5,743 research outputs found

    Reactor-Network Synthesis via Flux Profile Analysis

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    Conceptual design study for heat exhaust management in the ARC fusion pilot plant

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    The ARC pilot plant conceptual design study has been extended beyond its initial scope [B. N. Sorbom et al., FED 100 (2015) 378] to explore options for managing ~525 MW of fusion power generated in a compact, high field (B_0 = 9.2 T) tokamak that is approximately the size of JET (R_0 = 3.3 m). Taking advantage of ARC's novel design - demountable high temperature superconductor toroidal field (TF) magnets, poloidal magnetic field coils located inside the TF, and vacuum vessel (VV) immersed in molten salt FLiBe blanket - this follow-on study has identified innovative and potentially robust power exhaust management solutions.Comment: Accepted by Fusion Engineering and Desig

    Multiscale mathematical models for simulation and scale-up of green processes in the perspective of industrial sustainability

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    The present work presents research studies aimed at developing tools useful to design engineering solutions moving in the direction of industrial sustainability. The investigations hereinafter discussed regard an extraction process of active compounds \u2013 polyphenols \u2013 from agro-food industry wastes (olive and grape pomaces) and a biorefinery exploiting waste frying oil, solid organic wastes and algal biomass to produce biofuels. In particular, for the former topic, a procedure aimed at the evaluation of the technological feasibility at pilot scale of said process is discussed. The proposed approach takes into consideration the extended kinetic route coupled with mathematical simulation. Detailed physically-based dynamic mathematical models, taking into account mass and energy balance equations, are adopted to describe both the lab-scale and the pilot-scale reactors. Chemical physical parameters appearing in the models are estimated from the experimental data at lab-scale or are partially taken from literature. Different heating systems are designed for the pilot scale reactor and their performance is tested by simulation. Characteristic times are evaluated also during start-ups and different control loops are analyzed in order to set-up the best process and operating variables. Average yields in polyphenols are finally evaluated for both the batch and the continuous operated pilot reactor, by considering feed variability and fluctuations of process parameters. For what concerns the biorefinery, special attention was devoted to the modeling of the airlift reactor, its most delicate and complex component. In fact, to optimize this interesting microalgae cultivation system, a precise description of the moving interfaces formed by the liquid and gas phase is critical. In this study, coupled front capturing methods (standard and conservative level set methods) and finite difference method are used to simulate gas bubbles dynamics in a pilot-scale external loop air-lift photobioreactor in which microalgae are used to capture CO2 from flue gas and to treat wastewater. Numerical simulations are carried out on rectangular domains representing different sections of the vertical axis of the riser. The data employed was either acquired from previous experimental campaigns carried out in the airlift reactor or found in the literature. The rise, shape dynamics and coalescence process of the bubbles of flue gas are studied. Moreover, for each analyzed applications, a procedure based on Buckingham \u3c0-theorem to perform a rigorous scale-up is proposed. In this way, scale-invariant dimensionless groups describing and summarizing the considered processes could be identified. For the research focused on the scale-up of photobioreactors used to cultivate Chlorella Vulgaris, an experimental campaign at three levels was designed and carried out to evaluate the characteristic dimensionless numbers individuated by the theoretical formulation. Since scale-up regards both geometrical dimensions and type of reactor, passing from lab-scale stirred tanks to pilot scale tubular and airlift, particular attention was devoted to define characteristic lengths inside the dimensionless numbers

    Instrumentation and control of anaerobic digestion processes: a review and some research challenges

