Mekanistisen termohydraulisen mallinnustavan soveltaminen uudentyyppisten teollisten prosessien dynaamiseen simulointiin

The PDF file of the dissertation includes the summary part and also all five publications as full texts.The process and energy industries have a remarkable position in developing sustainable future. They play an important role in mitigating climate change. Whilst aiming at energy efficient, material recycling, and emission-free processes, the industrial systems are becoming more complex. Process automation is fundamental in confirming that also complex systems can be managed and operated in an easy and safe way. Dynamic system-wide process simulation is practically the only way to verify the interoperability of the process and control solutions before building up the system. For the systems in operation, it enables virtual realistic studies without disturbances or risks for the actual process or people. The qualitative research approach in this work is case study. The modelling and dynamic simulation software Apros is used in five distinct cases, which extend the modelling from traditional nuclear and conventional power plant applications to a board machine, a carbon dioxide capturing power plant, ship energy systems, a seawater desalination plant, and a molten salt based energy storage system. The methodology relies on mechanistic thermal-hydraulic modelling and dynamic simulation. Method development was performed to model and simulate the application specific unit operations and working fluids. The functionality of the basic methodology and the extensions are demonstrated in the cases. The results of the work can be used in research and commercial simulation projects. New unit operation models and improvements for the fluid property calculation provide a variety of new potential applications. The model validation results help to estimate prediction capability in similar applications. The simulation applications guide modellers to use the methodology in both the presented and new areas. Regarding the case-specific results, the board machine simulator helped to understand complex interactions related to grade changes, to tune the related automation, and thus to shorten the grade change times. The simulation of the ship energy systems revealed design deficiencies and assisted in troubleshooting related problems during the commissioning. The study on the thermal energy storage facility uncovered systematic anomalous behaviour in the molten salt flow path. Based on the cross-case analysis, it can be stated that the methodology can be successfully applied beyond its traditional application domain and that it provides meaningful and valuable benefits. Furthermore, the methodology supports versatile use of the simulation model during the life cycle of an industrial plant: in R&D, design, testing, operator training and further development of the operating plant. The challenges that the process and energy industries meet today, require consideration of the interactions and dynamics of the process and automation systems together. The methodology used and further extended provides a valuable tool for tackling these challenges.Prosessi- ja energiateollisuudella on suuri merkitys kestävässä kehityksessä. Niillä on merkittävä rooli ilmastonmuutoksen hillinnässä. Pyrittäessä energiatehokkuuteen, materiaalien kierrätykseen ja päästöttömiin prosesseihin tulee teollisista järjestelmistä monimutkaisia. Prosessiautomaatiolla on keskeinen rooli siinä, että monimutkaisiakin järjestelmiä voidaan hallita ja käyttää helposti ja turvallisesti. Dynaaminen laitosmittakaavan prosessisimulointi on käytännössä ainoa tapa testata ja varmistaa prosessin ja automaation yhteistoiminta ennen kohdejärjestelmän rakentamista. Käytössä olevissa laitoksissa sen avulla voidaan tutkia järjestelmiä todenmukaisesti aiheuttamatta häiriötä tai riskiä prosessille tai ihmisille.  Tässä tapaustutkimuksena toteutetussa työssä käytetään Apros-ohjelmistoa mallinnus- ja simulointiympäristönä. Mallinnusta ja simulointia laajennetaan perinteisiltä ydin- ja konventionaalisten voimalaitosten sovellusalueilta kartongin valmistukseen, hiilidioksidia talteen ottavaan voimalaitokseen, laivan energiajärjestelmiin, meriveden suolanpoistoon sekä sulasuolaa käyttävään lämpövarastoon. Perusmenetelmänä hyödynnetään mekanistisia malleja ja termohydraulista dynaamista simulointia. Menetelmäkehitystä tehtiin sovelluskohtaisten laitteiden ja fluidien mallintamiseksi. Käytetyn menetelmän ja tehtyjen laajennusten toimivuus demonstroidaan simulointisovelluksissa. Työn tuloksia voidaan hyödyntää sekä tutkimuksessa että kaupallisissa simulointiprojekteissa. Uudet laitemallit ja fluidilaskennan ominaisuudet mahdollistavat uusia sovelluskohteita termisten järjestelmien parissa. Laskennan ja mallien validointitulokset auttavat arvioimaan saman tyyppisten mallien ennustuskykyä. Menetelmän hyödyntäminen sekä esitellyillä että uusilla sovellusalueilla tehostuu esimerkkimallien avulla. Tapauskohtaisista tuloksista voidaan mainita, että simulaattori auttoi ymmärtämään kartonkikoneen lajinvaihtoihin liittyviä monimutkaisia vuorovaikutuksia. Uudelleenvirittämällä lajinvaihtoautomaatio lyhennettiin lajinvaihtoihin kuluvaa aikaa. Laivan energiajärjestelmien simulointi paljasti suunnittelun puutteellisuuksia ja auttoi käyttöönoton ongelmien tutkimisessa. Sulasuolaa käyttävän, lämmönsiirron ja varastoinnin tutkimusta tukevan laitteiston toiminnasta analysoitiin systemaattinen poikkeama.  Tapausten analysoinnin perusteella voidaan todeta, että käytetty mallinnusmenetelmä soveltuu hyvin myös perinteisen sovellusalueensa ulkopuolella ja tuo merkittäviä hyötyjä. Menetelmä tukee simulointimallien monipuolista hyödyntämistä teollisuuslaitoksen elinkaaren aikana: tutkimuksessa, suunnittelussa, testauksessa, käyttäjien koulutuksessa sekä toimivan laitoksen kehittämisessä. Teollisuuden suunnittelun ja laitosten kasvavia haasteita on kyettävä ratkaisemaan eri elinkaaren vaiheissa prosessin ja automaation yhteistoiminta ja dynamiikka huomioiden. Työssä sovellettu ja laajennettu mallinnus- ja simulointimenetelmä tarjoaa tähän hyödyllisen työkalun

