Determination Of Mass Transfer Coefficients Research Articles

Urban air PCDD/Fs: Dry deposition fluxes and mass transfer coefficients determined using a water surface sampler

Polychlorinated dibenzo-p-dioxins (PCDDs) and polychlorinated dibenzofurans (PCDFs) cause significant environmental concerns. Atmospheric PCDD/Fs permeate water bodies and other ecosystems through wet and dry deposition. In an urban site, dry deposition flux samples of gaseous phase PCDD/Fs were collected by a water surface sampler (WSS) operated between June 2022 and June 2023. There is a conspicuous absence of literature on the direct measurement of dry deposition flux levels in the gaseous phase of PCDD/Fs. In the study, PCDD/Fs in the gas phase reaching the WSS dissolved in the water according to Henry's Law. The PCDD/Fs in the water were transferred to an XAD-2 resin column, sorbing the dissolved PCDD/Fs. The average monthly gas phase dry deposition flux was 34.07 ± 9.35 pg/m2-day (7.35 ± 2.16 pg I-TEQ/m2-day). The highest flux was measured in March (49.53 pg/m2-day), and the lowest was in August (18.64 pg/m2-day). These values indicated the direct flux from air to water. The atmospheric concentration of the gas-phase ranged from 68.38 to 126.88 fg/m3 (13.22–25.01 fg I-TEQ/m3). Dry deposition fluxes and concentrations of atmospheric PCDD/Fs were bigger in the colder months than in the warmer months. This was probably due to a significant increase in residential heating during the colder months, decreased photochemical reactions, and lower mixing heights. Regarding congeners in the dry deposition flux and concentration values in I-TEQ units, 2,3,7,8-TCDD compound predominated with the proportions of 31.61 ± 7.76% and 29.09 ± 12.34%, respectively. Concurrently measured dry deposition flux (Fg) and ambient air concentration (Cg) of PCDD/Fs were considered in the determination of mass transfer coefficient (MTC = Fg/Cg) calculation for each PCDD/F congener. The average MTC for targeted 17 PCDD/Fs was 0.45 ± 0.15 cm/s, and it fluctuated between 0.89 ± 0.30 cm/s for 2,3,7,8-TCDF and 0.2 ± 0.16 cm/s for OCDD.

A roadmap to estimating agricultural ammonia volatilization over Europe using satellite observations and simulation data

Abstract. Ammonia (NH3) is one of the most important gases emitted from agricultural practices. It affects air quality and the overall climate and is in turn influenced by long-term climate trends as well as by short-term fluctuations in local and regional meteorology. Previous studies have established the capability of the Infrared Atmospheric Sounding Interferometer (IASI) series of instruments, aboard the Metop satellites, to measure ammonia from space since 2007. In this study, we explore the interactions between atmospheric ammonia, land and meteorological variability, and long-term climate trends in Europe. We investigate the emission potential (Γsoil) of ammonia from the soil, which describes the soil–atmosphere ammonia exchange. Γsoil is generally calculated in-field or in laboratory experiments; here, and for the first time, we investigate a method which assesses it remotely using satellite data, reanalysis data products, and model simulations. We focus on ammonia emission potential in March 2011, which marks the start of growing season in Europe. Our results show that Γsoil ranges from 2 × 103 to 9.5 × 104 (dimensionless) in fertilized cropland, such as in the North European Plain, and is of the order of 10–102 in a non-fertilized soil (e.g., forest and grassland). These results agree with in-field measurements from the literature, suggesting that our method can be used in other seasons and regions in the world. However, some improvements are needed in the determination of mass transfer coefficient k (m s−1), which is a crucial parameter to derive Γsoil. Using a climate model, we estimate the expected increase in ammonia columns by the end of the century based on the increase in skin temperature (Tskin), under two different climate scenarios. Ammonia columns are projected to increase by up to 50 %, particularly in eastern Europe, under the SSP2-4.5 scenario and might even double (increase of 100 %) under the SSP5-8.5 scenario. The increase in skin temperature is responsible for a formation of new hotspots of ammonia in Belarus, Ukraine, Hungary, Moldova, parts of Romania, and Switzerland.

