Phase Mass Transfer Coefficient Research Articles

Mass transfer coefficient for PZ + CO2 + H2O system in a packed column

The gas-phase mass transfer coefficient is one of the significant parameter for the determination of mass transfer in absorption columns. A novel correlation was obtained for the calculation of the gas phase mass transfer coefficient in the current research study based on the theoretical investigation and experimental data. Buckingham pi-theorem was utilized to develop an overall dimensionless correlation. The correlation was derived based on the experimental data conducted at the operating conditions’ range of temperature 40–100 °C, CO2 partial pressure of 18-66 kPa, and piperazine (PZ) concentration of 2-8 M. The correlation was validated using the experimental data with an acceptable error of 7.47%. The results showed that the gas-phase mass transfer coefficient was increased by enhancing the amount of holdup and Schmidt number (Sc) at different temperatures and PZ concentrations. Furthermore, by comparing the Sc number with holdup, it was observed that a higher temperature resulted in a higher hold-up amount in the gas-phase of the absorption column.

Mass transfer performance and correlation for CO2 absorption into aqueous 3-diethylaminopropylamine solution in a hollow fiber membrane contactor

3-Diethylaminopropylamine (DEAPA), a diamine with high reaction rate and large absorption capacity, was investigated in this work to evaluate its CO2 absorption mass transfer performance in a hollow fiber membrane contactor in terms of the CO2 absorption flux (JCO2). A series of experiments were conducted at various operation conditions and the effects of several influential parameters on JCO2 were examined and discussed in detail, including the liquid flow rate, the inlet gas flow rate, amine concentration, feed liquid temperature, CO2 partial pressure, lean CO2 loading, and membrane contactor height. Experimental results indicated that lean CO2 loading and membrane contactor height have negative effect on the total mass transfer performance since the value of JCO2 decreases with the increase of these two factors, while the other five parameters exhibit positive effect and their increase lead to the increase of JCO2 values. In addition, a numerical correlation was established to predict the overall gas phase mass transfer coefficient and the CO2 absorption flux, and the average absolute deviation (AAD) is 6.84%.

Determination of fluxes and mass transfer coefficients of polychlorinated biphenyls (PCBs)

This study evaluated a modified water surface sampler (MWSS) in terms of deposition characteristics of atmospheric polychlorinated biphenyls (PCBs). Water was employed as a collection surface for the atmospheric PCBs. The main difference between the MWSS and previous WSSs was its cover which prevented the deposition of particles and minimized wind effects. Therefore, lower particle-phase deposition fluxes were observed. Moreover, preventing wind from the water surface, which was the collection surface, caused lower dissolved phase fluxes and mass transfer coefficients (MTCs). Forty-eight flux and ambient air samples were taken by using an MWSS and a high volume air sampler (HVAS), respectively. The average dissolved phase PCB fluxes were 5.92 ± 5.37 ng/m2-day. Particle phase PCB fluxes were also determined by attaching a filter to the sampler. The particle phase flux ratio was 14% of the total flux, which was much smaller than previously reported ones. This difference was mainly due to the cover layer which minimized the wind effects. 4- CBs and lower chlorinated PCBs were dominant in the samples. Homolog groups obtained from both the MWSS and HVAS were highly correlated. This result indicated that both samplers collected similar atmospheric PCBs. Then, MTCs were calculated for each PCB congener. To calculate the MTCs, dissolved phase PCB fluxes were divided by gas-phase PCB concentration. The average MTC was determined to be 0.25 ± 0.23 cm/s which was smaller than the previously reported MTCs. This result illustrated that the MWSS configuration allowed us to determine the minimum MTCs and gas transfers to the water.

Determination of Mass Transfer Coefficients for Adsorption of Pb and Cd Onto Coir Pith and Statistical Analysis

Adsorption of Pb and Cd ions onto coir pith from single solute aqueous solutions was studied. Experimental data on variation of solute concentration in the solution with time were fitted to exponential kinetic model and model parameters were determined. New parameter, concentration decay constant, was introduced to comprehend the adsorption rate. Novel method was introduced to determine the liquid film mass transfer coefficient (kL) accurately using the exponential kinetic model equation. Liquid film mass transfer coefficient and Overall liquid phase mass transfer coefficient were calculated and the proposed method overcomes the errors due to approximation of initial rate of change of solute concentration and assumption of linear isotherm parameters. Statistical analysis of mass transfer coefficients showed that for all the parameters tested the variation of the parameters are significant with initial solution concentration for Pb.

