Abstract: Aiming at increasingly stringent emission standards of coal-fired industrial boilers,a novel low-NO_x swirl burner was proposedin this paper. The pulverized coal preheating was coupled with the air staging of burner and furnace,and the pulverized coal preheating combustion state was adjusted by changing the air distribution of the combustion system. The effects of primary air rate,inner and outersecondary air rate,outer secondary air injection method,recirculating flue gas rate and over fire air(OFA) rate on NO_x emissions werestudied. The results show that with the increase of primary air rate from 15.4% to 28.7% in the experimental conditions,the oxygen con-centration in the preheating chamber increases,and N which is present in nitrogen-containing compounds HCN,NH_3,etc. in the vola-tile matter from the pyrolysis of pulverized coal is directly oxidized to NO by the oxygen carried by primary air,resulting in increasing NO_x formation from 284.4 mg/m~3 to 326.7 mg/m~3. When the ratio of internal and external secondary air increases from 0.46 to 1.4,the NO_x emission concentration decreases first and then increases. The inner secondary air volume affects the excess air ratio and turbulence inten-sity in the preheating chamber,and the outer secondary air volume affects the turbulence intensity of pulverized coal combustion reaction inthe primary combustion zone inside the furnace. Due to the combined effects of changes in secondary air distribution,the lowest NO_x emission value is 211.2 mg/m~3 when the ratio of inner and outer secondary air is 1.0. As the ratio of the air volume injected from the inside ofthe preheating chamber to injected from the end face of the preheating chamber of the outer secondary air increases from 0 to 4.56,the NO_x formation concentration reduces first and then increases. The outer secondary air injected from the end face of the preheating chamber has alonger injection boundary,which makes the primary combustion zone relatively larger and the overall combustion is relatively uniform.Whereas,the outer secondary air injected from the inside of the preheating chamber promotes the mixing of preheating products at the outletof the precombustion chamber with combustion air in the furnace. When the inside/end face injection air ratio of the outer secondary air is 0.25,the turbulence intensity of pulverized coal in the outlet area of the preheating chamber is improved,and the NO_x formation has a minimum value of 230.9 mg/m~3 in a partially reducing atmosphere. As the recirculating flue gas rate increases from 0 to 30.6%,the oxy-gen concentration in the inner and outer secondary air decreases,which makes the reducing atmosphere in the preheating chamber and theprimary combustion zone enhanced. The probability that N which is present in nitrogen-containing compounds HCN,NH3,etc. in the volatile matter reacts to form N_2 increases,and NO_x emission gradually decreases from 250.7 mg/m~3 to 221.1 mg/m~3. As the OFA rate increa-ses from 0 to 29%,the NO_x emission value decreases first and then increases. With the increase of the OFA rate,the secondary air rate de-creases,and the turbulence diffusion capacity of the inner and outer secondary air is weakened,meanwhile,the reducing atmosphere in theprimary combustion zone is enhanced. The further increase of the OFA rate makes the oxygen content in the primary combustion zone insuf-ficient,and the oxidizing atmosphere in the burnout zone is strong. At this time,a large amount of coke and nitrogen-containing compoundsundergo oxidation reactions in the burnout zone,resulting in the increase in the NO_x formation. When the OFA rate is 19.6%,the lowest NO_x emission value is 253.5 mg/m~3. Overall,When the primary air rate is 17%-19%,the inner and outer secondary air ratio is 0.8-1.0,the outer secondary air is injected from the end face of the preheating chamber,the recirculating flue gas rate is 15%-20%,and the OFArate is 19%-22%,the NO_x emission value is 212-231 mg/m~3,which is 29%-35% lower than the maximum NO_x emissions in the experi-mental conditions.