A Study of the SO IND.2sorption by limestone in thermogravimetric analyser and coal combustion in fluidized bed / Um estudo da sorção de SO IND.2por calcário em analisador termogravimétrico e na combustão de carvão em leito fluidizado

AUTOR(ES)
DATA DE PUBLICAÇÃO

2008

RESUMO

This thesis investigates the sorption of SO IND.2by 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.2and 20% of SO IND.2for 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.-3and 7.07 x 10 POT.-3m/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.2sorption 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 müm. 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.2sorption 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.

ASSUNTO(S)

limestone fluidized bed dessulfuration termogravimetria carvão thermogravimetric analyser coal dessulfuração calcário leito fluidizado

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