Significant Reduction In Particle Size Research Articles

Evaluation of char combustion models: measurement and analysis of variability in char particle size and density

Char samples representing a range of combustion conditions and extents of burnout were obtained from a well-characterized laminar flow combustion experiment. Individual particles from the parent coal and char samples were characterized to determine distributions in particle volume, mass, and density at different extent of burnout. The data were then compared with predictions from a comprehensive char combustion model referred to as the char burnout kinetics model (CBK). The data clearly reflect the particle-to-particle heterogeneity of the parent coal and show a significant broadening in the size and density distributions of the chars resulting from both devolatilization and combustion. Data for chars prepared in a lower oxygen content environment (6% oxygen by vol.) are consistent with zone II type combustion behavior where most of the combustion is occurring near the particle surface. At higher oxygen contents (12% by vol.), the data show indications of more burning occurring in the particle interior. The CBK model does a good job of predicting the general nature of the development of size and density distributions during burning but the input distribution of particle size and density is critical to obtaining good predictions. A significant reduction in particle size was observed to occur as a result of devolatilization. For comprehensive combustion models to provide accurate predictions, this size reduction phenomenon needs to be included in devolatilization models so that representative char distributions are carried through the calculations.

A comparison of ultrasound treatment on primary and secondary sludges

Ultrasound treatment of primary and secondary sludges was conducted to improve the qualities of sludges for the anaerobic digestion. The impacts of different sonication times, sonication densities and solids concentrations on ultrasonication efficiency were examined. The experimental results indicated that the significant reduction in particle size and increase in soluble organics could be achieved, implying that ultrasonication could offer a feasible treatment method to efficiently disintegrate sludge. The greater decrease in particle size and increase in soluble organics of sludge indicated that the secondary sludge has a more remarkable improvement after sonication over the primary sludge. With respects to the extent of disintegration and energy consumption, higher sonication density performed more effectively in terms of specific energy. There exists an optimal solids concentration range for both the sludges for optimum sonication. Within the optimal solids concentration range, efficient sonication can be effected and sludge would be disintegrated efficiently. The ultrasound would be attenuated by scattering and absorption if the solids concentration exceeds the optimal range. It appeared from the study that the mechanical shear forces caused by ultrasonic cavitation could be a key factor for sludge disintegration and collapse of cavitation bubbles could significantly alter the sludge characteristics.

Comparative study of the sonication effect on the thermal behaviour of 1:1 and 2:1 aluminium phyllosilicate clays

The aim of this work is to compare the effect of sonication on the thermal behaviour of kaolinite and pyrophyllite. The results show that sonication produces a significant particle size reduction of both clays. Besides, this treatment modifies the thermal behaviour of these samples. Nevertheless, the change in particle size and in the modification of the thermal behaviour is different for both clays. Sonication facilitates the dehydroxylation of both clays, although, the temperature shift of the dehydroxylation is more significant for pyrophyllite than for kaolinite. Additionally, the exothermic effect at 987 °C for kaolinite is not affected by sonication while that at 1210 °C for phyrophyllite is shifted to lower temperatures.

Pulverizing and/or Defatting Effects on Electrical Energy Consumption and Particle Size and Moisture Levels of Poultry By-Products

Fine-grinding of high-fat animal protein meals often is necessary prior to inclusion in shrimp diets. The effects of pulverizing and defatting two types of poultry by-product meals (regular poultry by-product meal [PBM] and low-ash petfood-grade poultry by-product meal [PBMPG]) and the effects of pulverizing two types of feather meal (hydrolyzed feather meal [FM] and a high-digestibility feather meal [FMHD]) on particle size reduction, moisture loss, and electrical energy consumption were investigated. Pulverizing PBM resulted in a significant reduction in particle size (415 vs. 223 μm; P < 0.05), and defatting resulted in a similar apparent reduction (415 vs. 295 μm; P < 0.05). Defatting and pulverizing PBM resulted in an even greater change in particle size (295 vs. 119 μm; P < 0.05). Defatting PBM reduced grinding energy consumption dramatically (98 vs. 68 Kwh/MT; P < 0.05). Neither pulverizing (371 vs. 336 μm;P > 0.05) nor defatting (371 vs. 245 \\im;P> 0.05) significantly reduced particle size for PBMPG. Defatting had no effect on grinding energy (80.5 vs. 79.4 Kwh/MT; P > 0.05) for PBMPG. Pulverizing also significantly reduced particle size for both types ofFM (540 vs. 261 μm for FM, and 492 vs. 154 μm for FMHD; P< 0.05). Furthermore, pulverizing reduced moisture contents of all poultry by-products, especially FM. The average moisture reduction was 2.4% for both PBM and FM.

