17. The Role of Process Integration in the Nexus Energy-Water

Water and energy are two categories of resources which are fundamental for all human activities in general. In the context of end-use sectors, these are in general present in all sites (for instance, in the case of process industry, all plants possess a determinate number of water-using and energy-using processes). The research on all potential interdependencies possible to be established between water and energy resources, as encompassed by the concept of water-energy nexus, is relevant for the understanding of the improvement of the use of both these resources. A commonly implemented concept for the assessment and performance of the improvement of the use of several categories of resources in a determinate site has been process integration. Similarly to the concept of water-energy nexus, it deals with potential interdependencies between several resources, in this case with all potential interconnections between existing processes established by material and energy stream recirculation. The application of process integration principles to the case of the improvement of water and energy resource use in a simultaneous manner is thus significant of the promotion of the water-energy nexus character of a determinate site. In this chapter, it is performed and exploitation of the role of process integration in the context of the water-energy nexus, by exploiting several existing methodologies, with a particular focus being given to innovative paradigm of Water and Energy Integration Systems (WEIS) and its digital twin-based counterpart, designated as ThermWatt.