Bed Of Beads Research Articles

General methods to render macroporous stationary phases nonporous and deformable, exemplified with agarose and silica beads and their use in high-performance ion-exchange and hydrophobic-interaction chromatography of proteins

New general methods for the preparation of nonporous beads from macroporous beads are described. One method is based on filling the inner volume of the beads with a solution of a monomer which binds to the matrix at the same time as it is allowed to polymerize. The method is illustrated with agarose and silica as matrices and glycidol as monomer. In an alternative, but principally similar method, we first attached allyglycidyl ether to agarose via the epoxide groups and then allowed acrylamide to react with the immobilized allyl groups during polymerization. In an analogous way, nonporous silica beads were prepared by coupling γ-methacryloxypropyltrimethoxy silane to the macroporous beads followed by polymerization of acrylamide or N-methylolacrylamide on the immobilized methacryl groups. The latter monomer has the advantage of giving a polymer rich in OH groups, which can be used for crosslinking or/and attachment of different ligands (the glycidol polymers have the same advantage). The nonporous agarose beads have chromatographic properties similar to those of the previously described nonporous agarose beads prepared by shrinkage and subsequent crosslinking. For instance, the beds are compressible, which favors the resolution: compressed beds of large beads give the same or higher resolution than do beds of small beads. Another similarity is that the resolution is independent of flow rate or is even enhanced upon an increase in flow rate, maybe in part owing to the generation of a flow pattern which transports the solute from one bead to another faster than does diffusion. These similarities are demonstrated by anion-exchange and hydrophobic-interaction chromatography of proteins. Even the nonporous silica beads are somewhat deformable owing to the relatively thick polymer coating and share with the nonporous agarose beads the attractive relation between resolution and flow rate. In addition, in comparison with naked silica beads they exhibit very little protein adsorption and are more pH stable. A compressed bed of nonporous, coated 30–45 μm silica beads gave in an HIC experiment a resolution comparable to that obtained with a bed of noncompressed, nonporous 1.5-μm silica beads, which give a very high resolution, as shown by Unger and coworkers [5].

Burning Characteristics Of A Combustible Liquid Soaked In Porous Beds

An experimental study has been made on the burning characteristics of liquid methanol soaked in porous beds of glass beads. In order to study the effects of the soil properties on the burning characteristics, experiments were carried out for several bead diameters. The consumption rates of methanol and the temperature profiles in the porous beds were measured. The results showed that the total weight of the methanol consumed was only about half of the initial weight and the consumption rate decreased with time. The total weight of the consumed methanol and the consumption rate of methanol increased with decreasing bead diameter. The temperature profiles indicated that the dry region in a porous bed, in which only methanol vapor was assumed to exist, expanded downward with time. The discrepancy between the lower boundary of the dry region and the liquid level evaluated on the basis of methanol consumption for small beads suggested that the liquid moved upward by a capillary force. A simplified heat transfer model was proposed for large beads and the predicted results agreed qualitatively with the experimental ones. The consumption rate on large beads bed was inferred to be controlled mainly by the heat transfer in the porous bed.

Burning Characteristics Of A Combustible Liquid Soaked In Porous Beds

An experimental study has been made on the burning characteristics of liquid methanol soaked in porous beds of glass beads. In order to study the effects of the soil properties on the burning characteristics, experiments were carried out for several bead diameters. The consumption rates of methanol and the temperature profiles in the porous beds were measured. The results showed that the total weight of the methanol consumed was only about half of the initial weight and the consumption rate decreased with time. The total weight of the consumed methanol and the consumption rate of methanol increased with decreasing bead diameter. The temperature profiles indicated that the dry region in a porous bed, in which only methanol vapor was assumed to exist, expanded downward with time. The discrepancy between the lower boundary of the dry region and the liquid level evaluated on the basis of methanol consumption for small beads suggested that the liquid moved upward by a capillary force. A simplified heat transfer model was proposed for large beads and the predicted results agreed qualitatively with the experimental ones. The consumption rate on large beads bed was inferred to be controlled mainly by the heat transfer in the porous bed.

