Sieve Size Range Research Articles

Influence of type of aluminium stearate on triboelectrification of dry-coated surfaces of functionalised glass beads

Triboelectrification of powders and grains is deleterious in a large number of manufacturing operations, due to its adverse effect on process consistency and reliability. To mitigate it, charge neutralisers are commonly employed. However, their selection is often based on trial and error. This study is conducted to systematically examine the influence of the ionic polarity strength of a charge neutraliser, specifically aluminium stearate (AlSt), on charge transfer. AlSt has three types with different numbers of stearate chains, thereby influencing the electron exchange propensity of the molecule. The experiments involved surface-treated glass beads in the sieve size range of 90–150 µm (to make them hydrophilic by acid washing or hydrophobic by silanisation), then coated with the three forms of AlSt (mono-, di- and tri-) for charge mitigation. These coated beads were subjected to aerodynamic dispersion to cause triboelectrification, in order to quantitatively evaluate their charge neutralising effect. The experiments were conducted with four contact surfaces: stainless steel, copper, aluminium, and polytetrafluoroethylene (PTFE). Both acid-washed and silanised glass beads exhibited negative charging against aluminium, copper and stainless steel (typically around 22–44 nC/g), but positive charging against PTFE (around 90 nC/g and 19 nC/g for acid-washed and silanised, respectively), despite having significantly different surface functional groups. A complex trend is observed for the effect of the amount of AlSt present on the surfaces, the type of AlSt and the surface treatment. A relatively good charge reduction behaviour was seen for AlSt-coated acid washed glass beads, but for silanised glass beads, AlSt coating actually increases their charge level.

Application of finite and infinite functions in determining of the metalworking dusts particle size distribution

Particle size distribution is an important parameter for dust quality and properties assessment as well as a factor to estimate the air dustiness influence on humans and the choice of an appropriate dedusting means. The academic literature analysis shows that, unlike technological dust, there is practically no information available about theoretical models of metal machining dust size distribution. In addition, researchers rarely use finite functions, although an appropriate particle size distribution determination is crucial for dedusting ventilation systems designed for machine tools. The article examines the metal machining dust particle size distribution description using finite and infinite functions, and discusses the features and advantages of their application. As a result, it is concluded that infinite functions are good at describing dust with a high extremity of outliers. On the contrary, finite functions appropriately describe dust with low tailedness, the measure of which is the kurtosis. It should be noted that the obtained results are related to the dust analysis methods, including sieve analysis when selecting a sieve size range.

A single experiment with variable low-pressure air flow through a packed bed leads to two methods for determining particle size

Two piston-in-cylinders, charged with air at ambient temperature and pressure, are moved from rest to a constant displacement rate in a syringe pump. The air is pumped to a packed column and an elevated steady state pressure, measured just upstream of the bed, is quickly attained. Upon stopping the pistons' motion, the pressure decays back to its ambient level. The growth and decay phases are described by material balances and the Blake–Kozeny laminar-flow model. The unknown parameters in solutions to the resulting first-order differential equations are determined by fitting the pressure–time data. For the growth phase, the fit leads to the determination of the initial system volume and the steady state pressure, whereas for the decay phase the fit gives a pseudo-time constant. This provides sufficient information to calculate the permeabilities and mean particle sizes—the Sauter mean diameters—for both phases. Packed columns of Aldrich Sand, sieve-size range 0.211–0.297 mm, and glass beads, nominal size 1 mm, give the following means: for Aldrich sand, 0.26 ± 0.02 and 0.27 ± 0.02 mm; for the glass beads, 1.11 ± 0.06 and 1.09 ± 0.06 mm, for the growth and decay phases, respectively. Analogous experiments with a capillary tube, internal diameter 0.485 ± 0.001 mm, give the following internal diameters: 0.492 ± 0.007 and 0.501 ± 0.007 mm for the growth and decay phases, respectively.

