Mass Transfer Experiments Research Articles

Development of a miniature Taylor-Couette extractor column for nuclear solvent extraction

Miniature annular centrifugal contactors are nearly perfect for shielded hot-cell applications during flowsheet evaluation but these contactors require complex maintenance of electrical drive-motors during radioactive experiments. To reduce the number of electrical drives in the shielded cell, an indigenous design of miniature Taylor Couette (TC) mixing based countercurrent differential extraction column has been developed. In this paper, results of mass transfer experiments for an indigenously developed TC column with 30% TBP/aqueous nitric acid solutions are reported. The developed device worked perfectly in counter–current differential mode and demonstrated equivalence to multiple-extraction stages while working with a single electrical drive. The developed TC unit demonstrated operation with a reduced efficiency without flooding even in absence of rotor rotation. This observation is a vital step towards designing of robust contactors, which do not flood during temporary power failure or failure of drive mechanism.

Mass transport modeling and analysis on the mutual separation of lanthanum(III) and cerium(IV) through a hollow fiber supported liquid membrane

The mutual separation of lanthanum(III) and cerium(IV) was performed by using a hollow fiber supported liquid membrane. D2EHPA was used as an extractant. The effects of the sulfuric acid concentration in the feed solution, D2EHPA and strippant on the percentage of extraction and stripping were examined. The separation of lanthanum(III) by 4% (v/v) D2EHPA was achieved while cerium(IV) was rejected in the feed solution. A mathematical model focusing on the interface layer was presented to predict the thickness of the layer. The relationship between flux and layer thickness was in good agreement with experimental results and mass transfer theory.

Experimental and CFD study of wall effects on orderly stacked cylindrical particles heat transfer in a tube channel

In this study, the flow and heat transfer characteristics of regularly arranged cylindrical particles in a bed with bed-to-particle diameter ratio of 2.65 (The particle and bed diameter are 25 and 66mm respectively and the bed height is 200mm) have been studied in two different arrangements of particles. The first layout is coaxial particles which embrace 8 layers and 3 equilateral cylindrical particles in each layer); the second arrangement is similar to the first one but the intermittent layers have been rotated 60o. Three dimensional CFD simulation of air flow through these arrangements of particles in bed have been carried out by the standard κ-ε turbulence model with using of FEMLAB (Multiphysics in MATLAB) software version 2.3. For two configurations, comparisons between CFD results and experimental data have been drawn. Our results have been compared with prediction of empirical correlations for pressure drop of flow through the bed. The heat transfer CFD results were validated by naphthalene sublimation mass transfer experiments. The particle Nusselt number was obtained by using analogy between mass and heat transfer. A good quantitative and qualitative agreement between hydrodynamic of CFD simulation and experimental results was gained for both arrangements. The model predicts pressure drop of channel with two arrangements, coaxial and non-coaxial particles with an average error of 10% and 15%, respectively. Moreover, the CFD simulation has predicted the average particle Nusselt numbers of these two arrangements with an average quantitative error of 7% and 14%. Furthermore, the influence of wider range of Reynolds number (2500–6800) on particle Nusselt number has been investigated.

Hydrodynamics and Mass Transfer Behavior of a Novel Structured Packing with Diversion Windows

A novel structured packing with diversion windows is developed with the objective of achieving comparable pressure drop, high capacity and preferable mass transfer efficiency. The hydrodynamics and mass transfer performance of the packing have been investigated using a 384 mm diameter column. Carbon dioxide desorption process for mass transfer experiments at room temperatures and atmospheric pressures were conducted. Compared with the traditional Mellapak 350X, both the liquid holdup and mass transfer efficiency of the novel structured packing (350X with diversion windows) are increased by 15% or so; additionally, the pressure drop presented a slight growth trend, about 20% higher. It is concluded that the novel structured packing with adding diversion windows can change the flow pattern of the liquid film on the packing sheet and increase the effective mass transfer area, as well as the gas-liquid mass transfer efficiency.

