Powder Technology最新文献

The Theophylline and Salbutamol Bilayer Sustained-release Tablets (Yi Xi Qing®), prepared via wet granulation, discolor during long-term storage, and the process is less reproducible and more cumbersome. In this study, the direct compression (DC) method was used to prepare equivalent and stable theophylline-salbutamol bilayer sustained-release (TBS) tablets, using Yi Xi Qing® as a reference formulation (the relative bioavailabilities for theophylline and salbutamol were 96.3 % and 103.9 %, respectively, with release similarity factors of 60.12 and 80.99). Lipid microencapsulation of salbutamol via hot-melt extrusion (HME) and the use of HPMC with a particle size of less than 96.55 μm (D₉₀) in the theophylline layer enhanced the stability of salbutamol during long-term storage and controlled the release of theophylline from a minimal amount of gel matrix material, respectively. The results of this study may offer insights into the preparation of DC hydrophilic gel matrix bilayer tablets with high drug loading capacity.

Hydraulic impact hammers used for rock breaking play a crucial role in the mining industries, but their operation is complex and inefficient. To address these challenges, this paper investigates the rock breaking process of impact hammers. Utilizing stress wave theory, a mathematical model for impact rock breaking is established, and the size of broken rock is estimated. Subsequently, the DEM-based numerical analysis verifies the reliability of the mathematical model and elucidates the working mechanism of impact rock breaking. Additionally, the study explores the influence of different hammer parameters on the rock breaking performance. The results indicate that the essence of rock breaking lies in the formation of a rock crushed zone and the initiation and growth of cracks under the impact load, with the main macrocrack extending towards the free surface closer to the operating point. Regarding rock breaking efficiency, the impact velocity has a relatively minor influence, while the drill rod diameter shows a positive correlation with efficiency. The drill bit angle significantly affects the rock breaking efficiency and is accompanied by changes in the rock breaking pattern.

This study investigates the size-induced radial segregation of binary mixtures in different sized rotating drums. The results indicate that at a constant Froude number, the time to reach the stable segregation state increases with the drum size increasing, while the final particle segregation patterns remain similar. A correlation of the segregation rate as a function of scale-up ratio and Froude number is proposed, indicating that the segregation rate decreases with the drum size increasing. The similarity in particle velocity and particle-particle contact force is analyzed, showing that particle velocity distribution shows much difference in different sized drums at a low Froude number but less difference at a high Froude number. The average velocity increases with the drum size increasing. Contact force distribution shows significant difference at all Froude numbers, with the average force increasing with the drum size. Total power consumption per unit mass increases with the drum size increasing.

Large quantities of coal dust are generated during coal screening processes, which spread to the surrounding environment and severely affect air quality and employees' health. Here, we investigated the effectiveness of a self-developed positive- and negative-pressure composite dust removal system in controlling dust pollution in a coal preparation plant screening workshop. The dispersion law of dust pollution under two conditions, with and without this device, was numerically simulated. We then conducted orthogonal experiments to select the optimal position and air volume of the dust removal system device. The research findings indicate that without this system, dust pollution is severe, with an average dust concentration in the breathing zone reaching 86.8 mg/m³, posing a serious threat to workers' safety. After optimizing the dust removal system, the average dust concentration in the breathing zone reduced to 18.4 mg/m³, improving dust removal efficiency by 78.7 % compared to the original condition.

The present research aims to examine the influence of stress anisotropy on the small-strain Young's modulus of granular materials. To this end, a series of numerical tests, including isotropic compression, isotropic extension, triaxial extension (TE), triaxial compression (TC), reduced triaxial extension, and reduced triaxial compression tests, were conducted using the 3D Discrete Element Method. The findings revealed the presence of a threshold value of stress ratio (SR) in both TE and TC stress paths. When the SR falls within the range between two threshold values, the fabric of the specimen, represented by the contact normal distribution, remains nearly constant. In this range, the anisotropy of small-strain Young's modulus is primarily attributed to the anisotropy of stress. However, it was observed that the small-strain Young's modulus in a specific direction is affected by the value of SR, contradicting the prevailing belief that it is solely influenced by the principal stress in that direction. A novel factor R_s was introduced and incorporated into Hardin's equation to capture the influence of the SR on the small-strain Young's modulus. In addition, a relationship was established between mechanical coordination number and small-strain Young's modulus during triaxial tests by considering both stress anisotropy and fabric anisotropy.