Bed expansion characteristics and transition velocity in turbulent fluidized beds

The bed expansion and the transition velocity from slugging to turbulent fluidized beds of glass beads (d p = 0.362 mm) have been determined in a 0.1 m-I.D. × 3.0 m high Plexiglas column. The bed expansion in the slugging and turbulent flow regimes has been determined from the bed voidage obtained by the mean pressure drop in the bed. Change of slope in a logarithmic plot of bed voidage against gas velocity has been utilized to determine the transition velocity from the slugging to turbulent flow regimes. Bed expansion in both regimes was found to be smaller than that predicted from the two-phase theory. The effects of particle properties and column size on the transition velocity to the turbulent flow regime have been determined. The flow regimes and corresponding transitions spanning from the bubbling to dilute phase flows have been quantitatively predicted in terms of the Reynolds and the Archimedes numbers based on the data of the present and previous studies.

Assessing some aspects of deep bed filtration of clay suspensions via transport properties

This paper is devoted to the deposition of colloïdal particles from a suspension flowing through a granular bed; we focus on systems where deposition takes place in the bulk of the bed. This deposition is studied in a particular case (clay suspensions flowing through beds of glass beads), through its effects on the transport of the water and of the suspensions. A radioactive tracer is used to detect the colloïd. The analysis of the evolution as filtration proceeds of the residence time distributions brings much information about the deposition. In particular, it provides the amounts of deposited clay with good accuracy.

High-Performance Liquid Chromatography of Proteins on Deformed Nonporous Agarose Beads. Affinity Chromatography of Dehydrogenases Based on Cibacron Blue-Derivatized Agarose

Nonporous agarose beads, prepared by shrinkage and cross-linking in organic solvents, were derivatized with Cibacron Blue F3G-A. A compressed bed of these beads was used for purification of dehydrogenases (glucose-6-phosphate dehydrogenase, lactate dehydrogenase and alcohol dehydrogenase). The chromatographic conditions for the purification of glucose-6-phosphate dehydrogenase were optimized by varying the pH of the buffer; the concentrations of eluting agents, i.e. NADP (specific elution) and sodium chloride (nonspecific elution); flow rate; residence time of the protein on the column bed; and protein load. Specific elution with NADP (2 mM in 0.025 M Tris-HCl, pH 8.0) gave the highest recovery (140%) and highest purification factor (200-fold) of the enzyme. The ability of the compressed bed of nonporous agarose beads to tolerate high flow rates was essential, since the recovery of the enzyme activity increased with an increase in flow rate.

Axial mixing of solids in turbulent fluidized beds

Axial mixing of solids in a fluidized bed of glass beads (0.362 mm) in the slugging and turbulent flow regimes was studied in a Plexiglas column (inside diameter, 0.1 m; height, 3.0 m). The effective axial dispersion coefficient of the solid phase in the bed was determined from the axial transport of heat at steady state. The effective axial dispersion coefficient of the solid phase is almost constant in the slugging flow regime, and increases with an increase in gas velocity in the turbulent flow regime. The mixing of solids in the bed is assumed to be described by mixing tanks in series connected by perfectly mixed and plug flows. The fraction of perfectly mixed flow in the bed remains almost constant in the slugging flow regime, and increases with an increase in gas velocity in the turbulent flow regime. The effects of column size and properties of the solid particles on the effective axial dispersion coefficient of the coarse particles in the bed were determined. The effective axial dispersion dataof the solids, in terms of the Peclet number, were correlated with the Archimedes number.

PRESSURE DROP IN FLOW OF A NEARLY CRITICAL FLUID THROUGH PACKED BEDS OF SPHERES

The flow of nearly critical carbon dioxide through packed beds of glass beads and steel spheres has been investigated. Experiments have been carried out in the intermediate range of sphere Reynolds number. Results show that around the critical point effects of fluid compressibility are negligible, and, therefore, that the friction factor can be expressed as a function of Reynolds number only. Carman [1] and Dolejs and Lecjaks [2] equations show good agreement with the experimental data.