Intelligent techniques for dynamic and transient analysis of multi stage desalination plant

This thesis is concerned with dynamic and transient analysis of MSF desalination plants. The technique is developed using artificial neural networks (ANN) approach for the purpose of prediction, analysis, modelling, and control of MSF desalination plant. The applicability of the method to predict an approximation of the transient operating conditions as well as the control action are shown satisfactory. The network architecture and learning algorithm are developed based on the Multilayered Feed forward Networks (MFN) with the Back Propagation (BP) learning algorithm. It was shown that the approach could intelligently capture the dynamics of the system. An improved technique is developed for the BP learning algorithm based on Global Error Node Evaluation (GENE) approach for MFN to retains the function approximation requirements for a nonlinear dynamic behaviour. However, by using this approach considerable improvement for the generalization capability could be obtained for the case study under consideration. The technique provides the necessary dynamic learning, behaviour required for MFN. This approach appears to be effective for the input - output dynamic modelling of complex process systems and therefore on-line adaptation is possible (when the characteristic of the system is changing or when more test data are available for another operating range). The developed algorithm is used for the development and validation of an empirical multi-controller structure for MSF desalination plant. Satisfactory results are obtained from practical examples with the additional training ability

Dynamic modeling of multi stage flash (MSF) desalination plant

The world population is increasing at a very rapid rate while the natural water resources remain constant. During the past decades industrial desalination (reverse osmosis (RO) and multistage flash desalination (MSF)) became a viable, economical, and sustainable source of fresh water throughout the world. In the MSF units, the flashing of seawater involves formation of pure vapour, which flows through a wire mesh demister to remove the entrained brine droplets and then condenses into product water. The study presented in this thesis is motivated by the absence of detailed modelling and analysis of the dynamics of the MSF process and the demister. A detailed dynamic model can be used in design, control, startup/shutdown and troubleshooting. Most of the previous studies on MSF plant focused on model development and presented limited amount of performance data without any validation against plant data. Literature models of the MSF demister are either empirical or semi-empirical. This motivated use of a computational fluid dynamics (CFD) software to design a new demister that will reduce the pressure/temperature drop in the vapour stream without affecting the separation efficiency of brine droplets and allows the optimal design of complete MSF units. Lumped parameter dynamic models were developed for the once through (MSF-OT) and the brine circulation (MSF-BC) processes. The models were coded using the gPROMS modelling program. The model predictions for both MSF-OT and MSF-BC in steady state and dynamic conditions showed good agreement against data from existing MSF plants with an error less than 1.5%. Dynamic analysis was made to study plant performance upon making step variations in system manipulated variables and identify stable operating regimes. New stable operating regimes were reached upon changing the cooling water flow rate by + 15% and increasing the recycle brine flow rate by 15% and decreasing it by 7%. This was not the case for the steam temperature where its variation was limited to + 2-3 %. This behavior is consistent with the actual plant data. The FLUENT software was used to model the MSF demister using different combinations of Eulerian and Lagrangian approaches to model the vapour and the brine droplets. This provided the open literature with novel and new methodologies for design and simulation of the MSF demister using CFD. A new demister design was made upon varying the wire diameter. This led to an efficient design with low pressure drop and high separation efficiency. This design was used in the MSF/gPROMS model to predict its effect on the heat transfer area. The new design provided reductions of 3-39% in the condenser heat transfer area without affecting dynamic performance. Since the tubing system accounts for almost 70% of the capital cost, then this would reduce the plant capital cost and product unit cost. The modelling approach presented in this thesis enables design of thermal desalination units to determine optimal heat transfer area and optimized operating conditions

