Bowl centrifuge

These concepts are used to analyze separations in the botde centrifuge, the imperforate bowl centrifuge, and the disk centrifuge. Separation by density difference in other types of centrifuges can be analyzed by analogy. 

The Imperforate Bowl Centrifuge. In an imperforate bowl centrifuge the dow of the continuous Hquid phase is nominally axial, except for areas immediately adjacent to the feed inlet and efduent oudet. Tubular soHd-bowl basket and imperforate bowl conveyor-discharge centrifuges satisfy this definition. 

Centrifuges. Sohd-bowl centrifuges have been proposed as an alternative classifying device to hydrocyclones for cut sizes below 10 pm. The results appear to be mixed (21). In one apphcation, where the cut size was 6.5 pm and the sharpness index 0.7, there was essentially no apparent bypass. However, in other apphcations operating at higher feed concentrations, the cut size ranged from 5—8 pm, but the sharpness index was between 0.3—0.5 and the apparent bypass between 10—30% or higher (22). Smaller cut sizes have also been reported (23). 

Fig. 7. Sohds content of sludges dewatered by C, soHd bowl centrifuge VF, vacuum filter BP, belt press FP, filter press, and DFP, diaphragm filter press...

The hquid-handling capacity of the tubular-bowl centrifuge varies with use. The low end shown in Table 18-11 corresponds to stripping small bac teria from a culture medium. The high end corresponds to puri ng transformer oil and restoring its dielectric value. The sohds-handling capacity of this centrifuge is limited to 4.5 kg (10 lb) or less. Typically, the feed stream solids should be less than 1 percent in practice. 

Solid-Bowl Centrifuge The Bird solid-bowl centrifuge uses powder instead of gravity and can develop centrifugal forces up to 1800 times the force of gravity. It is therefore a unique type in classification practice. 

Separation Rates in Tubular-and Solid-Bowl Centrifuges To evaluate the radial velocity of a particle moving toward a centrifuge wall, the expression for particle settling in a gravitational field is applied ... 

One variation of the disk-type bowl centrifuge is the nozzle centrifuge, so named because nozzles are arranged on the periphery or on the bottom of the bowl in a... 

A solid-bowl centrifuge has the following dimensions Rj = 0.30 m, Rj = 0.32 m, = 0.30 m. It is designd to operate at 5,000 rpm, separating particles from a suspension where the particle specific gravity is 7.8. Determine the required horsepower needed to set the centrifuge into operation. 

The principle of the solid bowl centrifuge is illustrated in Figure 4.19. It is essentially a device for enhancing the rate of sedimentation. The application of high G, however, creates stress in the machine and is equivalent to the application of pressure (cf. pressure filtration). There is therefore a balance to be struck between separating effect and stress. 

Consider a thin layer solid bowl centrifuge as shown in Figure 4.20. In this device, particles are flung to the wall of the vessel by centrifugal force while liquor either remains stationary in batch operation or overflows a weir in continuous operation. Separation of solid from liquid will be a function of several quantities including particle and fluid densities, particle size, flowrate of slurry, and machine size and design (speed, diameter, separation distance, etc.). A relationship between them can be derived using the transport equations that were derived in Chapter 3, as follows. 

Consider a continuous screen bowl centrifuge as illustrated in Figure 4.21. In this device liquor passes through a filter medium and cake builds up inside as before. 

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