Final Particle Size Distribution Research Articles

Effect of Mixing on the Particle Size Distribution of Paracetamol Continuous Cooling Crystallization Products Using a Computational Fluid Dynamics–Population Balance Equation Simulation

Continuous crystallization is a widely viewed topic as it has many advantages in industrial production. However, it is very resource intensive and time-consuming to determine operation conditions through trial and error. Computer simulation appears to an effective method in continuous crystallization design. The continuous cooling crystallization of paracetamol in a 5 L crystallizer was modeled to investigate the effect of mixing on the particle size distribution (PSD). A novel coupled computational fluid dynamics–population balance equation (CFD–PBE) simulation was developed in which the PBE was discretized using a high-resolution central scheme and solved simultaneously with CFD equations in ANSYS FLUENT 15.0 utilizing user-defined scalars. The influences of both internal grid and external (spatial) grid on the final PSD were studied, and an appropriate grid was chosen. The spatial distribution of velocity, temperature, slurry density, and nucleation rate were simulated. The continuous cooling crystallization under different stirrer speeds, bath temperatures, and residence times was investigated. It was found that (a) higher stirrer speeds lead to uniform distribution but smaller PSD, and (b) as the average temperature gets higher, or the residence time gets longer, the influence of mixing on final PSD gets smaller.

Incense powder and particle emission characteristics during and after burning incense in an unventilated room setting

Despite being a recognized health hazard, burning incense remains in widespread use. A number of studies have investigated the emissions of air pollulants from incense burning, but less attention has been given to particle decay following incense burning. We have studied the elemental composition and indoor emission characteristics of incense sticks in terms of the size distribution and concentrations of fine particles. The results of chemical analysis and energy dispersive X-ray spectroscopy showed that the primary constituents of the emissions were CaCO3 and SiO2, together with lesser amounts of Mg, K, Al, Fe, and Cl. Analysis using a scanning mobility particle sizer revealed that the maximum total particle concentration at the end of the burning period was up to 30-fold higher than that of the initial background levels and that it remained elevated even 100 min after the incense sticks had been completely burned up. Emitted incense particles decayed in a biexponential manner, with particles of up to 100 nm in size decaying with lifetimes of several tens of minutes, while nanoparticles with diameters of 100–700 nm having lifetimes of > 100 min, as their removal mechanisms are slower. The peak particle size immediately following the end of incense burning was 85 nm, and this increased to 110 nm at 100 min after completion of burning. This result indicates that a high proportion of emitted particles can be inhaled into the alveolar region of the lung, where the potential for adverse health effects is the greatest. These findings provide a more detailed insight into particle decay mechanisms under conditions of low ventilation, with implications for human health.

The influence of processing parameters on morphology and granulometry of a wet-milled sol-gel glass powder

A quaternary bioactive sol-gel glass of high silica content was heat treated at different temperatures, and then wet ball milled under different balls-to-powder ratios. A total of sixteen experiments were performed to study in detail the effects of both experimental variables on the structure, morphology, particle size distributions and nitrogen adsorption isotherms. The balls–to–powder ratio exerts a tremendous influence on the final particle size distribution of the powders, while its effects on the pore volume and morphology are minimal. These structural features are mostly governed by the changes in calcination temperature. Therefore, understanding the specific roles of each experimental parameter is of paramount importance towards achieving optimum powders with the desired properties. This work sheds light on the importance of using a suitable combination of these two parameters for tuning the morphology and the granulometry of the sol-gel derived bioactive glass powders.

The application of STEP-technology® for particle and protein dispersion detection studies in biopharmaceutical research

