Thermogravimetric study of sulfur dioxide absorption by limestone / Estudo termogravimétrico da absorção de dióxido de enxofre por calcário

AUTOR(ES)
DATA DE PUBLICAÇÃO

2005

RESUMO

In this work thermogravimetry is applied to determine the effect of temperature and atmosphere on conversion, kinetics and effectiveness of SO IND.2 absorption by limestone. Ranges of temperature and particle size were applied that are typical of the fluidized bed coal combustion process. Isothermal experiments were performed for different temperatures (between 650 and 950 Celius degrees), at local atmospheric pressure (~ 697 mmHg), in dynamic atmospheres of air and nitrogen. The results of sulfation were evaluated using Arrhenius kinetics. The order of magnitude of the resulting activation energies (4.446 kJ/mol in air and 3.748 kJ/mol in nitrogen) suggest the reaction to be controlled by Knudsen diffusion. Optimum conversion resulted between 800 and 850 Celsius degrees in ar, and around 900 Celsius degrees in nitrogen. Effectiveness was defined as the ratio between the instantaneous reaction rate coefficient and its maximum value, indicating the time decay of reactivity as sulfation advances. The average effectiveness was determined for all the temperatures considering the whole sulfation time interval, which was always around 200 seconds. The highest values of average effectiveness were found at 800 Celsius degrees in air atmosphere (0,2854), and 900 Celsius degrees in nitrogen atmosphere (0,3142)

ASSUNTO(S)

sulfatação termogravimetria dióxido de enxofre limestone chemical kinetics thermogravimetry calcário cinética química sulfation sulfur dioxide

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