Pore Liquid Research Articles

Analytical solution for one-dimensional chemo-hydro-mechanical coupled consolidation under time-dependent loading in buffer clay layer

An analytical method is developed for solving the coupled chemo-hydro-mechanical consolidation in a clay buffer layer under time-dependent loading. The coupled governing equations for the chemo-hydro-mechanical process are established in the time and spatial domain first. Then the governing equations are decoupled into two partial differential equations by introducing two variables. The analytical solutions corresponding to ramp and exponential loadings are finally derived based on the initial and boundary conditions. The developed analytical solutions are verified via comparing with the numerical results simulated by COMSOL Multiphysics. Based on the developed solutions, selected parametric study is carried out to investigate the influence of major parameters and hydraulic boundary conditions on the contaminants transport and pore water pressure dissipation in buffer clay layer. The results show that the major parameters have effects on the generation and dissipation of pore pressure, while only effective coefficient of diffusion, coefficient of ultrafiltration and relative change of total density of pore liquid significantly affect the contaminant migration process. Compared with a single drainage boundary, the pore pressure dissipation and contaminant migration in a double drainage soil layer are much faster. The longer the loading time of mechanical loading, the more significant the negative pore pressure caused by the concentration gradient.

The effect of calcium stearate on the microbiological corrosion of cement stone concrete

To prevent biofouling of cement stone and its damage by fungal microorganisms, it is proposed to introduce 0,5 wt. % calcium stearate into the cement mixture. To ensure volumetric hydrophobization of cement stone, the additive is crushed to nanoparticles. The cement stone was cured in the air for 28 days. To study fungal corrosion, the surface of the cement stone was treated with a suspension of pores of Aspergillus niger fungi. The hydrophobic surface of the cement stone was not biofouled by fungal microorganisms Aspergillus niger during 6 months of the samples being in a humid environment, and black mold foci developed on the surface of ordinary cement stone during this period of time. The action of fungi and their waste products caused a decrease in the amount of calcium in the cement stone by 9 %, and had no effect on the hydrophobized cement stone. Due to the immunity of cement stone with a hydrophobizer to the action of microorganisms and water, free calcium hydroxide is not removed from the structure, but some amount is washed out of the surface layer and the pore liquid. A significant slowdown in mass transfer in cement stone under the action of liquids is provided by the hydrophobicity of the surface of cement stone and the walls of pores and capillaries, imparted by calcium stearate, as well as partial colmatation of the pore structure by means of the introduced additive.

The influence of nano-silica composite superabsorbent polymer on the autogenous shrinkage of mortar

To address the diminished shrinkage reduction capacity due to high ion sensitivity of superabsorbent polymers (SAP) within cement-based materials, this study employs solution polymerization where acrylic acid and acrylamide are copolymerized with nano-silica at varying concentrations to synthesize innovative SAPs. The investigation encompasses the structural groups, microscopic morphology, liquid absorption characteristics of these SAPs, and their effect on mortar's autogenous shrinkage. The results indicate that nano-silica can be encapsulated within polyacrylate-acrylamide network via physical adsorption and chemical grafting. The incorporation of nano-silica enhances the water absorption and retention capacities of SAPs in alkaline environments. Nano-silica composite SAPs absorb sufficient internal curing water and prolong the subsequent moisture gradient-driven water release process, continuously releasing water within matrix to maintain internal humidity, thereby further enhancing the shrinkage reduction effect on mortar. Based on Scanning Electron Microscopy (SEM) observations of SAPs morphologies within mortar and X-ray Computed Tomography (X-CT) monitoring of internal curing water distribution, it is revealed that nano-silica undergoes pozzolanic reactions, forming a tightly connected domain with matrix. This facilitates continuous water release to the surrounding through capillary action, thus maintaining capillary pore liquid levels. Consequently, it effectively mitigating shrinkage stress and deformation, leading to an enhancement in shrinkage reduction effects.

Conformal TiO2 Aerogel-Like Films by Plasma Deposition: from Omniphobic Antireflective Coatings to Perovskite Solar Cell Photoelectrodes.

