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Experiments in large-scale CFBC boilers are expensive and time-consuming, while simulations are economical, time-saving, and provide better control over the physical process. In the current research, mathematical modeling of industrial scale CFBC boiler (BG-043, 67TPH capacity, ACC cement factory Bargarh, Odisha, India) using coal and sawdust blended fuel (90% coal + 10% sawdust) is performed by considering the four distinct (coal, sawdust, sand, and mixture gas) phases using Eulerian–Eulerian multifluid model. Heterogenous chemical reactions kinetics are implemented using user-defined functions. The numerical methodology is validated with the onsite industrial data. The comparison of pressure drop, fluidized bed height, axial velocity profiles, sand, and mixture gas temperature variations, gas compositions, and pollutant emissions (SO2 and NO) using solo coal and sawdust blended fuel are presented in the result section. Hydrodynamics study reveals the recirculation of sand particles in the fluidized bed region of the boiler. The comparison of solo coal and sawdust blended fuel combustion study reveals a 10.61% reduction in pressure drop, 12.13% increase in O2 mass fraction, 9.63% reduction in CO mass fraction, 19.64% reduction in SO2 mass fraction, and 8.67% reduction in NO mass fraction while using the 10% sawdust blends with 90% coal. [ABSTRACT FROM AUTHOR]

Collective cell migration (CCM) is involved in multiple biological processes, including embryonic morphogenesis, angiogenesis, and cancer invasion. However, the molecular mechanisms underlying CCM, especially leader cell formation, are poorly understood. Here, we show that a signaling pathway regulating angiomotin (AMOT) cleavage plays a role in CCM, using mammalian epithelial cells and mouse models. In a confluent epithelial monolayer, full-length AMOT localizes at cell-cell junctions and limits cell motility. After cleavage, the C-terminal fragment of AMOT (AMOT-CT) translocates to the cell-matrix interface to promote the maturation of focal adhesions (FAs), generate traction force, and induce leader cell formation. Meanwhile, decreased full-length AMOT at cell-cell junctions leads to tissue fluidization and coherent migration of cell collectives. Hence, the cleavage of AMOT serves as a molecular switch to generate polarized contraction, promoting leader cell formation and CCM. [Display omitted] • The AMOT cleavage signaling pathway is indispensable for collective cell migration • Cleavage product AMOT-CT induces focal adhesion maturation and leader cell formation • AMOT cleavage leads to cell monolayer fluidization and collective migration • AMOT-CT expression promotes cancer cell invasion and metastasis Wang et al. demonstrate that the cleavage of AMOT is essential for collective cell migration (CCM) and tumor metastasis. The cleavage of AMOT results in its spatial redistribution from apical junctions to focal adhesions (FAs), promoting leader cell formation, cell fluidization, and coherent cell migration. [ABSTRACT FROM AUTHOR]

This study evaluates the transportability of clayey-silt natural gas hydrate (NGH) solid particles during solid fluidization in horizontal tubing, a crucial step in recovering marine NGH. Non-uniform solid particle distribution in horizontal flows can cause unstable operations and financial losses. Thus, assessing transportability is necessary to avoid these issues and harness the potential of NGH as an alternative energy source. This study introduces a model based on each phase's two-layer approach and momentum balance equation, considers potential hydrates (re)formation, and overcomes previous models' limitations. Moreover, it assumes that the critical settling velocity marks the moment when the lower bed of solid particles stagnates, thereby leading to the disappearance of frictional pressure in the lower bed. The proposed model is evaluated and compared with existing models using a laboratory dataset and the South China Sea offshore field dataset and found to provide the highest prediction accuracy and precision. Moreover, it reveals that the tubing diameter, solid particle diameter, and solid particle concentration are the major influential parameters affecting the solid particle conveyance. Consequently, the proposed model is suitable for evaluating the transportability of those solid particles in horizontal tubing, making it ideal for assessing their transportability in pipelines. [ABSTRACT FROM AUTHOR]

We investigate the rheological properties of ceramic slurries designed for laser stereolithography manufacturing in relation to their formulation, including the powder morphology, their volume fraction, and the concentration of dispersing agent. By combining dynamic strain sweep and Small‐Angle X‐ray Scattering (SAXS) experiments, we first illustrate that slurry viscosity follows an exponential trend with increasing particles content, with steeper increase observed for more aggregated particles. We then show that increasing the dispersant concentration up to an optimal value decreases slurry viscosity, as SAXS measurements reveal a reduction and homogenization in agglomerate size. Finally, we evidence that applying vertical oscillatory deformation during steady shear flow induces fluidization of the slurry. The shear viscosity exhibits a time–strain rate equivalence, enabling the generalization of this effect across a wide range of formulations. This methodology holds potential for industrial applications, where introducing vibration perpendicular to the scraping blade motion could improve the surface quality of the spread slurry prior to polymerization. [ABSTRACT FROM AUTHOR]

