1,720,960 research outputs found
Carbonation of BOF Slag in a Rotary Kiln Reactor in View of the Scale-Up of the Wet Route Process
No full textCarbonation of alkaline residues represents a potentially interesting technique for permanently storing in solid form CO 2 contained in flue gas, syngas or biogas, as well as for the valorization of the residues. In particular, the wet carbonation route requires a low amount of water, does not generate wastewater and can be exploited to produce aggregates. The efficacy of this route has been demonstrated at laboratory scale. In view of its scale-up, this study was aimed at evaluating the performance of a wet-route carbonation process applied to Basic Oxygen Furnace (BOF) steel slag employing an operating procedure that could be adopted also at demonstrative or full scale. Dry residues were directly fed by a loading hopper into a rotary kiln reactor, in which gas containing 40% CO 2 and steam were flown through. During the experiments, the flow and composition of the gas phase were continuously monitored, allowing to calculate the amount of CO 2 captured from the gas phase and to compare it with the CO 2 uptake of the solid product. In addition, the leaching behavior of the treated slag was assessed. The results of the tests were close to those obtained in previous experiments performed with pre-humidified BOF slag, both with the same reactor used in this study and at laboratory scale; this suggests that this more automated wet-route process could be employed for demonstration or full scale tests. The set up still needs to be optimized to obtain a product with physical and technical properties suitable for use as aggregate. © 2019 American Institute of Chemical Engineers Environ Prog, 38:e13140, 2019
Assessment of a carbonation-based CO2 utilization process for the valorization of CFBC ash
No full textThis work assesses a combined accelerated carbonation and wet granulation treatment applied to circulating fluidized bed combustion fly ash with the aim of producing secondary aggregates for civil engineering applications and of achieving a net storage of CO2. The experiments were carried out at both a laboratory scale and larger scale, and the effects of the CO2 content of the gas flow (40 or 100%), temperature (from 25 to 60 degrees C), and the use of an alkaline activator solution as binder for the granulation process were investigated. Specifically, the particle size distribution, aggregate crushing value, leaching behavior, and CO2 uptake of the products after 28 days curing under ambient air were analyzed. In addition, the energy requirements of the process were estimated on the basis of the results of the larger scale tests and were used to calculate the CO2 emissions of the process to estimate the net CO2 avoided that could be achieved per kilogram of produced aggregate. The carbogranulation process allowed us to achieve a relevant increase in particle size with respect to the starting material. The conditions that yielded the best performance in terms of product properties (both technical and environmental) and the maximum amount of CO2 avoided (above 75 g of CO2/kg aggregate) was the carbogranulation treatment performed at 60 degrees C with water as binder and a gas phase containing 40% CO2. Although the products obtained employing the alkaline activator solution presented a lower mobility of trace elements of potential environmental concern and generally a higher CO2 uptake compared to the granules produced with water as granulation binder, the carbon footprint of the additives (sodium silicate in particular) would make the process carbon positive, even considering the CO2 avoided by replacing natural aggregates
Scale up of the wet route carbonation of steel slag in a rotary kiln pilot-scale reactor
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Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe 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
Mechanical and environmental properties of carbonated steel slag compacts as a function of mineralogy and CO2 uptake
No full textAccelerated carbonation is a treatment for converting alkaline industrial residues into added-value products and storing CO2 in solid form. This work investigated the influence of reacting phases and CO2 uptake on microstructure development, mechanical properties and the environmental behavior of carbonated compacts produced from Basic Oxygen Furnace (BOF) and Electric Arc Furnace (EAF) slags, characterized by a different mineralogy. The compacts were cured under a 100% CO2 atmosphere at 50 °C and pressure of 1.3 or 10 bar for 15 min to 4 h. The BOF slag reacted very fast in the first 30-60 min due to the complete conversion of portlandite to calcite, amorphous calcium carbonate and aragonite, and continued to react over time due to the presence of slower reacting Ca-silicate phases. For the EAF slag, rich in Ca-silicates, the CO2 uptake was lower, and increased only slightly over time at 1.3 bar and became almost stable after 15 minutes at 10 bar; the EAF slag products however presented a higher compressive strength than the BOF slag ones, because of the different phases involved in the carbonation reaction. For the BOF slag, portlandite dissolution caused the formation of voids, only partially filled up by the reaction products. For the EAF slag, formation of a carbonate and amorphous silica layer around the reacting silicates yielded a denser matrix. pH and Ba leaching decreased for both types of slag, whereas V release increased due to the dissolution of reactive phases such as dicalcium silicates, which initially contained this element
Variations on the Author
Full text link“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
Full text linkWe 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
Full text linkWe 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
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