Abstract More than 900 papers related to organosolv pulping have been reviewed in this thesis. From the information included in those papers it can be concluded that organosolv pulping processes are still in a developing stage and are not yet ready to seriously threat the position of the kraft process as the main pulp manufacturing process in the world. Distillation seems to be the main alternative as the process for recovering the solvent in organosolv pulping. A good reason for this is that using simple distillation no potentially harmful components are introduced to the process. The effect of feed composition on the operation of a separation sequence in an organosolv process using aqueous formic and acetic acids and corresponding peroxyacids was studied. When simple distillation was used as the separation method the effect was found to be significant. The no ideal nature of the formic acid-acetic acid-water mixture, which separation was studied, makes the ternary composition space to divide into four distillation regions. Which region the feed is located in, obviously determines the economy of the distillation sequence. Shortcut calculation methods cannot be recommended to be used for designing a distillation sequence for the ternary mixture studied, but they give useful information for the comparison of such sequences. They were used to choose a limited number of alternatives for studies with rigorous calculation methods. Minimum work of separation can also be used to make a satisfying estimate for the relative easiness of separation of the formic acid-acetic acid-water mixture. Thermal integration using pinch technology was also tested and found very useful for decreasing the thermal energy consumption of distillation processes. Thermodynamic efficiencies for separating the formic acid-acetic acid-water mixture by simple distillation were estimated. They were found to be lower than the average value for distillation presented in literature.

Syftet med det här examensarbetet är att undersöka möjligheter för energieffektivisering i form av ökad värmeåtervinning hos Ahlström-Munksjö Aspa Bruk AB med målet att föreslå åtgärder som minskar behovet av färskånga till uppvärmning i processerna. Detta har gjorts med hjälp av en pinchanalys där de externa behoven, pinchöverträdelser och effektiviseringsmöjligheter har identifierats och analyserats för att avgöra hur effektiv värmeväxlingen på Aspa Bruk är. Strömdata har samlats in på plats på bruket främst genom givare som loggar data kontinuerligt men även genom mätningar, miljöbesiktningsrapporter och antaganden.  Ur pinchanalysen framkom det att de externa värmebehoven potentiellt skulle kunna reduceras med ca 19,2 MW, vid ett så energieffektivt system som möjligt, jämfört med dagens behov av färskånga som ligger på 71,5 MW. I praktiken är det dock inte möjligt att genomföra åtgärder för att minska det externa värmebehovet fullständigt till följd av tekniska- och ekonomiska begränsningar. Pinchöverträdelser står för ca 7,7 MW av de ca 19,2 MW och återfinns i sekundärvärmesystemet då det råder överskott av värme i varmvatten- och hetvattenproduktionen.  De åtgärdsförslag som läggs fram bygger på att effektivisera energianvändningen och avlägsna pinchöverträdelser med åtgärder som anses genomförbara. Tre åtgärder presenteras:  Använda värmeenergin från rökgaserna från sodapannan för att förvärma förbränningsluften till sodapannan och därmed ersätta delar av färskångan som används till detta. Öka andelen flashånga från tank 2 till förbasningsfickan där flisen förvärms innan kokaren istället för terpentinkondensorn. Detta skulle medföra en reducering av färskånga till förvärmningen av flisen.  Eliminera 3 bars ångan till hetvattentanken och kompensera med ett ökat varmvattenflöde genom ett ökat intag av råvatten som ska bli varmvatten.  Totalt skulle dessa åtgärder potentiellt kunna minska förbrukningen av färskånga med ca 12,5 MW. Potentiellt skulle även mer ånga kunna sparas om rökgaserna från sodapannan tilläts kondensera. Åtgärdsförslag nummer 3 är den som bidrar mest till reduceringen av färskånga på Ahlstrom-Munksjö Aspa Bruk AB. / The purpose of this master’s thesis is to investigate opportunities for a higher energy efficiency in terms of increased heat recovery at Ahlstrom-Munksjö Aspa Bruk AB with the goal of suggesting actions that reduces the need for live steam in process heating. In order to do this a pinch analysis was conducted where the utility consumptions, pinch violations and opportunities for increased energy efficiency were identified and analyzed in order to determine how efficient the heat exchange at Aspa Bruk is. Stream data was gathered at the mill mainly through continuously logging sensor data but also through measurements, environmental inspection reports and assumptions.       