Inter-phase Transfer Research Articles

Deciphering and Enhancing Rate‐Determining Step of Sodium Deposition towards Ultralow‐Temperature Sodium Metal Batteries

Achieving high ionic conductivity and stable performance at low temperatures remains a significant challenge in sodium‐metal batteries (SMBs). In this study, we propose a novel electrolyte design strategy that elucidates the solvation structure‐function relationship within mixed solvent systems. A mixture of diglyme and 1,3‐dioxolane was developed to optimize the solvation structure towards superior low‐temperature electrolyte. Molecular dynamics simulations and Raman spectra results reveal the solvent‐separated ion pairs and contact ion pairs dominated solvation structure in the designed electrolyte, displaying a superior ionic conductivity of 1.78×10‐3 S cm‐1 at ‐40 °C. Besides, comprehensive kinetic analysis shows Na+ transportation in the electrolyte shows a greater impact on sodium plating than Na+ transport through the solid electrolyte interphase or charge transfer. As a result, the electrolyte enables stable operation for over 12,000 hours in Na||Na cells at ‐40 °C. In Na||Na2/3Ni1/4Cu1/12Mn2/3O2 full cells, it maintains a high capacity retention of 92.4% over 600 cycles with an initial specific capacity of 89.4 mAh g‐1 at ‐40 °C, and achieves 81.7% capacity retention after 50 cycles with an initial specific capacity of 75.3 mAh g‐1 at ‐78 °C. These results pave the way for the development of high‐performance SMBs capable of operating under ultralow temperatures.

Deciphering and Enhancing Rate-Determining Step of Sodium Deposition towards Ultralow-Temperature Sodium Metal Batteries.

Achieving high ionic conductivity and stable performance at low temperatures remains a significant challenge in sodium-metal batteries (SMBs). In this study, we propose a novel electrolyte design strategy that elucidates the solvation structure-function relationship within mixed solvent systems. A mixture of diglyme and 1,3-dioxolane was developed to optimize the solvation structure towards superior low-temperature electrolyte. Molecular dynamics simulations and Raman spectra results reveal the solvent-separated ion pairs and contact ion pairs dominated solvation structure in the designed electrolyte, displaying a superior ionic conductivity of 1.78×10-3 S cm-1 at -40 °C. Besides, comprehensive kinetic analysis shows Na+ transportation in the electrolyte shows a greater impact on sodium plating than Na+ transport through the solid electrolyte interphase or charge transfer. As a result, the electrolyte enables stable operation for over 12,000 hours in Na||Na cells at -40 °C. In Na||Na2/3Ni1/4Cu1/12Mn2/3O2 full cells, it maintains a high capacity retention of 92.4% over 600 cycles with an initial specific capacity of 89.4 mAh g-1 at -40 °C, and achieves 81.7% capacity retention after 50 cycles with an initial specific capacity of 75.3 mAh g-1 at -78 °C. These results pave the way for the development of high-performance SMBs capable of operating under ultralow temperatures.

Cross-Scale Decoupling Kinetic Processes in Lithium-Ion Batteries Using the Multi-Dimensional Distribution of Relaxation Time.

To non-destructively resolve and diagnose the degradation mechanisms of lithium-ion batteries (LIBs), it is necessary to cross-scale decouple complex kinetic processes through the distribution of relaxation times (DRT). However, LIBs with low interfacial impedance render DRT unreliable without data processing and closed-loop validation. This study proposes a hierarchical analytical framework to enhance timescale resolution and reduce uncertainty, including interfacial impedance reconstruction and multi-dimensional DRT analysis. Interfacial impedance is reconstructed by eliminating simulated inductive and diffusive impedance based on a high-fidelity frequency-domain model. Multi-dimensional DRT decouples solid electrolyte interphase (SEI) and charge transfer (CT) processes by the reversibility of electrochemical reactions with state of charge (SOC) to characterize electrode kinetic evolution driven by SOC and temperature through timescales and peak area. The findings reveal that reconstructed impedance improves the accuracy of identified time constants by ≈20%. Cross-scale DRT results reveal that SOCs below 10% at 25 °C effectively distinguish electrode kinetics due to the high correlation between cathodic CT and SOC. Kinetic metrics characterize that anodic SEI or CT are different control steps limiting the low-temperature performance of different cells. This work underscores the potential of the proposed framework for non-destructive diagnostics of kinetic evolution.

