NOx Production Research Articles

The Impact of Lightning NOx Production on Ground‐Level Ozone in Tehran

AbstractLightning‐generated nitrogen oxides (LNOx) have an impact on the concentration of ground‐level ozone which acts as a toxic air pollutant, thereby negatively influencing human health and the environment. To understand the impact of LNOx on ground‐level ozone, we simulated four thunderstorm events in Tehran using the WRF‐Chem model. As observations of LNOx are not available, we evaluated the temporal distribution of the simulated ground‐level ozone concentration against an air quality monitoring station. We also compared the simulation results against the spatial distribution of the total column ozone from the Ozone Monitoring Instrument. WRF‐Chem performs well in the simulation of ground‐level ozone concentration, with the best performance for an event with the highest lightning activity (correlation coefficient of 0.91). The analysis of the spatial distribution of the observed and simulated total column ozone also indicates the good performance of WRF‐Chem. Hourly variation in the simulated LNOx during lightning activity is compared against both hourly variation in the observed ground‐level ozone and the number of lightning for four thunderstorm events. There is an agreement between the simulated LNOx and the observed ground‐level ozone during lightning for two events, with correlation coefficients of 0.55 and 0.57. LNOx emissions enhance ozone production in the middle to upper troposphere, which can subsequently contribute to an increase in ground‐level ozone by transport, vertical mixing, and chemistry. In addition, the initiation of chemical processes in response to cloud‐to‐ground lightning strikes may contribute to an increase in both LNOx and the concentration of ground‐level ozone.

Combustion Efficiency of Carbon-neutral Fuel using Micro-Combustor Designed for Aerospace Applications

Recent advancements in the field of micro combustor research are growing for achieving high-performance systems in micro power generation and microelectromechanical devices. To mitigate the hazardous emissions from carbon fuels, as an alternative, zero-carbon-free fuels ammonia, and hydrogen are being explored in micro combustion processes. The distinctive feature of a micro combustor lies in its significantly higher area to volume ratio in comparison with traditional combustion systems, leading to accelerated combustion reaction rates. However, the small size of micro combustors poses a challenge in achieving efficient mixing of highly reactive fuels like hydrogen and ammonia with oxidizers. The unique properties of micro combustors can lead to differences in the combustion behavior of hydrogen and ammonia compared to larger-scale combustion systems. Hence, examining the performance of carbon-free fuels in micro combustors is crucial for the advancement of clean energy combustion systems. A numerical investigation on a Y-shaped micro-combustor was carried out to identify the aspects of non-premixed combustion of ammonia/air and hydrogen/air. The findings reveal that in the case of hydrogen combustion, stable flames were reached, even at low equivalence ratios. Therefore, the distinct combustion properties of hydrogen and ammonia result in varying NOx emissions, with hydrogen generally leading to higher NOx levels due to its higher flame temperature and increased thermal NOx production.

Effect of thermal gas quenching on NOx production by atmospheric pressure rotating arc Plasma: A pathway towards Eco-Friendly fertilizer

Plasma nitrogen fixation allows an alternative ammonia production path compared to the classical industrial Haber-Bosch process, due to the emergence of low-cost and environment friendly renewable energy. However, the high energy cost due to high-temperature reaction condition and reverse reactions in typical “warm” plasmas (gliding arc and rotating gliding arc) lies as a bottleneck of its industrial application. As a possible solution to enhance the efficiency of the process, the effect of thermal gas quenching on nitrogen fixation by rotating arc plasma are investigated. The NOx (i.e. NO, NO2) yield, energy cost, and NOx selectivity are obtained under variable operating conditions (i.e. oxygen fraction in the feed gas, arc length, specific energy input, varying quench gas and quenching ratio). With the help of quenching, the maximum achievable NOx concentration was enhanced from 5.16 to 5.8%. The enhancement is achieved by mitigating loss reactions through quenching and it is supported by the integration of experimental findings, plasma diagnostics using optical emission spectroscopy, and the application of a zero-dimensional chemical kinetic model.