HCI Sorption by Dry NaHCO3 for Incinerator Emissions Control

The sorption of hydrochloric acid (HCI) by thermally decomposed sodium bicarbonate (NaHCO3) was investigated using a fixed-bed reactor containing sorbent particles dispersed in a bed of spherical glass beads. The gas flow rate (68° F and 760 mm Hg) was 0.039 cfm (1.1 liter/min) and the bed had a cross-sectional area of 0.0055 sq. ft. (5.1 sq. cm). The influence of particle diameter (10, 45 and 163 μm), temperature (225, 275, 375, 455, and 550° F), superficial gas velocity (11 and 21 fpm at reactor conditions, 375° F), and Inlet HCI gas concentration (415 ppm and 760 ppm in N2, 275 and 455° F) were studied. Results showed that HCI sorption increased strongly with increasing temperature but was only weakly dependent on particle diameter, superficial gas velocity, and HCI gas concentration.

Pressure fluctuations in a gas fluidized bed and fluidization quality

A pressure-measuring transducer probe is developed to record pressure fluctuations in gas-fluidized beds as a diagnostic tool to establish the quality of fluidization. It has been employed to investigate the behavior of four glass bead beds with average diameters of 147, 423, 1499, and 2685 μm. The pressure histories of these beds are recorded as functions of air velocity and the data are analyzed to compute the bubble or void renewal frequency. These results are interpreted in terms of the quality of bed fluidization. A similar technique is based on an analysis of temperature-history records and was developed in a previous paper. It is discussed here from the perspective of our new technique.

Subcooled pool film boiling from a cylinder and from a sphere placedin a liquid saturated bed of beads

In film-boiling heat transfer, the most important modeling assumption may be that the liquid and vapor phases are separated by a sharp boundary without intervening two-phase region. An effort is presently made to extend the results of Cheng et al. (1982) by using a model for a porous medium's effective conductivity which can account for the structure of the porous matrix used, which in this case is a bed of spherical glass beads. Theory and experiment are found to be in good agreement. 8 refs.

AN INTEGRAL MODEL FOR DRYING OF HYGROSCOPIC AND NONHYGROSCOPIC MATERIALS WITH DIELECTRIC HEATING

ABSTRACT Heat and mass transport phenomena in drying assisted by microwave or radio-frequency dielectric heating are analyzed. When drying at temperatures near boiling point or with high temperature gradients, the effect of the gas phase pressure gradient on moisture transfer within the solid can be important. The governing heat and mass transfer equations, including consideration of internal heat generation and the effect of the gas phase pressure gradient, are derived and solved in a one-dimensional system using an integral method. The integral model has been used to simulate dielectrically-enhanced convective drying of beds of polymer pellets, glass beads and alumina spheres with flow over the bed surface. Model predictions of drying rates and temperatures agree well with experimental data for these cases. The model provides a relatively fast and efficient way to simulate drying behavior with dielectric heating, and may be useful in design and optimization of dielectrically-enhanced convective drying p...

Particle growth characteristics in drying of orthophosphate solution in a fluidized bed.

The particle growth properties in drying of an aqueous mixture of sodium orthophosphates were studied in a 0.078 m-ID × 0.84 m-high fluidized bed. Glass beads and sodium tripolyphosphate (STPP) particles were used as the initial seed particles. Particle growth was mainly governed by the agglomeration of product particles in beds of glass beads and STPP particles. Particle growth conversion decreased with increasing gas velocity and bed temperature but increased with an increase in feed solution concentration. The particle size distribution of products can be represented by the lognormal distribution function. A semiempirical correlation is proposed to predict the size distribution of product particles in the bed.

GAS MIXING IN SLUGGING AND TURBULENT FLUIDIZED BEDS

Abstract The gas phase mixing in a fluidized bed of glass beads (dp = 0.362 mm) in the slugging and turbulent flow regimes has been studied in a 0.1 m-ID × 3.0 m high Plexiglas column. The gas dispersion in the downstream of the bed has been described by a diffusion process with the axial and radial dispersion coefficients. The radial dispersion coefficient of the gas phase is nearly constant with the variation of gas velocity in the slugging flow regime, but it increases with an increase in gas velocity in the turbulent flow regime. Appreciable backmixing of the gas phase is pronounced in the slugging flow regime whereas the lower gas backmixing is produced in the turbulent flow regime. The gas backmixing coefficient increases with an increase in gas velocity in the slugging flow regime, but it decreases slightly with an increase in gas velocity in the turbulent flow regime. The radial mixing and backmixing coefficients of the gas in terms of Peclet numbers have been correlated with the relevant dimensio...

