摘要
在一维炉上对煤粉再燃过程中烟气内主要气体体积分数随再燃区初始氧体积分数的变化规律进行了研究.再燃温度为1273 K时,脱硝效率及H2、CO体积分数曲线随再燃区氧体积分数升高均呈不规则"M"型.脱硝效率与H2体积分数出现峰值时的氧体积分数一致,CO体积分数峰值处的氧体积分数高一些.脱硝效率及H2、CO体积分数的第一次下降是由气相着火引起的.氧体积分数进一步上升时,煤焦被气相燃烧热引燃,颗粒温度的大幅跃升促使异相脱硝反应增强,脱硝效率及H2、CO、CH4体积分数再次上升.氧体积分数更高时煤焦燃烧开始受扩散控制,火焰自焦表面外移,颗粒升温趋缓,能够到达焦表面的氧气减少,必须有氧参与的异相还原反应减弱,脱硝效率再次下降.再燃温度更高时,脱硝效率及H2、CO体积分数的变化趋势与1273 K时基本类似,但稍平缓.
The variations of main gas volume fractions with initial oxygen volume fraction during pulverized coal reburning were investigated using a one-dimensional flame furnace. When the temperature in the reburning zone is 1 273 K, with the initial oxygen volume fraction increasing the curves of denitration efficiency, H2 and CO volume fractions are all of irregular ＂M＂ shape. The denitration effciency and H2 volume fraction reach the peak values under the same oxygen volume fraction, while CO volume fraction reaches the peak value under a little bit higher oxygen volume fraction. The first decrease of denitration efffciency, H2 and CO volume fractions is caused by gas phase ignition. With the further increase of oxygen volume fraction, coal char is ignited by combustion heat of gases, char temperature increases markedly, greatly accelerating the heterogeneous denitration, and then denitration efficiency, H2 , CO and CH4 volume fractions begin to increase again. When oxygen volume fraction further increases, char combustion begins to be controlled by diffusion, flames move away from char surface, thus slowing down temperature rising and decreasing oxygen volume fraction on the char surface, there- fore oxygen-assistant heterogeneous denitration reaction is weakened and whole denitration efficiency decreases again. At higher reburning temperatures the variation trends of denitration efficiency, H2 and CO volume fractions are similar to those at 1 273 K, but less obvious.
出处
《燃烧科学与技术》
EI
CAS
CSCD
北大核心
2009年第3期243-248,共6页
Journal of Combustion Science and Technology
基金
国家自然科学基金资助项目(50476018)
国家重点基础研究发展计划(973)资助项目(2006CB200303)
关键词
煤粉再燃
挥发分
着火
异相脱硝
扩散控制
pulverized coal reburning
volatile
ignition
heterogeneous denitration
diffusion-controlled
