Pulsed Corona Discharge Process Research Articles

Degradation of methyl orange by pulsed corona discharge process in water

Properties of methyl orange (MO) degradation and their dependence on experimental parameters such as electrical polarity, pulse frequency, the material, and thickness of the discharge electrode, as well as electrode gap distance were investigated in a laboratory scale pulsed corona discharge system. The MO degradation and H2O2 generation were significantly enhanced by positive polarity than negative polarity because of the numerous micro-discharges that were generated by the space charge effect induced by positive polarity. The increase of pulse frequency reduced the MO degradation even though it enhanced the number of streamers produced. An electrode material having low electrical and thermal conductivities resulted in more MO degradation. The smaller the curvature radius of the discharge electrode, the more efficient the MO degradation was. The number of electrode needles and the electrode gap distance also affected MO degradation during the discharge process.

Polarity effect of pulsed corona discharge for the oxidation of gaseous elemental mercury

The effect of polarity on the oxidation of Hg 0 was examined in the presence of O 2 via a pulsed corona discharge (PCD). The experimental result showed no difference in the energy yield of Hg 0 oxidation at both positive and negative PCDs (∼8 μg Hg W h −1 at following conditions: total flow rate = 2 L min −1 (Hg 0 = 50 μg N m −3, O 2 = 10%, and N 2 balance), temperature = 150 °C, and specific energy density = 5–15 W h N m −3). This suggests that the positive PCD process used to control gaseous air pollutants may play an essential key role in Hg 0 oxidation because it consumes enough energy (∼15 W h N m −3) but an electrical precipitator could not because it consumes less energy (∼0.3 W h N m −3) to oxidize Hg 0.

Sulfite oxidation in seawater flue gas desulfurization by a pulsed corona discharge process

For seawater flue gas desulfurization (SWFGD), oxidation of S(IV) to S(VI) in the effluent of the gas desulfurization (FGD) system is very critical for its industrial application, because the additional S(IV) results in high chemical oxygen demand (COD) value. This paper reports a novel pulsed corona discharge oxidation process to convert S(IV) to S(VI) by use of a cylindrical wetted-wall pulsed high voltage reactor. Several important parameters, including pH values, flow rate of the solution, voltage, electrode radius and the length of the plasma region, were investigated for S(IV) oxidation and energy efficiency (G) of the process. After discharge for 12 min, with the electrode radius of 8 mm, pH value of 3, flow rate of 40 L h −1, more than 95% of S(IV) was oxidized and the energy efficiency was about 5.8 × 10 −9 mol J −1. Compared with the traditional air oxidation process, the plasma-induced oxidation is a promising and attractive technology for the SWFGD system.

Influence of gas components on the oxidation of elemental mercury by positive pulsed corona discharge

This study examines the effect of flue gas components on the oxidation of gaseous elemental mercury (Hg0) to HgO and HgCl2 via pulsed corona discharge (PCD), where the reaction temperature was set to 90°C and the gas stream consisting of 3% H2O and 10% O2 in N2 was mixed with 45 μg m−3 Hg0, 108 ppm NO x , 80 ppm HCl, 200 ppm SO2 and 470 ppm NH3. It has been observed that O2 and HCl components in the gas stream act as oxidizing precursors through the generation of oxidizing species (O, O3, Cl and Cl2) in the PCD process. The presence of NO directly hampers Hg0 oxidation to HgO due to preferential reaction of NO with O and O3. In contrast, the presence of SO2 indirectly influences the oxidation of Hg0 to HgCl2 through the fast reaction of SO2 with OH radical, resulting in consuming OH radicals which are partially responsible for the formation of chlorine species, i.e. Cl and Cl2. It has been also found that NH3 component significantly hinders the oxidation of Hg0 to HgCl2 through the fast acid–base reaction...