From the pinch analysis it was discovered that the external hot utility potentially could be reduced by approximately 19,2 MW given that the system would be as energy efficient as possible, compared to the current need of live steam that is 71,5 MW. However, in reality it is not possible to accomplish this reduction due to technical and economic limitations. Pinch violations stand for about 7,7 MW of the 19,2 MW and are located in the secondary heat system since there is an excess of heat in the warm water- and hot water production.  The actions suggested are based on increasing the efficiency of the energy consumption and removing pinch violations and are also considered feasible. Three suggestions are presented:  Recover the heat in the fumes from the recovery boiler and use it to preheat the combustion air in to the recovery boiler and thereby replace some of the live steam used for this.  Increase the amount of flash steam from tank 2 to the preheating of the woodchips before the boiler by reducing flash steam to the turpentine condenser. This would lead to a reduction in live steam used to preheat the woodchips. Eliminate the 3-bar live steam to the hot water tank and compensate it by increasing the amount of cold water that is going to become warm water.  In total, these proposed arrangements will potentially lead to a reduction in the use of live steam of approximately 12,5 MW. Potentially even more live steam can be saved if the fumes from the recovery boiler are allowed to condense. Number 3 amongst the proposed actions is the one that has the biggest influence on the reduction of live steam at Ahlstrom-Munksjö Aspa Bruk AB.

Made available in DSpace on 2016-06-02T19:56:53Z (GMT). No. of bitstreams: 1 5833.pdf: 3594761 bytes, checksum: 22ca28a1942a7b8b691c4f52f98f2924 (MD5) Previous issue date: 2014-02-17 / Universidade Federal de Sao Carlos / The increase in demand for biofuels has driven the development of new technologies such as ethanol production from sugarcane bagasse hydrolysis. Given the importance of Brazil in the ethanol market, the inclusion of technology of second generation ethanol will intensify its production. Energy integration in a sugarcane biorefinery provides important advantages for industrial processes such as better energy management, environmental benefits and increased ethanol production. The last factor is due to lower steam consumption in plant with energy integration, so, less bagasse is needed for cogeneration and a fraction of the surplus can be made available for production of second generation ethanol. In this context, the present study conducted energy integration of a sugarcane biorefinery in order to reduce the consumption of utilities. The technique used was Pinch analysis, an established methodology in the area of energy integration. The biorefinery used in this work consists of process for first and second generation ethanol and electricity production simulated in EMSO software (Environment for Modeling, Simulation, and Optimization). Six different scenarios of biorefinery were evaluated, which differ by pretreatment for bagasse (hydrothermal, diluted acid and steam explosion) and by inclusion or not of pentoses fermentation step. Processes that consider pentoses fermentation step have higher ethanol production when compared to processes that do not make use of pentoses fraction, but steam consumption increases in the same order of magnitude of ethanol production. For the six scenarios evaluated energy integration demonstrated a reduction in energy consumption over 50% when compared to corresponding processes without energy integration and over 30% when compared to process with project integration, as commonly found in Brazilian plants. Besides the economic advantage due to decreased costs of hot and cold utilities, the energy integration provides better energy management, reduction in emission of gases and liquid effluents and increases the availability of bagasse for production of second generation ethanol and/or electricity. / O aumento na demanda por biocombustíveis tem impulsionado o desenvolvimento de novas tecnologias como a produção de etanol a partir da hidrólise do bagaço de cana-de-açúcar. Dada a grande importância do Brasil no mercado de etanol, a inserção da tecnologia de etanol de segunda geração potencializará o crescimento da produção. A integração energética em uma biorrefinaria de cana-de-açúcar proporciona importantes vantagens ao processo industrial como a melhor gestão de energia, benefícios ambientais e aumento na produção de etanol. O último fator se deve ao menor consumo de vapor na planta com a integração energética, logo, menos bagaço é necessário para o sistema de cogeração e parte do excedente pode ser disponibilizado para a produção de etanol de segunda geração. Neste contexto, o presente estudo realizou a integração energética de uma biorrefinaria de cana-de-açúcar com o objetivo de reduzir o consumo de utilidades. A técnica utilizada foi a análise Pinch, metodologia consagrada na área de integração energética. A biorrefinaria empregada