Showing papers on "Mass transfer coefficient published in 2010"
TL;DR: In this paper, the rate of CO 2 absorption into a falling thin film has been measured using a wetted-wall column for aqueous ammonia between 0.6 and 6.5 times smaller than MEA at the measured temperatures, and it was shown that the difference in mass transfer rate is likely due to both the reduced temperature and differences in reactivity between ammonia and MEA with CO 2.
215 citations
TL;DR: In this paper, a capillary micro-structured reactor is numbered up for six capillaries and the mass transfer performance is investigated for various operating conditions, including interfacial tension.
196 citations
TL;DR: In this article, the authors reported on the measured water uptake and water transport properties through an anion-exchange membrane, including the water diffusivity, the electro-osmotic drag (EOD) coefficient, and the mass transfer coefficient of water at the cathode catalyst layer/membrane interface.
179 citations
TL;DR: A tri-layer composite membrane consisting of active layer polydimethylsiloxane (PDMS, Sylgard® 184) and dual support layers of high porosity polyethylene (PE) and high mechanical stiffness perforated metal was investigated for the separation of 1-butanol from aqueous solution by means of pervaporation as mentioned in this paper.
167 citations
TL;DR: In this article, the application of a cross-flow membrane contactor is studied for CO2 absorption when the ionic liquid 1-ethyl-3-methylimidazolium ethylsulfate is used as solvent.
Abstract: Carbon dioxide (CO2) emissions have to be controlled and reduced in order to avoid environmental risks. Membrane processes in combination with the use of ionic liquids are recently under research and development in order to demonstrate a zero solvent emission process for CO2 capture. In this work, the application of a cross-flow membrane contactor is studied for CO2 absorption when the ionic liquid 1-ethyl-3-methylimidazolium ethylsulfate is used as solvent. A mathematical model considering a parallel flow configuration is applied for a cross-flow system in order to describe the mass transfer rate. At a macroscopic level, Koveralla is calculated considering different mixing models corresponding to plug flow and continuous stirred models and a first order mass transfer rate. A microscopic model based on laminar flow has been applied, obtaining a membrane mass transfer coefficient of km = 3.78 × 10−6 m·s−1, which is about five times higher than that obtained in the macroscopic model. The interfacial area, a...
162 citations
TL;DR: In this article, the effect of the presence in clean water of some compounds usually encountered in biological media and quantifying their consequences on liquid-side mass transfer coefficients was investigated, and it was shown that even if the properties of clean water (density, viscosity, surface tension) were not significantly changed by the addition of salts (NaCl), the liquid-sensor transfer coefficients could be, all the same, modified.
148 citations
TL;DR: In this article, a volume of fluid method is developed in order to simulate reactive mass transfer in two-phase flows and is applied to study reactive laminar liquid film, where the thermodynamic equilibrium of chemical species at the interface is considered using Henry's law.
137 citations
TL;DR: By considering both the kLa value and the statistical significance, the air‐lift reactor combined with a 20‐μm bulb diffuser was found to be the ideal reactor configuration for carbon monoxide mass transfer in an aqueous phase.
Abstract: Lignocellulosic biomass such as agri-residues, agri-processing by-products, and energy crops do not compete with food and feed, and is considered to be the ideal renewable feedstocks for biofuel production. Gasification of biomass produces synthesis gas (syngas), a mixture primarily consisting of CO and H(2). The produced syngas can be converted to ethanol by anaerobic microbial catalysts especially acetogenic bacteria such as various clostridia species.One of the major drawbacks associated with syngas fermentation is the mass transfer limitation of these sparingly soluble gases in the aqueous phase. One way of addressing this issue is the improvement in reactor design to achieve a higher volumetric mass transfer coefficient (k(L)a). In this study, different reactor configurations such as a column diffuser, a 20-μm bulb diffuser, gas sparger, gas sparger with mechanical mixing, air-lift reactor combined with a 20-μm bulb diffuser, air-lift reactor combined with a single gas entry point, and a submerged composite hollow fiber membrane (CHFM) module were employed to examine the k(L) a values. The k(L) a values reported in this study ranged from 0.4 to 91.08 h(-1). The highest k(L) a of 91.08 h(-1) was obtained in the air-lift reactor combined with a 20-μm bulb diffuser, whereas the reactor with the CHFM showed the lowest k(L) a of 0.4 h(-1). By considering both the k(L) a value and the statistical significance of each configuration, the air-lift reactor combined with a 20-μm bulb diffuser was found to be the ideal reactor configuration for carbon monoxide mass transfer in an aqueous phase.
