Liquid-phase Mass Transfer Coefficient Research Articles

Updated Review on the Available Methods for Measurement and Prediction of the Mass Transfer Coefficients in Bubble Columns

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.

Carbon dioxide capture in sodium carbonate solution: Mass transfer kinetics and DTAC surfactant enhancement mechanism

Sodium carbonate solvent absorbent has been widely studied for CO2 reduction to deal with global warming because of its green, low cost, and non-corrosive advantages. However, in the application of sodium carbonate as an absorbent for CO2 capture, there is no unified cognition of the mass transfer process, which leads to the lack of guidance for the industrial large-scale process. Moreover, the mechanism of mass transfer enhancement of surfactants, which can effectively improve the mass transfer performance, has not been effectively explored in the literature. Based on this, this paper firstly adopts the molecular dynamics method to analyze the solution characteristics after surfactant addition and optimize the surfactant. Subsequently, a classical dissolved oxygen test method was used to measure the gas-liquid mass transfer coefficient for CO2 absorption into sodium carbonate solution. And based on this mass transfer coefficient measurement method, the mass transfer process of sodium carbonate solution with surfactant was analyzed. The results showed that the sodium carbonate solution with 5 wt% concentration and 10 wt% concentration at 30 °C did not satisfy the pseudo first-order fast chemical reaction kinetics assumption. To improve CO2 absorption mass transfer rate, dodecyl trimethyl ammonium chloride (DTAC) surfactant was introduced, which was improved by 119 % compared with non-enhanced solvent at 5 wt% concentration solution, and the assumption of pseudo first order fast chemical reaction was satisfied. After the introduction of surfactant, the barrier effect decreased the liquid phase mass transfer coefficient, but the Marangoni effect happened in the 5 wt% concentration of sodium carbonate solution, which enhanced the liquid-phase mass-transfer coefficient. This finding reveals the mechanism of mass transfer promotion of sodium carbonate by the surfactant DTAC, which is of great engineering significance for the application in the field of decarbonization after the introduction of surfactant.

An additive approach toward determination of liquid-phase mass transfer coefficients in sandwich packings

An additive approach toward determination of liquid-phase mass transfer coefficients in sandwich packings

Analysis of effective area and mass transfer in a structure packing column using machine learning and response surface methodology

The study examined mass transfer coefficients in a structured CO2 absorption column using machine learning (ML) and response surface methodology (RSM). Three correlations for the fractional effective area (af), gas phase mass transfer coefficient (kG), and liquid phase mass transfer coefficient (kL) were derived with coefficient of determination (R2) values of 0.9717, 0.9907 and 0.9323, respectively. To develop these correlations, four characteristics of structured packings, including packing surface area (ap), packing corrugation angle (θ), packing channel base (B), and packing crimp height (h), were used. ML used five models, represented as random forest (RF), radial basis function neural network (RBF), multilayer perceptron (MLP), XGB Regressor, and Extra Trees Regressor (ETR), with the best models being radial basis function neural network (RBF) for af (R2 = 0.9813, MSE = 0.00088), RBF for kG (R2 = 0.9933, MSE = 0.00056), and multilayer perceptron (MLP) for kL (R2 = 0.9871, MSE = 0.00089). The channel base had the most impact on af and kL, while crimp height affected kG the most. Although the RSM method produced adequate equations for each output variable with good predictability, the ML method provides superior modeling capabilities.

CO2 desorption and mass transfer characteristic study in micropacked bed reactors

The chemical desorption method with amine-based solvent have been widely applied in CO2 capture and storage (CCS) industrial. However, there is still exist mass transfer limitation and difficult to achieve packing/catalyst immobilization in conventional reactors for CO2 desorption process. In this work, micropacked bed reactors (μPBRs) with glass beads are adopted to investigate CO2 desorption performance. Effects of absorbent type, temperature, initial concentration of absorbent, liquid superficial velocity, initial loading of absorbent, particle size, and N2 superficial velocity on the desorption efficiency and desorption rate are discussed. The desorption efficiency of μPBR is 36 ∼ 81 % based on the MDEA absorbent. The value of desorption rate in μPBR is from 0.38 to 3.37 mmol/min, which is bigger than microchannel reactor. Liquid phase mass transfer coefficient of μPBR is 0.06 ∼ 1.38 s−1 for CO2 desorption process, which is 1–3 orders higher than that of packed column. Then, an empirical correlation of mass transfer coefficient is developed in μPBR. μPBR has a high mass transfer rate with an advantage of fixed packing/catalyst compared with other CO2 desorption equipment.

