【作者】 王鹏；

【导师】 贾志刚；

【作者基本信息】 北京化工大学 ， 化学工程与技术， 2019， 硕士

【摘要】 传统的天然气火焰燃烧方式产生的大量NOx,对环境及人体健康造成了极大的危害,而催化燃烧方式可实现低NOx排放。催化燃烧器的NOx生成机理和排放特性受操作条件和反应器参数的共同影响,需要进行深入的分析与研究。本文采用了 Fluent对甲烷的催化燃烧过程进行了数值模拟,主要工作如下:(1)改进了甲烷催化燃烧与NOx生成过程的数学模型。建立了蜂窝型催化燃烧器二维单孔道结构模型,将甲烷在Pt表面的催化反应机理和甲烷气相反应机理GRI3.0相耦合。对不同操作条件如甲烷浓度、入口速度、入口温度,以及不同反应器参数如反应器长度和反应器孔径下,孔道内的温度场、速度场、甲烷浓度场、HC和CO排放量、NOx的组分、生成速率和机理进行了数值模拟。二维模型可以考虑到反应器径向的速度、温度和组分浓度分布对燃烧特性和污染物排放特性的影响,与实验结果的对比证明了使用该数学模型来描述甲烷催化燃烧过程的准确性。(2)对入口操作条件和反应器结构参数的甲烷催化燃烧特性和NOx生成过程进行了系统研究。甲烷浓度、预热温度和入口气速对催化燃烧器的燃烧特性和污染物排放特性影响较大。浓度、温度和气速存在合理的匹配,可减小反应器长度,降低污染物的排放量。在特定操作条件下,反应器长度和孔径存在优化值,使污染物排放量最低,提高反应器效能。(3)对甲烷催化燃烧过程中NOx的生成机理进行研究。NOx的生成方式与操作条件和反应器参数均有关,在甲烷的催化燃烧过程中应主要考虑热力型NOx和快速型NOx的生成,而在入口甲烷浓度较低和气相燃烧时也应考虑中间型NOx的生成。更多还原

【Abstract】 The emission of NOx produced by the traditional natural gas flame combustion has caused great harm to the environment and human health,and the catalytic combustion mode can achieve low Nox emissions.The NOx emission characteristics of a catalytic burmer are affected by both operating parameters and reactor parameters which require in-depth analysis and research.In this paper,Fluent is used to simulate the catalytie combustion process of methane.The main work is as follows:(1)Mathematical model of catalytic combustion and NOx generation process was improved.A two-dimensional single-channel model of a honeycomb catalytic burner was established.The catalytic reaction mechanism of methane on the surface of Pt and the gas phase reaction mechanism GRI3.0 of methane were involved.The temperature field,velocity field,methane concentration field,HC and CO emissions,NOx composition,formation rate and mechanism in the tunnel under different operating conditions such as methane concentration,inlet velocity,inlet temperature,and different reactor parameters such as reactor length and reactor pore size were numerically simulated.The results show that using the two-dimensional model,the influence of velocity,temperature and composition concentration distribution in the radial direction of the reactor on the nombustion characteristics and pollutant emission characteristics of the reactor were analyzed,compared with experimental results,the catalytie combustion process of methane is predicted more accurately.(2)The methane catalytic combustion characteristics and NOx generation process of different inlet operating conditions and reactor structural parameters were systematically studied.The methane concentration,preheating temperature and iulet gas velocity have a great influence on the combustion characteristics and pollutant emission characteristics of the catalytic burner.The concentration,temperature and gas velocity should be carefully chosen to reduce the reactor length and reduce pollutant emissions.Under certain operating conditions,there are optimized values for reactor length and pore size to minimize pollutant emissions and improve reactor performance.(3)The formation mechanism of NOx in the catalytic combustion of methane was studied.The formation mode of Nox is related to the operating conditions and reactor parameters.In the catalytic combustion of methane,the formation of thermal Nox and prompt NOx should be mainly considered,and intermediate NOx should also be considered in low methane concentration and gas phase combustion.更多还原