This report summarizes recent progress on a DOE-supported program to construct computer models for potential future combined coal gasification/fuel cell power generation systems. The approach is to develop physically well-founded descriptions for the performance of both molten carbonate fuel cells and coal gasifiers, and to utilize the models to prepare performance maps for each device, enabling selection of the optimum interfaces between fuel cells and gasifiers. In a previous phase of the study, we identified entrained flow gasification as the most appropriate type for providing fuel cell feed gas, on the basis of off-gas composition and the ability to handle a wide range of coal types. Accordingly, a substantial portion of the current effort is concerned with the development of a computer model for entrained flow gasifiers. Furthermore, several scaling laws have been developed for fuel cell performance. Mostly based on equilibrium (open-circuit) considerations to date, these address such issues as the requirements for avoiding carbon deposition, the potential effects of methane conversion, and the distribution of heat sources and sinks within the cell.

Integrated gasification fuel cell (IGFC) systems that combine coal gasification and solid oxide fuel cells (SOFC) are promising for highly efficient and environmentally friendly utilization of coal for power production. In this work, a dimensional finite volume model for planar SOFC has been developed for IGFC system design and analysis. The model can simulate SOFC overall performance and detailed internal profiles of species mole fractions, temperature, current density, and electrochemical losses. The model is capable of supporting recent SOFC improvements, including anode-supported design, the use of metallic interconnects, and reduced polarization losses. Sensitivity analysis is conducted to identify activation polarization parameters appropriate for modern SOFC modeling. The model is verified using literature available data and compared with state-of-the-art SOFC experimental data. Model results are shown for SOFC operation on humidified H2 and CH4-containing syngas, under co-, counter- or cross-flow configurations. The effects of fuel compositions and flow configurations on SOFC performance and thermal profiles are evaluated, and the implications of these results for system design and analysis are discussed. Innovative IGFC designs are analyzed in Aspen Plus first by employing a non-dimensional SOFC model. The sensitivity of IGFC thermal performance on the extent of carbon capture is also investigated. The most promising system identified consists of catalytic hydro-gasification, low-temperature gas cleaning, a hybrid fuel cell-gas turbine power block, and uniquely features recycling of the de-carbonized, humidified anode exhaust back to the hydro-gasifier. This system serves as a "baseline" case in the following work. The developed dimensional SOFC model is linked with Aspen Plus and employed for IGFC system analysis. The results further confirm the necessity of employing a dimensional SOFC model in IGFC design. To maintain the SOFC internal temperature within a safe operating range, the required cooling air flow rate is much larger than predicted by the non-dimensional SOFC model, which results in a large air compressor load and severely reduces the system efficiency. Options to mitigate the problem and improve IGFC performance are investigated and a design with staged SOFC stacks and cascading air flow can achieve a system efficiency of close to that of the baseline case.