Showing papers on "NOx published in 1977"

NOx Production in Lightning

Abstract: The rate of odd nitrogen (NOx) production by electrical discharge through air was theoretically and experimentally estimated to be about 60,000 trillion NOx molecules per joule. The theoretical treatment employed a cylindrical shock-wave solution to calculate the rate of NOx production in high temperature reactions. The limits obtained were experimentally verified by subjecting a regulated air flow to electrical discharges followed by a measurement of NOx production using chemiluminescence. These measurements also indicated that water vapor content has no detectable effect on the NOx production rate. The results imply that lightning is a significant source of NOx, producing about 30-40 megatons NOx-N per year and possibly accounting for as much as 50% of the total atmospheric NOx source.

Urea reduction of NOx in fuel rich combustion effluents

Abstract: Method of reducing NO x in fuel rich combustion effluents is provided comprising introducing urea at temperatures in excess of about 1900° F. in the presence of excess fuel, wherein said urea is introduced either as a solid or solution in amounts sufficient to reduce the NO x concentration.

The tropospheric and stratospheric composition perturbed by NO x emissions of high‐altitude aircraft

Abstract: The effect of aircraft flight altitude on atmospheric ozone has been studied by using NOx emitted from hypothetical fleets operating individually in an altitude range between 10.8 and 18 km. Three classes of aircraft fleets were chosen so as to cover the present subsonic types operating at a typical altitude of 10.8 km, advanced subsonics at either 12.7 or 14.5 km, and present SST's (Concorde and Tupolev) at about 18 km. The study is based on the use of an empirical two-dimensional (2-D) photochemical model of the troposphere and stratosphere. An important characteristic of this model is the incorporation of the methane oxidation reactions, which produce ozone in the troposphere and lowest stratosphere. The chemical system otherwise includes the mechanisms of stratospheric ozone destruction by NOx and HOx. The model did not include chlorine reactions. The 2-D model reproduces several characteristics of the latitudinal and seasonal variations in ozone and other species. Other characteristics of the model are (1) the numerical simulation of water vapor data in the natural troposphere and stratosphere and (2) the inclusion of Rayleigh scattering for wavelengths longer than 300 nm in the determination of photodissociation rates. Results are presented in terms of ozone column changes as a function of latitude and season for the assumed (not forecast) NOx injection rates for each fleet. In general, the results show (1) a small (less than 1%) enhancement in the ozone column due to the methane oxidation reactions in regions of heavy traffic for injections at 10.8 km,(2) almost no effect on the ozone column for injections at 14.5 km, and (3) a decrease in the ozone column due to the NOx catalytic cycle for SST injections at 18 km. These results for the present and advanced subsonics contradict earlier Climatic Impact Assessment Program results showing an ozone decrease due to subsonic aircraft. The conclusions from this 2-D model are still of a preliminary nature owing to the uncertainties in the knowledge of the atmospheric chemistry and dynamics. Furthermore, this study could not incorporate the effect of aircraft water emissions on the ozone balance, which may well be a significant factor to consider.

Ozone and oxides of nitrogen production during thunderstorms

Abstract: A theory on the production of ozone, nitrous oxide, nitric oxide, and nitrogen dioxide during a thunderstorm is presented. The catalytic agents for the production of the molecules are lightning and point discharges. The concept of an efficiency parameter giving the number of molecules produced per unit of energy absorbed by the atmospheric constituents from lightning or point discharges is central to the theory. Values of the efficiency parameters are given for two cases. In one case the parameters are for atomic oxygen and nitrogen recombining with the atmospheric constituents. In the other case the parameters are for an equal number of neutral and ionized atomic species of oxygen and nitrogen recombining with the atmospheric constituents. Parameters for the two cases, which should span the actual physical situation, are given because the degree of ionization of the recombining atoms is unknown. Parameters relevant to laboratory discharges and lightning are given. An assessment of the importance of thunderstorms as a worldwide source of ozone, nitric oxide, and nitrogen dioxide would require a much better understanding of the sinks and transport processes; however, thunderstorms are likely to be important as a large interim source of ozone and oxides of nitrogen for areas near and in thunderstorms. If certain suggested reactions for the production of nitrous oxide are verified, thunderstorms could be an important worldwide source of nitrous oxide.

