We present an unexplored regime, where the binary random close packing fraction ϕRCPb is smaller than that of the mono-sized one ϕRCPm. This is against previous observations and common perceptions that binary packing tends to be denser than mono-sized packing. We numerically confirm the critical condition for reaching this exceptional regime in the size ratio (Rr) and mole fraction (Xs) space, where Rr is close to 1, and the mole fraction of the smaller sphere Xs close to 0. Under the same loading condition, the stiffness of the packing at this exceptional regime is found to be significantly higher than that of the mono-sized packing. The formation and transition of this regime for varying Rr and Xs are theoretically modelled based on the hard-sphere fluid theory. This exceptional regime remains unreported in existing literature, yet significant for our fundamental understanding of binary packing systems.

The addition of pulsating flow in the conventional liquid-solid circulating fluidized bed (CLSCFB) to enhance liquid-solid mass transfer efficiency has been proposed. A pulsating continuous liquid-solid circulating fluidized bed (PCLSCFB) experimental system was designed and constructed. The liquid-solid mass transfer coefficient (kSL) in the PCLSCFB was measured by the experimental method of dissolving the insoluble benzoic acid particles. The effects of superficial liquid velocity, superficial solids velocity and pulsation property on the liquid-solid mass transfer coefficient (kSL) in the PCLSCFB were thus determined. It was concluded that the liquid-solid mass transfer coefficient (kSL) increases with the increasing pulsation amplitude and frequency in the experimental range. The addition of pulsating flow significantly strengthens the liquid-solid interphase transfer efficiency in comparison with the CLSCFB. The correlation of the mass transfer coefficient (kSL) for the PCLSCFB has been proposed based on experimental data and main parameters.

The hydraulic turbine performance is adversely affected by sediment erosion. The present study aims to explore the erosion behavior of radial hydraulic turbine. Numerous shapes, sizes, and concentrations of sediment particles striking the turbine were analyzed numerically and experimentally. Numerical analysis was performed in ANSYS-FLUENT and EDEM coupled system based on the Archard wear model, which is new for particle dynamics simulation within turbine. Experiments were performed by injecting various-sized particles into a transparent-casing turbine. The experimental analysis traced erosion in the blade's suction and leading side. The overall experimental uncertainty was 0.53%. Numerical analysis indicates that erosion occurs at the casing (62%), the blade's suction side (10.2%), and the leading side (12.9%). Finally, applying the genetic algorithm relationship between the normalized erosion rate density with the particle's velocity, size, concentration, and shape factor was established. Erosion loss increased with increased particle concentration and size and decreased shape factor.

Dense driven granular materials have garnered significant interest due to their complex rheological phenomena such as dynamical heterogeneities and frequency dependence. However, the unjamming/yielding transition induced by intruder deformation, which is critical for applications in living matter interactions with sand and foundation-soil, remains poorly understood compared to boundary- or friction-driven granular systems. To address this knowledge gap, we first study the relaxation dynamics of granular medium driven by oscillatory intruder deformation, and the evidence of an abrupt unjamming/yielding transition in frequency domain is provided. The evaluation was performed by combining the bulk rheology manifested as the temporal evolution of beam deformation, dynamical and mesostructural heterogeneities. We find that the transition is characterized by the emergence of vortices, which cause shear bands accompanied by superdiffusion, transforming spatial correlations from exponential to power-law decay. This study demonstrates the potential for controlling and predicting elastic and flow properties in the intruder-deformation-driven flow and provides future theoretical or numerical modeling of active mesorheology through comparisons with complex fluids and boundary-driven scenarios.

