1,721,049 research outputs found
Modeling of axial dispersion in rotating buckets contactor
No full textA rotating-bucket contactor is an interesting equipment used in liquid-liquid extraction. Of
course, as in other contactors, axial dispersion widely affects the extraction efficiency. A
theoretical approach to the problem is presented here. The paper reports also experimental data
obtained in a contactor of conventional geometry. The data are analyzed and compared with
model previsions. The agreement with the experiments is satisfactory. The obtained correlations
adequately describe also some literature experimental data related to smaller equipment.
Analysis and identification of the main fluid-dynamic aspects affecting axial dispersion can
suggest modifications of the internal geometry of the buckets and compartments. In this way,
the detrimental effects of the dispersion can be reduced, and the contactor efficiency can be
improved
Predizione della composizione di residui di distillazione petrolifera
No full textGli ultimi anni stanno vedendo, in tutto il mondo, una notevole
crescita nell‟utilizzo in raffineria di grezzi pesanti [1]. Le frazioni petrolifere ottenibili da questi grezzi di valore inferiore, sono in generale più difficili da trattare e determinano un peggioramento dell‟efficienza di produzione dei combustibili. Inoltre i residui di distillazione del grezzo, sia atmosferici che da vuoto, sono sempre più utilizzati nei processi termici per ottenerne prodotti ad alto valore aggiunto. In letteratura il problema dalla caratterizzazione dei residui non è affrontato in modo sufficientemente esauriente [2], [3], [4], [5]. In questo lavoro verrà illustrato come, a partire da informazioni normalmente disponibili in raffineria, è possibile arrivare ad una descrizione oddisfacente delle proprietà della miscela.In the last years heavy crudes are increasingly used into refineries [1]. Petroleum fractions derived from these crudes have a lower value and they generate more difficulties during treatments. Moreover, atmospheric and vacuum distillation residues of crude are increasingly used in thermal processes in order to recover more valuable products. The literature reports models for heavy fractions characterization [2], [3], [4], [5], but the problem of residues description is still poorly faced on. This paper shows how, starting from the few information usually available into the refinery, it is possible to obtain a description of these feedstocks in terms of model compounds. This characterization can constitute a good starting point for a realistic kinetic modeling of thermal processes
Dissolution of CO2 and CH4 Bubbles and Drops Rising from the Deep Ocean
Full text linkABSTRACT: The rise and dissolutions of CO2 or CH4 particles (bubbles or drops) from deep ocean is important for understanding the fate of the release of these components from marine sediments. In this paper is presented a complete fluiddynamic and dissolution model that accounts also the effect of the presence of gas hydrates at the interface of the particles. The rise velocity is a result of the effect of the particle deformation on the drag coefficient. The proposed model for evaluating the particle rise velocity has not be developed specifically for the case of CO2 and CH4 release here analyzed, but it is general for liquid−liquid or gas−liquid systems. The comparison of the model with experimental data reported in the literature shows agood agreement
Il contributo alla nascita e allo sviluppo di una cultura e di una coscienza dell'ingegneria chimica a Napoli e in Italia
No full textSingle Bubble and Drop Motion Modeling
No full textA model for the prediction of the terminal relative velocity of single gas bubbles or drops, moving into a quiescent liquid phase, is presented. Also the effect of contamination is taken into account. It has been compared with a large set of experimental literature data covering a wide range of physical properties and particle sizes. The agreements are quite satisfactory and confirm the reliability of the model
Coalescence between adjacent drops relying on the interface of two liquids
No full textThis paper is aimed to the study and characterization of the coalescence of two adjacent drops lying on, or
under (depending on the different densities), the macro-interface of two immiscible liquids. Experiments have
been performed and coalescence times measured by using an oil-water system. A mechanistic model of
coalescence is proposed. The comparison with experimental data is satisfactory
Modelling of a RDC column for glycerol recovery
No full textSince many years Rotating Disc Contactors (RDC) are adopted, in large scale plants of soap production, for recovery glycerol from soap solution. However no literature related to the modeling of this equipment is reported. Also equilibrium data and solution properties are not available. Here a theoretical approach to the problem is adopted. As usual in these kind of equipments axial dispersion widely affects the separation efficiency. Fluid-dynamic aspects (e.g. drop size, velocity and hold-up of the dispersed phase), mass transfer and axial dispersion coefficients affects column behavior. A mechanistic approach is proposed for their evaluation. Model predictions concerning glycerol, NaOH, NaCl concentrations and column hold-up have been compared with experimental data obtained from a commercial column. The results appear to be satisfactory. Part of the proposed methodology is fairly general and can be extended to the modeling of other liquid-liquid extractors like for instance the rotating buckets contactors (Dente and Bozzano 2004)
A comprehensive program for visbreaking simulation: products amount and their properties prediction
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