Production Of Fine Particles Research Articles

The impact of glacier retreat on Andean high wetlands: Assessing the geochemical transfer and sediment provenance in the proglacial area of Huayna-Potosí (Bolivia)

The accelerated decline of tropical Andean glaciers is affecting the water cycle of mountains in the region. In the Cordillera Real (Bolivia) on the Huayna-Potosí peak (6088 m a.s.l.), the rapid retreat of the Oeste Glacier is exposing new rock outcrops and glacial materials. Changes in the hydrological regime by glacier retreat are likely to modify the supply of sediments and subsequently affect the geochemical transfer of particle-bound elements within proglacial and downstream ecosystems. To address this issue, a sampling campaign in the proglacial area of Huayna-Potosí aimed to identify and collect sediments from the primary active landforms. To characterise elemental transfer and identify sediment provenance using fingerprinting techniques, streambed sediments were collected along the main stream from the glacier tongue at 5002 m a.s.l. to a wetland shallow lake at 4700 m a.s.l.. Geomorphological features control the production of fine particles and the distribution of particle-bound geochemical elements. Complex processes of solubilization, mobilisation, and retention govern the elemental transfer. Significant increases in 238U, as well as some major elements, were observed in the surface lake sediments, while Pb, Cr, and Cu decreased, and 137Cs was not detected. The spatial distribution patterns of geochemical elements and the assessment of the sediment provenance indicate that deglaciation fosters geochemical processes and the elemental transfer dynamics in the wetlands. Moraines and colluvium were found to be the primary contributors to sediment yield (93 %) while the rich organic soils in swamps contributed the least (7 %). The enhanced supply of sediments to the shallow lake in parallel to glacier decline may affect water quality and bring about further changes in the wetlands. Identifying primary sediment sources is essential for water management. Our findings enhance understanding of the compositional characteristics of mobilised sediment and their variations, aiding in more effective resource management to preserve these high-altitude wetlands.

Continuous synthesis of drug particles via spray drying of emulsions obtained by mechanical emulsification and ouzo effect

In the pharmaceutical field, nanoparticle formulation is an effective approach to improve the solubility of poorly water-soluble drugs. Spray drying is used for the synthesis of fine drug particles. The particle size obtained by spray drying generally depends on the size of the sprayed droplet. In this study, an emulsion spray drying method is proposed as a novel method for nanoparticle synthesis. Oil-in-water (O/W) nanoemulsions containing oil-soluble drugs were prepared. Spraying O/W emulsions could produce fine particles with the size of 122 nm. The particles obtained by emulsion spray drying were smaller than those obtained by spray drying without an emulsion. Furthermore, an Ouzo emulsion, which is a self-emulsification method, was investigated to improve the particle yield. The particles obtained by spray drying of the Ouzo emulsion had the size of 0.50 μm, which was smaller than those obtained without the Ouzo emulsion. Moreover, in-vitro dissolution tests were performed to evaluate the solubility of the obtained particles as well as the unprocessed drug powder. The particles obtained via spray drying of the Ouzo emulsions showed the highest dissolution rate. In summary, spray drying of O/W and Ouzo emulsions resulted in the production of fine drug particles.

INVESTIGATION OF ENERGY - TECHNOLOGY DEVELOPMENT IN ULTRA FINE GRINDING

Ultra-fine grinding refers to the process of reducing materials to extremely small particle sizes, typically in the micron or submicron range. It is commonly used in various industries such as mining, pharmaceuticals, ceramics, and chemicals, where the production of fine particles with specific properties is required.
 Energy plays a significant role in ultra-fine grinding processes. The reduction of materials to such small sizes requires a considerable amount of energy input. The energy consumption in ultra-fine grinding is typically higher compared to conventional grinding methods due to the higher surface area and increased particle-particle interactions.
 In the mining sector, with the depletion of high-grade ore deposits, it has become a necessity to operate very low-grade ore deposits with very small particle liberation sizes. In the enrichment of these ores, most of the energy required is spent on grinding. In micronized grinding, conventional mills (such as rod and ball mills) lose their efficiency and become uneconomical. 
 most of the energy spent in conventional mills is used directly in size reduction, and a significant portion is lost as heat and sound without doing any useful work (size reduction). In addition, for grinding below 75 µm , the efficiency of conventional mills is greatly reduced (energy consumption increases excessively), and grinding becomes uneconomical. 
 In this study, alternative fine and ultrafine grinding mills for ore dressing plants are introduced, and information about their working principles is presented. Unlike other studies, information on particle and grinding energy calculations is given. The reasons for the lack of a theory or model to perform newly developed calculations for ultrafine grinding theories are tried to be explained.

