Page 265 - Advanced thermodynamics for engineers

12.4 DISSOCIATION 253

Dissociation of CO 2
a
a CO 2 5 a CO þ O 2 (12.29)
2
Adding Eqns (12.28) and (12.29) gives

1 a

CO þ þ n O 2 /ð1 aÞCO 2 þ a CO þ þ n O 2 (12.30)
2 2

12.4.2 RICH MIXTURE WITH DISSOCIATION
Equation without dissociation

1
ð1 þ nÞCO þ O 2 / CO 2 þ n CO (12.31)
2
Dissociation of CO 2 (Eqn (12.29))
a
a CO 2 5 a CO þ O 2
2
Total reaction
1 a
ð1 þ nÞCO þ O 2 /ð1 aÞCO 2 þðn þ aÞCO þ O 2 (12.32)
2 2

12.4.3 GENERAL HYDROCARBON REACTION WITH DISSOCIATION
A general hydrocarbon fuel can be defined as C x H y , and this will react with the stoichiometric quantity
of air as shown in the following equation.
y y y

C x H y þ x þ ðO 2 þ 3:76N 2 Þ/xCO 2 þ H 2 O þ 3:76 x þ N 2 (12.33)
4 2 4
The dissociation of the CO 2 and H 2 O can be added in to this equation as
a 1
a 1 CO 2 5 a 1 CO þ O 2 12.29
2
and
a 2
a 2 H 2 O 5 a 2 H 2 þ O 2 (12.34)
2
which gives a general equation with dissociation
y

C x H y þ x þ ðO 2 þ 3:76N 2 Þ
4
y y x y y
/xð1 a 1 ÞCO 2 þ ð1 a 2 ÞH 2 O þ xa 1 CO þ a 2 H 2 þ a 1 þ a 2 O 2 þ 3:76 x þ N 2
2 2 2 4 4
(12.35)