Production Of Fine Particles Research Articles

Fine particles production in sand under triaxial compression

An experimental study, carried out in laboratory using a triaxial apparatus, proposes toevaluate the influence of grain size, grain shape and confining stress in fine particles production insand specimen subjected to triaxial loading. 16 triaxial tests were conducted on specimens of aninitial density index of 0.90 using the pluviation technique, with three different sands and underinitial confining pressure of 100, 400, 800 and 1200 kPa. The experimental results show that thefine particles production is considerably affected by confining stresses, even at low values (100kPa), and also by grain geometry. The experimental results show also that the fine particlesproduction increase with the strain level during the shearing test.

Experimental investigation of the effect of energy on the ore breakage

The comminution in Semi-Autogenous (SAG) mills depends on the impact conditions. It will be worthwhile to determine the efficient impact parameters. Drop weight test is employed to simulate the ball-flat impacts and study the effect of collision energy on ore breakage. Specimens are the copper ores of SAG mill feed of Sarcheshmeh copper complex. Minimum energy required for breakage is determined for each size. The size distribution of the broken ore due to the different specific input energies is determined and a relation is presented to predict it. Since the production of fine particles is important in SAG mill process, t 10 is measured and discussed. The results of present work can be used to optimize the comminution in SAG mills by controlling the milling parameters such as the mill speed, liner height and profile, feed size and ball size to achieve the efficient mill throughput.

Optimization of Particle Size and Specific Surface Area of Pellet Feed in Dry Ball Mill using Central Composite Design

Objective: The dimensional properties of iron ore pellet feed including specific surface area and particle size distribution in the ball mill was studied using response surface area method. Methods/Statistical analysis: The effect of the operational parameters of dry ball mill including ball charge (20-40%), grinding time (30-50 min) and balling distribution (Small, Mixed and Large) on dimensional properties of pellet feed was meticulously examined and optimized using response surface methodology based on Central Composite Design (CCD). Responses were 80% passing size (D80) and Blaine (BL). A total of 30 grinding experiments were designed and carried out in the CCD method. Regression models and response surfaces were obtained for each response. Findings: The results predicted by these models showed good agreement with experimental values. In the studied range it was deduced that D80 is decreased and BL increased when grinding time and ball charge increased. Also, the production of fine particles improved using balling distribution of level B (mix balls), instead of one ball size distribution. 3D graphs were applied to visually evaluate each parameter effect on responses. The optimum conditions of ball mill operational parameters to reach the best pellet feed for each blast furnace burden and direct reduction iron (DRI) pellet feed were revealed using CCD optimization. The predicted values BL and D80 were found to be in a reasonable agreement with the experimental values, with R2 as correlation factor being 0.91 and 0.92 for BL and D80, respectively. Improvements: The optimum condition for having a suitable blast furnace burden was: Ball distribution level B, Ball charge= 21.8-22.4 %, Grinding time= 40.1-42.9 min. Also, the optimal condition for DRI pellet feed preparation was: Ball distribution level B, Ball charge= 21.8-22.1 %, Grinding time= 42.1-44.6 min.

The milling factory: Componentry-dependent fragmentation and fines production in pyroclastic flows

Abstract In order to decipher the mobility of hazardous small-volume pyroclastic flows (PFs), we investigate here the role of clast fragmentation and production of fine particles (<2 mm) in controlling PF dynamics. We report a high-resolution textural data set (i.e., grain size distribution, clast componentry, and clast morphology) of andesitic scoriaceous PF deposits from Tungurahua volcano (Ecuador) based on a unique method and data processing procedure. The strong relationship shown between clast size and componentry in PF deposits is quantified through a componentry versus size index (CSI), which varies between −1 and +1 (all components in the coarse or fine fractions, respectively). Our results show that the incorporated old lava clasts (CSI of −0.33) control early grinding of the pristine juvenile bombs (CSI of −1), which produce smaller scoriaceous andesitic fragments (CSI of 0.26). These latter interact in the granular assemblage and release fine particles through the abrasion processes, as supported by the morphological data. The textural maturity of the deposits reveals that the “milling factory” works before sedimentation begins (i.e., on steep upper slopes) and that there is some balance between fines production and loss. The process evident here tends to redistribute stress into the moving flow and produces fines that contribute to fluidization of it. The milling factory is thus likely to enhance the mobility of geophysical flows, which has strong implications for modeling and hazard assessment purposes.

