Showing papers on "Mass transfer coefficient published in 2015"
TL;DR: In this article, the authors reviewed different ionic liquid-based solvents for CO 2 absorption and the most effective parameters on mass transfer phenomena between CO 2 and solvent, including the physiochemical properties of ionic liquids, Henry's constant and mass transfer coefficient and their correlations, and various factors for effective CO2 absorption.
Abstract: Concern has increased about climate change caused by carbon dioxide (CO 2 ) emissions through human activities in recent years. The Intergovernmental Panel on Climate Change predicts a 1.9°C rise in temperature by the year 2100, and this means a reduction in CO 2 is vital for human beings and all other life on earth. There- fore, there is an urgent need for the development of CO 2 separation processes to mitigate this potential problem. Post- combustion power plants can employ various types of separation technology. Among them, chemical absorp- tion using aqueous amine is more developed and more reliable. The conventional solvents used in the chemical absorption process together with the use of absorbents, ionic liquid, alkanolamines and their blended aqueous solutions are reviewed in this work. Different ionic liquid- based solvents for CO 2 absorption and the most effective parameters on mass transfer phenomena between CO 2 and solvent are reviewed. The major concerns for this tech- nology, including the physiochemical properties of ionic liquid-based solvents, Henry's constant and mass transfer coefficient and their correlations, and various factors for effective CO 2 absorption, are addressed.
118 citations
TL;DR: In this paper, the authors compared the performance of two ultrafiltration membranes for removal of humic acids using two different set-ups: circular flow and stirred dead end flow.
88 citations
TL;DR: In this paper, an internally-cooled dehumidifier made of thermally conductive plastic was designed, and it achieved superior corrosion resistance Its performance was investigated both experimentally and through simulation.
87 citations
TL;DR: In this paper, the authors investigated the operational and economic aspects of air stripping for ammonia recovery from source separated human urine and found that increasing pH enhanced ammonia removal efficiency by promoting the free ammonia fraction in the solution.
Abstract: BACKGROUND
The air stripping process has been widely used to treat wastewater to prevent undesirable substances from impairing the quality of water sources. This study aimed to investigate the operational and economic aspects of air stripping for ammonia recovery from source separated human urine.
RESULTS
The typical two-film model fails to explain the influence of pH on ammonia recovery. For that reason, modifications to the two-film model were applied to involve ammonia dissociation during mass transfer. It was found that increasing pH enhanced ammonia removal efficiency by promoting the free ammonia fraction in the solution. In addition, high air flow rate and temperature accelerated the stripping process due to the increase in mass transfer coefficient. From the economic point of view, unit operating cost was determined for 80% ammonia recovery. Results indicated that increasing air flow rate and temperature could reduce unit operating cost, whereas high pH could induce high unit operating cost due to the increase in chemical input.
CONCLUSION
The modified two-film model can precisely estimate the critical values for an economic, efficient stripping process. However, a test-bedding study is required to validate the experimental findings. © 2014 Society of Chemical Industry
87 citations
TL;DR: Improved mass transfer coefficients, mixing efficiency and energy efficiency of the novel microbubble generation method could offer significant savings to the water treatment plants as well as reduction in the carbon footprint.
86 citations
TL;DR: In this article, the authors focused on the absorption of CO 2 using aqueous diethanolamine solvent in microreactors having hydraulic diameters ranging from 254 to 762μm.
80 citations
TL;DR: The designed PBR, a cost-effective reactor, is promising for the mass cultivation of microalgae and the volumetric power is analyzed with a classic model, and then the aeration is optimized.
78 citations
TL;DR: In this paper, the CO2 absorption performance of aqueous 1-dimethylamino-2-propanol (1DMA2P) was comprehensively investigated in terms of CO2 equilibrium solubility, CO2 rate, CO 2 absorption heat, and mass transfer efficiency.