Evolutionary mechanism and particle characterization analysis of dust produced by wet-mix shotcrete in tunnels

Wet-mix shotcrete, an essential form of concrete support, has been widely applied in underground constructions such as tunnels and mines. This study analyzed the gas jet structure and particle velocity differential equations in the wet-mix shotcrete process and physicochemically characterized collected dust samples. Based on field measurements and laboratory analyses, we established an experimental platform and a numerical simulation model for wet-mix shotcrete to investigate dust generation characteristics. The results showed the following: 1) The particles generated during wet-mix shotcrete primarily consisted of cement particles, exhibiting a spherical and blocky shape with a relatively regular morphology. However, their surfaces possessed numerous burrs and pores, resulting in poor wettability. 2) Suspended aerosol particles mainly comprised particles below 10 µm, exhibiting a unimodal particle size distribution. Smaller particles showed a higher abundance, with particles below 2 µm accounting for over 95% of the total particles. 3) The dust generation during wet-mix shotcrete was significantly influenced by the compressed gas flow rate and material viscosity. An increase in the gas flow rate or material viscosity led to higher production of fine particles. This study elaborated the mechanisms underlying particle generation during wet-mix shotcrete, providing valuable insights for wet-mix shotcrete dust control techniques.

Thermodynamic and Kinetic Aspects of Gold Adsorption in Micrometric Activated Carbon and the Impact of Their Loss in Adsorption, Desorption, and Reactivation Plants.

The production and loss of fine particles of activated carbon (AC) loaded with gold in the adsorption processes is a worldwide problem, mainly due to the behavior of increasing its adsorption capacity with respect to the decrease in particle size, which becomes relevant to determine the thermodynamic and kinetic activity of the gold adsorption and the economic impact of its loss, with the escape towards the later stages of the system of adsorption, desorption, and reactivation (ADR) plants of AC. Through the adsorption of gold in a synthetic medium with sodium cyanide concentration, using different particle sizes, AC weights, and adsorption times, data were generated for analysis by three different isotherm models, resulting in a better tendency for the Freundlich isotherm, from which thermodynamic parameters of ΔG equal to -2.022 kcal/mol, ΔH equal to -16.710 kcal/mol, and ΔS equal to -0.049 kcal/molK were obtained, which shows that it is a spontaneous, exothermic process with a lower degree of disorder. The kinetic analysis was performed with two different models, from which the pseudo-second-order model was used due to a better tendency and displayed a behavior that leaves open the interpretation of the increase in adsorption with respect to the decrease in the AC particle size but demonstrated the importance of recovering these particles in relation to their gold concentration and the economic impact from their poor recovery, which, for this case study, amounted to ~0.3 million dollars per year.

Enhancing Fines Recovery by Hybrid Flotation Column and Mixed Collectors

The froth flotation technique can be considered one of the most efficient methods for the separation of minerals. Prior to utilizing any physicochemical separation method, the size of the mined ore must be decreased to facilitate the release of the valuable materials. This practice, along with the increased exploitation of ores that carry fine mineral particles caused the production of fine and ultrafine particles which are difficult to recover with classical enrichment methods, due to their different characteristics compared to coarser particles. It is established that fine and ultrafine particles are difficult to float, leading to losses of valuable minerals, mainly due to their low collision efficiency with bubbles. Moreover, fine particles require higher reagent consumption due to the fact that have a higher specific area, and finally, their flotation is limited by low kinetic energy. Flotation of fines can be enhanced by either decreasing bubble diameter or increasing their apparent size, or moreover, by enhancing the collector’s adsorption (their hydrophobic behavior) using alternative reagents (non-ionic co-collectors). In the present research, flotation experiments on a hybrid electrolytic flotation column that can produce microbubbles (−50 μm), were carried out for recovering fine magnesite (−25 μm) particles. In addition, the synergistic effect of anionic/non-ionic collectors were studied for the enhancement of fines recovery. Experimental flotation results so far designate the enhancement of fine magnesite particle recovery by approximately 8% with the addition of microbubbles. Finally, the synergistic effect of anionic/non-anionic collectors led to the improvement of flotation recovery by almost 12%.