Experimental measurement and phase equilibria calculation for ternary systems of carbon dioxide+ toluene + naphthalene and carbon dioxide+ ethanol + acridine, applicable for fine particle production in GAS process

In the present research, the equilibrium data of two ternary systems, carbon dioxide- toluene- naphthalene and carbon dioxide- ethanol- acridine are determined between 298.15K and 318.15K and pressure up to 8.9MPa using a high pressure apparatus. In each experiment, the equilibrium solubilities of naphthalene in toluene and acridine in ethanol decrease by increasing the pressure due to adding the carbon dioxide as the anti-solvent to the liquid phases. Also, the obtained experimental data was correlated by Peng-Robinson and Soave-Redlich-Kwong equation of states along with Van der Waals and Huron Vidal mixing rules. The adjustable parameters of mentioned models are obtained using the experimental data and reported along with average absolute relative deviation of each model. The results show that SRK equation of state with Huron- Vidal mixing rule has the minimum deviation from the experimental data between the studied models for both ternary systems.

Production of fine lactose particles from organic solvent in laboratory and commercial-scale spray dryers

ABSTRACT A laboratory spray dryer and a commercial dryer with a production rate 50 times greater, both using two-fluid nozzles, were used to dry the same formulation from organic solvent. Both dryers generated particles of similar size, with tight particle size distributions (span <2), which varied with atomization gas flow rate, liquid flow rate, and solids concentration. Small-scale results with an external mixing nozzle were fitted to a correlation based on literature recommendations. This also fitted well for the commercial dryer with external mixing, and an internal mixing nozzle gave a tighter size distribution. Hence, successful verification at scale has been achieved.

Modeling of Fine-Particle Formation in Turbulent Flames

The generation of nanostructured particles in high-temperature flames is important both for the control of emissions from combustion devices and for the synthesis of high-value chemicals for a variety of applications. The physiochemical processes that lead to the production of fine particles in turbulent flames are highly sensitive to the flow physics and, in particular, the history of thermochemical compositions and turbulent features they encounter. Consequently, it is possible to change the characteristic size, structure, composition, and yield of the fine particles by altering the flow configuration. This review describes the complex multiscale interactions among turbulent fluid flow, gas-phase chemical reactions, and solid-phase particle evolution. The focus is on modeling the generation of soot particles, an unwanted pollutant from automobile and aircraft engines, as well as metal oxides, a class of high-value chemicals sought for specialized applications, including emissions control. Issues arising due to the numerical methods used to approximate the particle number density function, the modeling of turbulence-chemistry interactions, and model validation are also discussed.

Experimental Study of Particle Size Reduction in Geophysical Granular Flows

Rock particles in debris flows and other geophysical granular flows are reduced in size through abrasion and fragmentation. A better understanding of the controls on particle wear in geophysical granular flows is needed for inferring flow conditions from flow deposits, estimating the initial size of sediments entrained in the flow, modeling flow dynamics, and mapping hazards. We used three rotating drums to create laboratory granular flows. Drum diameters range from 0.2 to 4.0 m, with the largest drum able to accommodate up to 2 Mg of debris, including boulders. We began the experiments with well-sorted, angular coarse particles in clear water. After each 0.25 km of travel distance, we quantified the particle size distribution. Rates of coarse particle wear, and production of fragments and fine particles scaled with the rate of energy expenditure per unit bed area, or unit drum power. We used this power scaling to estimate the rate of particle breakdown in a debrisflow dominated catchment in the Sierra Nevada, California.

Effects of CO2 Bubble Size, CO2 Flow Rate and Calcium Source on the Size and Specific Surface Area of CaCO3 Particles

The effects of CO2 flow rate and calcium source on the particle size (PS) and specific surface area (SSA) of CaCO3 particles were evaluated using microbubble generator (MBG) and air diffuser (AD) systems. The carbonate mineralization (CM) and precipitated calcium carbonate (PCC) methods were employed to produce CaCO3 using gypsum and Ca(OH)2 as the calcium sources, respectively. The CaCO3 particles prepared using the MBG were smaller (with larger specific surface area) than those obtained using the conventional AD, regardless of the calcium source. The average PSs were 2–3 and 7–9 μm for the MBG and AD systems, respectively. Moreover, the PS and SSA of the particles prepared using the MBG were not greatly affected by the CO2 injection rate. This study clearly demonstrates that the use of an MBG ensures the stable production of fine CaCO3 particles using various calcium sources and a wider range of CO2 flow rates.