ABSTRACT Understanding the hydrodynamics of the bed layer in a fluidized bed is essential for optimizing and improving fluidized bed flotation units. This study proposes a fluidized bed flotation column that incorporates auxiliary particles into the gas–liquid two‐phase system to address the shortcomings of traditional flotation units. Stainless steel particles (glass beads), tap water, and compressed air were used as the solid, liquid, and gas phases, respectively. Key factors affecting the bed hydrodynamics (such as bed fluctuation, minimum fluidization velocity, bed expansion, and porosity) in the fluidized column include gas and liquid flow rates as well as the initial bed height. Experimental results show that selecting appropriate filling particles can effectively enhance the fluidization performance of the bed, while appropriately increasing the gas flow rate can achieve fluidization at lower liquid velocities, thus reducing energy consumption during the flotation mineralization process. Theoretical analysis combined with extensive data reveals that the expansion characteristics of the fluidized bed and the use of high‐density filling particles can effectively mitigate bed layer fluctuations and stabilize the flow field environment. Additionally, based on a wide range of data, this study employs model factor analysis, dimensionless analysis, and multiple linear regression analysis to propose a standard dimensionless parameter model for the fluidized bed flotation column, which can effectively predict bed layer fluctuations and expansion characteristics. [ABSTRACT FROM AUTHOR]

In this paper, the micro fluidized bed investigated numerically at various bed inclination angles. Micro-fluidized beds are widely used in laboratories to improve and enhance the efficiency of fluidized beds in industries. Thus, ensure that the properties of large FBs are applicable upon implementation. CFD simulations are conducted using Ansys Fluent Software Program 2022R2. The effects of bed inclination on various model parameters were investigated. The investigation focused on analysing the pressure drop during the fluidization process at four different bed angles: 2, 6, 8 and 10 degrees. Additionally, the study explored the effects of inclination on turbulent viscosity, effective viscosity, turbulent kinetic energy and volume fraction of solid. The findings indicated that the pressure drop showed variations (decrease and increase) with time, turbulent and effective viscosities increased then decreased with inclined angles at different water velocities. Turbulent kinetic energy grew with increasing water velocity; however, the volume fraction of solids remained stable. [ABSTRACT FROM AUTHOR]

To clarify the impact of multiple startups and startup parameters on the mass flow rate characteristics of powder fuel in a powder ramjet engine, this paper employs experimental and modeling methods to conduct an in-depth analysis of the fluidization and transportation characteristics of boron-based powder fuel under different startup conditions. The results demonstrate that the intake process of the first startup compresses the volume of the powder fuel, and during the working phase, the powder fuel's stacking profile evolves from a flat surface to a conical surface. These factors result in a longer mass flow rate response delay in the first startup (Δt = 9.4 s) compared to the second startup (Δt = 2.8 s). Presetting the stacking profile of the powder fuel as a cone and increasing the initial pressure of the storage tank to 0.17 MPa can significantly shorten the powder mass flow rate response time in the first startup, to Δt = 3 s and Δt = 0.54 s, respectively. The obstruction of the powder fuel at the intake position causes pressure fluctuations, with frequencies ranging between 2 and 4 Hz. The reaction force of the conical inner wall surface has a greater volume compression effect on the powder fuel than the intake process alone. Furthermore, the powder mass flow rate model based on the powder compression equation can accurately predict the powder mass flow rate during the stable supply phase, with a prediction accuracy of 3.1%. [ABSTRACT FROM AUTHOR]

We investigate granular flows generated by the collapse of an initially fluidized column into a horizontal channel in order to evaluate the factors controlling the efficiency of fluidization in increasing the run-out distance of pyroclastic density currents. This configuration is analogous to flows generated by the collapse of volcanic domes or lava flow fronts. We use an incompressible two-phase numerical model able to simulate dam-break experiments, and we compare the numerical results with experimental data. This model permits us to describe depth-dependent variations of flow properties and the effect of pore pressure on the rheology of the granular material. We show that the interplay between timescales of column collapse and of flow front propagation plays a primary role in determining the effective influence of fluidization on run-out distance. For columns with a high aspect ratio (i.e., initial height/initial width), the collapse velocity decreases abruptly after reaching its peak, a significant portion of the collapse has occurred when the flow front has travelled a long distance from the reservoir and, importantly, the decrease of basal pore pressure with time in the reservoir translates into a reduced velocity of the granular material entering into the propagation channel during final phases of collapse. Thus, at some point, the collapsing material is not able to significantly affect the flow front dynamics. This behaviour contrasts with that of low aspect ratio collapsing columns. These results are consistent with complementary analogue experiments of high-aspect-ratio collapsing columns, which show that the granular material at the front of the deposit originates from lower levels of the column. Comparison with new experimental data also reveals that the effective pore pressure diffusion coefficient in the propagating flow is an increasing function of column height, and it can be considered as proportional to a weighted average of flow thickness during propagation. This is consistent with experiments on static defluidization columns, but had not been tested in dam-break experiments until this study. Considering this type of dependency, under our experimental and simulation conditions, the non-dimensional run-out distance presents a relative maximum for initial aspect ratios between 1 and 2, and beyond this critical range, the non-dimensional run-out distance decreases abruptly. [ABSTRACT FROM AUTHOR]

