BoCross Dynamic filter – high solids concentration and clear filtrate.

With the BoCross Dynamic filter, microfine to nanoscale suspensions are concentrated to unrivaled high concentrations in a quick and gentle way. Even at high feed concentrations or high viscosities can still be filtered and washed.

Dynamic crossflow filtration with the BoCross Dynamic filter is a unique process for microfiltration and ultrafiltration of microfine to nanoscale suspensions. Tasks such as thickening, washing and clarifying are performed by the BoCross Dynamic filter in continuous operation with permanently high throughput rates.

The dynamic shear gap principle ensures almost ideal physical conditions for the separation process. The process and machine principles allow an exceptionally high concentration of suspensions to be processed in one run. Under the influence of the shear forces, the concentrate still remains flowable even with high thickening. Therefore, highly viscous and highly concentrated suspensions can still be processed. Compared with conventional crossflow filtration, five to six times higher concentrations are achieved with the BoCross Dynamic filter.

The BoCross Dynamic filter has a modular and hermetically sealed construction. It is available with filter sizes from 0.1 m² to 8 m² and can be used for an operating pressure of up to 6 bar (a). and an operating temperature up to 100 °C.

BoCross Dynamic filters are characterized by:

  • separation and washing of solids in the particle range of 0.01–200 μm
  • high flow rates even with high feed concentration or high viscosity up to 25,000 mPas
  • very high final concentration of up to 80 wt.- %
  • pasty, spreadable solids discharge
  • no segregation or classification in the apparatus
  • absolute filtration – 100 % solids separation and particle-free filtrate
  • processing of slimy, gel-like particles
  • hermetic process – filtration without air contact
  • continuous or batch operation

The BoCross Dynamic filter consists of disc-shaped filter modules arranged in a row, forming a completely closed system of process chambers. Each filter module is equipped with filter media on both sides. The modules have central openings for the filter shaft, which carries the rotors of the individual suspension chambers. The suspension flows from chamber to chamber in a meandering manner, whereby the concentration increases successively, since filtrate drains off in each chamber. The thickened concentrate is discharged controlled in the last chamber by means of an exhaust valve. In each chamber separately washing liquid or other process liquids can be supplied.

The tangential overflow of the filter surface is induced by rotors in the suspension room and the transmembrane pressure difference is generated by the feed pump. The liquid flows over the filter medium in a shear gap with a high velocity gradient. This prevents blocking of the filter medium. The rotors ensure a uniform homogenization of the suspension and excellent mixing, e.g. with the washing liquid.

In each chamber wash liquid or other process liquids can be introduced separately. The rotors cause an intensive mixing of suspension and wash liquid and thus, an efficient washing out. It is also possible to replace the mother liquor with another process fluid.

The BoCross Dynamic filter is very gentle on the product. The desired process result is achieved not only after several circulations with circulating streams but in only one run with short residence times. The variable rotor speed ensures that no particle destruction takes place. A heating/cooling system which is integrated in the modules allows a tempering of the product by cooling or heating during filtration.

The BoCross Dynamic filter reacts flexibly on changes in the product characteristics – for example, in terms of viscosity or solids concentration in the feed or as a result of product changes – and thus, ensures reliable operation and constant operating results. This is particularly important for multi-purpose plants.

Due to the process and apparatus principle, the BoCross Dynamic filter also enables continuous operation with very small production volumes in the range of 1 kg/h.

The BoCross Dynamic filter can be used with a variety of filter media such as:

  • micro filtration membranes in the range of 0.1–1.0 μm
  • ultrafiltration membranes
  • sintered plastic or ceramic membranes
  • specially developed sieve composite sheets
  • metallic media

BoCross Dynamic filters work fully automatically and can be easily integrated into process automation. Startup and shutdown procedures as well as cleaning procedures are automated.

Filter Type [–] XS01 S04 M2 L8
Filter Area [m²] 0.13 0.4 1.8 8
Filter Diameter [mm] 145 200 375 555
No. of modules [–] 5 8 10 20
Drive [kW] 3 < 5.5 < 15 < 55


Crystallization and Precipitation Suspensions

Tailored Solutions for Smooth Solid Separation, Washing and Dehumidification.

In crystallization and precipitation processes, solids have to be separated from suspensions. The BOKELA filter series BoHiBar Drum and BoVac Drum allow a product-friendly, fully automatic solution for the often sensitive suspensions, while also reducing drying costs.

Plastic Precursors

Filtration Apparatuses for High Product Quality and Consistently Low Costs.

Filtration is often an important step in the production of plastics. BOKELA products such as BoHiBar Drum, BoVac Drum or BoCross Micro Screen provide reliability, long service life and excellent process results. Minimal energy consumption and reduced drying costs ensure an improved economy.

Pharmaceutical Precursors

For Maximum Hygienic and Economic Standards.

The production of pharmaceutical products naturally faces high regulatory standards. Apparatuses, process and filter technology have to meet those demands. BoCross Dynamic and BoVac Drum are unique solutions for different fields of application.

Pigments, Fillers & Dyes

BOKELA filters for Sensitive Solids and Smallest Particle Sizes.

Pigments, fillers and dyes are used very differently in the various fields of application. A feature all of them share is the very small size of particles, usually smaller than one micrometer. The technologies of the BoCross Dynamic, Boris MicroScreen, BoVac Drum and BoHiBar Drum series ensure a reliable and product-friendly separation.

Crossflow Filtration. For Difficult Suspensions

Macro, micro, or nano.

BoCross Dynamic and BoCross MicroScreen are dynamic crossflow filters for micro, ultra, dia or sieve filtration. With the BoCross filter series, suspensions with high concentrations or viscosities can be thickened, washed, cleared or classified.

Concentrating and Washing of Titanium

The BoCross Dynamic filter is used for concentrating and washing of a modified and very fine titanium dioxide which has to be further processed.

Concentrating and Washing of a Pharmaceutical Iron Hydroxide

A pharmaceutical suspension is synthesized so that a considerable amount of salt is formed during neutralization. This microfine suspension must be cleansed (washed out) of salt and further concentrated.

Concentrating and Washing of Calcium Carbonate

Special PCC Product

For concentrating a fine-particulate special PCC product a BoCross Dynamic filter with 6 m² filtration area is operated.


Low residual moisture is important for the further processing of the filter cake. With mechanical drying, an intelligent filter design and the right operation mode, production costs can be considerably reduced.

Filter Cake Washing

Filter cake is the name for the solids filtered from a suspension and collected at the surface of the filter medium. The washing of the filter cake is essential to the purity of the filtered solids and thus, for the reusability.

Solid Separation

Solid separation is the first process step with regard to separating solids from fluids. The driving force behind the process is the pressure difference with which the suspension flows through the filter medium.

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