Particle detection and analysis techniques are essential in biopharmaceutical industries to evaluate the quality of various parenteral formulations regarding product safety, product quality and to meet the regulations set by the authority agencies. Several particle analysis systems are available on the market, but for the operator, it is quite challenging to identify the suitable method to analyze the sample. At the same time these techniques are the basis to gain a better understanding in biophysical processes, e.g. protein interaction and aggregation processes. The STEP-Technology® (Space and Time resolved Extinction Profiles), as used in the analytical photocentrifuge LUMiSizer®, has been shown to be an effective and promising technique to investigate particle suspensions and emulsions in various fields.In this study, we evaluated the potentials and limitations of this technique for biopharmaceutical model samples. For a first experimental approach, we measured silica and polystyrene (PS) particle standard suspensions with given particle density and refractive index (RI). The concluding evaluation was performed using a variety of relevant data sets to demonstrate the significant influences of the particle density for the final particle size distribution (PSD). The most challenging property required for successful detection, turbidity, was stated and limits have been set based on the depicted absorbance value at 320 nm (A320 values). Furthermore, we produced chemically cross-linked protein particle suspensions to model physically “stable” protein aggregates. These results of LUMiSizer® analysis have been compared to the orthogonal methods of nanoparticle tracking analysis (NTA), dynamic light scattering (DLS) and micro-flow imaging (MFI). Sedimentation velocity distributions showed similar tendencies, but the PSDs and absolute size values could not be obtained.In conclusion, we could demonstrate some applications as well as limitations of this technique for biopharmaceutical samples. In comparison to orthogonal methods this technique is a great complementary approach if particle data e.g. density or refractive index can be determined.

Fabrication and characterization of nano-Y2O3 and Al2O3 dispersed W-Ni alloys by mechanical alloying and pressureless conventional sintering

Nano Y2O3 and Al2O3 dispersed W-Ni alloys with nominal composition of W89Ni10 (Y2O3)1 (alloy A), W89Ni10 (Al2O3)1 (alloy B) were mechanically alloyed for 10 h followed by compaction at 0.5 GPa pressure with 5 min of dwell time and conventional sintering at 1400°C with 2 h soaking time in Ar atmosphere with Ar flow rate of 100 ml/min. The microstructure of milled and sintered alloy was investigated using X-ray Diffraction (XRD), Scanning electron Microscopy (SEM), Energy dispersive spectroscopy (EDS) and Elemental mapping. Minimum crystallite size of 31.9 nm and maximum lattice strain, dislocation density of 0.23%, 9.12(1016/m2) respectively was found in alloy A at 10 h of milling. Uneven and coarse particles at 0 h of milling converted to elongated flake shape at 10 h of milling. Bimodal (fine and coarse) particle size distribution is revealed in both the alloys and minimum particle size of 0.69 μm is achieved in 10 h milled alloy A. Evidences of formation of intermetallic phases like Y2WO6, Y6WO12 and Y10W2O21 in sintered alloy A and Al2(WO4)3, NiAl10O16, NiAl2O4 and AlWO4 in sintered alloy B were revealed by XRD pattern and SEM micrograph. Minimum grain size of 1.50 μm was recorded in sintered alloy A. Both faceted and spherical W matrix is evident in both the alloys which suggests occurrence of both solid phase and liquid phase sintering. Maximum % relative sintered density and hardness of 85.29% and 5.13 GPa respectively was found in alloy A. Wear study at 20N force at 25 rpm for 15 min on ball on plate wear tester revealed that minimum wear depth (48.99 μm) and wear track width (272 μm) was found for alloy A as compared to alloy B.

A detailed characterization of the Saharan dust collected during the Fennec campaign in 2011: in situ ground-based and laboratory measurements