77 citations
TL;DR: This work presents a robust, high-power and highly efficient USMR by directly coupling a microreactor plate with a Langevin-type transducer to intensify gas-liquid mass transfer of slug flow in a microfluidic channel.
Abstract: The combination of ultrasound and microreactor is an emerging and promising area, but the report of designing high-power ultrasonic microreactor (USMR) is still limited. This work presents a robust, high-power and highly efficient USMR by directly coupling a microreactor plate with a Langevin-type transducer. The USMR is designed as a longitudinal half wavelength resonator, for which the antinode plane of the highest sound intensity is located at the microreactor. According to one dimension design theory, numerical simulation and impedance analysis, a USMR with a maximum power of 100 W and a resonance frequency of 20 kHz was built. The strong and uniform sound field in the USMR was then applied to intensify gas-liquid mass transfer of slug flow in a microfluidic channel. Non-inertial cavitation with multiple surface wave oscillation was excited on the slug bubbles, enhancing the overall mass transfer coefficient by 3.3-5.7 times.
76 citations
TL;DR: In this article, the mass transfer characteristics of passion fruit peels were evaluated using the analytical model proposed by Dincer and Dost, and the results showed a reasonably good agreement between the values predicted from the correlation and the experimental observations.
72 citations
TL;DR: Single cell microfluidics are used to obtain new insights into microbial behavior at changing operating conditions and novel fed-batch techniques are applied to assimilate the cultivation conditions between screening and production scale.
TL;DR: In this paper, a simplified method is presented for estimating the film mass transfer and the surface diffusion coefficients from batch adsorption kinetic data without solving partial differential equations, which shows a reasonable agreement with the experimental kinetics.
TL;DR: In this paper, the effects of viscous dissipation and second order slip on MHD boundary layer flow of an incompressible, electrically conducting water-based nanofluid over a stretching sheet were investigated.
Abstract: In this study, we investigate the effects of viscous dissipation and second order slip on MHD boundary layer flow of an incompressible, electrically conducting water-based nanofluid over a stretching sheet. The governing momentum boundary layer and thermal boundary layer equations with the boundary conditions are transformed into a system of nonlinear ordinary differential equations which are then solved numerically by using the Runge–Kutta–Fehlberg method. The effects of the flow parameters on the velocity, temperature, nanoparticle concentration, shearing stress, rate of heat transfer, and rate of mass transfer are analyzed, and illustrations are provided by the inclusion of figures and tables for various values of different parameters. We determine that the skin friction increases in magnitude, whereas the rate of heat transfer and rate of mass transfer decrease in magnitude as the strength of the magnetic field increases. In addition, the magnitudes of skin friction, rate of heat transfer, and rate of mass transfer decrease as the melting heat transfer and first-order slip parameter both increase.
TL;DR: In this article, the performance of CO2 absorption into a hybrid solvent such as monoethanolamine (MEA) in methanol (MeOH) was experimentally investigated in a lab-scale absorber packed with Sulzer DX-type structured packing.
TL;DR: In this article, the performance of microchannels and conventional stage-wise extractors for liquid-liquid extraction by using a standard phase system was compared on the basis of percentage extraction, overall volumetric mass transfer coefficient and specific extraction rate.
Abstract: The objective of the study is to compare the performance of microchannels and conventional stage-wise extractors for liquid–liquid extraction by using a standard phase system. Three different microchannels – a T-junction microchannel, a serpentine microchannel and a split-and-recombine microchannel – have been used in the experiments. Conventional extractors are represented by a mixer-settler and an annular centrifugal extractor. The phase system used in the experiments is water (succinic acid) n-butanol system which is one of the standard phase systems recommended by the European Federation of Chemical Engineering. The extractors have been compared on the basis of percentage extraction, overall volumetric mass transfer coefficient and specific extraction rate. When compared on the basis of percentage extraction, performance of the microchannels and the conventional stage-wise extractors is found to be almost similar. Maximum values of overall volumetric mass transfer coefficient and specific extraction rates are found to be more in the microchannels than in the conventional stage-wise extractors. The ratio of maximum overall volumetric mass transfer coefficient in microchannels and conventional stage-wise extractors is found to range from 1 to 8.1. The ratio of maximum specific extraction rate in microchannels and conventional stage-wise extractors is found to range between 2.3 and 9.7.