Performance and reaction kinetics of NO absorption by Fe(II)EDTA in a multistage zeolite absorption column-H2-MBfR system

Efficient NOX complexation absorption is a key to biological flue gas denitrification. In this study, the influencing factors, efficiency, and kinetic parameters of Fe(II)EDTA absorption of NO in a multistage zeolite absorption column were evaluated. The response surface methodology (RSM) was used to determine the ideal absorption conditions. Based on these results, a combined process of a multistage zeolite absorption column and a hydrogen-based membrane biofilm reactor (H2-MBfR) was built to verify the efficiency of denitrification. The optimal conditions for achieving maximum efficiency in the absorption of NO by Fe(II)EDTA were obtained as pH of 6.5, Fe(II)/EDTA molar ratio of 1:1.1, and temperature of 30 ℃. The kinetic parameters, including liquid phase mass transfer coefficient (KNO,L) and gas phase mass transfer coefficient (KNO,G), all increased with temperature, while the NO interfacial-area concentration (aNO) exhibited the opposite trend. The reaction for Fe(II)EDTA absorption of NO was a conjugation reaction, and its activation energy was 50.38 kJ·mol-1. More than 90 % of NO in flue gas on 14 days was removed in the combined multistage zeolite absorption column-H2-MBfR process, which provided a sustainable NO treatment solution without secondary pollutants or CO2 emissions and demonstrated its potential for NO removal in industrial applications.

Investigation of surfactant effect on ozone bubble motion and mass transfer characteristics

The low solubility and low mass transfer efficiency of ozone (O3) in water are important reasons for limiting the application of ozone oxidation technology and advanced ozone oxidation technology. Low-dose surfactants were introduced to affect the behavior of ozone bubbles, influencing the ozone mass transfer efficiency. The motion of ozone bubbles in three different types of surfactant solutions (polyoxyethylene lauryl ether (Brij35), sodium dodecylsulfate (SDS), and cetyltrimethylammonium bromide (CTAB)) was observed. The decrease in surface tension led to a decrease in bubble size, a tendency to spherical shape, an increase in gas content and residence time, a decrease in lateral displacement of a single bubble, and a more stable trajectory. The effect of surfactants on ozone mass transfer was further investigated. The addition of surfactant was found to increase the gas-liquid interface area but decrease the liquid phase mass transfer coefficient, and the extent of the two opposite effects varied for different surfactants. The analysis combined with the removal of pollutant p-Nitrophenol (PNP) showed that the addition of the nonionic surfactant Brij35 and the anionic surfactant SDS inhibited ozone mass transfer, while low concentrations of the cationic surfactant CTAB enhanced ozone mass transfer. When the CTAB concentration was 3 mg L−1, the ozone volume mass transfer coefficient reached a maximum of 0.2902 min−1.

Mathematical Modelling and CFD Simulation for Oxygen Removal in a Multi-Function Gas-Liquid Contactor

This paper presents and compares the mathematical models and computational fluid dynamics (CFD) models for degassing of oxygen from water in a laboratory-scale multi-function gas-liquid contactor under various operating conditions. The optimum correlations of the overall volumetric liquid-phase mass transfer coefficient (kLa) are determined by the mathematical models of specific contactors. Both the continuous-reactor model and semi-batch model can evaluate the degassing efficiency with relative errors within ±13%. Similarly, CFD models agree with experimental data with relative errors of ±10% or less. Overall, the mathematical models are deemed easy to use in engineering practice to assist the selection of efficient contactors and determine their optimum operation parameters. The CFD models have a wider applicability, and directly provide the local mass transfer details, making it appropriate for harsh industrial scenarios where empirical correlations for important quantities are unavailable. Combining these two types of models can effectively guide the design, optimization, and operation of the high-throughput degassing system.

