Experimental Study On Decomposing PAHs With Radical Shower Induced By DC Corona Discharge

In the thesis, the risk and sources of the polycyclic aromatic hydrocarbons (PAHs) were introduced in this thesis as well as the polycyclic aromatic hydrocarbons (PAHs), the pollution state and the controlling technologies. Some new corona discharge processes were mentioned here. The reaction mechanism was discussed, and the feasibility of the reaction was also analyzed in this paper.The output characteristics of the corona induced by DC were studied here. The experimental results showed that steady streamer corona could occur when water vapor existed in the region around the discharge electrode. The discharge voltage and the breakdown voltage increased as the moisture content increased. The increase of the flow rate of the oxygen from the nozzle electrode would influence the discharge process. The larger flow rate of the oxygen was, the higher discharge voltage and breakdown voltage would be, the more steady discharge would be and the much larger current would be. The discharge voltage and the breakdown voltage increased as the temperature of the gas increased, and at the same voltage, the discharge current would increase as the temperature of the gas increased. The increase of the distance between the electrodes resulted in increase of the discharge voltage and breakdown voltage, and decrease of the current. The velocity of the gas affected on the discharge process a little. The breakdown voltage changed a little when the velocity of the gas increased multiply, and at the same voltage, the current also changed a little.The experiment on decomposing of naphthalene using H2O and O2 as radical resource were carried out. The results showed that at the same supply power, the decomposing efficiency declined nonlinearly with various ratios as the concentration of the naphthalene increased. Because more radicals were induced as the streamer corona was enhanced by the increasing voltage, the oxidation efficiency and the decomposing efficiency increased. When the moisture content increased, the decomposing efficiency first increased and processed to decline with the highest efficiency at proper moisture content about 8%-10%. Experiment indicated that when the concentration of naphthalene was 57.8mg/m3, the best voltage was 27kV. When the specific energy increased, the energy efficiency declined. The most proper specific energy was 4 Wh/Nm3. By infrared spectrum analysis, the gases ejected from the reactor have the compositions such as carbon monoxide, carbon dioxide, and other organic byproducts.The optimization on corona discharge radical shower technology was investigated. The results showed that corona initiating voltage and breakdown voltage had an obvious increment after electrode reactor had a large-size and multi-electrode changing. The entire reactor was filled with streamer corona and produced radicals so that the contacting opportunities between radicals and naphthalene became more, so the removal efficiency of naphthalene increased. The decreasing of outer diameter of nozzles had led to the decreasing of corona discharge voltage and the increasing of radical amount. In the same discharge voltage, corona current had an obvious increment, which could produce more obvious streamer corona and increase the removal efficiency of naphthalene dramatically. When electrodes in horizontal allocation were changed to in vertical disposal, the discharge characteristics and the removal efficiency of naphthalene both had a promotion in some degrees. With various catalysis coating, degradation efficiency of negative electrode plane with catalysis coatings are larger than that of blank negative electrode plane at the same discharge voltage both in dry condition and in wet condition. And the degradation efficiency with MnO2 catalysis coating is larger than that with Fe2O3 catalysis coating. But the breakdown voltage changing is different in dry and wet condition. By infrared spectrum analysis, the gases ejected from the optimized reactor have the compositions such as carbon monoxide, carbon dioxide, and other organic b...