NOx Absorption Research Articles

Impact of aerosol-radiation interaction and heterogeneous chemistry on the winter decreasing PM2.5 and increasing O3 in Eastern China 2014–2020

In the context of the prevalent winter air quality issues in China marked by declining PM2.5 and rising O3, this study employed a modified WRF-Chem model to examine the aerosol radiation interaction (ARI), heterogeneous chemistry (AHC), and their combined impact (ALL) on the variations in O3 and PM2.5 during the 2014–2020 in eastern China. Our analysis confirmed that ARI curtailed O3 while elevating PM2.5. AHC reduced O3 through heterogeneous absorption of NOx and hydroxides while notably fostering fine-grained sulfate, resulting in a PM2.5 increase. Emission reductions mitigated the inhibitory impact of ARI on meteorological fields and photolysis rates. Emission reduction individually without aerosol feedback led to a 5.43 ppb O3 increase and a 22.89 µg/m3 PM2.5 decrease. ARI and AHC amplified the emission-reduction-induced (ERI) O3 rise by 1.83 and 0.31 ppb, respectively. The response of ARI to emission diminution brought about a modest PM2.5 increase of 0.31 µg/m3. Conversely, AHC, acting as the primary contributor, caused a noteworthy PM2.5 decrease of 4.60 µg/m3. As efforts concentrate on reducing PM2.5, the promotion of ARI on PM2.5 counterbalanced the efficacy of emission reduction and the AHC-induced strengthening of PM2.5 decrease. The ALL magnified the ERI O3 increase by 38.9% and PM2.5 decrease by 18.7%. Sensitivity experiments with different degrees of emission reduction demonstrated a consistent linear relationship between the ALL-induced enhancement of O3 increase and PM2.5 decrease to the ERI PM2.5 decline. Our investigation revealed the complex connection between emissions and aerosol feedback in influencing air quality.

Simultaneous absorption of SO2 and NOx from simulated flue-gas exploiting the enhancing oxidative ability of aqueous euchlorine as scrubbing solution

This paper reports the performances of a pilot-scale Wet Oxidative Scrubber (WOS) in the treatment of a simulated flue-gas containing 500 ppmv SO2 and 1030 ppmv NOx and operated at 60 °C and 1 atm. The scrubber is fed with an oxidizing solution containing NaClO2 at either 0.75 % or 1 % w/w initially at pH > 9 and then acidified to pH down to 3 with HCl, to obtain the additional oxidative contribution given by euchlorine species during the simultaneous absorption. Further experiments of single-component NOx absorption are performed to better understand the role exerted by SO2 in the simultaneous absorption. These experimental tests are carried out to investigate the effect of the acidity of the chlorite-based scrubbing solution on the simultaneous absorption performance of SO2 and NOx, highlighting the intensification with respect to the bare de-NOx system. Experiments also allow determining the optimal dosages and solution pH for a complete and optimized removal of NOx and SOx also being less energy-intensive. For a scrubbing solution under acid-induced conditions (pH = 3), the retrieved results show that the NaClO2 molar dosage needed for a complete simultaneous removal results 3.6 times greater than the total NOx concentration in the flue-gas. This allows an interesting reduction of 83 % in oxidant consumption and a water-saving of 70 % with respect to the same process applied to the simultaneous NOx absorption but without altering the solution pH. Overall, the results confirm the enhancing role exerted by euchlorine deriving from chlorite acidification and sulfur dioxide presence in the flue-gas.

Pilot-scale Validation of the Modeling of NOx Reactive Absorption Process Using Aqueous Solutions Containing Nitric Acid and Hydrogen Peroxide

NOx are harmful pollutants emitted by many industries and must be removed before the gases are released into the atmosphere. Among the various techniques used for NOx removal, reactive absorption by hydrogen peroxide in a packed column has the advantage of being able to transform NOx into nitric acid which can be recycled and reused in the plants. This work aimed at modeling the NOx absorption by means of aqueous solutions of hydrogen peroxide and nitric acid, applied in a packed column operating under different representative conditions. The model established using the Aspen software considers the equilibrium and the kinetics of the reactions taking place both in the gas phase and in the liquid phase as well as the thermodynamic properties of the chemical (molecular and ionic) components estimated using the Electrolyte NRTL model. It allows predicting NOx absorption performances in terms of efficiency and selectivity. The model was validated by comparing simulation results with experimental ones obtained in a pilot-scale absorption column and published previously. The predicted values are in satisfactory agreement with the experimental data showing a deviation between 5 and 8%. Therefore, the model developed in this work could be advantageously used to design industrial-scale reactive NOx absorption columns.

