Classification Of Fine Particles Research Articles

Morphological classification of fine particles in transmission electron microscopy images by using pre-trained convolution neural networks

Morphological classification of fine particles in transmission electron microscopy images by using pre-trained convolution neural networks

Study on the Application of a Reflux Classifier in the Classification of Ultrafine Ilmenite

Mineral classification is an important preparation operation in the process of beneficiation. The classification effect directly affects the production capacity of grinding machines, product quality, subsequent separation of the concentrate grade, and recovery. To improve mineral classification accuracy and provide technical ideas for enriching the separation of fine materials, this paper proposes the use of a trapezoidal inclined channel agitated reflux classifier (TARC) to classify ultra-fine ilmenite. The principle of this separating system is based on a hindered settling effect and fluidization theory. This study focuses on the factors influencing the particle separation through the optimization of different experimental conditions. A satisfactory 10 µm classification efficiency of 67.89% could be obtained when the ore pulp concentration was 15%, the agitation speed was 350 r/min, and the underflow flux was 16 cm3/min. The TARC realized a continuous feeding classification of fine particles within a narrow particle size range, with 10 µm as the limit size, and an effective reduction in the entrainment of fine particles in the underflow and coarse particles in the overflow phenomena, thus achieving improved classification efficiency.

New challenges for gravity concentration and classification of fine particles

“The net zero emission” mantra may prove to become the new “mother of invention” for minerals processing. The need for change is locked in, and rising, creating new opportunities, especially in gravity concentration and classification. The challenge is to identify and deliver what is required.This paper is concerned with the gravity concentration and classification of particles in a medium of water, involving particles typically finer than 1.0 mm. One of the greatest challenges is in delivering large scale, highly efficient, desliming at ∼10 μm to overcome the effects of viscosity, and in turn maximize the value of the resource. This need is most apparent in one of the world’s most significant commodities, iron ore.There should also be a much greater role for gravity concentration across this full-size range, increasingly in the range below 0.1 mm, the historical preserve of flotation. If the particle density can deliver sufficient selectivity, then in principle gravity concentration should be considered. This is especially true where reverse flotation is deployed, which requires a multi-stage flowsheet, very large footprint, and chemicals, to deliver what could be achieved in a single physical stage of gravity concentration. Mechanisms for amplifying segregation forces, including G forces and inclined settling, need to be exploited to deliver the necessary solids throughput.Classification will be challenged by the emerging requirements for gravity concentration, comminution, and coarse/fine particle flotation circuits to ensure beneficiation can straddle two decades in size ranges from 1.0 to 0.1 mm down to 0.1 to 0.01 mm, via classification at an intermediate size, nominally 0.1 mm. While in principle mechanical screens offer ideal classification, the hydrodynamic approach may ultimately deliver the optimum robustness, control, throughput, and efficiency, despite the variation in separation size with particle density, provided synergy can be realised by integrating it correctly within the overall circuit.

Morphological and chemical classification of fine particles over the Yellow Sea during spring, 2015–2018

Airborne fine particles can affect climate change and human health; moreover, they can be transported over significant distances. However, studies on characteristics of individual particles and their morphology, elemental composition, aging processes, and spatial distribution after long-range transport over the Yellow Sea are limited. Therefore, in this study, we conducted shipborne measurements of fine particulate matter of less than 2.5 μm in diameter (PM2.5) over the Yellow Sea and classified the individual particles into seven types based on their morphology and composition. Overall, the percentage of organic-rich particles was the highest, followed by that of sea spray, sulfur-rich, dust, metals, fly ash, soot, and other particles. Near Shandong, China, the percentage of fly ash and sulfur-rich particles increased, while an increased percentage of only sulfur-rich particles was observed near the Korean Peninsula. In the open sea, the PM2.5 concentrations were the lowest, and sea spray particles predominated. During the cruises, three types (Types 1, 2, and 3) of events with substantially increased PM2.5 concentrations occurred, each with different dominant particles. Type 1 events frequently featured air masses from northern China and Mongolia with high wind speeds and increased dust particles. Type 2 events involved air masses from China with high wind speeds; fly ash, soot, organic-rich particles, and the sulfate percentage in PM2.5 increased. Type 3 events displayed stagnant conditions and local transport (from Korea); soot, dust particles, and the secondary sulfate and nitrate percentages in PM2.5 increased. Thus, different types of transport affected concentrations and dominant types of fine particles over the Yellow Sea during spring.

A review of process models for wet fine classification with high frequency screens

Size control of particulate material is key in a mineral processing plant, allowing the downstream process equipment to separate the mineralogical components. Despite being extensively applied in millimetric particle size classification, recent advances in high frequency screens have allowed their application in grinding circuits, leading to production increases and better classification efficiency for the micrometric range. The development of models to simulate these systems is essential to allow estimating possible technological benefits in the plant performance. This study presents a review of models applied to screening processing, focusing on the wet classification of fine particles, and considering their applicability and limitations. The models review is combined with an assessment of their fitness to a high frequency screening trials database. Among the available alternatives, the model developed by Batterham et al. [1] presented the best fit to the dataset, but it has limited simulation capability. Mwale [2], in turn, was considered to offer the best compromise between fit to data and simulation readiness, since it does not demand a difficult sampling campaign and individualizes the process parameters from the model constants. However, a technology gap is still present, which would involve scale-up procedures from small-scale trials to industrial plants, since all the test work was developed using a real scale device.

