Yuquan Jin

Formaldehyde removal from gas streams by means of NaNO2 dielectric barrier discharge plasma.

Destruction of formaldehyde by means of NaNO2 ferro-electric packed bed dielectric barrier discharge plasma in a coaxial cylindrical reactor was carried out at atmospheric pressure and room temperature. The difference among four kinds of NaNO2 ferro-electric reactors was compared in terms of specific energy density (SED), energy yield (EY), and HCHO decomposition. In addition, by-products during the decomposition of HCHO and destruction mechanism were also investigated. The removal efficiency of HCHO increased by means of NaNO2 DBD plasma significantly and enhanced with increasing SED distinctly. More amount of NaNO2 contributed to higher HCHO removal efficiency in the reactors. Reactor C had the highest HCHO removal efficiency among the reactors. As an important by-product, ozone concentration increased with higher SED. The possible main products in the outlet effluent were CO, CO(2) and H(2)O.

Abatement of toluene from gas streams via ferro-electric packed bed dielectric barrier discharge plasma.

Destruction of gaseous toluene via ferro-electric packed bed dielectric barrier discharge plasma in a coaxial cylindrical reactor was carried out at atmospheric pressure and room temperature. The difference among three kinds of reactors was compared in terms of specific energy density (SED), energy yield (EY), toluene decomposition. In order to optimize the geometry of the reactor, the removal efficiency of toluene was compared for various inner electrode diameters. In addition, qualitative analysis on by-products and particular discussion on toluene abatement mechanisms were also presented. It has been found that ferro-electric packed bed DBD reactor could effectively decompose toluene. Toluene removal efficiency enhanced with increasing SED. With respect to toluene conversion, 1.62 mm electrode appeared to be superior to 1.06 mm electrodes. BaTiO3 reactor had the highest toluene removal efficiency among the reactors. For NaNO2 reactor, the highest EY could reach 17.0 mg/kWh to a certain extent.

Decomposition of benzene by non-thermal plasma processing: Photocatalyst and ozone effect

Plasma technology has some shortcomings, such as higher energy consumption and byproducts produced in the reaction process. However non-thermal plasma associated with catalyst can resolve these problems. Therefore this kind of technology was paied more and more attention to treat waste gas. A hybrid system comprising a non-thermal plasma reactor and nanometer titanium dioxide catalyst was used for benzene removal in the air. The paper described the synergistic effect of ozone and photocatalyst in the plasma reactor. Except of electric field strength, humidity and flow velocity, the synergistic behavior of ozone and photocatalyst was tested. The removal efficiency of benzene reaches nearly 99% when benzene concentration is 600 mg/m3, and the removal efficiency of benzene also reaches above 90% when benzene concentration is 1500 mg/m3. The plasma reactor packed with photocatalyst shows a better selectivity of carbon dioxide than that without photocatalyst. The final products is mostly carbon dioxide, water and a small quantity of carbon monoxide.

Synergistic effect of catalyst for oxidation removal of toluene

A series of experiments was performed for toluene removal from a gaseous influent at the normal temperature and atmospheric pressure by decomposition due to dielectric barrier discharge generated non-thermal plasma, by using MnO(2)/gamma-Al(2)O(3) as catalyst. The removal efficiency of toluene was significantly increased by combining MnO(2)/gamma-Al(2)O(3) with NTP. At the same time, the goal of improving energy efficiency and decreasing O(3) from exhaust gas treatment was accomplished.

Gaseous phase benzene decomposition by non-thermal plasma coupled with nano titania catalyst

Synergistic effect of atmospheric non-thermal plasma generated by dielectric barrier discharge and nano titania photocatalyst for benzene decomposition was tested. The paper indicated the effect of photocatalyst on removal efficiency of benzene, the compare of photocatalyst characteristic in different high temperatures by heat treatment, analysis of by-products. The results showed that the effect of degradation was visible by added photocatalyst in the plasma reactor. When concentration of benzene was 600 mg/m3 and electric field strength was 10 kV/cm, the removal efficiency of benzene was increased up to 81 % without photocatalyst. At the same condition, the removal efficiency was increased to 15 % higher with photocatalyst. Nano titania crystal was anatase crystal in 450 °C heat treatment which is best for benzene removal. The plasma reactor packed with photocatalyst shows a better selectivity of carbon dioxide than that without photocatalyst. By-products are mostly carbon dioxide, water and a small quantity of carbon monoxide.

Volatile organic compounds decomposition using nonthermal plasma coupled with a combination of catalysts

A series of experiments were performed for toluene decomposition from a gaseous influent at normal temperature and atmospheric pressure by nonthermal plasma coupled with a combination of catalysts technology. Nonthermal plasma was generated by dielectric barrier discharge. γ-Al2O3 was used to be a sorbent and a catalyst carrier. Nanocatalysts were MnO2/γ-Al2O3 coupled with modified ferroelectric of nano-Ba0.8Sr0.2Zr0.1Ti0.9O3. γ-Al2O3 played an important role in prolonging reaction time of nonthermal plasma with volatile organic compounds molecules. MnO2/γ-Al2O3 has an advantage for ozone removal, while nano-Ba0.8Sr0.2Zr0.1Ti0.9O3 is a kind of good ferroelectric material for improving energy efficiency. Thus these packed materials were incorporated together to strengthen nonthermal plasma power for volatile organic compounds decomposition. The results showed the synergistic technology resulted in greater enhancement of toluene removal and energy efficiencies and a better inhibition for ozone formation in the gas exhaust. Based on the data analysis of the Fourier transforms infrared spectrum, the reaction process of toluene decomposition and the mechanism of synergistic effect are discussed. The results showed in a complex oxidation mechanism of toluene via several pathways, producing either ringretaining or ringopening products. The final products were carbon dioxide and water.

