Design of a water allocation and energy network for multi-contaminant problems using multi-objective optimization

In this paper, a solution strategy based on an optimization formulation is proposed for the design of Water Allocation and Heat Exchange Networks (WAHEN) in the process industries. Such typical large problems involve many processes, regeneration units and multi-contaminants. For this purpose, a two-stage methodology is proposed. The first step is the Water Allocation Network (WAN) design by multi-objective optimization, based on the minimization of the number of network connections and of the global equivalent cost (which includes three criteria, i.e., freshwater, regenerated water and wastewater). The ɛ-constraint method is used to deal with the multi-criteria problem. In a second step, the Heat Exchange Network (HEN) is solved by two approaches, Pinch analysis and mathematical programming (MP). In both cases the HEN structure is found when the minimal energy requirement and the total annual cost are minimized for Pinch and MP, respectively. These results are compared and the best HEN network is then coupled to the WAN to verify the feasibility of the network. A case study including a change of phase among the streams is solved. The results show that this two-step methodology can be useful for the treatment of large problems

Development of a techno-economic energy model for low carbon business parks

To mitigate climate destabilisation, global emissions of human-induced greenhouse gases urgently need to be reduced, to be nearly zeroed at the end of the century. Clear targets are set at European level for the reduction of greenhouse gas emissions and primary energy consumption and for the integration of renewable energy. Carbon dioxide emissions from fossil fuel combustion in the industry and energy sectors account for a major share of greenhouse gas emissions. Hence, a low carbon shift in industrial and business park energy systems is called for. Low carbon business parks minimise energy-related carbon dioxide emissions by enhanced energy efficiency, heat recovery in and between companies, maximal exploitation of local renewable energy production, and energy storage, combined in a collective energy system. Moreover, companies with complementary energy profiles are clustered to exploit energy synergies. The design of low carbon energy systems is facilitated using the holistic approach of techno-economic energy models. These models take into account the complex interactions between the components of an energy system and assist in determining an optimal trade-off between energetic, economic and environmental performances. In this work, existing energy model classifications are scanned for adequate model characteristics and accordingly, a confined number of energy models are selected and described. Subsequently, a practical categorisation is proposed, existing of energy system evolution, optimisation, simulation, accounting and integration models, while key model features are compared. Next, essential features for modelling energy systems at business park scale are identified: As a first key feature, a superstructure-based optimisation approach avoids the need for a priori decisions on the system’s configuration, since a mathematical algorithm automatically identifies the optimal configuration in a superstructure that embeds all feasible configurations. Secondly, the representation of time needs to incorporate sufficient temporal detail to capture important characteristics and peaks in time-varying energy demands, energy prices and operation conditions of energy conversion technologies. Thirdly, energy technologies need to be accurately represented at equipment unit level by incorporating part-load operation and investment cost subject to economy of scale in the model formulation. In addition, the benefits of installing multiple units per technology must be considered. A generic model formulation of technology models facilitates the introduction of new technology types. As a fourth important feature, the potential of thermodynamically feasible heat exchange between thermal processes needs to be exploited, while optimally integrating energy technologies to fulfil remaining thermal demands. For this purpose, thermal streams need to be represented by heat –temperature profiles. Moreover, restrictions to direct heat exchange between process streams need to be taken into account. Finally, the possibility for energy storage needs to be included to enhance the integration of non-dispatchable renewable energy technologies and to bridge any asynchrony between cooling and heating demands. Starting from these essential features, a techno-economic optimisation model (Syn-E-Sys), is developed customised for the design of low carbon energy systems on business park scale. The model comprises two sequential stages. In the first stage, heat recovery within the system is maximised, while energy supply and energy storage technologies are optimally integrated and designed to fulfil remaining energy requirements at minimum total annualised costs. Predefined variations in thermal and electrical energy demand and supply are taken into account, next to a carbon emission cap. At the same time, heat networks can be deployed to transfer heat between separate parts of the system. In the second stage, the model generates an optimal multi-period heat exchanger network enabling