Presence Of Fine Particles Research Articles

Evaluation and Determination of the Physical Properties of Gasoline and the Presence of Fine Particles in the Ten Districts of the City of N'djamena

The context, which allowed to write this article is the fact that we have noticed an increase in the environmental impact caused by the poor management of car parks and fuel sellers as well as the proliferation of service stations that do not respect any standards. The illegal storage and marketing of petroleum products, especially gasoline, in the city of N'Djamena is the main factor of vulnerability and criticality of air pollutants, thus demonstrating the growing environmental impact in the city of N'Djamena. The presence of Polycyclic Aromatic Hydrocarbons (PAHs) as well as that of fine particles which are part of the Persistent Organic Pollutants (POPs) and characterize by their toxicities, their persistence in the environment, their bioaccumulation in living tissues, and their long-distance transport. Thus, the main objective of this work is to determine and evaluate the physical properties of gasoline and the presence of fine particles in the ten districts of the city of N'Djamena. These are the species sold on the street and presenting a danger to users. The main idea would be to look for gas stations and points of sale that comply with the regulations in force and those that do not. Then physical analyses were carried out on different types of gasoline consumed and then the air quality was measured with a Purple Air sensor. In conclusion, a complete structure of the ten districts with their degrees of pollution as well as the number of gas stations and fuel sellers on the street will be listed.

Enhancing fine particle removal by electrostatic precipitation from flue gas with a high PM concentration: Effect of various electrode configurations

Particle pollution has hazardous effects on air quality and human health, especially fine particle. However, the highly efficient removal of fine particles is an unsolved problem in electrostatic precipitators (ESPs). In this study, a transparent ESP was designed to investigate the effect of fine particles on the corona discharge performance and the role of ionic wind in particle migration. And five types of typical discharge electrodes were applied. The results showed that the presence of fine particles could weaken the corona current produced by electrode discharge. Among these electrodes, the spike electrode can reduce the adverse effect of the particle space charge. The maximum ionic wind velocity around the electrode tips and within the near-plate region could reached 5.67 m/s and 5.00 m/s under an applied voltage of 30 kV, respectively. Combining the effects of corona discharge and ionic wind, the collection efficiencies of fine particles decreased in the following order: spike electrode (medium needle) > spike electrode (longest needle) > arista electrode > spike electrode (shortest needle) > sawtooth electrode. In general, spike electrode discharge has better performance for particle charging and particle collection efficiency and is suitable for fine particle removal in ESPs. In addition, electrode configuration/arrangement optimization methods were proposed to enhance fine particle removal in ESPs.

Assessing the interactions of retarding admixtures and fine materials in long-term flowability of cement pastes

The incorporation of supplementary fine materials into mortars and concretes is a common strategy employed to enhance both their rheological and mechanical properties. While organic molecule-based admixtures are primarily utilized to regulate the setting time in pre-mixed concretes and mortars, their effects become more intricate in the presence of fine materials. This study delves into the interplay between flowability and setting times of cement pastes with 50 wt% of fines (basalt filler, fly ash and quartz filler) in place of cement and three organic admixtures at 0.5 % and 1.0 % (wt% of cement). The results unveil compelling insights: the incorporation of retarding additives proves notably advantageous, markedly decreasing viscosity and prolonging the initial stage of paste formation by as much as 305 h. Nevertheless, the efficacy of these additives diminishes significantly in the presence of fine particles, especially when utilizing basalt filler. This prompts an in-depth exploration into the intricate interactions transpiring between the fine materials and the setting retardants. The implications of these interactions underscore their pivotal role in refining the application of retarding additives in scenarios involving fine materials.

