Screw Press - Dewatering with Compaction

What is a Screw Press

A screw press, or compression screw, is a compact machine used for compaction, separation, dewatering, and volume reduction. It efficiently separates suspended solids from input materials across various industries, handling liquid slurries, sludges, processed products, waste streams, biogas digestate, and fruits and vegetables.

How a screw press works

Using a very straightforward design, screw presses only have one moving part to generate the required pressure to compact and squeeze out the liquid element, making them a cost-effective, minimal maintenance machine.

Compact in size, consists of a cylindrical sieve screen that has a slow revolving screw through its centre that has a specifically designed screw flight/spiral that gets progressively tighter towards the discharge end, to create the force needed for the compaction. The input material is delivered to the inlet of the machine (the method is determined by its form) and is taken into the sieve screen by the revolving screw, starting the separation process.

As the compaction pressure takes hold, liquid, and small solid particles (smaller than the sieve screens gap) start getting forced through the sieve screen and into the liquid channel or storage Vessel. The increasing compaction pressure continuously forces out more liquid as the ever-drying material is transported towards the discharge where varying levels of control can be applied to ensure the dry matter content of the exiting dry element is consistent.

This is achieved by controlling its flow with a restriction, fixed choke, or variable manual or automatic cone/flap type restriction:

A fixed choke is generally a bolt-on reducer, extended pipe, or chute.
Manual – set the position of the variable flap to the required aperture size.
Automatic – constantly adjusts the aperture size of the discharge with either weighted, spring-loaded, or pneumatic controlled flap/cone to maintain the desired back pressure.

Screw Press - Compaction with Dewatering

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How it works

Multi chamber solution

While the compaction principle remains consistent across all models, our product line offers a diverse range of sizes and designs tailored to address varied applications and capacity demands.

The input material entering the screw press inlet undergoes a profound transformation by the time it exits the outlet. This transformation is not solely due to increased dryness but is characterized by a significant reduction in volume. Moreover, the specific attributes of the input materials processed contribute to this transformation. For instance:

Low-Dry Matter Products: Upon entering the machine’s inlet chamber, low-dry matter products initiate immediate dewatering with minimal compaction.
The chamber is strategically designed to efficiently remove the liquid content, facilitating rapid dewatering before the denser, reduced-volume slurry advances into the compaction chamber.
Higher-Dry Matter Products: In contrast, higher-dry matter products necessitate compaction force right from the inlet.
The inlet chamber is adeptly configured to accommodate and initiate compaction for such materials.

Depending on the specific application, a customized configuration may involve the incorporation of inlet, compaction, and multi-chambers along the length of the screw press. This configuration serves to optimize compression, employing progressively smaller gap-sized sieve screens and tightening of screw flight/spiral as the compaction pressure intensifies. Such meticulous design considerations enhance the overall efficiency and performance of the screw press across diverse operational scenarios.

Screw Press - Compaction with Dewatering

How it works

Two sieve screen types

Depending on the application, and the forces & pressures exerted, we offer two options for the sieve screen:

Wedge Wire screens are generally used for fine sieving, to leave as much solid matter in the dry element as possible and where the input material is relatively clean (no chunks of wood or plastic, etc.).

Punch Plate screens are generally used for dirtier input material but cannot finely sieve to the same level as wedge wire. These screens can have built-in shearing bars that stop jamming from larger objects by breaking/slicing them into small pieces.

In most applications, the pressure of the compaction and the continual movement of the dry element being transported to the end, are enough to keep the screen sufficiently clean to maintain throughput and liquid removal. Certain sticky and fibrous inputted liquids/slurries can cause screen blinding/blockages. To overcome this, there are options for automatic cleaning systems that, when required, high-pressure water is jetted into the Screen area to flush the screen clean. See Filtration for products to enable the washing water to be recycled.

How it works

Mechanical compaction force

Using compaction to squeeze out the liquid provides many benefits over non-compaction units:

A vast array of slurries, sludges, pastes, liquids, and products can be dewatered with a screw press that cannot with non-compaction, for example, thick and unpumpable, high in dry matter, viscous, sticky/gloopy, pastes/creams, foodstuffs/fruit/veg, and highly compressible and absorbent solids content products. Most products that have suspended solids can be dewatered with these machines except for certain entrained incompressible solids, for example, certain aggregates, etc. as these can compact and/or bind, causing the screw to stall.
Higher levels of separation as finer sieve screens can be employed meaning greater quantities of solid matter in the dry element and less in liquid.
Compacting the dry element means it is considerably drier (high dry matter), smaller in volume, and generally stackable, therefore doesn’t need a contained storage area.
Certain applications require particles smaller than 100 microns to be removed. This can be overcome with coagulation and filtration technologies – visit Coagulation and Filtration on this site for more details.

How it works

Screw Press - Compaction with Dewatering

Throughput

The throughput of a screw press is determined by several factors:

Type and characteristics of the inputted slurry/product:
We can generally advise.

Size of the machine:
From 1.5Hp through to 10Hp

Particle size removal from the liquid:
Wedge wire Screens from 100 microns – 2mm
Punch plate screens from 1.0mm – 5mm

Screw Press pictures

Screw Press videos

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