1,721,179 research outputs found
Understanding the structural changes on Fe2O3/Al2O3 oxygen carriers under chemical looping gasification conditions
No full text9 figures, 2 tables.Chemical Looping Gasification (CLG) has emerged recently as a promising technology for producing non N2-diluted syngas without the need for an external power supply or the expensive use of pure O2. Many studies have focused on development of oxygen carriers since they are considered a crucial factor in CLG processes. Fe2O3/Al2O3 (FeAl) oxygen carriers have been proposed due to previous experience in Chemical Looping Combustion (CLC). However, the aggressive conditions of gasification cause a decrease in the mechanical stability of the particles, which can be a challenge for their use in CLG. In this work, the operating conditions and Fe-content required to maintain the particle integrity of oxygen carrier particles during redox cycles in both CLC and CLG operations were determined. Long-term tests, consisting of 300 redox cycles, were conducted in a TGA to simulate the operation in a continuous unit and the results were compared with attrition data obtained from a 1.5 kWth CLG unit. Three oxygen carriers with varying Fe2O3-content (10, 20 and 25 wt%) were used, and three different solid conversions (0–25 %, 75–100 % and 0–100 %) were performed to emulate CLC or CLG atmospheres at three temperatures (850 °C, 900 °C and 950 °C). The evolution of the microstructure of particles was analyzed using a scanning electron microscope (SEM) and it was found that the lower the Fe2O3 content in the particles, the greater their stability in redox cycles, an increase in the reaction temperature led to a more rapid degradation of the oxygen carrier particles, and the solid conversion variation and degree of reduction/oxidation during redox cycles strongly influenced the evolution of the mechanical stability of the oxygen carrier particles.This work was supported by the CO2SPLIT Project, Grant PID2020-113131RB-I00, funded by MICIN/AEI/10.13039/501100011033. I. Samprón thanks the Spanish Ministerio de Ciencia, Innovación y Universidades (MICIU) for the PRE2018-086217 predoctoral fellowship.Peer reviewe
Combustión con transportadores sólidos de oxígeno en bucle químico.
No full text7 figuras.-- Volumen 11 de Avances de ingeniería. Análisis de situación y prospectiva de nuevas tecnologías energéticas. Capítulo 1: Captura de CO2.El tema que se abordará en este capítulo es el "chemical looping combustion" o "combustión con transportadores sólidos de oxígeno".Introducción.-- Transportadores sólidos de oxígeno.-- Aplicación de la tecnología de "chemical looping combustion" a combustibles sólidos.-- CLC con gasificación "in situ".-- Proceso Looping CLOU (Chemical with Oxygen Uncoupling).-- Estado actual de "Chemical looping combustion" con combustibles sólidos
Current status of Chemical Looping Combustion process
No full text3 Figuras, 1 Tabla[EN] Today there are technologies that allow CO2 capture in power plants, but these technologies consume an important amount of energy due to the need of CO2 or O2 separation of the other gases. For this reason, new technologies for CO2 capture with low energy penalty are under developing. Among them, Chemical-Looping Combustion (CLC) process is suggested among the best alternatives to reduce the economic cost of CO2 capture because CO2 separation is inherent to the process. CLC involves the use of an oxygen carrier (OC), which transfers oxygen from air to the fuel avoiding the direct contact between them. CLC system is made of two interconnected reactors, designated as air and fuel reactors. A key issue for the LC technology development is the selection of an OC which is formed by an active metal oxide and inert that acts as support. Ni-, Cu-, Fe-, Co- and Mn-based OCs supported on different inert materials, in addition to CaS/CaSO4 transformation, have been studied to be used in a CLC process. Each material has different characteristics, and so, different advantages and disadvantages.Until now, most of the OCs have been used in small installations (up to 140 kWth) and with gaseous fuels, being the main objective with these fuels the scaling up of the technology to a higher power. Moreover, the use of the CLC with solid fuels has recently gained a great interest, being this aspect the main challenge of this technolgy.[ES] Actualmente existen tecnologías que permiten la captura de CO2 en centrales de producción de energía, pero éstas consumen gran cantidad de energía, bien en el proceso de separación del CO2 o en el de producción de oxígeno. Por ello, se están desarrollando nuevas tecnologías que permitan la captura de CO2 con bajas penalizaciones energéticas. Entre éstas, la tecnología de combustión con transportadores sólidos de oxígeno (conocida por su nombre en inglés como “Chemical-Looping Combustion”, CLC) presenta un gran potencial, ya que la separación del CO2 es inherente al propio proceso de combustión. El proceso CLC está basado en la transferencia de oxígeno del aire al combustible por medio de un transportador de oxígeno en forma de óxido metálico que circula entre dos reactores interconectados entresí y no poniéndose en contacto en ningún momento el combustible con el aire. Una pieza clave del proceso es el transportador de oxígeno, el cual está formado por un óxido metálico y un inerte que actua como soporte. Entre los metales existentes, los que pueden ser utilizados como transportadores de oxígeno son Ni, Cu, Fe, Co y Mn, y además el Ca en mediante la reacción CaS/CaSO4. Cada uno de ellos presenta diferentes características y por lo tanto diferentes ventajas e inconvenientes. Hasta el momento, los transportadores sólidos de oxígeno se han utilizado principamente en plantas pequeñas (de hasta 140 kWt) y con combustibles gaseosos, siendo el reto principal con estos combustibles su escalado a plantas de mayor potencia. Además, en los útimos años ha tomado un gran auge su uso con combustibles sólidos, siendo este el gran reto de esta tecnología.Este trabajo ha sido financiado por el Ministerio de Ciencia e Innovación (MICINN Project: ENE2011-26354) y por fondos FEDER.Peer reviewe
Going Beyond Counting First Authors in Author Co-citation Analysis
Get PDFThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Variations on the Author
Get PDF“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
Appropriate Similarity Measures for Author Cocitation Analysis
Get PDFWe provide a number of new insights into the methodological discussion about author cocitation analysis. We first argue that the use of the Pearson correlation for measuring the similarity between authors’ cocitation profiles is not very satisfactory. We then discuss what kind of similarity measures may be used as an alternative to the Pearson correlation. We consider three similarity measures in particular. One is the well-known cosine. The other two similarity measures have not been used before in the bibliometric literature. Finally, we show by means of an example that our findings have a high practical relevance.information science;Pearson correlation;cosine;similarity measure;author cocitation analysis
Dispelling the Myths Behind First-author Citation Counts
Get PDFWe conducted a full-scale evaluative citation analysis study of scholars in the XML research field to explore just how different from each other author rankings resulting from different citation counting methods actually are, and to demonstrate the capability of emerging data and tools on the Web in supporting more realistic citation counting methods. Our results contest some common arguments for the continued
use of first-author citation counts in the evaluation of scholars, such as high correlations between author rankings by first-author citation counts and other citation
counting methods, and high costs of using more realistic citation counting methods that are not well-supported by the ISI databases. It is argued that increasingly available digital full text research papers make it possible for citation analysis studies to go beyond what the ISI databases have directly supported and to employ more
sophisticated methods
koamabayili/VECTRON-author-checklist: VECTRON author checklist
No full textWe have done our best to complete the author checklist relating to the use of animals in the hut study. Note that the objective for the hut study was to evaluate the IRS treatment applications for residual efficacy against Anopheles mosquitoes, including the local An. coluzzii mosquito population. Cows were only used to attract mosquitoes into the huts and no tests were carried out directly on the cows. The author checklist is intended for use with studies where experiments are carried out on animals, which is why we have had such difficulty in completing this for the hut study, as many of the questions do not relate to how the cows were used
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