Desulfurization and simultaneous treatment of coke-oven wastewater by pulsed corona discharge

A recent investigation into the application of pulsed corona discharge process, in which simultaneous SO 2 removal from simulated flue gas and coke-oven wastewater degradation, was conducted at Wuhan Integrated Steel Plant. The outcome indicates that coke-oven wastewater has good desulfurization ability and pulsed corona discharge enhances the removal efficiency of SO 2; up to 85% SO 2 is removed from gas through absorption, neutralization and radical reactions. Coke-oven wastewater can also be degraded by pulsed corona discharge, and injection SO 2 is helpful to the degradation process; up to 99.98% cyanide and 66.8% phenols can be decomposed and this is of important value in solving the inactivation problem of aerobic bacteria in biological treatment of coke-oven wastewater. The ratio of biochemical oxygen demand content to chemical oxygen demand content increases greatly for the co-effect of SO 2 and pulsed corona discharge, which indicates the improvement of complete degradation of coke-oven wastewater by biological treatment. The experimental result suggests the possibility of the simultaneous processing of desulfurization and decontamination of coke-oven wastewater. This research may provide a new technology for desulfurization and coke-oven wastewater treatment in integrated steel plants.

Desulfurization and simultaneous treatment of coke-oven wastewater by pulsed corona discharge

A recent investigation into the application of pulsed corona discharge process, in which simultaneous SO2 removal from simulated flue gas and coke-oven wastewater degradation, was conducted at Wuhan Integrated Steel Plant. The outcome indicates that coke-oven wastewater has good desulfurization ability and pulsed corona discharge enhances the removal efficiency of SO2; up to 85% SO2 is removed from gas through absorption, neutralization and radical reactions. Coke-oven wastewater can also be degraded by pulsed corona discharge, and injection SO2 is helpful to the degradation process; up to 99.98% cyanide and 66.8% phenols can be decomposed and this is of important value in solving the inactivation problem of aerobic bacteria in biological treatment of coke-oven wastewater. The ratio of biochemical oxygen demand content to chemical oxygen demand content increases greatly for the co-effect of SO2 and pulsed corona discharge, which indicates the improvement of complete degradation of coke-oven wastewater by biological treatment. The experimental result suggests the possibility of the simultaneous processing of desulfurization and decontamination of coke-oven wastewater. This research may provide a new technology for desulfurization and coke-oven wastewater treatment in integrated steel plants.

Analysis on plasma chemistry and particle growth corona discharge process for NO/sub ξ removal using discrete-sectional method

The particle formation and growth combined with plasma chemistry in the pulsed corona discharge process (PCDP) to remove NO/sub x/ were analyzed by the discrete-sectional model. In the PCDP, most of the NO is converted into NO/sub 2/ and, later, into HNO/sub 3/ which reacts with NH/sub 3/ to form the NH/sub 4/NO/sub 3/ particle. In the beginning of the reactor, we have the high concentration of small size particles and, later, the particle size distribution in the reactor becomes bimodal with the large size and small size particles and, finally, becomes monodisperse with the large size particles. As the average electron concentration increases, it takes a shorter reactor length to remove the NO/sub x/. As the initial NO and H/sub 2/O concentrations decrease, the NH/sub 3/ is consumed more slowly to form the ammonium nitrates particles. As the averaged electron concentration and initial H/sub 2/O concentration increase, the large size particles grow more quickly and the particle size distribution becomes bimodal earlier. As the initial NO and NH/sub 3/ concentrations increase, the diameter of large size particles becomes larger by the faster coagulation between particles. The predicted NO/sub x/ conversion and particle size distribution were in close agreements with the published experimental results at the averaged electron concentration of 2/spl times/10/sup 5/ cm/sup -3/ in this study.

