Nozzle-discharge centrifuge

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. 

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

Because clay tends to pack hard, only the continuous nozzle discharge bowl would be satisfactory. Intermittently dischargiag disk centrifuges could not be used. 

The first three types, including the manual-discharge disk, are batch-feed centrifuges, whereas the latter three, including the intermittent and nozzle-discharge disks, are continuous centrifuges. 

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

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... 

To recover liquid in order of preference of settlers, Section 5.8, thickeners. Section 5.10 and sedimentation centrifuges. Section 5.12 clarifier, settler, washing tray thickener, reactortubular bowl centrifuge, batch automatic (horizontal or vertical bowl, disc with intermittent nozzle discharge) continuous disc bowl centrifuge with nozzle discharge. 

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... 

Figure 1.12 Schematic representation of a nozzle discharge disc stack sedimenting centrifuge.

A recently concluded series of large-scale tests in the UK revealed a dependence of cut size on feed concentration and volumetric feed rate (Figure 7.13). The feed rate is bound by two limiting values a minimum equal to the nozzle discharge rate (when no overflow occurs) and a maximum equal to the rate at which the centrifuge is flooded. The increase in cut size with increasing feed concentration is attributed to hindered settling. 

The disc-stack centrifuge with continuous solids discharge is called a nozzle discharge machine. The special nozzles mounted in the periphery of the bowl allow for continuous operation with a liquid-Uqnid-soUd feed, separating this mixture into two relatively clean liquid streams and a thick solids suspension. The concentration of this solids discharge can be controlled to meet process requirements. 

---