Showing papers on "Packed bed published in 2003"
TL;DR: Different abiotic and microbial-mediated mechanisms may be involved during shorter- and longer-term operation of Fe(0) systems and the role of iron precipitates should be further evaluated.
266 citations
TL;DR: In this paper, the authors investigated the absorption of carbon dioxide from gases containing 1−10 mol % CO2 in a rotating packed bed and found that the overall volumetric mass transfer coefficient was comparable to a tower packed with the EX packing, implying a great potential of a rotating packing bed applied to the reduction of the greenhouse gas CO2 from the exhausted gases.
Abstract: The absorption of carbon dioxide from gases containing 1−10 mol % CO2 in a rotating packed bed was investigated in this study. The aqueous solutions of NaOH, monoethanolamine, and 2-amino-2-methyl-1-propanol were used as the absorbents. The overall volumetric mass-transfer coefficient (KGa) was observed as a function of the rotating speed, gas flow rate, liquid flow rate, absorbent concentration, and CO2 concentration. The obtained results indicated that KGa of a rotating packed bed was comparable to a tower packed with the EX packing, implying a great potential of a rotating packed bed applied to the reduction of the greenhouse gas CO2 from the exhausted gases.
216 citations
TL;DR: In this article, a Monte-Carlo method was used to generate realistic random packings of spherical particles, and the subsequent numerical simulation of the 3D flow field and coupled mass transport of reacting species is done by means of lattice Boltzmann methods.
212 citations
TL;DR: In this article, the authors measured the radial heat transfer coefficient in a bed of ceramic foam by measuring outlet temperatures achieved when air at varying flow rates and inlet temperatures was passed through a foam pellets.
Abstract: Mass and heat transport properties have been determined for 30 PPI α-Al 2 O 3 ceramic foam containing 6 wt.% γ-Al 2 O 3 washcoat. The foam was loaded with 5 wt.% platinum and the rate of carbon monoxide oxidation measured for a 0.3 cm cylindrical segment of the foam operating with mass transfer controlling at 550 °C. This gave a mass transfer factor versus Reynolds number correlation that was equivalent to a packed bed of particles. A correlation for the radial heat transfer coefficient in a bed of ceramic foam was determined by measuring outlet temperatures achieved when air at varying flow rates and inlet temperatures was passed through a bed of foam pellets. Correlation parameters of a 1D model were fitted from 700 to 1000 °C using a Simplex optimization routine. Radial heat transfer coefficients were two to five times higher than those predicted from packed bed correlations.
194 citations
TL;DR: In this article, the mass and heat transfer characteristics of a composite structured catalytic reactor packing (Composite Structured Packing) are investigated, and the constants of the commonly used engineering correlation Nu = c 1 + c 2 Re n Pr 1/3 were obtained by fitting the CFD results for N = 1.00, 1.15,1.47, 2.00
172 citations
TL;DR: In this paper, a combined mesoscale-microscale predictive approach was developed to apprehend the aerodynamic macroscale phenomena in structured packing-containing columns, including the elbow loss and jet splitting at the packed bed entrance, elbow loss at the column wall, the elbow losses at the jump from one layer to another, and the collisional losses at crisscrossing junctions.
145 citations
TL;DR: Packed-bed bioreactors containing activated carbon as support carrier were used to produce H2 anaerobically from a sucrose-limiting medium while acclimated sewage sludge was used as the H2 producer and the effects of bed porosity and substrate loading rate on H2 fermentation were examined.
