Effect of internal on the hydrodynamics in external-loop airlift reactors

Zhang, Tongwang; Wang, Jinfu; Wang, Tiefeng; Lin, Jing; Ye, Jin

doi:10.1016/j.cep.2004.05.003

Cited by 38 publications

(21 citation statements)

References 28 publications

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“…The gas holdup increases due to the decrease in the size of the gas bubbles passing through the two packed‐bed sections of the reactor , . Zhang et al used an internal gas distributor in the riser of an external loop airlift bioreactor. They observed that when the air bubbles and the liquid passed through the internal gas distributor, the size of the air bubbles was reduced.…”

Section: Resultsmentioning

confidence: 99%

“…Airlift bioreactors are an important class of bioreactors that are widely employed in many engineering applications associated with aerobic and anaerobic fermentations, in addition to wastewater treatment and petrochemical industries . This class of bioreactors is divided into two main subclasses of internal and external loop airlift bioreactors.…”

Section: Introductionmentioning

confidence: 99%

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Dynamic and local gas holdup studies in external loop recirculating airlift reactor with two rolls of fiberglass packing using electrical resistance tomography

Hamood-Ur-Rehman

Ein‐Mozaffari

Dahman

2012

J of Chemical Tech & Biotech

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BACKGROUND: Airlift bioreactors have been used extensively in biotechnology industries in recent years in a variety of arrangements and applications. The insertion of packing inside the bioreactors has the potential to provide high productivity within a compact size through utilizing immobilized species. RESULTS: A novel recirculating external loop airlift bioreactor that has two rolls of fiberglass packing and a gas distributor in between was designed and built. Electrical resistance tomography (ERT) images showed that the gas holdup increased after installing the packing and the gas distributor. Gas holdup in the riser increased with decreasing static liquid height in the bioreactor. This decreased the liquid superficial velocity, which contributed to a higher gas holdup in the bioreactor. Results also showed that riser gas holdup varied slightly with different sparger configurations. Higher gas holdup increases the oxygen mass transfer rate by increasing the residence time and interfacial mass transfer area. CONCLUSION: ERT results showed that fiberglass packing with an installed gas distributor in bioreactors can achieve higher gas holdup at higher superficial gas velocity. This can contribute to improved conversion in bioreactors with packing through utilizing higher biomass concentrations and higher oxygen concentration. © 2012 Society of Chemical Industry

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Section: Resultsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Dynamic and local gas holdup studies in external loop recirculating airlift reactor with two rolls of fiberglass packing using electrical resistance tomography

Hamood-Ur-Rehman

Ein‐Mozaffari

Dahman

2012

J of Chemical Tech & Biotech

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“…[6][7][8][9][10][11][12], bubble columns [e.g. [13][14][15][16][17][18] and air-lift reactors [3,[19][20][21][22][23][24]. The problem of suitably accounting for bubble-turbulence interactions, including coalescence/breakage dynamics is particularly stringent.…”

Section: Introductionmentioning

confidence: 99%

Modelling and Simulation of Gas–liquid Hydrodynamics in a Rectangular Air-lift Reactor

Scargiali

Busciglio

Cipollina

et al. 2013

International Journal of Chemical Reactor Engineering

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Computational Fluid Dynamics is a quite well established tool for carrying out realistic simulations of process apparatuses. However, as a difference from single phase systems, for multiphase systems the development of CFD models is still in progress. Among the two-phase systems, gas-liquid systems are characterised by an additional complexity level, related to the fact that bubble sizes are not known in advance, being rather the result of formation and breakage-coalescence dynamics and therefore of complex phenomena related to flow dynamics and interfacial effects. In the present work, Euler-Euler Reynolds-averaged flow simulations of an air-lift reactor are reported. All bubbles are assumed to share the same size, and a simplified approach is adopted for modelling inter-phase momentum exchange, that involves bubble terminal velocity as the sole parameter needed. Good agreement between simulation results and literature experimental data is found for all the gas flow rates simulated. This result implies that, despite the many simplifications that have to be adopted in order to make them viable, fully predictive CFD simulations of gas-liquid systems can give rise to reasonably accurate predictions of reactor fluid dynamics.

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“…A few reports have described the usage of internal additions, such as baffles, plates and screens, to enhance this efficiency and to enable further control of the flow states in the reactor . In one example, a traditional AR was modified by three funnel internals in variable dimensions, and the hydrodynamic properties of the reactor were studied using computational fluid dynamics .…”

Section: Introductionmentioning

confidence: 99%

Oxygen mass transfer characteristics in an internal‐loop airlift reactor with preset trumpet‐shaped riser

Huang

et al. 2014

Asia-Pacific J Chem Eng

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A size-adjustable trumpet-shaped riser was installed into a conventional airlift reactor to form a modified internal-loop airlift reactor (ILAR). The volumetric oxygen mass transfer coefficient (k L a) and gas holdup of the ILAR were heavily influenced by the height ratio of riser to static fluid level above the spargers (h/H), the cross-sectional area ratio of riser to downcomer (A r /A d ) and the superficial gas velocity in the riser (U g ) when deoxidized distilled water was used as the oxygen absorbent. An oxygen transfer rate of (2.17 ± 0.11) × 10 À5 kg m À3 s À1 , k L a of (27.88 ± 1.12) × 10 À3 s À1 and gas holdup of 0.031 were obtained with the ILAR of A r /A d = 1.09 and h/H = 0.73 at U g = 18 mm s À1 . As the well-constructed preset trumpet-shaped riser provided ideal conditions for complete circulation and blending of the fluid, enhanced oxygen transfer efficiency was achieved. The gas holdup and k L a were increased by 16.2% and 10.2% at 19°C, as compared with those of the conventional airlift reactor without this preset riser. The fluid rising velocity in the riser (V R ) and falling velocity in the downcomer (V D ) may be expressed by power-law functions of U g and A r /A d , respectively. These metrics indicate that the ILAR has better performance, as compared with a conventional airlift reaction, for oxygen transfer and microorganism culture for chemical engineering, biological fermentation and environmental protection.

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Effect of internal on the hydrodynamics in external-loop airlift reactors

Cited by 38 publications

References 28 publications

Dynamic and local gas holdup studies in external loop recirculating airlift reactor with two rolls of fiberglass packing using electrical resistance tomography

Dynamic and local gas holdup studies in external loop recirculating airlift reactor with two rolls of fiberglass packing using electrical resistance tomography

Modelling and Simulation of Gas–liquid Hydrodynamics in a Rectangular Air-lift Reactor

Oxygen mass transfer characteristics in an internal‐loop airlift reactor with preset trumpet‐shaped riser

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