Convegni ATI - Accesso riservato soci CTI

Autore: F. Calise, M. Dentice d’ Accadia, L. Vanoli, M. R. von Spakovsky

Collana: CA - 60 - Roma 2005

Note:
The detailed synthesis/design optimization of a hybrid Solid Oxide Fuel Cell - Gas Turbine (SOFCGT) power plant is presented in this paper. In the first part of the paper, the bulk-flow model used to simulate the plant is discussed. The off-design performance of the centrifugal compressors and radial turbine is determined using maps, properly scaled in order to match required mass flow rate and pressure ratio values. Compact heat exchangers are simulated using Colburn and friction factor correlations while for the SOFC, the cell voltage versus current density curves (i.e. polarization
curves) are generated on the basis of the Nernst potential and overvoltages due to activation, Ohmic, and concentration losses using the Butler-Volmer, resistivity, and limiting current density equations, respectively. A SOFC configuration with internal reforming through anode re-circulation is chosen in order to avoid the use of an external heat recovery steam generator. Validation of the SOFC polarization curves is accomplished with data available from Siemens-Westinghouse. Both the steammethane
pre-reforming and internal reforming processes are modeled assuming the water-gas shift
reaction to be equilibrium controlled and the de-methanization reactions to be kinetically controlled.
Finally, a thermoeconmic plant and component model is developed by introducing capital cost functions for each plant component. The whole plant is first simulated for a fixed configuration of the most important synthesis/design parameters in order to establish a reference design configuration.
Next a synthesis/design optimization of the plant is carried out using a traditional single-level approach. These results and those for the synthesis/design optimization of the plant in general are presented in this paper.