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Circulation Velocity (circulation + velocity)

Distribution by Scientific Domains
Chemistry100%

Kinds of Circulation Velocity

  • liquid circulation velocity
    		•

    Selected Abstracts

    Gas Hold-up and Liquid Circulation Velocity in Gas-Liquid-Solid Airlift Reactors

    THE CANADIAN JOURNAL OF CHEMICAL ENGINEERING, Issue 6 2004
    Milan K. Popovi
    Abstract Simple empirical correlations for gas hold-up and liquid circulation velocity in two- and three-phase airlift reactors are presented in this paper and their applicability has been demonstrated. The empirical correlations are good alternatives to the semi-theoretical drift-flux approach to predictions of gas hold-ups and liquid circulation velocities in airlift reactors. Des corrélations empiriques simples pour la rétention de gaz et la vitesse de circulation liquide dans des réacteurs à air ascendant diphasiques et triphasiques sont présentées dans cet article et leur applicabilité est démontrée. Les corrélations empiriques sont de bonnes alternatives aux méthodes de dérive de flux semi-théoriques pour les prédictions des rétentions de gaz et des vitesses de circulation du liquide dans les réacteurs à air ascendant. [source]

    Effect of a gas,liquid separator on the hydrodynamics and circulation flow regimes in internal-loop airlift reactors

    JOURNAL OF CHEMICAL TECHNOLOGY & BIOTECHNOLOGY, Issue 5 2001
    Jaroslav Klein
    Abstract The role of the gas,liquid separator on hydrodynamic characteristics in an internal-loop airlift reactor (ALR) was investigated. Both gas holdup and liquid velocity were measured in a 30,dm3 airlift reactor with two different head configurations: with and without an enlarged separator. A magnetic tracer method using a neutrally buoyant magnetic particle as flowfollower was used to measure the liquid velocity in all sections of the internal-loop airlift reactor. Average liquid circulation velocities in the main parts of the ALR were compared for both reactor configurations. At low air flow rates the separator had no influence on gas holdup, circulation velocity and intensity of turbulence in the downcomer and separator. At higher superficial air velocities, however, the separator design had a decisive effect on the hydrodynamic parameters in the downcomer and the separator. On the other hand, the gas holdup in the riser was only slightly influenced by the separator configuration in the whole range of air flow. Circulation flow regimes, characterising the behaviour of bubbles in the downcomer, were identified and the effect of the separator on these regimes was assessed. © 2001 Society of Chemical Industry [source]

    Gas Hold-up and Liquid Circulation Velocity in Gas-Liquid-Solid Airlift Reactors

    THE CANADIAN JOURNAL OF CHEMICAL ENGINEERING, Issue 6 2004
    Milan K. Popovi
    Abstract Simple empirical correlations for gas hold-up and liquid circulation velocity in two- and three-phase airlift reactors are presented in this paper and their applicability has been demonstrated. The empirical correlations are good alternatives to the semi-theoretical drift-flux approach to predictions of gas hold-ups and liquid circulation velocities in airlift reactors. Des corrélations empiriques simples pour la rétention de gaz et la vitesse de circulation liquide dans des réacteurs à air ascendant diphasiques et triphasiques sont présentées dans cet article et leur applicabilité est démontrée. Les corrélations empiriques sont de bonnes alternatives aux méthodes de dérive de flux semi-théoriques pour les prédictions des rétentions de gaz et des vitesses de circulation du liquide dans les réacteurs à air ascendant. [source]

    Effect of a gas,liquid separator on the hydrodynamics and circulation flow regimes in internal-loop airlift reactors

