An Experimental Study of the Hydrodynamic Characteristics of External Loop Airlift Contactors

Bentifraouine, Chafaa; Xuereb, Catherine; Riba, J. P.

doi:10.1002/(sici)1097-4660(199707)69:3<345::aid-jctb719>3.0.co;2-a

Cited by 33 publications

(5 citation statements)

References 15 publications

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“…At low values of gas velocity the gas holdup increases relatively sharply with the increase in gas velocity. Similar behavior of gas holdup with superficial gas velocity has been reported by Vial et al (2002), Choi and Lee (1993), Guo et al (1997), Bentifraouine et al (1997a). In the region of lower gas velocities, an increase in gas velocity results in the formation of a large number of bubbles without appreciably increasing the bubble diameters.…”

Section: Effect Of Superficial Gas Velocity On Gas Holdupsupporting

confidence: 82%

“…The increase in holdup is possibly due to the finer dispersion of the gas achieved at higher liquid circulation velocity, which in turn increases with the increase in superficial gas velocity. Several researchers have reported that liquid circulation velocity greatly affects the gas holdup (Snape et al, 1995;Bentifraouine et al, 1997a). Fig.…”

Section: Effect Of Liquid Circulation Velocity On Gas Holdupmentioning

confidence: 99%

“…This is due to the fact that, for a given superficial gas velocity value, a large number of variables like gas or liquid physical properties, downcomer and riser cross section ratio, top and bottom riser and downcomer connecting sections geometry, phase separation conditions, liquid volume, reactor height or gas distributing plate etc. affect performance (Bentifraouine et al, 1997a).…”

Section: Introductionmentioning

confidence: 99%

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Hydrodynamics of a novel multi-stage external loop airlift reactor

Mohanty

Das

Biswas

2006

Chemical Engineering Science

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Section: Effect Of Superficial Gas Velocity On Gas Holdupsupporting

confidence: 82%

Section: Effect Of Liquid Circulation Velocity On Gas Holdupmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

See 1 more Smart Citation

Hydrodynamics of a novel multi-stage external loop airlift reactor

Mohanty

Das

Biswas

2006

Chemical Engineering Science

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“…These parameters also dramatically affect gas-liquid mass transfer (e.g. Bentifraouine et al, 1997). For design, operation and control purposes, it is therefore necessary to understand the interplay between gas holdup, overall liquid circulation velocity, liquid mixing and gas-liquid mass transfer.…”

Section: Introductionmentioning

confidence: 99%

Study of Hydrodynamics, Mixing and Gas-Liquid Mass Transfer in a Split-Rectangular Airlift Reactor

Gourich¹,

Azher²,

Vial

et al. 2008

Can. J. Chem. Eng.