Water-promoted oxidation of carbon monoxide over tin(IV) oxide-supported palladium

Abstract: CATALYTIC oxidation of CO, both by O2 and by nitrogen oxides (NOx), is of considerable relevance to the removal of toxic CO and/or NOx from exhaust gases. Certain applications such as automobile exhaust control in cold-start conditions, and the removal of CO from tobacco smoke by use of a catalytic filter, demand not only catalytic activity at moderately low temperatures, but also effectiveness in the presence of water vapour. The low-temperature activities of most catalysts are at best (for example precious metals) partially destroyed, or at worst (for example base metal oxides) totally destroyed by poisoning due to water vapour. The results presented here demonstrate that, not only is the low-temperature activity of the Pd–SnO2 system not poisoned by water vapour, but rather its presence causes a marked enhancement in activity for the oxidation of CO both by O2 and by NO.

Method and apparatus for reducing NO{HD x {b from furnaces

Abstract: NOx produced by combustion of nitrogen-containing fuels is reduced by a forced draft burner operating with below stoichiometric mixtures of air and fuel in a primary combustion chamber, combustion being completed by controlled injection of secondary air near the outlet of the chamber.

Method for reducing NOx emission to the atmosphere

Abstract: An improved method and apparatus for reducing NOx emissions to the atmosphere from stationary combustion sources. The improvement is accomplished by providing a plurality of zones and/or stages for injecting a suitable reducing gas and then injecting the reducing gas through one or more of said zones. The particular zone or zones actually used will be determined by temperature of the combustion effluent gas in the immediate vicinity thereof. Similarly, the exact composition of the reducing gas employed will be determined by the same temperature.

Process for abating concentration of nitrogen oxides in combustion flue gas

Abstract: Nitrogen oxides in a combustion flue gas are removed by reduction in a gaseous phase at a low temperature in the absence of any catalyst by adding urea and an oxidizing agent for decomposition of urea, such as ozone, nitric acid, hydrogen peroxide, chlorine, chlorine dioxide, or oxy acids of chlorine or their salts. NOx removal can be carried out in a very simplified manner with high percent NOx removal.

NOx formation in premixed turbulent flames

Abstract: NOx formation has been studied in lean, premixed, turbulent flames stabilized by perforated plates. The burner pressure was atmospheric, but other parameters were representative of gas turbine operating conditions. Prevaporized Jet A fuel was injected into preheated unvitiated air and thoroughly mixed prior to combustion. Mixture inlet temperature was 750°K and total residence times were approximately 4 msec. NOx, CO, CO2 and hydrocarbon levels were measured along the jet and recirculation zone axes. Results show a very rapid increase in NOx in the reaction zone which cannot be accounted for by O-atom radical overshoot. Post-flame zone NOx formation rates agree with the predictions of equilibrium theory. The relative contribution of “prompt NOx” to the final NOx levels increases with decreasing equivalence ratio. The rate of NOx formation in the reaction zone is found to be higher than in laminar flames. Turbulent transport processes are believed to be the dominant effect. NOx formation via nitrous oxide intermediate does not appear to be important under the present experimental conditions. Large amplitude temperature oscillations observed in turbulent premixed flames were found not to affect NOx formation rates.

Low pollution combustor

Abstract: A low pollution combustor is shown for controlling gas turbine pollutant emission, especially NOx. Fuel is injected and mixed with air upstream of the combustion zone. An axially movable baffle controls the air flow so that the fuel-air ratio is precisely controlled passing into the primary combustion zone. A baffle recirculation zone prevents overheating of the walls. Dilution air is provided downstream of the primary zone for temperature dilution of the gases and to inhibit further formation of nitrogen oxides.

Potential Ozone Column Increase Resulting from Subsonic and Supersonic Aircraft NOX Emissions

Abstract: A two-dimensional time-dependent photochemical model developed to describe the meridional distribution of the important trace species in the stratosphere and troposphere continuously throughout the year has been used to estimate the effect on ozone of NOX emissions; supplied by the Federal Aviation Administration (FAA), from a combined fleet of supersonic and subsonic aircraft projected to be operational in 1990. The net effect of this combined fleet is to increase the atmospheric ozone level slightly (maximum local column change <1.5%) for the given chemical system. High-altitude injections of NOX result in a decrease in the ozone column above approximately 15-16 km, as predicted in numerous previous studies. However, this reduction is smaller than the increase in the ozone column resulting from the production of ozone through the methane-smog chemical cycle resulting from the large amount of NOX deposited at lower altitudes (L 13 km). Relative latitudinal and seasonal variations of the ozone change are large, being greatest in the fall and least in the late spring and summer seasons. Since the changes in the ozone column are sensitive to the methane-smog reaction system, more information regarding the rates at which these reactions proceed is needed to affirm the present initial estimates.

