Microfiltration

Microfiltration is a process for the filtration. The main difference between the micro - and ultrafiltration lies in the different pore sizes and in different membrane structure as the materials used and filter materials involved. A filtration through membranes with a pore size < 0.1 microns is typically called ultrafiltration during the filtration at pore sizes > 0.1 microns is usually referred to as microfiltration.

Both are purely physical ( mechanical ) membrane separation process. The method disconnect according to the principle of the mechanical size exclusion ( filtration method ), ie all particles in the fluids that are larger than the membrane pores are retained by the membrane. A driving force in the two separation method is the differential pressure between the inlet and outlet of the filter surface, which is between 0.1 and 10 bar. The material of the filter area, depending on the application, made ​​of stainless steel, plastic, ceramic or textile fabrics consist. There are different manifestations of the filter elements: candle filters, flat membranes, bag filters and hollow fiber modules. Your preferred areas are the beverage and oil filtration and pre-filtration.

Candle filter ( in the micro- filtration)

The candle filter consists of a filter housing and one or more candle inserted therein through which the fluid flows from the outside to the inside. The candles can be constructed differently, the typical construction are so-called wound cartridges, which consist of a coiled filament of synthetic or natural material. Other candles, depending on the application, can be made of ceramics, its metal ( sintered metal layer or multilayer metal mesh ). In addition, there are candles but are rather used in the cake -forming filtration with a replaceable filtering media (usually fabric origin). Exceptions are bespannbare filter candles in applications in those with pre-coating ( = Precoatierung ) worked, while the micro- filtration takes place in a kind of depth filtration in the preceding geschwemmten filter cake of the filter aid. The advantages of closed candle filters are a closed filter system with no drip losses and a good regeneration. A drawback is the sometimes significantly higher requirement for the preparation and pre-treatment of the products, to avoid premature, costly relocations of the candles.

The combination of layers with a final membrane filter before filling in the beverage industry is a reliable version of the pre-treatment, especially if difficult to be filtered products are present. A service filter for the media supply cold water and hot water, steam and caustic avoid secondary problems caused by contaminated particulate regeneration and sterilization media and ensures optimum regeneration.

As Kerzenvorfilter two types have been optimized in terms of effective protection of downstream membrane filter.

• A pleated configuration consisting of glass fiber pre-filter and a 1.2 micron or 0.8 micron membrane
• Wound, asymmetric polypropylene matrix using a validated deposition rate of 1 micron or 0.5 micron ( β - value 5.000 ).

Another type, consisting of coordinated, pleated layers of nonwoven polypropylene is characterized by mechanical and chemical stability as well as excellent recoverability. It is also used as a validated 1 -micron prefilter cartridge for wines from southern growing areas with low colloidal load. For this candle there are now a variety of applications, for example in the beverage filtration.

Flat membranes

These are non-woven fabrics, ceramic castings, or polymer membranes, which are manufactured in a flat form. They play in large-scale applications hardly matters.

Bag filter

Bag filters are sac-like structures made of textile or paper. They are typically used as prefilters.

Hollow fiber modules

In hollow fiber modules hollow fibers (including capillary membranes or hollow fibers called ), combined with a length between 2 and 200 cm modules of a few square millimeters up to about 100 square meters of filter area, and at both ends against hydraulic short-circuit encapsulated ( potted ). Their advantage is the accommodation of a large filter area in a confined space, as well as the generally low manufacturing costs. Find application microfiltration modules of hollow fibers in medicine ( plasmapheresis, in - line particle filtration at infusions, sterile filtration) as well as in water filtration (potable water: Point -of-Use, Reverse Osmosis Pre-filtration ).