In recent years, the fast growth of computational power has allowed the application of computational fluid dynamics (CFD) in a wide range of areas of interest, such as gas–solid unit operations. In this context, the multiphase particle-in-cell (MP-PIC) method appears as an option to represent fluid–particle and particle–particle interactions, avoiding the complexity of tracking each particle and the high computational cost derived from this. The MP-PIC method can represent the particles as a group with the same characteristics, allowing the simulation of gas–solid systems at different scales. To achieve this, the particle–particle interactions are simplified using the solid stress tensor to represent them; this does not require explicit expressions. This approach has a low computational cost, allowing the simulation of industrial cases using just workstations. This paper provides a review of the literature on the solid stress tensor and its commercial and non-commercial applications, including its historical and mathematical development in the description of particle–particle interactions. In addition, to consolidate the knowledge and advancing understanding in this crucial aspect of multiphase flow simulations, this review identifies the current challenges and opportunities for future research in multiphase systems based on the solid stress tensor. In addition, this review identifies the current challenges and opportunities for future research in multiphase systems based on the solid stress tensor. [ABSTRACT FROM AUTHOR]

The abundance and replenishable nature of biomass make it a suitable fuel for power generation. Among the various technologies, dual fluidized bed gasification (DFBG) is a suitable technology to generate high-quality syngas from biomass. However, the complexity of hydrodynamics and heat transfer with bed geometry, flow conditions as well as feedstock demands effective research for the design of such system. This study, therefore, focuses on the simulation of hydrodynamics of a dual fluidized bed gasification system. The 2-D two-fluid model (TFM) simulations were performed using Multiphase Flow with Interphase eXchanges (MFiX) software by varying the superficial air velocities for both the gasifier and riser. The influence of superficial air velocity on static pressure, pressure drop, axial and radial voidage, solid velocities, and granular temperature was evaluated. From the simulations, it was observed that with the increase in superficial air velocities, there was an increase in the effective height of pressure drop (66%), voidage, and solid velocities of the gasifier. For the simulation of the riser, similar trends in the profile of hydrodynamic parameters were also observed. The optimum velocity for the gasifier and riser has been suggested to be between 0.15 and 0.35 m/s and 6–7 m/s, respectively. [ABSTRACT FROM AUTHOR]

China's significant reliance on imported iron ore is due to its poor resource endowment and low utilisation levels. Given the urgent demand for iron ore resources, it is crucial to conduct basic research and cutting-edge technology exploration around co-associated refractory iron ore to realise the efficient utilisation of these resources. This study reports on the physicochemical properties and beneficiation methods including conventional separation, leaching, deep reduction and smelting for refractory iron ore. This work focuses on summarising the four types of magnetisation roasting equipment, technology, parameter optimisation, mechanism characteristics, current challenges and trends: vertical furnace magnetisation roasting, rotary kiln magnetisation roasting, fluidisation magnetisation roasting and microwave magnetisation roasting. Based on this, a new method of hydrogen-based microwave fluidisation magnetisation roasting is proposed. This method offers selective, rapid heating and high efficiency in heat and mass transfer. It provides ideas for clean, efficient and low-carbon utilisation of refractory iron ore resources. [ABSTRACT FROM AUTHOR]

This study investigates the optimization of placer gold ore processing using a laboratory-scale Knelson concentrator through response surface methodology (RSM) and Box-Behnken experimental design. Fifteen experiments were conducted to assess the effects of three parameters: solid concentration (wt.%), G force (G), and fluidization water flow rate (l/min), on gold grade and recovery. Statistical analyses using Design Expert 13 revealed significant quadratic regression equations for both gold grade and recovery, with high coefficients of determination. The empirical models demonstrated the intricate relationships between the concentrator parameters and process responses. Interpretation of the equations revealed that increasing the solid concentration positively influenced gold grade and recovery, while higher G force and fluidization water flow rate negatively impacted these parameters. Moreover, synergistic effects were observed between certain parameter pairs, indicating the complex interplay of factors influencing gold concentration and extraction efficiency. The study highlights the importance of understanding the separation mechanisms within the Knelson concentrator, especially in the presence of flaky gold particles alongside spherical particles. Insights gained from this research provide valuable guidance for optimizing placer gold ore processing operations, ultimately enhancing efficiency and sustainability in mineral processing practices. [ABSTRACT FROM AUTHOR]

Solid fluidization is a promising method for the development of marine hydrate resources. The back pressure makes it difficult to backfill the separated sand to the well bottom, resulting in a decrease in separation performance and serious failure of hydrocyclone. This study is intended to study the effect of underflow diameter on the performance of the hydrocyclone by computational fluid dynamics method. The results show that with the increase of back pressure, the split ratio basically decreases linearly, and the LAVV gradually increases. Under the same back pressure, the underflow diameter is larger, the pressure drop is smaller. No matter how large the underflow diameter is, the hydrocyclone may fail once back pressure exceeds 60 kPa. Under the same back pressure, the larger the underflow diameter is, the higher the desanding efficiency is, while the purification efficiency is opposite. When back pressure exceeds 60 kPa, the desanding efficiency drops sharply, while the purification efficiency remains basically unchanged. This study is applicable to downhole in-situ separation for solid fluidization of marine hydrate. The purpose of this study is to guide the structure design of hydrocyclone and the optimization of hydrate production process parameters. [ABSTRACT FROM AUTHOR]