Reaction Mechanism of Combustion Synthesized ZrC–2ZrB<sub>2</sub>-Based Cu Cermets

The reaction process of ZrC–2ZrB2-based Cu cermets from the (1 − x wt.%)(1B4C–3Zr)–x wt.%Cu system (Zr/B4C = 3 in molar ratio) was explored. Results showed that ZrC and ZrB2 were mostly produced through the dissolution of B4C into a preformed Zr–Cu liquid. With an increase in x, the synthetic ZrC–2ZrB2 and generated heat were reduced. This effect decreased an ability for Zr–Cu liquid to propagate in the reactants, and restrained the dissolution Zr. As a result, the complete synthesis of ZrC–2ZrB2 failed in the systems with a higher Cu content (e.g., 50 wt.%). Furthermore, after the precipitation of ZrC and ZrB2, the liquid surrounding would prevent ZrC and ZrB2 from growing. Increasing Cu content enhanced the amount of Zr–Cu melt. This behavior contributed to a decline in ZrC–2ZrB2 particle sizes, and the production of fine ceramic particles (∼200 nm). It is also revealed that the formation of ZrC–2ZrB2 is a multistep process, which results in the inhomogeneity of ZrC–2ZrB2 particle sizes. A valuable approach was proposed to explore the relationship between reaction process and synthesized products of combustion synthesis-related technique.

Fractal approach of particle size distribution description of ball milling products: effects of ore type, feed and particle size

ABSTRACT Samples used for this study include chalcopyrite and ilmenite ores. Feed size was divided into two fractions of (+2.38 −4) and (+2 −2.38) millimeters, from which different feeds with different weight and size percent values were fed to mill at three feeds of 750, 1000, and 1250 gr. Particle size distribution (PSD) resulting from grinding operation was investigated through fractal approach to calculate fractal dimension of PSD of products. Fractal dimensions for PSD of products were equal (2.41–2.63) and (2.49–2.60) for chalcopyrite and ilmenite ores, respectively. Fractal dimensions of products are increased by increasing weight of particles for fraction of (+2.38 −4) millimeters in mill feed. This can be attributed to increased coarseness of feed particles, leading to increased dispersion of the products’ PSD. Fractal dimension of products would be reduced with an increase in feed weight, which can be due to lower grinding rate of particles and, consequently, lower production of fine particles. Fractal dimensions obtained for chalcopyrite products were bigger than those of ilmenite once. Fractal dimension has a direct relationship with feed size and an inverse relationship with feed.

Effect of Sands on the Evolution of the Modulus of Deformability and Longitudinal and Transverse Elasto-Instantaneous Deformations as a Function of the Relative Constraint in Concrete

Abstract The production of crushed sand is accompanied by the production of fine particles. The proportion of these fine particles varies from one sand to another. The current publications of standards for reference in the construction industry have been adapted by increasing the limit of fine particles in crushed sand, but this is insufficient because sands with high rate of fine particles are not used in the industry. The principal objective of this study is to investigate the influence of crushed sands with different mineralogical natures (limestone and siliceous) and with varying proportions of fine particles on the evolution of the modulus of deformability and of longitudinal and transverse Elasto-instantaneous deformations. The experimental results showed that the longitudinal and transverse Elasto-instantaneous deformations and the modulus of deformability varied according to the nature of the sands (river sand, quarry sand, dune sand) and according to the fine content of the sands. Logarithmic regressions showed an accurate fit for the correlation coefficient R2. The test results demonstrated that deformations are influenced by sand type and indicated an optimal of 10% of fine particles. Empirical equations can predict the modulus of deformability from prismatic concretes.

