通过燃烧优化有望实现煤粉高效低氮燃烧与颗粒物(PM)的协同源控制,也是完成低碳的重要清洁燃烧方式。为阐明预热-燃烧过程NO和PM生成特性和减排机理,针对预热过程中煤氮的析出、挥发分氮的转化以及预热-燃烧过程NO的生成和还原机制及PM生成展开研究。烟气中主要气体组分和PM分别采用烟气分析仪和荷电低压撞击器(ELPI+)测量和记录。结果表明,气相过量空气系数(αgas)可作为以气相反应为主的预热区反应性(氧化性或还原性)的有效判据。适当增大预热区过量空气系数(αp)会增加预热区NO生成,但明显降低整个预热-燃烧过程中NO生成。高预热温度可显著降低NO的生成,预热温度由1200K升至1600K时,NO降低效率由42.25%提高至51.44%。然而,αp持续增加将减弱NO脱除率的下降趋势。燃烧温度升高对焦炭氧化生成NO和焦炭还原NO过程均有促进作用,但对NO生成的促进作用更显著。同时,预热-燃烧降低细颗粒物生成,尤其是PM0.3生成量减少27.57%。预热-燃烧技术可实现燃烧过程中对PM和NO生成的协同源控制,对煤炭清洁燃烧有重要意义。

Combustion optimal is expected to realize efficient low-NOx combustion of pulverized coal with synergistic control of particulate matter (PM), and is also a crucial clean combustion method to accomplish low-carbon goals. To clarify the formation and reduction mechanisms of NO and particulate matter(PM), the release of coal nitrogen, the conversion of volatile nitrogen, the NO formationand reduction mechanism, and the PM formation have been investigated during the preheating-combustion. The main gas components andPM were measured by a flue gas analyzer and an electrical low pressure impactor ( ELPI +), respectively. The results indicate thatthe gas-phase excess air coefficient (αgas) serves as an effective criterion for the reactivity (oxidative or reductive) of the preheatingzone, which predominantly involves gas-phase reactions. An increase in excess air coefficient (αp) slightly impairs the operation of thepreheating zone, yet significantly enhances the reduction of NO during the entire preheating-combustion process. A higher preheating temperature notably decreases NO formation, with NO reduction efficiency increasing from 42.25% to 51.44% as preheating temperature risesfrom 1 200 K to 1 600 K. However, this effect diminishes with an increase in αp. Raising the temperature has a promoting effect onboth char oxidation for NO formation and char reduction of NO, but the effect on NO formation is more pronounced. Concurrently, the preheating-combustion process reduces the of PM, particularly 27. 57% reduction in PM0.3. The preheating - combustion technology canachieve the synergistic source control of PM and NO formation, which is important for the clean combustion of coal.

0 引言

1 试验

   1.1 试验系统

   1.2 燃料特性

   1.3 动力学模拟方法

2 结果与讨论

   2.1 气相过量空气系数

   2.2 预热-燃烧过程NO生成

   2.3 预热-燃烧PM生成特性

3 结论