An all-encompassing study on the joint effect of powder feedstock characteristics and manufacturing process parameters on the densification and mechanical properties of additively manufactured nickel alloy 718

Laser-powder bed fusion (L-PBF) is a commonly employed additive manufacturing (AM) technique in manufacturing 3D metallic parts with complex geometries from powder materials. It is a complex process with more than 100 process parameters affecting the properties of fabricated parts. Studies on AM of nickel alloy 718 are currently focusing on investigating the effect of the process parameters and heat treatment on final part properties. Nevertheless, the effect of different powder characteristics such as particle size distribution (PSD), the presence of fine particles, powder reuse, and moisture content has not been studied comprehensively in the literature. In this study, two types of powder: virgin and recycled, as well as four parameters: PSD, which is represented by the median particle size and the particle size range, moisture content, and volumetric energy density (VED), were studied. To reduce experimental cost and burden, statistical design of experiment (DOE) techniques were utilized. Then, the measured results were analyzed using analysis of variance (ANOVA) to ascertain the effect of the different powder characteristics on multiple quantities of interest (QoIs). Different densification and mechanical tests were performed, and their outputs were studied as the QoIs. This study revealed that VED, powder type, PSD range, and median are the most common significant factors for most QoIs. Meanwhile, moisture content had a significant effect only on the Charpy impact energy. Besides, the study showed that the presence of fine particles <20μm improved the densification of the fabricated parts but reduced the mechanical properties.

Role of hydrophobic fine particles in coarse particle flotation: An analysis of bubble-particle attachment and detachment

It is widely accepted that hydrophobic fine particles improve froth stability and thus increase the recovery of coarse particles in the froth phase. In fact, the presence of fine particles also enhances coarse particle recovery in the collection zone. It is not yet known what causes this, nor is it known how fine particles affect interactions between bubbles and coarse particles (collision, attachment, and detachment). In the present study, the role of hydrophobic fine particles in improving the recovery of coarse particles in the pulp phase was discussed from the perspective of bubble-particle interaction. Flotation tests of coarse particles with different fine particle contents were first carried out. The bubble collision-attachment test, bubble-particle aggregate stability test, and interaction force test were used to further explain the effects of fine particle coverage on bubble-particle interactions. The results show that the recovery of coarse particles increases as the fine particle content in the flotation feed increases. Although the presence of hydrophobic fine particles prevents the rupture of the liquid film and the formation of the contact line between bubble and coarse particle, it can also greatly increase contact angle hysteresis, increasing the maximum force required to pull coarse particle from the gas-liquid interface into the aqueous phase. Furthermore, the coverage of fine particles helps to improve the energy dissipation during the bubble collision and reduce the oscillation of the bubble-particle aggregates. As a result, the increase in coarse particle recovery in the presence of fine particles is due to the decrease in the detachment of the bubble-particle aggregate. The important findings of this study are expected to provide a basis for understanding the interaction between multiple particles and bubbles in actual flotation.

The Challenges and Prospects of Recovering Fine Copper Sulfides from Tailings Using Different Flotation Techniques: A Review

Flotation is a common mineral processing method used to upgrade copper sulfide ores; in this method, copper sulfide mineral particles are concentrated in froth, and associated gangue minerals are separated as tailings. However, a significant amount of copper is lost into tailings during the processing; therefore, tailings can be considered secondary resources or future deposits of copper. Particle–bubble collision efficiency and particle–bubble aggregate stability determines the recovery of target particles; this attachment efficiency plays a vital role in the selectivity process. The presence of fine particles in the flotation circuit is because of excessive grinding, which is to achieve a higher degree of liberation. Complex sulfide ores of markedly low grade further necessitate excessive grinding to achieve the maximum degree of liberation. In the flotation process, fine particles due to their small mass and momentum are unable to collide with rising bubbles, and their rate of flotation is very slow, further lowering the recovery of target minerals. This collision efficiency mainly depends on the particle–bubble size ratio and the concentration of particles present in the pulp. To overcome this problem and to maintain a favorable particle–bubble size ratio, different techniques have been employed by researchers to enhance particle–bubble collision efficiency either by increasing particle size or by decreasing bubble size. In this article, the mechanism of tailing loss is discussed in detail. In addition, flotation methods for fine particles recovery such as microbubble flotation, column flotation, nanobubble flotation, polymer flocculation, shear flocculation, oil agglomeration, and carrier flotation are reviewed, and their applications and limitations are discussed in detail.

