Showing papers on "Packed bed published in 1999"
TL;DR: In this article, the authors describe their updated equations for calculating gas and liquid side mass transfer coefficients, pressure drop of dry or irrigated random and structured packings, their loading and flooding points as well as their liquid holdup.
Abstract: A good knowledge of the relationship between the two-phase countercurrent flow of a packed mass transfer column is essential for the design of rectification, absorption and desorption columns. Based on a physical model the authors describe their updated equations for calculating gas and liquid side mass transfer coefficients, pressure drop of dry or irrigated random and structured packings, their loading and flooding points as well as their liquid holdup. Based on one of the largest experimental databases in the world, the calculated results give only small deviations from the database
382 citations
TL;DR: In this article, the degradation of enzymatic activity was attributed to the formation of an hydrophilic hindrance around the enzyme resulting in diffusion limitations of the hydrophobic substrate from the organic phase to the enzyme.
233 citations
TL;DR: The basics and implementation of expanded-bed chromatography, its advantages as well as problems encountered in the use of this technique for the direct extraction of proteins from unclarified feedstocks are addressed.
231 citations
TL;DR: In this paper, the authors evaluated the effective thermal conductivity from the packing structure of a packed bed of mono-sized spheres in the presence of a stagnant fluid, based on two aspects: (i) the heat transfer between particles, obtained under some simplified conditions; and (ii) the connectivity of particles in a packing, which is determined from the measuring structure measured by Finney.
199 citations
TL;DR: Reduction of the characteristic diameter, being the inside column diameter for open tubular columns and the particle size for packed columns, is the best approach to increase the separation speed in gas chromatography.
158 citations
TL;DR: Columns packed with reverse‐phase material subjected to silicate entrapment demonstrated faster separations of retained analytes and increased efficiencies compared with nonentrapped columns.
Abstract: Designed especially for capillary electrochromatography (CEC), silicate-entrapped columns are made by trapping particles of chromatographic packing material in a network of silica. Once entrapped, the capillary no longer requires frits. This renders a more homogeneous and stable packed bed. Accidental breakage of the fragile frits is not an issue with these robust columns. Columns packed with reverse-phase material subjected to silicate entrapment demonstrated faster separations of retained analytes and increased efficiencies compared with nonentrapped columns. The method was also used to prepare chiral CEC columns by entrapping a molecular imprinted polymeric (MIP) packing having minimal surface charge density, thus being unable alone to support sufficient electroosmotic flow for CEC.
143 citations
TL;DR: In this paper, the performance of the structured packings was evaluated in terms of the volumetric overall mass-transfer coefficient (KGav) as functions of the process operating parameters including gas load, CO2 partial pressure, liquid load, liquid temperature, solvent concentration, and structured packing type.
Abstract: The present study provides comprehensive experimental data on the performance of structured packings in CO2 absorption application. Over 90 runs of the absorption experiments were conducted in 3 different scale absorption units (laboratory-scale, pilot-scale, and industrial-scale units). The structured packings used in this study were Sulzer EX, Gempak 4A, and Sulzer BX. Aqueous solutions of sodium hydroxide (NaOH), monoethanolamine (MEA), and 2-amino-2-methyl-1-propanol (AMP) were employed as absorption solvents. The performance of the structured packings was evaluated in terms of the volumetric overall mass-transfer coefficient (KGav) as functions of the process operating parameters including gas load, CO2 partial pressure, liquid load, liquid temperature, solvent concentration, solvent type, and structured packing type. To emphasize the superior performance of the structured packings, performance comparisons between the used structured packings and common random packings are also given.
138 citations
TL;DR: In this article, the authors investigate the low-velocity filtration combustion reaction of lean methane/air mixtures flowing through a packed bed and compare to experimental results, showing that the computed wave speeds show the same trends as the theoretical predictions but are generally higher.
123 citations
TL;DR: In this paper, a pilot-scale process was designed and operated to investigate the continuous removal of ammonia from sewage using natural zeolite from Australia using a fixed-bed ion exchange system operated in the downflow mode.
Abstract: A pilot-scale process was designed and operated to investigate the continuous removal of ammonia from sewage using natural zeolite from Australia. The process consisted of a fixed-bed ion-exchange system operated in the downflow mode. Evaluation of the pilot process was initially undertaken for ammonia removal from tap water spiked with ammonium chloride to provide performance data in the absence of competing cations. The performance of the pilot process was then assessed using sewage as feed. Breakthrough curves were constructed for a range of treatment flow rates. Existing models for packed bed performance were shown to be able to predict the breakthrough behavior of the process. The results of a study are presented that show that Australian natural zeolite, clinoptilolite, may be successfully employed in a fixed-bed ion-exchange process to achieve high ammonia removal efficiencies from aqueous solutions at rates commensurate with sand filtration. The rate of uptake of ammonium by the zeolite is sufficient to support a continuous high rate process.
