A practical approach to heat exchanger network design in a complex natural gas refinery

In this paper, a real-life case study of a complex natural gas refinery has been analyzed using the pinch technology concept, so that heat recovery as well as total hot and cold utilities have been improved for the main process units. This can be done by total heat transfer area and cost targeting, which called supertargeting. Two basic approaches to this analysis were developed, one for all hot and cold process streams simultaneously, without any restrictions and constraints, which was called “overall pinch method”, and the other for five divided areas in the plant, each consisting of some processing units, called “zonal targeting method”. Then the results were compared with each other and the potential of improvements was determined for each case. The result of this study showed that the retrofitted HEN using zonal targeting method improved total energy consumption and heat recoveries dramatically. Also, some modifications have been proposed, using grid diagrams to retrofit the existing HEN, in order to comply with energy recoveries determined from pinch analysis. Off course, this can be done by considering more investment (capital cost) for installation of new heat exchangers, in such a way that the operating costs can be remarkably reduced.