Burning fuels in an O2/H2O atmosphere is regarded as the next generation of oxy-fuel\ncombustion for CO2 capture and storage (CCS). By combining oxy-fuel combustion and biomass\nutilization technology, CO2 emissions could be further reduced. Therefore, this work focuses\non investigating the combustion characteristics of single particles from bituminous coal (BC) and\npine sawdust (PS) in O2/N2, O2/CO2 and O2/H2O atmospheres at different O2 mole fractions\n(21%, 30%, and 40%). The experiments were carried out in a drop tube furnace (DTF), and a high-speed\ncamera was used to record the combustion processes of fuel particles. The combustion temperatures\nwere measured by a two-color method. The results reveal that the particles from BC and PS all\nignite homogeneously. Replacing N2 by CO2 results in a longer ignition delay time and lower\ncombustion temperatures. After substituting H2O for N2, the ignition delay time is shortened,\nwhich is mainly caused by the steam gasification reaction (C + H2O ââ? â?? CO + H2) and steam shift\nreaction (CO + H2O ââ? â?? CO2 + H2). In addition, the combustion temperatures are first decreased at\nlow O2 mole fractions, and then increased at high O2 mole fractions because the oxidation effect\nof H2O performs a more important role than its volumetric heat capacity and thermal radiation\ncapacity. At the same condition, particles from PS ignite earlier because of their higher reactivity,\nbut the combustion temperatures are lower than those of BC, which is owing to their lower\ncalorific values.
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