Comparative study of two dissolution methods for indomethacin suppositories from fatty and water-soluble bases

The continuous flow-through bead bed dissolution apparatus was compared to the rotating paddle method used by USP XXI for the dissolution testing of indomethacin suppositories. The comparison of the two dissolution techniques showed that the continuous flow-through bead bed technique is more suitable for experimental studies while the rotating paddle method is suitable for routine dissolution testing. Also, it was noted that the suppositories containing a mixture of PEG 400 and 4000 in a ratio of 5:1 presented the highest rate of drug release.

SURFACE STRENGTH OF A WATER-SATURATED BED OF GLASS BEADS WHEN POLYACRYLIC ACID IS COVALENTLY BONDED TO THE BEADS

According to Emerson's model of the soil aggregate, a large soure of physical weakness exists at the surface of sand particles within the aggregate, particularly when wet. The aim of this study was to simulate sand particles with glass beads and to test the hypothesis that a bed of glass beads can resist large compressive forces in water when a polymer is bonded to the bead surfaces using chemicals and conditions that produce hydrolytically stable, covalent bonding. Because carboxyl and amine functional groups can react to form the amide bond and silanes can bond to a silanol surface (e.g., sand or glass), polyacrylic acid (PAA: FW ≈ 50 000), amines, and silanes were used to test the hypothesis for glass beads (53-μm mean diameter). The pressure at which the bed surface of the glass beads (when water-saturated) was penetrated with a flat probe (radius = 1.37 mm) served as an index of strength imparted by various chemicals when these were introduced into the system individually and in various combinations. A dramatic increase in the strength of the bed surface occurred only when all the theoretical requirements were met for both covalent bonding between the polymer and the silane and silanol coupling between the silane and the glass surface. We conclude that the hypothesis is confirmed for a simple system of glass beads and that large increases in the efficiency of soil conditioners may be potentially realized in soil aggregates if the weak links between inorganic particulates (sand, silt, and clay particles) and organic polymeric materials (natural or synthetic) are augmented with, or replaced by, strong and water-resistant links. Key words: Soil structure, soil conditioners, polymers, coupling agents, soil aggregates

A new correlation for non-newtonian flow through porous media

The flow through porous media of wax containing oils which exhibited Herschel-Bulkley flow behaviour was studied experimentally and theoretically over a wide range of conditions. Darcy's law for the laminar flow of Newtonian fluids through porous media has been modified, also a more general friction factor-Reynolds number correlation for the flow through porous media which includes a fluid yield value was presented as: f* − f o* = 150/Re* Experiments in co-axial cylinder viscometer and packed bed of glass beads were carried out with solutions of paraffin wax in oils and with a crude oil, also the effect of some parameters on yield stress was investigated.

High-performance adsorption chromatography of proteins on deformed non-porous agarose beads coated with insoluble metal compounds : II. Coating: aluminium and zirconium (hydr)oxide with stoichiometrically bound phosphate

Two novel supports for adsorption chromatography of biomolecules, based on deformed non-porous cross-linked agarose beads coated with aluminium or zirconium (hydr)oxide, were prepared. Some fundamental chromatographic properties of these bed materials are discussed, including the adsorption mechanism and high-resolution separations of mixtures of proteins, nucleotides and coenzymes. Both aluminium and zirconium (hydr)oxide agarose irreversibly and stoichiometrically bind phosphate ions, thus some of the chromatographic properties resemble those of calcium phosphate and hydroxyapatite. Fractionation of a β-glucosidase preparation into two components possessing enzymatic activity was achieved on the aluminium (hydr)oxide phosphate agarose, whereas chromatography on zirconium (hydr)oxide phosphate agarose removed several inactive contaminants but gave only one peak associated with enzyme activity. This finding indicates that the adsorption mechanisms of the two adsorbents are not identical, although other experiments show that there are several analogies. For instance, model proteins chromatographed on these two supports were eluted in the same order, although the relative retention times differed, i.e., the chromatograms did not have the same appearance. Compressed beds of cross-linked non-porous agarose beads, including those coated with aluminium and zirconium (hydr)oxide, have the unique feature that the resolution is roughly independent of flow-rate and that there is no need for small beads of narrow size distribution.