Plug Flow Modeling of Particle Formation and Growth Combined with Plasma Chemistry in NO x Removal by a Pulsed Corona Discharge Process

We analyzed the plasma chemistry, particle formation, and growth in the pulsed corona discharge process (PCDP) to remove NO x and investigated the effects of several process variables (initial concentrations of NO, NH 3 , and H 2 O and electron concentration). In the PCDP, most of NO is converted into NO 2 and, later, HNO 3 , which reacts with NH 3 to form NH 4 NO 3 particles. As the initial NO concentration increases or as the initial H 2 O concentration and the electron concentration decrease, it takes longer reactor lengths to remove the NO x . With the increase of initial NO concentration, more NH 3 is consumed to remove the NO supplied initially and NH 3 disappears more quickly in the PCDP. In the beginning of the reactor, the particle concentration and the standard deviation of particle size distribution increase quickly because of fast particle formation from the NO supplied initially. The particle concentration and the standard deviation decrease in the PCDP, where the NO initially supplied is all...

Modeling of pulsed corona discharge process for the removal of nitric oxide and sulfur dioxide

A positive pulsed corona discharge process was applied to the removal of sulfur dioxide and nitric oxide from a simulated flue gas stream, and a mathematical model was proposed to describe this process theoretically. The proposed model takes into account generation of radicals by pulsed corona discharge, followed by radical utilization for the removal of the pollutants. Radicals such as O, OH, N, H, etc. may be concerned in the removal of the pollutants. Their concentrations were derived by considering direct electron impact on the dissociation of gaseous molecules (O 2, N 2, H 2O) and subsequent excitation transfer reactions of excited oxygen atoms to produce O and OH radicals. The effects of various operating parameters such as feed gas flow rate, initial concentration, oxygen content, humidity, peak voltage and pulse repetition rate on the removal were examined. So as to establish the validity of the model, the calculated results were compared with the experimental data. Although some discrepancy between the calculated and experimental results was observed at high pulse repetition rate, the proposed model was found to properly predict the experimental data on the whole.

Determination of decomposition rate constants of volatile organic compounds and nitric oxide in a pulsed corona discharge reactor

The decomposition of toluene, propylene and nitric oxide by using a pulsed corona discharge process was investigated. The performance equation of the pulsed corona reactor was derived with the assumption that the decomposition reaction rate is directly proportional to the concentration of the pollutant and the discharge power. From this model equation and the experimental data, the apparent decomposition rate constants of various gaseous organic compounds and nitric oxide were determined. Alkene and substituted alkene were found to have much larger decomposition rate constants than aromatic compounds and substituted alkane, which indicates that the derivatives of aromatics and alkane cannot readily be decomposed in this system. To verify the validity of the model derived, the experimental data in the present study and in the literature were compared with the calculation results using the decomposition rate constants. Despite the different reactor geometry and experimental condition, good agreement between the experimental data and the calculation results was shown.

Flue gas treatment using pulsed corona discharge generated by magnetic pulse compression modulator

A pilot-scale pulsed corona discharge process was applied to the treatment of industrial flue gas from an iron-ore sintering plant. The electrode structure of the corona reactor is similar to that of a conventional electrostatic precipitator. A two-stage magnetic pulse compression modulator whose average power is 40 kW was used to produce repetitive high voltage pulse. The dependencies of variables such as channel width, peak voltage level and discharging wire thickness on power delivery were examined. In this system, pulsed power with peak voltage of 180 kV and peak current of 3 kA was obtained. The energy conversion efficiency from the magnetic pulse compression modulator to the corona reactor was maximally 76%. Dust content in the flue gas up to 4.6 g/Nm 3 did not influence the power delivery. The maximum energy intensity obtained in this system was 0.6 J/pulse/m. The removal efficiencies of SO 2 and NO x were measured at a variety of conditions. In the presence of chemical additives such as ammonia and propene, about 95% of SO 2 and 60% of NO x were removed at an energy density of only 3.0 Wh/Nm 3.