Classification of Fine Particles Using the Hydrodynamic Forces in the Boundary Layer of a Membrane

AbstractThe wet classification of particles < 10 μm is a complex process that has been researched for many years. In this study, the usage of a modified cross‐flow filtration process as a classification process was investigated. With this process, particles in a fine micrometer range can be separated from suspensions. The upper particle size is dependent on hydrodynamic forces. The experimental results were compared with different hydrodynamic force models to predict upper size. The influence of the permeate flux and the particle concentration in the feed on the upper particle size is studied.

Study on the Classification of Fine Particles by Using a Multi-step Hydrocyclone for the Recycling of Waste Concrete Slurry

Study on the Classification of Fine Particles by Using a Multi-step Hydrocyclone for the Recycling of Waste Concrete Slurry

Behavior of Ultra Fine Particles in Electric Field.

The behavior of ultra fine particles in an electric field was measured in order to apply it to classification of fine particles. The sample particles used are spherical polystyrene particles with the average size of 0.03, 0.1, 1.0, 4.3 and 9.6 µm. The forces acting the particles in an electric field are considered to be electrical force, friction force and some other forces like the asymmetric effect and electrophoretic retardation effect which appear in ionic behavior. We found that the moving velocity of particles depends on the particle size. When the particle size is less than 1 µm, the velocity increases with increasing the particle size. On the other hand, the velocity deceases with an increase in the particle size, when the particle size is larger than 1 µm. We can apply the behavior to classification of fine particles. The phenomena could be explained by various forces acting the fine particles in the electric field.

Process monitoring and control for constant separation conditions in centrifugal classification of fine particles

Due to their high centrifugal acceleration tubular bowl centrifuges enable the separation and classification of fine particles. However, this type of centrifuge which is operated in a semi-continuous mode has a major disadvantage: sediment buildup in the rotor leads to a successive degradation of separation conditions over process time. In this study, a light scattering sensor was used to monitor this mechanism online by measuring the solids concentration in the overflow. Polyvinylchloride (low micrometer range) and fumed silica particles (nanometer range) served as experimental products. By incorporating the sensor signal in a control loop with the speed of the centrifuge, the mentioned drawback was compensated. As a result, grade efficiency and product loss were kept constant up to a high filling level of the rotor. It is outlined how this technology can be used for very demanding classification tasks, especially in case of fine, low-density materials.

Effects of gas flow and turbulent diffusion on the centrifugal classification of fine particles

Tthe mass movement of fine particles and changes in their trajectories under the effect of centrifugal, gravitational, and aerodynamic forces is studied by numerical modeling of turbulent swirling flow. The effect of turbulent migration of solid particles due to pulsating gas flow velocities on the aerodynamics of particles and, consequently, on the efficiency of the process of separation of particles by size is analyzed. The studies revealed the behavior laws of probability curve of separation of particles by size and showed the effect of regime and geometric parameters on the process of classification of fine powders.

Classification of Fine Particles in High‐Speed Centrifuges

AbstractThe classification of dispersed particles below 1 μm is a difficult task due to the high surface area‐to‐volume ratio. Tubular‐bowl centrifuges offer high centrifugal numbers, which enable the separation and classification of fine particles, biological cells and cell debris. This work presents the classification of two fine products with a mean particle size below 1 μm. Polydisperse silica and polystyrene were split successfully into a fine and a coarse fraction by a semi‐continuous tubular‐bowl centrifuge. The fine fractions exhibited narrow particle size distributions. An optimization of the process could be achieved by a comprehensive understanding of the flow patterns, which are accessible with computational fluid dynamics. The axial and tangential velocity profiles were calculated for rotational speeds up to 40,000 rpm and throughputs ranging from 0.1 to 2 L/min.

Continuous fine particle classification by water elutriator with applied electro-potential

In order to classify fine particles in slurry continuously, a horizontal type water elutriator with electrical potential is newly developed. The experimental classification performance was compared with the numerical calculation. Test particles used were pure silica particles with the mass median diameters of 3.5 and 2.5 μm. The effects of inlet flow rate, slurry concentration, applied electro-potential and the shape of inlet on the classification performance were also studied. The classification accuracy increased by applying the electro-potential and the cut size decreased with an increase in the electro-potential. The classification performance with a three-layer inlet was higher than that with a two-layer inlet. The experimental data agreed well with the numerical calculation. It is further shown that the 50% cut size was about 1 μm for a relatively short time, and the newly developed water elutriator is, therefore, effective for the classification of fine particles in slurries.

Spontaneous classification of functional fine particles by dynamics of the precipitation bands

When an outer electrolyte diffuses into a gel containing an inner electrolyte, rhythmic patterns of precipitate are formed, which is known as the Liesegang phenomenon. The patterns are static and stationary in the sense that the formed precipitation objects stay at the given position. Dynamically changing precipitation patterns can be formed if the complex formation of precipitate is possible. In this study, spontaneous appearance of traveling waves, spiral formation and chemical turbulence of precipitation bands is reported. The formation of spatiotemporal patterns allows us to spontaneous classification of fine particles because size distribution of particles varies with location. We investigated the effect of the inner electrolyte and gel concentrations on morphology of precipitation bands.

