Screw-press separators are extremely efficient units that use an auger to pressurise the solids laden slurry to squeeze/separate out the liquid fraction through a screen, maximising the dewatering process and enabling control over the solid fractions dry matter (DM).
Compact in size, they consist of a cylindrical screen (wedge wire) that has a slow revolving auger running through its centre. The slurry/mash to be dewatered is pumped, gravity fed, augered, bucketed or other (depending on its form) into the unit. The liquid immediately starts to pass through the screen, to be pumped, fed away; solids with particle sizes larger than the screens void (slot) size are left in the unit. As the slurry progressively dewaters, the short auger starts transporting this continuously thickening slurry towards the solids outlet.
Control over the solids DM is made by and adjustable restriction at the solids outlet point that causes a back-pressure against the auger, regulating the compaction. This is achieved by either an adjustable spring-loaded or weighed flap, a conical obstruction, or increasing/decreasing the length of an outlet pipe.
Generally used on applications where control or minimal weight of the solids fraction or maximum liquid removal is required that can be all, or combinations of these. These units are not recommended on slurries with none absorbent solids as compaction would make no measureable difference.
Screw Press’s are able to separate out more liquid than any other separating method and on difficult and/or very low DM slurries, are sometimes used as a secondary unit; the slurry is passed through a Rundown or Drum unit first to remove the majority of the liquid.
Throughput speed is determined by: