The effect of humidity on the form of water retention in a powder

At low relative humidities, the moisture associated with the particles of a powder is adsorbed water vapour. As the relative humidity increases, the thickness of the adsorbed layer also increases, until eventually condensation occurs at the contact points, generating liquid bridges.

The boundary between the two forms of water retention is determined by the stability of the liquid bridges, and occurs at a value of the relative humidity that can be derived from the B.E.T. isotherm for the adsorption of water vapour on the solid surface.

It is stressed that the relative humidity is the variable that defines the boundary condition rather than the moisture content of the powder.     

Lipid molarity affects liquid/liquid aroma partitioning and its dynamic release from oil/water emulsions

Initial dynamic flavor release from oil/water emulsions containing different TAG phases was studied using a computerized apparatus and thermodesorption GC. A significant influence of lipid molarity on liquid/liquid partitioning and release of some flavor compounds was found. The release of the least hydrophobic compounds was not affected by any type of lipid. Hydrophobic compounds showed a positive correlation between their release and decreasing molarity of the lipid phase, that is, with increasing number of lipid molecules; only the most hydrophobic compounds did not show such a correlation. A strong linear correlation between low-melting TAG/water partition coefficients and lipid phase molarity was validated by volatile partition data of C6, C11, and C16 alkane/water systems. Lipid phase transition from the liquid to solid state did not affect flavor partitioning and release. Neither experimental nor theoretical octanol/water partition coefficients agreed with experimental TAG/water and alkane/water partition coefficients.     

On the Predominant Electron-Donicity of Polar Solid Surfaces

The reasons for the predominant electron-donicity of almost all solid polar surfaces and its implications are discussed in this paper. By contact angle or interfacial tension measurements, the electron-accepting as well as the electron-donating properties of polar liquids can be ascertained, through the interplay between their energies of adhesion and cohesion. For the solid-liquid interface, direct interfacial tension measurements are not possible, but indirectly, solid/liquid interfacial tensions of polar systems can be obtained by contact angle measurement. However, as the energy of cohesion of a solid does not influence the contact angle formed by a liquid drop placed upon its surface, one can only measure the solid surface'ks residual polar property, manifested by the energy of adhesion between solid and liquid. This residual polar property is of necessity the dominant component; in most cases this turns out to be its electron donicity. When, by means of contact angle measurements with polar liquids, both electron-accepting and electron-donating potentials are found on a polar solid, it is most likely still partly covered with a polar liquid: usually water. The amount of residual water of hydration of a polar solid follows from its polar (Lewis acid-base) surface tension component (γ^AB). The degree of orientation of the residual water of hydration on a polar solid can be expressed by the ratio of the electron-donating to electron-accepting potentials (γ^⊖/γ^⊕), measured on the hydrated surface.     

Dewatering of Biomass Using Liquid Bio Dimethyl Ether

An interesting integrated configuration in a thermochemical conversion biorefinery that is producing dimethyl ether (DME) is to use a small fraction of the BioDME for dewatering of the solid biomass feedstock. Therefore, the use of liquid BioDME was investigated in this study for pressurized dewatering of biomass at room temperature. Water was removed in liquid form from wet sawdust and wet wood chips using liquid DME in a laboratory-scale batch unit. Both the sawdust and the wood chips could be dewatered in a short time (minutes) to a moisture content of 15% (w/w) from an initial content of approximately 55% (w/w). Longer DME treatment times (hours) lowered the moisture content even further down to 8% (w/w), indicating that the transport phenomena in the porous biomass and the solubility of DME in water influence the dewatering characteristics. The DME dewatering performance, 12–22 g DME per g water removed, was similar to literature data on coal dewatering using liquid DME. The present study showed that DME dewatering of the solid biomass feedstock has potential as an energy-efficient dewatering process, especially in an integrated thermochemical conversion biorefinery.     

Distribution of water in ceramic green bodies during drying

In order to investigate drying mechanisms at different stages, the distribution of water within the ceramic green bodies at different scales has been examined. The experimental measurements, using a simple weighing technique and Magnetic Resonance Imaging (MRI), show that during the first stage of drying involving shrinkage the material is constituted of uniquely solid and water with no gradient in water content within the sample. Then, during the second stage of drying, significant differences of water content as a function of position appear. As a complement, at the grain scale, observations using environmental scanning electron microscopy were made giving useful information on the solid–liquid–gas interfaces in the near surface part of the green body. Finally, the gradients in the water distribution were exploited to make a simple estimate of the diffusion coefficient of water with its dependence on the moisture content.     