Investigation of geometrical hopper and initial packing state on the inter-phase momentum transfer with granular flow in vertical packed bed

Abstract For the specific application of vertical packed bed design, the main task is to optimize and improve the granular flow pattern, since a worse granular flow pattern is detrimental to the performance of heat transfer and flow in vertical packed bed. To improve the uniformity of granular flow profiles, an application of the discrete element method is used to investigate the granular flow pattern in a vertically packed bed under the condition of different tapered hopper angles and initial packing states. The uniformity of granular dramatically decreases with an increase in the fluctuation of granular velocity distribution. The variation of structural parameters has a positive influence on enhancing the stability of the granular layer. Coefficient of variation and relative fluctuation kinetic energy are introduced as criteria to describe the stability of the granular layer. This study numerically reveals the evolution of initial packing states has a slight influence on improving the stability of granular flow.

Upgrading event driven Monte Carlo simulations for molecule‐based morphological control for battery and sensor applications

AbstractMultiphase polymeric materials and applications play a prominent role in our society. One of the key challenges is the design and modification of their macromolecules so that the composition and structuring of the phases as well as the interactions between them can be controlled from the molecular scale onwards. In the present contribution, it is highlighted that more recently developed event driven (kinetic) Monte Carlo models provide an interesting framework to grasp molecular variations over various length scales. The strength lies in the tracking of individual molecules per phase of interest so that interphase transfer events can be sampled based on the distributed nature of the (macro)molecules present. Hence, the micro‐scale of local concentrations and temperatures can be connected to the meso‐scale defining interphase transport and morphological variations, with an additional connection to the macro‐ or application scale within reach by adding macro‐scale transfer events to the overall sampling scheme. Starting from a benchmark coupled matrix based Monte Carlo (CMMC) study on the multiphase formation of engineering composites which explicitly acknowledges the type of (macro)molecules present in each phase, it is showcased that the CMMC framework can support the general field of energy and electronics applications. This is highlighted through (i) a case study devoted to the design of polymer electrolytes for batteries, and (ii) a case study on blend design for the regulated stretching of piezoresistive sensors.

CFD investigation of post-combustion CO2 capture using an industrial spray tower: Regulation effects of spray schemes

The use of spray towers for post-combustion CO2 capture has attracted growing industrial interest. However, its practical application is hampered by a lack of knowledge about CO2 spray absorption on an industrial scale. Herein, we developed a numerical model to explore the potential of the spray tower for CO2 removal at a 330 MW coal-fired power plant. The model was developed in the Euler-Lagrange framework integrated with interphase transfer models. The variations of gas-droplet flow, CO2 removal efficiency, CO2 loading of rich solution, and temperature distribution under different spray schemes were investigated. It was found that gas flow hydrodynamics and CO2 removal performance can be regulated by the spray scheme. Compared to the conventional downward spray scheme, the lower nozzle layer adopted an upward spray scheme can improve the uniformity of the gas flow and results in several advantages: (1) average droplet residence time is extended by 5.2 %; (2) CO2 removal efficiency increases from 79.1 % to 82.9 %. This improvement is attributed to two factors: one is the droplet’s re-distribution, lowering the gas flow resistance in the region below the first spray layer near the inlet; the other is the change in gas-droplet interaction whereby the upward-moving droplets entrain the gas to flow upwards. Moreover, we investigated the effects of the spray schemes under varying flue gas loads. Under these conditions, the upward spray mode adopted in the first layer shows the best CO2 removal performance. Further theoretical analysis reveals the mechanisms underlying the regulation effect. The findings in this work will benefit the design and optimization of the industrial-scale spray tower for CO2 removal.