The ability to control the porosity of thin oxide films is a key factor determining their properties. Despite the abundance of dry processes for synthesizing oxide porous layers, a high porosity range is typically achieved by spin-coating-based wet chemical methods. Besides, special techniques such as supercritical drying are required to replace the pore liquid with air while maintaining the porous network. In this study, we propose a new method for the fabrication of ultraporous titanium dioxide thin films at room or mild temperatures (T ≤ 120 °C) by a sequential process involving plasma deposition and etching. These films are conformal to the substrate topography even for high-aspect-ratio substrates and show percolated porosity values above 85% that are comparable to those of advanced aerogels. The films deposited at room temperature are amorphous. However, they become partly crystalline at slightly higher temperatures, presenting a distribution of anatase clusters embedded in the sponge-like open porous structure. Surprisingly, the porous structure remains after annealing the films at 450 °C in air, which increases the fraction of embedded anatase nanocrystals. The films are antireflective, omniphobic, and photoactive, becoming superhydrophilic when subjected to ultraviolet light irradiation. The supported, percolated, and nanoporous structure can be used as an electron-conducting electrode in perovskite solar cells. The properties of the cells depend on the aerogel-like film thickness, which reaches efficiencies close to those of commercial mesoporous anatase electrodes. This generic solvent-free synthesis is scalable and applicable to ultrahigh porous conformal oxides of different compositions, with potential applications in photonics, optoelectronics, energy storage, and controlled wetting.

Solvent Cavitation during Ambient Pressure Drying of Silica Aerogels.

Ambient-pressure drying of silica gels stands out as an economical and accessible process for producing monolithic silica aerogels. Gels experience significant deformations during drying due to the capillary pressure generated at the liquid-vapor interface in submicron pores. Proper control of the gel properties and the drying rate is essential to enable reversible drying shrinkage without mechanical failure. Recent in operando microcomputed X-ray tomography (μCT) imaging revealed the kinetics of the phase composition during drying and spring-back. However, to fully explain the underlying mechanisms, spatial resolution is required. Here we show evidence of evaporation by hexane cavitation during the ambient-pressure drying of silylated silica gels by spatially resolved quantitative analysis of μCT data supported by wide-angle X-ray scattering measurements. Cavitation consists of the rupture of the pore liquid put under tension by capillary pressure, creating vapor bubbles within the gels. We found the presence of a homogeneously distributed vapor-air phase in the gels well ahead of the maximum shrinkage. The onset of this vapor/air phase corresponded to a pore volume shrinkage of ca. 50 vol % that was attributed to a critical stiffening of the silica skeleton enabling cavitation. Our results provide new aspects of the relation between the shape changes of silica gels during drying and the evaporation mechanisms. We conclude that stress release by cavitation may be at the origin of the resistance of the silica skeleton to drying stresses. This opens the path toward producing larger monolithic silica aerogels by fine-tuning the drying conditions to exploit cavitation.

Finite element implementation of a seepage-stress coupling method for solid-liquid-gas three phases in porous media considering compressible gas

Some existing coupling models of porous media ignore the gas phase or gas compressibility, making them inadequate in describing the gas transport process and their effects on water infiltration and solid deformation. However, consideration of gas compressibility becomes crucial when involving the confined gas. Furthermore, the unsteady seepage free surface problem may make the numerical solution of seepage-stress coupling more complicated and difficult. To overcome the above problems, a new coupled seepage-stress method considering compressible gas is proposed. Based on the momentum balance equation of solid–liquid–gas, the three-phase model is constructed by making the pore liquid and compressible gas both satisfy the fluid equilibrium equation and continuity equation. Integration of the interface-correction level set method in the solid–liquid–gas three phases model provides a good solution for representing liquid–gas two-phase flow and solid deformation while describing the unsteady free surface between saturated and unsaturated zones. The primary variables in this model are solid displacement and liquid/gas pressure and its governing equations are discretized by finite element strategy. After comprehensively explaining the mathematical framework and numerical implementation, the reliability and effectiveness of the proposed method are validated through several benchmarking examples.

