摘要
针对某75 t/h四角切圆煤粉电站锅炉采用深度空气分级脱硝后带来的CO浓度提升问题,提出了高风速燃尽风射流对NO_(x)与CO协同控制的方法.使用计算流体力学(CFD)数值模拟方法,研究了该技术的工作原理以及对火焰燃烧特性的影响.研究结果表明:①对传统空气分级,燃尽风风率从20%增加到40%时,锅炉出口NO_(x)质量浓度从450 mg/m^(3)降低到263 mg/m^(3),同时折烟角处CO质量浓度从15.5 mg/m^(3)增加到428.3 mg/m^(3);②采用高速燃尽风,燃尽风风率为40%,风速提高至82 m/s,可以保证NO_(x)与CO同时有效控制;③高风速对CO燃尽的原因,归因于在炉内形成一个大回流区,此处有氧浓度高、停留时间长、湍流强度高等特点,这些都促进了CO燃尽,模拟也表明高风速燃尽风喷射不影响炉内煤粉燃烧过程.该新工艺的提出与数值模拟研究,对深度空气分级脱硝与CO同时控制的工业应用有一定理论指导意义.
The deeper air staging in a furnace helps control NO_(x) emission but also results in the increase of CO concentration at the furnace outlet.Therefore,high-speed separated over-fire air(SOFA)injecting is put forward to decrease both NO_(x) and CO emissions.A CFD modeling was conducted on a 75 t/h tangentially pulverized-coal-fired furnace to clarify its mechanism and its influence on combustion characteristics.The conclusions are as follows.First,with the SOFA ratio is enhanced from 20%to 40%,the NO_(x) emission decreases from 450 to 263 mg/m3,and the CO concentration rises from 15.5 to 428.3 mg/m3 at the smoke deflecting corner.Second,in the case of higher-speed SOFA injecting,i.e.,the blowing velocity of 82 m/s and SOFA ratio of 40%,the reduction of both NO_(x) and CO emissions can be guaranteed.Third,the influence of the new approach on accelerating CO burnout is due to a large reflux zone formed beneath the SOFA layer,with characteristics of a higher oxygen concentration,a longer residence time and a higher turbulence intensity of flue gas.This modeling also shows that the combustion process of pulverized coal is not impacted by higher-speed SOFA injecting.This study gives a new understanding of the control of both NO_(x) and CO emissions in industrial applications.
作者
张健
刘毅成
刘薇
马倩慧
白昊
张忠孝
Zhang Jian;Liu Yicheng;Liu Wei;Ma Qianhui;Bai Hao;Zhang Zhongxiao(School of Environment and Architecture,University of Shanghai for Science and Technology,Shanghai 200093,China;School of Mechanical Engineering,Shanghai Jiao Tong University,Shanghai 200240,China)
出处
《燃烧科学与技术》
CAS
CSCD
北大核心
2021年第5期507-513,共7页
Journal of Combustion Science and Technology
基金
国家重点研发计划资助项目(2018YFB0604202).
关键词
空气分级
数值模拟
燃尽风
NO_(x)
CO燃尽
air staging
numerical simulation
separated over-fire air(SOFA)
NO_(x)
CO burnout
