Retrofitting Heat Exchanger Networks Based on Simple Pinch Analysis

It has been well-established that the energy and capital costs of a heat exchanger network are both dependent upon the minimum allowable temperature approach Delta T-min. As a result of the rapidly growing oil prices in recent years, there appears to be an urgent need to retrofit the existing "optimal" networks so as to reduce the current utility consumption rates with smaller Delta T-min values. A simple pinch-based approach is proposed here to accomplish this task while keeping additional capital investment to a reasonable level. In particular, every cross-pinch match is removed, and its heat loads on the hot and cold streams are both divided into two according to the pinch temperatures. At either side of the pinch, the divided heat loads on each stream are combined and then matched according to a systematic procedure derived from simple pinch analysis. Two examples are provided to illustrate this procedure.