Radical density measurement at low-pressure discharge denitrification by appearance mass spectrometry

In discharge denitrification, radical production by electron collision with combustion gas is a key process which determines the denitrification process and its performance. In this study N, O, OH and H radical densities have been measured by appearance mass spectrometry in a low-pressure discharge field with parallel electrodes (2 cm gap) under simulated combustion gas flow. Also, electric field, electron number density and electron temperature at the radical sampling position have been measured by the Langmuir probe method. Under constant discharge pressure the radical density (cm^-3) was about 10¹¹ -10¹² cm^-3 and the density increased with increasing the discharge current. Under constant discharge current, both the radical concentration [-] and electron temperature increased with decreasing pressure. The radical concentration in the cathode fall region was greater than that for the outer region. Additionally, we measured the concentration change of NO mixed in the simulated combustion gas and observed a little change of the NO concentration.