An MILP model for the simultaneous design of mass and heat networks of a collaborative eco-industrial park
Résumé
Process integration methodologies have greatly addressed the issue of designing optimal
heat and mass recovery networks at the process scale. Lately, with the advent of the
Industrial Ecology concept, the interest for exploring untapped synergies between industrial
sites has arisen to reduce their resources consumption and the operating costs; thus,
forming an eco-industrial park. In such structure, sharing resources can be realized either
directly or indirectly. Companies sometimes choose to integrate streams provided directly
from neighboring industrial partners. Sometimes, for safety reasons or distance between
companies, exchanges must go through intermediate networks.
In this perspective, a new model is presented to design heat and mass recovery networks
between industrial sites on a territorial scale. Based on an MILP model (Ghazouani et al.,
2017) optimizing recovery networks at a process scale, specific concepts are introduced
enabling modeling direct and indirect exchanges between companies (sites, clusters, and
intermediate mass and heat networks). The purpose is to find a collaborative partnership
defined by a global economic objective without taking into account individual economic
strategies.
A case study is developed based on a virtual industrial zone containing three independent
processes found in the literature. In addition, potential interactions with urban water and
heat networks are considered in this case study. Finally, an additional opportunity to use
low grade heat locally via a thermal membrane distillation unit and to transform it into
fresh water is introduced. Since it is cheaper to transport water than heat through intermediate
networks, the model is dealing with a competition for the use of heat and water.
A sequential methodology is proposed consisting of first optimizing individual cluster.
Then, the remaining requirements met by external utilities as well as the wastes not recovered
internally in each cluster are made available to others through the intermediate
networks. These networks are put in competition with local utilities. Overall, despite the
sharp increase in capital costs, the optimal EIP manage to be profitable in many considered
scenarios. The cooling savings are very important in all the cases (more than 80%
of the operating costs). The marginal heat and water costs for the urban networks are
very competitive. This suggests that, in this case of a cooperative relationship between
industrial sites, the sharing and selling of resources and wastes can be profitable.