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Showing papers on "Mass transfer coefficient published in 2013"


Journal ArticleDOI
TL;DR: The present study compared the volumetric mass transfer coefficient (K(tot)A/V(L) of three reactor types; the TBR with 3 mm and 6 mm beads, five different modules of HFRs, and the STR using O2 as the gaseous mass transfer agent.

117 citations


Journal ArticleDOI
TL;DR: In this paper, the effect of flux (lime) addition on the reduction behavior of iron oxide in copper slag by solid carbon at 1773 K (1500 °C) was investigated.
Abstract: We investigated the effect of flux (lime) addition on the reduction behavior of iron oxide in copper slag by solid carbon at 1773 K (1500 °C). In particular, we quantified the recovery of iron by performing typical kinetic analysis and considering slag foaming, which is strongly affected by the thermophysical properties of slags. The iron oxide in the copper slag was consistently reduced by solid carbon over time. In the kinetic analysis, we determined mass transfer coefficients with and without considering slag foaming using a gas holdup factor. The mass transfer of FeO was not significantly changed by CaO addition when slag foaming was ignored, whereas the mass transfer of FeO when slag foaming was considered was at a minimum in the 20 mass pct CaO system. Iron recovery, defined as the ratio of the amount of iron clearly transferred to the base metal ingot to the initial amount of iron in the slag phase before reduction, was maximal (about 90 pct) in the 20 mass pct CaO system. Various types of solid compounds, including Mg2SiO4 and Ca2SiO4, were precipitated in slags during the FeO reduction process, and these compounds strongly affected the reduction kinetics of FeO as well as iron recovery. Iron recovery was the greatest in the 20 mass pct CaO system because no solid compounds formed in this system, resulting in a highly fluid slag. This fluid slag allowed iron droplets to fall rapidly with high terminal velocity to the bottom of the crucible. A linear relationship between the mass transfer coefficient of FeO considering slag foaming and foam stability was obtained, from which we concluded that the mass transfer of FeO in slag was effectively promoted not only by gas evolution due to reduction reactions but also by foamy slag containing solid compounds. However, the reduced iron droplets were finely dispersed in foamy and viscous slags, making actual iron recovery a challenge.

96 citations


Journal ArticleDOI
TL;DR: In this paper, a modified direct contact membrane distillation (MDCMD) with receiving solution in permeate was developed for accelerating ammonia removal from aqueous solution, and the effect of feed pH, temperature, flow rate and concentration on ammonia removal efficiency and the permeate flux in MDCMD process was studied.

92 citations


Journal ArticleDOI
TL;DR: In this article, a VOF-based numerical method for simulating mass transfer across deformable fluid interfaces is presented, which allows for different solubilities of the species in the respective fluid phases, while volume changes due to mass transfer are neglected.

86 citations


Journal ArticleDOI
TL;DR: In this paper, a new modeling approach was developed for prediction of ammonia removal from water by means of porous membranes, which was based on adaptive neurofuzzy interface system (ANFIS).
Abstract: A new modeling approach was developed for prediction of ammonia removal from water by means of porous membranes. The model was based on adaptive neurofuzzy interface system (ANFIS) to simulate ammonia stripping from water by means of hollow-fiber membrane contactors. The predictions aimed to obtain optimum conditions for ammonia stripping using the Taguchi method. The initial concentrations of ammonia, pH of the ammonia solution, velocity of the feed, and the presence of excess ions in the ammonia feed solution were considered as the input properties. On the other hand, mass transfer coefficient was considered as output. The prediction results revealed that the pH of the ammonia feed has a significant effect on the separation of ammonia from water. The results also showed that the prediction of ANFIS model and experimental data match well and that the model can be used for prediction of porous membranes. Furthermore, simulated annealing was also used to determine controllable conditions to find the highest mass transfer coefficient. POLYM. ENG. SCI., 53:1272‐1278, 2013. a 2012 Society of Plastics Engineers

81 citations


Journal ArticleDOI
TL;DR: In this article, the volumetric overall mass transfer coefficient (KGav) for carbon dioxide (CO2) absorption into aqueous diethylenetriamine (DETA) was experimentally determined in an absorption column packed with Sulzer DX-type structured packing over a temperature range of 30-50°C and at atmosphere pressure.

