Influence of the Sparger Type and Added Alcohol on the Gas Holdup of an External‐Loop Airlift Reactor

Kojić, Predrag; Tokic, Milenko; Šijački, Ivana M.; Lukić, Nataša; Petrović, Dragan Lj.; Jovičević, Dragica Z.; Popović, Sanja

doi:10.1002/ceat.201400578

Cited by 17 publications

(9 citation statements)

References 44 publications

(41 reference statements)

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“…The transition between regimes was identified by the change of the slope of the gas holdup vs. the gas velocity curves. A more detailed analysis of hydrodynamic regimes and transition superficial gas velocities was described in our earlier study (Kojić et al, 2015). The transition points in the ELAMR appeared at a slightly lower U G compared to the ELAR.…”

Section: Hydrodynamic Regimesmentioning

confidence: 83%

Hydrodynamics of an external-loop airlift reactor with inserted membrane

Kojić

Popović

Tokic

et al. 2017

Braz. J. Chem. Eng.

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-The objective of this study was to investigate the hydrodynamics of an external-loop airlift membrane reactor (ELAMR). The ELAMR was operated in two modes: without (mode A) and with bubbles in the downcomer (mode B), depending on the liquid level in the gas separator. The influence of the gas distributor's geometry and various alcohol solutions on the hydrodynamics of the ELAMR was studied. Results for the gas holdup and the downcomer liquid velocity are commented with respect to an external-loop airlift reactor of the same geometry but without the membrane in the downcomer (ELAR). Due to the presence of the membrane in the downcomer, acting as the local hydrodynamic resistance, the gas holdup in the riser of the ELAMR increases maximally by 16%, while the liquid velocity in the downcomer decreases up to 50%. The values of the gas holdup and liquid velocity predicted by the application of empirical power law correlations and a feed forward back propagation neural network (ANN) are in very good agreement with experimental values.

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Section: Hydrodynamic Regimesmentioning

confidence: 83%

Hydrodynamics of an external-loop airlift reactor with inserted membrane

Kojić

Popović

Tokic

et al. 2017

Braz. J. Chem. Eng.

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“…Also, it was visually observed that with the raise in methanol concentration the bubbles broke up into many smaller bubbles. The similar trend for the increase in gas holdup with a decrease in surface tension was observed in previous studies , . The results are also in accordance with the study of Besagni et al.…”

Section: Resultsmentioning

confidence: 99%

“…Earlier, researchers , investigated the effect of surfactant concentration on gas‐phase holdup in airlift reactors by considering different concentrations of aliphatic alcohols. They observed that with an increase in the concentrations of various alcohol solutions/number of carbon atoms and superficial gas velocity, the gas‐phase holdup became higher.…”

Section: Introductionmentioning

confidence: 99%

Effect of Surface Tension on Hydrodynamics and Mass Transfer Coefficient in Airlift Reactors

2020

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The hydrodynamics and volumetric mass transfer coefficient play important roles in the design and scale-up of airlift reactors. The effect of surface tension on hydrodynamics and volumetric mass transfer coefficient in internal loop airlift reactors was investigated. With reduction of the surface tension of the fluid, the hydrodynamic parameters raised, namely, gas phase holdup, flow regime transition point, and interfacial area, whereas the bubble diameter as well as the liquid velocity decreased and the volumetric mass transfer coefficient increased. Empirical correlations are proposed for gas-phase holdup and volumetric mass transfer coefficient in terms of dimensionless numbers and can be applied in the design of airlift reactors.

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“…This can be explained by changes in the surface tension gradient that causes the different coalescence suppression strength of specific alcohol. Therefore, alcohols with lower C-atoms show lower surface tension gradients and produce lower gas holdup values [44]. In the same manner, surface tension decrease with the augment of alcohol concentration, while surface tension gradient rises and consequently leads to increase in the gas holdup of the ELAR.…”

Section: Figurementioning

confidence: 86%

“…The results showed that the increase of the surface tension gradient, as a consequence of alcohol addition, has a strong impact on hydrodynamics and mass transfer characteristics of airlift reactor. The increase of surface tension gradient corresponds to the increase of the number of carbon atoms in alcohol molecule [42][43][44]. Alcohol addition has a remarkable effect on the gas holdup.…”

Section: Figurementioning

confidence: 99%

Numerical study of the hydrodynamics and mass transfer in the external loop airlift reactor

Kojić

Krulj

et al. 2022

CI&CEQ

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The objective of this study was to investigate the hydrodynamics and the gas-liquid mass transfer coefficient of an external-loop airlift reactor (ELAR). The ELAR was operated in three cases: different inlet velocities of fluids, different alcohols solutions (water, 0.5% methanol, 0.5% ethanol, 0.5% propanol and 0.5% butanol) and different concentration of methanol in solutions (0%, 0.5%, 1%, 2% and 5%). The influence of superficial gas velocity and various diluted alcohol solutions on hydrodynamics and gas-liquid mass transfer coefficient of the ELAR was studied. Experimentally, the gas hold-up, liquid velocities and volumetric mass transfer coefficient values in the riser and the downcomer were obtained from the literature source. A computational fluid dynamics (CFD) model was developed, based on two-phase flow, investigating different liquids regarding surface tension, assuming the ideal gas flow, applying the finite volume method and Eulerian-Eulerian model. The volumetric mass transfer coefficient was determined using CFD model, as well as artificial neural network model. The effects of liquid parameters and gas velocity on the characteristics of the gas-liquid mass transfer were simulated. These models were compared with appropriate experimental results. CFD model successfully succeed to simulate the influence of different alcohols regarding the number of C-atoms on hydrodynamics and mass transfer.

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Influence of the Sparger Type and Added Alcohol on the Gas Holdup of an External‐Loop Airlift Reactor

Cited by 17 publications

References 44 publications

Hydrodynamics of an external-loop airlift reactor with inserted membrane

Hydrodynamics of an external-loop airlift reactor with inserted membrane

Effect of Surface Tension on Hydrodynamics and Mass Transfer Coefficient in Airlift Reactors

Numerical study of the hydrodynamics and mass transfer in the external loop airlift reactor

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