BOKELA Ingenieurgesellschaft für Mechanische Verfahrenstechnik mbH

Drum Filters



The modern BOKELA drum filters represent a new generation of continuous vacuum drum filters. They are used for filtration, washing and dewatering of very different products. The different designs and numerous auxiliary components enable an ideal adaptation of the filter to the individual product and process conditions. The most widespread vacuum filters are used in all the industries, from the chemical one to the extractive one.

This is possible by:

  • filtration area of 0.5 to 125 m²
  • models with closed drum
  • models with single cell design, i.e. exchangeable filter cells (for filter of up to 7m²)
  • numerous methods of cake discharge:
    • compressed air blow back
    • roller discharge
    • discharge knife (for precoat filters)
  • different systems of cake washing
  • additional items like wash hood, steam hood, press belt, complete enclosure
  • numerous materials of construction available

BOKELA drum filters have an outstanding hydraulic design and so offer economical solutions for demanding applications of the process filtration. They are characterised by:

  • optimal cake washing in up to 3-step counter-current wash
  • sharp filtrate separation
  • high filter speed of up to 3rpm
  • 50 to 75% higher throughput rates compared to conventional drum filters
  • low residual cake moisture
  • complete cake discharge even at high filter speed
  • clear filtrate
  • outstanding cloth lifetime
  • high availability and flexibility
  • simple maintenance
  • innovations like:
    • single cell design, i.e. exchangeable filter cells
    • easily adjustable process zones
    • FrameTrakTM system – an innovative method of cloth fixing for both drum and pan filters

BOKELA drum filters are available with 0.5 to 125m² filtration area.

The biggest drum filters are mainly installed in the processing industry (minerals, salts) whereas the smaller ones are usually operated in the chemical, pharmaceutical and food industry. The filter design varies with the specific process demands.

All the components like the filter cells, filtrate pipes, control head, cake wash system, filter trough and slurry agitator are of most modern design and so care for both excellent hydraulics and a simple maintenance.

Filter Cells of Closed Drum

  • 16 to 24 hydraulically optimised filter cells for a quick and complete cell emptying
  • the hydraulically optimised cells improve the filtrate drainage and can be removed without any tool
  • different cloth fixing systems facilitate the cloth replacement and improve its lifetime
  • FrameTrakTM system – a brand-new method of cloth fixing for the simple exchange of individual panels.

Single Cells

Exchangeable filter cells available for filters of up to 7m² filtration area:

  • 24 to 48 smal individual cells
  • fast mounting and dismantling
  • singular quick replacement of the filter cloth (approx. 1h per filter) that is bag-shaped
  • simple and fast cell cleaning

Filtrate Piping

Leading and tailing filtrate pipes care for a quick and complete cell emptying as well as for a sharp separation of the mother liquor from the wash filtrate:

  • the filtrate pipes are inside the drum for closed drum design
  • the filtrate pipes are outside the drum for the single cell design

Control Head

For applications where a huge filtrate flow shall be separated, the control head is designed for the pre-separation that:

  • reduces the pressure losses by early separation of the filtrate from the air
  • prevents the carryover of the filtrate into the wash and dewatering zone, respectively
  • enables the connection of a second cake forming or dewatering zone for a quick adjustment to product changes (option mainly used in the chemical industry where different products are filtered on the same filter).

Cake Wash Systems

In order always to get the best efficiency, the homogeneous distribution of the wash liquid will be done, depending on the wash ratio required:

  • with adjustable overflow weirs at high wash liquid flow
  • with adjustable wash bars with nozzles at small wash liquid flow.

Cake Discharge Systems

  • air blow back with snap-blow valve for dry, friable and not too thin cake
  • roller discharge for fine-grained, thin and sticky filter cakes
  • discharge knife for very thin cakes filtered on precoat filters
    • cake thickness << 1mm
    • minimum knife feed: 10µm

Complementary Equipment

Numerous components can be installed on the BOKELA drum filters in order to optimise the separation process. Exemplary elements are:

  • pressure belt
  • wash hood
  • steam hood
  • filter enclosure

Automated Operation

The BOKELA drum filters works fully automatically:

  • automated filter start and stop
  • constantly high throughput
  • constant product quality
  • high filter availability of over 94%

The BOKELA drum filters are operated in all kinds of industries from the chemical to the bulk materials industry. Typical applications are:

  • aluminium hydroxide (i.e. oxalate washing)
  • backing yeast
  • gypsum
  • molybdenum concentrate
  • pigments
    • inorganic pigments
    • organic pigments
    • white pigments like titan dioxide, calcium carbonate
  • red mud
  • hot brine
  • sulfate

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