Settling batch tests

There is a gradual transition from particulate setthug into the zone-settling regime, where the particles are constrained to settle as a mass. The principal characteristic of this zone is that the setthug rate of the mass, as observed in batch tests, will be a function of its solids concentration (for any particular condition of flocculation, particle density, etc.). 

Batch-operated gravity separations avoid the complications of turbulence in continuous separators. They can be designed besed on Stokes Law for dilute dispersions, where die separation time is that for a dispersed-phase drop to go from the farthest point to the interface 6 = Hill, where 6 is separation dme, H is the height from the farthest point to die interface, and V, is the Stokes Law settling velocity. For systems where coalescence is the limiting mechanism, the ratio of die volume to cross-sectional area should be proportioanl to separation time and is the key parameter. Smell-scale batch tests can be used to confirm sizing or separation time. 

In a continuous thickener the total downward solids flux is made up of two parts the flux of solids carried by the downflowing liquid and the additional flux resulting from the settling of the solids through the liquid. The first is called the transport flux G, and is the product of the solids concentration c and the downward velocity w. The second is the settling flux which is the product of the solids concentration and the settling rate, dZldt, as measured in batch tests. 

Coe and Clevenger method. Since the slurry settling rate R varies with concentration of solids in the thickener batch settling tests are used to determine R over the concentration range of operation F S) and the corresponding... 

You must determine the maximum feed rate that a thickener can handle to concentrate a waste suspension from 5% solids by volume to 40% solids by volume. The thickener has a diameter of 40 ft. A batch flux test in the laboratory for the settled height versus time was analyzed to give the data below for the solids flux versus solids volume fraction. Determine ... 

Calculate the minimum area and diameter of a thickener with a circular basin to treat 0.1 m3/s of a slurry of a solids concentration of 150 kg/m3. The results of batch settling tests are ... 

Table 3. In order to test the hypothesis that heterogeneous catalyst is better than the homogeneous one, beeause the former allows improving the control over iron ions during the Fenton ehemistry, several consecutive degradations were performed with a fixed amount of eatalyst. Figure 19 shows the time needed for four consecutive batch degradations of 100 ml 50 mM Na2S04 (pH 2.8) + 0.06 mM RB5 + 10.7 mM H2O2 (twice of the stoiehiometrie amount required) + 0.1 g eatalyst Cl. At the end of each discoloration the solution was allowed to settle down into the reaetor and the solution was withdrawn carefully. Then, a fresh solution (100 ml 50 mM Na2S04 + 0.06 mM RB5 + 10.7 mM H2O2) was reloaded over the previous 0.1 g eatalyst Cl to start a new RB5 discoloration. The process was repeated three times.

Visual checks for cleanliness before each use of a piece of manufacturing equipment should be made in addition to chemical testing. Air monitoring should be implemented to ensure that any contamination released during manufacturing operations is not being spread. Both product-contact and nonproduct-contact surfaces should be monitored to determine the level of contamination settling out from the environment. A product or placebo batch may also be tested to show the absence of residues from previous batches. 

Critical concentration—In a batch settling or thickening test, the concentration of solids when the uniform velocity zone disappears. 

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