Soot Formation and Distribution in Coal Jet Flames over a Broad Range of Coal Concentration
Soot Formation and Distribution in Coal Jet Flames over a Broad Range of Coal Concentration
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不同煤浓度范围内煤喷射火焰中烟灰的形成和分布
DOI：
10.1021/acs.energyfuels.0c00760
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发表时间：
2020
期刊：
影响因子：
5.3
通讯作者：
Lyu Junfu
中科院分区：
文献类型：
--
作者：
Xu Kailong;Zhang Hai;Shen Wenfeng;Zhang Yang;Wu Yuxin;Lyu Junfu
采用激光诱导白炽（LII）技术，在较宽的煤质量浓度范围内，对煤粉射流火焰中碳烟的形成和分布进行了测量。实验采用旋流燃烧器进行。采用Mie散射成像技术对煤粉颗粒分布进行可视化，采用双波段比色测温法对火焰温度进行测量。结果表明，在低C煤条件下，Mie散射测量对火焰中的C煤是有效的，但在高C煤条件下，测量的准确性受到碳烟散射的影响。在低C煤时，大部分煤粒被单独燃烧，并形成少量的碳烟。当Ccoal超过某个值（例如，Ccoal≥ 0.60 kg/m3）时，煤粉火焰表现为“云火焰”，烟尘颗粒首先在煤粉射流的外边界生成，然后在射流中心附近大量生成。大部分碳烟颗粒在下游被氧化。碳烟体积分数的径向峰值与煤粉浓度的径向峰值重叠，因为高温区和低O2浓度区非常靠近煤粉射流的中心线。碳烟体积分数首先随着Ccoal的增加而显著增加，但是当Ccoal高时（即，≥ 1.0 kg/m3）。煤对碳烟生成的影响主要是由于煤的挥发分增加、缺氧区扩大和火焰温度的变化。
The soot formation and distribution in coal jet flames were measured using Laser-Induced Incandescence (LII) technique over a wide range of coal mass concentration (Ccoal). Experiments were conducted using an entrained-flow burner. The coal particle distributions were visualized using Mie scattering imaging technique and the flame temperature was measured using dual waveband colorimetric thermometry. The results showed that Mie scattering measurement was valid to detectCcoalin the flame under lowCcoalconditions, but its accuracy was affected by the soot scattering under highCcoalconditions. At lowCcoal’s, most coal particles were burned individually and a little amount of soot was formed. WhenCcoalexceeded a certain value (e.g.,Ccoal≥ 0.60 kg/m3), coal flames behaved as “cloud flames” and soot particles were first formed in the outer boundary of the coal jet and then massively produced near the centerline of the coal jet. Most soot particles were oxidized in the downstream. The radial peak soot volume fraction overlapped with that of coal concentration, as the high-temperature zone with low O2concentration located very close to the centerline of the coal jet. The soot volume fraction first remarkably increased asCcoalincreased, but the trend became less significant whenCcoalwas high (i.e., ≥ 1.0 kg/m3). The effects ofCcoalon the soot formation were attributed to the increase of the volatile amount, expansion of the O2-deficiency region, and the change of the flame temperature.