Abstract This study applied the high temperature stage microscope to investigate coal char combustion in air (O2/N2) and O2/CO2 (volume, 21%/79%) atmospheres with the effect of gasification. A reaction front combustion model was also proposed, coupled with effect of char gasification, to predict the key parameters of char combustion in the O2/CO2 atmospheres. The combustion process and particle evolution of coarse chars were observed and measured to calculate the carbon conversion. Experimental results showed that the burnout time of the char particle in the O2/CO2 atmosphere in the was prolonged about 20–25%, compared to the burnout time of chars in air. The overall reaction rates of char particles in the O2/CO2 atmosphere were lower than the rates in the air for different particle sizes. In addition, reaction rates from model prediction showed good agreements with the experimental data for different particle sizes both in the air and O2/CO2 atmospheres, which proved the reaction front combustion model was applicable for the char combustion in this study. The reaction front combustion model also predicted that the reaction front decreased with burning time and mass consumption of char particle. For the char combustion in the O2/CO2 atmosphere, the gasification with CO2 absorbed part of the combustion heat or radiation heat and caused lower particle temperatures and heat fluxes for different particle sizes. The proposed combustion model also predicted that although the effect of the gasification reaction was dominant at the beginning of combustion and then reduced, the conversion of particles was hindered compared to the combustion of char in air.

中文翻译：

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空气(O 2 /N 2 )和O 2 /CO 2 气氛气化作用下粗颗粒煤焦燃烧原位试验及模拟研究

摘要 本研究应用高温载物台显微镜研究了煤焦在空气（O2/N2）和O2/CO2（体积，21%/79%）气氛中的燃烧和气化作用。还提出了反应前沿燃烧模型，结合炭气化的影响，预测 O2/CO2 气氛中炭燃烧的关键参数。观察和测量粗炭的燃烧过程和颗粒演化以计算碳转化率。实验结果表明，与空气中炭的燃尽时间相比，空气中炭颗粒在 O2/CO2 气氛中的燃尽时间延长了约 20-25%。不同粒径的炭颗粒在 O2/CO2 气氛中的总体反应速率低于空气中的速率。此外，模型预测的反应速率与空气和 O2/CO2 气氛中不同粒径的实验数据显示出良好的一致性，证明反应前沿燃烧模型适用于本研究中的炭燃烧。反应前沿燃烧模型还预测反应前沿随着燃烧时间和炭颗粒的质量消耗而减少。对于 O2/CO2 气氛中的炭燃烧，CO2 气化吸收了部分燃烧热或辐射热，导致不同粒径的颗粒温度和热通量较低。所提出的燃烧模型还预测，虽然气化反应的影响在燃烧开始时占主导地位，然后降低，