Degradation of railway ballast under impact loading considering the morphological properties of aggregate

Degradation of railway ballast aggregate is ensued from breakage of single particle as well as from abrasion of angular corners. The present study evaluates the change in morphological characteristics as well as particle size distribution of ballast aggregate degraded under applied impact loads to further illuminate the degradation mechanism of particles. The utilized drop-weight impact loading apparatus implemented on prepared ballast specimens is modified to take into account the real stress levels applied over ballast course. The morphological features of aggregate including angularity and surface roughness are quantified by establishment of extended image processing method. Generally, the obtained results uphold the evident effect of parent rock type on degradation mechanism. Also, the percent reduction of indices related to angularity and surface roughness are in line with increment of degradation level measured by fouling index (FI). Furthermore, the change in morphological indices is not significant in case of using particle size distribution with higher uniformity coefficient compared with more uniform gradation. Indeed, major effect of selection of broader sieve size range is exhibited on reduction of breakage of larger-sized aggregate. Meanwhile, provision of flexible subgrade instead of rigid type considerably diminishes the percentage of reduction of sharp corners and surface roughness which confirms evident effect of stiffness of underlying layer on level of abrasion of coarse particles.

Mechanical evaluation of aggregate gradation to characterize load carrying capacity and rutting resistance of asphalt mixtures

The gradation and mechanical properties of aggregates impressively affect the load carrying capacity and rutting resistance of asphalt mixtures. They are able to provide some fundamental parameters that are linked to mixture performance. In order to accurately detect critical controlled sizes and obtain more fundamental parameters that can characterize load carrying capacity and rutting resistance of asphalt mixtures, this paper aims to develop a mechanics-based approach to evaluate aggregate gradation, which contains the theoretical packing analysis and discrete element simulation.An extended theoretical morphology framework is developed by checking the local and global interlock of graded aggregates in the theoretical packing analysis. The sieve size range of primary structure which has an interactive interlock can be determined in the local interlock check model. The relationship between the transferred force and the induced force is proposed in the densest and loosest packing arrangements, respectively. The morphological parameters of disruption factor and weighted average size for the global scale are also proposed in theoretical packing analysis.Then the discrete element method is used to validate the theoretical framework. The advanced gradation input algorithm procedure is established in the discrete element simulation to simulate the compression test of graded aggregates. The mechanical parameters of contact force, contact points and stress–strain curves are extracted from the simulation results.The results show that the discrete element method can validate the theoretical framework and output the performance related parameters. The contact force analysis shows that the aggregates retaining on sieve sizes of 2.36 and 4.75 mm provide more than 50% contribution to resist load, and the aggregates retaining on sieve sizes of 1.18, 0.6 and 0.3 mm provide more than 50% contribution to stabilize the structure. The coordination number analysis suggests that the gradation with more fine aggregates might lead to a greater number of voids but smaller air-void size when the asphalt content and porosity remain constant. The stress–strain curve analysis shows that the modulus and secondary strain are highly related to the rutting performance of an asphalt mixture.

Effect of Milling Parameters on the Concentration of Copper Content of Hammer-Milled Waste PCBs: A Case Study

The current study reports optimization of hammer milling parameters to achieve crushed waste printed circuit boards (WPCBs) of − 16 BSS (British Standard Specification) sieve size. The WPCBs, having 22 wt% copper, have been crushed to − 16 BSS sieve size by means of a hammer mill. The result showed that initial milling takes place rapidly and then decreases gradually. Approximately 94% feed material is ground to − 16 BSS sieve size within 7 min, and further increase in the time does not affect the milling rate. It is also revealed that with the increasing feed rate, lower milling rate is experienced due to the distribution of impact energy among more pieces of WPCBs. Study of the size distribution of milled WPCBs (− 16 BSS sieve size) revealed that it follows the similar trend, and the crushed material is mostly concentrated in − 240 BSS and + 72 to − 52 BSS sieve size range. Further, 50–55% crushed fraction attains + 100 BSS sieve size, while the rest is smaller than this sieve size. Chemical analysis of the crushed material of various size fractions elucidated that a fraction above 100 BSS sieve size is copper rich (43 wt%), while − 100 BSS sieve size fraction has lesser copper because the nonmetals which account for majority concentration in WPCBs are milled to a finer size. Microscopic examinations of crushed fraction showed that copper has metallic luster and ruptured foil-type morphology. The fibrous structure of glass fiber and gray/black-colored polygon morphology of nonmetals were also visible.

