Automatic Synthesis of Alternative Heat-Integrated Water-Using Networks

A novel sequential approach is developed in this work to identify alternative heat-integrated WUNs with four mathematical programming models. The proposed synthesis method can be implemented in two stages. In the first stage, the objective is to identify all alternative optimal configurations featuring the minimum freshwater usage, the minimum energy consumption and the minimum total interconnection number respectively. These structures can be determined by solving two distinct models in sequence. The possible WUN designs are identified exhaustively by adopting the 'solution pool' technique provided by Solver CPLEX in GAMS. The HEN designs are then generated in the second stage. From each candidate obtained in the first stage, the stream data can be readily extracted and utilized in the transshipment models for determining the minimum utility usage and the minimum number of heat transfer units. The advantages of this approach are twofold: (1) more than one alternative designs can be found, and (2) all model scales can be kept to manageable levels. A case study is provided in this paper to illustrate the effectiveness of the proposed method.