烟气再循环对 350 MW CFB 锅炉深调运行特性影响

To solve the problems of fluidization safety and ultra-low NO_x emission of supercritical CFB boiler under ultra-low load,flue gas recirculation technology was introduced. Taking a supercritical 350 MW CFB boiler as the research object,a flue gas recirculation auxiliary peak-shaving system after semi-dry desulfurization was built. Based on the data of field operation,the effects of operating parameters such as the average bed temperature,separator inlet temperature,exhaust temperature,NO_x,CO mass concentration of outlet flue gas,combustible content of fly ash and bottom ash,steam-water parameter at 30%-60% load were studied under the flue gas recirculation. The results show that under the coordination of flue gas recirculation,the final emission of NO_x at 30%-60% load is less than 50 mg/ m³ after SNCR, the original NO_x emission is less than 50 mg/ m³ at 30% load; the bed temperature is reduced by 15-22 ℃,the boiler exit flue temperature increases 10-13 ℃,and the primary and reheat steam temperature is above 558 ℃. With the decrease of boiler load,the carbon content of fly ash and bottom slag increases,and the mass concentration of CO does not increase significantly. The NO_x is reduced about 15 mg/ m³ by SNCR arranged at secondary air; the minimum change rate of load rise/ fall is 1.23% Pe; the boiler keeps dry operation above 30% load,the maximum deviation of water wall temperature is 55 ℃ at 30% load,the maximum deviation of overheated and reheated heating surfaces is 55 and 47 ℃ respectively,and no over-temperature appears.