Sermon : predicado en la santa iglesia catedral de Malaga el dia 19 de agosto de 1893, aniversario de la Reconquista de dicha ciudad ...

Copia digital. realizada por la Biblioteca de Andalucí

Heat transfer in oxy-fuel fluidized bed boilers

In spite of the stabilization of coal demand in developed countries, the role of coal in the next decades energy mix is still essential. Particularly relevant will be in the great developing economies, such as India or China, where this fuel is abundant and avoid external energy dependences. In parallel, the international community needs to drive its efforts towards politics that commit fossil fuels energetic companies to drop their CO2 emissions drastically for 2015. In this regard, great advances have been made towards gaining plant efficiency and therefore, reducing the tones of CO2 per produced kWh. Still, emissions need a more drastic reduction if we want to avoid an increment of atmosphere temperature higher than 2ºC. Here, the CO2 capture and storage (CCS) technologies will have the potential of reducing up to 25% of CO2 from stationary sources as soon as they will be commercially available. Among the CO2 capture technologies, grouped in pre-combustion, post-combustion and oxy-fuel combustion, this last one is receiving outstanding support by the national and European authorities. The possibility of implementing oxy-fuel combustion into circulating fluidized bed technology, contributes to approaching the concept of clean-coal technology. Fluidized bed combustors have the outstanding feature of offering the possibility of burning a wide variety of fuels They have the possibility to capture SO2 emissions, adding in-bed limestone. Their working temperature is lower than in pulverized fuel boilers, which avoids thermal NOx formation. Additionally to these characteristics, already exploited under air-firing, applying oxy-fuel combustion technology and being able to capture the CO2 emissions from the coal combustion, or even from blends of coal and other fuels, makes oxy-fuel combustion in fluidized bed a great opportunity to turn the coal sustainable in the future power plant designs. About the implications derived of applying oxy-fuel technology to a commercial scale CFB boiler, scarce literature exits, especially when considering high O2 concentrations at inlet. A one dimensional model has been developed. The overall modeling strategy, in which the model has been based on, is explained in the first part of Chapter 2. It is based on the already known and validated air-firing semi-empirical expressions. The model has been divided into three sub-models interacting with each other: fluid-dynamics, combustion and energy balance of plant. For attributing reliability to the developed model, the scarce public experimental measurements of real air-firing boilers have been compared with the model results. Additionally, three studies regarding the modeling of large oxy-fuel CFB boilers have also been used for comparing the model predictions. In spite of having insufficient information about the published models details, the model developed in this work fairly fits the predictions in the literature. This has allowed making the sensibility analysis, trying to draw the main consequences of oxy-fuel deployment in CFB boilers. For retrofitting purposes, i.e. with no changes on an air-firing boiler configuration, the adequate O2 proportion of oxygen at entrance should be around 30%. Higher O2 concentrations lead to smaller cross sectional areas of the boiler. For a given fuel power required in a boiler, feeding 45% O2 in the comburent, would reduce the cross sectional area down to 54% of the original one. This involves a reduction of heat transfer surface along the boiler walls of 23% approximately. The immediate consequence is the need of resorting to external heat transfer surfaces, i.e., external heat exchangers (EHE). This device would need to remove almost 50% of the total heat of combustion in the case of feeding comburent with 60% O2 content. The importance of the EHE resides not only in compensating the reduction of heat transfer surface in the riser, but in managing higher amount of elutriated solids. The simulations have shown that higher solids densities in the boiler will enhance heat transfer coefficients to the riser walls. For certain boiler geometry, if increasing boiler load, higher recycled solids rate will be required. Feeding 60% of O2 at inlet, fuel input can be increased from 600 to 800 MW if elutriated solids increase from 25 to 40 kg/m2s. This refers us again to the higher solids crossing the EHE. An increase of 10% of heat removal will be required in this device for said changing load. Applying EHEs to conventional boilers was not essential during air-firing operation. But for oxy-fuel combustion it was here demonstrated to be crucial for accomplishing the boiler energy balance. However, several operational and design uncertainties will need to be solved, before deploying first demonstration oxy-CFB boiler. The design of the future EHE will imply two relevant distinguishing features of oxy-firing operation: the influence of gas composition on the determination of the heat transfer coefficients and the