Settling of suspensions

Hawksley, P. G. W. Inst, of Phys. Symposium (1950) 114. The effect of concentration on the settling of suspensions and flow through porous media. 

Data for the settling of suspension of diatomite with different particle size has been reported, where the flocculants used were ... 

Gravity is the driving force for settling of suspensions. When the gravity force exceeds the Brownian diffusion (kT) sedimentation occurs,... 

Gravity settling of suspensions has less effect than in cone and plate... 

Fig. 5. Effect of polymer dosage on different observed properties of flocculated slurry (40). Comparison of five parameters in a flocculation system (8%fluorite suspension + polyacrylamide Cyanamer P250). A, Rate of settling of floe boundary, in cm/s B, height of settled bed, cm C, height of consoHdated filter-cake, cm D, refiltration rate, arbitrary units and E, clarification, % optical transmission of 1 cm of supernatant Hquid after 3 min settling...

As shown in Figure 2, adsorption of dispersants on particle surfaces can increase 2eta potential further, enhancing electrostatic repulsion. Increased repulsion between particles is evidenced by lower viscosity in concentrated slurries, or decreased settling rates in dilute suspensions. The effect of added dispersants on settling of (anhydrous) iron oxide particles is shown in Figure 3. 

Circffiation in the standard short-tube vertical evaporator is dependent entirely on boiling, and when boihng stops, any sohds present settle out of suspension. Consequently, this type is seldom used as a ciystaUizing evaporator. By instalhng a propeller in the downtake, this objection can be overcome. Such an evaporator, usually called a pro-... 

Filtration of suspensions, e.g. in filter presses, rotary vaeuum filters Sedimentation, gravity settling... 

There are a large number of processes in the chemical industries that handle a variety of suspensions of solid particles in liquids. The application of filtration techniques for the separation of these heterogeneous systems is sometimes very costly. If, however, the discrete phase of the suspension largely contains settleable particles, the separation can be effected by the operation of sedimentation. The process of sedimentation involves the removal of suspended solid particles from a liquid stream by gravitational settling. This unit operation is divided into thickening,... 

The most favorable filtration operation with cake formation is process whereby no clogging of the filter medium occurs. Such a process is observed at sufficiently high concentrations of solid particles in suspension. From a practical standpoint this concentration may conditionally be assumed to be in excess of 1% by volume. Filtration is frequently accompanied by hindered or free gravitational settling of solid particles. The relative directions of action between gravity force and filtrate... 

Sedimentation I he process of settling solid particulates out of suspension in a fluid or a gas. 

A suspension uniformly dispersed in an upright cylindrical vessel at time t = 0 begins to settle immediately. If two horizontal planes, p and p2, are taken at depths hj and h2 below the upper surface (ht > h2), then, at time t, the mass of suspension remaining between Pi and p2 will be determined by (ht — h2)a, plus particles that have fallen thru p2 minus particles that have fallen thru pj, where a = mass per unit dearth of original suspension... 

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