摘要
燃煤锅炉运行中氮氧化物(NO_(x))初始排放浓度高,影响其系统运行的经济性。为减少煤粉燃烧NO_x的生成量,从源头控制NO_(x),提出了煤粉富氧部分气化耦合燃烧的低氮燃烧技术思路。煤粉在燃烧器内低过量空气系数和富氧气氛条件下生成强还原性气体,并通过炉膛分级配风实现控制煤粉燃烧初始NO_(x)排放的目的。数值模拟,气相反应模型采用有限速率/涡耗散(FR/ED)模型,考虑了煤粉在气化反应中涉及的反应动力学机理,更适合于煤粉富氧部分气化反应模拟。结果表明:采用氧体积分数为25.9%的富氧气氛时,燃烧器内反应进行程度明显提升,燃烧器内温度由897℃升至1 007℃,燃烧器出口温度由1 255℃升至1 356℃,CO体积分数由5.48%升至7.17%,碳转化率由61.54%升至86.27%。7 MW双锥燃烧器的富氧试验结果验证了数值模拟的结论,燃烧器内采用合适的氧浓度和过量空气系数,可形成强还原性气氛;燃烧器内过量空气系数越低,燃烧器出口CO和CH_4等还原性气体的浓度越高,燃烧器内空气中氧体积分数由21.0%升至28.3%时,燃烧器出口中心处CO体积分数由9.540%提高至20.258%,燃烧器出口NO_(x)生成量为0。工业现场试验结果表明,富氧部分气化和空气分级均能起到降低锅炉NO_(x)初始排放的作用,两者结合低氮效果更好,在富氧比例为28.3%、分级配风比例为41.2%时,锅炉NO_(x)初始排放质量浓度可由546 mg/m^(3)降至159 mg/m~3。
The problem of high initial emission of nitrogen oxides(NO_(x))is common in the operation of coal-fired boilers,which affects the economy of system operation.In order to reduce the amount of NO_(x)generated during pulverized coal combustion from the origin,a new low-NO_(x)combustion technology with oxygen-enriched partial gasification coupled combustion was proposed in this paper.The pulverized coal combustion generates strong reducing gases under the conditions of low excess air coefficient and oxygen-enriched atmosphere.The purpose of controlling the initial NO_(x)emission from pulverized coal combustion was achieved by air-staging technology in the furnace.The FR/ED model was used to simulate the gas phase reaction,which took into account the gasification reaction of pulverized coal.It is more suitable for the simulation of oxygen-enriched partial gasification reaction of pulverized coal.According to the simulation results,when using a 25.9%oxygen-enriched atmosphere,the combustion reactions in the burner was improved sufficiently.The inner temperature and the exit temperature in the burner were increased from 897℃to 1007℃,and from 1255℃to 1356℃,separately,while the CO content was increased from 5.48%to 7.17%,and the carbon conversion rate was increased from 61.54%to 86.27%.The oxygen-enriched experimental results of 7 MW double-cone burner showed a quite good agreement with that of simulation works,strong reducing atmosphere was achieved by proper oxygen content and excessive ratio in the burner,and the lower the excessive ratio,the stronger the reductive gas composition such as CO and CH4 at the burner outlet.When the oxygen content in the air of the burner was increased from 21%to 28.3%,the CO content in the outlet center of the burner was increased from 9.54%to 20.258%,and the NO_(x)production at the outlet of the burner was zero.Industrial experiments showed that,oxygen partial gasification and air-staging can both reduce the initial emission of NO_(x)from boilers,and the combination of the two methods could made a better low-NO_(x)effect.When the oxygen enrichment ratio was 28.3%and the air distribution ratio was 41.2%,the initial emission of NO_(x)from boilers can be reduced from 546 mg/m^(3) to 159 mg/m^(3).
作者
程晓磊
CHENG Xiaolei(China Coal Research Institute Company of Energy Conservation,Beijing 100013,China;State Key Laboratory of Coal Mining and Clean Utilization,Beijing 100013,China;National Energy Technology&Equipment Laboratory of Coal Utilization and Emission Control,Beijing 100013,China)
出处
《煤炭科学技术》
CAS
CSCD
北大核心
2021年第3期215-221,共7页
Coal Science and Technology
基金
中国煤炭科工集团科技创新创业资金专项资助项目(2018-TD-ZD001)
中国煤炭科工集团科技创新创业资金专项资助项目(2019-TD-MS012)。
关键词
煤粉燃烧
低氮燃烧
富氧分级燃烧
NO_x排放控制
pulverized coal conbustion
low-NO_(x)combustion
oxygen enrich and air staging combustion
NO_(x)emission contouing
