Physical properties and reactivity of char obtained from downdraft gasification of sorghum and eastern red cedar

Downdraft gasification of forage sorghum and red cedar wood was studied with the aim of determining the characteristics of produced char for its further application, such as soil amendment, sorbent and solid fuel. Ultimate, proximate, XRD and NMR were used to investigate physical and chemical properties of char and thermo-analytic methods were used to determine kinetics of char gasification. The NMR results showed that red cedar and sorghum chars both contain aromatic carbon, but aliphatic carbon and o-alkyl carbon are more evident in the red cedar char than in the sorghum char. Char derived from downdraft gasification had higher heating values and lower ash contents than char derived from fluidized bed gasification, indicating char derived from downdraft gasification is more suitable for applications, such as soil amendment, than char from fluidized bed gasification. Micropores and mesopores were found in both red cedar and sorghum chars. The gasification reactivity of red cedar char was higher than that of sorghum char. Activation energies were found to be 163 and 167 kJ/mol based on shrinking core model and 147 and143 kJ/mol based on random pore model for sorghum char and red cedar char, respectively.