Gas Mutant

The present status of knowledge of the gas-phase reactions of inorganic Ox, HOx and NOx species and of selected classes of volatile organic compounds (VOCs) [alkanes, alkenes, aromatic hydrocarbons, oxygen-containing VOCs and nitrogen-containing VOCs] and their degradation products in the troposphere is discussed. There is now a good qualitative and, in a number of areas, quantitative understanding of the tropospheric chemistry of NOx and VOCs involved in the photochemical formation of ozone. During the past five years much progress has been made in elucidating the reactions of alkoxy radicals, the mechanisms of the gas-phase reactions of O3 with alkenes, and the mechanisms and products of the OH radical-initiated reactions of aromatic hydrocarbons, and further progress is expected. However, there are still areas of uncertainty which impact the ability to accurately model the formation of ozone in urban, rural and regional areas, and these include a need for: rate constants and mechanisms of the reactions of organic peroxy (RȮ2) radicals with NO, NO3 radicals, HO2 radicals and other RȮ2 radicals; organic nitrate yields from the reactions of RȮ2 radicals with NO, preferably as a function of temperature and pressure; the reaction rates of alkoxy radicals for decomposition, isomerization, and reaction with O2, especially for alkoxy radicals other than those formed from alkanes and alkenes; the detailed mechanisms of the reactions of O3 with alkenes and VOCs containing >CC< bonds; the mechanisms and products of the reactions of OH-aromatic adducts with O2 and NO2; the tropospheric chemistry of many oxygenated VOCs formed as first-generation products of VOC photooxidations; and a quantitative understanding of the reaction sequences leading to products which gas/particle partition and lead to secondary organic aerosol formation.Atmospheric Environment

Volume 187, August 2018, Pages 410-416

The impact of NOx emissions from lightning on the production of aviation-induced ozone

Author links open overlay panelArezooKhodayariaDonald J.Wuebblesd

Outline

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https://doi.org/10.1016/j.atmosenv.2018.05.057Get rights and content

Highlights

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We calculated the impact of NOx emissions from lightning on the production of aviation-induced ozone.

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Three sensitivity studies were conducted with varying levels of NOx emissions (LNOx) from lightning.

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By doubling LNOx the global mean aviation-induced O3 burden decreased by about 18%.

Abstract

Volume 45, Issue 17, 27 March 2020, Pages 10580-10591

Progress on the studies about NOx emission in PFI-H2ICE

Author links open overlay panelDong-ShuoMaaZ.Y.Sunab

Outline

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https://doi.org/10.1016/j.ijhydene.2019.11.065Get rights and content

Highlights

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The studies about NOx emissions of hydrogen engines were reviewed.

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Port fuel injection hydrogen fuelled engines were taken as the object.

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Various current technical approaches to reduce NOx were discussed.

Abstract

Owing to its brilliant combustion performance and cleanest combustion products, hydrogen has been widely considered as one best alternative fuel for internal combustion engines. However, in the cylinder of hydrogen internal combustion engines, high combustion temperature and oxygen enrichment make NOx is still one but the only combustion pollutant. Therefore, it is particularly important to control NOx emission for hydrogen fuelled engines. Since PFI-H2ICE (port-fuel-injection hydrogen internal combustion engine) is the normal type of hydrogen fuelled engines, the present article will focus on the studies about NOx emission in PFI-H2ICE researches. First, the present article reviews the mechanism of NOx generation in PFI-H2ICE; upon chemical kinetics, the generation of NOx will be summarized and discussed into three major paths which including thermal NO path, NNH–NO path and N2O–NO path. Then, the researches on the control methods of NOx for PFI-H2ICE in recent years will be systematically reviewed, the influencing factors to reduce NOx emission will be summarized in some aspects which including combustion component control strategy, injection control strategy, ignition control strategy and engine compression ratio control strategy. To the PFI-H2ICE operated at lean fuel conditions (like equivalence ratio is less than 0.5) or rich fuel conditions (like equivalence ratio is higher than 1), the technologies and the strategies of EGR (exhaust gas re-circulation) will be reviewed and discussed. It is hoped this literature review would enable researchers to systematically understand the progress of NOx emissions research in PFI-H2ICE and explore further research directions.Atmospheric Environment

Volume 117, September 2015, Pages 1-8

Evaluating NOx emission inventories for regulatory air quality modeling using satellite and air quality model data

Author links open overlay panelSusanKemball-CookaMarkEstesb

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https://doi.org/10.1016/j.atmosenv.2015.07.002Get rights and content

Highlights

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We used OMI and CAMx NO2 columns to estimate NOx emissions over the southeast U.S.

