Combined exergy and pinch approach to process analysis

The integration of pinch analysis to the thermodynamic analysis of a process by the exergy load distribution method is demonstrated in the case of a process improvement study. The process used for the illustration of this combined approach is a typical hydrogen production unit by methane reforming. Pinch analysis with energy targeting is used to treat the heat exchanger network as a single unit operation, thus greatly simpifying the graphical representation of the exergy analysis and necessary computations. It is shown that this method of exergy analysis allows the identification of process changes which are likely to produce a desired effect with minimum computational efforts. For the case treated, it is found that a reduction of 15 degrees C of the high temperature shift reactor and a 0.05% purity improvement of the absorber effluent produce a 2% increase in hydrogen yield at the expense of 1.4% of the exportable steam without equipment modifications.