Natural slurry flows

Slurry is essentially a mixture of solids and liquids. Its physical characteristics are dependent on many factors such as size and distribution of particles, concentration of solids in the liquid phase, size of the conduit, level of turbulence, temperature, and absolute (or dynamic) viscosity of the carrier. Nature offers examples of slurry flows such as seasonal floods that carry sUt and gravel. Every year during the flood season, the Nile transports massive amounts of silt over thousands of miles to the Saharan desert. To rephrase Herodotus, who once said Egypt is the gift of the NUe, one may consider that one of the most ancient civilizations was dependent on natural slurry flows for its survival. 

A simplified flow sheet (Figure 1-1) of the Nile illustrates this natural slurry flow. The... 

Figure 11-25 shows the nature of that disruption. The unsonicated crystals (top) are disrupted by sonication along cleavage planes (bottom), a mechanism which produces few fines to elutriate out of the seed bed. For this product, the sonicators were located in the column bottom (Fig. 11-26). Whether the sonicators are located internally, as shown, or in a slurry flow system, as shown in Fig. 11-28, the crystal population fed to the sonicators is always drawn from the bottom of the seed bed, where the largest particles are located.

Slurry flows occur in nature in different ways. They are often associated with the transportation of silt from one region to another. Strong rains lead to soil erosion, mud slides, and the eventuai drainage of slurries toward rivers. These are dilute slurries, in the sense that the soils mix naturally at a weight ratio of solids to liquids smaller than 15%. 

The physical properties of the fatty acid ethoxylates depend on the nature of the fatty acid and even more on ethylene oxide content. As the latter increases, consistencies of the products change from free-flowing Hquids to slurries to firm waxes (qv). At the same time, odor, which is characteristic of the fatty acid, decreases in intensity. Odor and color stabiUty are important commercial properties, particularly in textile appHcations. Oleic acid esters, though possessing good functional properties, cannot be used because they tend to yellow on exposure to heat and air. 

Nonsettling slurries are formed with fine particles or plastics or fibers. Although their essentially homogeneous nature would appear to make their flow behavior simpler than that of settling slurries, they often possess non-Newtonian characteristics which complicate their flow patterns. In Newtonian flow, the shear stress is proportional to the shear strain,... 

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