Removal of NO and SO2 by pulsed corona discharge process

Overall examination was made on the removal of NO and SO2, by pulsed corona discharge process. The mechanism for the removal of NO was found to largely depend on the gas composition. In the absence of oxygen, most of the NO removed was reduced to N2; on the other hand, oxidation of NO to NO2 was dominant in the presence of oxygen even when the content was low. Water vapor was an important ingredient for the oxidation of NO2, to nitric acid rather than that of NO to NO2. The removal of NO only slightly increased with the concentration of ammonia while the effect of ammonia on the removal of SO2 was very significant. The energy density (power delivered/feed gas flow rate) can be a measure for the degree of removal of NO. Regardless of the applied voltage and the flow rate of the feed gas stream, the amount of NO removed was identical at the same energy density. The production of N2O increased with the pulse repetition rate, and the presence of NH3 and SO2 enhanced it. Byproducts generated from propene used as additive were identified and analyzed. The main byproducts other than carbon oxides were found to be ethane and formaldehyde, but their concentrations were negligibly small.

Effects of Process Variables on NOx Conversion by Pulsed Corona Discharge Process

We investigated the effects of several process variables (initial concentrations of NO, NH3, and H2O and electron concentration) on NOx conversion by the pulsed corona discharge process (PCDP). In the PCDP, most of the NO is converted into NO2 and, later, into HNO3 which reacts with NH3 to form NH4NO3 particles. We solved the model equations of chemical species in the PCDP considering 23 chemical species and 54 chemical reactions. As the initial NO concentration increases or electron concentration decreases, it takes a longer reactor length to remove the NOx by the PCDP. As the initial H2O, it takes a shorter reactor length to remove the NOx. As the initial NO and H2O and electron concentration decreases, or as the initial NH3 concentration increases, it takes a longer reactor length to consume the NH3 by the particle formation reactions. The information on the effects of several process variables on the plasma chemistry in NOx conversion can be the basis guideline to develop a more efficient PCDP and this study can be extended to obtain the information on particle characteristics of ammonium salts.

Study on Reduction of Energy Consumption in Pulsed Corona Discharge Process for NOx Removal

We investigated the reduction of electrical energy consumption in thepulsed corona discharge process for the removal of nitrogenoxides. Hydrocarbon chemical additives used in the laboratory-scaleexperiment are responsible for the enhancement of the NO conversionthrough the chain reactions of free radicals, such as, R, RCO, RO,and others. Electrical energy consumption per converted NO moleculehas a minimum value of 17 eV when pentanol is injected. When ethyleneand propylene are injected, 30 and 22 eV of electrical energy consumptionare required for the conversion of a NO molecule, respectively. The ratioof the pulse-forming capacitance (Ce) to the reactor capacitance (CR)plays an important role in the energy transfer efficiency to thereactor. The maximum energy transfer efficiency of approximately 72%could be obtained by the pulse-forming capacitance, which is 3.4 timeslarger than the reactor capacitance; the maximum NO conversionefficiency was also observed with the same condition.

Positive pulsed corona discharge process for simultaneous removal of SO/sub 2/ and NO/sub x/ from iron-ore sintering flue gas

We investigated the application of pulsed corona discharge process to the removal of SO/sub 2/ and NO/sub x/ from industrial flue gas of an iron-ore sintering plant. The study was performed on a pilot scale, which is the most advanced demonstration of this process. The flow rate of 5000 m/sup 3//h of the flue gas was successfully treated. The electrode structure of the corona reactor is the same as that of the conventional electrostatic precipitator. We made use of magnetic pulse compression technology to produce repetitive high voltage pulses. The pulse width (full width at half maximum) was reduced to less than 1 /spl mu/s by connecting a resister in parallel with the corona reactor. An inductor was added to the resister in series to minimize the loss by restricting the current flowing through the resister. By this method, we were able to deliver pulse power with peak voltage of 110 kV and peak current of 2.3 kA to the corona reactor. Chemical additives such as ammonia (NH/sub 3/) and propylene (C/sub 3/H/sub 6/) were used to increase the removal efficiencies of SO/sub 2/ and NO/sub x/.

