Conical plate centrifuge

Disc bowl centrifuge (also known as conical plate centrifuge or disc stack separator) is a type of centrifuge that has a series of conical discs which provides a parallel configuration of centrifugation spaces.

The conical plate centrifuge is used to remove solids (usually impurities) from liquids or to separate two liquid phases from each other by means of an enormously high centrifugal force. The denser solids or liquids which are subjected to these forces move outwards towards the rotating bowl wall while the less dense fluids moves towards the centre. The special plates (known as disc stacks) increase the surface settling area which speeds up the separation process. Different stack designs, arrangements and shapes are used for different processes depending on the type of feed present. The concentrated denser solid or liquid is then removed continuously, manually or intermittently, depending on the design of the conical plate centrifuge. This centrifuge is very suitable for clarifying liquids that have small proportion of suspended solids.

The centrifuge works by using the inclined plate settler principle. A set of parallel plates with a tilt angle θ with respect to horizontal plane is installed to reduce the distance of the particle settling. The reason for the tilted angle is to allow the settled solids on the plates to slide down by gravitational force so they do not accumulate and clog the channel formed between adjacent plates.

This type of centrifuge removes solid matter from liquid feed from the plates. A centrifugal pump creates a pressure to discharge the clear liquid from the centrifuge. The solid is extracted through nozzles continuously, as shown in Figure 2. The quantity of concentrate depends on speed of bowl rotation, number of nozzles per centrifuge, radius of the nozzle’s position and the nozzle diameter. The quality depends on volume of concentrate discharged, and concentration and volume of the liquid fed into the centrifuge. The concentration of the discharge through the nozzle is varied by adjusting the diameter of the nozzle and initial volume of liquid feed.

Pre-treatment includes strainers in the feed lines to prevent coarse solid impurities clogging the nozzles. Generally, the diameter of the holes of the pre-treatment filter is about 10% smaller than nozzle diameter.

Lighter and heavier liquid exit separately through the top of the centrifuge, while the sludge is discharged intermittently through the nozzles. Another type of self-cleaning centrifuge has a removable chamber bottom. Both methods can be controlled independently or automatically, either time-controlled or depending on quality of discharge through nozzle

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