Water extraction from the atmosphere using solid desiccants is becoming an increasingly viable option for human consumption. Using sustainable raw materials is imperative to reduce the carbon footprint in the mass production of such desiccants. In this paper, we synthesized microporous activated carbon from sunflower seed shells (SSS-AC) to capture water vapors from humid or moist air. Sunflower seed shells (SSS) are an agricultural waste product that makes the final product a sustainable and environment-friendly alternative to traditional solid desiccants. Chemical activation was carried out using KOH as the activating agent, and the ratio of activating agent to carbon was 2:1. Different structural and morphological properties of synthesized microporous activated carbon (SSS-AC) were studied using FTIR, XRD, SEM, EDAX, and TGA characterization techniques. The surface area and pore distribution were characterized using N2 adsorption/desorption studies, where a steep initial uptake with a wide capillary condensation step was observed for SSS-AC. The pore distribution of SSS-AC showed high pore volume in the microporous range. The pHpzc value for the SSS-AC was measured to be 10.24 while the HI value was found to be 6.26, indicating an alkaline and hydrophobic surface. Water adsorption studies were carried out at 25, 35, and 45 °C, and the material was found to exhibit type-V isotherm, which is common for microporous activated carbons and indicates the likely occurrence of pore condensation. The SSS-AC reported a maximum adsorption capacity of 0.454 gwat/gads at 90% relative humidity and 25 °C, which is higher than some complex desiccants reported in the literature. The adsorption capacity of SSS-AC decreased with increasing temperature since, at higher temperatures, the pore-filling mechanism is hindered.

Chaotic invariant and recurrence quantification analysis measures have characterised fully developed gas-solid flow in horizontal pneumatic conveying of plastic pellets. These measures describe the complexity in phase spaces (attractors) and recurrence plots, reconstructed from pressure and bottom arc-shaped electrostatic signals to characterise the behaviour of flow patterns. Different flow patterns were identified using high-speed video imaging of a transparent pipeline and classified at several operating conditions in a flow pattern map and state diagram. Recurrence plots were analysed for the identified flow patterns, which showed different qualitative structures. The chaotic invariant and recurrence quantification analysis measures were correlated with the state diagram, indicating that the fluctuations of pressure senor and electrostatic sensor signals can classify the flow patterns at different operating conditions. Combining the analysis measures for electrostatic signals can indicate whether the flow condition is above, near or below the minimum energy consumption operating conditions.

Combustion of sewage sludge is technology with high relevance both, regarding energy efficiency and recovery of valuable products like phosphor. The combustion is usually performed in a fluidized bed. CFD modelling is a central element of the optimization of this process. However, there are a number of modelling approaches available, with different advantages and disadvantages concerning accuracy and computational power. In this study, a new simplified reactor design for sewage sludge fluidized bed combustion was analyzed by CFD simulations based on the Eulerian multiphase approach and a formulated model for thermal conversion. The CFD simulations were carried out in 2D as well as 3D and the numerical results were utilized for a methodological comparison. This enables a scientifically sound recommendation on a suitable numerical approach based on the evaluation parameters of interest. As a conclusion of the investigations, the computationally more expensive 3D approach regarding simulation time should be used if the quantitative flow evaluation of the entire reactor is in focus. The 2D approach is well suitable to resolve fluidization and sludge mixing behavior within the sand bed, if the general combustion behavior is of interest. In the light of the significantly faster simulation, it can be recommended as a suitable method for preliminary analyses. The numerical results for typical evaluation parameters like gas temperature or the residual oxygen content at the gas outlet are presented. Local flow differences within the freeboard are deduced between the 2D and 3D approaches so that expectable differences are better assessable during the reactor design phase.

A mechanically induced phase transition in tin‑tellurium (SnTe) system and its dependence on the milling time of the masses of metastable SnTe phase(s) produced during ball milling have been investigated. The synthesis approach involves top-down ball milling of elemental Sn and Te powders in an argon environment with a milling time of 1 to 5 h at a low ball milling speed of 300 RPM. The SnTe solid solution forms as particles, resulting in large masses due to the ball milling operation. Ball milling of initial micron-sized powders of Sn and Te resulted in a homogenized nano-sized powder mixture. This mechanical mixture of Sn and Te powders exhibiting intermediate phases with a crystal structure similar to that of elemental Sn and Te were detected in the ball-milled mixtures at various milling times, which resulted in a stable phase that ultimately transformed into a SnTe solid solution. Morphological and structural modifications at different stages of ball milling were investigated through X-ray diffraction, field emission scanning electron microscopy, transmission electron microscopy, differential scanning calorimetry, dynamic light scattering, density measurement, and surface analysis. Subsequently, dense pellets were fabricated by spark plasma sintering from synthesized SnTe solid-solution powders produced by ball milling for 5 h. The sintered samples showed excellent structural integrity with densities of up to 6.35 g/cm3. It is to be noted that the formation of large quantities of uniform SnTe powder alloy produced by ball milling is reported for the first time in this study. These findings could be extended in the future to prepare bulk quantities of many solid solutions of the elements of the same periodic group.