Effects of Sulfur and Phosphorus on Binder Decomposition Behavior of Nickel Powder

Fine Ni particles are utilized as internal electrode materials for multilayer ceramic capacitors. Despite extensive research, the effects of the surface properties (additional elements) remain unclear. To the best of our knowledge, the present study is the first to demonstrate the effects of the addition of sulfur (S) and phosphorus (P) on surface modification and binder decomposition during the production of fine Ni particles. Scanning electron microscopy, X-ray diffractometry, thermogravimetry-differential thermal analysis, hydrogen temperature-programmed reduction, temperature-programmed decomposition, and X-ray photoelectron spectroscopy were performed to analyze non-doped Ni, S-doped Ni and P-doped Ni powder. S existed as S–O or Ni–S on the particle surface in the S-doped Ni powder, whereas P existed solely as P–O on the particle surface in the P-doped Ni powder. When formed into a paste with these powders, the decomposition temperature of the binder is lower than that of the binder alone owing to the catalytic effect of the unmodified surface of Ni in non-doped Ni. However, the catalyst poisoning effect of S in S-doped Ni and the coating effect of P–O in P-doped Ni suppressed the lowering of the binder decomposition temperature due to the catalysis of the Ni surface. The results of the present study are expected to inspire future research on the optimization of the manufacturing process of multilayer ceramic capacitors.

Effect of torrefied biomass on hydrophobicity and mechanical properties of polylactic acid composite

In this study, the physicochemical properties of torrefied biomass (larch and yellow poplar) were investigated based on torrefaction temperature. The effect of torrefied biomass on the hydrophobicity and mechanical properties of a polylactic acid (PLA) composites was evaluated. Hemicellulose was removed from the biomass during torrefaction, whereas the cellulose and lignin contents increased slightly. The color of the biomass changed from brown to black. The grindability of the torrefied biomass improved as the torrefaction temperature increased, which contributed to the production of fine particles (>100 mesh). A PLA composite was prepared using torrefied biomass (10 %) and polylactic acid. At 280 °C, water contact angle was the highest, regardless of the particle size and biomass species. Tensile strength of the PLA composite was slightly lower than that of PLA alone, regardless of the particle size of torrefied biomass. Nevertheless, the strength increased with the torrefaction temperature, except for larch with a relatively large particle size (<100 mesh). The tensile strength of the control was 68.0 MPa, whereas that of the torrefied biomass ranged from 61.1 to 65.8 MPa.

Analysis of grinding aid performance effects on dry fine milling of calcite

The control mechanism in the production of fine particles is important in dry grinding processes, which are popular in the grinding of some minerals. The behavior of the fine particles with each other and with the mill environment is complex and needs to be investigated in detail (on a micro-scale) in every application. One of the parameters controlling the fine particles in a mill is the use of the correct amount and type of grinding aid. Mechanisms of action must be understood well to develop grinding aids and fully utilize their positive effects. As a general explanation, with the use of grinding aids, the production tonnage can be increased at the desired product fineness, as well as achieving a finer product at the same production tonnage. However, it is necessary to know other mechanisms and effects to increase efficiency and correct use. The influence of grinding aids on the dry fine grinding of calcite using several analysis methods was revealed in the present study. Within the context, the results were assessed considering grinding performance (particle size distribution and size reduction ratio), product quality (color properties), flowability, adsorption properties (FTIR), and agglomeration behavior (SEM). Moreover, the tested effect of each grinding aid was discussed for each analysis, and the collected results were combined around a summary core diagram.

SUSTAINABILITY ASSESSMENT OF THERMAL AND MECHANICAL RECLAMATION OF FOUNDRY CHROMITE SAND

After usage, foundry chromite sand is recycled to reduce production costs and comply with environmental regulations. Thermal and mechanical reclamation are the most prominent methods of sand recycling. The sand reclamation techniques used in the foundry sector are typically not evaluated through the green alternative or environmental sustainability concept’s lenses. When contrasting mechanical and thermal reclamation, operational costs are the main factor to be taken into account. Therefore, this study compares mechanical and thermal reclamation of chromite sand by replicating the industrial processes in simulated laboratory tests. The methodology is designed to quantify the production of fine particles during reclamation, which has an array of negative effects on the environment, human health, the economy, and society. The findings show that, in general, mechanical reclamation produced more fine particles than thermal reclamation. The disparity in terms of fine percentage between the two processes could occasionally be as high as 15%. Therefore, mechanical reclamation was a less effective procedure than thermal reclamation when considering environmental sustainability, especially the impact on human health, which goes against conventional wisdom in the foundry sector. Keywords sand recycling; chromite sand; environmental sustainability; green process

