Abstract Although numerous studies on CO 2 gasification during coal char combustion have been documented, the effects of CO 2 gasification on high-temperature carbon oxidation, which is important for evaluation of carbon conversion during pulverized coal combustion under oxy-fuel and flue gas recirculation conditions, are unclear. Thus, the char conversion characteristics at various contents of O 2 and CO 2 were studied in a drop-tube furnace at 1373 K. Due to the cumulative effects of CO 2 gasification, which can not only suppress carbon conversion due to endothermicity but also consume part of carbon directly, there exists a minimal carbon conversion point around the CO 2 content of 9–13 vol%, where the growth of promotion effect with CO 2 content catches up with the suppression effect, and an inflection point around the CO 2 content of 17–25 vol%, where the promotion effect of the direct gasification reaction on carbon consumption surpasses the suppression effect. Increasing O 2 shifts both points towards high CO 2 contents, whereas increasing combustion gas temperature decreases the values. A mathematical formula including oxidation, effect of gasification on oxidation, and CO 2 gasification, is presented, which gives well prediction on high-temperature carbon conversion. With increasing CO 2 content, the reduction degree of CO 2 gasification on oxidation rate increases, and the synthesis oxidation rate slightly decreases, whereas there always exists a minimal point for gasification rate, gross carbon conversion rate, and gasification weightiness. With increasing O 2 content, the oxidation rate, reduction degree of CO 2 gasification on oxidation rate, and gross carbon conversion rate increase; the gasification rate increases below the minimal point, whereas decreases above the minimal point; the gasification weightiness decreases. Combustion gas temperature shows positive effect on all abovementioned parameters. The results derived here provide meaningful guidelines for practical application and kinetics research on pulverized coal combustion.

中文翻译：

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CO 2 气化反应对煤粉燃烧的影响

摘要 虽然已经有大量关于煤焦燃烧过程中 CO 2 气化的研究，但 CO 2 气化对高温碳氧化的影响对于评估氧燃料和烟气再循环条件下粉煤燃烧过程中的碳转化率很重要。 ，不清楚。因此，在 1373 K 的滴管炉中研究了不同 O 2 和 CO 2 含量下的炭转化特性。由于 CO 2 气化的累积效应，不仅可以抑制因吸热引起的碳转化，而且消耗部分碳直接，在CO 2 含量9-13 vol%附近存在最小碳转化点，在该点处，随着CO 2 含量的增加，促进效应的增长赶上抑制效应，并且在CO 2 含量为17-25 vol％附近的拐点处，直接气化反应对碳消耗的促进作用超过抑制作用。增加 O 2 将两个点移向高 CO 2 含量，而增加燃烧气体温度会降低这些值。给出了包括氧化、气化对氧化的影响和CO 2 气化的数学公式，对高温碳转化给出了很好的预测。随着CO 2 含量的增加，CO 2 气化对氧化速率的还原程度增大，合成氧化速率略有下降，而气化速率、总碳转化率和气化重量始终存在极小值点。随着 O 2 含量的增加，氧化速率、CO 2 气化降低程度对氧化率、总碳转化率的提高；气化率在极小点以下增加，而在极小点以上则降低；气化重量降低。燃烧气体温度对所有上述参数均显示出积极影响。这里得出的结果为粉煤燃烧的实际应用和动力学研究提供了有意义的指导。