Critical Evaluation of Different Mass Transfer Models Taking Zinc Extraction as an Example

AbstractDifferent mass transfer models were evaluated on the basis of zinc extraction with the liquid ion exchanger di(2‐ethylhexyl)phosphoric acid. Comparison of the models showed that the film model inadequately describes the time dependence of zinc concentration in aqueous solution. The best match of the measured time‐concentration profiles was achieved by adapting the film‐penetration model. Studies were carried out in a stirred cell with a planar interface stabilized by the mixing conditions. Under the chosen experimental conditions mass transfer was limited by zinc transfer in the aqueous phase. The mass transfer equations of each model were solved analytically using empirical correlations for the modeling parameters.

Cooperative WebLab in chemical engineering between France and Brazil: Validation of the methodology

A WebLab is an experiment operated remotely via Internet. Besides the strictly technical aspects of such an experiment, which may contribute to the learning of Chemical Engineering fundamentals, there is also important feedback when teams of students of two different countries are working together: the WebLab becomes an intercultural experience, enhancing the communication skills of the students. A WebLab between Universidade Federal de São Carlos (DEQ/UFSCar) and the Ecole Nationale Supérieure d’Ingénieurs en Arts Chimiques et Technologiques (ENSIACET) is presented in this work. A mass transfer experiment in a bench scale reactor (stirred and aerated) had to be studied by mixed teams, thus emulating challenges that will be common in future working environments. In order to perform the experiment, students in Brazil and in France were put into groups. The students had to make decisions about the procedure for executing the experiments. All the students were able to control the equipment, no matter where they were physically. Students communicated using video conference software. The students’ and teachers’ opinions of this experience were very positive. This methodology is an important contribution to the education of engineers in a world integrated by modern communication technologies.

Connection Between Liquid Distribution and Gas-Liquid Mass Transfer in Monolithic Bed

With a particular focus on the connection between liquid flow distribution and gas-liquid mass transfer in monolithic beds in the Taylor flow regime, hydrodynamic and gas-liquid mass transfer experiments were carried out in a column with a monolithic bed of cell density of 50 cpsi with two different distributors (nozzle and packed bed distributors). Liquid saturation in individual channels was measured by using self-made micro-conductivity probes. A mal-distribution factor was used to evaluate uniform degree of phase distribution in monoliths. Overall bed pressure drop and mass transfer coefficients were measured. For liquid flow distribution and gas-liquid mass transfer, it is found that the superficial liquid velocity is a crucial factor and the packed bed distributor is better than the nozzle distributor. A semi-theoretical analysis using single channel models shows that the packed bed distributor always yields shorter and uniformly distributed liquid slugs compared to the nozzle distributor, which in turn ensures a better mass transfer performance. A bed scale mass transfer model is proposed by employing the single channel models in individual channels and incorporating effects of non-uniform liquid distribution along the bed cross-section. The model predicts the overall gas-liquid mass transfer coefficient with a relative error within ±30%.