The formation of complex craters requires some form of transient weakening of target rocks. Acoustic fluidization is one proposed mechanism applied in many numerical simulations of large crater formation. In a companion paper, we describe implementing the Melosh model of acoustic fluidization in the iSALE shock physics code. Here, we explore the effect of Melosh model parameters on crater collapse and determine the range of parameters that reproduce observed crater depth‐to‐diameter trends on the Earth and Moon. Target viscosity in the Melosh model is proportional to the vibrational wavelength, λ $\lambda $, and the longevity of acoustic vibrations is ∝λQ $\propto \lambda Q$ (Q $Q$—quality factor). Our simulations show that λ $\lambda $ affects the size of the fluidized region, its fluidity, and the magnitude of the vibrations, producing a variety of crater collapse styles. The size of the fluidized region is strongly affected by the Q $Q$. The regeneration factor, e $e$, controls the amount of (re)generated acoustic energy and its localization. We find that a decrease in e $e$ leads to less crater collapse and that there are trade‐offs between e $e$ and Q $Q$. This trade‐off contributes to the more realistic Q $Q$ values than those used in the Block model. The diffusion of vibrations in regions with high stress and strain is controlled by the scattering term, ξ $\xi $. Compared to the Block model, the Melosh model results in a shallower zone of weakening in complex craters and enhanced strain localization around the crater rim. The parameter set that produces best depth‐diameter trends is λ $\lambda $ = 0.2× ${\times} $impactor radius, Q $Q$ = 10–50, e $e$ = 0.025–0.1, and ξ $\xi $ = 10–105 ${10}^{5}$m2s−1 ${\mathrm{m}}^{2}{\mathrm{s}}^{-1}$. Plain Language Summary: Impact craters are the most common geological features on planetary surfaces. As craters get larger in diameter, they express more complex morphology. Complex crater morphology results from target rocks behaving fluidly upon hypervelocity impact. The rocks behave as fluids because of the temporary reduction in strength, which results from vibrations that remain in the target after the passage of the shock wave. These vibrations cause pressure fluctuations and reduce the rock's strength. This concept is called acoustic fluidization. Here, we explore how vibrations' wavelength, dissipation, scattering, and (re)generation affect crater collapse. Our models show a larger subsurface deformation variety, which the previous simplified model lacked. We determine bounds for each explored parameter, show trade‐offs between them, and their success in reproducing depth‐to‐diameter trends on Earth and the Moon. Key Points: We explore the parameters of the Melosh model of acoustic fluidization (full model) and their effect on crater collapseWe find that the final crater size is a product of the trade‐off between the quality (Q) $(Q)$ and regeneration (e) $(e)$ factors and that vibrational wavelength, λ $\lambda $,affects the style of crater collapseConsidering the full model of acoustic fluidization produces a variety of subsurface deformation in the complex craters lacking in the hitherto applied models [ABSTRACT FROM AUTHOR]

This study utilized passive acoustic emissions from a fluidized bed containing spherical inert ABS particles, captured by an external piezoelectric microphone, to monitor fluidization agitation intensity. Acoustic signals were recorded during fluidization profiles achieved under air velocities ranging from 0.5 to 3.0 m/s and during the drying of water or maltodextrin aqueous solution (1:5 w/w) introduced as droplets. Analyzing audio features like waveforms, the Discrete Fourier Transform (DFT), and Mel Frequency Cepstral Coefficients (MFCCs) revealed changes corresponding to the agitation intensity of the particles. The MFCC coefficients were input into a three-layer artificial neural network (ANN) to predict fluidization dynamics based on air velocity, liquid flow rate, and drying time. The ANN efficiently learned from the data, achieving high predictive accuracy (R2 > 0.8) after 15 epochs of training, showcasing the robustness of MFCC coefficients for modeling. This approach highlights that the application of passive acoustic signals and neural networks allows for real-time monitoring of fluidization behavior during drying processes. [ABSTRACT FROM AUTHOR]

A novel compact and efficient pulse bed mineral scrubber (PBMS) has been designed. The scrubber has a hybrid design incorporating a U-type particle flow path, bed pulsation like a jig and fluidization. The hydrodynamic characteristics and response of this scrubber for the scrubbing of low-grade iron ore fines have been reported in this article. The response methodology with a central composite design was used to evaluate the hydrodynamics of the PBMS hutch section. The results indicate that the hydrostatic head increases with an increase in solid percentage in the hutch section and decreases with an increase in pulsation frequency. The pressure and load model prediction matched the experimental data well. The model predicts that at 54 rpm pulsation frequency and a 25% solid percentage, the pressure will be 0.0285 bar and the motor load 25.54 W. The R2 of the pressure and load model are 0.9536 and 0.9936, respectively. Scrubbing performance on −10 mm iron ore fines with 54.17% Fe, 8.15% SiO2 and 12.75% Al2O3 at 10, 15, and 20 l/min water rate has been validated with characterization of products after scrubbing. The desliming efficiency of the particle in the range of 0.045–0.3 mm is ± 88% at a water rate above 15 l/min. The best cleaning and segregation of fines are reported at a 15 l/min water rate. The Fe value of clean coarse products increases from 54% to 59%. The scrubbing improves the grade of ore, and the alumina and silica content reduction is 19% and 40%, respectively. [ABSTRACT FROM AUTHOR]

