyzed. Finally, was concluded that the correlations obtained could be used for the determination of the kinetic parameters of the thermal decomposition of several biomasses, contributing to the modeling process by reducing the time invested in the iteration process.    El objetivo de este trabajo fue el análisis cinético de la descomposición térmica de cuatro biomasas lignocelulosicas procedentes de Brasil: madera de caixeta (Tabebuia cassinoides Lam.), cascarilla de arroz (Oryza sativa L.), bagazo y residuo de corte de la caña de azúcar (Saccharum officinarum L.). Los experimentos de descomposición térmica fueron llevados a cabo en un analizador termogravimétrico, utilizando tasas de calentamiento de 10 °C/min. El análisis cinético de la descomposición térmica de las biomasas fue realizado aplicando un esquema de tres reacciones paralelas independientes. Los resultados mostraron que el modelo se ajustó muy bien a los datos experimentales, y las energías de activación estuvieron entre 118-130 kJ/kmol, 200-215 kJ/kmol, y 100-150 kJ/kmol, para las reacciones modeladas de la hemicelulosa, celulosa, y lignina, respectivamente. También, fueron determinadas correlaciones entre el logaritmo del factor pre-exponencial y la energía de activación para cada reacción evaluada, y probadas con cada una de las biomasas analizadas. Finalmente, fue concluido que las correlaciones obtenidas pueden ser utilizadas para la obtención de los parámetros cinéticos de la descomposición térmica de diversas biomasas, contribuyendo con el proceso de modelado a través de la reducción del tiempo que se invierte en el proceso iterativo