SO2 Removal Efficiency Research Articles

A novel method for the synchronous absorption of SO2 and NO from marine diesel engines

A novel method based on a Na2S2O8/urea composite system was used to both synchronously absorb SO2 and NO from marine diesel engine emissions and reduce the nitrate residues in cleaning wastewater. In the Na2S2O8/urea solution, a temperature of over 60 °C and a Na2S2O8 concentration of >0.05 mol/L were found to fully absorb SO2 by overcoming the SO2 release and effectively absorb NO. Urea successfully reduced the residual nitrate concentration and improves NO absorption at a concentration below 2 mol/L. The NO and SO2 removal efficiencies reached 97.8 ± 1.5% and 100%, respectively, at 70 °C in 0.1 mol/L Na2S2O8 and 1.5 mol/L urea solutions. The residual nitrate concentration was 8.12 ± 0.25 mg/L, far below the regulatory limit of 60 mg/L. Acidic conditions (pH ≤ 5.5) could be conducive to absorbing NO and reducing the residual nitrate concentration. Based on the experimental results, this novel method is highly promising for reducing ship emissions.

Application of dielectric barrier discharge (DBD) plasma packed with glass and ceramic pellets for SO2 removal at ambient temperature: optimization and modeling using response surface methodology

Air pollution is a major health problem in developing countries and has adverse effects on human health and the environment. Non-thermal plasma is an effective air pollution treatment technology. In this research, the performance of a dielectric barrier discharge (DBD) plasma reactor packed with glass and ceramic pellets was evaluated in the removal of SO2 as a major air pollutant from air in ambient temperature. The response surface methodology was used to evaluate the effect of three key parameters (concentration of gas, gas flow rate, and voltage) as well as their simultaneous effects and interactions on the SO2 removal process. Reduced cubic models were derived to predict the SO2 removal efficiency (RE) and energy yield (EY). Analysis of variance results showed that the packed-bed reactors (PBRs) studied were more energy efficient and had a high SO2 RE which was at least four times more than that of the non-packed reactor. Moreover, the results showed that the performance of ceramic pellets was better than that of glass pellets in PBRs. This may be due to the porous surface of ceramic pellets which allows the formation of microdischarges in the fine cavities of a porous surface when placed in a plasma discharge zone. The maximum SO2 RE and EY were obtained at 94% and 0.81 g kWh−1, respectively under the optimal conditions of a concentration of gas of 750 ppm, a gas flow rate of 2 l min−1, and a voltage of 18 kV, which were achieved by the DBD plasma packed with ceramic pellets. Finally, the results of the model’s predictions and the experiments showed good agreement.

Operation parameters and design optimization based on CFD simulations on a novel spray dispersion desulfurization tower

In this work, simulations were performed on a novel two-stage SO2 absorption tower, namely, spray dispersion tower which consists of a spray section as the first stage and a bubble section as the second stage. The desulfurization performance of the spray dispersion tower was investigated by Computational Fluid Dynamics (CFD) method. After calculation, the predicted results were in good agreement with the measured results to validate the reliability of the simulation model.The operational parameters optimization indicated that the appropriate tubes' immersion depth and liquid-to-gas ratios were 0.14 m–0.16 m and 3.03 L/Nm3–3.6 L/Nm3 to attain higher energy and economic savings, respectively. In the optimal bubble section, less time was required for the multiphase flow and chemical reaction values to reach the quasi-static state than that of the original one.Overall, the SO2 removal efficiency was 3% higher in the optimal spray section than the original spray section, and the desulfurization efficiency was 8% higher in the optimal bubble section than the original bubble section.

Desulfurization Performance and Kinetics of Potassium Hydroxide-Impregnated Char Sorbents for SO2 Removal from Simulated Flue Gas.

Potassium hydroxide-impregnated char sorbents (KOH/char) prepared via an ultrasonic-assisted method were used for SO2 removal from flue gas. The desulfurization experiment was analyzed using a fixed-bed reactor under 40–150 °C temperature range, using simulated flue gas. X-ray diffraction (XRD), Fourier-transform infrared spectroscopy, and scanning electron microscopy/energy-dispersive X-ray spectroscopy (SEM/EDS) were used to analyze both the chemical and physical characteristics of the sorbents. The analyzed results exposed that the complete elimination of SO2 from flue gas was achieved when using the char/KOH sorbent with a mass ratio of char to KOH of 11:1. It was noted that temperature had a substantial influence on the desulfurization performance with sulfur capacity maximized at 100 °C. Experimental results also revealed that a small amount of O2 present in the solvent could improve the SO2 removal efficiency of the sorbent. The analyzed XRD patterns showed that K2SO4 was the main desulfurization product, which was consistent with the SEM/EDS analysis. The experimental results were well-described with the Lagergren first-order adsorption kinetics model with the activation energy (Ea) of the SO2 adsorption by KOH/char sorbent of 20.25 kJ/mol.