all required heat exchanges. Syn-E-Sys builds upon a multi-period energy integration model that can deal with restrictions in heat exchange. It is combined with a generic technology model, that features part-load operation as well as investment cost subject to economy of scale, and a generic energy storage model. The technology model can be manipulated to represent various thermal or electrical energy conversion technology units, and serves as a building block to model more complex technologies. The storage model covers electrical as well as thermal energy storage, taking into account the effect of hourly energy losses on the storage level, without increasing the number of time steps to be analysed. For this purpose, time sequence is introduced by dividing the year into a set of time slices and assigning them to a hierarchical time structure. In addition, a more complex model for storage of sensible heat is integrated, consisting of a stack of interconnected virtual tanks. To enable the optimisation of the number of units per technology in the energy system configuration, an automated superstructure expansion procedure is incorporated. Heat transfer unit envelope curves are calculated to facilitate the choice of appropriate temperature levels for heat networks. Heat networks that are embedded within this envelope, completely avoid the increase in energy requirements that would result from the heat exchange restrictions between separated parts of the energy system. Finally, the heat exchanger network is automatically generated using a multi-period stage-wise superstructure. Two problems inherent to the heat cascade formulation are encountered during model development. As a first issue, heat networks can form self-sustaining energy loops if their hot and cold streams are not completely embedded within the envelope. This phenomenon is referred to in this work as phantom heat. As a second issue, the heat cascade formulation does not prevent that a thermal storage releases its heat to a cooling technology. To demonstrate the specific features of Syn-E-Sys and its holistic approach towards the synthesis of low carbon energy systems, the model is applied to a generic case study and to a case study from literature. The generic case study is set up to demonstrate the design of an energy system including non-dispatchable renewable energy and energy storage, subject to a carbon emission cap. For this purpose, the year is subdivided into a set of empirically defined time slices that are connected to a hierarchical time structure composed of seasons, daytypes and intra-daily time segments. The results obtained by Syn-E-Sys show a complex interaction between energy supply, energy storage and energy import/export to fulfil energy demands, while keeping carbon emissions below the predefined cap. The model enables optimisation of the intra-annual charge pattern and the capacity of thermal and electrical storage. Moreover, an optimal heat exchanger network is automatically generated. In the second case study, heat recovery is optimised for a drying process in the paper industry. To avoid the energy penalty due to heat exchange restrictions between two separated process parts, heat transfer units need to be optimally integrated. Firstly, a simplified version of the original problem is set up in Syn-E-Sys and the obtained results correspond well to literature. Subsequently, the original problem is extended to demonstrate the optimal integration of heat transfer units in a multi-period situation. In conclusion, Syn-E-Sys facilitates optimal design of low carbon energy systems on business park scale, taking into account the complex time-varying interactions between thermal and electrical energy demand, supply and storage, while the potential for heat recovery is fully exploited

Synthesis of Heat-Integrated Water Allocation Networks: A Meta-Analysis of Solution Strategies and Network Features

Industries consume large quantities of energy and water in their processes which are often considered to be peripheral to the process operation. Energy is used to heat or cool water for process use; additionally, water is frequently used in production support or utility networks as steam or cooling water. This enunciates the interconnectedness of water and energy and illustrates the necessity of their simultaneous treatment to improve energy and resource efficiency in industrial processes. Since the seminal work of Savulescu and Smith in 1998 introducing a graphical approach, many authors have contributed to this field by proposing graphically- or optimization-based methodologies. The latter encourages development of mathematical superstructures encompassing all possible interconnections. While a large body of research has focused on improving the superstructure development, solution strategies to tackle such optimization problems have also received significant attention. The goal of the current article is to study the proposed methodologies with special focus on mathematical approaches, their key features and solution strategies. Following the convention of Jeżowski, solution strategies are categorized into: decomposition, sequential, simultaneous, meta-heuristics and a more novel strategy of relaxation/transformation. A detailed, feature-based review of all the main contributions has also been provided in two tables. Several gaps have been highlighted as future research direction

