氨能作为一种零碳燃料,取代部分煤炭混燃可有效降低电厂原有污染物排放,促进燃煤电厂向煤氨混燃电厂的转型。但由于氨能中含氮量过高,导致NOx排放问题备受关注。在复杂的氨煤混燃过程中,有必要探索NOx排放与煤灰之间存在的关联性。燃煤电厂中高碱煤作为一类开发应用前景广阔的煤种,其中高含量的金属氧化物对氨氧化反应的排放特性却鲜有研究。为探讨氨煤混燃过程中不同种类高碱煤灰对氨氧化反应排放特性的影响,通过搭建立式管式炉氨氧化反应试验平台进行变工况分析,对比不同温度下各类煤灰表面NH3转化率及NO生成率两大指标,从试验结果和反应机理2个层面阐述了煤灰中各类金属氧化物对氨氧化反应排放特性的影响。结果表明:煤灰中主要金属氧化物CaO、MgO及Al2O3可促进氨煤混燃过程中煤灰表面气固氨氧化反应的进行,提高NH3转化率。400~600℃,煤灰对NH3转化率的促进作用依次为:HM-2>HM-1>CJ>AKS>EERDS,与煤灰中CaO含量由高到低的排列顺序对应,与MgO排序基本吻合。且这3类金属氧化物均可促进NH3向NO定向转化,以CaO催化效果最显著,其中,Ca含量最高的HM-2对NO生成的选择性相较于空白组而言可提高67.86%。CaO和MgO可促进NH3和NO在催化剂表面氧化,有利于N2O快速产生,使N2O生成温度提前,而Na2O和Fe2O3的存在则抑制NH3氧化,促进NH3还原NO。

Ammonia can be used as a zero-carbon fuel to replace part of coal for co-firing process, which can effectively reduce the original pollutant emissions of power plants and promote the transformation of coal-fired power plants to coal and ammonia co-firing powerplants. However, due to the high nitrogen content in ammonia, the problem of NOx emission has attracted much attention. In the complex coal and ammonia co-firing process, the correlation between NOx emissions and coal ash is also worthy of further exploration andanalysis. High-alkali coal in coal-fired power plants is a kind of coal with broad development prospects, but the emission characteristicsof high-content metal oxides on ammonia oxidation reaction are rarely studied. In order to explore the influence of different kinds of high-alkali coal ash on the emission characteristics of ammonia oxidation reaction during the coal and ammonia co-firing process, an ammoniaoxidation reaction test platform was built to analyze the variable working conditions, and the two indexes of NH3 conversion rate andNO generation rate on the surface of various types of coal ash at different temperatures were compared. The specific influence of various metal oxides in coal ash on the emission characteristics of ammonia oxidation reaction was expounded from two aspects of test resultsand reaction mechanism. The results show that the main metal oxides CaO, MgO and Al2O3 in coal ash can promote the gas-solid ammonia oxidation reaction on the surface of coal ash during the coal and ammonia co-firing process, and improve the NH3 conversion rate. At400-600 ℃ , the promoting effect of coal ash on the conversion rate of NH3 is as follows: HM-2>HM-1>CJ>AKS>EERDS, which corresponds to the order of CaO content in coal ash from high to low, which is basically consistent with the order of MgO. In addition, the abovethree kinds of metal oxides can promote the directional conversion of NH3 to NO, and the catalytic effect of CaO is the most significant.Among them, the selectivity of HM- 2 with the highest Ca content to NO formation can be increased by 67.86% compared with thepure gas phase ammonia oxidation reaction. CaO and MgO can promote the oxidation of NH3 and NO on the catalyst surface, which is conducive to the rapid production of N2O the advance of N2O formation temperature. However, the presence of Na2O and Fe2O3 has an inhibitory effect on the oxidation reaction of NH3, and it has excellent performance in promoting the reduction of NO by NH3. Among them,the mechanism of Na2O and Fe2O3 promoting NO reduction is not the same.

0 引言

1 试验

   1.1 试验装置

   1.2 工况设计

2 试验煤灰

3 典型高碱煤灰对氨氧化反应的排放特性

   3.1 典型高碱煤灰对氨氧化反应中NH3转化率影响

   3.2 典型高碱煤灰对氨氧化反应中含氮物质生成率影响

4 结论