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Fluids
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Mass Transfer in Multiphase Reactors
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Mass Transfer in Multiphase Reactors

A special issue of Fluids (ISSN 2311-5521). This special issue belongs to the section "Flow of Multi-Phase Fluids and Granular Materials".

Deadline for manuscript submissions: 31 May 2025 | Viewed by 7766

Special Issue Editor

Prof. Dr. Stoyan Nedeltchev

E-Mail Website
Guest Editor
Institute of Chemical Engineering, Polish Academy of Sciences, 44-100 Gliwice, Poland
Interests: mass transfer; hydrodynamics; mixing; turbulence; nonlinear chaos theory; information entropy theory
Special Issues, Collections and Topics in MDPI journals

Special Issue Information

Dear Colleagues,

Mass transfer is the most important process in multiphase reactors. In many applications in the chemical industry, the mass transfer time determines the operational time of the multiphase reactors. The successful prediction of the volumetric liquid-phase mass transfer coefficients under various operating conditions is a challenging task. The effects of various parameters (including pressure and temperature) should be taken into account. The applicability of the classical mass transfer theories to newly proposed chemical reactors needs to be validated. A possible correction should be considered. The effects of turbulence and catalyst particles on the enhancement of mass transfer should be better characterized. Last but not least, the presence of a chemical reaction (especially a complex one) changes the mass transfer conditions and the bubble shape and behavior (in the case of bubbling) in the multiphase reactors and the process should be well modeled. Especially interesting are multiphase reactors operated with foaming systems (for instance aqueous alcohol solutions), electrolytes (salts), and surface active substances. Manuscripts dealing with these scientific problems are welcome in this new Special Issue.

Prof. Dr. Stoyan Nedeltchev
Guest Editor

Manuscript Submission Information

Manuscripts should be submitted online at www.mdpi.com by registering and logging in to this website. Once you are registered, click here to go to the submission form. Manuscripts can be submitted until the deadline. All submissions that pass pre-check are peer-reviewed. Accepted papers will be published continuously in the journal (as soon as accepted) and will be listed together on the special issue website. Research articles, review articles as well as short communications are invited. For planned papers, a title and short abstract (about 100 words) can be sent to the Editorial Office for announcement on this website.

Submitted manuscripts should not have been published previously, nor be under consideration for publication elsewhere (except conference proceedings papers). All manuscripts are thoroughly refereed through a single-blind peer-review process. A guide for authors and other relevant information for submission of manuscripts is available on the Instructions for Authors page. Fluids is an international peer-reviewed open access monthly journal published by MDPI.

Please visit the Instructions for Authors page before submitting a manuscript. The Article Processing Charge (APC) for publication in this open access journal is 1800 CHF (Swiss Francs). Submitted papers should be well formatted and use good English. Authors may use MDPI's English editing service prior to publication or during author revisions.

Keywords

  • liquid-side mass transfer coefficient
  • classical mass transfer theories
  • correction factors
  • bubble shape effect
  • dilute alcohol solutions
  • electrolytes
  • surface active substances
  • local isotropic turbulence theory
  • new and classical multiphase reactors

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Published Papers (7 papers)