Process for catalytically treating exhaust gas containing NOx in the presence of ammonia gas

Abstract: A process for treating an exhaust gas containing nitrogen oxides, oxygen and ammonia gas with a catalyst consisting essentially of titanium oxide, copper oxide in an amount of 0.02 to 0.3 mole and molybdenum oxide or tungsten oxide in an amount of 0.01 to 0.5 mole per one mole of the titanium oxide. Because the catalyst exhibits good properties for decomposition of ammonia as well as for decomposition of nitrogen oxides it is possible to avoid secondary pollution due to unreacted ammonia.

Hydroxyl radical and atomic oxygen concentrations in high-intensity turbulent combustion

Abstract: Spectroscopic measurements of OH-radical and O-atom concentrations are analyzed for high-intensity turbulent combustion of methane/air in a modified Longwell jet-stirred reactor at conditions P=0.92 atm, ΦFA=0.57 to 1,33, andm0307/V=1.89×10−2 to 4.03 ×10−2 g/cm3-s. Absolute OH concentrations were determined from the measured integrated absorption of resolved spectral lines in the OH2π-2+ (0,0) band. Atomic oxygen was inferred from chemiluminescence measured at 3500due to the radiative recombination CO+O→CO2+hv. Thermocouple temperatures varied from 1440 to 1910°K, with the OH rotational temperature being greater by ca. 7%. Hydroxyl radical concentrations versus equivalence ratio exhibited an apparent maximum near ΦFA≅0.85, and increased with increasingm0307/V. Partial equilibrium between OJ and O-atom was also observed in the vicinity of ΦFA≅0.85. The peak O-atom concentration occurred at FA≅0.8. Form0307/V=1.89×10−2 g/cm3-s, the peak values for OH and O-atom were 2700 and 720 ppm (molar), respectively. Calculations of NOx formation, using the PSR model with the measurements of OH and O-atom concentrations and rotational temperature as input, fell below measurements of NOx determined by gas sampling.

Aircraft emissions: potential effects on ozone and climate: a review and progress report. Final report

Abstract: A critical review is made of information relative to effects of aircraft emissions (NOx, SO2, H2O) projected to 1990 on the earth's protective ozone shield and on mean surface temperature, as estimated from appropriate mathematical models. Potential biological effects are not reviewed. The review provides information showing the large uncertainties in computations of effects on ozone, due to uncertainties in NOx emission indices (accepted values may be several-fold low), in chemistry, in troposphere-stratosphere interchange processes, and in future stratospheric composition (principally chlorine content); estimates of effects can be expected to change as new data are obtained. Current results indicate that aircraft NOx effects on the ozone column change sign with aircraft altitude: subsonic aircraft, cruising at 6-km to 14-km altitude, enhance or have almost no effect on the ozone column; supersonic aircraft (mach-2 class), cruising at 16-km to 19-km, reduce total ozone, but, for given NOx rates, by amounts less than previously reported. Computations based on a 'high' (rapid growth) estimate for the 1990 total fleet of subsonic and supersonic aircraft, assuming current engines and accepted NOx emission indices, including an estimated 142 Concordes and Tupolevs, showed an average ozone enhancement in the Northern Hemisphere of about 0.4 percent tomore » 0.9 percent, varying with season.« less

NOx formation from nitrogen in fuel and air during turbulent diffusion combustion

Abstract: To examine the comprehensive processes for NO x formation from nitrogen molecules in the air or in the nitrogen compounds in the fuel during turbulent diffusion combustion, radial and axial profiles of NO x , HCN and NH 3 were measured in turbulent diffusion flames with or without addition of nitrogen compound (NH 3 or NO) to the fuel or the air. High concentrations of HCN were detected in the propane flames without addition of nitrogen compounds which confirms the significance of NO formation by reactions related to HCN. Addition of NH 3 to the fuel results in higher concentrations of NO and HCN in the propane flames but HCN decays when mixed with excess air and decomposition of NO is observed in the fuel-rich region accompanying HCN formation. In CO+H 2 flames, however, scarcely any HCN is observed and the overall conversion rate of NH 3 into NO is very low as compared with that of propane flames. The behavior of the NO concentration observed in these flames is determined by its formation and destruction via HCN or NH x , coupled with mixing with air. The comprehensive reaction processes are also discussed.