Nd–Sr isotope geochemistry of fine-grained sands in the basin-type deserts, West China: Implications for the source mechanism and atmospheric transport

The basin-type deserts of West China are among the greatest dust emission areas in the world. Mineral dust that is emitted from the deserts is transported and deposited in east-central China and even in far-east regions. This study investigates the Nd–Sr isotopic compositions of fine-grained surface sands (<75μm) from two basin-type deserts of West China (the Taklimakan and Gurbantunggut deserts) to clarify the source areas and atmospheric transport of mineral dust. The Nd isotopes are useful for tracing the provenance and transport of sediments because they depend on the source rocks and are usually used with Sr isotopes which are affected by multiple factors such as chemical weathering, particle sorting and parent rock. The radiogenic isotopic compositions of the dune sands from the Taklimakan Desert range from εNd (0)=−10.9 to −15 and 87Sr/86Sr=0.714 to 0.718, while those of the dune sands from the Gurbantunggut Desert range from εNd (0)=−4.5 to −6 and 87Sr/86Sr=0.711 to 0.713. The isotopic compositions of the fine-grained surface sands are not spatially uniform within each desert and are controlled by the lithological characteristics of the tectonic units in which the deserts are located. The isotopic comparison of the dune sands with other sediments indicates that tectonic denudation and fluvial processes are the main mechanisms of fine particle production of the modern desert sands. In terms of isotope analyses and forward trajectory results, it is further found that the mineral dust is deposited not only in proximal areas, such as the Hexi Corridor, the Chinese Loess Plateau and the Tibet–Qinghai Plateau, but also in distal regions, such as Japan, the Pacific Ocean and Greenland once it is blown out of the Taklimakan Desert. However, the transport and sinks of mineral dust vary with the atmospheric currents.

Application of Mechanochemical Synthesis to Manufacturing of Permanent Magnets

Synthesis of permanent magnet powders through mechanically and thermally activated reduction of metal oxides with calcium, which allows for the production of fine single crystal particles, may contribute to the ongoing search for alternatives to the Nd-Fe-B magnets. The reviewed efforts demonstrate the possibilities to prepare (1) high-coercivity SmCo5 nanoparticles for anisotropic exchange-coupled nanocomposites, (2) YCo5/LaCo5 powders with the magnetic properties superior to those obtained through other manufacturing methods and (3) submicron Mn-Bi powders with large concentration of the MnBi phase. Also discussed are less successful attempts to prepare Mn-Al, Zr-Co and Hf-Co hard magnetic alloys in which the principal phases are known or likely to be metastable.

Air quality status and trends over the Metropolitan Area of São Paulo, Brazil as a result of emission control policies

Abstract 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 Sao Paulo (MASP). MASP includes one of the largest cities in the world (Sao 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 PM 10 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.

Wet Grindability of Calcite to Ultra-Fine Sizes in Conventional Ball Mill

An experimental practice on the ultra-fine wet grinding of calcite ore in a conventional batch ball mill is reported. In this study, the effect of wet grinding conditions on the production of fine particles was researched. The influence of operating parameters such as operation speed (% of critical speed), ball filling ratio, calcite filling ratio, pulp density, ball size distribution, and grinding time on the grindability of calcite ore was systematically examined. Experimental results were evaluated on the basis of d80 product size. As a result of this study, optimum experimental conditions were found to be 80% of critical speed for operation speed, 35% for ball filling ratio, 15% for calcite filling ratio, 75% for pulp density, 50% (1 cm) and 50% (2 cm) for ball size distribution, and 60 min for grinding time. It was found that the best product has d10 = 1.51, d50 = 12.53, and d80 = 30.02 µm particle size and its steepness factor is 3.75. The outcomes indicate that the wet grinding technique in conventional ball mill for calcite ore is effective to obtain ultra-fine size products.

Changes in permeability of sand during triaxial loading: effect of fine particles production

Various mechanisms can affect the permeability of dense unconsolidated sands: Volumetric dilation can lead to permeability increase, whereas strain localization in shear bands may increase or decrease the permeability depending on the state of compaction and on the level of grains breakage inside the band. To investigate these various mechanisms, an experimental study has been performed to explore the effect of different factors such as grain size and grain shape, confining pressure, level of shear, stress path, and formation of one or several shear bands on the permeability of dense sands under triaxial loading. The experimental results show a reduction of permeability during the consolidation phase and during the volumetric contraction phase of shear loading, which can be related to the decrease of porosity. The experimental results also show that, depending on the confining pressure, the permeability remains stable or decreases during the volumetric dilation phase despite the increase of total porosity. This permeability reduction is attributed to the presence of fine particles, which result from grains attrition during pre-localization and grains breakage inside the shear band during the post-localization phase.