Abstract. Millions of tons of mineral dust are lifted by the wind from arid surfaces and transported around the globe every year. The physical and chemical properties of the mineral dust are needed to better constrain remote sensing observations and are of fundamental importance for the understanding of dust atmospheric processes. Ground-based in situ measurements and in situ filter collection of Saharan dust were obtained during the Fennec campaign in the central Sahara in 2011. This paper presents results of the absorption and scattering coefficients, and hence single scattering albedo (SSA), of the Saharan dust measured in real time during the last period of the campaign and subsequent laboratory analysis of the dust samples collected in two supersites, SS1 and SS2, in Algeria and in Mauritania, respectively. The samples were taken to the laboratory, where their size and aspect ratio distributions, mean chemical composition, spectral mass absorption efficiency, and spectral imaginary refractive index were obtained from the ultraviolet (UV) to the near-infrared (NIR) wavelengths. At SS1 in Algeria, the time series of the scattering coefficients during the period of the campaign show dust events exceeding 3500 Mm−1, and a relatively high mean SSA of 0.995 at 670 nm was observed at this site. The laboratory results show for the fine particle size distributions (particles diameter < 5µm and mode diameter at 2–3 µm) in both sites a spectral dependence of the imaginary part of the refractive index Im(m) with a bow-like shape, with increased absorption in UV as well as in the shortwave infrared. The same signature was not observed, however, in the mixed particle size distribution (particle diameter < 10 µm and mode diameter at 4 µm) in Algeria. Im(m) was found to range from 0.011 to 0.001i for dust collected in Algeria and 0.008 to 0.002i for dust collected in Mauritania over the wavelength range of 350–2500 nm. Differences in the mean elemental composition of the dust collected in the supersites in Algeria and in Mauritania and between fine and mixed particle size distributions were observed from EDXRF measurements, although those differences cannot be used to explain the optical properties variability between the samples. Finally, particles with low-density typically larger than 10 µm in diameter were found in some of the samples collected at the supersite in Mauritania, but these low-density particles were not observed in Algeria.

Modeling and simulation of particle size distribution behavior in gas–liquid–solid polyethylene fluidized bed reactors

In this work, population balance model (PBM) that describes particle size distribution (PSD) and liquid vaporization modeling scheme (VMS) (including the heat transfer model and droplet vaporization model), which describes liquid evaporation, were incorporated into a three-fluid computational fluid dynamics (CFD) model to analyze PSD behavior in an industrial–scale gas–liquid–solid three–phase polyethylene fluidized bed reactor (FBR). The validation of this CFD–VMS–PBM coupled model was conducted through comparing results with industrial and calculated data, which then was applied to discuss the characteristics of PSD behavior in terms of the effects of particle kinetics, node number, and condensed liquid content. Unlike gas–solid polyethylene conventional FBRs, although the PSD behavior was dominated by particle agglomeration, particle breakage kinetics exerted a great impact on PSD, especially at the initial polymerization period when it competed with aggregates to decrease the defluidization risk of the reactor. Furthermore, the number of nodes strongly affected PSD simulation results, and using three nodes was the best configuration. In this three–phase system, the increase in the condensed liquid content improved the particle growth rate, which affected the reactor's productivity and product's properties, such as mean particle size and final PSD.

Energy distribution during the quasi-static confined comminution of granular materials

A method is proposed to calculate the distribution of energy during the quasi-static confined comminution of particulate assemblies. The work input, calculated by integrating the load-displacement curve, is written as the sum of the elastic deformation energy, the breakage energy and the redistribution energy. Experimental results obtained on samples subjected to compression stresses ranging between 0.4 and 92 MPa are used to calibrate the model. The elastic energy stored in the samples is obtained by simulating the compression test on the final particle size distributions (PSDs) with the discrete element method and by extracting the contact forces. A PSD evolution law is proposed to account for particle breakage. The PSD is related to the total particle surface in the sample, which allows calculating the breakage energy. The redistribution energy, which comprises the kinetic energy of particles being rearranged and the friction energy dissipated at contacts, is obtained by subtracting the elastic energy and breakage energy from the work input. Results show that: (1) at least 60% of the work input is dissipated by particle redistribution; (2) the fraction of elastic deformation energy increases, and the fraction of redistribution energy decreases as the compression stress increases; (3) the breakage energy accounts for less than 5% of the total input energy, and this value is independent of the compressive stress; (4) the energy dissipated by redistribution is between 14 and 30 times larger than the breakage energy.