Method for reducing the concentration of nitrogen oxide in combustion effluent gas

Abstract: PURPOSE: A nitrogen oxide eliminating method capable of effectively eliminating NOx in low concentration contained in combustion effluent gas and applied to dirty gas containing a large amount of smoke dust. COPYRIGHT: (C)1978,JPO&Japio

Oxygen concentration detector

Abstract: The present invention relates to an oxygen concentration detector to be used in a system which can simultaneously dispose of the three harmful elements in automotive emissions, i.e., unburnt hydrocarbons (unburnt HC), carbon monoxide (CO) and nitrogen oxides (NOx) through reaction with catalyst. In said detector an oxygen concentration cell comprises a solid electrolyte of a special ceramic material characterized by oxygen ion-conductivity; and the oxygen concentration of a measured gas can be analyzed by measuring the electromotive force generated through a difference in the oxygen partial pressure between the measured gas and a reference gas.

Method and means for reducing pollutants from the exhaust of hydrocarbon fuel combustion means

Abstract: Method and apparatus for reducing the nitrogen oxide component from the oxygen-poor combustion products of a hydrocarbon fuel combustion device, which product would ordinarily contain an undesirable excess quantity of oxides of nitrogen. The method and apparatus include the means for associating gaseous hydrocarbon compounds in said products of combustion at a sufficiently high temperature in a related selected contained volume such that a degree of acceleration of the reduction of oxides of nitrogen is obtained so that the NO is reduced to an acceptable level within a selected reaction time related to said volume which reaction time, volume and temperature are reasonably associated with or present within said combustion device.

Evaluating Characteristic Time Emissions Predictions for Three Vehicular Gas Turbine Combustors

Abstract: The standard GT-309 combustor and two modified versions were tested in a flow-rig over the range of steady-state conditions simulating combustor operation in a GT-309 regenerative gas turbine engine. Based on measured emissions of the standard combustor, a characteristic time model developed by Mellor was used to predict the carbon monoxide, total oxides of nitrogen, and total hydrocarbons emissions for the two modified combustors. The total oxides of nitrogen emissions were predicted to within one standard deviation for all conditions. The carbon monoxide emissions were not usually predicted within one standard deviation, and the predicted and experimental trends were conflicting. The predicted total hydrocarbons emissions suffered the same inaccuracy. However, the modified combustors did exhibit reduced emissions. The strong dependence of carbon monoxide emissions from the standard combustor on atomizing-air pressure drop at low engine-power conditions was successfully correlated by the model as a shift in quenching location. The oxides of nitrogen emissions for the standard combustor at high power conditions were not accurately correlated by the model because the quenching of nitric oxide formation was not completed within the combustor. 16 figures.

Performance and emissions of a catalytic reactor with propane, diesel, and jet a fuels

Abstract: Tests were made to determine the performance and emissions of a catalytic reactor operated with propane, No. 2 diesel, and Jet A fuels. A 12-cm diameter and 16-cm long catalytic reactor using a proprietary noble metal catalyst was operated at an inlet temperature of 800 K, a pressure of 300,000 Pa and reference velocities of 10 to 15 m/s. No significant differences between the performance of the three fuels were observed when 98.5 percent purity propane was used. The combustion efficiency for 99.8-percent purity propane tested later was significantly lower, however. The diesel fuel contained 135 ppm of bound nitrogen and consequently produced the highest NOx emissions of the three fuels. As much as 85 percent of the bound nitrogen was converted to NOx. Steady-state emissions goals based on half the most stringent proposed automotive standards were met when the reactor was operated at an adiabatic combustion temperature higher than 1350 K with all fuels except the 99.8-percent purity propane. With that fuel, a minimum temperature of 1480 K was required.