Simultaneous Removal of NO and SO2 with a Novel Oxidation-Absorption Process Based on Air Microbubble Water System

Microbubbles (MBs) can spontaneously generate hydroxyl radicals (·OH) with high oxidizing capacity. In this study, a novel oxidation-absorption process based on a microbubble system in the indirect removal mode was proposed for the simultaneous removal of nitric oxide (NO) and sulfur dioxide (SO2). In this process, an air microbubble water system (AMBW) was produced by a microbubble generator (MBG) inhaling air and tap water and injected into an oxidation-absorption column reactor by the MBG, meanwhile the mixed gas composed of NO and SO2 passed through a micron-sized gas distributor at the bottom of the reactor and flowed into the AMBW. Important parameters including initial pH and temperature of tap water, operation time, NO concentration, SO2 concentration, and NaCl concentration were assessed to investigate the feasibility of the AMBW for the simultaneous removal of NO and SO2. The results showed that ·OH generated from the collapsed MBs played a critical role in the removal and the simultaneous removal of NO and SO2 was successfully achieved with the AMBW. Even with only tap water used as the absorbent, the removal efficiencies of NO and SO2 reached 92.7% and above 99%, respectively, when the experiment conditions were initial water pH 11.5, initial water temperature 298 K, 600 ppm NO, and 3,000 ppm SO2. Compared with the microbubble system in the direct removal mode, this new system is more suitable for the treatment of flue gases with low NO concentration and high volume. Moreover, this novel process should have a good prospect of industrial application in the flue gas treatment due to its high efficiencies of desulfurization and denitration and some advantages such as low usage cost of the reagents, simple system, and small occupation space.

Simultaneous Removal of SO2 and Hg0 by Composite Oxidant NaClO/NaClO2 in a Packed Tower.

Based on the implementation of the global Minamata Convention, developing an efficient and economical technology for mercury reduction in coal-fired flue gas becomes a hotspot in the field of air pollution control. The composite oxidant NaClO/NaClO2 combined with limestone was used in the simultaneous removal of SO2 and Hg0 in this study, and the three-factor and four-level orthogonal experiments were performed in a packed tower. The influential sequence of various factors on SO2 and Hg0 removals was investigated through range analysis of the orthogonal experiments. Results showed that factors affecting desulfurization was C > A > B (liquid–gas ratio > oxidant concentration ratio > initial pH of absorption liquid), while factors affecting Hg0 removal was A > C > B (oxidant concentration ratio > liquid–gas ratio > initial pH of absorption liquid). Optimum conditions of simultaneous desulfurization and demercuration by NaClO/NaClO2 were A4B1C4; that is, the oxidant concentration ratio was 10/4 (mmol/L:mmol/L), the initial pH was 5, and the liquid–gas ratio was 18 (L/m3). The simultaneous removal efficiencies of SO2 and Hg0 reached 99.5 and 85.4% under these optimum conditions, respectively. Analysis of the characteristics of the solid products showed that the main products of the wet oxidation were CaSO4 and CaSO3. Analysis of the existing form of oxidized mercury showed that 23% of mercury was in the gypsum, while 77% was in the supernatant. Results of this research would provide a practical reference for promoting the simultaneous removal of SO2 and Hg0 by NaClO/NaClO2 with limestone in industrial application.

Characterization of mass transfer coefficients and pressure drops for packed towers with Mellapak 250.X

This paper presents an experimental procedure and an extended modelling analysis aimed to characterize the mass transfer coefficients and the pressure drops of structured packings to support the design of packed absorption columns. The study is applied to Hastelloy C-22 Mellapak 250.X, an effective packing for distillation and absorption processes. The experimental campaign is performed with model aqueous solutions to separately address the mass transfer coefficients in the gas and liquid films and to evaluate the column pressure drops in the operating conditions typically adopted for absorption processes. An extensive analysis of the main available models for mass transfer coefficients and pressure drops available in the open literature is presented. Subsequently, the experiments are used to calibrate the models for the investigated packing and to select the most reliable for its thorough characterization. The predictive capacity of the calibrated mass transfer models is implemented in an ASPEN PLUS® simulation and successfully tested through a set of new desulphurization experimental data carried out on a model flue-gas at different SO2 concentrations and temperatures and with different sorbents. The calibrated simulations accurately predict the experimental SO2 removal efficiency, the wash water pH and temperature.