Modeling of NO mass transfer characteristics absorbed in sodium persulfate solution with a bubble reactor

ABSTRACT: Sodium persulfate solution is considered as an effective wet denitrification medium, however, it is unclear that the influence of the operating conditions on mass transfer characteristics parameters during the absorption of NO with sodium persulfate solution. To determine the key mass transfer characteristics parameters, the specific interfacial area and the mass transfer coefficients were determined based on the Danckwerts method during CO2 absorption in a bubble column. and were calculated by correlations between the mass transfer coefficients of NO and CO2. Results showed that the specific interfacial area increased 77.64 m−1, the liquid phase mass transfer coefficient increased 2.49 × 10−4 m·s−1, and the gas phase mass transfer coefficient increased 0.71 × 10−5 mol·Pa−1·s−1·m−2 with superficial gas velocity increasing from 0.6 to 1.4 L·min−1. With the temperature of sodium persulfate solution increasing from 293 to 333 K, the specific interfacial area decreased 42.66 m−1, while the liquid phase mass transfer coefficient and the gas phase mass transfer coefficient increased 3.89 × 10−4 m·s−1 and 1.18 × 10−5 mol·Pa−1·s−1·m−2, respectively. The experiments results determined the correlations of and with the temperature of the absorption phase and the superficial velocity of the gas. It can serve as a guide to the enhancement of the sodium persulfate wet denitrification process.

Effects of channel wall wettability on gas–liquid dynamics mass transfer under Taylor flow in a serpentine microchannel

The wall wettability of microchannels plays an important role in the gas–liquid mass transfer dynamics under Taylor flow. In this study, we regulated the contact angle of the wall surface through surface chemical grafting polymerization under controlled experimental conditions. The dynamic changes of CO2 bubbles flowing along the microchannel were captured by a high-speed video camera mounted on a stereo microscope, whilst a unit cell model was employed to theoretically investigate the gas–liquid mass transfer dynamics. We quantitatively characterized the effects of wall wettability, specifically the contact angle, on the formation mechanism of gas bubbles and mass transfer process experimentally. The results revealed that the gas bubble velocity, the overall volumetric liquid phase mass transfer coefficients (kLa), and the specific interfacial area (a) all increased with the increase of the contact angle. Conversely, gas bubble length and leakage flow decreased. Furthermore, we proposed a new modified model to predict the gas–liquid two-phase mass transfer performance, based on van Baten's and Yao's models. Our proposed model was observed to agree reasonably well with experimental observations.

Absorption of Tar Content in Producer Gas using Used Cooking Oil in a Packed-bed Column

<span lang="EN-US">The tar content in producer gas may cause crusting on the engine if it is utilized as a fuel gas, thus it needs to be removed. This study aims to determine the liquid phase mass transfer coefficient in process of removing tar from producer gas in a packed-bed contactor column. This process is carried out continuously using used-cooking oil as absorbent. This was carried out by contacting the producer gas as a product of cacao pod-husk gasification at temperature range of 491-940<sup>o</sup>C at a certain counter-current flow rate with used-cooking oil in a column with a Raschig ring packing bed. The study used packed-bed materials with specific surface areas of 29.3927 m<sup>2</sup>/m<sup>3</sup>, 49.7532 m<sup>2</sup>/m<sup>3</sup>, 95.4113 m<sup>2</sup>/m<sup>3</sup>, 96.8182 m<sup>2</sup>/m<sup>3</sup>, 101.6840 m<sup>2</sup>/m<sup>3</sup>, and 105.0128 m<sup>2</sup>/m<sup>3</sup>, and with the linear velocity of used-cooking oil ranging from 0.0229 m/s to 0.0827 m/s. A mass transfer coefficient mathematical model has been constructed based on the research results. The model applies to the ranges (As.dt), (D<sub>L</sub>/dt.v<sub>L</sub>), and (µ<sub>L</sub> / ρ<sub>L</sub>.v<sub>L</sub>.dt) from 2.2397 to 8.0020, 2.26.10-10 to 1.72.10-9, and 0.0331 to 0.3102, respectively, with an average error of 9.33%. The average tar removed was 87%</span>

