Interactions between the structure of the filtering layer and the filtration kinetics during the clogging phase in the dust separation with fibrous filter media up to the beginning of the cake-forming filtration

• Applicant: Dr.-Ing. Qian Zhang
• Subject Area: Mechanical Process Engineering
• Term: since 2021
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 496511469

A new, clean filter medium for surface filtration always starts with the initial phase in which the dust separation can be described by the principle of depth filtration in the given medium. The term filtration kinetics refers to the time behaviour of the separation efficiency of the entire filtering layer, which includes both the given medium and the deposited particles in the medium. If the dust separation on a given filter medium is carried out for a sufficiently long time, a dust cake is formed after a completed clogging phase, which is often a gradual process. A fully formed dust cake has, in addition to the core area of the cake, in which the packing density practically no longer changes, a highly porous packing area on its surface, which has a characteristic, stable height profile of the packing density in the direction of the gas flow. This packing area on the surface of the cake acts as the actual, active separation zone of the cake for the coming dust particles, since hardly any particles penetrate into the core area of the cake below. Therefore, with surface filtration which is named in relation to the original filter medium, there is always a special, highly effective depth filtration in the highly porous packing area of the dust cake on the microscopic level. This special depth filtration achieves a dynamic equilibrium of the filtration kinetics in which the structure of the active separation zone in the sense of a filtering layer no longer changes. For this reason, the filtration kinetics, actually the change in the filtration kinetics, of the overall process of dust separation on a given clean filter medium can be characterised through a description of the mechanism of the systematic change in the deposition profile of newly deposited particles in the changing porous structure. In this study, the overall filtration process is therefore viewed from a completely new perspective: There is a continuous, systematic change in the active separation zone of a given filtering system which is transformed from the initial clean filter medium via continuous particle separation under the given filtration conditions to a new, dynamically preserved stable porous structure - this is the active separation zone of the dust cake. The driving force behind the dynamic process of restructuring is the filtration. It will be theoretically and experimentally investigated in the research project, how the filtration kinetics can be described by considering the systematic change in the deposition profile of newly deposited particles in the entire porous structure that grows out of a given clean fibrous filter medium under given filtration conditions.

• DFG Programme: Research Grants
• Co-Investigator: Professor Dr.-Ing. Eberhard Schmidt