Biofuels in Engines: Isobutanol
Aaron Carvell, Jason Ferns, Toby Green, Prof. Alison Tomlin
Abstract
Biofuels are fuels derived from biological resources. They can play a part in reducing the effects of global warming by minimising future greenhouse gas emissions. Isobutanol
is one such biofuel with a high potential for greenhouse gas reduction. A full analysis of the potential of Isobutanol for spark ignition engines was considered, comprising a Life
Cycle Analysis (LCA), Chemical Kinetics Modelling and Experimental measurements of the ignition delay within a Rapid Compression Machine.
Introduction
Isobutanol is a biofuel with promising fuel properties and an improved performance compared to other biofuels on the market, such as Biodiesel and Bioethanol [1].
Full combustion properties through experimental and modelling methods to show the viability of isobutanol as a drop-in/replacement for gasoline are yet to be fully
established [2], LCA of the production routes are also in a preliminary phase as the technology transitions from demonstration to commercial stage [3].
Methodology
LCA
Modelling
Experimental
• A field-to-wheel analysis was conducted for
Isobutanol under different scenarios.
• The impact of assumptions [3] and counterfactuals
[4] regarding energy sources and feedstock
type/production was seen through C emissions.
• A closed homogenous batch reactor (CHBR) was
used to model the behaviour of the RCM using
ChemKin Pro.
• Operation conditions with 740<T<910K and
φ=0.5,0.8 & 1 [5].
• A rapid compression
machine was used at φ=1,
850<T<1050K and P=20
bar [6].
Results
Total CO2 emissions per MJ of fuel produced
Isobutanol experimental and simulation data compared to a gasoline surrogate
Sensitivity of combustion initiation of Isobutanol at 770K
T (K)
ic4h9oh+ho2=ic4h8oh1+h2o2
ic4h8oh-1+o2=ic4h8oh-1o2
100
1000
1
1000
1.1
910
1.15
870
1.2
833
1.25
800
1.3
770
1.35
740
1.4
714
1000
iB100, φ=1, P=20 bar (RCM)
iB100 (simulation by OH peak)
iB100 (simulation by max dT/dt)
iB100, φ=1, P=15bar (Weber)
iB100, φ=1, P=30 bar (Weber)
TRF, φ=1 (simulation by OH peak)
ic4h9oh+oh=ic4h8oh-3+h2o
h2o2(+M)=2oh(+M)
50
1.05
952
ic4h8oh-1o2=ic4h7oh-1ooh-3
ic3h7o2=c3h6+ho2
-1
-0.8
-0.6
-0.4
0
-0.2
0
0.2
0.4
0.6
0.8
1
Normalized sensitivity value
ic4h9oh+oh=ic4h8oh-1+h2o
Sensitivity of combustion initiation of Isobutanol at 910K
ic4h9oh+ho2=ic4h8oh1+h2o2
h2o2(+M)=2oh(+M)
-50
100
100
10
10
2ho2=h2o2+o2
Ignition Delay, ms
gCO2/MJ
ic4h8oh-1o2=ic3h6choh+ho2
ic4h8oh-1+o2=ic4h8oh-1o2
ic4h9oh+oh=ic4h8oh-3+h2o
ic4h8oh-3o2=ic4h7oh-3ooh1
ic4h8oh-1o2=ic4h7oh-1ooh3
ic4h9oh+ho2=ic4h8oh2+h2o2
ic4h9oh+oh=ic4h8oh-1+h2o
-100
-1
-150
-0.8
-0.6
-0.4
-0.2
0
0.2
Normalized sensitivity value
0.4
0.6
0.8
1
2ho2=h2o2+o2
1
1.00
1.05
Conclusion
Poor repeatability is observed at low temperature conditions experimentally possibly due to deflagration. Simulations agree with this assertion with
……………………………………….
better
correlation experienced at higher temperatures of 910 K. The effect of energy source and feedstock on life cycle emissions is shown to be
extremely impactful.
References
[1] Durre, P. Fermentative production of butanol--the academic perspective. Curr. Opin. Biotechnol. 22, (2011).
[2] Weber, B.W. and Sung, C.-J. Comparative Autoignition Trends in Butanol Isomers at Elevated Pressure. Energy Fuels 27, (2013).
[3]Tao, L., Tan, E.C.D., McCormick, R., Zhang, M., Aden, A., He, X. & Zigler, B.T. Techno-economic analysis and life-cycle assessment of cellulosic
isobutanol and comparison with cellulosic ethanol and n-butanol. BIOFUEL BIOPROD BIOR. 8, (2013).
[4] Elliot, J., Sharma, B., Best, N., Glotter, M., Dunn, J.B., Foster, I., Miguez, F., Mueller, S. & Wang, M. Environ. Sci. Technol. 48, (2014).
[5] Agbro, E., Tomlin, A.S., Lawes, M., Park, S. & Sarathy, S.M. Fuel. 187, (2017).
[6] Materego, M. Auto-ignition characterisation of synthetic fuels via Rapid Compression Machine. [Manuscript]. At: University of Leeds, Doctor of
Philosophy. (2015).
1.10
1.15
1.20
1000/T (K-1)
1.25
1.30
1.35
1
1.40