133 citations
TL;DR: In this article, a hollow fiber membrane photo-bioreactor (HFMPB) was investigated to increase the interfacial contact area available for gas transfer, treat high nutrient strength (412 mg NO 3 - -N L -1 ) wastewater, and produce algal biomass that can be used as a biofuel.
Abstract: BACKGROUND: In the presence of light, micro-algae convert CO 2 and nutrients to biomass that can be used as a biofuel. In closed photo-bioreactors, however, light and CO 2 availability often limit algae production and can be difficult to control using traditional diffuser systems. In this research, a hollow fiber membrane photo-bioreactor (HFMPB) was investigated to: (1) increase the interfacial contact area available for gas transfer, (2) treat high nutrient strength (412 mg NO 3 - -N L -1 ) wastewater, and (3) produce algal biomass that can be used as a biofuel. RESULTS: A bench scale HFMPB was inoculated with Spirulina platensis and operated with a 2-15% CO 2 supply. A mass transfer model was developed and found to be a good tool to estimate CO 2 mass transfer coefficients at varying liqu id velocities. Overall mass transfer coefficients were 1.8 × 10 -6 , 2.8 × 10 -6 , 5.6 × 10 -6 m s -1 at Reynolds numbers of 38, 63, and 138, respectively. A maximum CO 2 removal efficiency of 85% was observed at an inlet CO 2 concentration of 2% and a gas residence time (membrane-lumen) of 8.6 s. The corresponding algal biomass concentrations and NO 3 removal efficiencies were 2131 mg L -1 and 68%, respectively. CONCLUSION: The results show that the combination of CO 2 sequestration, wastewater treatment and biofuel production in an HFMPB is a promising alternative for greenhouse gas mitigation.
124 citations
TL;DR: Using the developed gut model, it is demonstrated that absorption of nutrients can be controlled by mass transfer limitations, and glucose available for absorption can be significantly reduced by altering the lumen viscosity.
Abstract: There is an increasing need to understand how food formulations behave in vivo from both food and pharma industries. A number of models have been proposed for the stomach, but few are available for the other parts of the gastrointestinal tract. An experimental rig that simulates the segmentation motion occurring in the small intestine has been developed. The objective of developing such an experimental apparatus was to study mass transport phenomena occurring in the lumen and their potential effect on the concentration of species available for absorption. When segmentation motion was applied the mass transfer coefficient in the lumen side was increased up to a factor of 7. The viscosity of the lumen, as influenced by guar gum concentration, had a profound effect on the mass transfer coefficient. The experimental model was also used to demonstrate that glucose available for absorption, resulting from starch hydrolysis, can be significantly reduced by altering the lumen viscosity. Results suggest that absorption of nutrients could be controlled by mass transfer. Practical Application: To address health-related diseases such as obesity, novel foods that provide advanced functions are required. To achieve the full potential offered by the latest developments in the field of food material science, a fundamental understanding of the behavior of food structures in vivo is required. Using the developed gut model we have demonstrated that absorption of nutrients can be controlled by mass transfer limitations.
121 citations
TL;DR: In this article, a steady state simulation of the hydrodynamics and mass transfer in bubbly flow in an axisymmetric internal airlift loop reactor with the special treatment of interphase decoupling and outlet boundary conditions is performed, which is based on a Favre averaging two-fluid model for multiphase flow.
TL;DR: The self-diffusivity exceeds the transport diffusivity in a novel type of nanoporous material (MOF ZIF-8), rationalized by considering the strong intermolecular interaction and the dominating role of intercage hopping in mass transfer in the systems under study.
Abstract: Diffusion is known to be quantified by measuring the rate of molecular fluxes in the direction of falling concentration. In contrast with intuition, considering methanol diffusion in a novel type of nanoporous material (MOF ZIF-8), this rate has now been found to be enhanced rather than slowed down by an opposing flux of labeled molecules. In terms of the key quantities of random particle movement, this result means that the self-diffusivity exceeds the transport diffusivity. It is rationalized by considering the strong intermolecular interaction and the dominating role of intercage hopping in mass transfer in the systems under study.