neste trabalho consiste do processo de produção de etanol de primeira e segunda geração e energia elétrica por simulação computacional realizada no software EMSO (Environment for Modeling, Simulation, and Optimization). Foram avaliados seis cenários diferentes da biorrefinaria, os quais diferem pelo tipo de pré-tratamento para o bagaço (hidrotérmico, ácido diluído e explosão a vapor) e pela consideração ou não da etapa de fermentação das pentoses. Os processos com os pré-tratamentos hidrotérmico, ácido diluído e explosão a vapor com a inclusão da etapa de fermentação das pentoses tem maior produção de etanol quando comparado aos processos que não fazem uso da fração de pentoses, porém o consumo de vapor aumenta na mesma ordem de grandeza da produção de etanol. Para os seis cenários avaliados a aplicação da integração energética demonstrou uma redução no consumo de energia acima de 50% se comparada aos correspondentes processos sem integração energética e acima de 30% se comparada aos processos com integração de projeto, como comumente encontrados nas usinas brasileiras. Além da vantagem econômica, devido à diminuição nos custos de utilidades quentes e frias, a integração energética do processo proporciona melhor gestão de energia, redução na emissão de gases e efluentes líquidos e aumenta a disponibilidade de bagaço para a produção de etanol de segunda geração e/ou energia elétrica.

Orientador: Roger J. Zem / Dissertação (mestrado) - Universidade Estadual de Campinas, Faculdade de Engenharia Quimica / Made available in DSpace on 2018-07-27T02:36:46Z (GMT). No. of bitstreams: 1 Santos_LucianaCristinados_M.pdf: 3430679 bytes, checksum: 28d163db7620c9a4ecc0df34b7ae538b (MD5) Previous issue date: 2000 / Resumo: Um novo procedimento de estimativa de área e custos de capital para sistemas sob integração energética é proposto. Este método permite que restrições de troca térmica e trocadores com mais de uma passagem nos tubos sejam utilizados. O método desenvolvido resulta em um modelo não linear onde, balanços de energia, restrições de troca térmica e o fator de correção para trocadores do tipo casco e tubo 1-2 (com 1 passagem no casco e duas ou mais passagens pares nos tubos) são incluídos. As dificuldades de convergência decorrentes da adição de restrições não lineares, devido a utilização de trocadores com múltiplas passagens nos tubos, levaram ao uso de uma estratégia nova. Esta estratégia é constituída pela resolução de dois problemas não lineares. O primeiro estima a área para trocadores contracorrente constituindo a primeira aproximação para obtenção dos fatores de correção para trocadores com múltiplas passagens nos tubos, e outro onde é estimado o capital para trocadores 1-2. Os fatores de correção dos trocadores com múltiplas passagens nos tubos são calculados externamente ao modelo e entram como parâmetro conhecido. Este procedimento é repetido até que uma diferença tolerável entre as estimativas de capital seja atingida. Para completar o projeto de recuperação de energia, uma metodologia que fornece o projeto da rede de trocadores de calor considerando restrições de troca térmica é proposto. O modelo de síntese resulta na formulação de um MIP (Mixed Integer Programming), onde o problema é dividido em estágios e submetido a balanços de energia para minimizar o número de trocadores.Uma comparação dos custos de capital entre os métodos da estimativa de área e o de síntese de rede mostrou bons resultados, já que a diferença de capital entre os métodos foi inferior a 10% / Abstract: A new procedure for estimating area and capital cost targets of constrained heat exchanger networks is presented. The method allows for match constrained networks and exchangers with more than one tube passo The procedure is based on modelling the problem as a non-linear formulation where the forbidden exchanger matches are included as constraints and the temperature difference correction due to multipass exchangers is included in the modeI. The difficulty of converging to a solution due to the additional non-linear constraints imposed by the multipass exchangers required the use of a two-Ievel approach: at the inner leveI, the area targets for simple pass exchangers are obtained, and at the outer leveI the temperature difference required for multipass exchangers are computed and fed back to the inner leveI. The procedure is repeated until an appropriate tolerance between two iterations was achieved. A procedure for the authomatic synthesis of contrained heat exchanger network was developed, using a mixed integer programming approach and minimising the overall number of heat exchangers. A comparison between the estimated exchanger areas and costs estimated by the new procedure and the area and costs obtained from the final heat exchanger design shows a very good agreement / Mestrado / Sistemas de Processos Quimicos e Informatica / Mestre em Engenharia Química