Hybrid rich- and lean-premixed ammonia-hydrogen combustion for mitigation of NOx emissions and thermoacoustic instabilities

The large-scale direct utilization of two carbon-free fuels, ammonia and hydrogen, is currently attracting significant interest in the context of the development of new gas turbine combustion technologies, with paying close attention to the reduction of nitrogen oxides and unburned ammonia emissions. Motivated by recent observations that rich-premixed conditions tend to mitigate excessive NOx emissions from ammonia combustion, and that uniformly blended ammonia-hydrogen fuel/air mixtures tend to increase NOx production exponentially, here we propose a hybrid configuration of hydrogen-doped rich-premixed ammonia-air flames (inner stage) and lean-premixed pure hydrogen-air flames (outer stage) in a radially stratified primary reaction zone. This fuel staging scheme offers a possible mechanism for chemical kinetics-controlled NOx abatement and asymmetry-induced thermoacoustic instability suppression. The relevance and feasibility of the unconventional premixing approach are rigorously evaluated based on detailed measurements of exhaust gas concentrations and self-excited pressure fluctuations, in conjunction with OH*/NH2*/NH* chemiluminescence and OH PLIF imaging measurements. We observe that drastically different non-homogeneous reaction regions can be stably established in a comparatively compact combustion volume without producing negative flame stabilization effects – such as blowoff of less reactive ammonia flames and flashback of more reactive hydrogen flames. As compared with the uniform-blend baseline condition, the hybrid staging method is shown to significantly mitigate total nitrogen oxides emissions, from 7764 to 310 ppmvd (96 % reduction), and achieving an approximately two-fold reduction in dynamic pressure amplitude. Interestingly, hydrogen-enriched rich-premixed ammonia flames are revealed to exhibit anomalous oscillatory states originating from the preferential diffusion of hydrogen molecules and reaction rate-dependent separation of reactive layers, enabling interacting non-homogeneous reaction zones with markedly different characteristic time scales to resist the growth of intense pressure perturbations.

NOx formation processes in rotating detonation engines

High-fidelity simulations of RDEs with H2-Air-NOx chemistry are employed to study NOx emissions in such devices. Discrete injection of gaseous hydrogen fuel and continuous injection of air oxidizer is used at various mass flow rate conditions in several 3D RDE simulations to understand resulting NOx production behaviors. Simulations are also performed for two different injector configurations, one in which air is injected axially into the detonation chamber [Axial Air Inlet (AAI)] and one in which air is injected radially [Radial Air Inlet (RAI)]. It is seen that the AAI RDE produces much less NOx than the RAI RDE, mainly due to the weaker waves seen in this system as a result of parasitic combustion losses from product gas recirculation. Parasitic combustion does lead to NOx formation in its own right, but the emissions levels from this process are negligible compared to emissions stemming directly from detonation processes. In regards to detonation strength in particular, it is generally seen that detonation strength increases with increasing mass flow rate, in turn increasing peak pressure, peak heat release and NOx emissions levels. Nevertheless, even the highest recorded NOx levels at the combustor exit in this study remain on the same order of magnitude as compared to gas turbine exhaust emissions levels, supporting the claim that significant differences between detonative and deflagrative combustion do not necessarily lead to significant differences in NOx levels. Overall, this study provides greater understanding into the behaviors of NOx formation in RDEs and how these behaviors are affected by changes in operating parameters.

Three-stage hybrid NSD/DC plasma assisted n-C5H12/O2/N2 ignition: Improved energy efficiency and reduced NOx/N2O emissions

