What is plate and frame filter press？

The plate and frame filter press is a device for separating solid and liquid, and is the first machine used in chemical dehydration. Although plate and frame filter presses are generally intermittent, they are still widely used in some sewage plants because of the advantages of large filter driving force, high solid content of filter cake, clear filtrate, high solid recovery rate, and high consumption of conditioning drugs.

Plate and frame filter presses are of great significance to wastewater plants. With the development of science and technology, people’s living standards have improved, and the requirements for environment are getting higher and higher. With the enhancement of environmental awareness, the sewage treatment plant has also received considerable attention. Due to the large driving force of filter press and the low consumption of conditioning drugs, it is very popular among small sewage plants.

After the sludge is concentrated and precipitated, it still has a moisture content of about 95% to 97%, and the volume is still large. Sludge dewatering can further remove void water and capillary water in sludge and reduce its volume.

After dehydration treatment, the moisture content of sludge can be reduced to 20%, and its volume is 1/10~1/4 of the original volume, which is conducive to subsequent transportation and treatment. The sludge mechanical dewatering method includes filtration dehydration, centrifugal dehydration and press dewatering, and filtration dehydration have vacuum filtration and pressure filtration; centrifugal dewatering is performed by a centrifuge; dewatering by a press is performed by a screw press or a roller press.

Commonly used are pressure filtration and centrifugal dewatering methods. Sludge filtration dewatering is based on the pressure difference between two sides of the filter medium to force sludge moisture to pass through the filter medium to form a filtrate, and the solid particles are trapped on the medium to form a filter cake, thereby achieving the purpose of sludge dewatering.

Plate and frame filter press dewatering process

The plate and frame are arranged one on another, and the filter cloth is covered on both sides of the filter plate, and the plate and frame are pressed by the pressing device, that is, the filter press chamber is formed between the plate and frame.

In the same part of the upper end of the plate and frame, there is a small hole, which is pressed into a channel, pressurized to 0.2~0.4MPa sludge, and the channel enters the filter press chamber, the surface of filter plate is engraved with a groove, the lower end has a hole for discharging the filtrate is drilled, and the filtrate is discharged under pressure through a filter cloth and along a groove and a channel to discharge the sludge.

The plate and frame filter press can withstand higher sludge specific resistance than vacuum filter, which can reduce the consumption of conditioner. When the specific resistance of sludge is 5×1011 to 8×1012 m/kg, it can be directly filtered without pre-conditioning.

The mud cake yield and mud cake moisture content of plate and frame filter press shall be determined based on test data or similar operating experience. The moisture content of the mud cake can generally be 20%.