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NOx emissions estimates were developed using DOMINO v2.0 and NASA SP2 retrievals.

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The two top–down NOx estimates were quite different over the southeast U.S.

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These disparities were due to differences in the two NO2 retrievals.

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It was not possible to constrain the TCEQ's NOx inventory with these estimates.

Abstract

The purpose of this study was to assess the accuracy of NOx emissions in the Texas Commission on Environmental Quality's (TCEQ) State Implementation Plan (SIP) modeling inventories of the southeastern U.S. We used retrieved satellite tropospheric NO2 columns from the Ozone Monitoring Instrument (OMI) together with NO2 columns from the Comprehensive Air Quality Model with Extensions (CAMx) to make top–down NOx emissions estimates using the mass balance method. Two different top–down NOx emissions estimates were developed using the KNMI DOMINO v2.0 and NASA SP2 retrievals of OMI NO2 columns. Differences in the top–down NOx emissions estimates made with these two operational products derived from the same OMI radiance data were sufficiently large that they could not be used to constrain the TCEQ NOx emissions in the southeast. The fact that the two available operational NO2 column retrievals give such different top–down NOx emissions results is important because these retrievals are increasingly being used to diagnose air quality problems and to inform efforts to solve them. These results reflect the fact that NO2 column retrievals are a blend of measurements and modeled data and should be used with caution in analyses that will inform policy development. This study illustrates both benefits and challenges of using satellite NO2 data for air quality management applications. Comparison with OMI NO2 columns pointed the way toward improvements in the CAMx simulation of the upper troposphere, but further refinement of both regional air quality models and the NO2 column retrievals is needed before the mass balance and other emission inversion methods can be used to successfully constrain NOx emission inventories used in U.S. regulatory modeling.Atmospheric Environment

Volume 36, Issue 9, March 2002, Pages 1509-1519

The importance of NOx production by lightning in the tropics

Author links open overlay panelDonald WBondaRichard EOrvillea

Outline

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https://doi.org/10.1016/S1352-2310(01)00553-2Get rights and content

Abstract

The importance of NOx production by lightning in the tropics has been assessed by using satellite lightning measurements from the Lightning Image Sensor (LIS). The lightning data from LIS over the period of 1998–2000 are analyzed and partitioned based on the latitude to obtain the numbers of cloud-to-ground (CG) and cloud-to-cloud (intracloud or IC) flashes. The average annual lightning counts over the 3-yr period are 3.0×108 CG flashes and 1.1×109 IC flashes between 35°N and 35°S. The resulting lightning distributions are employed to calculate the production of NOx. We obtain a lightning NOx production of 6.3 Tg N yr−1 over this latitudinal region, using representative production values of 6.7×1026 and 6.7×1025 NO molecules for each CG and IC flash, respectively. NOx production by lightning varies slightly on a seasonal basis in accordance with the lightning distribution, with the maximum production occurring in the months of September, October, and November. The geographical and seasonal production of NOx by lightning is compared to NOx emissions from other sources (i.e., from anthropogenic activity, biomass burning, and soil emissions). The results indicate that production of NOx by tropical lightning is significant throughout the year. Lightning accounts for almost all of the NOx emitted over the oceans and 50–90% of NOx emitted over some continental areas on a seasonal basis. On the annual basis, the contribution of lightning to total NOx production is 23% in the tropics, and globally the lightning NOx production occurs predominately in this region. The uncertainty in estimating NOx production by lightning over the tropics is discussed.This work presents the results of an experimental investigation on NOx emissions from coal combustion in a pilot scale test facility. Three oxidiser atmospheres have been compared, namely air, CO2/O2, and O2 enriched recirculated flue gas. NOx emissions from two different combustion modes have been studied, swirl flame and flameless combustion. The influence of the burner oxygen ratio and the oxidiser O2 concentration on NOx formation and reduction have been analysed. With increasing burner oxygen ratio, an increase of NOx emissions has been obtained for air and CO2/O2 in both, swirl flame and flameless combustion. In case of the swirl flame, flue gas recirculation leads to a reduction of NOx emissions up to 50%, whereas in case of flameless combustion this reduction is around 40% compared to CO2/O2. No significant impact of the oxidiser O2 concentration in the CO2/O2 mixture on NOx emissions is observed in the range between 18 and 27 vol.% in swirl flames. An analysis of NOx formation and reduction mechanisms showed, that the observed reduction of NOx emissions by flue gas recirculation cannot be attributed to the reduction of recirculated NOx alone, but also to a reduced conversion of fuel-N to NO.Atmospheric Environment. Part A. General Topics

