Dense particles

There have been several studies involving the use of media consisting of fine dense particles suspended in water for transporting coarse particles. The fine suspension behaves as a homogeneous fluid of increased density, but its viscosity is not sufficiently altered to have a significant effect on the pressure drop during turbulent flow, the normal condition for hydraulic transport. The cost of the dense particles may, however, be appreciable and their complete separation from the coarse particles may be difficult. 

Silicas with surface areas up to 300 g consist of dense particles with diam-... 

This expression shows that, unlike the terminal velocity of the particle, its initial acceleration is independent of the particle size and depends only on the densities of the solid particle and the fluid. This type of acceleration, known as differential acceleration, may be exploited by designing equipment which provides frequent opportunities for accelerating the particles from rest. If a particle is allowed to accelerate from rest for a brief period of time and then arrested and subsequently allowed to fall once more, the total distance travelled by it will be influenced more by the differential acceleration and, therefore, by the specific gravities of the particle and of the liquid, than by its terminal velocity, or in other words, by its size. In this way, as the preferential movement of dense particles to the bottom of a bed... 

It is not clear where cohesive forces will become important. The use of very dense particles (for the models of the one atmospheric bed) will cause a shift of the boundary of cohesive influence as given, for example, by Geldart s classification. However, adequate experimental data is still lacking with such dense fine particles to definitely set the limits of cohesive influence. 

Some researchers have noted that this approach tends to underestimate the lean phase convection since solid particles dispersed in the up-flowing gas would cause enhancement of the lean phase convective heat transfer coefficient. Lints (1992) suggest that this enhancement can be partially taken into account by increasing the gas thermal conductivity by a factor of 1.1. It should also be noted that in accordance with Eq. (3), the lean phase heat transfer coefficient (h,) should only be applied to that fraction of the wall surface, or fraction of time at a given spot on the wall, which is not submerged in the dense/particle phase. This approach, therefore, requires an additional determination of the parameter fh to be discussed below. 

Inorganic particles are used extensively in various bioapplications, too. Gold nanoparticles long have been used as detection labels for immunohistochemical (IHC) staining and lateral flow diagnostic testing. These dark, dense particles provide single particle detection capability... 

Dry Process. Ten kg each of the ground field pea and fababean were passed through an Alpine Pin Mill model 250 CW (Alpine American Corp., Natick, MA) (Figure 1). Two passes through the mill reduced the particle size to less than 325-mesh. The pin-milled flours were then fractionated into light and dense particles by a single pass through the Alpine Air Classifier Type 132 MP at a cut point of 15 microns (800-mesh) diameter between the two fractions (9 ), followed by a reclassification of the dense fraction (20). The two protein fractions were combined. 

The upper limit of gas velocity for particulate expansion is termed the minimum bubbling velocity, umb. Determining this can present difficulties as its value may depend on the nature of the distributor, on the presence of even tiny obstructions in the bed, and even on the immediate pre-history of the bed. The ratio umb/umf, which gives a measure of the degree of expansion which may be effected, usually has a high value for fine light particles and a low value for large dense particles. 

C3, 12, J2, M3, S8). The amplitude of angular oscillations decreases as E increases, and a very long cylinder falls steadily to high Rey(I2, J2). If Re > 3500 (S8), motion also occurs in a horizontal plane. For relatively low y, the cylinder oscillates about a vertical axis (12, S8), while for dense particles in liquids or particles in gases the cylinder rotates continuously about a vertical axis (C3,12). A cylinder with E = 1 follows a trajectory inclined to the vertical, and tumbles in the direction of horizontal travel (12). For F < 1, the axis oscillates and rotates about a vertical line, so that the secondary motion resembles the final stages of motion of a coin spinning on a flat surface (12). 

Unlike TEOS hydrolysis, Si02 particles have been also prepared by hydrolysis of Na2Si02 and Na4Si02 in nonionic reversed micelle systems. Spherical and poly-disperse particles of 31.8 nm mean diameter were produced in polyoxyethylene(9.5) octylphenyl ether-hexanol-cyclohexane systems (25), but more uniform and dense particles were precipitated by hydrochloric acid-catalyzed hydrolysis in a mixture of polyoxyethylene(5) nonylphenyl ether and polyoxyethylene(9) nonylphenyl ether in cyclohexane systems at pH 11 (26). The uniform particle formation at higher pH is attributed to the charge repulsion by OH- adsorbed on particle surface. The particles of specific surface area of 347 m2 g-1 can be obtained by calcination of particles produced at pH 2. 

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