This work presents a three-stage hybrid nanosecond discharge (NSD) and direct current (DC) discharge assisted n-C5H12/O2/N2 ignition with lower discharge energy and higher energy efficiency. The reaction rate coefficients between O2(a1Δg) and n-C5H12 are updated by mass/Master equation simulation. The promotive ignition enhancement via reaction channel O2(a1Δg) + n-C5H12 → C5H10 + H2O2 in the hybrid NSD/DC discharge is demonstrated. The results show that the ignition delay time of the three-stage hybrid plasma assisted ignition is 1–2 orders of magnitude shorter than that of the two-stage hybrid discharge when the reduced electric field strength in the DC discharge stage is over 10 Td. Meanwhile, the plasma-enhanced energy efficiency of three-stage hybrid discharge increases. This improved efficiency on ignition enhancement is due to the kinetic enhancement by the electronically excited species and radicals (O2(a1Δg), O(1D), N2(B) and O). The kinetic and thermal effects by plasma are effectively intergated to enhance ignition. However, more discharge energy deposited in the vibrationally excited states N2(v) in the two-stage hybrid discharge is less efficient on ignition enhancement due to the thermal contribution via vibrational-translational relaxation. In the aspect of NOx/N2O emissions, reduction efficiency of the three-stage hybrid discharge is two times higher than that of the two-stage hybrid discharge. By controlling the N/N(2D) production pathway e + N2 → e + N + N(2D), the three-stage hybrid discharge reduces NOx and N2O production by 61.1 % and 90 %, respectively. The results show that the ignition delay time is non-monotonically dependent on the discharge pulse number. There exist optimal pulse number, reduced electric field and effective threshold power density of DC discharge to achieve maximum ignition enhancement and low NOx/N2O emissions. This study provides valuable insights into the use of NSD/DC hybrid discharge technology in advanced engines to achieve energy-efficient ignition enhancement and reduce NOx/N2O emissions.

Impact of temperature-dependent non-PAN peroxynitrate formation, RO2NO2, on nighttime atmospheric chemistry.

The formation of peroxynitrates (RO2NO2) from the reaction of peroxy radicals (RO2) and nitrogen dioxide (NO2) and their subsequent redissociation are typically not included in chemical mechanisms. This is often done to save computational time as the assumption is that the equilibrium is strongly towards the RO2 + NO2 reaction for most conditions. Exceptions are the reactions of the methyl peroxy radical due to its abundance in the atmosphere and of acyl-RO2 radicals due to the long lifetime of peroxyacyl nitrates RO2NO2 (PANs). In this study, the nighttime oxidation of cis-2-butene and trans-2-hexene in the presence of NO2 is investigated in the atmospheric simulation chamber SAPHIR, Forschungszentrum Jülich, Germany, at atmospherically-relevant conditions at different temperatures (≈276 K, ≈293 K, ≈305 K). Measured concentrations of peroxy and hydroperoxy radicals as well as other trace gases (ozone, NO2, volatile organic compounds) are compared to state-of-the-art zero-dimensional box model calculations. Good model-measurement agreement can only be achieved when reversible RO2 + NO2 reactions are included for all RO2 species using literature values available from the latest SAR by [Jenkin et al., Atmos. Chem. Phys., 2019, 19, 7691]. The good agreement observed gives confidence that the SAR, derived originally for aliphatic RO2, can be applied to a large range of substituted RO2 radicals, simplifying generalised implementation in chemical models. RO2NO2 concentrations from non-acyl RO2 radicals of up to 2 × 10 cm-3 are predicted at 276 K, impacting effectively the kinetics of RO2 radicals. Under these conditions, peroxy radicals are slowly regenerated downwind of the pollution source and may be lost in the atmosphere through deposition of RO2NO2. Based on this study, 60% of RO2 radicals would be stored as RO2NO2 at a temperature of 10 °C and in the presence of a few ppbv of NO2. The fraction increases further at colder temperatures and/or higher NO2 mixing ratios. This does not only affect the expected concentrations of RO2 radicals but, as the peroxynitrates can react with OH radicals or photolyse, they could comprise a net sink for RO2 radicals as well as increase the production of NOx (= NO + NO2) in different locations depending on their lifetime. Omitting this chemistry from the kinetic model can lead to misinterpreted product formation and may prevent reconciling observations and model predictions.

CARACTERIZACIÓN COMPUTACIONAL DEL USO DE HIDRÓGENO EN UN QUEMADOR DE HORNO, EN EL QUE ACTUALMENTE SE QUEMA GAS NATURAL

The implementation of hydrogen as a fuel in industrial applications is an upward trend, and poses a challenge for the design of furnace burners. This article aims to advance in the knowledge of hydrogen combustion, through numerical simulation using SIEMENS STAR-CCM+ code. Several simulations have been carried out with the geometry of a 2.5 MW burner of the current SIDENOR furnace. The fuel burning there, is natural gas. Using the same geometry and the same mesh, a comparison is made between current temperatures and those that would arise when burning hydrogen, as well as mass fractions of other elements such as NOx. Maintaining the power of 2.5 MW and taking into account the lower heating value of methane and hydrogen, the inlet boundary conditions are calculated for the different fuel compositions. In this way it can be seen, qualitatively, the amount of hydrogen needed to meet the necessary temperatures in the billets, without excessive NOx production. Key Words: Hydrogen, burners, Computational Fluid Dynamics, NOx

