Wan Alwi S., Manan Z., Chezghani M., 2014, A Graphical Method for Simultaneous Targeting and Design of Multiple Utility Systems, Chemical Engineering Transactions, 39, 1045-1050.
Utility targeting as well as optimal placement are among the key steps in the design of a cost-effective process utility system. Composite Curves, Grand Composite Curves (GCC) and Balanced Composite Curves are the established graphical tools for targeting and optimal placement of multiple utilities based on the Pinch Analysis technique. Although the composite graphical tools can provide valuable graphical insights and yield acceptable utility targets in terms of loads and levels, they could not pinpoint the exact heat recovery matches between process and utility streams. As a result, these composite graphical tools could not be used to perform heat allocation between the process and the individual utility streams, and for targeting the process-utility surface area targets. This paper presents an extended Stream Temperature versus Enthalpy Plot (STEP) method that is used to simultaneously target the multiple utilities and perform heat allocation between the utilities and the individual process streams. Due to the composite nature of the GCC, targeting involving variable-temperature utilities can yield inaccurate results. A case study has been used to demonstrate how this limitation can be overcome by using the extended STEP method.