80 citations


Journal ArticleDOI
TL;DR: In this article, a new method of measuring local mass transfer for highly complex geometries is demonstrated, combining gypsum dissolution and X-ray computed tomography (CT).
Abstract: A new method of measuring local mass transfer for highly complex geometries is demonstrated. The method combines gypsum dissolution and X-ray computed tomography (CT). An object coated in gypsum is CT scanned before and after exposure to fluid flow. Digital three-dimensional pre- and post-flow geometries are created using the CT data, and the local dissolution thickness is determined by subtracting the post-flow from the pre-flow object. The method is first demonstrated for cylinders in cross-flow and validated with mass and heat transfer data. The measurements agree with values from correlations reported in the literature when scaled using Reynolds, Sherwood, and Schmidt numbers. The method is then applied to measure local mass transfer for the complex geometry of a 0.75-scale branching scleractinian coral Stylophera pistillata. Local Sherwood numbers vary between nearly zero on the backward facing surfaces of the downstream branches of the coral and nearly 200 at the tips of the branches at the top of the coral. The upstream facing surfaces at radii between 20 and 70 % of the overall radius of the coral experience Sherwood numbers close to 100. The local measurements are integrated to produce a bulk mass transfer coefficient that lies within the range of previous bulk measurements in the literature for similar coral species. With this method, local mass transfer rates can be measured for complex objects in laboratory or natural in situ flow environments. These are geometries for which only bulk measurements were previously possible.

79 citations


Journal ArticleDOI
01 Nov 2013-Fuel
TL;DR: In this paper, the authors studied the kinetics of heterogeneous methanolysis of sunflower oil and used vegetable oil at different temperatures, ranging from 60 to 96°C using CaO·ZnO as catalyst (2.5% on the basis of oil) and methanol to oil molar ratio of 10:1.

75 citations


Journal ArticleDOI
TL;DR: In this article, an alkaline hydrolysis reaction was used as the model reaction to investigate the performance of liquid-liquid slug flow microchannel, and the specific interfacial area was determined through the photographic snapshot method physically by means of measuring the lengths of relevant slugs.
Abstract: An alkaline hydrolysis reaction was used as the model reaction to investigate the performance of liquid–liquid slug flow microchannel. The specific interfacial area was determined through the photographic snapshot method physically by means of measuring the lengths of relevant slugs. The overall volumetric mass transfer coefficients were calculated through the Danckwerts’ model chemically. The influences of various operating conditions on the slug length, the overall volumetric extraction rate and the mass transfer coefficient were investigated quantitatively. A decreasing trend of volumetric mass transfer coefficients along the channel length was found. The linear dependence of the volumetric extraction rate on the volumetric mass transfer coefficient indicates that the overall rate of the process is determined by the mass transfer process. In addition, the volumetric mass transfer coefficients were correlated for different channel lengths.

72 citations


Journal ArticleDOI
TL;DR: In this article, the gas holdup, bubble size distribution, and Sauter mean diameter for oxygen micro-bubble dispersions in water in an acrylic-acid resin column with an inner diameter of 0.15m, and with a working liquid height varying from 0.500 to 1.850m.

60 citations


Journal ArticleDOI
TL;DR: This is the first kLa correlation that has been defined and validated for the cited bioreactor system on a bench-to-pilot scale and can be universally applied to calculate the mass transfer coefficient for any of seven relevant cultivation parameters within an accuracy range of +/− 30%.
Abstract: Background Among disposable bioreactor systems, cylindrical orbitally shaken bioreactors show important advantages. They provide a well-defined hydrodynamic flow combined with excellent mixing and oxygen transfer for mammalian and plant cell cultivations. Since there is no known universal correlation between the volumetric mass transfer coefficient for oxygen kLa and relevant operating parameters in such bioreactor systems, the aim of this current study is to experimentally determine a universal kLa correlation.

Journal ArticleDOI
TL;DR: In this article, a series of experiments performed on the two main types of hollow fiber membrane contactors (microporous PTFE and dense PMP skin composite membrane) under different sets of operating conditions were compared with the membrane mass transfer coefficient as the only adjustable parameter.

Journal ArticleDOI
TL;DR: In this article, a kinetic study of the biosorption of lead ions by olive tree pruning was analyzed according to six different kinetic models: pseudo first, pseudo second, pseudo n -order, Elovich, solid diffusion and double exponential models.

Journal ArticleDOI
TL;DR: In this paper, a three dimensional CFD model at small scale for hydrodynamics and physical mass transfer in structured packing elements is developed, and the results from the present model are validated with theory and reported experimental data.

Journal ArticleDOI
TL;DR: In this article, the volumetric overall mass transfer coefficient (KGaV) and the overall absorption rate of carbon dioxide into aqueous ammonia solution using packed column were investigated.

