W火焰多次引射分级燃烧机理研究

Low volatile coal accounts for more than 40% of China's power coal, W down-fired boiler is a better furnace type for burning this kind of coal, but suffering universal problems such as high combustible contents in fly ash, high NOx emissions and heavy slagging. Available technology is difficult to solve the above problems comprehensively, therefore, a new down-fired combustion mechanism was raised, namely multi-injection multi-stage combustion technology, which could achieve multi-stage combustion, and keep high efficiency, low NOx emissions and prevent slagging effectively. The first industrial implementation showed that the combustible content in fly ash and NOx emissions were significantly lower than the similar technology, but the targets of high efficiency and low NOx emissions still have a large space of advancement and the mechanism of multi-injection multi-stage combustion technology should be studied deeply .. This topic will use sedimentation furnace to study the mechanism of NOx generating and self-reduction different phase reaction of low volatile coal coke; Researches on the influence of arrangement form and position of burner nozzles, air distribution and angles of airflow on single-phase and gas-solid flow characteristics will be carried out by hot-wire anemometer and PDA test system; The influence of operation parameters on furnace combustion and NOx emissions characteristics will be studied by numerical calculation combined with industrial tests. Using above methods to systematicly optimizate the multi-injection multi-stage combustion technology, which will be helpful for developing the new type furnace with the following advantages: high efficiency, low NOx and burning low quality coal.

低挥发分煤占我国动力用煤的40%以上，W火焰锅炉是燃用此类煤的主力炉型，但普遍存在飞灰可燃物含量高、NOx排放量高及结渣严重的问题，现有技术难以综合解决以上问题。本课题组提出的多次引射分级燃烧技术，通过其独特的燃烧组织方式，有效保证高效、低NOx排放同时防止结渣。首次工业示范表明飞灰可燃物含量及NOx排放量明显低于同类技术，且结渣轻微，但仍存在很大的提升空间，需要对其机理开展深入的研究。.本课题将采用沉降炉研究低挥发份煤焦炭燃烧过程中NO生成及自还原异相反应机理。利用单相及气固两相试验研究燃烧器喷口布置形式及布置位置、炉内配风及送风角度对炉内流动特性的影响规律，利用数值计算结合工业试验研究运行参数对炉内燃烧特性的影响，并根据研究结果对多次引射分级燃烧技术进行系统性优化。

在我国发电行业的动力用煤中，低挥发分的贫煤和无烟煤占40%以上，W火焰锅炉作为燃用低挥发分煤种的成熟炉型在我国发展迅速。本课题利用自主研发的W火焰锅炉多次引射分级燃烧新技术对超临界W火焰锅炉进行燃烧系统的方案设计与优化。.利用烟雾示踪进行了燃烧器圆形喷口和矩形喷口的示踪试验，试验结果表明仅在采用矩形喷口且喷口间距较小时，可以保证拱上射流的刚性，一次风可以被内二次风、外二次风和三次风引射，到达冷灰斗中部，充分利用了冷灰斗的空间，炉内的气流的对称性良好。建立单相冷态试验，利用恒温热线风速仪对炉内的流场进行了测量，研究不同结构和运行参数对流场的影响。建立气固两相冷态试验，利用激光颗粒动态分析仪对炉内气固两相的流动特性进行测量，研究不同运行参数下对炉内两相流场的影响。发现在合适的结构和运行参数下，炉内流场对称，气流下射到冷灰斗中部，炉膛利用空间较大。.借助数值计算方法对炉内燃烧及NOx生成特性进行数值预测。浓、淡煤粉气流粉量比由6:4增大到9:1后，浓煤粉气流着火距离由1.2m缩短到0.7m。对应飞灰可燃物含量由5.87%减小到5.52%，NOx排放浓度由778mg/m3 (O2=6%)减小到662mg/m3 (O2=6%)。随着内二次风率由19.66%减小到7.66%，浓煤粉气流着火距离由1.0m减小到0.8m。拱上气流下冲深度有所减小，NOx排放浓度由662mg/m3 (O2=6.0%)增大到726mg/m3 (O2=6.0%)。通过全面的工业热态试验，推荐优化二次风、三次风、燃尽风及内二次风挡板开度分别为95%、70%、55%和100%，该挡板开度组合下的NOx排放浓度和飞灰可燃物含量分别为589mg/m3 (O2=6.0%)和6.18%。 .最终，采用沉降炉研究低挥发份煤焦炭燃烧过程中NO生成及自还原异相反应机理。进行了单因素焦炭燃烧试验，对烟气成分及含量进行在线检测，对燃烧前、后焦炭进行元素分析和物理结构分析，研究了各因素对低挥发份煤焦炭 NO 生成及自还原异相反应的影响，建立焦炭的 N、 O、 C 等元素的含量、物理结构与 NO 生成之间的关联。

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