Magnetic separation of micron-sized particles: process study and regression modelling using moving least squares and multivariable power least squares method

The presence of fine particles has reduced the quality of water resources. Unfortunately, the fine particles normally take a longer time to be removed. Realizing this, the present study aims to employ a magnetic adsorbent to assist a fast separation of the fine particles from their solution. Here, micron-sized SiO2 particles were used as the model fine particles; meanwhile, the magnetic adsorbent was designed by functionalizing iron oxide nanoparticles (IONPs) with chitosan. A process study was done based on the effects of medium pH, IONPs concentration, and contact time. Results implied that both bare IONPs and chitosan functionalized-IONPs (denoted as CF-IONPs) were best in removing SiO2 at pH 4 owing to the electrostatic attraction force. However, as compared to the bare counterpart, CF-IONPs is more suitable for large scale application as it is effective in a wider pH range, requires lesser adsorbent dosage and shorter adsorption time. Despite that, removal of SiO2 using both types of adsorbents were found to follow pseudo-second order kinetic. The obtained data was modeled using either the moving least squares (MLS) or multivariable power least squares (MPLS) method. In particular, the indices of each parameter obtained from the MPLS-generated equation indicated that the most dominant parameter that governing the SiO2 removal by bare IONPs is medium pH, while the one for CF-IONPs is contact time.

Effect of Particle Size Distributions and Shapes on the Failure Behavior of Dry Coke Aggregates.

Carbon anodes participate in chemical reactions to reduce alumina in the Hall–Héroult process, of which coke aggregates make up a major part. The failure analysis of coke aggregates not only leads to a better understanding of the deformation mechanisms of anode paste under compressive loading but also can identify potential causes of structural defects in carbon anodes, such as horizontal cracks. The coke aggregates are composed of particles with different size distributions and shapes, which may strongly affect the failure behavior of the anode during compaction. In this paper, the effects of particle size distributions and shapes on the mechanical behavior and the failure of coke aggregates are investigated using the discrete element method modeling technique. The numerical results reveal that, although the mechanical behavior of coke mixtures is generally dependent on larger particles, the presence of fine particles in the coke aggregates reduces fluctuations in the stress–strain diagram. In addition, the rolling resistance model is employed as a parameter representing the effect of particle shape. It is shown that the rolling resistance model can be an alternative to the overlapped spheres model, which has a higher computational cost than the rolling resistance model. The second-order work criterion is used to evaluate the stability of the coke aggregates, the results of which indicate that the addition of fine particles as well as increasing the rolling resistance between the particles increases the stability range of the coke aggregates. Moreover, by using the analysis of micro-strain contour evaluations during the compaction process, it is shown that, both by adding fine particles to the coke mixture and by increasing the rolling resistance between the particles, the possibility of creating a compression band in the coke aggregates is reduced. Since the presence of the compaction bands in the anode paste creates an area prone to horizontal crack generations, the results of this study could lead to the production of carbon anodes with fewer structural defects.

Mechanical behavior of hydrate-bearing sands with fine particles under isotropic and triaxial compression

The presence of fine particles has a significant impact on the mechanical behavior of hydrate-bearing sediments. In this study, a series of isotropic compression and triaxial tests were conducted using a customized testing system for the hydrate-bearing sediment. Carbon dioxide hydrate was formed in the host sediments, which were mixtures of sand and silty-sized quartzitic or illite fine particles. The isotropic and triaxial compression tests offered valuable datasets of the compression and the swelling indices, yielding stress, strength, stiffness, and dilatancy for hydrate-bearing sediments. The results highlighted that the addition of illite particles enhances compressibility but restricts stiffness and dilatancy. The strength is highly increased by hydrate saturation and less dependent on the mineralogy of fine particles. The cohesion is significantly enhanced by the hydrate saturation due to cementation. With the increasing hydrate saturation, the angle of internal friction increases slightly at lower hydrate saturation but it decreases slightly at higher hydrate saturation. The experimental results and mechanism analysis can be used to assess the stability of the hydrate reservoir under methane-carbon dioxide replacement and provide a reference to estimate the mechanical properties of the methane hydrate reservoir.

