A Simple Method for Finding Optimal Paths of Hot and Cold Streams inside Shell and Tube Heat Exchangers to Reduce Pumping Cost in Heat Exchanger Network Problems

In this paper, a simple method is presented for the synthesis and retrofit of heat exchanger networks (HENs) by considering pressure drop as well as finding proper path of streams inside heat exchangers (HEs) to reduce the pumping cost of network. Generally, HEN problems lead to MINLP models which have convergence difficulties due to the existence of both continuous and integer variables. In this study, instead of solving these variables simultaneously, a combination of Genetic Algorithm (GA) with Quasi Linear Programming (QLP) and Integer Linear Programming (ILP) was used for solving the problem. GA was used to find optimal HENs structure and streams paths, whereas continuous variables were solved by QLP. For the retrofit of HENs, a modified ILP model was used. Results show that the proposed method has the ability to reduce the cost of annual pumping due to considering optimal paths for streams in the HEs compared to the literature. This work is licensed under a Creative Commons Attribution 4.0 International License

Synthesis of optimal heat and mass exchange networks using a two-step hybrid approach including detailed unit designs

This PhD thesis develops a methodology for the synthesis of optimal heat and mass exchanger networks through a novel hybrid method. The two-step procedure makes use of simplified exchanger models in a network optimisation step, followed by a detailed design where the exchangers found in the network synthesis step are modelled in detail. Subsequent iterations of the network design step are then updated with information from the detailed network designs. The algorithm has certain advantages over previous methods in that the network optimisation is based on more realistic representations of the actual units therein and also that the method increases the likelihood of attaining a globally optimal solution through the generation and assessment of multiple candidate networks throughout the algorithm. The method can be used in a variety of applications and is demonstrated to be effective for large problems and multi-period scenarios. The thesis also shows that the method can be used in conjunction with multiple individual unit optimisation techniques including heuristics and fully explicit optimisation methods

Optimización de un intercambiador de placas para calentamiento de crudo pesado en emulsión con agua

En los pozos de extracción de crudos se presentan emulsiones de crudo-agua. Para el transporte de estas, es necesario romper la emulsión. Existen variadas formas de lograr este fin, una de ellas es el calentamiento del fluido. Normalmente son usados intercambiadores de calor de coraza y tubos, que son difíciles de transportar por sus grandes dimensiones, tópico que aumenta el costo de operación en perforaciones nuevas. En este trabajo se propone como opción de calentamiento el uso de intercambiadores de placas, los cuales tienen unas dimensiones considerablemente menores logrando resultados satisfactorios y haciendo posible la portabilidad de los mismos. Se hizo una optimización mediante superficies de respuesta para hallar una geometría de PHE (Plate Heat Exchanger) ideal para operar con crudos pesados. Los resultados muestran como con una misma superficie de transferencia, el PHE logra una temperatura de salida mayor al STHE (Shell and Tube Heat Exchanger), mientras que en caída de presión este último tiene un rendimiento muy superiorCrude-water emulsions are present in oil extraction wells. To transport these, it is necessary to break the emulsion. There are several ways to achieve this; one of them is the heating of the fluid. Shell and tube heat exchangers are often used, which are difficult to transport due to their large dimensions, which increases the cost of operation in new drilling. In this work, it has proposed as heating option the use of plate heat exchangers, which have considerably smaller dimensions making them portability possible and so achieving satisfactory results. An optimization was made by response surfaces to find an ideal PHE (Plate Heat Exchanger) geometry to operate with heavy crudes. The results show that with the same transfer surface, the PHE achieves a higher outlet temperature than the STHE (Shell and Tube Heat Exchanger), while in pressure drop the latter has a higher efficiencyMagíster en Gestión Energética Industria

Optimisation d'échangeurs de chaleur : condenseur à calandre, réseau d'échangeurs de chaleur et production d'eau froide

La présente étude porte sur l'optimisation de systèmes thermiques servant soit à récupérer de la chaleur ou à produire de la chaleur ou du froid. Essentiellement, le travail portera sur les condenseurs de type tubes et calandre, sur les réseaux d'échangeurs de chaleur ainsi que sur les systèmes de production d'eau froide. L'objectif ultime est de développer une méthode permettant de déterminer le design minimisant les coûts reliés à l'achat et à l'opération de ces systèmes thermiques. Pour atteindre cet objectif, on doit d'abord créer un modèle mathématique permettant de calculer les surfaces d'échanges requises et les puissances de pompage requises pour faire fonctionner un échangeur de chaleur. Basé sur des relations analytiques et empiriques, le modèle doit tenir compte des variables design considérées dans le problème, soit une dizaine de paramètres géométriques et le régime d'opération. Il s'agit d'identifier les valeurs à accorder à chacune de ces variables de design afin de faire le meilleur compromis entre la minimisation des surfaces d'échange de chaleur requises et la quantité d'énergie requise pour faire fonctionner les systèmes. Autrement dit, on cherche à minimiser le coût total, constitué du coût d'achat du matériel et des coûts d'opération. Une fois cette démarche réalisée pour le condenseur à tubes et calandre, on applique une méthode similaire pour optimiser une série d'échangeurs de chaleur dans le cas des réseaux d'échangeurs de chaleur et finalement pour un cycle de réfrigération composé de deux échangeurs, un condenseur et un évaporateur, ainsi qu'un compresseur. Étant donné le nombre important de variables de design considéré pour chacun de ces problèmes, le nombre total de design possible est trop élevé pour calculer le coût de chacun d'entre eux et choisir le meilleur. Cela serait trop coûteux en temps de calcul. C'est pourquoi nous ferons appel à l'utilisation d'algorithmes génétiques. Ces derniers nous permettront d'identifier avec une excellente probabilité le design optimal et ce, dans un laps de temps acceptable en pratique. La méthode est finalement validée grâce à des exemples d'application