119 citations
TL;DR: In this paper, the authors address the relation between the fluid-dynamics imposed by packing geometry and the mass transfer efficiency, and introduce a performance prediction method which does not require packing specific constants to describe mass transfer coefficients of phases.
Abstract: Although the structured packing is a well established gas–liquid contacting device, the understanding of its function is insufficient and often leads to poor exploitation of the available phase separating potential. This is a consequence of a rather superficial approach to modelling the packing performance through the years resulting in a lack of information on the nature and extent of interaction between counter-currently flowing gas and liquid phases and the micro and macro geometry of a rather ordered structure with a pronounced flow discontinuity at the transition among packing elements. This paper addresses the relation between the fluid-dynamics imposed by packing geometry and the mass transfer efficiency, and introduces a performance prediction method which does not require packing specific constants to describe mass transfer coefficients of phases.
104 citations
TL;DR: In this article, a model for predicting the flow regime in Katapak®-S is presented and successfully compared to experimental data, and experimental results for the residence time behavior and separation efficiency are presented and discussed.
TL;DR: Production of conidia of the biocontrol fungus Coniothyrium minitans by solid-state cultivation in a packed-bed reactor on an industrial scale is feasible and adequate temperature control can be achieved with acceptable air flow rates for all four solid matrices.
Abstract: Production of conidia of the biocontrol fungus Coniothyrium minitans by solid-state cultivation in a packed-bed reactor on an industrial scale is feasible. Spore yield and oxygen consumption rate of C. minitans during cultivation on oats and three inert solids (hemp, perlite, and bagasse) saturated with a liquid medium were determined in laboratory-scale experiments. The sensitivity of the fungus to reduced aw, and the water desorption isotherms of the four solid materials were also determined. C. minitans is very sensitive to reduced aw: 50% inhibition of respiration was found at aw 0.95, spore formation was completely inhibited at aw 0.97. A simplified mathematical model taking into account convective and evaporative cooling was used to simulate temperature and moisture gradients in the bed during cultivation. Adequate temperature control can be achieved with acceptable air flow rates for all four solid matrices. Moisture control is the limiting factor for cultivation in a packed bed. Oats cannot be used due to the shrinkage and aw reduction caused by evaporative cooling. Of the three inert supports tested, hemp provides the best spore yield and control of water activity, due to its high water uptake capacity. A spore yield of 9 x 10(14) conidia per m(3) packed bed can be achieved in 18 days, using hemp impregnated with a solution containing 100 g dm(-3) glucose and 20 g dm(-3) potato extract. Sufficient water is predicted to be available after 18 days, to allow a higher initial nutrient concentration, which may lead to higher spore yields.
TL;DR: In this paper, a comprehensive experimental study of the hydrodynamics of structured packed columns of 0.1 and 0.24 m diameter is presented. And the results of this study show that a structured packed column has a much larger operating window at a much lower pressure drop.
TL;DR: In this article, the authors compared two approaches for scale-up of solid-state fermentation processes in packed-bed bioreactors, one based on a dynamic heat transfer model, and the other based on modified Damkohler number.
TL;DR: In this paper, an experimental study indicated a significant effect of column diameter on the pressure drop and capacity of corrugated sheet structured packing is presented, which suggests that column diameter(s) based on small scale data can be too large.
Abstract: The results of an experimental study indicating a significant effect of column diameter on the pressure drop and capacity of corrugated sheet structured packing are presented. The experiments were carried out with Montz-pak B1-250, using an air/water system at ambient conditions in perspex columns with internal diameters of 0.2 m, 0.45 m, 0.8 m and 1.4 m. The results clearly show that both the pressure drop increase and capacity decrease become significant when the column diameter approaches the value equal to that of the height of a packing element. This observation suggests that column diameter(s) based on small scale data can be too large.
TL;DR: In this paper, an axial heat transfer model was used to explore two strategies designed to prevent the temperature reaching undesirable levels, namely periodic reversal of the direction of airflow, and periodic mixing.
TL;DR: In this article, a column aspect ratio (length/diameter) analysis was performed for column packing and a preliminary stress-strain analysis during column packing was reported, which showed that the stress distribution depends strongly upon column aspect ratios and is most favorable for low values.
