Particle Fineness Research Articles

Environmental factors affecting geotextile filter design in coal refuse impoundments

The US Mine Safety and Health Administration (MSHA) issued the Second Edition of Engineering and Design Manual for Coal Refuse Disposal Facilities prepared by D'Appolonia in 2009. This second edition provides design guidance on the use of nonwoven geotextiles for drainage applications when replacing graded granular filters in coal waste impoundments. Coal refuse is susceptible to slaking that produces an increase in fine particles which may lead to geotextile clogging. This article presents the results of research which investigated the effects of slaking on the hydraulic conductivity of permeated refuse specimens in order to identify parameters influencing the design criterion for selecting candidate nonwoven geotextiles for drainage applications. Permeability tests were performed on refuse–geotextile samples at different compaction energies and varying moisture contents, followed by post-grain size distribution (GSD) tests. Conclusions indicate that (i) the k soil of the acid-permeated refuse samples is one order of magnitude higher than the k soil of the water-permeated refuse samples and was attributed to fine particle aggregation. Any potential increase in the k soil due to continued particle aggregation may approach a failure criterion where the soil permeability is too high. The long-term effects of low-pH groundwater may cause an increase in refuse permeability, leading to criterion failure due to particle aggregation; (ii) comparisons of the coarse coal GSDs for the pre- and post-compacted, water-permeated specimens showed an increase in the production of particle fines due to slaking at critical indices.

Potential environmental pollution hazards by coal based power plant at Jhansi (UP) India

Coal, a fossil fuel, is the largest source of energy for the generation of electricity in India. In order to study the potential environmental hazards by coal based power plants, particulate matters were collected using Stack Monitoring Kit and gaseous pollutants by Automatic Flue Gas Analyzer. The morphological and chemical properties, mineralogical composition and particle size distributions have been determined by SEM–EDX, XRD and CILAS. The data revealed the presence of particulate matters, SO2, NOx in the range of 236–315, 162–238, 173–222 mg/Nm3 respectively. The emission of CO2 was in the range of 43,004–60,115 Nm3/h with an average of 52,830 Nm3/h. Among the elements, Fe > Mn > Al > Zn > B > Ni > Cr > Cu were present in substantially higher proportion than Pb > Mo > Cd > Se > As > Hg. It was found that most of the elements were concentrated on fly ash surface rather than coal, bottom ash and pond ash. This variation may be attributed to the fineness of fly ash particles with large surface ratio to mass. Mineralogical studies of coal and fly ash by X-ray diffraction revealed the presence of mullite, quartz, cristobalite and maghemite. Presence of mullite and quartz found in fly ash indicate the conversion of complex minerals to mullite and quartz at high temperature. Transfer Coefficient was calculated to determine the ratio of the enrichment of trace elements in fly or bottom ash with respect to coal and pond ash.

Characterization of biologically active insulin-loaded alginate microparticles prepared by spray drying

Background: Spray drying has been used as a means to encapsulate therapeutics in polymeric matrices to improve stability and alter pharmacokinetics. This research aims to characterize alginate microparticles formed by spray drying to encapsulate insulin for therapeutic delivery applications.Methods: Particle size was characterized by laser diffraction spectroscopy, morphology by scanning electron microscopy, and protein and polymer distribution by confocal laser scanning microscopy. In addition, particle fines collected from the spray-dryer exhaust unit were characterized for size and morphology. The insulin encapsulation efficiency (EE) was determined after particle dissolution through quantification by spectrophotometric analysis. An in-vitro bioassay involving stimulation of rat L6 myoblasts was developed to confirm the bioactivity of released insulin.Results: Mean diameter of the product was 2.1 ± 0.3 μm. Larger particles appeared spherical, with some smaller particles presenting surface topography variability and divoting. Protein EE was 38.2% ± 9.5%, with confocal microscopy showing the protein and polymer concentrated at the surface of larger particles, but more evenly distributed throughout smaller particles. A bioassay for the in-vitro quantification of insulin bioactivity was developed by calibrating the ratio of phosphorylated to total cellular protein kinase B (PKB; also known as AKT). in insulin-stimulated rat L6 myoblasts. Insulin released from the particles was 88% ± 15% bioactive, showing that spray drying had minimal impact on protein structure.Conclusion: Spray drying was effective in producing microparticles containing bioactive insulin. Future studies will focus on the improvement of the EE and particle uniformity with the aim of developing this technology further for the encapsulation and delivery of peptide or protein-based therapeutics.

