MOE Key Laboratory of Thermo-Fluid Science and Engineering, Xi’an Jiaotong University

煤粉预热燃烧技术已被证明是一种清洁高效的燃烧技术。针对大型燃煤机组四周空间及承重受限，提出采用结构紧凑的对冲气流床气化炉预热解煤粉并耦合燃烧的技术与系统，搭建了新型气流床气化炉预热燃烧实验台，对煤粉在气化炉内预热特性和预热燃料在燃烧室内燃烧特性进行研究，探索煤中氮元素在预热燃烧过程中的迁移和转化规律。结果表明，新型气流床气化炉预热燃烧实验系统能够自维持稳定运行，系统压力和温度波动很小；气化炉内温度梯度较大，高温区位于烧嘴平面附近，最高温度可达1 115 ℃，而出口温度降至850 ℃。气流床气化炉能够为下行燃烧室稳定提供高温煤气和预热半焦；高温煤气中CO、H2、CH4质量分数(干基)分别可达13.15%、8.72%、0.78%；预热半焦颗粒相比于原煤颗粒粒径减小，原煤50%切割粒径d50=43 μm，而预热半焦颗粒d50=24 μm，预热后颗粒比表面积从4.05 m2/g增到216.44 m2/g，同时，孔容积也增大，颗粒燃烧特性得到改善；预热过程中96.33%的挥发分和40.23%的固定碳释放到高温煤气中；同时，转化到气相中的煤N达69.74%，其中47.67%转化为N2，其余转化为NH3和HCN。预热燃料进入下行燃烧室后能够稳定燃烧，不存在着火延迟，温度分布均匀；主燃区预热燃料中的NH3和HCN，以及焦炭中析出的氮大部分转化为N2，主燃区内没有NO生成。实验台燃烧室出口NOx和CO排放质量浓度分别为143.02 mg/Nm3 (6% O2)和8.17 mg/Nm3 (6% O2)，燃烧效率高达99.75%。煤粉经过新型气流床气化炉预热后燃烧，煤N仅有4.69%转化为NO。

Pulverized coal preheating combustion technology has been proven to be a clean and efficient combustion technology. In view of the limited space and load-bearing capacity around the large coal-fired boiler, a novel technology and system with a compact entrained-flow gasifier to preheat pulverized coal is proposed for the first time. The preheating characteristics in the gasifier and the combustion characteristics of the preheated fuel in the down-fire combustor (DFC) are studied on the novel self-built preheating combustion test rig. The migration and transformation of coal nitrogen during the preheating combustion are investigated. The results show that the experiment system can operate continuously and steadily with small fluctuations in pressure and temperature. The temperature gradient in the gasifier is large, and the high temperature zone is located near the burner plane. The maximum temperature can reach 1 115 ℃, while the outlet temperature of the gasifier decreases to 850 ℃. The high temperature coal gas and char produced by the entrained-flow gasifier are provided to the DFC continuously and steadily. The volume fractions (dry basis) of CO, H2 and CH4 in high temperature coal gas are 13.15%, 8.72% and 0.78%, respectively. Compared to the raw coal, the size of the preheated char decreases. The 50% cut particle size of raw coal is 43 μm, while the preheated semi-coke is 24 μm. The specific surface area increases from 4.05 m2/g to 216.44 m2/g after preheating. At the same time, the pore volume of the char particles increases, and the combustion characteristics are improved. During the preheating process, 96.33% of volatile matter and 40.23% of fixed carbon are released into high temperature coal gas. Also, 69.74% of coal nitrogen is transformed in the gas phase, and 47.67% is converted into N2, the rest into NH3 and HCN. Stable combustion could be achieved with preheated fuels in the DFC with no ignition delay and a uniform temperature distribution. Most of the NH3 and HCN and the nitrogen released from char are converted into N2 in the main combustion zone. There is no NO generation in the main combustion zone. The CO and NOx emissions at the outlet of the DFC are 8.17 mg/Nm3 (6% O2) and 143.02 mg/Nm3 (6% O2), respectively. The combustion efficiency is 99.75%. After the pulverized coal is preheated by the new entrained-flow gasifier and burn in the DFC, only 4.69% of coal N is converted into NO.

国家重点研发计划资助项目(2022YFB4100500)

谭厚章，王肖肖，周必茂，等. 煤粉气流床气化炉预热燃烧特性及NOx排放试验研究[J]. 煤炭学报，2023，48(11)：4192−4204.

TAN Houzhang，WANG Xiaoxiao，ZHOU Bimao，et al. Experimental study on preheating combustion characteristics and NOx emission of pulverized coal based on an entrained-flow gasifier[J]. Journal of China Coal Society，2023，48(11)：4192−4204.