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Research

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19 pages, 5127 KiB  
Article
Towards Efficient Bio-Methanation: A Comparative Analysis of Disperser Designs and Process Optimization in Bubble Columns
by Florian Klapal and Mark Werner Hlawitschka
Fluids 2025, 10(2), 37; https://doi.org/10.3390/fluids10020037 - 31 Jan 2025
Viewed by 515
Abstract
This study aims to contribute to the optimization of bio-methanation in bubble columns, making it a more viable alternative to stirred tank reactors. The primary challenge to be addressed is the enhancement of mass transfer, which strongly depends on parameters such as bubble [...] Read more.
This study aims to contribute to the optimization of bio-methanation in bubble columns, making it a more viable alternative to stirred tank reactors. The primary challenge to be addressed is the enhancement of mass transfer, which strongly depends on parameters such as bubble size and gas hold-up. Various disperser designs were examined in a 0.14 mm diameter column, comparing their performance in terms of bubble diameter distribution and gas hold-up. The results indicate that an optimized plate disperser featuring a porous structure outperformed other designs by maintaining high gas retention without significant coalescence. Additionally, newly developed plug-in dispersers allowed for counter-current flow operation, enhancing process flexibility. Commercially available porous pin dispersers produced smaller bubbles compared to the other designs, yielding high gas hold-ups at lower gas velocities. Correlations between disperser type and column design parameters were established, laying the foundation for apparatus optimization. The findings contribute to the development of digital twin models, facilitating the refinement of bio-methanation processes within bubble columns for increased efficiency. Full article
(This article belongs to the Special Issue Mass Transfer in Multiphase Reactors)
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18 pages, 5358 KiB  
Article
Liquid–Liquid Flow and Mass Transfer Enhancement in Tube-in-Tube Millireactors with Structured Inserts and Advanced Inlet Designs
by Feng Zhu, Xingxing Pan, Xichun Cao, Yandan Chen, Rijie Wang, Jiande Lin and Hanyang Liu
Fluids 2025, 10(2), 26; https://doi.org/10.3390/fluids10020026 - 24 Jan 2025
Viewed by 466
Abstract
Liquid–liquid mass transfer is crucial in chemical processes like extraction and desulfurization. Traditional tube-in-tube millireactors often overlook internal flow dynamics, focusing instead on entry modifications. This study explores mass transfer enhancement through structured inserts (twisted tapes, multi-blades) and inlet designs (multi-hole injectors, T-mixers). [...] Read more.
Liquid–liquid mass transfer is crucial in chemical processes like extraction and desulfurization. Traditional tube-in-tube millireactors often overlook internal flow dynamics, focusing instead on entry modifications. This study explores mass transfer enhancement through structured inserts (twisted tapes, multi-blades) and inlet designs (multi-hole injectors, T-mixers). Using high-speed imaging and water–succinic acid–butanol experiments, flow patterns and mass transfer rates were analyzed. Results show annular and dispersion flows dominate under tested conditions with structured inserts lowering the threshold for dispersion flow. Multi-hole injectors improved mass transfer by over 40% compared to T-mixers in plain tubes, while C-tape inserts achieved the highest volumetric mass transfer coefficient (2.43 s−1) due to increased interfacial area and droplet breakup from energy dissipation. This approach offers scalable solutions to enhance tube-in-tube millireactor performance for industrial applications. Full article
(This article belongs to the Special Issue Mass Transfer in Multiphase Reactors)
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17 pages, 6420 KiB  
Article
Impact of Solid Particle Concentration and Liquid Circulation on Gas Holdup in Counter-Current Slurry Bubble Columns
by Sadra Mahmoudi and Mark W. Hlawitschka
Fluids 2025, 10(1), 14; https://doi.org/10.3390/fluids10010014 - 16 Jan 2025
Viewed by 524
Abstract
In this study, in a three-phase reactor with a rectangular cross-section, the effects of liquid circulation rates and solid particle concentration on gas holdup and bubble size distribution (BSD) were investigated. Air, water, and glass beads were used as the gas, liquid, and [...] Read more.
In this study, in a three-phase reactor with a rectangular cross-section, the effects of liquid circulation rates and solid particle concentration on gas holdup and bubble size distribution (BSD) were investigated. Air, water, and glass beads were used as the gas, liquid, and solid phases, respectively. Different liquid circulation velocities and different solid loads were applied. The results demonstrate that increasing solid content from 0% to 6% can decrease gas holdup by 50% (due to increased slurry phase viscosity and promotion of bubble coalescence). Also, increasing the liquid circulation rate showed a weak effect on gas holdup, although a slight incremental effect was observed due to the promotion of bubble breakup and the extension of bubble residence time. The gas holdup in counter-current slurry bubble columns (CCSBCs) was predicted using a novel correlation that took into account the combined effects of solid concentration and liquid circulation rate. These findings are crucial for the design and optimization of the three-phase reactors used in industries such as mining and wastewater treatment. Full article
(This article belongs to the Special Issue Mass Transfer in Multiphase Reactors)
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13 pages, 4096 KiB  
Article
Gas–Liquid Mass Transfer Intensification for Selective Alkyne Semi-Hydrogenation with an Advanced Elastic Catalytic Foam-Bed Reactor
by Mohamad Fayad, Maïté Michaud, Han Peng, Vincent Ritleng and David Edouard
Fluids 2024, 9(6), 132; https://doi.org/10.3390/fluids9060132 - 1 Jun 2024
Viewed by 1197
Abstract
