Liquid Holdup Distribution Research Articles

Experimental Investigation of Liquid Holdup in a Co-Current Gas–Liquid Upflow Moving Packed Bed Reactor with Porous Catalyst Using Gamma-Ray Densitometry

This study explores the dynamics of liquid holdup in a lab-scale co-current two-phase upflow moving packed bed reactor, specifically examining how superficial gas velocity influences the line average external liquid holdup at a fixed superficial liquid velocity. Utilizing gamma-ray densitometry (GRD) for precise measurements, this research extends to determining line average internal porosity within catalyst particles. Conducted with an air–water system within a bed packed with 3 mm porous particles, the study presents a novel methodology using Beer–Lambert’s law to calculate liquid, gas, and solid holdups and catalyst porosity that is equivalent to the internal liquid holdup that fills the catalyst pores. Findings reveal a decrease in liquid holdup corresponding with increased superficial gas velocity across axial and radial locations, with a notable transition from bubbly to pulse flow regime at a critical velocity of 3.8 cm/sec. Additionally, the lower sections of the packed bed exhibited higher external liquid holdup compared to the middle sections at varied gas velocities. The liquid holdup distribution appeared uniform at lower flow rates, whereas higher flow rates favored the middle sections.

A Modified Model to Predict Liquid Loading in Horizontal Gas Wells

Abstract Liquid loading is inevitable during mature gas-well production, leading the liquids to accumulate at the bottomhole and additional pressure loss. Accurately predicting the liquid-loading initiation is crucial to gas-well production optimization. Significant efforts have been made to model liquid-loading behavior. However, few mechanistic models are capable of easily and accurately tackling the complicated non-uniform liquid-film distribution in the slanted section of horizontal wells. Based on liquid-film inversion, this study developed a simple and comprehensive model to calculate liquid-loading initiation for horizontal gas wells. First, the models for film thickness and critical velocity in the vertical pipe are developed. Then, considering the effect of inclination and velocity difference in liquid-film thickness and liquid-holdup distribution between vertical and inclined pipes, the relationship in vertical and inclined pipes between liquid holdup, liquid-film thickness, and angle correction term is established based on the liquid-holdup correlation for horizontal and inclined pipes described in the empirical model developed by Beggs and Brill, so that the thickness of the film and the corresponding critical velocity at any inclination can be calculated. Finally, the new modified model has been evaluated against both experimental and field-measured data set. In comparison to the Luo et al.’s model, the proposed model has been proven to be simple, accurate, and well-performed in predicting the liquid-accumulation initiation in horizontal wells.

Comparative Analysis of Riser Base and Flowline Gas Injection on Vertical Gas-Liquid Two-Phase Flow

Gas injection is a frequently used method for artificial lift and flow regime rectification in offshore production and transportation flowlines. The flow behaviour in such flowlines is complex and a better understanding of flow characteristics, such as flow patterns, void fraction/hold up distributions and pressure gradient is always required for efficient and optimal design of downstream handling facilities. Injection method and location have been shown to strongly affect downstream fluid behaviour that can have important implications for pumping and downstream facility design, especially if the development length between pipeline and downstream facility is less than L/D = 50 as reported by many investigators. In this article, we provide the results of an experimental investigation into the effects of the gas injection position on the characteristics of the downstream upwards vertical gas flow using a vertical riser with an internal diameter of 52 mm and a length of 10.5 m. A horizontal 40-m-long section connected at the bottom provides options for riser base or horizontal flow line injection of gas. The flowline gas injection is performed 40 m upstream of the riser base. A 16 by 16 capacitance wire mesh sensor and a gamma densitometer were used to measure the gas-liquid phase cross-sectional distribution at the riser top. A detailed analysis of the flow characteristics is carried out based on the measurements. These include flow regimes, cross-sectional liquid holdup distributions and peaking patterns as well as analysis of the time series data. Our findings show that flow behaviours differences due to different gas injection locations were persisting after a development length of 180D in the riser. More specifically, core-peaking liquid holdup occurred at the lower gas injection rates through the flowline, while wall-peaking holdup profiles were established at the same flow conditions for riser base injection. Wall peaking was associated with dispersed bubbly flows and hence non-pulsating as against core-peaking was associated with Taylor bubbles and slug flows. Furthermore, it was found that the riser base injection generally produced lower holdups. It was noted that the circumferential injector used at the riser base promoted high void fraction and hence low liquid holdups. Due to the bubbly flow structure, the slip velocity is smaller than for larger cap bubbles and hence the void fraction is higher. The measurements and observations presented in the paper provides valuable knowledge on riser base/flowline gas introduction that can directly feed into the design of downstream facilities such as storage tanks, slug catchers and separators.