Determination of the ability of migrating steel corrosion inhibitors to passivate corroding reinforcement in reinforced concrete structures

Introduction. The corrosion condition of steel reinforcement in reinforced concrete structures and products is the main factor determining their bearing capacity and durability. The alkalinity of the pore liquid of concrete (at pH > 11.8) in reinforced concrete structures and products under normal conditions ensures the passive state of steel reinforcement. In the presence or when chloride, sulfate and other analogous ions enter the concrete, the steel reinforcement of reinforced concrete structures and products depassives, despite the pH value > 11.8, and begins to corrode. In addition, depassivation and subsequent corrosion of steel reinforcement occur during carbonation (neutralization) of the protective layer of concrete due to a decrease in pH < 11.8. One of the promising options for slowing down or stopping the corrosion processes of steel reinforcement is currently the use of migrating corrosion inhibitors.
 
 The aim of the work was to obtain experimental data on the ability of migrating steel corrosion inhibitors to inhibit or completely stop the corrosion of reinforcement in reinforced concrete structures and products initiated by the presence of chloride ions (Cl-) in concrete or neutralization of the protective layer of concrete in relation to steel reinforcement.
 
 Materials and methods. The following types of migrating steel corrosion inhibitors were used for testing:
 
 – Cortec MCI-2020 (manufacturer – KORTEK RUS (KORTEK) LLC, suppliers – Ettrilat LLC, MONUMENT LLC);
 
 – IFKHAN-80 (manufacturer and supplier – IFKHAN LLC);
 
 – Basf Master-Protect 8000 CI (former name Protectosil ® CIT. Suppliers – MBS Construction Systems LLC, MPKM LLC, LKM-FLEET LLC).
 
 The determination of the ability of migrating steel corrosion inhibitors to inhibit or completely stop the corrosion of reinforcement was carried out by accelerated electrochemical research methods in accordance with State Standard 31383-2008 "Protection of concrete and reinforced concrete structures from corrosion. Test methods".
 
 Results. All three types of migrating steel corrosion inhibitors inhibit corrosion of steel reinforcement initiated by the presence of chloride ions in concrete by the age of 90 days. All three types of migrating steel corrosion inhibitors by the age of 30 days do not inhibit the corrosion of steel reinforcement initiated by concrete carbonation.
 
 Conclusions. According to the results of the work, it was revealed that the migrating steel corrosion inhibitors inhibit the corrosion of steel reinforcement initiated by the presence of chloride ions in concrete, while the corrosion initiated by the carbonation of concrete is not slowed down or stopped by migrating steel corrosion inhibitors.

Comparison of water and benzene as probe liquids in thermoporometry of mesoporous carbons

Water and benzene were compared as probe liquids for thermoporometric characterization of mesoporous carbons. For testing, four different carbonaceous materials were prepared by soft- or hard-templating procedures with mesopore diameters in the range 3–12 nm. In addition, all materials were tested in hydrophobic (pristine, carbonized at 900 °C) and hydrophilic (moderate oxidation by persulphate) form. The results show that both tested liquids express a good linear correlation between heat of melting in pores (measured as DSC peak area) and volume of mesopores. Melting point depression of probe liquid confined in pores related to mesopore size was found out to be steeper for benzene confirming a higher value of Gibbs-Thomson constant of benzene compared to water. Neither heat of melting in pores nor melting point depression were affected by carbon surface oxidation. Contrary, the non-freezing layer (δ layer) of a liquid in pores was considerably wider for most of hydrophilic samples than hydrophobic ones when water was employed, while it stayed nearly constant when benzene was applied. Nevertheless, both tested probe liquids generally enable to obtain similar pore size distributions if appropriate values of δ layers are used. Benzene as a probe liquid in thermoporometry of carbons have some advantages compared to water but only in limited cases. Benzene can be recommended for characterisation of large mesopores and its usage can be beneficial for comparison of analogous samples with different surface chemistry.