Considering the advantages of circulating fluidized bed in industrial-scale processing production. A new biofilm reactor, anaerobic circulating fluidized bed reactor (ACFBr), was initially proposed, and the hydrogen production of the reactor were completed by dark fermentation from synthetic wastewater. In this study, Escherichia coli and Polyamide 6-carrier were used to evaluate the effects of reactor fluidization velocity and particle circulation rate (Gs) on hydrogen production. The experiments were conducted across a range of fluidization velocities:1.1U t ,1.2U t ,1.3U t and 1.4U t (U t :terminal velocity), combined with the Gs of 0.320, 0.415 and 0.510 kg/m2·s) in a crossover experimental design. The system operated with synthetic wastewater of 2 g-glucose/L and hydraulic retention time of 4 h. The results indicated that: When the fluidization velocity reached 1.2U t , the ACFBr showed better performance, and the hydrogen production effect improved with the increase of Gs. Peak hydrogen yield and hydrogen production rate of the system was obtained under operating conditions of 1.2U t and 0.510 kg/m2·s, reaching 0.447 mol-H 2 /mol-glucose and 26.23 ml-H 2 /L·h, respectively. Maximum COD removal efficiency attained 35.75% under operating conditions of 1.2U t and 0.415 kg/m2·s. The predominant metabolites included acetic acid (341.65–392.08 mg/L), propionic acid (60.41–74.28 mg/L), butyric acid (98.26–121.12 mg/L) and ethanol (83.73–101.25 mg/L). Obtained results proved the feasibility and stability of ACFBr for long-term production of biohydrogen and chemical substances via dark fermentation. • Circulating fluidized bed is first applied in dark fermentation to produce hydrogen. • Effects of fluidization velocity and particle circulation rate on system are studied. • Feasibility and stability of anaerobic circulating fluidized bed system are verified. • Anaerobic circulating fluidized bed has great potential for energy conversion. [ABSTRACT FROM AUTHOR]

The large deformation and fluidization process of a solid–fluid mixture includes significant changes to the temporal scale of the phenomena and the shape and properties of the mixed material. This paper presents an extended B‐spline (EBS)‐based implicit material point method (EBS‐MPM) for the coupled hydromechanical analysis of saturated porous media to enhance the overall versatility of MPM in addressing such diverse phenomena. The proposed method accurately represents phenomena such as high‐speed motion in both the quasi‐static and dynamic states by employing a full formulation of coupled hydromechanical modeling. The weak imposition of boundary conditions based on Nitsche's method allows representing the boundary conditions independent of the relative position of the particles and computational grid. In addition, it enables dynamic changes in the boundary domain based on the deformation. The robustness of this boundary representation is reinforced using EBS basis functions, which prevent the degradation of the condition number of the system matrices regardless of the position of the boundary domain with respect to the computational grid. Furthermore, a stabilization method based on a variational multiscale method (VMS) approach is employed to provide the flexibility in choosing arbitrary basis functions for spatial discretization, facilitating the effective construction of EBS. Numerical examples including comparisons between a full formulation and a simplified formulation are presented to demonstrate the performance of the developed method under various boundary conditions and loading states across different time scales. [ABSTRACT FROM AUTHOR]

Natural gas hydrate solid fluidization mining technology is a new hydrate mining technology, but due to the lack of combined nozzle design theory and basis, the crushing efficiency of mining tools is low. To solve this problem, the characteristics of the combined jet flow fields of nozzles with diameters from 1 mm to 4 mm and combination angles from 10° to 20° were studied in this paper by means of experiments and simulations. The results show that the maximum velocity at the merging point increases negatively linearly with increases in the combination angle and positively linearly with increase in the nozzle diameter. The position of the merging point changes little with the nozzle diameter and increases exponentially with increases in the combination angle. The effective crushing lengths of nozzles with different diameters all turn (increase first and then decrease) when the combination angle is 12.5°. The optimal combination angle for nozzles with diameter less than 4.5 mm is 12.5°, and 15° is for nozzles with diameter more than 4.5 mm. This study reveals the flow field variation mechanism for the combined nozzle and provides guidance for the design of the combined nozzles of gas hydrate combined nozzles. [ABSTRACT FROM AUTHOR]

When supercooled, liquid's viscosity increases dramatically as the glass transition temperature is approached. Although the physical origin of this behavior is still not understood, it is now well established that the addition of a few activated particles is able to reverse that increase in viscosity. Here we further raise the question of a limit in that fluidization process and of the differences between the fluidized liquid and its viscous counterpart. The results show that a few percent active molecules are enough to trigger a phase transition leading to diffusion coefficients typical of liquids while the medium retains cooperative properties of the viscous phase. The similarity between cooperative properties of the active and non-active molecules suggests that the mobility of active molecules is transmitted to inactive ones via the medium's cooperative mechanisms, a result in agreement with facilitation theories. This result is then confirmed by the compared behavior of the distinct Van Hove correlation functions of most mobile active and non-active molecules. Interestingly enough, in our simulations, the cooperative mechanisms are not induced or related to a decrease in the excitation concentration. [ABSTRACT FROM AUTHOR]