Volume 25, Issue 9, 1991, Pages 1961-1969

Measurements of reactive nitrogen compounds

The production of atmospheric NOx and N2O from a fertilized agricultural soil

Author links open overlay panelM.F.ShepherdD.R.Hastie

Outline

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https://doi.org/10.1016/0960-1686(91)90277-EGet rights and content

Abstract

The source strength of atmospheric trace gases from rural or remote locations must be quantified in order to assess the effect of such inputs on the background tropospheric chemistry. To assess the importance of biological production of NOx and N2O from fertilized agricultural soil, enclosure techniques have been used to determine the emission fluxes of NOx and N2O at a site in Southern Ontario, Canada. NOx fluxes on the unfertilized soil range from 1.5 to 41.6 μg(NO) m−2 h−1. The corresponding N2O fluxes are 0–61.8 μg(N2O)m−2h−1. For the most fertilized soil NOx fluxes range from 3.1 to 583 μg(NO) m−2h−1 and the N2O fluxes from 0 to 446 μg(N2O) m−2h−1. The fluxes increase linearly with fertilizer application, with 11% of the nitrogen in the fertilizer converted to NOx and 5% to N2O. The emission rates were studied as functions of the soil parameters temperature, moisture, ammonium, nitrate and pH, to attempt to understand better the production mechanisms, although a model for the process could not be developed. In rural areas away from transportation corridors the increased NOx emission from fertilized soil may dominate local oxidant production but is not significant on the Province-wide scale.In this paper, the annual data of 50 China Ⅳ public transit buses fueled with diesel in five cities have been analyzed, and the effects of vehicle speed and acceleration on real-road NOx emission and fuel consumption characteristics have been discussed. Results showed that the annual percentage of low speed range (0-30.0 km/h) was over 70%, the acceleration range of -0.5-0.5 m/s2 accounted for nearly 75%, and distribution of each month remained roughly stable. The highest NOx emission was concentrated in region with low vehicle speed (10.0-30.0 km/h) and high acceleration (1.0-2.0 m/s2), and the highest fuel consumption was concentrated in region with high vehicle speed (40.0-50.0 km/h) and high acceleration (1.0-2.0 m/s2). Both the NOx emission and fuel consumption characteristics deteriorated in summer and winter, which was mainly attributed to the using of air conditioning.Compared to conventional diesel fuel, use of biodiesel is generally found to reduce emissions of hydrocarbons (HC), carbon monoxide (CO), and particulate matter (PM); but to increase oxides of nitrogen (NOx) emissions. This paper reviews and summarizes relevant literature regarding the so-called "biodiesel NOx effect, and presents theories" to explain this effect. In modern diesel engines, several factors related to fuel composition and engine control strategies are important, though no single theory provides an adequate explanation of the biodiesel NOx effect under all conditions. There is evidence to suggest that effects on injection timing, ignition delay, adiabatic flame temperature, radiative heat loss, and other combustion phenomena all play some role. The biodiesel NOx effect can be mitigated by modifying engine control settings — particularly by retarding injection timing and increasing exhaust gas recirculation (EGR). The absolute magnitude of the biodiesel NOx effect appears to be reduced with modern engines, although there are cases where the percentage change is still substantial. Sophisticated after-treatment systems required to achieve the 2010 diesel engine emissions standards do not appear to be significantly affected by use of biodiesel. However, longer term study is warranted, as such systems have only been in commercial use for a short time.