Experimental analysis of the hydrodynamic performance of an industrial-scale cross-flow sieve tray

This work reports the hydrodynamic description of a large-scale sieve tray equipped in an air/water column mockup. The test tray accommodated a novel multi-probe flow profiler for simultaneous conductivity measurements. For the first time, 3D liquid holdup distribution, liquid residence time distribution and effective froth height distribution were obtained at very high spatiotemporal resolution for several gas and liquid loadings. The liquid flow and mixing patterns were visualized via tracer-based experiments. The methodologies used for acquiring these distributions are thoroughly discussed in this work. Diligent examination of the processed experimental data revealed the hydrodynamic characteristics of an operational sieve tray for the studied loadings. Uniform effective froth height persisted over the majority of the tray, whereas homogenous liquid holdup distribution was observed at multiple elevations above the deck with the highest holdup occurring near the average effective froth height. Based on tracer experiments, axisymmetric liquid flow and mixing patterns were detected with parabolic velocity distribution near the inlet. Overall, the liquid velocities over the remaining tray deck were nearly uniform for the studied loadings.

Flow pattern identification and measurement techniques in gas-liquid-liquid three-phase flow: A review

The simultaneous flow of gas, oil, and water forms various flow patterns due to the complex interfacial relationships. Three-phase flow patterns are classified as the gas-liquid and liquid-liquid flow patterns. Pressure drop, void fraction, liquid holdup, and phase distribution are important characteristics of the three-phase flow. These characteristics are generally associated with the three-phase flow patterns. Hence, the knowledge about flow patterns can help to predict the overall behavior of the three-phase flow. Studies have been conducted to identify three-phase flow pattern and their characteristics at various superficial velocities of gas, oil, and water. The major purpose of the studies is to gather information about the three-phase co-current flow and use it for improvement of the efficiency of the flow systems. Therefore, the accuracy of the measurement technique is critical. Several types of flow pattern identification and measurement techniques have been developed to improve accuracy and provide high-quality results. In this article, classical and advanced techniques used for the three-phase flow identification and measurement have been reviewed. The survey will help the researchers working in the area of multiphase flow to choose the right technique based on the objectives of the studies.

Analysis of flow pattern transition from segregated to slug flow in upward inclined pipes

Segregated and slug flows are two of the most common flow patterns encountered in two-phase upward inclined pipe flow. However, the transition between them is ambiguous. Coherent and distinctive structures have been observed within the transition. These structures have been classified as pseudo-slug flow. The nature of pseudo-slug flow is not well understood due to the complexity of the structure. At low liquid loading conditions, this flow pattern can occupy a large operating region and cannot be neglected. This paper presents a detailed experimental work conducted in a facility with a valley configuration, focusing on the transition region between segregated and slug flows. Wire-mesh sensors were employed to investigate the liquid phase distribution within the flow structure.The current paper investigates the flow patterns and their transition in upward inclined pipe from different perspectives. The investigation includes analysis of images from high-speed videos, evaluation of 2-D liquid holdup axial evolution, 2-D liquid holdup distribution at pipe cross-section, 3-D interfacial structure evolution, and analysis of pressure gradient and liquid holdup measurement, flow characteristics, etc. Differences between slug and pseudo-slug flows are also presented.Three superficial liquid velocities (0.001, 0.005 and 0.01 m/s) and five inclination angles (2°, 5°, 10°, 15°, and 20°) are studied. Simplified correlations are proposed for pseudo-slug structural velocity, showing fair agreement.

