An axial tangentially swirl low nitrogen burner is designed based on flue gas internal circulation and staged combustion

and the effects of the burner's load

fuel staging

and recycled high-temperature flue gas on combustion and NO_x emission characteristics are studied through industrial experiments and numerical simulations. The results indicate that

the loads and fuel staging ratios have a synergistic effect on NO_x generation.Under medium and low load conditions

the NO_x emissions increase monotonically with the secondary fuel ratio

large amount of NO_x generates in the secondary flame zone. At full load

there exists an optimal primary to secondary fuel ratio(88:12)

which minimizes the NO_x emissions. When the secondary fuel ratio falls below 12%

the primary flame zone becomes dominant in NO_x production. The length of the primary fuel mixing pipe can alter the fuel and air mixing process

thereby affecting NO_x generation. When the relative length of primary fuel mixing pipe is shortened to 0.74

the main combustion zone moves upstream in the furnace

and the main flame is anchored in the middle of the furnace

resulting in a more uniform temperature distribution at the rear of the furnace. The NO_x emission mass concentration decreases by 10%～20% across all loads

all below 30 mg/m3(with O_2 volume fraction of 3.5%

the NO_x is calculated as NO_2).