Combustion Kinetics of Corncob Charcoal and Partially Demineralized Corncob Charcoal in the Kinetic Regime

Charcoals produced by a modern, efficient method were studied in the kinetic regime, at oxygen partial pressures of 0.2 and 1 bar by thermogravimetric experiments and their reaction kinetic modeling. The charcoals were ground to an average particle size of 5-13 (mu)m. A partial removal of minerals from the feedstock (corncobs) by an acid-washing procedure resulted in ca. 6 times higher specific surface area in the charcoal. Despite the increased surface area, this sample evidenced a much lower reactivity. A model based on three reactions gave an adequate description over a wide range of experimental conditions. Thirty-eight experiments on four charcoal samples were evaluated. The experiments differed in their temperature programs, in the ambient gas composition, and in the grinding of the samples. Characteristics of the combustion process were determined including activation energy values characteristic for the temperature dependence of the burnoff, formal reaction orders characterizing the dependence on the oxygen content of the ambient, and functions describing the conversion dependence of the partial processes.