1,721,068 research outputs found
Modelling of H₂ production in a packed bed reactor via sorption enhanced steam methane reforming process
Full text linkThe sorption enhanced steam reforming (SE-SMR) of methane over the surface of 18 wt. % Ni/ Al₂O₃ catalyst and using CaO as a CO₂-sorbent is simulated for an adiabatic packed bed reactor. The developed model accounts for all the aspects of mass and energy transfer, in both gas and solid phase along the axial direction of the reactor. The process was studied under temperature and pressure conditions used in industrial SMR operations. The simulation results were compared with equilibrium calculations and modelling data from literature. A good agreement was obtained in terms of CH₄ conversion, hydrogen yield (wt. % of CH₄ feed), purity of H₂ and CO₂ capture under the different operation conditions such as temperature, pressure, steam to carbon ratio (S/C) and gas mass flux. A pressure of 30 bar, 923 K and S/C of 3 can result in CH₄ conversion and H₂ purity up to 65% and 85% respectively compared to 24% and 49% in the conventional process
Modelling of H2 production via sorption enhanced steam methane reforming at reduced pressures for small scale applications
Full text linkThe production of H2 via sorption enhanced steam reforming (SE-SMR) of CH4 using 18 wt. % Ni/ Al2O3 catalyst and CaO as a CO2-sorbent was simulated for an adiabatic packed bed reactor at the reduced pressures typical of small and medium scale gas producers and H2 end users. To investigate the behaviour of reactor model along the axial direction, the mass, energy and momentum balance equations were incorporated in the gPROMS modelbuilder®. The effect of operating conditions such as temperature, pressure, steam to carbon ration (S/C) and gas mass flow velocity (Gs) was studied under the low-pressure conditions (2 – 7 bar). Independent equilibrium based software, chemical equilibrium with application (CEA), was used to compare the simulation results with the equilibrium data. A good agreement was obtained in terms of CH4 conversion, H2 yield (wt. % of CH4 feed), purity of H2 and CO2 capture for the lowest (Gs) representing conditions close to equilibrium under a range of operating temperatures pressures, feed steam to carbon ratio. At Gs of 3.5 kg m-2s-1, 3 bar, 923 K and S/C of 3, CH4 conversion and H2 purity were up to 89% and 86% respectively compared to 44% and 63% in the conventional reforming process
Modelling of high purity H2 production via sorption enhanced chemical looping steam reforming of methane in a packed bed reactor
Full text linkSorption enhanced chemical looping steam reforming of methane (SE-CLSR) relies on the exothermicity of both a metal catalyst’s oxidation and the in situ CO2 capture by carbonation onto a solid sorbent to provide the heat demand of hydrogen (H2) production by steam reforming while generating a nearly pure H2 product. A brief thermodynamic analysis to study the main features of the SE-CLSR process is done prior to the reactor modelling work. Later, one dimensional mathematical model of SE-CLSR process in the packed bed configuration is developed using gPROMS model builder 4.1.0® under the adiabatic conditions. This model combines reduction of the NiO catalyst with the steam reforming reactions, followed by the oxidation of the Ni-based reduced catalyst. The individual models of NiO reduction, steam reforming with in situ CO2 capture on Ca-sorbent, and Ni re-oxidation are developed by using kinetic data available in literature and validated against previous published work. The model of SE-CLSR is then applied to simulate 10 alternative cycles of the fuel and air feed in the reactor. The performance of the model is studied in terms of CH4 conversion, CO2 capture efficiency, purity and yield of H2. The sensitivity of the process is studied under the various operating conditions of temperature, pressure, molar steam to carbon ratio (S/C) and mass flux of the gas phase. In this work, the operating conditions used for the production of H2 represent realistic industrial production conditions.The sensitivity analysis demonstrates that the developed model of SE-CLSR process has the flexibility to simulate a wide range of operating conditions of temperature, pressure, S/C and mass flux of the gas phase
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
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
Kinetics study and modelling of steam methane reforming process over a NiO/Al2O3 catalyst in an adiabatic packed bed reactor
Full text linkKinetic rate data for steam methane reforming (SMR) coupled with water gas shift (WGS) over an 18 wt. % NiO/α-Al2O3 catalyst are presented in the temperature range of 300-700 °C at 1 bar. The experiments were performed in a plug flow reactor under the conditions of diffusion limitations and away from the equilibrium conditions. The kinetic model was implemented in a one-dimensional heterogeneous mathematical model of catalytic packed bed reactor, developed on gPROMS model builder 4.1.0®. The mathematical model of SMR process was simulated, and the model was validated by comparing the results with the experimental values. The simulation results were in excellent agreement with the experimental results. The effect of various operating parameters such as temperature, pressure and steam to carbon ratio on fuel and water conversion (%), H2 yield (wt. % of CH4) and H2 purity was modelled and compared with the equilibrium values
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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