Influence of temperature on the production and size distribution of fine particles released from beech wood samples

Fine particles generated from laboratory biomass combustion are discussed in this study. The approach combines the thermogravimetric analysis during thermal decomposition of beech wood sample with detailed monitoring of the size distribution of fine particles produced. Thermogravimetric analysis (TGA) allows monitoring the exact temperature influence of a small fuel sample (wood) according to the desired schedule. The cool aerosol stream leaving TGA enters a Scanning Mobility Particle Sizer (SMPS) where the particle size fractions are separated. The monodisperse aerosol is counted by the condensation particle counter (CPC). The parametrical study was carried out to assess the influence of composition, size and surface of the wood sample on the production and size distribution of ultrafine particles

Mineralogical evolution of cement pastes at early ages based on thermogravimetric analysis (TG)

Ordinary thermogravimetric analysis (TG) and high-resolution TG tests were carried out on three different Portland cement pastes to study the phases present during the first day of hydration. Tests were run at 1, 6, 12 and 24 h of hydration, in order to determine the phases at these ages. High-resolution TG tests were used to separate decompositions presented in the 100–200 °C interval. The non-evaporable water determined by TG was used to determine hydration degree for the different ages. The effect of particle size distribution (PSD) on mineralogical evolution was established, as well as the addition of calcite as mineralogical filler. Finer PSD and calcite addition accelerate the hydration process, increasing the hydration degree on the first day of reaction between water and cement. According to high-resolution TG results, it was demonstrated that ettringite was the only decomposed phase in the 100–200 °C interval during the first 6 h of hydration for all studied cements. C-S-H phase starts to appear in all cements after 12 h of hydration.

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

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

Simulation of fine polydisperse particle condensational growth under an octadecane–nitrogen atmosphere

The evolution of particle size distribution (PSD) of fine polydisperse particles at high number concentrations (>105cm−3) was simulated through a combined model employing direct quadrature method of moments (DQMOM) with heat and mass transfer equations. The PSD was assumed to retain log-normal distribution during the heterogeneous condensation process. The model was first verified by exact solution and experimental data prior to investigating the influence of initial conditions on final PSD under an octadecane–nitrogen atmosphere. Low particle number concentrations and high vapor concentrations were beneficial to shift the PSD to larger particles having a narrower distribution. Additionally, vapor depletion has more influence on the final PSD than the heat release parameter for a number concentration of 106cm−3. This study may assist the design process of a gas–solid separating cyclone, to eliminate dust from high-temperature volatiles by pyrolysis of solid fuels.

Colour as reliable tracer to identify the sources of historically deposited flood bench sediment in the Transkei, South Africa: A comparison with mineral magnetic tracers before and after hydrogen peroxide pre-treatment

The fingerprinting of historically deposited sediment has shown valuable potential for reconstructing past environmental changes over the previous <100years. However, changes to sediment particle size distribution, organic matter content, and post-depositional chemical alterations to tracers are significant sources of uncertainty. Most tracers are also expensive to measure, creating barriers to wider adoption of the source fingerprinting approach. Sediment colour represents an inexpensive tracer which can make the method more accessible, provided that it is conservative in the environment and can adequately discriminate between potential sediment sources. The sediment provenance results derived using colour and mineral magnetic tracers are compared to determine if colour can be a reliable tracer when used with historically deposited sediment. This study also explores the usefulness of hydrogen peroxide (H2O2) pre-treatment to reduce uncertainties associated with sediment-associated organic matter. Neither tracer type could discriminate between surface and subsurface sources. However, both could discriminate between igneous and sedimentary sources. The H2O2 treatment had little effect on source discrimination. There was a good agreement between source apportionment results derived using the treated and untreated colour and magnetic tracers in three of the four cores analysed. Both tracer types identified that low sediment contributions from distal igneous sources reach the catchment outlet during low magnitude floods, but distal igneous sources are important during high-magnitude floods. A poor agreement was found between the results derived using magnetic and colour tracers for one core, which was likely caused by a low rate of sediment deposition and the fine particle size distribution of the sediments when compared to the sieved source materials. Colour was a useful tracer for use with historically deposited flood bench sediments. Its usefulness is, however, dependent upon a comparable particle size distribution between sources and sediments, low sediment-associated organic matter concentrations and minimal post-depositional alterations to the sediment. The H2O2 treatment proved to potentially be an additional source of uncertainty rather than a method to reduce it.