Co3O4 as an efficient passive NOx adsorber for emission control during cold-start of diesel engines

The Co3O4 nanoparticles, dominated by a catalytically active (110) lattice plane, were synthesized as a low-temperature NOx adsorbent to control the cold start emissions from vehicles. These nanoparticles boast a substantial quantity of active chemisorbed oxygen and lattice oxygen, which exhibited a NOx uptake capacity commensurate with Pd/SSZ-13 at 100 °C. The primary NOx release temperature falls within a temperature range of 200-350 °C, making it perfectly suitable for diesel engines. The characterization results demonstrate that chemisorbed oxygen facilitate nitro/nitrites intermediates formation, contributing to the NOx storage at 100 °C, while the nitrites begin to decompose within the 150-200 ºC range. Fortunately, lattice oxygen likely becomes involved in the activation of nitrites into more stable nitrate within this particular temperature range. The concurrent processes of nitrites decomposition and its conversion to nitrates results in a minimal NOx release between the temperatures of 150–200 °C. The nitrate formed via lattice oxygen mainly induces the NOx to be released as NO2 within a temperature range of 200–350 °C, which is advantageous in enhancing the NOx activity of downstream NH3-SCR catalysts, by boosting the fast SCR reaction pathway. Thanks to its low cost, considerable NOx absorption capacity, and optimal release temperature, Co3O4 demonstrates potential as an effective material for PNA applications.

Enhanced NOx absorption in flue gas by wet oxidation of red mud and phosphorus sludge

The environmental problem caused by industrial emissions of NOx has been studied in the past dacades. In this study, red mud coupling with phosphorus sludge were used to enhance the solution to absorb NOx from the flue gas. Firstly, red mud reacted with the binder silicic acid in the phosphorus sludge, destroying the emulsion structure of the phosphorus sludge. Then, the P4 in the phosphorus sludge is completely released, and the P4 reacted with O2 in the flue gas to produce O3 and O. NO and NO2 contained in the flue gas reacted with the active O and O3 to produce high-valent NOx, such as NO3, N2O5. At last, the mixed slurry of red mud and phosphorus sludge absorbed the high-valent NOx, resulting in the formation of Ca5(PO4)3F along with HNO3. Using phosphorus sludge to produce O3 in the reaction process can reduce the production cost of O3 and achieve waste utilization. Meanwhile, the interaction between red mud and phosphorus sludge can promote phosphorus sludge to produce O3 and remove F- from phosphorus sludge, as well as avoid the problem of secondary pollution. This study should be helpful for red mud and phosphorus sludge utilization and flue gas denitration.

Undercovering the role of physicochemical properties of amides in two-phase absorbent systems for ship exhaust pollutant removals

The use of two-phase absorbents containing amides to treat ship pollutants is a new research solution that can achieve high NO oxidation rates and NO2 absorption rates. This paper studies the physicochemical properties of five different amides and their relationship with the desulfurization and denitrification processes. It was found that nitrous acid molecules undergo an isomerization rearrangement in the amide and combine in a more stable form during the NOx absorption process. The polarity and viscosity of the amide are more critical than the min ESP value in removing pollutants. The high polarity and low viscosity of DBA (N,N-Dibutylacetamide) provide dual advantages, facilitating the interaction between the organic and aqueous phases, as well as enhancing the mass transfer process and the combination of an inorganic acid. The system containing DBA achieved removal efficiencies of 99.6% for SO2, 86.33% for NO, and 86.3% for NOx in 10 min. Overall, this study provides valuable insights into the use of organic-containing two-phase absorbents to reducing ship exhaust pollution.

Effect of different adding methods of Nano-TiO2 to micro-surfacing layer on NOx degradation

This paper aimed to investigate the effect of Nano-TiO2 as a semi-conductor additive on the pollutant’s absorption of a micro-surfacing layer. In this research, micro-surfacing samples with Nano-TiO2 values of 5, 7, 9, 11, and 13% (by weight of bitumen) and two types of aggregates (immersed and non-immersed aggregates in Nano-TiO2) were tested to determine contaminant absorption and evaluate rutting performance at two temperatures of 20 and 40°C. The results revealed that NOX absorption improved with increasing Nano-TiO2, reaching 40% in samples with the optimal amount of Nano-TiO2 (11% by weight of bitumen). Wheel track test results showed that the optimum sample had a better performance compared to the control sample. Also, it was observed that the absorption of pollutants decreased after conducting the wheel track test.