Active fuel particles dispersion by synthetic jet in an entrained flow gasifier of biomass: Cold flow

Pulverized fuel (PF) burners play a key role for the performance of PF fired gasification and combustion plants, by minimizing pollutant emission, fuel consumption and hence fuel costs. However, fuel diversity in power generation plants imposes limitations on the performance of existing PF burners, especially when burning solid fuel particles with poor flowability like biomass sawdust. In the present study, a vertically downward laminar flow was laden with biomass particles at different particle mass loading ratios, ranging from 0.47 to 2.67. The particle laden flow was forced by a synthetic jet actuator over a range of forcing amplitudes, 0.35–1.1kPa. Pulverized pine particles with a sieve size range of 63–112μm were used as biomass feedstock. Two-phase particle image velocimetry was applied to measure the velocity of the particles and air flow at the same time. The results showed that the synthetic jet had a large influence on the flow fields of both air and powdered pine particles, via a convective effect induced by vortex rings that propagate in the flow direction. The particle velocity, particle dispersion and hence inter-particle distance increased with increasing forcing amplitude. Moreover, particles accumulated within a specific region of the flow, based on their size. The effect on particle dispersion was more pronounced in the forced flows with low mass loading ratios.

The stability of soil aggregates in tilled fallow areas in Hyderabad district, Pakistan

Abstract Arid areas are particularly susceptible to soil erosion due to long dry periods and sudden heavy downpours. This study investigates the aggregate size distribution and aggregate stability of twelve tilled fallow areas of Hyderabad district, Sindh, Pakistan. This study determined aggregate size distribution by dry sieving to evaluate the seedbed condition and aggregate stability using wet sieving to assess the susceptibility of tilled fallow areas to soil erosion. The aggregate size distribution of the soils of the selected areas was highly variable. Gulistan-e-Sarmast had the largest number of clods (51.0%) followed by Kohsar (49.0%), Latifabad # 10 (41.10%) and Daman-e-Kohsar (39.0%). Fazal Sun City, the left side of the Indus River, the Village Nooral Detha and the left side of the Abdullah Sports city had a greater number of large (>8.0 mm) and small aggregates (<0.5 mm). The optimum aggregate size distribution was found in the left side of the channel, which had the largest number of aggregates (50.50%) in the 0.5–8.0 mm sieve size range. Maximum aggregate stability (AS) was found in Gulistan-e-Sarmast (46%), Kohsar (42%) and Latifabad # 10 (34%), while all other soils had minimum aggregate stability (<14%). The minimum aggregate stabilities demonstrate that the tilled fallow areas of Hyderabad district are highly susceptible to erosion. Therefore, the present study suggests investigating potential ways to enhance the aggregate stabilities of soils.

Fischer–Tropsch synthesis: Effect of catalyst particle (sieve) size range on activity, selectivity, and aging of a Pt promoted Co/Al2O3 catalyst

Abstract The effect of cobalt–alumina catalyst particle (sieve) size range on the performance of a traditional cobalt catalyst (platinum promoted cobalt/alumina) was investigated during Fischer–Tropsch synthesis (FTS) using a continuously stirred tank reactor (CSTR). In this study, the catalyst was sieved into four different size ranges: 20–63, 63–106, 106–180 and 180–355 μm. CO conversion varied with varying sieve size range under similar reaction conditions. With increasing catalyst sieve size, the CO conversion decreased, except for the smallest sieve size range (20–63 μm). These results are consistent with the view that, for the larger sieve size range, losses in CO conversion beyond catalyst aging may be explained by filling of the interior of the catalyst particle with heavy wax, thereby blocking available catalytically active sites. The adverse selectivities are directly the result of significant deactivation, since in FT synthesis, selectivity is a function of CO conversion. The loss in CO conversion for the 20–63 μm range catalyst was higher compared to the other three catalysts; due to the presence of heavy wax (Polywax 3000), the results suggest that the small particles tended to flocculate to larger clusters or were small enough to move at the speed of the liquid.