Journal ArticleDOI
TL;DR: In this paper, a computational fluid dynamics (CFD) technique is used to simulate the complicated unsteady-state turbulent flow field formed in baffled flasks, and the results show that the specific power input and specific interface area are both greatly influenced by shaking frequency and filling volume.

Journal ArticleDOI
TL;DR: In this article, the authors investigated the mass transfer of ferricyanide ions through electrolyte nanofluids in a circular tube and found that mass transfer coefficient increased with the concentration of nanoparticles up to 0.01%.

Journal ArticleDOI
TL;DR: In this article, the nature and mechanisms of dyes adsorption by chromium-tanned leather waste (CTLW) are proposed and discussed on the basis of isotherms, adaption kinetics, and thermodynamics of three dyes: Red 357, Black 210 and Yellow 194 in aqueous solutions.
Abstract: Tannery solid waste (leather) is a possible adsorbent of dye contaminants in wastewater. In this paper the nature and mechanisms of dyes adsorption by chromium-tanned leather waste (CTLW) are proposed and discussed on the basis of isotherms, adsorption kinetics, and thermodynamics of three dyes: Red 357, Black 210, and Yellow 194 in aqueous solutions. Langmuir, Brunauer–Emmett–Teller (BET) and Henry isotherm models were used to fit the adsorption equilibrium data, respectively. The kinetic data were evaluated using boundary layer mass transfer and intraparticle diffusion models. The boundary layer mass transfer coefficient was in the order of 10–6 and 10–5 m·min–1 for the three studied dyes. However, the intraparticle diffusion were of the order of 10–8 and 10–11 m2·min–1 for the Red 357 and Black 210 dyes, respectively, demonstrating that intraparticle diffusion is the predominant mass transfer mechanism of these dyes. The values of ΔH, ΔS, ΔG, and Ea suggest that adsorption is spontaneous, exothermic, a...

Journal ArticleDOI
TL;DR: In this paper, a finite-element implementation of the phase field method was used to predict the hydrodynamics of the two-phase flow in mini/micro-channel reactors.

Journal ArticleDOI
TL;DR: In this paper, the authors investigated turbulent mass transfer in straight circular tube and found that the mass transfer coefficients increased with nanoparticles concentration up to an optimum concentration (0.01 % in γ-Al2O3/electrolyte nanofluid and 0.015 % in TiO2/electronically-charged polypropagation-coated polyethylene (PPE) nanofluid.
Abstract: Experimental study was performed to investigate turbulent mass transfer in straight circular tube. Electrochemical limiting diffusion current technique was used to measure the mass transfer coefficient in fully developed hydrodynamics and under developed mass transfer region. TiO2 and γ-Al2O3 nanoparticles were added into the electrolyte solution (ES) to make electrolyte nanofluids (ENF). Measurements revealed that enhancement in mass transfer reaches 10 % in a 0.01 vol% γ-Al2O3/electrolyte nanofluid while 18 % in a 0.015 vol% TiO2/electrolyte nanofluid relative to the base ES. Mass transfer coefficients increased with nanoparticles concentration up to an optimum concentration (0.01 % in γ-Al2O3/electrolyte nanofluid and 0.015 % in TiO2/electrolyte nanofluid) while decreased by increasing nanoparticles concentration further. Enhancement ratio which is the ratio of the mass transfer coefficient of nanofluid to that of the base fluid was a function of nanoparticle concentration and was independent of Reynolds number. The mechanisms of nanoparticles Brownian motion and nanoparticles clustering were used to describe the behavior of the enhancement ratio in ENF.

Journal ArticleDOI
TL;DR: In this paper, the rates of dephosphorization and rephosphoration of liquid iron with simulated steelmaking slags were investigated at 1873 K (1600° C).
Abstract: In the current study, the rates of dephosphorization and rephosphorization of liquid iron with simulated steelmaking slags were investigated at 1873 K (1600° C). The experiments were conducted in an induction furnace with supplemental heating to maintain a consistent temperature within both the metal and slag phases. An integrated form of the rate equation was used to evaluate the results, assuming mass transfer in both the slag and metal was rate controlling. The results of the current and previous studies indicate that the mass transfer parameter, the slag-metal surface area, and the overall mass transfer coefficient (A*k0), decreased as the reaction proceeded. It is proposed that initially when the rate and oxygen flux are high, the interfacial energy decreases, and the interfacial fluid velocity increases causing disruption of the slag metal interface. The consequent increases in interfacial area and interfacial fluid flow cause A*k0 to be high initially and then decrease as the oxygen flux decreases.

Journal ArticleDOI
TL;DR: The feasibility of utilizing a super-hydrophobic polyether ether ketone (PEEK) hollow fiber membrane contactor in combination with chemical solvents to separate and capture CO 2 from simulated flue gases was investigated in this article.