The purpose of this project is to find an identification tag that can be used in a future automated pinch analysis tool. It can be used to further analyse composite curves and pinch results by tracking the original streams that was converted. In real life situations, retrofitting a process industries streams, can decrease heat demands and costs. A pinch analysis and a heat exchange network is created with fixed and flexible flows to show a recommendation on how the system model can handle this type of situations. The models have been created by hand with support from pinch literature and the calculations validated with mathematical software such as matlab and other graphing tools. The literature study and pinch modelling resulted in a recommendation of tagging Hstart and Hend for each individual stream. By using a geographical tag in a coordinate system the analyst will be able to find the original streams in the pinch analysis and composite curves. The project also resulted in a heating exchange network created from the fixed and flexible data set. The enthalpy differences between the ideal pinch result and the fixed data set is smaller than one might expect because of enthalpy abundance in the specific intervals.

Este trabalho tem como objetivo analisar a tecnologia do ciclo refrigerante misto para obtenção de gás natural liquefeito (GNL). Nessa tecnologia, o GNL é obtido por meio do seu resfriamento através de um ciclo de refrigeração, cujo fluido refrigerante é formado por uma mistura de diversos componentes. O ciclo de refrigeração é usado para resfriar a corrente de gás natural até as condições criogênicas por meio de um trocador de calor. A determinação da composição ótima dessa mistura de refrigerantes é de suma importância para a correta e eficiente operação da planta. O modelo termodinâmico para o cálculo de equilíbrio de fases dos componentes da mistura refrigerante é o baseado na Lei de Raoult, válido para misturas e soluções ideais. Inicialmente, revisam-se os conceitos de refrigerantes mistos, curvas compostas e o ponto de pinça (pinch point), utilizados na implementação da solução computacional. A aplicação dos modelos de gás e solução ideal influencia nos resultados, mas, não obstante, produz bons resultados como os obtidos no presente trabalho. A operação eficiente do ciclo depende, sobretudo, de três parâmetros principais, quais sejam: vazão da mistura refrigerante, razão de pressões alta e baixa do ciclo de refrigeração e composição da mistura refrigerante. Da análise dos resultados obtidos conclui-se que a alteração nas proporções da composição do refrigerante muda significativamente a forma das curvas composta quente e composta fria, quando comparados à alteração dos níveis de pressão e da vazão do ciclo refrigerante. Entretanto, a operacionalização do ciclo somente ocorre se um dado conjunto de valores daqueles parâmetros satisfaça uma determinada diferença mínima de temperatura, ou ponto de pinça, entre as curvas composta quente e composta fria dentro do trocador de calor. Assim, a operação eficiente do ciclo de refrigeração requer a otimização daqueles três parâmetros operacionais. / This work has the objective of analyzing the technology of mixed refrigerant cycle for obtaining liquefied natural gas (LNG). In that technology, the liquefied natural gas is obtained by means of cooling through a refrigeration cycle, whose fluid refrigerant is formed by a mixture of various components. The refrigeration cycle is used to cool the natural gas stream to cryogenic condition with the use of a heat exchanger. The determination of the optimal composition of this refrigerant mixture is very important for the correct and efficient operation of the plant. The thermodynamic model for the equilibrium phase calculation of the refrigerant mixture is based on the Law of Raoult, which is valid for ideal mixtures and solutions. Initially, the concepts of refrigerant mixture, composite curves and pinch point used in the implementation of the numerical solution were reviewed. The application of ideal-gas and ideal-solution models has influence on the results. Nevertheless, it produces good results as those obtained in the present work. The efficient operation of the cycle depends essentially of three key parameters, which are: refrigerant flow rate, the ratio of high to low pressures of the refrigerant cycle and the mixed refrigerant composition. The results indicated that the composition variation of the refrigerant changes significantly the shape of hot and cold composite curves in comparison to the modification in the pressure levels and the refrigerant flow rate of the refrigerant cycle. However, the process will operate only if a given set of values of those parameters satisfies a minimum temperature difference, or pinch point, between the hot and cold composite curves within the heat exchanger. Thus, the efficient operation of the refrigerant cycle requires the optimization of those three operational parameters.