A Systematic Approach to Coupling Energy with Carbon Integration to Reduce Carbon Footprint from Industrial Parks

The depletion of natural resources and the increase in greenhouse gases emissions, which constitute mainly from carbon dioxide, has led many policymakers to issue policies to reduce carbon emissions and fuel consumption. However, reducing the energy consumption is constrained by meeting the increase in goods demands governed by the growth in global population. This problem can be tackled by improving process efficiencies which leads to a decrease in fuel consumption and hence the emissions. Moreover, end-of-pipe treatment approaches reduce carbon emissions by capturing carbon dioxide and store it or utilize it. While the first method is achieved via heat integration, the second method is achieved through carbon integration. In the first method, heat is exchanged between processes to minimize fuel consumption whereas the additional low grade heat is removed using cooling utilities. Moreover, carbon integration requires heat and power to capture and ship carbon dioxide from sources to sinks. This introduces a potential for synergy, where excess heat is used in the capture unit. This work explores this potential via two approaches: sequential and simultaneous. In the first approach, the energy and carbon integration are applied separately to minimize fuel consumption and carbon dioxide emissions. Afterwards, the excess waste heat is utilized to partially or fully offset the carbon integration heat and power demand, resulting in additional savings and further carbon reduction. This approach was demonstrated through a case study, where substantial savings were realized. In the second approach, the energy and the carbon problems were implemented simultaneously through an MINLP model. The same case study was used in order to demonstrate the further benefits that can be obtained from solving the problems simultaneously

A Systematic Approach for Designing Industrial Park Integration Networks Across the Water-Energy Nexus

Nowadays, water-energy resource faces growing demands and constraints in many regions as a result of economic, population growth and climate change. The water-energy nexus and integration has been recently proposed to minimize water-energy footprint of an industrial park. It is required to develop a systematic approach for water-energy network and interconnections among the processes. Previous research work has presented the general superstructure and approach to develop economically optimal water networks that achieve a specified footprint target. In this work, the previous approach for water network has been extended with cooling systems options in order to capture the linkages between water and energy within industrial cities. The objective of this paper is to develop a framework for optimizing energy and water resources from processes that have a surplus of energy at various qualities. A systematic procedure is developed for optimizing and maximizing the benefits of these nexuses, considering power generation from a net surplus of waste heat energy from each plant by accounting for different sustainability metrics. The developed approach includes the use of composite curve analysis to first identify the potential for excess heat and then used to develop the combined water-energy network. A superstructure is generated to embed various configurations and related optimization formulation is solved to obtain an optimal process that economically satisfies the demand for water and energy considering some environmental metrics. Special emphasis is placed on capturing the synergy potentials from utilizing excess process heat and synergies across cooling and desalination systems, as well as synergies with the surroundings in terms of power and water exports from the industrial cluster. The work considers multiple objectives to explore trade-offs between minimum total annual cost and environmental sustainability metrics. A case study of an industrial cluster of typical processes operating in Qatar is presented to highlight the benefits of integration. It is shown how economically very attractive solutions across the nexus are identified by the proposed optimization-based approach. The results indicate that by water-energy integration the footprint reduction can be significant while economically is attractive too. Therefore, there is a great potential for savings water-energy resources by water-energy integrations. The work is contributed to sustainable development such as less pollution and resource minimization

