Pressure effects on the hydrodynamic behavior of gas-liquid-solid fluidized beds

Jiang, Peng; Arters, David C.; Fan, Liang Shih

doi:10.1021/ie00010a010

Cited by 30 publications

(13 citation statements)

References 15 publications

Supporting

Mentioning

Contrasting

Unclassified

Order By: Relevance

“…increasing pressure or temperature delays the regime transition. Similar pressure effects on the transition velocity were also reported by and Jiang et al (1992). However, Ug,,,m becomes insensitive to the increase in pressure as the pressure exceeds a critical value.…”

Section: Regime Transition Velocitysupporting

confidence: 83%

On the measurements of regime transition in high‐pressure bubble columns

1999

View full text Add to dashboard Cite

Two approaches are adopted in this study to identify the flow transition in a bubble column from the homogeneous regime to the heterogeneous regime at pressures up to 15.2 MPa and temperatures up to 78°C. These approaches, which yield essentially identical results, include those based on the standard deviation of the pressure fluctuation and the drift flux model. The experimental results obtained indicate that the regime transition velocity is delayed when the system pressure and temperature increase. The correlation proposed for the transition velocity by Wilkinson et al. (1992) predicts the present results to a reasonable extent, provided that the experimentally measured values for the physical properties of the fluids are used in the correlation. It is clear, however, that an improved correlation or model is needed for a quantitative account of the transition velocity for high-pressure bubble column systems with different gas distributing capability.On a adopte deux approches dans cette etude afin d'etudier la transition de I'ecoulernent dans une colonne a bulles du regime homogene au regime heterogene a des pressions allant jusqu'a 15,2 MPa et des temperatures allantjusqu'a 78OC. Ces approches, qui donnent essentiellement les m&mes resultats, incluent la methode basee sur l'ecart type de la fluctuation de pression et le modele de flux de decalage. Les resultats experimentaux obtenus indiquent que la vitesse de transition du regime est retardee lorsque la pression et la tempkrature du systeme augmentent. La correlation proposee pour la vitesse de transition par Wilkinson et a].(1 992) predit assez correctement les presents resultats, dans la mesure oh on utilise dans la correlation les valeurs'mesurees experimentalement pour les proprietes physiques. I1 est cependant clair qu'une correlation ou un modele ameliore est necessaire pour une prise en compte quantitative de la vitesse de transition pour des systemes a colonne a bulles a haute pression avec une capacite de distribution de gaz differente.

show abstract

Section: Regime Transition Velocitysupporting

confidence: 83%

On the measurements of regime transition in high‐pressure bubble columns

1999

View full text Add to dashboard Cite

show abstract

“…Instead, the flow within the column exhibited turbulent swirl patternsupwards, downwards and sideways -that appeared and disappeared quickly (as observed also by Jiang et al, 1992). As a result, bubbles did not continuously rise vertically but traveled in all directions with a small number (less than 1%) even descending for brief periods.…”

Section: Resultsmentioning

confidence: 68%

Bubble characteristics of a scaled‐down three‐phase fluidized bed

2002

View full text Add to dashboard Cite

Experiments were carried out in a 0.29 m diameter column to provide information on bubble characteristics relevant to an industrial three‐phase fluidized bed reactor. Using a specially built electrical conductivity probe, together with a series of computer programs to gather and filter the data, local bubble properties (rise velocities, pierced chord lengths, frequencies, and direction of travel) were measured. The data are compared to existing correlations. Since the operating conditions were within the dispersed bubble regime, uniform bubbling was anticipated. However, the actual system indicated considerable non‐uniformity, with individual bubbles, large swarms of bubbles and particles traveling at all angles. As a result, it is shown that bubble rise velocities are not necessarily a good measure of the bubble properties and must be vectorized to provide a good means of estimating gas hold‐up.

show abstract

“…The near-zero velocities are default measurements recorded by the instrument when the pulse is completely blocked or scattered away from the receiver. Very high acoustic velocities measurements were obtained close to the distributor and are attributed to higher concentration of small bubbles in this region (Jiang et al, 1992). The change in velocity due to small bubbles can be calculated using the theoretical formulation proposed by Gaunaurd and Uberall (1981).…”

Section: Data Preprocessing and Filteringmentioning

confidence: 89%