Expressing variable mass transfer coefficients for gas fermentation in trickle bed reactor

Gasification of lignocellulosic biomass and syngas biomethanation are promising technologies for producing biomethane. Trickle bed reactors (TBR) are efficient for syngas fermentation allowing for higher concentration of microbial cells and high surface area for mass transfer. Optimized scaling up and dimensioning of the reactor is crucial when it comes to industrial applications. The first step towards this goal and the scope of the present study is to develop a model able to simulate the mass transfer of gases to the liquid phase as a function of the operating conditions and reactor geometry. Experiments were performed in a lab scale TBR with co-current flow of syngas and water, representing the growth medium, to determine the volumetric mass transfer coefficient (kLa) of each gas compound and its dependence on the flowrate of syngas and water and reactor structural characteristics. The kLa achieved were in the range of 6.18–13.6 hr−1 for H2, 2.6–5.79 hr−1 for CO and 1.53–3.43 hr−1 for CO2. A dimensionless equation was fitted to the experimental data and a model was developed to predict kLa of a specific gas at various gas and liquid flowrates, and reactor configurations. A kinetic model was also developed to simulate the concentrations of syngas in gas phase and liquid phase by applying the kLa values predicted by the dimensionless correlation. Finally, the model was validated using experimental data obtained by mass transfer coefficient determination in pilot scale TBR with pure argon gas and literature data where the predicted kLa had a coefficient of variance of ± 15% and ± 25% respectively within a realistic range of liquid and gas flowrates.

Determination of mass transfer coefficient of CO2 removal in water-in-oil emulsion

The removal of carbon dioxide is an important process in natural gas purification since its lower down the calorific value of the natural gas. In addition, carbon dioxide also capable of forming corrosion in the pipeline, thus its removal is crucial. Water-in-oil emulsion was proposed in this research since the absorption of carbon dioxide in emulsion would be an effective method to prevent corrosion. However, the absorption capability of the emulsion and the mass transfer coefficient of carbon dioxide during absorption process needs further investigation. The aim of this study is to determine the diffusivity and mass transfer coefficient of carbon dioxide in the emulsion and observed the correlation between mass transfer coefficient and the carbon dioxide absorption values obtained from experiment. In this study, water-in-oil emulsion was prepared by mixing the aqueous phase and organic phase solutions under two different formulation conditions. Firstly, the methyldiethanolamine (MDEA) and 2 amino-2-methyl-1-propanol (AMP) blending was mixed in different alkaline solution; sodium hydroxide (NaOH) solution, potassium hydroxide (KOH) solution and distilled water (H2O) to form aqueous phase solution. Secondly, MDEA was combined with different alkanolamines; dimethylethanolamine (DMEA), diethanolamine (DEA) and triethanolamine (TEA) in KOH solution to form another aqueous phase solution. The synthesized aqueous phase is then mixed with the organic phase consists of kerosene and Span-80 mixtures. Furthermore, viscosity and particle sizes of the emulsions at different emulsion formulations were measured and the diffusivity and mass transfer coefficients of carbon dioxide were calculated. This study showed that, by using suitable emulsion formulation containing MDEA/AMP in KOH solution, the estimated value of diffusivity and mass transfer coefficient of carbon dioxide was 1.0876 × 1010 m2/s and 1.15 × 103 m/s respectively, with viscosity of 261.03 mPa s and particle size of 189.71 nm was achieved. It was found the diffusion coefficient and mass transfer coefficient of carbon dioxide is highly influenced by the characteristics of emulsion such as viscosity and particles sizes.

