煤粉气流床气化炉预热燃烧特性及NO_(x)排放试验研究  

Experimental study on preheating combustion characteristics and NO_(x) emission of pulverized coal based on an entrained-flow gasifier

作　　者：谭厚章[1] 王肖肖 周必茂 周上坤 王毅斌[1] 王学斌[1] TAN Houzhang;WANG Xiaoxiao;ZHOU Bimao;ZHOU Shangkun;WANG Yibin;WANG Xuebin(MOE Key Laboratory of Thermo-Fluid Science and Engineering,Xi’an Jiaotong University,Xi’an 710049,China)

机构地区：[1]西安交通大学热流科学与工程教育部重点实验室,陕西西安710049

出　　处：《煤炭学报》2023年第11期4192-4204,共13页Journal of China Coal Society

基　　金：国家重点研发计划资助项目(2022YFB4100500)。

摘　　要：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1115℃,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=43μm,而预热半焦颗粒d50=24μm,预热后颗粒比表面积从4.05 m^(2)/g增到216.44 m^(2)/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N_(2),其余转化为NH_(3)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NH_(3)和HCN,以及焦炭中析出的氮大部分转化为N_(2),主燃区内没有NO生成。实验台燃烧室出口NO_(x)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 1115℃,while the outlet temper-ature 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 temperat-ure coal gas are 13.15%,8.72%and 0.78%,respectively.Compared to the raw coal,the size of the preheated char de-creases.The 50%cut particle size of raw coal is 43μm,while the preheated semi-coke is 24μm.The specific surface area increases from 4.05 m^(2)/g to 216.44 m^(2)/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 N_(2),the rest into NH_(3)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 NH_(3)and HCN and the nitrogen re-leased from char are converted into

关 键 词：煤粉 预热燃烧 NOX排放 气流床气化炉 

分 类 号：TK16[动力工程及工程热物理—热能工程]