Fundamental investigations of the filtration behaviour of surface filters under low operating pressures (p << 100 mbar)

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The drying of heat-sensitive products like battery components or pharmaceutical formulations requires low process pressures (p << 100 mbar) to avoid overheating of the products. Vacuum dryers are usually used for this purpose in industry. The steam generated during drying can entrain fine particles from the product bulk. In order to prevent contamination of downstream equipment and to recover the product, the particles are separated in so-called vapour filters, usually surface filters. The design of vapour filters is usually based on empirical values regarding the filter areas from the standard pressure range for dust filters. However, this leads to incorrectly dimensioned filter areas and consequently to unstable filtration behaviour, higher costs and increasing energy consumption. The filters can only be correctly dimensioned with a fundamental understanding of the filtration behaviour of surface filters at low pressures. However, there is a lack of fundamental work on this topic in the literature. In order to fill this gap in the literature, various investigations on the filtration behaviour of surface filters at low pressures are conducted. First, a pilot plant will be developed and put into operation. The differential pressure of unloaded and loaded filter media will be investigated at this test facility. Needle felts, needle felts coated with membranes, sintered metal mesh and woven metal filters are used. The measured differential pressures are compared with calculated differential pressures from existing calculation equations from the literature. In addition, experiments are realised on the separation behaviour (separation efficiency, filter cake structure, ...) and regeneration (cleaning efficiency, optimal cleaning pressure, ...) at reduced system pressures. All the results collected at low pressures are compared with those at ambient conditions.