39 research outputs found

    Exergetic balances and analysis in a Process Simulator: A way to enhance Process Energy Integration

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    Energy issue is becoming increasingly crucial for industrial sector that consumes large quantities of utilities. Although the scientific world should continue to look for alternate sources of energy, a short-term solution would rather rely on a more rational use of energy. To face this challenge, exergy analysis appears a very efficient tool as it would enable to increase efficiency and reduce environmental impact of industrial processes. Unfortunately, contrary to enthalpy, this concept is rather difficult to handle and exergy analysis is rarely implemented in process simulators. In this context, the major objective of the study presented in this dissertation is to make exergy analysis more understandable by coupling it with the use of a process simulator and also to demonstrate the value of this approach for analysis of energy efficiency of processes and utilities. This dissertation presents a generic formulation for exergy of material streams that does not depend on the thermodynamic model, so that it could be easily implemented in a process simulator. The different contributions of exergy (thermal, mechanical and chemical) have been developed and new concept such as the maximal thermal and mechanical recovery potential has been introduced in order to pave the way for exergy analysis. The formulations of exergy balances on a real process are presented. For that purpose, the formulation of exergy for heat and work flux is developed. The formulation of exergy balances has been introduced for both design and retrofit situations and then a set of hints for the interpretation of this exergy balance has been given. Synthetic tables providing solutions to reduce irreversibilities and external losses have been introduced. Moreover, different kinds of exergy efficiency have been defined to provide a new criterion for the optimization of the process. A new structured methodology for exergy analysis is developed to overcome the limitations of existing methodologies. To make exergy analysis easier for any engineer, a first prototype has been developed to implement the calculation of exergy for the material streams in a process flowsheet modeled in ProSimPlus. Thanks to this prototype, exergy of each material stream appears in a synthesis table next to the traditional thermodynamic values such as the enthalpy. Finally, a case study on Natural Gas Liquids recovery process is presented to demonstrate the benefit of the exergy analysis for the improvement of existing processes. First, the exergy analysis permits to make an energy diagnosis of the process: it pinpoints the inefficiencies of the process which relies not only on irreversibilities but also on external exergy losses. Then, based upon respective values of internal and external losses and also thanks to the breaking down of exergy into it thermal, mechanical and chemical contributions, some technological solutions are suggested to propose a retrofit process. Finally, the exergy efficiency criteria enable to optimize the operating parameters of the process in order to improve its energy efficiency

    Exergetic balances and analysis in a Process Simulator: A way to enhance Process Energy Integration