Critical assessment of gassing-in methods to determine mass transfer coefficient in miniature and microbioreactors with gas-liquid flow

Accurate measurements of mass transfer coefficients are critical for reliable characterization of bioreactors. While standardized methods to measure mass transfer coefficients have been established for simple stirred tank reactors, existing methods to characterize mass transfer coefficients have not yet been standardized for alternative reactor types such as miniaturized and biofiltration reactors, leading to inconsistencies in implementation and confusion about the validity of comparisons across different methodologies, volume scales, or reactor types. This study evaluated the accuracy of two commonly used lab-scale methods for the measurement of mass transfer coefficients in a miniature plug-flow reactor: the Dynamic Gassing-In and the Steady State Gassing-In Methods were evaluated. Results revealed that while both experimental methods can be equally accurate and applicable at small scales, there must be careful consideration of mass transfer and volumes peripheral to the reactor itself. To address these findings, a detailed mathematical model was developed and applied to each experimental method, which enabled accurate calculation of the mass transfer coefficients. This approach can be used to analyze experimental data and determine mass transfer coefficients for many reactor types and at any scale. We also propose best practices for mass transfer methods which will enable more consistency in testing and clarity in comparisons between studies.

Mass/Heat Transfer Analogy Method in the Research on Convective Fluid Flow through a System of Long Square Mini-Channels.

The paper presents the results of experimental investigations of mass transfer processes with the use of the limiting current technique. This experimental work analyzed the not fully developed entrance laminar region. The tested case refers to the convective fluid flow through a system of nine long, square mini-channels that are 2 mm wide and 100 mm long. The method used in the measurements allows one to determine mass transfer coefficients during the electrolyte flow by utilizing electrochemical processes. The received mass transfer coefficients were applied to the analogous heat transfer case. The Chilton–Colburn analogy between mass and heat transfer was applied. The obtained results, in the form of the dependence of Nusselt number within the function of Reynolds and Prandtl numbers, can be a useful formula in the design and analysis of heat transfer processes in mini heat exchangers.

Determining the Mass Transfer Coefficient of the Water Boundary Layer at the Surface of Aquatic Integrative Passive Samplers.

Passive sampling devices (PSDs) offer key benefits for monitoring chemical water quality, but the uptake process of PSDs for hydrophilic compounds still needs to be better understood. Determining mass transfer coefficients of the water boundary layer (kw) during calibration experiments and in situ monitoring would contribute toward achieving this; it allows for combining calibration data obtained at different temperature and hydrodynamic conditions and facilitate the translation of laboratory-derived calibration data to field exposure. This study compared two kw measurement methods applied to extraction disk housings (Chemcatcher), namely, alabaster dissolution and dissipation of performance reference compounds (PRCs) from silicone. Alabaster- and PRC-based kw were measured at four flow velocities (5-40 cm s-1) and two temperatures (11 and 20 °C) in a channel system. Data were compared using a relationship based on Sherwood, Reynolds, and Schmidt numbers. Good agreement was observed between data obtained at both temperatures, and for the two methods. Data were well explained by a model for mass transfer to a flat plate under laminar flow. It was slightly adapted to provide a semi-empirical model accounting for the effects of housing design on hydrodynamics. The use of PRC-spiked silicone to obtain in situ integrative kw for Chemcatcher-type PSDs is also discussed.

Modelo matemático para estimar el coeficiente volumétrico de transferencia de oxígeno en biorreactores usando cálculo conformal

This work proposes a novel mathematical model based on time conformable derivative convective mass transfer equation to calculate the volumetric oxygen transfer coefficient (kLa) in a bioreactor. To validate the novel model, a full mixed-level experimental design was proposed with two factors: agitation speed and dispersed phase. The model employs the conformable derivate order operator (α) and the electrode constant (kp), which changes with electrode use and the operating conditions of the bioreactor. The results show that when the viscosity increases and the agitation decreases, the value α increases, and vice versa. Therefore, α is a parameter that has a physical meaning in the process. The correlation coefficient of the proposed model with the experimental data (R2 > 0.985) is higher than the one obtained with conventional models. The Akaike information criterion determined that the proposed conformal model describes the experimental data by 59%, while the conventional models describe the experimental data by 25% and 15%. There are no reports of similar mathematical models that determine mass transfer coefficients in bioprocesses.

