Surface filters are used in various technical processes to separate particles from a particle laden gas stream. The particles are mainly separated on the surface of the filter medium and on the surface of the already formed dust cake. A main focus in the operation of surface filters lies on the particle emission and the stable operation of the filtration plant.

Besides widely-used flat filter media (e.g. bag filters), folded (pleated) filter media can be applied to increase the theoretical filtration area. When applying pleated filter media or pleated filter elements (e.g. cartridge filters), certain problems can occur during operation, such as insufficient regeneration or an unstable operation of the filter. These problems can mainly be attributed to the pleats of the filter media or the pleating process itself.

The pleating process can lead to differences in media permeability and thus a homogeneous flow through the entire media is not possible. The inhomogeneous flow can result in velocity gradients between the pleats and lead to a loss in effective filtration area. Besides the arising problems due to manufacturing, the filter operation can be influenced by certain geometrical aspects. An increase in the pleat density (pleats per area) results in an increase in theoretical filtration area, but the effective filtration area does not follow the same trend. This is due to a few factors, such as insufficient regeneration of the pleat bottom. The insufficient regeneration leads to blockage of a certain filtration area and as a result to a reduction of effective filtration area. The loss of effective filtration area increases the mean filtration velocity and leads, assuming a Darcy pressure drop model, to an increase of pressure drop. The increase of pressure drop and the blockage of pleats can hinder stable filter operation.

The main focus of this contribution is the experimental determination on the influence of pleating and of different pleat densities on the operating behaviour of filter media in a filter media test rig ....