Utility-heat exchanger grid diagram: a tool for designing the total site heat exchanger network

Abstract

The world industrial energy consumptions have gained the focus from the sustainability experts. Industrial Energy Efficiency is one of the important aspects that contributed to the energy consumptions. Process Integration using Pinch Analysis is a very well established tool for energy conservation through systematic design methodology of Heat Exchanger Network - HEN. The HEN for heat recovery within a single process is design using the Grid Diagram. The streams temperature and heat duty are the main aspect in design a HEN through Grid Diagram. The hot utility at above Pinch region is typically placed at the highest temperature, while cold utility at below Pinch is located at lowest temperature. Heat Integration is extended for covering multiple processes heat recovery via utility system, known as Total Site Heat Integration. There is a lot of research done on graphical and numerical targeting of the minimum utility requirement for a Total Site (TS) system. Some mathematical models of the TS utility system have been introduced to optimise the TS utility consumption. However, these methodologies have not discussed the heat exchanger arrangements in the TS HEN. The heat exchangers arrangement in a TS system should be able to produce steam at the high temperature, while the hot utility consumption should be placed as low temperature as possible. This design requirement is not the same as the design terminology for Grid Diagram in single process heat integration. In this paper, the Utility-HEN Grid Diagram is introduced for assisting the HEN design for a TS system to maximise the heat recovery using indirect heat transfer. This tool is able to visualise the heat transfer between processes in the TS system. The Utility-HEN Grid Diagram allows the heat exchangers to be designed according to utility temperature. The design process would be very much beneficiated by the Multiple Utility Problem Table Algorithm (MU-PTA) and the Total Site Utility Distribution (TSUD) Table.