Abstract: Packed-bed bioreactors containing activated carbon as support carrier were used to produce H2 anaerobically from a sucrose-limiting medium while acclimated sewage sludge was used as the H2 producer The effects of bed porosity (eb) and substrate loading rate on H2 fermentation were examined using packed beds with eb of 70–90% being operated at hydraulic retention times (HRT) of 05–4 h Higher eb and lower HRT favored H2 production With 20 g COD l−1 of sucrose in the feed, the optimal H2 production rate (74 l h−1 l−1) was obtained when the bed with eb=90% was operated at HRT = 05 h Flocculation of cells enhanced the retention of sludge for stable operations of the bioreactor at low HRTs The gas products resulting from fermentative H2 production consisted of 30–40% H2 and 60–70% CO2 Butyric acid was the primary soluble product, followed by propionic acid and valeric acid
136 citations
TL;DR: In this paper, the authors developed a flexible and stable numerical method to predict the thermal decomposition of large wood particles due to drying and pyrolysis, which can deal with particles of different sizes, shapes and properties.
133 citations
TL;DR: In this article, a single particle model for the conversion of beech wood during pyrolysis and char combustion is presented, where the conservation equations for mass, momentum and energy are solved on a Cartesian mesh by a finite volume method.
132 citations
TL;DR: In this paper, the performance of a membrane microreactor was compared with that of a micro-reactor, a packed bed reactor, and a packed-bed membrane reactor for the Knoevenagel condensation reaction of benzaldehyde and ethyl cyanoacetate.
121 citations
TL;DR: In this paper, the velocity distributions in a pore that models a simple-packed bed were measured directly by a magnetic resonance imaging technique, and the results indicated that inertial forces dominate over viscous forces.
Abstract: The detailed characteristics of the interstitial velocity distributions in pores are critical to understanding heat and mass transfer in a packed bed of granular material. The velocity distributions in a pore that models a simple-packed bed were measured directly by a magnetic resonance imaging technique. With an increase in the Reynolds number from 12.17 to 59.78-204.74, the increase and decrease in main flow velocity did not correspond to the local pore geometry, as is the case with a creeping flow. This indicated that inertial forces dominate over viscous forces. For example, at the Reynolds number of 204.74, the fluid penetrated through the center of the pores like a jet with negligible change of velocity. Circulation in the surrounding stagnant spaces generated eight symmetrical eddies in the plane perpendicular to the main flow direction.
TL;DR: In this paper, the authors presented a route of synthesizing nano-fibrillar aluminum hydroxide (AH) by carbonation in a novel rotating packed bed (RPB) reactor and thermal hydrolysis.
TL;DR: In this paper, carbon nanotubes (CNTs) prepared from ethylene decomposition over the Fe/Al 2 O 3 catalyst are studied in a packed bed (PB) reactor and a nanoagglomerate fluidized bed reactor (NABR), respectively.
Abstract: Carbon nanotubes (CNTs) prepared from ethylene decomposition over the Fe/Al 2 O 3 catalyst are studied in a packed bed (PB) reactor and a nanoagglomerate fluidized bed reactor (NABR), respectively. CNTs sampled at different reaction times are characterized by TEM, Raman spectroscopy, and particle size analysis. The bulk density and agglomerate size of CNTs increase significantly with reaction time in a PB, while it remains at a stable level in NABR. Also, CNTs with good morphology, narrow diameter distribution, and fewer lattice defects are obtained in an NABR, rather than in a PB. In contrast to the unavoidable jamming due to volume increase of CNTs observed in a PB, a continuous CNT growth process is attained in an NABR, even though the amount of CNTs in an NABR is 6-7 times that in a PB. The flow dynamics, available space for growing, and mass and heat transfer can be controlled in an NABR, which favors the large-scale production of CNTs with uniform properties.
TL;DR: In this paper, a mechanistic model that can predict mass-transfer performance and provide an insight into dynamic behavior within structured packings used for CO 2 absorption was presented, which was built upon the kinetics and thermodynamics of the absorption system, as well as the liquid irrigation features and the geometry of packing elements.
TL;DR: An FAU-type zeolite membrane was formed on a porous α-Al2O3 support tube, for use in the selective separation of benzene and hydrogen from cyclohexane as discussed by the authors.
