Thermogravimetric analysis of the combustion of dry distiller's grains with solubles (DDGS) and pyrolysis char under kinetic control

The combustion behavior of dry distiller's grains with solubles (DDGS) and the corresponding pyrolysis char using a thermogravimetric system is studied. Comparison with beech wood indicates that DDGS devolatilization occurs with a slower rate and the char consists of two fractions with different reactivity. Thermogravimetric curves, obtained with heating rates between 2.5 and 20 K/min, are used to develop a multi-step global reaction mechanism. The description of DDGS devolatilization requires four reactions, representative of the evolution of lumped classes of components, with activation energies of 95, 107, 106 and 100 kJ/mol, which are lower than those typically associated with wood devolatilization. DDGS char combustion is well described by two reaction steps with activation energies of 137 and 153 kJ/mol that again barely touch the lower limit of the typical range of values reported for lignocellulosic chars.