Woven filter media used in wet filtration processes: investigation of pore size distribution, air and water permeability and finding correlations between them

Currently, methods for evaluating the performance of woven filter media used for filtration processes are mainly reduced to air permeability and filtration resistance. However, filtration processes are not limited to dry filtration only. Moreover, critical performance-related factors such as the pore size distribution and liquid permeability are studied but often omitted and ignored in the characterization process. The present study aims to investigate and analyze three characteristics, namely air and liquid permeability and pore size distribution, and to examine correlations between the studied characteristics. The results of the present study show that correlations between the studied characteristics do exist. Polynomial and exponential functions could describe the correlation between the mean flow pore diameter and permeability. At the same time, the dependency between air and water permeability is characterized by a logarithmic function. Consequently, the characterization and selection of filter cloths should be done by analyzing several different parameters simultaneously. These correlations could become the basis of a system of media indexing in the future.

Evaluation of the efficiency of coconut dust extract as a corrosion inhibitor for steel reinforcement in concrete by mass spectrometry

Ethanol extraction was employed to isolate a range of compounds from waste products derived from coconut fiber production (coconut dust) in Ben Tre, Vietnam. Phytochemical screening confirmed the presence of flavonoids, tannins, polyphenols, saponins, alkaloids, flobatannins, and anthraquinones among the extracted substances. FT-IR spectroscopy analysis supported the identification of oxygen and nitrogen atoms within functional groups (e.g., O–H, N–H, C–O) and aromatic rings, characteristic of typical corrosion inhibitors. Mass spectrometry investigations indicated that when St3 steel was exposed to an alkaline solution lacking chlorides, a passive film composed of FeOOH formed on the surface. However, upon the addition of NaCl at a concentration of 1.00 mol/dm3, FeCl, FeCl2Cl–, and FeCl3Cl– compounds were detected across the analyzed surface, while peaks corresponding to FeOO– were absent. Remarkably, areas with the highest concentration of particles corresponded to regions exhibiting visible corrosion damage under magnification. The addition of 2.00 g/dm3 of coconut dust extract to the chloride solution prevents the formation of Fe and Cl compounds on the steel surface. Consequently, only peaks characteristic of FeOO– and organic fragments containing oxygen atoms from the extract were observed. Based on these results, it can be assumed that coconut dust extract has the potential to inhibit local (pitting) corrosion of low-carbon steel (St3) when exposed to aqueous alkaline solutions simulating concrete pore liquid containing chlorides. The addition of 2.00 g/dm3 of the extract has been shown to prevent pitting formation at a chloride concentration of 1.00 mol/dm3. Conversely, in the absence of the extract, visible local corrosion damage was observed upon magnification. These findings provide a basis for further exploration of the protective properties of coconut dust extract as an environment-friendly corrosion inhibitor for mild steel in concrete environments containing chlorides.

Salt scaling resistance of pre-cracked ultra-high performance concrete with the coupling of salt freeze-thaw and wet-dry cycles

Wet-dry cycles and cracking are unavoidable problems of concrete structures and reduce durability by enhancing the penetration of harmful ions and water, which may have a synergistic adverse influence with severe surface damage caused by salt freeze-thaw cycles. This study aims to investigate the salt scaling resistance of ultra-high performance concrete (UHPC) under multiple harsh environments including wet-dry cycles and pre-cracking. The relationship between workability, absorption behavior, and scaling resistance with fiber content increases is assessed. Mass loss, chloride binding behavior, pore structure, and pore morphology are analyzed to describe the influences of pre-cracking and wet-dry cycles. The results reveal that the workability of fresh concrete and the distribution of steel fibers are the key factors in determining the salt scaling resistance of UHPC. Pre-cracking and wet-dry cycles inhibit the rapid scaling damage of UHPC by accelerating chloride accumulation, which reduces the icing pressure of pore liquid and refining the micropores (<200 nm) capable of remaining non-frozen at low temperatures through the chemical binding of chloride. However, the combined effect of pre-cracking and wet-dry cycles can lead to the corrosion of internal steel fibers and more scaling damage, and the crack width should not be greater than 0.1 mm.