Performance evaluation and optimization of a suspension-type reactor for use in heterogeneous catalytic ozonation

Packed fixed-bed reactors are traditionally used for heterogeneous catalytic ozonation. However, a high solid-to-liquid requirement, poor ozone dissolution, ineffective utilization of catalyst surface area, and production of large amounts of catalyst waste impede application of such reactors. In this study, we designed a suspension catalytic ozonation reactor and compared the performance of this reactor with that of a traditional fixed-bed catalytic ozonation reactor employing oxalic acid (OA) as the target contaminant. Our results showed that total O3 dissolved into the suspension reactor (117–134 mg.L−1) was much higher compared to that measured in the fixed-bed reactor (53 mg.L−1) due to a higher O3(g) interphase mass transfer rate in the suspension reactor. In accordance with the higher O3(g) interphase mass transfer, we observed a much higher proportional OA removal (32 %) compared to that achieved in the fixed-bed reactor (10%) employing an Fe-oxide catalyst supported on Al2O3 (Fe-oxide@Al2O3) in both reactors. Use of a double-layered Cu-Al hydroxide (Cu-Al LDHs) catalyst in the suspension reactor further enhanced the performance with nearly 90 % OA removal observed. Given the superior performance of the suspension reactor, we investigated the impact of operating conditions (catalyst dosage, hydraulic retention time and ozone dosage) employing Cu-Al LDHs as the catalyst. We also developed a mathematical kinetic model to describe the performance of the suspension reactor and, through use of the kinetic model, showed that O3(g) interphase transfer rate was the rate-limiting step in OA removal. Thus, improvement in ozone gas diffuser design is required to improve the performance of the suspension reactor. Overall, the present study demonstrated that suspension reactors were more effective than fixed-bed reactors for oxidation of surface-active organic compounds such as OA due to the higher ozone interphase mass transfer rate and effective utilization of the catalyst surface area that can be achieved. As such, further research on suspension reactor design and development of catalysts suitable for use in suspension reactors should facilitate large-scale application of catalytic ozonation processes by the wastewater treatment industry.

Non-invasive diagnosis of solid electrolyte interphase and charge transfers resistances for degraded lithium-ion batteries

Modeling the electrical behavior of cells is often complex because several parameters have to be determined simultaneously, which may lead to inconsistencies and inaccuracies. In the present paper, we modeled the “surface resistance” by using a method based on rules of dependence, already presented in the literature, which makes it possible to separate the contributions of the SEI (Solid Electrolyte Interphase) layer and the charge transfers as a function of the temperature and the current. A physical model is able to provide a consistent estimate of the surface resistance values at untested operating points. We transposed this model to NCA (LiNixCoyAl1−x−yO2) and NMC-622 (LiNi0.6Mn0.2Co0.2O2)/graphite+Si cells and we characterized them for different states of health (SOH). For a SOH of 87%, we found that the charge transfers resistance was multiplied at least by 5.8, while the SEI resistance was multiplied at least by 1.5. As the cell ages, the proposed model should be easier to recalibrate than lookup tables. For that, we propose two methods, one that provides more detailed and accurate results and one that is more practical from an engineering point of view.

Impact of interphase component transfer on CO2 distribution and pH during CO2 injection in the subsurface

Single phase CO2 injection and CO2 water alternating gas (WAG) injection processes are simulated using reactive transport modelling to understand the inter-phase component transfer between CO2, brine and oil, and to address geochemical (aqueous) reactions induced by CO2 in the near wellbore region. In this research, calculations are performed using a numerical one-dimensional cartesian model with homogenous properties. We investigate how fast the pH changes as CO2 is injected into the system and how the presence of oil affects the velocity of the pH front. We measure the velocity of the front at which oil becomes completely desaturated with respect to CO2 – referred to as the “CO2 desaturation front” and compare it with the classical Buckley-Leverett saturation front displacement during WAG injection. We also study the impact of the WAG cycles on the CO2 desaturation front velocity and the pH change. The study showed that the presence of hydrocarbons in the model buffers and delays the pH drop. By the end of each water cycle all the CO2 was removed from the contacted oil phase within the first few meters from the well. The CO2 desaturation front travels at approximately one twentieth of the phase saturation front velocity during the first three WAG cycles, but it then stopped for later cycles, which gives an indication of the extent of the desaturation of oil. During the WAG injection, different pH fronts developed due to the impact of each cycle on the fluid composition and component transfer. The pH reduction during the last WAG cycles was greater near the injection well as most of the lighter hydrocarbon components were displaced out of the residual “oil”, meaning the CO2 content of this residual phase was higher than for initial cycles. This would result in a greater risk of calcite dissolution around the injection well if there were calcite present in the rock formation.

