The combination of fuel cells with conventional mechanical power generation technologies (heat engines) promotes effective transformation of the chemical energy of fuels into electrical work. The implementation of solid oxide fuel cells (SOFCs) within gas turbine systems powered by natural gas (methane) requires an intermediate step of methane conversion to a mixture of hydrogen and carbon monoxide. State-of-the-art Ni-YSZ (yttria-stabilized zirconia) anodes permit methane conversion directly on anode surfaces, and contemporary designs of SOFC stacks allow this reaction to occur at elevated pressures. An exergy analysis of a gas turbine cycle integrated with SOFCs with internal reforming is conducted. As the efficiency of a gas turbine cycle is mainly defined by the maximum temperature at the turbine inlet, this temperature is fixed at 1573K for the analysis. In the cycle considered, the high-temperature gaseous flow from the turbine heats the input flows of natural gas and air, and is used to generate pressurized steam, which is mixed with natural gas at the SOFC stack inlet to facilitate its conversion. This technological design permits avoidance of the generally accepted recirculation of the reaction products around the anodes of SOFCs, which reduces the capacity of the SOFC stack and the entire combined power generation system correspondingly. At the same time, the thermal efficiency of the combined cycle is shown to remain high and reach 65–85% depending on the SOFC stack efficiency. The thermodynamic efficiency of the SOFC stack is defined as the ratio of electrical work generated to the methane oxidized (through the intermediate conversion). For a given design and operating condition of the SOFC stack, an increase in the thermodynamic efficiency of a SOFC is attained by increasing the fuel cell active area. Achieving the highest thermodynamic efficiency of the SOFC stack leads to a significant and nonproportional increase in the stack size and cost. For the proposed steam generating scheme, increasing the load of the SOFC stack is accompanied by a decrease in steam generation, a reduction in the steam to methane ratio at the anode inlet, and an increased possibility of catalyst coking. Accounting for these factors, the range of appropriate operating conditions of the SOFC stack in combination with steam generation within a gas turbine cycle is presented.

1.
Safonov
,
M.
,
Granovskii
,
M.
, and
Pozharskii
,
S.
, 1993, “
Thermodynamical Efficiency of Cogeneration of Electrical Energy and Hydrogen in Gas-Turbine Cycle of Methane Oxidation
,”
Dokl. Akad. Nauk
0869-5652,
328
, pp.
202
204
.
2.
Granovskii
,
M.
,
Safonov
,
M.
, and
Pozharskii
,
S.
, 2002, “
Integrated Scheme of Natural Gas Usage With Minimum Production of Entropy
,”
Can. J. Chem. Eng.
0008-4034,
80
, pp.
998
1001
.
3.
Granovskii
,
M.
, and
Safonov
,
M.
, 2003, “
New Integrated Scheme of the Closed Gas-Turbine Cycle With Synthesis Gas Production
,”
Chem. Eng. Sci.
0009-2509,
58
, pp.
3913
3921
.
4.
Weber
,
A.
,
Sauer
,
B.
,
Muller
,
A.
,
Herbstritt
,
D.
, and
Ivers-Tiffee
,
E.
, 2002, “
Oxydation of H2, CO and Methane in SOFCs With Ni∕YSZ-Cermet Anodes
,”
Solid State Ionics
0167-2738,
152–153
, pp.
543
550
.
5.
Dicks
,
A.
, 1998, “
Advances in Catalysts for Internal Reforming in High Temperature Fuel Cells
,”
J. Power Sources
0378-7753,
71
, pp.
111
122
.
6.
Larminie
,
J.
, and
Dicks
,
A.
, 2003,
Fuel Cell Systems Explained
2 ed.
,
Wiley
,
Chichester
.
7.
Campanari
,
S.
, 2001, “
Thermodynamic Model and Parametric Analysis of a Tubular SOFC Module
,”
J. Power Sources
0378-7753,
92
, pp.
26
34
.
8.
Chan
,
S.