Feasibility of Electrical Resistance Tomography for measurements of liquid holdup distribution in a trickle bed reactor

Trickle bed reactors (TBRs) are widely used in chemical and oil industries. Owing to complex nature of flow in TBRs, measurements of local liquid holdup distribution are rather limited. While several non-invasive measurement techniques have been used to measure liquid distribution in TBRs, the applicability of Electrical Resistance Tomography (ERT) for quantitative measurement of liquid holdup distribution is not yet verified. In the present work, measurements of local liquid distribution in a laboratory-scale TBR are carried out using ERT for trickle to transition flow regimes. The time-averaged liquid holdup distributions measured using the ERT and BLC methods were compared using the liquid maldistribution factor to demonstrate the feasibility of the ERT to measure liquid holdup distribution. The effect of liquid-distributor configurations (semi-uniform, local and one-sided) was investigated on the radial liquid distribution at different axial locations of TBR. Further, the ability of ERT to measure time-resolved local liquid distribution was verified using multi-point conductivity sensors for artificially created pulsing flow. Also, the comparison of liquid pulse width with multi-point conductivity sensor measurements was carried out and of the dispersion of liquid pulse along the length of TBR was analyzed. The ERT measurements were performed to quantify the effects of gas and liquid flow rates, and particle size on the local liquid holdup. The void-scale flow structure measured by multi-point conductivity sensors was used to analyze the macroscopic (bed-scale) liquid holdup distribution measured by ERT. Thus, the comparison of ERT measurements with time-averaged BLC and time-resolved multi-point conductivity sensor measurements is important to establish the applicability of ERT for quantitative spatial and in particular the time-resolved measurements of liquid holdup in TBRs.

Pressure Drop, Liquid Holdup, and Liquid Distribution in Additively Manufactured Periodic Open Cellular Structures (POCS)