Particle Bounce During Filtration of Particles on Wet and Dry Filters

This paper experimentally examines the bounce and immediate re-entrainment of liquid and solid monodisperse aerosols under a stable filtration regime (precake formation) by wet and dry fibrous filters. PSL and DEHS were the solid and liquid aerosols, respectively, used in four monodisperse sizes of 0.52, 0.83, 1.50, and 3.00 w m. Three different fibrous filters were used to filter the aerosol streams, and the efficiency of the filtration process for each aerosol type under dry and wet regimes was measured. It was found that the solid particles generally exhibited a lower fractional filtration efficiency than liquid particles, although this difference decreased in the smaller size fractions. The difference between solid and liquid efficiencies was found to be greatest in the 1.5 w m size range. As particle sizes of liquid/solid aerosols and filtration parameters were similar, this difference is most likely to be due to the effect of particle bounce and or immediate re-entrainment occurring inside the filter, with the greater efficiency of filtration of the liquid particles being due to their greater capacity to plastically/elastically deform in order to absorb the impact forces. However, for the wet filtration regime (each fibre of the filter was coated by a film of water), no significant difference in filtration efficiency was detectable between solid and liquid aerosols. Therefore, the conclusion can be drawn that the either the bounce effect of the particles is inhibited by the liquid film, or the filtration conditions in the wet filter are so different that the aerosol properties are less significant with respect to capture.     

Wetting and Interfacial Bonding of Metals with Ionocovalent Oxides

The adhesion and interfacial bonding between nonreactive liquid metals and solid inocovalent oxides are studied on the basis of the experimental work of adhesion W data. An analysis of the experimental W values of different liquid metals on various solid oxides is first performed to put into evidence the dependences of the work of adhesion of a metal/oxide system on the electron density of the metal and on the thermodynamic stability of the oxide. An electronic model is then proposed to describe the microscopic mechanism of metal–oxide interactions. Based on the model, the work of adhesion and the contact angle of different liquid metals on various solid oxides can be interpreted and estimated, and their correlations to the various physical properties of the oxides can be easily deduced. The basic consideration of the model is that the adhesion between a metal and an oxide is assured by the electron transfer from the metal into the oxide valence band which is not completely filled with electrons at high temperatures, and is enhanced when this electron transfer at the metal/oxide interface is increased. The extension and application of the model to solid metal/solid oxide systems is also presented.     

A comparison of novel ozone-based systems and photocatalysis for the removal of water pollutants

Three ozone-based systems and a photocatalytic system have been compared for the removal of a reactive dyestuff, orange RO16, and 2-chlorophenol in relation to degradation performances and ozone and energy consumptions. These systems were (1) liquid/gas–ozone (LGO): ozone was applied as it is produced in the gas phase; (2) liquid/solid–ozone (LSO): ozone was adsorbed on particulate silica-based material and then applied to water; (3) liquid/liquid–ozone (LLO): ozone was dissolved in a water-immiscible solvent and then applied to water; and (4) photocatalytic system using titanium dioxide catalyst (PHC). All four systems were capable of degrading the pollutants but presented different characteristics. The LSO system offered the possibility of using long contact times for slow ozone reactions and the LLO system is most suitable for fast ozone reactions. Both systems offer the prospect of more efficient use of ozone by extracting specific pollutants away from the water phase to the solid or the solvent phases. The PHC system presented the lowest rates and the highest energy consumptions by a factor of up to 400 times as compared to the ozone-based systems. The four systems were classified on the basis of their energy consumption as follows: for the degradation of RO16 (LLO相似文献   

Modeling influence of gas/liquid/solid three-phase boundary zone on cathodic process of soil corrosion

Geometric properties of gas/liquid/solid three-phase boundary (TPB) zones of dispersive liquid on a metal surface in soils, play an important role in the cathodic and corrosion behavior of metals. The correlation between the TPB geometric parameters (e.g. its length and width) and the soil water content is established, and on this basis, the influence of TPB parameters on the cathodic oxygen reduction process of soil corrosion is simulated. The simulation result shows an initial increase and a subsequent decrease in cathodic limiting current with increasing soil water content, and a maximum is present at about 60% water content of their water holding capacity (WHC), in good agreement with the experimental results. In addition, a parameter b is proposed to evaluate the liquid dispersion in soils, and a linear dependence of cathodic limiting current on parameter b is calculated from the model, confirming the important role of liquid dispersion in soil corrosion systems.     