Achievements and perspectives of process integration in cis countries

Due to the rapid growth in the world population, there has been an increase in energy consumption globally. The problem of efficient energy use becomes more relevant and stimulates research and development of new energy and resource-saving technologies. This task is becoming more complicated when the other factors are accounted for, resulting in multiple-factor trade-offs, such as the water-energy-food nexus. This paper highlights the main points for the development of Process Integration in the Commonwealth of Independent States (CIS) countries. It shows the main achievements in the field to date and demonstrates the scientific schools that are working on these problems. A comprehensive review of modern approaches and methods, which are now being developed or have been recently developed, was done. It shows a research gap in Process Integration in CIS and other leading countries. It demonstrates the significant research potential as well as practical applications. The main challenges in process systems engineering and for the sustainable development of industrial energy systems are also discussed. Industry digital transformation, energy transition, circular economy, and stronger energy and water integration are pointed out as priorities in analysis, design, and retrofit of society in the future. A state-of-the-art review in the area of integration of continuous and batch processes, mass integration technologies, and process intensification is presented to show the variety of existing approaches. The necessity of Process Integration development in the CIS is shown to be a necessary condition for building a more sustainable society and a resource-efficient economy

Decision support strategies for the efficient implementation of circular economy principles in process systems

Economic growth at any expense is no longer an option. Awareness of the growing human footprint is crucial to face the problems that the impoverishment of ecosystems is causing and will cause in the future. One of the key challenges to address it is moving toward approaches to manage resources in a more sustainable way. In this light, circular economy stands as a promising strategy to improve the lifetime of resources by closing material and energy loops. The Process Systems Engineering (PSE) community has been developing methods and tools for increasing efficiency in process systems since the late 1980s. These methods and tools allow the development of more sustainable products, processes, and supply chains. However, applying these tools to circular economy requires special considerations when evaluating the introduction of waste-to-resource technologies. This Thesis aims at providing a set of models and tools to support in the decision-making process of closing material cycles in process systems through the implementation of waste-to-resource technologies from the circular economy perspective. The first part provides an overview of approaches to sustainability, presents the optimization challenges that circular economy and industrial symbiosis pose to PSE, and introduces the methodological and industrial scope of the Thesis. Part two aims at assessing the environmental and economic reward that may be attained through the application of circular economy principles in the chemical industry. With this purpose, a systematic procedure based on Life Cycle Assessment (LCA), economic performance and Technology Readiness Level (TRL) is proposed to characterize technologies and facilitate the comparison of traditional and novel technologies. The third part describes groundwork tasks for optimization models. A methodology is presented for the systematic generation of a list of potential waste-to-resource technologies based on an ontological framework to structure the information. In addition, this part also presents a targeting approach developed to include waste transformation and resource outsourcing, so a new dimension of potential destinations for waste are explored for the extension of material recovery. Finally, part four includes the development of decision-making models at the strategic and tactical hierarchical levels. At the network level, a framework is presented for the screening of waste-to-resource technologies in the design of process networks. The most promising processing network for waste recovery is identified by selecting the most favorable waste transformation processes among a list of potential alternatives. After the network selection, an optimization model is built for the detailed synthesis of individual processes selected in the resulting network. The developed methodologies have been validated and illustrated through their