Particuology最新文献

Accurate assessment and prediction of airflow dynamics and particle deposition in the human respiratory tract are essential for human health, involving inhaled drugs for treating various diseases and toxic particles that can cause illnesses. This intricate process involves complex multiphase flow with distinct respiratory characteristics. Computational fluid dynamics (CFD) acts as a bridge, overcoming the limitations of in vivo and in vitro experiments and providing a means to fully comprehend and reveal the fundamental mechanisms of respiratory flow and particle behavior on a microscopic scale. This paper provides a comprehensive overview and concise summary of recent advancements in the numerical simulation of airflow and particle deposition in the human respiratory tract. Particularly, it summarizes the transition of respiratory tract models from segmented models to emerging physiological characteristic models and whole-lung airway models, and the latest developments on the effects of key factors such as geometric variations, respiratory patterns, and particle physical/chemical properties on respiratory flow and particle deposition. A notable focus of this review is on emerging physiological characteristics models and their associated complex airflow and particle dynamics inside it. The paper concludes with recommendations for future research to further advance the development of this field.

Au hierarchical architectures with special morphology and structures are strongly desired in varied applications. Herein, a simple synthesis method was developed for the one-step preparation of Au micronails (MNs) at the planar liquid-liquid interface under mild conditions. The well-defined Au MNs were grown and constructed at CHCl₃–H₂O interface at room temperature using aniline in CHCl₃ as reducing agent and HAuCl₄ in H₂O as precursor and no surfactant or seed is required. The intriguing Au MNs with rough surface consist of big heads and thin rods, just like iron nails in outline. Furthermore, through simple changing the reagent concentrations, the length and surface roughness of Au MNs can be adjusted conveniently. The effects of a series of factors on the morphology and structure of the products are studied in detail. With p-aminothiophenol as a molecular probe, the as-obtained Au MNs all exhibit dramatically improved surface enhanced Raman scattering sensitivity and high reproducibility, the enhancement factor and limit of detection of Au MNs are 5.4 × 10⁵ and 1.0 × 10⁻¹⁰, respectively.

Rotary kiln is widely used for thermal disposal of solid waste due to its effectiveness and high efficiency in recent years. To further improve the processing efficiency, a newly designed rotary kiln with three-section structure is proposed, and the behaviours of particle motion and heat transfer are investigated. Firstly, a lab-scale rotary kiln is manufactured, and experiments are carried out. Verified by experimental data, a CFD-DEM numerical model is developed to analyze the particle motion and heat transfer characteristics with the effects of inlet flue gas temperature, feeding rate and rotating speed. The results show that the outlet temperature increases linearly with the flue gas temperature, while it is negatively correlated with the feeding rate and rotating speed. In addition, the volumetric heat transfer coefficient in this complex rotary kiln is analyzed, the overall heat transfer coefficient is between 200 and 700 W/(m³ K).

Aluminum is an attractive alternative fuel, but it burns very inefficiently due to the formation of a dense Al₂O₃ layer which prevents O₂ from diffusion to the surface of Al particles. In previous experiments, the combustion of millimeter-sized Al (mAl) particles in the fluidized bed has achieved a substantial increase in the combustion efficiency, but further improvements are still needed. In this study, the effects of reaction atmosphere on the fluidized combustion of mAl particles were investigated. The experiments with different O₂/H₂O/CO₂ concentrations were conducted. The experimental results indicate that the combustion efficiency of mAl particles in fluidized bed increases as the mole fraction of O₂, H₂O or CO₂ increases, and the highest combustion efficiency can reach 38.7%. After the analysis of the oxide film on the surface of aluminum particles, it was found that it is easier to generate the unstable θ-Al₂O₃ under CO₂ atmosphere, and it is easier to generate the unstable γ-Al₂O₃ and θ-Al₂O₃ under H₂O atmosphere. The unstable Al₂O₃ film is more likely to be abraded in the fluidized bed, which leads to the effective improvement of the combustion efficiency.

A roasting-leaching test was carried out for the efficient utilization of clay-type lithium ore in the central region of Yunnan province. The test used the mixed acid of sulfuric acid and phosphoric acid as the leaching agent. Under the conditions of roasting temperature of 600 °C, roasting time of 1 h, liquid-solid ratio of 5:1, volume ratio of H₂SO₄ solution to H₃PO₄ solution of 45:5, leaching time of 2 h and leaching temperature of 80 °C, the leaching rate of lithium was as high as 97.83%. The leaching mechanism was studied by SEM, pore property analysis, XRD and XPS. It was found that the morphology of the ore changed obviously after roasting and leaching, and a certain degree of collapse and fragmentation occurred, which provided favorable spatial conditions for the leaching of lithium. The porosity, total intrusion volume and total pore area also increased after roasting and leaching, thus promoting the leaching of Li⁺. The results showed that chemical reaction taken placed during the roasting and leaching. The phase of the sample changed from chlorite, kaolinite and diaspore (boehmite) mainly to corundum, hematite, periclase and quartz after roasting. However, after leaching, no new phase was produced in the ore sample, and no S and P elements were found on the surface of the ore sample, indicating that the leaching mechanism of lithium might be the ion exchange between H⁺ and Li⁺.