A la veille d’une nouvelle conférence sur le climat, les questions environnementales demeurent plus que jamais au premier plan de la vie publique. La lutte contre le réchauffement climatique, et les émissions de gaz à effet de serre, dont l’attribution à l’activité humaine fait globalement l’objet d’un consensus scientifique, constituent l’un des plus grands défis de l’humanité pour les prochaines années. Dans ce contexte, l’amélioration de l’efficacité énergétique des sites de production est une des préoccupations des industriels. Les réglementations environnementales, et les fluctuations des cours de l’énergie les forcent à continuellement améliorer leurs procédés pour en maintenir la compétitivité. Ceux-ci doivent ainsi pouvoir disposer d’outils leur permettant d’effectuer des diagnostics énergétiques sur les installations, leur facilitant la prise de décision et leur permettant d’élaborer des solutions d’efficacité énergétique sur leurs sites industriels. Les travaux présentés dans ce document visent à introduire une méthodologie d’analyse et de rétro-conception pour l’amélioration énergétique des procédés industriels. Cette méthodologie, qui s’appuie sur une utilisation combinée de la méthode du pincement et de l’analyse exergétique, se décompose en trois grandes étapes : la première comprend le recueil des données, la modélisation et la simulation du procédé. La deuxième étape, dédiée à l’analyse du procédé, est elle-même divisée en deux phases. La première, qui s’appuie pour l’essentiel sur l’utilisation de la méthodologie du pincement, s’intéresse uniquement à l’analyse du système de fourniture et de récupération de l’énergie thermique. Si cela s’avère nécessaire, le procédé complet est étudié dans une deuxième phase. L’analyse pincement se limitant à l’étude des procédés thermiques, une méthodologie d’analyse exergétique est mise en œuvre. Cette méthodologie s’appuie sur l’implémentation de l’analyse exergétique dans l’environnement ProSimPlus, entreprise par Ali Ghannadzadeh, et poursuivie pendant cette thèse. Les formules d'exergie ont été affinées pour s’ajuster aux différents modèles thermodynamiques. L’approche d’analyse proposée dans ce manuscrit est basée sur l’utilisation d’une nouvelle représentation graphique des bilans exergétiques : le ternaire exergétique. Ce dernier permet d’illustrer tous les aspects des bilans exergétiques et ainsi d'assister l’ingénieur dans l’analyse du procédé. La troisième étape s’intéresse à la conception pour l’amélioration énergétique. Alors que l’analyse du pincement propose des solutions d’amélioration, l’analyse exergétique ne le permet pas. Elle nécessite l’apport d’une certaine expertise pour aboutir au développement de solutions d’améliorations. Pour pallier ce problème, l’expertise est en partie capitalisée dans un système de raisonnement à partir de cas. Ce système permet de proposer des solutions à des problèmes nouveaux en analysant les similarités avec des problèmes anciens. Cet outil se révèle utile pour définir des solutions locales d’améliorations énergétiques. L’analyse du pincement associée à des outils numériques est ensuite utilisée pour concevoir des propositions complètes d’améliorations. La seconde partie de ce manuscrit présente cette étape. / On the eve of a new conference on climate change, environmental issues remain more than ever at the forefront of public life. Tackling climate change, and reducing greenhouse gases emissions, that are largely attributable to human activity, represents one of the biggest challenges for humanity in the coming years. In such a context, the promotion of best practices to enable an efficient utilization of energy has emerged as one of the major point of focus. High volatility of energy prices and the increasingly stringent environmental regulations have forced industrials to continuously improve their processes in order to cut the energy consumption down and reduce GHG emissions. For this purpose, industrials need tools to perform energy audits on facilities, to ease decision-making and to enable them to develop their energy efficiency solutions on their sites. In this context, the study presented in this dissertation aims at introducing a new systematic procedure for energy diagnosis and retrofit of industrial processes. This methodology