Characteristics Of Fine Particles Research Articles

DEM-CFD coupling verification and analysis of a sand control medium structure with weakened particle blockage performance

This study addresses the prominent contradiction between solid phase control and production capacity release during the exploitation of natural gas hydrate in fine silty sand reservoirs. A novel mechanical sand control medium structure incorporating the filter slots/nets (referred to as the sand control component, SCC) and the cylindrical/spherical structures placed outside the SCC (referred to as the blockage control component, BCC) has been designed. Concurrently, a DEM-CFD sand-retaining numerical model is developed, and the traditional/new structural screens have been separately simulated for sand retention. Through the spatiotemporal evolution of DEM and CFD characteristic model parameters during simulation, the blockage mechanism and characteristics of fine particles are obtained. Compared to the traditional screen structure without a BCC, the existence of a BCC effectively evacuates particles within the accumulated sand body towards the wellbore, reducing the compactness and stress level within the sand body; while the pressure loss generated by fluid flow through the sand body decreases, significantly improving the porous and permeable conditions within the sand body. The degree of influence of a BCC on different DEM and CFD characteristic model parameters is further determined and ranked. A comprehensive blockage optimization index is introduced to quantify the performance of weakening sand blockage by the BCC and optimize the spatial position of the BCC. The BCC enables the design of sand control schemes to reduce the filter aperture of the SCC to a sufficiently small size to effectively control the fine silty sand production, while avoiding gradually severe blockage as production progresses.

Particle deposition and clogging as an Obstacle and Opportunity for sustainable energy

Fine particle motions have significant implications in porous media, manifesting in various natural phenomena and industrial applications. The movement of particles can lead to channel blockage, resulting in clogging. Depending on the context, clogging can be either advantageous or detrimental. At the scale of fine particles, physiochemical interactions play a crucial role in the clogging process. To examine the influence of these interactions, we have coupled the Derjaguin-Landau-Verwey-Overbeek (DLVO) theory into the Computational Fluid Dynamic-Discrete Element (CFD-DEM) approach. Aside from the physical properties of the fracture systems and the characteristics of fine particles, the injection rate also plays a pivotal role in clogging occurrence. Consequently, we investigated 10 different injection rates and modeled 20 simulation setups with identical particle insertion rates to concurrently analyze the effects of the DLVO theory and injection rate. Our study focused on examining the impact of these parameters on particle behavior in various regions of the domain, including particle-particle force, fluid-particle force, transitional velocity, rotational velocity, fluid velocity, and fluid-particle momentum exchange. Our findings reveal that the DLVO force significantly influences fluid and particle characteristics within the throat blockage. Our results indicated that DLVO consideration increased the particle concentrations by more than 40% before the throat. Moreover, our results demonstrate a transition between different injection rates, where a slight change in injection rate (i.e., 0.06μm/s) can change the system's behavior. We identified a critical fluid injection rate, whereby injecting fluid into the system at a rate surpassing the critical velocity can prevent clogging, while lower rates result in clogging occurrence.

Characteristics of fine particles from incense burning at temple premises of Kathmandu Valley, Nepal.

The impact of incense burning on ambient air quality was investigated by measuring the concentrations of fine particles (PM2.5), elemental carbon (EC), organic carbon (OC), and their oxidative potential (OP) at three temple premises in Kathmandu Valley, Nepal. These temples, namely, Bajrabarahi, Bagalamukhi, and Bhadrakali, are located in three distinct environments: forest, residential, and roadside, respectively. During the incense burning event days, the PM2.5 concentration at Bhadrakali (431.4 μgm-3) was significantly higher than that measured at the Bagalamukhi (135.2 μgm-3) and Bajrabarahi (84.7 μgm-3) temple premises. This observation is consistent with the fact that Bhadrakali Temple had the highest intensity of incense burning. Additionally, the temple premises were also influenced by vehicular emissions from transportation facilities. Carbonaceous aerosols significantly increased during incense burning events, indicating that incense burning contributes significantly to the formation of primary and secondary OC. Moreover, the OP of PM2.5 during the incense burning event days was higher compared to non-event days (p < 0.05), suggesting an elevated health risk due to the increased concentration and toxicity of fine particles. These findings highlight the substantial impact of incense burning on air quality in temple premises, emphasizing the need to implement effective strategies to mitigate the associated health risks.