TL;DR: In this paper, an experimental investigation has been carried out on a low porosity packed bed solar air heater, where correlations have been developed for the Colburn j factor and friction factor for a low range of porosities from 0.667 to 0.880.
TL;DR: The presented results provide a clear quantitative support for Knox's recent argumentation that the use of more uniform beds could greatly enhance the efficiency of pressure-driven LC.
Abstract: A series of theoretical calculations is presented to quantify the gain in LC separation efficiency that can be expected if the traditionally used packed bed columns were replaced by columns with a perfectly ordered flow-through pore network. It is shown that a perfectly ordered 2-D array of porous cylindrical pillars could yield reduced plate heights as small as h = 0.65 (for k' ' = 0.75) to h = 0.85 (for k' ' = 2) and separation impedances as small as E = 200 (for k' ' = 0.75) to E = 300 (for k' ' = 2) without having to compromise on the porosity (epsilon = 0.4) and the retention capacity of the packed bed of spheres. Fitting the calculated van Deemter plots with Knox's equation especially shows a strong decrease of the A-term contribution, hence confirming that the improved column performance indeed stems from the increased homogeneity of the packing. The presented results, hence, provide a clear quantitative support for Knox's recent argumentation that the use of more uniform beds could greatly enhance the efficiency of pressure-driven LC.
TL;DR: The feasibility of applying a novel rotating packed bed to the ozone oxidation process is investigated in this paper, where various operating variables affect the decolorization of dyes in aqueous solutions system.
Abstract: The feasibility of applying a novel rotating packed bed to the ozone oxidation process is investigated. Ozone oxidation experiments were conducted to examine how various operating variables affect the decolorization of dyes in aqueous solutions system. Rotor speeds ranged from 380 to 1748 rpm, providing 10∼202 equivalent gravitational force. Experimental results indicate that the centrifugal force positively affects the decolorization efficiency. Furthermore, it is shown that owing to its low ozone mass transfer resistance, a rotating packed bed can be used to increase the efficiency of the ozone oxidation process. The results further demonstrate that the decolorization efficiency increases with either an decreasing initial dye concentration or liquid flow rate.
TL;DR: In this paper, the adsorption-enhanced reaction (AER) process is theoretically analyzed for hydrogen production by steam-methane reforming (SMR) using a fixed-bed packed column of an admixture of a SMR catalyst and an adsorbent for selective removal of CO2 from the reaction zone.
TL;DR: In this article, a comparison of the test results with other modern and standard random packings as well as to structured packings is made, where the same specific surface area is taken as the comparison basis.
Abstract: Since its introduction to the market in 1995, numerous mass transfer columns have been packed with Raschig Super-Rings in various chemical process, petrochemical, refining, and environmental applications. To support these applications, the Raschig Super-Ring No. 2 was tested at the Fractionation Research Inc. (FRI) test facility at the end of 1998. The purpose of this paper is to discuss the FRI experimental results. The tests verified that the Raschig Super-Ring No. 2 provides exceptional low pressure drop, high capacities, and excellent mass transfer efficiency. Special attention is given to a comparison of the test results with other modern and standard random packings as well as to structured packings. The comparison shows that a modern random packing design has mass transfer efficiency advantages compared to structured packings, if the same specific surface area is taken as the comparison basis. Industrial applications are shown where Raschig Super-Ring's have been used successfully. New column design is explained as well as revamp situations.
TL;DR: In this article, the dry reforming reaction has been carried out in an Ru-based ceramic tubular membrane reactor, in which two Ru depositions have been performed using the co-condensation technique.
TL;DR: In this article, a down-flow compact porous burner system was developed for burning kerosene without the need of using a spray atomizer, and the effect of the introduced packed bed emitter with suitable bed length and its installation location was investigated as an efficient method for enhancement of evaporation and combustion of the liquid fuels.
TL;DR: The Montz B1-M® series is a high capacity structured packing with a smooth bend in the bottom third of the corrugation with continuously increasing base width as discussed by the authors.