presented in this dissertation is divided into three stages: the first involves the data collection, the modeling and simulation of the process. The second stage, dedicated to the analysis of the process, is subdivided into two phases. The first, which is essentially relying on the Pinch methodology, is only concerned with the analysis of the thermal energy supply and recovery system. If necessary, the complete process is studied in the second phase of the analysis. Pinch analysis being limited to the analysis of thermal systems, an exergy analysis methodology is then implemented. This methodology is based on the implementation of the Exergy analysis in the ProSimPlus modelling and simulation environment, undertaken by A. Ghannadzadeh, and pursued in this study. The formulas proposed by Ali Ghannadzadeh have been adjusted to take into account different thermodynamic approaches. A new graphical representation of exergy balances, the exergetic ternary diagram, is also introduced to assist engineers in the analysis process. It enables to illustrate all aspects of exergy balances, i.e. the irreversibility, the exergy losses and the exergy efficiencies of each unit operation. The automation of this new graphical layout was made possible by the implementation of a generic exergy efficiency in the simulator. This analysis paves the way to the third step of the overall methodology dedicated to retrofitting. This methodology is detailed in the first part of this dissertation. While Pinch analysis proposes improvement solutions, the Exergy analysis does not. The key to achieving a significant exergy analysis lies in the engineer’s ability to propose alternatives for reducing thermodynamic imperfections, thus exergy analysis is supposed to be undertaken by an experienced user. To overcome this problem, the expertise is partly capitalized in a case-based reasoning system. This system allows the proposition of solutions to new problems by analyzing the similarities with solved problems. This tool is useful for defining local solutions for energy improvements. The Pinch analysis combined to numerical tools is then used to develop alternatives. This third step is developed in the third part of the manuscript.

Orientador: Prof. Dr. Marcelo Modesto / Dissertação (mestrado) - Universidade Federal do ABC. Programa de Pós-Graduação em Energia, 2015. / Nas últimas décadas, a integração energética tem se desenvolvido em busca do melhor uso da energia e de recursos em processos industriais e consequente redução do consumo de combustíveis fósseis e dos impactos negativos ao meio ambiente. Dentre os métodos de integração energética, o Método Pinch é, sem dúvida, o mais popular devido a sua simplicidade de implementação e eficiência. Os repetitivos cálculos que a metodologia requer levaram ao desenvolvimento de softwares a fim de agilizar e simplificar o trabalho do projetista. No presente trabalho, foi desenvolvida uma ferramenta computacional para realizar a integração energética de correntes pelo Método Pinch que será utilizada como módulo auxiliar ao programa principal do Projeto Temático FAPESP (Processo Fapesp 2012/04179-2) da Biorrefinaria Virtual de 1ª Geração, a ser desenvolvido na plataforma EMSO. A ferramenta foi desenvolvida na forma de um plug-in, o que facilita o seu uso e distribuição entre vários usuários, na linguagem de programação C++ e fornece ao usuário as metas energéticas, subsidiandoo na elaboração da rede preliminar de trocadores de calor e indicando possibilidades de integração entre correntes que demandem utilidades quentes ou frias. A validação da ferramenta se deu por meio de sua aplicação na integração energética de cinco casos de diferentes níveis de complexidade, sendo um voltado à indústria sucroalcooleira. Os resultados obtidos pelo plug-in foram comparados aos encontrados na literatura e aos da consagrada ferramenta Aspen Energy Analyser®, comprovando-se a consistência e eficiência do plug-in, até mesmo para casos mais complexos, como problemas limiares e de múltiplos pontos Pinch. Como o EMSO não oferece suporte à criação de gráficos, uma planilha suporte em Excel® foi desenvolvida a fim de construir as Curvas Compostas e a Grande Curva Composta, funcionando de modo inteiramente automatizado. / Over the last few decades, heat integration