Minimizing water and energy consumptions in water and heat exchange networks.

This study presents a mathematical programming formulation for the design of water and heat exchangers networks based on a two-step methodology. First, an MILP (mixed integer linear programming) procedure is used to solve the water and energy allocation problem regarding several objectives. The first step of the design method involves four criteria to be taken into account., ie, fresh water consumption (F1), energy consumption (F2), interconnection number (F3) and number of heat exchangers (F4). The multiobjective optimization Min [F1, F2] is solved by the so-called ɛ-constraint method and leads to several Pareto fronts for fixed numbers of connections and heat exchangers. The second step consists in improving the best results of the first phase with energy integration into the water network. This stage is solved by an MINLP procedure in order to minimize an objective cost function. Two examples reported in the dedicated literature serve as test bench cases to apply the proposed two-step approach. The results show that the simultaneous consideration of the abovementioned objectives is more realistic than the only minimization of fresh water consumption. Indeed, the optimal network does not necessarily correspond to the structure that reaches the fresh water target. For a real paper mill plant, energy consumption decreases of almost 20% as compared with previous studies

A multiobjective optimization framework for multicontaminant industrial water network design.

The optimal design of multicontaminant industrial water networks according to several objectives is carried out in this paper. The general formulation of the water allocation problem (WAP) is given as a set of nonlinear equations with binary variables representing the presence of interconnections in the network. For optimization purposes, three antagonist objectives are considered: F1, the freshwater flow-rate at the network entrance, F2, the water flow-rate at inlet of regeneration units, and F3, the number of interconnections in the network. The multiobjective problem is solved via a lexicographic strategy, where a mixed-integer nonlinear programming (MINLP) procedure is used at each step. The approach is illustrated by a numerical example taken from the literature involving five processes, one regeneration unit and three contaminants. The set of potential network solutions is provided in the form of a Pareto front. Finally, the strategy for choosing the best network solution among those given by Pareto fronts is presented. This Multiple Criteria Decision Making (MCDM) problem is tackled by means of two approaches: a classical TOPSIS analysis is first implemented and then an innovative strategy based on the global equivalent cost (GEC) in freshwater that turns out to be more efficient for choosing a good network according to a practical point of view

On the flexibility of an eco-industrial park (EIP) for managing industrial water

In a recent paper, a generic model, based on a multiobjective optimization procedure, for water supply system for a single company and for an eco-industrial park was proposed and illustrated by a park involving three companies A, B and C. The best configuration was identified by simultaneously minimizing the fresh water flow rate, the regenerated water flow rate and the number of connections in the eco-industrial park. The question is now to know what the maximal increase/decrease in pollutant flow rates is, so that the eco-industrial park remains feasible, economically profitable and environmentally friendly. A preliminary study shows that the park can accept an increase of pollutant flow rates of 29% in company A, 12% in company B and only 1% in company C; beyond these limits the industrial symbiosis becomes not feasible. The proposed configuration is not flexible with a very limited number of connections. Indeed, the solution implemented for conferring some flexibility to this network is to increase the number of connections within the park. However, connections have a cost, so the increase of their number needs to remain moderate. The number of connections is augmented until the symbiosis becomes unfeasible, or until the gain for each company to participate to the park becomes lower than a given threshold. Several cases are studied by increasing the pollutant flow rates under two different scenarios: 1) in only one company, 2) in two or three companies simultaneously

Industrial water management by multiobjective optimization: from individual to collective solution through eco-industrial parks.

Industrial water networks are designed in the first part by a multiobjective optimization strategy, where fresh water, regenerated water flow rates as well as the number of network connections (integer variables) are minimized. The problem is formulated as a Mixed-Integer Linear Programming problem (MILP) and solved by the ε-constraint method. The linearization of the problem is based on the necessary conditions of optimality defined by Savelski and Bagajewicz (2000). The approach is validated on a published example involving only one contaminant. In the second part the MILP strategy is implemented for designing an Eco-Industrial Park (EIP) involving three companies. Three scenarios are considered: EIP without regeneration unit, EIP where each company owns its regeneration unit and EIP where the three companies share regeneration unit(s). Three possible regeneration units can be chosen, and the MILP is solved under two kinds of conditions: limited or unlimited number of connections, same or different gains for each company. All these cases are compared according to the global equivalent cost expressed in fresh water and taking also into account the network complexity through the number of connections. The best EIP solution for the three companies can be determined