Natural Convection in a Newtonian Nanoliquid-Saturated Porous Enclosure with Local Thermal Non-Equilibrium Effect

Buoyancy-driven convective flow and heat transfer characteristics in a Newtonian nanoliquid-saturated porous square enclosure are analyzed numerically using a local thermal non-equilibrium model. An enclosure’s horizontal walls are considered free–free and adiabatic, and the vertical walls are free–free isothermal boundaries. The dimensionless governing equations are solved using a central finite difference scheme with second-degree accuracy, and the results are in satisfactory agreement with the earlier works. The impact of various parameters on streamlines and isotherms is analyzed and depicted graphically. The effect of Darcy number, thermal Rayleigh number, and the ratio of thermal conductivities slow down the liquid flow. The temperature distribution is maximum at sidewalls and diminishes the amount of heat transport. The opposite phenomenon is observed for the solute Rayleigh number and interphase transfer coefficient of liquid-particle phases. For large values of interphase heat transfer coefficients, liquid-solid and liquid-particle are said to be in the local thermal equilibrium phase. The amount of heat transfer increases with an increasing interphase heat transfer coefficient and the ratio of the phases’ thermal conductivities. Results of local thermal equilibrium situation can be obtained as the particular case of the study. The amount of heat transfer is maximum in the local thermal non-equilibrium situation, and enhanced by 0.09% compared with the local thermal equilibrium situation. Heat transport is 0.74% less in the sparsely packed porous medium compared with the low-porosity medium.

Experimental study on the addition of pulsating flow to enhance liquid-solid mass transfer in the circulating fluidized bed

The addition of pulsating flow in the conventional liquid-solid circulating fluidized bed (CLSCFB) to enhance liquid-solid mass transfer efficiency has been proposed. A pulsating continuous liquid-solid circulating fluidized bed (PCLSCFB) experimental system was designed and constructed. The liquid-solid mass transfer coefficient (kSL) in the PCLSCFB was measured by the experimental method of dissolving the insoluble benzoic acid particles. The effects of superficial liquid velocity, superficial solids velocity and pulsation property on the liquid-solid mass transfer coefficient (kSL) in the PCLSCFB were thus determined. It was concluded that the liquid-solid mass transfer coefficient (kSL) increases with the increasing pulsation amplitude and frequency in the experimental range. The addition of pulsating flow significantly strengthens the liquid-solid interphase transfer efficiency in comparison with the CLSCFB. The correlation of the mass transfer coefficient (kSL) for the PCLSCFB has been proposed based on experimental data and main parameters.

A mega study of antibiotics contamination in Eastern aquatic ecosystems of China: occurrence, interphase transfer processes, ecotoxicological risks, and source modeling

