A Three-Step Method to Improve the Flexibility of Multiperiod Heat Exchanger Networks

Abstract

This paper addresses the design of flexible multiperiod heat exchanger networks (HENs) when the disturbances of operating parameters in subperiods occur. In this work, a three-step method is developed, where a multiperiod HEN synthesis step, a flexibility analysis step, and a subperiod debottlenecking step are involved. In the proposed method, a nominal multiperiod HEN is first determined through the representative subperiod method. The flexibility index of the nominal multiperiod HEN in each subperiod is then analyzed to identify the bottlenecks that restrict the flexibility of the HEN. Finally, a subperiod debottlenecking model is solved to finalize the design of flexible multiperiod HEN. The application of the proposed method is verified through a case study of a multiperiod HEN in a vacuum gas oil (VGO) hydrotreating unit. Results show that the proposed method is effective to obtain a cost-effective multiperiod HEN with sufficient operating flexibility.