Numerical simulation to estimate the droplet size in aerosol solvent extraction system

The aerosol solvent extraction system (ASES) is one of the emerging processes for the production of fine particles of pharmaceutical compounds. This process involves atomization of the solution (pharmaceutical compound + organic solvent) in an antisolvent environment. The atomized droplet comes in contact with the antisolvent, the latter diffuses into the droplet and the solvent evaporates from the droplet surface. This work presents a mathematical model to calculate the dynamic size of a droplet moving in a precipitator used in the supercritical antisolvent process. The system considered for this work is carbon dioxide (CO2)-dimethyl sulfoxide (DMSO). Two Film Theory of mass transfer is used to estimate the mass transfer to and from the droplet. This two-way mass transfer process results in extremely high, very rapid and uniform supersaturation, which leads to the formation of very small size particles with narrow size distribution. The simultaneous diffusion of CO2 and the evaporation of solvent from the droplet cause swelling of the droplet which may be followed by shrinking. The effects of process parameters such as nozzle diameter, flow rate on droplet size are also studied in this work.

Global automotive catalyst market (2020–2028) – Size, share and analysis report

Fourteen years of regulated air pollutants concentrations were analyzed in order to characterize the benefits of Brazil's emission control policies on air quality conditions and to evaluate the temporal patterns between 1996 and 2009 over the Metropolitan Area of São Paulo (MASP). MASP includes one of the largest cities in the world (São Paulo) and its light-duty vehicular fleet has a very important characteristic in that it uses, on a large scale, fuels such as ethanol derived from sugar cane and compressed natural gas. Nowadays, ethanol makes up more than 50% of the fuel used in Brazil. The frequent episodes with high ozone and PM10 concentration values in the MASP are mostly associated with vehicular emissions – primary emission of particles and gases enrolled in ozone photochemical production and formation of secondary fine particles. Although the fleet has increased at a substantial rate, annual mean values show a diminishing tendency for all pollutants except for ozone, which presents no significant tendency. This diminishing tendency in the analyzed period is due to the vehicular emission control program established by the Brazilian Government in 1986, called PROCONVE (Program for the Control of Vehicular Emission). Monthly mean values, as expected, show higher concentrations of all pollutants except for ozone during wintertime. The diurnal cycle of the pollutants in most of the stations shows two peaks, associated with rush hours, except for ozone, whose peak follows the maximum radiation incidence. Secondary (nocturnal) ozone concentration maxima were sometimes verified around three and four LST. Average values for weekdays and weekends showed that the different air quality stations showed different patterns for the pollutants. For ozone the concentrations were higher during the weekend when compared to weekdays.

Crust breakage in production of fine particles using pulse combustion drying: Experimental and numerical investigations

The mechanism that leads to fine particle production during pulse combustion drying is still unclear. Although droplet breakup could happen, it cannot result in particles below micron-size. Here production of fine particles during pulse combustion drying is investigated experimentally and numerically. Experiments with three different materials, namely SiO2, TiO2, and maltodextrin, have been conducted to see how the material types and process conditions influence the physical properties of the products. The results show that fine particles can be obtained with and without pulsation, and no significant differences are observed with the variation of pulsation frequency. The volume fraction of the fine particles is, however, very low. Based on these results, a model of particle production through repetitive crust breakage and drying cycles is proposed. The obtained results are in agreement with the experimental data, and the proposed mechanism could explain the production of fine particles with and without gas pulsation.

Photoluminescence studies and synthesis of BaSO3 Cl2 :Ce3+ blue-emitting lamp phosphor.

