Environmental Engineering Reference
In-Depth Information
ð
B
k
f
k
;
T
torr
exp
E
k
f
k
¼
ð
1
a
k
Þ¼
exp
t
t
start
;
fixed T
Þ
;
T
¼
T
torr
ð
9
Þ
RT
torr
where B
k
is the
pr
e-exponential rate constant, E
k
the activation energy for the kth
component, and R is the universal gas constant. The overall conversion (F) during
the torrefaction process can be determined from the conversion of each biomass
component (f
k
) using Eq. (
3
).
2.4 Respiratory Quotient (RQ)
Considering a power plant producing a
fixed amount of power, heat input from the
fuel and oxygen consumption for most fuels are
fixed. Hence, a fuel with higher RQ
factor will result in more CO
2
being released into the environment. Fuel chemical
composition can be used to determine the fuel heating value using an empirical
relation given by Boie (Annamalai and Puri
2007
).
HHV
ð
kJ
=
kmol
Þ¼
422
;
270
C
þ
117
;
385
H
177
;
440
O
þ
87
;
985
N
þ
335
;
510
S
ð
10
Þ
where C, H, O, N, and S are the number of carbon, hydrogen, oxygen, nitrogen, and
sulfur atoms, respectively, in the fuel. Stoichiometric oxygen needed for complete
combustion of a C
C
H
H
N
N
O
O
S
S
can be determined from the fuel chemical com-
position using the following relation.
4
2
þ
32
C
þ
S
m
O
2
ð
kg of oxygen/kg of fuel
Þ¼
M
fuel
4
C
2
C
þ
S
C
32
C
1
þ
¼
ð
11
Þ
M
fuel
From Eqs. (
10
) and (
11
), Higher heating value of fuels per kg of stoichiometric
oxygen (HHV
O
2
) can be determined. It was estimated that HHV
O
2
calculated for all
the fuels was around 14,000 kJ/kg O
2
(Annamalai and Puri
2007
; Thanapal
2014
).
Based on the fuel composition, RQ of a particular fuel with C atoms of carbon
which can produce C moles of carbon dioxide can be determined using the fol-
lowing equation.
1
RQ
¼
þ
C
ð
12
Þ
4C
2C
1
þ
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