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    The final publication is available at Springer via http://dx.doi.org/10.1007/s11157-015-9382-6[EN] To enhance energy production from methane or resource recovery from digestate, anaerobic digestion processes require advanced instrumentation and control tools. Over the years, research on these topics has evolved and followed the main fields of application of anaerobic digestion processes: from municipal sewage sludge to liquid mainly industrial then municipal organic fraction of solid waste and agricultural residues. Time constants of the processes have also changed with respect to the treated waste from minutes or hours to weeks or months. Since fast closed loop control is needed for short time constant processes, human operator is now included in the loop when taking decisions to optimize anaerobic digestion plants dealing with complex solid waste over a long retention time. Control objectives have also moved from the regulation of key variables measured online to the prediction of overall process perfor- mance based on global off-line measurements to optimize the feeding of the processes. Additionally, the need for more accurate prediction of methane production and organic matter biodegradation has impacted the complexity of instrumentation and should include a more detailed characterization of the waste (e.g., biochemical fractions like proteins, lipids and carbohydrates)andtheirbioaccessibility andbiodegradability characteristics. However, even if in the literature several methodologies have been developed to determine biodegradability based on organic matter characterization, only a few papers deal with bioaccessibility assessment. In this review, we emphasize the high potential of some promising techniques, such as spectral analysis, and we discuss issues that could appear in the near future concerning control of AD processes.The authors acknowledge the financial support of INRA (the French National Institute for Agricultural Research), the French National Research Agency (ANR) for the "Phycover" project (project ANR-14-CE04-0011) and ADEME for Inter-laboratory assay financial support.Jimenez, J.; Latrille, E.; Harmand, J.; Robles Martínez, Á.; Ferrer Polo, J.; Gaida, D.; Wolf, C.... (2015). Instrumentation and control of anaerobic digestion processes: a review and some research challenges. Reviews in Environmental Science and Biotechnology. 14(4):615-648. doi:10.1007/s11157-015-9382-6S615648144Aceves-Lara CA, Latrille E, Steyer JP (2010) Optimal control of hydrogen production in a continuous anaerobic fermentation bioreactor. 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    Measurement, modelling, and closed-loop control of crystal shape distribution: Literature review and future perspectives

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    Crystal morphology is known to be of great importance to the end-use properties of crystal products, and to affect down-stream processing such as filtration and drying. However, it has been previously regarded as too challenging to achieve automatic closed-loop control. Previous work has focused on controlling the crystal size distribution, where the size of a crystal is often defined as the diameter of a sphere that has the same volume as the crystal. This paper reviews the new advances in morphological population balance models for modelling and simulating the crystal shape distribution (CShD), measuring and estimating crystal facet growth kinetics, and two- and three-dimensional imaging for on-line characterisation of the crystal morphology and CShD. A framework is presented that integrates the various components to achieve the ultimate objective of model-based closed-loop control of the CShD. The knowledge gaps and challenges that require further research are also identified

    Optimal Sensor Placement with Adaptive Constraints for Nuclear Digital Twins

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    Given harsh operating conditions and physical constraints in reactors, nuclear applications cannot afford to equip the physical asset with a large array of sensors. Therefore, it is crucial to carefully determine the placement of sensors within the given spatial limitations, enabling the reconstruction of reactor flow fields and the creation of nuclear digital twins. Various design considerations are imposed, such as predetermined sensor locations, restricted areas within the reactor, a fixed number of sensors allocated to a specific region, or sensors positioned at a designated distance from one another. We develop a data-driven technique that integrates constraints into an optimization procedure for sensor placement, aiming to minimize reconstruction errors. Our approach employs a greedy algorithm that can optimize sensor locations on a grid, adhering to user-defined constraints. We demonstrate the near optimality of our algorithm by computing all possible configurations for selecting a certain number of sensors for a randomly generated state space system. In this work, the algorithm is demonstrated on the Out-of-Pile Testing and Instrumentation Transient Water Irradiation System (OPTI-TWIST) prototype vessel, which is electrically heated to mimic the neutronics effect of the Transient Reactor Test facility (TREAT) at Idaho National Laboratory (INL). The resulting sensor-based reconstruction of temperature within the OPTI-TWIST minimizes error, provides probabilistic bounds for noise-induced uncertainty and will finally be used for communication between the digital twin and experimental facility