電圧印加型の水簸装置による微粒子の高精度分級

In order to classify fine particles in slurry continuously, a horizontal type water elutriator with electro potential is newly developed. The experimental classification performance was compared with the numerical calculation. Test particles used were pure silica particles with the mass median diameters of 3.5 and 2.5μm.The effects of inlet flow rate, slurry concentration, applied electro-potential and the shape of inlet on the classification performance were also studied. The classification accuracy increased by applying the electro-potential and the cut size decreased with an increase in the electro-potential. The classification performance with a three-layer inlet was higher than that with a two-layer inlet.The experimental data agreed well with the numerical calculation. It is further shown that the 50% cut size was about 1μm for a relatively short time, and the newly developed water elutriator is, therefore, effective for the classification of fine particles in slurries.

303 微粒子分級の高精密化に関する研究

303 微粒子分級の高精密化に関する研究

Industrial classification in a new impeller wheel classifier

Air classification is an important process step to optimize product quality. Especially after a grinding process, a certain amount of fine particles has to be removed. The reduction of fine particles above 10 μm is state-of-the-art. Particles below 10 μm are still difficult to separate if a high sharpness of cut is required or if particles have a low density. In order to realize economical production rates in the range below 5 μm, a reasonable throughput has to be achieved. The newly developed MikroCut MC was designed to enable optimized conditions for the classification of fine particles. The MikroCut MC classifies particles from a few 10 μm down to the submicron range. Very fine particle size distributions could be produced, e.g., talcum with 97% below 1.7 μm and a throughput of several 100 kg/h. Results with powder coatings show, for instance, that the yield of coarse material could be increased by 22% in comparison to existing technology. This is equivalent to a reduction in product loss of more than 70%.

Classification of Fine Particles

ABSTRACT Experimental results with two new classifiers for in-line and off-line operation are presented. The first type is a cyclone classifier, in which the vortex finder is exchanged with an impeller wheel enabling cut sizes between 5 and 100 µm. The second classifier is a high-end model, aiming at cut sizes in the range of l µm This classifier consists of a flat housing with tangential feed of product and secondary air. Experimental results with limestone, powder paint, and talcum are presented. The influence of main parameters such as air flow rate, circumferential velocity, and mass loading on the grade efficiency, as well as fines and coarse yield, will be discussed.

Basic Study on Classification of Fine Particles in Almost Rigidly Rotating Flow. 5th Report. Numerical Aanlysis of Classification Efficiency.

A numerical analysis on the classification of fine particles in an almost rigidly rotating flow is reported. The almost rigidly rotating flow between a coaxially rotating housing and a rotor can be regarded as a system for classification. The flow consists of an Ekman layer, an interior region, a Stewartson layer and a rigidly rotating region. The numerical method is composed of two stages. The first stage involves numerical simulation of the flow field using Navier-Stokes and continuity equations. The second stage involves computation of fine particle motion through the almost rigidly rotating flow. The mechanism of classification of the system is considered using the numerical results. The partial fractional efficiency of the system is computed for various particle diameters and flow parameters ; then the cut size and sharpness index of the system are estimated.

Basic Study on Classification of Fine Particles in Almost Rigidly Rotating Flow. 4th Report. Experimental Consideration of Classification Efficiency.

We took into consideration the classification efficiency in our experiments of an almost rigidly rotating flow between the rotating housing with a spherical wall and the rotor with combined spherical and cylindrical walls. The conclusions are as follows. (1) We obtained the highest sharpness index value of 1.25, which is comparable to that of the recent centrifugal classifiers, in spite of the low rotation number. (2) The values of the cut size and the sharpness index decrease with decreasing Ekman number (rotation number) or Rossby number (through-flow rate). (3) The dispersion rate of feed particles is improved by installing a dispersion nozzle and an orifice near the classification field.

Basic Study on Classification of Fine Particles in Almost Rigidly Rotating Flow. 3rd Report, Conditions of Occurrence of a Stable Regime of Almost Rigidly Rotating Flow.

We have experimentally investigated the conditions of occurrence of a steady axisymmetric flow regime and the velocity distributions in the interior region and the Stewartson layer for an almost rigidly rotating. through-flow in a concentric-sphere system and a disk-cylinder system (the rotor and housing walls consist of disk and cylinder surfaces). The conclusions are as follows. (1) The steady axisymmetric flow regime occurs when ε≤2.0E0.48 in both systems, where ε and E are the Rossby and Ekman numbers, respectively. (2) The experimental results of the velocity distributions in the interior region agree with their linear analytical solutions. (3) The absolute value of the axial velocity component increases downstream and with a decrease of the Ekman number in the Stewartson layer along the rotor in the disk-cylinder system. (4) The reverse flow in the Stewartson layer which occurs in the gap between the rotor and housing walls is prevented by narrowing the gap.