수직 원형관 내부에서 발생하는 자연대류 열전달에서 상·하단 마개의 영향

수직 원형관 내부의 자연대류 열전달 현상이 상 하단 마개 유무 그리고 마개의 가열 및 단열조건에 따라 어떻게 변화하는지 <TEX>$Ra_{Lw}$</TEX> 수 <TEX>$9.26{\times}10^9\sim7.74{\times}10^{12}$</TEX>의 범위에 대해 실험적으로 연구하였다. 상사성의 원리를 이용하여 열전달 실험을 대신하여 황산-황산구리 수용액의 전기도금계를 이용한 물질전달 실험을 수행하였다. 실험결과, 수직 원형관의 위와 아래가 열린 경우 자연대류 열전달은 기존의 수직평판에 대한 그것과 일치하였고 상 하단 마개의 영향 따른 열전달의 변화는 Krysa 등, Sedahmed 등과 Chung 등이 실험한 현상과 일치하였다. 구리 마개를 사용한 경우 측정된 열전달은 층류와 난류영역에서 원형관의 아래만 막혔을 때가 가장 높게 측정되었고 다음으로는 위와 아래가 모두 막힌 경우, 위만 막힌 경우 그리고 위와 아래가 모두 열린 경우의 순으로 열전달이 변화하였다. 한편, 아크릴 마개를 사용한 경우에는 그 경향은 비슷했지만 위와 아래가 모두 열린 경우가 위만 막힌 경우보다 열전달이 높았다. 구리 마개를 사용한 경우 아크릴 마개보다 열전달이 높았다. 이는 서로 다른 가열벽면에서 발생된 유동의 상호작용에 기인하였기 때문인 것으로 판단된다. 본 실험을 통하여 기존연구보다 확장한 유동영역과 기하구조에 대하여 열전달의 영향을 관찰하였고, 층류와 난류영역에 대한 자연대류 열전달 상관식을 제시하였다. The effects of top and bottom lids on the natural convection heat transfer phenomena inside vertical cylinders were investigated experimentally for <TEX>$Ra_{Lw}$</TEX> from <TEX>$9.26{\times}10^9$</TEX> to <TEX>$7.74{\times}10^{12}$</TEX>. Using the concept of analogy between heat and mass transfer, a cupric acid-copper sulfate electroplating system was employed as mass transfer experiments replacing heat transfer experiments. The natural convection heat transfer of both-open cylinders in laminar and turbulent flows was in good agreement with the existing heat transfer correlations developed for vertical plates. The effects of top and bottom lids on the heat transfer rates were very similar to the studies of Krysa et al. and Sedahmed et al. and Chung et al. With the copper lids, the bottom-closed cavity showed the highest heat transfer rates and then followed both-closed, top-closed, both-open ones in both laminar and turbulent flows. However with the acryl lids, the similar trends were observed except that the heat transfer rates for both-open were higher than top-closed one. The use of the copper lids increased the heat transfer rates compared to the acryl lids due to the hydrodynamic interaction of the flows developed for the different heated faces. This study extended the ranges of flow conditions of the existing literatures and proposed the empirical correlations.

Experimental Study and Modeling NaCl Mass Transfer during Feta Cheese Ripening

The NaCl spatial distribution and model development during two ripening stages of Feta cheese were studied in the paper. The results showed that NaCl spatial distribution of 12 locations for each layer had no significant differences (P&gt;0.05) during the whole ripening, while the values of NaCl spatial distribution of each layer had significant differences (p&lt;0.05) during stage I (from day 1 to day 20) but no significant differences (P&gt;0.05) during stage II (from day 20 to day 60). Based on statistical analysis of experimental data, the power models with three sets of parameters for three layers were developed during stage I, and a sigmoid model was developed for the entire cheese during stage II. The R2 of the four models were 0.975, 0.978, 0.991 and 0.997, respectively. The models had a good fit of experimental values and can be used to predict the spatial distribution of NaCl content in Feta cheese ripening.

Micellar Extraction of Zinc with Di(2-ethylhexyl)phosphoric Acid and the Addition of the Cationic Surfactant Cetyltrimethylammonium Bromide

The addition of surfactants can influence extraction processes. In cases where the surfactant concentration is above the critical micelle concentration, the mass transfer rate increases due to the formation of inverse micelles and, thus, through the mechanism of micellar extraction of zinc. The influence of the added surfactant cetyltrimethylammonium bromide on zinc extraction with the cation exchanger di(2-ethylhexyl)phosphoric acid was analyzed based on extraction equilibrium and mass transfer experiments. The observed experimental results are explained phenomenologically.