Chemical engineering kinetics of p-xylene chlorination in a gas-liquid agitated reactor

This study aims at determining both the rate constants of chlorination of p-xylene with molecular chlorine and FeCl3 as a catalyst at 70 °C and 90 °C and the related chemical engineering parameters to be used in the design of an effective chemical reactor.This was accomplished by a novel approach of constructing a linear mathematical function for a gas–liquid semi-batch agitated reactor correlating all engaged physical and chemical factors. Collecting values for all the necessary parameters for the application of the function, or in the absence of them calculating them, and exploiting the intercept and slope of the linear function became possible the apparent and the catalytic reaction rate constants to be calculated. It was found that the calculated values were of the same order of magnitude as values obtained by other researchers.The parameters needed to be calculated were Henry’s constant, the diffusion coefficient of the solute A (chlorine) to the solvent B (p = xylene), DAB, and the mean liquid phase mass transfer coefficient, kl. Other parameters of chemical engineering interest were also determined, namely, the interface per unit volume of liquid, a, the thickness of the liquid film, δl, and the Hatta number, MH.Evaluating the Hatta number estimated, it was concluded that the chlorination of p-xylene with molecular chlorine is very slow at both temperatures investigated, and almost no reaction occurs in the film compared to the bulk of the liquid. Thus, to increase the overall reaction rate, a large volume of liquid is needed while the increase of agitation intensity is of no value here.Combining the rate constant ratios obtained recently for the four consecutive second-order irreversible chlorinations of p-xylene with molecular chlorine with FeCl3 as a catalyst at 70 °C and under identical conditions it was possible to determine the values of all rate constants up to the fourth chlorinated product.

Unified Approach for Prediction of the Volumetric Mass Transfer Coefficients in a Homogeneous and Heterogeneous Bubble Column Based on the Non-Corrected Penetration Theory: Case Studies

A critical review on the improvement of penetration theory is presented in this work. The volumetric liquid-phase mass transfer coefficients kLa in seven different liquids (1-butanol, 2-propanol, anilin, decalin, nitrobenzene, tetralin, and ethylene glycol) aerated with air in a small bubble column (BC) (inner diameter: 0.095 m) were measured at ambient conditions and further analyzed. It was found that the kLa values can be predicted satisfactorily on the basis of the classical Higbie’s penetration model. The gas–liquid contact time was defined as the ratio of the Sauter-mean bubble diameter to bubble rise velocity. Moreover, the experimental kLa values were well predicted, not only in the homogeneous regime, but also in the transition and heterogeneous regimes. This is a new finding, since to date, it was considered that the penetration theory needs a correction factor for a successful application to any liquid, even in the homogeneous regime. The predictions of the mass transfer coefficients kLa in the above-mentioned seven liquids imply that the mean bubble diameters are always ellipsoidal or spherical, which is the key condition for the applicability (without a correction) of penetration theory. In the presented (in this work) model-based kLa predictions, the Sauter-mean bubble diameters were estimated by means of the reliable correlation of Wilkinson et al., which always predicts a gradually decreasing bubble size at higher gas velocities.

Evolution behaviour of interfacial structure between quicklime and converter slag: slag-forming route based on FetO component

ABSTRACT In order to enable the steel companies to achieve carbon peaks and carbon neutrality, the f-CaO content in steel slag should be reduced. For this reason, this study investigates the interface reaction evolution of the quicklime and different slag in the ‘iron’ slagging route of the CaO-FetO-SiO2-MgO system at the converter steelmaking temperature. The microstructure of the reaction interface was observed by an electron microscope. The results showed that the interface reaction formed CaO-FeO solid solution, (Ca, Mg) olivine phase, and 2CaO·SiO2. The change in thickness of CaO-FeO and (Ca, Mg) olivine shows a clear trend with the change in slag components.Therefore, the dissolution mechanism of quicklime in the slag was discussed, and the liquid phase mass transfer coefficients in different slags were obtained. The results will provide a theoretical basis for the faster dissolution of lime in slag and reduction of f-CaO content in slag.