Quantitative relationship between the density and structural unit of alpha alumina prepared from gibbsite and boehmite

Increasing the density of α-Al2O3 powder can improve the performance of alumina-bearing materials and broaden their application. In this study, the relationship between the density and structural unit content of α-Al2O3 prepared from gibbsite and boehmite is systemically studied. The density of α-Al2O3 powder prepared from gibbsite is larger than that from boehmite after calcination at 1500 °C for 5 h. The density of α-Al2O3 powder prepared from commercial gibbsite reaches 3.96 g⋅cm−3, with 0.73 m2⋅g−1 specific surface area, after calcination at 1500 °C for 5 h. In addition to particle size, the precursor, heating program, seeds, and additives also determine α-Al2O3 density. Furthermore, α-Al2O3 density almost linearly increases with the AlO6 content in α-Al2O3 prepared from gibbsite. The presence of fine particles, remarkable change in specific surface area, notable variation in morphology, and similar hexagonal close packing of κ-Al2O3 and α-Al2O3 favor the formation of high-density α-Al2O3. However, reconstructive transformation from θ-Al2O3 to α-Al2O3 requires high energy, leading to the low density and large specific surface area of α-Al2O3 produced from boehmite. Prolonging the calcination time, adopting a long duration at 400 °C-900 °C, and adding an appropriate amount of α-Al2O3 seeds (<20 wt%) or AlF3 (<10 wt%) can increase the AlO6 content, thereby improving α-Al2O3 density.

Phase reddening on asteroid Bennu from visible and near-infrared spectroscopy

Context.The NASA mission OSIRIS-REx (Origins, Spectral Interpretation, Resource Identification, and Security–Regolith Explorer) has been observing near-Earth asteroid (101955) Bennu in close proximity since December 2018. In October 2020, the spacecraft collected a sample of surface material from Bennu to return to Earth.Aims.In this work, we investigate spectral phase reddening – that is, the variation of spectral slope with phase angle – on Bennu using spectra acquired by the OSIRIS-REx Visible and InfraRed Spectrometer (OVIRS) covering a phase angle range of 8–130°. We investigate this process at the global scale and for some localized regions of interest (ROIs), including boulders, craters, and the designated sample collection sites of the OSIRIS-REx mission.Methods.Spectra were wavelength- and flux-calibrated, then corrected for the out-of-band contribution and thermal emission, resampled, and finally converted into radiance factor per standard OVIRS processing. Spectral slopes were computed in multiple wavelength ranges from spectra normalized at 0.55μm.Results.Bennu has a globally negative spectra slope, which is typical of B-type asteroids. The spectral slope gently increases in a linear way up to a phase angle of 90°, where it approaches zero. The spectral phase reddening is monotonic and wavelength-dependent with highest values in the visible range. Its coefficient is 0.00044μm−1 deg−1in the 0.55–2.5μm range. For observations of Bennu acquired at high phase angle (130°), phase reddening increases exponentially, and the spectral slope becomes positive. Similar behavior was reported in the literature for the carbonaceous chondrite Mukundpura in spectra acquired at extreme geometries. Some ROIs, including the sample collection site, Nightingale, have a steeper phase reddening coefficient than the global average, potentially indicating a surface covered by fine material with high micro-roughness.Conclusions.The gentle spectral phase reddening effect on Bennu is similar to that observed in ground-based measurements of other B-type asteroids, but much lower than that observed for other low-albedo bodies such as Ceres or comet 67P/Churyumov-Gerasimenko. Monotonic reddening may be associated with the presence of fine particles at micron scales and/or of particles with fractal structure that introduce micro- and sub-micro roughness across the surface of Bennu.