Dynamic changes in the characteristics of fine particles and their oxidative potential in the city of Taj (Agra, India): the untold story of fireworks display

Dynamic changes in the characteristics of fine particles and their oxidative potential in the city of Taj (Agra, India): the untold story of fireworks display

Characteristics of Fine Particles during Cold Front Passage in Busan, on March 19, 2020

Characteristics of Fine Particles during Cold Front Passage in Busan, on March 19, 2020

Study on Fine Particle Flow Characteristics with Different Air Supply Parameters

With the help of FLUENT software, the flow characteristics of fine particles in the upper air supply room with different air supply parameters were studied. The particle trajectory model was established to calculate the concentration distribution characteristics of fine particles in the upper air supply room, and the optimal air supply parameters in the working area of the personnel were researched to reduce the impact of the particles on the human health. By calculating the distribution of air flow field and particle concentration under four different air supply parameters, the optimal operating conditions were obtained by comparative analysis, that is, the air supply temperature was 20°C and the air supply speed was 3m/s, which provided a theoretical basis for the setting of the air supply parameters of the upper air supply room in the future.

Characteristics of Fine Particles at Roadside and Urban Residential Locations in Busan

Characteristics of Fine Particles at Roadside and Urban Residential Locations in Busan

Effect of wet flue gas desulfurization (WFGD) on fine particle (PM2.5) emission from coal-fired boilers.

In this study, the characteristics of fine particles before and after wet flue gas desulfurization (WFGD) in three coal-fired heating boilers in northern China were investigated by using a dilution-based emission sampling experimental system. The influences of the WFGD process on the mass and number concentrations as well as the chemical composition of fine particles were analyzed. The removal efficiency of desulfurization processes on particulate matter mass was 30.06%-56.25% for the three study units. The WFGD had a great influence on the size distributions of particle mass concentration and number concentration. A significant increase in the number and mass concentration of particles in the size range of 0.094-0.946 μm was observed. The water-soluble ion content accounted for a very large proportion of PM2.5 mass, and its proportion in PM2.5 increased from 28.39%-41.08% to 48.96%-61.21% after the WFGD process for the three units. The desulfurizing process also drastically increased the proportion of cation component (Ca2+ for unit A, Mg2+ for unit B, and Na+ for unit C) and the proportion of SO42- in PM2.5, and it increased the CE/AE values of PM2.5 from 0.82-0.98 to 0.93-1.27 for the three study units.

Commentary on “Experimental study on the moving characteristics of fine grains in wide grading unconsolidated soil under heavy rainfall” by CUI Yi-fei, ZHOU Xiao-jun and GUO Chao-xu

A paper, which was recently published in Journal of Mountain Science by Cui et al. (2017), reported a series of laboratory flume experiments designed to illuminate the moving characteristics of fine particles for wide grading unconsolidated soils by considering three factors, slope gradient, rainfall duration and rainfall intensity. This commentary is prompted to further provide some viewpoints about the fine particle migration phenomenon during landslide initiation and offer some recommendations as the future research focus for better understanding the related processes.

Understanding of formation mechanisms of fine particles formed during rapid pyrolysis of biomass

Fine particles formed during pyrolysis are the precursors of particulate matters (PM) after combustion and/or gasification. This study aims to conduct a preliminary research on the characteristics of fine particles. The rapid pyrolysis of raw and acid-washed biomass was conducted in a drop tube furnace (DTF) with a wall temperature 1073–1473 K and varied residence times. Components of fine particles formed during rapid pyrolysis were determined by investigating their morphologies and element contents. Particle size distributions (PSDs) of fine particles were also measured by granulometry technique. The results showed that the yields of fine particles increased significantly with increasing pyrolysis temperature. PSDs of fine particles formed at different conditions varied from each other, and trimodally distribution was identified for fine particles derived from pyrolysis of raw biomass at 1473 K. Those independent fine particles consisted of abundant small fragments, and slight soot and ash particles. The size of soot and melting ash particles increased with residence time and temperature, and the size ranges of small fragments broadened as residence time increased.

Entrainment characteristics of fine particles under high speed airflow

Fine silicon particles (mean size of 2.7 μm) are used as entrained materials, and the entrainment characteristics of fine particles are investigated in a cylindrical fluidized-bed (inner diameter of 28 mm and height of 1000 mm) under high speed airflow. The effects of the volume flow of gas (Q , 1 m3 /h to 2.5 m3 /h), the number of holes (N , 1 to 4), the size of holes (D , 1 mm to 3 mm), and the distance between holes and the upper surface of the material layer (H , -100 mm to 200 mm) on the entrainment characteristics (entrainment rate W and entrained powder-gas ratio R ) are experimentally studied through orthogonal experiment. The experimental results show that an increase in Q and H constantly improves the entrainment characteristics; a decrease in D enhances such characteristics, whereas the number of holes N has no significant effect on the entrainment characteristics. An optimal operating condition can result in optimal entrainment characteristics (W , 3.1 g/min and R , 0.058 g/g), which can be achieved with a Q of 2.5 m3 /h, N of 1, D of 2 mm and H of 200 mm.