Chemie Ingenieur TechnikVolume 90, Issue 9 p. 1230-1230 VortragFree Access Pressure Drop, Liquid Holdup, and Liquid Distribution in Additively Manufactured Periodic Open Cellular Structures (POCS) G. Horak, Corresponding Author G. Horak giulia.horak@fau.de Friedrich-Alexander-Universität Erlangen-Nürnberg, Lehrstuhl für chemische Reaktionstechnik, Egerlandstraße 3, 91058 Erlangen, Germany Friedrich-Alexander-Universität Erlangen-Nürnberg, Zentralinstitut für Neue Materialien und Prozesstechnik (ZMP), Dr.-Mack-Straße 81, 90762 Fürth, GermanyCorrespondence: G. Horak (giulia.horak@fau.de), Friedrich-Alexander-Universität Erlangen-Nürnberg, Zentralinstitut für Neue Materialien und Prozesstechnik (ZMP), Dr.-Mack-Straße 81, 90762 Erlangen, GermanySearch for more papers by this authorM. Lämmermann, M. Lämmermann Friedrich-Alexander-Universität Erlangen-Nürnberg, Lehrstuhl für chemische Reaktionstechnik, Egerlandstraße 3, 91058 Erlangen, Germany Friedrich-Alexander-Universität Erlangen-Nürnberg, Zentralinstitut für Neue Materialien und Prozesstechnik (ZMP), Dr.-Mack-Straße 81, 90762 Fürth, GermanySearch for more papers by this authorW. Schwieger, W. Schwieger Friedrich-Alexander-Universität Erlangen-Nürnberg, Lehrstuhl für chemische Reaktionstechnik, Egerlandstraße 3, 91058 Erlangen, Germany Friedrich-Alexander-Universität Erlangen-Nürnberg, Zentralinstitut für Neue Materialien und Prozesstechnik (ZMP), Dr.-Mack-Straße 81, 90762 Fürth, GermanySearch for more papers by this authorH. Freund, H. Freund Friedrich-Alexander-Universität Erlangen-Nürnberg, Lehrstuhl für chemische Reaktionstechnik, Egerlandstraße 3, 91058 Erlangen, Germany Friedrich-Alexander-Universität Erlangen-Nürnberg, Zentralinstitut für Neue Materialien und Prozesstechnik (ZMP), Dr.-Mack-Straße 81, 90762 Fürth, GermanySearch for more papers by this author G. Horak, Corresponding Author G. Horak giulia.horak@fau.de Friedrich-Alexander-Universität Erlangen-Nürnberg, Lehrstuhl für chemische Reaktionstechnik, Egerlandstraße 3, 91058 Erlangen, Germany Friedrich-Alexander-Universität Erlangen-Nürnberg, Zentralinstitut für Neue Materialien und Prozesstechnik (ZMP), Dr.-Mack-Straße 81, 90762 Fürth, GermanyCorrespondence: G. Horak (giulia.horak@fau.de), Friedrich-Alexander-Universität Erlangen-Nürnberg, Zentralinstitut für Neue Materialien und Prozesstechnik (ZMP), Dr.-Mack-Straße 81, 90762 Erlangen, GermanySearch for more papers by this authorM. Lämmermann, M. Lämmermann Friedrich-Alexander-Universität Erlangen-Nürnberg, Lehrstuhl für chemische Reaktionstechnik, Egerlandstraße 3, 91058 Erlangen, Germany Friedrich-Alexander-Universität Erlangen-Nürnberg, Zentralinstitut für Neue Materialien und Prozesstechnik (ZMP), Dr.-Mack-Straße 81, 90762 Fürth, GermanySearch for more papers by this authorW. Schwieger, W. Schwieger Friedrich-Alexander-Universität Erlangen-Nürnberg, Lehrstuhl für chemische Reaktionstechnik, Egerlandstraße 3, 91058 Erlangen, Germany Friedrich-Alexander-Universität Erlangen-Nürnberg, Zentralinstitut für Neue Materialien und Prozesstechnik (ZMP), Dr.-Mack-Straße 81, 90762 Fürth, GermanySearch for more papers by this authorH. Freund, H. Freund Friedrich-Alexander-Universität Erlangen-Nürnberg, Lehrstuhl für chemische Reaktionstechnik, Egerlandstraße 3, 91058 Erlangen, Germany Friedrich-Alexander-Universität Erlangen-Nürnberg, Zentralinstitut für Neue Materialien und Prozesstechnik (ZMP), Dr.-Mack-Straße 81, 90762 Fürth, GermanySearch for more papers by this author First published: 24 August 2018 https://doi.org/10.1002/cite.201855217AboutPDF ToolsRequest permissionExport citationAdd to favoritesTrack citation ShareShare Give accessShare full text accessShare full-text accessPlease review our Terms and Conditions of Use and check box below to share full-text version of article.I have read and accept the Wiley Online Library Terms and Conditions of UseShareable LinkUse the link below to share a full-text version of this article with your friends and colleagues. Learn more.Copy URL Share a linkShare onFacebookTwitterLinkedInRedditWechat No abstract is available for this article. References 1 A. Inayat et al., Chem. Eng. J. 2016, 287, 704. 2 M. Lämmermann et al., Catal. Today 2016, 273, 161. 3 A. E. Sáez, R. G. Carbonell AIChE J. 1985, 31 (1), 52. 4 M. Lämmermann et al., Chem. Eng. Process. 2018, 126, 178. Volume90, Issue9Special Issue: ProcessNet-Jahrestagung und 33. DECHEMA-Jahrestagung der Biotechnologen 2018September 2018Pages 1230-1230 ReferencesRelatedInformation

Experimental and numerical investigation on slug initiation and initial development behavior in hilly-terrain pipeline at a low superficial liquid velocity

The initiation and initial development behavior of gas–liquid slug flow is experimentally and numerically investigated in a hilly–terrain pipeline at a low superficial liquid velocity. The test section consists of three parts: three sections of horizontal pipe, one ascending pipe, and one descending pipe. The inclined pipes are at an angle of 10°, all sections are connected by elbow pipes, and the inner diameter is 40 mm. Air and water, with a superficial liquid velocity ranging from 0.002 m/s to 0.1 m/s, are used as working fluids, which are operated at ambient temperature and pressure. Differential pressure transmitters and ultrasound Doppler velocimetry are used to measure the pressure drop and liquid film height, and velocity, respectively. Numerical simulation is simultaneously carried out using the coupled level-set and volume of fluid method, and is verified through comparison with experimental data. Slug initiation mechanisms are discussed based on experimental observation and numerical prediction. The characteristics of liquid slug initiation and initial development are also explained using pressure drop fluctuation, liquid holdup, and phase distribution features. The overall qualitative and quantitative analysis can contribute to the improvement of recent theoretical and numerical models.

Fischer-Tropsch synthesis in vertical, inclined and oscillating trickle-bed reactors for offshore floating applications

Fischer-Tropsch synthesis performance in vertical, inclined and oscillating trickle-bed reactors for offshore floating applications was examined via a complex dynamic three-dimensional multiphase model based on volume-averaged mass, momentum, and species balance equations in liquid and gas phases and simultaneous diffusion and chemical reactions within the catalyst. Angular sinusoidal oscillatory motion of the trickle-bed reactor between vertical and an inclined position and between two inclined symmetrical/asymmetrical positions was examined. The behavior of inclined and oscillating Fischer-Tropsch trickle-bed reactors is atypical because the reactants in the main reactions originate from the gas phase and because a fraction of useful CO can be redirected in water gas-shift reaction. The performance of Fischer-Tropsch synthesis in the presence of water-gas shift reaction increases slightly with amplification of packed bed inclination even if the distortion of axial symmetry of liquid holdup and axial velocity radial distributions becomes considerable. Also, in asymmetric oscillating trickle-bed reactors the performance of Fischer-Tropsch synthesis is slightly improved. This enhancement is maximal for the reactor moving between vertical and an inclined position when the time-dependent waves of CO and H2 conversion develop around the steady-state solution of the middle inclination angle. The oscillatory Fischer-Tropsch performance moves towards the steady-state solution of the vertical state when the asymmetry between two inclined positions diminishes. Symmetric oscillating trickle-bed reactors generate an oscillatory Fischer-Tropsch performance around the steady-state solution of vertical state which is affected by the angular motion parameters of the reactor.

Advanced understanding of local wetting behaviour in gas-liquid-solid packed beds using CFD with a volume of fluid (VOF) method

Gas-liquid-solid packed bed reactors or trickle-bed reactors (TBRs) have been widely employed in various industrial applications such as hydrocracking, selective hydrogenation process of gas oil, wastewater treatment and so on. Since the multiphase flow in TBRs is complex, uniform liquid distribution can hardly be obtained. The liquid coverage on particles at various locations in the bed affects the overall reactor performance. In this work, computational fluid dynamics (CFD) simulations with a volume of fluid (VOF) model were employed to investigate liquid mal-distribution at the micro-level in a packed bed reactor. In this study, two different parameters (the local liquid coverage (HL) and local liquid holdup (hL)) were employed to describe liquid distribution on individual particles. The liquid distribution at different particle layers was investigated. The results revealed that the distributions for local liquid coverage and local liquid holdup were similar. The wetting efficiency and the liquid residence time decreased with increasing the voidage. In a packed bed with cylindrical particles, the capillary effect cannot be ignored in smaller channels formed between the particles, leading to higher flow resistance. It was also found that the wetting efficiency and liquid film thickness increased with an increase in the liquid velocity. Both wetting efficiency and the time required to reach steady state decreased when increasing the contact angle. The flow on particle surface could change from rivulet to film as the liquid density decreased. The newly unveiled information of local liquid holdup distribution could significantly advance the understanding of gas-liquid flow hysteresis inside packed beds, based on which the reactor performance can be further improved.

Numerical Study of the CO2 Absorber Performance Subjected to the Varying Amine Solvent and Flue Gas Loads

The paper is devoted to the amine-based post-combustion carbon dioxide capture technology. The aim of the paper was to analyze the effect of varying flow conditions on the CO2 capture efficiency of the absorber column. As a research tool, a numerical model of the chemical absorption with aqueous monoethanolamine solution in a packed bed was employed. A complex physio-chemical process including two-phase flow hydrodynamics, heat transfer, and absorption chemistry was simulated by Ansys Fluent commercial software. The parametric study was focused on CO2 capture efficiency in terms of varying loads of amine solvent (liquid) and flue gas. The corresponding changes of liquid holdup, species concentration, temperature and reaction rate distributions are discussed in detail allowing to better understand the absorption column operation. The simulation results have shown clearly the mutual interactions of partial processes and the sensitivity of the system to varying column loads. They have been found to be useful in defining the optimal ranges of operational parameters.

Numerical analysis of the two-phase flow characteristics in vertical downward helical pipe

In this research, the Eulerian multiphase flow model is validated to calculate the two-phase flow in vertical downward helical pipes. The development of pressure fields and liquid distribution along the helical pipe are presented. The results shows that the curvature, torsion and liquid holdup exert great effect on the distribution of the pressure field and liquid holdup distribution in the helical pipe. In addition, it is found that the two-phase frictional pressure drop relates to the curvature and torsion of helical pipe, and that the inlet sectional liquid holdup also has great effect on the pressure drop. The correlation developed predicts the two-phase frictional factor in helical pipe with acceptable statistical accuracy.

Numerical simulation of flow field characteristics in a gas-liquid-solid agitated tank

Computational fluid dynamics simulation was carried out to investigate flow field characteristics in a gas-liquid-solid agitated tank. The Eulerian multifluid model along with standard k-e turbulence model was employed in the simulation. A multiple reference frame approach was used to treat the impeller rotation. Liquid velocity, gas holdup and solid holdup distributions in the agitated tank were obtained. The effect of operating conditions on gas and solid distributions was investigated. The predicted flow pattern was compared with results in literature. The simulation results indicate that local hydrodynamic behaviors such as velocity, gas and solid holdup distribution, are strongly influenced by operating conditions. Within the scope of our study, increasing gas inlet rate caused liquid circulation to be weakened and was not in favor of gas dispersion. Solid holdup in the upper part of the tank, especially near the wall region decreased. Adding solid loadings resulted in liquid mean velocity near the surface region decreased, gas dispersion and solid suspension becoming worse.

Quantitative cross-sectional measurement of solid concentration distribution in slurries using a wire-mesh sensor

Wire-mesh sensors have so far been widely applied in gas–liquid flows where resistance or capacitance distributions are measured and converted into gas or liquid holdup distributions. In this work we report on the qualification of the wire-mesh imaging technique for the measurement of cross-sectional solid concentrations in solid–liquid mixtures. As the dielectric constants of solid particles are different from those of gas, water or oil in the flow, measuring this property can be used as an indication of solid distribution. Experiments were performed in a stirred tank of 100 mm diameter equipped with a capacitance wire-mesh sensor. The wire-mesh sensor was operated at an acquisition speed of 4000 frames per second and has a spatial resolution of 6.25 mm. As solids we used silica sand particles (diameter ~250 μm) which were suspended in water in a volume concentration range of 1% to 35% to form slurries. By varying the stirring speed, different solid concentration distributions were produced and investigated. In order to convert the measured relative permittivity distribution into a solid concentration distribution, an empirical approach was employed.

