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Classification of chemical processes: a graphical approach to process synthesis to improve reactive process work efficiency / Baraka Celestin Sempuga in Industrial & engineering chemistry research, Vol. 49 N° 17 (Septembre 1, 2010) 

Public ISBD [article]  in Industrial & engineering chemistry research > Vol. 49 N° 17 (Septembre 1, 2010) . - pp 8227–8237 Titre : Classification of chemical processes: a graphical approach to process synthesis to improve reactive process work efficiency Type de document : texte imprimé Auteurs : Baraka Celestin Sempuga, Auteur ; Brendon Hausberger, Auteur ; Bilal Patel, Auteur Année de publication : 2010 Article en page(s) : pp 8227–8237 Note générale : Chimie industrielle Langues : Anglais (eng) Mots-clés : Chemical  processes  Process  work  efficiency. Résumé : To reduce carbon dioxide emissions for chemical processes, one should make them as reversible as possible. Patel et al. [Ind. Eng. Chem. Res. 2005, 44, 3529−3537] showed that, in some cases, one can analyze processes in terms of their work and heat requirements. In particular, for processes, there exists a temperature that is called “the Carnot temperature”, at which one can satisfy the work requirement for the process, using the heat that must be added or removed. The analogy of a heat engine and Carnot temperature is applied to chemical processes, particularly on reactive processes, using a graphical approach. This approach looks at chemical processes holistically, where only the inlet and outlet streams are considered. The process is represented in a ΔH−ΔG space. Chemical processes are classified in different thermodynamics regions as defined in the ΔH−ΔG space, and their feasibility in terms of heat and work requirement is discussed. This approach allows one to determine whether heat at an appropriate temperature is sufficient to meet the work requirement of a chemical process, or if other means should be considered. The approach is used to investigate and discuss the possibility of combining reactive chemical processes classified in different thermodynamic regions in the ΔH−ΔG space, with the purpose of making infeasible processes possible, or to minimize, or even eliminate, the work requirement of the combined process. DEWEY : 660 ISSN : 0888-5885 En ligne : http://pubs.acs.org/doi/abs/10.1021/ie100288h [article] Classification of chemical processes: a graphical approach to process synthesis to improve reactive process work efficiency [texte imprimé] / Baraka Celestin Sempuga, Auteur ; Brendon Hausberger, Auteur ; Bilal Patel, Auteur . - 2010 . - pp 8227–8237. Chimie industrielle Langues : Anglais (eng) in Industrial & engineering chemistry research > Vol. 49 N° 17 (Septembre 1, 2010) . - pp 8227–8237 Mots-clés : Chemical  processes  Process  work  efficiency. Résumé : To reduce carbon dioxide emissions for chemical processes, one should make them as reversible as possible. Patel et al. [Ind. Eng. Chem. Res. 2005, 44, 3529−3537] showed that, in some cases, one can analyze processes in terms of their work and heat requirements. In particular, for processes, there exists a temperature that is called “the Carnot temperature”, at which one can satisfy the work requirement for the process, using the heat that must be added or removed. The analogy of a heat engine and Carnot temperature is applied to chemical processes, particularly on reactive processes, using a graphical approach. This approach looks at chemical processes holistically, where only the inlet and outlet streams are considered. The process is represented in a ΔH−ΔG space. Chemical processes are classified in different thermodynamics regions as defined in the ΔH−ΔG space, and their feasibility in terms of heat and work requirement is discussed. This approach allows one to determine whether heat at an appropriate temperature is sufficient to meet the work requirement of a chemical process, or if other means should be considered. The approach is used to investigate and discuss the possibility of combining reactive chemical processes classified in different thermodynamic regions in the ΔH−ΔG space, with the purpose of making infeasible processes possible, or to minimize, or even eliminate, the work requirement of the combined process. DEWEY : 660 ISSN : 0888-5885 En ligne : http://pubs.acs.org/doi/abs/10.1021/ie100288h

Efficient combustion / Baraka Celestin Sempuga in Industrial & engineering chemistry research, Vol. 51 N° 26 (Juillet 2012) 

