MISTURAS BI-DISPERSAS DE AREIAS: EFEITOS DA GRANULOMETRIA NO EMPACOTAMENTO E FLUIDEZ

Este trabalho teve como o objetivo avaliar o efeito da granulometria (tamanho das partículas e faixa de distribuição granulométrica) nas principais propriedades físicas de leitos bi dispersos, tais como densidade aparente, porosidade, coesão, compressibilidade e energia básica de fluxo. Para tanto foram confeccionados dois grupos de misturas envolvendo areias comerciais com diferentes granulometrias. O primeiro grupo (G1) consistiu na incorporação de dois tipos de areias de quartzo (partículas menores que mesh 200 e mesh 600) em um de tipo de areia de sílica comercial 50/60 (grosso). O segundo grupo (G2) constituiu em misturas de areias de sílica 40/50 (grosso) mediante adição de partículas de menor granulometria de areia de sílica 50/60 e 80/100. Todas as misturas foram analisadas em condições estáticas, dinâmicas e na iminência do movimento (cisalhamento). Como resultado observou-se uma maior tendência por parte das partículas de tamanho reduzido em formar aglomerados, aumentando a porosidade e diminuindo densidade aparente quando não consolidadas. A presença de partículas de tamanho reduzido nas misturas do grupo 1 também melhorou a fluidização das misturas deste grupo, mas prejudicou a fluidez aumentando a coesão do meio. Os resultados obtidos para o grupo 2 de misturas não apresentaram diferenças significativas em suas características com a incorporações de finos. Isto se deve a baixa relação entre o tamanho das partículas, de maneira que as partículas menores não cabem nos interstícios das partículas maiores.The present work aims to evaluate the effect of granulometry (particle size and particle size distribution) on the manly physical properties of bidisperse bulk solids, such as bulk density, porosity, cohesion, compressibility and basic flow energy. Therefore, two groups of mixtures comprising commercial sands with different sizes were prepared. The first group (G1) consisted on adding two sort of fine quartz powder (particle undersize of 200 and 600 mesh) into commercial sand 50/60 (coarse). The second group (G2) was formulated adding commercial sand (80/100 and 50/60) added into coarse one (40/50). All mixtures were tested at static and dynamic conditions and at incipient transition (shear test). As result, it was observed higher interactions for smaller quartz’s particles that lead to form agglomerates, increasing bulk porosity and reducing bulk density of non-consolidated mixtures comprising this sort of material. Fine particles at group 1 mixtures have also improved the quality of fluidization, but decrease powder flowability increasing cohesion. The results obtained for group 2 mixtures have revealed no significant changes on bulk properties as increasing fine particle into coarse one. This is could be attributed to the low ratio between fine and coarse particles, changing particle packing, once the interspaces between coarse particles could not be filled with fine one.

Download Full-text

Contribution of Fine Particles to Air Emission at Different Phases of Biomass Burning

Atmosphere ◽

10.3390/atmos10050278 ◽

2019 ◽

Vol 10 (5) ◽

pp. 278 ◽

Cited By ~ 2

Author(s):

Niloofar Ordou ◽

Igor E. Agranovski

Keyword(s):

Particle Size ◽

Particle Size Distribution ◽

Fine Particles ◽

Combustion Process ◽

Coarse Particles ◽

Biomass Smoke ◽

Smoke Particles ◽

Air Emission ◽

Entire Duration ◽

Diffusion Properties

Particle size distribution in biomass smoke was observed for different burning phases, including flaming and smouldering, during the combustion of nine common Australian vegetation representatives. Smoke particles generated during the smouldering phase of combustions were found to be coarser as compared to flaming aerosols for all hard species. In contrast, for leafy species, this trend was inversed. In addition, the combustion process was investigated over the entire duration of burning by acquiring data with one second time resolution for all nine species. Particles were separately characterised in two categories: fine particles with dominating diffusion properties measurable with diffusion-based instruments (Dp < 200 nm), and coarse particles with dominating inertia (Dp > 200 nm). It was found that fine particles contribute to more than 90 percent of the total fresh smoke particles for all investigated species.