TL;DR: Hydrogen production by Clostridium butyricum was investigated in batch Biochemical Hydrogen Potential tests and in a 2.5 L anaerobic sequenced batch reactor under different operating conditions regarding liquid-to-gas mass transfer to show that hydrogen production was improved by a higher liquid- to-gas hydrogen transfer resulting in a lower dissolved hydrogen concentration in the culture medium and therefore in a higher bacterial inhibition.
TL;DR: In this article, experimental measurements of the volumetric liquid mass transfer and bubble size distribution in a vertically oriented semi-batch gas-liquid Taylor-Couette vortex reactor with radius ratio η = ǫ/r/rǫ −075 and aspect ratio Γ −= h/(ro −− �) −40 were performed, and the results were presented for axial and azimuthal Reynolds number ranges of Rea −119 −143 and ReΘ −= 0 −35 −×104, respectively.
TL;DR: In this article, effective diffusivity is substituted for molecular diffusivities in the Grober equation for prediction of dispersed phase overall mass transfer coefficients for a 117 diameter Kuhni extraction column using axial diffusion model for two different liquid-liquid systems.
Abstract: Mass transfer performance has been presented for a 117 diameter Kuhni extraction column using axial diffusion model for two different liquid–liquid systems. The influence of operating variables including the rotor speed as well as the continuous and dispersed phase flowrates on the volumetric overall mass transfer coefficients is investigated. Effective diffusivity is substituted for molecular diffusivity in the Grober equation for prediction of dispersed phase overall mass transfer coefficients. The enhancement factor is determined experimentally and there from an empirical correlation is derived for prediction of enhancement factor in terms of Reynolds number and dispersed phase holdup. The prediction of overall mass transfer coefficients from the presented equation is in good agreement with experimental data.
TL;DR: In this article, the magnetic field has been used for absorption of CO2 in a packed column in the presence of magnetic field and adding nanoparticles into the solvent enhances mass transfer characteristics.
Abstract: Magnetic nanofluids have been used for absorption of CO2 in a packed column in the presence of magnetic field. Adding nanoparticles into the solvent enhances mass transfer characteristics. The optimum concentrations of Fe3O4/water and NiO/water nanofluids are 0.005, and 0.01 % respectively, and the maximum enhancement of mass transfer rate in comparison with pure water is 12 and 9.5 % respectively. The magnetic field showed positive effect on the CO2 absorption performance.
TL;DR: In this article, the authors investigated the effects of dimensionless filament spacing of feed spacer on flow and concentration patterns on membrane surfaces and found that spacers with higher SCE values would lead to higher mass transport of solute away from the membrane walls with moderate energy losses.
Abstract: Cross-flow membrane operations often experience material build-up on membrane surfaces leading to maintenance issues. Although several studies addressed the flow distributions and concentration patterns during membrane operations, the prediction of fouling propensities of top and bottom membranes are non-existent. Present study investigates the effects of dimensionless filament spacing of feed spacer on flow and concentration patterns on membrane surfaces. Comparisons of spacers in terms of a novel concept ‘Spacer Configuration Efficacy’, SCE ( Sh / Pn ) revealed that spacers with higher SCE values would lead to higher mass transport of the solute away from the membrane walls with moderate energy losses. Among the 16 spacer arrangements studied, spacer with filament spacing of 4 was found to be the optimal ( Re h up to 200) with moderate pressure drop and higher values of mass transfer coefficient for the two membrane walls, further mass transfer coefficient values for the two membrane surfaces were found to be equal which leads to equal and lower fouling tendencies of the membrane walls.