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Until recently, most investigations were focused on the effects of the downcomer-to-riser cross-section area (Snape et al., 1995), the clear liquid height and the gas-liquid separator confi guration (Siegel et al., 1986;Siegel and Merchuk, 1988;Choi and Lee, 1993), or the gas distributor type and location (Merchuk, 1986) on local and global hydrodynamic parameters. The infl uence of the physicochemical properties of the liquid phase was also taken into account, for example by Kernnard and Janekeh (1991), Li et al. (1995), Lu and Hang (1995), Molina et al. (1999) and Lin et al. (2004). Similarly, many experimental Global hydrodynamic characteristics, liquid mixing and gas-liquid mass transfer for a 63 L split-rectangular airlift reactor were studied. Correlations for gas holdup and overall liquid circulation velocity were derived for the air-water system as a function of the specifi c power input; these were compared to data and correlations for reactor volumes between 4.7 L and 4600 L. A partial recirculation of small bubbles in the riser was observed when U gr > 0.03 m/s, which was attributed to the use of a single-orifi ce nozzle as the gas phase distributor. The dimensionless mixing time and the overall axial dispersion coeffi cient were nearly constant for the range of gas fl ow rates studied. However, values of K L /d B were greater than those reported in previous studies and this is caused by the partial recirculation of the gas phase in the riser. While scale effects remain slight, the use of a gas distributor favouring this partial recirculation seems adequate for mass transfer in split-rectangular airlift reactors.On a étudié les caractéristiques hydrodynamiques globales, le mélange de liquide et le transfert de matière gaz-liquide pour un réacteur à air ascendant rectangulaire divisé. Des corrélations pour la rétention de gaz et la vitesse de circulation de liquide globale ont été calculées pour le système air-eau en fonction de la puissance spécifi que; ces corrélations ont été comparées aux données ainsi qu'à des corrélations pour des volumes de réacteur compris entre 4,7 L et 4600 L. Une recirculation partielle des petites bulles dans la colonne montante a été observée quand U gr > 0,03 m/s, qui est attribuée à l'utilisation d'un seul orifi ce pour la distribution de la phase gazeuse. Le temps de mélange adimensionnel et le coeffi cient de dispersion axiale globale sont presque constants dans la gamme de débits de gaz étudiés. Toutefois, les valeurs de K L /d B sont plus grandes que celles des études antérieures, en raison de la recirculation partielle de la phase gazeuse dans la colonne montante. Tandis que les effets d'échelle demeurent légers, l'utilisation d'un distributeur de gaz favorisant cette recirculation partielle semble adéquate pour le transfert de matière dans les réacteurs à air ascendant rectangulaire divisés.

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“…Many empirical correlations have been proposed, but due to the strong influence of reactor geometry on hydrodynamics, their application is often limited to the reactor studied. In fact, downcomer to riser cross section area ratio (Chisti, 1989), reactor height (Russell et al, 1993;Bentifraouine et al, 1997), gas-liquid separator configuration (Siege1 and Merchuk, 1991), size of passage area in the bottom section (Merchuk et al, 1994) and sparger type and location (Becker et al, 1994), all affect flow characteristics considerably.…”

mentioning

confidence: 99%

Local measurements for the study of external loop airlift hydrodynamics

et al. 1999

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Hot-film anemometq and an optical biprobe are used to measure local flow characteristics in the riser of an external loop airlift reactor. Important flow asymmetries are observed above the sparger and developing flow persists through a large part of the riser. As gas flow rate increases, radial gas hold-up profiles change from relatively flat to parabolic while the shape of radial liquid velocity profiles remains constant and Sauter bubble diameter increases. At large gas superficial velocities, slip velocity is found to deviate considerably from the frequently used value of 0.25 d s . Local measurements allow a better understanding of two-phase flow in airlift reactors and can be used for CFD-modeling development and validation.L'anemometrie a film chaud et une bisonde optique ont servi a caracteriser I'hydrodynamique locale de la zone ascendante d'un airlift a boucle externe. Des asymetries importantes de I'ecoulement sont observees au-dessus du distributeur et l'ecoulement se developpe dans une grande partie du riser. Avec I'augmentation du debit de gaz, les profils radiaux de taux de vide passent de relativement plats a paraboliques tandis que la forme des profils de vitesse du liquide demeure constante et que le diametre de Sauter des bulles augmente. Aux grands debits de gaz, la vitesse de glissement est considerablement differente de 0.25 m/s, valeur classiquement utilisee. Les mesures locales permettent une meilleure comprehension de I'ecoulement diphasique en reacteur airlift et peuvent itre utilisees pour le developpement et la validation de modeles de mecanique des fluides numeriques.

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An Experimental Study of the Hydrodynamic Characteristics of External Loop Airlift Contactors

Cited by 33 publications

References 15 publications

Hydrodynamics of a novel multi-stage external loop airlift reactor

Hydrodynamics of a novel multi-stage external loop airlift reactor

Study of Hydrodynamics, Mixing and Gas-Liquid Mass Transfer in a Split-Rectangular Airlift Reactor

Local measurements for the study of external loop airlift hydrodynamics

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