Patterned Dielectric Barrier Discharges for environmental and biomedical applications

From fundamentals to process control

The project „Patterned Dielectric Barrier Discharges for environmental and biomedical applications: From fundamentals to process control“ funded by the DFG started in June 2020. The project aims to fundamentally understand Patterned Dielectric Barrier Discharges for environmental applications of Volatile Organic Compounds (VOCs) pollutant removal from gas streams.

Packed bed dielectric barrier discharges (DBDs) or packed-bed plasma reactors (PBPRs) are attractive for multiple gas reprocessing applications of high societal relevance, such as exhaust gas cleaning. In a PBPR, the volume between the electrodes is filled with spherical dielectric pellets loaded with catalyst, and the plasma is generated in the void between the pellets. The combination of plasma and catalyst generally improves the macro-scale performance of the reactor in a synergetic manner. The utilization of PBPRs is limited due to the gap in fundamental understanding of the micro-scale plasma and surface interactions, such as the spatio-temporal electron dynamics. This is because the complex and irregular design of PBPRs provides poor diagnostics access, and it generates inconsistent electron dynamics in successive periods of the driving voltage waveform. Hence, experimental diagnostics requiring averaging over multiple periods cannot be applied. Therefore, the reactors are inefficiently optimized using empirical methods. Further, the design generates a significant pressure drop due to the limited available volume between pellets for the gas flow.

A simplified version of a PBPR, a patterned DBD (pDBD) design, has been developed to address these challenges, which provides quasi-3D optical access and avoids the pressure drop. In a pDBD, only one of the dielectrics covering the electrodes is patterned as a single layer of regularly arranged hemispherical pellets. Preliminary investigations show that this design drastically improves the discharge stability regarding the spatio-temporal dynamics of energetic electrons in consecutive periods of the driving voltage waveform. This allows the use of state-of-the-art diagnostics requiring averaging over multiple cycles to reveal these dynamics.

This project aims to systematically study the pDBD design using experimental diagnostics combined with 2D fluid simulation in a He / O2 / N2 gas mixtures. The influence of the applied voltage, design and catalyst parameters on the electron dynamics, -density, -temperature and RONS will be investigated. Finally, VOC removal from gas streams will be studied and optimized based on fundamental scientific understanding.