The working principle of the screw press is based on the combination of spiral extrusion and gravity filtration. The equipment mainly consists of a spiral shaft, multiple fixed rings, and floating rings stacked together. When the sludge enters the screw press, most of the free water naturally flows out through the gap between the fixed ring and the floating ring under the action of gravity, achieving preliminary dehydration. As the spiral shaft rotates, the sludge moves axially from the feed end to the discharge end under the push of the spiral shaft.

During this process, as the pitch of the spiral shaft gradually decreases and the gap between the fixed and floating rings narrows, the squeezing effect on the sludge intensifies. Under strong squeezing pressure, the interstitial and bound water in the sludge are further extracted and discharged through the gap between the fixed and floating rings, achieving deep dehydration. The dehydrated sludge forms a mud cake with low moisture content and is discharged from the outlet.