Production Of Nitrogen Oxides Research Articles

Investigation of selective catalytic reduction for control of nitrogen oxides in full-scale dairy energy production

Selective catalytic reduction (SCR) was used to reduce exhaust gas nitrogen oxides (NOx) from the emissions of a 710kW combined heat and power system fueled by dairy biogas. Exhaust gas NOx was reduced from 63.1±31.9 to 14.2±17.5ppmvd@15% O2 such that emissions were 0.33±0.40gkW−1h−1, based on data averaged over 15min intervals. Online exhaust gas sensors with integrated process control algorithms were effective in improving NOx removal by automated control of urea, the ammonia source used for catalysis of NOx reduction reactions. Pre-SCR NOx was most strongly correlated with equivalence ratio (R2=0.39), indicative of the air–fuel ratio. A concave relationship between NOx production and thermal conversion efficiency was not observed since lean-burn operation of the engine was consistent and only altered under low engine load. Following installation of pre- and post-SCR NOx sensors, average daily exhaust gas NOx reduction in the SCR was 82.6±8.5%. Post-SCR NOx emissions were typically impacted by pre-SCR NOx (R2=0.36), suggesting that altered operation of the anaerobic digesters or modifications to the engine would be effective in reducing NOx emissions as well as urea demand. After nearly three years of operation, the SCR catalyst remains in service without requiring replacement. Average daily urea demand was 31.8±16.3Ld−1 for the system that produced 369±136kW of electricity. During the second year of observation the regulatory limit of 0.804gkW−1h−1 was met 94% of the time while the regulatory target of 0.201gkW−1h−1 was only met 45% of the time, based on data averaged over 15min intervals. These results provide guidance for dairy energy projects in locations with stringent NOx emissions standards.

Lightning Applications in Weather and Climate Research

Thunderstorms, and lightning in particular, are a major natural hazard to the public, aviation, power companies, and wildfire managers. Lightning causes great damage and death every year but also tells us about the inner working of storms. Since lightning can be monitored from great distances from the storms themselves, lightning may allow us to provide early warnings for severe weather phenomena such as hail storms, flash floods, tornadoes, and even hurricanes. Lightning itself may impact the climate of the Earth by producing nitrogen oxides (NOx), a precursor of tropospheric ozone, which is a powerful greenhouse gas. Thunderstorms themselves influence the climate system by the redistribution of heat, moisture, and momentum in the atmosphere. What about future changes in lightning and thunderstorm activity? Many studies show that higher surface temperatures produce more lightning, but future changes will depend on what happens to the vertical temperature profile in the troposphere, as well as changes in water balance, and even aerosol loading of the atmosphere. Finally, lightning itself may provide a useful tool for tracking climate change in the future, due to the nonlinear link between lightning, temperature, upper tropospheric water vapor, and cloud cover.

Geomagnetic storms affect ozone in mesosphere

During geomagnetic storms, energetic electrons enter the upper mesosphere around 70 kilometers above the Earth's surface. These energetic electrons enhance the chemical reactions that produce nitrogen oxides (NOx), which can destroy ozone. If the nitrogen oxides are transported downward to lower altitudes in the stratosphere (below about 40 kilometers in altitude), they can destroy ozone in the ozone layer that protects life on Earth's surface from harmful ultraviolet radiation. Large solar energetic particle events have been shown to cause decreases in stratospheric ozone, but those large events are uncommon. The extent to which more common moderate‐sized geomagnetic storms affect middle atmosphere chemistry has been uncertain.

Efficiencies for production of nitrogen oxides by proton impact in air

We present the first laboratory measurements of nitrogen oxides generated by proton impact in air. Experiments were conducted at the Tandem Laboratory of Uppsala University. A proton beam with known current and energy was injected into an air tight ionising chamber for a fixed time duration and the resulting nitrogen oxides were measured by the method of chemiluminescence. The data are presented in terms of number of produced NOX (NO+NO2) molecules for different proton energy, proton beam current and duration. The efficiency for NOX production by proton impact in air can on average be estimated to about 0.2 NOX molecules per ion-pair based on 1cm diameter proton beam with energies from 2 to 4MeV and varied currents from 0.1 to 10nA.

