Effects of biomass char structure on its gasification reactivity

The structural features and combustion reactivity of chars prepared from the fast pyrolysis of mallee wood were investigated using Raman spectroscopy and thermogravimetric analysis. The Raman spectra were curve-fitted by using 10 Gaussian bands, representing different structural features of chars. The total Raman peak areas between 800 and 1800 cm⁻¹ and combustion reactivity of chars were seen to decrease with increasing pyrolysis temperature. The curve-fitting Raman spectra represented that the formation of amorphous carbon structure with smaller polyaromatic rings are dominant in chars from bigger particles of biomass and at lower temperature. The condensed and larger aromatic ring systems are preferentially formed in chars from smaller particles and at higher temperature. The former structure is higher reactive than the latter one, which is reflected in the char reactivity. The retention of inherent catalytic species (AAEM) also plays an important role in char reactivity. However, our results suggested that the structure of char played a more dominant role than the catalytic effects of AAEM species in the char intrinsic combustion reactivity.