<p></p><p>The
combustion of coal in air, its gasification with carbon dioxide, and oxyfuel
combustion in oxygen/carbon dioxide mixtures was studied at high process temperatures
in a bubbling fluidised bed reactor where burning is controlled by external
mass transfer conditions. Theoretical
analysis of the burn-out times of an isothermal particle of coal char in air is
provided for the case where a fraction of carbon monoxide is oxidized close to
the char particle. Burn-out time equations are provided for the gasification of
char in carbon dioxide. Both burn-out time equations are compared to analytical
equations derived for the oxy-fuel combustion of char particles in
oxygen/carbon dioxide mixtures. The results are particularly relevant for
retrofitting existing bubbling fluidised bed reactors for sustainable energy
generation to meet global warming targets. </p><p></p>
Reactivity of Coal Char with Steam and Carbon Dioxide