    Optoelectronic optimization of photocatalytic processes for wastewater treatment

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    Water pollution is an alarming problem that endangers the health of all living beings. The textile industry is listed as one of the most contaminating industries, since in order to carry out its dyeing and finishing processes, it requires a large amount of water resources; by decades, this industry has used Advanced Oxidation Processes (AOPs), since they have several advantages (e. g. destruction of toxic substances, reduction of heavy metals, allowing their use in conjunction with other processes, among others). Among the AOPs, heterogeneous photocatalysis stands out for its high efficiency for the removal of contaminants, including azo dyes. In order to perform a photocatalytic process, it is necessary to have a photoreactor, which will require a photocatalyst and at least one light source that activates the catalyst. This type of photoreactors can present several problems, such as the use of high cost photocatalysts, the generation of toxic byproducts in some low photocatalysts, the high electrical consumption caused by the use of traditional lighting sources and even difficulties with the geometry of the photoreactors. Hence the scientific community has tried to optimize the photocatalytic processes, some scientists have worked in the generation of new photocatalysts to be able to use them in wavelengths generated by low cost lighting sources (e. g. visible light), nevertheless, which in many times it increases the price of the photocatalyst. Another approach is to reduce electricity consumption by opting for the replacement of traditional lamps with low consumption lighting, for example, LED lighting; However, this substitution is currently done arbitrarily, so sometimes some authors doubt the ability to use these sources in this type of process. Moreover, when trying to improve the lighting sources, the photoreactor can be altered, so it is important to take into account its characteristics in order to achieve a significant improvement. This thesis focuses on an optoelectronic optimization to improve the efficiency of the lighting sources used in photocatalytic reactors. For this, a methodology has been generated to calculate LED arrays using uniform irradiance models, this irradiance must be homogeneous, with enough energy to photoactivate the catalyst with the aim to replace the traditional lamps, avoiding the chemical alteration of the photocatalysts; Likewise, a photocatalytic reactor has been designed and implemented on a laboratory scale with ultraviolet illumination adjusted to its characteristics (i.e. geometry, dimensions, among others) to work with a low cost photocatalyst (TiO2) in the decolorization of wastewater with textile dyes. Finally, in-situ monitoring has been designed and implemented in order to analyze the decolorization of textile water, this type of monitoring avoids the collection of water samples during the process, without altering the geometry of the reactor or reducing the volume of treated water in the reactor.La contaminación del agua es un problema alarmante que pone en peligro la salud de todos los seres vivos. La industria textil está catalogada como una de las industrias más contaminantes, puesto que para realizar sus procesos de teñido y acabado requieren de una gran cantidad de recursos hídricos; desde hace décadas esta industria ha usado los Procesos de Oxidación Avanzada (AOPs) al presentar diversas ventajas (e. g. destrucción de sustancias tóxicas, reducción de metales pesados, permitir su uso en conjunto con otros procesos, entre otros). Entre los AOPs, sobresale la fotocatálisis heterogénea, por su alta eficiencia para la remoción de contaminantes, incluidos los colorantes azoicos. Para realizar un proceso fotocatalítico, es necesario tener un fotorreactor, el cual requerirá de un fotocatalizador y al menos una fuente de iluminación que active el catalizador. Este tipo de fotorreactores pueden presentar diversos problemas, tales como, el uso fotocatalizadores de alto costo, la generación de subproductos tóxicos en algunos fotocatalizadores de bajo, el alto consumo eléctrico causado por la utilización de fuentes tradicionales de iluminación e incluso dificultades con la geometría de los fotorreactores. Por lo tanto la comunidad científica ha intentado optimizar los procesos fotocatalíticos, algunos científicos han trabajado en la generación de nuevos fotocatalizadores para poder utilizarlos en longitudes de onda generada por fuentes de iluminación de bajo coste (e. g. luz visible), no obstante, lo que en muchas ocasiones incrementa el precio del fotocatalizador. Otro enfoque se encuentra en la reducción del consumo eléctrico optando por la sustitución de las lámparas tradicionales por iluminación de bajo consumo, por ejemplo, iluminación LED; sin embargo, actualmente esta sustitución se realiza de manera arbitraria, por lo que en ocasiones algunos autores dudan de la capacidad de utilizar estas fuentes en este tipo de procesos. Además al intentar mejorar las fuentes de iluminación puede alterarse el fotorreactor, por lo que es importante tomar en consideración sus características para lograr una mejora significativa. Esta tesis se enfoca en una optimización optoelectrónica para mejorar la eficiencia de las fuentes de iluminación utilizadas en reactores fotocatalíticos. Para ello se ha generado una metodología para calcular arreglos de LEDs utilizando modelos de irradiancia uniforme, esta irradiancia debe ser homogénea, con energía suficiente para fotoactivar el catalizador y sustituir las lámparas tradicionales, evitando la alteración química de los fotocatalizadores; asimismo, se ha diseñado e implementado un reactor fotocatalítico a escala de laboratorio con iluminación ultravioleta ajustada a sus características (geometría, dimensiones, entre otros) para trabajar con un fotocatalizador de bajo coste (TiO2) en la decoloración de agua con colorantes textiles. Para finalizar se ha diseñado e implementado un sistema de monitorización in-situ para la decoloración de aguas teñidas, este tipo de monitorización evita la toma de muestras de durante el proceso, sin alterar la geometría del reactor ni disminuir el volumen de agua tratada del reactor.Postprint (published version

    Prediction interval-based modelling and control of nonlinear processes

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     Novel computational intelligence-based methods have been investigated to quantify uncertainties prevalent in the operation of chemical plants. A new family of predication interval-based controlling algorithms is proposed and successfully applied to chemical reactors in order to minimise energy consumption and operational cost
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