The photoluminescence excitation and emission spectra of BaSO3 Cl2 :Ce3+ phosphor were investigated. Excitation wavelength was 323 nm. The phosphor was prepared using a combustion synthesis method. The emission spectrum exhibited a well defined asymmetric band with a maximum at 445 nm for higher emission concentrations. The prepared samples were characterized by X-ray diffraction, scanning electron microscopy, photoluminescence and Commission Internationale de l'éclairage colour coordinates; emission intensity was related to relative Ce3+ concentration. These developments enabled the rapid and energy-efficient production of fine particles in the powder form with little expenditure. No additional emission band was observed in the emission spectra, demonstrating that the Ce3+ ion occupied one category of site in the prepared host phosphor.

Computational Study of Atomization Models and Optimal Design of a Pressurized Inhaler

Respiratory drug delivery has been under the spotlight of research for the past few decades, mainly due to rapid increase of pulmonary diseases. This type of drug delivery offers the highest efficiency for treatment. Despite its numerous benefits, there are some drawbacks in the method of respiratory drug delivery-the most important being poor delivery efficiency and high drug deposition in undesirable regions, such as the oropharynx. This study is focused on improving pressurized inhaler device, which is one of the most used devices for inhalation therapy throughout the world using the results and findings obtained from numerical analysis. In this study, three atomizer models are investigated and found that pressure swirl atomizer model closely represents the atomization phenomenon from a pressurized inhaler device. Parametric study is carried out using three parameters: nozzle diameter, dispersion angle and sheet constant to optimize the performance of the device. It is revealed that a reduction in nozzle diameter and dispersion angle help in generating fine (smaller diameter) particles, whereas increase in sheet constant is responsible for fine particle production. The values of nozzle diameter, dispersion angle and sheet constant are tuned to get the particles with minimum diameter as output which is desirable for the drug particles to get deposited in the smaller airways of lungs and increase the efficiency of drug delivery and improve the device performance.

Application of Enhanced Gravity Separators for Fine Particle Processing: An Overview

Beneficiation of low-grade ore is of critical importance in order to meet the growing demand for coal and mineral industries. But, low-grade ores require fine grinding to obtain the desired liberation of valuable minerals. As a result, production of fine particles makes the beneficiation process difficult through conventional gravity separators. Hence, alternative beneficiation techniques are being investigated for upgradation of metal values from low-grade ores. The gravitational force effecting the separation is replaced by the centrifugal force to usher in enhanced gravity separators. The objective of the present paper is to summarize the applicability aspect of enhanced gravity separators for different mineral systems including non-ferrous, precious, ferrous, and industrial minerals. These mineral systems include run off mine ore, secondary products like tailings and plant slags, etc. For this purpose, the design, operational features, types, and separation mechanism of enhanced gravity separators, such as Falcon concentrator, Knelson concentrator, multi-gravity separator (MGS), and Kelsey Jig, are discussed. Based on our review, research scope and future possibilities of enhanced gravity separators are also proposed.

Kinetics and mechanistic aspects of removal of heavy metal through gas-liquid sulfide precipitation: A computational and experimental study

The production of fine particles from extremely high supersaturation has challenged the application of sulfide precipitation in treating heavy metal wastewater due to the difficulty of solid-liquid separation. To this end, a gas-liquid sulfide precipitation reactor for the removal of Cu2+ was designed by controlling the mass transfer and supersaturation levels during sulfidation processes. Particularly, a computational fluid dynamics (CFD) model of the reactor, integrating sulfidation reaction kinetics with two-phase flow hydrodynamics, was first built, followed by examining the effects of H2S(g) bubble diameter and flow rate. Based on the CFD simulation, the rate-limiting step of the gas-liquid sulfide precipitation reaction is the gas-liquid mass transfer process. Either reducing H2S(g) bubble diameter or increasing H2S(g) flow rate can result in the control of reaction rate and supersaturation level in the system. In order to validate the CFD simulations, we measured Cu2+ concentrations during the sulfidation process with the batch experiments. The agreement between computational and experimental results indicated that our mechanistic model can provide a protocol for the design and optimization of the reaction system, allowing one to visualize the time-dependent reaction process and evaluate the performance of a reactor.