Nitrogen fixation by rotational gliding arc plasma at surrounding conditions

Nitrogen fixation (NF) was investigated in a rotational gliding arc plasma based on various energy inputs, flow rates, and N2:O2 ratios under atmospheric conditions. For practical application, the effect of water content in the feed, self-heating during plasma discharge, prolonged operation, and comparison between plasma and thermal process for N2 oxidation were also conducted. The comparison results reveal that NF by the gliding arc plasma is superior to the thermal process in terms of NOx yield and energy consumption at low temperatures and atmospheric pressure. Herein, energy input and flow rate are two controlled factors that significantly influence NOx production rate. Simultaneously, O2 content played a crucial role in determining NOx yield, selectivity of NO/NO2, and energy consumption. Observations during plasma discharge indicated an initial rise in gas and reactor body temperatures, coinciding with decrease in total NOx formation. Moreover, the presence of water had a negative effect on NOx yield. Accordingly, the optimized conditions for NF by gliding arc plasma for NOx formation was identified at a N2 to O2 ratio of 3:2 without water vapor in the feed gas. Furthermore, a 14-h continuous operational test validated the robustness of our reactor configuration, affirming its long-term viability. The study concludes by performing oxidation of the NOx gas followed by dissolution in water, successfully generating nitric acid. These findings underscore the potential of gliding arc plasma for efficient NF processes, offering insights into optimal operational conditions and downstream applications for nitric acid generation.

Impact of K-H Instability on NOx Emissions in N2O Thermal Decomposition Using Premixed CH4 Co-Flow Flames and Electric Furnace

This study systematically investigates the formation of NOx in the thermal decomposition of N2O, focusing on the impact of Kelvin–Helmholtz (K-H) instability in combustion environments. Using premixed CH4 co-flow flames and an electric furnace as distinct heat sources, we explored NOx emission dynamics under varying conditions, including reaction temperature, residence time, and N2O dilution rates (XN2O). Our findings demonstrate that diluting N2O around a premixed flame increases flame length and decreases flame propagation velocity, inducing K-H instability. This instability was quantitatively characterized using Richardson and Strouhal numbers, highlighting N2O’s role in augmenting oxygen supply within the flame and significantly altering flame dynamics. The study reveals that higher XN2O consistently led to increased NO formation independently of nozzle exit velocity (ujet) or co-flow rate, emphasizing the influence of N2O concentration on NO production. In scenarios without K-H instability, particularly at lower ujet, an exponential rise in NO2 formation rates was observed, due to the reduced residence time of N2O near the flame surface, limiting pyrolysis effectiveness. Conversely, at higher ujet where K-H instability occurs, the formation rate of NO2 drastically decreased. This suggests that K-H instability is crucial in optimizing N2O decomposition for minimal NOx production.

Solar influences on the Earth’s atmosphere: solved and unsolved questions

Solar influences on the Earth’s atmosphere: solved and unsolved questions

Lightning‐Produced Nitrogen Oxides Per Flash Length Obtained by Using TROPOMI Observations and the Ebro Lightning Mapping Array

AbstractLightning is one of the main sources of NOx in the Earth's atmosphere. However, there is a large variability in NOx production during the lifetime of thunderstorms. In this study, we used the TROPOspheric Monitoring Instrument (TROPOMI) cloud and NO2 research products along with Lightning Mapping Array (LMA) measurements to investigate the possible relation between the amount of NOx produced per lightning flash and flash channel length in the Ebro Valley. We found that there is a positive relationship between both variables. In turn, the vertical structure of the analyzed lightning flashes indicates that longer flashes could release more LNOx at lower altitudes than shorter flashes, while higher flash rates produce less LNOx per flash.

