Classification particle shapes

The concept of particles and particle shape corresponds to that used in the recommended and internationally accepted classification of pigment particles given in [1.9] (see Fig. 1 and Table 5). 

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This basic classification is complemented by transportation methods because materials must be fed to or discharged from process steps and storage may be necessary before, between, and/or after processing. Particle size analysis quantitatively determines the distribution of particle sizes in the disperse system, a task of utmost importance since particle size, distribution, particle shape, and particle concentration decisively influence the behavior of a particulate system. 

Calcium hydroxide is a product new to the market. There have been, in past, positive scientific reports of its usefulness. The benefits of calcium hydroxide over calcium carbonate are its functionality, particle shape (more spherical and thus less abrasive to the equipment) (Figure 2.18), its lower density (decreases the density of product and lowers the price), a refractive index closer to many polymers, and its lower cost (approximately half of the price of calcium carbonate). The manufacturing equipment includes an excitement chamber, metered conveying, pneumatic transportation, flash drying, classification, and silo storage. The manufacturer delivers product to customers by its own silo-trucks. 

Although classification as applied to solids is synonymous with different sizes of the same material it should be pointed out that other classifications, such as particle density or mass, and even particle shape, can also cause mixing or segregation. It has recently been established (Alonso et al., 1992) that size and density differences can, indeed, be combined to reduce segregation through mutual compensation. 

Based on the mutual interaction between fillers and polymers, it is possible to classify fillers into two groups, active and inactive [22]. This classification is rather arbitrary [24], since it is based not only on differences in chemical composition but also on characteristics of filler particles surfaces, particle shape and size, and treatment of the surface by coupling agents (see Section 4.4). 

Particle shape can affect flow, filtration, crystallization, classification, mixing, bulk density, and particle size measurement (depending on the technique used). 

As part of preliminary studies, the separation model in Eq.(3) was applied for the classification of sand/split and gravel, Table 3. In Fig. 3, the measured values for the three separation experiments with the cut size dr = 2,1 4.6 and 6.7 mm are shown. Despite reduction by particle shape impact, the quasi-statlonary settling velocity of spheres v,t at this cut-point is higher than the averaged channel air flow rate u being characteristically for the predominant cross-flow separation principle. 

Dry bulk powder classification is usually accomplished using vibrating screen or air classifiers. There are, however, many industrial classification processes for which neither of the above technologies is well suited. Problems may arise because of particle size or density, or the requirement to classify on the basis of particle shape. SorTech has developed a new technology, which overcomes many of these problems. It is very effective for dry bulk powders with mean sizes in the range of 10 to 300p. 

It is still questionable whether the criteria to classify wear particles could be applied to different wear situations. Relations between processes of particle formation and particle shapes in the ball-on-disk experiment, and in most of normal wear situations, are not so simple and clear as those in the dual-pin/disk configuration. It is necessary to clarify any deviations between them, and to find how to incorporate the deviations in the classification of wear particles. Any progress in this respect will be useful in condition monitoring as well as in exploring mechanisms of wear. 

In sohd—sohd separation, the soHds are separated iato fractions according to size, density, shape, or other particle property (see Size reduction). Sedimentation is also used for size separation, ie, classification of soHds (see Separation, size separation). One of the simplest ways to remove the coarse or dense soHds from a feed suspension is by sedimentation. Successive decantation ia a batch system produces closely controUed size fractions of the product. Generally, however, particle classification by sedimentation does not give sharp separation (see Size MEASUREMENT OF PARTICLES). 

Glassification. Classification (2,12,26,28) or elutriation processes separate particles by the differences in how they settle in a Hquid or moving gas stream. Classification can be used to eliminate fine or coarse particles, or to produce a narrow particle size distribution powder. Classification by sedimentation iavolves particle settling in a Hquid for a predetermined time to achieve the desired particle size and size distribution or cut. Below - 10 fim, where interparticle forces can be significant, gravitational-induced separation becomes inefficient, and cyclone and centrifugation techniques must be used. Classification also separates particles by density and shape. Raw material separation by differential sedimentation is commonly used in mineral processiag. 

Soil texture, or appearance, depends on particle size, shape, and gradation. Therefore, using the classification in Figure 2-60 the soil texture can be specified as sandy clay or clay-sand. 

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