TL;DR: In this article, the authors compared the performance of packed and multi-capillary columns with respect to their deployment in fast gas chromatography (GC) and showed that the contribution of the stationary phase to peak broadening can be neglected (low liquid phase loading and thin film columns, respectively).
TL;DR: In this paper, a novel biotrickling filter was developed for the treatment of off-gases containing low concentrations of pollutants, characterized by the use of an organic solvent.
Abstract: Biological techniques are highly cost-effective for the treatment of off-gases containing low concentrations of pollutants (<5 g/m3). They may also be attractive for the elimination of higher concentrations of explosive hydrocarbons (when compared to incineration). Conventional techniques such as biofilters have low elimination capacities for hydrophobic compounds caused by a poor mass transfer from the gas to the aqueous phase. To overcome solubility problems, a novel biotrickling filter was developed and is characterized by the use of an organic solvent. In such a biotrickling filter, a mixture of an organic solvent and water is continuously trickled over a packed bed, while the polluted gas passes counter-current to the liquid. The microorganisms exist on the packing material in the calculating liquid. The alkanes are absorbed in the oil phase of the liquid, transferred to the microorganisms and biodegraded. Laboratory-scale experiments at 20 l scale with hexane as a model pollutant and silicon oil as a solvent revealed that a 90% elimination efficiency can be reached at a volumetric loading rate of 100 g hexane per m3 filterbed per hour. The influent gas contained 10 g hexane per m3 and had a temperature of 29 °C. The method described in this paper can be a cost-effective way to treat gases containing hexane, other alkanes or other strongly hydrophobic compounds. Biological co-oxidation of other biodegradable pollutants from the gas is to be expected.
TL;DR: Continuous polymer beds (acrylic-based beds) have the following advantages over beds packed with beads: (1) they can be synthesized in one step by sucking a solution of appropriate monomers into a chromatographic tube and polymerizing it under such conditions that a polymer rod forms containing channels which permit hydrodynamic flow of the mobile phase at a relatively low back pressure; (2) the monomers are water-soluble, which means that the polymer bed is biocompatible and that no organic solvents are required for the synthesis, which is attractive
Abstract: Continuous polymer beds (acrylic-based beds) have the following advantages over beds packed with beads: (1) For most chromatographic modes they can be synthesized in one step by sucking a solution of appropriate monomers into a chromatographic tube and polymerizing it under such conditions that a polymer rod forms containing channels which permit hydrodynamic flow of the mobile phase at a relatively low back pressure. The expensive and time-consuming preparation of beads by the conventional suspension−polymerization procedure is thus omitted, as well as the packing step. (2) The monomers are water-soluble, which means that the polymer bed is biocompatible and that no organic solvents are required for the synthesis, which is attractive from an environmental and economical point of view (the destruction or regeneration of organic solvents often costs more than the purchase). (3) The bed can be prepared in situ as described above or, alternatively, by simple packing with bed material synthesized separately ...
TL;DR: Expanded bed protein A affinity chromatography using Streamline rProtein A media is an efficient method for purifying a recombinant humanized monoclonal antibody from unclarified Chinese hamster ovary cell culture fluid and that it provides purification performance comparable to using a packed bed.
TL;DR: In this article, the removal efficiency and pressure drop of 10 commercial filters, including 8 made of granule or powdered activated carbon, 1 activated carbon fiber filter, and 1 packed bed made of an ozone catalyst, were measured for an influent ozone concentration of 120 ppb at 50% relative humidity and 2.54 m/sec face velocity.
Abstract: Performance of filters for the removal of ozone at ambient concentration is characterized. The removal efficiency and pressure drop of 10 commercial filters—including 8 made of granule or powdered activated carbon, 1 activated carbon fiber filter, and 1 packed bed made of an ozone catalyst—were measured for an influent ozone concentration of 120 ppb at 50% relative humidity and 2.54 m/sec face velocity. Activated carbon filters can be very effective at ozone removal, although not indefinitely because chemical reactions of ozone and carbon change the carbon. Initial efficiencies of the 1.27-cm thick flat samples varied from 4.6 to 98.3%. Analysis of the structure and composition of the filters with scanning electron microscopy and X-ray photoemission spectrometry showed chemical reactions permanently changed the composition of the carbon and decreased the surface area. Consequently, removal efficiency decreased with use. Moreover, it was not feasible to regenerate the filters by simply removing them from o...
TL;DR: In this article, an instrumental set-up was designed and used which combines a micro-column in the first dimension and a column packed with non-porous particles in the second dimension.