The Elastic Catalytic Foam-bed Reactor (EcFR) technology was used to enhance a model catalytic hydrogenation reaction by improving gas–liquid mass transfer. This advanced technology is based on a column packed with a commercial elastomeric polyurethane open-cell foam, which also acts as a catalyst [...] Read more.
The Elastic Catalytic Foam-bed Reactor (EcFR) technology was used to enhance a model catalytic hydrogenation reaction by improving gas–liquid mass transfer. This advanced technology is based on a column packed with a commercial elastomeric polyurethane open-cell foam, which also acts as a catalyst support. A simple and efficient crankshaft-inspired system applied in situ compression/relaxation movements to the foam bed. For the first time, the catalytic support parameters (i.e., porosity, tortuosity, characteristic length, etc.) underwent cyclic and controlled changes over time. These dynamic cycles have made it possible to intensify the transfer of gas to liquid at a constant energy level. The application chosen was the selective hydrogenation of phenylacetylene to styrene in an alcoholic solution using a palladium-based catalyst under hydrogen bubble conditions. The conversion observed with this EcFR at 1 Hz as cycle frequency was compared with that observed with a conventional Fixed Catalytic Foam-bed Reactor (FcFR). Full article
(This article belongs to the Special Issue Mass Transfer in Multiphase Reactors)
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27 pages, 18300 KiB  
Article
Statistical Analysis of Bubble Parameters from a Model Bubble Column with and without Counter-Current Flow
by P. Kováts and K. Zähringer
Fluids 2024, 9(6), 126; https://doi.org/10.3390/fluids9060126 - 28 May 2024
Viewed by 1073
Abstract
Bubble columns are widely used in numerous industrial processes because of their advantages in operation, design, and maintenance compared to other multiphase reactor types. In contrast to their simple design, the generated flow conditions inside a bubble column reactor are quite complex, especially [...] Read more.
Bubble columns are widely used in numerous industrial processes because of their advantages in operation, design, and maintenance compared to other multiphase reactor types. In contrast to their simple design, the generated flow conditions inside a bubble column reactor are quite complex, especially in continuous mode with counter-current liquid flow. For the design and optimization of such reactors, precise numerical simulations and modelling are needed. These simulations and models have to be validated with experimental data. For this reason, experiments were carried out in a laboratory-scale bubble column using shadow imaging and particle image velocimetry (PIV) techniques with and without counter-current liquid flow. In the experiments, two types of gases—relatively poorly soluble air and well-soluble CO2—were used and the bubbles were generated with three different capillary diameters. With changing gas and liquid flow rates, overall, 108 different flow conditions were investigated. In addition to the liquid flow fields captured by PIV, shadow imaging data were also statistically evaluated in the measurement volume and bubble parameters such as bubble diameter, velocity, aspect ratio, bubble motion direction, and inclination. The bubble slip velocity was calculated from the measured liquid and bubble velocities. The analysis of these parameters shows that the counter-current liquid flow has a noticeable influence on the bubble parameters, especially on the bubble velocity and motion direction. In the case of CO2 bubbles, remarkable bubble shrinkage was observed with counter-current liquid flow due to the enhanced mass transfer. The results obtained for bubble aspect ratio are compared to known correlations from the literature. The comprehensive and extensive bubble data obtained in this study will now be used as a source for the development of correlations needed in the validation of numerical simulations and models. The data are available from the authors on request. Full article
(This article belongs to the Special Issue Mass Transfer in Multiphase Reactors)
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13 pages, 4017 KiB  
Article
Characterization Data for the Establishment of Scale-Up and Process Transfer Strategies between Stainless Steel and Single-Use Bioreactors
by Vincent Bernemann, Jürgen Fitschen, Marco Leupold, Karl-Heinz Scheibenbogen, Marc Maly, Marko Hoffmann, Thomas Wucherpfennig and Michael Schlüter
Fluids 2024, 9(5), 115; https://doi.org/10.3390/fluids9050115 - 16 May 2024
Cited by 3 | Viewed by 2558
Abstract
The reliable transfer of bioprocesses from single-use bioreactors (SUBs) of different scales to conventional stainless steel stirred-tank bioreactors is of steadily growing interest. In this publication, a scale-up study for SUBs with volumes of 200 L and 2000 L and the transfer to [...] Read more.
The reliable transfer of bioprocesses from single-use bioreactors (SUBs) of different scales to conventional stainless steel stirred-tank bioreactors is of steadily growing interest. In this publication, a scale-up study for SUBs with volumes of 200 L and 2000 L and the transfer to an industrial-scale conventional stainless steel stirred-tank bioreactor with a volume of 15,000 L is presented. The scale-up and transfer are based on a comparison of mixing times and the modeling of volumetric mass transfer coefficients kLa, measured in all three reactors in aqueous PBS/Kolliphor solution. The mass transfer coefficients are compared with the widely used correlation of van’t Riet at constant stirrer tip speeds. It can be shown that a van’t Riet correlation enables a robust and reliable prediction of mass transfer coefficients on each scale for a wide range of stirrer tip speeds and aeration rates. The process transfer from single-use bioreactors to conventional stainless steel stirred-tank bioreactors is proven to be uncritical concerning mass transfer performance. This provides higher flexibility with respect to bioreactor equipment considered for specific processes. Full article
(This article belongs to the Special Issue Mass Transfer in Multiphase Reactors)
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Review

