Process simulation of hydrogen production by steam reforming of diluted bioethanol solutions : effect of operating parameters on electrical and thermal cogeneration by using fuel cells

The possibility to exploit diluted bioethanol streams is discussed for hydrogen production by steam reforming. An integrated unit constituted by a steam reformer, a hydrogen purification section with high- and low-temperature water gas shift, a methanator reactor and a fuel cell were simulated to achieve residential size cogeneration of 5 kW electrical power + 5 kW thermal power as target output. Process simulation allowed to investigate the effect of the reformer temperature, of bioethanol concentration and of catalyst loading on the temperature and concentration profiles in the steam reformer. The net power output was also calculated on the basis of 27 different operating conditions. Pelectrical output ranging from 3.3 to 6.0 kW were obtained, whereas the total heat output Pthermal, total ranged from 3.9 to 7.2 kW. The highest overall energy output corresponded to Pelectrical = 4.8 kW, PThermal, FC = 3.1 kW, Pheat recovery = 4.1 kW, for a total 12 kW energy output. This was achieved by feeding a mixture with water/ethanol ratio = 11 (mol/mol), irrespectively of the catalyst mass, and setting the ref split temperature so to have an average temperature of 635 °C in the ESR reactor.