(757c) Steam Gasification Reactivity of Char from Rapid Pyrolysis of Bio-Oil/char Slurry

Oil/char mixtures from rapid pyrolysis of wood-waste are an attractive feedstock for gasification because of their relatively high energy density, and fluid-like characteristics. Steam gasification of bio-oil/char slurry consisting of 80 wt.% of bio-oil, and 20 wt.% of char from fast pyrolysis of wood is being investigated. The char is crushed and sieved to a size below 38 μm, and added to the bio-oil. The resulting slurry is heated to 900°C in nitrogen at nominal heating rates of 10 to 10000 K/s in a CDS Instruments Pyroprobe, in order to simulate rapid heating in a steam gasification reactor. The resulting chars from the slurry and the original char are gasified at 900°C in a thermogravimetric analyzer (TGA) with a mixed gas of 10 vol.% steam and 90 vol.% nitrogen at a total pressure of 100 kPa, and the gasification reactivity (dX/dt), where X is the fractional conversion, is determined. There are no significant differences in the steam gasification reactivities of chars originating from the slurries at the different heating rates tested. Under 10% steam at 900°C reactivity values of 0.9-1.1×10^-3 s^-1, 0.8-1.0×10^-3 s^-1, 0.7-0.9×10^-3 s^-1 and 0.5-0.7×10^-3 s^-1 are found at fractional conversions of 0.2, 0.4, 0.6 and 0.8, respectively. For the original char, the gasification reactivity was 1.0×10^-3 s^-1 at conversions of 0.2-0.6, and 0.9×10^-3 s^-1 at a fractional conversion of 0.8. Thus the gasification reactivities of chars made from bio-oil/char slurry are close to that of the original char, except for the final stage of the reaction at which char from the slurry is less reactive. Gasification temperature and steam concentration effects on the char gasification reactivity are also presented. A laboratory scale apparatus has been constructed for continuous steam gasification of bio-oil/char slurry.