SOSダイオードを用いたパルスパワー電源によるNOx除去におけるストリーマ—グロー転移の影響

ABSTRACTThe simultaneous oxidation and removal efficiencies of SO2 and NO from simulated coal‐fired flue gas by UV irradiation were investigated experimentally. The influencing factors, such as the reaction temperature, the content of O2, H2O, SO2, and NO, on the removal of SO2 and NO were studied. The results indicated that NO had positive effect on the removal of SO2. Compared with the NO‐free case, the removal efficiency of SO2 was improved from 8% to 55% in the presence of 250 ppm NO. When the NO concentration rose from 250 to 700 ppm, the SO2 removal efficiency further increased from 55% to 64%. The increasing of reaction temperature enhanced the removal efficiencies of SO2 and NO, which increased by 28% and 36%, respectively, with the reaction temperature rising from 270 to 350 °C. It was found that O2 was conducive to the photochemical oxidization due to the generation of free radicals. As the O2 content increased from 0% to 8%, the removal efficiencies of NO and SO2 reached 40% and 55%, respectively. The positive effect of H2O on the simultaneous removal of NO and SO2 was also observed. The optimal conditions (250 ppm NO, 100 ppm SO2, 8% O2, 5% H2O, and reaction temperature 350 °C) were determined, and the removal efficiencies of SO2 and NO were 55% and 40%, respectively. © 2014 Curtin University of Technology and John Wiley & Sons, Ltd.

H2O2 was adopted to oxidize NO in simulated flue gas at 100–500°C. The effects of the H2O2 evaporation conditions, gas temperature, initial NO concentration, H2O2 concentration, and H2O2:NO molar ratio on the oxidation efficiency of NO were investigated. The reason for the narrow NO oxidation temperature range near 500°C was determined. The NO oxidation products were analyzed. The removal of NOx using NaOH solution at a moderate oxidation ratio was studied. It was proven that rapid evaporation of the H2O2 solution was critical to increase the NO oxidation efficiency and broaden the oxidation temperature range. the NO oxidation efficiency was above 50% at 300–500°C by contacting the outlet of the syringe needle and the stainless-steel gas pipe together to spread H2O2 solution into a thin film on the surface of the stainless-steel gas pipe, which greatly accelerated the evaporation of H2O2. The NO oxidation efficiency and the NO oxidation rate increased with increasing initial NO concentration. This method was more effective for the oxidation of NO at high concentrations. H2O2 solution with a concentration higher than 15% was more efficient in oxidizing NO. High temperatures decreased the influence of the H2O2 concentration on the NO oxidation efficiency. The oxidation efficiency of NO increased with an increase in the H2O2:NO molar ratio, but the ratio of H2O2 to oxidized NO decreased. Over 80% of the NO oxidation product was NO2, which indicated that the oxidation ratio of NO did not need to be very high. An 86.7% NO removal efficiency was obtained at an oxidation ratio of only 53.8% when combined with alkali absorption.

Pilot-scale study of simultaneous desulfurization and denitration using hexamminecobalt(II) solution

Removal of NO by using sodium persulfate/limestone slurry: Modeling by response surface methodology

This paper describes an experimental study of NO removal from a simulated exhaust gas by repetitive surface discharge on a glass barrier subjected to polarity‐reversed voltage pulses. The very fast polarity‐reversal with a rise time of 20 ns is caused by direct grounding of a charged coaxial cable 10 m in length. The influence of the voltage rise time on energy efficiency for NO removal is studied. The results of NO removal using a barrier‐type plasma reactor with a screw‐plane electrode system indicate that the energy efficiency of very fast polarity reversal caused by direct grounding is higher than that of slower polarity reversal caused by grounding through an inductor at the cable end. The energy efficiency of direct grounding is approximately 80 g/kWh for a 50% NO removal ratio and approximately 60 g/kWh for a 100% NO removal ratio. Very intense discharge light is observed at an initial time of 10 ns for fast polarity reversal, whereas the intensity of the initial discharge light for slower polarity reversal is relatively small. To confirm the effectiveness of the polarity‐reversed pulse application, a comparison of the energy efficiency of polarity‐reversed voltage pulses and an AC 60‐Hz voltage is presented. © 2011 Wiley Periodicals, Inc. Electr Eng Jpn, 178(4): 32–38, 2012; Published online in Wiley Online Library (wileyonlinelibrary.com). DOI 10.1002/eej.21215

A plasma-assisted catalytic system for NO removal over CuCe/ZSM-5 catalysts at ambient temperature

Effect of Mn-doped CaO on NO removal by CO in carbonation of calcium looping for CO2 capture in a fluidized bed reactor

The effect of pulse corona discharge on NOx and SO2 concentrations in air has been studied. The initial concentrations and ammonia addition have been shown to influence the removal efficiency. An SO2 removal efficiency of 96% and an NO removal efficiency of 70% in pulse corona have been achieved with ammonia addition, for initial SO2 and NO concentrations of 480 ppm and 230 ppm, respectively. A numerical model for NO and SO2 conversion in homogeneous gas flow has been developed. The spatial nonuniformity of gas parameters associated with the existence of many streamer channels in a discharge chamber is taken into account. A comparison between experiments and modeling shows that SO2 removal is mainly determined by OH and O3-. NO conversion is achieved the reactions of O3, OH and N.