Taking the fluidized pre-reduction process of iron ore powder bubbling fluidized bed as the background, for the problem of non-uniform structure in the bed of gas-solid fluidization process, the non-uniform fluidization characteristics of bicomponent particles are investigated in a cold two-dimensional bubbling fluidized bed by using a combination of physical experiments and mathematical simulations. Fluidization experiments were carried out under typical working conditions by using glass beads to study the effects of apparent gas velocity, mass ratio, and other factors on the non-uniform structure in the bed. Through the experimental observation of the bubble behavior, the effect of the cyclic change in bubble formation, rise and growth to rupture on the bed uniformity were analyzed. The experiments showed that the fluidized bed of two-component particles would be stratified, and the non-uniformity was strong in the upper part and weak in the lower part, and the apparent gas velocity and particle size were the main influencing factors. Based on the Euler-Lagrange reference frame modeling, the fluidization process of the two-dimensional bubble bed was simulated by the CFD-DEM method. The simulations of typical experimental conditions were carried out to further analyze the velocity distribution and the volume ratio of each phase in the bed from the gas-solid interaction level, revealing that the velocity distribution in the upper part of the bed is not uniform, and the gas flow is strongly perturbed, with intense bubble aggregation. The results reveal the reasons for the non-uniform phenomenon of gas-solid fluidization, which can provide a theoretical basis for the regulation of the non-uniform structure of the fluidization process. [ABSTRACT FROM AUTHOR]

In this paper, the characteristics of the axial and the radial density distribution and the density stability of a gas-solid fluidized bed formed by microfine magnetite powder were studied under different fluidizing gas velocities and magnetic field intensities, and the separation experiments of −6 mm fine coal were carried out. The experimental results show that the axial density of the bed with magnetic field applied is lower than that without magnetic field applied under different gas velocities. The density fluctuation of the gas-solid fluidized bed with magnetic field is smaller than that of the ordinary gas-solid fluidized bed, and the stability of the bed density decreases with the increase of the fluidization number. The experimental results of separation of −6 mm fine coal show that the Ep value increases with the increase of fluidization number. Under the same fluidization number, the Ep value of −6 + 3 mm coal is smaller than that of −3 + 0.5 mm coal. When the fluidization number is 1.1, the Ep value of −6 + 3 mm coal is 0.0375 g/cm3, and the Ep value of −3 + 0.5 mm coal is 0.0475 g/cm3. This shows that the magnetically fluidized bed of microfine particles has a good separation effect for −6 mm coal. [ABSTRACT FROM AUTHOR]

Extreme rainfall events, within the context of climate change, pose a heightened risk of geohazards to mountainous regions. On 22 June 2022, a rainstorm-induced landslide-mudflow occurred in a terraced field in Longsheng County, Guangxi Zhuang Autonomous Region, China. The disaster began as a rotational slide, and mobilized into a mudflow with high mobility and long runout, causing significant damage to the local community. This event served as a wake-up call not only for the safety of mountain settlements, but also for the protection of terraced fields as Globally Important Agricultural Heritage Systems. To elucidate the trigger and mudflow mobilization of the event, field investigation, hydrological and agricultural analyses, and laboratory tests were conducted. It was found that the persistent and record-breaking rainfall directly triggered the disaster by increasing pore water pressure. The transition from paddy terraces to dry terraces was deduced to have contributed to a lack of maintenance in the terrace drainage system, thereby heightening the likelihood of landslides. The mudflow mobilization was attributed to excess pore water pressure generated by soil contraction and an undrained condition maintained by low permeability soil. Soil experiencing sliding may be more susceptible to shear contraction, consequently resulting in long-runout motion. Under conditions of increasing extreme rainfall, greater attention needs to be paid to geo-disaster prevention and terraced field protection in mountainous regions. [ABSTRACT FROM AUTHOR]

The direct reduction process is an important development direction of low-carbon ironmaking and efficient comprehensive utilization of poly-metallic iron ore, such as titanomagnetite. However, the defluidization of reduced iron particles with a high metallization degree at a high temperature will seriously affect the operation of fluidized bed reduction. Coupling the pre-oxidation enhancing reduction and the particle surface modification of titanomagnetite, the behavior and mechanism of pre-oxidation improvement on fluidization in the fluidized bed reduction of titanomagnetite are systematically studied in this paper. Pre-oxidation treatment of titanomagnetite can significantly lower the critical stable reduction fluidization gas velocity to 0.17 m/s, which is reduced by 56% compared to that of titanomagnetite reduction without pre-oxidation, while achieving a metallization degree of >90%, Corresponding to the different reduction fluidization behaviors, three pre-oxidation operation regions have been divided, taking oxidation degrees of 26% and 86% as the boundaries. Focusing on the particle surface morphology evolution in the pre-oxidation–reduction process, the relationship between the surface morphology of pre-oxidized ore and the reduced iron with fluidization properties is built. The improving method of pre-oxidation on the reduction fluidization provides a novel approach to prevent defluidization by particle surface modification, especially for the fluidized bed reduction of poly-metallic iron ore. [ABSTRACT FROM AUTHOR]

