Dilute Ethanol Fueled SOFCs: A Symbiotic Solution Strategy

Biofuels have been broached as being more commercially viable under the biorefinery concept wherein multiple product streams enhance overall economics. An example of this concept is presented in which solid oxide fuel cells (SOFCs) and bioethanol are explored in light of the symbiotic pairing of these two promising alternative energy thrusts. Mutual benefit is manifested via dilute ethanol fueled SOFCs. Due to high operating temperatures SOFCs reject high quality heat that can be used for indirect internal reformation of ethanol in the presence of sufficient water. Additionally, carbon monoxide present in hydrogen-rich reformate can be used as a fuel through shift to hydrogen. Thus, the optimization of an additional dilute product stream for SOFC applications can contribute to the realization of the bioethanol infrastructure. This contribution is two-fold. First, across a domain of viable operating conditions the use of dilute ethanol can potentially improve SOFC system performance above cell stack performance and enable distributed SOFC generation fueled by dilute ethanol, providing a secondary market for higher energy ratio bioethanol. Second, integrating in-plant SOFC co-generation fueled by a fraction of dilute ethanol diverted from the process stream is shown to improve the energy ratio of bioethanol. This improvement results from the electricity and by-product heat from the SOFC partially offsetting the energy intensive anhydrous ethanol production.