Combustion kinetics of char obtained by flash pyrolysis of pine wood

The combustion kinetics of rapidly pyrolyzed wood have been investigated within the temperature range of 573−773 K and the oxygen concentration range of 2.25−36 vol %. These kinetics are, for instance, required for the design of a char combustion section in an integrated flash pyrolysis pilot plant. Two different experimental techniques were used: a standard thermogravimetrical technique (TGA) and flue gas analysis after combustion in a diluted packed bed. The pyrolysis char was prepared in a small screen heater reactor, enabling heating rates of over 300 K/s. The results of the TGA and the packed-bed measurements are in good agreement for temperatures above 648 K. Below that temperature, the reaction rate observed in the TGA appears to be (up to 1.5 times) lower than that in the packed-bed reactor. The combustion kinetics can be described by the following simple rate equation which has an average deviation of 20%: r = 5.3 × 105e-125×103/RTPO20.53(1 − X)0.49. Several pore models reported in the literature were tested against the experimental data, but they could not improve the accuracy of the fit. In comparison with available data, this specific type of char shows a notably higher rate of combustion.