Dissertation
Dissertation > Environmental science, safety science > Environmental pollution and its prevention > Atmospheric pollution and its control > Particulate pollutants

Removal of Volatile Organic Compounds by Non-thermal Plasma Technology

Author ZhangXuMing
Tutor ZuoKePing
School Zhejiang University
Course Environmental Science
Keywords Organic volatiles Corona power supply technology Low-temperature plasma Aerosol Purification process
CLC X513
Type PhD thesis
Year 2011
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Emissions of volatile organic compounds (VOCs), and the level of industrial development of the region showing a positive correlation. In 2008, China's total annual emissions of about 20 million tons, including Zhejiang Province, including the seven provinces of the total annual emissions of over one million tons. In the next few years, with GDP growth will remain high at 7-9%, organic chemical products will be more urgent needs caused by pollution of VOCs will also more serious. Traditional control technology in the treatment of wind capacity, low concentrations of VOCs when the cost is too high, the development of new technologies is imperative. The low-temperature plasma technology has the advantage of a variety of VOCs can be processed simultaneously, but to realize the depth of purification are still experiencing double difficulty of high energy consumption and byproduct difficult to control. Purification treatment for low temperature plasma technology VOCs in the practical application of technical difficulties and the corresponding need to solve the key scientific questions to study the mechanism of VOCs purification reaction triggered degradation process, the basis of the byproducts of the causes and collection techniques. First, compare new closed loop experimental platform of styrene in the positive and negative DC corona purification process, designed to study a different power supply VOCs treatment effect under the same experimental conditions. The experimental results show that the negative corona current-voltage curves less interference by humidity and styrene content. When the ozone production is about 80 ppm, positive and negative corona energy required density was about 38 J / L, and 200 J / L,. For the negative voltage supply, when the energy density of about 280 J / L in the air of a relative humidity of 20% and 72% of the discharge, the amount of generation of ozone were 121 ppm and 50 ppm; for a positive high voltage power supply that, when the energy density of about 40 J / L, the discharge, the amount of generation of ozone in the air of a relative humidity of 19% and 72% respectively for 106 ppm and 12 ppm. Styrene processing efficiency in the vicinity of 67%, phenylacetaldehyde byproducts affect its purifying effect. Fourier transform infrared spectroscopy and gas chromatography measurements show that air discharge degradation product of styrene benzaldehyde, benzene, acetaldehyde, carbon dioxide, carbon monoxide, and N2O. Then a new AC / DC power supply system in the closed-loop experiment platform discharge characteristics VOCs purification effect, pathways, and other issues. The experimental results show that the peak power and energy transmission efficiency of the AC / DC power up to 53.6 kW and 87.3% respectively, both closely related to the shunt capacitance. When the plasma energy density of 37 J / L, the processing efficiency of the styrene nF shunt capacitance value Ca = 0 and Ca = 3.86 nF case of respectively about 95% and 74%. When the energy density of 42 J / L, the processing efficiency of the styrene in the repetition frequency f = 30 PPS and f = 120 pps case were about 93% and 83%. Benzene and toluene in the purification process in any humidity are the first order reaction kinetics, the processing of the styrene in the high and low humidity, respectively, for a reaction, and zero-order reaction kinetics. Different gas components, the order in which the ozone production is followed by air GT; benzene gt; toluene gt; GT; styrene. Styrene purification process is mainly caused by the outside of the benzene ring with C = C bond and the O and OH radical reaction; the toluene purification process at the same time the oxidation reaction is related to the ring-opening reaction of the benzene ring and outside the ring-CH3; while benzene purification is mainly caused by the ring-opening reaction of the benzene ring. The process of purification of styrene, benzene and toluene are competing with oxygen O radicals, so that the decline in the amount of generated ozone. Styrene in the second order in the purification process consume a lot of ozone, benzene and toluene are almost non-ozone depleting. The inorganic product N2O, CO, and CO2 production increased along with the increase of the energy density. Finally, the solid phase byproduct aerosol formation and collection processes. Produce aerosol particle size distribution between 28-384 nm. When the energy density in the 27-32J / L, a styrene purification process to obtain the number of aerosol concentration of about 9 × 105 # / cm3, 3-4 times this value is the purification process of benzene and toluene. Nucleation and initial growth after saturation charged aerosol plasma system behavior is electrostatic collection. Fourier transform infrared spectra indicate that deposited in the low voltage plate of aerosol containing a-COH and-COOH functional group. In the processing of styrene, a particle size of 28 nm, 55 nm, 93 nm and 157 nm at aerosol yields were 4 × 105 # / (cm3 · ppm), 1.1 × 105 # / (cm3 · ppm) 5 × 104 # / (cm3 · ppm) and 1 x 104 # / (cm3 · ppm). The two-stage plasma system, in the case of the AC / DC discharge power determining relative hierarchical collection efficiency depends ESP itself aerosol production. The best collection efficiency at 157 nm, about 75%. By coagulation may further improve the performance of the ESP. Best operating conditions, particle size 28 nm and 264 nm at relatively hierarchical collection efficiency can improve by 16% and 21%, respectively.

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