Isolation of fine powder faction obtained by electroerosion dispersion method

The fundamental properties of metal powders with small particles change, which opens up a wide range of applications of such materials. Currently, nanopowders are used in many industries to improve the quality of the resulting products. (Research purpose) The research purpose is in isolating a fine fraction of metal powders obtained by electroerosive dispersion for further experiments with this material, and also proving the possibility of obtaining such fractions by this method. (Materials and methods) A fine fraction of metal powders obtained by the method of electroerosive dispersion was isolated, which proved its effectiveness in obtaining conductive powder materials with the desired final physical and mechanical properties. This method results in a fairly large spread across fractions. Authors received material for research on experimental installations of the "Nano-Center" Center for Collective Use. The article presents the methods of experimental research of fractional composition on the example of metal powders of hard alloy grades T15K6 and VK8, copper powder M1, brass powder LTs38MTsS2 and bronze powder BrAZh9-12 obtained by electroerosive dispersion. (Results and discussion) The metal powder was divided into three fractions, depending on the particle size: more than 0.071 mm, from 0.02 to 0.071 mm and less than 0.02 mm. The presence of fine particles of less than 1.5 microns in the total mass of the studied powders was proved using a membrane method with a ceramic filter. Sedimentation showed specific sizes of minimal particles (from 86.4 to 116 nm). (Conclusions) Based on the results of experiments, it is possible to obtain metal powders of a fine fraction using the method of electroerosive dispersion.

Mathematical Model of Low-Concentration Disperse Suspension Fractionation in a Plane Vertical Hydroclassifier

A continuum mathematical model of low-concentration suspension transfer without mixing in a plane vertical gravitational classifier under conditions of phase flux balance is suggested. The flow of a carrier medium is assumed to be laminar, and no limitations on the particle sedimentation rate are imposed. Analytical relationships to calculate the local counting functions of the particle size distribution density have been derived. A computational experiment has confirmed the fractionation of a monodisperse suspension and the presence of fine particles in the “heavy” fractions of polydisperse suspensions. The latter fact is explained by a low velocity of the disperse medium at the “wetted” surfaces of the hydroclassifier. The results are in agreement with available experimental data and data calculated in terms of classical kinetic models.

Changes in Atmospheric, Meteorological, and Ocean Parameters Associated with the 12 January 2020 Taal Volcanic Eruption

The Taal volcano erupted on 12 January 2020, the first time since 1977. About 35 mild earthquakes (magnitude greater than 4.0) were observed on 12 January 2020 induced from the eruption. In the present paper, we analyzed optical properties of volcanic aerosols, volcanic gas emission, ocean parameters using multi-satellite sensors, namely, MODIS (Moderate Resolution Imaging Spectroradiometer), AIRS (Atmospheric Infrared Sounder), OMI (Ozone Monitoring Instrument), TROPOMI (TROPOspheric Monitoring Instrument) and ground observations, namely, Argo, and AERONET (AErosol RObotic NETwork) data. Our detailed analysis shows pronounced changes in all the parameters, which mainly occurred in the western and south-western regions because the airmass of the Taal volcano spreads westward according to the analysis of airmass trajectories and wind directions. The presence of finer particles has been observed by analyzing aerosol properties that can be attributed to the volcanic plume after the eruption. We have also observed an enhancement in SO2, CO, and water vapor, and a decrease in Ozone after a few days of the eruption. The unusual variations in salinity, sea temperature, and surface latent heat flux have been observed as a result of the ash from the Taal volcano in the south-west and south-east over the ocean. Our results demonstrate that the observations combining satellite with ground data could provide important information about the changes in the atmosphere, meteorology, and ocean parameters associated with the Taal volcanic eruption.

