Multi-disc Screw Press dewatering

The Principle of Screw press is using mesh or sludge cake filtration technologies to achieve the solids-liquid separation. The screw pitch narrows from thickening zone towards the dewatering zone, thus making the pressure in the dewatering drum to increase. The End Plate increases the inner pressure even more, thereby dewatering sludge fully. The most popular Dewatering screw press are ROTAMAT ® Screw Press RoS 3 in German, FKC Screw Press and Volute Dewatering Press in Japan.

Traditional screw press separates solid and water by using dewatering drum, the mesh gap can be 0.05mm in order to maintain high solids capture rate of sludge. Now most screw press dewatering takes the form of wedge-shaped filter mesh to prevent clogging, provides with brushes for continuous internal cleaning and increases the external backwash water to clean filter at the same time. Sludge with high viscosity is difficult to achieve stable filter. It can not achieve a stable filtration separation without stable mesh size.

   Multi-disc Screw press dehydrator is using sludge cake in the fine gaps between fixed and moving rings to allow the sludge to be squeezed. Those rings mobilized by the screw, continuously clean sludge out of the gaps, so as to ensure the stability of the filter area load and dewatering result.

  Multi-disc Screw press has been widely used in municipal sewage sludge, oily sludge, especially for food, daily chemical, petrochemical, pharmaceutical and other industries. It is capable of dewatering low-concentrated sludge without sludge concentration tank and storage tank. Multi-disc Screw press has low running speed, small size, low power consumption and 24-hour automated operation. 

  Choosing Multi-disc Screw press to dewater sludge, the following aspects should be considered:
1) Type of the dics：the early discs in thickening zone using resin which has short lifetime and lack of precision ,can only use for small sewage treatment intermittently. Stainless steel rings are now mostly considered;
2) The number of fixed and moving rings：determines the filter area and dewatering capability;
3) The precision of fixed and moving rings: determines the precision and power consumption of the device itself;
4) A design of real seal or not: quick opening waterproof seal and open-type sludge discharge port were the most popular in the early days.

Comparison with Various Dewatering Machines   

Model	Belt Press	Screw Press	Multi-disc Screw Press	Rotary Press	Centrifuge
Principle	Mesh filtration	Mesh filtration	Cake filtration	Mesh filtration	Centrifuge
Driving force	Gravity +pressure	pressure	pressure	pressure	Centrifuge force
Separation	Mesh Pressurized filtration	Mesh Pressurized filtration	Cake Pressurized filtration	Mesh Pressurized filtration	Centrifugal force
Dewatering	Pressure	Pressure + press	Pressure + press	Pressure + press	press
Filter medium	Filter cloth	Perforated metal	Multi-disc metal	Perforated metal	NO
Filter updates	Water rinse	Water rinse +scrub the surface	Update the cake	Water rinse +scrub the surface	NO
Power Consumption	High	Low	Low	Low	High
noise	Low	Low	Very Low	Low	Very High
recovery rate	High	Low	High	High	High
rinse water	Very High	Less	Very Less	Less	Very Less
Footprint	Large	Small	Small	Small	Small
Oily sludge	Difficult	Difficult	easy	Difficult	easy
Vibration	High	Less	Less	Less	Very High
Maintenance	Difficult	Easy	Easy	Difficult	Very Difficult
Maintenance Cost	High	Low	Low	High	Very High
24 hour Operation	No	Yes	Yes	Yes	No