CONICET | Buscador de Institutos y Recursos Humanos

The development of biofuels has gained much attention in recent years. Thermodynamicanalyses to obtain energy from biofuels using fuel cells were addressed in previousworks for a variety of processes. In those processes, the determination of the bestconditions to achieve high efficiency values in the conversion of chemical energy intoelectrical power is a critical issue from the net global energy efficiency point of view. Inthis regard, a main aspect is to address the energy integration of the whole process. In aprevious paper, the authors dealt with energy integration studies for glycerin- andethanol-based processors coupled to PEM fuel cells resorting on the multi-stream heatexchanger feature provided by the simulation tool HYSYS. In that work, the aim wasto maximize the energy recovery from the process streams that renders the maximumachievable net global efficiency. In this paper, the aim is to synthesize and design theoptimal heat exchangers network (i.e. determination of the process configuration andunits sizes) while maintaining the net global efficiency of the whole system at itsachievable value.Three modifications to the original SYNHEAT model developed in 1990 by Yee andGrossmann for synthesizing heat exchanger networks are proposed in this work aimingat a better problem description, and consequently searching for best problem solutions.First, a modification in computing the minimum approach temperature difference isproposed. Second, the called operation line method is coupled to the SYNHEATmodel to built-up the network superstructure to be optimized. Finally, the SYNHEATmodel‟s hypothesis of constant cp value for modeling heat exchange between processstreams is improved by considering enthalpy variable instead of temperature variable,which is convenient when latent heat is transferred.The model variables number involved in the heat exchanger network synthesis problemssolved has been reduced to less than a half by applying the operation line method.The proposed methodology and modifications made are of general application and notjust for the specific cases addressed in this work.