Improving a process's efficiency by exploiting heat pockets in its heat exchange network

On the grand composite curve of a heat exchange network, a heat pocket exists when a local heat source above the pinch point or a local heat sink below the pinch point appears. In this paper, heat recovery in the heat pocket is presented by combining the pinch technology and exergy analysis. When the heat pocket is big, hot streams in the pocket can be used to generate a higher level utility, and the cold streams in the pocket can be heated by a lower level utility. In this way, exergy loss can be reduced, and the process's efficiency can be improved. The heat exchange network of a hydrogen production process is used as a case study. The energy performance of the heat exchange network can be further improved by recovering the heat in the heat pocket, compared with the scheme based only on pinch technology.