Non-porous Glass Beads Research Articles

Numerical Simulation on Dispersion of Hydrogen Leaked in Particle Layers of Glass Beads and Soil

In order to understand the dispersion of hydrogen (H2) leaked in packed beds of nonporous/porous particles in a partially open space practically, the dispersion of H2 in the particle layers of glass beads and soil was analytically studied using a computational fluid dynamics code to be compared with the experiments and to elucidate the effects of the particle layer. The packed beds in the partially open space can be considered as a basic model for all processes of transfer, treatment, storage, and disposal of radioactive materials containing fuel debris in the decommissioning of nuclear facilities after a severe accident. The H2 flowing out from a single leak point in the particle layer of nonporous glass beads was affected by buoyancy around the leak point and diffused directly above the leak point in an elliptical shape faster than in the horizontal direction. After that, when it reached the air layer in the head space above the particle layer, the H2 spread horizontally, formed a large concentration gradient near the boundary between the particle layer and the air layer, and further diffused in the air layer until the H2 concentration became about 1/3 or less of the concentration near the surface of the particle layer. When the particle diameters were 512 μm and 1200 μm, this tendency was more pronounced when the porosity was the same and the particle diameter was smaller. The calculations largely reproduced the experimental concentration distributions. When the particle layer was porous decomposed granite soil, the diffusion behavior of H2 in the particle layer proceeded in the same manner as in the case of the glass beads. However, a large concentration gradient was formed near the boundary between the particle layer and the air layer, and then H2 diffused in the air layer until the H2 concentration became below the lower combustion limit. It was suggested through sensitivity analysis that the air permeability coefficient had a large effect on the time course of the H2 concentration distribution. Based on this information, we further simulated H2 behavior in the vessel containing the H2 leaked particle layer. By inserting multiple vent pipes without considering H2 generation distribution and particle properties in the particle layer, H2 accumulated from one pipe was discharged by buoyancy without depending on the H2 generation distribution and particle properties in the particle layer and air flowed in from the other pipe. It was suggested that such a natural ventilation process would reduce the H2 concentration in the container.

External Wetting Efficiency in a Three-Phase Fixed Bed Loaded with Porous and Non-Porous Packings

Films and rivulets are the two basic forms of dynamic liquid in a three-phase fixed bed (trickle bed), which determines the wetting efficiency of the catalyst. This paper is devoted to the conflicting wetting performance observed between non-porous glass beads and less wettable porous alumina, and a parallel zone model is applied to resolve the complex liquid flow texture. It shows in both cases of glass beads and aluminium pellets, the pressure drop, film flow and rivulet flow fractions all display pronounced multiplicities along with the liquid flow rates in increasing and decreasing branches, although the rivulet flow fraction is reduced to 0 in the liquid decreasing branch started from pulsing flow in both cases. Different from the glass beads, there is almost no wetting efficiency difference for the alumina pellets with respect to liquid flow rate increasing or decreasing, which is in agreement with the dynamic liquid holdup measurements. The liquid is significantly more uniformly distributed over the crosssection in the Al2O3 bed since rivulet flow is much reduced than in the case of glass beads.

Effects of moisture content on electrostatic sensing based mass flow measurement of pneumatically conveyed particles

Mass flow rate measurement of pneumatically conveyed particles is desirable for the optimal control of many industrial processes. The unpredicted variation of moisture content in particles affects the accuracy of mass flow measurement of particles in enclosed pipelines using electrostatic electrodes. In this study, the characteristics of measured electrostatic signals from particle flow under different flow conditions are analysed to study the effect of moisture content on the mass flow rate measurement. The measurement principle of ring-shaped electrostatic electrodes, the effects of moisture content on electrification of solid particles, and the experimental setup used in the study are presented. Two types of electrostatic electrodes with different axial widths and structure are adopted to measure the electrostatic signals of nonporous glass beads and porous activated carbon powder on the vertical pipeline of a 74mm bore gas–solid two-phase flow test rig under various moisture content, mass flow rate and conveying velocity conditions. The experimental results indicate that the amplitude and frequency characteristics of the electrostatic signals change with the moisture content. The deviation of mass flow measurement that caused by the variation of moisture content is analysed, and a recalibration process is demonstrated to be effective for the improvement of measurement accuracy.