TL;DR: In this article, the authors evaluated the absorption capacity and velocity performances of polydimethylsiloxane (i.e., silicone oil) and verified its non-biodegradability.
Abstract: BACKGROUND: Hydrophobic volatile organic compounds (VOCs), such as toluene, dimethyl sulfide (DMS) and dimethyl disulfide (DMDS), are poorly soluble in water and classical air treatment processes like chemical scrubbers are not efficient. An alternative technique involving an absorption step in an organic solvent followed by a biodegradation phase was proposed. The solvent must fulfil several characteristics, which are key factors of process efficiency, and a previous study allowed polydimethylsiloxane (or PDMS, i.e. silicone oil) to be selected for this purpose. The aim of this paper was to determine some of its characteristics like absorption capacity and velocity performances (Henry's constant, diffusivity and mass transfer coefficient), and to verify its non-biodegradability. RESULTS: For the three targeted VOCs, Henry's constants in silicone oil were very low compared to those in water, and solubility was infinite. Diffusivity values were found to be in the range 10 -10 to 10 -11 m 2 s -1 and mass transfer coefficients did not show significant differences between the values in pure water and pure silicone oil, in the range 1.0 × 10 -3 to 4.0 × 10- 3 s -1 for all the VOCs considered. Silicone oil was also found to be non-biodegradable, since its biological oxygen demand (BOD 5 ) value was zero. CONCLUSION: Absorption performances of silicone oil towards toluene, DMS and DMDS were determined and showed that this solvent could be used during the first step of the process. Moreover, its low biodegradability and its absence of toxicity justify its use as an absorbent phase for the integrated process being considered.
TL;DR: The external mass transfer coefficient estimated with the film diffusion model has a physical meaning that helps to explain the diffusion of solutes across the film resistance in agro-waste biosorbents.
TL;DR: In this article, commercially available zeolites (CBV28014, CBV901) with a high Si/Al ratio were tested as adsorbents to recover 1-butanol from aqueous solutions such as acetone butanol-ethanol fermentation broth.
TL;DR: The rotor-stator spinning disc (RSDF) as discussed by the authors showed high rates of gas-liquid mass transfer in comparison to conventional multiphase reactors, with a volumetric mass transfer coefficient of 20.5 m L 3 m G - 3 s - 1 for a bubble column.
TL;DR: In this paper, the influence of power ultrasound on convective drying of natural materials addressing the kinetic as well as the product's microstructure was discussed. But, the authors did not consider the effects on mass transfer properties from microestructural observations.
TL;DR: In this article, a high-flux asymmetrically structured hollow fiber membrane distillation module was tested under various conditions, and the results showed that increasing velocity and temperature are positive for flux, and salt rejection was more than 99% over the entire experimental range.
TL;DR: In this article, the authors present analytical criteria for determining the transition temperatures of a catalytic monolith to the external mass transfer control regime at sufficiently high temperatures (or after ignition).
TL;DR: In this paper, two types of novel porous plate packing were investigated respectively in a cross-flow rotating packed bed to examine their gas pressure drop and mass transfer characteristics with CO2−NaOH solution system.
Abstract: Structured packing were proposed and designed according to gas−liquid mass transfer and kinetic balance characteristics in a cross-flow rotating packed bed (RPB). Two types of novel porous plate packing were investigated respectively in a cross-flow RPB to examine their gas pressure drop and mass transfer characteristics with CO2−NaOH solution system. Compared with the literature, the pressure drop of the cross-flow rotating packed bed with new structured packing was slower than that of wire-gauze packing and was no more than a tenth that of the countercurrent rotating packed bed in the same operational condition. The volume mass transfer coefficient of RPB with new structured packing was higher than that with wire-gauze packing, which was higher than that of countercurrent RPB and was 1−2 orders of magnitude higher than that of the conventional packed tower. Moreover, the correlative expressions of gas pressure drop and volume mass transfer coefficients of RPB were obtained using the MATLAB program and i...
TL;DR: In this article, an analysis has been performed for heat and mass transfer of a steady laminar boundary-layer flow of an electrically magnetic conducting fluid of second-grade subject to suction and to a transverse uniform magnetic and electric field past a semi-infinite stretching sheet.
