Destruction of tar during volatile-char interactions at low temperature

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This study aims to investigate the mechanisms of tar destruction during volatile-char interactions at low temperature (400–700°C). A bio-char was subjected to interactions with biomass volatiles at different temperatures (400–700°C). The results indicate that tar is converted into gaseous and solid products (coke) during volatile-char interactions and the proportion of coke formed on the bio-char from the total converted tar steadily increases with increasing temperature. The non-aromatic structures (e.g. aliphatic and/or O-containing structures) in tar are mainly converted into gases by catalytic cracking and/or reforming reactions on char, while the aromatic structures in tar primarily go through condensation/polymerisation reactions to form coke on char surface. The UV-fluorescence spectroscopic results imply that the non-aromatic structures in tar are easier converted on char than aromatic structures at low temperature (e.g. 400–500°C) and the conversion of aromatic structures through coke formation on char will be enhanced at higher temperature (e.g. 600–700°C). The Raman spectroscopic results show that some O-containing species in tar molecules are transferred to the char and form additional O-containing structures into the entire char matrix during the volatile-char interactions.