application to a case study under different viewpoints in the process industry, in particular to the chemical recycling of plastic waste. Despite the low Technology Readiness Level of some chemical recycling technologies, the results of this Thesis reveal pyrolysis as a promising technology to close the loop in the polymer sector. Overall, all these positive outcomes prove the advantages of developing tools to systematically integrate waste-to-resource processes into the life cycle of materials. The adaptation to this change of perspective of the well-established methods developed by the PSE community offers a wide range of opportunities to foster circular economy and industrial symbiosis. This Thesis aims to be a step forward towards a future with more economically efficient and environmentally friendly life cycles of materials.El crecimiento económico a cualquier precio ha dejado de ser una opción viable. Tener conciencia sobre nuestra creciente huella ambiental es clave para afrontar los problemas que el empobrecimiento de los ecosistemas está causando y causará en el futuro. Uno de los desafíos clave para abordarlo es avanzar hacia técnicas que permitan una gestión de recursos más sostenible. En esta línea, la economía circular es una estrategia con gran potencial para mejorar la vida útil de los recursos mediante el cierre de ciclos de materiales y energía. Desde finales de los años ochenta, la investigación en Ingeniería de Procesos y Sistemas (PSE) ha permitido generar métodos y herramientas para el desarrollo sostenible de productos, procesos y cadenas de suministro. Sin embargo, su aplicación en economía circular requiere consideraciones especiales al evaluar la introducción de nuevas tecnologías para el reciclaje de materiales. Esta Tesis tiene como objetivo proporcionar un conjunto de modelos y herramientas para apoyar el proceso de toma de decisiones sobre el aprovechamiento de materiales a través de la lente de la economía circular mediante la implementación de tecnologías de conversión de residuos en recursos. La primera parte presenta una visión general de los enfoques de sostenibilidad, lista los desafíos que la economía circular y la simbiosis industrial plantean en PSE, e introduce el alcance metodológico e industrial de la Tesis. La segunda parte tiene como objetivo evaluar los beneficios ambientales y económicos que se pueden obtener mediante la aplicación de los principios de la economía circular en la industria química. Con este propósito, se desarrolla un método sistemático basado en el análisis del ciclo de vida, el rendimiento económico y el nivel de madurez tecnológica para caracterizar las tecnologías de recuperación y facilitar la comparación entre técnicas tradicionales y en desarrollo. La tercera parte describe las tareas previas al desarrollo de los modelos de optimización. Se presenta una metodología para la generación sistemática de una lista de posibles tecnologías de conversión de residuos en recursos utilizando en un marco ontológico para estructurar la información. Además, se expone un método para acotar la transformación de residuos y la externalización de recursos, que permite explorar una nueva dimensión de destinos potenciales para los residuos, extendiendo así el grado de recuperación de materiales. Por último, la cuarta parte incluye el desarrollo de modelos de toma de decisiones a nivel estratégico y táctico. A nivel estratégico, se presenta un marco para la detección de tecnologías de reciclaje de residuos en el diseño de redes de procesos. Tras sintetizar la red, a nivel táctico se construye un modelo de optimización para el diseño detallado de los procesos individuales seleccionados en el mismo. Las metodologías desarrolladas han sido ilustradas y validadas a través de su aplicación en un caso de estudio con diferentes perspectivas sobre el reciclaje químico de residuos plásticos. A pesar del bajo nivel de madurez tecnológica de los procesos de reciclaje químico, los resultados de esta Tesis permiten identificar el gran potencial económico y ambiental de la pirolisis de residuos plásticos para cerrar su ciclo de materiales. En conjunto, los resultados demuestran las ventajas de desarrollar herramientas para integrar sistemáticamente los procesos de reciclaje de residuos en el ciclo de vida de los materiales. La adaptación a las necesidades de este cambio de perspectiva de métodos bien establecidos en la comunidad PSE ofrece grandes oportunidades para fomentar la economía circular y la simbiosis industrial. Esta tesis pretende ser un paso adelante hacia un futuro con ciclos de vida de materiales económica y ambientalmente más eficientes

Methodologies for simultaneous optimization of heat, mass, and power in industrial processes