Chemical Kinetic Modeling in Coal Gasification Processes: an Overview

<p>Coal is the fuel most able to cover world deficiencies in oil and natural gas. This motivates the development of new and more effective technologies for coal conversion into other fuels. Such technologies are focused on coal gasification with production of syngas or gaseous hydrocarbon fuels, as well as on direct coal liquefaction with production of liquid fuels. The benefits of plasma application in these technologies is based on the high selectivity of the plasma chemical processes, the high efficiency of conversion of different types of coal including those of low quality, relative simplicity of the process control, and significant reduction in the production of ashes, sulphur, and nitrogen oxides. In the coal gasifier, two-phase turbulent flow is coupled with heating and evaporation of coal particles, devolatilization of volatile material, the char combustion (heterogeneous/porous oxidation) or gasification, the gas phase reaction/oxidation (homogeneous oxidation) of gaseous products from coal particles. The present work reviews literature data concerning reaction kinetic modelling in coal gasification. Current state of related kinetic models for heterogeneous/homogeneous oxidation of coal particles, included plasma assisted, is reviewed.</p>

Response of Atmospheric Biomarkers to NOx-Induced Photochemistry Generated by Stellar Cosmic Rays for Earth-like Planets in the Habitable Zone of M Dwarf Stars

Understanding whether M dwarf stars may host habitable planets with Earth-like atmospheres and biospheres is a major goal in exoplanet research. If such planets exist, the question remains as to whether they could be identified via spectral signatures of biomarkers. Such planets may be exposed to extreme intensities of cosmic rays that could perturb their atmospheric photochemistry. Here, we consider stellar activity of M dwarfs ranging from quiet up to strong flaring conditions and investigate one particular effect upon biomarkers, namely, the ability of secondary electrons caused by stellar cosmic rays to break up atmospheric molecular nitrogen (N(2)), which leads to production of nitrogen oxides (NO(x)) in the planetary atmosphere, hence affecting biomarkers such as ozone (O(3)). We apply a stationary model, that is, without a time dependence; hence we are calculating the limiting case where the atmospheric chemistry response time of the biomarkers is assumed to be slow and remains constant compared with rapid forcing by the impinging stellar flares. This point should be further explored in future work with time-dependent models. We estimate the NO(x) production using an air shower approach and evaluate the implications using a climate-chemical model of the planetary atmosphere. O(3) formation proceeds via the reaction O+O(2)+M→O(3)+M. At high NO(x) abundances, the O atoms arise mainly from NO(2) photolysis, whereas on Earth this occurs via the photolysis of molecular oxygen (O(2)). For the flaring case, O(3) is mainly destroyed via direct titration, NO+O(3)→NO(2)+O(2), and not via the familiar catalytic cycle photochemistry, which occurs on Earth. For scenarios with low O(3), Rayleigh scattering by the main atmospheric gases (O(2), N(2), and CO(2)) became more important for shielding the planetary surface from UV radiation. A major result of this work is that the biomarker O(3) survived all the stellar-activity scenarios considered except for the strong case, whereas the biomarker nitrous oxide (N(2)O) could survive in the planetary atmosphere under all conditions of stellar activity considered here, which clearly has important implications for missions that aim to detect spectroscopic biomarkers.

Nitrous oxide pollution from aircraft to increase by 2050

The transportation industry is not only one of the biggest sources of air pollution and a significant player in greenhouse gas–induced global warming, but, as a new study shows, the industry could also be responsible for episodes of ozone (O3 ) pollution, particularly over the United States and northern Europe. Combustion of fuel in cars, shipping vessels, and low‐flying aircraft produce nitrogen oxides (NOx), which not only decrease the lifetime of greenhouse gases such as methane but also react with other molecules in the atmosphere to form tropospheric O3, another, more lethal, air pollutant. Hauglustaine and Koff used a global three‐dimensional chemistry‐climate model to investigate how different components of the transportation industry—cars, ships, and low‐flying aircraft—would contribute to NOx pollution over the next few decades under several projected emission scenarios. They found that as road transportation stagnates or even declines due to stricter regulations and congestion, NOx emissions from cars will decrease over time. However, aircraft will increase in number and could contribute between 25% and 48% of NOx emissions, which will be most severe over the United States and Europe—two regions with the highest growth rate in commercial aviation.

Emission of Nitrogen Compounds by Incineration of a Wastewater Sludge Particle Under Fluidized Bed Conditions: A Numerical Approach