has been developed in search for the better use of energy and resources in industrial processes and eventual reduction in fossil fuels consumption and in the negative environmental impacts. Among the heat integration methods, Pinch technology is without a doubt the most popular one due to its implementation simplicity and efficiency. The monotonous calculations it requires have led to the development of computer software to reduce time and simplify the designer¿s work. In the present study, a computational tool was developed for heat integration through Pinch Analysis to be used as an auxiliary module to the main FAPESP Thematic Project (Fapesp process 2012/04179-2) program of the 1st generation virtual biorefinery, which is being developed on EMSO platform. The computational tool was developed in the form of a plug-in, making its use and distribution among several users easier, in the C++ programming language and it supplies the user with the energy targets, aiding him or her with the design of the preliminary heat transfer network and indicating integration possibilities between hot or cold utility requiring streams. The tool validation was carried out through its application in five case studies of different complexity levels, one of them being related to the sugarcane industry. The plug-in¿s results were compared to the ones gathered from the literature and the ones obtained from the well-stablished heat integration tool Aspen Energy and Analyser®, proving the plug-in¿s consistency and efficiency even for more complex cases such as threshold problems and multiple Pinch problems. As EMSO does not support the design of charts like the Composite Curves and the Grand Composite Curve, an Excel® spreadsheet was developed for this purpose, working on an entirely automated way.

Este trabalho tem como objetivo analisar a tecnologia do ciclo refrigerante misto para obtenção de gás natural liquefeito (GNL). Nessa tecnologia, o GNL é obtido por meio do seu resfriamento através de um ciclo de refrigeração, cujo fluido refrigerante é formado por uma mistura de diversos componentes. O ciclo de refrigeração é usado para resfriar a corrente de gás natural até as condições criogênicas por meio de um trocador de calor. A determinação da composição ótima dessa mistura de refrigerantes é de suma importância para a correta e eficiente operação da planta. O modelo termodinâmico para o cálculo de equilíbrio de fases dos componentes da mistura refrigerante é o baseado na Lei de Raoult, válido para misturas e soluções ideais. Inicialmente, revisam-se os conceitos de refrigerantes mistos, curvas compostas e o ponto de pinça (pinch point), utilizados na implementação da solução computacional. A aplicação dos modelos de gás e solução ideal influencia nos resultados, mas, não obstante, produz bons resultados como os obtidos no presente trabalho. A operação eficiente do ciclo depende, sobretudo, de três parâmetros principais, quais sejam: vazão da mistura refrigerante, razão de pressões alta e baixa do ciclo de refrigeração e composição da mistura refrigerante. Da análise dos resultados obtidos conclui-se que a alteração nas proporções da composição do refrigerante muda significativamente a forma das curvas composta quente e composta fria, quando comparados à alteração dos níveis de pressão e da vazão do ciclo refrigerante. Entretanto, a operacionalização do ciclo somente ocorre se um dado conjunto de valores daqueles parâmetros satisfaça uma determinada diferença mínima de temperatura, ou ponto de pinça, entre as curvas composta quente e composta fria dentro do trocador de calor. Assim, a operação eficiente do ciclo de refrigeração requer a otimização daqueles três parâmetros operacionais. / This work has the objective of analyzing the technology of mixed refrigerant cycle for obtaining liquefied natural gas (LNG). In that technology, the liquefied natural gas is obtained by means of cooling through a refrigeration cycle, whose fluid refrigerant is formed by a mixture of various components. The refrigeration cycle is used to cool the natural gas stream to cryogenic condition with the use of a heat exchanger. The determination of the optimal composition of this refrigerant mixture is very important for the correct and efficient operation of the plant. The thermodynamic model