Flue gas recirculation(FGR) is an important technical mean to improve the safety of circulating fluidized bed(CFB) boiler and reduce the generation of NOx under low-load operation. In the present work

the relationships between temperature distribution of the boiler

NOx

CO mass concentration and O_2 volume fraction of the flue gas at furnace outlet

the combustible matter content of fly ash and bottom slag and the flow rate of FGR under the load of 20%

30% and 40% BMCR(boiler maximum continuous rating) were studied using one-dimensional chamber CFB combustion quasi-static model at a supercritical 350 MW CFB boiler. The results show that both the bed temperature and furnace exit flue gas temperature decrease with the increase of FGR flow rate

which the former decreases less than the latter. The temperature difference between the upper and lower furnace gradually decreases with the increase of FGR flow rate

which is more significantly affected by FGR flow rate at lower loads. The NO_x mass concentration of flue gas at the furnace exit shows a trend of decreasing first and then increasing with the increase of FGR flow rate

and the existence of the optimal FGR flow rate can make the unit operation economically and environmentally friendly. In addition

with the increase of the FGR flow rate

the CO mass concentration at the furnace outlet

combustible matter content of fly ash and bottom slag shows an increasing trend. The FGR significantly reduces the primary air oxygen volume fraction while ensuring that the fluidized air flow rate in the dense phase area is always higher than the protection value

which ensures the operation safety of the boiler under low load furtherly.