| As a significant atmosphere pollutant, SO2 mainly come from exhaust of burning coal boiler. Besides CO and CO2, N2 and H2O are also high content gas produced in this process. So the study of kinetics process of removal SO2 by pulsed streamer discharge must take the influence of N2 and H2O into account. Besides, the characteristic of pulsed streamer discharge plasma directly concern the removal efficiency. The methods of the fluorescence emission spectrum are used to study the characteristic parameter of pulsed streamer discharge,the excitated and dissociation process of H2O and the dissociation process of SO2. Through the experiment, we find some innovative production.First, N2 plasma characteristics in pulsed streamer discharge at atmosphere pressure is studied by using trace Ar dispersion fluorescence spectrometry method. According to the elements of fluorescence spectra intensity direct ratio to particle distribution, recuring to the different excited state fluorescence spectra intensity, plasma electron excited temperatures and electron density of pulsed streamer discharge and dielectric barrier discharge are obtained using relative fluorescence intensity ratio method and Boltzmann plot method. This fact shows that the calculated plasma electron excited temperature from Boltzmann plot method are (7474±500)K and (4041±400)K,which are both higher than the electron excited temperature from relative fluorescence intensity ratio method, (6725±1500)K and (3887±1500)K. And the electron density are 15.76175×1015cm-3 and 10.35165×1015cm-3 respectively. The fact also indicate that pulsed streamer discharge plasma and dielectric barrier discharge plasma approximately the state of local thermodynamic equilibrium(LTE).Secondly, we study the excited dissociation kinetics of H2O gas in the pulsed streamer discharge plasma at the atmospheric pressure. The main spectrums detected in the experiment are assigned to C3Πu→B3Πg for N2,A2Σ+→X2Πfor OH radical and n=3→n=2 for H atom respectively. The temporal-resolved measurements at 337.2nm,308.4nm,656.5nm show that the occurrences of OH* and H* are later than that of N2* for 7.4ns and 17.6ns respectively. So dissociation process of H2O can be described as H2O is excited to high vibrational level of first excited state by non-elasticity collision with electron, and then dissociates to OH radical at excited state and H atom at ground state. Furthermore, the results of spatial-resolved measurements show that the densities of active particles reach the maximum at 0.5mm away from negative electrode corresponding to the negative glow region of streamer discharge. In the end, through analyze the pulsed streamer discharge spectrum of SO2,the spectrums of 237.3nm,330nm,370nm and 430nm detected in the experiment are assigned to A3Π→X3Σfor SO radical,B1B1→X1A1, A1A2,α3B1→X1A1 for SO2,respectively. Under comdition of little O2, SO2 could be removed through oxidation reaction and reduction reaction, and final products are SO3,S, respectively. SO radical is the key middle product in the process of SO2 removal. SO radical could be produced through direct dissociation and dissociation via electronic excited states of SO2 by high energy eletrons.
|
PDF Full Text Request