Limestone or quicklime is a necessary flux in the iron ore sintering process. Its production and application process will cause CO₂ emissions and various environmental pollution, but this has not attracted enough attention. Carbide slag (CS) is a calcium-rich solid waste produced in acetylene production, the harmless disposal of which is still incomplete, resulting in soil and groundwater pollution. This study investigated the granulation characteristics and sintering performance of the sintering mixture with different proportions of CS. The results show that replacing limestone with an appropriate proportion of CS is promising and beneficial to the formation of high-quality bonding phase. When CS accounts for 75% of the total mass of CS and limestone, the tumbler index increases by 8.10% and the comprehensive index decreases only from 100 to 96.16, which is within the acceptable range. The application of CS in iron ore sintering can achieve a clean disposal of it and a considerable carbon emission reduction, as the main component of which is Ca(OH)₂.

The complex physical properties of supercritical water (SCW) make the heat transfer characteristics of particles within a particle cluster complicated. The heat transfer characteristics of single particle within a particle cluster in SCW, influenced by surrounding particles, have not been effectively explored. The numerical simulations were conducted to investigate the heat transfer characteristics of particle clusters in SCW under different conditions. The results were compared and analyzed with those from constant property flow. It was found that Reynolds number (Re) and the void fraction of particle cluster have no special effects on the variation trends of Nusselt number (Nu) for the focused particle. However, the particle temperature had a significant effect on the variation trends of Nu. The effect of Re on the heat transfer rate exponent (η) of the focused particle can be divided into two zones: a significant effect zone and a non-significant effect zone. The effect of void fraction on η in the non-significant effect zone was minimal. Within the non-significant effect zone, η decreased with the increasing particle temperature. In the significant effect zone, the variation trends of η became more complex. The fundamental reason for this series of phenomena is the changes in distribution of physical properties. A model for η was developed for the non-significant effect zone. This model can filter out the effects of Re and certain particle cluster spatial configurations, and it demonstrates good predictive performance.

The solid-liquid viscous system formed by high viscosity crystallization solution impacts the flow and separation performance. Therefore, it is very important to study the viscosity mechanism to improve viscosity and regulate crystallization, ensuring a seamless production process. Herein, the viscosity of crystallization solution was taken as the measurement parameter of caffeine as a model drug. We investigated the viscosity mechanism of caffeine crystallization solutions by combining experiment and simulation. The results indicated that the weak interactions between caffeine and water result in increased viscosity of the caffeine crystallization solutions. Moreover, caffeine crystals possess elongated needle-like shapes, featuring a substantial specific surface area. Additionally, there is π-π stacking occurring between the (2 0 0) crystal face and (1 1 0) crystal face, effectively fostering coalescence of the crystals towards the radial side of the crystal along its elongated axis, resulting in a more viscous crystallization system. The results contribute to comprehending the viscosity mechanism of crystal systems and provide theoretical foundation to enhance engineering efficiency in crystallization.

In continuous biomass torrefaction plants, the products' yields, composition and homogeneity highly depend on the residence time of particles. A characterization of particle residence time distribution (RTD) was therefore carried out in an industrial-scale multiple hearth furnace on poplar wood chips using radio frequency identification tracers. The effects of operating conditions, namely, mass flow rate of biomass, shaft speed of the rabbling system and interdental length on the RTD were studied. The increase of shaft speed and mass flow rate reduces particles’ mean residence time. Lowering the length between two successive teeth also increases the bed speed. Uncontrollable biomass accumulation (also called “bulldozing”) was observed during several tests. This phenomenon is favored by a high mass flow rate of resources, a small interdental length between the teeth and a low shaft speed. RTD measurements were compared to the axial dispersion model. For all tests, the Peclet number is ranging between 20 and 62, indicating that the multiple hearth furnace cannot be modelled as an ideal plug flow reactor.

The polymer on modulating the crystal's habit is an evolving research in pharmaceutical crystallization. This study demonstrates the crystal habit modification of chlorzoxazone (CHZ) by heterogeneous crystallization (HC) in the binary solvent acetonitrile-ethanol (A-E (1:1)) in the presence of polyvinylpyrrolidine (PVP) at concentrations of 0.50, 0.75, and 1.00 wt%. The A-E (1:1) and PVP in HC experiments influenced to change the shape of crystals from needle to plate shape and reduced the crystal size producing a lower aspect ratio (in the range of 1.5–2.3). In the presence of PVP, the CHZ size distribution is 65–78 μm which tends to enhance the powder flow-ability of CHZ crystals and as the PVP concentration increases, the nucleation rate decreases. The solubility of size-reduced CHZ crystals at different pH is found to be improved by 1.2–1.4 times. Hence, HC is deemed effective in modifying the physicochemical attributes of CHZ.