Hydrodynamics and oxygen mass transfer in a packed bed split-cylinder airlift reactor containing dilute alcoholic solutions

Moraveji, Mostafa Keshavarz; Fakhari, Mona Ebrahimi; Mohsenzadeh, Elmira; Davarnejad, Reza

doi:10.1007/s00231-012-1056-0

Cited by 13 publications

(2 citation statements)

References 26 publications

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“…This would likely suggest that the hydraulic behavior does not influence the aeration performance in a simple way. Second, the K La behavior seems to be quite linear, which we found to be a common occurrence in the literature [16,18,22,25,26].…”

Section: Discussionsupporting

confidence: 58%

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Preliminary Study on Mini-Modus Device Designed to Oxygenate Bottom Anoxic Waters without Perturbing Polluted Sediments

Perin

Romagnoli

Perin³

et al. 2020

Environments

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The Tangential Guanabara Bay Aeration and Recovery (TAGUBAR) project derives its origins from a Brazilian government decision to tackle the planning and management challenges related to the restoration of some degraded aquatic ecosystems such as Guanabara Bay (state of Rio de Janeiro), Vitória Bay, and Espírito Santo Bay (state of Espírito Santo). This was performed by using the successful outcomes of a previous Ministry of Foreign Affairs and Directorate General for Cooperation and Development (i.e., Direttore Generale alla Cooperazione allo Sviluppo, MFA–DGCS) cooperation program. The general objective of the program was to contribute to the economic and social development of the population living around Guanabara, Vitória, and Espírito Santo Bays, while promoting the conservation of their natural resources. This objective was supposed to be achieved by investing money to consolidate the local authorities’ ability to plan and implement a reconditioning program within a systemic management framework in severely polluted ecosystems such as Guanabara Bay, where sediments are highly contaminated. Sediments normally represent the final fate for most contaminants. Therefore, it would be highly undesirable to perturb them, if one wishes to avoid contaminant recycling. In this context, we explored a bench-scale novel technology, called the module for the decontamination of units of sediment (MODUS), which produces an oxygenated water flow directed parallel to the sediment floor that is aimed to create “tangential aeration” of the bottom water column. The purpose of this is to avoid perturbing the top sediment layer, as a flow directed toward the bottom sediment would most probably resuspend this layer. Three kinds of tests were performed to characterize a bench-scale version of MODUS (referred to as “mini-MODUS”) behavior: turbulence–sediment resuspension tests, hydrodynamic tests, and oxygenation–aeration tests. In order to understand the functioning of the mini-MODUS, we needed to eliminate as many variables as possible. Therefore, we chose a static version of the module (i.e., no speed for the mini-MODUS as well as no water current with respect to the bottom sediment and no flume setting), leaving dynamic studies for a future paper. The turbulence tests showed that the water enters and exits the mini-MODUS mouths without resuspending the sediment surface at all, even if the sediment is very soft. Water flow was only localized very close to both mouth openings. Hydrodynamic tests showed an interesting behavior. An increase of low air flows produced a sharp linear increase of the water flow. However, a plateau was quickly reached and then no further increase of water flow was observed, implying that for a certain specific geometry of the equipment and for the given experimental conditions, an increase in the air flow does not produce any reduction of the residence time within the aeration reactor. Oxygenation–aeration tests explored three parameters that were deemed to be most important for our study: the oxygen global transfer coefficient, KLa; the oxygenation capacity, OC; and the oxygenation efficiency, OE%. An air flow increase causes an increase of both KLa and OC, while OE% decreases (no plateau was observed for KLa and OC). The better air flow would be a compromise between high KLa and OC, with no disadvantageous OE%, a compromise that will be the topic of the next paper.

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Section: Discussionsupporting

confidence: 58%

“…All these represent fundamental aspects Some observations can be made. First of all, it is interesting to note that in the diagrams in Figures 7 and 8, no plateau was observed [3,18,24,25]. This would likely suggest that the hydraulic behavior does not influence the aeration performance in a simple way.…”

Section: Discussionmentioning

confidence: 90%

Preliminary Study on Mini-Modus Device Designed to Oxygenate Bottom Anoxic Waters without Perturbing Polluted Sediments

Perin

Romagnoli

Perin³

et al. 2020

Environments

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Packing size effects on the liquid circulation property in an external‐loop packed bubble column

2022

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Packing size effects on the fluid dynamics in an external-loop packed bubble column with Raschig rings of three different effective diameters (4.9, 14.1, and 40.7 mm) in the riser were investigated. The overall gas holdup, liquid circulating velocity and gas-liquid mass transfer coefficient were respectively measured by volume expansion, tracer-response, and dynamic oxygen-absorption techniques. CFD simulation with the Euler-Euler two-fluid method was used to predict the liquid circulating velocity by treating the packing as a porous medium. Compared to the empty column, the gas holdup was found to increase in the presence of packing, however, the liquid circulating velocity and gas-liquid mass transfer coefficient are rather complicated.Specifically, the gas holdup increases with the decrease of packing size, while the liquid circulating velocity is on the contrary, and the maximal gas-liquid mass transfer coefficient is achieved under packing diameter of 14.1 mm.

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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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Hydrodynamics and oxygen mass transfer in a packed bed split-cylinder airlift reactor containing dilute alcoholic solutions

Cited by 13 publications

References 26 publications

Preliminary Study on Mini-Modus Device Designed to Oxygenate Bottom Anoxic Waters without Perturbing Polluted Sediments

Preliminary Study on Mini-Modus Device Designed to Oxygenate Bottom Anoxic Waters without Perturbing Polluted Sediments

Packing size effects on the liquid circulation property in an external‐loop packed bubble column

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

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