Experimental and theoretical mass transfer transient analysis of copper extraction using hollow fiber membrane contactors

Extraction of copper (II) from aqueous solutions using trifluoro-acetylacetone (TFA) diluted in 1-decanol, MIBK and tetradecane at 298 and 313 K was investigated experimentally and theoretically. Experimental part of the study concerns with the partitioning of copper (II) in both phases at equilibrium. Distribution of copper (II) in aqueous and organic phases was studied to investigate the hypothesis of constant partition coefficient for solvent extraction mass transfer analysis in hollow fiber membrane contactors (HFMCs). Partition coefficient of copper complexant was measured from extraction equilibrium analysis. Hatta number was calculated to define the kinetic regime. In the second part of experimentation, copper (II) extraction with TFA diluted in 1-decanol using hollow fiber membrane contactor closed system was examined based on aforementioned batch extraction kinetics. Previously developed theoretical model [M. Younas, S. Druon-Bocquet, J. Sanchez, Kinetic and dynamic study of liquid–liquid extraction of copper in a HFMC: experimentation, modeling and simulation, AIChE J. 56 (2010) 1469–1480] was modified to a more robust single-fiber flow model for mass transfer in non-dispersive solvent extraction in HFMC-based integrated plant. The model was, then, validated with the experimental results for dynamic responses of the solute concentration in reservoir. Experimental results were analysed with various shell side mass transfer correlations. It has been shown, by model simulations that the extent and speed of the extraction depend upon the copper (II) and TFA initial concentration, temperature and physical characteristics of solute and solvents. Likewise flow configuration affects the speed of extraction depending upon the nature of solute and solvent.

A population balance approach considering heat and mass transfer—Experiments and CFD simulations

Bubble condensation in sub-cooled water is a complex process, to which various phenomena contribute. Since the condensation rate depends on the interfacial area density, bubble size distribution changes caused by breakup and coalescence play a crucial role. Experiments on steam bubble condensation in vertical co-current steam/water flows have been carried out in an 8 m long vertical DN200 pipe. Steam is injected into the pipe and the development of the bubbly flow is measured at different distances to the injection using a pair of wire mesh sensors. By varying the steam nozzle diameter the initial bubble size can be influenced. Larger bubbles come along with a lower interfacial area density and therefore condensate slower. Steam pressures between 1 and 6.5 MPa and sub-cooling temperatures from 2 to 12 K were applied. Due to the pressure drop along the pipe, the saturation temperature falls towards the upper pipe end. This affects the sub-cooling temperature and can even cause re-evaporation in the upper part of the test section. The experimental configurations are simulated with the CFD code CFX using an extended MUSIG approach, which includes the bubble shrinking or growth due to condensation or re-evaporation. The development of the vapour phase along the pipe with respect to vapour void fractions and bubble sizes is qualitatively well reproduced in the simulations. For a better quantitative reproduction, reliable models for the heat transfer at high Reynolds number as well as for bubble breakup and coalescence are needed.

Elongated gas bubble dissolution under a turbulent liquid flow

Mass transfer between an elongated homogeneous gas bubble under a turbulent liquid flow in a duct is investigated experimentally. Elongated gas bubble dissolution is encountered in bioengineering tubular photobioreactors. Such reactors are interesting because they are compact, they have a low contamination risk and a low mechanical stress for a liquid phase containing fragile microalgae cells. It is demonstrated from experimental mass transfer measurements, that the interface of an immobilised elongated bubble can be approximated to a flat plane. Measured mass transfer experimental data, estimated using this simplification, appear to be well fitted by Sh L = 1.76 × 10 −5 × Re 1.506 × Sc 0.5, a correlation from Lamourelle and Sandall [8], given for a turbulent liquid flow in wetted-wall columns. A formula drawn from this hypothesis is proposed for mass transfer prediction in photobioreactors. For different applications, it is suggested that the results obtained for the studied geometry could be used to build mass transfer feedback control systems.