The Elder Problem with Reactive Infiltration Effects

The occurrence of buoyancy-driven flow and reactive solute transport in a fluid-saturated porous medium can be induced by either natural processes or human activities. Typical examples include the groundwater salinization in carbonate-rock aquifers and the acid treatment of oil wells in petroleum drilling industry. In this paper, the classical Elder problem of buoyancy-driven convection in two-dimensional porous media is extended to include the local chemical interactions between the solute in the pore liquid (e.g. salt such as NaCl or acids such as HCl and HCl/HF mixtures) and the solid space of the porous medium (e.g. minerals such as calcite and dolomite). Effects of the geochemical processes on the flow and mass transport are investigated. For the reactive, strongly solute-driven case in the regime dominated by the diffusive mass transport, a decrease in the net solute concentration is found as compared to the non-reactive case. This decrease is pronounced at higher values of the Damköhler number when the solute reaction rate becomes larger than the solute diffusion rate. Furthermore, the flow structure is affected by products generated by the chemical reaction when the Rayleigh number for the products is sufficiently high. In that case, numerical simulations show the formation of diluted fluid tongues exhibiting damped periodic oscillations about a nonzero mean. The results are obtained using the pseudospectral numerical method, verified against the analytical solution for the non-reactive, purely diffusive case.

Centrifuge modeling of slope failure induced by elevated gas pressure in wet municipal solid waste landfill

Understanding triggering mechanisms of slope failure is of great importance to the stability analysis and safety warning of waste landfill. This paper presents a centrifuge model test on slope failure induced by elevated gas pressure in wet landfill. The formation process of liquid level and gas pressure in the landfill is simulated by means of liquid and gas injections under a centrifugal acceleration of 66.7 g. The injected liquid contains surfactants, which allow it to generate foam in the waste pores when mixed with the injected gas. The pore gas and liquid pressures under two-phase flow condition are monitored separately to clarify the instability process. It is found that the continuous gas injection makes the pore gas pressure increase to peak values of 83.0 kPa–100.8 kPa, which are higher than the peak liquid pressures of 61.3 kPa–75.6 kPa. The formation of high gas pressure zone is attributed to the low gas permeability, which is affected by high liquid saturation as well as foam generation. The slope failure occurs when the pore gas pressure increases to the peak value and the corresponding shear strength decreases to the critical value. Although the gas injection raises the liquid level, the factor of safety of landfill slope will be overestimated if only considering the effect of liquid pressure. According to the response curves of displacement to gas pressure rise, the critical ratios of gas pressure to earth pressure are determined to be 0.74–0.84, which fall within the range of the prototype landfill. The difference between foam and air on pore pressure distribution is also calculated and discussed.

Air sparging remediation of VOCs contaminated low-permeability soil based on pressure gradient control

Air sparging (AS) is deemed unacceptable for remediating VOCs contaminated soil with low-permeability. To improve air flow and contaminant removal in sparging process, an original approach, termed as pressure gradient-enhanced air sparging (PGEAS) approach, is proposed by controlling pressure gradient in soil. Then the remediation efficiency, mass transfer characteristics, and remediation mechanism are investigated. Results showed that, the PGEAS approach accelerates gaseous contaminant exhaust, reduces residue contamination in soil, and promotes total contaminant removal, finally results in an improved remediation efficiency compared to the conventional approach. Controlled by sparging pressure and flow distance, the pressure gradient is created in soil, and a critical value needs to be exceeded to enhance the VOCs removal and mass transfer characteristics. The measured results of pore pressure and liquid saturation confirm a notable pressure gradient and drainage behavior in soil, which indicate the massive air subchannel formation during air sparging. At a two-dimensional scale, discrete distributions of contaminant concentrations in exhaust air and soil are presented, the removal extent and area are both enhanced using the PGEAS approach with a pressure gradient higher than the critical value. The reached conclusions are of great importance to contaminant removal in heterogeneous stratigraphy at sites.

