Advances in Process Integration for Batch Processes: Superstructure-based MINLP Formulation for Synthesis of Heat and Mass Exchange Networks

摘要

The starts and endings of available process streams are time-dependent for semiconsecutive processes. This paper aims at proposing an optimization-based strategy for synthesizing intermittent heat exchange networks (HEN’s) or continuous mass exchange networks (MEN’s) for energy/mass integration in batch plants. For synthesis of intermittent HEN’s, an intermediate fluid is used absorbing surplus heat from hot streams and temporarily stored in storage tanks and then supplying heat to latter cold streams. For synthesis of continuous MEN’s for batch processes, its associated storage policy including the time-dependent operations for collecting process streams into storage vessels/tanks and releasing accumulated material into the continuous MEN’s for subsequent treatment, is considered simultaneously. A periodically partitioned stagewise superstructure is presented for modeling the intermittent HEN’s or continuous MEN’s configurations as well as the time-dependent operations for energy/mass storage. Not using any heuristics that are based on the concepts of pinch limitation, the proposed superstructure-based representation for synthesis of intermittent HEN’s and continuous MEN's for semi-consecutive process is formulated as a mixed-integer nonlinear program (MINLP) for targeting utility consumption or total annual cost (TAC). Several examples are supplied to demonstrate the applicability of the proposed HEN’s or MEN’s synthesis method for semi-consecutive processes.