Experiment Study and Process Parameters Analysis on Turbo Air Classifier for Talc Powder

Talc powder is widely used in building engineering, especially preparation for coating, waterproof material and ceramics. With increasing demands for building material quality, the requirement for the particle fineness and particle-size distribution of talc power becomes higher than ever. A new method of process parameters analysis on turbo air classifier for talc powder is put forward in this paper. The effect of the two process parameters on a classification performance index is reflected visually through the 3-D drawing based on Matlab, so the one-dimensional process parameter analysis method is expanded to the two-dimensional process parameters analysis method. In the present study, a turbo air classifier is used as the classification system and fine talc powder is used as materials. The sample data is gathered through setting different process parameters. The experiment results show that process parameters analysis can be implemented quickly and visually. In actual production applications of turbo air classifier system, the user can select the suitable process parameters flexibly considering the production requirements according to the 3-D meshes based on Matlab. This method is also applicable for classification of other powder.

Synthesis of coral-like and spherical nickel nanoparticles using Taguchi L8 experimental design

In this article, spherical nanoparticles with narrow diameter range (4–10·7 nm) and coral-like nickel architectures have been synthesised in a laboratory scale in a mixture of 1∶1 (v/v) ethylene glycol and water of pH 10–11·5 using microwave as heating source. The reducing agent used was hydrazine hydrate. Samples have been tested by X-ray diffraction (XRD), SEM, laser light scattering, thermogravimetry–differential thermogravimetry, Brunauer–Emmett–Teller and Fourier transform infrared spectroscopy. The fineness of spherical nickel particles was optimised using the Taguchi L8 experimental design. The reaction mechanism was also discussed.

The self-heating of sulfides: Galvanic effects

Under certain conditions of moisture and oxygen, sulfides can spontaneously heat or self-heat. In this paper, we test a hypothesis that galvanic interaction between some sulfides can promote self-heating. Using a self-heating test procedure, four cases were examined. Case 1 (specimen sulfides) and case 2 (concentrates) comprised four sulfides: pyrite, chalcopyrite, sphalerite and galena. They were tested individually and as 50:50 weight mixtures. The individual samples and mixtures of low rest-potential difference did not self-heat but mixtures of high rest-potential difference did. In case 3, pyrite was mixed 50:50 with two materials that self-heated alone, pyrrhotite and nickel concentrate, and self-heating further increased. For case 4, mixtures of pyrite–sphalerite were tested as a function of particle size. Self-heating increased as particle size decreased and it was the fineness of the pyrite (high rest-potential or cathodic mineral) that governed the response. The increase in self-heating with high rest-potential difference and increasing particle fineness of cathodic mineral supports that galvanic interaction can contribute to sulfide self-heating. A possible mechanism based on the hydrogen sulfide hypothesis is proposed where the reduction reaction on the cathodic mineral surface is ferric to ferrous. The understanding gained will be of interest to those involved in mining, storage, shipping and disposal of sulfide minerals.

Understanding expansion in calcium sulfoaluminate–belite cements

Calcium sulfoaluminate–belite (CSAB) cements are promoted as sustainable alternatives to portland cement because of their lower energy and CO 2 emissions during production and comparable performance. However, the formation of ettringite, the main hydration product in CSAB cements, can be expansive, sometimes resulting in cracking. The factors controlling expansive behavior in CSAB cements have not been completely elucidated. In this study, three CSAB cements synthesized from reagent-grade chemicals with varied phase compositions were examined for dimensional stability in water and sulfate solutions. The interdependent effects of C 4A 3Ŝ (Ye'elimite) content, calcium sulfate content, water-to-cement ratio, and particle fineness on CSAB cement expansion were evaluated. The results show that the expansive behavior can be controlled by altering chemical and physical factors in CSAB clinker, cement, and paste.

Filler effect and pozzolanic reaction of ground palm oil fuel ash

This research examines the compressive strength of mortar and how the filler effect and pozzolanic reaction of ground palm oil fuel ash (POFA) contribute to this strength. POFA and river sand were ground to three different particle sizes and used to replace Type I Portland cement at 10–40% by weight of binder to cast the mortar. The compressive strengths of ground POFA and ground river sand mortars were determined at various ages between 7 and 90 days. The results showed that the compressive strength of mortar due to the filler effect of ground river sand was nearly constant during the 7–90 day period for a specified replacement rate of cement. However, the compressive strength of mortar due to the filler effect tended to increase slightly with increased cement replacement. The pozzolanic reaction of ground POFA increased with increasing particle fineness of ground POFA, replacement rate of cement, and age of the mortar. The compressive strength contribution from the pozzolanic reaction of ground POFA was much more pronounced than the contribution from the filler effect when the smallest sizes of both materials were considered.

