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Solid Systems (solid + system)

Distribution by Scientific Domains

Chemistry	80%

Selected Abstracts

Waschverfahren partikulär-disperser Systeme , Verfahrensspektrum und Aspekte der Verfahrensauswahl

CHEMIE-INGENIEUR-TECHNIK (CIT), Issue 9 2003
B. Hoffner Dipl.-Ing.
Abstract Die Waschung disperser Feststoffsysteme ist ein weit verbreiteter und komplexer Verfahrensschritt. Durch die Tatsache, dass er meist in andere Prozessoperationen eingebunden ist, unterliegt er vielfältigen Anforderungen, die deutlich über die primären Ansprüche eines hohen Abtrenngrades und niedrigen Waschflüssigkeitsbedarfs hinausgehen. Aufgrund der Wirkungsweise und Grenzen unterschiedlicher Waschverfahren ist die Auswahl eines geeigneten Waschverfahrens schwierig, da die dominierenden Wirkmechanismen z.,T. nicht ausreichend bekannt sind. Dieser Beitrag gibt einen Überblick über bestehende Waschverfahren, deren zahlreiche Einflussgrößen und über Anforderungen, die an sie gestellt werden. Eine Kategorisierung von Waschprozessen, zusammen mit der Einordnung der Verfahren hinsichtlich makroskopischer Transporteigenschaften, führt zur Entwicklung eines Bewertungsschemas, das bestehende Waschprozesse bewertet, vergleicht und Grenzen der einzelnen Verfahren aufzeigt. Die Arbeit dient als grober Leitfaden für die Auswahl eines geeigneten Waschverfahrens. Washing of Disperse Solid Systems , Existing Washing Processes and Guidelines for Choosing the Appropriate Washing Procedure Washing of disperse solid systems is a widely used and complex operation. Since the washing-step is mostly integrated into other process operations, it is subject to numerous demands, which exceed the primary demands like a good separation result and a low specific wash liquid demand. Because of the phenomenology and limits of different washing procedures it is difficult to choose an appropriate washing process. Additionally, the acting transport mechanisms of some washing procedures are not yet sufficiently understood. This work shows a broad overview over the existing washing processes, the numerous parameters and the demands they have to fulfill. A categorization of washing procedures as well as a classification of the processes concerning their macroscopic transport phenomena are the base for a broad decision chart which compares and evaluates existing washing processes and shows their individual limits. The work can be seen as a rough guideline for choosing the appropriate washing procedure. [source]

Efficient non-linear solid,fluid interaction analysis by an iterative BEM/FEM coupling

INTERNATIONAL JOURNAL FOR NUMERICAL METHODS IN ENGINEERING, Issue 11 2005
D. Soares Jr
Abstract An iterative coupling of finite element and boundary element methods for the time domain modelling of coupled fluid,solid systems is presented. While finite elements are used to model the solid, the adjacent fluid is represented by boundary elements. In order to perform the coupling of the two numerical methods, a successive renewal of the variables on the interface between the two subdomains is performed through an iterative procedure until the final convergence is achieved. In the case of local non-linearities within the finite element subdomain, it is straightforward to perform the iterative coupling together with the iterations needed to solve the non-linear system. In particular a more efficient and a more stable performance of the new coupling procedure is achieved by a special formulation that allows to use different time steps in each subdomain. Copyright © 2005 John Wiley & Sons, Ltd. [source]

Comparative analysis of CFD models of dense gas,solid systems

AICHE JOURNAL, Issue 5 2001
B. G. M. van Wachem
Many gas,solid CFD models have been put forth by academic researchers, government laboratories, and commercial vendors. These models often differ in terms of both the form of the governing equations and the closure relations, resulting in much confusion in the literature. These various forms in the literature and in commercial codes are reviewed and the resulting hydrodynamics through CFD simulations of fluidized beds compared. Experimental data on fluidized beds of Hilligardt and Werther (1986), Kehoe and Davidson (1971), Darton et al.(1977), and Kuipers (1990) are used to quantitatively assess the various treatments. Predictions based on the commonly used governing equations of Ishii (1975) do not differ from those of Anderson and Jackson (1967) in terms of macroscopic flow behavior, but differ on a local scale. Flow predictions are not sensitive to the use of different solid stress models or radial distribution functions, as different approaches are very similar in dense flow regimes. The application of a different drag model, however, significantly impacts the flow of the solids phase. A simplified algebraic granular energy-balance equation is proposed for determining the granular temperature, instead of solving the full granular energy balance. This simplification does not lead to significantly different results, but it does reduce the computational effort of the simulations by about 20%. [source]

Experimental and computational study of the bed dynamics of semi-cylindrical gas,solid fluidized bed

THE CANADIAN JOURNAL OF CHEMICAL ENGINEERING, Issue 1 2009
A. Sahoo
Abstract With computational fluid dynamics (CFD) it is possible to get a detailed view of the flow behaviour of the fluidized beds. A profound and fundamental understanding of bed dynamics such as bed pressure drop, bed expansion ratio, bed fluctuation ratio, and minimum fluidization velocity of homogeneous binary mixtures has been made in a semi-cylindrical fluidized column for gas,solid systems, resulting in a predictive model for fluidized beds. In the present work attempt has been made to study the effect of different system parameters (viz., size and density of the bed materials and initial static bed height) on the bed dynamics. The correlations for the bed expansion and bed fluctuations have been developed on the basis of dimensional analysis using these system parameters. Computational study has also been carried out using a commercial CFD package Fluent (Fluent, Inc.). A multifluid Eulerian model incorporating the kinetic theory for solid particles was applied in order to simulate the gas,solid flow. CFD simulated bed pressure drop has been compared with the experimental bed pressure drops under different conditions for which the results show good agreements. La simulation par ordinateur de la dynamique des fluides (CFD) permet de décrire le comportement des écoulements dans les lits fluidisés. Une étude fondamentale et approfondie de la dynamique de lit, tels la perte de charge de lit, le taux d'expansion de lit, le taux de fluctuation de lit et la vitesse de fluidisation minimale de mélanges binaires homogènes, a été réalisée dans une colonne fluidisée semi-cylindrique pour des systèmes solides de gaz, permettant d'obtenir un modèle prédictif pour les lits fluidisés. Dans le présent travail, on a tenté d'étudier l'effet de différents paramètres de système (à savoir, la taille et la masse volumique des matériaux de lit et la hauteur statique initiale de lit) sur la dynamique de lit. Des corrélations ont été établies pour l'expansion de lit et les fluctuations de lit en s'appuyant sur l'analyse dimensionnelle de ces paramètres de système. Une étude par ordinateur a également été menée à l'aide du logiciel commercial de CFD Fluent (Fluent, Inc.). Un modèle eulérien multifluide faisant appel à la théorie cinétique pour les particules solides a été utilisé afin de simuler l'écoulement gaz-solides. La perte de charge de lit simulée par la CFD a été comparée à la perte de charge de lit expérimentale dans différentes conditions et les résultats montrent un bon accord. [source]