This work proposes a simplified model to simulate the incineration of a single particle of wastewater sludge under fluidized bed conditions. The wet particle is burned in a first completely stirred reactor (CSTR1) containing gas and sand and operating under the usual conditions of a fluidized bed emulsion. The gas generated by the sludge decomposition reacts into CSTR1 according to different homogeneous and heterogeneous mechanisms, then it enters a second completely stirred reactor (CSTR2), which simulates the post-combustion zone. In this reactor only homogeneous reactions occur, and the composition of the gas at the outlet may approach the one of a real process. The analysis of the simulation results indicates that the homogeneous reactions occurring in CSTR1 have little effect on the distribution of the nitrogen compounds within the gas at the outlet of the reactor. At the opposite, the heterogeneous reactions have a significant effect on the production of nitrogen oxides from char combustion. The homogeneous reactions occurring in CSTR2 enable the conversion of the main nitrogenous volatile compounds, such as HCN and NH3 in N2, NO and N2O. An increase in the volume of this second reactor (post-combustion zone) enables a reduction in the emissions of HCN, NH3 and N2O at the outlet of the system. The NO content is essentially related to the amount of nitrogenous volatiles (notably NH3), whereas the N2O depends widely on the amount of nitrogen within the char. The effect of some simulation parameters (percentage of NH3 and HCN into the volatiles, the fraction of nitrogen in the char, the volume of the post-combustion zone) on the emission of oxide nitrogen compounds is also investigated.

Titanium Dioxide Photocleans Polluted Air

Titanium Dioxide Photocleans Polluted Air

Modelling of Nitrogen Oxides Production during Wood Combustion

The process of elaboration and consequent verification of mathematical model of NOx production during wood combustion based on the dimensional analysis theory is presented in this paper. The model is based on selected physical quantities which can be measured continually during boiler operation. Primarily, the model was elaborated for boiler type VERNER V210 of 20 kW performances and its validity was also verified for the same construction type of boiler of lower performance (14 kW). Lump wood of lower calorific value approximately 15 MJ∙kg-1 was used as fuel in the boilers. The results showed that the dimensional analysis can be applied to describing such a complicated phenomenon as the NOx production during wood combustion is.

Nitrifying and denitrifying pathways of methanotrophic bacteria

Nitrous oxide, a potent greenhouse gas and ozone-depleting molecule, continues to accumulate in the atmosphere as a product of anthropogenic activities and land-use change. Nitrogen oxides are intermediates of nitrification and denitrification and are released as terminal products under conditions such as high nitrogen load and low oxygen tension among other factors. The rapid completion and public availability of microbial genome sequences has revealed a high level of enzymatic redundancy in pathways terminating in nitrogen oxide metabolites, with few enzymes involved in returning nitrogen oxides to dinitrogen. The aerobic methanotrophic bacteria are particularly useful for discovering and analysing diverse mechanisms for nitrogen oxide production, as these microbes both nitrify (oxidize ammonia to nitrite) and denitrify (reduce nitrate/nitrite to nitrous oxide via nitric oxide), and yet do not rely on these pathways for growth. The fact that methanotrophs have a rich inventory for nitrogen oxide metabolism is, in part, a consequence of their evolutionary relatedness to ammonia-oxidizing bacteria. Furthermore, the ability of individual methanotrophic taxa to resist toxic intermediates of nitrogen metabolism affects the relative abundance of nitrogen oxides released into the environment, the composition of their community, and the balance between nitrogen and methane cycling.

Density Functional Theory Study of the Oxidation of Ammonia on the IrO2(110) Surface

In this study, we employed density functional theory (DFT) to investigate the oxidation of ammonia (NH(3)) on the IrO(2)(110) surface. We characterized the possible reaction pathways for the dehydrogenation of NH(x) species (x = 1-3) and for the formation of the oxidation products N(2), N(2)O, NO, NO(2), and H(2)O. The presence of oxygen atoms on coordinatively unsaturated sites (O(cus)) of the oxygen-rich IrO(2)(110) surface promotes the oxidation of NH(3) on the surface. In contrast, NH(3) molecules prefer undergoing desorption over oxidation on the stoichiometric IrO(2)(110) surface. Moreover, the O(cus) atoms are also the major oxidants leading to the formation of oxidation products; none of the oxidations mediated by the bridge oxygen atoms were favorable reactions. The energy barrier for formation of H(2)O as a gaseous oxidation product on the IrO(2)(110) surface is high (from 1.83 to 2.29 eV), potentially leading to the formation of nitrogen-atom-containing products at high temperature. In addition, the selectivity toward the nitrogen-atom-containing products is dominated by the coverage of O(cus) atoms on the surface; for example, a higher coverage of O(cus) atoms results in greater production of nitrogen oxides (NO, NO(2)).

Anthraquinones from the roots of Knoxia valerianoides

Five new 9,10-anthraquinones (1–5) were isolated from an ethanol extract of the roots of Knoxia valerianoides. Their structures including absolute configuration of 1 were determined by spectroscopic analysis. Compounds 4 and 5 showed moderate activity against nitrogen oxide production in macrophages induced by lipopolysaccharide, at 10− 5 M, with inhibition ratios of 50.4 ± 3.6 and 41.7 ± 2.1%, respectively.

