Gas Turbine Cycles With Solid Oxide Fuel Cells—Part I: Improved Gas Turbine Power Plant Efficiency by Use of Recycled Exhaust Gases and Fuel Cell Technology

The energy conversion efficiency of the combustion process can be improved if immediate contact of fuel and oxygen is prevent4ed and an oxygen carrier is used. In a previous paper (Harvey et al., 1992), a gas turbine cycle was investigated in which part of the exhaust gases are recycled and used as oxygen-carrying components. For the optimized process, a theoretical thermal efficiency of 66.3% was achieved, based on the lower heating value (LHV) of the methane fuel. One means to further improve the exergetic efficiency of a power cycle is to utilize fuel cell technology. Solid oxide fuel cells (SOFC) have many features that make them attractive for utility and industrial applications. In this paper, the authors will therefore consider SOFC technology. In view of their high operating temperatures and the incomplete nature of the fuel oxidation process, fuel cells must be combined with conventional power generation technology to develop power plant configurations that are both functional and efficient. In this paper, the authors will show how monolithic SOFC (MSOFC) technology may be integrated into the previously described gas turbine cycle using recycled exhaust gases as oxygen carriers. An optimized cycle configuration will be presented based upon a detailed cyclemore » analysis performance using Aspen Plus[trademark] process simulation software and a MSOFC fuel cell simulator developed by Argonne National Labs. The optimized cycle achieves a theoretical thermal efficiency of 77.7%, based on the LHV of the fuel.« less