OPTIMAL SCHEDULING OF CYCLIC BATCH PROCESSES FOR HEAT INTEGRATION .2.EXTENDED PROBLEMS

Two key simplifying assumptions, made in Part I of this work, are that the heat exchange times are negligible compared with the batch proces sing time and that matches occur between batches of material as they a re transferred from unit to unit. The latter assumption results in cou ntercurrent heat exchanges. In this paper, these assumptions are relax ed and an extension to the formulation developed which accommodates fi nite exchange times as well as heat exchange with batches during their processing. The extended formulation thus addressed multiple heat exc hange modes: countercurrent, cocurrent, and combinations of the two. T he basic mixed integer linear programming formulation is further augme nted to accommodate heat integration across independent cyclically ope rated batch production lines. A solution approach to the resulting lar ge scale MILP formulation is developed based on Benders' decomposition and is demonstrated with a two production line example. Finally, the issue of sharing of heat exchange units across multiple matches and th e related design problem of minimizing the number of multipurpose heat exchange units are discussed. The sharing feature is shown to lead to complex mixed integer nonlinear constraints.