EXPOSURE TO METALS AND GENE-SPECIFIC METHYLATION IN COMMUNITY-DWELLING ELDERLY MEN

Background and Aims: Methylation changes in promoter regions of genes have been linked to gene expression changes and subsequent human disease. Heavy metals are known to trigger oxidative stress, changes in immune response, and inflammation throughout the body. DNA methylation is a potential pathway through which heavy metals exert their toxicity. We aimed to evaluate the association between exposure to arsenic, cadmium, mercury, manganese and lead and DNA methylation in nine different genes related to inflammation, immune response, and endothelial function in a population of environmentally exposed elderly men. Methods: Our study population was 773 participants from the Normative Aging Study cohort in Boston, USA, with repeated visits between 1999 and 2009. Our associations of interest were explored in a minimum of 423 and a maximum of 611 participants depending on the availability of the exposure and outcome measurements. We measured the concentration of metals in toenails (in mcg/gr) while DNA methylation (in % of 5methyl cytosine) in promoter regions of the IL6, IFN-gamma, iNOS, ICAM, CRAT, OGG, TLR2, F3 and GCR genes was measured in blood leukocytes. The toenail metal concentrations were natural logarithm-transformed. We used multivariable linear mixed effects models to evaluate the associations of interest. Results: Toenail arsenic and manganese concentrations were negatively associated with the iNOS gene methylation [b=-0.2, 95%CI: -0.3 to -0.1 for ten percent increase in toenail arsenic; b= -0.1, 95%CI: -0.1 to -0.01 for ten percent increase in toenail manganese). We did not find any statistically significant associations between the other metals and gene-specific methylation. Conclusions: Both arsenic and manganese concentrations were associated with decreased iNOS methylation which can potentially lead to increased iNOS gene function and subsequent increased nitrogen oxide production, a process involved in inflammation. Our results indicate that heavy metal exposures may exert their effects through epigenetic mechanisms.

Experimental and Numerical Study of NOx Formation From the Lean Premixed Combustion of CH4 Mixed With CO2 and N2

This paper describes an experimental and numerical study of the emission of nitrogen oxides (NOx) from the lean premixed (LPM) combustion of gaseous fuel alternatives to typical pipeline natural gas in a high intensity, single-jet, stirred reactor (JSR). In this study, CH4 is mixed with varying levels CO2 and N2. NOx measurements are taken at a nominal combustion temperature of 1800K, atmospheric pressure, and a reactor residence time of 3 ms. The experimental results show the following trends for NOx emissions as a function of fuel dilution: (1) more NOx is produced per kg of CH4 consumed with the addition of a diluent, (2) the degree of increase in emission index is dependent on the chosen diluent; N2 dilution increases NOx production more effectively than equivalent CO2 dilution. Chemical kinetic modeling suggests that NOx production is less effective for the mixture diluted with CO2 due to both a decrease in N2 concentration and the ability of CO2 to deplete the radicals taking part in NOx formation chemistry. In order to gain insight on flame structure within the JSR, three dimensional computational fluid dynamic (CFD) simulations are carried out for LPM CH4 combustion. A global CH4 combustion mechanism is used to model the chemistry. While it does not predict intermediate radicals, it does predict CH4 and CO oxidation quite well. The CFD model illustrates the flow-field, temperature variation, and flame structure within the JSR. A 3-element chemical reactor network (CRN), including detailed chemistry, is constructed using insight from spatial measurements of the reactor, the results of CFD simulations, and classical fluid dynamic correlations. GRI 3.0 is used in the CRN to model the NOx emissions for all fuel blends. The experimental and modeling results are in good agreement and suggest the underlying chemical kinetic reasons for the trends.

Use of the Orbita Apparatus for Correction of Prolonged Disorders of Tissue Perfusion

The use of the Orbita apparatus for correction of prolonged disorders of peripheral tissue perfusion is discussed. Peripheral perfusion was simulated using long-term immobilization stress. Exposure to electromagnetic radiation of the Orbita apparatus at nitrogen oxide emission and absorption frequencies 150, 176–150, and 664 GHz was shown to restore tissue perfusion in laboratory animals subjected to immobilization stress. The nitrogen oxide absorption electromagnetic radiation of such frequencies induces complete recovery of perfusion index and partial restoration of blood microcirculation. Exposure to the Orbita radiation stimulates basal and induced nitrogen oxide production. This reduces capillary resistance and increases microcirculation rate. The results obtained in this work provide a methodological basis for clinical use of the Orbita apparatus.