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    Dans un contexte de réduction des émissions de gaz à effet de serre (GES) et de forte volatilité du prix des énergies, les investissements en efficacité énergétique des sites industriels résultent souvent d'un processus de décision complexe. L'industriel doit pouvoir disposer d'outils lui permettant d'élaborer les solutions d'efficacité énergétique envisageables sur son site. Outre la recherche des sources d'énergie alternatives, que sont les énergies renouvelables, qui n'atteindront leur maturité technologique que sur le long terme, une solution à court terme consiste plutôt à favoriser une utilisation plus rationnelle de l'énergie. Pour relever ce défi, l'analyse exergétique apparaît comme un outil très efficace, car elle permet d'identifier précisément les sources d'inefficacité d'un procédé donné et de proposer des solutions technologiques visant à y remédier. Malheureusement, contrairement au concept d'enthalpie traditionnellement utilisé pour réaliser des bilans énergétiques sur un procédé, ce concept demeure assez difficile à appréhender et n'est que très rarement implémenté dans les simulateurs de procédés. Les travaux présentés dans ce document visent d'abordà rendre l'analyse exergétique plus accessible en l'intégrant dans un simulateur de procédés, puis à démontrer la pertinence d'une telle analyse pour l'amélioration de l'efficacité des procédés et des utilités associées. Dans un premier temps, une formulation générique et indépendante du choix du modèle thermodynamique pour l'évaluation de l'exergie des flux de matière est introduite. Une méthode de calcul des différentes contributions de l'exergie (contributions thermique, mécanique et chimique) est développée et un nouveau concept visant à évaluer les potentiels de récupérations thermique et mécanique maximales est introduit. Par la suite, la notion de bilan exergétique sur un système donné (opération unitaire ou procédé complet) est introduite. Pour l'évaluation des exergies des flux de travail et de chaleur, deux cas de figure sont étudiés : le cas de l'amélioration de procédés existants (« retrofitting ») et le cas de la conception de nouveaux procédés (« design»). Dans le cas de l'amélioration de procédés existants et afin d'aider au diagnostic énergétique de ces systèmes, des tableaux synthétiques proposant des solutions technologiques visant à réduire les irréversibilités ou les pertes exergétiques externes du procédé sont proposés. Par ailleurs, après une analyse comparative des différentes formulations d'efficacité exergétiques existant dans la littérature, la notion d'efficacité intrinsèque est retenue comme le critère le plus adapté pour une optimisation de l'efficacité exergétique d'un procédé complexe. Enfin, une nouvelle méthodologie structurée dédiée à l'analyse exergétique et permettant de pallier les lacunes des méthodologies existantes est présentée. L'ensemble de ces concepts est implémenté dans un premier prototype logiciel écrit en langage VBScript et intégré au simulateur de procédés ProSimPlus. Enfin, l'efficacité de la procédure est démontrée à travers une étude de cas portant sur la production de gaz naturel. ABSTRACT : Energy issue is becoming increasingly crucial for industrial sector that consumes large quantities of utilities. Although the scientific world should continue to look for alternate sources of energy, a short-term solution would rather rely on a more rational use of energy. To face this challenge, exergy analysis appears a very efficient tool as it would enable to increase efficiency and reduce environmental impact of industrial processes. Unfortunately, contrary to enthalpy, this concept is rather difficult to handle and exergy analysis is rarely implemented in process simulators. In this context, the major objective of the study presented in this dissertation is to make exergy analysis more understandable by coupling it with the use of a process simulator and also to demonstrate the value of this approach for analysis of energy efficiency of processes and utilities. This dissertation presents a generic formulation for exergy of material streams that does not depend on the thermodynamic model, so that it could be easily implemented in a process simulator. The different contributions of exergy (thermal, mechanical and chemical) have been developed and new concept such as the maximal thermal and mechanical recovery potential has been introduced in order to pave the way for exergy analysis. The formulations of exergy balances on a real process are presented. For that purpose, the formulation of exergy for heat and work flux is developed. The formulation of exergy balances has been introduced for both design and retrofit situations and then a set of hints for the interpretation of this exergy balance has been given. Synthetic tables providing solutions to reduce irreversibilities and external losses have been introduced. Moreover, different kinds of exergy efficiency have been defined to provide a new criterion for the optimization of the process. A new structured methodology for exergy analysis is developed to overcome the limitations of existing methodologies. To make exergy analysis easier for any engineer, a first prototype has been developed to implement the calculation of exergy for the material streams in a process flowsheet modeled in ProSimPlus. Thanks to this prototype, exergy of each material stream appears in a synthesis table next to the traditional thermodynamic values such as the enthalpy. Finally, a case study on Natural Gas Liquids recovery process is presented to demonstrate the benefit of the exergy analysis for the improvement of existing processes. First, the exergy analysis permits to make an energy diagnosis of the process: it pinpoints the inefficiencies of the process which relies not only on irreversibilities but also on external exergy losses. Then, based upon respective values of internal and external losses and also thanks to the breaking down of exergy into it thermal, mechanical and chemical contributions, some technological solutions are suggested to propose a retrofit process. Finally, the exergy efficiency criteria enable to optimize the operating parameters of the process in order to improve its energy efficiency

    General methodology for exergy balance in ProSimPlus® process simulator

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    This paper presents a general methodology for exergy balance in chemical and thermal processes integrated in ProSimPlus® as a well-adopted process simulator for energy efficiency analysis. In this work, as well as using the general expressions for heat and work streams, all of exergy balance is presented within only one software in order to fully automate exergy analysis. In addition, after exergy balance, the essential elements such as source of irreversibility for exergy analysis are presented to help the user for modifications on either process or utility system. The applicability of the proposed methodology in ProSimPlus® is shown through a simple scheme of Natural Gas Liquids (NGL) recovery process and its steam utility system. The methodology does not only provide the user with necessary exergetic criteria to pinpoint the source of exergy losses, it also helps the user to find the way to reduce the exergy losses. These features of the proposed exergy calculator make it preferable for its implementation in ProSimPlus® to define the most realistic and profitable retrofit projects on the existing chemical and thermal plants

    The CIRCULAR pathway: a new educational methodology for exploratory circular value chain redesign