A new type of nonpowered airflow dust removal device was designed and manufactured. The dust control mechanism was studied through numerical simulation and experimental study, and the influence of the length of the nonpowered airflow dust removal device and the belt speed of the conveyor on the dust removal effect was analysed. The results showed that the dust removal effect was positively correlated with the length of the dust removal device and the belt speed of the conveyor. To verify the dust control effect, the field application was carried out at Anhui Huayi Chemical Co., LTD, and an obvious dust control effect was obtained with the dust concentration reducing from 227.3 mg/m3 to 8.3 mg/m3.

The vibration-induced compaction deformation of gap-graded mixtures is caused by changes in particle spatial distributions. This study utilizes the discrete element method (DEM) to obtain spatial distribution information and verifies the accuracy of DEM models through physical tests. Spatial autocorrelation analysis and neighbor matching tests quantify spatial distributions in terms of particle aggregation. The correlations between mixture deformation and particle spatial distribution are investigated, with discussions on the influences of size ratio (SR) and fine content (FC). Results show a strong correlation between deformation and particle motions in mixtures with SR = 3, while the correlation becomes complex for mixtures with SR ≥ 4.45. Weakened aggregation facilitates pore-filling by fine particles and promotes deformation in mixtures with FC = 10%. Mixtures with 20% ≤ FC ≤ 30% exhibit the smallest deformation due to opposing particle motions and effective pore-filling by dispersed fine particles. Mixtures with FC > 40% experience deformation related to the aggregation state of coarse particles, despite being primarily composed of fine particles. This study sheds light on the vibration-induced deformation mechanism of mixtures through a mesoscopic perspective of particle spatial distributions.

To overcome the challenge of large particle number concentration in the simulation of realistic particle acoustic agglomeration process, the implementation and validation of an efficient three-dimensional simulation method with a fine-grained Graphical Processing Unit (GPU) based parallel strategy is proposed. In detail, the motion of the simulated particles is solved with the Discrete Element Method (DEM) that includes three major particle acoustic agglomeration mechanisms, two particle collision processes and varying agglomerate porosity. Under the framework of the spatial decomposition method, the fine-grained parallel algorithm allocates the computation workload of each simulated particle one-by-one to one GPU thread. Speed test shows that the developed algorithm could achieve relatively elevated efficiencies and high speedup ratios. For method validation, the predicted particle agglomeration rate is compared with experimental measurements in the literature. The agreement of the results demonstrates that the developed method could reproduce realistic particle agglomeration rate as in the experiment.

The continuous mining face is the main dust-producing area in a coal mine. The dust produced endangers the physical and mental health of underground workers and increases their risk of pneumoconiosis. To improve the lack of spraying in the middle part of the continuous mining machine and the poor dust reduction effect, we developed a wind-assisted spraying device placed in the middle of the continuous mining machine. Spraying experiments have shown that a round nozzle with a 2.4-mm aperture containing an X-shaped guide core has a longer effective range and wider atomization angle. Numerical simulations have shown that when the spray pressure is 7 MPa, a dust reduction spray field with uniform droplet size distribution can be formed. After applying the spray parameters obtained in the coal mine field and using the dust removal device, the total dust concentration in the driver's area of the continuous mining machine was significantly reduced.

In this paper, the erosion characteristics in a circulating fluidized bed (CFB) were investigated on time scale with Euler-Lagrange model based computational particle fluid dynamics (CPFD). By analyzing average erosion rate data, two different erosion characteristics were found. In addition to the common linear erosion caused by downflow particles, another type of erosion is characterized by step growth and is caused by upwelling particles. Linear erosion at the height of 0.1 m is close to that at 0.2 m from the air distributor, but the value of stepped erosion at 0.1 m is much greater than that at 0.2 m. The simulation results show that stepped erosion is the main cause of erosion in the simulated object, accounting for about 70% of the total erosion. The present numerical study implies that the special gas-solid flow of CFB will bring different characteristics of erosion, and the anti-wear method should be targeted at the causes of erosion.

