煤燃烧过程生成氮氧化物前驱体的研究
煤燃烧过程生成氮氧化物前驱体的研究
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摘要: 对煤中氮在燃烧条件下生成NOx前驱体（HCN、NH3）进行了研究。实验采用石英玻璃管流化床反应系统，测定了神木煤、澳大利亚烟煤、澳大利亚褐煤在400 ℃～900 ℃HCN、NH3的生成，用离子色谱测定了HCN、NH3的生成量，用差热分析测定了三种煤的燃烧峰温及起始燃烧温度。实验结果表明，在燃烧条件下煤中氮转化为HCN、NH3的比例很高，这一释出过程伴随着煤燃烧过程而发生; 在400 ℃～500 ℃燃烧时HCN、NH3的生成量占煤中总氮质量分数的50%～70%,无论是煤挥发分还是半焦中的氮都在此条件下转化生成了HCN、NH3, 这一实验规律与热解条件的实验结果不同。煤样在更高的温度下燃烧（>700 ℃）时，气体产物中的HCN、NH3的质量分数很少，这是HCN、NH3进一步氧化生成了NOx的缘故。Abstract: The formation of Nox precursors (HCN and NH3) during the coal combustion at 400 ℃～900 ℃ was investigated in a fluidized bed reactor made of quartz tube, in which the concentration of HCN and NH3 was measured by an ion chromatogram system and the coal combustion characteristic under the air atmosphere was analyzed by a TG-DTA (Thermogravimetry-Differential Thermal Analysis) system. The results show that the nitrogen in the coal can produce high proportion of HCN and NH3 during combustion. In the temperature range 400 ℃～500 ℃, about 50%～70% of coal-N was transformed to HCN and NH3. It can be clearly seen that not only the volatile-N of coal but also the char-N can produce NOx precursors. It is very different from the pyrolysis experiments at same temperature. The combustion of coal sample at temperature higher than 700 ℃ will yield less NOx precursors due to the increase of HCN and NH3 transformed to NOx.
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