Particuology最新文献

Turbulent fluidized bed proves effective in industrial processes due to superior heat and mass transfer and chemical reaction performance. However, understanding the transition to turbulent fluidization remains limited, especially at temperatures exceeding 1000 °C, making it challenging to develop high-temperature fluidized bed applications. This paper presents an experimental investigation on the turbulent fluidization onset velocity (U_c), measured in a 30 mm diameter bed using corundum particles with average diameters from 0.68 mm to 1.58 mm in temperatures from ambient to 1600 °C. Experimental results reveal that U_c increases with temperature up to 600 °C, stabilizes within the 600–1200 °C range, and then decreases above 1200 °C, demonstrating the varying relative significance of hydrodynamic and interparticle forces at different temperatures. To help design and operate high-temperature applications of turbulent fluidization, we developed U_c correlations based on experimental data from both literature sources and this study, covering temperatures of up to 1600 °C and particles of Groups A to D.

The degradation of filtration performance in electret filter media during usage poses a significant challenge. Pre-charging of aerosols has been identified as an effective method to mitigate this issue. However, the effects of particle charging characteristics on the loading characteristics of electret filters still need a comprehensive understanding. In this study, a needle-cylinder corona charger was employed to pre-charge aerosols, and the particle charge state was determined by multiphysics simulation. The effects of particle charge polarity and charge quantity on the loading performance of the electret filter were quantitatively investigated. The results showed that the particle charge polarity had a negligible impact on the loading performance under the condition of the equivalent particle charge quantity. In addition, the charged particles effectively improved the efficiency degradation during the loading process of electret media, with higher charge quantities resulting in more pronounced improvements. The electrostatic attenuation factor showed a negative exponential correlation with the particle charge quantity. This was attributed to the uneven particle deposition on fiber surface due to the attraction of charged particles by the opposite charges on the electret fibers, which alleviated the effect of electrostatic shielding.

Hierarchical porous magnesium silicate hydrate (MSH) microspheres composed of sheets are successfully developed under facile conditions using a hard template. The role of hexadecyltrimethylammonium bromide (CTAB) on the formation and adsorption behavior was also observed for the methyl orange and methylene blue. The formed MSH possesses a surface area of 453.24 m²/g, an average pore size of 6.38 nm, and a pore volume of 0.75 cm³/g without CTAB. Based on the role of CTAB and the change in the ratio of Mg/Si, the MSH retained its sphere-like structure with a variation in pore parameters. The formed MSH was used as an adsorbent to remove methylene blue and methyl orange. The pseudo-second-order kinetic and Langmuir Isotherm models are well-fitted, with a 256.4 mg/g removal capacity and 84.2 mg/g for methylene blue and methyl orange, respectively. The modified MSH with CTAB played a positive role for the methyl orange and a negative role for the methylene blue regarding removal performance.

Understanding the breakage characteristics of rice grains is an important means to reduce rice breakage rate. However, the dynamic breakage mechanism of rice grain is unclear due to the lack of a reasonable breakage model. In this study, the uniaxial compression test and drop weight test of single rice were carried out, the breakage model of rice grain was constructed, the reliability of rice model was verified by the experiment and simulation results. The results showed that the fracture energy distribution of rice can be obtained by uniaxial compression test, the specific fracture energy of rice accords with a lognormal distribution, and the median specific fracture energy of rice is 479.75 J/kg. The damage accumulation coefficient and fragment size distribution of rice can be acquired by drop test, the result of damage accumulation coefficient of rice was 4.3. Rice grain breakage mainly occurs in the milling section of the vertical circulation rice mill.

Iron ore pellets are the main feedstock in ironmaking processes. While extensive research has addressed numerical modeling of the iron ore pellet induration process, little effort has been made to describe the intricate thermochemical processes occurring within the reactor starting from the pellet and particularly at the intra-particle scale. In this regard, discrete-continuous methods like CFD-DEM can generate more realistic, irregular particle assemblies, which leads to significantly more accurate predictions of voidage variation, wall effects, temperature distribution, and associated mass transfer phenomena. This study presents a numerical model based on computational fluid dynamics (CFD) coupled with the discrete element method (DEM) to simulate the thermal induration process of iron ore pellets. The presented model solving heat, mass, and momentum conservation equations for both continuous and discrete phases, provides detailed information on the thermochemical aspects of the process. Pilot-scale induration experiment was conducted to validate model predictions in terms of thermal history and final conversion fraction. It was found that inlet charge specifications, such as particle and pellet size, significantly impact the productivity of pelletizing plants, highlighting the potential of the presented model to optimize the process and improve plant productivity.