Dynamic modelling and simulation of industrial scale multistage flash desalination process

YesMultistage Flash (MSF) desalination process is still a dominant process, especially in the Gulf region, to produce high quality freshwater. Although there has been energy price surge in recent years, MSF process will continue to operate in that region for some foreseeable future. The key challenge is how to make such processes still profitable. Understanding the dynamics of any processes under uncertainty and disturbances is very important to make a process operationally feasible and profitable. The main aim of this work is to understand the dynamics of industrial scale MSF process using high fidelity and reliable process model. For this purpose, a detailed dynamic model for the MSF process incorporating key and new features is developed and validated against the actual data of a large-scale seawater desalination plant. The model is then used to study the behaviour of large scale MSF processes for disturbances in steam temperature, feed temperature and the recycle brine flow rate. The simulation results show that the last stage requires a longer time to settle compared to the preceding stages. In addition, steam temperature shows insignificant influence on the performance ratio compared to the inlet seawater temperature and recycle brine flow rate. Furthermore, it is found that the productivity of plant can increase in the winter compared to that in the summer. However, this benefit comes at the expense of increased steam consumption in the winter, resulting in a low performance ratio

Dynamic Modeling, Sensor Placement Design, and Fault Diagnosis of Nuclear Desalination Systems

Fault diagnosis of sensors, devices, and equipment is an important topic in the nuclear industry for effective and continuous operation of nuclear power plants. All the fault diagnostic approaches depend critically on the sensors that measure important process variables. Whenever a process encounters a fault, the effect of the fault is propagated to some or all the process variables. The ability of the sensor network to detect and isolate failure modes and anomalous conditions is crucial for the effectiveness of a fault detection and isolation (FDI) system. However, the emphasis of most fault diagnostic approaches found in the literature is primarily on the procedures for performing FDI using a given set of sensors. Little attention has been given to actual sensor allocation for achieving the efficient FDI performance. This dissertation presents a graph-based approach that serves as a solution for the optimization of sensor placement to ensure the observability of faults, as well as the fault resolution to a maximum possible extent. This would potentially facilitate an automated sensor allocation procedure. Principal component analysis (PCA), a multivariate data-driven technique, is used to capture the relationships in the data, and to fit a hyper-plane to the data. The fault directions for different fault scenarios are obtained from the prediction errors, and fault isolation is then accomplished using new projections on these fault directions. The effectiveness of the use of an optimal sensor set versus a reduced set for fault detection and isolation is demonstrated using this technique. Among a variety of desalination technologies, the multi-stage flash (MSF) processes contribute substantially to the desalinating capacity in the world. In this dissertation, both steady-state and dynamic simulation models of a MSF desalination plant are developed. The dynamic MSF model is coupled with a previously developed International Reactor Innovative and Secure (IRIS) model in the SIMULINK environment. The developed sensor placement design and fault diagnostic methods are illustrated with application to the coupled nuclear desalination system. The results demonstrate the effectiveness of the newly developed integrated approach to performance monitoring and fault diagnosis with optimized sensor placement for large industrial systems

Theoretical analysis of high efficient multi-effect distillation processes and their integration into concentrating solar power plants

