Thermogravimetric Analysis of Tobacco Combustion Assuming DAEM Devolatilization and Empirical Char-Burnoff Kinetics

Two blends of tobacco (Virginia and Burley) were studied by thermogravimetry at linear and nonlinear heating programs in gas flows containing 2, 4, and 9% oxygen. A kinetic scheme of successive devolatilization and char-burnoff reactions was assumed. A distributed activation energy model was assumed for devolatilization with a Gaussian distribution and a constant preexponential factor. The evaluations were also carried out using nonconstant preexponential factors that depended on the activation energy. The char burnoff was described by first-order kinetics and by an empirical model that took into account the change of the reactivity with conversion of the sample. The dependence of the rate of combustion on the oxygen concentration was approximated by a power function. Series of 15 and 30 experiments were used for the determination of the model parameters by simultaneous least-squares evaluation of the experiments. The considerations, methods, and results can also be used in the fields of biomass gasification and combustion.