DRYING KINETICS AND MOISTURE TRANSFER PARAMETERS OF HAZELNUT

In this experimental study, drying kinetics, sorption isotherms and mass transfer parameters (mainly the diffusion coefficient and hm) of hazelnut are investigated under various drying air conditions. Experiments were conducted in a lab-scale convective drier under the following drying conditions: temperatures at 25C, 35C, 45C and 55C; velocities at 0.3, 0.6 and 0.9 m/s; relative humidity values at 20%, 40%, 60% and 80%. Initially, sorption isotherms of the dried hazelnut are determined for different temperatures and equilibrium relative humidity values. Then, the drying characteristics of hazelnut are determined for various values of drying air parameters tested. In addition, the mass transfer parameters (i.e., Bi, moisture diffusion coefficient and hm) of hazelnut were evaluated using a correlation. The Bi numbers were in the range 0.4216–1.4806 and moisture diffusion coefficient and hms in the range from 0.7056 × 10−9 to 3.2933 × 10−9 and from 1.2401 × 10−7 to 1.7361 × 10−7 m/s, respectively. PRACTICAL APPLICATIONS Turkey is the largest hazelnut-producing country, providing most of world hazelnut production. Supplying the market with the best product available is always critical. Therefore, ensuring better harvesting and processing conditions of hazelnut attracts a great deal of research interest. To prevent field losses by unfavorable weather conditions, there is a tendency to harvest hazelnuts at moisture contents above safe storage levels. In this regard, drying seems to be necessary.

나란히 수직으로 배열된 두 개의 수평관에서 피치-직경비에 따른 자연대류 열전달 영향

수평으로 놓인 두 개의 원형관(Cylinder)에 대하여 Sc 수를 2,014 8,334, RaD 수를 1.5×10?~4.5×10<SUP>10</SUP>, 두 수평관의 피치-직경비를 1.02 9로 변화시키면서 자연대류 열전달 실험을 수행하였다. 유사성개념을 이용하여, 열전달 실험을 대신하여 황산-황산구리 수용액의 전기도금계를 이용한 물질전달 실험을 수행하였다. 실험결과 하단 수평관의 열전달 계수는 단일 수평관에 대한 상관식과 일치하였다. 층류에서 상단 수평관의 열전달은 이격된 거리가 수평관 지름의 1.5배 이하일 경우 하단 수평관의 열전달계수 보다 낮게 측정되었고, 그 이상에서는 높게 측정되었다. 그러나 난류에서는 두 수평관의 이격된 거리가 1에 가까울 경우에도 상단과 하단의 수평관의 열전달계수가 유사한 것으로 나타났으며, 이격 거리가 멀어지면 상단 수평관의 열전달계수가 하단의 그것보다 높은 것으로 나타났다.

Effect of some solid properties on gas–liquid mass transfer in a bubble column

Abstract The knowledge about the effects of solids on gas–liquid systems and the respective physical mechanisms are not yet totally clarified. In this work, the effect of the solids on the mass transfer characteristics in a bubble column was studied experimentally for the systems air/water/expandable polystyrene (EPS) beads and air/water/glass beads. Volumetric liquid side mass transfer coefficient, k L a, was determined under different solid concentrations (up to 30 vol.%), superficial gas velocities (up to 2.7 mm/s) and mean diameters (1100, 770 and 591 μm for EPS and 9.6 μm for glass beads). The presence of EPS solids affects negatively k L a being this effect more pronounced for the smaller particles. Also, a decrease in k L a occurs when the solid loading increases. Experiments done with large polystyrene particles ( d p ≥ 591 μm) contaminated with very fine EPS particles ( d p ≅ 0.1 μm) indicate that very fine particles play an important role on gas–liquid mass transfer. Mass transfer experiments in a hollow glass spheres three-phase slurry showed a dual effect of solids loading on k L a, contrarily to what happens with the previous particles. These results can be associated with the different surface properties of the particles studied. An empirical correlation for k L a on the experimental variables was developed.

