An experimental study of thermal de-NO

x

using NH

3

as reductant in O

2

/CO

2

atmosphere with the effect of SO

2

and different additiveswas performed in a drop tube furnace. Results show that the optimum temperature window is 841-1184℃

and the optimumreaction temperature is about 900℃ with a de-NO

x

efficiency of 95.4%. A certain amount of SO

2

has an inhibiting effect on NO reduction. The effect of additives

including Na

2

CO

3

C

2

H

5

OH and FeCl

3

on NO reduction by NH

3

is also explored. The addition of Na

2

CO

3

and FeCl

3

is useful towiden the temperature window and shift the reaction to lower temperature for the efficiency is increased from 30.5% to 74.0% and 67.4% respectively at 800℃. Qualitatively

the modeling results using a detailed kinetic modeling mechanism represent well most of the process features. The effect of Na

2

CO

3

C

2

H

5

OH and FeCl

3

addition can be reproduced well by the Na

2

CO

3

C

2

H

5

OH and Fe(CO)

5

sub-m

echanism respectively. The reaction mechanism analysis shows that the effects of these additives on NO reduction are achievedmainly by promoting the production of OH radicals at lower temperature.