Centrifuges nozzle solid-bowl

FIGURE 3.4-8 Nozzle solid-bowl centrifuge. The peripheral nozzles are for solids dischaige. Solids are washed before discharge. Courtesy of Alfa-Laval Inc. 

Centrifuges are used for the classification of particles in size ranges below 10 /im. Two types are used solid bowl centrifuges, usually with a cylindrical, conical bowl, rotated about a horizontal axis and nozzle bowl machines, fitted with discs. 

Partide size and shape may be manipulated by centrifugation using a combination of solid-bowl and disk-nozzle centrifuges to classify the particles according to size. The... 

In the second type of nozzle-discharge disc-stack centrifuge the solids are collected in a triangular storage space with nozzles located around the largest diameter of the bowl. The size and number of nozzles can be... 

FIG. 18-142 Disk-centrifuge bowls (a) separator, solid wall (b) recycle clarifier, nozzle discharge. 

Another type of disc centrifuge has nozzles or orifices at the periphery where thickened solids are discharged continuously, and sometimes a fraction of this discharge is recycled to ensure that the nozzles are able to prevent breakthrough of the clarified supernatant liquid. Sometimes these nozzles are internally fitted to the bowl. Others are opened and closed electrically or hydrostatically from a build up of the sludge within the bowl. 

In the case of the nozzle disk centrifuge, the flow of the solids phase through the discharge nozzles may be so restricted that an excessive layer can accumulate inside the bowl shell. When this layer reaches the zone utilized by the fresh feed stream entering the disk stack, reentrainment of the sedimented solids by the fresh feed may lead to poor sedimentation performance. 

Disc Nozzle Centrifuges In the nozzle-discharge disc centrifuge, sohds are discharged continuously, along with a portion of the liquid phase, through nozzles spaced around the periphery of the bowl, which are tapered radially outward, providing a space for solids... 

Disk stack separators are vertical bowl centrifuges that are characterized by the presence of a nested conical stack of disks. The centrifuges are usually categorized by the method of solid removal from the bowl and include solids-retaining, solids-ejecting, and nozzle-discharge units. The feed enters the bowl at... 

In a nozzle discharge centrifuge, the bowl is a solid, two-cone design. Orifices are located along the maximum diameter to allow solids to flow continuously. Liquid loss must be minimized and orifice sizes are therefore closely matched to the solids capacities. Thickened solids can be recycled to satisfy nozzle flow to maintain a dry effluent. This also circumvents plugging when using larger than usual orifices. 

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