Marianne Boix

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: F(1), the freshwater flow-rate at the network entrance, F(2), the water flow-rate at inlet of regeneration units, and F(3), 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.

Water integration in eco-industrial parks using a multi-leader-follower approach

The design and optimization of industrial water networks in eco-industrial parks are studied by formulating and solving multi-leader-follower game problems. The methodology is explained by demonstrating its advantages against multi-objective optimization approaches. Several formulations and solution methods for MLFG are discussed in detail. The approach is validated on a case study of water integration in EIP without and with regeneration units. In the latter, multi-leader-single-follower and single-leader-multi-follower games are studied. Each enterprises objective is to minimize the total annualized cost, while the EIP authority objective is to minimize the consumption of freshwater within the ecopark. The MLFG is transformed into a MOPEC and solved using GAMS® as an NLP. Obtained results are compared against the MOO approach and between different MLFG formulations. The methodology proposed is proved to be very reliable in multi-criteria scenarios compared to MOO approaches, providing numerical Nash equilibrium solutions and specifically in EIP design and optimization.

Eco Industrial Parks for Water and Heat Management

Abstract An EIP is a cluster of several processes that are not necessarily part of the same company, that share common infrastructure designed and operated to induce integration of materials exchange, discharge and waste treatment. Here three companies are concerned and the EIP is related to the management of fresh and waste water and the energy consumption. First each company is optimized alone according to fresh water and waste treatment, number of connections between processes, number of heat exchangers and energy consumption. Then the energy consumption of the EIP is minimized according to bounds on fresh water and wastewater treatment, the problem being parameterized by the number of heat exchangers and the number of connections. An example adapted from the literature is solved, showing the potentiality of the method for providing pertinent answers for reducing energy consumption, fresh water demand and wastewater treatment. The proposed methodology presents a real economic interest, with together a significant ecological impact.

Multiobjective optimization of industrial water networks with contaminants

Abstract 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.

Biodiesel Production from Waste Vegetable Oils: Combining Process Modelling, Multiobjective Optimization and Life Cycle Assessment (LCA)

The objective of this work is to propose an integrated and generic framework for eco- design that generalizes, automates and optimizes the evaluation of the environmental criteria at earlier design stage. The approach consists of three main stages. The first two steps correspond to process inventory analysis based on mass and energy balances and impact assessment phases of LCA methodology. The third stage of the methodology is based on the interaction of the previous steps with process simulation for environmental impact assessment and cost estimation through a computational framework. Then, the use of multi-objective optimization with a multicriteria choice decision making allows to select optimal solutions. The methodology is illustrated through the acid-catalyzed biodiesel production process.

Water Exchanges in Eco-industrial Parks through Multiobjective Optimization and Game Theory

The current environmental context makes urgent the development of robust methodologies able to design innovative industries. Industrial ecology, and most particularly the concept of eco-industrial parks, aims at proposing at several companies to gather in a same geographical site to share several fluxes (water, energy, utilities…) in order to decrease environmental impacts of their industrial activities. A recent literature analysis has shown the emergence of new works devoted to the application of optimization methodologies to design greener and more efficient eco-industrial parks. In this work, the method of goal programming is applied for the first time to design optimal exchanges of water in an academic case of park. Goal programming is employed to deal with several conflicting objectives: the cost for each company included in the park. This method is proven to be reliable in this context because it proposes to obtain one solution instead of a set of optimal solutions that takes directly into account the preferences of the decision maker. Although the solution obtained in this study is quite interesting and is a good compromise, the main perspective of this work is to be extended by being coupled with a game theory approach so that an more equilibrate solution can be obtained

Spatial-based Approach of the Hydrogen Supply Chain in the Midi-Pyrénées Region, France

Abstract A mathematical programming approach is developed to optimize the hydrogen supply chain in Midi-Pyrenees, the largest region of France. The aim of this study is to use a Geographical Information System (GIS) as a new tool for multi-criteria decision making after multiobjective optimization step. To have a more precise snapshot of the results obtained, the map is confronted with the one constructed with ArcGis® that contains all the geographic and demographic data of the region. This study focuses on the need to take into account such geographic data so that the various facilities can really be positioned: the results show that the production centers (small, medium and large) and the refueling stations are near as possible to the main road. This post-optimization step allows analyzing the feasible and the best solutions considering geographic criteria.

Benefits analysis of optimal design of eco-industrial parks through life cycle indicators

Abstract Industrial symbiosis offers to companies the possibility to make economic benefits and to minimize environmental impacts by sharing flows and increasing inter-enterprise exchanges. However, even if some studies have demonstrated the benefits of the development of eco-industrial parks (EIP), there is no consensus to evaluate their benefits in a global point of view and there is a lack of integrated indicators for the assessment of EIPs. The aim of this study is to propose a holistic approach to evaluate the global impacts of an EIP. To reach this goal, the potential eco-industrial park of Mongstad in Norway has been chosen. Several steps are considered: a simulation through Aspen Properties®, then the superstructure optimization problem solved within GAMS® environment by minimizing the total cost of the EIP is done. Finally, an evaluation of the optimal solution through a life cycle approach is carried out. The results show that companies included in the EIP have environmental impacts reduced from 45% to 80% compared to the impacts of stand-alone companies.

Modelling of Environmental Impacts and Economic Benefits of Fibre Reinforced Polymers Composite Recycling Pathways

In the last few years, composites have been used increasingly in different applications (aerospace, automobile, industry, sports…). Both environmental and economic factors have driven the development of recycling pathways for the increasing amount of fibre reinforced polymer (FRP) scrap generated. A recycling system for FRP has to be designed to recover and reuse the fibre and matrix content of the scrap. The objective of this paper is to model and compare the different routes of end-of-life FRP from both environmental and economic viewpoint combining Life Cycle Assessment and Cost-Benefit Analysis. More precisely, mechanical recycling, pyrolysis and fluidized bed are investigated and compared to low value end-of-life solutions (incineration, co-incineration and landfill) both for Glass and Carbon FRPs. Pyrolysis turns out to be an attractive recycling solution for CFRP that satisfies both environmental and economic benefit while co-incineration seems more promising for GFRP.

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.