Examining the properties of bubble parameters within a three-phase system is crucial for enhancing and optimizing fluidized bed flotation column cells. This research focuses on the variations in primary bubble parameters within such columns, with the goal of offering a theoretical foundation for the advancement of fluidized bed flotation technology. The experiment utilized steel balls, tap water, and compressed air as the solid, liquid, and gas phases, respectively. Bubble parameters were measured directly using an electrical conductivity probe. Key factors influencing bubble size in the fluidized bed flotation column included the initial static bed height(H*), superficial liquid velocity (UL), superficial gas velocity (UG), and reagent concentration. The study assessed how bubble size and gas holdup are distributed in the fluidization zone and identified how bubble parameters vary with different operating conditions. Findings show that incorporating steel ball particles in the fluidization zone significantly improves bubble stability, reduces the variability of bubble size, and ensures a more consistent bubble distribution. Proper selection of filling particles and accurate bed height adjustment can notably enhance the local gas holdup within the bed. Additionally, it has been found that local gas holdup increases rapidly when the liquid-to-gas velocity ratio drops below a certain threshold. [ABSTRACT FROM AUTHOR]

Vibrofluidization in monodisperse granular materials is a hierarchical phenomenon involving different spatial and temporal behaviors, known to produce macroscopic structures with well-defined properties and high reproducibility. However, as witnessed by the paucity of relevant results in the literature, investigating the collective organization of particles across such different length and time scales becomes particularly challenging when multi-component systems are considered, i.e. if the considered vibrated material is not monodisperse. In this work, this problem is addressed through numerical simulation of the governing equations accounting for (dissipative) inelastic and frictional effects in the framework of a DEM (Discrete Element Method) method. Binary and ternary particle distributions are considered and, in order to filter out possible density-driven particle segregation or mixing mechanisms, particles are assumed to be iso-dense. The problem is initially analyzed through the coarse-grained lens of patterning behavior (supported by a Voronoi analysis for many representative cases) and then from a micromechanical level in which statistical data based on particle collisions and related dissipative effects are used to gain additional insights into the observed macroscopic trends. It is found that, starting from the initial traditional monodisperse case, the addition of particles with smaller sizes (while keeping the overall mass and depth of the considered layer almost unchanged) generally leads to a corrugation in the otherwise perfect symmetry of the original patterns, which is similar to that already seen in companion situations related to viscoelastic fluids. Moreover, while in the case of an initially hexagonal pattern, this topology is generally retained, in other situations, the initial perfection is taken over by less regular waveforms. Specific circumstances also exist where the initial square symmetry is lost in favor of a triangular symmetry. In all cases, segregation effects simply manifest as a preferential concentration of particles with larger size in an intermediate layer, which apparently behaves as a cohesive entity during each vibration cycle. [ABSTRACT FROM AUTHOR]

This study investigates the impact of kaolin and boehmite alumina binders on the synthesis, catalytic properties, and attrition resistance of a La0.7Sr0.3FeO3 (LSF) perovskite catalyst designed for the chemical looping partial oxidation (CLPO) of methane to produce synthesis gas sustainably. The as-synthesized and used catalysts with varying kaolin and boehmite alumina contents (KB(x,y)/LSF) were scrutinized by a variety of characterization methods, including XRD, FE-SEM/EDS, BET, TPD-NH3, and TPD-O2 techniques. The catalytic activity of the synthesized samples was tested at 800 to 900 °C in a fixed-bed reactor producing syngas through the CLPO process over the consecutive redox cycles. Additionally, the attrition resistance of the fresh and used catalyst samples was examined in a jet cup apparatus to assess their durability against the stresses induced by thermal shocks or changes in the crystal lattice caused by chemical reactions. The characterization results showed the pure perovskite crystal structure of KB(x,y)/LSF catalysts demonstrating adequate oxygen adsorption capacity, effective coke mitigation capability, robust thermal stability, and resilience to agglomeration during repetitive redox cycles. Among the tested catalysts, KB(25,15)/LSF was identified as the superior sample, as it could consistently produce syngas with a suitable H2:CO molar ratio varying from 2 to 3 within ten redox cycles at 900 °C, with CH4 conversion and CO selectivity values up to 64% and 87%, respectively. The synthesized catalysts demonstrated a logarithmic attrition pattern in the jet cup tests at room temperature, featuring high attrition resistance after the erosion of particle shape irregularities or weakly bound particles. Moreover, the KB(25,15)/LSF catalyst used at 900 °C showed great resistance in the attrition test, warranting its endurance in the face of extraordinarily harsh conditions in fluidized bed reactors employed for the CLPO process. [ABSTRACT FROM AUTHOR]

Achieving high fluidization quality and bed stability is a paramount challenge in pulsed fluidized beds. 2D hydrodynamics models were studied using the Eulerian-Eulerian method with KTGF. This study investigates the impact of rectangular pulsation superimposed on steady airflow, while maintaining a constant temporal average gas velocity, on fluidization quality. Numerical results indicated that superimposing pulsations on steady airflow and increasing the steady airflow velocity to three times the minimum fluidization velocity resulted in a decrease in the bed expansion ratio. This decrease was most notable particularly at a pulsation frequency of 0.05Hz, with a reducing of approximately by about 21%. By decreasing the velocity ratio from 9.52 to 6.52, the pressure drop increased by 27% and 4.5% at 0.05 Hz and 10 Hz, respectively. Additionally, the fluidization index increased by 32% and 2% under these conditions. The optimal range of pulsed airflow velocity fell between 2.76 and 1.17 times the steady airflow velocity and was most effective at 0.05 – 0.1 Hz. [ABSTRACT FROM AUTHOR]

