Microchannel plasma reactor for gaseous remediation and destruction

Summary form only given. The ability to generate steady atmospheric pressure microdischarges has become feasible as micro-manufacturing technologies have continued to improve. At present, there are a small number of developing technologies surrounding microplasmas, perhaps most prominently as a low-profile light source. Other potential applications of such research include the cost-effective remediation of various gaseous waste streams (e.g., CO₂), and the reformation of hydrogen gas from common sources such as methane (CH₄) and ammonia (NH₃). The reaction kinetics in a microplasma channel can be controlled to some extent through electric field strength and frequency, reactant gas flow rate, and the geometry of the channel itself. The microchannel for this work is fabricated on a MACOR™ ceramic surface using micro-machining technology available at the Univ. of Illinois at Urbana Champaignt, which has the advantage of being easily machinable, unlike alumina, while still bearing the high dielectric constant required. Microchannels for this device are 80 micrometers deep and 150 micrometers wide, and range from simple straight channels to highly complex shapes and paths. The recessed microchannels are covered by a glass microscope slide cover with a thin indium tin oxide (ITO) coating, allowing voltage to be put across the channel while simultaneously permitting spectroscopic measurements. In the experimental setup for this work, power is applied across the microchannel using a variable autotransformer and a high-voltage transformer. The latter is capable of producing ~5.7 kVpp at 20 kHz. Residence time can be varied by changing intake gas flow rate, and also by changing the electric field strengths within the channel. Positive pressure from a feedstock gas is applied into a mass flow controller that feeds into the microchannel; the exhaust of the microchannel is evacuated using a mechanical vacuum pump. Three iterations of rea- tors were built and tested to iteratively improve on design. Initial experiments consisted of inert gases followed by more complex diatomic and polyatomic gases. Plasma properties are measured by observing the intensity of its light with a spectrometer. Plasma properties of primary interest in this experiment are: species residence time, electron density, electron temperature, ion temperature, and ionization fraction. These quantities can be determined through the use of spectroscopic line ratio measurements in addition to some simple chemical reaction modeling.