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Airlift Reactor (airlift + reactor)

Distribution by Scientific Domains

Chemistry	88%

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]

Comparison, Combination and Validation of Measuring Techniques for Local Flow and Turbulence Analysis in Bubble Columns and Airlift Reactors

THE CANADIAN JOURNAL OF CHEMICAL ENGINEERING, Issue 3-4 2003
Christophe Vial
Abstract The applicability of velocimetry techniques based on the Doppler effect , such as laser and ultrasound Doppler velocimetry , for investigating local hydrodynamics in bubble columns and airlift reactors have been extended to non-coalescing media. Their limitations are highlighted, especially as a function of gas sparger and reactor type. The ultrasound technique was shown to be able to measure either bubble or liquid velocity. Differences in local hydrodynamics due to coalescence behaviour were used to support the analysis. Data validation was carried out both by mass balance and by comparison with other techniques, such as electrochemical probes, Pavlov tubes and optical probes. L'applicabilité des techniques de vélocimétrie laser Doppler et de vélocimétrie ultrasonore pour décrire l'hydrodynamique locale dans les colonnes à bulles et les airlifts est étendue aux milieux non-coalescents. On étudie leurs limitations, notamment en fonction du type de distributeur et de réacteur. On montre que la technique ultrasonore permet à la fois la mesure de la vitesse locale des bulles et du liquide. Les différences dues à l'aptitude à la coalescence du milieu sont démontrées. Les résultats sont validés par des bilans et par la comparaison avec d'autres techniques (sonde électrochimique, tube de Pavlov et sonde optique). [source]

Modelling of the fluid dynamic processes in a high-recirculation airlift reactor

INTERNATIONAL JOURNAL OF ENERGY RESEARCH, Issue 6 2001
David A. Sanders
Abstract This paper describes the creation of two models of the steady-state fluid dynamic processes occurring in a high-recirculation airlift reactor. The new models were created to provide information to assist in the design of a reactor, in particular considering the selection of parameters to adjust in order to achieve a steady state solution. The modelling of two-phase flow of air and water in small-scale airlift bioreactors is considered. This modelling was applied to the high-recirculation airlift reactor process. New computer simulations were created and tests performed to evaluate the new models. The results of this evaluation are presented. The evaluation showed that variation of the superficial gas velocity or the simultaneous variation of the downcomer and riser diameters could be used to produce a steady-state design solution. Copyright © 2001 John Wiley & Sons, Ltd. [source]

Measurement of mass transfer coefficient in an airlift reactor with internal loop using coalescent and non-coalescent liquid media

JOURNAL OF CHEMICAL TECHNOLOGY & BIOTECHNOLOGY, Issue 12 2004
M Bla
Abstract In this work the sulfite oxidation (SOM), dynamic pressure-step (DPM) and gassing-out (GOM) methods were compared for volumetric mass transfer coefficient measurement in an airlift reactor with internal loop. As a liquid phase both, non-coalescent and coalescent media were used. Among the methods discussed here, the mass transfer coefficient (kLa) values obtained by the DPM appear as the most reliable as they were found to be independent of oxygen concentration in the inlet gas, which confirmed the physical correctness of this method. The difference between data measured using air and oxygen was not higher than 10%, which was comparable to the scatter of experimental data. It has been found that the sulfite oxidation method yielded kLa values only a little higher than those obtained by the DPM and the difference did not exceed 10%. Up to an inlet gas velocity (UGC) of ,0.03 m s,1 the GOM using oxygen as a gas medium gave kLa values in fact identical with those obtained by the DPM. At higher flows of the inlet gas, the GOM yielded kLa values as much as 15% lower. The enhancement in oxygen mass transfer rate determined in non-coalescent media was estimated to be up to +15%, when compared with a coalescent batch. The experimental dependence of kLa vs the overall gas hold-up was described by an empirical correlation.1 Copyright © 2004 Society of Chemical Industry [source]

Hydrodynamic considerations on optimal design of a three-phase airlift bioreactor with high solids loading

JOURNAL OF CHEMICAL TECHNOLOGY & BIOTECHNOLOGY, Issue 9 2003
Jaroslav Klein
Abstract The hydrodynamic study of a three-phase airlift (TPAL) bioreactor with an enlarged gas,liquid dual separator was carried out. Different lengths and diameters of the draft tube were tested to show how the design of the separator zone affects the hydrodynamic performance of the TPAL reactor. Ca-alginate beads with entrapped yeast biomass at different loadings (0, 7, 14 and 21% v/v) were used in order to mimic the solid phase of conventional high cell density systems, such as those with cells immobilized on carriers or flocculating cells. Important information on multiphase flow and distribution of gas and solid phases in the internal-loop airlift reactor (ALR) with high solids loading was obtained, which can be used for suggesting optimal hydrodynamic conditions in a TPAL bioreactor with high solids loading. It is finally suggested that the ALR with a dual separator and a downcomer to riser cross-sectional area ratio (AD/AR) ranging from 1.2 to 2.0 can be successfully applied to batch/continuous high cell density systems, where the uniform distribution of solid phase, its efficient separation of particles from the liquid phase, and an improved residence time of air bubbles inside the reactor are desirable. Copyright © 2003 Society of Chemical Industry [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]

CFD study of mixing characteristics of bubble column and external loop airlift reactor

ASIA-PACIFIC JOURNAL OF CHEMICAL ENGINEERING, Issue 2 2008
S. Roy
Abstract In the present work, a computational fluid dynamics study has been carried out to bring out the mixing characteristics of bubble column and external loop airlift reactor. A comparison of mixing time for two reactors has been presented on the basis of the same reactor volume as well as the total power input. The CFD model was validated by simulating flow, both in bubble column and external loop airlift reactor. An agreement was observed between the predicted and the experimental data available in the published literature. The validated CFD model has been extended for the simulation of the mixing time for both the reactors. The CFD predictions of mixing time show good agreement with the experimental values published in literature. A systematic numerical study was then carried out to bring out the mixing characteristics of both the reactors. Copyright © 2008 Curtin University of Technology and John Wiley & Sons, Ltd. [source]

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

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

Comparison, Combination and Validation of Measuring Techniques for Local Flow and Turbulence Analysis in Bubble Columns and Airlift Reactors

Effect of seeding sludge type and hydrodynamic shear force on the aerobic sludge granulation in sequencing batch airlift reactors

ASIA-PACIFIC JOURNAL OF CHEMICAL ENGINEERING, Issue 5 2009
K. Y. Koh
Abstract Two sequencing batch airlift reactors (SBARs) were operated simultaneously for two separate runs. In the first run, two different types of seeding sludge were cultivated in two separate reactors under the same superficial air velocity (SAV). In the second run, the same seeding sludge was cultivated in both reactors but under different SAV, i.e. 1.2 and 3.6 cm s,1. Both runs were carried out for a period of about 20 days, during which the chemical oxygen demand (COD) removal efficiency and morphology of sludge were examined. Batch tests using sodium acetate as the main carbon source were conducted to investigate the COD removal efficiency, and the morphologies of sludge were examined under light microscopy. Results showed that the COD removal efficiency improved with cultivation time. Morphological study showed that all cultivated sludge lost their filamentous species after a few days of cultivation, leaving behind communities of loosely packed pellet-like groups. Although the SAV recommended by other researchers was applied to the SBAR, granulation did not take place at the end of both experimental runs. It was suspected that the failure for aerobic sludge to granulate under the selected operating strategies and reactor configuration was partly due to the intrinsic traits of the sludge microbial community. Copyright © 2009 Curtin University of Technology and John Wiley & Sons, Ltd. [source]