The structural features of chars derived from pyrolysis of mallee wood of different particle sizes in a novel fluidized-bed/fixed-bed reactor have been investigated. Raman spectroscopy was used for structural evaluation of chars. Spectra were curve-fitted with 10 Gaussian bands representing typical structural features of the chars. The temperature had a significant influence on the evolution of char structure and thus the total Raman peak area between 800 and 1800 cm(-1) is seen to decrease significantly with increasing pyrolysis temperature for all chars. On the other hand, the ratio I-D/I(Gr + Vl + Vr) between the band intensities of condensed aromatic ring systems (>6 rings) and amorphous char structures with small aromatic ring (35 rings) systems is seen to increase with increasing temperature. The particle size of biomass has a great role in char structure at fast heating rate (>1000 degrees C/s) pyrolysis although it has no effect on char structure at slow heating rate pyrolysis (0.17 degrees C/s). However, in the bigger biomass particle, the structure of char prepared under fast heating rate pyrolysis is similar to that of the structure of char prepared under slow heating rate pyrolysis. (C) 2009 Elsevier B.V. All rights reserved.