Enhancing NOx removal in a high-gravity rotating packed bed with gaseous ClO2 oxidation-absorption: Kinetic, mass transfer, and cost analysis

The application of ClO2(g) for NO oxidation presents a promising approach to improving air pollution control technology. In this study, an integration of ClO2(g) with absorption using a high-gravity rotating packed bed (HiGee RPB) was proposed for NOx removal. The results showed that ClO2(g) has a comparable oxidation efficiency (close to 100%) to O3 in converting NO to NO2, while the dosage of ClO2(g) required was two times smaller than that of O3. The gas-phase oxidation kinetic analysis between ClO2(g)-NOx, using an ideal plug flow model, simulated the potential amount of NOx species produced in a short reaction distance in the pipeline. Furthermore, at higher gas-liquid ratios and in high-gravity fields, the effective mass transfer interfacial area for NO2 absorption was mainly controlled by the liquid film rather than droplet behavior, resulting in decreased absorption capacity. The empirical model for predicting the gas-side mass transfer coefficient confirmed that the interaction between mass transfer performance and chemical absorption was independent. Therefore, selecting the appropriate absorbent is a key factor in achieving high-loading NO2 concentrations after oxidation by ClO2(g). Another interesting finding is that balancing system energy consumption and the target treated NOx concentration played a critical role in enhancing the NOx absorption capacity. The cost analysis showed that substituting existing scrubbers with RPB processes could facilitate NOx absorption capacity (g-NOx/kWh) with cost-effectiveness. Overall, this study provides valuable insights into the development of effective and efficient NOx removal technologies, and future research in this area can build on these findings.

Performance evaluation of NOx absorption by different denitration absorbents in wet flue gas denitration

BackgroundDeveloping efficient denitration absorbents transforming the NOx of flue gas into nontoxic species are critical for wet flue gas denitration (WFGD). MethodPerformance of various denitration absorbents and their unique mechanisms were investigated by a laboratory-scale apparatus, and the denitration efficiency was quantified via response surface method. ResultsThe denitration efficiency were Na2SO3>Na2S>(NH4)2SO3>TEA>KI>Na2S2O3>NaOH>CO(NH2)2>NH3∙H2O>H2O. Na2SO3, Na2S, (NH4)2SO3, TEA, KI and Na2S2O3 removed NO2 by reducing it into NO2− ion, where the denitration efficiency showed positive correlation with reducing ability. The CO(NH2)2 eliminated NO2 by reducing it into nontoxic N2, but the efficiency was limited due to its low reactivity at low temperatures. The alkaline reagents including NaOH and NH3∙H2O promote NOx absorption via acid-base neutralization mechanism leading to both NO2− and NO3− ions formation. For Na2SO3 with highest denitration efficiency, pH significantly affects its efficiency by changing the proportions of its hydrolysate, oxygen weakens the NOx absorption capacity of absorbent by oxidizing SO32− into inert SO42−, and the accumulation of NO2− ions greatly suppresses the denitration efficiency, whereas NO3− ions had negligible effect. The quadratic regression model could accurately quantify and predict the effects of various factors on denitration efficiency.

The underlying mechanisms of PM2.5 and O3 synergistic pollution in East China: Photochemical and heterogeneous interactions

The rapid development of Chinese cities is accompanied by air pollution. Although the implementation of air pollution control strategies in recent years has alleviated PM2.5 pollution, O3 pollution and the synergistic pollution of PM2.5 and O3 have become more serious. To understand the underlying chemical interaction mechanisms between PM2.5 and O3, we applied the modified Weather Research and Forecasting model with Chemistry (WRF-Chem) to study the effects of aerosol-photolysis feedback and heterogeneous reactions on the two pollutants and revealed the contribution of different mechanisms in different seasons and regions in Yangtze River Delta (YRD) in eastern China. We found that, through the aerosol-photolysis feedback, PM2.5 decreased the surface photolysis rates JNO2 and JO1D, resulting in a decrease in O3 concentration in the VOC-sensitive area and a slight increase in the NOx-sensitive area. The heterogeneous reactions reduced O3 concentration in the YRD in spring, autumn and winter by consuming HxOy. While in summer, the heterogeneous absorption of NOx decreased O3 in the NOx-sensitive areas and increased O3 in the VOC-sensitive areas. Heterogeneous reactions also promoted the secondary formation of fine sulfate and nitrate aerosols, especially in winter. Through the combined effect of two chemical processes, PM2.5 can lead to a decrease in O3 concentration of −3.3 ppb (−7.6 %), −2.2 ppb (−4.0 %), −2.9 ppb (−6.3 %), and − 5.9 ppb (−18.7 %), in spring, summer, autumn and winter in YRD. Therefore, if the PM2.5 concentration decreases, the weakening effect of PM2.5 on the ozone concentration will be reduced, resulting in the aggravation of ozone pollution. This study is important for understanding the synergistic pollution mechanism and provides a scientific basis for the coordinated control of urban air pollution.