Download Full-text

The Role of Particle Size Distribution in the Performance and Modelling of Filtration

Water Science & Technology ◽

10.2166/wst.1993.0199 ◽

1993 ◽

Vol 27 (10) ◽

pp. 19-34 ◽

Cited By ~ 9

Author(s):

R. I. Mackie ◽

R. Bai

Keyword(s):

Particle Size ◽

Particle Size Distribution ◽

Size Distribution ◽

Fine Particles ◽

Coarse Particles ◽

Large Particles

The paper examines the importance of size distribution of the influent suspension on the performance of deep bed filters and its significance with regard to modelling. Experiments were carried out under a variety of conditions using suspensions which were identical in every respect apart from their size distribution. The results indicate that the presence of coarse particles does increase the removal of fine particles. Deposition of fine particles leads to a greater headloss than deposition of large particles. Changes in size distribution with time and depth play an important role in determining the behaviour of a filter, and models of both removal and headloss development must take account of this.

Download Full-text

MPT Influence on the Rheological Behaviour of Self-Flow Refractory Castables

Materials Science Forum ◽

10.4028/www.scientific.net/msf.587-588.133 ◽

2008 ◽

Vol 587-588 ◽

pp. 133-137 ◽

Cited By ~ 5

Author(s):

Abílio P. Silva ◽

Ana M. Segadães ◽

Tessaleno C. Devezas

Keyword(s):

Particle Size ◽

Particle Size Distribution ◽

Mechanical Strength ◽

Size Distribution ◽

Fine Particles ◽

Rheological Behaviour ◽

Response Surfaces ◽

Coarse Particles ◽

Aggregate Particle ◽

Refractory Castables

The success of a refractory castable is largely due to the quality of its properties and ease of application. Self-flow refractory castables (SFRC), with high flowability index (>130%), can be easily accommodated in a mould without the application of external energy, being ideal for the manufacture of monolithic linings. SFRC castables without cement require a matrix of very fine particles, which guarantees improved rheological behaviour and performs the role of the binder in the absence of the refractory cement. The presence of the aggregate (coarse particles) hinders the flowability index, but improves the castable mechanical strength and reduces firing shrinkage, and also contributes to the reduction of the castable costs. The control of the maximum paste thickness (MPT) allows the reduction of the coarse particles interference, minimizing the number of contact points among the grains and avoiding the formation of an aggregate skeleton that impairs the flowability of the mixture. In the present work, 100% alumina SFRCs without cement were produced with a fixed matrix of fine particles, whose particle size distribution was optimized using statistical techniques (mixtures design and triangular response surfaces). Different aggregate particle size distributions were used, with several MPT values, with the objective of evaluating which was the mean distance that maximized the flowability index, simultaneously ensuring good mechanical strength for the refractory castable. Ensuring a minimum surface area of 2.22m2/g, the mixtures reach the self-flow turning point with a minimum water content and the maximum flowability is obtained for an aggregate particle size distribution modulus of q=0.22, and consequently an optimized MPT value. SFRC with high mechanical strength (>60MPa) were obtained.

Download Full-text

Size Characteristics of Sediments Eroded under Different Masson Pine Litter Covers in South China

Water ◽

10.3390/w13162190 ◽

2021 ◽

Vol 13 (16) ◽

pp. 2190

Author(s):

Fangfang Zhu ◽

Yuchen Li ◽

Jinhua Cheng

Keyword(s):

Particle Size ◽

Soil Erosion ◽

Particle Size Distribution ◽

Size Distribution ◽

Fine Particles ◽

Enrichment Ratio ◽

Coarse Particles ◽

Characteristic Parameters ◽

Sediment Distribution ◽

The Relationship

The particle size distribution characteristics of runoff sediments are vital for understanding the effect of the mechanism of soil erosion on slopes. The objective of this study was to investigate the particle-size distribution of sediments eroded from slopes covered by different litter coverage masses under artificial rainfall simulation. Litter was spread on the surface of a soil tank according to different biomasses (0 g·m−2, 100 g·m−2, 200 g·m−2 and 400 g·m−2). The mean weight diameter (MWD), fractal dimension (D) and enrichment ratio (ER) are characteristic parameters of sediment particle size. The MWD and D were more sensitive to soil erosion and had a significant negative correlation with the slope angle and rainfall intensity. The performance of the MWD on the slope (5°) was less than the MWD on the slope (10°). The relationship between eroded sediment distribution characteristic parameters and the litter coverage mass had a significant influence on the content of coarse particles. The content of fine particles accelerated, decreased and then stabilized, whereas coarse particles increased first and then stabilized. The litter diameter and surface area were the main parameters that affected the MWD and D. Under different rain intensities and slopes, the ER varied inconsistently with litter coverage mass. Coarse particles were eroded easily and selectively, and soil erosion had no sorting effect on fine particles. These findings support the quantitative study of the relationship between the amount of litter coverage mass and the particle size of soil sediments.