greater amount of elutriated solids, cooled down in the EHE. The CIRCE bubbling fluidized bed pilot plant presents the adequate bubbling working regime to obtain results of heat transfer coefficient for a wide range of oxy-fuel conditions and extracting further conclusions on possible effects of gas composition on heat transfer coefficients. The range of O2 concentration at inlet reached values as high as 60%. Such a high concentration was scarcely achieved in pilot plants due, in most cases, to the limiting bed cooling capacity. Measurements of heat transfer coefficients were taken when cooling was needed to control the combustion temperature. Water could circulate through one or more of the four cooling jackets, depending on the cooling requirements. Heat transfer coefficients were indirectly measured by energy balance with the water mass flow and temperatures. There are no previous results on heat transfer measurements under oxy-fuel combustion, up to date. The pilot plant is characterized by two important performance parameters: the fluidizing velocity and the bed temperature. These two parameters are common for all the fluidized bed plants working on combustion. Particularly for characterizing oxy-fuel combustion, the composition of the oxidant gas is the other key parameter in the plant operation. These three factors have been analyzed and their influence on heat transfer was examined. The three of them are, however, interrelated. O2 concentration and bed temperature varied the gas density and thus, the fluidizing velocity. At the same time, the fluidizing velocity will affect the heat transfer coefficients and consequently, bed temperature would be influenced. For accounting for this kind of dependences, non-dimensional numbers have been used for comparison. It was detected no dominant effect of non-dimensional numbers on the heat transfer. This is mainly offset by the different fluidization velocities in AF and OF operation. In the former, uf was kept over 1 m/s, whereas OF required lower velocities, around 0.9 m/s. It was then determined the adequate semi-empirical correlations for the effective thermal conductivity and the residence time of particles at the heat transfer surface. Hence, a semi-empirical mechanistic approach is recommended for a good agreement with the experimental heat transfer coefficients obtained during oxy-fuel operation. It was demonstrated the relevance of the gaseous film resistance in the oxy-fuel tests, and a new empirical coefficient was deduced for both modes. As examined in Chapter 3, section 3.5, the recommended expressions to predict heat transfer coefficients during oxy-fuel combustion modified the thermal film resistance, fitting the empirical parameter M with experimental data. Where: M=6.51 for oxy-firing and M=11.33 for air-firing The larger amount of solids arriving at the EHE will influence the values and distribution of the average and local heat transfer coefficients, respectively. A review of the difficulties associated with the estimation of heat transfer to the tubes of a heat exchanger has been examined. By the use of a scaled-down EHE, it was possible to experimentally confirm the influence of heat transfer coefficients when horizontal movement of solids took place. The increase of solids rate stressed the inequalities of the local heat transfer coefficient, whereas the longer residence time taken by particles to travel through the EHE allows higher average heat transfer coefficient. The contribution of this parameter to the average heat transfer coefficient was correlated by means of a new expression, as developed in Chapter 4, section 4.4. This expression allows modifying the heat transfer coefficient previously deduced for stationary conditions, and therefore, accounting for the enhancement of heat transfer when recirculation of solids takes place. A real design of an EHE was then simulated and integrated in the existing CFB model previously developed. This is the first time that such a model is developed to predict the heat transfer area required in oxy-fuel operation. The EHE sub-model must fulfill the energy balance requirements previously set for the CFB model. The temperature, at which solids must be recycled back into the boiler, in order to keep the desired boiler temperature, is accomplished with this sub-model. The expressions for the heat transfer coefficient and the enhancement due to recycled mass flow of solids were included in the EHE sub-model. Hence, it was possible to determine the increase on the heat transfer surface, for different O2 concentration in the oxidant stream, and two ranges of boiler temperature required. It was then recognized that, in spite of doubling the heat transfer surface requirements, when O2 concentration increased 10%, the heat transfer surface increases less than expected if solids flow influence were not included in the heat transfer evaluation. This thesis demonstrates that heat transfer surface design, arrangement and allocation, will differ in future oxy-fuel CFB boilers. Particularly, the heat transfer in the EHE will need address the influence of fluidizing gas composition and recycled solids, for an adequate and efficient heat exchanger configuration

