Analysis of Control Configuration Changes with Relative Gain Array and Relative Exergy Array for Units in Plants with Recycle

Abstract

Exergy accounts for the quality of energy. The thermodynamic concept of exergy can be used to analysis a process in terms of its efficiency. The Relative Gain Array (RGA) concept is extended into the exergy domain by defining a Relative Exergy Array (REA) by placing the exergy thermodynamic property gain in the place of simple gain. The REA is a new tool that measures the relative exergetic efficiency and controllability of a process. It permits a deeper insight into process control interactions. It can be used for the quick comparison between several process/control structure candidates. But REA results are based on steady state conditions. As mostly processes are dynamic in nature, therefore REA may not be helpful in this dynamic situation. In this paper a new concept of Dynamic Relative Exergy Array (DREA) is proposed to extend the concept of simple REA for dynamic processes. The use of the DREA is illustrated by process simulation case studies.