Abstract Steam-moderated combustion has been proposed to supress flue gas recycling in oxy-fired units, but the influence of replacing CO2 by H2O has to be deeply studied. In this paper, oxy-fuel combustion of anthracite with large steam addition has been experimentally characterized, and main results are discussed as concerns the influence upon the ignition temperature, the burnout and the NOx formation. The tests have been carried out in an electrically-heated entrained flow reactor for a set of O2/CO2 and O2/H2O/CO2 atmospheres, with steam addition up to 40% vol. The results show that ignition temperature diminishes when steam is added in low rates (maximum decrease of 16 °C), but the trend is reversed for the higher steam concentrations (maximum increase of 18 °C). The effect of steam addition on coal burnout rates is more significant for the 21% vol. O2 atmosphere, with a decrease of 2.2–5.3 percentage points, and almost negligible for the 35% vol. O2. An outstanding reduction of NO specific emissions is detected when adding H2O, with decrements ranging 28–45% compared to the dry conditions. The transition from O2/CO2 combustion to O2/H2O combustion barely affects the anthracite conversion but significantly diminishes NOx formation rates.

中文翻译：

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从 O2/CO2 到 O2/H2O 燃烧：大量蒸汽添加对无烟煤着火、燃尽和 NOx 形成的影响

摘要 已提出蒸汽慢化燃烧来抑制富氧装置烟气回收，但H2O替代CO2的影响有待深入研究。在本文中，对无烟煤在大量蒸汽添加情况下的富氧燃烧进行了实验表征，讨论了主要结果对着火温度、燃尽和NOx形成的影响。这些测试是在电加热的气流反应器中进行的，用于一组 O2/CO2 和 O2/H2O/CO2 气氛，蒸汽添加量高达 40% vol。结果表明，当蒸汽以低速率加入时（最大降低 16 °C），着火温度会降低，但随着蒸汽浓度的升高（最大升高 18 °C），该趋势相反。对于 21% vol，蒸汽添加对煤燃尽率的影响更为显着。O2 气氛，下降 2.2-5.3 个百分点，对于 35% vol 几乎可以忽略不计。氧气。添加 H2O 时检测到 NO 特定排放量的显着减少，与干燥条件相比减少了 28-45%。从 O2/CO2 燃烧到 O2/H2O 燃烧的转变几乎不影响无烟煤转化率，但显着降低了 NOx 形成率。