Semi-industrial technology tests of the sanitary cleaning of metallurgical enterprises waste gases from sulfur and nitrogen oxides

Nitrogen emissions in the form of NOx with flue gases from thermal power plants are the most serious pollutants generated during the combustion of coal. The calcium carbonate gas scrubbing process used today is expensive, generates a lot of waste, and leaves a significant amount of SO2 in the gas. Virtually no NOx removal. In this paper, we consider the behavior of nitrogen oxides during the purification of exhaust gases from thermal power plants with a carbonate melt of alkali metals. Based on the thermodynamic analysis of reactions between NOx and alkali metal carbonates, the possibility of reducing their concentrations in the exhaust gases is shown. It has been established that the process of NOx absorption in the temperature range of 573…823K is accompanied by the formation of stable potassium nitrite (KNO2) in the melt, as evidenced by the high negative values of the Gibbs energies of the reactions. The results of balance experiments fully confirm the established regularities. One can foresee that carbonate melt-based SO2 removal may become a practical and economical scrubbing method for sulfur-poor flue gases emitted by nonferrous metal production plants, thereby contributing to the limiting of harmful sulfur and NOx emissions into the atmosphere. The research was carried out within the framework of grant funding of the Science Committee of the Ministry of Education and Science of the Republic of Kazakhstan for 2020–2022 in the priority area “Rational use of natural resources, including water resources, geology, processing, new materials and technologies, safe products and structures” project No. AP08856384 “Development of a new high-tech technology for the utilization of the SO2 and CO2 from flue gases from thermal power plants and metallurgical plants with the production of marketable products”.

A novel method for removing NOx from simulated marine exhaust gas in wet absorption system using Na2SO3/THS composite solution

AbstractSince it is difficult to deal with high‐concentration nitrates in scrubbed wastewater onboard vessels, the application of traditional wet denitration technology is limited to some extent. Here a novel method for removing pre‐oxidized NOx by using Na2SO3/THS composite solution is proposed with the aim to obtain high NOx absorption efficiency and low nitrate concentration in scrubbed wastewater simultaneously. The effects of Na2SO3 concentration, THS concentration, NOx oxidation degree, coexistence of SO2 and O2 in flue gas, initial pH value and temperature of absorption solution on denitration performance were discussed in detail. The results showed Na2SO3 could reduce NOx to nitrate, nitrite, and N2. The addition of THS could promote NOx absorption greatly by forming complexes with SO32−. When initial NOx concentration was 1000 ppm with a NOx oxidation degree of 50%, O2 concentration was 8%, Na2SO3 and THS concentrations were 25 and 20 mmol/L, a NOx absorption efficiency of 87% could be achieved, while nitrate and nitrite concentrations were 32.97 and 14.19 mg/L, respectively.

Performance and mechanism of CO2 absorption during the simultaneous removal of SO2 and NOx by wet scrubbing process

The co-removal of CO2 while removing SO2 and NOx from industrial flue gas has great potential of carbon emission reduction but related research is lacking. In this study, a wet scrubbing process with various urea solutions for desulfurization and denitrification was explored for the possibility of CO2 absorption. The results showed that the urea-additive solutions were efficient for NOx and SO2 abatement, but delivered < 10% CO2 absorption efficiency. The addition of Ca(OH)2 dramatically enhanced the CO2 absorption, remained the desulfurization efficiency, unfortunately restricted the denitrification efficiency. Among various operating parameters, pH of solution played a determining role during the absorption. The contradictory pH demands of CO2 absorption and denitrification were observed and discussed in detail. A higher pH of solution than 10 was favorable for CO2 absorption, while the oxidizing of NO to NO2, NO2− or NO3− by NaClO2 was inhibited in this condition. When 7 < pH < 10, it was favorable for the conversion and absorption of NO and NOx. However, the conversion of HCO3− to CO32− was significantly inhibited, hence preventing the absorption of CO2. Large part of Ca(OH)2 became CaCO3 with a finer particle size, which covered the unreacted Ca(OH)2 surface after the reaction. Kinetic analysis showed that the CO2 absorption in urea-NaClO2-Ca(OH)2 absorbent was controlled by chemical reaction in early stage, then by ash layer diffusion in later stage.

