Experimental study of new flue gas recirculation in pulverized coal industrial boiler
WANG Xuewen
ZHANG Chao
WANG Naiji
WANG Xin
LI Wenxiong
Abstract：As an important means of low nitrogen combustion,flue gas recirculation(FGR)technology is widely used in CFB boilers and chain boilers,but the application of FGR technology has yet to be explored in pulverized coal industrial boilers.With the advancement of energy conservation and emission reduction in the 14th Five-Year Plan,pulverized coal industrial boilers are facing more stringent pollutant emission requirements.The author proposes a new type of flue gas recirculation method for secondary and tertiary air mixed recirculation flue gas,and then coupled with SNCR to explore its combustion characteristics,NOx emission characteristics and coordinated operation ability,in or-der to provide design thinking for low-nitrogen combustion system based on flue gas recirculation and theoretical basis for ultra-low emission transformation of pulverized coal industrial boilers.The flue gas recirculation test was carried out on a 30 t/h pulverized coal industrial boiler.The effects of flue gas recirculation rate and excess oxygen coefficient of pre-combustion chamber on temperature distribution and NOx emission characteristics were analyzed.The combus-tion characteristics of flue gas recirculation staged-air distribution and air staged-air distribution were compared.The results show that under the condition of no air staged-air distribution,the larger the flue gas circulation rate is,the more the temperature decreases,and the maximum temperature at the outlet of the pre-combustion chamber decreases by about 730℃.Compared with the air staged-air distribution condition,the NOx mass concentration is lower under the flue gas recirculation staged-air distribution condition,which is less than 260 mg/Nm3,and the fly ash burnout rate is higher.It can be seen from the comprehensive analysis that the excess oxygen coefficient of the pre-combustion chamber reaches the best 0.7 under the flue gas recirculation staged-air distribution.At this time,the NOx mass con-centration decreases from 553 mg/Nm3 to 150 mg/Nm3 at the boiler outlet,the NOx removal efficiency reaches 73%,and the fly ash burnout rate reaches 94.86%.Compared with the air staged-air distribution condition,the coupling effect of flue gas recirculation staged-air distribution and SNCR is better.Under this condition,the mass concentration of NOx is lower than 60 mg/Nm3.Under the same molar ratio of ammonia nitrogen(NSR),the pollutants are effectively controlled,and the amount of denitrification agent is also significantly reduced.When the excess oxygen coefficient of the pre-combustion chamber is 0.7,the mass concentration of NOx at the outlet of the boiler is 28.24 mg/Nm3,and the urea consumption is reduced from 21.74 to 7.04 kg/h,which is 14.7 kg/h lower than that of the same period.
Keywords：flue gas recirculationpulverized coal industrial boilerflue gas recirculation staged-air distributionflue gas recirculation rateair staged-air distributionexcess oxygen coefficient of pre-combustion chamberfly ash burnout rateremoval efficiency
Publication Date：2025-05-31
Pages：11( 86-96 )