| Down-fired boiler,due to its unique furnace structure and coal-fired principle,has played a unique advantage in burning low volatile coal.However,the reserves of this kind of coal in China are huge and the price is low.Therefore,how to use Downfired boiler to achieve more efficient combustion of difficult coal is a problem that relevant scientific research institutions and commercial groups are facing and need to solve.During the application of 600 MW Down-fired boiler with central air swirl burner in a power plant,there are some problems,such as high NOx emission,serious slagging,partial combustion in the boiler,etc The particle volume flow rate and other parameters were measured,and the characteristics and influencing factors of various dynamic characteristics were analyzed.The numerical simulation of different exhaust gas declination angles was carried out,and the influencing factors of different exhaust gas angles on its velocity field,temperature field and NOx emission characteristics were studied.The most favorable exhaust gas declination angle for pulverized coal burnout and the lowest pollutant emission was obtained,It provides a reference for the practical industrial application.The gas-solid two-phase test of a 600 MW Down-fired boiler with central air swirl burner was carried out 15°,25 °,35° The horizontal velocity,horizontal pulsating velocity,vertical velocity,vertical pulsating velocity,particle volume flow rate and other parameters of gas-solid two-phase flow in the furnace under three kinds of exhaust gas percentages of 20%,60% and 100%,and the gas-solid two-phase flow characteristics under different working conditions were analyzed 15°,25°,The declination angle is 25 ° Under the working condition,the vertical pulsation velocity of gas-solid two-phase near the water wall is larger,and the turbulent diffusion in the furnace is stronger.When the airflow on the arch reaches the classified wind area,the angle of exhaust downward is 25 ° The maximum particle volume flow rate is located at the angle of 15 °,45 ° It is obviously close to the water wall.In conclusion,the declination angle of exhaust gas should be set to 25°.When the exhaust angle is set to 25 ° The results show that the heat and mass transfer in the furnace increase when the temperature is high,which is beneficial to burnout.Therefore,the angle of declination should be 25 ° Set the percentage of exhaust gas to 20%.The combustion numerical simulation of the W flame boiler with the central wind swirl burner was carried out,and the flow and combustion characteristics of the600 MW central wind swirl burner Down-fired boiler with the exhaust gas downward inclination angles of 15°,25°,40° and 45° were studied..It is found that when the exhaust gas downward inclination angle is 25° and 35°,the flow field in the furnace is relatively stable and the two sides show strong symmetry.The area of the low oxygen zone is small,which can effectively protect the furnace.When the exhaust gas downward inclination angle is 15°,the reflux effect of the lower part of the cold ash hopper is too strong,causing a large amount of high-temperature gas to be entrained and burned,so that the temperature rises rapidly,the combustion is unstable,partial burning occurs,and the temperature reaches more than 1400 k.Therefore,when the exhaust gas downward inclination angle is 25° and 40°,considering the gas-solid two-phase flow test results and the combustion and NOx emission characteristics of the boiler,the exhaust gas downward inclination angle is selected to be 25°. |
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