Highlights

► Use of biodiesel usually, but not always, increases NOx exhaust emissions. ► Fuel composition, engine technology and operating conditions all affect NOx. ► The biodiesel NOx effect can be mitigated by changes in engine operation parameters.Renewable Energy

Volume 148, April 2020, Pages 1321-1326

Effect of antioxidant additives on oxides of nitrogen (NOx) emission reduction from Annona biodiesel operated diesel engine

Author links open overlay panelSilambarasanRajendran

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https://doi.org/10.1016/j.renene.2019.10.104Get rights and content

Highlights

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The NOx emission was reduced with all antioxidant additives.

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250 mg concentration of antioxidant additive shows drastic reduction in NOx emission.

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PPDA shows identical performance to that of A20 and maximum reduction of NOx emission.

Abstract

In this present study experimental investigation has been carried out to mitigate the NOx emission in 20% Annona biodiesel-diesel blend (A20) operated diesel engine by addition of antioxidant additives. The antioxidant additives used in the present study are p-phenylenediamine (PPDA), A-tocopherol acetate (AT) and l-ascorbic acid (LA). The addition of antioxidant additives to A20 blend did not cause and negative effect of properties of A20 blend. According to the test results, antioxidant additives are effective in controlling the Oxides of nitrogen (NOx) emission in diesel engine. Result shows that 250 mg concentration of PPDA additive with A20 blend was optimum for NOx mitigation up to 25.4% when compared to that of diesel without any major modification.Control Engineering Practice

Volume 40, July 2015, Pages 27-44

Semi-physical mean-value NOx model for diesel engine control

Author links open overlay panelC.QuérelaC.Letellierb

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https://doi.org/10.1016/j.conengprac.2015.02.005Get rights and content

Highlights

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New control-oriented model to predict NOx emissions in diesel engines.

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Semi-physical mean-value burned gas temperature and average NOx kinetic models.

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Experimental validation of the virtual NOx sensor in steady-state and transient operations.

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Computation time compliant for online NOx estimation on series ECU.

Abstract

A semi-physical model has been developed to predict nitrogen oxide (NOx) emissions produced by diesel engines. This model is suitable for online NOx estimation and for model-based engine control. It is derived from a zero-dimensional thermodynamic model which was simplified by only retaining main phenomena contributing to NOx formation. The crank angle evolution of the burned gas temperature, which has a strong impact on NOx formation rate, is described by a semi-empirical model whose key variable is the maximum burned gas temperature. This variable presents a good correlation with the molar fraction of NOx at the end of combustion and can be expressed as a function of the intake burned gas ratio and the start of combustion. The maximum burned gas temperature sub-model is then coupled to an averaged NOx formation kinetic model (based on the Zeldovich mechanism) to form a mean-value model for NOx computation. This latter model was validated using data sets recorded in two diesel engines for steady-state operating conditions as well as for several driving cycles including parametric variations of the engine calibration.IFAC-PapersOnLine

Volume 48, Issue 30, 2015, Pages 385-390

Model based NOx emission monitoring in natural gas fired hot water boilers

Author links open overlay panelTimoKorpela1AnnaHäyrinen2

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https://doi.org/10.1016/j.ifacol.2015.12.409Get rights and content

