A Dewatering screw press is a press that separates liquids from solids. A screw press can be used in
place of a belt press or centrifuge. It is a simple, slow-moving device that accomplishes dewatering
by continuous gravitational drainage. Screw presses are often used for materials that are difficult to
press, for example, those that tend to pack together. The screw press squeezes the material against a
screen or filter and the liquid is collected through the screen for collection and use.
In the first part of the screw press, the supernatant is quickly removed by a large filter surface at a
low primary pressure. A pressure probe in the feed area controls the primary pressure thus ensuring
a constantly high filtrate quality.
In the second part of the screw press, the volume of material between the screw flights is reduced by
the conical screw and the sludge pressed against the inner screen surface so that the sludge is
dewatered, with a continuous reduction of the filter cake thickness.
In the third part of the screw press, the residual water is pressed out of the sludge, at a minimum
filter cake thickness, by the pneumatic counter pressure cone at the press discharge. The dewatered
sludge is pushed by the conveying screw past the pressure cone into the discharge chamber. The
sludge residence time in the screw press and thus the filtration time can be adjusted to individual
requirements by adjusting the rotational speed of the screw shaft.