Multi-plant heat integration with shell-and-tube heat exchangers for multi-period operations

Abstract

Multi-period heat exchanger network (HEN) can provide various system configurations for seasonal changes in demands, supplies, and different operation conditions of process streams. Current multi-period heat integration has mainly focused on the single-plant recovery, while a chemical industrial park usually consists of several plants that can be linked together through streams. In this study, multi-period HEN has been extended to a multi-plant scale to recover more waste heat. However, as the drawback of a multi-plant HEN, if an unplanned shutdown happens in one plant, other plants will be influenced due to the connected invalid heat exchangers and resort to extra utilities to reach target temperatures. To overcome this, a heat exchanger network with safety redundancy (HEN-SR) model is established for guaranteeing the continuous operation of remaining plants during an unplanned shutdown. Besides, to meet the industrial application, parameters of the real exchanger design are included, including temperature difference correction factor and the number of shell passes. The optimization results of two cases indicate that the mode switching of multi-period HEN-SR model can avoid huge economic losses caused by plant shutdowns, and the one-step synthesis method using a bi-level optimization strategy can find the HEN configuration with a lower total cost.