Page 241 - Air pollution and greenhouse gases from basic concepts to engineering applications for air emission control

7.7 NO x 217

The overall rate of NO formation from char-bound nitrogen is also described by
Williams et al. [48]

N ½Š char
r NO ¼ r char ð7:83Þ
C ½Š
char
where the reaction rate of char is

2 n
r char ¼ 254 exp 2:16 10 T P ð7:84Þ
0
The analysis above is also applicable to biomass combustion with the following
differences. First of all, most (80 % or more) of the biomass is volatile and there is
little char left. The combustion of char fraction is minor compared to volatile
combustion.

7.7.2 Nitrogen Dioxide

The oxidation of NO leads to the formation of NO 2 through the overall reaction

1
NO þ O 2 $ NO 2
2
ð7:85Þ

6923 1=2
4
¼ 2:5 10 exp atm
K P;NO 2
T
The corresponding step reactions are
NO þ NO þ O 2 $ NO 2 þ NO 2
ð7:86Þ
3 6
ð
k f ¼ 1:2 10 exp 530=TÞ m mol s
NO þ O þ M $ NO 2 þ M
( )
3 6
k f ¼ 1:5 10 exp 940=Tð Þ m mol s ð7:87Þ
10 3
k b ¼ 1:1 10 exp 33;000=Tð Þ m mol s
The conversion of NO to NO 2 can also take place when there are enough
hydrogen peroxide radicals (HO 2 ).
NO þ HO 2 $ NO 2 þ OH
ð7:88Þ
6 3
k f ¼ 2:1 10 exp 240=Tð Þ m mol s