The Effect of the Microstructure on Oxidation of Sulfide-Metal Alloys of Copper and Nickel

The methods of thermal, thermogravimetric, mass spectrometric and high-temperature X-ray analysis have been used to determine the chemism of the processes involving the oxidation of a sulfide-metal copper-nickel alloy during continuous heating to 1190 K in an air flow. It has been found that the fineness of particles, the size of the sulfide phases in these particles, and the phase composition influence the phase transformation temperatures, as well as the kinetics and the sequence of the oxidation processes.

Effect of Sodium Dodecyl Sulphate on the Composition of Electroless Nickel – Yttria Stabilized Zirconia Coatings

The influence of a surfactant on the composition of nickel – yttria stabilised zirconia (YSZ) cermet coatings, applied by electroless nickel plating technique was examined. The amphiphilic characteristics of anionic surfactant sodium dodecyl sulphate (SDS), was relied upon for enhanced dispersion of YSZ particles co-deposited for use as anodes in solid oxide fuel cell technology and potential heat absorbing layers in thermal barrier coatings. Optical microscopy was employed to study the correlation between the plating thickness, level of ceramic loading and SDS concentration while the effect of the surfactant and fineness of YSZ particles on the as-deposited coating’s ceramic to metal ratio, was analysed using energy dispersive X-ray analysis (EDXA) characterisation technique.

The Design of Software Parallel Engineering Model Based on Petri Net

In the paper, Using Petri net to a component-based reuse-driven software model for parallel engineering is proposed. The model applies Petri net to analyze parallelism in the entire software process. The model excavates fully Parallelism during software life cycle, supports various parallel of different particle size coarse and fine. The model can greatly enhance the software development, software productivity and shorten the development cycle.

Effect of particle size distribution on the hydration and compressive strength development of α-calcium sulfate hemihydrate paste

Particle size distribution (PSD) of α-calcium sulfate hemihydrate (α-HH) was quantitatively analyzed by Rosin–Rammler–Bennett (RRB) distribution function. The hydration of plaster and the compressive strength development of paste were correlated with the RRB parameters, focusing on the singular effect of particle fineness (described by the characteristic particle size, De) and distribution width (described by the uniformity coefficient, n) on the water–hemihydrate weight ratio (W/H) for standard consistency, hydration rate, compressive strength and microstructure of paste. The effect of particle fineness is more pronounced than that of distribution width. The microstructure details are in general agreement with the impact of PSD on the hydration and the compressive strength development of paste. The plaster with the optimum PSD hydrates completely without a hydration barrier at a relatively lower W/H for standard consistency. Then, homogeneous and well-grown calcium sulfate dihydrate (DH) crystals and a more compact structure are obtained, leading to a higher compressive strength. For pastes of standard consistency, an optimum PSD is characterized by De≈35μm and n≈0.82.

Influence of soil grading on properties of compressed cement-soil

Compressed cement-soil block is known as low cost building materials. This paper studies the effects of soil grading and the characteristics of soil on the properties of compressed cement-soil such as compressive strength, dry density and water absorption. Compacting pressure of 10 MPa and 30% binder with respect to cement content of 10% were used. The results obtained from crushed soil particles were better than those from natural soil. Mixture of 35% soil and 65% sand produced the optimum of strength, dry density and water absorption. Strength and dry density increased with the fineness of soil particles. Moreover, soil properties also affect the strength properties of cement-soil. Its strength is significantly reduced with increasing plasticity index or liquid limit.

Hydration properties of basic oxygen furnace steel slag

Basic oxygen furnace steel slag is the most common steel slag in China. In this study, the hydration properties of this kind of steel slag were investigated. Steel slag was ground separately to 458 m 2/kg as well as 506 m 2/kg. Different hydration conditions were set by changing the temperature or pH value. Hydration exothermic rate was measured within 4 days. Non-evaporable water content, hydration products and hardened paste morphologies were investigated at 1, 3, 7, 28 and 90 days. The results showed that the hydration process of steel slag was similar with that of cement. However, its hydration rate was much lower than cement. The hydration rate of steel slag at the early age could be accelerated by raising the fineness of particles, curing temperature or alkalinity of solution. However, raising the pH value of solution had little efficiency for the later hydration of steel slag and raising curing temperature even had negative influence on its later hydration. CSH gel and Ca(OH) 2 were the main hydration products of steel slag. A part of C 3S and C 2S crystal in steel slag had very low activity and unhydrated after 90 days. RO phase was almost inert. The interface between the particles of RO phase and CSH gel was a weak region in the system.

