烟气再循环的综合性能模拟研究与评价

Comprehensive performance simulation and evaluation of flue gas recirculation

目前燃气锅炉多采用烟气再循环降氮技术。为了深入探析烟气再循环技术的降氮效果与燃烧特性,利用CHEMKIN分析不同再循环率对NO生成的影响及其主要生成路径分析;利用FLUENT研究不同再循环率对炉内燃烧速度场、温度场和浓度场的影响;从不同角度对烟气再循环技术进行分析并给出综合评价。结果表明:25%再循环率时,NO质量浓度仅为19.26 mg/m^(3),降低了89.79%。18%再循环率时,排烟中CO质量浓度最低,约为150 mg/m^(3)。炉内燃烧温度可从1927℃下降至1595℃,N_(2)直接转化为热力型NO的反应路径占比大幅降低,仅为29.14%。燃气锅炉随再循环率的提升呈现出低NO排放以及低锅炉效率的趋势。

Currently,flue gas recirculation technology is widely used in gas boilers for nitrogen oxide reduction.In order to thoroughly analyze the denitration effect and combustion characteristics of flue gas recirculation technology,the impact of different recirculation rates on NO generation and the main generation pathways were analyzed using CHEMKIN.FLUENT was used to study the effect of different recirculation rates on the combustion velocity field,temperature field,and concentration field inside the furnace.An analysis and comprehensive evaluation of flue gas recirculation technology were conducted from different perspectives.The results show that at a recycling rate of 25%,the NO content is only 19.26 mg/m^(3),a decrease of 89.79%.When the recirculation rate is 18%,the CO mass concentration in the exhaust gas is the lowest,about 150 mg/m^(3).The combustion temperature inside the furnace decreases from 1927℃to 1595℃.And the proportion of the reaction pathway for direct conversion of N_(2)to thermal NO is significantly reduced,only 29.14%.Gas boilers show a trend of low NO emission and low boiler efficiency with the increase of recirculation rate.