Study on Osmotic Consolidation and Hydraulic Conductivity Behavior of an Expansive Soil Inundated with Sodium Chloride Solution

Canals are a very imperative source of irrigation for the agricultural sector in India. Seepage causes major water loss in canals, and hence, the installation of liners becomes necessary. Compacted clay soils are commonly used as liners in the canals. This structure will most probably be subjected to salinization and desalinization cycles throughout its life. Because of the interaction between the pore liquid and clay particles, physico-chemical influences considerably impact the behavior of clay barriers. In this paper, the effect of interacting fluid on volume change, consolidation parameters, and hydraulic conductivity of compacted clay soil is investigated with the help of a one-dimensional consolidation test. The compacted clay specimens were immersed alternatively with distilled water (DW) and sodium chloride (NaCl) solutions (SW) at constant loading of 10 kPa, which replicates the load conditions in the field canal due to 1 m head of water and incremental loading as per IS 2720 part 15 standards. The experimental results proved that there is a percentage volume change increase of about two times for each stage inundated with 4M NaCl solution than its preceding stages inundated with distilled water at constant loading of 10 kPa. The consolidation rate was accelerated with 4M NaCl solution than the normal consolidation at incremental loading. The permeability coefficient in the salt water-induced sample increased by 217% more than the distilled water-induced sample at incremental loading. Therefore, the soil specimen subjected to alternate salinization and desalinization cycles significantly affects the volumetric and consolidation behavior, leading to decreased life of clay barrier structures.

SPECTRAL AND STRUCTURAL ANALYSIS FOR SODIUM SILICATE-BASED AEROGEL VIA NORMAL DRYING PRESSURE

Five types of silica aerogel were prepared at ambient pressure: sodium silicate, TEOS, and sodium silicate, with TEOS utilized as precursors. We investigated the effects of catalysis, mixing water or ethanol with the precursors, as well as the procedure of modification. Aqueous is a low-cost alternative, and many applications utilize it. A manufacturing colloidal silicic acid hydrosol was created from the ion exchange of an industrial water glass. The properties of physical, chemical, and hydrophobicity were examined via density, XRD, FTIR, and contact angle. BET, FESEM, and EDS analysis determined the structural properties. The silica hydrogel's pore liquid (H20) was successively removed. The spectral properties confirmed the modification by the derived high contact angle of 152º, low transparency, and amorphous structure. The resulting aerogel monoliths have a well-developed mesoporous structure, a large specific surface area of 961 m2/g, and a low density of 0.04 g/cm3.

Design of Anti-blocking and Anti-seepage shield grouting materials and their performance enhancement mechanism analysis

To solve the current problems of long-distance pumping blockage and poor stability of shield grouting material in the construction of subway tunnels, we studied the effects of thickener and water reducing type, dosage, and water-to-binder (W/B) ratio on the workability and mechanical properties of shield grouting materials with high-volume crushed sand and ultrafine powder. The mechanism of thickeners' effects on improving mortar properties was analyzed using the cryo-scanning electron microscopy (Cryo-SEM). The results show that proper compatibility of components and proportion optimization make it possible to prepare high-performance shield grouting materials with excellent anti-blocking and anti-seepage properties. These materials exhibit high fluidity, low pressure bleeding rate, homogeneous distribution of components, and meet the engineering requirements regarding setting time and strength of grouting material. A comparison of the performance of three types of thickening agents reveals that although hydroxypropyl methylcellulose (HPMC) improves the pressure bleeding rate of mortar significantly compared to seaweed gum, it leads to a significant delay in the setting time and a decrease in mortar strength. Welan gum (WG) has a minor impact on grouting materials' setting time and strength, and its water retention performance is similar to that of HPMC. However, WG is expensive and causes significant fluidity loss of slurry over time. On the other hand, seaweed gum demonstrates comprehensive advantages in enhancing various aspects of shield grouting materials, exhibiting good anti-blocking and anti-seepage effects. For its calcium-induced gelation property, seaweed gum forms an orderly screen structure of an “egg-box” shape in the pore liquid, then fills the pores between the screens through the film effect of the gel. Finally, the gels form a “screen-printing-like” overall effect, so that seaweed gum has the three-dimensional space network effect as WG and the film forming effect as that of HPMC, which can significantly improve the stability of the grouting material. Therefore, seaweed gum has almost no adverse impact on the strength of shield grouting material but has a relatively lower price.

