BOKELA Ingenieurgesellschaft für Mechanische Verfahrenstechnik mbH

Membrane Filters

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The dynamic membrane filtration with the DYNO Filter is a very versatile and high-performing cross flow process for micro-, ultra- or diafiltration of micro- to nano-sized particles in slurry. Tasks like separation of solids, Concentration or washing of highly concentrated slurries are performed by the DYNO Filter with high throughput capacity in a continuous operation or in batch operation.

  • Separation and washing of solids between 0.01 and 200 microns (micro-, ultra- or diafiltration)
  • High throughput rates even for highly concentrated or very viscous slurries
  • Very high final concentration
  • Pasty, spreadable solids output
  • Absolute filtration (complete separation of solids, no particle in the filtrate)
  • Filtration of sticky, slimy particles
  • Treatment of slurries with high viscous, plastic or thixotropic characteristics
  • Continuous or batch operation
  • Cooling or warming up during the filtration process with integrated heating/cooling system
  • Hermetical process
  • Filtration without air contact

With the DYNO Filter, the suspensions are treated in a quick and gentle way with unrivaled high concentrations. Even highly concentrated and/or highly viscous products can be filtered and washed. This means savings in wash medium, residence time and footprint. Whereas conventional cross flow filters (e.g. with tubes) achieve final concentrations of 10 - 20 Vol-%, the DYNO Filter produces final concentrations up to 65 Vol-% in one step.

The DYNO Filter is available with filtration areas of 0.013 to 8 m². Applications in the pharmaceutical industries are managed with the specifically designed DYNO Filter.

Modular Construction

The operation of the DYNO Filter is based on the principle of the dynamic cross flow filtration. The DYNO filter consists of several disk-shaped filter modules that are arranged in series and form a completely closed hermetical chamber system. The slurry flows meander-like from one chamber to the next one and becomes accordingly more concentrated since filtrate is discharged from each chamber. After the last chamber, the concentrate (retentate) is extracted with an automated drain valve.

Dynamic Cross Flow Filtration

The tangential cross flow is generated by the rotors in the slurry chamber whereas the trans-membrane pressure difference results from the feed pump. The liquid flows in a shear gap with high velocity gradient over the filter medium what avoids a blocking of the filter medium. The rotors ensure the homogeneous mixing of the slurry and also of the wash liquid, when applicable.

Washing

The serial arrangement of the filtration chambers and the intensive mixing of the slurry enable an effective washing and extraction. Since each chamber is independent, the input of wash water or any other wash liquid can be varied on demand.

Automated Operation / Control Loop for Slurry Upgrading

The power demand of the rotor shaft increases proportionally with increasing solids concentration of the slurry. Thus, the discharge of retentate/concentrate can be controlled by means of the required power of the drive. The outlet valve is opened only when a certain, free adjustable setpoint has been reached, discharging the concentrate at the proper concentration.

Apparatus Data

  • Filtration area: 0.013 m² - 8 m²
  • Number of modules: 1 - 20
  • Diameter of the modules: 145 - 550 mm
  • Hermetically sealed, explosion-proof system
  • Automated and self-cleaning process
  • Maximum filtration pressure: 6 bar, abs.
  • Maximum process temperature: 100 °C (up to 200°C for specific applications)
  • Low to moderate rotor speeds (depending on the filter size), i.e. no contamination by abrasion

Filter Media

Polymeric membranes with pore sizes of 0.1 to 1.0 microns (microfiltration) as well as ultrafiltration or metallic membranes are used as filter medium.

Application Areas

The DYNO Membrane Filter permits to concentrate and wash especially high concentrated suspensions with micro sized to nano sized particles. But also slurries with viscous, plastic or thixotropic characteristics or with gelatinous particles that are difficult to separate can be filtered in a continuous or discontinuous way.

Some examples are

  • fine minerals
  • inorganic pigments
  • organic pigments
  • pharmaceutics
  • products from the biotechnology

Filter Sizing by Lab or Pilot Tests

Testing equipment for lab tests with a filtration area of 0.013 m² and for pilot tests with a filtration of 0.4 m² are available. Thus, quick results but also continuous operation at pilot size can be carried out, ensuring a reliable filter sizing.

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