加压O₂/CO₂燃烧技术是一种可以实现CO₂高效捕集的新型燃烧技术。为探究煤粉在加压O₂/CO₂气氛下的燃烧特性和污染物释放特性，采用加压沉降炉试验系统在0.9 MPa压力下对神华烟煤的加压燃烧（燃烧时间0.3 s）特性和N元素迁移释放特性进行研究。通过在线测量手段分析了O₂/CO₂气氛下，温度（1 073～1 273 K）对燃烧过程中气相产物CO、N₂O以及NO生成规律的影响。通过离线表征手段分析了温度对燃烧残炭物理化学结构变化的影响。结果表明，煤粉加压燃烧过程中，升高燃烧温度会导致煤中燃料N的气相NO_x转化率先升高后降低，相比N2O，升高燃烧温度对NO释放的影响较弱，煤中燃料N向气相NOx转化主要由N₂O决定。煤粉加压O₂/CO₂燃烧过程中，CO和NO浓度随燃烧温度的升高逐渐减小和增大，而N₂O释放随燃烧温度的升高先增后减。燃烧温度1 273 K时，CO、NO、N₂O体积分数分别达到363.5×10^-6、10.2×10^-6和6.8×10^-6。FTIR结果表明，煤粉颗粒表面O—C═O结构含氧官能团比C—OH结构含氧官能团具有更高的燃烧反应活性。燃烧温度从1 073 K升至1 273 K时，C—O相对含量变化较小，O—C═O、C═O、C—H相对含量分别减小了1%、1%和7%，而C═C/C—C相对含量增加了7%。表明加压燃烧过程中升高温度会促进C—H结构快速消耗，同时提升残炭的芳香程度。1 273 K时，煤粉燃烧残炭表面以N-5、N-6形式赋存的N元素相对含量分别减少7%以及增加5%。加压O₂/CO₂燃烧过程中释放的NOx含氮前驱物主要来源于焦炭中固有的N-Q结构，其相对含量变化较小。

Pressurized O₂/CO₂ combustion technology is a new combustion technology that can achieve efficient CO2 capture. In order to explore the combustion and pollutant emissions characteristics of pulverized coal in a pressurized O₂/CO₂ atmosphere, the pressurized combustion (residence time is 0.3 s) and N transformation characteristics of Shenhua bituminous coal were investigated by a pressurized drop tube furnace (PDTF) experimental system at a pressure of 0.9 MPa. Effect of combustion temperature (1 073-1 273 K) on the formation rules of gaseous products (CO, N₂O and NO) in the O₂/CO₂ combustion process was analyzed by online measurement, and effect of combustion temperature on the physical and chemical structure of combustion residues was analyzed by off-line characterization. In the pressurized combustion process of pulverized coal, the increase of combustion temperature causes the conversion rate of fuel nitrogen to NOx in coal to increase first and then decrease. In the combustion temperature range of 1 073-1 273 K, compared with N2O, the increase of combustion temperature has less effect on NO release, and the conversion of fuel nitrogen in coal to gas-phase NOx is mainly determined by the generation of N2O. In the process of coal pressurized O2/CO2 combustion, the concentrations of CO and NO gradually decrease and increase with combustion temperature, while the release of N2O increases first and then decreases with combustion temperature. At 1 273 K, the emission concentrations of CO, NO and N₂O reach 363.5×10^-6, 10.2×10^-6 and 6.8×10^-6, respectively. The FTIR results show that the oxygen-containing groups of the O—C═O structure on the surface of pulverized coal particles have higher combustion reactivity than C—OH structure. As the combustion temperature increases from 1 073 K to 1 273 K, the relative content of C—O dose not change much, and the relative contents of O—C═O, C═O and C—H decrease by 1%, 1% and 7%, respectively, while the relative content of C═C/C—C increases by 7%. It shows that the increasing pressurized combustion temperature can promote the rapid consumption of the C—H structure, and increase the aromatization of the carbon residues. When the temperature is 1 273 K, the relative content of N elements in the form of N-5 and N-6 on the surface of pulverized coal combustion residues decreases and increases by 7% and 5%, respectively. The main source of NOx nitrogen-containing precursors released during pressurized O2/CO2 combustion is the inherent N-Q structure in coke, and its relative content varies little.

0 引言

1 试验

   1.1 试验样品制备

   1.2 试验分析方法

2 试验结果与讨论

   2.1 温度对燃烧气相产物生成特性的影响

   2.2 温度对燃烧固相产物生成特性的影响

3 结论