Pore flow and solute rejection in pilot-scale air-gap membrane distillation

Membrane distillation (MD) is a desalination technology with promising applications in treating brines generated by reverse osmosis. Theoretically, MD can achieve 100% rejection of non-volatile contaminants such as organic and inorganic solutes and pathogens because only the vapor phase permeates through the membrane. However, polymeric membranes are subject to a wide distribution of pore sizes that may result in pore flow or liquid flux through even a new membrane resulting in poor contaminant rejection. In pilot-scale MD systems, a larger membrane area increases the hydraulic pressure in the flow channel and the transmembrane hydraulic pressure difference, thus increasing the probability of pore flow of non-volatile contaminants through the membrane and providing enhanced resolution of contaminant detection. This work reports membrane rejection of organic and inorganic non-volatile solutes in a pilot-scale air-gap MD (AGMD) element and quantifies, for the first time, transport of non-volatile solutes through the membrane because of pore flow. Pathogen rejection in the pilot-scale MD system was also measured using enteric virus surrogates MS2 and PhiX174 as tracers. Organic and inorganic solutes and both viruses were detected in the distillate, suggesting the presence of pore flow. No difference between organic and inorganic solute rejection was observed, and both decreased (from 2.5-log10 to 1.5-log10) with an increase in air-gap vacuum (from 50 to 500 mbar). At 50 mbar and low evaporator inlet temperature (40 °C), virus rejection (2.4 -log10) was higher than organic and inorganic solute rejection (1.7-log10).

Challenges in the Simulation of Drying in Fluid Bed Granulation

Fluid bed granulation is faced with a high level of complexity due to the simultaneous occurrence of agglomeration, breakage, and drying. These complexities should be thoroughly investigated through particle–particle, particle–droplet, and particle–fluid interactions to understand the process better. The present contribution focuses on the importance of drying and the associated challenges when modeling a granulation process. To do so, initially, we will present a summary of the numerical approaches, from micro-scale to macro-scale, used for the simulation of drying and agglomeration in fluid bed granulators. Depending on the modeled scale, each approach features several advantages and challenges. We classified the imposed challenges based on their contributions to the drying rate. Then, we critically scrutinized how these challenges have been addressed in the literature. Our review identifies some of the main challenges related to (i) the interaction of droplets with particles; (ii) the drying kinetics of granules and its dependence on agglomeration/breakage processes; as well as (iii) the determination of drying rates. Concerning the latter, specifically the surface area available for drying needs to be differentiated based on the state of the liquid in the granule: we propose to do this in the form of surface liquid, pore liquid, and the liquid bridging the primary particles.

Potential of an electric field generated during the scattering of an elastic wave on a fluid-filled vug in a porous rock

Propagation of elastic waves in porous fluid-saturated formations is often accompanied by electromagnetic radiation (seismoelectric effect), which has an electrokinetic nature. The magnitude of the generated electric current depends on the velocity of the relative flow between solid grains and a liquid in the primary pores. When the elastic wave is scattered by an inclusion, an additional liquid flow is generated. This flow induces a supplemental electromagnetic field.In this work, we have calculated an additional electric field generated by the scattering of an elastic wave on the vug (spherical cavity) located in an electrolyte-saturated poroelastic rock. The solution of the corresponding electrokinetic equations was obtained in the quasi-static approach. We have considered the problem for “open” and “closed” interfaces between the porous matrix and the vug. The solution was obtained for conducting and non-conducting fluids in the vug. The dependences of the magnitude of the generated electric field on the frequency and the rock parameters are presented.The results obtained demonstrate that the magnitude of the generated electric field depends considerably on the parameters of the rock (porosity and hydrodynamic permeability), as well as on the parameters of the fluid inside the inclusion (electric conductivity and bulk modulus). The calculations show that for an open interface the amplitude of the generated electric field is larger by more than an order of magnitude than for a closed interface. This is because the amplitude of the filtration flow near the vug surface is larger.