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    The circular economy (CE) is gaining global relevance across countries and institutions as a tool to solve some of the most pressing global challenges derived from linear production and consumption systems. However, transitioning to a CE requires significant changes in how businesses and supply chains operate, including redesigning products, processes, and business models. These changes require that future professionals acquire knowledge and skills on the principles of CE, Life Cycle Thinking, and Systems Thinking. However, research on existing higher education programs signals a need for educational resources to develop these skills and knowledge in real-world settings. This paper outlines a new eight-step methodology to introduce students to the principles of CE through the exploratory redesign of a real-world product and value chain in a project-centered learning environment. This methodology was developed in four iterations and was used to teach 251 students from the BSc. Business Engineering at Maastricht University during the academic years 2020–2022. The findings indicate that this method supports students' understanding of complexity, linearity, and the importance of systemic change across the entire value chain, as well as their critical thinking, problem-solving, and decision-making skills. The methodology provided in this paper supports and encourages educational bodies to implement Education for CE in their curricula and further strengthens the complementary fields of Education for Environmental Sustainability and Education for Sustainable Development. Furthermore, educators, professionals and businesses can make use of this tested methodology for exploratory product redesign toward sustainable circularity transitions

    Assessment of power generation from natural gas and biomass to enhance environmental sustainability of a polyol ether production process for rigid foam polyurethane synthesis

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    Polyol ether production process can result in emission of extremely hazardous substances besides it requires high energy demand which can also cause environmental impacts. This paper presents an exergy-aided life cycle assessment (LCA) to pinpoint avoidable key causes of the environmental unsustainability in the period of clean energy transition, and enhance the sustainability as much as achievable. The power generation system is pinpointed as the mitigable key source of the unsustainability of the polyol ether production under the strict process constraints imposed by the energy transition. Then, a set of possible scenarios supported by Monte Carlo simulations are defined, resulting in reducing environmental impacts from 7.17 to 7.11 MJ equivalent of nonrenewable energy sources according to the Cumulative Exergy Demand or from the dimensionless normalized results of 3.43E-04 to 2.98E-04 according to ReCiPe. Moreover, LCA is advantageous to quantify precisely environmental impacts of each chemical component, showing that CO2 has much more adverse impacts on human health than the hazardous substances. Additionally, LCA reveals that natural gas can even be less sustainable than residual fuel oil in terms of freshwater ecotoxicity (75%), marine ecotoxicity (51%), terrestrial acidification (27%), human toxicity (43%), particulate matter formation (18%), and fossil depletion (64%) impacts. (C) 2017 Elsevier Ltd. All rights reserved

    Approche combinant analyse pinch, analyse exergétique et optimisation pour la minimisation de la consommation énergétique dans des industries de procédés

