Thermodynamically guided intensification of separation processes

A method is described to assess the potential of intensification of a finite size steady state separation process. A criterion of performance called power of separation is derived from exergy balance considerations; it characterizes both the quantity and quality of the production yield. Using the endoreversible model based on Finite Time Thermodynamics, one defines an exergy transfer equation with a bilinear dependence on extensive and intensive characteristics of mass and energy flows going through a separation process. This equation allows a specific graphical representation of the power of separation. It is shown that the maximum power of separation is achieved when the thermodynamic efficiency is 50%. This means that half of the exergy rate expended within the process is destroyed due to irreversibility and the other half is transformed into the power of separation. The application of the method is demonstrated for a hydrogen purification process operating out of a methane-hydrogen mixture. Crown Copyright (C) 2006 Published by Elsevier Ltd. All rights reserved.