Intensification of CO₂ capture by monoethanolamine solution containing TiO2 nanoparticles in a rotating packed bed

This study investigates the mass transfer intensification in the absorption of carbon dioxide (CO₂) into a monoethanolamine (MEA) solution enhanced by TiO2 nanoparticles in a typical rotating packed bed (RPB). The overall volumetric gas phase mass transfer coefficients (KGa) were investigated in a counter-current RPB with blade packings. The effects of TiO2 and MEA concentrations, rotational speed, initial concentration of CO₂, gas and liquid flow rates on KGa were specified. The rotational speed had positive effects on KGa. It is deduced that TiO2 nanoparticles led to enhanced CO₂ capture efficiency of over 26.9 % and enhancement in KGa from 7.5%–96.1% for MEA based TiO2 suspension in comparison with MEA solution without nanoparticles. Therefore, TiO2 nanoparticles can augment the mass transfer coefficient and intensify the CO₂ absorption, even in a high-efficiency equipment like a high gravity RPB.

Mathematical modeling of CO2 membrane absorption system using ionic liquid solutions

This research presents a 2D mathematical modeling based on finite difference method (FDM) for absorption of CO2 into aqueous solution of ionic liquids ([bmim][BF4] and [bmim][PF6]) by means of hydrophobic polypropylene hollow fiber membrane contactor (HFMC). Governing equations with their corresponding boundary conditions were solved and the results were validated against reported experimental data and excellent agreement was found. This study has provided an opportunity to investigate the effects of various ionic liquids with different concentrations as well as liquid and gas flow rate on CO2 absorption system in membrane contactors. The results demonstrated that molar flux of carbon dioxide for 25 wt% and 50 wt% solution of [bmim][PF6] is 1.29 and 1.98 times that of pure water, respectively. Also [bmim][BF4] has a weaker performance than [bmim][PF6] due to lower carbon dioxide solubility, and the addition of 50 wt% of it to the pure water has increased the absorption rate by 32 %. Overall and liquid phase mass transfer coefficient has decreased in ionic liquid solutions. Reynolds number in tubes has been decreased by increasing of ionic liquid mass fraction and also a sharp decrease in the Reynolds number can be observed in the ionic liquids mass fractions greater than 60 wt%.

Deep CO2 removal using high pressure membrane contactors with low liquid-to-gas ratio

Membrane contactor is a technology that intensifies conventional absorption column. However, liquid-to-gas ratios (L/G) of membrane contactor in existing reports are much higher compared to CO2 absorption column, which results in higher solvent circulation rate and higher consumption in heating energy. This makes the technology less attractive for deep CO2 removal. Direct reduction of liquid flow rate was not effective in lowering down L/G. Experimental results showed that 50% reduction in liquid flow rate could reduce L/G by 25%, but the reduction in CO2 flux (33%) was higher due to decrease in liquid phase mass transfer coefficient which was dependent on liquid velocity. An alternative method to reduce L/G through membrane module length increase was proven, where L/G was reduced 70% with only 16% flux reduction. The flux reduction was only observed when L/G dropped below 0.80L/mol and it was due to depletion of unreacted amine for CO2 absorption. The lowest L/G value obtained in this study was 36% lower than the conventional absorption column in liquefied natural gas (LNG) process, showing that membrane contactor technology is not only energy-viable and more compact for deep CO2 removal, but it also offers energy saving advantage.