CFD Prediction with Eulerian/Eulerian Approach of SO2 Absorption from Flue Gases in Bubble-Dispersion Tower

Accurate prediction of SO2 absorption efficiency under different physical and chemical parameters is of significant importance for desulfurization of the flue gas. In order to understand the mechanism of SO2 absorption inside a bubble-dispersion tower, a three-dimensional twin Eulerian model together with two-film theory was applied to simulate the flue gas desulfurization processes in a bubble-dispersion tower. After comparing the predicted desulfurization efficiencies by using calculated gas holdup with the experimental parameters, the deviation of simulated model with the measured ones was small. Moreover, it was observed that the larger the fractional hole area, the better desulfurization performance. The bubble tower showed fine adaptability when the superficial gas velocity varies from 0.3 to 0.7 m/s. Also, there was a positive correlation between the SO2 removal ability and the hydrogen ion concentration. Considering the crystallization of calcium sulfite, the PH of slurry tank inside bubble tower is recommended to be set between 5.5 and 6, and the initial CaCO3 mass fraction is suggested to be set around 10–15% under prediction conditions. Moreover, the SO2 absorption capability could be increased by lifting the initial liquid height, while the SO2 removal efficiency would level off when tube insertion depth/column diameter H/D was over 0.128, so the H/D is suggested to be set from 0.08 to 0.128 to achieve high SO2 absorption and avoid soil erosion. It was observed that the smaller the size of bubbles generated in the slurry, the higher SO2 absorption efficiency could be.

Research on removal of NOX, SO2 and PM from flue gas of coal-fired boilers and engineering application

Removal of NOX and SO2 from flue gas by Ozone (O3) oxidation and NaOH absorption was carried out in practical engineering. The effects of the liquid to gas ratio (L/G), the molar ratio of O3 dosage and initial content of NOX (O3/NOX), pH and NaOH concentrations on the removal efficiencies of NOx and SO2 were investigated. In addition, the influences of O3/NOX and voltage on the removal of PM were analyzed. The results show that the NOX removal efficiency increases with the increasing of O3/NOX (0∼2.0), solution pH (4∼7) and L/G (2∼8), while is slightly affected by NaOH concentration (0.05∼1%). The SO2 removal efficiency increases with the increase of L/G from 2 to 8 L/Nm3, but is hardly changed by O3/NOX (0∼2.0), NaOH concentration (0.05∼1%) and solution pH (4∼10). It was found that the outlet concentration of PM (CPM) decreased with the rise of voltage ranging from 0 to 40 kV, however, slightly increases with the increment of O3/NOX at a range from 1.6 to 2.0. The optimal operating conditions can be established when taking running costs and rigorous ultra-low emission standards into consideration. Under the optimal conditions, the removal efficiencies of NOX and SO2 reached more than 75% and 98% respectively, and CPM could be also controlled within 5 mg/Nm3.

Wet oxidation scrubbing (WOS) for flue-gas desulphurization using sodium chlorite seawater solutions

This paper reports the experimental and modelling results of the absorption of sulphur dioxide by seawater solutions doped with sodium chlorite, a strong oxidant, to improve the conversion of the S(IV) ions produced by SO2 absorption to the more soluble S(VI) ones. The experiments show that sodium chlorite oxidation is very fast and determines a constant SO2 solubility regardless of the solution pH, i.e. its alkalinity. However, it was demonstrated the effect of chlorite is alternative but not additive to that of alkalinity. In fact, during tests carried out at acidic pH and with a dosage of chlorite identical to that of carbonate in a natural seawater, the solubility resulted the same as the figure observed for natural seawater. The results show that the absorption increases by increasing the sodium chlorite content because of the higher solubility. Also in this case, the absorption efficiency of sodium chlorite solutions keeps almost constant regardless of the solution pH. This result suggests that the rate controlling step for chemical absorption is the diffusion of chlorite and S(IV) ions at the gas–liquid interface, with a fast reaction kinetics, similar to the case of reactions with bicarbonate. Finally, a modelling analysis show that ASPEN PLUS® simulations provide excellent predictions of SO2 solubility and removal efficiency data.