Balance experiments on the purification of waste gases of thermal power plants from SO2 and NOХ by carbonate melt

The conceptual scheme of the waste gas treatment technology of the CHP includes the organization of interconnected processes of chemical absorption of SO2 and NOx by the carbonate melt of alkali metals and further regeneration of the carbonate-sulfate melt by natural gas. In previous studies, it was shown that it is possible to purify waste gases from sulfur and regenerate the melt with carbon monoxide. The limitations of these works were the use of CO as a reducing agent during the regeneration of the melt, and the practical lack of data on the behavior of nitrogen compounds. These gaps are eliminated in this paper. Based on the results of balance experiments of the process of chemical absorption of SO2 and NOx from waste gases by a carbonate melt, and the regeneration of a carbonate-sulfate melt by natural gas, the principal possibility of implementing a closed technology for deep purification of gases from SO2 and NOx is shown. It is shown that the process of chemical absorption of gases by a carbonate melt and the regeneration of the melt by natural gas at the same temperature of 500 °C allows the technology to be implemented using a single reactor. It was found that during the chemical absorption of SO2 and NOx from the waste gases of the CHP by the carbonate melt of alkali metals, more than 95 % of sulfur and ~60 % of nitrogen compounds are captured. It is shown that in the process of regeneration of a carbonate-sulfate melt with natural gas, 100% extraction of sulfur and nitrogen into the gas phase is achieved with the formation of alkali metal carbonates in the melt. The results of the material balance of the process of chemical absorption and regeneration of the carbonatesulfate melt by reduction with natural gas are presented.

Buffer effect of MgO on Na2SO3 to stabilize S(IV) for the enhancement in simultaneous absorption of NOx and SO2 from non-ferrous smelting gas.

Oxidation-reduction-absorption based on sulfite is a promising process for simultaneous removal of NOx and SO2. However, excessive oxidation of sulfite and competitive absorption between NOx and SO2 limit its application. A matching strategy between antioxidants and alkaline agents has been proposed to solve these problems and enhance the absorption process. The comparison results of inhibitors showed that hydroquinone exhibited long-term high-efficiency inhibition of S(IV) (SO32-/HSO3-) oxidation. The comparison of alkaline agents showed that the Na2SO3 solution with heterogeneous mixture of MgO and hydroquinone exhibited better absorption performance than that with other combinations. The absorption amounts of NOx in 0.15mol/L Na2SO3 50mL solution added 0.1% hydroquinone (HQ) with 0.09mol/L MgO were 2.24mmol, which improved 5 times than that without additives. In addition, studies on the influence of pH showed that the pH of MgO mixture could be stabilized at 9-10 for a long time, while the pH of Na2CO3 mixture decreased faster. Further studies suggested that the hydration of MgO resulted in the solution with MgO keeping high pH. This is also the main reason why the combination of MgO and hydroquinone is superior to the combination of Na2CO3 and hydroquinone in desulfurization and denitration performance.

Effect of Low-Cost Perovskite Based Lean NOx Trap to Reduce the NOx Emission for CRDI Engine

Lean NOx trap (LNT) is an after-treatment technology that targets NOx emissions from an IC Engine and reduces it by using fuel as the reductant. The main mechanisms involved in this process are (i) oxidation of NO into NO2, (ii) Entrapment of NO2 over an alkali Earth metal in the form of nitrates, and (iii) Regeneration and reduction of NO2. The oxidation and reduction reactions are usually performed over rare Platinum Group Metals (PGM). The alternate cycling of operation modes helps in the regeneration and reduction stage due to the presence of unburnt hydrocarbons and carbon monoxides. These HC and CO generated during profitable operation can reduce agents similar to ammonia in SCR (Selective Catalytic Reduction). In the case of LNT, the fuel-injected for reduction imposes a penalty on the system. Cobalt-based perovskites with the chemical formula “ACoO3” (where “A” denotes Ba, Sr, etc.) show excellent absorption and reduction tendencies towards NOx and are highly suited for LNT as they have higher NO oxidation capacity. This research experimented with two different coating procedures (with and without binder) with three other perovskite catalysts–BaCoO3, SrCoO3, and Ba0.5Sr0.5CoO3. Both the coatings were tested for their adherence, and it revealed that the binder-less layer had only 4% coating loss after 2 hrs of sonication. BaCoO3 showed higher NOx absorption due to the higher electropositive nature of barium. The peak conversion efficiency attained in this experiment was 84% at a catalyst temperature of 350°C and 40% load condition.