Water scarcity and energy supply are currently two of the major problems faced by the global society. The growth of the world’s population along with the rise of industrial activities, especially in developing countries, is leading to a rapid increase of the energy consumption and the construction of new power plants. Most of these plants are based on fossil fuels, which emit harmful greenhouse gases (mainly CO2) and contribute to global warming on Earth. Power production technologies which use renewable energies (solar, wind, geothermal, etc.) as energy source represent clean and environmentally friendly alternatives to traditional methods, particularly Concentrating Solar Power (CSP) plants, which have been proved as a reliable system for power generation. On the other hand, although more than 70% of the Earth’s surface is water, fresh water represents only 2.5% of the total volume in the hydrosphere, approximately, being the rest saline water. Furthermore, of that fresh water percentage, a 69% is contained in form of glaciers and ice sheets, from which its extraction does not result neither economically nor environmentally viable. Therefore, the fresh water production by means of seawater desalination can help to solve water supply problems in arid areas of the world, as it has been proved in Middle East countries since the middle of the twentieth century. In addition, regions of the world suffering from water stress habitually have high levels of solar irradiation and access to the sea, which suggest the use of solar energy to produce fresh water by seawater desalination in those regions. Also, the power and water supply issues are linked, because power generation, either by conventional or renewable technologies, need great amounts of water (particularly for the cooling requirements of the power cycle), and fresh water production by seawater desalination require high amounts of energy. Therefore, the combined generation of power and fresh water by integrating desalination processes and concentrating solar power plants, concept known as CSP+D, may help to solve the issues emerged regarding the power and water supply in such regions of the world. The specific objectives and goals set out in the present research work are to develop a partial-load model for the Multi-Effect Distillation (MED) seawater desalination process with Thermal Vapour Compression (TVC) (variable nozzle thermocompressors) integrated in a CSP plant (similar to Andasol I plant) as a tool to simulate the plant performance regarding both, electricity and water production, and to analyse high efficient MED processes and their integration within parabolic trough concentrating solar power plants. To that end, firstly a literature review on CSP+D has been performed to present the state-of-the-art of this technology and different approaches to this concept. Then, a preliminary thermo-economic study has been carried out for a particular case of the combination of a parabolic trough CSP plant with direct steam generation and two different desalination technologies, Reverse Osmosis (RO) and multi-effect distillation. Results obtained show that the bet coupling option, which produce the lower levelised cost of water, is the RO process. Also, it is recommended its indirect integration with the CSP plant, connected directly to the local grid. It is concluded that, in view of the lack of agreement among scientific community about the most suitable technology for integrating with a CSP plant and due to the potential of the combined freshwater and power production with MED and CSP, further investigation with higher efficient MED plants is needed. In this regard, two methods to improve the efficiency of MED processes have been investigated: the increase of the number of effects, which leads to an increase in the Top Brine Temperature (TBT), and its coupling with thermocompressors. The first case has been assessed by using seawater pretreatments that permit to elevate the temperature of the MED process without scale formation, like the nanofiltration membranes. For this purpose, a detailed mathematical model has been developed for a MED plant with forward-feed configuration and the model was implemented within Engineering Equation Solver (EES) software environment. Such feed arrangement has been selected in order to minimize the scale risk on the tubes of the heat exchangers. Results show that the Gain Output Ratio (GOR) is greatly improved (up to a 70%), while the specific heat transfer area and specific energy consumption are significantly reduced (11 and 45%, respectively). Despite of the great potential of this improvement to the MED process, the analysis of its integration into a CSP plant has been not pursued because there are not commercial MED plants using the forward feed scheme. Moreover, the increase of auxiliary consumption attributable to nanofiltration pretreatment may be not suitable for solar applications. Most commercial MED plants are based on the parallel feed MED-TVC process, which presents several advantages for its coupling with power plants. Therefore, this technology has been selected for the analysis of its coupling with CSP plants. A preliminary evaluation has been performed for a particular case study, simulating the power and water productions of a parabolic trough CSP plant of 50 MWe, with features similar to commercial Andasol-I CSP plant, and a MED-TVC unit of 10,000 m3/d, based on commercial Trapani plant (Italy), during three representative days in winter and summer periods. Two different steam extractions have been considered to feed the MED-TVC unit, one from the high pressure turbine, and other from the low pressure turbine. The CSP model has been taken from the literature and implemented in MATLAB software environment, and the power block model, implemented in EES, has been developed to simulate part load conditions. From this assessment it is concluded that different integration schemes are needed to accomplish for the different profile demands of power and water during the year, in order to promote the power generation or the water production. Later, a parametric study of the integration of a parallel/cross MED-TVC, based on Trapani commercial plant, with a Rankine cycle power block similar to that one of Andasol-I, has been carried out in order to identify the best coupling arrangement, in terms of efficiency and minimum specific heat transfer area. To that end, a detailed design mathematical model of the MED-TVC unit has been developed and validated against actual data. It is found that the maximum GOR and minimum specific area are reached for a particular thermocompressor location, depending on the motive steam pressure fed into the thermocompressor. Also, an operation MED-TVC model has been developed, based on the design model, and used to determine the operational limits of the integration with a Rankine cycle power block that allowed the MED unit to work in nominal conditions (which has been possible by considering variable nozzle thermocompressors), for four different steam extractions of the turbines. For this purpose, the power block has been simulated at different loads, and a control algorithm has been also introduced in order to maintain the maximum brine salinity under 70,000 ppm and the end condenser temperature around 37 °C. Finally, annual simulations of the coupling between a parallel/cross MED-TVC unit and a parabolic trough CSP have been performed, considering Almería (Spain) as the geographical location of the cogeneration plant. The models previously presented for the solar field, power block and desalination unit (off-design models) have been used. As a particular case study, the daily, monthly and yearly power and water productions have been estimated, using two different steam extractions, equal to those ones identified in the previous analyses: one from the high pressure turbine, at 45.4 bar, and other from the low pressure turbine, at 3.63 bar, which have been used alternatively to feed the MED-TVC unit depending on the monthly power demand for that location.La escasez de agua y el abastecimiento energético son actualmente dos de los mayores retos a los que se enfrenta la sociedad global. El crecimiento de la población mundial junto con el aumento de las actividades industriales, especialmente en los países en vía de desarrollo, está provocando un rápido incremento del consumo energético y, en consecuencia, de la construcción de nuevas plantas de producción de potencia. La mayoría de dichas plantas están basadas en la utilización de combustibles fósiles, los cuales emiten en su combustión gases de efecto invernadero (principalmente CO2), contribuyendo al calentamiento global del planeta. Las tecnologías de producción de potencia que emplean energías renovables (solar, eólica, geotérmica, etc.) como fuente energética representan una alternativa limpia y respetuosa con el medio ambiente, en particular las plantas