Strassburger Filter - MicroCross Unit Crossflow Technique The Crossflow filtration is a tangential (cross current) filtration prcedure with hollow fibre modules.  The walls of the hollow fibres consist of membranes with exactly defined pores of 0.2 um.  In the hollow fibre modules there is a high velocity of approx. 2.5 m3m/s along the surface of the membrane.  The filtrate is pressed through the pores.  The high velocity of flow prevents the pores from clogging by constantly keeping the solids suspended.  The filtrate is pressed through the pores.  The membrane area of a modules is 17 square meters. During the filtration process the concentration of the retained solids rises inside the system which can lead to a clogging or blocking of various membrane types.  Blocking or clogging can occur by forming a layer of gel (colloids) An improvement of the filtration capacity is achieved by the asymmetric membrane.  The asymmetric membrane has pores that become larger towards the outside and has a completely smooth surface inside.  This structure produces a very high flow rate and a low susceptibility of adsorption.  Clogging is largely prvented and by backflashing and cleaning the initial capacity can always be achieved Filtration Procedure A rotary pump provides a constant flow in circulation through the hollow fibres and creates the required filtration pressure inside the hollow fibres.  Unfiltered liquid is automatically fed into the circulation, according to the filrate flow, whereby also a small amount of retentate is continously taken form the circulation and fed back into the feed tank.  Thus the amount of solids steadily concentrates in the feed tank One pump in the circulation system provides the required revolution at low pressure in the system, the second pump provides the required filtration pressure and transports the respective amount of unfiltered liquids from the feed tank. In order to keep the average filtration capacity constant there is a perodic backwash of the membranes every 5 - 15 minutes.  This interval is freely selectable. For regeneration the membrnaes have to be flushed with hot or cold water after each filtration process.  In case of 24 hour operation a chemical cleaning with hot caustic soda solution is necessary aprrox. two times a week.

Substantial ecological advantages ♦no filter aids necessary and thus no disposal problems ♦complete sterilisation with only one filtration (without prefiltration) ♦no influence on taste ♦no heating ♦no loss of colour ♦very favourable overflow relation which is only 1:20 whereas all other manufacturers have an overflow relation of approx. 1:60.  This means that only approx. 20,000 litres of wine flow in cycle in order to filter approx. 1,000 litres.  This, of course, has a postitive effect on the wine. ♦cleaning only with hot water possible (up to 65C) ♦saving of operation cost ♦safe microbiological stablisation Field of application ♦filtration of young wines after fermentation or sedimentation ♦filtration of grape juice ♦filtration before filling There are more than one hundred STRASSBURGER MicroCross units in operation.

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