TL;DR: In this article, a method was proposed for the simultaneous determination of the effective diffusivity and convective mass transfer coefficient in solids which can be considered as infinite cylinders, and the inverse method was used to fit the analytical solution of the diffusion equation with convective boundary condition to experimental data of thin-layer drying kinetics of products with cylindrical shape.
TL;DR: This specifically designed protocol can provide key information regarding the kinetic performance of columns used in liquid chromatography and explain why different columns behave so differently.
TL;DR: In this article, the authors investigated the selective absorption of H2S from a gas mixture with CO2 into N-methyldiethanolamine (MDEA) in a rotating packed bed (RPB).
Abstract: In this work, selective absorption of H2S from a gas mixture with CO2 into N-methyldiethanolamine (MDEA) is investigated experimentally and theoretically in a rotating packed bed (RPB). In the RPB, various rotating speeds, gas flow rates, liquid flow rates, and concentrations of MDEA aqueous solutions were studied by means of the evaluation of removal efficiency, selectivity, and overall volumetric mass transfer coefficient. The reaction−diffusion mass transfer model based on penetration theory for the selective absorption process is developed, accordingly. The results of experiment and model show that the uppermost function of RPB in selective absorption of H2S is to restrain the CO2 removal efficiency but sharply intensify the absorption of H2S. The mass transfer coefficient of CO2 absorption is enhanced in RPB. However, the total amount of CO2 mass transfer virtually is low because of the short gas−liquid contact time, small volume of packing, and large gas−liquid ratio within the RPB, and the CO2 remo...
TL;DR: In this paper, heat and mass transfer of fruit leather drying with combination of hot air and far-infrared has been carried out, and the heat and the mass transfer coefficients were analyzed by heat-mass analogy.
TL;DR: In this paper, a new procedure for modelling the simultaneous heat and mass transfer in direct contact membrane distillation (DCMD) in a hollow fiber configuration was presented, where iterative calculations in classic dimensionless analysis were applied to develop semi-empirical models.
TL;DR: In this article, the volumetric mass transfer coefficient (k L a ), the gas hold-up ( ǫ ), and the mixing time ( t m ) as a function of superficial gas velocity (U G ) in a flat-panel photobioreactor (PBR) with high light path were evaluated.
Abstract: This work evaluates the volumetric mass transfer coefficient ( k L a ), the gas hold-up ( ɛ ) and the mixing time ( t m ) as a function of superficial gas velocity ( U G ) in a flat-panel photobioreactor (PBR) with high light path. CO 2 utilization efficiency and volumetric power consumption ( P / V ) were also evaluated. A 50 L working volume photobioreactor was developed, 0.67 m in length, 0.57 m in height and 0.15 m in width (light path). The height-width ratio was 3.8, which is lower than reported in most PBRs. Initially, experiments were performed with air and tap water (biphasic system) and, subsequently, using a Spirulina sp. culture (triphasic system: air, culture medium, cells). Minimum and maximum superficial gas velocity values were 5 × 10 −5 and 8.4 × 10 −3 m s −1 , respectively. Maximum values for k L a and ɛ were 20.34 h −1 (0.0057 s −1 ) and 0.033 in the biphasic system, and 31.27 h −1 (0.0087 s −1 ) and 0.065 in the triphasic system. CO 2 utilization efficiency was 30.57%. Results indicate that the hydrodynamic and mass transfer characteristics of this photobioreactor are more efficient than those reported elsewhere for tubular and other flat-plate PBRs, which opens the possibility of using PBRs with higher light paths than yet proposed.
TL;DR: In this article, a mathematical model was developed to simulate the concentration profile in a gas absorption membrane (GAM) system, where three GAM modules were potted with polytetrafluoroethylene (PTFE) membranes and connected in series to measure CO 2 concentration and CO 2 loading profiles along the length of the GAM system.
TL;DR: In this paper, the authors investigated the potential process for the removal of carbon dioxide (CO2) from flue gas using fundamental membrane contactor, which is a membrane gas absorption (MGA) system.
TL;DR: In this paper, a high-intensity vortex spray scrubber was used to enhance CO2 capture efficiency by imparting swirl to the gas flow, which has the ability to augment the rates of heat and mass transfer.