With their unique properties and structure, gas hydrates are a highly promising energy resource. In this research, we have experimentally studied the methane hydrate dissociation behavior when exposed to various sources of fire hazard. The experiments involved the ignition schemes most commonly identified as causes of fires: an open flame, a massive heated surface, a short circuit, and a local source of fire hazard. We have for the first time explored the impact of the following combination of the key factors on the ignition behavior: gas hydrate dissociation rate, heat flux, coverage of the free surface of the sample, gas diffusion rate, CO2 hydrate dissociation time during the combined methane hydrate and CO2 hydrate dissociation, as well as the background of the thermal field evolution in the gas hydrate. The experimental findings have become a foundation for a model predicting the critical conditions of hydrate ignition.

Particle-resolved direct numerical simulations (PR-DNS) are carried out to investigate the momentum (quantified by the drag coefficient, Cd) and heat (quantified by the average Nusselt number, Nu) transfer of two interactive non-spherical porous particles in a fluid. The leading particle (relevant parameters marked by a subscript ‘L') is a spheroid with different shapes and porosities, and the trailing particle (relevant parameters marked by a subscript ‘T') is a sphere. The numerical model is firstly well validated against previously published data and then the effects of the leading particle aspect ratio (ArL), orientation (θL), porosity (εL), distance (L) and Reynolds number (Re) are stressed, respectively, on the CdT and NuT of the trailing one. New findings from the current numerical results are: CdT increases when increasing θL for a leading oblate spheroid but decreases with θL for a leading prolate spheroid. When θL = 0°, CdT increases with increasing ArL but the opposite trend is found when θL = 90°. When θL = 45° and the distance between the two particles is small, CdT increases with the increase of ArL. However, when the distance between the two interactive particles gets larger, CdT first decreases and then increases with ArL. When the leading particle is a spheroid and the two interactive particles are far away from each other, NuT increases first and then decreases with increasing θL. When the leading particle is a spheroid and the two interactive particles are close to each other, the changing trend of NuT with θL can be more greatly influenced by εL. That is, when εL = 0.9, NuT increases with θL for a leading oblate spheroid but decreases with θL for a leading prolate spheroid. On the contrary, when εL = 0 and εL = 0.5, NuT increases first and then decreases with θL for both leading oblate and prolate spheroids. When θL = 45°and the two interactive particles are close to each other, a large εL of the leading spheroid plays an important role in affecting NuT which makes it drop significantly. When θL = 45°and the two interactive particles are far away from each other, and the effects of a leading inclined spheroid on both CdT and NuT are weaker than that of a leading sphere. Generally speaking, both CdT and NuT decrease with increasing εL. At last, a back propagation neural network (BPNN) model is established in this study for prediction purposes.

Electrostatics is known to cause significant disturbance to particles in gas-solid fluidized beds, necessitating the deployment of an efficient electrostatic suppressor. As such, this study delves into the electrostatic suppression effects of carbon fiber, carbon fiber powder, and their hybrids in a fluidized bed, including their fluidization characteristics, using electrostatic measurements and CFD-DEM simulations. The results show that the additives had noteworthy electrostatic inhibition effects, albeit with distinct limitations. Carbon fiber was effective at high air velocities, but its performance was subpar at low gas velocities. In contrast, carbon fiber powder was suitable for low gas velocities, but turbulence diluted its effectiveness. Such limitations can, however, be mitigated through optimization of a specific mixing ratio between the two additives. The proposed carbon fiber (powder) composite reveals its potential as an effective electrostatic suppressor.