Impact of Preheating on Flame Stabilization and NOx Emissions From a Dual Swirl Hydrogen Injector

Abstract Flame stabilization, flame structure, and pollutant emissions are investigated experimentally on a swirled injection system operating with globally lean air/hydrogen mixtures at atmospheric conditions and moderate Reynolds numbers. This injector consists of two coaxial ducts with separate injection of hydrogen into a central channel and of air into an annular channel. Both streams are swirled. The resulting flames exhibit two stabilization modes. In one case, the flame takes an M-shape and is anchored to the hydrogen injector lips. In the second case, the flame is aerodynamically stabilized above the injector and takes a V-shape. Regions of existence of each stabilization mode are determined according to the operating conditions. For low air flow rates, the flame can be either anchored or lifted above the hydrogen injector lips depending on the path followed to reach the operating condition. At high air flow rates, the flame is always lifted regardless of the trajectory followed. The impact of air inlet temperature on these stabilization regimes is then evaluated from T= 300 K up to 770 K. Flame re-attachment is shown to be controlled by edge flame propagation and the impact of preheating is well reproduced by the model. Unburnt hydrogen and NOx emissions are finally evaluated. Unburnt hydrogen is only observed for global equivalence ratios below 0.4 and at ambient inlet temperature. NOx emissions decrease when the global equivalence ratio is reduced. Furthermore, at fixed global equivalence ratio, NOx emissions decrease as the thermal power increases, regardless of air preheating and the flame stabilization regime. At high power, NOx emissions reach an asymptotic value that is independent of the thermal power. The impact of flame shape, air preheating, and combustion chamber wall heat losses on NOx production is also evaluated. NOx emissions are shown to scale with the adiabatic flame temperature Tad at the global equivalence ratio and the residence time inside the combustor.

Classification and characteristics of ammonia combustion in well stirred reactor

The present work investigates the regime classification and chemical characteristics of the premixed ammonia combustion in a well stirred reactor (WSR). Three combustion regimes can be classified based on the lowest autoignition and highest extinction temperatures and the reacting temperature increment, which are: (i) flameless combustion (FLC); (ii) high temperature combustion (HTC); (iii) traditional combustion (TC). When introducing the upper limit of NOx emission into the classification, MILD combustion can be defined as a sub-regime of FLC. Relative to the methane counterpart, the ammonia combustion is found to exhibit larger FLC and smaller HTC regimes delimited by the inlet temperature and oxygen fraction. It is also revealed that the MILD combustion of ammonia differs significantly from its burning under other regimes in heat production and NO formation mechanisms. In the MILD combustion, multiple reactions dominate the heat production while the DeNOx route greatly reduces the NO formation. Contrarily, in other combustion regimes, heat is controlled by one or two specific reactions while notably the Extended Zeldovich route dominates the NO destruction. Moreover, the working temperature controls the top reactions for both heat and NOx productions, regardless of different combustion regimes.

Effects of hydrogen blending and exhaust gas recirculation on NO[formula omitted] emissions in laminar and turbulent [formula omitted] flames at 25 bar

In this work, the effect of Exhaust Gas Recirculation (EGR) on NOx emissions in a CH4/H2/air combustion at 25 bar, at an equivalence ratio Φ = 0.7, is analyzed in laminar and turbulent partially premixed flames. Numerical simulations of twenty premixed and partially premixed counterflow flames with H2 ranging from 0 to 100%, with and without EGR, are carried out. Analysis of NO formation mechanisms shows that the thermal path is the main responsible for the NOx production in each flame, with a contribution of nearly 80%. In laminar flames an increase of H2 leads to an increase in NOx emissions. The addition of the exhaust gas decreases the flame temperature and therefore NOx: each laminar flame shows a NOx reduction of about 60% with the presence of exhaust gas. Four turbulent slot jet flames with a CH4/H2/Air/EGR premixed central core and Air/EGR as coflow are studied in a two-dimensional framework using the Reynolds Averaged Navier–Stokes (RANS) approach and the Large Eddy Simulation (LES) methodology, to take into account some flame dynamics, despite the 2D context. Accurate molecular transport properties are considered and, a reduced specifically designed chemical mechanism for methane/hydrogen-air combustion at Φ=0.7, consisting of 48 transported species and 465 elementary reactions is adopted. The four turbulent flames were simulated with 0 and 50% hydrogen concentration, with and without EGR. The presence of hydrogen reduces CO2 emissions, but at the same time increases NO concentration, the thermal path being the main NO formation mechanism. The use of exhaust gas recirculation leads to NO reduction as in laminar flames. The results obtained in this work show that at high pressure, the hydrogen enrichment of natural gas in the EGR mode leads to lower NOx as well as CO2 emissions.

