Diagnostics of Atmospheric-Pressure Non-thermal plasmas for Air Polluion Control using Laser-induced Fluorescence Spectroscopy

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Non-thermal plasma process has been considered to be an effective method to remove NOx from flue gas. In order to optimize the reactor and provide the information for numerical simulation of NOx removal, it is important to study directly the discharge induced plasma chemical processes responsible for NOx removal in the reactor. Laser-induced fluorescence (LIF) is a useful diagnostic method for in-situ observation of the phenomena during the NOx removal. The main objective of the presented work is visualization of two-dimensional NO concentration and monitoring the process of NOx removal inside the corona radical shower reactor. Planar laser induced fluorescence (PLIF) was employed for this purpose. The corona radical shower reactor consists of a nozzle-to-plate electrode system, having an electrode gap of 50mm. Stable dc streamer corona discharge was generated and laser pulses in the form of the sheet were shot between the electrodes during the discharge. LIF signal emitted at 90 degree to the laser sheet was imaged onto a gated ICCD camera and the two-dimensional LIF images from the various regions of the reactor were recorded. By the wide range imaging of NO (image size: 240mm in width and 160mm in height), two-dimensional distributions of NO could be observed not only the discharge zone but also both the downstream and the upstream regions of the reactor. In the present reactor at a low main gas flow rate, electrohydrodynamic (EHD) flow became dominant, and the flow towards the upstream affected the decrease of NO along the reactor from the upstream region. It is considered that this information is important for modeling and optimizing the plasma processes and designing the non-thermal plasma reactors.