Continuous Settling

Gravity Settlers Decanters These are tanks in which a liqmd-liquid dispersion is continuously settled and coalesced and from wriich the settled liquids are continuously withdrawn. They can be either horizontal or vertical. Figure 15-24 shows some typical horizontal decanters. For an uninstrumented decanter the height of the heavy-phase-liquid leg above the interface is balanced against the height of the hght-hquid phase above the interface, Eq. 15-50. 

Th is extremely insoluble and adheres to the surface of particles in the ocean soon after it forms from the decay of Because these particles continuously settle from the water column, °Th is rapidly removed from the oceans to the seafloor. The combined process of surface adsorption, followed by particle settling, is termed scavenging. Measurement of the very low °Th concentrations in seawater that result from this... 

A common problem in both chemical and metallurgical practice is that of separating relatively coarse particles, which are called sands, from a slurry of fine particles, which are called slimes. The most common method is to use continuous settling equipment called classifiers. 

Since detrital POM is continuously settling out of the surface waters of all the world s ocean, water masses moving laterally through the ocean basins are continuously receiving a rain of detrital POM. Aerobic respiration of this detrital POM causes the O2 concentration in a water mass to decrease as it travels through the deep sea. The amount of O2 consumed since a water mass was last at the sea surface can be... 

In commercial installation, the acid is applied to the deasphalted oil in propane solution and the sludge is removed by continuous settling. The acidic oil-propane solution is neutralized continuously with a solution of caustic and water-washed for removal of the last traces of caustic. The oil after removal of propane may be finished by conventional percolation through clay to produce a green cast finished bright stock (4). 

The melt used in this work was prepared from the residue of hydrogen-donor extraction of Colstrip coal with tetralin solvent in such a way as to simulate the composition of an actual spent melt. The extraction was conducted in the continuous bench-scale unit previously described (17) at 412°C and 50 min residence time. The residue used was the solvent-free underflow from continuous settling (17) of the extractor effluent. The residue was then precarbonized to 675°C in a muffle furnace. The melts were blended to simulate the composition of a spent melt from the direct hydrocracking of the Colstrip coal by blending together in a melt pot zinc chloride, zinc sulfide, and ammonium chloride, ammonia, and the carbonized residue in appropriate proportions. Analysis of the feed melt used in this work is given in Table I. 

The suspension of solids in a liquid is perhaps the most common application of stirred tanks. Usually, the solid particles are denser than the carr3ung fluid resulting in continuous settling of the particles towards the bottom of the tank. To avoid permanent settling of solids and to obtain a satisfactory mass transfer flux to the solid surface, mixing is provided to keep the solids in suspension. 

Thickeners and Centrifitgals. The simplest form of thickener is an ordinary settling tank arranged for the decantation of the clear liquid after settling. Nonmechanical, continuous settling tanks have conical bottoms from which thickened slurries high in solids are continuously discharged. The most widely used thickener is the mechanical type, of, which the Dorr is typical. Cost estimates for continuous thickeners are shown in Fig. 6-29. 

Continuous Settling Dilute Systems. When apphed to continuous sedimentation the long tube test is used to model the settling of particles in an elemental vertical volume of liquid moving throu the length of the clarifier. The corresponding overflow rate Vc, of a continuous ideal basin is given by H/ta, where H is the sanq)le point depth. 

Continuous Settling Hindm ed Systems/Thickening, This process is usually conducted in a raked cylindrical tank with a sloping conical base leading to a central outlet for the shidge, an overflow launder around flie per hery of flie tank for the clear liquid and a central feed point. 

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