Selection of suitable model for the supercritical fluid extraction of carrot seed oil: A parametric study

To investigate suitable model for supercritical fluid extraction of carrot seed oil, different mathematical models are selected from literature and solved using COMSOL Multiphysics software. Operating parameters such as pressure, temperature, solvent flow rate, and addition of co-solvent are varied in ranges as 200–400 bar, 50–70 °C, 5–15 g/min, and 0–10 wt%, respectively. Solvent and solid phase mass transfer coefficients, easily accessible oil content and equilibrium constant are considered as tuning parameters to fit the model with experimental data. Oil yield is increased with pressure (400 bar) and temperature (70 °C) whereas, its value is highest at the solvent flow rate of 10 g/min, and co-solvent of 5 wt%. Thus, these values of parameters are considered as optimum points.

Kinetics of CO2 Absorption in Novel Tertiary N-Methyl-4-Piperidinol Solvent

In the present work, the reaction kinetics of CO2 absorption into aqueous solutions of novel N-methyl-4-piperidinol (MPDL) was experimentally determined in a stirred cell reactor over a MPDL concentration range of 0.5-2.0 M and a temperature range of 303-333 K. Based on the pseudo-first order assumption, a drop of pressure technique was used to extract the reaction rate constant, in terms of overall reaction rate constant (kov) and second-order reaction rate constant (k2,MPDL), from the experimental absorption data. Additionally, the physical properties and mass transfer data (i.e., density, viscosity, Henry’s constant, and liquid phase mass transfer coefficient) of aqueous MPDL solutions were experimentally measured and comprehensively discussed. In the present work, the experimental k2,MPDL is firstly introduced and can be expressed as: k2,MPDL=1.66×107Exp-3903.6T. The results also show that the CO2 absorption kinetics of MPDL can be ranked as: MEA > DEA > AMP > MPDL > MDEA. Even though novel MPDL has faster kinetics than conventional MDEA, it possesses too slow absorption kinetics to be used as a single solvent. Thus, it should be promoted with a very reactive amine to improve the overall CO2 absorption performance.

Experimental study of the surfactants effects on gas phase mass transfer coefficients in gas condensate reservoirs

Surfactant flooding in gas-condensate reservoirs, shown to be an effective treatment method to remediate condensate blockage in near well bore regions, have been the focus of several studies in the recent decades. However, the effect of these chemicals on the gas phase mass transfer coefficients has not been yet addressed though they have to be incorporated in non-equilibrium compositional simulators to imitate the reservoir behavior reliably. Besides, any knowledge of the overall effect of the surfactants on these coefficients can shed light on the side effects of the surfactant flooding on mass transfer phenomenon and evaluate its suitability as a treatment strategy.In this study, separate empirical correlations were developed for methane and isobutane representing light and intermediate components respectively in the absence and the presence of surfactants at the temperature of 40 °C. In all the developed correlations for both components in the presence of surfactants, while spreading coefficient has a positive exponent, equilibrium adsorption constant possesses a negative exponent. This implies that surfactants with a larger former parameter and a smaller latter parameter like SDS have more opportunity to enhance the volumetric mass transfer coefficient. The results also confirm the positive effect of pore gas velocity on gas phase mass transfer coefficients even in low gas flow rates. Similarly, this effect has already been reported in NAPL (Non Aqueous Phase Liquid) volatilization related studies. Effective diffusion coefficient, condensate saturation, mean grain size, component type, surfactant type and residual water saturation were also shown to affect these mass transfer coefficients. In addition, it has been shown that surfactants which are conventionally believed to reduce volumetric mass transfer coefficients in gas-liquid systems like bubble columns, improve gas phase mass transfer coefficients in gas condensate reservoirs. This improvement is considered a drawback for the cited technique.

Evaluation of superficially porous particle based zwitterionic chiral ion exchangers against fully porous particle benchmarks for enantioselective ultra-high performance liquid chromatography

