Influence of Coal Reactivity on Carbon Composite Briquette …
77
Fig. 1 Concept of CCB
reaction model in BF. (Color
figure online)
Table 1 Reactions involved in model
No
Reaction
Reaction rate/(mol·m −3 s −1 )
1
3 Fe 2 O 3 (s) + CO(g) =
2 Fe 3 O 4 (s) + CO 2 (g)
R i = 1500
(PCO−PCO 2 /Ki)/(8.314T )
(K i /(k i (1+K i ))
(1 − f i ) 2/3 ) (i = 1,
2, 3)
k 1 = exp(−1.445 − 6038/T )
K 1 = exp(7.255+3720/T )
k 2 = 1.70 exp(2.515 − 4811/T )
K 2 = exp(5.289−4711/T )
k 3 = exp(0.805 − 7385/T )
K 3 = exp(−2.946 + 2744.63/T )
2
Fe 3 O 4 (s) + CO(g) =
3 FeO(s) + CO 2 (g)
3
FeO(s) + CO(g) =
Fe(s) + CO 2 (g)
4
C(s) + CO 2 (g) = 2 CO(g)
R 4 = ρ C,0 k 4 (1− f 4 )
2/3 (P CO2 /1.01 × 10
5 )/M C
k 4 = k 0 exp(−E C /RT ), k 0 = 1500
∂(α P co 2 )
∂t
=
1
r 2
∂
∂r
(r
2 D eff, CO 2 -N 2
∂ P co 2
∂r
) + RT (R 1 + R 2 + R 3 − R 4 )
(1)
∂(α P co )
∂t
=
1
r 2
∂
∂r
(r
2 D eff, CO - N 2
∂ P co
∂r
) + RT (2R 4 − R 1 − R 2 − R 3 )
(2)
where, D eff,CO-N 2 =D CO-N 2 α
2
/
√
3 and D eff,CO 2 -N 2 =D CO 2 -N 2 α
2
/
√
3.
For Eqs. (1, 2), the boundary conditions are Eqs. (3–5) and the initial conditions
are Eq. (6).
r = 0 :
∂ P CO
∂r
= 0,
∂ P CO 2
∂r
= 0.
(3)
r = d/2 : D eff, CO-N 2
∂ P CO
∂r
= (D CO-N 2 (2.0 + 0.6Re
1/2 Sc
1/3
CO-N 2
)/d)(P CO − P CO,BF )
(4)