Optimisation multicritère de réseaux d'eau

Cette étude concerne l’optimisation multiobjectif de réseaux d’eau industriels via des techniques de programmation mathématique. Dans ce travail, un large éventail de cas est traité afin de proposer des solutions aux problèmes de réseaux les plus variés. Ainsi, les réseaux d’eau monopolluants sont abordés grâce à une programmation mathématique linéaire (MILP). Cette méthode est ensuite utilisée dans le cadre d’une prise en compte simultanée des réseaux d’eau et de chaleur. Lorsque le réseau fait intervenir plusieurs polluants, le problème doit être programmé de façon non linéaire (MINLP). L’optimisation multicritère de chaque réseau est basée sur la stratégie epsilon-contrainte développée à partir d’une méthode lexicographique. L’optimisation multiobjectif suivie d’une réflexion d’aide à la décision a permis d’améliorer les résultats antérieurs proposés dans la littérature de 2 à 10% en termes de consommation de coût et de 7 à 15% en ce qui concerne la dépense énergétique. Cette méthodologie est étendue à l’optimisation de parcs éco-industriels et permet ainsi d’opter pour une solution écologique et économique parmi un ensemble de configurations proposées. ABSTRACT : This study presents a multiobjective optimization of industrial water networks through mathematical programming procedures. A large range of various examples are processed to propose several feasible solutions. An industrial network is composed of fixed numbers of process units and regenerations and contaminants. These units are characterized by a priori defined values: maximal inlet and outlet contaminant concentrations. The aim is both to determine which water flows circulate between units and to allocate them while several objectives are optimized. Fresh water flow-rate (F1), regenerated water flow-rate (F2),interconnexions number (F3), energy consumption (F4) and the number of heat exchangers (F5) are all minimized. This multiobjective optimization is based upon the epsilon-constraint strategy, which is developed from a lexicographic method that leads to Pareto fronts. Monocontaminant networks are addressed with a mixed linear mathematical programming (Mixed Integer Linear Programming, MILP) model, using an original formulation based on partial water flow-rates. The obtained results we obtained are in good agreement with the literature data and lead to the validation of the method. The set of potential network solutions is provided in the form of a Pareto front. An innovative strategy based on the GEC (global equivalent cost) leads to the choice of one network among these solutions and turns out to be more efficient for choosing a good network according to a practical point of view. If the industrial network deals with several contaminants, the formulation changes from MILP into MINLP (Mixed Integer Non Linear Programming). Thanks to the same strategy used for the monocontaminant problem, the networks obtained are topologically simpler than literature data and have the advantage of not involving very low flow-rates. A MILP model is performed in order to optimize heat and water networks. Among several examples, a real case of a paper mill plant is studied. This work leads to a significant improvement of previous solutions between 2 to 10% and 7 to 15% for cost and energy consumptions respectively. The methodology is then extended to the optimization of eco-industrial parks. Several configurations are studied regarding the place of regeneration units in the symbiosis. The best network is obtained when the regeneration is owned by each industry of the park and allows again of about 13% for each company. Finally, when heat is combined to water in the network of the ecopark, a gain of 11% is obtained compared to the case where the companies are considered individually

Holistic framework for land settlement development project sustainability assessment : comparison of El Hierro Island hydro wind project and Sivens dam project

Project developer in the domain of land settlement project are involved with many stakeholders and are usually overflown by data relative to technical, economic and social issues. This paper contributes to the necessary multi-scale approach challenge and we propose a holistic framework that enables to describe the development process of land settlement project and assess its sustainability. It would help developers to take decisions compliant with the project complexity. In the model driven engineering perspective, the metamodel framework is described with the ISO 19440 four views to represent complex systems: architectural, structural, functional and behavioural. We confront it to describe two case studies: the successful project of hydro-wind power plant in El Hierro in the Canaries, and the Sivens Dam project in France sadly famous for its deadly outcome. Their comparison enables us to draw hypothesis on what are the ingredients of success and validate the framework

