分级空气高速射流对煤掺氨燃烧中氨预分解与NO_(x)生成影响  

Effect of staged air with a high-speed jet on ammonia pyrolysis and NO_(x)formation in an ammonia-coal co-firing flame

作　　者：余荣浩 徐义书[1] 王华坤 韩金克 谢智成 张凯[1] 刘小伟[1] YU Ronghao;XU Yishu;WANG Huakun;HAN Jinke;XIE Zhicheng;ZHANG Kai;LIU Xiaowei(State Key Laboratory of Coal Combustion and Low Carbon Utilization,Huazhong University of Science and Technology,Wuhan 430074,China;Jxic Energy Tech Research Institute Co.,Ltd.,Nanchang 330096,China)

机构地区：[1]华中科技大学煤燃烧与低碳利用国家重点实验室,湖北武汉430074 [2]江西江投能源技术研究有限公司,江西南昌330096

出　　处：《洁净煤技术》2024年第5期72-84,共13页Clean Coal Technology

基　　金：国家重点研发计划资助项目(2023YFB4005702)。

摘　　要：氨作为零碳清洁燃料,对碳减排有重要作用,但其燃烧过程中NO_(x)生成倾向大。针对煤掺氨燃烧NO_(x)生成控制问题,以某50 kW一维试验炉系统所用旋流燃烧器为原型,提出一种内置高速空气射流阵列结构的新型煤掺氨旋流燃烧器结构,以实现炉内氨预分解后燃烧和分级燃烧。进一步用CFD燃烧数值模拟探究空气分级比、过量空气系数及氨燃料喷口尺寸对氨煤掺烧火焰结构及NO_(x)排放影响,优化新型燃烧器结构及运行参数。结果表明,相比于原型燃烧器,采用空间分散高速三次风射流会导致燃烧区域滞后,加深空气分级,减小主燃烧区域局部过量空气系数,抑制氨过度氧化形成NO_(x),也降低火焰温度峰值,利于抑制热力型NO_(x)产生。同时通过调控总过量空气系数使氨热解发生区域沿炉膛轴向逐渐延伸,火焰前部高温欠氧区增大,促进氨受热预分解为N_(2)和H 2,进一步减少氨中燃料氮直接转化形成NO_(x)。空气分级比20∶22∶58时,NO_(x)生成体积分数由原燃烧器的3309×10^(-6)降至新型燃烧器的1069×10^(-6),降幅达67.69%。增大过量空气系数,或过量空气系数不变、控制一次风率不变而增大三次风率将促进上述效应,进一步减少NO生成。氨管内径变化范围仅考虑5~9 mm,氨喷射速度和分散高速三次风带来的协同效应有待进一步研究。As a zero-carbon clean fuel,ammonia plays an important role in carbon emission reduction,but its tendency of NO_(x)generation during combustion is large.To control NO_(x)formation during ammonia-coal co-firing,an improved ammonia doped cyclone burner structure with a built-in high-speed air jet array structure was proposed using a cyclone burner used in a 50 kW one-dimensional test furnace system as a prototype,in order to realize ammonia pyrolysis before combustion and air-staged combustion in the furnace.CFD combustion numerical simulation was further used to investigate the effects of air staged ratio,excess air coefficient and ammonia fuel nozzle size on the flame structure and NO_(x)emission of ammonia-coal co-firing,and to optimize the structure and operating parameters of the new combustor.The results show that compared with the prototype burner,the use of spatially dispersed high-speed tertiary air jets leads to lagging in the combustion zone,deepens the air staging,reduces the local excess air coefficient in the main combustion zone,and inhibits the excessive oxidation of ammonia to form NO_(x),and also reduces the peak flame temperature,which is conducive to the inhibition of the formation of thermal NO_(x).At the same time,by regulating the total excess air coefficient so that the ammonia pyrolysis occurs along the axial extension of the furnace,the high-temperature under-oxygenized zone in front of the flame increases,to promote the pyrolysis of ammonia into N_(2)and H 2,and further reduce the ammonia direct conversion to form NO_(x).At the air staged ratio of 20∶22∶58,the volume fraction of NO_(x)formed by the prototype burner of 3309×10^(-6) decreases to 1069×10^(-6 )of the improved burner,a reduction of 67.69%.Increasing the excess air coefficient,or keeping the excess air coefficient constant and controlling the primary air ratio constant while increasing the tertiary air ratio will promote the above effect and further reduce NO formation.The variation range of the inner diameter of the ammo

关 键 词：氨掺烧 深度空气分级 氨预分解 高速空气射流 三次风 

分 类 号：TK227.1[动力工程及工程热物理—动力机械及工程]