Vibration-induced enhanced mass transfer within membrane contactors for efficient CO2 capture

Membrane gas-solvent contactors are a hybrid separation technology that has significant potential to replace conventional solvent columns in a range of industrial applications. One industry application where the technology has shown promise is for carbon dioxide capture. The performance of membrane gas-solvent contactors is limited by the mass transfer resistance on chemical species traversing from the gas to the solvent phases, with the boundary layer of the solvent phase representing the rate limiting stage. Here, enhancements to mass transfer were achieved by applying vibration to the membrane module. An increase in the overall liquid phase mass transfer coefficient (KL) was associated with both the frequency and amplitude of the vibration. A vibration amplitude displacement between 0 and 16% resulted in overall mass transfer being 10 to 21% higher than the non-vibrational case. Similarly, a vibrational frequency of 2.3 Hz corresponded to mass transfer enhancement of up to 20% higher than the non-vibrational case. This represents a significant improvement in the membrane contactor’s mass transfer performance for carbon dioxide separation. To quantify vibration improvement in membrane contactors, a mass transfer correlation for the solvent phase of the membrane contactor system was established, based on a vibrational dimensionless number. This correlation enabled the performance of membrane contactors under vibration conditions to be model and provide insight into the vibrational conditions that will enhance mass transfer. Subsequently, an analysis of the power requirement for module vibration was undertaken to demonstrate the most effective applications of vibrations.

Influence of Sparger Type on Mass Transfer in a Pilot-Scale Internal Loop Airlift Reactor

In a pilot-scale internal loop airlift reactor with a height of 5.5 m and a main column diameter of 0.484 m, the influence of three gas sparger structures (ladder distributor, tri-nozzle sparger and perforated plate) on the volumetric mass transfer coefficient kLa was investigated. It was found that the perforated plate produces the highest gas holdup difference and circulating liquid velocity between the riser and the downcomer. The perforated plate provides the most efficient mass transfer due to the more uniform gas distribution and higher circulating liquid velocity, followed by the ladder distributor and tri-nozzle spargers. Compared with the tri-nozzle sparger, the perforated plate increases the value of kLa by up to 16% at a superficial velocity of 0.15 m/s. Interestingly, the analysis of the liquid-phase mass transfer coefficient kL and specific area a with respect to gas velocity shows that the mass transfer rate is primarily controlled by a. By comparing the predictions of different mass transfer models, the slip velocity model based on penetration theory yields a satisfactory agreement with the experimental results within ±15% error. Meanwhile, empirical correlations regarding gas holdup and kLa were developed and were found to have good consistency with experimental values.

Process Modeling of CO2 Absorption with Monoethanolamine Aqueous Solutions Using Rotating Packed Beds

A first-principle process simulation model is presented for the chemical absorption of carbon dioxide (CO2) with monoethanolamine (MEA) aqueous solutions using rotating packed beds (RPB). Built on a proven rate-based packed bed absorber model, the RPB model rigorously simulates the phase and chemical equilibria at the vapor–liquid interface, the heat and mass transfer across the gas and liquid films, the fast reactions between MEA and CO2 in the liquid film, and the RPB hydraulics. Estimation of the rate of transfer of mass across the liquid film is central to accurate simulation of the CO2 absorption process with MEA aqueous solutions. We show that the literature lab-scale RPB data for CO2 removal efficiency can be satisfactorily correlated by introducing a correction factor for the effective packing surface area predicted by the Onda correlation. Given the validated RPB model, we further show that, among the gas-phase mass transfer coefficient, the liquid-phase mass transfer coefficient, and the reaction rate constant for the reaction between amine and CO2, the reaction rate constant is the controlling step with the greatest potential to enhance the CO2 absorption performance in RPB.

