CO2 Gasification of torrefied wood. A kinetic study.

The CO2 gasification of torrefied wood samples was examined by thermogravimetry (TGA) at linear, modulated and constant reaction rate (CRR) temperature programs. The untreated raw materials and chars prepared at 750°C were also included in the study. The gasification temperature range separated sufficiently from the pyrolysis in the experiments for its separate analysis. Characteristic gasification reactivity differences were observed between the samples that were due to the differences of the char-forming reactions at different conditions. Various groups of experiments were evaluated together by the method of least squares, under various hypotheses on the dependence of the reaction rate on the reacted fractions. The differences between the samples were described by different pre-exponential factors while the rest of the kinetic parameters were kept identical during an evaluation. The effect of thermal annealing on the gasification kinetics was also expressed by the values of the pre-exponential factors. When the experiments of the samples prepared from birch were evaluated together, self-accelerating kinetics was obtained with E=225kJ/mol. The experiments belonging to the samples prepared from spruce resulted in n-order kinetics with E=223kJ/mol