Environmental Engineering Reference
In-Depth Information
Fig. 12 Variation of RQ with
H/C ratio and O/C ratio of the
fuel. Gaseous and liquid fuels
have lower RQ factor when
compared to that of solid
fossil and renewable fuels
(Thanapal
2014
)
2
O
/C
=
0
O
/C = 0.2
O
/C
=
0
.4
O
/C = 0.6
O
/C
=
0
.8
O
/C = 1
C
arb
on
M
o
n
o
xid
e
C
a
r
b
on
Pure Hydrocar bonfuels
Co
a
l
R
i
c
e
st
ra
w
W
oody Biomass (mesquite and juniper)
Glucose
Pr
o
t
ei
n
Ga
s
o
li
n
e
a
n
d
d
i
e
s
el f
u
e
l
s
F
a
t
s
1.5
Ethano
l
Me
t
h
a
ne
M
ethano
l
1
0.5
0
0.5
1
1.5
2
2.5
3
3.5
4
H/C
different fuel compositions is shown in Fig.
13
. Just as Environmental Protection
Agency (EPA) sets limit on NO
x
in lb per mmBTU or kg /GJ, the CO
2
amount must
be estimated in kg per unit GJ or lb per mmBTU rather than kg of CO
2
per kg fuel
since heat input must be maintained the same, when fuel is switched. Both Figs.
12
and
13
follow the same trend in terms of increased emissions with increase in
oxygen content and C/H ratio in the fuel. From results on RQ factor and carbon
dioxide emissions from fuels, it can be seen that the liquid fuels currently used in
automobiles have the least RQ factor next only to natural gas. Biofuels produced
from renewable energy sources are limited by the energy density and oxygen
content.
Fig. 13 Effect of H/C and O/
C on the CO
2
emission from
fuels. Fuels with higher RQ
factor emit higher amounts of
carbon dioxide
O
/C = 0
O
/C = 0.2
O
/C = 0.4
O
/C = 0.6
O
/C = 0.8
O
/C = 1
170
Carbon monox
i
de
160
Carbon
150
W
oody Biomass (
M
esquite and Jun
i
per)
Hydrocarbon fuels
140
Gasoline and diesel
130
Fats
M
ethanol
120
M
ethane
110
Ethanol
100
90
80
70
60
50
0
0.5
1
1.5
2
2.5
3
3.5
4
H/C
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