A novel combined system using Na2S2O8/urea to simultaneously remove SO2 and NO in marine diesel engine exhaust

The novel combined system using Na2S2O8/urea was used to simultaneously absorb nitric oxide and sulfur dioxide emissions from marine diesel engines as well as inhibit the formation of nitrate in cleaning wastewater to meet the increasingly stringent requirements of regulations. The influences of reaction temperature, Na2S2O8 concentration, urea concentration, SO2 concentration, NO concentration and pH value on SO2 removal efficiency, NO removal efficiency and nitrate concentration were investigated. The experimental results showed that different reaction temperatures had different influences on SO2 removal efficiency, NO removal efficiency and nitrate concentration. An increase in Na2S2O8 could improve the absorption of NO. The addition of urea could effectively improve the removal efficiency of NO and reduce the nitrate concentration. The removal efficiencies of 1000 ppm NO and 1000 ppm SO2 achieved 100 % with 0.2 mol/L Na2S2O8 and 2 mol/L urea at 70℃, and the nitrate content was 8.56 mg/L which was far lower than the regulatory requirement of 60 mg/L. The acidic condition (pH ≤ 5.5) not only facilitated the absorption of NO but also reduced the generation of nitrate. According to the experimental results, the novel combined system was promising to be applied to the control technology of marine diesel engine exhaust.

Pretreated water-quenched-manganese-slag slurry for high-efficiency one-step desulfurization and denitrification

Presently, researches on the use of low-cost pulp or slag for desulfurization and denitrification has attracted much attention globally. However, the efficiency of the NOx conversion remains low and has a short duration. Therefore, we tried to activate the water-quenched-manganese-slag (WQMS) through the pretreatment method of calcination and additive calcination then mixed with KMnO4 (oxidation and absorption in one step without pre-oxidation). The obtained removal efficiency of NOx and SO2 was high as 84.9% and 100% under optimal conditions. After adding the pre-treated WQMS, the absorption of NOx by the slurry increased to 228.65 mg/L when denitrification rate was more than 65%, which is 3.6 times that of pure KMnO4. The increased denitrification efficiency after pre-processing was affected by the phase structure change of the WQMS, increased valence state of manganese, as well as the higher alkalinity of the WQMS. Furthermore, the mechanism of simultaneous desulfurization and denitrification was proposed. In summary, this study provided a new one-step strategy to simultaneously remove SO2 and NOx.

Ultrasound‐assisted modification of Al2O3@TiO2‐Ce core‐shell structure adsorbent for simultaneous desulfurization and denitrification

AbstractBACKGROUNDIn order to improve the desulfurization and denitrification performance of Al2O3@TiO2‐Ce adsorbent, ultrasound‐assisted surface modification using different pore‐forming agents (CTAB (Cetyl Trimethyl Ammonium Bromide), NH4NO3, and Urea) was introduced into the preparation process of Al2O3@TiO2‐Ce core‐shell structure adsorbent.RESULTSAmong the adsorbent modified by various pore‐forming agent, CTAB modified Al2O3@TiO2‐Ce adsorbent showed the best denitrification efficiency, and the ultrasound‐assisted modification of CTAB had a positive effect on the removal efficiency of SO2 and NOx. The adsorption performance increased with the increase of addition amount of CTAB in the range of 5% to 10% but decreased with the increase of CTAB addition amount in the range of 10% to 20%. Petal‐like wrinkles appeared on the surface of CTAB modified adsorbent, and the distribution of the pores on the surface was dispersed uniformly by ultrasound.CONCLUSIONThe petal‐like wrinkle could effectively increase the specific surface area and pore volume of the adsorbent, and pore size distribution was more evenly, which was considered to be the key to improve the adsorption performance. The SO2 and NOx adsorption followed the pseudo‐first order rate expression, and the adsorption process was limited by both external diffusion and intraparticle diffusion. This work provides an experimental and theoretical basis for the surface modification of simultaneous desulfurization and denitrification adsorbents. © 2020 Society of Chemical Industry

Simultaneous desulfurization and denitrification of flue gas by pre-ozonation combined with ammonia absorption