Abstract

Due to new emission regulations, coverage of monitoring requirements extends to new boiler classes. In Europe, Industrial Emission Directive brings new 15-50 MW boilers under the directive in special cases, so inexpensive NOx emission monitoring tools are appreciated. This paper presents models to estimate NOx emission in two similar natural gas fired municipal hot water boilers. The models utilize online process measurements also available in relatively simple set-ups. In the context, the performance of linear regression model and nonlinear neural network model are introduced. Despite the similarity, the results state that the examined boilers behave differently in terms of linearity and emission levels. Therefore, every boiler should be identified separately to exploit the simplest models in practical installations.The aim of this work is to improve the knowledge of modeling NOx formation in hydrogen flames. Four different detailed reaction mechanisms have been tested for eight laminar flames, and two of these mechanisms have been tested for a turbulent jet flame. The numerical results have been compared with experimental data from the literature. Sensitivity and integral reaction flow analyses are applied to identify important reaction steps. Formation of NO through NNH radicals was found to be important in the hydrogen-air flames investigated. This work suggests that the H2/O2 mechanism of Li et al. for pure hydrogen combustion may be combined with the N/H/O subset from Glarborg et al. for prediction of NOx in hydrogen-air flames. However, the pressure-dependency of the reaction N2O+M⇌N2+O+M should be further investigated and accounted for. For the turbulent hydrogen jet flame, the agreement between the predicted and measured NO levels was better with the mechanism of Glarborg et al.Journal of the Energy Institute

Volume 93, Issue 1, February 2020, Pages 324-334

A comprehensive study on NOx emission and fuel nitrogen conversion of solid biomass in bubbling fluidized beds under staged combustion

Author links open overlay panelPin-WeiLiChien-SongChyang

Outline

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https://doi.org/10.1016/j.joei.2019.02.007Get rights and content

Highlights

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Lowering temperature by water is able to reduce NOx and agglomerates simultaneously.

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Excess oxygen is more influential than bed temperature on NOx variation in FBC.

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NOx reduction by staged combustion is mainly from the extension of residence time.

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Fuel-N conversion is more representative in correlation with nitrogen content.

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CH/N is only correlated well with fuel-N conversion for temperature >800 °C.

Abstract

Despite the relatively low emissions in fluidized-bed combustion, NOx emission for biomass combustion is still a major concern because of increasingly stricter regulations. To realize NOx emission behavior in fluidized beds comprehensively, the effects of bed temperature, excess oxygen, staged combustion, and flue gas recirculation (FGR) are investigated in this study. In particular, three different types of operation are applied in staged combustion to find out the key parameter. The results indicate that NOx emissions increase with both bed temperature and excess oxygen, in which the influence of excess oxygen is greater than the other. Lowering bed temperature by water addition seems to be able to simultaneously reduce NOx emission and agglomerate formation, especially for fuels with high nitrogen content, but the pros and cons should be considered. The results in staged combustion infer that the residence time is much more critical than the stoichiometry in the bed. As for FGR, its impact appears to depend on the type of fuel. The correlation between NOx emission behavior and fuel characteristics is also scrutinized; it is concluded that the fuel-N conversion to NOx is essentially related to some features of fuels.Owing to its brilliant combustion performance and cleanest combustion products, hydrogen has been widely considered as one best alternative fuel for internal combustion engines. However, in the cylinder of hydrogen internal combustion engines, high combustion temperature and oxygen enrichment make NOx is still one but the only combustion pollutant. Therefore, it is particularly important to control NOx emission for hydrogen fuelled engines. Since PFI-H2ICE (port-fuel-injection hydrogen internal combustion engine) is the normal type of hydrogen fuelled engines, the present article will focus on the studies about NOx emission in PFI-H2ICE researches. First, the present article reviews the mechanism of NOx generation in PFI-H2ICE; upon chemical kinetics, the generation of NOx will be summarized and discussed into three major paths which including thermal NO path, NNH–NO path and N2O–NO path. Then, the researches on the control methods of NOx for PFI-H2ICE in recent years will be systematically reviewed, the influencing factors to reduce NOx emission will be summarized in some aspects which including combustion component control strategy, injection control strategy, ignition control strategy and engine compression ratio control strategy. To the PFI-H2ICE operated at lean fuel conditions (like equivalence ratio is less than 0.5) or rich fuel conditions (like equivalence ratio is higher than 1), the technologies and the strategies of EGR (exhaust gas re-circulation) will be reviewed and discussed. It is hoped this literature review would enable researchers to systematically understand the progress of NOx emissions research in PFI-H2ICE and explore further research directions.A little decrease in NOx emission of biodiesel compared to diesel is observed at low loads under low and medium engine speeds. An overall experimental investigation on NOx emission based on combustion characteristics of biodiesel has been carried out. Negative effects of high viscosity and distillation temperature on the spray quality and homogeneity of air fuel mixture are clear at low loads under low and medium speeds. Brake thermal efficiency (BTE) and combustion temperature of biodiesel are lower than those of diesel, resulting in a lower level of NOx emission. With the increase of load, in-cylinder thermal condition and the injection pressure are improved, and with the increase of speed, air swirl movement is strengthened. Oxygenated biodiesel produces more reactive radicals than diesel, and these radicals will surely accelerate the combustion speed, improves the intensity of diffusion combustion, shortens the combustion duration and increase the BTE. Consequently, the diffusion combustion temperature, especially the peak combustion temperature of biodiesel is higher than that of diesel. On the whole, NOx emission of biodiesel is higher than that of diesel in most cases, except in the condition of low loads under low and medium speeds.Ambient trends in nitrogen oxides (NOx) and nitrogen dioxide (NO2) for many air pollution monitoring sites in European cities have stabilised in recent years. The lack of a decrease in the concentration of NOx and in particular NO2 is of concern given European air quality standards are set in law. The lack of decrease in the concentration of NOx and NO2 is also in clear disagreement with emission inventory estimates and projections. This work undertakes a comprehensive analysis of recent vehicle emissions remote sensing data from seven urban locations across the UK. The large sample size of 84,269 vehicles was carefully cross-referenced to a detailed and comprehensive database of vehicle information. We find that there are significant discrepancies between current UK/European estimates of NOx emissions and those derived from the remote sensing data for several important classes of vehicle. In the case of light duty diesel vehicles it is found that NOx emissions have changed little over 20 years or so over a period when the proportion of directly emitted NO2 has increased substantially. For diesel cars it is found that absolute emissions of NOx are higher across all legislative classes than suggested by UK and other European emission inventories. Moreover, the analysis shows that more recent technology diesel cars (Euro 3–5) have clear increasing NOx emissions as a function of Vehicle Specific Power, which is absent for older technology vehicles. Under higher engine loads, these newer model diesel cars have a NOx/CO2 ratio twice that of older model cars, which may be related to the increased use of turbo-charging. Current emissions of NOx from early technology catalyst-equipped petrol cars (Euro 1/2) were also found to be higher than emission inventory estimates – and comparable with NOx emissions from diesel cars. For heavy duty vehicles, it is found that NOx emissions were relatively stable until the introduction of Euro IV technology when emissions decreased by about 30%. The more limited data available for urban buses shows that there has been little change in NOx emissions from Euro I to Euro IV. There is general much better consistency across the different estimates of heavy duty vehicle NOx emissions than for light duty vehicles.

