Flexible and Operable Heat Exchanger Networks

This paper presents the application of the proposed model-based methodology in solving integrated process design and control (IPDC) of heat exchanger networks (HENs). Many methods for HENs synthesis have been developed over the past decades, which aim to provide HENs designs that yield a reasonable trade-off between capital and operating costs. However, in most of HENs synthesis activities, the sole consideration in solution derivation is about design cost. Process operational issue especially controllability is frequently not a concern in the process design. As a result, the controllability of a designed HEN may be questionable. Industrial practice has made it clear that process controllability should be considered during process synthesis. The HENs design can be further improved to ensure that the design is more cost efficient and controllable. This can be achieved by developing a new model-based integrated process design and control methodology, which includes cost optimality and controllability aspects at the early HEN design stage. The IPDC for HEN problem is decomposed into four hierarchical sequential stages: (i) target selection, (ii) HEN design analysis, (iii) controllability analysis, and (iv) optimal selection and verification. The set of constraint equations in the IPDC problem for HEN design is decomposed into four sub-problems which correspond to four hierarchical stages. The capability of the proposed methodology in solving IPDC of HEN problem was tested using biomethanol production plant. The results show that the proposed methodology was able to find the best solution which satisfied design, control and economic criteria in easy, efficient and systematic manner.