Análisis de Ciclo de Vida de la captura de CO2 en una central térmica y evaluación de alternativas basadas en energías renovables

En este proyecto se realiza el Análisis del Ciclo Vida (ACV), de una planta de captura y almacenamiento de CO2 (CAC) implementada en una central térmica convencional, con el objeto de evaluar los impactos ambientales asociados a su implantación en una central de generación eléctrica con combustible fósil, que en este trabajo es el lignito. Se realizan también el ACV de la central térmica convencional y el ACV de una turbina de viento. Para realizar los ACV, se utiliza el software SimaPro 8.02, que es una herramienta especializada para este tipo de análisis, cuyos procedimientos están estandarizados por la norma ISO 14044, 2006. Se ha aplicado la metodología IMPACT 2002+ en todos los ACV realizados en este trabajo, en la que los resultados representan los indicadores de daño a la salud humana, a la calidad del ecosistema, a los recursos naturales (agotamiento) y la contribución al cambio climático. El método IMPACT 2002+, que es una combinación y mejora de los métodos Eco-indicador 99 y CML 2001, utiliza indicadores de punto medio e indicadores de punto final ó indicadores de daño, proporcionando una perspectiva más completa de los daños y cargas ambientales. Finalmente, se comparan los resultados obtenidos de los ACV de la central térmica con captura de CO2 con los resultados obtenidos de la turbina de viento. Se discuten los resultados y se establecen las conclusiones oportunas. Los resultados que se obtienen indican que la planta de captura de CO2 permite reducir los impactos ambientales de forma muy importante con respecto a una central térmica convencional. Así, el impacto a las salud humana, a la calidad del ecosistema y al cambio climático al incluir la captura de CO2 en una central térmica de carbón, se reducen un 98-99% de sus valores originales sin captura de CO2. Asimismo, cuando se compara el impacto ambiental provocado por una central térmica con captura de CO2 con respecto al provocado por la generación eólica, se obtiene como resultado que el mayor impacto ambiental lo provoca la central térmica con captura. El mayor daño se produce a los recursos que utiliza la central térmica con captura frente a la generación eólica

Análisis de dos metodologías de cálculo de la huella de carbono para un sistema de trigeneración optimizado

En este trabajo se ha desarrollado el análisis de metodologías y procedimientos para el cálculo de emisiones de CO2, aplicándolos a un sistema de trigeneración optimizado. Estas metodologías incluyen la investigación de bases de datos para aplicar adecuadamente los mismos. Se ha considerado un sistema de trigeneración optimizado de un hospital de tamaño medio con 500 camas, ubicado en Zaragoza que tiene que atender las demandas de calor (agua caliente sanitaria y calefacción), refrigeración, y electricidad. Se ha procedido a calcular las emisiones de CO2 mediante el Análisis del Ciclo de Vida ACV, por medio de la metodología CML2 baseline 2000, para su categoría de impacto Cambio Climático, utilizando el software Sima Pro 7.3. Las emisiones de CO2 para la Huella de Carbono se han calculado mediante el Método Compuesto de las Cuentas Contables, MC3, utilizando la Hoja de Cálculo MC3v2. El MC3, recoge los consumos de las principales categorías de productos que una empresa necesita, existiendo también.Esos consumos/residuos serán transformados a toneladas de CO2 equivalentes, que sirven para el cálculo de la Huella de Carbono. Se ha procedido a analizar los resultados obtenidos comparándolos. Se ha mostrado que aun siendo metodologías muy diferentes conceptualmente los resultados son similares, lo que sugiere que el método MC3, de un modo comprensible y sencillo, puede ser una herramienta útil a las empresas y organizaciones para evaluar la Huella de Carbono de sus bienes y servicios

Infraestructura tecnológica para la extracción de recursos de información agrarios disponibles en Internet

Son considerados datos abiertos todos aquellos datos accesibles y reutilizables, sin exigencia de permisos específicos. En la actualidad, se está produciendo constantemente la publicación de datos abiertos, fundamentalmente por parte de administraciones públicas, siendo el ámbito agropecuario una zona donde hay multitud de recursos de información que se publican periódicamente en la web ajustados a diferentes formatos y modelos. Esta periodicidad supone que determinados días de la semana o del mes, aparece un nuevo conjunto de datos disponible en la Web.El desarrollo de este Trabajo Fin de Grado (TFG) tiene como objetivo principal crear una infraestructura que posibilite la extracción periódica de recursos de información agropecuarios publicados en Internet, y su integración en un data lake (o data hub). El proyecto hace hincapié en la generalización de los procesos de Extracción, Procesado y Carga (ETL) de cara a permitir la adición de nuevos recursos según éstos se vayan identificando. Para ello, se ha realizado una identificación de patrones en las fuentes de datos para el desarrollo de procesos de extracción generalistas por patrones, permitiendo que se puedan incorporar nuevos lectores de manera directa.El sistema desarrollado se ha validado con la integración de dos recursos distintos como es el porcino y los cereales y con el desarrollo de una aplicación web que permite la planificación de los trabajos ETL, y otra que muestre las posibilidades de explotación.La aplicación directa de este software es la extracción de diferentes recursos para su tratamiento, análisis y fácil visualización, permitiendo su posterior integración en otras herramientas como el uso de Inteligencia Artificial para el establecimiento del precio de referencia del porcino.<br /

Elaboración de una plataforma web colaborativa con información geográfica voluntaria para articular procesos de SIG participativo.