Wet removal of NO from coal-fired flue gas by UV/H2O2 Advanced Oxidation Process (AOP) were investigated in a self-designed UV-bubble reactor. Several main influencing factors (UV intensity, H2O2 initial concentration, initial pH value, solution temperature, NO initial concentration, liquid-gas ratio and O2 percentage content) on the NO removal efficiency were studied. The results showed that UV intensity, H2O2 initial concentration, NO initial concentration and liquid-gas ratio are the main influencing factors. In the best conditions, the highest NO removal efficiency by UV/H2O2 advanced oxidation process could reach 82.9%. Based on the experimental study, the influencing mechanism of the relevant influencing factors were discussed in depth.

Photocatalytic removal of nitric oxide by multi-walled carbon nanotubes-supported TiO2

Pulsed discharge plasmas have been used to treat exhaust gases. Since pulse duration and the rise time of applied voltage to the discharge electrode has a strong influence on the energy efficiency of pollutant removal, the development of a short-pulse generator is of paramount importance for practical applications. In this work, it is demonstrated that the non thermal plasma produced by the 2 ns pulsed discharge has a higher energy efficiency than the 5 ns pulsed discharge plasma for NO removal and ozone generation. Typically, the NO removal efficiency was 1.0 mol kW-1 h-1 for 70% NO removal (initial NO concentration = 200 ppm, gas flow = 10 L/min). Meanwhile, the ozone yield was 500 g kW-1 h-1 for 20 g/m3 ozone concentration in the case of oxygen feeding. These energy efficiencies are the highest in the literature.

The removal process of NO from SO2-containing simulated flue gas using an ultraviolet (UV)/Fenton-like reaction in a photochemical reactor was investigated. The effects of several operating parameters, such as the H2O2 concentration, Cu2+ concentration, solution pH, NO concentration, solution temperature, gas flow, SO2 concentration, and O2 concentration on NO removal were studied using a single-factor method. The liquid anions were measured by ion chromatography, and the material balances for NO and SO2 were also calculated. The results show that, with the increase in the Cu2+ concentration, NO removal efficiency significantly increases. With the increase in the H2O2 concentration, NO removal efficiency increases, but the changes gradually become smaller. NO removal efficiency greatly reduces with an increasing gas flow and NO concentration. An increasing solution temperature or SO2 concentration slightly decreases NO removal efficiency. An increase in the O2 concentration can promote the removal of NO. The anions in the liquid phase are mainly SO42– and NO3–. The calculated values of SO42– and NO3– are overall in agreement with the measured values.

In order to enhance the mass transfer efficiency between gas–liquid interfaces, NaClO2 mist generated by an ultrasonic humidifier was used to remove NO from simulated flue gas. The effects of some key parameters (the gas flow rate, the NaClO2 concentration in the solution, the inlet NO concentration, the NaClO2 solution pH) on NO removal efficiency were investigated preliminarily. The results showed that NaClO2 mist could oxidize NO with a much higher efficiency compared with other mists containing either NaClO or H2O2 as oxidants. With an increase in the gas flow rate from 1.5 to 3.0 L·min−1, the atomizing rate of the NaClO2 solution increased almost linearly from 0.38 to 0.85 mL·min−1. When the gas flow rate was 2.0 L·min−1, a complete removal of NO had been reached. NO removal efficiency increased obviously with an increase in the NaClO2 concentration in the solution. With an increase in the inlet NO concentration, the ratio of NO in the flue gas and NaClO2 in the mist increased almost linearly. Furthermore, the NaClO2 mist exhibited a relatively stable and high NOx removal efficiency in a wide pH range (4–11) of NaClO2 solutions. The reason for the high NO removal efficiency was mainly ascribed to both the strong oxidative ability of NaClO2 and the improved mass transfer at the gas-liquid interface.

The removal of NO from flue gas by NaOH-catalyzed H2O2 system: Mechanism exploration and primary experiment

Photocatalytic NOx degradation of concrete surface layers intermixed and spray-coated with nano-TiO2: Influence of experimental factors