Abstract A process of simultaneous desulfurization and denitrification of flue gas was conducted in this study. The flue gas containing 200 mg·m−3 NO, 1000–4000 mg·m−3 SO2, 3%–9% O2, and 10%–20% CO2 was first oxidized by O3 and then absorbed by ammonia in a bubbling reactor. Increasing the ammonia concentration or the SO2 content in flue gas can promote the absorption of NOX and extend the effective absorption time. On the contrary, both increasing the absorbent temperature or the O2 content shorten the effective absorption time of NOX. The change of solution pH had substantial influence on NOX absorption. In the presence of CO2, the NOX removal efficiency reached 89.2% when the absorbent temperature was raised to 60 °C, and the effective absorption time can be maintained for 8 h, which attribute to the buffering effect in the absorbent. Besides, both the addition of Na2S2O3 and urea can promote the NOX removal efficiency when the absorbent temperature is 25 °C, and the addition of Na2S2O3 had achieved better results. The advantage of adding Na2S2O3 became less evident at higher absorbent temperature and coexistence of CO2. In all experiments, SO2 removal efficiency was always above 99%, and it was basically not affected by the above factors.

Effect of additives on mercury partitioning in wet-limestone flue-gas desulfurization

AbstractThe wet-flue-gas desulfurization (FGD) process plays an important role in removing water-soluble flue-gas components such as sulphur dioxide (SO2) and oxidized mercury compounds. Under the reducing environment of the FGD, there is the possibility of re-emission of the already absorbed mercury (Hg) to the gas phase, which may be diminished by the utilization of specific additives. In this study, the effect of two different additives on Hg re-emission from the aqueous phase and Hg partitioning in gypsum and filtrate of a lab-scale wet-limestone FGD is investigated. Furthermore, the behaviour of additives in the presence of different halides is studied. The studied additives are TMT 15® as a sulphidic precipitating agent, which forms non-soluble mercury compounds, and activated lignite (AL) as a carbon-based sorbent, which adsorbs Hg compounds from the aqueous phase. TMT 15® has no significant effect on SO2 absorption; on the other hand, addition of AL improves the SO2-removal efficiency by up to 30%. Using both additives, Hg re-emission is suppressed in all the experimented cases except for AL in the absence of halides, in which Hg re-emission shows no change. Thus, the need to form nucleophilic oxidized mercury compounds in the slurry for the adsorption of oxidized mercury on AL can be concluded. Usage of both additives improves Hg retention in the slurry to different extents. It is shown that, for the additive-free slurries, the Hg-adsorption capacity of the solid fraction of the slurry is the limiting parameter. Moreover, the utilization of both additives results in a significant increase in the Hg concentration of solid fraction. The correlation between redox potential and partitioning of Hg in the slurry is presented by comparing the change in the redox potential of slurries when additives are used.

Direct conversion of NO and SO2 in flue gas into fertilizer using ammonia and ozone

This study focused on the simultaneous removal of NO and SO2 from an industrial flue gas stream. To evaluate the removal efficiency of NO and SO2 using O3 and NH3, the consumption of two reactants (O3 and NH3) in line with the conversion of NO and SO2 was quantified experimentally. In addition, NO and SO2 were converted to valuable fertilizers, NH4NO3 and (NH4)2SO4. To identify a principle strategy to enhance the generation of fertilizer, Fourier transform infrared spectroscopy was used to examine the reaction mechanisms for the formation of NH4NO3 and (NH4)2SO4. Acceleration of SO2 oxidation could be achieved effectively by adding NO to a gas mixture of SO2, NH3, and O3. The formation of HNO3 might be enhanced by the simultaneous feeding of NO and SO2. Particle generation was also 10 times higher for NH3/(NO + SO2) than for NH3/NO and for NH3/SO2, which is a prominent feature of this study. Moreover, the introduction of steam had a positive influence on particle generation. This method offers dual applications for NO and SO2 removal from a flue gas stream and direct fertilizer generation.

Simultaneous desulfurization and denitrification by electrodialysis

In recent years, simultaneous desulfurization and denitrification technology has gradually become a research hotspot at home and abroad. The purpose of this paper is to study simultaneous desulfurization and denitrification of electrodialysis/Fe(II) system. In order to study the electrochemical effect on simultaneous desulfurization and denitrification by electrodialysis, simultaneous purification experiments on SO2, NO2 and NO were carried out under the conditions of electrification and non-electrification respectively. The purification effects of electrodialysis/Fe(II) system on SO2, NO2 and NO were investigated. The results show that the simultaneous purification of SO2 and NOx is inhibited by each other when no power is applied, mainly because of the competition between Fe (II) and O2. The synergistic effect between SO2 and NOx occurs after charging. The desulfurization product SO32− is reduced to S and S2− in the cathode. The system enhances the purification effect of SO2 and NOx through the oxidation-reduction cycle of S2− in the cathode. After that, the effects of oxygen content, current and Fe (II) content on desulfurization and denitrification efficiency were further investigated. The effect of current on SO2 purification rate was first increased and then decreased, while the purification rate of NOx increased with the increase of current; The removal efficiency of SO2 and NOx is better under oxygen-free and hypoxia conditions; The effect of Fe(II) content on SO2 purification rate was not significant, but on NOx purification was significant. The purification rate of NOx increased significantly after adding 0.1 mol/L Fe(II) into the system, but decreased continuously afterwards with the increase of Fe(II) content. Finally, the reaction mechanism of simultaneous desulfurization and denitrification was analyzed, and the transformation process of sulfur and nitrate in the system was discussed.

