Bioreactor/Fuel Cell Integrated System: Thermal, Electrical and Sizing Issues

摘要

Organic wastes can be efficiently converted into biogas - a mixture of methane, carbon dioxide and small amounts of other gases - in anaerobic digesters, or bioreactors, using anaerobic bacteria digestion. This gas can be collected, separated from other gases and burned directly to produce heat and/or power; it can also be converted into fuels [1]. In the present work, a new approach to energy production from biomass is proposed which involves the integration of anaerobic digesters with solid oxide fuel cells (SOFC). The use of anaerobic digesters combined with fuel cells is thought to result in higher generating efficiencies than traditional combustion engines; however, the technology is still at an early stage of development. The SOFC holds particular promise for use with biogas since its high temperature operation means that the hydrocarbon rich fuel can be processed directly and it is more resilient to many fuel impurities than low temperature fuel cells ([2], [3], [4]). However, the presence of sulphur, even at low levels (ppm), has a negative impact on SOFC performance [5]. Thus, a gas cleanup system to remove H2S is considered. In order to derive the greatest efficiency and performance from the hybridisation of these two technologies, it is important that the relative size of each stage is set such that the fuel requirement of the fuel cell and the thermal requirement of the anaerobic digester are satisfied. Three different system sizes are considered, each representative for a different application: single house, residential block and a municipal facility. For each scale, the system integration and operational issues are examined.