Fundamental mechanisms of soluble dust cake components penetration through gas cleaning filter media

• Applicant: Professor Dr.-Ing. Achim Dittler
• Subject Area: Mechanical Process Engineering
• Term: from 2018 to 2023
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 406085079

The quality of dust separation during gas cleaning processes by surface filters is strongly dominated by the particle structures on the filter medium, the filter cake. While research concerning the filtration of inert particles has already lead to major reductions in emissions and energy consumption by these processes, the fundamental mechanisms taking place during the filtration in a non-ideal system, such as dust filtration in the presence of soluble particles and liquid aerosol are still unknown. Within the framework of this project, the fundamental mechanisms of the penetration of soluble dust cake components through surface filters during gas cleaning are being investigated. In the first project phase, a suitable material system was identified, methods to analyze the filters were studied and tested and experiments concerning the influence of short-term exposure of soluble filter cakes to water droplets were carried out. Therefore, the first phase of the penetration of the salt particles, the uptake of liquid and rearrangement of the soluble particles on the filter surface, and its effect on the operating behavior (pressure drop) of the filter was investigated. The focus of this new phase of the project, building on the present results, will be the investigation of the influence of the operating mode during the exposure to water droplets and the influence of the composition of the filter cake of soluble and insoluble particles on the penetration. Therefore it will be systematically investigated, which effect an intermittently exposure to water droplets compared to a continuous exposure has. Additionally it will be analyzed how the penetration of the salt depends on the proportion of soluble and insoluble particles in the originally dry filter cake. For a detailed analysis of the filter, a camera system observing the filter upstream and downstream simultaneously is implemented to observe the dissolving and rearranging of the particles and the film formation drainage of the solution and correlate it to the observed operating behavior (pressure drop, drainage). Furthermore, during the final phase of the project, the limit of the observations, and conclusions will be examined, by investigating the penetration of salt through filters with very different structural parameters (depth filtration). Therefore, also the applicability of already existing models such as the jump-and-channel-model from oil-mist filtration applications will be examined. At the end of this second project phase it will be clear, which mechanisms determine the penetration of soluble particles through filter media and how they depending on the operating mode, the proportion of soluble particles in the filter cake and the structure of the filter affect the operating behavior of the filter (pressure drop, draunage, separation efficiency).

• DFG Programme: Research Grants