In situ compatibilization of polyamide 6/natural rubber blends with maleic anhydride

The rheology, thermal and dynamic-mechanical properties and phase morphology of blends of polyamide 6 with natural rubber (NR) are explored. The objective was to investigate in situ formation of a graft copolymer between NR and polyamide 6 during processing. Addition of maleic anhydride (MA) to the rubber was done prior to blending with polyamide 6. During processing MA can react with both NR and polyamide 6 leading to the graft copolymer formation. Molau test was used to confirm this graft copolymer formation. Rheology and thermal properties as well as dynamic-mechanical analysis also indicated the graftization. Blend morphology analysis showed a significant reduction in particle size as the MA was added to the rubber.

Ultrafine BaFe 12O 19 powder synthesised by mechanochemical processing

Ultrafine BaFe 12O 19 powder has been synthesised by a novel mechanochemical preparation method. Mechanical milling of 1.2BaCl 2 + 12FeCl 3 + 38.4NaOH led to a mixture of NaCl and iron and barium hydroxide or oxidehydroxide. The formation of BaFe 12O 19 required annealing at 800°C in air. A significant reduction of particle size was achieved by dilution with NaCl. High coercivity values above 5 kOe were measured for BaFe 12O 19 platelets of 20–100 nm in diameter and 10–20 nm thick.

Self-similar cataclasis in the formation of fault gouge

Particle-size distributions have been determined for gouge formed by the fresh fracture of granodiorite from the Sierra Nevada batholith, for Pelona schist from the San Andreas fault zone in southern California, and for Berea sandstone from Berea, Ohio, under a variety of triaxial stress states. The finer fractions of the gouge derived from granodiorite and schist are consistent with either a self-similar or a logarithmic normal distribution, whereas the gouge from sandstone is not. Sandstone gouges are texturally similar to the disaggregated protolith, with comminution limited to the polycrystalline fragments and dominantly calcite cement. All three rock types produced significantly less gouge at higher confining pressures, but only the granodiorite showed a significant reduction in particle size with increased confining pressure. Comparison with natural gouges showed that gouges in crystalline rocks from the San Andreas fault zone also tend to be described by either a self-similar or log-normal particle distribution, with a significant reduction in particle size with increased confining pressure (depth). Natural gouges formed in porous sandstone do not follow either a self-similar or a log-normal distribution. Rather, these are represented by mixed log-normal distributions. These textural characteristics are interpreted in terms of the suppression of axial microfracturing by confining pressure and the accommodation of finite strain by scale-independent comminution.

Aerodynamic shattering of ice crystals in hypersonic flight

2 ~* } but not until recently has significant effort been devoted to the interaction of ice crystals with the shock layer. Wu12 has studied the melting and vaporization of an ice crystal in a hypersonic shock layer and demonstrated a significant reduction in particle size and impact velocity for ice crystals initially of the order of 10-jLt diameter. Larger crystals were relatively unaffected by melting and vaporization. In the same report, Teare12 demonstrated that ice crystals may shatter at the vehicle bow shock. This introduces the possibility that the fractured ice crystal or may deform as it passes through the vehicle shock layer. This deformation will be lateral to the relative velocity and will tend to increase the drag area of the fragment cloud. Hence, the velocity of the fragment cloud will decrease more rapidly than that of a particle, and the velocity with which the fragment cloud impacts the vehicle may be significantly lower than that with which a rigid ice crystal would impact the vehicle. To study this phenomenon, we examine the interaction of the ice crystal with the shock layer over three distinct time scales: fracture, breakup, and deformation. The first time scale is the time required for a stress wave to propagate across the ice crystal and generate multiple fractures. Analysis of this event requires the development of a dynamic fracture criterion. Such a criterion is developed in Sec. II. We consider a monochromatic stress wave and determine an appropriate monochromatic yield criterion. We then assert that a dynamic yield criterion may be obtained by Fourier expanding the applied load and applying the monochromatic yield criterion to each wave. Using this basic hypothesis, we determine the maximum size (Q of the ice crystal fragments allowed by the highest mode that can just fracture the ice crystal. The behavior of a cloud or gas of such fragments is needed to describe the motion of the fractured ice crystal through the vehicle shock layer.

Effect of Ultrasound on Particle Size of Suspensions of Polyethylene Spheres

The effect of ultrasound energy on the particle size of polyethylene spheres in aqueous suspension, with and without additives such as surfactants and deflocculating agents, and using variable times of exposure to ultrasound, were studied. Particle size was determined microscopically and expressed as the mean diameter of the particles. It was found that ultrasonic waves, at a frequency of 100 kc., caused a significant reduction in particle size only if surfactants were present. It was also observed that surfactants having high HLB values were the most efficient of all additives. Increasing time of exposure to the ultrasound waves brought about a continued reduction of particle diameter up to 2 hr., but that after this time the particle size stabilized, and further exposure produced no significant decrease in the mean diameter of the polyethylene spheres.