Gas Conversion in Patterned Dielectric Barrier Discharges for Environmental Protection

• Applicant: Professor Dr. Julian Schulze
• Subject Area: Microsystems ; Electrical Energy Systems, Power Management, Power Electronics, Electrical Machines and Drives ; Optics, Quantum Optics and Physics of Atoms, Molecules and Plasmas
• Term: since 2020
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 432514770

In the light of climate change and human health, environmental protection is a key task of our time. Currently, huge amounts of harmful gasses are emitted by factories, households, and vehicles. Depending on the emitted gas species, such emissions can contribute to global warming or be directly toxic to humans and other lifeforms. Thus, exhaust gas streams must be cleaned from harmful constituents by converting them into less harmful or, ideally, value-added products. This must be done in an energy efficient way based on excess renewable electrical energy, which requires short switch on- and off-times of the gas cleaning procedure. Existing methods, e.g., adsorption, thermal or catalytic oxidation, are often energy inefficient, cannot be switched on and off quickly, and the generation of reaction products can hardly be controlled. Low temperature atmospheric pressure plasmas represent an attractive alternative. As they are driven electrically, short switch on- and off-times can be realized. In such plasmas, the electrons are heated and initiate the gas conversion, while the heavy particles remain cold. By controlling the electron energy distribution function, the energy efficiency of gas conversion can be improved and the generation of reaction products can be controlled. In this project and based on previous fundamental studies of the electron power absorption dynamics in such plasmas, the use of a novel atmospheric pressure plasma source, a patterned dielectric barrier discharge (pDBD), will be tested for gas conversion. In contrast to existing plasma sources, it includes a structured electrode design based on custom engineered dielectric pellets embedded into an electrode at strategically selected positions rather than spherical pellets located in the volume at uncontrolled positions. In this way the plasma generation is stabilized, the gas flow is not blocked and diagnostic access is optimized. The pDBD combines the presence of surface and volume streamers in contrast to classical surface/volume DBDs. In this way the active plasma volume is enlarged and the gas mixing by plasma induced gas vortex flows is expected to be enhanced. For selected Volatile Organic Compounds (VOC) and fluorocarbon gasses admixed to different carrier gas streams the use of pDBDs for gas conversion will be tested systematically. By using several diagnostics, the conversion, its energy efficiency, and product selectivity will be investigated as a function of the reactor design and external plasma control parameters such as the driving voltage waveform shape, gas mixture and flow. The obtained results will be compared to those obtained in classical DBDs and correlated with the streamer dynamics measured space and time resolved in the pDBD to understand the observed effects of such control parameters on the gas conversion based on a fundamental understanding of the plasma physics. Finally, a compact array of pDBDs will be built and tested to handle larger gas flows.

• DFG Programme: Research Grants
• Major Instrumentation: High Voltage Generator
• Instrumentation Group: 6060 Hochspannungsspeisegeräte (über 1 kV, außer 268)