Fast Pyrolysis of Oil Mallee Woody Biomass:  Effect of Temperature on the Yield and Quality of Pyrolysis Products

This paper presents an investigation of the production of crude bio-oil, char, and pyrolytic gases from the fast pyrolysis of mallee woody biomass in Australia. The feedstock was ground, sieved to several narrow particle size ranges, and dried prior to pyrolysis in a novel laboratory-scale fluidized-bed reactor. The effects of pyrolysis temperature (350−600 °C), and biomass particle size (100−600 μm), on the yields and composition of bio-oil, gas, and char are reported. In agreement with previous reports, the pyrolysis temperature has an important impact on the yield and composition of bio-oil, char, and gases. Biomass particle size has a significant effect on the water content of bio-oil. It is interesting to note that the temperature for maximum bio-oil yield, between 450 and 475 °C, resulted in an oil with the highest content of oligomers and, consequently, with the highest viscosity. Such observations suggest that the conventional viewpoint of pyrolyzing biomass at temperatures over 400 °C to maximize bio-oil yield needs to be carefully reevaluated, considering the final use of the produced bio-oil. The increases in oil yield with increasing temperature from 350 to 500 °C were mainly due to the increases in the production of lignin-derived oligomers insoluble in water but soluble in CH2Cl2. The yield and some fuel properties of the pyrolysis products were compared with those herein obtained for pine as well as those reported in the literature for other lignocellulosic feedstocks but using similar reactors.