烟气再循环对大型循环流化床锅炉低负荷运行特性的影响研究  

Influence of flue gas recirculation on operation characteristics of large scale CFB boiler under low load

作　　者：元泽民 柯希玮 黄中[1] 杨云凯 武广剑 刘青[1] 马素霞[2] 程亮 赵振宁 YUAN Zemin;KE Xiwei;HUANG Zhong;YANG Yunkai;WU Guangjian;LIU Qing;MA Suxia;CHENG Liang;ZHAO Zhenning(Department of Energy and Power Engineering,Tsinghua University,Beijing 100084,China;College of Electric and Power Engineering,Taiyuan University of Technology,Taiyuan 030024,China;Jinneng Datuhe Power Plant Co.,Ltd.,Lvliang 033000,China;State Grid Jibei Electric Power Research Institute,Beijing 100054,China)

机构地区：[1]清华大学能源与动力工程系,北京100084 [2]太原理工大学电气与动力工程学院,山西太原030024 [3]晋能大土河热电有限公司,山西吕梁033000 [4]国网冀北电力有限公司电力科学研究院,北京100054

出　　处：《热力发电》2023年第9期58-64,共7页Thermal Power Generation

基　　金：国家重点研发计划项目(2022YFB4100301);国网冀北电力公司科技资助项目(SGTYHT/21-HS-225)。

摘　　要：烟气再循环(flue gas recirculation,FGR)是提高循环流化床(circulating fluidized bed,CFB)锅炉低负荷运行安全性、减少NOx原始生成的重要技术手段。以某电厂超临界350 MW CFB锅炉为研究对象,采用一维小室CFB燃烧准静态数学模型研究了该锅炉在20%、30%、40%BMCR(最大连续负荷)下炉内温度分布,炉膛出口烟气NOx、CO质量浓度,O2体积分数,飞灰底渣可燃物含量等性能指标与FGR流量之间的关系。结果表明:床层温度、炉膛出口温度均随FGR流量的增加而降低,床层温度相对炉膛出口温度降低幅度较大,炉膛上下温差随FGR流量的增加逐渐缩小,较低负荷时炉膛上下温差受FGR影响更为显著;炉膛出口烟气NOx质量浓度随FGR流量的增加呈现先降低再升高的趋势,存在最优FGR流量可使机组经济环保运行;随FGR流量的增加,炉膛出口烟气CO质量浓度、飞灰及底渣可燃物含量均呈现增加趋势;FGR的投入在显著降低一次风氧含量同时,保证密相区流化风量始终高于保护值,进一步保障了低负荷下锅炉运行安全性。Flue gas recirculation(FGR)is an important technical mean to improve the safety of circulating fluidized bed(CFB)boiler and reduce the generation of NOx under low-load operation.In the present work,the relationships between temperature distribution of the boiler,NOx,CO mass concentration and O2 volume fraction of the flue gas at furnace outlet,the combustible matter content of fly ash and bottom slag and the flow rate of FGR under the load of 20%,30%and 40%BMCR(boiler maximum continuous rating)were studied using one-dimensional chamber CFB combustion quasi-static model at a supercritical 350 MW CFB boiler.The results show that both the bed temperature and furnace exit flue gas temperature decrease with the increase of FGR flow rate,which the former decreases less than the latter.The temperature difference between the upper and lower furnace gradually decreases with the increase of FGR flow rate,which is more significantly affected by FGR flow rate at lower loads.The NOx mass concentration of flue gas at the furnace exit shows a trend of decreasing first and then increasing with the increase of FGR flow rate,and the existence of the optimal FGR flow rate can make the unit operation economically and environmentally friendly.In addition,with the increase of the FGR flow rate,the CO mass concentration at the furnace outlet,combustible matter content of fly ash and bottom slag shows an increasing trend.The FGR significantly reduces the primary air oxygen volume fraction while ensuring that the fluidized air flow rate in the dense phase area is always higher than the protection value,which ensures the operation safety of the boiler under low load furtherly.

关 键 词：循环流化床锅炉 低负荷 烟气再循环 一维小室CFB燃烧模型 锅炉运行特性 

分 类 号：TM621.2[电气工程—电力系统及自动化]