Design and Evaluation of Processes to Obtain Antioxidant-Rich Extracts from tropical fruits cultivated in Amazon, Caldas and Northern Tolima Regions

En esta tesis se presenta un análisis del diseño del proceso para la obtención de extractos ricos en antioxidantes a partir de cinco frutas tropicales (Cordata matisia, Physalis peruviana, Solanum betaceum, Theobroma grandiflorum, Renealmia alpinia). Se utilizaron procedimientos de simulación basado en la caracterización experimental para evaluar el rendimiento de las diferentes tecnologías para las etapas de pretratamiento, extracción y concentración utilizando el software Aspen Plus. Se utilizaron dos tecnologías para el pretratamiento: secado convencional y secado por liofilización; para la extracción se evaluaron extracción supercrítica y con solventes, mientras que para la etapa de concentración se utilizó destilación al vacío y procesos de separación por membranas "ultrafiltración". Teniendo en cuenta lo anterior, ocho posibles configuraciones de proceso con integración másica fueron evaluadas con y sin integración energética en términos técnicos, económicos y ambientales de cada fruta. Además, se utilizaron modelos termodinámicos para determinar las condiciones de operación para todas las tecnologías, esto permitió minimizar los altos costos y el tiempo que implican los experimentos. Las evaluaciones técnicas que se presentan, incluyen la evaluación de los impactos económicos y ambientales. No obstante, estudios posteriores son necesarios para poner en práctica este tipo de proceso a escala industrial, pero este tipo de análisis sirven como base para el desarrollo de procesos eficientes. La principal desventaja asociada con las tecnologías convencionales es la degradación de los compuestos antioxidantes dado a la oxidación de compuestos antioxidantes, mientras que las tecnologías de gama alta conservan la calidad del producto, sin embargo, su costo es relativamente alto. Una característica común en las configuraciones de proceso fue la gran influencia de los costos de las materias primas en el coste de producción total. Este trabajo es un punto de partida para mejorar la cadena productiva de frutas tropicales e integrar como posibles nuevas alternativas de transformación. Con el fin de comparar los resultados obtenidos por simulación, los compuestos polifenólicos de cada fruta tropical fueron extraídos por las diferentes configuraciones de proceso y se evaluaron la actividad antioxidante de cada extracto con el propósito de comparar la calidad del producto final. Además, se diseño una biorefinería a base de copoazu a la cual se le realizó un análisis económico y ambiental. Se encontró que el uso de los datos experimentales, junto con el procedimiento de simulación son herramientas poderosas para el diseño y análisis de los procesos de extracción de antioxidantes. Como resultado final se demostró la viabilidad de la extracción de antioxidante para todas las frutas estudiadas con excepción de la fruta copoazú. Además, es importante tener en cuenta que la cáscara de Alpinia R. contiene relativamente cantidades más altas de compuestos polifenólicos con mayor actividad antioxidante. Por último, la producción de extractos ricos en antioxidantes a partir de frutas tropicales podría ser considerada como una oportunidad para promover el desarrollo rural con la participación de los productores en pequeña escala, como proveedores de materia prima.Abstract : In this thesis, a process design to obtain antioxidant-rich extracts from five tropical fruits (i.e. Matisia cordata, Physalis peruviana, Solanum betaceum, Theobroma grandiflorum, Renealmia alpinia) is presented. Simulation procedures based on experimental characterization were used to evaluate the yield of different technologies for pretreatment, extraction and concentration procedures using the Aspen Plus software. Both the conventional and freeze drying technologies were evaluated as pretreatment methods whereas conventional solvent and supercritical fluids were used for the extraction procedure. The concentration stage was performed by using vacuum distillation or ultrafiltration processes. Eight possible process configurations with mass integration were evaluated with and without energetic integration in technical, economic and environmental terms for each fruit. In this study, thermodynamic models were used in order to provide convenient use of the operation conditions for all the technologies, this methodology permit minimize the high costs and time that involve the experiments. The technical evaluations presented in this work provide the feasibility of process configurations, which included the evaluation of economic and environmental impacts. Nonetheless, several adjustments must be done to implement this type of process at industrial scale, but this kind of analysis serve as the basis draw recommendations for the efficient development processes. In this work was also proposed several process configurations with both conventional and high-end technologies for pretreatment, extraction and concentration stages. The major disadvantage associate with the conventional technologies is the degradation of antioxidant compounds by the possibility of oxidation of antioxidant compounds while the high-end technologies retain the product quality. However, the major disadvantage of high-end technologies is its relatively high cost. A common feature found in the process configurations for all considered feedstock was the high influence of raw material costs in total production cost. This work is a starting point to improve the tropical fruits productive chain and integrate as possible new transformation alternatives. In order to compare the simulation results, the polyphenolic compounds from each tropical fruit were extracted by the different process configurations and the antioxidant activities of extracts were evaluated with the purpose of compare the quality of the final product. Additionally, a process design and an economic and environmental analysis for a biorefinery-based on an exotic fruit as copoazu were performed. It was found that the uses of experimental data together with simulation procedure are powerful tools for designing and analyzing the processes for antioxidant rich-extracts. As final results it was demonstrated the feasibility of antioxidant extraction for all fruits studied excepting the copoazu fruit. Additionally, it is important to note that the R. alpinia peel contained relatively the highest amounts of polyphenolic compounds with highest antioxidant activity. Finally, the antioxidant rich-extracts production from tropical fruits could be considered as an opportunity to promote rural development with the participation of small scale producers as feedstock suppliers.Doctorad