Volatile Organic Compounds (VOCs) Removal by Using Dielectric Barrier Discharge

An experimental study on volatile organic compounds (VOCs) removal with non-thermal plasma generated by dielectric barrier discharge (DBD) in a coaxial cylindrical reactor was carried out at atmospheric pressure and room temperature. During plasma processing to decompose toluene, electrical parameters such as discharge power, equivalent capacitance of the gap (Cg) and the dielectric barrier (Cd), were analyzed using the Q -V Lissajous diagram. In order to optimize the geometry of the DBD reactor, the removal efficiency of toluene was compared for various inner electrode diameters (1.20 mm, 1.65 mm, 2.0 mm) and different reactor materials (ceramic and PMMA). It suggested that, the specific input energy (SIE) depended linearly on the voltage in all cases, and Cg decreased with increasing voltage and gap length. However, with the voltage increasing, Cd increased initially and stabilized at about 700 pF. With respect to toluene conversion, 2.0 mm electrode appeared to be superior to 1.20 mm and 1.65 mm electrodes. In contrast to PMMA reactor, abatement of toluene was enhanced by ceramic reactor possessing high permittivity, especially in the high input energy condition, 73% for ceramic and 62% for PMMA at 660J/1. The energy efficiency for toluene removal stabilized at 5 g/kWh approximately with removal ratio exceeding 50%.

Abatement of toluene from gas streams by using dielectric barrier discharge

Abatement of gaseous toluene via alterable frequency dielectric barrier discharge (DBD) plasma in a coaxial cylindrical reactor was carried out at atmospheric pressure and room temperature. During plasma processing to decompose toluene, discharge power was analyzed by using the Q-V Lissajous diagram. It suggested that, the specific energy density (SED) increased with the increasing of applied voltage and AC frequency, respectively. Furthermore, the experiment was focused on the effect of gas flow rate and initial concentration on the toluene abatement efficiency and abatement amount. It is obviously that the toluene abatement efficiency descends when gas flow rate and initial concentration is increased, however with the increasing of gas flow rate and initial concentration, the toluene abatement amount ascended earlier, and then began to descend. Moreover whether voltage or AC frequency is fixed, gas flow rate of the largest abatement amount is 6.3 cm/s, and initial concentration of the largest abatement amount is 2066 mg/m3. With the increasing of the applied voltage, the toluene energy efficiency descended. Comparing various gas flow rates, it can be found that ηEnergy(6.3cm/s)> ηEnergy(10.1cm/s)> ηEnergy(2.5cm/s). Furthermore, when applied voltage ascended from 10kV to 15kV, the energy efficiency dropped rapidly. But when applied voltage increased from 15kV to 20 kV, the energy efficiency dropped slowly.

Purification of Low Concentration Toluene Waste Gas by an Enlarged Cross-Flow Bio-Trickling Filter

For make full rational use of the packed media surface, the fluent software was used to the section area of the bio-trickling filters inlet is enlarged and the outlet gradually converged. The enlarged cross-flow bio-trickling filter is characterized with low pressure drop and uniform distribution of gas and spray liquid. The filter inoculated with efficient Pseudomonas putida on the ceramic pellets was developed to degrade toluene. With inlet concentration ranging from 342 mg/m3 to 690 mg/m3, at the residence time of 140 s and the temperature ranging from 13.5 ℃ to 29.6 ℃, 8 days were needed to start the filter and the removal efficiency of toluene was up to 85 %. The effects of nutrient N, P content was studied, which showed that the improved type of MS culture medium (N: P = 5:1) of the microbial biofilm play an important role in promoting biofilm forming. In the stable operation stage, the temperature ranging from 16.5 ℃ to 35.7 ℃, when the residence time is 47 s, the removal efficiency fluctuates with the inlet concentration increases during 40 days. When the inlet concentration is lower than 650 mg/m3, removal efficiency is higher than 95 %, and with the inlet concentration increases to 1000 mg/m3, the removal efficiency decreases to 84 %. But the efficiency increases in a short time and residences in a high level. When the residence time is for 140 s, 93 s, 70 s, 56 s, 47 s, 40 s, 35 s and 32s respectively, and the inlet toluene concentration is about 500 mg/m3, the average removal efficiency is 100 %, 99.5 %, 99.2 %, 96.2 %, 94.1 %, 91.8 %, 91.6 % and 88.8 % respectively. Contamination and circulation fluid bed filter in the cross-flow operation, circulating fluid pH value of 7.0 ～8.0, the biofilm system can better adapt to the changes of inlet toluene concentration.

Study of Hydrogen Sulfide Removal Using Dielectric Barrier Discharge

An experimental research on hydrogen sulfide removal by DBD was carried out. This study explored the influences of initial concentration ,gas flow rate, applied voltage and frequency on hydrogen sulfide removal. In addition, the differences among the no packing and ceramic raschig-ring packing in the reactor were discussed. Meanwhile, during plasma processing to decompose hydrogen sulfide, SIE was analyzed using the Q–V Lissajous diagram. The experiment data suggested that hydrogen sulfide removal efficiency raised with the addition of the applied voltage, frequency and the reducing of the initial concentration of hydrogen sulfide and gas flow; it was found that under the following conditions: applied voltage 19 kV, frequency 300 Hz, gas flow rate 8 L/min, inlet gas concentration of hydrogen sulfide 30.1 mg/m3, the hydrogen sulfide removal reached the maximum of 100%. In the presence of the packing, hydrogen sulfide removal efficiency was higher than in the case of no packing, 93.26% for the former reactor and 69.29% for the latter.