借助计算流体力学软件FLUENT,对一台600,MW超超临界墙式布置切圆燃烧锅炉进行数值模拟.详细分析了深度分级条件下,燃料型NO、热力型NO和总NO生成速率在炉内的分布特性,以及燃烧初期NO和HCN生成特性.结果表明,挥发分析出阶段会产生大量...借助计算流体力学软件FLUENT,对一台600,MW超超临界墙式布置切圆燃烧锅炉进行数值模拟.详细分析了深度分级条件下,燃料型NO、热力型NO和总NO生成速率在炉内的分布特性,以及燃烧初期NO和HCN生成特性.结果表明,挥发分析出阶段会产生大量的燃料型NO,焦炭在缺氧的气氛下燃烧,促进了焦炭燃烧时释放产生HCN与已经产生的NO发生均相消减反应生成N2.在焦炭剧烈燃烧区,温度较高,SOFA(seperated over fire air)区域温度和氧气浓度都较高,这两区域热力型NO生成较多.主燃区总NO与燃料型NO生成速率分布相似,SOFA区NO生成速率大致为燃料型和热力型NO二者的叠加.主燃区集中布置二次风不利于降低NOx排放.距离燃烧器3,m内,NO生成速率变化较大.HCN与NO的生成速率变化趋势相同,都与早期挥发分析出与焦炭燃烧密切相关.优化配风的结果,在25%SOFA风率下,出口NO最低.组织空气分级低氮燃烧技术的关键为主燃区焦炭燃烧在缺氧条件下进行,SOFA区域氧浓度不能太高,合理的优化主燃区与SOFA区氧量配比是关键.展开更多
Hexagonal WO_3 nanorods were synthesized through a facile hydrothermal method. The nanorods properties were investigated by scanning electron microscope（SEM）, transmission electron microscope（TEM）, energy dispersi...Hexagonal WO_3 nanorods were synthesized through a facile hydrothermal method. The nanorods properties were investigated by scanning electron microscope（SEM）, transmission electron microscope（TEM）, energy dispersive spectroscopy（EDS）, and x-ray diffraction（XRD）. The NO_2-sensing performances in terms of sensor response, response/recovery times and repeatability at room temperature were optimized by varying the heat treatment temperature of WO_3 nanorods. The optimized NO_2sensor（400-℃-annealed WO_3 nanorods） showed an ultra-high sensor response of 3.2 and short response time of 1 s to 5-ppm NO_2. In addition, the 400-℃-annealed sample exhibited more stable repeatability.Furthermore, dynamic responses measurements of annealed samples showed that all the annealed WO_3 nanorods sensors presented p-type behaviors. We suppose the p-type behavior of the WO_3 nanorods sensor to be that an inversion layer is formed in the space charge layer when the sensor is exposed to NO_2 at room temperature.Therefore, the 400-℃-annealed WO_3 nanorods sensor is one of the most energy conservation candidates to detect NO_2 at room temperature.展开更多
文摘借助计算流体力学软件FLUENT,对一台600,MW超超临界墙式布置切圆燃烧锅炉进行数值模拟.详细分析了深度分级条件下,燃料型NO、热力型NO和总NO生成速率在炉内的分布特性,以及燃烧初期NO和HCN生成特性.结果表明,挥发分析出阶段会产生大量的燃料型NO,焦炭在缺氧的气氛下燃烧,促进了焦炭燃烧时释放产生HCN与已经产生的NO发生均相消减反应生成N2.在焦炭剧烈燃烧区,温度较高,SOFA(seperated over fire air)区域温度和氧气浓度都较高,这两区域热力型NO生成较多.主燃区总NO与燃料型NO生成速率分布相似,SOFA区NO生成速率大致为燃料型和热力型NO二者的叠加.主燃区集中布置二次风不利于降低NOx排放.距离燃烧器3,m内,NO生成速率变化较大.HCN与NO的生成速率变化趋势相同,都与早期挥发分析出与焦炭燃烧密切相关.优化配风的结果,在25%SOFA风率下,出口NO最低.组织空气分级低氮燃烧技术的关键为主燃区焦炭燃烧在缺氧条件下进行,SOFA区域氧浓度不能太高,合理的优化主燃区与SOFA区氧量配比是关键.
基金Project supported by the National Natural Science Foundation of China(Grant Nos.60771019,61271070,and 61274074)the Tianjin Key Research Program of Application Foundation and Advanced Technology,China(Grant No.11JCZDJC15300)
文摘Hexagonal WO_3 nanorods were synthesized through a facile hydrothermal method. The nanorods properties were investigated by scanning electron microscope（SEM）, transmission electron microscope（TEM）, energy dispersive spectroscopy（EDS）, and x-ray diffraction（XRD）. The NO_2-sensing performances in terms of sensor response, response/recovery times and repeatability at room temperature were optimized by varying the heat treatment temperature of WO_3 nanorods. The optimized NO_2sensor（400-℃-annealed WO_3 nanorods） showed an ultra-high sensor response of 3.2 and short response time of 1 s to 5-ppm NO_2. In addition, the 400-℃-annealed sample exhibited more stable repeatability.Furthermore, dynamic responses measurements of annealed samples showed that all the annealed WO_3 nanorods sensors presented p-type behaviors. We suppose the p-type behavior of the WO_3 nanorods sensor to be that an inversion layer is formed in the space charge layer when the sensor is exposed to NO_2 at room temperature.Therefore, the 400-℃-annealed WO_3 nanorods sensor is one of the most energy conservation candidates to detect NO_2 at room temperature.