Determination of mass transfer coefficient in flow assisted corrosion of steel in liquid Pb[sbnd]Bi. Rotating cylinder geometry

The aim of this experimental and numerical work is to determine the mass transfer at the wall of a steel cylinder rotating within liquid Lead-Bismuth blend. This is a crucial parameter for the analysis of corrosion tests performed in the CICLAD experimental set-up for the investigation of flow assisted corrosion of steel by liquid metals. As a reliable numerical modelling must rely on experimental validation, and since no direct wall mass transfer measurement is possible in CICLAD, a scaled electrochemical model has been achieved. Modelling the turbulence in this rotating configuration is shown to require the use of a Reynolds-Stress Model. A sensitivity to the Schmidt number is observed in the numerical simulations representing the measured mass transfer in the electrochemical model. Simulations dedicated to liquid PbBi are thus presented in addition to those dedicated to the aqueous solution used in the electrochemical model. Following correlations are proposed for the prediction of Fe mass transfer at the wall of a steel rotating cylinder in liquid Pb-Bi:Sh = 1.9 × 10−1(Re2Sc)0.31 for 2 × 109 < Re2Sc < 5.3 × 1010;Sh = 1.4 × 10−3(Re2Sc)0.51 for 5.3 × 1010 < Re2Sc < 8.5 × 1011;Sh = 1.1 × 10−2(Re2Sc)0.43 for 8.5 × 1011 < Re2Sc < 1013.This mass transfer coefficient has recently been used to get a better understanding of corrosion in PbBi [1].

Interfacial Phenomena and Reaction Kinetics between High Al Molten Steel and CaO-SiO2-Type Flux

To understand the reaction mechanism between high Mn-high Al steel and slag, the reaction experiment of Fe-Mn-Al melts with CaO-SiO2-type flux was carried out in MgO crucible at 1873 K. The evolution of the morphology of interface was inspected firstly, and then the global reaction kinetics was modeled in consideration of the effect of dynamic interfacial phenomena. The results show that in the reaction of Fe-5 mass % Al alloy with high SiO2 or low SiO2 protective slag, the strong chemical affinity between the metal and flux leads to strong spontaneous emulsification and attenuated with the progression of the reaction. Combined with the change of interfacial area caused by emulsification, it is found that the global reaction kinetics can be described satisfactorily by the mass transfer model of Al in liquid steel, and the determined mass transfer coefficient was about k[Al]=4.46×10−5 m/s. However, the emulsification phenomenon in the reaction of Fe-13%Mn-5%Al alloy with low SiO2 slag did not disappear with the reaction, which can be attributed to the decreasing of the interfacial tension with Mn addition and the accumulation of C on the interface. This reaction process can be modeled by assuming the mass transfer of SiO2 in the slag as the rate-controlling step with the estimated transfer coefficient of k(SiO2)=5.12×10−6 m/s.

Method for determination of mass transfer coefficients for dissolution of dense ceramics in liquid slags

This paper presents a numerical method to determine the mass transfer coefficients in the dissolution of dense ceramics in liquid slags. Simulations are based on a typical rotating finger test as the experimental set-up, where a cylindrical sample is immersed in a slag bath and rotated with a constant angular speed. CFD simulations of the flow field are conducted using the volume of fluid method to incorporate both the slag and air phases. Owing to the very large Schmidt number of the arrangement and to avoid using extremely fine meshes, an asymptotic boundary layer approach is employed. This approach allows for the calculation of local, steady-state mass transfer coefficients along the sample in a postprocessing step without resorting to solving the species transport equation within the CFD calculations. The method is verified by comparing the results to those obtained via well-established equations. Resultant mass transfer coefficients are discussed with respect to values obtained from mass transfer equations in literature. The presented approach serves as an effective calculation method for the mass transfer coefficient and offers the opportunity to obtain the inverse calculation of diffusivities in systems where the Schmidt number reaches large values.

Determination of mass transfer coefficient from biogas purification process by mono ethanol amine (MEA)

Biogas is a renewable energy source, which can be produced from organic waste such as palm oil mill effluent (POME), through an anaerobic fermentation process. Biogas requires a purification process to remove the content of hydrogen sulfide (H2S) and carbon dioxide (CO2). The purpose of this study is to calculate the value of mass transfer coefficient in biogas purification process, namely in the process of chemical absorption of H2S and CO2 gases in raw biogas by monoethanolamine (MEA) absorbent. Biogas purification was carried out using a bubble column absorber, where raw biogas was flowed into a column containing a MEA absorber of 0.678 L. The biogas content from the column was analyzed using biogas content measuring device (Biogas 5000 ©). The overall mass transfer coefficient values in gas phase obtained from this study are 0.182–1.027 s−1 for H2S – MEA system, and 0.674–3.993 s−1 for CO2 –MEA system. The overall mass transfer coefficient of CO2 – MEA from this study is greater than that of previous studies.

