1,721,025 research outputs found
Analysis of biomass chars thermal decomposition: Experimental tests and modelling in N2 and CO2 atmosphere
No full textChar is a by-product of biomass gasification; nonetheless, it can be valorized in several ways, for wastewater treatment, for instance, or as bio-fertilizer. Char has also been observed to have a high potential for catalytic tar reduction. With a view to designing a char-based gas filtering system for tar cracking applications, it is of key importance to study the behavior of char in terms of mass degradation. For this purpose, the process of char thermal decomposition under different operating conditions has been addressed in the present work. Char samples collected from a local small-scale gasification plant have been studied both under inert (nitrogen) and under reactive (carbon dioxide) atmosphere. Thermogravimetric tests and thermal degradation tests in a lab-scale fixed-bed reactor have been performed. In carbon dioxide, the char mass loss resulted to be much more conspicuous, since many and complex reactions are involved in the kinetics of CO2 gasification. As regards the thermal decomposition of char in inert atmosphere, it has then been modelled by means of a first-order kinetic model coupled with a fluid-dynamic model, thus reproducing the temperature distribution and the mass loss occurring inside the fixed-bed reactor. The developed model predicted the char degradation in a satisfactory way
Building Simulation Applications BSA 2013 - Proceedings of 1st IBPSA Italy conference
Full text linkBuilding Simulation application 2013 was the first IBPSA Italy regional conference on building performance simulation. The two-day event focused on three main subjects: simulation of building performance, actual perspectives in building physics and simulation tools. The principal mission is to promote and advance the practice of building performance simulation in order to improve the design, construction, operation and maintenance of new and existing building
Experimental and Modelling Analysis of Char Decomposition: Experiences with Real Scale Gasification Systems
No full textThe main issue to be faced when dealing with gasification processes is the removal of tars in order to obtain a good quality producer gas for later use, either as energy vector or for production of chemicals. Char has been observed to have a high potential for catalytic tar reduction, but the properties that promote this activity are still being investigated. An understanding of the mechanisms involved in the process of tar removal is needed, including the deactivation of the char as a catalyst and its degradation. This work addresses the process of thermal decomposition of char with different operating conditions and under inert atmosphere (N2), in order to determine the mass loss occurring under high temperature treatment. For this purpose, chars collected from local gasification plants have been used. Firstly, a complete characterization of the chars has been carried out to determine their composition, heating value and BET surface area. Secondly, thermogravimetric analyses have been used to calibrate a one-step kinetic model for describing the kinetics involved in the process of char thermal decomposition. The coupling of the kinetics with a CFD model allowed then to consider mass, heat, and momentum transfer phenomena, and to quantitatively estimate the decomposition in a fixed-bed test reactor. The model, whose results have been compared to reference experimental tests, predicts satisfactorily the thermal behavior of the char inside the reactor and its mass loss
THE AIR ENERGY BALANCE EQUATION PARADOX
No full textIn building physics applications, mainly related to the building energy performance simulations, the master equation is the inner air energy balance equation. Historically the followed approach in writing down such master equation was to adopt the simplifying hypothesis of incompressible fluid for the air assumed dry. This hypothesis, among others, reduces the general integral energy balance equation to the usual formulation which is reported in textbooks and manuals and has been used in available energy simulation programs, such as Energy Plus, Esp-r, TRNSYS, etc. Later the moist air problem, the indoor air humidity control, has been faced just by adding a new integral balance equation: the water vapour mass balance equation. In this work it is pointed out how this "layered" historical approach leads to a paradox: an incompressible fluid is used to describe an ideal gas in an ideal gas mixture. Herewith the general integral energy balance equation is directly written in terms of moist air under ideal gas hypothesis and it is shown how, under acceptable specific hypothesis, it is possible to obtain a similar but conceptually different final formulation, which mainly differs in the transient storage term
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
Valorization of orange peels in a biorefinery loop: recovery of limonene and production of volatile fatty acids and activated carbon
Full text linkOrange peels (OPs) were valorized in a lab-scale biorefinery loop for the recovery of limonene and the subsequent production of volatile fatty acids (VFAs) and activated carbon (AC). Solid/liquid extraction of limonene was optimized using n-hexane at 85 degrees C with an OPs-to-solvent ratio of 2:1, allowing for a limonene recovery yield of 1.20% w/w. Then, post-extraction OPs were used for the production of both VFAs and AC. For VFA production, a hydraulic retention time (HRT) of 5 days and a total solid (TS) inlet content of 10% w/w were adopted leading to a VFA yield of about 43% gVFAs/gTS. Adsorption tests revealed that, among all the solid matrixes tested, only powdered activated carbon (PAC) was able to discriminate no-VFA compounds and allowed for VFA purification. For AC production, post-extraction OPs were firstly converted into biochar through slow pyrolysis at 550 degrees C for 1 h and then physically activated with CO2 at 880 degrees C for 1 h. Extraction did not appreciably affect OP properties, while pyrolysis increased the carbon content (from 43 to 83%) and the heating value (from 17 to 29 MJ/kg) of the material. Physical activation of OP biochar increased its surface area by almost ten times, from 40 to 326 m(2)/g, proving the effectiveness of the treatment
Experimental study on H2S adsorption on gasification char under different operative conditions
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