A detailed description on the role of activated carbon in tar
removal has been given elsewhere [24,26]. According to the
mechanism, activated carbon removes tar both by adsorption and
by catalytic cracking over its ash components. Regarding the catalytic
cracking of tar, Zeng, Xi et al. also reported that coal char as a
catalyst could induce the catalytic reforming of tar [30]. In particular,
Fe, which existed in the activated carbon used for the present
work, is known to be an active tar-cracking component [31]