Understanding the occurrence, sources, transfer mechanisms, fugacity, and ecotoxicological risks of antibiotics play a pivotal role in improving the sustainability and ecological health of freshwater ecosystems. Therefore, in order to determine the levels of antibiotics, water and sediment samples were collected from multiple Eastern freshwater ecosystems (EFEs) of China, including Luoma Lake (LML), Yuqiao Reservoir (YQR), Songhua Lake (SHL), Dahuofang Reservoir (DHR), and Xiaoxingkai Lake (XKL), and were analyzed using Ultra Performance Liquid Chromatography/Tandem Mass Spectrometry (UPLC-MS/MS). EFEs regions are particularly interesting due to higher urban density, industrialization, and diverse land use in China. The findings revealed that a collective total of 15 antibiotics categorized into four families, which included sulfonamides (SAs), fluoroquinolones (FQs), tetracyclines (TCs), and macrolides (MLs), exhibited high detection frequencies, indicating widespread antibiotic contamination. The pollution levels in the water phase were in the order of LML > DHR > XKL > SHL > YQR. The sum concentration of individual antibiotics for each water body ranged from not detected (ND) to 57.48 ng/L (LML), ND to 12.25 ng/L (YQR), ND to 57.7 ng/L (SHL), ND to 40.50 ng/L (DHR), and ND to 26.30 ng/L (XKL) in the water phase. Similarly, in the sediment phase, the sum concentration of individual antibiotics ranged from ND to 15.35 ng/g, ND to 198.75 ng/g, ND to 1233.34 ng/g, ND to 388.44 ng/g, and ND to 862.19 ng/g, for LML, YQR, SHL, DHR, and XKL, respectively. Interphase fugacity (ffsw) and partition coefficient (Kd) indicated dominant resuspension of antibiotics from sediment to water, causing secondary pollution in EFEs. Two groups of antibiotics, namely MLs (erythromycin, azithromycin, and roxithromycin) and FQs (ofloxacin and enrofloxacin), showed a medium-high level of adsorption tendency on sediment. Source modeling (PMF5.0) identified wastewater treatment plants, sewage, hospitals, aquaculture, and agriculture as the major antibiotic pollution sources in EFEs, contributing between 6% and 80% to different aquatic bodies. Finally, the ecological risk posed by antibiotics ranged from medium to high in EFEs. This study offers valuable insights into the levels, transfer mechanisms, and risks associated with antibiotics in EFEs, enabling the formulation of large-scale policies for pollution control.

EFFECT OF THE HYDRODYNAMIC CONDITIONS FOR SODIUM ALGINATE–PAPAIN COLLOIDAL SYSTEM SYNTHESIS ON THE SORPTION PROPERTIES OF THE BIOCOMPOSITE

The regularities have been studied for the formation of molecular associates upon the introduction of papain into a sodium alginate colloidal solution in the laminar low-speed, transient, and turbulent stirring regimes. The relationship between variations in the sorption capacity of the biopolymer composition and the kinetic regularities of the interphase transfer has been studied during the sorption binding of albumin, which is one of the protein-based components of wound exudates, with such components being subject to ensimatic cleavage. The state of the dispersed phase of the colloidal solutions has been estimated by the dynamic light scattering method. The properties of the formed biopolymer films have been studied using the methods of scanning electron microscopy, low-temperature nitrogen adsorption, and static albumin sorption from solutions of limited volumes. The data of the sorption experiments have been analyzed using the Boyd, Morris–Weber, and gel diffusion models, as well as the Lagergren pseudo-first-order and Ho–McKay pseudo-second-order kinetic models. The data have been obtained for substantiating the dosages of the biopolymermatrix used on wound-healing bandages and for the efficient binding of wound necrotic contamination during the time preset according to the technical requirements.

Voltammetric determination of phosphates using ion-selective electrode based on organotin ionophore

This work describes the development of an amperometric phosphate-selective electrode with a plasticized membrane that includes bis(2-ethylhexyl)tin (IV) dichloride as an ionophore. The potentiometric response of the plasticized membrane was investigated, in addition to its selectivity for hydrophilic anions. The membrane provided a linear potential response with respect to HPO42- ions in the concentration range from 4·10-5 to 3·10-2 mol/L with a Nernst slope of 29 ± 2 mV·decade-1 activity. By using cyclic voltammetry, we characterized the ionophore-facilitated transfer of mono- and dihydro phosphate ions at the water/PVC-2-nitrophenyl octyl ether phase interface. An interphase distribution coefficient, a galvanic potential, a half-wave potential, the Gibbs energy of facilitated interphase transfer, as well as the Gibbs energy of facilitated interphase transfer were determined. Alternating current voltammetry was used to quantify phosphate ions in aqueous solutions. The linear response was observed in the range of phosphate concentrations from 2 to 10-6 to 1·10-4 mol/L and the detection limit was 8·10-7 mol/L under these conditions. This AISE has demonstrated high selectivity for phosphate ions in comparison to the most common anions in aqueous solutions. It has been used to determine the amount of phosphates in two fertilizers.