Continuous photofermentative production of hydrogen by immobilized Rhodobacter sphaeroides O.U.001

Photofermentative hydrogen production applying Rhodobacter sphaeroides O.U.001 immobilized on porous glass plates or porous and non-porous glass beads in presence of malic acid (Biebl and Pfennig medium) was studied under continuous and semicontinuous conditions. The applied bacteria operating under continuous regime showed the best performance and stability while immobilized on porous glass plate modified with (3-(2-aminoethyl)aminopropyl)trimetoxysilane (AEAPTMS). Here, the total amount of produced hydrogen was 4.19 L/reactor whereas average hydrogen production rate was 12.7 mL/L medium/h at hydraulic retention time (HRT) of 22 h. For experiments in suspension cumulative hydrogen amount was only 2.39 L/reactor. Accumulation of VFA's (mainly formic acid) in reaction medium as well as accumulation of biomass on supports was responsible for the decreasing activity. Comparison of different parameters in experiments with porous and non-porous glass beads proved that HRT plays a crucial role in photofermentative hydrogen production.

Studying the effect of nature of glass surface on immobilization of glucose isomerase

Immobilization of glucose isomerase (GI) (EC 5.3.1.5) has been carried out on non-porous glass surfaces using γ-aminopropyltriethoxysilane and polyethyleneimine as an activator and gluteraldehyde as cross linking agent for its potential use. Polyethyleneimine was found to be a superior immobilization activator than γ-aminopropyltriethoxysilane. Further, the effects of rough and smooth surfaces of non-porous glass beads on immobilization of glucose isomerase have been investigated. Polyethyleneimine on rough glass beads was found to be better activator material than that of γ-aminopropyltriethoxysilane. The prime objective of study was to immobilize glucose isomerase on an improved surface of non-porous glass beads which will give a significantly higher immobilization yield. After optimizing the parameters the immobilization yield increased from an initial value 29.43% to 79.6%.

Immobilisation of lipase on the surface of magnetic nanoparticles and non‐porous glass beads for regioselective acetylation of prednisolone

Magnetic nanoparticles (MNPs) were prepared by co-precipitation of Fe+3/Fe+2 (2:1; molar ratio) with a mean size of 40 ± 5 nm. Scanning electron microscopy, dynamic light scattering, X-ray diffraction, vibrating sample magnetometer and thermogravimetric analysis were used to characterise the MNPs. The MNPs and also hydroxylated nonporous glass beads were similarly functionalised with the aid of glutaraldehyde to be cross-linked to lipase originated from Thermomyces lanuginosus (TLL). The yield and efficiency for immobilised lipase on the MNPs were calculated as 72 ± 2.4 and 63 ± 3.5%, whereas a yield and efficiency of 60 ± 2.1 and 55 ± 4.1%, respectively, were measured for the corresponding parameters of the immobilised enzyme on the glass beads. When the immobilised TLL was compared with its free form, Michaelis-Menten kinetics indicated an insignificant change in the Michaelis constant (Km) and a drastic decrease in the maximum substrate conversion rate (Vmax). The immobilised TLL and six other commercial lipases were then checked for regioselective acetylation of prednisolone. The highest and lowest yields of the product were observed for Novozym 435 and immobilised TLL on the glass beads, respectively. Immobilised TLL retained its bioacetylation activity of prednisolone in five successive catalytic processes.

The effect of particle porosity on liquid holdup in heap leaching

The inter- and intra-particle porosities of heaps have two distinct length scales (of order millimetres between the particles versus tens of microns within the particles) and therefore the dominant flow mechanisms within and around the particles are quite different. This paper investigates the effect of particle porosity on heap hydrodynamics by comparing the behaviour of a model system consisting of non-porous glass beads with a system of actual ore particles. The overall liquid holdup behaviour of these two systems initially appears quite different. However, when the effect of the liquid holdup around the particles is separated from that within the particles, the same theoretical flow model can be applied to both the model and ore systems. This demonstrates that correlating the liquid flow to the overall liquid holdup is problematic and that the effect of the inter- and intra-particle liquid holdup should be considered separately. This is important as the amount of liquid held within the ore particles in these experiments was nearly as large as that held around the particles. The model for the external liquid flow proposes a power law relationship between the relative flow rate (flow rate divided by residual holdup) and the excess relative holdup (the steady state liquid holdup divided by the residual holdup minus one) with an exponent of two. It was found that the pre-factor in this relationship was quite a strong function of particle size for the spherical glass beads, but relatively constant for the more angular ore particles.