Zwitterionic chiral ion-exchange selectors (ZWIX) obtained by conjugation of quinine and 2-aminocyclohexanesulfonic acid via a carbamate bond were immobilized on three different silica particle types, viz. 120 Å 3 μm fully porous particles (FPP), 200 Å 3 μm FPP and 160 Å 2.7 μm superficially porous particles (SPP). Selector densities were determined by elemental analysis and the porosities of packed columns measured by inverse size exclusion chromatography with polystyrene standards. Liquid chromatographic tests with a set of chiral zwitterionic, acidic and basic analytes showed that the surface chemistry was successfully transferred to the distinct particle morphologies. The chromatographic performance of the three columns was evaluated by acquiring van Deemter curves. The results showed that the column packed with the SPP particles gives the best performance and kinetic plots further demonstrated that they represent the most favorable compromise in terms of speed, efficiency and pressure drop. Sub-minute separations could be accomplished at much lower pressure drop on the core-shell column, e.g. 2-amino-2-phenylbutyric acid was baseline separated in less than 15 s on a 5 cm long column. The Maxwell effective medium theory with second order approximation was applied to calculate effective diffusion in the mesoporous zones of SPP and FPP, which allowed eventually to deconvolute the individual peak dispersion contributions (ha, hb, hc,m, hc,s, hc,ads). The efficiency gain of the 160 Å SPP column compared to the 120 Å FPP (benchmark) column was mainly due to lower eddies (ha), smaller c-term accounting for slow adsorption-desorption kinetics in enantioselective chromatography (hc,ads), and also due to lower stationary mass transfer resistance (hc,s). Enhanced effective diffusion (Deff) in the SPP column contributed to a lower longitudinal diffusion (hb). In contrast, the mobile phase mass transfer coefficient was similar in the two columns leading to comparable hc,m contributions. This study discloses some options for improvement of the efficiency of ZWIX-type chiral columns such as replacing narrow pore (120 Å) by wide pore (200 Å) particles, substituting FPP by SPP and reducing the selector density on the surface.

Evaluation of the adsorption kinetics of brilliant green dye onto a montmorillonite/alginate composite beads by the shrinking core model

Montmorillonite/alginate composite beads have been studied for adsorption of brilliant green dye in batch experiments. The geometry and features of this clay/polymer composite, in combination with the strong color of the dye, were very useful to apply and test in a simple way the shrinking core model (SCM). This model is very popular for describing adsorption in porous systems, but not in clay/polymer composite beads. The SCM describes the adsorption as a diffusion process of the adsorbate through a spherical shell. The great advantage of using the clay and the dye is that they allow observing with the naked eye or through digital photographs the progress of the front of adsorption (penetration radius) as the reaction takes place. This was never informed in the literature. The experimental changes in penetration radius and dye concentration with time were compared with SCM predictions at different initial concentrations of brilliant green. There was an excellent agreement between theory and experiments, and thus the kinetics of the process could be thoroughly evaluated. The estimated values of the parameters liquid phase mass transfer coefficient and effective diffusion coefficient in the adsorbent are kf > 0.00008 m s−1 and Dp = 5 × 10−10 m2 s−1 respectively.

Mass Transfer Performance and Empirical Correlations of CO2 Absorption from CO2-Rich Gas Stream in a Random Packed Column

CO2 chemical absorption from the gas streams featured with high CO2 concentration into diethanolamine (DEA), potassium glycinate (PG) and potassium L-argininate (PA) was investigated in a random packed column. Effects of main operation parameters including absorbent concentration, solvent flow rate, solvent temperature, the initial CO2 loading, gas flow rate and CO2 partial pressure on CO2 mass transfer performance were experimented according to the overall volumetric gas phase mass transfer coefficient (KGae) . Based on the experimental data, the empirical correlations for easily predicting the KGae value were proposed for all the three solvents, and most of the calculated KGae values are in agreement with the experimental KGae values with an average absolute deviation less than 8%. PA can obtain the highest KGae value than PG and DEA. According to the empirical correlations of KGae, the most significant influence factor to KGae is the solvent temperature for PG, the solvent flow rate for PA and the active absorbent concentration for DEA, respectively.

