ECN publication
Solid oxide fuel cell in combination with a gas turbine [ECN-I--95-020]
Published by: Publication date:
ECN 1995
ECN report number: Document type:
ECN-I--95-020 Other
Number of pages: Full text:
102 Download PDF  

The results of an assessment study on the 5 MWe title system aredescribed. The goal of the study is to analyze different configurations of the combination, as described in literature, with special attention for the integration of these two components and the efficiencies that can be achieved. Natural gas is one of the most attractive fuels for fuel cells. The fuel cell system is based on the planar concept of SOFC with a co-flow configuration. Several parameter variations and system options are performed for each configuration in order to have an indication of the effect of these parameters and options on the system performance. Based on the results of these case studies seven 'optimal' options are developed. Finally, an exergy analysis of these options is performed to indicate the exergy losses of the individual components and of the complete system. The following seven options are considered: (1) SOFC combined with a gas turbine used as bottoming cycle and a cathode recycle; (2) An option similar to option 1 with both anode and cathode recycles; (3) An option similar to option 1 but operating at atmospheric pressure; (4) An option similar to option 2 which is operating at atmospheric pressure; (5) SOFC combined with a gas turbine in which the fuel is fed parallel to both components. A cathode recycle is applied in this option; (6) An option similar to option 5 with both anode and cathode recycles; (7) SOFC combined with the commercial version of the Heron gas turbine. The exergy analysis indicates that the highest exergy losses occur respectively in the combustor, fuel cell, steam generation unit, the power turbine and the air compressor. Overall exergy losses decrease when an anode recycle is applied in different configurations. The lowest exergy loss is obtained with the second option of the bottoming configuration. The following aspects will help to minimize the exergy losses and increase the overall exergetic efficiencies: applying an anode recycle; increasing the isentropic efficiency of compressors and turbines; avoiding high temperature differences in heat exchangers; avoiding direct combustion of fuel. 16 figs., 40 tabs., 5 appendices, 22 refs.

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