FRANCESCONI Javier Andres
Analysis of the energy efficiency of an integrated ethanol processor for PEM fuel cell systems
JAVIER A. FRANCESCONI; MIGUEL C. MUSSATI; ROBERTO O. MATO; PIO A. AGUIRRE
JOURNAL OF POWER SOURCES
Año: 2007 vol. 167 p. 151 - 151
The aim of this work is to investigate the energy integration and determine maximum efficiency of an ethanol processor for hydrogen production and fuel cell operation. Ethanol, which can be produced from renewable feed stocks or agriculture residues, is an attractive option as feed to a fuel processor. The fuel processor investigated is based on steam reforming, followed by high- and low-temperature shift reactors and preferential oxidation, which are coupled to a polymeric fuel cell. The performance of the complete system has been examined for a variety of operating conditions and possible reforming reactions pathways. The main operating variables were determined for those conditions. The endothermic nature of the reformer has a significant effect on the overall system efficiency. The highest energy consumption is demanded by the reforming reactor, the evaporator and re-heater operations. To obtain an efficient integration, the heat exchanged between the reformer outgoing streams of higher thermal level (reforming and combustion gases) and the feed stream should be maximized. Another process variable that affects the process efficiency is the water-to-fuel ratio fed to the reformer. Large amounts of water involve large heat exchangers and the associated heat losses.A net electric efficiency, based on the LHV of ethanol, of approximately 38% was calculated. The responsibilities for the remaining 62% are: dissipation as heat in the PEMFC cooling system (41%), energy in the flue gases (10%) and irreversibilities in compression and expansion of gases. Besides, it has been possible to determine the self-sufficient limit conditions and analyze the effect of: input temperatures of the clean-up system reactors, combustion preheating, expander unit and crude ethanol as fuel, over the net efficiency.