Liquid velocity in a high‐solids‐loading three‐phase external‐loop airlift reactor

BACKGROUND: Airlift reactors are of interest for many different processes, especially for three‐phase systems. In this study the behavior of a high‐loading three‐phase external‐loop airlift reactor was examined. In particular, the effect of parameters such as airflow rate (riser superficial gas velocities between 0.003 and 0.017 m s^?1), solids loading (up to 50%, v/v) on liquid circulation velocity in the air‐water‐alginate beads system as a crucial hydrodynamic parameter was studied. RESULTS: It was observed that increase of the airflow rate resulted in increase of the liquid velocity in the system. The same result but less pronounced was observed by introducing small amounts of solid particles up to 7.5% v/v. However, further introduction of solids caused decrease of the liquid velocity. Laminar regime for the liquid circulation was observed for low gas velocities. Minimum gas velocities for recirculation initiation in the reactor were determined for all solid loadings and linear dependence on the solid content was found. Gas holdups for the three‐phase system were larger than for the two‐phase system in all experiments. A simple model for predicting the liquid circulation velocity in the three‐phase system with high solid loading of low‐density particles was developed. This model is based on the viscosity of integrated medium (solid + liquid) which is a new aspect to analyze this phenomenon. CONCLUSIONS: The developed model shows very good agreement with the experimental results for all solid loadings. It also includes the influence of reactor geometry on the liquid circulation velocity thus enabling optimization. Copyright © 2012 Society of Chemical Industry     

Impact of a draft tube on industrial‐scale Fluid Coker™ Spray Jets in fluidized beds

In fluidized bed reactors such as Fluid Cokers?, liquid injections are used. Good contact between liquid and bed solids is required to maximize product yields and quality, and gas‐atomized nozzles are, therefore, used in all these processes. The spray nozzle technology is known to affect the liquid distribution. Therefore, the objective of this study is to assess the effect on liquid distribution of a draft tube located downstream of the spray nozzle, inside the fluidized bed. Experiments were conducted at a relevant scale, using a commercial‐scale nozzle with a liquid flow rate of about 100 L/min in a large‐scale pilot fluid bed containing about 7 tonnes of silica sand. Liquid injected into a fluidized bed either forms liquid‐solid agglomerates or free moisture, consisting of individual particles coated with a thin layer of liquid. Several electrodes were used to map the free moisture distribution throughout the bed. A draft tube greatly improves the contact efficiency throughout the bed. It also increases the penetration of the gas‐liquid jet formed by spray inside the fluidized bed.     

On the Predominant Electron-Donicity of Polar Solid Surfaces

The reasons for the predominant electron-donicity of almost all solid polar surfaces and its implications are discussed in this paper. By contact angle or interfacial tension measurements, the electron-accepting as well as the electron-donating properties of polar liquids can be ascertained, through the interplay between their energies of adhesion and cohesion. For the solid-liquid interface, direct interfacial tension measurements are not possible, but indirectly, solid/liquid interfacial tensions of polar systems can be obtained by contact angle measurement. However, as the energy of cohesion of a solid does not influence the contact angle formed by a liquid drop placed upon its surface, one can only measure the solid surface'ks residual polar property, manifested by the energy of adhesion between solid and liquid. This residual polar property is of necessity the dominant component; in most cases this turns out to be its electron donicity. When, by means of contact angle measurements with polar liquids, both electron-accepting and electron-donating potentials are found on a polar solid, it is most likely still partly covered with a polar liquid: usually water. The amount of residual water of hydration of a polar solid follows from its polar (Lewis acid-base) surface tension component (γ^AB). The degree of orientation of the residual water of hydration on a polar solid can be expressed by the ratio of the electron-donating to electron-accepting potentials (γ^?/γ^⊕), measured on the hydrated surface.     

