What is membrane filtration?
Industrial membrane filtration plants were introduced in the dairy industry in the beginning of the 70's. The basis for using membrane filtration in the dairy industry is that the dry matter components in milk and whey particles consist of of different sizes. . By selecting filters/membranes of differrent poresizes and apply pressure on the product to be filtered, it is possible to divide the milk and whey in different fractions. What passes the filter/membran = permeate and what does not pass = retentate.
| Particles |
Diameter |
| Fatglobules (and bacterias) |
500-10,000 nm |
| Casein particles |
10-300 nm |
| Whey Protein |
3-6 nm |
| Lactose |
Approx. 1 nm |
| Salts |
0,4-1 nm |
| Water |
Approx. 0,3 nm |
What is membrane filtration used for?
Membrane filtration is today used in the Food & Dairy industry and likewise in other process plants delivered by the GEA Group of Companies.
Here is introduced four kinds of membrane filtration:
• Reverse Osmosis is used to remove water from a product to increase the solids content, evaporator condensate is often 'polished' by reverse osmosis, so that it can be used elsewhere in the dairy.
• Nanofiltration is used to remove mainly the monovalent ions from whey. A partly demineralization and water removal is obtained.
• Ultrafiltration is typically used for whey, where the whey proteins are separated to form a product with 35, 60 or 80 % WPC. If ultra filtration is applied to skim milk, then Milk Protein Concentrate is obtained. The protein fractions are typically evaporated in multi-effect evaporators with either TVR or MVR recompression to save steam, before spray drying.
• Microfiltration is a low pressure membrane process for separating colloidal and suspended particles in the range of 0.05-10 microns, and as such used for bacteria removal.