,
Low
,
C.
, and
Ding
,
O.
, 2002, “
Energy and Exergy Analysis of Simple Solid-Oxide Fuel-Cell Power Systems
,”
J. Power Sources
0378-7753,
103
, pp.
188
200
.
9.
Douvartzidis
,
S.
,
Coutelieries
,
F.
, and
Tsiakaras
,
P.
, 2002, “
Exergy Analysis of a Solid Oxide Fuel Cell Power Plant Fed by Either Ethanol or Methane
,”
J. Power Sources
0378-7753,
103
, pp.
188
200
.
10.
Kuchonthara
,
P.
,
Bhattacharya
,
S.
, and
Tsutsumi
,
A.
, 2003, “
Combinations of Solid Oxide Fuel Cell and Several Enhanced Gas Turbine Cycles
,”
J. Power Sources
0378-7753,
124
, pp.
65
75
.
11.
Chan
,
S.
,
Ho
,
H.
, and
Tian
,
Y.
, 2002, “
Modelling of Simple Hybride Solid Oxide Fuel Cell and Gas Turbine Power Plant
,”
J. Power Sources
0378-7753,
109
, pp.
111
120
.
12.
Campanary
,
S.
, 2002, “
Carbon Dioxide Separation From High Temperature Fuel Cell Plants
,”
J. Power Sources
0378-7753,
112
,
273
289
.
13.
Fontell
,
E.
,
Kivisaari
,
T.
,
Hansen
,
J.-B.
, and
Palsson
,
J.
, 2004, “
Conceptual Study of a 250kW Planar SOFC System for CHP Application
,”
J. Power Sources
0378-7753,
131
, pp.
49
56
.
14.
Singhal
,
S.
, 2000, “
Advances in Solid Oxide Fuel Cell Technology
,”
Solid State Ionics
0167-2738,
135
, pp.
305
313
.
15.
Bannister
,
R.
,
Cheruvu
,
N.
,
Little
,
N.
, and
McQuiggan
,
G.
, 1995, “
Development Requirements for an Advanced Gas Turbine System
,”
ASME J. Eng. Gas Turbines Power
0742-4795,
117
, pp.
724
733
.
16.
Kirillin
,
V.
,
Sychev
,
V.
, and
Sheindlin
,
A.
, 1979,
Engineering Thermodynamics
,
Nauka
,
Moscow
.
17.
Hinderink
,
A.
,
Kerkhof
,
F.
,
Lie
,
A.
,
Arons
,
J.
, and
Kooi
,
H.
, 1996, “
Exergy Analysis With a Flowsheeting Simulator—II. Application: Synthesis Gas Production From Natural Gas
,”
Chem. Eng. Sci.
0009-2509,
51
, pp.
4701
4715
.
18.
1987,
Reference Book for Industrial Workers in Ammonia Industry
,
E.
Melnikov
ed.,
Himiya
,
Moscow
.
19.
1981,
Brief Reference Book of Physical and Chemical Values
,
K.
Mischenko
and
A.
Ravdel
. eds.,
Himiya
,
Moscow
.
20.
Hengyong
,
T.
, and
Stimming
,
U.
, 2004, “
Advances, Aging Mechanism and Lifetime in Solid-Oxide Fuel Cells
,”
J. Power Sources
0378-7753,
127
, pp.
284
293
.
21.
Haile
,
S.
, 2003, “
Fuel Cell Materials and Components
,”
Acta Mater.
1359-6454,
51
, pp.
5981
6000
.
22.
Dokiya
,
M.
, 2002, “
SOFC System and Technology
,”
Solid State Ionics
0167-2738,
152–153
, pp.
383
392
.
23.
Williams
,
M.
, 1999,
Status of Solid Oxide Fuel Cell Development and Commercialization in the US. Electrochemical Society Proceedings
,
Pennington, NJ
,
S.
Singhal
and
M.
Dokiya
, eds., Pennington, NJ, PV 99-19, pp.
3
9
.
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