La era digital ha traido una avalancha de información sin precedentes que esta provocando una desadaptación de nuestro entorno local. Este trabajo explora la posibilidad de filtrar espacialmente la información geográfica generada en internet y localizarla en el propio territorio para articular procesos de SIG participativo. Esto se realiza a través de la elaboración de una plataforma web colaborativa para la georreferenciación y visualización de eventos en la ciudad de Zaragoza con el uso de herramientas libres. La consecución del objetivo permite la colección de datos espaciales aportados por los usuarios, de sus conexiones a la aplicación y de su interacción con la misma; que son representados mediante análisis espaciales realizados en el navegador web. La estructura de la plataforma permite la articulación de procesos participativos, siempre que exista una comunidad, y se reivindica como una alternativa real a otras agendas culturales.<br /

La Catedral de Malaga [manuscrito]

Copia digital : Diputación de Málaga. Biblioteca Canovas del Castillo, 201

Colloidal mobilization of arsenic from mining-affected soils by surface runoff

Received 2 June 2015, Revised 2 September 2015, Accepted 24 September 2015, Available online 23 October 2015Scorodite-rich wastes left as a legacy of mining and smelting operations pose a threat to environmental health. Colloids formed by the weathering of processing wastes may control the release of arsenic (As) into surface waters. At a former mine site in Madrid (Spain), we investigated the mobilization of colloidal As by surface runoff from weathered processing wastes and from sediments in the bed of a draining creek and a downstream sedimentation-pond. Colloids mobilized by surface runoff during simulated rain events were characterized for their composition, structure and mode of As uptake using asymmetric flow field-flow fractionation coupled to inductively plasma mass spectrometry (AF4-ICP-MS) and X-ray absorption spectroscopy (XAS) at the As and Fe K-edges. Colloidal scorodite mobilized in surface runoff from the waste pile is acting as a mobile As carrier. In surface runoff from the river bed and the sedimentation pond, ferrihydrite was identified as the dominant As-bearing colloidal phase. The results from this study suggest that mobilization of As-bearing colloids by surface runoff may play an important role in the dispersion of As from metallurgical wastes deposited above ground and needs to be considered in risk assessment.The Spanish Ministry of Economy and Competitiveness (research project CGL 2010-17434) supported this study.A. Gomez-Gonzalez was supported by the Ph.D. Spanish FPI fellow-ship (BES-2011-046461) and by graduate students (EEBB-I-14-08063) programs.Peer reviewe

Por Francisco Garcia altera appendix

Copia digital : Diputación Provincial de Zaragoza. Servicio de Archivos y Bibliotecas, 2010Datos de tit. tomados de p.1, mención de responsabilidad del final del textoInic. grab. xil. en p.

Una experiencia docente internacional para la elaboración de material docente práctico sobre la Farmacología

La Farmacología es una asignatura árida y difícil de comprender. Desde hace pocos años se realizan sesiones prácticas de problemas que facilitan a los estudiantes la comprensión y aprendizaje esta asignatura. En colaboración con profesores del área de Farmacología de las universidades de Montevideo (Uruguay) y la Nacional de Tucumán (Argentina), nos planteamos la elaboración de nuevos problemas que comprendieran todas las ramas de la Farmacología, con mayor o menor dificultad, para que pudieran ser útiles a estudiantes de Ciencias de la Salud, ya sean de grado o de postgrado, y estudiantes de Ciencias sociales y Jurídicas. Los problemas se han aplicado a estudiantes de grado en la Universidad de Alicante (Grado en Enfermería y Grado en Criminología) y en la Universidad de Tucumán (Grado en Odontología). En la Universidad de Montevideo los problemas han sido presentados a los estudiantes de dos Maestrías: Medicina de Familia y Comunitaria, y Farmacología Clínica. La calidad del aprendizaje se midió de forma cuantitativa (grado de acierto a las preguntas que se realizaban después de cada problema) y de forma cualitativa (valoración de las actitudes mediante encuesta con escala Likert). Resultados preliminares muestran una valoración positiva de los problemas en las tres universidades