洁净煤技术

2021, v.27;No.134(04) 123-131

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基于动态自适应反应的煤粉无焰燃烧燃料氮转化机理研究
Study on fuel nitrogen conversion mechanism in flameless combustion of pulverized coal based on dynamic adaptive chemistry

刘璐;李鹏飞;成鹏飞;刘耀蔚;胡帆;柳朝晖;郑楚光;
LIU Lu;LI Pengfei;CHENG Pengfei;LIU Yaowei;HU Fan;LIU Zhaohui;ZHENG Chuguang;State Key Laboratory of Coal Combustion,Huazhong University of Science and Technology;

摘要(Abstract):

无焰燃烧是近年来广受关注的新型高效清洁燃烧技术之一,具有容积式低反应速率燃烧区和典型中低温燃烧特性,需耦合详细反应机理并考虑湍流与化学反应交互,以提高无焰燃烧及其NO生成数值模拟精度。基于动态自适应反应机理对煤粉无焰燃烧和NO生成特性进行了高保真数值模拟研究。通过采用动态自适应机理简化算法,模拟过程实时对自主发展的含氮骨架机理进行当地简化。评估发现,相较于单纯采用骨架机理模拟,采用动态自适应反应可在不牺牲计算精度的条件下获得约3倍的计算加速,且对炉内NO生成的预测精度显著优于传统NO后处理模拟方法。基于经试验验证的模拟结果,还获得了HCN和NH_3等典型含氮前驱体的炉内分布,并进一步分析了煤粉无焰燃烧燃料氮转化路径、炉内活跃组分和活跃反应等氮转化关键信息。结果表明,煤粉无焰燃烧NO生成主要取决于NH_3、HCN和N_2O中间体,而NCO和HNO是较为关键的中间组分。HCN中间体主要通过HNCO/CN和NCO路径生成NO。NH_3中间体由HNCO生成,并进一步转化为NH_2和HNO,最终生成NO。N_2O路径主要参与NO还原,对NO生成贡献较低。CH_3CN也是生成NO的重要中间组分,可通过NCO路径生成NO。
Flameless combustion is one of the new high-efficiency and low-pollutant combustion technologies widely concerned in recent years. Due to the volumetric combustion zone with relatively low reaction rate and typically medium or low temperature region in flameless combustion, it is necessary to consider the turbulence-chemistry interaction coupled with detailed reaction mechanisms in numerical simulations to improve the prediction accuracy of the combustion and NO formation. In this paper, the high-fidelity numerical simulations on the flameless combustion of pulverized coal and NO formation were performed based on the dynamic adaptive chemistry mechanism. The dynamic adaptive mechanism simplification algorithm was adopted to realize the local reduction of the in-house-developed nitrogen-containing skeletal mechanism during simulation. It is found that compared with the simulation with a skeletal mechanism, the dynamic adaptive chemistry can obtain nearly three times calculation acceleration without sacrificing the accuracy. And the prediction accuracy of in-furnace NO formation is significantly improved relative to the traditional NO post-processing simulation method. After experimental validation, the distributions of typical in-furnace nitrogen-containing precursors such as HCN and NH_3 were obtained. The key information on nitrogen conversion, such as fuel nitrogen conversion pathway, active species and reactions in the furnace, were further analyzed. The results show that the NO formation from pulverized coal flameless combustion mainly depends on NH_3,HCN,and N_2O intermediates, while NCO and HNO are the key intermediate components. HCN is converted to NO mainly by the HNCO/CN and NCO paths. NH_3 is converted from HNCO,and is further converted to NH_2 and HNO,and finally leads to NO formation. The N_2O path mainly participates in the NO reduction and is insignificant to the NO formation. CH_3CN is also an important intermediate component for NO formation, which can be converted to NO by the NCO path.

关键词(KeyWords): 煤粉无焰燃烧;燃料氮;详细反应机理;动态自适应反应;数值模拟
flameless combustion of pulverized coal;fuel nitrogen;detailed reaction mechanism;dynamic adaptive chemistry;numerical simulation

Abstract:

Keywords:

基金项目(Foundation): 国家自然科学基金资助项目(52076095);; 国家重点研发计划资助项目(2018YFB0605300)

作者(Author): 刘璐;李鹏飞;成鹏飞;刘耀蔚;胡帆;柳朝晖;郑楚光;
LIU Lu;LI Pengfei;CHENG Pengfei;LIU Yaowei;HU Fan;LIU Zhaohui;ZHENG Chuguang;State Key Laboratory of Coal Combustion,Huazhong University of Science and Technology;

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DOI: 10.13226/j.issn.1006-6772.CE21042701

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