A study on the distribution characteristics of fine particles from manufacture of oriental herb medicine

A study on the distribution characteristics of fine particles from manufacture of oriental herb medicine

Filler from crushed aggregate for concrete: Pore structure, specific surface, particle shape and size distribution

Characteristics of fine particles (0–125μm diameter) from seven different crushed and natural sands from five different Norwegian rock types were determined. The results suggest that the same water absorption values, as determined by EN 1097-6 on coarser sand fractions, can be applied to the fines. The values of specific surface area measurements vary widely between different materials and between different measurement methods. BET measurements seem to be strongly affected by the mineralogical composition (presence of mica) and surface morphology (weathering) of the particles. Specific surface area calculated from the particle size distributions (PSD) is mainly dependent on the precision of the test methods in the size range below about 3–5μm, because these small particles contain most of the surface area. Shape measurements by both Dynamic Image Analysis (DIA), which is a 2-D method, and X-ray microcomputed tomography (μCT), which is a 3-D method, have yielded similar relative length-to-thickness aspect ratios of the particles between different mineralogies, though with lower absolute values for DIA due to 2-D projection of 3-D quantities.

The Distribution Characteristics of Fine Particles by Flow Cytometry in the Yangtze Estuary and the Adjacent East China Sea

The fine particles play a major role not only in complex processes of estuarine area but also in the distribution, transfer and transformation of pollutants in the estuarine environment. In this study, fine particles were detected and analyzed by flow cytometry in the Yangtze Estuary and the adjacent East China Sea. Two groups of organic autotrophic particles (R1 and R2) were detected by flow cytometry analysis. Another group of R3 was organic but nonliving, or inorganic particles. Particles of R1 and R2 only represent between 0.18% and 3.16% of total particles at the sampling stations. Particles of R3 dominated the estuarine stations. Their concentration had large fluctuations. We observed a seaward decrease in the number of organic nonliving particles and inorganic particles. Flow cytometry made it possible that study on the dynamics of fine particles. It is important in discovering the transfer mechanism and environmental behavior of fine particles in the estuarine area.

Chemical characteristics of fine particles during spring dust storm dominant period in two Chinese cities, Baotou and Wuwei

Chemical characteristics of fine particles during spring dust storm dominant period in two Chinese cities, Baotou and Wuwei

P‐95: Behavior of Fine Particles in Mobile Fine Particle Display (MFPD) Cells

AbstractWe proposed a novel display mode, which is called a Mobile Fine Particle Display (MFPD) with liquid crystal, the fine particles are moved to a horizontal direction for switching the display by the applied electric field. Fine particles are migratable by the synergistic effect of the flow of liquid crystal and the electrophoresis of the fine particles. In our MFPD cells, we measured the migration characteristics for the particles with both the organic type and the inorganic type depend on the cell temperature. It was proven that the temperature is high in the MFPD cells, quality of migration characteristics of fine particles which are the inorganic is better than that of the organic type.

Hydrodynamic characteristics of fine particles in the riser and standpipe of a circulating fluidized bed

The hydrodynamic properties in the riser and standpipe. and the cyclone efficiency have been determined in a circulating fluidized bed (CFB) unit consisting of a riser (0.05 m-IDX3.8 m high), a standpipe (0.068 m-IDX2.5 m high) as a primary cyclone/bubbling fluidized bed, and a secondary cyclone. Silica gel powder (mean diameter = 46 μm) was used as the bed material. The effects of gas velocity in the riser and initial solid loading on the solid circulation rate, and the solid holdups in the riser and standpipe have been determined. The effects of gas velocity in the standpipe on the efficiencies of primary and secondary cyclones have been also determined as functions of solid circulation rate and solid entrainment rate. The solid circulation rate increases with increases in the gas velocity in the riser and in the initial solid loading. The efficiencies of primary and secondary cyclones increase with an increase in the gas velocity in the riser. However, the efficiency of primary cyclone decreases and that of secondary cyclone increases slightly, with an increase in the gas velocity in the standpipe.

Effect of Production Conditions on Characteristics of Fine Particles by Spray-Pyrolysis.

Effect of Production Conditions on Characteristics of Fine Particles by Spray-Pyrolysis.

特集 微粉末・微粒子・超微粒子技術 微粒子の特性とその工学的応用

特集 微粉末・微粒子・超微粒子技術 微粒子の特性とその工学的応用

Electrostatic Aggloaration of Fine Particles in the Electrostatic Precitator

This paper was dealt with the characteristics of fine particles in the electric field with corona discharge. The experimental apparatus Was consisted with the needle type electrodes and cylindrical type collecting tower. The generator has rather high voltage up to 120kV, and dusty gas was induced tangentially into the bottom of the tower. The measurements distribution at each vertical section of the tower were carried out to observe the agglomeration phenomena. From these measurements the agglomeration velocity was assumed.