Highlights

► Trends in ambient NOx concentrations have tended to stabilise in recent years. ► Little change in light duty vehicle NOx emissions over 20 years or so. ► Increased diesel car power demand leads to increased NOx for newer vehicles. ► Older catalyst-equipped vehicles emit more NOx than previously thought. ► Important implications at a European level for meeting NO2 limits.

Keywords

Vehicle emissions

Remote sensing

Primary NO2

Emissions inventory

Ambient trends

Recommended articlesCiting articles (156)

View full text.

Science of The Total Environment

Volume 408, Issue 19, 1 September 2010, Pages 3976-3989

Review

Trends in NOx abatement: A review

Author links open overlay panelKingaSkalskaStanislawLedakowicz

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https://doi.org/10.1016/j.scitotenv.2010.06.001Get rights and content

Abstract

Implementation of stringent regulations of NOx emission requires the development of new technologies for NOx removal from exhaust gases. This article summarizes current state of NOx abatement strategy. Firstly, the influence of NOx on environment and human health is described. The main focus is put on NOx control methods applied in combustion of fossil fuels in power stations and mobile vehicles, as well as methods used in chemical industry. Furthermore the implementation of ozone and other oxidizing agents in NOx oxidation is emphasized.Atmospheric Environment

Volume 187, August 2018, Pages 410-416

The impact of NOx emissions from lightning on the production of aviation-induced ozone

Author links open overlay panelArezooKhodayariaDonald J.Wuebblesd

Outline

Cite

https://doi.org/10.1016/j.atmosenv.2018.05.057Get rights and content

Highlights

•

We calculated the impact of NOx emissions from lightning on the production of aviation-induced ozone.