solares de concentración, las cuales han demostrado ser un sistema fiable para la generación de energía eléctrica. Por el contrario, aunque más del 70% de la superficie terrestre es agua, el agua dulce representa aproximadamente el 2.5% del volumen total de la hidrosfera, siendo el resto agua salada. Además, de dicho porcentaje de agua dulce, alrededor del 69% está incluida en glaciares y nieves permanentes, siendo su extracción poco viable, tanto desde un punto de vista económico como medioambiental. Por lo tanto, la producción de agua dulce mediante la desalación de agua de mar puede ayudar a resolver los problemas de abastecimiento de agua en las zonas áridas del planeta, como ha sido probado en los países de Oriente Medio desde la segunda mitad del siglo XX. Asimismo, aquellas regiones del mundo que sufren problemas de estrés hídrico presentan habitualmente altos niveles de irradiación solar, lo que sugiere la utilización de la energía solar para producir agua dulce mediante la desalación de agua de mar en dichas zonas con acceso directo a la costa. Existe también una conexión entre los problemas asociados al abastecimiento de agua y energía, debido a que la generación de electricidad, ya sea por medios convencionales o tecnologías renovables, requiere grandes cantidades de agua (en particular para la refrigeración del ciclo de potencia), y a su vez, la producción de agua mediante desalación de agua de mar precisa de un alto consumo energético. De los anteriores razonamientos puede concluirse que la cogeneración de agua y electricidad mediante la integración de procesos de desalación de agua de mar y plantas termosolares de concentración, podría ayudar a resolver, al menos parcialmente, los problemas de suministro energético y de agua dulce en dichas zonas del planeta. Los principales objetivos de este trabajo de investigación son el desarrollo de un modelo a carga parcial para procesos de destilación multiefecto (Multi-Effect Distillation, MED) con compresión térmica de vapor (Thermal Vapor Compression, TVC), integrados en una planta termosolar de concentración (Concentrating Solar Power, CSP) con tecnología de captadores cilindroparabólicos (Parabolic Trough, PT) de similares características a la planta CSP comercial Andasol-I, como una herramienta que permita simular la eficiencia de la producción conjunta de agua y electricidad, y el análisis de procesos MED de alta eficiencia integrados en plantas PT-CSP. A este fin, primero se ha llevado a cabo una revisión bibliográfica sobre dicho tema para presentar el estado actual de la tecnología propuesta y los diferentes acercamientos a este concepto. Posteriormente, se ha realizado un estudio termoeconómico preliminar para un caso particular de la integración de una planta de termosolar de captadores cilindroparabólicos con generación directa de vapor y dos tecnologías de desalación: ósmosis inversa y destilación multiefecto. Los resultados han revelado que la ósmosis inversa es la mejor opción de integración ya que genera los menores costes anualizados de producción de agua. Además, se recomienda la integración indirecta con la planta termosolar, conectándose directamente a la red eléctrica local. De dichos análisis se ha concluido que no existe acuerdo entre la comunidad científica en cuanto a la tecnología de desalación más adecuada para su combinación o acoplamiento con una planta termosolar de concentración. Además, debido al potencial mostrado por la destilación multiefecto para su integración con plantas CSP, se requiere una investigación más profunda sobre las posibilidades de aumento de eficiencia de esta tecnología. En esta línea, han sido evaluados dos métodos para aumentar la eficiencia del proceso de destilación multiefecto: el aumento del número de efectos, que conduce a un incremento de la temperatura máxima de salmuera, y la introducción de la compresión térmica de vapor. En el primer caso, el aumento de la temperatura máxima de salmuera sin aparición de incrustaciones salinas en los tubos de los intercambiadores de calor (scaling) precisa la utilización de un pretratamiento del agua de mar tal como la nanofiltración, la cual elimina los iones bivalentes causantes de dicho efecto. Para este propósito se ha desarrollado un modelo matemático detallado del proceso de destilación multiefecto con alimentación frontal (o hacia delante), el cual ha sido implementado en el entorno Engineering Equation Solver (EES). Dicha configuración ha sido elegida para minimizar los riesgos de aparición incrustaciones en los tubos de los intercambiadores de calor. Los resultados han mostrado que la eficiencia térmica del proceso, medida mediante el Gain Output Ratio (GOR), se incrementa considerablemente (hasta en un 70%), mientras que el área específica de transferencia y consumo energético específico se reducen significativamente (en un 11 y 45%, respectivamente). A pesar del gran potencial mostrado por esta mejora del proceso MED, no se ha analizado su integración en plantas CSP debido a que no existen unidades MED comerciales utilizando dicha configuración, y además el aumento del consumo auxiliar causado por el pretratamiento de nanofiltración podría no ser adecuado para aplicaciones solares. La mayoría de plantas comerciales tienen configuración de flujo paralelo/cruzado con compresión térmica de vapor, la cual presenta ventajas para su acoplamiento con plantas CSP. Una primera evaluación de esta integración ha sido realizada para un caso particular de estudio, simulando la producción conjunta de agua y electricidad en una planta PT-CSP de 50 MWe, con características similares a la planta comercial Andasol-I en Granada (España), y una unidad MED-TVC de 10,000 m3/d, basada en la planta comercial de Trapani (Italia), durante tres días representativos de invierno y tres días de verano. Se han considerado dos extracciones diferentes de turbina para alimentar la planta desalinizadora, una del cuerpo de turbina de alta presión y otra del cuerpo de turbina de baja presión. El modelo del campo solar de la planta CSP se ha tomado de la literatura científica y ha sido implementado en el entorno MATLAB, mientras que el bloque de potencia, implementado en EES, se ha desarrollado para simular condiciones de operación a carga parcial. De este estudio se ha concluido que se requieren diferentes esquemas de integración para cumplir con los diferentes perfiles de demanda de agua y electricidad durante el año, de manera que se otorgue mayor prioridad a la producción de agua o la generación de energía eléctrica. Más tarde se ha realizado un estudio paramétrico de la integración de una planta desalinizadora MED-TVC, basada en la configuración de la planta comercial de Trapani, con un ciclo de potencia Rankine similar al de la planta CSP Andasol-I, con objeto de identificar el mejor acoplamiento, desde el punto de vista de eficiencia y área de intercambio de calor mínima. A este fin, se ha desarrollado un modelo matemático detallado del proceso MED-TVC con alimentación en paralelo/cruzado y se ha validado con datos de una planta real. Se ha encontrado que el máximo GOR y la mínima área específica se obtienen para una posición particular del termocompresor, dependiendo de la presión del vapor motriz que alimenta al termocompresor. Además, se ha desarrollado un modelo de operación del proceso MED-TVC, basado en el modelo de diseño, y se ha utilizado para determinar los límites de operación de la integración con ciclos de potencia Rankine tales que permitían trabajar a la unidad MED en condiciones nominales (lo cual fue posible considerando termocompresores de área variable), para cuatro extracciones de vapor diferentes. Para este propósito, se ha simulado la operación del bloque de potencia a diferentes cargas y se ha introducido un algoritmo de control para mantener la salinidad máxima de la salmuera en valores por debajo de 70,000 ppm y la temperatura del condensador final alrededor de su valor de diseño, 37 °C. Para finalizar, se han efectuado simulaciones anuales de la integración de una unidad de destilación multiefecto con compresión térmica de vapor (en flujo paralelo/cruzado) y una planta termosolar de captadores cilindroparabólicos, considerando Almería (España) como la localización geográfica de la hipotética planta de cogeneración. Los modelos presentados previamente del campo solar, bloque de potencia y unidad de desalación (modelos para la operación a caga parcial) han sido utilizados en las simulaciones. Como un caso particular de estudio, se ha estimado la producción diaria, mensual y anual de electricidad y agua considerando dos extracciones de vapor de diferentes presiones, iguales a las identificadas en el estudio anterior: una perteneciente a la turbina de alta presión, a 45.4 bar, y otra de la turbina de baja presión, a 3.63 bar, las cuales se han utilizado alternativamente para alimentar la unidad MED-TVC dependiendo de la demanda mensual de electricidad y agua en dicha localización