Modelling of CO2 absorption in a rotating packed bed using an Eulerian porous media approach

The rotating packed bed (RPB) is a promising reactor for CO2 capture with liquid amine because of its high mass transfer rate and energy and space savings. The CFD simulations of RPBs generally use the volume of fluid (VOF) method, but this method is prohibitively expensive for 3D simulations, in particular for large-scale reactors. The Eulerian method is a promising and effective method; however, there are still several difficulties, such as the settings for the porous media models in the gas-liquid counter-current flow and the interfacial area between the gas and liquid. To overcome these difficulties in the Eulerian method, this paper uses a new porous media model, a novel liquid generation-elimination model for numerically investigating the gas-liquid counter-current flow in RPBs and a new interfacial area model derived from the VOF simulation. These new models, incorporating the two-film reaction-enhancement mass transfer model, have successfully simulated the CO2 capture process with monoethanolamine (MEA) solutions in a RPB under both low (30 wt%) and high (90 wt%) concentration conditions. The results show that the overall gas phase mass transfer coefficient (KGa) increases with increasing the rotation speeds and the liquid to gas mass flow rate (L/G ratio). The simulations were validated by the experimental data and the results were analysed and discussed.

Study on Macro Kinetics of the Desulfurization Processes of Heteropoly Compounds in Ionic Liquids and Aqueous Solutions

Ionic liquids and heteropoly compounds have been found to be effective systems for H2S removal due to their unique properties. This study, which investigated the absorption kinetics of these new systems, continues our earlier research. Specifically, the macro kinetic characteristics of the H2S absorption for three systems, viz., a [Bmim]3PMo12O40/BmimCl solution, an aqueous solution of peroxo phosphomolybdic acid and an aqueous solution of CuH2PMo11VO40, were determined using a gas-liquid reaction cell. The gas and liquid phase mass transfer coefficients were measured, and the activation energy was calculated. The H2S absorption for the [Bmim]3PMo12O40/BmimCl solution can be expressed as a macro kinetic equation: NH2S = 6.6 × 10–2∙[exp(–1064/T)]∙CH2S1.120∙C[Bmim]3PMo12O400.099. For the aqueous solutions of peroxo phosphomolybdic acid and CuH2PMo11VO40, the absorption can be expressed as NH2S = 2.68 × 10–6∙[exp(–790/T)]∙CH2S0.252∙CPHPMo0.131 and NH2S = 1.02 × 10–6∙[exp(607/T)]∙CH2S0.510∙CCuH2PMo11VO400.431, respectively.

An optimization framework to investigate the CO2 capture performance by MEA: Experimental and statistical studies using Box-Behnken design

The absorption of carbon dioxide gas by monoethanolamine (MEA) in the packed tower is the most common method for the CO2 capture. The present study describes the set-up and operation of a laboratory-scale CO2 capture unit in detail, as the closed cycle of the absorption/desorption process continuously operated at the different operating conditions. The effect of six independent variables was investigated on CO2 absorption in three levels. To analyse the results, Response Surface Box-Benhken design method was applied. The absorption unit was evaluated in terms of absorption percentage (Φ), the overall gas phase mass transfer coefficient (KGaV), and the specific heat duty of the reboiler (η).The results of the analysis indicated that the MEA concentration in the solvent had the most significance, whereas the input solvent temperature had the least effect upon the overall gas phase mass transfer coefficient.The response surface optimization was also carried out to determine the optimal operating conditions to maximize KGaV and minimize η. The results demonstrated that at an inlet solvent temperature of 45 °C, solvent flow rate of 1.25 L/min, gas flow rate of 100 L/min, reboiler heat load 1.4 kW, MEA concentration 30 wt.%, and the CO2 concentration of 15 vol.%, η was at the minimum value of 3.88 MJ/kg CO2, while KGaV was at the maximum value of 4.59 kmol/m3.h.kPa.

Experimental study of gas phase mass transfer coefficients in gas condensate reservoirs

Gas condensate reservoirs as a proportion of worldwide gas reservoirs experiencing retrograde condensation throughout their production period have been consistently attracting research interests in recent decades. However, their compositional simulators usually consider local equilibrium assumption and neglect the non-equilibrium effect represented by gas phase mass transfer coefficients. Since no independent research has yet targeted mass transfer coefficients in gas condensate reservoirs, in this study, a series of flow tests were carried out using a novel experimental setup to address the issue. Correspondingly, separate empirical correlations were developed for methane and isobutane representing light and intermediate components respectively at two temperatures, thus two condensate saturation ranges. The results confirm the positive effect of pore gas velocity on gas phase mass transfer coefficients reported in NAPL volatilization related studies even in low gas flow rates. Also temperature, effective diffusion coefficient, condensate saturation, mean grain size and component types were shown to affect these coefficients.