Usage of Crushed Concrete Fines in Decorative Concrete

The article is devoted to the questions of usage of crushed concrete fines from concrete scrap for the production of high-quality decorative composite materials based on mixed binder. The main problem in the application of crushed concrete in the manufacture of decorative concrete products is extremely low decorative properties of crushed concrete fines itself, as well as concrete products based on them. However, crushed concrete fines could have a positive impact on the structure of the concrete matrix and could improve the environmental and economic characteristics of the concrete products. Dust fraction of crushed concrete fines contains non-hydrated cement grains, which can be opened in screening process due to the low strength of the contact zone between the hydrated and non-hydrated cement. In addition, the screening process could increase activity of the crushed concrete fines, so it can be used as a fine aggregate and filler for concrete mixes. Previous studies have shown that the effect of the usage of the crushed concrete fines is small and does not allow to obtain concrete products with high strength. However, it is possible to improve the efficiency of the crushed concrete fines as a filler due to the complex of measures prior to mixing. Such measures may include a preliminary mechanochemical activation of the binder (cement binder, iron oxide pigment, silica fume and crushed concrete fines), as well as the usage of polycarboxylate superplasticizers. The development of specific surface area of activated crushed concrete fines ensures strong adhesion between grains of binder and filler during the formation of cement stone matrix. The particle size distribution of the crushed concrete fines could achieve the densest structure of cement stone matrix and improve its resistance to environmental effects. The authors examined the mechanisms of structure of concrete products with crushed concrete fines as a filler. The results of studies of the properties of the crushed concrete fines were provided. It is shown that the admixture of the crushed concrete fines has little effect on the colour characteristics of the decorative concrete products. The preferred options to improve the surfaces of decorative concrete are also proposed.

Similar Soils but Different Soil-Forming Factors: Converging Evolution of Inceptisols in Brazil

Soils result from the interaction of five independent formation factors. If one factor varies, while the others remain constant, different soils can be produced. Herein, we demonstrated an opposing trend, wherein two soils were similar, despite considerable differences in all factors of soil formation. We sampled two Inceptisols (Oxic Dystrudepts) formed on different parent materials (gneiss vs. mica schist), climate (tropical altimontane vs. warmer, drier plateau), topography (1 650 m, 45% slope vs. 1 000 m, 8% slope), time (rejuvenated vs. old, stable surface), and vegetation (rainforest vs. Cerrado savanna). The two soils had similar chemical properties, whereas the soil on mica schist had finer particle size distribution, lower porosity, and lower saturated hydraulic conductivity. These properties were related to a coarser blocky microstructure compared to the soil on gneiss. Both soils presented active mineral weathering and pronounced pedoplasmation, demonstrated by clay contents > 300 g kg−1, although only the Dystrudept on gneiss possessed coarse rock fragments. The C horizons of both soils presented fragmented clay coatings suggestive of argilluviation, likely relict, because they were not observed in the B horizons. The similarities in many properties of the two Dystrudepts, despite contrasting factors of soil formation, suggest converging evolution and that soil classification at the subgroup level was efficient in grouping similar formative processes in tropical conditions. Moreover, this work revealed that similar pedogenic processes acting on different factors of soil formation can result in similar soil properties, at least for Inceptisols where further soil development is hindered by topographic limitations.

Seasonal variation of columnar aerosol optical properties and radiative forcing over Beijing, China

Long-term seasonal characteristics of aerosol optical properties and radiative forcing at Beijing (during March 2001–March 2015) were investigated using a combination of ground-based Sun/sky radiometer retrievals from the AERONET and a radiative transfer model. Aerosol optical depth (AOD) showed a distinct seasonal variation with higher values in spring and summer, and relatively lower values in fall and winter. Average Angstrom exponent (AE) in spring was lower than other seasons, implying the significant impact of dust episodes on aerosol size distribution. AE mainly distributed between 1.0 and 1.4 with an obvious uni-peak pattern in each season. The observation data showed that high AODs (>1.0) were clustered in the fine mode growth wing and the coarse mode. Compared to AOD, seasonal variation in single scattering albedo (SSA) showed an opposite pattern with larger values in summer and spring, and smaller ones in winter and fall. The highest volume size distribution and median radius of fine mode particles occurred in summer, while those of coarse mode particles in spring. The averaged aerosol radiative forcing (ARF) at the top of the atmosphere (TOA) in spring, summer, fall and winter were −33 ± 22 W m-2, -35 ± 22 W m-2, -28 ± 20 W m-2, and -24 ± 23 W m-2 respectively, and these differences were mainly due to the SSA seasonal variation. The largest positive ARF within atmosphere occurred in spring, implying strong warming in the atmosphere. The low heating ratio in summer was caused by the increase in water vapor content, which enhanced light scattering capacity (i.e., increased SSA).

