The Experimental Study Of The VOCs Decomposibility By Pluse Modulated Plasma

Volatile organic compounds(VOCs) is one of the air pollutants that is harm to human being and environment. So the emission control and the degradation of VOCs is received more and more attention. Recently, non-thermal plasma technology is regarded as a more promising new technology in VOCs control around the world. In room temperature and at atmospherical pressure, different kinds of VOCs at various concentrations can be decomposed by plasma in a short time with the advantage of high efficiency and non-selective. Plasma treatment becomes a significant way to control the VOCs pollution.In this thesis, decomposition of single and mixed VOCs by pulse modulated DBD plasma was carried out. Experimental results show that the pulse modulated plasma can reduce the energy cost and increase the energy yield effectively in the VOCs degradation process. It also largely reduce the ohmic heating of the reactor chamber and low the temperature of the chamber wall. The energy yield can be improved from10g/kW-h in continue mode to24g/kW-h in pulse modulated mode for750ppm benzene with0.9L/min flow rate. In addition, the temperature of DBD wall is reduced from200℃to60℃. The effect of initial VOCs concentration, the pulse frequency and duty cycle of the power supply on the decomposition properties are investigated. The results show that decomposition rate decrease while the energy yield increase with increasing of initial concentration. Toluene is easier to be removed than benzene, both in pure and mixed state. The removal rate increase with increasing duty cycle while the energy yield has its maximum value at an optimal duty cycle which varied with the change of discharge voltage. Under certain duty cycle, removal rate decrease with increasing pulse frequency. In the case of mixture, benzene’s decomposability decreased but toluene’s decomposability is barely influenced.The study of carbon balance indicates that the carbon balance is deteriorated when the initial concentration increased and will reach their lowest level with50%and40%for benzene and toluene respectively. At high IED region, the carbon balance is increased significantly and the lower the initial concentration, the larger the increment. For the CO2selectivity, the lower of initial concentration VOCs, the better of the CO2selectivity will be achieved. CO2selectivity in mixed benzene and toluene is lower than in their pure state.By using FT-IR spectra, the by-products of the decomposition process are studied-. The results show that the by-products of benzene mainly include formic acid, oxalic acid, methanol. methylamine. NO2,etc. By-products of toluene has more kinds of species than benzene, contain benzyl alcohol, formic acid, benzoic acid, benzaldehyde, xylene, ethylbenzene, methylamine, NO2, etc There are no new compounds produced in the mixture of benzene and toluene decomposition.