Heat transfer in a pressurized fluidized bed with continuous addition of fines

The goal of this work was to investigate the impact of pressure and the presence of fine particles (i.e., a surrogate for pulverized fuel) on the overall surface-to-bed heat transfer coefficient in relation to an oxygen-fired pressurized fluidized bed combustor. Experiments were conducted in a pilot-scale fluidized bed with an inner diameter of 0.15 m under cold flow conditions. A tube bundle consisting of five horizontal staggered rows was completely submerged in the bed. One of the tubes was replaced by a heating cartridge housed in a hollowed copper rod. Five thermocouples distributed at 45° intervals along the copper rod circumference measured the surface temperature and ensured that local effects were included. The bed material was glass beads of 1.0 mm in diameter while the fines were glass beads of 60 μm in diameter and thus susceptible to entrainment. The fine particles were continuously fed to the fluidized bed and then captured downstream by a filter system. Fluidization was conducted at 101, 600 and 1200 kPa (abs) with excess gas velocities (Ug-- Umf) of 0.21, 0.29 and 0.51 m/s. Fine particle feed rates were 0, 9.5 and 14.4 kg/h. Two heating rod positions (2nd row and 4th row) were studied. Overall, the heat transfer coefficient approximately doubled when pressure was increased from 101 to 1200 kPa. At atmospheric conditions, where the slug flow regime occurred, the maximum heat transfer coefficient was at the bottom of the rod, while it moved to the side of the rod at high pressures where the bubbling regime occurred. When the heating rod was moved from the 2nd row to the 4th row, the averaged heat transfer coefficient increased by 18%, 9% and 6% at 101, 600 and 1200 kPa. The addition of fine particles decreased the average heat transfer coefficient by 10 to 20 W/m2 K, where the averaged coefficients were approximately 220 and 450 W/m2 at 101 and 1200 kPa respectively, but there was no effect on the angular heat transfer profile around the tube surface. The results showed that average heat transfer coefficients matched the correlation developed by Molerus et al. (1995) within a 5% difference across all conditions when fines were not present.

Recycled Mineral Raw Materials from Quarry Waste Using Hydrocyclones.

Mining activities in general, and quarrying processes in particular, generate huge amounts of tailings with a considerable presence of fine particles and with a variable composition of minerals, which could limit the direct application of those wastes. Under the paradigm of a circular economy, more effort has to be made to find adequate applications for those secondary raw materials. In this study, a process was proposed and tests were performed to valorise fine particle product as a raw material for the building and construction industry. Samples were taken from wastes in several aggregate production plants, being characterized and processed to remove the clayey components to obtain the cleanest quartz fraction. Then, different characterization and validation tests were carried out to analyse the application of these products as raw materials in the building and construction industry (cement and ceramics). Results showed that with no complex technologies, the tailings can be considered as a mineral raw material in different applications.

Relieved Air Pollution Enhanced Urban Heat Island Intensity in the Yangtze River Delta, China

ABSTRACT The National Air Pollution Control Plan implemented by China in 2013 reduced the concentrations of air pollutants, especially PM2.5 (aerosol particles with an aerodynamic diameter equal to or less than 2.5 µm), between 2014 and 2017. This reduction in PM2.5 potentially affected the intensity of urban heat islands (UHIs), as the presence of fine particles can influence the energy balance of the earth-atmosphere system. In this study, the effect of the pollution control plan on the UHI intensity in the Yangtze River Delta, China, was investigated via observational analysis and numerical modeling. According to the observational data, the PM2.5 concentrations in the megacities of the Yangtze River Delta, viz., Shanghai, Nanjing, Hangzhou and Hefei, in 2017 were ~35 µg m–3, showing decreases of approximately 48.36%, 28.25%, 29.41% and 32.5%, respectively, compared to 2014. Furthermore, these reductions in the PM2.5 concentration correlated well with the strengthened diurnal intensity (increasing by up to 1 K) and the weakened nocturnal intensity (decreasing by up to 1 K) of the UHIs. Numerical simulations confirmed that this “seesaw effect” on the UHI intensity was due to the decrease in PM2.5 and the consequent increase in the downward surface shortwave radiation and the outgoing top-of-the-atmosphere longwave radiation. Thus, the Air Pollution Control Plan noticeably affected the UHI intensity by reducing PM2.5—a factor which should be considered in future studies on urban climate and environmental planning.