Optimal seed recipe design for crystal size distribution control for batch cooling crystallisation processes

The paper presents a novel quality-by-design framework for the design of optimal seed recipes for batch cooling crystallisation systems with the aim to produce a desired target crystal size distribution (CSD) of the product. The approach is based on a population balance model-based optimal control framework, which optimises the compositions of seed blends, based on seed fractions that result from standard sieve analysis. The population balance model is solved using a combined quadrature method of moments and method of characteristics (QMOM-MOCH) approach for the generic case of apparent size-dependent growth. Seed mixtures are represented as a sum of Gaussian distributions, where each Gaussian corresponds to the seed distribution in a particular sieve size range. The proposed methods are exemplified for the model system of potassium dichromate in water, for which the apparent size-dependent growth kinetic parameters have been identified from laboratory experiments. The paper also illustrates the simultaneous application of in situ process analytical tools, such as focused beam reflectance measurement (FBRM) for nucleation detection, attenuated total reflection (ATR) UV/Vis spectroscopy for concentration monitoring, as well as the in-line use of laser diffraction particle sizing for real-time CSD measurement.

Micrometer-scale 3-D shape characterization of eight cements: Particle shape and cement chemistry, and the effect of particle shape on laser diffraction particle size measurement

Eight different portland cements were imaged on a synchrotron beam line at Brookhaven National Laboratory using X-ray microcomputed tomography at a voxel size of about 1 µm per cubic voxel edge. The particles ranged in size roughly between 10 µm and 100 µm. The shape and size of individual particles were computationally analyzed using spherical harmonic analysis. The particle shape difference between cements was small but significant, as judged by several different quantitative shape measures, including the particle length, width, and thickness distributions. It was found that the average shape of cement particles was closely correlated with the volume fraction of C 3S (alite) and C 2S (belite) making up the cement powder. It is shown that the non-spherical particle shape of the cements strongly influence laser diffraction results, at least in the sieve size range of 20 µm to 38 µm. Since laser diffraction particle size measurement is being increasingly used by the cement industry, while cement chemistry is always a main factor in cement production, these results could have important implications for how this kind of particle size measurement should be understood and used in the cement industry.

Solid-assisted melt disintegration (SAMD), a novel technique for metal powder production

A new process termed “solid-assisted melt disintegration (SAMD)” has been developed for the preparation of aluminum alloy powder particles. The method consists of introducing and mixing a specified amount of as-received alumina particles (in the range of +700 to 500 μm) in A356 aluminum melt at the temperature of 715 °C. Melt disintegration occurs in 10 min by kinetic energy transfer from a rotating impeller (450 rpm) to the metal via the solid atomizing medium (alumina particles). The resulting mixture of aluminum droplets and alumina particles was cooled in air and screened through 300 μm sieve to separate alumina from solidified aluminum powder particles. A356 aluminum alloy was also gas atomized by using a free-fall atomizer operating by nitrogen gas at the pressure of 1.1 MPa and the sub-300 μm of the produced powder was used as a base of comparison. The SAMD produced powders of diameter above 53 μm were mostly spherical while powders less than 53 μm showed various elongated shapes. No evidence was found for satelliting of small particles on to large ones or agglomerated particles. While gas atomized particles in the +53 μm sieve size range showed some signs of porosity, the SAMD particles were dense and did not show any signs of internal porosity in any of the sieve fractions investigated. Comparison of the microstructure of the SAMD and gas-atomized powders revealed that for the same size powder of A356 alloy, the former exhibited a coarser microstructure as a result of a slower cooling rate.

The Role of Particle Shape in Size Analysis and the Evaluation of Comminution Processes

The shape of the particles produced by comminution is affected by the kind of breakage action employed. Furthermore, the procedures used to determine product particle size are themselves influenced by shape. Illustrative examples of the effects of shape on particle size analysis and of shape variations in comminuted material are presented. Light scattering size measurements on narrow sieve fractions were found to indicate size distributions that were significantly broader than the sieve size range, especially for irregularly shaped particles. The distributions were also shifted to coarser sizes for the irregular particles but not for spheres. The apparent size shift is attributed to differences in the definition of size, while it is proposed that the apparent broadening of the distribution is a result of orientation effects. It is shown that broadening is relatively insignificant for broad, continuous distributions due to compensation effects. Applications to the determination of composite distributions by combining sieving and light scattering data are described. Distributions of particle shape descriptors, obtained by image analysis of comminution products, are shown to depend on the comminution method used. A slight variation with size was observed for coal particles but not for quartz. The implications of the size/shape interaction on the evaluation of comminution process performance are discussed.