Download Full-text

Bazı Model Toz Gıdaların Akışkanlığına ve Sıkıştırılabilirliğine Partikül Boyutunun Etkisinin PFT Toz Akışı Test Cihazı Kullanılarak Belirlenmesi

Turkish Journal of Agriculture - Food Science and Technology ◽

10.24925/turjaf.v6i1.55-60.1622 ◽

2018 ◽

Vol 6 (1) ◽

pp. 55

Author(s):

Ertan Ermiş ◽

Rabia Güneş ◽

İnci Zent

Keyword(s):

Particle Size ◽

Bulk Density ◽

Rock Salt ◽

Flow Behaviour ◽

Powder Flow ◽

Particle Size Range ◽

Powder Samples ◽

Powder Flowability ◽

Varied Size ◽

Sugar Powder

Determination of powder flow behaviour is very important due to the importance of their technological applications. Use of powder flowability data in the design of hoppers is one example. Investigation of the parameters such as particle size, particle size distribution, particle shape, chemical composition, water content and temperature which affect flowability is necessary. Within this work a powder flow tester (PFT) from Brookfield Engineering Laboratories Inc. was employed to assess the flow behaviour of table sugar and rock salt powders having varied size fractions. Flow function, bulk density as well as compressibility of powder samples were tested. The rock salt and table sugar powders were grinded, screened and fractioned into 5 fractions of rock salt and 7 fractions of table sugar powder. The results indicated that increasing particle size led to increasing flowability and bulk density while decreasing compressibility. The threshold particle size range which changes these parameters significantly was notes as 100-200 µm.

Download Full-text

Identification of key aerosol populations through their size and composition resolved spectral scattering and absorption

Atmospheric Chemistry and Physics ◽

10.5194/acp-13-2455-2013 ◽

2013 ◽

Vol 13 (5) ◽

pp. 2455-2470 ◽

Cited By ~ 48

Author(s):

F. Costabile ◽

F. Barnaba ◽

F. Angelini ◽

G. P. Gobbi

Keyword(s):

Particle Size ◽

Optical Properties ◽

Fine Particles ◽

Single Scattering ◽

Optical Measurements ◽

Coarse Particles ◽

Spectral Variability ◽

General Validity ◽

Aerosol Properties

Abstract. Characterizing chemical and physical aerosol properties is important to understand their sources, effects, and feedback mechanisms in the atmosphere. This study proposes a scheme to classify aerosol populations based on their spectral optical properties (absorption and scattering). The scheme is obtained thanks to the outstanding set of information on particle size and composition these properties contain. The spectral variability of the aerosol single scattering albedo (dSSA), and the extinction, scattering and absorption Angstrom exponents (EAE, SAE and AAE, respectively) were observed on the basis of two-year measurements of aerosol optical properties (scattering and absorption coefficients at blue, green and red wavelengths) performed in the suburbs of Rome (Italy). Optical measurements of various aerosol types were coupled to measurements of particle number size distributions and relevant optical properties simulations (Mie theory). These latter allowed the investigation of the role of the particle size and composition in the bulk aerosol properties observed. The combination of simulations and measurements suggested a general "paradigm" built on dSSA, SAE and AAE to optically classify aerosols. The paradigm proved suitable to identify the presence of key aerosol populations, including soot, biomass burning, organics, dust and marine particles. The work highlights that (i) aerosol populations show distinctive combinations of SAE and dSSA times AAE, these variables being linked by a linear inverse relation varying with varying SSA; (ii) fine particles show EAE > 1.5, whilst EAE < 2 is found for both coarse particles and ultrafine soot-rich aerosols; (iii) fine and coarse particles both show SSA > 0.8, whilst ultrafine urban Aitken mode and soot particles show SSA < 0.8. The proposed paradigm agrees with aerosol observations performed during past major field campaigns, this indicating that relations concerning the paradigm have a general validity.

Download Full-text

Analysis of the Influence Factors on High Compressibility Water Atomized Iron Powder

Materials Science Forum ◽

10.4028/www.scientific.net/msf.859.118 ◽

2016 ◽

Vol 859 ◽

pp. 118-124

Author(s):

Guo Ping Li ◽

Li Bo Guo ◽

Li Hui Sun ◽

Feng Hua Luo ◽

Jiao Du ◽

...

