1,720,970 research outputs found
Hydrochar fractionation and composition in batch and continuous hydrothermal liquefaction
Full text linkUnderstanding differences in hydrochar characteristics in batch and continuous hydrothermal liquefaction (HTL)
is crucial in determining suitable valorisation routes for this byproduct, given its high nutrient load and carbon
sequestration potential.
This study thoroughly characterised hydrochar from batch and continuous HTL at 300, 325 and 350 ◦C,
elucidating their main differences and shedding light on the operational parameters causing them. For this
purpose, a bench-scale continuous HTL unit with in-line solids separation was commissioned. It was possible to
differentiate primary and secondary char and infer their formation mechanism.
The results showed that batch hydrochar yields were higher (24–26%) than continuous (primary and secondary)
char yields (15–19%). In both reactions, higher temperatures led to chars with lower carbon and nitrogen
contents. The ash content of batch hydrochars was lower than that of continuous primary chars, revealing
that the in-line char separator effectively removed inorganic impurities at reaction conditions and produced a
cleaner biocrude. The nutrient distribution in the HTL products showed batch biocrudes were more contaminated
by Na, K and Fe, while in the continuous biocrudes, only Fe was detected. Moreover, less carbon migrated
to the solids from continuous HTL, indicating that removing inorganics may reduce secondary char formation.
Batch hydrochars showed a higher presence of oxygenated and nitrogenated compounds, while the continuous
primary chars had a higher share of alkanes and alkenes.
These differences may imply that batch reactions may not serve as indicators, in terms of hydrochar characteristics,
for HTL upscaling to industrial plants
Sequential hydrothermal dechlorination and liquefaction of PVC
Full text linkPoly(vinyl chloride) (PVC) is globally the third most produced plastic, but recycling PVC waste through mechanical means is difficult. Due to the high presence of chlorine in PVC, it is unsuitable for both pyrolysis and combustion. Consequently, there is a need to explore innovative methods for harnessing its energy potential. Hydrothermal liquefaction (HTL) is a topic of growing interest in the literature for chemical recycling of waste plastic or conversion into liquid energy carriers. In this work an innovative sequential hydrothermal processing strategy was tested for oil production from PVC. PVC at high loadings (20 wt.%) was first processed under subcritical conditions to produce a chlorine-free solid, which was then liquefied in supercritical conditions. Different temperatures were tested for the dechlorination stage, and at 300 °C 99% of chlorine was removed, while 94% of carbon remained in the solid residue. The mechanism behind the solid's formation was investigated by assessing activation energies, both with the addition of KOH as a neutralizing agent (120 kJ/mol) and without it (186 kJ/mol). Different temperatures were screened for an HTL supercritical stage (420-480 °C), but the maximum conversion of the dechlorinated solid was 47%, and the maximum mass yield of oil was 10%. Overall, the subcritical phase demonstrated its potential as a technology for producing chlorine-free solid material with a high energy density. The subsequent supercritical step partially valorized the dechlorinated solid by producing an aromatic-rich oil phase
Biochar characterization for its environmental and agricultural utilization. Occurrence, distribution and fate of labile organic carbon and polycyclic aromatic hydrocarbons
No full textIn this thesis the potential risks associated to the application of biochar in soil as well the stability of biochar were investigated. The study was focused on the potential risks arising from the occurrence of polycyclic aromatic hydrocarbons (PAHs) in biochar. An analytical method was developed for the determination of the 16 USEPA-PAHs in the original biochar and soil containing biochar. The method was successfully validated with a certified reference material for the soil matrix and compared with methods in use in other laboratories during a laboratory exercise within the EU-COST TD1107. The concentration of 16 USEPA-PAHs along with the 15 EU-PAHs, priority hazardous substances in food, was determined in a suite of currently available biochars for agricultural field applications derived from a variety of parent materials and pyrolysis conditions. Biochars analyzed contained the USEPA and some of the EU-PAHs at detectable levels ranging from 1.2 to 19 µg g-1. This method allowed investigating changes in PAH content and distribution in a four years study following biochar addition in soils in a vineyard (CNR-IBIMET). The results showed that biochar addition determined an increase of the amount of PAHs. However, the levels of PAHs in the soil remained within the maximum acceptable concentration for European countries. The vineyard soil performed by CNR-IBIMET was exploited to study the environmental stability of biochar and its impact on soil organic carbon. The stability of biochar was investigated by analytical pyrolysis (Py-GC-MS) and pyrolysis in the presence of hydrogen (HyPy). The findings showed that biochar amendment significantly influence soil stable carbon fraction concentration during the incubation period. Moreover, HyPy and Py-GC-MS were applied to biochars deriving from three different feedstock at two different pyrolysis temperatures. The results evidenced the influence of feedstock type and pyrolysis conditions on the degree of carbonisation
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
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
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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