TL;DR: In this paper, an investigation of local gas side overall mass transfer coefficient (KG) of the membrane gas absorption process determined from CO2 concentration gradients was presented, which was compared with simulation results of non-wetted and partially wetted modes of operation from a plug flow and rated based model to study the effects of various operating parameters on the partial wetting of a membrane and its process performance.
TL;DR: In this article, magnetically excited nanoparticles were used as an inert material in a Y-type micromixer for enhancing liquid-liquid mass transfer between two immiscible fluids.
Abstract: In this work, magnetically excited nanoparticles were used as an inert material in a Y-type micromixer for enhancing liquid–liquid mass transfer between two immiscible fluids Water–succinic acid– n -butanol was chosen for mass transport analyzing Magnetic nanoparticles (MNPs) were dissolved in n-butanol as organic phase, and the MNPs were remotely excited by subjecting them into a static magnetic field The magnetic field intensity was 1500 G, accompanied with different MNPs concentrations within 0002–001 (w/v) The fluid flow patterns and quantitative analysis of mixing in two layouts, with and without MNPs, at various aqueous-to-organic volumetric flow rate ratios were compared Three different volumetric flow rate ratios of two phases were analyzed to determine the effect of aqueous and organic flow rates on the overall mass transfer coefficient ( K La ) and extraction efficiency ( E ) Moreover, the effect of the magnet position including next to and underneath the mixing channel was investigated Results show that the case, which the magnet placed next to the mixing channel, was more effective for liquid–liquid mass transfer rather than other layout At optimum concentration, 36–69% enhancement in K La and 32–41% in E were obtained for layout with MNPs compared with plain one
TL;DR: In this paper, three thin film composite membrane contactors are trialed for the absorption of CO2 into monoethanolamine (MEA) solvent, and it was found that after 1 ¼h of operation, the PTMSP and PIM-1 membranes provided the highest overall mass transfer coefficient, while Teflon AF1600 performance was lower.
07 Jan 2015-Metallurgical and Materials Transactions B-process Metallurgy and Materials Processing Science
TL;DR: In this paper, a mathematical model for predicting the composition evolutions of the slag and the metal phases as the blow proceeds in an LD converter is developed, where the process dynamics are modeled by dividing the LD convertor into three separate continuous stirred tank reactors.
Abstract: Slag–metal emulsion plays an important role in the oxidation kinetics of metalloids in oxygen steelmaking. The importance of droplet generation rate, droplet size, and its residence time in the slag–metal emulsion on the overall reaction kinetics has become evident in recent times. Residence times of the droplets are strongly dependent on the decarburization rate, the CO bubbles giving a buoyant force to the droplets. The present work aims at developing a mathematical model for predicting the composition evolutions of the slag and the metal phases as the blow proceeds in an LD converter. The process dynamics are modeled by dividing the LD convertor into three separate continuous stirred tank reactors. Oxidation reactions are assumed to be primarily taking place at the interface between the slag and the metal phases in the emulsion. Among the different mass transfer and reaction steps controlling the kinetics, the mass transfer of FeO in the slag phase and that of the metalloids within the metal droplet are assumed to be rate-controlling. For a Fe-C-X (X = Mn, Si etc.) droplet, simultaneous removal of elements have been modeled by Gibbs’ free energy minimization at the slag–metal interface. Effects of droplet size, mass transfer coefficient, and initial carbon content on the mean residence time of metal droplets in the slag–metal emulsion have also been identified. Mixing in the metal phase is simulated in terms of metal exchange rate and the reactor weight ratio between the upper and the lower parts of the bath.
TL;DR: In this paper, the instantaneous mass transfer coefficients of a zigzagging CO 2 bubble were calculated from the bubble-volume shrinkage with ms time-resolution using two high-speed cameras and mirrors.
TL;DR: In this article, the external liquid-solid mass transfer properties of horizontal gas-liquid and liquid-liquid (L-L) "slurry Taylor" flow are investigated. But no influence of slug length was detected, and the particle size appeared likewise to have no effect for particles larger than 50 μm.