Epoxy (EP) powder is widely used in the industrial field of electrostatic coating due to its excellent physicochemical properties. However, the dust explosion risk caused by its flammability cannot be ignored. Calcium carbonate (CaCO₃) is often added into EP as an inorganic fillers because of its low cost and wide availability. This study explores the effects of different proportions of CaCO₃ on the explosion characteristics and pyrolysis behavior of EP powder. The results show that the maximum explosion pressure (P_max), the minimum ignition energy (MIE), and the minimum ignition temperature (MIT) of EP are 6.82 bar, 6 mJ, and 460 °C, respectively. The addition of CaCO₃ reduces the explosion sensitivity and severity of EP dust to a certain extent. The thermal decomposition of CaCO₃ absorbs heat and produces CaO and CO₂. This process hinders the oxygen transfer, and dilutes the flammable volatiles, thereby reducing the explosion hazard of EP dust.

Through nanoparticle modulation, fast fluidization of Group C particles (d_p < 35 μm) is achieved in a circulating fluidized bed (CFB) with an inner diameter of 0.07 m and a height of 2.5 m. Hydrodynamic behaviors of the CFB riser are investigated. Compared to Group A and unmodified Group C particles, a much lower superficial gas velocity in the range of 0.4–0.7 m/s is sufficient to accomplish circulating operation for nano-modulated Group C powders. The average solids holdup is notably denser than traditional CFBs, reaching 0.10–0.15 and remaining relatively homogeneous up to 1.5 m of the riser. Increasing superficial gas velocity results in reduced solids concentration in the riser. Solids circulation rate and auxiliary gas flowrate both positively impact solids holdup, with higher rates leading to increased average solids concentration. The impact of the quantity of incorporated nanoparticles appears to differ across various powders, as the distinct properties of powders present difficulties in identifying the optimal nanoparticle concentration.

To investigate the flow characteristics in gas-liquid-solid fluidized bed, an optimized volume of fluid (VOF) and discrete element method (DEM) combined multiscale solver is implemented. The gas-liquid interface is captured by VOF with a sharpening algorithm, while particles are tracked using DEM. The particle volume fraction is calculated by a divided volume-averaging technique and several well-established drag closures are incorporated for gas-liquid-solid three-phase coupling. The solver is first adopted in a particle water-entry process to validate the volume conservation of the VOF-DEM method. Then the solver is separately utilized in liquid-solid and gas-solid systems for a detailed verification of liquid-solid and gas-solid interactions. The results show that the van der Hoef drag closure is the most appropriate for both liquid-solid and gas-solid interactions among the investigated drag closures. Using van der Hoef drag closure, the flow characteristics in a mini gas-liquid-solid fluidized bed are investigated, identifying different flow patterns.

The feasibility of the enhanced cyclone with split flow (ECSF) for applications in high temperature conditions and complex spaces was validated through numerical simulation, investigating the influence of operating temperature and tilt angle on ECSF performance and flow field. The Reynolds stress model and discrete phase model were employed to calculate the intricate rotating turbulence and trajectories of particle motion within the ECSF, respectively. The findings demonstrate that the separation capacity of ECSF diminishes with the increment of operating temperature. Moreover, the tilt angle has negligible influence on both performance and flow field characteristics of ECSF regardless of high or low feed flow rates or operating temperatures. This means that ECSF can be flexibly installed. This research provides valuable insights for promoting wider applications of ECSF.

Considering the food potential of trapiá and the feasibility of its commercial exploitation through pulp processing, this study aimed to investigate the microencapsulation by spray drying and freeze-drying blends of trapiá pulp with tropical fruits (orange, lemon, and pineapple), evaluating the effect of partial substitution of maltodextrin with inulin on the resulting powders. Formulations for spray drying underwent ultrasound-assisted pretreatment, which improved the yield of spray-dried powders by approximately 46 %. Partial substitution of maltodextrin with inulin effectively preserved the total phenolic content of the powders obtained via spray drying and significantly enhanced their antioxidant capacity as measured by the ABTS assay. This study provides valuable data to the academic community regarding the processing of trapiá with Brazilian tropical fruits, aiming to enhance the value of this raw material, offering insights into the optimization of the drying process, and contributing to the feasibility of exploiting trapiá pulp for industrial purposes.