Microalgal biomass production and on-site bioremediation of carbon dioxide, nitrogen oxide and sulfur dioxide from flue gas using Chlorella sp. cultures

The growth and on-site bioremediation potential of an isolated thermal- and CO2-tolerant mutant strain, Chlorella sp. MTF-7, were investigated. The Chlorella sp. MTF-7 cultures were directly aerated with the flue gas generated from coke oven of a steel plant. The biomass concentration, growth rate and lipid content of Chlorella sp. MTF-7 cultured in an outdoor 50-L photobioreactor for 6days was 2.87gL−1 (with an initial culture biomass concentration of 0.75gL−1), 0.52gL−1d−1 and 25.2%, respectively. By the operation with intermittent flue gas aeration in a double-set photobioreactor system, average efficiency of CO2 removal from the flue gas could reach to 60%, and NO and SO2 removal efficiency was maintained at approximately 70% and 50%, respectively. Our results demonstrate that flue gas from coke oven could be directly introduced into Chlorella sp. MTF-7 cultures to potentially produce algal biomass and efficiently capture CO2, NO and SO2 from flue gas.

A Mixed Exponential Distribution Model for Retrieving Ground Flash Fraction from Satellite Lightning Imager Data

Abstract A Bayesian inversion method is introduced for retrieving the fraction of ground flashes in a set of flashes observed from a (low earth orbiting or geostationary) satellite lightning imager. The method employs a constrained mixed exponential distribution model to describe the lightning optical measurements. Because the method also retrieves certain population statistics of ground and cloud flash optical properties, the method can be applied to an arbitrary geographical region, including those regions where the lightning optical statistics either are not known or are difficult to obtain. The approach is tested by performing simulated retrievals, and retrieval error statistics are provided. A first-attempt retrieval of the global geographical distribution of ground flash fraction is obtained using the 5-yr Optical Transient Detector (OTD) dataset; the spatially averaged ground flash fraction over the global-scale domain studied was 0.151 with a standard deviation of 0.081. The ability to retrieve ground flash fraction has important benefits to the atmospheric chemistry community. For example, using the method to partition the existing OTD/Lightning Imaging Sensor (LIS) satellite global lightning climatology into separate ground and cloud flash climatologies would improve estimates of regional and global lightning nitrogen oxides (NOx) production; this, in turn, would improve both regional air quality and global chemistry/climate model predictions.

Airway and Plasma Leptin and Adiponectin in Lean and Obese Asthmatics and Controls

Introduction. Obesity-mediated changes in plasma adipokines have been associated with increased systemic inflammation and oxidative stress. However, it is unknown whether obesity induces similar changes in airway levels of these adipokines and whether these changes are associated with increased airway biomarkers of inflammation and oxidative stress. Methods. Lean and obese asthmatics and controls underwent bronchoscopy with bronchoalveolar lavage (BAL), spirometry, and provided fasting plasma leptin and adiponectin. Biomarkers of oxidation and inflammation in the BAL included exhaled nitric oxide (NO), 8-isoprostanes, pH, and nitrogen oxide products (NOx). Results. Out of a total of 48 subjects, 44% had asthma and 56% were healthy controls. Among subjects with asthma, 66% were obese, 10% overweight, and 24% lean; in the controls these proportions were 63%, 11%, and 26%, respectively. After adjusting for age, sex, smoking history, ethnicity, and prebronchodilator forced exhalation in 1 second (FEV1), obesity was associated with higher BAL and plasma leptin levels in asthmatics and controls. Increasing BMI was associated with increased BAL leptin and was marginally and inversely associated with BAL adiponectin. Significant associations between BAL and plasma levels were only observed for leptin. No significant associations were observed between BAL and plasma adipokines with the airway biomarkers of oxidation and inflammation. Conclusion. Increasing BMI is associated with changes in the concentrations of airway adipokines in asthmatics and healthy controls; however, these associations are not related with biomarkers of airway oxidation or inflammation.

The potential role of flaxseed oil on lead acetate- induced kidney injure in adult male albino rats

+2 caused injury, as revealed by some improvement in the histological structure of kidney as well as the restoration of the body weights loss of Pb +2 treated animals. At the same time, flaxseed oil decreased the levels of serum creatinine, blood urea nitrogen, uric acid, lipid peroxidation and nitric oxide production with concomitant elevation in glutathione, catalase, superoxide dismutase, glutathione reductase, glutathione-S-transferase and glutathione peroxidase activities. Thus, this study suggests the possibility of flaxseed oil usefulness in limiting toxicant induced by environmental heavy metals.