Enhanced catalytic performance of immobilized Parvibaculum lavamentivorans alcohol dehydrogenase in a gas phase bioreactor using glycerol as an additive

The efficacy of glycerol as an additive at enzyme immobilization on the catalytic performance (activity, stability, enantioselectivity and productivity) of immobilized (R)-specific Parvibaculum lavamentivorans alcohol dehydrogenase in a continuous gas phase reactor was investigated. The enantioselective reduction of 4-methyl-2-pentanone with concomitant NADH regeneration by 2-propanol as co-substrate was used as a model reaction. Non-porous glass beads were used as immobilization carriers. The immobilized alcohol dehydrogenase performance was markedly enhanced by the addition of glycerol. Interestingly, the enantioselectivity was stabilized during the reaction progress. The optimal glycerol amount, thermodynamic activity of water in the feed gas phase, and reaction temperature were obtained at 10mg/g-glass carriers, 0.8 and 313K in terms of the productivity, respectively. As a function of the thermodynamic activity of substrate in the feed gas phase, it was also optimized at 0.103 for 2-propanol and 0.250 for 4-methyl-2-pentanone. Compared to the glycerol-free immobilized enzyme system, the productivity of the chiral compound was ca. 15-fold higher, on the other hand, based on the kinetic analysis the maximum reaction rate was found to be about 2-times higher, while the Michaelis constant for 2-propanol was about 2-fold lower and that for 4-methyl-2-pentanone decreased slightly. These findings indicate that the gas phase enzyme reaction exhibits an excellent catalytic performance in the presence of additive glycerol for chiral compound production, however needs to optimize the additive amount and reaction conditions for effective industrial operation.

Assessing and predicting granular‐materials hydrophobicity by parametrizing a general equation of state§

AbstractWettability is related to forces or surface tensions (σ) acting at the solid–liquid–vapor interface. Given that surface tensions are difficult to assess directly, contact angles (CA) are used as indicators of the balance of forces acting in the system. In this context, the ES theory was developed as an alternative to assess the σ parameters of the Young's equation. This research evaluates the applicability of a proposed equation of state (ES), which is in theory also able to predict the CA of a sample when two σ parameters of the Young's equation and two fitting parameters (β and α) of the function Φ = (σSL) are known (Φ: molecular interaction parameter, σSL: solid–liquid surface tension). These parameters were determined by different experimental methods assessing the CA, in order to determine which method is more suitable to validate the ES theory: Capillary Rise Method (CRM) and Wilhelmy Plate Method (WPM). For WPM, two modes (advancing and equilibrium CA) were applied. Finally, results of CA between the experimental measurements obtained by WPM and those predicted by the ES were compared. Samples of coarse silt, fine sand, and nonporous glass beads with different levels of water repellency were used as test materials. In line with previous research, all methods showed lower values of σ for samples with increasing hydrophobicity. At the same time, Φ reduces consistently with higher hydrophobicity, up to ≈ 0.5–0.6 based on CRM and WPM‐ECA data, and even lower (≈ 0.1–0.2) in WPM‐ACA. α increased with higher hydrophobicity, having relatively stable values in samples having σSV > 40 mN m–1. β showed stable values for samples having σSV > 35–40 mN m–1. In hydrophobic samples (σSV < 35 mN m–1), β decreased in calculations based on WPM‐ACA data, and to a minor degree in WPM‐ECA. The agreement between the CA directly measured (WPM) and those predicted by the ES was low, although better for the WPM‐ECA, suggesting that this last approach can be considered more suitable to evaluate the ES theory.