Optimization methods applied to the design of eco-industrial parks: a literature review

With the growing environmental concern, there is evidence that increasing symbiotic relationship between plants in the same industrial area, highly contributes to a more sustainable development of industrial activities. The concept of industrial ecology extended to the terms of eco-industrial park (or ecopark) or industrial symbioses is the topic of extensive research since the five last years. More particularly, even if a lot of ecopark examples and realizations already exist throughout the world, a lot of ecopark proposals are in progress but not achieved. Recently, this vision leads the research community to focus on works proposing methods to optimize the exchanges of an ecopark prior to its design and construction. We find it especially interesting for the scientific community to propose a detailed paper review focused on optimization works devoted to the design of eco industrial parks. This paper is based on a comprehensive literature search in Web of Science database for publications that listed ‘industrial symbiosis’ (or ‘eco industrial park’, or ‘inter plant integration’) and ‘optimization’. This study is segmented into different sections with first, a description of the different concepts evoked in the literature. Then, the several types of networking in an eco-industrial park are detailed in association with the optimization methods employed to solve each problem. The following sections reviews the different objective functions that are formulated to optimally design an eco-industrial park. The last part of the paper is devoted to a critical analysis of the state of the art by proposing several routes to improve the methodologies found in the literature. Another aim of this paper review consists in finding the gaps existing in previous studies. These major gaps are found to be: the lack of multiobjective optimization studies, the absence of social/societal objectives formulation also needs to be addressed and the lack of works taking into account flexibility of ecoparks in an operational point of view

Minimizing water and energy consumptions in industrial water networks

This study gives a MILP framework for solving a heat and water allocation problem. Both energy and water consumptions are taken into account for proposing numerous optimal solutions for a fixed number of connections between processes in the network. Results are represented on Pareto fronts for each number of connections. Networks proposed are optimal in terms of energy and water consumptions and can easily be applied at industrial scale because they involve low flow rates and their complexity is also topologically limited. In previous studies, the optimal network reaches the fresh water target but it is not always an optimal choice, as shows the economical study carried out here. A low increase in fresh water consumption leading to a significant decrease in energy consumption allows designing a cheaper networ

Multiobjective optimization of industrial water networks with contaminants

This paper presents a multiobjective MILP formulation for optimizing industrial water networks. By expressing balance equations in terms of partial mass flows instead of total mass flows and concentrations, and because the contaminant mass flow (ppm) is very small compared to the water mass flow (T.h-1), the problem becomes linear. The integer variables are related to the interconnections into the network. The biobjective optimization of the fresh water flow rate at the network entrance and the water flow rate at regeneration unit inlets, parameterized by the number of interconnections, is carried out according to a lexicographic procedure. A monocontaminant network involving ten processes and one regeneration unit illustrates the approach. Even if the results are specific, the methodology guide can be applied to a large panel of networks. On the one hand, this example shows that the Pareto front is a straight line where each point is a feasible solution, when the number of connections is maximal (120). On the other hand, the Pareto front is reduced with the number of connections (11) and constituted by isolated points located mainly on a straight line with the same slope as for 120 connections, but no feasible solution exists between these points

Resilience study applied in eco-industrial Parks

An Eco-Industrial Park (EIP) is a community of businesses that seeks to reduce the global impact through material sharing. Even though an EIP presents an environmental improvement when compared with a set of stand-alone industrial plants, the established connections among the industrial participants can propagate failures, and become in a source of risk. For this reason, this work proposes an indicator to follow the resilience of EIPs, which is constructed to be applied on the design phase of eco-industrial parks, by means of an optimization problem. This indicator is based on two aspects of an industrial network: its topology and its operative flexibility. These aspects are measured by two respective sub-indicators, Network Connectivity Index (NCI) and Flow adaptability index (ϕ). Both sub-indicators are integrated to compose a global resilience indicator. Finally, we apply the resilience indicator over five illustrative cases in order to analyze its applicability, obtaining consistent results