Smart Filter Media in Gas-Particle-Filtration: Fundamental investigations with stretchable filters

• Applicant: Professor Dr.-Ing. Achim Dittler
• Subject Area: Mechanical Process Engineering
• Term: since 2019
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 427981860

Depth filtration is commonly used for particulate matter removal in various fields of applications such as air-conditioning and cleanroom technology. The primary factors to characterize the operational behavior of depth filters are separation efficiency, pressure drop and loading capacity. In typical depth filters the pressure drop across the filter system rises with increasing deposited particulate mass in the filter. This effect occurs especially after the "clogging point". The increase in pressure drop is followed by an increase of energy consumption. In order to delay the steep, more void space especially at the upstream part of in the filter is needed. A possibility to clear up space for new particles would be to release blocked pores in the filter. One way to achieve this would be to stretch the entire filter structure or the individual fibers. By using this adaption for the structure some void space could be cleared. The aim of the overall project is to investigate the re-arrangement and detachment processes from a stretchable collector, which is exposed to a flow at operational velocity.In the first phase of the project, measurement equipment a new fiber-mounting device was designed and built to examine investigations on a single fiber (micro level). Initial tests were performed on the influence of the elongation velocity of the fiber and the airflow velocity (superficial velocity). Furthermore, the influence of several stretching cycles on the detachment behavior and the size of particle structures could be determined. Based on the observed re-arrangement and detachment of particle structures on/from the fiber, basic approaches of a theoretical dependence and a newly DEM-model between loading height, fragment length and stress state were developed. The focus of the second project phase is to transfer these investigations about the re-arrangement and detachment process from the micro level (single fiber) to the meso (fiber array). Thus, the second phase starts with AFM measurements of adhesion forces between particles and fiber(s), as well as particles and particles of different materials. The change of the adhesion force between particle and fiber(s) in different stretching states will be investigated. The measured values are integrated in the DEM model. In order to observe and quantify the processes at the fiber array, a build-up of the equipment for a multi-perspective observation of the formation of voids within the clogged structures will be executed. In the following, the clogging point and evolution of particle structure at the fiber array is investigated. Afterwards, process parameters such as superficial flow velocity, fiber elongation velocity, fiber spacing and inflow direction are varied at the fiber array. Finally, a summary of the results of the single fiber and fiber array is given, as well as a transfer of values for a future adaptive overall filter.

• DFG Programme: Research Grants