Experimental researches are focused oil the effects of O-2 concentration and sodium carbonate on Selective Non-Catalytic Reduction (SNCR) performance in a tube reactor, and plug flow reactor model and perfectly stirred reactor model in CHEMKIN are adopted to Simulate the reactions processes. It is found that there is a conversion temperature point (CTP), on the two sides of which oxygen performs different effect. Below CTP, which is 1273 K in our experiments, higher NO reduction efficiency can be gained with higher oxygen concentration because more O-2 results in more radicals to drive the reduction chain reactions by speeding Lip the reactions O-2 + H = O + OH and H2O + O = 2OH. At 1473 K without oxygen, 60% of NO reduction H2O can be achieved and a 15 ppm Na2CO3 addition improves it to 90%. In this case the reaction H2O + H = OH + H-2 becomes fast enough to provide the radical Oil Without the aid of O-2 to produce NH2 which reduces NO. And H-2 is the byproduct Of this reaction. Na2CO3 addition shifts the optimal temperature of SNCR 50 K towards lower temperature and more NO is removed in the temperature window. The reactions NaO + H2O = NaOH + OH and NaOH + O = NaO2 + OH and NaOH + M = Na + M + OH offer new pathways to produce Oil radical, which results in more Oil and more NH2 to reduce NO. The promotion effect of Na2CO3, is significant when temperature is lower or O-2 concentration is lower, which means the radicals are insufficient. (C) 2009 The Combustion Institute. Published by Elsevier Inc. All rights reserved,