Separation of aliphatic amino acids from aqueous media with an aminophosphonic ion exchanger

The sorption of the aliphatic amino acids glycine and α-alanine by an aminophosphonic ion exchanger is studied and the dynamics of sorption is described using a kinetic equation. Experimental studies were carried out on a designed experimental setup with a fixed ion exchanger layer, in which the purified and regenerating solutions are passed through the sorbent layer in various directions. The heterogeneous ion exchange process includes the transport of sorbent ions in the liquid phase to the grain surface and the removal of desorbed ions from it, interphase transfer, diffusion of sorbed and desorbed ions inside the grain, since not all functional groups of the sorbent are localized on the surface, and a reversible ion exchange reaction. The kinetic equation of the Thomas model takes into account the multistage sorption and adequately describes the dependence of the degree of extraction of the component on the duration of contact of the solution with the ion exchanger layer. The equation of the Thomas model has been modernized taking into account the effect on the dynamics of the process of diffusion resistances in the channels of the layer and the grains of the ion exchanger in a column with a fixed loading. The upgraded model is applied to describe the dynamics of ion exchange of aliphatic amino acids on an aminophosphonic ion exchanger and the possibility of using a one-dimensional capillary flow model to estimate the diffusion resistance during fluid movement in the channels of the ion exchanger layer is shown. The agreement of the calculated and experimental output curves of sorption of aliphatic amino acids from aqueous solutions of various concentrations has been verified. It is shown that the upgraded model adequately describes the dependence of the degree of amino acid extraction on the duration of contact of the solution with the polyampholite layer at different feed rates of the purified solution.

Modelling of Catalytic Combustion in a Deformable Porous Burner Using a Fluid–Solid Interaction (FSI) Framework

The various concepts involved in the mathematical modeling of the fluid-solid interactions (FSIs) of catalytic combustion processes occurring within a porous burner are presented and discussed in this paper. The following aspects of them are addressed: (a) the relevant physical and chemical phenomena appearing at the interface between the gas and the catalytic surface; (b) a comparison of mathematical models; (c) a proposal of a hybrid two/three-field model, (d) an estimation of the interphase transfer coefficients; (e) a discussion of the proper constitutive equations and the closure relations; and (f) a generalization of the Terzaghi concept of stresses. Selected examples of application of the models are then presented and described. Finally, a numerical verification example is presented and discussed to demonstrate the application of the proposed model.

A 3D Framework with Li3 N-Li2 S Solid Electrolyte Interphase and Fast Ion Transfer Channels for a Stabilized Lithium-Metal Anode.

The Li-metal anode has been recognized as the most promising anode for its high theoretical capacity and low reduction potential. However, the major drawbacks of Li metal, such as high reactivity and large volume expansion, can lead to dendrite growth and solid electrolyte interface (SEI) fracture. An in situ artificial inorganic SEI layer, consisting of lithium nitride and lithium sulfide, is herein reported to address the dendrite growth issues. Porous graphene oxide films are doped with sulfur and nitrogen (denoted as SNGO) to work as an effective lithium host. The SNGO film enables the in situ formation of an inorganic-rich SEI layer, which facilitates the transport of Li-ions, improves SEI mechanical strength, and avoids SEI fracture. In addition, COMSOL simulation results reveal that the microchannels fabricated by the 3D printing technique further shorten the Li-ion transfer pathways and homogenize heat and stress distribution in the batteries. As a result, the assembled anode shows low capacity fading of 0.1% per cycle at 2 C rate with the sulfur cathode. In addition, the high lithium utilization of the SNGO host enables the anode to provide a stable capacity at low negative/positive electrode ratios under 3 in LiS batteries.

