The heat transfer characterisitcs of activated carbon suspended slurry near the critical point of water was determined experimentally using a double-pipe heat exchanger. The preliminary experiment to measure the heat transfer coefficient of water showed the value predicted by the previous study. There is hardly any effect of activated carbon addition and change of its concentration. This result suggests that heat transfer of biomass slurry with suspended catalyst powders near the critical point of water can be estimated using the heat transfer characteristics of water, which is of practical importance.
The influence of nickel catalyst on the tar evolution in the pyrolysis and the amount of hydrogen evolution in the steam gasification of Japanese cedar (hereafter referred to as Sugi) below 500 °C was examined in this study. The pyrolysis of Sugi without nickel catalyst produced 22.6 and 20.6 wt.% (dry ash free, daf) of char at 450 and 500 °C, respectively. The char yield increased gradually with increasing the amount of nickel catalyst and reached 32.0 and 27.6 wt.% (daf) at 450 and 500 °C for the Sugi with 8.3 wt.% of nickel, respectively. The XRD showed that the nickel catalyst in the pyrolyzed char existed as a metallic state for all nickel-loaded samples and the crystallite size was very small. The steam gasification of Sugi without nickel catalyst did not occur below 500 °C. On the other hand, the char conversion for the Sugi with nickel catalyst drastically increased more than 95 wt.% (daf) at 500 °C. And the amount of hydrogen evolution reached 130-140 mmol/g-Char (daf) for all samples, which corresponded to the amount calculated from the carbon content in the pyrolyzed char.