Conversion of NO to NO 2 in air by a pulsed corona discharge process

A kinetic model was proposed to describe the behavior of pulsed corona discharge process applied to the removal of nitrogen oxides. The proposed model takes into account radical production at every pulse and NO removal by the radicals. On the basis of the direct electron impact on dissociation of gaseous molecules, the expressions for radical concentrations were derived by considering subsequent excitation transfer reactions of excited oxygen atoms for additional radical production. Experimental study on NO removal by using the pulsed corona discharge process is also reported in which the dependence of removal efficiency on electric field intensity, pulse frequency, treatment time and initial NO x (NO+NO 2) concentration was examined. The validity of the kinetic model was established by good agreement between model calculations and experimental results.

Role of Organic Chemical Additives in Pulsed Corona Discharge Process for Conversion of NO.

We have applied the pulsed corona discharge process to the removal of NO from a simulated gas stream. The effect of alcoholic and aliphatic hydrocarbon additives on the oxidation of NO to NO 2 was investigated, and some possible reaction schemes for the role of the additives in enhancement of NO conversion were suggested on the basis of their cracking patterns. The conversion of NO increased with the chain length of the alcohol used. In the presence of aliphatic hydrocarbon, the conversion of NO was also greatly enhanced. Comparison between alkyl alcohol or alkane and its isomer showed that alkyl alcohol or alkane gave better removal performance than its isomer. By using the alcoholic and aliphatic hydrocarbons, large reduction in energy requirement for NO removal was achieved.

EVALUATION OF ENERGY UTILIZATION EFFICIENCIES FOR SO2 AND NO REMOVAL BY PULSED CORONA DISCHARGE PROCESS

Pulsed corona discharge process was applied to the removal of sulfur dioxide and nitrogen oxides from simulated flue gas. The energy transfer efficiency of the pulse generation circuit and the energy utilization efficiencies for SO 2 and NO removal are evaluated and discussed. When the pulse-forming capacitance was five times larger than the geometric capacitance of the reactor, the energy utilization efficiency was maximized, and the energy requirements for NO and SO 2 removal could be lowered. With regard to radical utilization efficiency, producing small amounts of radicals frequently was found to be more advantageous than producing large amounts of radicals less frequently. Removal efficiency of SO 2 increased with the applied peak voltage, but the energy utilization efficiency was nearly independent of the peak voltage when the peak field intensity was high enough to induce corona discharge (above 10 kV cm −1 in this system).

Mathematical analysis of positive pulsed corona discharge process employed for removal of nitrogen oxides

A mathematical model was proposed to describe the behaviour of the removal of nitrogen oxides (NO/sub x/) in a positive pulsed corona discharge reactor. The proposed model takes into account radical production at each pulsing and subsequent radical utilization for NO/sub x/ removal. The production efficiencies of radicals such as O, OH, H, and N were derived by considering direct electron impact on dissociation of gaseous molecules, followed by excitation transfer reactions of excited oxygen atoms. The production efficiencies of those species were used for the model calculations. The proposed model could adequately predict the experimental data. Of the active species present, the ozone (O/sub 3/) produced by the reaction of O radical with oxygen was found to play the crucial role in oxidation of NO to NO/sub 2/, both theoretically and experimentally.

97/05122 Removal of SO 2 and NO x using a pulsed streamer corona discharge process : Lee, Y. K. et al. Energy Bus. Technol. Sources., [World Energy Eng. Congr.], 19th., 1996, (Pub. 1997), 97–102. Edited by Ricketts, J., Fairmont Press, Lilburn, GA

97/05122 Removal of SO 2 and NO x using a pulsed streamer corona discharge process : Lee, Y. K. et al. Energy Bus. Technol. Sources., [World Energy Eng. Congr.], 19th., 1996, (Pub. 1997), 97–102. Edited by Ricketts, J., Fairmont Press, Lilburn, GA