Optimum Integration of Regeneration in Heat-Integrated Water Networks Through a Hybrid Approach

Heat-integrated water networks facilitate the conservation of energy and water collectively. Heat exchanger units are used to recover thermal energy, and regeneration units are utilized in process industries to improve water utilization. A hybrid algorithm is developed in this paper to optimize water consumption and the throughput of the regeneration unit by minimizing the total annualized costs. In this algorithm, the interactions between water and regeneration and their effect on energy consumption are established through a non-linear programming model, and the heat exchanger requirements for overall thermal integration are targeted through pinch analysis. The notions of pinch analysis are employed in the proposed algorithm to develop heuristics to reduce the energy requirements by enforcing non-isothermal mixing of water streams. The energy and water targeting approach presented in this paper combines the capability of mathematical programming of handling multiple contaminants with the proficiency of pinch analysis to impart physical insights. Two demonstrative examples are solved to establish the significance of the proposed algorithm. In most instances, heat-integrated water networks with lower costs are achieved through this hybrid algorithm compared to literature. It is identified that the installation of regeneration units may reduce the total annualized costs depending on the specific example.