Determination of mass transfer coefficient in an L-shaped pulsed column with sieve-plate structure: Application of best-fit technique, drop size distribution, and forward mixing model

The mass transfer coefficient in extraction columns is extremely affected by the size of the droplets. Among the available models to describe the extraction columns, only the forward mixing model (FMM) has considered the effect of droplets size on the column performance. In this research, the performance of an L-shaped pulsed sieve-plate column (LPSPC) was studied using the FMM. A real-code using the best-fit technique and PSO algorithm was developed for finding the optimal values of the axial dispersion and overall mass transfer coefficients. The effect of the operating parameters including pulsing velocity, continuous and dispersed phase flow rate on the volumetric overall mass transfer coefficient, the axial dispersion coefficients, and the mass transfer driving force was studied for two standard chemical systems. It was found that the LPSPC has an optimal operation at the pulsing velocity of 0.95 cm/s in each of the horizontal and vertical sections. Moreover, the performance of the column is strongly dependent on the ratio of the inlet velocity of the phases. It is worth noting that, the separation efficiency in the vertical section is slightly (on average 5%) higher than in the horizontal section of the column.

Determination of mass transfer coefficients in high-pressure CO2-H2O flows in microcapillaries using a colorimetric method

This study presents a method for the experimental determination of the local volumetric mass transfer coefficient kLaL in a high-pressure two-phase flow of water (H2O) and carbon dioxide (CO2) in a micro-capillary using a colorimetric method. H2O and CO2 are fed continuously and co-axially injected at high-pressure (10 MPa) and moderate temperature (303 K) into a microcapillary. Under the flow conditions studied, a segmented flow of CO2 in H2O is formed. The CO2 dissolves into the H2O-rich phase, thereby reducing the pH to about 3.3, depending on the pressure and temperature. The pH of the H2O-rich phase is determined over the entire length of the capillary using a pH sensitive indicator coupled with high-speed imaging and analysis. The concentration of CO2 in the water-rich phase is deduced from this pH value using literature experimental data. The CO2 concentration data and the unit-cell model, which has been modified to account for high pressure conditions, have then been used to determine the volumetric mass transfer coefficient, kLaL, of CO2 into the liquid phase along the entire length of the microreactor. The experimentally derived kLaL ​​ranges between 1 and 13 s−1.

Influence of counterdiffusion effects on mass transfer coefficients in stirred tank reactors

Accurate knowledge of volumetric oxygen mass transfer coefficients in multiphase systems is important for successfully designing and efficient operation of process plants. As a result, a large number of papers on the determination of volumetric mass transfer coefficients kLa have been published in the literature. The dynamic degassing method is probably the most common method for determining the volumetric mass transfer coefficient. However, little work is known on the influence of countercurrent diffusion effects, arising from further dissolved components, on the volumetric mass transfer coefficient.For this reason, the effect of countercurrent diffusion is investigated in the present work by using different stripping gases to determine the volumetric oxygen mass transfer coefficient. Furthermore, the effect of counterdiffusion is investigated for both conventional aeration and aeration with microbubbles.The present work shows that the choice of stripping gas has a decisive influence on the determination of the volumetric oxygen mass transfer coefficient. Moreover, it can be shown that this effect is directly proportional to the solubility of the stripping gas in the aqueous phase. Simultaneous measurements of bubble size distributions allow determining mass transfer coefficients kL. A model is developed describing the decrease in the mass transfer coefficient as a function of the solubility of the stripping gas.Furthermore, it can be shown that for the experimental determination of volumetric oxygen mass transfer coefficients, the choice of stripping gas should be adapted to secondary gas types occurring within real processes achieving a better comparability.