Public ISBD [article]  in Industrial & engineering chemistry research > Vol. 51 N° 26 (Juillet 2012) . - pp. 9061-9077 Titre : Efficient combustion : A process synthesis approach to improve the efficiency of coal - fired power stations Type de document : texte imprimé Auteurs : Baraka Celestin Sempuga, Auteur ; Bilal Patel, Auteur ; Diane Hildebrandt, Auteur Année de publication : 2012 Article en page(s) : pp. 9061-9077 Note générale : Industrial chemistry Langues : Anglais (eng) Mots-clés : Coal  Combustion Résumé : Much of our energy reserves are locked in the chemical potential of chemicals such as fossil fuels. The majority of CO2 emissions caused by human activities come from the combustion of these fuels. Typically, the fuel is burned with oxygen (air), and heat is released. This heat is then used to drive power cycles to produce, for example, electricity in a power plant or motion in the motor car engine. Often, the performance of these processes is assessed in term of thermal efficiency (ηth), which considers how much of the energy released in the combustion process is turned into work. This is not a good representation of how efficient the process is, however, as an idealized Carnot engine, which takes heat from a heat source at a temperature TH and rejects heat to a heat sink at the reference temperature To = 298.15 K, is reversible and thus takes all of the work potential (exergy) of heat and converts this to work. Thus, the Carnot engine might have only 40% efficiency in terms of converting heat to work (ηth), but because it is fully reversible, it generates no entropy, and therefore, it is 100% efficient in terms of recovering the work potential of heat. However, there is a much more fundamental efficiency that should be considered, namely, how much of the chemical potential of the fuel is turned into work. When combustion processes are considered in this way, it becomes clear that some of the major inefficiencies are in the chemical transformations that produce heat, rather than in the power cycles that convert heat to work. A very important question remains: Is it possible to do these transformations more efficiently and thereby conserve the work potential or chemical potential in fuel? This article shows, from a fundamental thermodynamic analysis, that it is not possible to combust carbon-based materials efficiently, that is, that the process of combustion of carbon-based materials is irreversible and that a considerable amount of the chemical potential of the fuel is lost during the combustion process. However, other substances or chemistries are explored in this work, and it is shown that some of these have the potential for more reversible combustion. These options are explored, and their potential implementation is examined by considering a coal-based power plant as an example. In particular, it is shown that CO2 emissions could be significantly reduced by using different chemical pathways to do the combustion and by combining power and chemical production. ISSN : 0888-5885 En ligne : http://cat.inist.fr/?aModele=afficheN&cpsidt=26107463 [article] Efficient combustion : A process synthesis approach to improve the efficiency of coal - fired power stations [texte imprimé] / Baraka Celestin Sempuga, Auteur ; Bilal Patel, Auteur ; Diane Hildebrandt, Auteur . - 2012 . - pp. 9061-9077. Industrial chemistry Langues : Anglais (eng) in Industrial & engineering chemistry research > Vol. 51 N° 26 (Juillet 2012) . - pp. 9061-9077 Mots-clés : Coal  Combustion Résumé : Much of our energy reserves are locked in the chemical potential of chemicals such as fossil fuels. The majority of CO2 emissions caused by human activities come from the combustion of these fuels. Typically, the fuel is burned with oxygen (air), and heat is released. This heat is then used to drive power cycles to produce, for example, electricity in a power plant or motion in the motor car engine. Often, the performance of these processes is assessed in term of thermal efficiency (ηth), which considers how much of the energy released in the combustion process is turned into work. This is not a good representation of how efficient the process is, however, as an idealized Carnot engine, which takes heat from a heat source at a temperature TH and rejects heat to a heat sink at the reference temperature To = 298.15 K, is reversible and thus takes all of the work potential (exergy) of heat and converts this to work. Thus, the Carnot engine might have only 40% efficiency in terms of converting heat to work (ηth), but because it is fully reversible, it generates no entropy, and therefore, it is 100% efficient in terms of recovering the work potential of heat. However, there is a much more fundamental efficiency that should be considered, namely, how much of the chemical potential of the fuel is turned into work. When combustion processes are considered in this way, it becomes clear that some of the major inefficiencies are in the chemical transformations that produce heat, rather than in the power cycles that convert heat to work. A very important question remains: Is it possible to do these transformations more efficiently and thereby conserve the work potential or chemical potential in fuel? This article shows, from a fundamental thermodynamic analysis, that it is not possible to combust carbon-based materials efficiently, that is, that the process of combustion of carbon-based materials is irreversible and that a considerable amount of the chemical potential of the fuel is lost during the combustion process. However, other substances or chemistries are explored in this work, and it is shown that some of these have the potential for more reversible combustion. These options are explored, and their potential implementation is examined by considering a coal-based power plant as an example. In particular, it is shown that CO2 emissions could be significantly reduced by using different chemical pathways to do the combustion and by combining power and chemical production. ISSN : 0888-5885 En ligne : http://cat.inist.fr/?aModele=afficheN&cpsidt=26107463

