The feasibility of power cogeneration through fuel cells using bioethanol with different concentration has been considered. Data and layout have been inspired by an existing unit Helbio, GH2 -BE-5000 (5 kWelectrical + 5 kWthermal) system for combined heat and power generation (CHP). The system is constituted by six reactors connected in series for hydrogen production and purification and by a fuel cell of the mentioned capacity.To evaluate process efficiency and the possibility to operate with diluted bioethanol feed, characterized by lower purification cost, different process layouts have been tested. Particular attention is paid to the intensification of the heat exchange network, to increase the overall plant efficiency. Heat supply to the steam reformer has been accomplished by burning part of the reformate, since diluted ethanol is not suitable to feed the burner as in the experimental process layout.The water/ethanol feeding ratio has been taken as major parameter for simulation. An increase of this variable improved H2 yield due to promotion of the water gas shift reaction and lower impact of the hydrogen-consuming methanation step. However, higher heat input was required by the reformer, implying the delivery of a higher fraction of the reformate to 1 Corresponding author: fax 0039-02-50314300; email ilenia.rossetti@unimi.it the burner instead than to the fuel cell. This means lower electric output and efficiency.However, the presence of a high enthalpy steam exhaust increased the available thermal output, with consequent increase of the thermal and overall efficiency of the plant.Keywords: Bio-ethanol steam reforming; Process simulation; H2 production; Fuel cells.
-INTRODUCTIONIn order to find out alternative routes for the co-generation of heat and power (CHP) from renewable sources, different strategies have been proposed. Among these, H2 production from bioethanol, coupled to fuel cells raised considerable attention in recent years [1][2][3]. In addition, highly innovative solutions for the production of second generation biofuels are becoming available, leading to environmentally, ethically and economically sustainable bioethanol. The economical plan proposed by Biochemtex, for instance, is based on 0.3 euro/L for the production of lignocellulosic anhydrous bioethanol [4].A 250 W system based on authothermal reformer and a fuel cell stack has been studied [5].A minimum amount of process controls and little internal heat integration kept system architecture simple, as required for portable applications, at difference with the presently studied system, in which heat integration was part of the optimization. Indeed, for stationary applications the increase of efficiency is seen as a predominant factor with respect to simplification.A similar system has been proposed, with reformate purification from CO based on preferential oxidation and attention to the control logic and heat integration [6][7][8]. On a completely different scale, the technical feasibility of using existing steam reforming and...
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