燃煤电厂烟囱排口可凝结颗粒物气-粒转化规律模拟研究

Simulation of Gas-Particle Transformation of Condensable Particulate Matter at Chimney Outlet of Coal-Fired Power Plants

随着燃煤电厂超低排放改造的实行,可凝结颗粒物(CPM)成为烟气治理难点.本文通过烟雾箱系统,系统考察了烟气组分以及相对湿度、紫外线强度等环境因素对SO_(2)、NO_(2)和NH_(3)转化为硫酸根离子(SO_(4)^(2−))和硝酸根离子(NO_(3)^(−))过程的影响.结果表明:①NH_(3)是体系中SO_(4)^(2−)和NO_(3)^(−)浓度增长的重要因素,SO_(2)和NO_(2)可以共同促进SO_(4)^(2−)和NO_(3)^(−)浓度增长.②通过对萃取液中和滤膜上颗粒物的微观分析发现,NH_(3)在颗粒物成核过程中起关键作用;颗粒物中主要元素为N和S,硫酸盐和硝酸盐是颗粒物主要成分.③相对湿度对SO_(4)^(2−)和NO_(3)^(−)的生成有促进作用,高湿条件下SO_(2)^(-)NH_(3)-NO_(2)体系中SO_(4)^(2−)增长率最高为104%,NO_(3)^(−)增长率最高为333%.④在不同强度的紫外线照射下,各反应体系生成的SO_(4)^(2−)与NO_(3)^(−)浓度均随紫外线强度的增大而增加,且光化学氧化对硝酸盐生成的影响大于对硫酸盐的影响.研究显示,烟气组分、相对湿度和紫外线强度等因素都会对可凝结颗粒物气-粒转化过程产生不同程度的影响.

The adoption of ultra-low-emission technologies in coal-fired power plants brings challenges to the treatment of condensable particulate matter(CPM)in flue gas.Although extensive research has focused on the composition distribution and mass measurement of CPM,the formation and transformation of CPM under complex flue gas compositions and environmental conditions are still key areas that require research.The effects of flue gas components,relative humidity,ultraviolet intensity and other environmental factors on the conversion of SO_(2),NO_(2)and NH_(3)into SO_(4)^(2−)and NO_(3)^(−)were studied using flue gas simulation and a smoke box system.The results showed that:(1)NH_(3)substantially contributed to the increase in SO_(4)^(2−)and NO_(3)^(−)concentrations in the system,and SO_(2)and NO_(2)collaboratively contributed to this increase in concentration.(2)Microscopic analysis of particles in the extraction solution and on the filter membrane highlighted the pivotal role of NH_(3)in the nucleation process.It is worth noting that the primary constituents of CPM were N and S,of which sulphate and nitrate were the main components.(3)Relative humidity was identified as a contributing factor to SO_(4)^(2−)and NO3-production.Under high humidity conditions,the SO_(2)^(-)NH_(3)-NO_(2)system exhibited the highest growth rates of SO_(4)^(2−)(104%)and NO_(3)^(−)(333%).(4)Ultraviolet irradiation of different intensities led to an increase in the concentrations of SO_(4)^(2−)and NO_(3)^(−)in different reaction systems,and the photochemical oxidation effect had a greater impact on the formation of nitrate than on the formation of sulphate.Understanding the formation mechanism of CPM and the impact of environmental factors is crucial to developing PM_(2.5)precursor strategies in coal-fired power plants.The study shows that flue gas composition,relative humidity and ultraviolet intensity have different effects on the gas particle transformation process of condensable particulate matter.