Abstract: In this work, the external liquid–solid mass transfer properties of horizontal gas–liquid (G–L) and liquid–liquid (L–L) “slurry Taylor” flow are investigated. The catalytic particles (dP = 40–200 μm) are transported in a cylindrical capillary (dT = 1.6–1.65 mm) in the form of a suspension in the aqueous liquid phase and kept in motion due to the recirculation patterns present in the liquid slugs. Ion exchange particles are used to follow the neutralization of dilute sodium hydroxide solutions in order to estimate the mass transfer coefficients. The influence of two phase velocity, particle size, slug length, and inert physical properties was investigated. No influence of slug length on the liquid–solid mass transfer coefficient was detected, and the particle size appears likewise to have no effect for particles larger than 50 μm. The mass transfer coefficient depends mainly on overall flow velocity and an adequate circulation of solid particles in the liquid phase. For toluene–water L–L Taylor flow, parti...
TL;DR: In this paper, the effect of different surfactants (n -octyltrimethylammonium bromide (OTABr), sodium dodecyl benzene sulfonate (SDBS) and Tween 80) with different critical micelle concentrations (CMC) on the CO 2 absorption into aqueous solutions in a bubble column is analyzed.
TL;DR: Investigation of mechanism confirms that the increasing amount of ultrasonic fields yields the increase in cavitation activity that improves the mass transfer and decomposition of ozone, resulting in acceleration of OH initiation, which determines the degradation of nitrobenzene in aqueous solution.
TL;DR: In this paper, the effects of operating temperature, NaOH concentration and flow rates on percentage of free fatty acids (FFA) removal, oil loss, soap entrainment and overall mass transfer coefficient were evaluated.
Abstract: Performance of chemical deacidification of crude palm oil (CPO) using aqueous NaOH solution in a polysulfone hollow fiber ultrafiltration membrane was investigated. The effects of operating temperature, NaOH concentration and flow rates on percentage of free fatty acids (FFA) removal, oil loss, soap entrainment and overall mass transfer coefficient were evaluated. Overall mass transfer coefficients, soap content in oil and neutral oil loss all increased when the temperature was increased from 60 to 70°C due to an increase of the FFA distribution value. A minimum 0.25 N of NaOH or a NaOH to FFA molar ratio of about 7.62 was required to facilitate the expected extraction efficiency. The increased oil flowrate slightly enhanced the solute transport kinetics, while the aqueous phase flowrate did not significantly influence deacidification efficiency or mass transfer coefficient. About 97% of FFA removal was achieved within 4 hours. The maximum oil loss observed was 11% and the highest soap content in the oil without separation step was 3150 ppm. The values of the overall mass transfer coefficient varied from 2.97×10 -7 to 7.71×10 -7 m/s. These results show the potential of using the non dispersive membrane contacting process for chemical deacidification of CPO as well as other vegetable oils.
TL;DR: In this paper, the authors proposed a new method for the determination of the mass diffusion coefficient in hygroscopic materials, which allows several samples to be measured simultaneously, simply by multiplexing the RH sensors.
Abstract: This work proposes a new method for the determination of the mass diffusion coefficient in hygroscopic materials. The experiment consisted of submitting one face of the sample to a variation in time of the relative humidity (RH) and measuring the RH on its back face. The imposed RH and temperature were measured during the test and served as boundary conditions in a comprehensive computational code to solve heat and mass transfer in porous media. This model uses a physical engine embedded in the inverse procedure to determine the mass diffusion coefficient. Compared with classical methods, this new method has several advantages: It allows several samples to be measured simultaneously, simply by multiplexing the RH sensors.Accurate values can be obtained even when starting and ending out of equilibrium, which allows the characterization time to be drastically reduced.The external mass transfer coefficient has a negligible effect on the identified value.Nonstandard Fickian behaviors can be detected by the di...