Internal and Total Site Water Network Design with Water Mains Using Pinch-Based and Optimization Approaches

Abstract

This work addresses the internal and Total Site Water Network design with water mains. A Material Recovery Pinch Diagram is used for freshwater targeting and a Water Integration Network design with a water main framework, and a mathematical model is formulated for total cost optimization. The Pinch-based method can target an optimum number of water mains, flow rates, and concentrations in the water mains, which can achieve the identified freshwater target. The proposed method can be used for both single and multiple contaminants and applied on both process and total site scales. Two case studies are used to illustrate the application procedure of the proposed method for single- and multiple-contaminant cases. The case study results showed that the optimum number of water mains is three in both single-contaminant and multiple-contaminant Total Site Water Network designs (excluding freshwater and wastewater mains). In the single-contaminant case, the water network of internal integration with three water mains can achieve a total annual cost reduction of 82% compared to direct Water Integration and a total annual cost of 42% in the multiple-contaminant case. The proposed method is beneficial as it provides a graphical interface for the water main targeting and design, and the mathematical optimization enables the selection of optimum options with a minimum cost. To pursue a more accurate design, water piping cost based on real plant locations should be incorporated in future studies.