Removal of methylene blue from aqueous solution by ozone microbubbles

In this work, ozone microbubbles (OMBs) technique was used to remove methylene blue dye (MB) from water in a semi- batch reactor. The removal efficiency of methylene blue dye were investigated under various reaction conditions such as effect of initial solution pH, ozone generation rate, initial methylene blue dye concentration and determination of mass transfer coefficient. The removal of methylene blue by Ozonation microbubbles were very high at the acidic media and upon increasing ozone generation rate from 0.498 to 0.83 mg s−1, the removal efficiency dramatically increased from 8 to 98%.The overall rate of the oxidation reaction fitted well a second order kinetic model. The results demonstrated that ozone microbubbles were effective in terms of the elimination of methylene blue concentration and its complete mineralization.

Determination of mass transfer coefficients in high-pressure two-phase flows in capillaries using Raman spectroscopy

This study presents a method for the experimental determination of local volumetric mass transfer coefficients kLaL in a high-pressure two-phase flow of water (H2O) and carbon dioxide (CO2) in a micro-capillary using Raman spectroscopy. H2O and CO2 are continuously and co-currently fed at high pressure (8, 9 and 10 MPa) and moderate temperature (303 K) into a fused silica micro-capillary. A segmented two-phase flow is obtained therein and the fraction of CO2 in the water-rich phase is measured in-situ at different points along the capillary using Raman spectroscopy. A modified Henry’s law is used to compute the equilibrium compositions of the water-rich phase at the desired pressure and temperature. A mixture density model is used to convert the fraction of CO2 in the water-rich phase into a CO2 concentration. The volumetric liquid mass transfer coefficient is computed at various axial locations along the capillary, from the contacting zone to the end of the capillary. Experimentally derived kLaL values range between 2.10−3 and 5.10−3 s−1.

Experimental work on decontamination of wastewaters containing organic dye by liquid phase micro extraction method

ABSTRACT Nowadays, the innovative processes for refining industrial dye wastewater are often used to reduce the toxicity of these pollutants due to satisfy the treatment standards. This paper presents a study on the removal of methylene blue (MB) and thymol blue (TB) dyes from contaminated water using a mono-and di-ester mixture(MDEHPA) as the extractant in a Y-Y junction microchannel. Operating parameters such as aqueous solution pH, and extractant and residence time were optimized. The maximum rates of TB and MB extraction were achieved to be 97.9% and 98.4%, respectively. Mass transfer performance is surveyed using overall volumetric mass transfer coefficient determination ().

Numerical simulations and modelling of mass transfer through random assemblies of catalyst particles: From dilute to dense reactive particulate regime

We study mass transfer through random assemblies of fixed spherical catalyst particles experiencing an external convective-diffusive fluid stream. Chemical species are transported through the array and are diffused from fluid to solid phase through particles surface. An internal first order irreversible chemical reaction takes place within the porous catalyst particles. We address the determination of mass transfer coefficient by performing direct numerical simulations with fully internal-external coupling using concentration and flux continuity boundary conditions at the solid-fluid interface. We derive a theoretical prediction of the profiles of cup-mixing concentration, average of mean surface and average of mean volume concentration of the particles along the height of the domain. The model for the dimensionless mass transfer coefficient (‘reactive’ Sherwood number) is accounting for the five dimensionless parameters that control the physics of the system: the Reynolds number Re, the Schmidt number Sc, the Damköhler number Da, the internal-to-external diffusion coefficient ratio γ and the solid volume fraction αs. We use a coupled Sharp Interface/ Discrete Lagrange Multiplier-Fictitious Domain Method (SIM-DLM/FD), thoroughly validated in our previous study (Sulaiman et al., 2019) to test the accuracy of the model over a wide range of dimensionless parameters and solid volume faction (from dilute αs=0.1 to dense regime αs=0.5). We show and discuss the limitations of the proposed model.

Kinetic Study of Reactive SO2 Absorption in a Jet Bubbling Reactor: Experimental Determination of Mass Transfer Coefficients and Absorption Rate

The reactive absorption kinetics for SO2 removal from flue gas was studied by the use of a saturated solution of Ca(OH)2 in a bench-scale jet bubbling reactor (JBR). Gas and liquid sides mass trans...