Gasification of a pulverized sub-bituminous coal in CO2 at atmospheric pressure in an entrained flow reactor

Char gasification by CO2 may play an important role in oxy-fuel applications and affect particle temperature histories and overall reaction rates during combustion. This paper presents the results of a complete set of experiments of char gasification in CO2 performed with a pulverized Indonesian sub-bituminous coal in an entrained flow reactor under realistic conditions; series of burnout curves at different reactor temperatures (1040–1300 °C) and CO2 concentrations (0.7–100%) reveal consistent trends in the gasification rates. The study included also devolatilization and oxidation tests with this coal in the same experimental facility. The data are used to derive apparent kinetics for the three processes, in a manner similar to that followed in a previous work for the oxidation of a pulverized coal. The gasification kinetic parameters and reaction rates measured are then compared with values taken or derived from previous works by others, obtained by thermogravimetric analysis or experiments in entrained flow reactors. Finally, the relevance of char gasification in the overall reaction rate under conditions representative of those in an industrial boiler is explored, in particular for the case of oxy-coal combustion.