Continuous filtration of sedimenting substances

Rubber belt filter


Rubber belt filter

The rubber belt filter of type BFR is a continuously operating, horizontal vacuum filter used for the reliable separation of quickly sedimenting solids from suspensions. It is characterized by high throughput rates and a robust design. Cake treatment involving one or more washing stages is possible.

The rubber belt filter (BFR) for efficient separation of fly ash and washing water


The rubber belt filter (BFR) for efficient separation of fly ash and washing water

ERZ Entsorgung + Recycling Zurich produces 5,000 tons of fly ash per year, which is continuously washed out. To efficiently separate the fly ash suspension from the washing water, ERZ is using the fully automatic, heavy-duty rubber belt filter (BFR) from BHS-Sonthofen.


The BHS rubber belt filter stand out thanks to its robust construction that specifically addresses typical applications. A firm supporting structure made of steel or stainless steel allows this system to be used even in harsh environments. BHS rubber belt filters are designed for a long service life under heavy load. This minimizes both maintenance and operating costs.

Low maintenance requirements

Due to the small number of individual parts installed, a rubber belt support in the form of a roller table and optimum accessibility to the vacuum box, the rubber belt filter is extremely resistant to wear and easy to service. Robust systems for belt support and belt guidance result in a long service life and reduced maintenance times.

High performance

BHS rubber belt filters are designed to deliver top filtration performance. Depending on the application, suspension capacities of up to 15 m³/m²/h can be achieved. Downstream cake processing, such as one- or multi-stage cake washing, is also possible on demand. Filter surfaces can be dimensioned up to 162 m² per filter.

Flexible production

By using tried and tested measuring and control equipment to measure cake thickness and belt speed, the filter can be flexibly adapted to the respective requirements in terms of production output. Downtimes due to retrofitting or adaptation are eliminated.

Customer-specific designs

Various materials are available for the design of the carrying belt, the supporting structure and attachments. Given the large selection of plastics for the filter cloth and vacuum box, the rubber belt filter can be used in a wide range of applications. Accessories such as a vacuum station or blower, filtrate or pre-thickening station enable the filter to be designed as a complete system perfectly adapted to the respective application.


  1. Suspension feeding
  2. Cake washing
  3. Roller table
  4. Wear belt
  5. Vacuum box
  6. Rubber belt
  7. Filter cloth
  8. Cake discharge & scraper
  9. Drive roller
  10. Cloth washing
  11. Collection pipe
  12. Belt guide
  13. Belt tensioning roller
  14. Cloth tensioning unit


Functional description

A circulating filter cloth, which is continuously moved, serves as the filter medium. A rubber support belt is used to support the filter medium. The belt features milled grooves for filtrate discharge. It moves over a stationary vacuum box on a roller conveyor as well as on wear and sealing belts. The box collects and discharges the filtrates.

The filter cake builds up on the membrane. This can be further treated by washing out (possibly several times in a counter-current), steaming, extraction or dry suction. The filtrates can be acquired individually by each process stage and processed without any intermixing. The take-off roller is where the rubber belt filter ejects the cake. A mechanical scraper system can be integrated for additional support. The membrane is cleaned in the lower part of the filer when the conveyor belt is reversed.

The design with roller support of the carrying belt results in considerable water savings and at the same time increases the system’s reliability compared to conventional designs.

Roller table

Use of the roller table eliminates the need to consume operating media such as compressed air or water. Tried and tested roller systems support and guide the rubber belt. This system offers high reliability and is easy to maintain.

Vacuum box with wear belt

The vacuum box is located underneath the filter. It is used to apply a vacuum to the rubber belt and thus to the filter cloth. Wear belts with a sealing water supply system reliably seal off the production space from the atmosphere. The vacuum box is delivered in plastic or stainless steel. Easy accessibility and low sealing water consumption are guaranteed.


Filtrate separator station

Filtrate separator stations are used to separate gaseous and liquid media. The filtrates are pumped out of the separators using suitable pumps, or they are barometrically submerged. The gas is guided to the vacuum pump unit via a common collecting pipe.

Vacuum pump unit

An optionally available vacuum pump unit serves to generate the vacuum for the rubber belt filter. This creates the necessary negative pressure necessary for the rubber belt filter to operate. In general, liquid ring pumps are used for complete systems.

Hydrocyclone station for pre-thickening

The hydrocyclone station serves the purpose of pre-thickening the suspension, which is subsequently fed to the rubber belt filter.

Technical specifications

Performance Data, Dimensions, and Weights

TypeActive filter widthActive filter lengthActive filter areaMotor powerDimensionsWeight
BFR 1201.050 mm6 - 10 m6 - 11 m²bis 11 kW9,5 - 13,5 m2,2 m2,3 m3 - 10 t
BFR 1601.450 mm8 - 14 m12 - 20 m²bis 15 kW11,5 - 17,5 m2,6 m2,3 m4 - 15 t
BFR 2001.850 mm10 - 18 m18 - 33 m²bis 18,5 kW13,5 - 21,5 m3 m2,3 m6 - 20 t

All specifications apply to the standard version.
Technical data for customized designs may differ from the specified data.
All technical data may change due to development.
Subject to modification without notice. 

Operating criteria
Operating methodcontinious
Operating pressurevacuum
Operating temperatureup to 90 °C
Solids content (suspension)up to 60 % (by weight)
Cake thicknessup to 80 mm
Grain size10 - 500 µm
Filter output – suspensionup to 15 m³/m²/h
Filter output – dry solidsup to 5.000 kg/m²/h
Active filter surface6 - 33 m²


Tests give certainty

Which technology is the right one for your process? Don’t leave anything to chance. In our test center and filtration laboratory, we test according to your specifications and identify the optimal solution for you.
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