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    Dans un contexte de réduction des émissions de gaz à effet de serre (GES) et de forte volatilité du prix des énergies, les investissements en efficacité énergétique des sites industriels résultent souvent d'un processus de décision complexe. L'industriel doit pouvoir disposer d'outils lui permettant d'élaborer les solutions d'efficacité énergétique envisageables sur son site. Outre la recherche des sources d'énergie alternatives, que sont les énergies renouvelables, qui n'atteindront leur maturité technologique que sur le long terme, une solution à court terme consiste plutôt à favoriser une utilisation plus rationnelle de l'énergie. Pour relever ce défi, l'analyse exergétique apparaît comme un outil très efficace, car elle permet d'identifier précisément les sources d'inefficacité d'un procédé donné et de proposer des solutions technologiques visant à y remédier. Malheureusement, contrairement au concept d'enthalpie traditionnellement utilisé pour réaliser des bilans énergétiques sur un procédé, ce concept demeure assez difficile à appréhender et n'est que très rarement implémenté dans les simulateurs de procédés. Les travaux présentés dans ce document visent d'abordà rendre l'analyse exergétique plus accessible en l'intégrant dans un simulateur de procédés, puis à démontrer la pertinence d'une telle analyse pour l'amélioration de l'efficacité des procédés et des utilités associées. Dans un premier temps, une formulation générique et indépendante du choix du modèle thermodynamique pour l'évaluation de l'exergie des flux de matière est introduite. Une méthode de calcul des différentes contributions de l'exergie (contributions thermique, mécanique et chimique) est développée et un nouveau concept visant à évaluer les potentiels de récupérations thermique et mécanique maximales est introduit. Par la suite, la notion de bilan exergétique sur un système donné (opération unitaire ou procédé complet) est introduite. Pour l'évaluation des exergies des flux de travail et de chaleur, deux cas de figure sont étudiés : le cas de l'amélioration de procédés existants (« retrofitting ») et le cas de la conception de nouveaux procédés (« design»). Dans le cas de l'amélioration de procédés existants et afin d'aider au diagnostic énergétique de ces systèmes, des tableaux synthétiques proposant des solutions technologiques visant à réduire les irréversibilités ou les pertes exergétiques externes du procédé sont proposés. Par ailleurs, après une analyse comparative des différentes formulations d'efficacité exergétiques existant dans la littérature, la notion d'efficacité intrinsèque est retenue comme le critère le plus adapté pour une optimisation de l'efficacité exergétique d'un procédé complexe. Enfin, une nouvelle méthodologie structurée dédiée à l'analyse exergétique et permettant de pallier les lacunes des méthodologies existantes est présentée. L'ensemble de ces concepts est implémenté dans un premier prototype logiciel écrit en langage VBScript et intégré au simulateur de procédés ProSimPlus. Enfin, l'efficacité de la procédure est démontrée à travers une étude de cas portant sur la production de gaz naturel.Energy issue is becoming increasingly crucial for industrial sector that consumes large quantities of utilities. Although the scientific world should continue to look for alternate sources of energy, a short-term solution would rather rely on a more rational use of energy. To face this challenge, exergy analysis appears a very efficient tool as it would enable to increase efficiency and reduce environmental impact of industrial processes. Unfortunately, contrary to enthalpy, this concept is rather difficult to handle and exergy analysis is rarely implemented in process simulators. In this context, the major objective of the study presented in this dissertation is to make exergy analysis more understandable by coupling it with the use of a process simulator and also to demonstrate the value of this approach for analysis of energy efficiency of processes and utilities. This dissertation presents a generic formulation for exergy of material streams that does not depend on the thermodynamic model, so that it could be easily implemented in a process simulator. The different contributions of exergy (thermal, mechanical and chemical) have been developed and new concept such as the maximal thermal and mechanical recovery potential has been introduced in order to pave the way for exergy analysis. The formulations of exergy balances on a real process are presented. For that purpose, the formulation of exergy for heat and work flux is developed. The formulation of exergy balances has been introduced for both design and retrofit situations and then a set of hints for the interpretation of this exergy balance has been given. Synthetic tables providing solutions to reduce irreversibilities and external losses have been introduced. Moreover, different kinds of exergy efficiency have been defined to provide a new criterion for the optimization of the process. A new structured methodology for exergy analysis is developed to overcome the limitations of existing methodologies. To make exergy analysis easier for any engineer, a first prototype has been developed to implement the calculation of exergy for the material streams in a process flowsheet modeled in ProSimPlus. Thanks to this prototype, exergy of each material stream appears in a synthesis table next to the traditional thermodynamic values such as the enthalpy. Finally, a case study on Natural Gas Liquids recovery process is presented to demonstrate the benefit of the exergy analysis for the improvement of existing processes. First, the exergy analysis permits to make an energy diagnosis of the process: it pinpoints the inefficiencies of the process which relies not only on irreversibilities but also on external exergy losses. Then, based upon respective values of internal and external losses and also thanks to the breaking down of exergy into it thermal, mechanical and chemical contributions, some technological solutions are suggested to propose a retrofit process. Finally, the exergy efficiency criteria enable to optimize the operating parameters of the process in order to improve its energy efficiency

    Exergy-aided environmental sustainability assessment of an ethylene dichloride-vinyl chloride production process

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    Vinyl chloride is a carcinogen and ethylene dichloride is a toxic chemical besides the high-energy demand of their production process, which can also cause environmental impacts. This paper presents an exergy-aided LCA to pinpoint the avoidable key cause of the unsustainability in the period of energy transition, and enhance the sustainability as much as achievable. The electricity generation system is pinpointed as the main source of the unsustainability of the ethylene dichloride-vinyl chloride production process under the strict process constraints imposed by the energy transition. Then, a set of possible scenarios supported by Monte Carlo simulation are defined, resulting in reducing environmental impacts from 5.19 to 5.15 MJ equivalent of nonrenewable energy sources according to CExD or from dimensionless normalized results of 2.47E-04 to 1.36E-04 according to ReCiPe, thus paving the way towards sustainable ethylene dichloride-vinyl chloride production process. In addition, LCA is advantageous to quantify precisely the environmental impacts of each chemical component, showing that CO2 has much more adverse impacts than the hazardous substances on human health. Moreover, LCA reveals that natural gas can even be less sustainable than residual fuel oil in terms of freshwater ecotoxicity, marine ecotoxicity, terrestrial acidification, human toxicity, particulate matter formation, and fossil depletion impacts. 13/4(C) 2017 Institution of Chemical Engineers. Published by Elsevier B.V. All rights reserved

    Exergy aided pinch analysis to enhance energy integration towards environmental sustainability in a chlorine-caustic soda production process