The co-cofiring of biomass and coal has become an important means of reducing carbon dioxide emission. The mixing and separation behaviors of particles affect the performance of the reactor. Due to the significant difference of particle size between biomass and coal, traditional gas-solid two-phase flow methods have limitations in the prediction of gas-solid flow with a clear particle size difference. Based on a fluidized bed reactor, fluidization behaviors of biomass and coal particles with large difference in particle size are studied by simulated research and the influence of pulsating airflow on particle motion behaviors in the bed is analyzed. The results show that in contrast to the rectangular wave pulsation form, the pulsating airflow in the form of the sine wave makes the particle distribution in the bed more uniform. The mixing of biomass and coal particles in the bed can be effectively promoted by increasing the frequency of pulsating airflow. The relationship between the amplitude of pulsating airflow and particle mixing is not monotonic. As the amplitude increases, the mixing index firstly decreases and then increases. [ABSTRACT FROM AUTHOR]

In this paper, the hydrogen direct reduction of iron ore fines is numerically studied by using the Dense Discrete Phase Model (DDPM) in the fluidized bed. The fluidization behavior at different inlet gas velocities (Ug) as well as the influence of Ug and hydrogen concentration on reduction degree (RD) are comprehensively investigated. The result indicates the increase of time-averaged solids volume fraction for the same cross-sectional heights with increasing Ug when the bed height (H) exceeds 0.06 m. Furthermore, the reduction rate of mineral powder increases with higher Ug value, and the RD reaches almost 100 pct after 4000 seconds of reduction time with Ug ranging from 0.35 to 0.65 m/s. The reduction rate increases noticeably with the increase of hydrogen concentration in the range of 10 to 100 pct, and Fe2O3 can be completely converted to Fe under condition of 65 pct H2 concentration after 4000 seconds. Moreover, higher H2 concentration leads to faster rate of Fe2O3 consumption and Fe production. The mass fraction peak values of Fe3O4 and FeO are in the range of 0.29 to 0.34 and 0.21 to 0.24 under different H2 concentrations, respectively. [ABSTRACT FROM AUTHOR]

Coke and ore sizes are important to the efficiency and stability of blast furnace (BF) operation in practice. However, their selection is usually determined by experience and there is no systematic study on the effects of ore and coke sizes on BF operation. This paper presents a numerical study on the multiphase flow and thermochemical behaviors inside the BF with different ore and coke sizes. This is done based on a recently developed 3D multifluid BF process model. The validation of this model is first confirmed by various applications. It is then used to study the effect of particle size on BF performance. The results show that as coke and ore sizes decrease, the thermochemical utilization efficiency is improved, which is reflected in low coke rate, low top gas temperature, high top gas utilization factor, and high productivity. However, there may be a minimum particle size for a given BF. Three indicators, namely gas pressure drop, liquid flooding in the dripping zone, and particle fluidization at the burden surface are used to determine this minimum particle size. Under the present conditions considered, the suggested minimum coke size should not be less than 20 mm and the suggested ore size should not be less than 12.5 mm. In addition, the effect of ore size on BF global performance indicators, e.g., fuel rate and productivity, is more significant than coke size. In terms of inner states, as ore size increases, the solid temperature drops in the BF shaft and the CZ position drops accordingly. On the contrary, as coke size increases, the solid temperature increases significantly in the BF shaft and the CZ position increases accordingly. Consistently, the increase of ore and coke sizes both increases the CZ thickness. Furthermore, the effect of locally charging large ore and coke particles is also studied. The results show that under the preset simulation conditions, locally charging large ore particles significantly reduces the gas pressure drop, but increases the fuel rate; however, locally charging large coke particles has limited influence on BF global performance indicators. The results provide some valuable guidance for coke and ore size selection in BF practice. [ABSTRACT FROM AUTHOR]

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The two‐fluid model–kinetic theory of granular flow (TFM–KTGF) model and the sub‐grid‐scale (SGS) model are used to conduct a three‐dimensional numerical simulation study on the hydrodynamic characteristics of a two‐stage fluidized bed with an integrated overflow pipe. Using various drag models, the gas–solid flows, bed expansions, pressure drop distributions, and equilibrium conditions in the two‐stage bed are compared, and the conditions for the formation of a stable overflow in the two‐stage bed are thoroughly investigated. In addition, during the simulation of the secondary distribution in the bed, the porous media model simulates the momentum loss caused by the redistribution plate to avoid the direct simulation of the redistribution plate, which requires extensive grid division work and calculation costs. This work can provide technical direction for the industrialization of one‐step coal to multistage fluidized bed natural gas technology. [ABSTRACT FROM AUTHOR]

Copyright of Petroleum Refinery Engineering is the property of Petroleum Refinery Engineering Editorial Office and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)