(719e) Design of a Sabatier Reactor for CO2 Conversion into Synthetic Methane

Authors: 
Simakov, D., University of Waterloo
Sun, D., University of Waterloo

Design of a
Sabatier reactor for CO2 conversion into synthetic methane

Duo Sun and David Simakov

Department of Chemical
Engineering, University of Waterloo, Waterloo, ON N2L 3G1, Canada

Converting CO2-reach streams
(e.g., biogas, fermentation off-gas, flue gas) into synthetic natural gas (SNG)
via Sabatier reaction (CO2 hydrogenation into CH4) is an
attractive route for CO2 utilization [1-3]. There is a potential to
decrease CO2 emissions significantly and, at the same time, to
reduce the consumption of fossil natural gas. To make the process sustainable,
H2 which is required for this reaction should have zero or very low
carbon footprint. This requirement is achievable if H2 is produced
via water electrolysis using renewable electricity (hydro, wind, solar) or
surplus (e.g., nuclear) electricity. Electrolysis can be done in a highly
efficient way using polymer electrolyte membrane (PEM) electrolyzes [4]. However,
a number of technological issues remain to be resolved, including catalyst deactivation
and thermal management (Sabatier reaction is highly exothermic) [5]. The study
presented herein focuses on the design of a highly efficient and compact
Sabatier reactor for CO2 hydrogenation into synthetic natural gas.

The
general concept is a heat-exchanger type packed bed with active cooling for
efficient heat removal. Compressed air, steam, or molten salt can be used as a
coolant; molten salts are excellent heat transfer fluids due to their high heat
capacity and thermal conductivity [6-9]. To identify the optimal configuration,
we performed numerical simulations, using a transient pseudo-homogeneous model [10].
We searched for optimal operating conditions to maximize methane yield and to
prevent at the same time reactor overheating and catalyst deactivation. We have
identified several configurations that allow highly efficient CO2
hydrogenation, providing CO2 conversions and CH4 yields higher than
90%. A preliminary techno-economic evaluation demonstrates the potential of
this approach for commercialization.

References

[1] Rönsch, S. et al.
Review on methanation – From fundamentals to current projects. Fuel 2016,
166, 276-296.

[2] Schaaf, T. et al. Methanation
of CO2 – storage of renewable energy in a gas distribution system. Energy
Sustain. Soc.
2014, 4, 29.

[3] Götz, M et al.
Renewable Power-to-Gas: A technological and economic review. Renew. Energ.
2016, 85, 1371-1390.

[4] Gahleitner, G. Hydrogen
from renewable electricity: An international review of power-to-gas pilot
plants for stationary applications. Int. J. Hydrogen Energ. 2013, 38,
2039-2061.

[5] Kao, Y.-L.; Lee, P.-H.;
Tseng, Y.-T.; Chien, I.-L.; Ward, J.-D. Design, control and comparison of
fixed-bed methanation reactor systems for the production of substitute natural
gas. J. Taiwan Inst. Chem. Eng. 2014, 45, 2346-2357.

[6] Simakov, D. S. A.;
Wright, M. M.; Ahmed, A.; Mokheimer, E. M. A.; Román-Leshkov, Y. Solar thermal
reforming of natural gas: a review on chemistry, catalysis and system design. Catal.
Sci. Technol.
2015, 5, 1991-2016.

[7] Said, S. A. M.;
Waseeuddin, M.; Simakov, D. S. A. A review on solar reforming systems. Renew.
Sust. Energ. Rev.
2016, 59, 149-159.

[8] Said, S. A. M.; Simakov,
D. S. A.; Mokheimer, E. M. A.; Habib, M. A.; Ahmed, S.; Waseeuddin, M.;
Román-Leshkov, Y. Computational fluid dynamics study of hydrogen generation by
low temperature methane reforming in a membrane reactor. Int. J. Hydrogen
Energ.
2015, 40, 3158-3169.

[9] Said, S. A. M.;
Simakov, D. S. A.; Waseeuddin, M.; Román-Leshkov, Y. Solar molten salt heated
membrane reformer for natural gas upgrading and hydrogen generation: A CFD
model. Sol. Energy 2016, 124, 163-176.

[10] Simakov, D. S. A.;
Sheintuch, M. Design of a thermally balanced membrane reformer for hydrogen
production. AICHE J. 2008, 54, 2735-2750.