•

Three sensitivity studies were conducted with varying levels of NOx emissions (LNOx) from lightning.

•

By doubling LNOx the global mean aviation-induced O3 burden decreased by about 18%.

Abstract

Due to the non-linear nature of ozone production in the troposphere, ozone production as a function of aviation nitrogen oxide (NOx = NO + NO2) emissions varies based on the background NOx levels. Of the several different sources of background NOx in the atmosphere, NOx from lightning (LNOx) contributes a substantial amount of NOx to the upper troposphere and has an effect on the ozone production efficiency, even though the LNOx source still has significant uncertainty. In this study, CAM5, the atmospheric component of the Community Earth System Model (CESM), was used to study the effect of uncertainties in NOx emissions from lightning on the production of aviation-induced ozone. Three sensitivity studies were analyzed with varying LNOx values of 3.7, 5, and 7.4 TgN/yr, representing the best current range estimates for LNOx. Results show a decrease in the aviation-induced ozone production rate and radiative forcing (RF) as LNOx increases. This is tied to the decreased ozone production under NOx saturated conditions. The ozone production per unit of NOx emission from lightning ranges from 2.38 TgO3/TgN for the case with 3.7 TgN from lightning to 0.97 TgO3/TgN for the case with 7.4 TgN from lightning. Similarly, the O3 RF decreases from 43.9 mW/m2 for the 3.7 TgN/yr case to 34.3 mW/m2 for 7.4 TgN/yr case. Understanding the current sensitivity of aviation-induced ozone production to the LNOx strength is important for reducing the uncertainty in ozone production from aviation NOx emissions.This paper presents the results of fundamental research on gas turbine cogeneration systems with steam injection that attains high thermal efficiency and low pollutant emissions. The concentration of OH radical may be affected significantly in these systems. To prove the behavior of OH radical in the combustion zone and to clarify the relationship between OH radical production and NOx emission, the characteristics of methane-air counterflow flames with steam addition have been simulated numerically by applying GRI-Mech detailed chemical kinetics. To investigate the chemical reaction effects of steam addition on the OH radical and NO formation with the effect of the temperature decrease because of steam addition excluded, the maximum flame temperature was adjusted to the same value by varying the initial temperature. The calculated results clearly show that with steam addition, the decomposition reaction of steam is suppressed and the production rate of the OH radical is decreased regardless of the increase in steam concentration. These results can be explained by the significant decrease in flame temperature for the same initial temperatures of fuel and oxidizer. For the same flame temperature, the OH concentration becomes higher. The increase in the OH concentration because of steam addition in itself results in the increase in NOx emissions. However, because of the decrease in CH concentration with steam addition, the production rates of HCN and N radicals decrease dramatically, and NO formation is suppressed as a whole. These results may be useful to predict NOx emissions in a high-temperature gas turbine system with steam or water addition.Post combustion CO2 capture using amine absorbents is the most mature process and therefore the most relevant choice for realising full-scale capture within the next few years. The health and environmental impact of emissions to air is, however, a potential risk. Amines may react in the process or in the atmosphere post emission to form new substances that may be more harmful than the parent amine itself.

The main objective of the current work was to investigate the flue gas degradation of monoethanolamine (MEA) in the process with special emphasis on the NOx induced chemical reactions. Degradation experiments have been carried out at absorber like conditions in the Aminox™ rig, followed by further degradation of the used solvent at higher temperature in a lab scale autoclave. Liquid samples were analysed by a range of methods to identify the formation of degradation by-products, with special focus on potential harmful compounds like nitrosamines and nitramines. On-line FT-IR and MS instruments were used for qualitative detection of volatile degradation products and to measure amine slip.

MEA is a primary amine which in itself is unable to form a stable nitrosamine. However, experiments show that under the influence of NOx, MEA degrades to the secondary amine diethanolamine (DEA) which is then nitrosated. This work shows that some nitrosamine formation in the process must be expected from any amine. Based on data from real emission measurements, health and environmental risk assessment should be investigated in further studies.

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