1,721,022 research outputs found
Experimental and Simulation Studies of Industrial Scale Finishing Reactive Distillation Column
No full textRD is the process developed by integrating two different operations (chemical reaction and multi-stage distillation) simultaneously in a single unit. Reactive distillation (RD) has been successfully implemented for the production of the Ethyl acetate (EtAc).The RD feature of shifting the equilibrium in the forward direction is useful for EtAc production by the reversible esterification reaction of acetic acid with ethanol.
The main advantages of using the RD with a pre-reactor for the production of the EtAc is that, the existing plants based on the conventional process can be easily revamped to use the RD technology. Also, in case of RD with pre-reactor, a smaller RD column (as compared to complete RD process) is required which reduces the capital investment. At IOL Chemicals and Pharmaceuticals Ltd., the EtAc is produced by the esterification of HAc with EtOH in the presence of the homogeneous acid catalyst (para-toluene-sulfonic acid) using RD with pre-reactor. Most of the reaction takes place in the reactor and the reacted mixture is fed to the column where simultaneous removal of product improves the conversion and product yield. The work reported in this thesis was aimed at generating the experimental data from an industrial scale RD column (situated at IOL Chemicals and Pharmaceuticals Limited, Trident Complex, Barnala, Punjab, India) and to compare the simulation results with this RD column data.
The provision for the collection of vapor and liquid samples from each tray was made during a scheduled shutdown of the plant. The simulation was carried out using the rate based model of Aspen PlusTM, as the column hardware information was readily available. A new set of thermodynamic parameters for the NRTL model was established for the highly the non-ideal liquid mixture, of this reaction system, by regression of the vapor-liquid equilibrium data available in literature. Predicted vapor and liquid composition profiles are in good agreement with plant data. The simulation results indicate that stages 20 to 30 are the most active stages of the column from the hydrodynamic point of view.
Like a conventional distillation column, in this case too, an increase in organic reflux (keeping the distillate flow rate constant) causes an asymptotic increase in distillate purity (i.e., EtAc concentration). A linear increase in re-boiler duty and decrease in ethanol conversion was also observed with an increase in reflux flow rate. However, at high reflux flows, a higher EtAc concentration suppresses the forward reaction, thus, overall conversion in the column decreases.
The simulation results further show that the column is having more number of trays (about 6 trays) in the rectification section than required. The effect of feed stage location is also discussed to utilize these extra trays. The results show that re-boiler and condenser duties decrease on moving the feed stage up in the column (from stage 39 to stage 33). Also, the ethanol conversion increases as the reaction zone in the column increases with the shifting of feed stage from stage 39 to stage 33.
It is observed that the extra stages can be utilized in a more effective way by changing the feed location (moving the feed stage up in the column) so that reaction zone in the column increased; and by addition of a fresh feed of ethanol at stage 49 to improve the forward reaction. A fresh feed of ethanol (150 kg/h) is added in the down-comer of 49th stage and the feed from the pre-reactor was introduced at stage 34. The ethanol conversion in the RD column increased from 17.43 kg to 93.44 kg, the ethanol conversion (wt%) increased to 39.94 % from 18.76%. The specific energy (kcal/kg of EtAc) requirement of re-boiler reduced from 1115 to 1054, and condenser duty (kcal/kg of EtAc) reduced from 684 to 654.
Comparison of the column composition profiles, for liquid and vapor phases, with EQ and rate-based model simulations show that, for all the components, the rate based model’s predictions are far more superior to the EQ model predictions. The rate-based model predicted lower EtAc generation rates, than the EQ model, as introduction of mass transfer resistance reduced the reaction rates
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
Author-wise bibliometric analysis based on entropy.
No full textAuthor-wise bibliometric analysis based on entropy.</p
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