Coarse particles, definition

Fig. 5. Particle distribution (upper line) before and (lower line) after action of the separator where the cross-hatched areas represent the particles separated out. By definition, all particles of d > are separated out. A number of particles having d < d are also separated, (a) Fiae and (b) coarse particle...

This result can also be applied directly to coarse particle swarms. For fine particle systems, the suspending fluid properties are assumed to be modified by the fines in suspension, which necessitates modifying the fluid properties in the definitions of the Reynolds and Archimedes numbers accordingly. Furthermore, because the particle drag is a direct function of the local relative velocity between the fluid and the solid (the interstitial relative velocity, Fr), it is this velocity that must be used in the drag equations (e.g., the modified Dallavalle equation). Since Vr = Vs/(1 — Reynolds number and drag coefficient for the suspension (e.g., the particle swarm ) are (after Barnea and Mizrahi, 1973) ... 

Classification Food starch modified Definition Chemically modified and stabilized food starch crosslinked with adipic anhydride and esterified with acetic anhydride Properties Wh. or nearly wh. powd. or gran. flakes, amorphous powd., or coarse particles if pregelatinized... 

It will be noted that there is a definite relationship between the process in which fine particles stick to coarse particles, i.e., the ratio KfjKff, and the adhesion of particles to a surface, i.e., the adhesion number yp. The greater the ratio > the greater the adhesion number. This indicates a direct relationship between adhesion processes when a suspension comes into contact with a vessel wall and the sticking of fine particles to larger particles in a suspension. 

At speeds in excess of 3.3 m/s (10 ft/s), all solids may move in a symmetric pattern (but not necessarily uniformly). Sometimes this flow is called pseudohomogeneous because of its symmetry around the pipe axis. Power consumption is a linear relationship of the stat ic head multiplied by the velocity, but is proportional to the cube of velocity needed to overcome friction losses. Power consumption in pseudohomogeneous mixtures of coarse and fine particles may be excessive for long pipelines. Pseudohomogeneous mixtures of fine or ultrafrne particles may occur at speeds as low as 1.52 m/s (5 ft/s). One definition of fine and coarse particles was explained Govier and Aziz (1972), who proposed the following ... 

Isobutyhdene diurea [6104-30-9] is a nonhygroscopic white crystalline soHd available in fine (0.5—1.0 mm), coarse (0.7—2.5 mm), and chunk (2.0—3.0 mm) particle sizes. The AAPFCO official definition requires a minimum nitrogen content of 30% with 90% of the nitrogen in water-insoluble form prior to grinding (3). 

The definitions coarsely chopped to finely powdered , which formerly in the pharmacopoeias were given as mesh sizes, are mostly nowadays indicated without such a requirement in the DAB 10, V. 4.N6, only coarsely chopped (4000 to 2800 sieve), finely chopped (2000 sieve), and powdered (710 to 180 sieve) are distinguished. The wide particle-size ranges have rightly been criticized [1, 2], partly on the basis of extensive investigations. 

The weighted or product type of definition, i.e., Eqs (2) and (5), tends to under-emphasize the influence of the finer particles (or overemphasize the coarse end of the size distribution),... 

As Table 7-16 shows, the relative abundances of the major elements in the aerosol do not differ greatly from those in bulk soil, crustal rock, or average shale—that is, the elements are neither greatly enriched nor seriously depleted. A good match with any of the three reference materials is not obtained, however. The differences must be significant, since they are greater than conceivable analytical errors. Consider silicon as an example. Tables 7-13 and 7-16 indicate an average Si/Al ratio of 2.7, which is lower than that for either bulk soil or crustal rock and is more similar to that in shales. Fly ash exhibits a particularly low Si/Al ratio. It is possible that the low aerosol value in heavily industrialized Tees-side (Table 7-13) is due to a mixture of natural and combustion aerosols, but this explanation cannot be extended to the remote continental aerosol. A more likely explanation for the silicon deficiency is the size distribution of the Si/Al ratio in soil particles. The very coarse quartz particles, which are rich in silicon, are not readily mobilized. Since only the fine fraction of soil particles contributes to aerosol formation, the Si/Al ratio in the aerosol will be determined by that of silts and clays (see Table 7-7 for definitions). Common clay... 

---