Generation of (synthetic) influent data for performing wastewater treatment modelling studies

The success of many modelling studies strongly depends on the availability of sufficiently long influent time series - the main disturbance of a typical wastewater treatment plant (WWTP) - representing the inherent natural variability at the plant inlet as accurately as possible. This is an important point since most modelling projects suffer from a lack of realistic data representing the influent wastewater dynamics. The objective of this paper is to show the advantages of creating synthetic data when performing modelling studies for WWTPs. This study reviews the different principles that influent generators can be based on, in order to create realistic influent time series. In addition, the paper summarizes the variables that those models can describe: influent flow rate, temperature and traditional/emerging pollution compounds, weather conditions (dry/wet) as well as their temporal resolution (from minutes to years). The importance of calibration/validation is addressed and the authors critically analyse the pros and cons of manual versus automatic and frequentistic vs Bayesian methods. The presentation will focus on potential engineering applications of influent generators, illustrating the different model concepts with case studies. The authors have significant experience using these types of tools and have worked on interesting case studies that they will share with the audience. Discussion with experts at the WWTmod seminar shall facilitate identifying critical knowledge gaps in current WWTP influent disturbance models. Finally, the outcome of these discussions will be used to define specific tasks that should be tackled in the near future to achieve more general acceptance and use of WWTP influent generators