Calculating breakage parameters of a batch vertical stirred mill

The paper discusses the outcome of a series of test work carried out in a screw type batch vertical stirred mill to evaluate the effect of experimental conditions on the product particle size distribution and generation of fines. A time-based population balance model has been utilized to develop mill selection and breakage function for different operating conditions. A systematic variation in both selection and breakage functions of the population balance model with changes in process conditions are fitted through regression models.

Preparation of La&lt;sub&gt;0.7&lt;/sub&gt;Sr&lt;sub&gt;0.3&lt;/sub&gt;Co&lt;sub&gt;0.2&lt;/sub&gt;Fe&lt;sub&gt;0.8&lt;/sub&gt;O&lt;sub&gt;3-δ &lt;/sub&gt;(LSCF 7328) by Combination of Mechanochemical and Solid State Reaction

Structure evolution and morphology of La0.7Sr0.3Co0.8Fe0.2O3-δ (LSCF 7328) were investigated during two different preparation methods namely mechanochemical and combination of mechanochemical-solid state. The result shows that no characteristic peak of perovskite oxide was found on the diffractogram of the product of sole mechanochemical method at 600 rpm and up to 12 h of high energy milling process. On the other hand, the manual grinding method that was followed by solid state calcination produces irregular particle size. Due to the result, the combination of both methods was proposed to obtain the fine structure formation and particle size distribution. Rietveld refinement was used to investigate the lattice distortion. It was found that unit cell remains unchanged at increasing milling time. Moreover, the combination method produces regular particle size at milling time of 0.5 h. At longer milling time, the more regular particle size is formed which comes from highly energy transfer of milling.

Ultrasound Assisted Particle Size Control by Continuous Seed Generation and Batch Growth

Controlling particle size is essential for crystal quality in the chemical and pharmaceutical industry. Several articles illustrate the potential of ultrasound to tune this particle size during the crystallization process. This paper investigates how ultrasound can control the particle size distribution (PSD) of acetaminophen crystals by continuous seed generation in a tubular crystallizer followed by batch growth. It is demonstrated that the supersaturation ratio at which ultrasound starts seed generation has a substantial effect on the final PSD while the applied power is insignificant in the studied conditions. The higher the supersaturation ratio, the smaller the final crystals become up to a supersaturation ratio of 1.56. Furthermore, it was shown that ultrasound can also impact the final PSD when applied during the growth phase. Frequencies of 850 kHz or below reduce the final particle size; the lower the applied frequency, the smaller the crystals become. In conclusion, one could state that ultrasound is able to control the particle size during seed generation and subsequent growth until the final particle size.

Recycling waste tire rubber by water jet pulverization: powder characteristics and reinforcing performance in natural rubber composites

Abstract Pulverization is a general strategy used prior to any practical application of recycled waste tire rubber (WTR). Mechanical grinding, in use currently, is an inefficient technique due to low-quality rubber powder production and certain indispensable additional pretreatments. The aim of this study is to propose a novel pulverization technique of WTR by ultrahigh pressure water jet. Efficient pulverization of WTR was accomplished by water jet without any pretreatment. Powder characteristics, including particle size distribution (PSD), surface area, thermal behavior and chemical structure changes, were investigated. The curing, mechanical and morphological properties of natural rubber (NR) vulcanizates filled with ground tire rubber (GTR) from water jet pulverization (WJPULV) were evaluated. The results indicate that GTR granules from WJPULV possess a quite fine PSD and large surface area, show similar thermal degradation behaviors to the original WTR and have been partially devulcanized. The improvement of tensile and tear strength of the composites reveals that GTR from WJPULV can be added up to 40 phr without adverse effect. The morphological analysis corroborates the homogeneity of GTR in the NR matrix. All findings confirm that water jet can be an excellent choice for pulverization of WTR.