PetraŠiūnų Dolomito Atsijų Ir Dolomitmilčių Tinkamumo ĮPrastinio Sunkiojo Ir Susitankinančio Betono MišIniuose Prielaidos

The objective of these experimental studies is to evaluate (verify) the possibility of applying by-products (0/2 mm fraction dolomite screenings or dolomite powder) obtained in the process of producing crushed dolomite from Petrašiūnai dolomite quarry rocks in concrete technology. A rational application of this material expands the range of concrete mix aggregates and provides an integrated use of dolomite rock by consuming less attractive by-products of dolomite processing. The article discusses the possibilities of using the above introduced dolomite by-products in concrete applications and gives a preliminary assessment of physical, mechanical and technological characteristics of commercial and technological concrete with dolomite screenings. 0/2 mm fraction dolomite screenings from Petrašiūnai dolomite quarry with an average density of 2600 kg/m3, a bulk density of 1690 kg/m3, a bulk porosity of 39.1%, fine particle content (contamination with dust and clay particles) of < 4,9%, a specific surface of 1085 cm2/g determined by Blaine tester were used for experimental study. The physicalcharacteristics of dolomite powder and dolomite screenings additionally crushed in a lab ball mill were similar: an average density of 2600 kg/m3, a bulk density of 1210 kg/m3, a bulk porosity of 53,5% and a specific surface after additional milling of 3030 cm2/g and 4070…4200 cm2/g respectively. Dolomite particles have a rough, conchoidal and porous surface, however, their form is close to cubic or even oval while their edges are less sharp (mechanically grated) compared to granite or other crushed stone screenings. Therefore, dolomite particles bond very well with cement stone and almost do not increase water demand for producing a paste of normal consistency and do not weaken the rheological properties of the mixes. Dolomite screenings or dolomite powder from Petrašiūnai quarry have stable mineral composition, but the XRD patterns of rock provide little information: although dolomite peaks are prevailing, quartz and feldspar peaks can also be noticeable. Moreover, ferrous minerals (pyrite, limonite) are present in dolomite, nevertheless, so few particles of these impurities are so small (< 0.2 mm in diameter) that they pose no risk of the potential destruction of concrete. Energy consumption of crushing dolomite screenings to reach the fineness of cement particles is much lower compared to crushing granite screenings. The crushed granite screenings are 1.5–2 times finer compared to the fineness of dolomite screenings crushed for the same time. Besides, the fineness of carbonate rock powder can be easily adjusted by changing crushing time. Therefore, dolomite screenings is a very perspective raw material for producing concrete micro-aggregates. No pozzolanic behaviour of dolomite screenings and dolomite powder during the short-term curing of cement stone or concrete under normal (room) temperature conditions were observed, and therefore a rational application of these mineral admixtures in conventional concretes would be only as substitutes for fine aggregate (sand) and only partly for cement. Most probably, dolomite powder can behave as a weak pozzolanic admixture at higher temperatures (above 50 oC); however more detailed studies are required to prove this supposition. The powdered dolomite admixture does not increase water demand for obtaining the paste of normal consistency but improves the structure of cement stone pores and frost resistance. The crushed dolomite screenings reduce the compressive and bending strength of concrete cured under ordinary temperature conditions; however, a small content of these admixtures (up to 15 ÷ 20 per cent of cement mass) can be recommended for self-compacting concrete and other fine-grained concrete mixes because the deterioration of the mechanical characteristics of cement stone is insignificant, i.e. about 10 ÷ 12 per cent. Dolomite screenings substituting for sand (or a part of sand) in conventional Portland cement concrete improve the granular composition of the mix, increase the content of fine (0.063 ÷ 0.25 mm) fractions and grow in the compressive strength of such concrete by 12 per cent. Such concrete has a better structure dominated by closed pores. Therefore, fine aggregate from dolomite screenings (or with them) is recommended for Portland cement mixes or cement grouts.

