Combustion characteristics of residues from co-liquefaction of lignite and sawdust under syngas

The combustion characteristics of residues from co-liquefaction of lignite and sawdust under different operation conditions including solvent, temperature, atmosphere, and with/without water added were examined by a thermogravimetric analyzer. The effects of different liquefaction operation conditions on the combustion characteristics of the corresponding residues were investigated through comparing their characteristic parameters such as ignition temperature, peak temperature of maximum weight loss rate and burnout temperature. Based on the TG /DTG profiles, a residue combustion kinetics model was also proposed and the kinetics parameters were obtained by Coats-Redfern method. The results show that the residue with tetralin as solvent has a better combustion reactivity than the residue with toluene as solvent, and the residue from liquefaction at 360℃ has a better combustion reactivity than that at 420℃. Syngas is beneficial to the residue having higher combustion reactivity than hydrogen atmosphere. While adding water to the feedstock during liquefaction lowers the combustion reactivity of the residue compared to the case without water added. The different atomic ratios of H/C, specific surface area and ash content of the residues that arise from the different operation conditions may contribute to the different combustion characteristics of the residues. The kinetics of residue combustion could be described by a threestage second order kinetic model. The activation energy of three stages almost follows the order of high-low-high.