Multiobjective Optimization of Interplant Heat Exchanger Networks Considering Utility Steam Supply and Various Locations of Interplant Steam Generation/Utilization

A multiobjective optimization (MOO) framework considering the dual objectives of the economy and the environment is presented in this work for the extended integration of interplant heat exchanger networks (HENs) and the shared utility system. Herein, the HENs of enterprises are integrated by allowing process streams to produce steam and using the steam as an intermediate fluid for cross-plant heat recovery, offsetting the utility steam supply in terms of interplant cooperative utilization of energy. The resultant new issues associated with steam generation (which and where), utilization (which and where), and the management of utility systems are addressed within the optimal design of the overall system by taking into account various possibilities. The framework is modeled as a mixed-integer nonlinear programming that accounts simultaneously for the minimum total annualized cost and the minimum environmental impact. A case with five specified scenarios is studied to demonstrate the benefit of structural extension and the conflict of the two objectives. Finally, the MOO problem is solved with Pareto solutions obtained, revealing the impact of network structure on the economy and the environment, which is more specific than a simple trade-off between energy consumption and equipment investment or a trade-off between different fuel sources.