This work investigates numerically a catalytic postcombustor for a micro-solid oxide fuel cell (SOFC) system. The postcombustor oxidizes toxic and explosive carbon monoxide (CO) and hydrogen exiting a solid oxide fuel cell to carbon dioxide and water. A single 1 mm diameter monolith reactor channel coated with platinum catalyst is modeled in this work. The inlet stream composition is provided by a semi-analytical 2D model of a detailed SOFC system. The model of the postcombustor includes the 2D axisymmetric Navier–Stokes equations, heat conduction in the channel wall, and a multistep finite-rate mechanism for the surface reactions. It is shown that under the operation conditions considered, the influence of homogeneous (gas phase) reactions can be neglected. The model predicts the expected adiabatic temperatures at the postcombustor outlet correctly and can be used for dimensioning and optimization. Postcombustor performance varies significantly with the choice of the operating parameters of the fuel cell. The most critical molecule at the SOFC outlet is shown to be CO because its depletion is slower than that of H2 for the entire operating range of the SOFC. It can be shown that the postcombustor is able to reduce the level of CO below the toxicity threshold of 25 ppm. Although higher voltages of the fuel cell lead to faster CO conversion in the postcombustor, they also result in a significant increase in wall temperature of the catalyst device. Furthermore, the percentage of SOFC power output used for pump work is lowest for the voltage where the maximum power is reached. For postcombustion the optimal operation point of the SOFC is at the voltage for maximum power of the SOFC system.

1.
Hotz
,
N.
,
Senn
,
S. M.
, and
Poulikakos
,
D.
, 2006, “
Exergy Analysis of a Solid Oxide Fuel Cell Micropowerplant
,”
J. Power Sources
,
158
(
1
), pp.
333
347
. 0378-7753
2.
Stutz
,
M. J.
,
Hotz
,
N.
, and
Poulikakos
,
D.
, 2006, “
Optimization of Methane Reforming in a Microreactor—Effects of Catalyst Loading and Geometry
,”
Chem. Eng. Sci.
,
61
(
12
), pp.
4027
4040
. 0009-2509
3.
Hotz
,
N.
,
Stutz
,
M. J.
,
Loher
,
S.
,
Stark
,
W. J.
, and
Poulikakos
,
D.
, 2007, “
Syngas Production from Butane Using a Flame-Made Rh/Ce0.5Zr0.5O2 Catalyst
,”
Appl. Catal., B
,
73
(
3–4
), pp.
336
344
. 0926-3373
4.
ACGIH
, 1994, “
Threshold Limit Values for Chemical Substances and Physical Agents and Biological Exposure Indices (1994–1995)
,”
American Conference of Governmental Industrial Hygienists
, Cincinnati, OH.
5.
Mortimer
,
C. E.
, 1993,
Chemistry
,
Wadsworth
,
Belmont, CA
.
6.
Hayes
,
R. E.
, and
Kolaczkowski
,
S. T.
, 1997,
Introduction to Catalytic Combustion
,
Gordon and Breach
,
Amsterdam
.
7.
Chao
,
Y. C.
,
Chen
,
G. B.
,
Hsu
,
C. J.
,
Leu
,
T. S.
,
Wu
,
C. Y.
, and
Cheng
,
T. S.
, 2004, “
Operational Characteristics of Catalytic Combustion in a Platinum Microtube
,”
Combust. Sci. Technol.
0010-2202,
176
(
10
), pp.
1755
1777
.
8.
Deutschmann
,
O.
,
Maier
,
L. I.
,
Riedel
,
U.
,
Stroemman
,
A. H.
, and
Dibble
,
R. W.
, 2000, “
Hydrogen Assisted Catalytic Combustion of Methane on Platinum
,”
Catal. Today
0920-5861,
59
(
1–2
), pp.
141
150
.
9.
Raja
,
L. L.
,
Kee
,
R. J.
,
Deutschmann
,
O.
,
Warnatz
,
J.
, and
Schmidt
,
L. D.
, 2000, “
A Critical Evaluation of Navier–Stokes, Boundary-Layer, and Plug-Flow Models of the Flow and Chemistry in a Catalytic-Combustion Monolith
,”
Catal. Today
0920-5861,
59
(
1–2
), pp.
47
60
.
10.
Geus
,
J. W.
, and
van Giezen
,
J. C.
, 1999, “
Monoliths in Catalytic Oxidation
,”
Catal. Today
,
47
(
1–4
), pp.
169
180
. 0920-5861
11.
Stutz
,
M. J.
, and
Poulikakos
,
D.
, 2005, “
Effects of Microreactor Wall Heat Conduction on the Reforming Process of Methane
,”
Chem. Eng. Sci.
,
60
(
24
), pp.
6983
6997
. 0009-2509
12.
Bird
,
R. B.
,
Stewart
,
W. E.
, and
Lightfoot
,
E. N.
, 1960,
Transport Phenomena
,
Wiley
,
New York
.
13.
Chattopadhyay
,
S.
, and
Veser
,
G.
, 2006, “
Heterogeneous-Homogeneous Interactions in Catalytic Microchannel Reactors
,”
AIChE J.
,
52
(
6
), pp.
2217
2229
. 0001-1541
14.
Warnatz
,
J.
,
Allendorf
,
M. D.
,
Kee
,
R. J.
, and
Coltrin
,
M. E.
, 1994, “
A Model of Elementary Chemistry and Fluid-Mechanics in the Combustion of Hydrogen on Platinum Surfaces
,”
Combust. Flame
0010-2180,
96
(
4
), pp.
393
406
.
15.
Smith
,
G. P.
,
Golden
,
D. M.
,
Frenklach
,
M.
,
Moriarty
,
N. W.
,
Eiteneer
,
B.
,
Goldenberg
,
M.
,
Bowman
,
C. T.
,
Hanson
,
R. K.
,
Song
,
S.
,
Gardiner
,
W. C.
, Jr.
,
Lissianski
,
V. V.
, and
Qin
,
Z.
, 2006, Gri-Mech 3.0, http://www.me.berkeley.edu/gri_mech/http://www.me.berkeley.edu/gri_mech/.
16.
Deutschmann
,
O.
,
Schmidt
,
R.
,
Behrendt
,
F.
, and
Warnatz
,
J.
, 1996, “
Numerical Modeling of Catalytic Ignition
,”
Proceedings of the 26th International Symposium on Combustion
, The Combustion Institute, Pittsburgh, PA, pp.
1747
1754
.
17.
Perednis
,
D.
, and
Gauckler
,
L. J.
, 2004, “
Solid Oxide Fuel Cells With Electrolytes Prepared Via Spray Pyrolysis
,”
Solid State Ionics
0167-2738,
166
(
3–4
), pp.
229
239
.
18.
Park
,
S. D.
,
Vohs
,
J. M.
, and
Gorte
,
R. J.
, 2000, “
Direct Oxidation of Hydrocarbons in a Solid-Oxide Fuel Cell
,”
Nature (London)
0028-0836,
404
(
6775
), pp.
265
267
.
19.
Morley
,
C.
, 2005, GASEQ: A Chemical Equilibrium Program for Windows.
20.
Vandoormaal
,
J. P.
, and
Raithby
,
G. D.
, 1984, “
Enhancements of the Simple Method for Predicting Incompressible Fluid-Flows
,”
Numer. Heat Transfer
0149-5720,
7
(
2
), pp.
147
163
.
21.
Kundu
,
P. K.
, and
Cohen
,
I. M.
, 2004,
Fluid Mechanics
,
3rd ed.
,
Elsevier
,
San Diego, CA
, Chap. 9.5.
You do not currently have access to this content.