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

The thesis reviewed the situation of decomposing volatile organic compounds (VOCs), and discussed the imminence of empoldering new high-efficiency economic technology, and introduced the research results of removal of VOCs with corona discharge technologies.Using O2+H2O as radical resources, the feasibility is researched from bond energy. The results showed that the experiment method is feasible.The experiments on decomposing of benzene from organic exhaust gas using O2+H2O as radical resources were carried out. The results showed that Increasing the concentration of benzene makes the removal efficiency lower, but in the same time, makes the energy efficiency higher. It is moderate that organic exhaust gas residues in the reactor for 15-20 seconds. To improve the decomposing efficiency by the way of lengthening residence time of organic exhaust gas in the reactor is not economical. The rise of temperature will make the decomposing efficiency of benzene fall, but the trend of the fall of the efficiency is gentle. The increase of water vapor will improve the decomposing efficiency, the quantity of benzene that decomposed by unit energy from organic exhaust gas that contained 8%~10% of water vapor is the highest. Subsequently the decomposing efficiency will decline. Plating some metal Cu, Fe, Mn on the electrode, the results showed that decomposing efficiencies vary little. But plating them on the cathode board, the results showed that the three metals' catalyze activity is different, the Mn's catalyzing activity is strongest, but the Cu's is the weakest.The experiments on decomposing benzene loop with side chain (e.g.: toluene and xylene) were carried out. The results showed that the decomposing efficiencies of both toluene and xylene are lower than benzene's. The order of three organic substances' decomposing efficiencies is xylene, toluene, and benzene. When residence time is short, the difference of the three organic substances' decomposing efficiencies is much. Benzene's decomposing efficiencies is lower about 40% than toluene's, and toluene's is lower about 40% than xylene. But the residence time is longer, the difference is less. The influences of temperature, humidity and discharge were carried out, the results showed that the three organic substances' character is alike.The decomposing products were analyzed. The results showed that thedecomposing products contain CO2, CO, H2O and the moleculars of toluene that are not decomposed because there is no still time. Xylene's contain little toluene, benzene and benzene anhydride, besides CO2, CO, H2O.The degradation mechanism and process of VOCs was investigated. The results showed that the molecular structure of VOCs affected their degradation properties remarkably. The less stable of the molecular structure of VOCs were with the higher decomposing efficiency. The little outgrowths were examined in the xylene's products, but no outgrowth was examined in the toluene's and benzene's. That is to say, the most of organic substances can be decomposed fully under corona discharge process.In the research, we find that the main reactions of volatile organic compounds is:RH + O·→R· +OH·RH + O·→R1· +R2O·RH + OH→R· +H2O Thereinto, R·, R1· , R2O· etc are the radicals of dissociated VOCs.