Gas–liquid distribution in a bubble column using industrial gamma-ray computed tomography

A gas absorption column used as a simulator bubble column for industrial processes was evaluated, using the third-generation industrial computed tomography developed at the IPEN. Gamma ray tomography experiments were carried out, using the simulator column empty and filled with water plus gas bubbling. The tomographic measurements were taken at three positions relative to the point of generation of the bubbles: above 20mm, 120mm and 320mm. The resulting images describe the liquid or gas phase holdup distributions for bubbles generated in a hole of ∅=5mm, located at 15mm of the column wall. The developed third generation CT had a spatial resolution of 4.5mm and a temporal resolution around 5h/image. The trend of bubble dispersions, as they rise in the column, was shown.

A new multi‐scale model based on CFD and macroscopic calculation for corrugated structured packing column

A multi‐scale approach with the combination of computational fluid dynamic (CFD) and macroscopic calculation methods has been proposed to predict the hydrodynamics behavior in the corrugated structured packing column. On the basis of the concept of the representative unit, the three‐dimensional (3‐D) volume of fluid (VOF) model of the structured packing is applied in the small scale simulation, and the stream split fraction coefficients and effective wetted area ratio are calculated. The unit network model, which is a mechanistic model, is applied in large scale calculation basing on the small scale results. The liquid holdup distribution in the entire column can be available by this multi‐scale method. A comparison between the simulation results and the experimental data of our previous work is given to validate the present model. The multi‐scale model is proved to be prospective to assist the analysis and design of structure packing columns in chemical engineering. © 2013 American Institute of Chemical Engineers AIChE J, 59: 3119–3130, 2013

Enhancing foam drainage by spiral internal components of different thread pitches and inclined angles and their applications to enrichment of SDS

For further enhancing foam drainage and comprehensive knowledge of the spiral internal component (SIC), the effects of its thread pitch and inclined angle were experimentally and theoretically investigated. The results showed that the decrease of the thread pitch, and the increase of the inclined angle contributed to more enhancement of foam drainage. Under batch conditions, the SDS enrichment ratio obtained with SIC of thread pitch 30mm and inclined angle 30° was about 2.4 times of that obtained without SIC. The theoretical analyses predicted the liquid holdup distribution in the column with SIC and gave better explanations for the experimental results. It is found that the decrease of the thread pitch resulted in a larger number of the SIC units by which the more enhanced foam drainage was obtained. The increase of the inclined angle sped the reflux of the drained liquid, thus leading to faster decrease of the liquid holdup. However, the inclined angle had the weaker ability to enhance foam drainage than the thread pitch.

X-ray CT study of the influence of liquid viscosity on fluid phase distribution in modular catalytic packings

In the frame of the present study, the influence of liquid viscosity on liquid holdup distribution in a packed column equipped with the modular catalytic packing KatapakSP 11 is measured. Water and an aqueous solution of glycerine, the viscosity of which equals 10 cP, are used as feed liquids. The estimation of liquid holdup is of great interest due to its strong influence on pressure drop, on solid wetting and on heat and mass transfer coefficients. The experimental technique used is high energy X-ray tomography, which is a unique technique to visualize the local liquid distribution inside the complex structure of packings and to quantify the liquid holdup at different scales.

Determination of liquid hold-up and flow distribution inside modular catalytic structured packings

This paper presents the results of a study carried out to examine liquid hold-up and flow distribution in a 0.1 m internal diameter column filled with catalytic structured packing Katapak-SP. Information has been gathered at local scale by means of a non-intrusive high energy X-ray tomograph. Measurements have been carried out in a large number of packing cross sections situated at different heights between the top and bottom of the packed column, giving access to the evolution of axial profiles of liquid hold-up in the open channels (separation zone) and in the catalytic baskets (reaction zone) as a function of the liquid load. The total hold-up, evaluated by averaging local tomographic values over the packed volume, was compared with global hold-up data obtained by traditional methods, like draining and RTD measurements. A method was also proposed to deduce the distribution of liquid flowrate, between the reaction and the separation zones, from hold-up distribution measured by tomography. The methodology was validated by comparison with experimental data obtained by collecting separately the liquid flowing out of the two zones at the bottom of the packed bed. The obtained results are invaluable to improve the description of hydrodynamics in rate based performance models.