CFD modeling of MEA-based CO2 spray scrubbing with computational-effective interphase mass transfer description

Great concerns for global warming and stringent regulations have spurred the development of feasible technologies to reduce CO2 emissions from the power generation sector. In thermal power plants, spray scrubbing is one of the most used methods for separating gaseous pollutants, which inspires the idea of applying spray scrubbing in CO2 capture. However, this new idea still necessitates investigation, particularly in developing a novel modeling tool. This motivates us to present the CFD modeling of CO2 spray scrubbing using MEA solution in this work. CO2 spray scrubbing is a complex process. Herein, the established model combines the multiphase flow with interphase transfer and chemical reactions in the Euler-Lagrange framework. To efficiently describe the interphase mass transfer, we proposed a new method based on the thermodynamic consistency between the CO2 equilibrium pressure and the enthalpy of CO2 absorption. Validated by the experimental data, this method can achieve an acceptable balance between accuracy and computational cost. The zwitterion mechanism was employed to describe the chemical reactions. Kinetic analysis shows that E = (1 +Ha2)0.5 can reasonably evaluate the enhancement factor value in a wide range of MEA concentrations. Additionally, the effects of operating parameters on CO2 removal were numerically studied, focusing on mass transfer characteristics. Therefore, the proposed numerical model will be beneficial for facilitating the deployment of CO2 spray scrubbing in the power sector, and the numerical results provide helpful information for design and optimization.

Experimental study on flow characteristics of liquid-solid circulating fluidized bed with central pulsating liquid flow

A novel liquid-solid circulating fluidized bed with central pulsating liquid flow has been proposed and constructed. The central sinusoidal pulsating liquid flow was introduced to improve the interphase transfer efficiency between liquid and solids phases. The hydrodynamic characteristics in the riser were investigated experimentally using the acrylic particles and glassbeads. The axial solids holdup and cross-sectional solids holdup distributions under different operating conditions, which directly related to the contact and mixing effect between the liquid and solids phases, were studied by conductivity probes and waveform analysis method. It was concluded that compared with the conventional liquid-solid circulating fluidized bed, the introduction of the central pulsating liquid flow increased the turbulence in the bed within the experimental range, enhanced the radial movement of the particles, and improved the mixing degree and transfer efficiency between the liquid and solids phases. • The novel liquid-solid CFB with central pulsating liquid flow is proposed. • The flow characteristics are investigated experimentally using conductivity probes. • The flow characteristics are compared with the conventional liquid-solid CFB. • A prediction model of the average solids holdup is obtained.

A comparison of mixture and separated-phase models of heat transfer in a stationary wet granular bed

Solvent removal by thermal drying of granular mixtures is encountered in many industrial operations. A mixture model that treats the granular solid and the liquid solvent along with any interstitial gas phase as a single phase, is a useful first approximation to estimate the time required to heat the system to the wet-bulb temperature at which the solvent starts to vaporize. An analytical solution for the transient, axisymmetric temperature distribution in a stationary wet granular mixture in a heated cylindrical vessel is developed as an approximation to the typical geometry of an industrial dryer . Besides being a good first approximation to obtain an order-of-magnitude estimate of the heating time, the analytical solution serves as an excellent verification case for numerical simulations. A parametric study to assess the effect of fill height and wall temperature on the heating time is performed. Before analyzing the mass transfer aspects of the drying phenomena, it is critical to understand the fundamentals of interphase heat transfer in multiphase mixtures that can be found in such assemblies. Therefore, a 0-D separated-phase (multiphase) heat transfer model is developed to account for the effect of interphase heat transfer in the prediction of heating time of wet granular mixtures in cylindrical vessels. The 0-D model is extended to 3-D simulations using a newly developed OpenFOAM solver with multiphase heat transfer capability. The same problem that was solved using the analytical solution is solved using the 0-D model, and in 3-D using the newly developed OpenFOAM solver, to study the effect of interphase heat transfer on the prediction of heating time. It was found that inclusion of interphase heat transfer in the heat diffusion equations has a significant impact on the predictions of heating time. Further analysis of the problem results in the identification of the non-dimensional thermal interphase transfer number that determines the conditions under which a mixture model can be used in place of a separated phase model in problems involving heat transfer.