Technical note: use of laser diffraction for particle size distribution measurements in duodenal digesta.

Duodenal samples from three lactating cows were used to measure the particle size distribution by wet sieving and by laser diffraction (LD). The median particle size was calculated in the size range where the methods overlapped, and the median particle size was not different between the methods (P = 0.98). The particle size data were also fitted to a log normal distribution function. The logarithmic mean particle size (log10mean) tended to be larger for wet sieving (P = 0.06), and the logarithmic standard deviation (log10SD) was similar for the two methods (P = 0.32). In addition, duodenal samples from the same three animals were fractionated into five different size classes by wet sieving. Particle size distributions were measured by LD and by microscopic image analysis (MIA) for each of the size classes. The log10mean particle size calculated by LD was inside the sieve size range of the four smallest size classes. Log10mean particle size calculated by LD was smaller than log10mean calculated by MIA for two size classes (106 to 300 microm and 300 to 600 microm), and LD gave generally broader particle size distributions than MIA. This study showed that duodenal particle size distributions measured by LD and wet sieving were similar and LD is therefore an alternative method for particle size distribution measurements in postruminal digesta.

Biodegradable Progesterone Microsphere Delivery System for Osteoporosis Therapy

The purpose of this study was to formulate and characterize a controlled-release biodegradable delivery system of progesterone for the treatment or prevention of osteoporosis. Microspheres of progesterone were formulated using copolymers of poly(glycolic acid-co-dl-lactic acid)(PGLA 50/50 and PGLA 15/85) and poly(L-lactic acid)(L-PLA) of similar molecular weight by the emulsion solvent evaporation technique. The effects of process variables, such as volume fraction, polyvinyl alcohol (PVA) concentration, polymer composition, and stir speed during preparation, on the yield, encapsulation efficiency (EEF), particle size distribution, in vitro release profiles of progesterone, and surface morphology of progesterone microspheres were investigated. Increasing the volume fraction from 9% to 22% increased the EEF without significantly increasing the yield; however, the rate of progesterone release from the microspheres decreased. Increasing the PVA concentration from 1% to 5% had no significant influence on the EEF, but the rate of progesterone release from microspheres increased. Polymer composition had no significant effect on the EEF, but had a significant effect on the particle size distribution, surface morphology, and release rate of progesterone from the microspheres. Stir speed did not have a significant influence on the EEF; however, stir speed influenced particle size distribution and the rate of progesterone release from microspheres of the same sieve-size range. The results suggest that controlled release of progesterone is possible by varying the different process variables, and that PGLA 50/50 provided the slowest release of progesterone. This should provide a means of delivering progesterone for months for the treatment or prevention of osteoporosis in postmenopausal women.

Analysis on the Efficiency of the Air Classification of Fly Ash

ABSTRACT The efficiency of the air classification of fly ash was investigated. Due to the wide variations in the size consist of fly ash, it is commonly practiced to use more than techniques to measure the entire size range. Especially for fly ash, the sieving techniques are used to obtain information not only on the size distribution but also on the carbon distribution throughout the size. However, there is a substantial amount in the sub- sieve size range, and consequently, sub-sieve analyzer is used to obtain the information on the size distribution in the finer end. Since the size definitions differ depending on the measurement methods, it is necessary to convert one type of data to the other. Using a recently developed technique for inter-conversion of sizes, the separation efficiency of a commercial classifier was analyzed using the Tromp curve. The results showed that the cut size was about 55 mm and the bypass was 17%. Sharpness Index was calculated to be 0.25, which indicated an inefficient separation. This could be reasoned from the heterogeneous nature of the fly ash particles, which limited sharp separation of the particles in the range of 30–100 μm.

