Dorr classifier

Analysis of this type of classifier (15) suggests that the sharpness iadex is between 0.5 and 0.6, consistent with calculated results, because the degree of turbulence can be high ia these devices (16). A DSF Dorr classifier (1.8 m x 7 m), operating at 19 strokes per minute and having a weir depth of 100 cm and a slope of 19.4 cm/m, produced a cut size equal to 240 p.m, a sharpness iadex of 0.5, and an apparent bypass of approximately 26% when the water spht was 26% (15). 

Dorrgemiise, n. dried vegetables. Dorr-klassierer, -klassifikator, m. Dorr classifier. 

Figure 10.4. Flow of solids and liquids in Dorr classifier...

The Hildebrandt extractor consists of a U-shaped screw conveyer with a separated helix in each of the downward, horizontal, and upward sections. Solids are fed to one leg and fresh solvent is fed to the other to give countercurrent flow. In a Dorr classifier, soUd is introduced near the bottom of a sloping tank and is gradually moved up by means of a rake. The solvent enters at the top and flows in the opposite direction of the sohd and passes under a baffle before finally being discharged over a weir. A number of these units can be connected in series to give countercurrent flow. 

The Dorr classifier uses a flight-pulling mechanism. On the upward or push motion of the blades they dip into the material which has settled in the enclosing tank and on the return motion they are raised above the bed of material being advanced. The back and forth motion of the rakes is given by a bell crank. The... 

Akins ClassijSer.—This machine is designed to accomplish separation in the same way as the Dorr classifier. In it the intermittently acting rakes are replaced by a continuously moving helix, the flights being interrupted at intervals to allow washing of the solids and return of the liquids. 

The Dorr classifier and the Dorr thickener it will be noted are designed to handle two different types of material. The classifier handles quick-settling sandy material which does not require long-washing periods while the thickener is best adapted to handling slow-settling slimes which require longer periods of detention in the washes. 

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