Particuology最新文献

This study investigates the adverse effects of fine clay minerals on low-rank coal (LRC) flotation. Zeta potential analysis, X-ray photoelectron spectroscopy, flotation experiments, and the particle-bubble attachment index (PBAI) were employed to assess these effects. Results indicate that quartz and chlorite particles are more prevalent in the flotation concentrate than kaolinite and montmorillonite, likely due to their preferential adsorption of flotation collectors, which inhibits the hydrophobicity of the LRC surface. Montmorillonite, however, exhibits greater adhesion to LRC surfaces due to its positive charge. Extended DLVO theoretical analysis reveals that polar surface interaction energy is a primary driving force in coal-mineral interactions and is crucial in overcoming the energy barrier posed by electrostatic double-layer forces. The impact of clay minerals on LRC flotation is highly dependent on clay type.

In this study, the discrete element method was combined with physical experiments to examine the capsule filling practice in the hot-isostatic-pressing process and to study the densification of spherical particles in a three-way pipe capsule for offshore engineering under mechanical vibration conditions. The effects of vibration parameters—such as the vibration time, vibration frequency, vibration amplitude, rolling friction coefficient, sliding friction coefficient, recovery coefficient, and other particle properties—on the filling density were analyzed. The results showed that the packing density in the three-way capsule could be increased considerably using a vibration frequency of 40 Hz and a vibration amplitude of 2.5 mm. The contact form between particles in the vibration-assisted mold-filling process was determined and the particle velocity field, compression force, and coordination number under a single harmonic vibration period were analyzed. The real-time motion of the particles at the micro level was visualized, and the mechanism of the mechanical vibration effect on mold filling and densification was explored. The distribution and evolution of the coordination number indicated that the distribution of the filling density was uneven, and that the change in the coordination number of particles at the bottom exhibited no major response to the vibration.

Wet-milling in liquid-solid system can achieve ultra-fine mechanical dissociation of solid wastes with low energy consumption, thereby efficiently improving the potential pozzolanic reactivity. However, the wet-milling kinetics of ultrafine dissociation in liquid-solid system has not been fully investigated. This paper systematically investigates the wet-milling kinetics of fly ash (FA). Results showed that before wet-milling of FA for 360 min, no agglomeration effect was observed. The particle dissociation of FA during wet-milling can be divided into three stages: rapid dissociation, slow dissociation and stabilization. The evolution process of particle size distribution during wet-milling is consistent with the Rosin-Rammler-Bennet distribution. Both the particle uniformity coefficient and fractal dimension showed highly positive linear correlation with the strength activity index of wet-milled FA. The grey correlation analysis showed that FA particles between 1.1 and 3.1 μm had the greatest impact on both the early and late strength activity index. Simultaneously, D₁₀ of wet-milled FA has the largest impact on strength activity index at each age, while D₁₀₀ has the least impact. Therefore, D₁₀ and proportion of particles in 1.1–3.1 μm can be an important basis for judging the reactivity of wet-milled FA as ultrafine supplementary cementitious materials.

The Jahn-Teller effect and the dissolution of Mn are significant factors contributing to the capacity degradation of spinel LiMn₂O₄ cathode materials during charging and discharging. In this study, Mo⁶⁺-doped polycrystalline octahedral Li_1.05Mn_2-xMo_xO₄ (x = 0, 0.005, 0.01, 0.015) cathode materials were prepared by simple solid-phase sintering, and their crystal structures, microscopic morphologies, and elemental compositions were characterized and analyzed. The results showed that the doping of Mo⁶⁺ promoted the growth of (111) crystalline facets and increased the ratio of Mn³⁺/Mn⁴⁺. The electrochemical performance of the materials was also tested, revealing that the doping of Mo⁶⁺ significantly improved the initial charge/discharge specific capacity and cycling stability. The modified sample (LMO-0.01Mo) retained a reversible capacity of 114.83 mA h/g with a capacity retention of 97.29% after 300 cycles. Additionally, the doping of Mo⁶⁺ formed a thinner, smoother SEI film and effectively inhibited the dissolution of Mn. Using density-functional theory (DFT) calculations to analyze the doping mechanism, it was found that doping shortens the Mn-O bond length inside the lattice and increases the Li-O bond length. This implies that the Li⁺ diffusion channel is widened, thereby increasing the Li⁺ diffusion rate. Additionally, the modification reduces the energy band gap, resulting in higher electronic conductivity.

This study aims to conduct a sensitivity analysis of closure models and modeling parameters for the Dense Discrete Phase Modeling (DDPM) approach in order to investigate the hydrodynamics of a 3D lab-scale Tapered Fluidized Bed (TFB). The closure models and model parameters under investigation include the gas-solid drag force, viscous models, particle-particle interaction models, restitution coefficient, specularity coefficient, and rebound coefficient. The primary objective of this sensitivity analysis is to optimize the numerical model's performance. The numerical results, in terms of axial and lateral Solid Volume Fraction (SVF) profiles obtained from the sensitivity analysis, indicate that the drag force and restitution coefficient significantly influence the hydrodynamics of the TFB. Properly selecting these parameters could result in the improved performance of the numerical model. However, the sensitivity of turbulence models, particle-particle interaction models, specularity coefficient, and rebound coefficient has a lesser impact on the hydrodynamics results. This work concludes with the recommendation of a set of closure models and modeling parameters that offer the most accurate prediction of the hydrodynamics of the TFB.