Research on Full Premixed Combustion and Emission Characteristics of Non-Electric Gas Boiler

NOx has become one of the main culprits causing the global greenhouse effect, and excessive emissions of NOx can also cause some common diseases in humans. The denitrification of power plant boilers has been 100% popularized, and their denitrification efficiency has reached national and local environmental requirements (such as Selective Catalytic Reduction, SCR). However, small gas boilers, due to their use of relatively clean fuels, have relatively low NOx emissions. But, local environmental protection departments have weak supervision of small clean fuel boilers, and these equipment generally lack specialized denitrification equipment, resulting in NOx emissions still not meeting standards. In addition, there are many small gas boilers, resulting in high total emissions. The fully premixed burner of a small gas boiler has the effect of suppressing NOx production during combustion. This study designed a surface porous burner with different combustion intensities at different positions. The experimental results and numerical calculations show that for horizontal combustion, the burner has different intake rates at different axial positions, enabling uniform combustion throughout the entire furnace, with NOx emissions below 30 mg/Nm3. The numerical simulation results show that the NOx emissions are 26.6 mg/m3. The calculated results are in good agreement with the actual situation. The generation of NOx is mainly thermal, with a maximum error of 15.4% between the calculated and experimental values. The difference between the calculated value of O and the experimental one is 5.1%. It can be seen that numerical simulation has considerable accuracy.

Dynamic analysis and performance improvement of a GDI engine and fuel cell under real driving conditions using machine learning technique

This study assesses the fuel consumption and emissions of fuel cell vehicles (FCVs) and internal combustion engines (ICEs) under real driving conditions, considering an FC component and a vehicle equipped with a gasoline direct injection (GDI) engine. The simulation model for the internal combustion engine is based on machine learning and implements the Wiebe combustion model. The study uses weather conditions in Tehran and natural navigation routes in the city to increase the model's realism. The results show that fuel consumption depends on critical cycle parameters, such as average speed, maximum speed, and stopping time. Driving behavior and routes also significantly impact pollution levels, with HC and NOx showing no clear correlation, indicating that each particle's production pattern is independent. The study found that navigation time for fuel cell cars is directly related to hydrogen consumption and battery state of charge. Machine learning can be used to improve the performance of both types of vehicles under real driving conditions. Additionally, the study shows that driving behavior and route can reduce NOx production in engine production by 52 % and energy consumption by 38 %.

Evaluation of nitrous oxide emission during ammonia retention from simulated industrial wastewater by microaerobic activated sludge process

Considering the reciprocating processes of nitrogen gas (N2) fixation to ammonia (NH4-N) and NH4-N removal to N2 through nitrification and denitrification during wastewater treatment, a microaerobic activated sludge process (MAS) is proposed in this study as a pretreatment to retain NH4-N from high-strength nitrogenous wastewater for further NH4-N recovery through membrane technology, that is, inhibit nitrification, with sufficient removal of total organic carbon (TOC). With DO and pH control, the 3-reactor bench-scale MAS systems successfully realized an NH4-N retention rate of over 80 %, with TOC removal rates of over 90 %. In addition, the emissions of carbon dioxide (CO2) and nitrous oxide (N2O) during MAS were evaluated. The total N2O emissions were 407 and 475 mg-N/day when pH was controlled at 6.2 (S1) and 6.8 (S2), respectively, with average emission factors to total nitrogen load over 2 % in both systems. Also, the global warming potential of N2O is one order of magnitude larger than that of CO2, indicating the significance of N2O in the MAS process. Therefore, the mechanisms of N2O emission from each reactor were investigated. The first reactor, where most of the TOC was adsorbed, emitted only 1.98 % (S1) and 2.43 % (S2) of the total N2O emissions through the denitrification of nitrite and nitrate (NOx) from the return sludge. The second reactor emitted 79.9 % (S1) and 69.0 % (S2) of the total N2O with the emission rates the same order of magnitude as the NOx production rates. Multiple pathways were considered to contribute to the high N2O emissions, and biotic NH2OH oxidation was one potential pathway at pH 6.2. Finally, the third reactor emitted 9.98 % (S1) and 16.8 % (S2) of the total N2O by nitrifier denitrification. Overall, this study showed that the large N2O emissions under nitrification-inhibiting conditions of the MAS process owed to the incomplete nitrification under acidic conditions and large abundances of denitrifiers. On the other hand, the lower N2O emissions at pH 6.2 evidenced the potential N2O mitigation under slightly more acidic conditions, underlining the necessity of further study on N2O mitigation when adapting to the trend of NH4-N recovery.