Novel process for nitrite removal driven by S(IV): NOx absorption and reductive denitrification in smelting industry

The absorption products of NOx by SO32−-contained solution are mainly NO2− or NO3− which may cause secondary pollution and increase difficulty for further disposal in wastewater. Conversion of NO2− into N2 using S(IV) (HSO3−/SO32−) reduction is a promising method for denitrification, yet it is difficult to be realized under SO2-rich conditions. Here, a self-removal method was put forward for N element conversion driven by S(IV) ions. The first step was the reduction of NO2− into trisulfonic acid (NTS) or amine disulfonic acid (ADS). Followed that the NTS/ADS was hydrolyzed into NH2SO3H. Then the NO2− was reduced to N2 by NH2SO3H. The experimental results indicated that such method guarantee a higher NOx absorption efficiency and the higher than 95% absorption products were NO2−. When S(IV)/NO2− was higher than 4.2, 95% of NO2− was reduced to NTS or ADS, then further hydrolyzed into NH2SO3H with higher than 90% efficiencies. Moreover, the gas chromatograph-mass spectrometer (GC–MS) and ion chromatography (IC) results confirmed that the main products of the reactions between NO2− and self-generated NH2SO3H were N2 and SO42−. This study provides a new route for the safety disposal of NO2− in non-ferrous smelting industry.

CFD modeling for NOx absorption accompanying with SO2 in wet flue gas desulfurization scrubber based on gas-phase ozone oxidation

NOx removal performance accompanying with SO2 is investigated in a two-step process containing O3 pre-oxidation of NO and NOx post-absorption in the scrubber of wet flue gas desulfurization (WFGD) unit. Based on EulerianLagrangian framework, a comprehensive CFD model is established to describe the reactions of NO2 and N2O5 with S(IV) in droplets coupled with NOx transfer process and hydrodynamics in the scrubber. Taking the WFGD scrubber of 330 MW coal-fired power unit as case study, the results indicate NOx absorption efficiency in scrubber is increased by increasing O3/NO molar ratio from 1.0 to 2.2 and decreasing reaction temperature from 423 K to 363 K in O3 pre-oxidation process. The obtained highest removal efficiency is 85.79% for pH of 5.5 or 96.32% for pH of 9.0 in droplets. NO2 absorption is much slower than N2O5 and more sensitive to chemical compositions in droplets or hydrodynamics in scrubber. The overall mass transfer coefficient (KG) for NO2 is mainly determined by pH and S(IV) concentration in droplets, while the specific interfacial area (a) is largely influenced by gasdroplet hydrodynamics in scrubber. Finally, a correlation is proposed to predict the volumetric mass transfer coefficient (KGa) for NO2 absorption accompanying with SO2 in WFGD scrubber.

Study on Efficient Nox Absorption from Simulated Ship Exhaust Gas Using O3/Urea Wet System: Analysis of Removal Efficiency and Ions Concentration

Study on Efficient Nox Absorption from Simulated Ship Exhaust Gas Using O3/Urea Wet System: Analysis of Removal Efficiency and Ions Concentration

Experimental study on removal performance of SO2 and NOx in marine exhaust gas using seawater/urea peroxide solution and analysis of ions concentration change

The removal of SO2 and NOx emitted by marine diesel engines was still very important for the development of shipping industry. In this study, a novel method based on seawater/urea peroxide composited absorption solution was used to remove NOx and SO2 efficiently and can keep nitrate concentration lower in liquid phase. And the key parameters were investigated, such as removal efficiency, ions concentration, solution composition, reaction temperature and absorbent concentration. The selected reaction temperature and urea peroxide concentration was 60 °C and 5%, and the SO2 and NOx removal efficiency was close to 100% and 80% respectively. Compared with fresh water, the seawater can improve the NOx absorption capacity of urea peroxide solution, so as to meet the emissions regulation requirements. The concentration of NO3− increased with the oxygenation and absorption capacity of the absorbing solution increasing. However, the addition of seawater could make the concentration of NH4+ decrease a little bit. The ions concentration also increased with the reaction time, and when it came to practical application, the reaction time should be strictly controlled.