Abstract This study examined the combustion of pulverized char under an O2/CO2 atmosphere to (1) attempt to achieve a moderate or intense low-oxygen dilution (MILD) combustion process and (2) investigate the effects of gas distribution modes on NO emissions. First, fuel was preheated in a circulating fluidized bed (CFB) and then high-temperature preheated fuel from the CFB was burned in a down-fired combustor (DFC). The study was conducted with two secondary gas nozzle positions, three tertiary gas position arrangements, and four secondary oxygen ratios in the DFC. During the test process, the combustion temperature was uniform in the CFB and the CO2 concentration in the flue gas reached approximately 90%. MILD combustion was achieved when the secondary gas nozzle position was center and the char combustion reaction dispersed into the upper low-oxygen space in the DFC. The obvious flame front disappeared and the temperature profile in the DFC was more uniform which is also one of the important features of MILD combustion. This reduced NO emissions by around half while maintaining high combustion efficiency. NO emissions were further reduced by a particular arrangement of tertiary gas positions, but at the cost of reducing combustion efficiency.

中文翻译：

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循环流化床预热O 2 /CO 2 气氛中MILD燃烧煤粉NO排放的实验研究

摘要 本研究检查了粉状炭在 O2/CO2 气氛下的燃烧，以 (1) 尝试实现中等或强烈的低氧稀释 (MILD) 燃烧过程，以及 (2) 研究气体分布模式对 NO 排放的影响。首先，燃料在循环流化床 (CFB) 中预热，然后来自 CFB 的高温预热燃料在下燃燃烧室 (DFC) 中燃烧。该研究是在 DFC 中使用两个二级气体喷嘴位置、三个三级气体位置布置和四个二级氧气比率进行的。试验过程中，CFB燃烧温度均匀，烟气中CO2浓度达到90%左右。当二次气体喷嘴位置居中且焦炭燃烧反应分散到 DFC 上部低氧空间时，实现温和燃烧。明显的火焰锋面消失，DFC 内的温度分布更加均匀，这也是 MILD 燃烧的重要特征之一。这将 NO 排放量减少了大约一半，同时保持了高燃烧效率。通过特定的三次气体位置布置进一步减少了 NO 排放，但代价是降低了燃烧效率。