Perforate basket centrifuge

Fixed-Bed Centrifuges. The simplest of the fixed-bed centrifuges is the perforated basket centrifuge (Fig. 31) which has a vertical axis, a closed bottom, and a Hp or overflow dam at the top end. Some domestic machines of this type are ia use for straining vegetable or fmit juices. Ia the iadustrial versioas, the basket housiag is oftea supported by a three-point suspeasioa called the three-column centrifuge. 

Variable-speed basket centrifuges rotate on a vertical axis. The cyhndrical perforated basket, connected at one end to a bowl head or hub, is driven from below or suspended from above by a driveshaft. It is capped at the other end with a weir ring. The hub may be a solid piece or with an annular opening. If the hub is a sohd piece, the shiny is introduced into the basket at low speed despite the fact that the earths gravity may influence the annular pool. The settled sohds can be removed from the top only when the machine is at rest. Otherwise,... 

Perforate basket centrifuges, 16 660 operation, 5 529, 543-545 Perforated bowl centrifuge, theory of performance, 5 515 Perforated-drum dryers, 9 120 Perforated-plate columns, 10 772-774 Perforated plates, 11 810 Performance. See also Filter performance of BJTs, 22 248-249 of FETs, 22 165... 

The centrifugal method meets these requirements by giving high unit capacity, sharpness of separation, both with respect to loss of polymer in the hquid phase and dryness of the separated polymer particles and particularly in the case of the perforated basket centrifuge by good washing efficiency—i.e., maximum elimination of soluble impurities with minimum consumption of washing solvent. 

Figure 2 is a batch perforated basket centrifuge with a capacity of 0.2 cu. foot of solids per charge. It is designed to permit observation of drain rate and terminal volatile content of the recovered solids in centrifugal fields of from 109... 

Experience has shown that the perforated basket centrifuge may have poor operating characteristics in this system. In the case of polypropylene, the isotactic polymer particles in contact with hydrocarbon usually have low mechanical strength and under pressure tend to form a nonpermeable cake. In addition, the soft polymer particles tend to coat out on the filter medium and cause it to blind off and become impervious with undesirably high frequency. 

Experience has shown that this system is now in satisfactory condition for further separation and purification on perforated basket centrifuges. These, on systems with which they are compatible, have the advantages of more completely separating the solid and liquid phases, recovering the solids at lower residual volatile content, and greatly improved rinsing of the solids for reduction of their mother liquor impurity content, than is possible on the solid bowl type of centrifuge. 

Figure 6. C-4iF, Super-D-Hydratory automatic perforated basket centrifuge...

For the third stage of the typical process when the vehicle is methanol or water, the same automatic perforated basket centrifuge described under the second stage would be applicable and the capacity and performance would be substantially identical to those reported under second stage operation. 

Mechanical Design The vertical basket centrifuge is equipped with a cylindrical basket rotating about the vertical axis. The basket shell is normally perforated and lined with filtration media consisting of filter cloth, and backing screens to provide liquid drainage paths to the basket holes. Securing the filter cloth may be by hook and loop attachment or with snap-in retainers. 

Fig. 8 Vertical perforate basket centrifuge. (View this art in color at www.dekker.com.)...

The basket centrifuges are constructed with baskets, as their name suggests. Generally, the mantle surface of the basket is perforated with a large number of holes covered on the inside by one or more coarse screens. The latter serves as a backup for the filter medium that can have the shape of a bag lining the perforated wall of the basket. The feed slurry enters the rotating basket... 

The frames of a plate and frame press (two 50-mm-thick frames, 150-mm squares) fill with a liquid slurry (1000 kg/m density) in 3.5 ksec at a pressure of 450 kN/m. If the slurry is then filtered in a perforated basket centrifuge (300-mm diameter, 200 mm deep) with an inner slurry surface of 75 mm, how long will it take (speed of 3900 rpm) to produce the same amount of filtrate from a cycle from the filter press Cloth resistance is equal to 3 mm of incompressible cake. 

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