Assessment of thermodeactivation during gasification of a bituminous coal char

The annealing-induced loss of gasification reactivity of a bituminous coal char with respect to carbon dioxide was studied by means of a combination of experimental techniques. Heat treatment of coal samples under inert atmosphere for different time intervals was accomplished at temperatures as high as 2000 degrees C by means of thermogravimetric analyzers and of a specially designed heated-strip reactor. Gasification reactivities of untreated and heat-treated coal samples were determined by isothermal thermogravimetric analysis in carbon dioxide atmospheres. The influence of the time-temperature history of the coal sample on the parameters of the apparent gasification kinetics (preexponential factor, activation energy) has been assessed. Results were further analyzed in the framework of a simple annealing kinetic model suitable for implementation in gasification modeling.