Journal ArticleDOI
TL;DR: In this article, an experimental study of bubble absorption in a plate heat exchanger using ammonium/lithium nitrate and ammonia/(Lithium Nitrate+water) mixtures has been carried out at operating conditions of air-cooled absorption systems driven by low temperature heat sources.

Journal ArticleDOI
TL;DR: In this paper, the effects of ammonia concentration, L/G, gas flow rate, gas temperature, CO2 partial pressure and other factors on the volumetric overall mass transfer coefficient (KGaV), the gas phase mass transfer coefficients (kG) and the effective mass transfer cross-sectional area (aV) were investigated with ammonia solution as the absorbent in homemade spray tower.

Journal ArticleDOI
TL;DR: In this article, an opposite-flowing T-shaped microchannel has been proposed to form favorable monodispersed droplet flow in a wide range of volume flow rate ratio.

Journal ArticleDOI
TL;DR: In this article, the mass transfer coefficient at different concentrations and adsorbates of activated carbon cartridges is calculated and the validity of the LDF constant pattern model is evaluated. But the authors do not consider the effect of the adsorbents on the mass.
Abstract: Modelling of activated carbon cartridges is essential in personal protective equipments against toxic gases in order to know the duration of protection. The linear driving force model seems to be more adapted than the actual Wheeler–Jonas model because it has more physical significance. The difficulty is that the mass transfer coefficient can not be calculated a priori. Values of the LDF mass transfer coefficient are disseminated in the literature and thus there is no overview of the range and variations with different adsorbents, adsorbates and concentrations. The object of this paper is thus twofold: obtaining values of the mass transfer coefficient at different concentrations and adsorbates in order to have a comprehensive view of variations and appreciating the validity of the LDF constant pattern model.

Journal ArticleDOI
TL;DR: In this article, the effect of silica nanoparticles on mass transfer was studied in circular tube by using electrochemical limiting current technique in both laminar and turbulent flow regimes, which indicated that mass transfer coefficient increased with nanofluid volume fraction up to 0.0057% and decreased with increasing the volume fraction of nanoparticles further.

Journal ArticleDOI
TL;DR: The functionality of the pressure exponent with temperature, pressure and membrane thickness is provided, showing that the Sieverts-type empirical law can be used to incorporate the external mass transfer influence just up to a moderate external resistance.

01 Jan 2013
TL;DR: The aim of this work is to obtain several correlations for evaluation of k L a in three type gas-liquid reactors (stirred tanks, bubble columns and airlift) and to select the most suitable method as a function of the type of bioreactor used.
Abstract: The volumetric mass transfer coefficient (k L a) is often used in order to compare the efficiency of bioreactors and as an important scale-up factor. In bioreactors, a number of methods are available for estimation the overall volumetric oxygen mass transfer coefficient: the dynamic method, the steady-state method based on a preliminary determination of the oxygen uptake rate, the gaseous oxygen balance, the carbon dioxide balance. Each method provides a different estimation of the value of k L a. We examined the sensitivity of the various methods and compare the k L a values obtained in order to select the most suitable method as a function of the type of bioreactor used. In this work we applied dynamic gassing-out method for measuring the volumetric mass transfer coefficient k L a in three type gas-liquid reactors (stirred tanks, bubble columns and airlift). Тhe aim of this work is on the basis of our experimental data to obtain several correlations for evaluation of k L a.

Journal ArticleDOI
TL;DR: In this paper, the authors investigated the performance of a T-junction microchannel with both reaction intrinsic kinetics and mass transfer and found that the maximum extraction efficiency is about 0.96, and the apparent overall volumetric mass transfer coefficient (kappa) is in the range of 0.02-0.2s-1.
Abstract: The extraction performance in a T-junction microchannel was investigated experimentally. CuSO4/H2SO4/AD-100/260# solvent oil was chosen as the working system. The velocities of the aqueous and oil phases were varied from 0.0016 to 0.45 ms-1, with ReM varying between 9 and 200. The experimental results show that the extraction process of copper in the microchannel is controlled by both reaction intrinsic kinetics and mass transfer, depending on the characteristics of the reaction and the fluid hydrodynamics. The maximum extraction efficiency is about 0.96, and the apparent overall volumetric mass transfer coefficient (kappa) is in the range of 0.02-0.2s-1. In addition, the effects of the Cu2+ concentration and the pH in the aqueous phase, the volumetric fraction of AD-100 in the oil phase, and the temperature on the extraction performance were investigated in detail.