摘要
煤燃烧过程中痕量元素排放的研究已成为燃煤污染中的一个新兴前沿领域。特别是一些易挥发元素或化合物,它们排放进入大气,成为环境污染的一个重要来源。其中最易挥发的痕量元素砷引起人们的广泛关注。选取清水沟煤焦,利用自制的恒温燃烧实验台,研究了5%氧体积分数下煤焦在800,1 000和1200℃燃烧过程中水蒸气对砷释放的影响。通过改变不同停留时间,并进一步探究水蒸气在不同温度、不同粒径下对砷释放特性的影响,得出煤焦燃烧过程中砷释放比例随时间的变化曲线。实验结果表明:水蒸气对煤和煤焦中砷释放的影响是同步的,水蒸气主要是与焦炭发生气化反应促进了煤焦中砷释放进而影响了煤中砷释放;燃烧气氛中水蒸气对煤焦燃烧砷释放具有一定的促进作用,原因是低氧下水蒸气与煤焦发生了气化反应,提高了砷的释放速率并增加最终的释放比例,但促进作用随着水蒸气体积分数的增加逐渐减弱;不同温度下,水蒸气对煤焦燃烧砷释放的促进存在差异,1 000℃下水蒸气对煤焦燃烧砷释放的促进作用较800℃和1200℃下更明显;在同一条件(温度和气氛)下,煤焦粒径越小,砷的最终释放比例越大,且砷释放峰值对应的温度随着粒径的减小向低温区移动;气氛中含20%水蒸气时,煤焦燃烧砷释放的表观活化能和频率因子均大于气氛中不含水蒸气。
The study of trace element emissions has become a new frontier field in coal combustion pollution.Especially some volatile elements or compounds which are discharged into the atmosphere become an important source of environmental pollution.The most volatile trace element arsenic has attracted wide attention.Qingshuigou char was selected for investigating the effect of steam on the release of arsenic in combustion at 800,1 000 and 1 200℃with 5%oxygen concentration in a customized isothermal combustion system.By changing the residence time,and further exploring the influence of steam on the arsenic release characteristics at different tem-peratures and particle sizes,the variation curve of arsenic release ratio with time during coal char combustion was obtained.The results show that the effect of steam on arsenic release from coal and coal char is synchronous,and the gasification reaction between steam and coke promotes arsenic release from coal char and then affects arsenic release from coal char.The presence of steam in the combustion atmosphere can promote the release of arsenic during the coal char combustion.The cause is that the steam reacted with coal char and accelerated the coal com-bustion.The promotion effect decreases with the increase of steam concentration.The promotion effect of steam on the release of arsenic at 1 000℃is more obvious than that at 800 and 1 200℃.Under the same temperature and atmosphere,the smaller the particle size is,the greater the final release ratio of arsenic is.The temperature corre-sponding to the release peak of arsenic will move along the low temperature region with the decrease of particle size.The apparent activation energy and frequency factor of arsenic release with 20%steam are greater than those without steam.
作者
郭辉
王春波
邹潺
邢佳颖
GUO Hui;WANG Chunbo;ZOU Chan;XING Jiaying(School of Energy,Power Engineering and Mechanical Engineering,North China Electric Power University(Baoding),Baoding 071003,China)
出处
《煤炭学报》
EI
CAS
CSCD
北大核心
2019年第6期1899-1905,共7页
Journal of China Coal Society
基金
国家重点研发计划资助项目(2016YFB0600701)
关键词
水蒸气
煤焦燃烧
气化反应
砷释放
steam
coal char combustion
gasification reaction
arsenic release