浆态床内固含率轴向分布的数值模拟

采用DBS曳力模型计算气液相间作用,分别采用Gidaspow曳力模型、经Brucato修正的Gidaspow曳力模型和Schiller?Naumann曳力模型计算液固相间作用,忽略气固间的直接作用,对比了浆态床内不同颗粒粒径体系轴向固含率的模拟和实验结果. 结果表明,不同液固相间曳力模型对气含率的预测影响不大;在颗粒粒径较大(140 ?m)的体系中,较低表观气速下气液DBS与液固Schiller?Naumann曳力模型组合模拟的固含率随床高度增加而减小,与实验结果吻合,而其它曳力模型组合的模拟结果较差,轴向分布较均匀;在颗粒粒径较小(35 ?m)的体系中,几种曳力模型组合的模拟结果均与实验结果吻合较好,轴向分布较均匀.     

Characterization of epoxy resin surface energetics

This study has characterized the energetics of both the liquid state and the solid state of two commercially available epoxy resins: a DGEBA- and a TGMDA-based epoxy system. The surface properties of the liquid epoxies were evaluated by wetting measurements using a dynamic contact angle analysis (DCA). The Lifshitz-van der Waals components of the surface tension were found to be similar for both epoxy systems, while the acid-base components were found to be slightly different. Two different techniques were used to characterize the cured epoxy surface properties: wetting measurements and vapor adsorption measurements by means of inverse gas chromatography (IGC). The Lifshitz-van der Waals components of the surface energy were observed to be nearly the same for both epoxies, confirming that both resins have the same potential for non-specific interactions, in both liquid and solid states. Evaluations of the acid-base components of the work of adhesion by DCA and the Gibbs free energy change by IGC suggest that both cured epoxies show non-negligible specific interactions with both acidic and basic probes. However, computations of the accepticity and donicity parameters showed that both cured epoxies are predominantly basic, but also possess non-negligible acidity. It is likely that the presence of water on the solid surface contributes to the acidic character of the cured epoxies. The temperature dependence of the liquid surface tension for both epoxy systems was investigated. The same temperature dependence was observed: the surface tension decreased with temperature, following a linear regression. Corrections for viscous-drag effects on the liquid surface tension measurements were also made.     

Zusammenhang zwischen dem Wasser- und Festfettgehalt und der Austrocknungsgeschwindigkeit beim Auskanten von Margarine

Relationship between Water- und Fat-Content and the Drying-out Rate During Edging of Margarine A mathematical equation has been derived for the correlation between the water and solid fat contents and the drying-out rate of margarine and other plasticised W/O emulsions. A model has been used indicating that under the surface of the product, a completely dried out layer is formed which continuously thickens towards the interior of the product. During this process, the diffusion of the water dissolved in the fat towards the surface, is rate-determining. The experimentally found relations between moisture loss and storage time as well as between moisture loss and water content are in agreement with the formula derived. Using these experimental values, a correction factor has been calculated being dependent on the amount and the particle size of the solid fat phase. With the aid of this factor, the water and solid fat contents and physical constants, the expected moisture loss of plasticised W/O emulsions can be calculated.     

Activated carbon surface heterogeneity seen by parallel probing by inverse liquid chromatography at the solid/liquid interface and by gas adsorption analysis at the solid/gas interface

The energetic surface heterogeneity of four different activated carbons was assessed by the parallel probing at the solid/liquid and solid/gas interfaces. At the solid/liquid interface a method of inverse liquid chromatography, frontal analysis by characteristic point was applied using phenylalanine in water solution as a probe molecule. At the solid/gas interface, argon was used as a probe in the low pressure quasi equilibrium volumetry method. The treatment of the adsorption isotherms by the derivative isotherm summation procedure revealed similar adsorption energy distributions for both argon and phenylalanine. Such an agreement between both methods suggests that, at the solid/liquid interface and on the solid/gas interface, the adsorption was mainly controlled by geometric parameters and no specific interaction was observed and physisorbed water did not played a significant role in adsorption process on three from four studied carbons.     