Simultaneous removal of SO2 and NOx from biomass flue gas by ozone oxidation + wet scrubbing method

In this work, factors affecting NO and SO2 removal were systematically investigated, including O3/NO ratio (V/V), different oxidant types, NaOH and KMnO4 concentrations. Results indicate that the degree of oxidation cannot be pursued too much and the best O3 / NO ratio (V/V) is 0.5. The increased amount of KMnO4 and NaOH promoted the removal efficiency of NOx. The key to the removal of NOx by KMnO4 was mainly that when the KMnO4 was 0.013 mol / L, the removal efficiency of SO2 and NOx reached 100% and 93.75%, respectively. This indicates that the technology can not only efficiently remove NO and SO2, but also has a great application prospect.

The simultaneous removal of SO2 and NO from flue gas over activated coke in a multi-stage fluidized bed at low temperature

A multi-stage fluidized bed (MSFB) process was explored to simultaneously remove the SO2 and NOx from flue gas by use of activated coke (AC) as active medium in low temperature range of 100–200 °C. The various technological tests (e.g., temperature, feeding rate, superficial gas velocity, bed numbers) were carried out to make clear the removal features of SO2 and NOx in MSFB system. The MSFB process could not only increase both the removal efficiency and capacity of SO2 over AC, but also eliminate SO2 in the first layer of bed to avoid poisoning the AC by ammonium sulphate in upper beds for denitration. 100% desulfurization efficiency and 73.2% denitration efficiency could be acquired over regenerated AC through the four-stage bed at 180 °C in the presence of 10 vol% H2O, which was even much more efficient than moving bed process. Moreover, the fresh AC could be activated after the use/regeneration circulation of AC, and the removal efficiency for both SO2 and NO was significantly elevated over the regenerated AC. The multiple structural characterizations (BET, FT-IR, TPD, XPS) revealed that the microporous structure of regenerated AC was expanded with increased surface area and pore volume to provide more adsorption sites for SO2, and meanwhile abundant surface nitrogen/sulfur/oxygen groups were produced as catalytic sites for denitration, accounting for the significantly promoted removal efficiency over the regenerated AC. The demonstrated advantages of MSFB system signify its promising application prospect for the simultaneous removal of SO2 and NOx in industry.

Removal of high concentrations of NOx and SO2 from diesel off-gases using a hybrid electron beam technology

The removal of high inlet concentrations of NOx (>1000 ppm) and SO2 ( >500 ppm) from diesel engine off-gases was studied using hybrid electron beam technology, i.e. electron beam combined with a wet scrubber method. Five different wet scrubbing solutions were examined: 3.5% NaCl solution (simulated sea water), NaOH solution, NaCl-NaClO2-phosphate buffer solution, NaCl-NaClO2 solution, and NaCl-H2O2 solution. The SO2 removal efficiency for all hybrid experiments was 100% at 10.9 kGy irradiation dose for inlet concentrations of SO2 varying between 501 ppm and 723 ppm. The NOx removal efficiency increased with increasing the absorbed dose and decreased with increasing the gas flow rate. NOx removal efficiency also increased with increasing the oxidant concentration (NaClO2) in the wet scrubber solution. The order of the NOx removal efficiency from lowest to highest in the hybrid system with the different scrubber solution is as follows: (NaOH, salty water) < H2O2 < NaClO2. The addition of oxidant to the wet scrubber solution increased NOx removal efficiency. An NOx removal efficiency of greater than 89.6% was achieved at 10.9 kGy irradiation dose for inlet NOx concentrations around 1500 ppm when 3.5% NaCl-5mMNaClO2-phosphate buffer solution was used. After treatment, the cleaned off-gases can be released into the atmosphere.