Work to chemical processes / Baraka Celestin Sempuga in Industrial & engineering chemistry research, Vol. 50 N° 14 (Juillet 2011) 

Public ISBD [article]  in Industrial & engineering chemistry research > Vol. 50 N° 14 (Juillet 2011) . - pp. 8603-8619 Titre : Work to chemical processes : the relationship between heat, temperature, pressure, and process complexity Type de document : texte imprimé Auteurs : Baraka Celestin Sempuga, Auteur ; Diane Hildebrandt, Auteur ; Bilal Patel, Auteur Année de publication : 2011 Article en page(s) : pp. 8603-8619 Note générale : Chimie industrielle Langues : Anglais (eng) Mots-clés : Chemical  processes  Temperature  Process  complexity Résumé : For a chemical process to be feasible, two levels of energy must be met: the heat and work requirements of the process. Whereas, for most processes, the heat requirement can easily be satisfied, supplying the amount of work needed is a major challenge and is usually the determinant of the process complexity. In some cases, heat, by virtue of its temperature, can satisfy the work requirement for a process; it is the simplest method for supplying work but could result in major irreversibility when applied inappropriately to a process. This article discusses different techniques that can be used to supply work to a process. A graphical approach, namely, the gh diagram, is used to analyze the heat and work requirements of chemical processes and to determine which method of supplying work is suitable for the process to be feasible and reversible. An ammonia process is analyzed as a case study, in which different methods of supplying work are compared and an attempt is made to elucidate the consequences of operating conditions, namely, temperature, on the reversibility and complexity of the process. This is a novel approach to process synthesis that requires knowledge of ΔH and ΔG only to determine the target for a process in terms of heat and work requirements, to determine which method of supplying work is suitable, to provide means of manipulating the process in order to use available technology and get as close to reversibility as possible, and to provide an early understanding of what the process structure would be. It also allows for the assessment of irreversibilities and where they occur within a process; therefore, it can be applied to existing processes to reveal opportunities for improvement and determine how they can be achieved. DEWEY : 660 ISSN : 0888-5885 En ligne : http://pubs.acs.org/doi/abs/10.1021/ie2004785 [article] Work to chemical processes : the relationship between heat, temperature, pressure, and process complexity [texte imprimé] / Baraka Celestin Sempuga, Auteur ; Diane Hildebrandt, Auteur ; Bilal Patel, Auteur . - 2011 . - pp. 8603-8619. Chimie industrielle Langues : Anglais (eng) in Industrial & engineering chemistry research > Vol. 50 N° 14 (Juillet 2011) . - pp. 8603-8619 Mots-clés : Chemical  processes  Temperature  Process  complexity Résumé : For a chemical process to be feasible, two levels of energy must be met: the heat and work requirements of the process. Whereas, for most processes, the heat requirement can easily be satisfied, supplying the amount of work needed is a major challenge and is usually the determinant of the process complexity. In some cases, heat, by virtue of its temperature, can satisfy the work requirement for a process; it is the simplest method for supplying work but could result in major irreversibility when applied inappropriately to a process. This article discusses different techniques that can be used to supply work to a process. A graphical approach, namely, the gh diagram, is used to analyze the heat and work requirements of chemical processes and to determine which method of supplying work is suitable for the process to be feasible and reversible. An ammonia process is analyzed as a case study, in which different methods of supplying work are compared and an attempt is made to elucidate the consequences of operating conditions, namely, temperature, on the reversibility and complexity of the process. This is a novel approach to process synthesis that requires knowledge of ΔH and ΔG only to determine the target for a process in terms of heat and work requirements, to determine which method of supplying work is suitable, to provide means of manipulating the process in order to use available technology and get as close to reversibility as possible, and to provide an early understanding of what the process structure would be. It also allows for the assessment of irreversibilities and where they occur within a process; therefore, it can be applied to existing processes to reveal opportunities for improvement and determine how they can be achieved. DEWEY : 660 ISSN : 0888-5885 En ligne : http://pubs.acs.org/doi/abs/10.1021/ie2004785