Wenjun Liang

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.

Toluene degradation by non-thermal plasma combined with a ferroelectric catalyst.

Degradation of toluene in a gas by non-thermal plasma with a ferroelectric catalyst was studied at normal temperature and atmospheric pressure. Spontaneous polarization material (BaTiO3) and photocatalyst (TiO2) were added into plasma system simultively. Toluene degradation efficiency and specific energy density during the discharge process were investigated. Furthermore, byproducts and degradation mechanisms of toluene were also investigated. The toluene degradation efficiency increased when non-thermal plasma technology was combined with the catalyst. The toluene degradation efficiencies of the different catalysts tested were in the following order: BaTiO3/TiO2>BaTiO3>TiO2>no catalyst. A mass ratio of 2.38:1 was optimum for the BaTiO3 and TiO2 catalyst. The outlet gas was analyzed by gas chromatography and Fourier transform infrared spectroscopy, and the main compounds detected were CO2, H2O, O3 and benzene ring derivatives.

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.

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.

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.

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.

Study on a New Dechlorinating Agent Based on Sewage Sludge

An activated carbon derived from sewage sludge was prepared by orthogonal test, and it had a BET surface area of 300.90 m2/g. A new dechlorinating agent using the activated carbon as the main active component was studied. The agent had a breakthrough chlorine content of 19.38% and a saturated chlorine content of 37.32% (under conditions of 200 ¿, 3000 h-1 space velocity, 0.45~0.90 mm particle size and 5120~5423 mg/m3 input concentration). The effects of space velocity, temperature and particle size on the HCl-removal behavior of the sorbent and the saturation curve ware also studied in this paper.

Photocatalytic Degradation of Toluene over Titanium Dioxide Thin Film

An experimental study on VOCs removal with photocatalyst in a batch reactor was carried out at atmospheric pressure and room temperature. TiO 2 thin film photocatalyst coated on glass spring was prepared with dip-coating method. The photocatalyst was extensively characterized by means of spectroscopy (XRD) and microscopy (SEM). Toluene was taken as the typical VOCs for photocatalytic degradation as a function of gas flow rate and single versus mixed gases. The study indicated that flow rate influenced the degradation significantly and there were the optimal values; the difference between single gas and the mixed gas was remarkable and the degradation rate of mixed toluene in VOCs were higher than single toluene. Mechanism of titania-assisted photocatalytic degradation of toluene was also investigated in the paper, toluene molecule was turned into CO 2 and H 2 O in the end.