Effects of fabomatisol under lead intoxication in rat experiment

The conducted study indicates the priority use of the drug fabomatizole to protect living systems from the negative effects of lead acetate.Aim: To study the mechanisms of fabomatizole effect on the nature of changes in redox reactions, NO-forming function of the endothelium, cholesterol metabolism and functional parameters in rats with lead intoxication.Material and Methods. The study was carried out on 60 Wistar rats. Lead intoxication was induced by intramuscular administration of lead acetate at a dose of 5 mg/kg of animal weight for a month. At the end of the intoxication period, Fabomatizol was administered at a dose of 10 mg/kg for a month. Next, blood and tissue samples were taken from rats to determine the activity of oxidative, antioxidant, enzymatic systems, nitric oxide metabolism, and blood lipid spectrum.Results. The data obtained showed that intramuscular administration of fabomatisol in case of lead intoxication has an antioxidant effect and inhibits lipid peroxidation (LPO) activity. Under the influence of fabomatizol, nitric oxide metabolism andtotal nitric oxide metabolites (NOx) content significantly increased, and a negative correlation was found between the malondialdehyde level, superoxide dismutase activity and NOx. At the same time, the study found a decrease in the expression level of eNOS as the cause of a reduced concentration of NOx in the blood. L-arginine availability for eNOS was disturbed by atherogenic low density lipoprotein (LDL). Treatment with fabomatizol against the background of lead intoxication caused a decrease in total cholesterol, LDL cholesterol and an increase inhigh density lipoprotein cholesterol. By inhibiting lipid peroxidation in the cells of the renal and hepatic tissues, fabomatizol contributed to the restoration of lipid-protein interactions and the functional activity of Na and K-activated ATPase in the renal interstitium. Simultaneously, there is an activation of Na,K-ATP-ase in the hepatocyte and a decrease in the level of organ-specific enzymes in the blood plasma.Conclusion. The results obtained are evidence of the antioxidant properties of fabomatisol in lead intoxication, its ability to induce the activity of antioxidant system (AOS enzymes, stimulate the NO-forming function of the endothelium, NOx production and the activity of the membrane enzyme – Na,K-ATP-ase in the renal and hepatic tissues and reduce the level of organ-specific enzymes in blood plasma.

Cascade N2 Reduction Process with DBD Plasma Oxidation and Electrocatalytic Reduction for Continuous Ammonia Synthesis.

Due to the extremely high bond energy of N≡N (∼941 kJ/mol), the traditional Haber-Bosch process of ammonia synthesis is known as an energy-intensive and high CO2-emission industry. In this paper, a cascade N2 reduction process with dielectric barrier discharge (DBD) plasma oxidation and electrocatalytic reduction as an alternative route is first proposed. N2 is oxidized to be reactive nitrogen species (RNS) by nonthermal plasma, which would then be absorbed by KOH solution and electroreduced to NH4+. It is found that the production of NOx is a function of discharge length, discharge power, and gas flow rate. Afterward, the cobalt catalyst is used in the process of electrocatalytic reduction of ammonia, which shows high selectivity (Faradic efficiency (FE) above 90%) and high yield of ammonia (45.45 mg/h). Finally, the cascade plasma oxidation and electrocatalytic reduction for ammonia synthesis is performed. Also, the performance of the reaction system is evaluated. It is worth mentioning that a stable and sustainable ammonia production efficiency of 16.21 mg/h is achieved, and 22.16% of NOx obtained by air activation is converted into NH4+. This work provides a demonstration for further industrial application of ammonia production with DBD plasma oxidation and electrocatalytic reduction techniques.