Numerical techniques for determining heat energy targets in pinch analysis

Abstract

A direct and straightforward streamlining of the existing problem table algorithm (PTA) is proposed. An improved algorithm labelled the simple problem table algorithm (SPTA) is developed. The SPTA eliminates the lumping stage in the PTA. The outputs from both the PTA and SPTA are used to generate the grand composite curve (GCC) that is used in determining the heat energy targets (hot and cold utilities and pinch temperature). The close relationship between the GCC and the data composite curves (CCs) has led to the development of CC-based numerical techniques to determine heat energy targets, CCs, and the GCC. The horizontal shift, B, between the CCs is used as an optimization variable in the proposed CC-based numerical techniques. Without the use of temperature shift, two B-based numerical techniques are developed to determine the logical lower and upper bounds on the horizontal shift and their corresponding minimum temperature differentials. A third B-based numerical technique is proposed to determine the corresponding heat energy targets for a given intermediate temperature differential and subjecting the stream characterization data to temperature shift. The proposed approach is different from the conventional one since it starts with the determination of the optimally positioned CCs and then proceeds to determine the energy targets, pinch point location, and GCC. In the conventional approach, PTA is employed first.