Fabric filters are specifically adapted to the requirements of flue gas filtration. The term flue gas describes the exhaust air produced during the combustion of substances. This form of filtration is used, for example, in metal processing, die-casting or to purify the exhaust air during the processing of biomass.
One sub-type, for example, is bag filters. These are used for the high-grade separation of particulate emissions as part of a multi-stage filter concept. It consists of several filter chambers, separated from each other by sealing flaps. Each filter chamber contains a fixed number of bag filter elements. The number of bag filters depends on the size of the filtration module. Depending on the composition of exhaust air, the bag filter elements consist of glass, mineral, metal or textile fibres.
During filtration process, the incoming exhaust air diffuses through the fabric of the bag filters. In doing so small solid particles are absorbed and form the so-called dry cake, or filter cake. This encrustation from filtration residues supports the extraction process: due to the enlarged receiving surface of the bag filter, more particles can be removed from the exhaust air stream. However, the disadvantage of a filter cake, is that due to the increasing pressure inside the filter module the energy consumption increases exponentially. In addition, fabric filters must be replaced at regular intervals.
For comprehensive exhaust air purification, fabric filters are usually combined with other filter components such as a gas scrubber or an electrostatic precipitator module.