Waste printed circuit boards (WPCBs) contain a significant amount of valuable components found in e-waste, including numerous metals and can be considered as secondary resources. Crushing is the primary stage for recycling useful components from WPCBs. Due to the varying dominant sizes of different separation processes, the size distribution of crushed WPCBs plays an important role in determining recovery efficiency. Therefore, controlling the size of crushed products is essential for improving recovery rates. A method for calculating the specific size yield of crushed WPCBs was proposed based on the breakage probability model. The mass yield and copper yield smaller than a certain size were fitted using the breakage probability model. The applicability of different breakage probability models was investigated, and the calculating method for specific size yield was verified. Excellent fitting applicability in mass yield and copper yield of crushed WPCBs was demonstrated by the Logistic model. The variation of mass yield and copper yield smaller than a certain size with energy can be effectively predicted. The theoretical specific size yield can be calculated by the difference between the theoretical yields smaller than different sizes. The prediction of specific size mass yield and copper yield can effectively promote the pre-concentration during crushing and help to optimize the crushing process. The utilization of the breakage probability model in WPCBs has the potential to improve component recovery and serve as a benchmark for optimizing the crushing process of other e-wastes.

Pumice, with low pozzolanic reactivity, was ground for 1, 3, and 6 h with a laboratory ball mill in dry conditions and it was ground for 1 h in wet conditions via an industrial-scale ball mill. Based on derivative particle distribution, grinding for longer periods led to the disappearance of bimodal distribution and the development of unimodal distribution. Furthermore, the phase characterization, assessed through XRD, demonstrated appreciable changes in intensities of the peaks of quartz and dachiardite. The extension of grinding time resulted in a significant uptake at the early-age lime consumption and evolution of hydration heat. According to SEM images, the number of particles between 10 and 20 μm was less in the powder ground for 3 and 6 h. Moreover, it was found that the prismatic shapes of raw pumice tended to transform to spheroid shapes after prolonged grinding, and the smooth surfaces of pumice particles became more rugged.

In industry sectors, such as power, petroleum, and natural gas production, many fluids contain solid particles in gas/liquid-solid two-phase flows. Thus, resistance and wall erosion, which mainly occur at pipe resistance components, such as elbows and reducers, should be considered in the design of conveying pipelines. To examine the interaction of two resistance components, the flow irreversibility versus wear of an elbow-reducer connection with a gas–solid two-phase flow were studied via the CFD–DEM coupling method. The studied connection structures include a reducer at the elbow downstream with distances of 0, 1, and 3 pipe diameters, and a reducer at the elbow upstream with distances of 0, 1, and 3 pipe diameters. Results show that turbulence and wall entropy generation are main reasons for the total entropy generation and flow irreversibility, which are mainly distributed in the interior wall of the elbow and the pipe. The reducer located downstream of the elbow has a good inhibition effect on the fluid with a separation phenomenon. The total entropy generation and maximum erosion rate for the elbow-reducer connections are lower than that for the reducer-elbow connections. Moreover, influences of solid particle mass flow rate and particle size on partial entropy generations, including mean, turbulent, and wall entropy generations, and wall erosion were comparatively analyzed. The simulation results can provide a reference for the design of pipelines to reduce energy consumption and pipeline wear.

Maintaining the viability of probiotic bacteria in food products for intestinal delivery remains a challenge. Consequently, the objective of this study was to encapsulate Lactobacillus rhamnosus (NCDC 18) in calcium alginate–maltodextrin hydrogel systems by combining electrospraying and freeze-drying techniques. The microparticles were produced using varying concentrations of sodium alginate (SA) (2, 3, and 4%) in conjunction with maltodextrin (MD) (0, 2, and 4%). A definitive screening design (DSD) was used to design experiments and explain the effect of independent variables (concentrations of SA, calcium chloride, and MD and electrospraying voltage) on the response variables: loss of viability, encapsulation efficiency, drying yield, Carr's index, and Hausner ratio. The obtained microparticles were characterized by employing Scanning Electron Microscopy (SEM), Fourier Transform Infrared Spectroscopy (FTIR), and Differential Scanning Calorimetry (DSC). The addition of MD significantly increased encapsulation efficiency up to 75.19% and decreased viability loss up to 2.539 log CFU/mL in microparticles. The morphological analysis revealed the particle surface structure and variation in porosity in response to varying variables. The FTIR spectra confirmed that the addition of SA, MD, and probiotics caused synergistic changes in the functional bonding. The XRD analysis could further elucidate the interactions of SA with MD in the microcapsules. Our study could confirm that MD acted as a cryoprotectant and decreased the concavities and pores on the surface of the microparticles, thereby enhancing their probiotic-related properties.