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    This paper presents a case study on the improvement of energy integration in a chlorine-caustic soda process based on the main sources of thermal exergy losses. Exergy analysis has been performed to pinpoint the causes of thermal exergetic inefficiency. Thermal solutions have been then developed, leading to a comprehensive list of cold and hot process streams. Finally, pinch analysis has been brought into action to estimate the minimum energy requirement, to select utilities and to design heat exchanger network. As a result, the combined methodology followed here takes advantages of both exergy and pinch analyses. This bilateral thermal-exergy-based pinch approach helps to set energy targets in a way that all the possible thermal solutions supported by exergy analysis are considered, including all hot and cold process streams that have a high potential for heat integration during pinch analysis. To demonstrate this, energy targeting through conventional pinch analysis leads to 7.74 MW and 13.00 MW of hot and cold utility energy demand, respectively. These figures change to 8.17 MW and 0.40 MW of hot and cold utility energy demand, respectively through streams screening by the combined methodology. (C) 2017 Elsevier Ltd. All rights reserved

    Combined pinch and exergy analysis of an ethylene oxide production process to boost energy efficiency toward environmental sustainability

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    Ethylene oxide production process is one of the highest energy consumers in chemical industry, and therefore even a slight improvement in its overall efficiency can have a significant impact on the sustainability of the process. Efficiency improvement can be carried out using the exergy-aided pinch analysis outlined in this paper. The overall exergy loss distribution in different unit operations of an ethylene oxide process was first evaluated and mapped out in the form of "visualized exergetic process flowsheet". An initial analysis of the four main functional blocks of the process showed that the exothermic reaction block contained the largest exergy loss (6043 and 428 kJ/kg of internal and external losses, respectively) which can be reduced by isothermal mixing, as well as increasing reaction temperature and reduction in pressure drop. The absorption block was also estimated to have the second highest contribution with total exergy losses of 3640 kJ/kg which were mainly due to the cooling column. These losses were then recommended to be reduced by improvements in the concentration and temperature gradients along the tower. Following the block-wise analysis, exergy analysis was then carried out for individual unit operations in each block to pinpoint the main sources of thermal exergetic inefficiency. Thermal solutions to reduce losses were also proposed in accordance with the identified sources of inefficiency, leading to a comprehensive list of cold and hot process streams that could be introduced to reduce losses. Finally, pinch analysis was brought into action to estimate the minimum energy requirements, to select utilities, and to design heat exchanger network. Thus, the methodology used in this work took advantage of both exergy and pinch analyses. The combined thermal-exergy-based pinch approach helped to set energy targets so that all the thermal possible solutions supported by exergy analysis were considered, preventing exclusion of any hot or cold process stream with high potential for heat integration during pinch analysis. Results indicated that the minimum cold utility requirement could be reduced from 601.64 MW (obtained via conventional pinch analysis) to 577.82 MW through screening of streams by the combined methodology

    Exergy analysis as a scoping tool for cleaner production of chemicals:a case study of an ethylene production process

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    High energy consumption is one of the main challenges of the chemical industry. The energy footprint of most processes can, however, diminish through the solutions presented in the current paper, leading to cleaner ways of producing chemicals. Ethylene production process is selected as a case study to demonstrate the approach as it is one of the most energy consuming processes in the chemical industry. The study involves an exergetic diagnosis and does not only find the low-exergy-efficient unit operations, but also proposes tools to improve these units based on their key sources of irreversibility. For the ethylene production process, this is conducted by first splitting the flowsheet into four main functional blocks (namely cracking, compression, refrigeration, and separation and purification) according to their exergy losses. This results in identifying the cracking block as the most inefficient block with more than 45% of total exergy losses and thus the first block to be improved so that overall losses reduce (examples of which include increasing the number of furnace tubes while reducing their lengths). Although the compression block is-found to have the lowest contribution to internal exergy losses, the inefficient unit operations such as the water cooler (with an exergy loss of 214 4J/kg) can still be improved through solutions such as system isolation. The refrigeration block is also shown to have the second highest exergy losses with its ethylene and propylene compressors being the main contributors. Solutions are again provided to improve the block performance with specific focus on intercooler design improvement and system isolation. Finally, exergy losses in the purification and separation block are identified to be mainly due to demethanator, deethanator, and ethylene column where modifications in column design might be helpful as concentration and temperature gradients along the towers are the main sources of exergy losses. The approach used in the current study can also be applied to other chemical processes and the findings suggest that even for a well-developed process technology, there is still opportunity for thermodynamically justifiable energy efficiency improvements. Therefore, it is important for process developers to continuously revisit existing processes, in order to ensure lessons learned in one area can be applied to another one. Using a panel of solutions, which has been constructed from a number of previous case studies helps to make this approach more systematic and user-friendly. (C) 2016 Elsevier Ltd. All rights reserved
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