Book of abstracts of the 10th International Chemical and Biological Engineering Conference: CHEMPOR 2008

This book contains the extended abstracts presented at the 10th International Chemical and Biological Engineering Conference - CHEMPOR 2008, held in Braga, Portugal, over 3 days, from the 4th to the 6th of September, 2008. Previous editions took place in Lisboa (1975, 1889, 1998), Braga (1978), Póvoa de Varzim (1981), Coimbra (1985, 2005), Porto (1993), and Aveiro (2001). The conference was jointly organized by the University of Minho, “Ordem dos Engenheiros”, and the IBB - Institute for Biotechnology and Bioengineering with the usual support of the “Sociedade Portuguesa de Química” and, by the first time, of the “Sociedade Portuguesa de Biotecnologia”. Thirty years elapsed since CHEMPOR was held at the University of Minho, organized by T.R. Bott, D. Allen, A. Bridgwater, J.J.B. Romero, L.J.S. Soares and J.D.R.S. Pinheiro. We are fortunate to have Profs. Bott, Soares and Pinheiro in the Honor Committee of this 10th edition, under the high Patronage of his Excellency the President of the Portuguese Republic, Prof. Aníbal Cavaco Silva. The opening ceremony will confer Prof. Bott with a “Long Term Achievement” award acknowledging the important contribution Prof. Bott brought along more than 30 years to the development of the Chemical Engineering science, to the launch of CHEMPOR series and specially to the University of Minho. Prof. Bott’s inaugural lecture will address the importance of effective energy management in processing operations, particularly in the effectiveness of heat recovery and the associated reduction in greenhouse gas emission from combustion processes. The CHEMPOR series traditionally brings together both young and established researchers and end users to discuss recent developments in different areas of Chemical Engineering. The scope of this edition is broadening out by including the Biological Engineering research. One of the major core areas of the conference program is life quality, due to the importance that Chemical and Biological Engineering plays in this area. “Integration of Life Sciences & Engineering” and “Sustainable Process-Product Development through Green Chemistry” are two of the leading themes with papers addressing such important issues. This is complemented with additional leading themes including “Advancing the Chemical and Biological Engineering Fundamentals”, “Multi-Scale and/or Multi-Disciplinary Approach to Process-Product Innovation”, “Systematic Methods and Tools for Managing the Complexity”, and “Educating Chemical and Biological Engineers for Coming Challenges” which define the extended abstracts arrangements along this book. A total of 516 extended abstracts are included in the book, consisting of 7 invited lecturers, 15 keynote, 105 short oral presentations given in 5 parallel sessions, along with 6 slots for viewing 389 poster presentations. Full papers are jointly included in the companion Proceedings in CD-ROM. All papers have been reviewed and we are grateful to the members of scientific and organizing committees for their evaluations. It was an intensive task since 610 submitted abstracts from 45 countries were received. It has been an honor for us to contribute to setting up CHEMPOR 2008 during almost two years. We wish to thank the authors who have contributed to yield a high scientific standard to the program. We are thankful to the sponsors who have contributed decisively to this event. We also extend our gratefulness to all those who, through their dedicated efforts, have assisted us in this task. On behalf of the Scientific and Organizing Committees we wish you that together with an interesting reading, the scientific program and the social moments organized will be memorable for all.Fundação para a Ciência e a Tecnologia (FCT