Abstract: Total reflux distillation results of a comprehensive experimental study are reported for a new generation of Montz high capacity structured packings. The major feature of the Montz B1-M® series is a smooth bend in the bottom third of the corrugation with continuously increasing corrugation base width. A comparison is made with the performance of conventional structured packing under the same test conditions. The relationships between specific surface area, pressure drop, capacity, and separation efficiency are discussed.
TL;DR: In situ magnetic resonance (MR) visualisation techniques are used to study chemical conversion within a fixed-bed reactor as mentioned in this paper, where the reaction chosen for study is the esterification of acetic acid by methanol, catalysed by an acidic ion exchange catalyst.
TL;DR: In this paper, the upper and lower bounds of the effective thennal conductivity of packed beds of rough spheres are evaluated using the theoretical approach of the elementary cell for two-phase systems.
Abstract: The upper and lower bounds of the effective thennal conductivity of packed beds of rough spheres are evaluated using the theoretical approach of the elementary cell for two-phase systems. The solid mechanics and thermal problems are solved and the effects of roughness and packed bed structures are also examined. The numerical solution of the thermal conduction problem through the periodic regular arrangement of steel spheroids in air is determined using the Finite Element Method. The numerical results are compared with those obtained from an experimental apparatus designed and built for this purpose
TL;DR: In this article, a two-dimensional supercritical fluid chromatographic system with conventional packed columns was developed for triglycerides separation in fats and oils. The system used a computer-controlled ten-port valve, a capillary trap, and a restrictor to transfer the trapped solute into the second column by switching the valve.
Abstract: A comprehensive two-dimensional supercritical fluid chromatographic system with conventional packed columns was developed. The system used a computer-controlled ten-port valve, a capillary trap, and a restrictor. The mobile phase was pure carbon dioxide. The first dimension column was operated under constant pressure in the stopped-flow mode, while the second dimension column was operated in the constant flow mode. The effluent of the first column was depressurized through the restrictor and solute was trapped within the capillary trap. Then the trapped solute was transferred into the second column by switching the valve. Since the solute transfer process is very rapid, the valve can be switched back after a short injection period in order to collect next fraction. This allowed the sampling time to be changed without changing any of the other conditions, such as the second dimension run time. The system was applied to the separation of triglycerides in fats and oils. Separations were performed using the same ODS packing materials for both columns, and the first column was operated under subcritical conditions and the second column under supercritical conditions.
TL;DR: In this paper, the top surface of a shallow packed bed, consisting of several layers of spherical catalytic pellets (Pd/Al2O3), was used for atmospheric oxidation of carbon monoxide.
TL;DR: In this paper, the authors investigated the two steps in the treatment process, namely, adsorption of metal ions onto the packed bed of resin and electromigration (i.e., the transport of these ions in the complex system under the applied electrical field).
Abstract: Hybrid ion exchange electrodialysis processes allow the removal of metal ions from dilute waste liquids and the recovery of more concentrated solutions. The work reported here was aimed at investigating the two steps in the treatment process, namely, adsorption of metal ions onto the packed bed of resin and electromigration (i.e., the transport of these ions in the complex system under the applied electrical field). The case of copper sulfate was investigated. Dowex™ resins with a cross-linking degree of 2 and 8% were used. The flux of copper through the resin bed and the current efficiency for ion transfer to the cathode compartment were determined as a function of potential gradient and copper ionic fraction in the bed. Apparent diffusion coefficients of Cu2+ in the overall system were deduced from the experimental data.
TL;DR: An electroosmotic pump (EOP) capable of generating pressure above 3 MPa and μl/min flow rate with reverse phase mobile phases of HPLC was constructed and evaluated as mentioned in this paper.
TL;DR: In this article, a model with a linear variation of λer in the vicinity of the wall is proposed to the description of the radial heat transfer in the packed bed, which allows simple correlation between the wall Nusselt number and the bed core effective radial thermal conductivity.