Thermochemical conversion of biomass in a Swirling Fluidized Bed: a design procedure and numerical simulation

Process intensification of biomass conversion as a route to a low-carbon manufacturing industry pursues novel solutions able to achieve safe, cost-efficient, energy-efficient, and environment-friendly processes. Implementation of process intensification in gas-solid operations enhances mass, heat, and momentum transfer rates, while develops multifunctional equipment to increase production capacity per size of installation. The Swirling Fluidized Bed reactor is a gas-solid contacting device that replaces the Earth's gravitational field with a centrifugal field generating a centrifugal bed that achieves more uniform beds, higher transfer rates, and shorter processing times than conventional fluidized beds. However, there is a gap of research in two points: a binary-phase numerical simulation to study both gas and solid hydrodynamics, and the constructive design of the swirling fluidized bed reactor related to expected operating conditions. In the present work, a design procedure of swirling fluidized beds for thermochemical conversion of biomass is proposed. The study of the swirling fluidized bed reactor comprises three stages: a systematic literature review, a numerical simulation of the reactor, and the development of the design procedure. The simulation gives insight of the SFB reactor operation useful for the decision making during early stages of design. Thermochemical and mechanical models together with technical procedures are used for the reactor design. The proposed design shows good agreement with an operational reactor used for rice husk combustion.MaestríaMagister en Ingeniería Mecánic