Thickening process

FIG. 14-97 The Flotator dissolved-air flotation thickener. (Process Kngineets, Inc., a division ofEtmco Corp., now Envitotech Corporation.)... 

Pyknosis refers to a degenerative (thickening) process in a cell in which the nucleus shrinks in size and chromatin condenses to a solid mass that has no defined structure. 

In a DAF thickening process, air is added at pressures in excess of atmospheric pressure (2.1 to 4.9 kg/cm1 2 3 4 30 to 70psig) either to the incoming sludge stream or to a separate liquid stream. When the pressure is reduced and turbulence is created, air in excess of that required for saturation at atmospheric pressure leaves the solution as very small bubbles of 50 to 100 pm in diameter. The bubbles adhere to the suspended particles or become enmeshed in the solids matrix. As the average density of the solids-air aggregate is less than that of water, the agglomerate floats to the surface. The floated solids build to a depth of several inches at the water surface. Skimmers continuously remove the float.58... 

The lamella thickening depends sensitively on the initial lamella thickness as well as on the annealing temperature. We first considered the thickening of very thin lamella of about 18-bonds thick this thickness nearly corresponds to that of the lamella crystallized at 0 K (Fig. 7). The temperature of annealing Ta was taken between 20 K and 150 K a quick jump to a higher temperature resulted in partial melting and re-crystallization and a continuous thickening process could not be observed. 

Fontaine et al. [81] concluded that the increase in crystallinity by further heating material, crystallized at 200 °C, to 215 °C involves a crystal (lamellae) thickening process which is probably due to crystal perfection at the boundary layers. Further annealing of this material at temperatures above 215 °C led to a melting temperature increase that was attributed to crystal perfection alone and not to crystal thickening. 

When the lamellae are annealed at a given temperature, they thicken with time. The thickening is usually continuous and L increases logarithmically with time. However, there are several examples, where the lamellar thickness increases in a stepwise manner. For example, the initial lamella may contain chains each with four folds (five stems). As thickening process continues, the lamellar thickness jumps discontinuously to three folds, and so on. This phenomenon is referred to as quantized thickening [25]. 

The use of different alkanes with different crystal thicknesses and numbers of folds within the crystal enables us to assert with confidence that the contraction in the lattice is due to the thickening process. The fact that the alkanes, due to their strict monodispersity, form crystals with only a few closely defined thicknesses enables this contraction to be seen much more clearly than it is in polyethylene. In polyethylene a range of different crystal thicknesses may be present, and the thickening process generally occurs over a wider range of temperatures, smearing out any step-like effect that may exist. 

Fig. 2 Description of the craze thickening process according to Kramer [31] as drawing in new polymer chains from the craze/bulk interface into the fibrils. The fibrils have a diameter D and spacing of D0...

Compression zone—In a settling or thickening process, this is the zone B where the thickened sludge from the thickening zone is further compressed, compacted, and consolidated. 

Within a cohesive zone representation of a craze, heat generated during the viscous craze thickening process is accounted for by defining a heat flux along the surfaces of the cohesive zone as discussed in the next section. 

Takacs, I., Patry, G.G., Nolasco, D., 1991. A dynamic model of the clarification-thickening process. Water Research, 25(10), 1263-1271. 

Fig. 8 (A) Coexistence of a VGCF and an SWNT (with a diameter of about 20 nm) obtained by the catalytic decomposition of benzene. (From Ref l) The deposition of a partial carbon layer on a carbon nanotube during the thickening process is observed. (B) Double-walled carbon nanotube (obtained by benzene decomposition) and subsequently heat treated at 2800 °C, yielding the same structure as nanotubes prepared by the arc method. (From Ref l) Insert is a schematic diagram of DWNTs. (From Ref (C) Fligh-resolution transmission electron microscope image of two crossing SWNTs coated with amorphous carbons indicates that the structure consists of an individual graphene cylinder in projection. (From Ref. . )...

Tc, is increased the temperature of peak L is found to increase in direct proportion while that of peak H increases only slightly. As Tc is further increased, the L endotherm Increases in size while the H endotherm diminishes and eventually disappears. These trends generally confirm those reported previously (2 ). and suggest that the multiple peaks are most likely the result of lamellar thickening processes, perhaps requiring melting and recrystallization (23). 

The lap-shear test was used to determine the room-temperature cohesive strength of the modified asphalts and to follow the thickening process in both air and water. Two aluminum strips 1 mm thick and 2.5 cm wide were overlapped 2.5 cm and firmly bonded together with a drop of molten asphalt. The test pieces were held in this position with alligator clips until ready for shear testing. In a few experiments pieces of traprock were polished and similarly bonded together as shown in... 

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