Improvement of the Electrocatalytic Activity of Zirconium Oxide-Based Catalyst for ORR

Development of non-platinum electrocatalyst for oxygen reduction reaction (ORR) is required for real commercialization of polymer electrolyte fuel cells. We focused on group 4 and 5 transition metal oxides, because they have high chemical stability under acidic atmosphere even in high potential region, and are less expensive than platinum. In this study, we prepared zirconium oxide based electrocatalysts prepared by the oxidation of oxy-zirconium phthalocyanine in low oxygen pressure and tried to disperse the starting material on carbon support to improve the ORR activity. It was revealed that the use of tetrahydrofuran (THF) as a solvent with impregnation method was more effective to obtain the large ORR current density than that of N-methylpyrrolidone (NMP). This is because the production of fine secondary particles using tetrahydrofuran (THF) as a solvent.

Response Surface Modelling of Electrosprayed Polyacrylonitrile Nanoparticle Size

Electrospraying (electrohydrodynamic spraying) is a method of liquid atomization by electrical forces. Spraying solutions or suspensions allow production of fine particles, down to nanometer size. These particles are interesting for a wide variety of applications, thanks to their unprecedented chemical and physical behaviour in comparison to their bulk form. Knowledge of the particle size in powders is important in many studies employing nanoparticles. In this paper, the effect of some process parameters on the size of electrosprayed polyacrylonitrile particles is presented in the form of response surface model. The model is achieved by employing a factorial design to evaluate the influence of parameters on the polyacrylonitrile nanoparticle size and response surface methodology. Four electrospraying parameters, namely, applied voltage, electrospraying solution concentration, flow rate, and syringe needle diameter were considered.

Pyroclastic density currents at Stromboli volcano (Aeolian Islands, Italy): a case study of the 1930 eruption

Pyroclastic density currents (PDC) related to paroxysmal eruptions have caused a large number of casualties in the recent history of Stromboli. We combine here a critical review of historical chronicles with detailed stratigraphic, textural, and petrographic analyses of PDC deposits emplaced at Stromboli over the last century to unravel the origin of currents, their flow mechanism and the depositional dynamics. We focus on the 1930 PDC as they are well described in historical accounts and because the 1930 eruption stands as the most voluminous and destructive paroxysm of the last 13 centuries. Stromboli PDC deposits are recognizable from their architecture and the great abundance of fresh, well-preserved juvenile material. General deposit features indicate that Stromboli PDC formed due to the syn-eruptive gravitational collapse of hot pyroclasts rapidly accumulated over steep slopes. Flow channelization within the several small valleys cut on the flanks of the volcano can enhance the mobility of PDC, as well as the production of fine particles by abrasion and comminution of hot juvenile fragments, thereby increasing the degree of fluidization. Textural analyses and historical accounts also indicate that PDC can be fast (15–20 m/s) and relatively hot (360–700 °C). PDC can thus flow right down the slopes of the volcano, representing a major hazard. For this reason, they must be adequately taken into account when compiling risk maps and evaluating volcanic hazard on the Island of Stromboli.

Anti‐solvent effect of crystallization by feeding ethanol under microwave radiation

The nucleation and crystal growth of sodium chloride in aqueous solution during crystallization by ethanol droplet feeding were investigated by determining the suspension density and crystal size distribution. Crystallization was conducted in a microwave reactor, and the effect of the power, stirring speed, and ethanol concentration were investigated to clarify the anti‐solvent effect under microwave radiation. Molecular diffusion was accelerated by fine particle production due to microwave radiation when the stirring speed was low and ethanol concentration was high. However, moderate microwave power and stirring speed were required for efficient molecular diffusion.

A metathesis reaction route to obtain fine Mg2Si particles

We have developed a novel synthetic route for the production of fine Mg2Si particles (<1 μm) using NaSi, MgCl2, and Na. Mg2Si was suggested to be formed by a solid-state metathesis reaction, in which MgCl2 reacts with Na to form Mg and NaCl, and then Mg reacts with NaSi.

Deposition and fine particle production during dynamic flow in a dry powder inhaler: A CFD approach

In this work the dynamic flow as well as the particle motion and deposition in a commercial dry powder inhaler, DPI (i.e., Turbuhaler) is described using computational fluid dynamics, CFD. The dynamic flow model presented here is an extension of a steady flow model previously described in Milenkovic et al. (2013). The model integrates CFD simulations for dynamic flow, an Eulerian-fluid/Lagrangian-particle description of particle motion as well as a particle/wall interaction model providing the sticking efficiency of particles colliding with the DPI walls. The dynamic flow is imposed by a time varying outlet pressure and the particle injections into the DPI are assumed to occur instantaneously and follow a prescribed particle size distribution, PSD. The total particle deposition and the production of fine particles in the DPI are determined for different peak inspiratory flow rates, PIFR, flow increase rates, FIR, and particle injection times. The simulation results for particle deposition are found to agree well with available experimental data for different values of PIFR and FIR. The predicted values of fine particle fraction are in agreement with available experimental results when the mean size of the injected PSD is taken to depend on the PIFR.