Continuous Stereoselective Reduction Catalyzed by Thermophilic Alcohol Dehydrogenase in a Gas Phase Bioreactor

The present study investigates continuous gas phase stereoselective reduction catalyzed by commercial thermophilic alcohol dehydrogenase. The alcohol dehydrogenase and cofactor β-nicotinamide adenine dinucleotide phosphate were simultaneously immobilized on non-porous spherical glass beads. The reduction of 4-methyl-2-pentanone to (S)-4-methyl-2-pentanol with concomitant cofactor regeneration by 2-propanol was employed as a model reaction. According to the differing buffer pH dependence of the enzyme activity on both substrates, the maximal reactivity was obtained at a pH of 7.5 used for immobilized enzyme preparation. Owing to the higher stereoselective production, the water activity in the feed gas phase and reaction temperature were optimized at 0.9 and 333 K, respectively.

Leaching of BTEX from Aged Crude Oil Contaminated Model Soils: Experimental and Modeling Results

It is generally assumed that soil properties such as organic matter content, porosity, and mineral surface area have a significant effect on the bioavailability and leachability of aged petroleum hydrocarbons. In order to test this hypothesis, nine model soils or sorbents (i.e., fine and coarse quartz sand, montmorillonite and kaolinite clay, peat, 60Å and 150Å silica gel, a loam soil, and non-porous glass beads) were spiked with a crude oil, aged for 27 months in the laboratory, and transferred to glass columns for the performance of continuous flow leaching experiments. The column effluents were periodically sampled for 43 days and analyzed for BTEX. A one-dimensional flow model for predicting the dissolution and dispersion of individual hydrocarbons from a multi-component NAPL such as crude oil was used to fit the leaching data (i.e., the BTEX concentration versus time curves) by adjusting the equilibrium oil-leachate partitioning coefficient (K ol ) for each respective hydrocarbon. The Peclet number, which is a measure of dispersion and a required modeling parameter, was measured in separate chloride tracer experiments for each soil column. Results demonstrate that soil properties did not significantly affect the leaching kinetics of BTEX from the columns. Instead, BTEX leaching curves could be successfully fitted with the one-dimensional NAPL dissolution flow model for all sorbents with the exception of montmorillonite clay. The fitting parameter K ol for each hydrocarbon was found to be similar to the K ol values that were independently measured for the same crude oil by Rixey et al. (Journal of Hazardous Materials B, 65: 137–156, 1999). In addition, the fitted K ol values were very similar for BTEX leaching from aged compared to freshly spiked loam soil. These findings indicate that leaching of BTEX in the aged soils that are contaminated with crude oil at the high concentrations commonly found in the environment (i.e., > 20,000 mg/kg) was not affected by soil properties or aging but rather was governed by the equilibrium dissolution of these hydrocarbons from the crude oil NAPL that is coating the soil particles.

Vacuum Contact Drying Kinetics: An Experimental Parametric Study

Vacuum contact drying kinetics of a model system consisting of nonporous glass beads and water has been experimentally measured on a laboratory scale. A methodology for determination of drying curves from experimental data in a statistically robust way has been developed. The effects of jacket temperature, head-space pressure, particle bed depth, vessel diameter, and particle size on drying rate during constant and falling rate periods have been studied. It was found that in the range of parameters investigated, drying rate does not depend on the means of realization of the driving force (by temperature or pressure); drying rate in the constant-rate period decreases with increasing bed depth while the overall heat-transfer rate increases due to increased surface area. A very strong dependence of drying rate and regime on particle size was observed; the constant-rate period disappeared for small particles.

NMR imaging of mass transport processes and catalytic reactions

NMR imaging and spectroscopy techniques are applied to study flow and filtration of liquids, gases and granular solids in various geometries and to the in situ studies of the interplay of mass transport and catalytic reactions in porous media. In particular, quantitative spatially resolved maps of flow velocities of liquids and gases in the channels of monoliths have been obtained. A comparative study of the filtration of water and propane through model porous media has revealed that the dispersion coefficients for water are dominated by the holdup effects even in a bed of nonporous glass beads. Similar experiments performed with the gravity driven flow of liquid-containing fine solid particles through a porous bed have yielded the distributions of particle velocities for various flow rates. The NMR imaging technique was employed to visualize the propagation of autocatalytic waves for the Belousov–Zhabotinsky reaction carried out in a model porous medium. It was demonstrated that the wave propagation velocity decreases as the wave crosses the boundary between the bulk liquid and the flooded bead pack. The images detected during the catalytic hydrogenation of α-methylstyrene on a single catalyst pellet at elevated temperatures have revealed that the reaction and the accompanying phase transition alter the distribution of the liquid phase within the pellet.