A preliminary study of reservoir sludge as a raw material of inorganic polymers

The feasibility of using calcined reservoir sludge as a raw material of inorganic polymers is evaluated by conducting a series of microstructural and mechanical tests. The reservoir sludge particles in Taiwan containing aluminosilicate minerals were first calcined at various high temperatures ranging from 500 °C to 900 °C to enhance the subsequent alkali-activated reaction and polycondensation for making an inorganic polymer. Then, the change of crystalline structure of calcined reservoir sludge particles due to dehydroxylation at high temperatures was characterized by using FTIR and XRD methods. Furthermore, uncalcined and calcined reservoir sludge particles were separately mixed with an alkaline activating solution to produce inorganic polymers and their compressive strengths were measured. From the variations of crystalline structure and compressive strength, an optimum calcination temperature for reservoir sludge is obtained. The effect of fineness of reservoir sludge particles on the compressive strength of inorganic polymers is also discussed.

Influence of Inorganic Additive Particle Fineness on the Structure and Properties of Linear Polyethylene

Influence of Inorganic Additive Particle Fineness on the Structure and Properties of Linear Polyethylene

Fabrication of ultrafine powder from eri silk through attritor and jet milling

Fibroin protein derived from silk fibres has been extensively studied with exciting outcomes for a number of potential advanced biomaterial applications. However, one of the major challenges in applications lies in engineering fibroin into a desired form using a convenient production technology. In this paper, fabrication of ultrafine powder from eri silk is reported. The silk cocoons were degummed and the extracted silk fibres were then chopped into snippets prior to attritor and air jet milling. Effects of process control agents, material load and material to water ratio during attritor milling were studied. Compared to dry and dry–wet attritor milling, wet process emerged as the preferred option as it caused less colour change and facilitated easy handling. Ultrafine silk powder with a volume based particle size d(0.5) of around 700 nm could be prepared following the sequence of chopping ➔ wet attritor milling ➔ spray drying ➔ air jet milling. Unlike most reported powder production methods, this method could fabricate silk particles in a short time without any pre-treatment on degummed fibre. Moreover, the size range obtained is much smaller than that previously produced using standard milling devices. Reduction in fibre tenacity either shortened the milling time even further or helped bypassing media milling to produce fine powder directly through jet milling. However, such reduction in fibre strength did not help in increasing the ultimate particle fineness. The study also revealed that particle density and particle morphology could be manipulated through appropriate changes in the degumming process.

Effects of Coal Composition and Flotation Reagents on the Water Resistance of Binderless Briquettes

The difference in the physical properties, particularly the water resistance or wet strength, of the binderless coal briquettes produced from flotation feed and concentrate was investigated using six bituminous coals from two collieries in the Witbank Coalfield. The coal samples were analyzed for their proximate, petrographic, and mineralogical properties. The presence, in the flotation concentrates, of the reagents used during the froth flotation process was also investigated using gas chromatography. Pillow-shaped binderless briquettes were produced from coal samples at various moisture contents and a pressure of approximately 17 Mpa using a Komarek B-100A double-roll press. The briquettes were tested for some physical properties (i.e., dry- and wet-compressive strengths), which were thereafter compared with the properties determined for the coal samples. The binderless briquettes produced from the flotation concentrates were more water-resistant than those produced from the flotation feed. The flotation feed and concentrates of the coals tested were found to have similar petrographic properties. As expected, the ash and kaolinite contents were found to be lower in the flotation concentrates than in the flotation feed. Flotation reagents were detected in the flotation concentrates from both collieries. From the results obtained it is concluded that the increased water resistance of the binderless briquettes produced from flotation concentrates of the coals tested is due to a combination of the fineness of the coal particles, assisted by the amount of reactive macerals (most particularly vitrinite) with the lower ash and kaolinite contents, together with the presence of the flotation reagents, particularly the collector, in the flotation concentrate.

Examination of Industrial Practice of Ceramic Glaze Making with Emphasis on Particle Size Distribution

This article examines the existing industrial practice of glaze making with emphasis on particle size and particle size distribution of glazes. The importance of fine grinding affecting reduction in particle size on lowering the maturing temperature has been clearly established taking sanitaryware glaze as an example. Studies on gloss and thermal expansion of glazes having varied particle size distribution have also been carried out. An attempt has also been made to redefine the particle size distribution, which could produce better results. It has been found that the ceramic glazes can safely be ground to d100 of 20 μm from the existing industrial practice of maintaining d100 in the range of 45 to 32 μm. It has also been established that, along with the increase in particle fineness, not only the maturing temperature of glaze reduces by ∼80°C but also the maturing range of sanitaryware glaze significantly increases from 1150° to 1230°C as evident from the consistent gloss values of glazes (92–95 GU) and matching thermal expansion values.