Wood–polymer composites made with acrylic monomers,isocyanate, and maleic anhydride

Wood could provide better service in some applications if it were harder and more dimensionally stable. In this study, wood–polymer composites (WPC) made with different chemical combinations were evaluated for dimensional stability, ability to exclude water vapor and liquid water, and hardness. Pine, maple, and oak solid wood were combined with different combinations of hexanediol diacrylate, hydroxyethyl methacrylate, hexamethylene diisocyanate, and maleic anhydride. Treatment slowed the rates of water vapor and liquid water absorption. Although the resultant dimensional stability was not permanent, the rate of swelling of WPC specimens was less than that of unmodified wood specimens. In addition, WPC were harder than unmodified wood. The chemical combination of hexanediol diacrylate, hydroxyethyl methacrylate, and hexamethylene diisocyanate greatly decreased wetting and penetration of water into the wood. This chemical combination also gave the hardest and most dimensionally stable WPC. In general, WPC prepared using hydroxyethyl methacrylate were harder than specimens made without hydroxyethyl methacrylate and excluded water and moisture more effectively. © 1999 John Wiley & Sons, Inc. J Appl Polym Sci 73: 2493–2505, 1999     

Analysis of the moisture sorption behavior of amorphous drug–polymer blends

Hydrophobic drugs are often formulated with hydrophilic polymers to form miscible blends called amorphous solid dispersions. The interaction of moisture with these blends is an important topic, both from stability as well as processing perspectives. In this study, the moisture sorption profiles of four different drug–polymer blends, [felodipine–poly(vinylpyrrolidone) (PVP), indomethacin–PVP, felodipine–hypromellose (HPMC), and felodipine–hypromellose acetate succinate (HPMCAS)] were experimentally determined at 25°C, and analyzed using various mathematical models. It was found that the moisture sorption profiles of the drug–polymer blends could not be reconstructed using the weight‐averaged sum of the moisture sorbed by each of the components. Application of the Flory–Huggins model for ternary systems to extract drug–polymer interaction parameter (χ₂₃) values using known values of water–drug and water–polymer interaction parameters led to ambiguous conclusions about the systems' thermodynamics. χ₂₃ values extracted for felodipine–PVP and indomethacin–PVP using this model ranged from ?9.6 to 26.9 and ?20.4 to 22.0, respectively. It is thought that the presence of specific drug–polymer interactions changed the water–drug and the water–polymer interactions in the system. Combined with the mathematically small contribution from the term encompassing χ₂₃ to the predicted amount of moisture sorbed by the drug–polymer blends, it was concluded that this method cannot be used to unambiguously determine drug–polymer interaction parameters in solid dispersions. Instead, a model with a mean interaction parameter (χ_1,23) that considers the drug and the polymer in the blend as a single unit was found to better describe the changing affinity of water for the solid matrix with a change in composition or polymer type. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

Filter system makes re-use of paper mills' white water possible

Paper mills require large quantities of water, but with rising freshwater costs many are looking to recycle their wastewater. Traditional liquid/solid separation systems, however, often struggle to provide the fine filtration needed to turn a mill's white water, with its high suspended solids content, into re-usable water. Now, the Petax™ filtration system from Kadant AES, USA, claims to be able to achieve just that.     

Estimation of ion pair formation constants of lithium salts in mixtures of glymes and 1,4-dioxane

This paper presents data coming from ¹⁹F NMR spectroscopy and conductivity measurements used as two independent methods for the determination of ion pair formation constants. The studied systems were limited to lithium tetrafluoroborate and trifluoromethylsulfonate solutions in mixtures of 1,4-dioxane and glyme, diglyme or water. The systems containing glyme and diglyme have coordinating properties (donor and acceptor numbers) very similar to liquid poly(ethylene glycol) dimethyl ether and solid poly(ethylene oxide) and their composition can be tailored to have the dielectric constants similar to those of the polymeric systems. The obtained results are compared with the electrochemical and spectroscopic data found in the literature for liquid poly(ethylene glycol) dimethyl ether and solid poly(ethylene oxide). The main stress of the discussion is focused on ion-ion and ion-solvent interactions and the influence of the oligooxyethylene chain length on ionic pair formation. Additionally, on the basis of the electrochemical data for the dioxane-water solutions, the difference in behavior between water-free and water containing samples of similar polarity is discussed. To check the influence of the cation on ion pairing, a similar set of experiments was performed for tetraalkylamonium salts with identical anions.