Environmental Engineering Reference
In-Depth Information
Table 5 RQ factor for
different fuels along with their
respective O/C and H/C ratios
Fuel
O/C
H/C
RQ
Gaseous fuels
Methane
0.00
4.00
0.50
Ethane
0.00
3.00
0.57
Ethylene
0.00
3.00
0.57
Propane
0.00
2.67
0.60
Acetylene
0.00
1.00
0.80
Liquid fuels
Methanol
a
1.00
4.00
0.67
Ethanol
a
0.50
2.99
0.67
Gasoline (C
8
H
18
)
0.00
2.25
0.64
Diesel (C
12
H
23
)
0.00
1.92
0.68
Biodiesel
a
0.10
1.90
0.70
Free fatty acid from peanut oil soap
stock
a
0.07
1.83
0.70
Canola oil
a
0.08
1.63
0.73
Heavy oil
0.01
1.55
0.72
Bio oil (wood pyrolysis)
a
0.50
1.34
0.92
Solid fuels
Softwood (juniper)
a
0.56
1.39
0.94
Hardwood (mesquite)
a
0.58
1.37
0.95
Fibrous (rice straw)
a
0.66
1.33
1.00
Animal based (LAPCDB)
a
0.40
1.26
0.89
WYO coal
0.18
0.70
0.92
TXL coal
0.19
0.68
0.93
a
Renewable fuels
coals RQ = 0.92
0.95) have a RQ factor of
around 0.95. Gaseous and liquid fuels have RQ between 0.50 and 0.80. It is noted
that renewable biomass fuels have slightly higher RQ (e.g., coal with RQ of 0.92
and biomass with RQ of 0.97).
Figure
12
shows the plot for variation of
-
0.93, and animal wastes RQ = 0.92
-
with H/C and O/C ratio of the
fuels. Since HHV
O
2
is constant for most fuels, then for given thermal input, the
O
2
mol consumed will remain the same. Hence, a fuel with higher RQ produces
more CO
2
for same thermal heat input, i.e., more tons of CO
2
per GJ. RQ scaling is
applied only to oxidation processes, for example, RQ tends to
“
RQ
”
for anaerobic
digestion which produces CH
4
and releases CO
2
since no O
2
is consumed. It does
not imply that it has highest global warming potential. Here, the production of CH
4
becomes important. Even in human body, senior people seem to have a higher RQ
compared to young adults (Rizzo et al.
2005
) due to anaerobic digestion in O
2
starved cells.
Using the Boie equation, one can estimate the amount of carbon emissions from
a fuel. Carbon dioxide emitted on a mass basis (g/MJ or kg/GJ) determined for
∞
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