Biomass char gasification by H2O, CO2 and their mixture: Evolution of chemical, textural and structural properties of the chars

The present study aims to understand the phenomenology of char gasification by monitoring the chemical, structural and textural char characteristics through the gasification reaction. Chars from beech wood were gasified under 20%H2O, 20%CO2 and 20%H2O + 20%CO2 in N2 at 900° C. The gasification reactions were stopped at 20%, 50% and 70% of char conversion. The char properties were analysed by different analytical techniques such as temperature programmed desorption coupled to mass spectrometry, Raman spectroscopy, Scanning Electron Microscopy, N2 manometry and X-ray Fluorescence. These analyses provide valuable information on the unfolding of the gasification reactions with H2O, CO2 and their mixtures. In particular, it is noted that H2O and CO2 gasification reactions follow different pathways. Moreover, during mixed atmosphere, despite that the char reactivity can be fairly expressed by summing the two individual reactivities, this apparent additivity appears to be the result of several competitions and synergies between H2O and CO2 reactions.