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Doctoral Thesis
DOI
10.11606/T.18.2008.tde-09112009-144713
Document
Author
Full name
Ivonete Ávila
E-mail
Institute/School/College
Knowledge Area
Date of Defense
Published
São Carlos, 2008
Supervisor
Committee
Milioli, Fernando Eduardo (President)
Coury, Jose Renato
Crnkovic, Paula Cristina Garcia Manoel
Pécora, Araí Augusta Bernárdez
Zen, Leandro Dalla
Title in Portuguese
Um estudo da sorção de 'SO IND.2' por calcário em analisador termogravimétrico e na combustão de carvão em leito fluidizado
Keywords in Portuguese
Calcário
Carvão
Dessulfuração
Leito fluidizado
Termogravimetria
Abstract in Portuguese
Nesta tese investiga-se a sorção de 'SO IND.2' por um calcário dolomítico brasileiro em duas diferentes configurações experimentais: um analisador termogravimétrico e um combustor de carvão em leito fluidizado atmosférico borbulhante. Os experimentos termogravimétricos foram realizados em condições tão próximas quanto possível àquelas observadas no processo de combustão em leito fluidizado. Coeficientes intrínsecos de taxa de reação, efetividades e conversões foram determinados através de termogravimetria em atmosfera contendo 65% de ar sintético, 15% de 'CO IND.2' e 20% de 'SO IND.2', para quatro diferentes granulometrias do calcário dolomítico (385, 545, 725 e 775 µm) em quatro diferentes temperaturas de processo (800, 830, 860 e 890 graus Celsius). Os coeficientes intrínsecos de taxa de reação, na condição de máxima taxa de reação, resultaram entre 3,86 x '10 POT.-3' e 7,07 x '10 POT.-3' m/s. As efetividades médias para 200 segundos de reação resultaram entre 0,37 e 0,49/s. As conversões após 600 segundos de sulfatação resultaram entre 0,40 e 0,49 kmol('SO IND.2')/kmol('CA'+'MG') . Nos experimentos em combustor de leito fluidizado obteveram-se coeficientes globais de taxa de reação, conversões e eficiência de sorção de 'SO IND.2'. Considerou-se um calcário dolomítico em cinco diferentes granulometrias médias (385, 545, 718, 725 e 775 µm) e um carvão mineral brasileiro (CE4500) com granulometria média de 385 µm. Aplicaram-se temperaturas entre 798,2 e 886,6 graus Celsius, U/Umf entre 5,6 e 10,8 m/s, e relações molares ('CA'+'MG')/S na alimentação entre 3,7 e 11,9 kmol('CA'+'MG')/kmol(s). O coeficiente global de taxa de reação resultou entre 0,009 e 0,072 m/s, a conversão resultou entre 0,020 e 0,064 kmol('SO IND.2')/kmol('CA'+'MG'), e a eficiência de sorção de 'SO IND.2' resultou entre 46,4 e 83,9%. Os coeficientes globais de taxa de sulfatação obtidos em leito fluidizado foram comparados com os coeficientes intrínsecos de taxa de reação obtidos via termogravimetria. Concluiu-se que condições termogravimétricas mais realistas são necessárias para que a composição de coeficientes de taxa de reação intrínsecos e globais permita análises de controle de reação em reatores de leito fluidizado.
Title in English
A Study of the 'SO IND.2' sorption by limestone in thermogravimetric analyser and coal combustion in fluidized bed
Keywords in English
Coal
Dessulfuration
Fluidized bed
Limestone
Thermogravimetric analyser
Abstract in English
This thesis investigates the sorption of 'SO IND.2' by a brazilian dolomite in two different experimental setups: a thermogravimetric analyzer and an atmospheric bubbling fluidized bed coal combustor. The thermogravimetric experiments were carried out in conditions as close as possible to those observed in the fluidized bed combustion process. Intrinsic coefficient of reaction rate, effectiveness and conversion were determined through thermogravimetry in synthetic atmosphere containing 65% of air 15% of 'CO IND.2' and 20% of 'SO IND.2' for four different dolomite particle sizes (385, 545, 725 and 775 µm) and four different temperatures (800, 830, 860 and 890 Celsius degrees). The results of the intrinsic reaction rate coefficient in the maximum reaction rate conditions were between 3.86 x '10 POT.-3' and 7.07 x '10 POT.-3' m/s, while the resuls of the average effectiveness for 200 seconds of reaction were between 0.37 and 0.49/s. The values of conversion after 600 seconds of sulfation were between 0.40 and 0.49 kmol('SO IND.2')/kmol('CA'+'MG') . Global reaction rate coefficient, conversion and 'SO IND.2' sorption efficiency were obtained from the fluidized bed combustor experiments for five different dolomite particulate sizes (average diameters of 385, 545, 718, 725 and 775 µm) and a brazilian coal (CE4500) with particle size of 383 'mü'm. Temperatures between 798.2 and 886.6 Celsius degrees, U/Umf between 5.6 and 10.8 m/s, and ('CA'+'MG')/S molar feeding ratios between 3.7 and 11.9 kmol('CA'+'MG')/kmol(s) were applied. The results of the global reaction rate coefficient were between 0.009 and 0.072 m/s, the ones of the conversion were between 0.020 and 0.064 kmol('SO IND.2')/kmol('CA'+'MG'), and those of the 'SO IND.2' sorption efficiency were between 46.4 and 83.9%. The global sulfation rate coefficients obtained in fluidized bed were compared to the intrinsic reaction rate coefficients obtained through thermogravimetry. It was concluded that more realistic thermogravimetric conditions are required so that the composition of intrinsic and global reaction rate coefficients can allow for the analyses of reaction rate control in fluidized bed reactors.
 
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Publishing Date
2009-11-30
 
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