높은 Pr 수의 유체를 사용한 수직 원형관 외부의 자연대류 실험

유사성 원리를 이용하여 매우 높은 Pr 수의 유체를 사용하여 수직 원형관 외부의 자연대류 열전달 현상을 실험적으로 연구하였다. 황산-황산구리 수용액의 전기도금계를 물질전달계로 채택하였으며, 실험은 직경 0.005m~0.035m의 음극을 사용하여 Pr 수 그리고 2,094~4,173 RaH 수 1.4×10?~4×10₁₃에서 열전달계수를 측정하였다. 층류에서 실험한 결과는 King, Jakob와 Linke, McAdams, Bottemanne의 수직원형관 자연대류의 열전달 상관식에 일치하였고 난류에서는 수직평판 난류 자연대류 상관식인 Fouad의 상관식과 일치하였고 Pr 수에 대한 의존성이 나타났다. 실험을 통하여 도출한 층류 상관식은 Nu<SUB>H</SUB>=0.55Ra<SUP>0.25</SUP><SUB>H</SUB>, 난류 상관식은 Nu<SUB>H</SUB>=0.12Ra<SUP>0.28</SUP><SUB>H</SUB>Pr<SUP>0.1</SUP>였다. 층류와 난류사이의 천이는 . Ra<SUB>H</SUB> 수 약 10¹²에서 발생하였다.

Transport Phenomena of Falling Liquid Film Flow on a Plate with Rectangular Holes

Falling liquid film flow is a sort of ubiquitous transport phenomenon occurring in chemical engineering. Fundamental research on the flow and mass transfer behavior of falling liquid film flow on plates with different structures can help engineers to develop more efficient equipment. In this paper, falling liquid film flow on a plate with rectangular holes is investigated with both numerical and experimental methods. Mass transfer experiments show that opening rectangle-shaped narrow holes on a plate can enhance the mass transfer efficiency. Compared to an ordinary plate, the vapor−liquid mass transfer rate on a holed plate can be increased by 10−20%. To analyze the detailed flow and mass transfer behavior, the computational fluid dynamics model (CFD) based on the volume of fluid (VOF) method is developed. In this model, the Marangoni effect induced by mass transfer is considered. The new model was demonstrated to give more satisfactory results than the previous model.

Hydrodynamic study and optimization strategy for the surfactant recovery from aqueous solutions

Foam fractionation for recovery of cetyl pyridinium chloride (CPC) from aqueous medium was studied. The effect of process parameters such as air flow rate, foam height, feed concentration, pH, and time was investigated to optimize the process. The maximum recovery of CPC obtained was 97.71% to 94.18% with an enrichment ratio of 3 and 1.21 for 8 CMC to 20 CMC. The average bubble size of the foam in the fractionation column was estimated by the photographic technique from which interfacial area was determined. Effect of surfactants on the theoretical liquid side mass transfer coefficient ( k L) was also investigated which is based on the determination of the diffusivity coefficient of surfactant on the surface of the liquid and was found to be 7.52 × 10 − 3 m/s whereas the experimental liquid side mass transfer coefficient was determined from the local volumetric mass transfer coefficient ( k La) and was found to be 7.01 × 10 − 3 m/s for the feed concentration of 20 CMC.

Electrocatalytic reduction of nitrite on a polycrystalline rhodium electrode

This paper addresses the mechanism of the electrochemical reduction of HNO 2 and NO 2 - on polycrystalline rhodium. Intermediates and/or reaction products were detected by means of various (combined) techniques: rotating ring-disk voltammetry (for NH 2OH detection), online electrochemical mass spectrometry (for volatile products) and transfer experiments (for NO ads). In acidic media, HNO 2 depletion due to homogeneous-phase reactions generates dissolved NO: the latter species can be adsorbed at Rh and is reduced to N 2O when 0.3 < E < 0.5 V (vs. RHE), while HNO 2 is reduced in a diffusion-limited wave to mainly NH 3 at potentials preceding hydrogen evolution. In alkaline media, the predominant product for the reduction of NO 2 - when E < 0.2 V is still NH 3, which can poison the electrode via dehydrogenation to NH x ,ads species. For more positive potentials, reduction still occurs via NO ads and stops at NH 2OH for E > 0.3 V. The behavior of Rh is compared to Pt and explained in terms of general properties of these metals. A mechanistic scheme including NO, HNO 2 and NO 2 - is discussed.