Optimization of an integrated biomass gasifier-fuel cell system: An experimental study on the cell response to process variations

Coupling biomass gasification with high temperature Solid Oxide Fuel Cells (SOFCs) is a promising solution to increase the share of renewables and raise energy efficiency. Optimal system integration and high durability of its components are both required for this purpose. Moreover, system optimization may ask for a compromise between optimal SOFC operating temperature and system thermal integration. Nevertheless, the producer gas quality and operating temperature have a noticeable impact on SOFC performance, which has to be considered. In order to address the challenges mentioned, this study focuses on experimental investigation of commercial SOFC single cells of industrial size fuelled with different gas mixtures. Namely, typical producer gas compositions from downdraft fixed bed gasification with air (with and without drying) and fluidized bed gasification with steam are considered. In addition to that, the effect of temperature variation is analysed. The results show that, although a higher cell temperature (800°C) and a dry product gas composition lead to higher efficiencies, it is feasible to run the SOFC on wet producer gas at lower cell temperatures (750°C). Despite a decreased efficiency, this would optimize the gasifier-SOFC coupling. Moreover, the presence of water in the producer gas (when drying is not included) reduces the possibility of carbon deposition, thus increasing the cell durability. Therefore, cases with low cell temperatures and presence of water in the gas should be considered as viable alternatives for the system coupling and possible SOFC degradation in such cases is going to be extensively analysed.