TL;DR: In this article, a 3D polygonal model was used to describe an arbitrarily complex packing object and a simple container object, and a search algorithm found stable equilibrium positions for the packing objects of arbitrary shapes using a collision-detection algorithm in a 3-D space.
Abstract: Using advances in computational geometry and collision-detection algorithms, an algorithm was developed to analyze and predict the geometrical properties of a randomly packed structure using packing objects of arbitrary shape. A 3-D polygonal model was used to describe an arbitrarily complex packing object and a simple container object. The dynamics of the packing process is not simulated, but a search algorithm finds stable equilibrium positions for the packing objects of arbitrary shapes using a collision-detection algorithm in a 3-D space. A modified conjugate gradient optimization method determines the packing object's final packing location and orientation. Once the bed is packed, both macroscopic quantities like the overall porosity, the specific surface area, and the number of packing objects per unit volume and microscopic properties like the porosity variation in any direction could be determined. For accurate porosity calculation inside a given 3-D polygonal sample space, the Sutherland-Hodgman polygon clipper algorithm was used. Predicted results are validated against available experimental data for spheres, Raschig rings, Pall rings, and cascade minirings.
TL;DR: In this paper, a detailed experimental investigation of the heat and mass transfer between a liquid desiccant (triethylene glycol) and air in a packed bed regenerator using high liquid flow rates is presented.
Abstract: Liquid desiccant cooling can provide control of temperature and humidity, while at the same time lowering the electrical energy requirement for air conditioning. Since the largest energy requirement associated with desiccant cooling is low temperature heat for desiccant regeneration, the regeneration process greatly influences the overall system performance. Therefore, the effects of variables such as air and desiccant flow rates, air temperature and humidity, desiccant temperature and concentration, and the area available for heat and mass transfer on the regeneration process are of great interest. Due to the complexity of the regeneration process, which involves simultaneous heat and mass transfer, theoretical modeling must be verified by experimental studies. However, a limited number of experimental studies are reported in the literature. This paper presents results from a detailed experimental investigation of the heat and mass transfer between a liquid desiccant (triethylene glycol) and air in a packed bed regenerator using high liquid flow rates. To regenerate the desiccant, it is heated to temperatures readily obtainable from flat-plate solar collectors. A high performance packing that combines good heat and mass transfer characteristics with low pressure drop is used. The rate of water evaporation, as well as the effectiveness of the regeneration processmore » is assessed based on the variables listed above. Good agreement is shown to exist between the experimental findings and predictions from finite difference modeling. In addition, the findings in the present study are compared to findings previously reported in the literature. Also, the results presented here characterize the important variables that impact the system design.« less
TL;DR: In this paper, the performance of a representative sheet metal structured packing (Mellapak 250.Y) in commercial-scale experimental columns (1.2 m i.d.) is presented over a wide range of test systems and conditions.
Abstract: The performance of a representative sheet metal structured packing (Mellapak 250.Y) in commercial-scale experimental columns (1.2 m i.d.) is presented over a wide range of test systems and conditions. Pressures span the range of 0.02−27.6 bar. Systems include o-xylene/p-xylene, cyclohexane/n-heptane, and i-butane/n-butane. The operations were carried out in two separate columns (high and low pressure) utilizing two identical loads of packing. Internal bed samplers were utilized. Capacity, separation efficiency, and pressure drop are reported and compared to the predictions of published models. Some of the more important results were obtained at the extreme ends of the operating range. It was found that, with an appropriate distributor, separation efficiency is maintained down to extremely low liquid rates, indicating that dewetting is not significant. At the other end of the operating range (high pressure and high liquid rate) a “hump” or region of decreased mass-transfer performance was observed at the s...
TL;DR: In this paper, a statistical model of liquid flow is used to analyse new experimental results obtained by X-ray computed tomography (X-ray tomography) in packed beds.
Abstract: Ideas which have developed during this century about liquid maldistribution in packed beds are summarized. A statistical model of the liquid flow is used to analyse new experimental results obtained by X-ray computed tomography.
TL;DR: In this paper, a novel structured catalyst packing is proposed, which consists of a common structured distillation packing, on which a binderless film of zeolite crystals is grown via in-situ hydrothermal synthesis.
TL;DR: In this paper, two-dimensional simulations of packed beds composed of binary and ternary particle mixtures were made and image analysis of the bed structure was used to determine the bed porosity and tortuosity.
TL;DR: In this paper, the liquid-phase residence time distribution has been measured in two structured packed column configurations, of 0.1 and 0.24 m diameter, in which the catalyst particles are enclosed within wire gauze envelopes (sandwiches).