Influence of Total Aggregate Gradation on Freeze-Thaw Durability and Other Performance Measures of Paving Concrete

Transportation-related agencies are experimenting with increased control of aggregate gradation in their concrete pavement specifications. There is anecdotal evidence that shows that total aggregate gradation can be optimized to yield improved concrete performance during construction and service life. Strong scientific data are less numerous in supporting this idea because of the variability in aggregates that can occur and practical considerations in avoiding waste particle sizes. The influence of total aggregate gradation on the freeze-thaw durability of concrete test specimens that employed a variety of sedimentary and igneous aggregates common in Wisconsin is examined. Optimized gradations consisted of increased amounts of aggregate particles in the No. 4 to No. 16 sieve size range and decreased amounts of fines in the No. 50 to No. 200 sieve size range. A near-gap gradation was fabricated by removing some particles in the No. 4 to No. 16 sieve size range and increasing the amount of fine material in the No. 30 to No. 100 sieve size range. Several methodologies and practical considerations were considered in establishing the aggregate gradations. A control gradation utilized a 60-40 blend of coarse/fine aggregate with gradations determined by the naturally occurring particle sizes. The concrete specimens prepared in this study were subject to strength, shrinkage, permeability, and accelerated freeze-thaw testing. All concretes had well-controlled water-cement ratios and showed excellent freeze-thaw durability. The optimized gradation mixes did not show consistently improved performance compared with the control mixes. The near-gap mixes showed reduced strength, reduced freeze-thaw durability, and increased shrinkage.

Method of evaluation of sustained release microsphere formulations using the open chemostat system

The sustained release of cephalexin (CPX) as the monohydrate and ciprofloxacin (CFX) as the hydrochloride from separate 100000 Mol. Wt poly( l-lactic acid) microspheres (250–425 gmm sieve size range) was evaluated in an open chemostat system. Drug concentrations in pH 7.4 phosphate buffer solution (PBS) reached peak levels which were sustained for different periods of time, depending on the flow rate of PBS at a constant volume of 120 ml in the chemostat. At 0.46 ml/min flow rate CPX microspheres (33% w/w loading) sustained CPX concentrations for approx. 90 min (solubility = 40 mg/ml at pH 7.4, 37° C) whereas CFX (solubility = 5 mg/ml) was sustained for at least 6 h. Increasing drug loading increased peak levels of either antibiotic but decreased the sustained period of CPX only. Decreasing microsphere size to 125–250 gmm increased CPX or CFX concentration levels and decreased the sustained period to about 45 min and 2 h, respectively. At higher doses, CFX was sustained at higher concentrations over the 6 h period. Decreasing the flow rate in the chemostat increased sustained levels of CFX while increasing the flow rate decreased sustained levels. Thus, the chemostat system is convenient for testing the sustained release of drugs as a function of formulation parameters and to obtain information about the optimum doses of sustained release medication for in vivo administration.

Physicochemical aspects of drug release. VI. Drug dissolution rate from solid particulate dispersions and the importance of carrier and drug particle properties

Solid dispersions of a hydrophobic, sparingly soluble drug, griseofulvin, and a hydrophilic carrier, polyethylene glycol, were prepared by both a melting and a solvent method, with griseofulvin concentrations ranging from 1% to 20% w/w/ All the dispersions prepared contained particulate griseofulvin in which, the size, surface and shape characteristics of the particles had been determined. The aqueous solubilities of griseofulvin incorporated in solid dispersions were analyzed. The dissolution rate measurements were determined with the paddle method (100 rpm), of the USP XXI. It was concluded that the use of solid dispersion particles in the sieve size range 300–500 μm was preferable in dissolution testing, since problems due to both floatation and sedimentation could be avoided. For both the melting and the solvent methods used the dissolution rate decreased with increasing drug concentration. This effect was more pronounced in the solvent method where the reduction was almost entirely due to an increase in drug particle size. All the griseofulvin concentrations prepared by the melting method gave relatively fine particulate dispersions, and the drug particle size could only to a limited extent explain the dissolution rate data. It was found that the dispersions prepared by the melting method containing higher drug concentrations, corresponded to a reduction in the dissolution rate of the carrier. The aqueous solubility of griseofulvin was higher after incorporation in solid dispersion compared to the untreated raw material. The highest solubility was obtained for the melting method containing higher concentrations of griseofulvin.

Shape factors for barium chromate crystals in the sieve size range

The use of a simple microscopic counting technique, which was applied to the sieve cuts of a standard fourth root of two sieve progression, to determine particle shape factors for polydisperse samples of barium chromate crystals, is described. Results obtained in the sieve size range up to 295 μm, for the ratio of mean equivalent spherical volume diameter to mean sieve diameter, are presented and discussed.