GAS-TURBINE CYCLES WITH SOLID OXIDE FUEL-CELLS .2. A DETAILED STUDY OF A GAS-TURBINE CYCLE WITH AN INTEGRATED INTERNAL REFORMING SOLID OXIDE FUEL-CELL

In conventional energy conversion processes, the fuel combustion is us ually highly irreversible, and is thus responsible for the low overall efficiency of the power generation process. The energy conversion eff iciency can be improved if immediate contact of air and fuel is preven ted. One means to prevent this immediate contact is the use of fuel ce ll technology. Significant research is currently being undertaken to d evelop fuel cells for large-scale power production. High-temperature s olid oxide fuel cells (SOFC) have many features that make them attract ive for utility and industrial applications. However, in view of their high operating temperatures and the incomplete nature of the fuel oxi dation process, such fuel cells must be combined with conventional pow er, generation technology to develop power plant configurations that a re both functional and efficient. Most fuel cell cycles proposed in th e literature use a high-temperature fuel cell running at ambient press ure and a steam bottoming cycle to recover the waste heat generated by the fuel cell. With such cycles, the inherent flexibility and shorter start-up time characteristics of the fuel cell are lost. In Part I of this paper (Harvey and Richter, 1994), a pressurized cycle using a so lid oxide fuel cell and an integrated gas turbine bottoming cycle was presented. The cycle is simpler than most cycles with steam bottoming cycles and more suited to flexible power generation. In this paper, we will discuss this cycle in more detail, with an in-depth discussion o f all cycle component characteristics and losses. In particular, we wi ll make use of the fuel cell's internal fuel reforming capability. The optimal cycle parameters were obtained based on calculations performe d using Aspen Technology's ASPEN PLUS process simulation software and a fuel cell simulator developed by Argonne National Laboratory (Ahmed et al., 1998). The efficiency of the proposed cycle is 68.1 percent. A preliminary economic assessment of the cycle shows that it should com pare favorably with a state-of-the-art combined cycle plant on a cost per MWe basis.