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14 pages, 462 KiB  
Review
Updated Review on the Available Methods for Measurement and Prediction of the Mass Transfer Coefficients in Bubble Columns
by Stoyan Nedeltchev
Fluids 2025, 10(2), 29; https://doi.org/10.3390/fluids10020029 - 27 Jan 2025
Viewed by 611
Abstract
This review summarizes the most important measurement techniques for determination of the volumetric liquid-phase mass transfer coefficient kLa. In addition, the main empirical correlations (with their applicability ranges) for kLa estimation are presented. It is clearly underlined that [...] Read more.
This review summarizes the most important measurement techniques for determination of the volumetric liquid-phase mass transfer coefficient kLa. In addition, the main empirical correlations (with their applicability ranges) for kLa estimation are presented. It is clearly underlined that in tall bubble columns, a system of two differential equations (involving the gas and liquid axial dispersion coefficients) should be solved in order to obtain the accurate kLa value. The semi-empirical correlations for kLa prediction based on the correction of the penetration theory are also summarized. The need for a correction of the penetration theory is explained. The different definitions of the gas–liquid contact time, including the one based on the local isotropic turbulence theory, are presented. Finally, the various chemical methods for the determination of the gas–liquid interfacial area are summarized. Additionally, the main correlation for the prediction of the interfacial area is reported. The effects of pressure, temperature, and viscosity on the interfacial area and kLa are discussed. Full article
(This article belongs to the Special Issue Mass Transfer in Multiphase Reactors)
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