Energy-economic multi-objective modeling framework for simultaneous multistream heat exchangers and process optimization

Abstract This paper presents a multi-objective modeling framework for simultaneous processheat integration optimization with multistream heat exchangers (MHEXs). The trade-off between operating cost and heat integration of the process is considered. The proposed framework comprises heat recovery of MHEXs, thermodynamics, vapor-liquid equilibrium, and other unit operations of process. The MHEXs model takes advantage of the compact formulation of the multi-M approach (Hui, 2014) to improve solution efficiency. The model is formulated as a mixed-integer nonlinear programming (MINLP) model and applied to an industrial air separation unit (ASU) to demonstrate its effectiveness. Multi-objective optimization is performed to investigate the trade-off between heat recovery of MHEXs and energy consumption of air compressors.