In recent years, the development, innovation, and promotion of the screw press sludge dewatering machine have made significant strides in China. Due to its characteristics of easy separation and non-clogging, the screw press sludge dewatering machine is now widely used in municipal sewage treatment, industrial wastewater treatment, petrochemicals, pharmaceuticals, textiles, metallurgy, food and beverage, mining, and many other fields.
- What is a Screw Press?
The screw press sludge dewatering machine utilizes the principle of screw extrusion. It employs the powerful extrusion force generated by the changes in screw diameter and pitch, along with the small gap between the movable and fixed rings, to achieve the squeezing and dewatering of sludge. It is a new type of solid-liquid separation equipment.
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Components of the Screw Press
- Screw Body The screw body consists of fixed rings, movable rings, a screw shaft, screws, gaskets, and several connecting plates. The fixed rings are connected together by six screws, and gaskets and movable rings are installed between the fixed rings. Both fixed and movable rings are made of wear-resistant materials to ensure a longer machine life. The screw shaft passes through the middle of the fixed and movable rings, with the movable ring loosely fitting on the screw shaft.
- Screw Shaft The screw shaft is composed of a shaft and helical blades. The shaft is welded from a core and hollow shaft. During welding, the core and hollow shaft are first welded together, followed by rough machining to ensure coaxiality at both ends of the shaft. Then, the helical blades are welded to the shaft using a full welding method.
- Drive Unit The drive unit serves as the power source for the equipment, and its performance directly affects the overall performance of the machine. Therefore, a high-performance motor is generally chosen, with a protection level of IP54 and an insulation level of F.
- Filtrate Trough The filtrate trough is welded from plate pieces and is used to collect the filtrate pressed down by the screw press main body. The filtrate trough is connected to the frame with screws around it, and a flange is provided on the side of the filtrate trough for external device connections.
- Mixing System The mixing system is mainly used to thoroughly mix sludge with chemicals to form a floc for pressing and dewatering by the screw press main body.
3. Dewatering Principle of the Screw Press
After the sludge is concentrated in the thickening section through gravity concentration, it is transported to the dewatering section of the screw press. In the forward movement process, with the gradual reduction of the filter gap and pitch and the obstruction of the backpressure plate, a significant internal pressure is generated, causing the volume to continuously shrink and achieving full dewatering.
- Concentration: When the screw drive shaft rotates, multiple fixed and movable stacked plates set on the periphery of the drive shaft move relative to each other. Under the action of gravity, water is filtered out through the gaps between the relative moving plates, achieving rapid concentration.
- Dewatering: The sludge, after concentration, continues to move forward with the rotation of the screw drive shaft. Along the direction of the sludge cake outlet, the pitch of the screw drive shaft gradually decreases, and the gap between rings also narrows. The volume of the screw chamber continuously contracts, and under the action of the backpressure plate at the outlet, the internal pressure gradually increases. As the screw drive shaft continuously rotates, the water in the sludge is squeezed out, and the solid content of the filter cake keeps rising, ultimately achieving continuous sludge dewatering.
- Self-cleaning: The rotation of the screw drive shaft continuously turns the movable ring, and the equipment relies on the movement between the fixed and movable rings to achieve a continuous self-cleaning process, cleverly avoiding the common clogging problems in traditional dewatering machines.