The influence of ammonia and Brown gas injection on the iron ore sintering characteristics was explored through sintering pot experiments based on biochar substitution to increase biochar substitution proportion and reduce fossil energy consumption. By dividing the high-temperature stage of the sintering bed, the heating rate and cooling rate were calculated, and the reasons for poor sintering quality under a high biochar substitution ratio were explored. The results showed that under the 40% biochar substitution ratio, the cooling rate of the sintering bed significantly increased, the high-temperature duration time was short, and the sintering quality deteriorated severely. Additional injection of 0.5–1% vol ammonia or 1–2% vol Brown gas can reduce the cooling rate, prolong the high-temperature duration, and optimize the sintering quality. Based on 1% vol ammonia or 2% vol Brown gas injection, reducing the proportion of biochar with equal calorific value further increases the sintering comprehensive index, which means that using 1% vol ammonia or 2% vol Brown gas injection to assist sintering can reduce the proportion of coke usage to 60%, while the proportion of biochar substitution is 33.76% and 32.47%, respectively. The research results provide an effective solution for low-carbon sintering.

A double-tube cooler with liquid-solid circulating fluidization operation and corresponding parameter measuring system are developed to avoid fouling of inner walls of heat exchange tubes in a cryogenic temperature external cooler of ammonium chloride solution in soda ash production. Wall-scaling prevention performance of the cooling process is experimentally evaluated using convection and overall coefficients, enhancement factor, wall temperature and fouling resistance. Effects of different volume fractions of added particles, particle size, superficial liquid velocity, and cooling medium temperature on heat transfer are examined. Under present conditions, convection coefficient of liquid-solid flow inside the tube of external cooler is higher than that of the liquid phase flow, increased by 0.7–2.8 times, enhancing cooling performance obviously. Convection coefficient initially increases and then decreases as the volume fraction of added particles increases, reaching its maximum value at a volume fraction of 2.0%. The wall-scaling prevention effect of glass beads mainly depends on the volume fraction of added particles; optimal anti-fouling effects are achieved when adding particles at a volume fraction of 2.0%, regardless of changes in superficial liquid velocity or cooling medium temperature. This study lays a foundation for industrial applications of this new technique of fluidized bed external coolers.

Coating with viscous formulations has been essential in numerous industries as it can be a means for providing functionalization, additional properties, as well as other benefits. However, there have been scarce studies that have investigated and proposed methodologies in literature. Continuous coating of powders with viscous liquids poses as a promising technology, which has been mentioned in some studies, but has not yet been thoroughly investigated. This paper employs the use of image processing and analysis, in combination with statistical analysis of particles to evaluate the effectiveness of foams and liquids as a means of coating powder beds. Two different sizes of twin screw mixers that are working in continuous operation are employed, and a new continuous foaming device is fabricated and used for the experiments of coating. The effect of materials and process parameters (as for example rotational speed, and flowrate) on the quality of coating are investigated. Image analysis is used to assess the coating quality. The results clearly showcase the potential of using twin screw mixers for coating purposes and not only for mixing. The hypothesis that using large bubble foams to improve the coating of viscous liquids on particles is proven correct, as they provide higher quality coatings compared to their equivalent liquids, when used in the twin screw mixer. Surprisingly, using a larger scale twin screw mixer, does not show a substantial effect on the mixing, regarding quality, however there is still a requirement for mix optimization for achieving scale-up of this process. These results provide a new pathway for coating powders with viscous formulations in industrial applications, requiring less energy and effort in this process, and can pave the way towards introducing more sustainable industrial methodologies for coating.

The design and operation of radial flow adsorber are crucial in large-scale industrial oxygen production, which necessitate accurate prediction of gas-solid transfer behavior. In this work, a developed Computational Fluid Dynamics-Discrete Element Method (CFD-DEM) model combined with the adsorption model is proposed. The developed CFD-DEM model is validated by comparing simulated results with experimental data and empirical correlation. Subsequently, the effect of particle packing structure and particle shapes on the dynamic adsorption process are analyzed in detail. The results reveal the mechanism of particle packing structure affecting axial velocity distribution, showing that uneven distribution of resistance on the outer flow channel side leads to uneven axial velocity distribution in the bed. Compared to cylindrical adsorbents, the use of spherical adsorbents results in a more uniform axial velocity distribution, consequently reducing bed pressure drop. The study holds significant potential for optimizing gas distribution and improving separation efficiency in future industrial applications.

The supersonic gas-particle two-phase transverse jet is a typical flow process in many applications, such as solid rocket scramjet. This study carried out experimental tests as well as Large Eddy Simulation (LES) to investigate the evolution process of transverse gas-particle two-phase jets in supersonic crossflow, especially focusing on the phenomena called preferential concentration. The simulation is based on the Eulerian-Lagrangian method, which successfully reproduces the characteristic phenomena observed in experiments. The particle cloud forms three different characteristic distribution patterns: tooth-like waves near the jet port, quasi-ordered structures near counter-rotating vortex pairs (CVP), and filamentous clouds in the upper part. The turbulence and small unstable shock play a suppressing role in mixing small-diameter particles, which tend to aggregate in regions of high density and low vorticity. Furthermore, it is found that there exists a specific range of particle sizes, as particles' sizes approach this specific range, the influence of compressibility of the airflow on particle distribution becomes increasingly prominent. Overall, this study shed some light on the understanding of the complex and intricate nature of the supersonic gas-particle two-phase transverse jet.