Bacillus licheniformis α-amylase immobilized on glass beads and equilibrated at low moisture content: potentials as a Time–Temperature Integrator for sterilisation processes

Time–Temperature Integrator (TTI) systems based on Bacillus licheniformis α-amylase (BLA), sucrose and salts immobilized at the surface of non-porous glass beads (inert filler) and under several low moisture conditions ( a w in the range 0–0.63 after equilibrium at 4 °C) were studied. These systems showed interesting thermal stabilities in the range 100–132 °C under isothermal conditions. More precisely, the TTI system equilibrated at a w=0.48 (BLAGB48) showed capabilities, under non-isothermal conditions, for monitoring the process value z TTI=9.4 °C F 121.1 °C in the range 0–30 min with an absolute average % error of 14%. Although this error is comparable to already reported systems, this TTI showed numerous advantages over the latter: (i) The time required for the moisture equilibration of the systems was significantly reduced (2–3 days instead of 3 weeks). (ii) The aggregation of the α-amylase during heating could be overcome enhancing the solubilization of the α-amylase after heat treatment in only 1 min. (iii) Consequently, it became possible to use convenient residual activity reading method (only 5 min required) instead of a residual heat denaturation enthalpy reading (15 min required) as a response property of the system. (iv) The amount of α-amylase required per TTI was 50-fold smaller. (v) Finally, larger thermal impacts (process values up to 30 min) could be monitored.

Determination of adsorption and diffusion parameters in zeolites through a structured approach

Temporal analysis of products (TAP) is a transient pulse-response technique that allows to extract kinetic information from reacting and adsorbing systems. In a previous work (Chem Eng Sci 57(2002) 1835), a detailed-transport model for the Multitrack set-up, a TAP-like system, was developed, which allows studying systems with a low bed resistance. The use of structured beds, having both a low bed resistance and small sorbent particles, is required to determine adsorption and diffusion parameters when strong adsorption and slow diffusion occurs. A method is presented to extend the range of measurable adsorption and diffusion parameters in zeolitic sorbents in the TAP technique by a structured approach. Small zeolite crystals are coated on larger non-porous glass beads. Adsorption and diffusion parameters for n-butane, SF 6 and 3-methylpentane have been determined in MFI-type zeolites. Absolute diffusivity values in the zeolite coating are estimated by using a well-defined silicalite sample as a reference to determine the effective diffusion length in the coating. Two criteria have been derived, one for the characteristic time for transport through the bed, 0.05 s<t bed <4 s , and one for the ratio of the latter and the characteristic diffusion time in the zeolite crystal, 0.01< α<200 t bed/(1+ t bed), which should be satisfied both to be able to determine values of the zeolite diffusivity.

Polymorph selectivity under nanoscopic confinement.

Polymorph selectivity has been achieved during crystallization of anthranilic acid (AA) and 5-methyl-2-[(2-nitrophyenyl)amino]-3-thiophenecarbonitrile (ROY), both considered benchmarks of polymorphic behavior, within nanoporous glass beads and polymer monoliths. Whereas polymorph III of AA crystallizes from the melt on nonporous glass beads or within larger pores, the metastable polymorph II crystallizes in pores with diameters <23 nm, with the selectivity toward this form increasing with decreasing pore size. Of the six ROY polymorphs characterized by single-crystal X-ray diffraction, the yellow form (Y) crystallizes during evaporation of pyridine solutions imbibed by the 30-nm cylindrical pores of porous polycyclohexylethylene (p-PCHE) monoliths. Although both R and ON grow from the melt on the external surfaces of PCHE, only the red form (R) crystallizes in the pores. Amorphous ROY also forms in p-PCHE pores during evaporation from pyridine solutions, subsequently crystallizing to the R nanocrystals upon heating. Although heterogeneous nucleation on the pore walls may play a role, these observations suggest that nucleation and polymorph selectivity is governed by critical size constraints imposed by the ultrasmall pores. The ability to achieve polymorph selectivity in both glass and polymer matrices suggests wide-ranging compatibility with various organic crystalline solids, promising a new approach to controlling polymorphism and searching for unknown polymorphs.

