Study On Gas Temperature Deviation At The Furnace Exit Of A 330MW Tangentially Fired Boiler

Tangentially fired boilers are widely used in China because of their high degree of fullness of the furnace flame,high efficiency of pulverized coal combustion,and uniform heat absorption on the heating surface.With the continuous upgrading of boilers,the problem of tangentially fired boilers has been exposed.Since the influence of the residual swirl of flue gas,causing the flue gas velocity deviation of left and right sides of the furnace exit,the temperature deviation of flue gas is formed.In severe cases,it can cause problems of heat transfer equipment squib.In this paper,a numerical simulation and experimental study of the deviation of the flue gas temperature at the exit of the furnace was carried out for a 330 MW tangentially fired boiler.In order to reduce the deviation of the flue gas temperature,the SOFA nozzle offset method was proposed to weaken the residual swirl of the furnace exit.The research results can be used as a reference for the flue gas temperature deviation in actual tangential fired boiler.Firstly,according to the actual structure of the boiler,reasonable geometric and mathematical models were established to carry out detailed numerical simulation,and compared with the field experimental data for verification,the simulation results were consistent with the experimental results.The results show that,a good tangential combustion is formed in the center of the furnace,the temperature in the center of the furnace is high,and the temperature in the surrounding area is low.As the height of the furnace increases,there is still a certain residual swirl when the flue gas reaches the bottom of the separate screen,which makes the flue gas temperature deviation phenomenon on the left and right sides of the horizontal flue.The problem of flue temperature deviation appears on the lower side of the flue exit section,and the high temperature area is mainly concentrated on the lower right side of the flue.Secondly,the optimized numerical simulation of the flue gas temperature deviation was carried out.The effects of the SOFA yaw angle and air rate on the residual swirl and gas temperature deviation of the furnace exit were carefully studied.The results show that,with the increase of the yaw angle of the SOFA nozzle,the residual swirl of the furnace exit is weakened,and the deviation of the flue gas temperature at the furnace exit is reduced.On the basis of the reverse tangent,if the SOFA flow rate increases,the flue gas temperature at the furnace outlet will be further reduced,the flue gas temperature at the bottom of the screen will rise,and the NOx emission concentration at the furnace exit will decrease significantly.If the SOFA nozzle swings downward,it is beneficial to reduce the deviation of the flue gas temperature at the exit of the furnace and increase the burnout rate of pulverized coal.Finally,an online monitoring system for section temperature field was introduced.Four furnace flame detectors were installed on the section of the boiler.The temperature distribution of the section was calculated by processing the flame radiation image.At the same time,the spectral data collected by the spectrometer was used to calculate the temperature of the flame.The results of the image temperature measurement method and the spectral temperature measurement method were in good agreement.The SOFA nozzle vertical swing angle experiment was carried out using this system.From the results,it can be known that the temperature monitoring system can reflect the flue temperature deviation of the furnace section in real time.