CFD modeling of different mass transfer coefficients on hydrogen sulfide emission in a flux chamber.

Hydrogen sulfide (H2S) is commonly used as an indicator for odorous gas emission monitoring in wastewater treatment plants. The H2S emission estimations can be performed using algebraic mathematical models or carrying out measurements at the source, with the dynamic flux chamber, for example. This work brings together these two methodologies in a computational fluid dynamics analysis. Fifteen liquid-phase mass transfer coefficient ([Formula: see text]) models were initially evaluated in establishing, at the liquid-gas interface in a flux chamber, an H2S emission flux based on the friction velocity field from three different inlet flows (2, 5, and 10 L min-1). Ten [Formula: see text] models were fully simulated, and the numerical results were compared with available experimental data. The higher the inlet flow, the higher the friction velocity at the interface, and the higher the H2S emission. The H2S emission was also strongly dependent on the constant coefficients of the existing [Formula: see text] models. Small variability on those coefficients generates considerable changes in emissions at the interface. Few and different models performed well in describing the available concentration data at the outlet sampling probe for different inlet flows, which shows there is still no single model capable of representing all simulated friction velocity ranges (0.005 to 0.017ms-1).

Effect of microbubbles on preparation of precipitated silica by carbonization: physical-chemical structure, kinetic parameters and mass transfer characteristics

Silica is widely applied in industrial fields due to its good properties, while preparation of high-quality SiO2 by carbonization is an important way to utilize CO2. The experiment was carried out in a microbubble/bubbling experimental device, with its mass transfer kinetics of carbonization analyzed according to the pH-t curves. Under microbubble conditions, with the increasing temperature of 20∼60°C, the specific surface area, oil absorption value and particle size of silica varies at 336.80∼231.29 m2/g, 1.12∼1.81 ml/g and 16.49∼14.60 μm, respectively, which is similar as that with bubble. Aging at 20∼90 °C, they involve in the range of 35.82∼128.76 m2/g, 1.59∼2.44 ml/g and 23.15∼14.46 μm. With total concentration of solution >0.5 M, the concentration increases, the specific surface area and particle size of microbubbles are larger than those of the bubbling silica, and oil absorption value increases at 1.81∼2.44 ml/g. The kinetic analysis shows that it is more consistent with theoretical value, which can be judged as the secondary-reaction process. The microbubbles increase the CO2 utilization rate and volumetric mass transfer coefficient of carbonization by 2-4 times, while the liquid-phase mass transfer coefficient decreases. It indicates that microbubble mass transfer is achieved by significantly increasing the specific surface area.

Hydrodynamics and Mass Transfer in a Concentric Internal Jet-Loop Airlift Bioreactor Equipped with a Deflector

The gas–liquid hydrodynamics and mass transfer were studied in a concentric tube internal jet-loop airlift reactor with a conical bottom. Comparing with a standard design, the gas separator was equipped with an adjustable deflector placed above the riser. The effect of riser superficial gas velocity uSGR on the total gas holdup εGT, homogenization time tH, and overall volumetric liquid-phase mass transfer coefficient kLa was investigated in a laboratory bioreactor, of 300 mm in inner diameter, in a two-phase air–water system and three-phase air–water–PVC–particle system with the volumetric solid fraction of 1% for various deflector clearances. The airlift was operated in the range of riser superficial gas velocity from 0.011 to 0.045 m/s. For the gas–liquid system, when reducing the deflector clearance, the total gas holdup decreased, the homogenization time increased twice compared to the highest deflector clearance tested, and the overall volumetric mass transfer coefficient slightly increased by 10–17%. The presence of a solid phase shortened the homogenization time, especially for lower uSGR and deflector clearance, and reduced the mass transfer coefficient by 15–35%. Compared to the gas–liquid system, the noticeable effect of deflector clearance was found for the kLa coefficient, which was found approx. 20–29% higher for the lowest tested deflector clearance.