Mass transfer performance for CO2 absorption into aqueous blended DMEA/MEA solution with optimized molar ratio in a hollow fiber membrane contactor

Combination N,N-dimethylethanolamine(DMEA) and monoethanolamine (MEA) may represent a potential absorbent for CO2 capture due to the high absorption rate, high cyclic CO2 capacity and low energy requirement for solvent regeneration. Both the absorption and regeneration performances for 2 kmol/m3 DMEA/MEA with molar ratios of 2.0:0.0, 1.5:0.5, 1.0:1.0, 0.5:1.5, and 0.0:2.0 were estimated in terms of the absorption rate, regeneration rate and cyclic CO2 capacity using an improved rapid screening method. The experimental results showed that the highest cyclic CO2 capacities (i.e. low energy requirement) for the cyclic reaction time of 30 min and 60 min were obtained both by 1.0 M DMEA + 1.0 M MEA solution, indicating the synergistic effects existing in CO2 absorption into DMEA/MEA solution. Additionally, the mass transfer performance of CO2 absorption into 1.0 M DMEA + 1.0 M MEA solution was investigated in a hollow fiber membrane contactor. The effects of key operational parameters such as liquid velocity, inlet gas flow rate, CO2 partial pressure, feed temperature range, CO2 lean loading, amine concentration and membrane contactor height on the CO2 flux and overall gas phase mass transfer coefficient were investigated. Furthermore, a developed correlation was successfully applied for the prediction of overall gas phase mass transfer coefficient (KG) for CO2 absorption into DMEA/MEA solution, with an average absolute relative deviation (AARD) of 8.31%. Thus, a potential absorbent (i.e. DMEA/MEA) for CO2 capture was proposed in this work.

Development and Application of the TUM-WelChem Cell Model for Prediction of Liquid Distribution in Random Packed Columns

Liquid maldistribution is, next to the prediction of interfacial phase area and mass transfer coefficients, one of the bigger uncertainties in random packed column design. In a joint project, “Cell Model for Packed Column and Liquid Distributor Design” supported by the Bavarian Research Foundation, liquid maldistribution experiments were conducted in three packed columns with diameters of 0.4, 1.2 and 2.0 m at Technical University of Munich (TUM), RVT Process Equipment GmbH and Linde AG. Experiments covered varying experimental and operating parameters – gas/liquid system, type of packing, packing height, type of liquid distributor, liquid load, and gas load. An evaluation of the acquired database provided insight into influencing factors on liquid distribution (Hanusch et al., 2017). In 2007, Wild and Engel first presented their WelChem Cell Model. The original model predicted liquid distribution in random packing from cell layer to cell layer based on directional dispersion coefficients, deduced from virtual 3D irrigation simulations with a CAD model of one random packing element (Wild and Engel, 2007). Further development at TUM included implementation of the influencing factors liquid load and gas load, considering local loading effects and increasing liquid dispersion. Wall effects were refined by distinction of packing elements and voids at the column wall. Liquid distribution profiles predicted with the TUM-WelChem Cell Model are in good agreement with experimental data.WelChem GmbH implemented the TUM-WelChem Cell Model in their column design software TrayHeart, thus making the research results directly accessible for TrayHeart users. Application of the TUM-WelChem Cell Model ranges from prediction of maldistribution in random packed columns, through liquid distributor design, considering interactions with random packing, to process simulation, considering maldistribution in parallel column models (Schultes, 2000).

Desorption of isobutyl acetate into air as a low-cost alternative system for the measurement of liquid phase mass transfer coefficients

CITATION: Lamprecht, J. H. & Burger, A. J. 2018. Desorption of isobutyl acetate into air as a low-cost alternative system for the measurement of liquid phase mass transfer coefficients. Chemical Engineering Transactions, 69:712, doi:10.3303/CET1869002.