Combustion kinetics of pine sawdust biochar
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The combustion kinetics of biochar derived from fast pyrolysis of pine sawdust was investigated by using nonisothermal thermogravimetric analysis under air atmosphere at different heating rates. The experimental conversion (α–T) curves contain some experimental errors, and the corresponding derivative conversion (dα/dT–T) curves have many fluctuations. Two strategies of obtaining the smooth dα/dT–T curves were used based on the robust locally weighted scatterplot smoothing method coupled with the corrected AIC smoothing parameter selection method. In the strategy of firstly smoothing α–T data and then differentiating smoothed α–T data, although the smoothed α–T data are relatively smooth, the dα/dT–T curves obtained from the differentiation of the smoothed α–T data have fluctuations. In the strategy of firstly differentiating α–T data and then smoothing dα/dT–T data, the obtained dα/dT–T curves with the optimal smoothing parameters are smooth enough, which indicates that the second strategy is effective. The isoconversional kinetic analysis of the smoothed dα/dT–T curves was performed by using the Friedman differential isoconversional method. The effective activation energies of biochar combustion were obtained and found to significantly vary with the conversion degree (from about 150 to 250 kJ mol−1 in the range of conversion degree from 0.05 to 0.95).
KeywordsBiochar Combustion Kinetics Data smoothing Biomass Isoconversional methods
Financial support from the National Natural Science Foundation of China (Grant No. 51176121) and the National High Technology Research and Development Program of China (863 Program, Grant No. 2012AA101808-05) is greatly acknowledged.
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