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

Particle separation with a new, clean filter medium always starts with the initial phase that 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 filter layer, which includes both the given medium and the deposited particles in the medium. If dust separation is carried out on a given filter medium for a sufficiently long time, a dust cake forms after a completed clogging phase. In addition to the core area, where the packing density practically no longer changes, a fully formed dust cake has a highly porous packing area on its surface, which has a characteristic, stable profile of the packing density in the direction of gas flow. This packing area on the surface of the cake acts as the actual active separation zone of the cake for subsequent dust particles, as hardly any particles penetrate into the core area of the cake below. Therefore, in surface filtration, which gets its name from the actual filter medium, a special, highly effective depth filtration always takes place at the microscopic level in the highly porous packing area of the dust cake. This achieves a dynamic equilibrium state of the filtration kinetics - the structure of this active separation zone no longer changes. For this reason, the filtration kinetics of the entire process of dust separation on a filtering medium, which begins with depth filtration in the initial filter medium and transitions to regular cake-forming filtration via a completed clogging phase, can be described in terms of its interactions with the systematic change in the deposition profile of newly separated particles throughout the porous structure. The research project takes a completely new look at the entire filtration process: it involves a continuous, systematic change in a given structure which, due to its filtering effect, transforms into a new, dynamically stable structure through continuous particle separation under the given filtration conditions; the driving force here is filtration. Theoretical and experimental investigations are being conducted to determine how the filtration kinetics can be described by observing the systematic change in the deposition profile of newly deposited particles throughout the porous structure that grow out of a given filter medium under given filtration conditions. By clarifying the interactions between the two characteristics of a filtration process - simultaneous changes in the filtering structure and the composition of the particulate system in the gas - new perspectives are opened up for further applications of the filtering separation of solid particles in a broader context of particle technology.

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