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Research Papers

Syngas Production via High-Temperature Coelectrolysis of Steam and Carbon Dioxide

[+] Author and Article Information
Carl M. Stoots

 Idaho National Laboratory, Idaho Falls, ID 83415-3890carl.stoots@inl.gov

James E. O’Brien, J. Stephen Herring

 Idaho National Laboratory, Idaho Falls, ID 83415-3890

Joseph J. Hartvigsen

 Ceramatec, Inc., Salt Lake City, UT 84119jjh@ceramatec.com

J. Fuel Cell Sci. Technol 6(1), 011014 (Nov 07, 2008) (12 pages) doi:10.1115/1.2971061 History: Received June 12, 2007; Revised January 23, 2008; Published November 07, 2008

This paper presents results of recent experiments on simultaneous high-temperature electrolysis (coelectrolysis) of steam and carbon dioxide using solid-oxide electrolysis cells. Coelectrolysis is complicated by the fact that the reverse shift reaction occurs concurrently with the electrolytic reduction reactions. All reactions must be properly accounted for when evaluating results. Electrochemical performance of the button cells and stacks was evaluated over a range of temperatures, compositions, and flow rates. The apparatus used for these tests is heavily instrumented, with precision mass-flow controllers, online dewpoint and CO2 sensors, and numerous pressure and temperature measurement stations. It also includes a gas chromatograph for analyzing outlet gas compositions. Comparisons of measured compositions to predictions obtained from a chemical equilibrium coelectrolysis model are presented, along with corresponding polarization curves. Results indicate excellent agreement between predicted and measured outlet compositions. Cell area-specific resistance values were found to be similar for steam electrolysis and coelectrolysis. Coelectrolysis significantly increases the yield of syngas over the reverse water gas shift-reaction equilibrium composition. The process appears to be a promising technique for large-scale syngas production.

Copyright © 2009 by American Society of Mechanical Engineers
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References

Figures

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Figure 1

Schematic of INL coelectrolysis test apparatus

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Figure 2

Photograph of the INL coelectrolysis apparatus

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Figure 3

Detail of the button cell

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Figure 4

Ten-cell stack mounted on test fixture on furnace base, ready to test

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Figure 5

Close-up of ten-cell stack, showing intracell thermocouples, voltage leads, and power leads

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Figure 6

Diagram of solid-oxide stack components

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Figure 7

Open-cell potential during heatup, measured and predicted

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Figure 8

Polarization curves and area-specific resistances for sweeps 1–3

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Figure 9

Measured outlet gas compositions with comparisons to the chemical equilibrium model, sweeps 1–3

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Figure 10

Measured outlet dewpoint values, with comparisons to predictions from the chemical equilibrium coelectrolysis model, sweeps 1–3

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Figure 11

Heat-up profiles for stack Nos. 1, 2, and 3 (a, b, and c, respectively)

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Figure 12

Polarization curves for H2O electrolysis, H2O∕CO2 coelectrolysis versus CO2 electrolysis, with mean ASR values

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Figure 13

Internal stack temperature (thermocouple No. 2) for various test conditions

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Figure 14

Effect of varying chemical equilibrium coelectrolysis model equilibrium temperature (Eq. 16) with comparison to test No. 1 experimental data

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Figure 15

Test No. 2 experimental and chemical equilibrium coelectrolysis model results, Teq=800°C

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Figure 16

Test No. 3 experimental and chemical equilibrium coelectrolysis model results, Teq=800°C

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Figure 17

Test No. 4 experimental and chemical equilibrium coelectrolysis model results, Teq=800°C

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Figure 18

Test No. 5 experimental and chemical equilibrium coelectrolysis model results, Teq=800°C

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Figure 19

Test No. 6 experimental and chemical equilibrium coelectrolysis model results, Teq=800°C

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