for the equilibrium phase calculation of the refrigerant mixture is based on the Law of Raoult, which is valid for ideal mixtures and solutions. Initially, the concepts of refrigerant mixture, composite curves and pinch point used in the implementation of the numerical solution were reviewed. The application of ideal-gas and ideal-solution models has influence on the results. Nevertheless, it produces good results as those obtained in the present work. The efficient operation of the cycle depends essentially of three key parameters, which are: refrigerant flow rate, the ratio of high to low pressures of the refrigerant cycle and the mixed refrigerant composition. The results indicated that the composition variation of the refrigerant changes significantly the shape of hot and cold composite curves in comparison to the modification in the pressure levels and the refrigerant flow rate of the refrigerant cycle. However, the process will operate only if a given set of values of those parameters satisfies a minimum temperature difference, or pinch point, between the hot and cold composite curves within the heat exchanger. Thus, the efficient operation of the refrigerant cycle requires the optimization of those three operational parameters.

La méthode du Pincement a été développée et utilisée dans le secteur de la pétrochimie. Le nombre de flux y est important et la consommation énergétique est un critère décisionnel fort. D'autres secteurs énergivores tels la métallurgie, la production de papier et de pâte à papier ou l'industrie agroalimentaire peuvent bénéficier de cette approche structurée. Par ailleurs, l'intégration d'utilités thermodynamiques complexes comme les pompes à chaleur ou les unités de cogénération peut réduire significativement la consommation d'énergie d'un procédé, sans avoir à en modifier la technologie.Un algorithme de conception d'un réseau d'échangeurs à partir de flux thermiques à été choisi dans la littérature, puis deux fonctionnalités lui ont été ajoutées : la différenciation des technologies d'échangeur et la prise en compte de flux "disponibilités" à température de sortie variable. Un module de présélection a été développé pour proposer et dimensionner des utilités thermodynamiques à partir de la grande courbe composite et d'un critère exergétique. Il est utilisé en amont de la conception du réseau d'échangeurs.Ces deux algorithmes ont été intégrés dans un logiciel dédié à l'intégration énergétique de procédés à partir des flux thermiques des opérations unitaires. Plusieurs validations ont été faites sur des cas théoriques de référence issus de la littérature ainsi que sur des cas industriels réels nécessitant la modélisation des procédés. L'enchainement des deux algorithmes débouche sur l'obtention de résultats concrets et technologiquement réalistes. L'amélioration apportée par les solutions est calculable à chaque étape. / The pinch analysis has been developed and exploited in the petrochemical sector. There are numerous heat fluxes and energy consumption is a strong decision criterion. Other energy-intensive sectors such as metallurgy, pulp and paper and food & drink industry can benefit from this systemic approach. Moreover, integration of complex thermodynamic utilities such heat pumps or Combined Heat and Power units can significantly reduce the energy consumption of a process, without having to interfere with the process technology.An algorithm for heat exchangers network design from heat fluxes was chosen in the literature and two features were added to it: Ability to pick different heat exchanger technology and creation of "availabilities" heat fluxes whose outlet temperature is variable. Preselection tool has been developed from grand composite curve and exergetic criterion to propose and pre-size thermodynamics utilities. It is used upstream of the heat exchangers network design step.These two algorithms have been integrated into a software for energy integration of process unit operations heat fluxes. Several validations were made on study cases from the literature as well as on industrial cases which require process modelling. The both algorithms sequence allows achieving practical and technologically feasible results. Improvement on energy consumption provided by the solutions can be calculated at each step.