Efficient Exergy Analysis of Chemical Processes through Process Engineering Software

Abstract

In this work, authors present a simple methodology for computing physical, chemical and total exergies, and the exergy destruction and the exergetic efficiency of simple and complex processes by using the object linking and embedded (OLE) automation by connecting Aspen HYSYS to MS Excel VBA. For this purpose, a simple flowsheet was added to the main one with the same number of streams as that of the components. By introducing all these streams in a mixer and then consecutively conducted to a heater to condition the outlet stream, a separator and a mixer, the VBA application was able to compute the chemical exergy of the different streams of the main flowsheet. To demonstrate the procedure here described seven cases were considered: single streams, a CO2 mixer, a cooler, a distillation column, a reactor, a multiple recirculation process, and different configurations of separating components by distillation, which can be extended to very complex processes. The former was selected to validate the methodology here proposed whereas the rest of cases were used to demonstrate the potential of the tool here developed, which in turn could be used for discriminating among different process alternatives.