Compared to transient simulation, steady-state simulation of circulating fluidized bed risers is more efficient, but is also harder to perform due to the complex scale-dependency of dense gas-solid flows. In this work, steady-state computational fluid dynamics (CFD) simulation of a riser is performed using the steady energy-minimization multi-scale (EMMS) drag. It is found that the steady state corresponds to an extremely large scale of length and time, thus the grid size required in steady-state simulation is larger than that in transient one. The time-averaged two-fluid model (TFM) coupled with the steady-state EMMS/1M drag model enables a good prediction of the S-shaped, axial solids distribution and the choking transition, whereas the two-phase turbulence and solids stress models are important in predicting the radially core-annular distribution of solids. So far as we know, this is the first time that one can predict the choking transition in a steady-state CFD simulation. Further improvement may need an EMMS modeling of the time-averaged solid stresses.

Voidage (porosity or void fraction) in packed particles (or pebbles) is of fundamental importance in calculating the pressure drop, obtaining the drag, predicting the bed permeability, estimating the neutron streaming, etc. For the case when particles are deformed, a method of voidage correction during the packing state is proposed using a Discrete Element Method (DEM) simulation of 3D pebble flow inside a bed of cycloidal base. A function to evaluate the remaining volume of a pebble intercepted by horizontal and vertical planes is proposed for voidage calculation. After that, the process of solving voidage distribution is provided in detail. Using this method, the voidage inside the cycloidal-base pebble bed is obtained to refer to reported similar data for validation. This method can be potentially used for dynamical voidage calculation in CFD-DEM simulation which can get suitable voidage distribution after the correction.

Granular bed filter (GBF) has become one of the current research hot topics due to its excellent performance in removing fine particles. In this paper, a three-dimensional fixed bed GBF filtration model was established and its accuracy was verified. Then, the GBF filtration performance at high temperature were studied. The results demonstrate that elevating the temperature diminishes the filtration efficiency, albeit to a limited extent. The increasing of inlet gas velocity can significantly improve pressure drop for GBF and the filtration efficiency for fine particles of sizes larger than 5 μm. As the diameter of stacked granular particle diameter grows, the filtration efficiency and pressure drop drops. The density of fine particles almost does not affect the filtration efficiency for fine particles of 1∼7 μm, but a higher density leads to a higher filtration efficiency for fine particles of sizes bigger than 9 μm. Additionally, as the fine particles size increases, the change of the filtration efficiency roughly goes through three stages: Stage 1: the filtration efficiency is basically unchanged; Stage 2: the filtration efficiency increases rapidly; Stage 3: the filtration efficiency increases steadily, but the rate of increase slows down. With the increase of the fine particles Stokes number, the filtration efficiency of GBF will pass through two phases of stabilization and rapid increase.

Due to the typical intercalation-deintercalation mechanism, TiO₂ holds great promise as a sustainable anode for next-generation lithium-ion batteries (LIBs). However, commercial TiO₂ (C–TiO₂) is granular and shows slow ionic conductivity, which greatly hinders its development due to sluggish kinetics, leading to low reversible capacity and inferior rate capability. In this study, a two-dimensional layered TiO₂ (L-TiO₂) anode is prepared via a one-step calcination process, which can effectively shorten the lithium ions diffusion path and improve its lithium ions conductivity. We elucidated the enhanced electrochemical performance of L-TiO₂ as an anode in LIBs through pseudocapacitive acceleration of lithium ions intercalation and deintercalation using various characterization techniques, including different scan rate cyclic voltammetry tests, in situ electrochemical impedance spectroscopy, in situ Raman spectroscopy, and in situ X-ray diffraction. In comparison to C–TiO₂ material, L-TiO₂ material showcases remarkable electrochemical performance, achieving a capacity of 166 mAh/g after 100 cycles at 0.1 C. Additionally, the lithium-ion diffusion coefficient calculated for the L-TiO₂ is two orders of magnitude greater, underscoring its potential as a negative electrode material for LIBs.

Granulation is an effective method for improving the flowability of drugs, particularly when they are in needle form. Carbamazepine-hesperetin (CBZ-HPE) cocrystal is a needle-like crystal with low solubility and poor flowability, which limits its application. To address this issue, this study aimed to obtain CBZ-HPE microspheres using the quasi-emulsion solvent diffusion (QESD) technique. The preparation process was monitored using polarized light microscopy, and the formation mechanism was elucidated using the radial distribution function (RDF). The microspheres were extensively characterized using PXRD, DSC, TGA, and SEM. Furthermore, the effects of surfactants, contents, and rotational speeds on the morphology and particle size distribution of microspheres were analyzed to determine the optimal experimental conditions. Based on these findings, naringenin and quercetin, the active ingredients of traditional Chinese medicine, were chosen to successfully prepare CBZ-HPE multicomponent microspheres. This research provides a foundation for increasing drug powder properties and drug conjugation through the preparation of microspheres.