High-performance adsorption chromatography of proteins on deformed non-porous agarose beads coated with insoluble metal compounds : I. Coating: Ferric oxyhydroxide with stoichiometrically bound phosphate

A new support for adsorption chromatography of proteins based on crosslinked agarose gels containing ferric (hydr)oxide is described. Two methods have been used for immobilization of the ferric (hydr)oxide on agarose beads; namely,entrapment of preformed ferric oxide particles in connection with the preparation of macroporous agarose beads and precipitation of ferric oxyhydroxide on and in preformed non-porous agarose beads. In the former method many of the adsorption sites of the ferric oxide may become sterically blocked, resulting in chromatographic properties which are similar to those of cation exchangers. Therefore, attention was focused on the second method. Upon using compressed beds of non-porous agarose beads the resolution became independent of the flow-rate, even when the bead diameter was relatively large. When ferric oxyhydroxide agarose is equilibrated with phosphate buffer, some phosphate becomes stoichiometrically and irreversibly bound to the matrix. The separation mechanism of this ferric oxyhydroxide phosphate agarose is discussed. It differs from those of ion-exchange, hydrophobic-interaction, and molecular-sieve chromatography. One characteristic is that phosphate buffers are the most efficient eluting agents. Chromatography on ferric oxyhydroxide phosphate-agarose is accordingly a good complement to these three conventional methods. Some chromatographic properties of the adsorbents are described (resolution as a function of gradient time, flow-rate and protein load; and the pH dependence of the adsorption). A successful separation of a model mixture of six proteins was achieved. Purification of a commercial preparation of β-glucosidase is also presented.

High-performance liquid chromatography on continuous polymer beds

Current research in this laboratory is directed toward the investigation of various possible means to increase performance in electrophoresis and chromatography. These methods are studied in parallel because the separation mechanisms are analogouP, which means that solutions of methodological problems in electrophoresis are often applicable to analogous problems in chromatography and vice versa. In the chromatographic field we give an high priority to practical solutions (with the aid of theoretical considerations) of the following fundamental questions: (1) Is it possible to design chromatographic beds such that the resolution is independent of or even increases with an increase in the flow-rate and bead size? Classical chromatographic theory says no. However, the experiments described in refs. 4-6 and forthcoming papers show that compressed beds of non-porous agarose beads have the desired unique relationship between the resolution, flow-rate and bead-size. (2) Is it possible to design a chromatographic bed by bulk polymerization directly in the chromatographic tube? It has been taken for granted that a chromatographic bed must be built up of granulated particles, preferably in spherical form. Even when the spheres are monodisperse the packing is never perfect. The theoretical maximum resolution can therefore never be attained. Further disadvantages of packed beds are the time-consuming and expensive steps required for preparation of the beads, the sieving of the beads to select the desired size (if not monodisperse in the preparation) and the packing of the column with the beads, A continuous gel plug with channels sufficiently large to permit an hydrodynamic flow might be the ideal chromatographic column. One could then expect the zones to be almost as sharp as those obtained in agarose or polyacrylamide gel electrophoresis. Unfortunately, the latter continuous gels cannot be used for chromatography, since they collapse when pressure is applied, i.e., water cannot be pressed through them. However, more than 20 years ago we prepared a polyacrylamide gel (cross-linked in a special way) directly in a glass tube and on this gel plug separated monomers and dimers of albumin by molecular-sieve chromatography. The flow-rate was relatively low, which limited its usefulness. We have now resumed these experiments and at the same time have tried to improve the mechanical properties of the gel plug so that it will withstand higher pressures and thereby permit higher flow-rates. The polymerization technique is still under development and will be published else-