Efficient consumption of energy and material resources, including water, is the primary focus for process industries to reduce their environmental impact. The Conference of Parties in Paris (COP21) highlighted the prominent role of industrial energy efficiency in combatting climate change by reducing greenhouse gas (GHG) emissions. Consumption of energy and material resources, especially water, are strongly interconnected; and therefore, must be treated simultaneously using a holistic approach to identify optimal solutions for efficient processing. Such approaches must consider energy and water recovery within a comprehensive process integration framework which includes options such as organic Rankine cycles for electricity generation from low to medium temperature heat. This thesis addresses the issue of how to efficiently manage energy and water in industrial processes by presenting two systematic methodologies for the simultaneous optimization of heat and mass and combined heat and power production. A novel iterative sequential solution strategy is proposed for optimizing heat-integrated water allocation networks through decomposing the overall problem into three sub-problems using mathematical programming techniques. The approach is capable of proposing a set of potential energy and water reduction opportunities that should be further evaluated for technical, economical, physical, and environmental feasibilities. A novel and comprehensive superstructure optimization methodology is proposed for organic Rankine cycle (ORC) integration in industrial processes including architectural features, such as turbine-bleeding, reheating, and transcritical cycles. Meta-heuristic optimization (via a genetic algorithm) is combined with deterministic techniques to solve the problem: by addressing fluid selection, operating condition determination, and equipment sizing. This thesis further addresses the importance of holistic approaches by applying the proposed methodologies on a kraft pulp mill. In doing so, freshwater consumption is reduced by more than 60%, while net power output is increased by a factor of six. The results exhibit that interactions among these elements are complex and therefore underline the necessity of such methods to explore their optimal integration with industrial processes. The potential implications of this work are broad, extending from total site integration to industrial symbiosis

Energy-Water Nexus in Eco-Industrial Park with Thermal Hydrolysis Process for Bio-Waste Utilization

Because of the cost and environmental issues, what to do with the waste, mainly sludge, from wastewater treatment is a critical issue to make a cleaner and more sustainable world. Thermal hydrolysis process (THP) before anaerobic digestion of the sludge is getting attention because of its simple implementation and advantages for both economic and environmental aspects. THP needs energy and additional cost, but more benefit can be gained by using sludge as a renewable energy source, fertilizer or feedstock for the monetization strategy because of reduction of operating cost and Green House Gas (GHG) emission. Since GHG is a primary reason of climate change which raises the devastation of sustainability of the world, it is momentous to make an effort to reduce the emission of GHG. In the eco-industrial park (EIP), for more process water reuse and water disposal under the stricter regulation, the need for wastewater treatment facilities is growing. Also, there is surplus energy from the processes that can be used to operate the THP, so the EIP can serve as a ‘sustainable center’ where GHG emission is reduced by treating bio-waste in the centralized structure with its surplus heat. By having THP, EIP can improve its sustainability and economy while preparing for the impact of a carbon tax in the near future. In this study, economic feasibility of THP, impact of carbon tax on the economy of the biological wastewater treatment system with THP, adequate tipping fee range for the outer bio-waste, sensitivity analysis on the characteristic of bio-waste, and impact of THP within EIP having a centralized water exchange network were investigated to assess the possibility of EIP as a sustainable center. Through this study, the spectrum of water-energy nexus can be broadened to deal with the interconnection between energy, water, and waste to improve the sustainability and economic benefit to the EIP and communities around it as well

Power quality and electromagnetic compatibility: special report, session 2

The scope of Session 2 (S2) has been defined as follows by the Session Advisory Group and the Technical Committee: Power Quality (PQ), with the more general concept of electromagnetic compatibility (EMC) and with some related safety problems in electricity distribution systems. Special focus is put on voltage continuity (supply reliability, problem of outages) and voltage quality (voltage level, flicker, unbalance, harmonics). This session will also look at electromagnetic compatibility (mains frequency to 150 kHz), electromagnetic interferences and electric and magnetic fields issues. Also addressed in this session are electrical safety and immunity concerns (lightning issues, step, touch and transferred voltages). The aim of this special report is to present a synthesis of the present concerns in PQ&EMC, based on all selected papers of session 2 and related papers from other sessions, (152 papers in total). The report is divided in the following 4 blocks: Block 1: Electric and Magnetic Fields, EMC, Earthing systems Block 2: Harmonics Block 3: Voltage Variation Block 4: Power Quality Monitoring Two Round Tables will be organised: - Power quality and EMC in the Future Grid (CIGRE/CIRED WG C4.24, RT 13) - Reliability Benchmarking - why we should do it? What should be done in future? (RT 15