Keyword(s):

Particle Size ◽

Iron Powder ◽

Oxygen Content ◽

Fine Particles ◽

Influence Factors ◽

Impurity Content ◽

Processing Parameters ◽

Coarse Particles ◽

Green Density ◽

Powder Particles

In this paper, the influence factors on high compressibility water atomized iron powder LAP100.29 were studied such as the processing parameters, the proportion of coarse particles, powder oxygen content and impurity. The results showed that, by increasing the purity of molten steel and improving atomization temperature, the iron content of water atomized iron powder particles reached more than 99.67 %, the oxygen content was less than 0.08 %, acid insoluble was less than 0.08 %, green density reached 7.21~7.22 g/cm3. The contents of +80 and -80～+100 mesh powder were 1.6 % and 7.5 %, respectively. The compressibility could be improved by the increase of the coarse particles and the reduction of the fine particles (for example, lowering the content of -325 mesh particles). Generally speaking, the compressibility of the water atomized iron powder can be improved fundamentally by reducing oxygen content, impurity content and the reasonable distribution of particle size.

Download Full-text

Effects of carbonaceous materials and particle size on oral and inhalation bioaccessibility of PAHs and OPEs in airborne particles

10.21203/rs.3.rs-266917/v1 ◽

2021 ◽

Author(s):

Yuan Zeng ◽

shejun Chen ◽

Yun Fan ◽

Qiqi Li ◽

Yufeng Guan ◽

...

Keyword(s):

Particle Size ◽

Elemental Carbon ◽

Fine Particles ◽

Airborne Particles ◽

Coarse Particles ◽

Strongly Correlated ◽

Oral Bioaccessibility ◽

Polycyclic Aromatic ◽

Potential Factors ◽

Scientific Attention

Abstract Bioavailability of environmental contaminants is attracting considerable scientific attention due to growing awareness of its importance for risk assessment. In this study, potential factors governing bioaccessibility of airborne particles-bound polycyclic aromatic hydrocarbons (PAHs) and organophosphorus esters (OPEs) in stimulated gastrointestinal and respiratory tracts were elucidated. Particle concentrations of PAHs and OPEs at the eight sites were 2.4−32.3 ng/m3 and 1.6−19.9 ng/m3, respectively. In fine particles (with aerodynamic diameter less than 2.5 µm), 4- to 6-ring PAHs were more strongly correlated with organic carbon (OC) than elemental carbon (EC); while 3- and 4-ring PAHs in coarse particles (2.5−10 µm) tended to associate with EC. OPEs mostly showed significant correlations with EC in both fine and coarse particles. OC and EC exerted a significantly restraining effect on the oral and inhalation bioaccessibility of most HOCs in fine particles due to sorption of HOC molecules to these components. Furthermore, the effects varied, which could depend either on the emission sources (for oral bioaccessibility of PAHs) or the physicochemical properties of HOCs (for bioaccessibility of OPEs and inhalation bioaccessibility of PAHs). Linear regression indicated that EC should play a more important role in the inhalation bioaccessibility than the oral bioaccessibility. Particle size of airborne particles is a relatively less significant factor determining the bioaccessibility.

Download Full-text

Composite materials for the restoration of historical monuments made of soapstone (steatite): a statistical approach

Journal of Building Material Science ◽

10.30564/jbmr.v1i1.546 ◽

2019 ◽

Vol 1 (1) ◽

Author(s):

Tulio Hallak Panzera

Keyword(s):

Particle Size ◽

Composite Materials ◽

Epoxy Polymer ◽

Fine Particles ◽

Particle Packing ◽

Particle Size Range ◽

Cultural Patrimony ◽

Particle Size Fractions ◽

Historical Monuments ◽

Maximum Particle

Currently many works of art made of soapstone and recognized as cultural patrimony of humanity are in an advanced stage of degradation. Hence, it is necessary to interrupt this process and recover the deteriorated parts. Composite materials consisted of steatite particles and epoxy polymer are designed and characterised for their application in the repair of sculptures made of soapstone. The material applied in restorations should provide coloration and texture similar to soapstone besides structural requirements. The degree of similarity of the artificial material to the rock is enhanced by the proper selection of the particle size range and the increase of steatite incorporation in the composites. A statistical methodology based on the mixture design is used to optimize the relative amount of three particle size fractions of steatite particles in order to maximise the proportion of the dispersed phase in the composites. The maximum particle packing density (1.50 g/cm³) is obtained for a ternary mixture, composed of 62% of coarse particles (1.18 mm - 0.60 mm), 6% of medium sized particles (0.60 mm - 0.30 mm) and 32% of fine particles (0.30 mm - 0.15 mm). In this manner, the fabrication of composites based on an epoxy polymer matrix with 70wt% of incorporated steatite particles has been possible, increasing the maximum amount by 10% as used in previous works.

Download Full-text