    JOURNAL OF CHEMICAL TECHNOLOGY & BIOTECHNOLOGY, Issue 5 2001
    Jaroslav Klein
    Abstract The role of the gas,liquid separator on hydrodynamic characteristics in an internal-loop airlift reactor (ALR) was investigated. Both gas holdup and liquid velocity were measured in a 30,dm3 airlift reactor with two different head configurations: with and without an enlarged separator. A magnetic tracer method using a neutrally buoyant magnetic particle as flowfollower was used to measure the liquid velocity in all sections of the internal-loop airlift reactor. Average liquid circulation velocities in the main parts of the ALR were compared for both reactor configurations. At low air flow rates the separator had no influence on gas holdup, circulation velocity and intensity of turbulence in the downcomer and separator. At higher superficial air velocities, however, the separator design had a decisive effect on the hydrodynamic parameters in the downcomer and the separator. On the other hand, the gas holdup in the riser was only slightly influenced by the separator configuration in the whole range of air flow. Circulation flow regimes, characterising the behaviour of bubbles in the downcomer, were identified and the effect of the separator on these regimes was assessed. © 2001 Society of Chemical Industry [source]

    Mechanisms of solids drawdown in stirred tanks

    THE CANADIAN JOURNAL OF CHEMICAL ENGINEERING, Issue 4 2008
    Oscar Khazam
    Abstract Agitated tanks are used in several industrial processes to achieve complete drawdown of floating solids in liquids. The design requirements for this process are not completely defined, and are currently limited to heuristics regarding the use of a surface vortex and the effect of wettability on the difficulty of mixing, along with several initial studies in the literature. In this study, the effect of the type of impeller, particle size and shape, solids concentration, impeller submergence, and baffle configuration on the minimum drawdown speed (Njd) are investigated. It was found that the formation of a large surface vortex acts to hold particles close to the surface. Suppression of the surface vortex is recommended. In baffled tanks where the formation of a large surface vortex is suppressed, the intensity of turbulence and mean circulation velocity of the liquid are responsible for solids drawdown and distribution in the tank. The submergence of the impeller relative to the liquid surface and the pumping mode of the pitched blade turbine (PBT) were found to be the controlling parameters. CFD simulations were carried out to obtain a better understanding and interpretation of the flow patterns and drawdown mechanisms for the different baffle configurations. Les réservoirs agités servent dans plusieurs procédés industriels pour réaliser l'immersion complète des solides flottant sur les liquides. Les besoins de conception pour ce procédé ne sont pas complètement définis et sont actuellement limités à une approche heuristique utilisant un vortex de surface et à l'effet de la mouillabilité sur la difficulté de mélange, en complément de plusieurs études initiales dans la littérature scientifique. Dans cette étude, l'effet du type de turbine, de la taille et de la forme des particules, de la concentration de solides, de la submersion de la turbine et de la configuration des chicanes sur la vitesse d'immersion (Njd) est étudié. On a trouvé que la formation d'un vortex de surface important a pour effet de garder les particules proches de la surface. La suppression du vortex de surface est recommandée. Dans les réservoirs munis de chicanes où la formation du vortex de surface important est supprimée, l'intensité de la turbulence et la vitesse de circulation moyenne du liquide sont responsables de l'immersion des solides et de leur distribution dans le réservoir. On a trouvé que la hauteur d'immersion de la turbine par rapport à la surface du liquide et le mode de pompage de la turbine à pales inclinées (PBT) étaient les paramètres gouvernants. Des simulations en CFD ont été menées pour une meilleure compréhension et interprétation des profils d'écoulement et des mécanismes d'immersion pour différentes configurations de chicanes. [source]

    Gas Hold-up and Liquid Circulation Velocity in Gas-Liquid-Solid Airlift Reactors

    THE CANADIAN JOURNAL OF CHEMICAL ENGINEERING, Issue 6 2004
    Milan K. Popovi
    Abstract Simple empirical correlations for gas hold-up and liquid circulation velocity in two- and three-phase airlift reactors are presented in this paper and their applicability has been demonstrated. The empirical correlations are good alternatives to the semi-theoretical drift-flux approach to predictions of gas hold-ups and liquid circulation velocities in airlift reactors. Des corrélations empiriques simples pour la rétention de gaz et la vitesse de circulation liquide dans des réacteurs à air ascendant diphasiques et triphasiques sont présentées dans cet article et leur applicabilité est démontrée. Les corrélations empiriques sont de bonnes alternatives aux méthodes de dérive de flux semi-théoriques pour les prédictions des rétentions de gaz et des vitesses de circulation du liquide dans les réacteurs à air ascendant. [source]