The influence of seawater on magnetite tailing rheology

It is well known that seawater affects mineral beneficiation, especially in the presence of fine particles. In the present paper, the effect of seawater fraction on the rheology of unflocculated fine magnetite tailings has been studied. Slurry data has been interpreted as both Bingham and Herschel-Bulkley fluids. To relate the experimental results with surface physicochemical properties, zeta potential measurements have been performed to the samples. Results show that besides the well known result that the yield stress and Bingham viscosity have a strong dependency on the particle concentration, the yield stress has been found highly sensitive to the seawater fraction. In contrast, the plastic viscosity observed a comparatively weaker dependency on this variable.

Effect of Soil Types on the Development of Water Levels and Erosion Processes during Overtopping Test

The construction of dike materials is an essential parameters in controlling the safety of hydraulic engineering. The dike material is an earthfill material constructed from non-cohesive materials or mixed from cohesive and non-cohesive materials. Overtopping failure can affect the dike stability during water cross above dike crest and could threat people lives and property. It is reduced the matric suctions binds soil particles due to the increasing volumetric water content during the transition of water level from the upstream into downstream slopes. In this paper, two spatial overtopping tests are conducted in Hydraulic Geotechnical laboratories at the Universiti Sains of Malaysia to observe the evolution of horizontal and vertical water levels as well as the development of lateral and vertical erosion processes under constant inflow discharge of 30 L/min. The vertical and horizontal water levels as well as the vertical erosion process are measured using one digital camera installed in front of dike embankment, while the horizontal erosion process was measured using another digital camera installed in front of downstream slope. Two types of coarse sand and very silty sand soils are used to construct dike embankment in small flume channel. The small flume is constructed from transparent PVC material to observe the development of water distributions and erosion processes with sediment box to collect the eroded materials. A pilot channel is cut in dike crest along the side wall of small flume channel to initiate breach channel in the dike crest. The initiation of breach channel is crucial for the evolution breach channel failure in the downstream and upstream slopes. The results show that the vertical and horizontal water levels are distributed faster in coarse sand soil compared with those in the very silty sand soil while the horizontal water levels are distributed faster than vertical water levels for both soils. The permeability of coarse sand increases the velocity of water flow for occupation soil particles and beginning failure in dike crest faster. The presence of fine particles in the very silty sand has reduced the rate of erosion processes inside dike particles in horizontal and vertical directions. The fine particles absorb a large amount of water content and, thus reduce the easiest water infiltration into particles with higher matric suctions. The analyzing of the distributions of water levels and erosion process help to understand the behavior of dike embankment during overtopping failure and increase the maintenance for dikes parts to reduce the potential danger.

CFD modeling a fluidized bed large scale reactor with various internal elements near the heated particles feeder

A numerical study of the fluidized bed industrial reactor in the presence of various internal elements is carried out by CFD methods A simple reactor heating efficiency function of chemical reaction with heat absorption is considered. The main emphasis is placed on the circulation flows of the catalyst particles and heating of the reactor. The analysis of the impact of various design elements on the heating efficiency of the reactor is carried out. Particular attention is paid to the possibility of baffles applying, which allows redirecting the flow. This effect may have an especially important value when the rapid heating of the reactor is required for temperature dependent reactions. The influence of heated catalyst feeder design on the efficiency of whole reactor heating is educed. The influence of the fractional composition of the catalyst, namely the presence of fine particles, on the reactor heating efficiency for different reactor design features is also studied. The results are carried out for a specific reactor example, but contribute to the overall branch of fluidized bed engineering.