Fluidized Bed Steam Gasification of Biomass with Dolomite and with a Commercial FCC Catalyst

Abstract

The use of dolomite and of a commercial FCC (fluid catalytic cracking) catalyst is studied for the steam gasification of biomass in fluidized bed. This process is carried out in a small pilot plant based in a 15 cm. i.d., 1.20 m. total height, fluidized bed, with the biomass fed at the bottom of the bed. Pine sawdust was used as biomass. Two different working methods have been used: i) the dolomite (-600 + 300 µm) initially in the bed, instead of the sand and ii) sand in the bed and a feed of biomass mixed with the catalyst (dolomite or FCC catalyst). These two catalysts have shown to be efective for the tar cracking and for the reforming of the product gas. However, several problems have been found: the FCC catalyst is quickly elutriated from the bed, thus preventing its use in a single fluidized bed although being very promising for a circulating system. The dolomite is soft, it erodes very quickly and is also elutriated. When used mixed with the biomass in the feed, it behaved as a very effective cracking catalyst. However it is also elutriated from the bed and causes plugging of the exit pipes.