Efficient and ultra-clean use of biogas in the fuel cell - the DFC experience

Abstract

FuelCell Energy, Inc. (FCE) in Danbury, CT, currently offers three types of stationary fuel cell power plants: the DFC300, DFC1500, and DFC3000, rated 300, 1,400, and 2,800 kW, respectively, to operate on methane-rich fuels including renewable biogas. These products use the Direct FuelCell (DFC), which has the distinctive ability to generate electricity directly from a hydrocarbon fuel by reforming it inside the fuel cell and supplying hydrogen for fuel cell reactions. Biogas, which is available from distributed sources, contains 50% to 70% methane depending on the source and is an exceptionally desired fuel for DFC power plants. FCE has placed many biogas units ranging from 250 kW to 2.8 MW around the world, achieving an electricity conversion efficiency of 45% to 49% (LHV). A unique feature of the DFC is that its performance is not impacted by biofuels diluted with CO2 (20% to 50%). In fact, the DFC plants operating on biogas are consistently showing a higher fuel cell conversion efficiency (approximately 0.5% on a normalized basis) compared to pipeline natural gas plants. This is an advantage as removing CO2 from biogas (as is the case with the 'directed biogas') is energy intensive and adds cost. The existing DFC biogas applications focused on wastewater treatment, food processing, and brewery industries where the contaminants are primarily sulfur and siloxanes. FCE has used operational experience with these plants to improve gas supply reliability, understanding of the biogas contaminants, and improvement of removal process effectiveness.