A novel method for immobilization of chitosan onto nonporous glass beads through a 1,3-thiazolidine linker

A new method for the surface modification of nonporous glass beads (average diameter, 6 μm), which characterized by formation of a 1,3-thiazolidine ring between l-cysteine linkers on the glass bead and reducing ends of chitosan, has been developed. γ-Aminopropyltriethoxysilane (APES)-treated glass bead was first subjected to condensation with an l-cysteine derivative, l-4-carboxy-3-formyl-2,2-dimethylthiazolidine (CFMT), in the presence of water-soluble carbodiimide hydrochloride (WSC) and HOBt. After deprotection by diluted hydrochloric acid, the glass beads with activated cysteine linkers on the surface were treated with reducing chitosan in aqueous acetic acid solution at room temperature. The maximum content of chitosan immobilized on the glass beads estimated by acid-hydrolysis and subsequent glucosamine analysis by Svennerholm method after was 0.73% (w/w). This was obtained by using chitosan having an average molecular weight of 14 kD. Model reactions of the cysteine derivatives with reducing chitosan were also performed and the product was examined by IR and NMR spectroscopy to verify the linkage between cysteine and chitosan.

Surface modification of nonporous glass beads with chitosan and their adsorption property for transition metal ions

A new hybrid material that adsorbs transition metal ions was prepared by immobilizing chitosan on the surface of nonporous glass beads. The glass beads, prepared by etching in aqueous NaOH at 100°C, were first reacted with γ-aminopropyltriethoxysilane (APES) to introduce amino groups on the surface. Subsequently, the resulting aminated beads were treated with glutaraldehyde at 25°C to change the amino groups into aldehyde groups. Finally, chitosan of average molecular weight 40,000 was introduced via the aldehyde groups through a Schiff's reaction. After complete acid-hydrolysis of the immobilized chitosan, the Svennerholm method for glucosamine analysis showed that 0.3% (w/w) chitosan had been successfully introduced on the glass beads. Atomic absorption spectroscopic analysis of eluants of a column of the chitosan-modified glass beads showed that metal ions such as Cu 2+, Ag +, Pb 2+, Fe 3+, and Cd 2+ were more than 90% entrapped on a column of beads prepared in this manner.

A STUDY OF THE PARAMETERS AFFECTING THE INTERPARTICULAR VOID VOLUME USING A NEW TITRATION METHOD

A new titration method proposed by Huyhn et al., which directly measures the interparticular pore volume between the particles in a concentrated suspension, has been further investigated. It is expected that for an ideal powder with uniform spherical particles, the plot of weight versus the void volume should be a straight line passing through the origin. Glass beads, which are nonporous and expected to be ideal, were used in this study and the results were compared with the results of the experiments by Huyhn et al. Glass beads of different size ranges are used to study the effect of particle size on voidage. It was observed that the voidage increases with a decrease in particle size, However, the non-porous glass beads were also found not to be ideal.

Freeze–purged–desorption method for quantitative evaluation of CO 2-solubility in polymeric films

A new experimental method, named as freeze–purged–desorption (FPD) method, to evaluate quantitatively the amount of gases sorbed in polymeric films, has been developed by using carbon dioxide gas and five different films (low density polyethylene: LDPE, polypropylene: PP, polystyrene: PS, polyacrylonitrile copolymer: PAN, polycarbonate: PC). The FPD method consisted of three operational periods of time based on the stepwise change in the system temperatures, the freeze periods of sorbed CO 2 at −196°C, the purging period of atmospheric CO 2 at −78°C and the desorption period of the freezed CO 2 in the film at −9°C. The evaluated values for LDPE, PP, PS, PAN and PC were 0.310, 0.65, 3.90, 0.098 and 6.90 (cm 3(STP)/cm 3 atm), respectively, which were about 20–40% higher than the reference values. The validity of the method was reconfirmed by a good reproducibility of the desorption curves of sorbed gases referring to a blank curve obtained from the non-porous glass beads.