Significance of peroxynitric acid in atmospheric chemistry of nitrogen oxides

Abstract: KNOWLEDGE of the life cycle and budget of nitrogen oxides in the atmosphere is important for several reasons. In the stratosphere, NO and NO2 (NOX) play a dominant part in maintaining the structure and stability of the ozone distribution. In the troposphere, NOX is involved in the production and destruction of OH radicals which control the fluxes of many important species such as CH4, CO, H2 and CH3Cl, to the stratosphere. In polluted urban areas, NOX chemistry provides the basic formation mechanism of photochemical air pollution. In all these areas of atmospheric chemistry, the interactions of NOX with HOX species (HO, HO2 and so on) are of great significance, particularly the reactions of HO2 with NO and of HO with NO2. A further HOX–NOX interaction is the proposed1 formation of peroxynitric acid in reactions (1) and (−1): We present here a study of the extent to which reaction (1) and (−1) acts as a sink for HOX and NOX in the atmosphere.

Oxygen recycle ozone generator

Abstract: PURPOSE: To accomplish prolonged continuous supply of O 3 by means of NOx removal equipment installed between ozone adsorption towers and an ozone generator to prevent adsorption of NOx by the ozone adsorption towers, NOx removal maintain constant adsorption of ozone, and restrain change in the concentration of removable ozone. COPYRIGHT: (C)1978,JPO&Japio

Diesel engine combustion unti

Abstract: PURPOSE:In a combustion unit consisting of two sub-chambers and a main chamber which are communicated to each other, the control of the increase of the fuel consumption rate and the waste fuel concentration and the lowering of NOx concentration are preformed by establishing the air flow rate of the nozzle of the second sub-chamber which is opened at the main chamber at a comparatively low speed area.

Sintered metal oxide semiconductor having electrical conductivity highly sensitive to oxygen partial pressure

Abstract: Tin oxide doped with magnesium oxide or niobium pentoxide and prepared as a sintered material is found to be highly sensitive to oxygen partial pressure both in the presence of free oxygen and in the presence of oxidizable gases, such as carbon monoxide or the lower oxides of nitrogen, and even in the presence of mixtures of both, such as in the exhaust gas of an internal combustion engine. The electrical conductivity varies by substantially more than an order of magnitude in response to a change in the oxygen partial pressure of about one-half an order of magnitude. The doped oxides operate as poor catalysts for the oxidation of oxidizable components of the exhaust gases. Chromium oxide doped with tin oxide shows the effect of an excessively good catalysis from the point of view of range of measurement, but is usable to give a sharp indication of the appearance or disappearance of free oxygen in a gas mixture. Zinc oxide doped with aluminum oxide has a conductivity that is good for measuring the content of free oxygen, but is of questionable value in the presence of a substantial concentration of carbon monoxide.

Aircraft Emissions: Potential Effects on Ozone and Climate - A Review and Progress Report

Abstract: : A critical review is made of information relative to effects of aircraft emissions (NOx, SO2, H2O) projected to 1990 on the earth's protective ozone shield and on mean surface temperature, as estimated from appropriate mathematical models. Potential biological effects are not reviewed. The review provides information showing the large uncertainties in computations of effects on ozone, due to uncertainties in NOx emission indices (accepted values may be several-fold low), in chemistry, in troposphere-stratosphere interchange processes, and in future stratospheric composition (principally chlorine content); estimates of effects can be expected to change as new data are obtained. Current results indicate that aircraft NOx effects on the ozone column change sign with aircraft altitude: subsonic aircraft, cruising at 6-km to 14- km altitude, enhance or have almost no effect on the ozone column; supersonic aircraft (mach-2 class), cruising at 16-km to 19-km, reduce total ozone, but, for given NOx rates, by amounts less than previously reported. Computations based on a 'high' (rapid growth) estimate for the 1990 total fleet of subsonic and supersonic aircraft, assuming current engines and accepted NOx emission indices, including an estimated 142 Concordes and Tupolevs, showed an average ozone enhancement in the Northern Hemisphere of about 0.4 percent to 0.9 percent, varying with season.

A Potential Low NOx Emission Combustor for Gas Turbines Using the Concept of Hybrid Combustion

Abstract: An experimentally verified NOx emission model has been described previously to predict accurately the NOx emission characteristics of conventional gas turbine combustors as well as laboratory scaled premixed combustor. Experimental data and analyses indicated that a hybrid combustor, which utilizes features of both the conventional and the premixed combustors, has the potential to be a viable low NOx emission combustor. Initial calculations indicated low NOx emission levels for the hybrid combustor. This hybrid combustion concept was tested in the laboratory. The measured NOx emissions from this laboratory-scaled hybrid combustor were in excellent agreement with the analytical predictions. The emissions of carbon monoxide and unburned hydrocarbons were also measured. It has been concluded from an analysis of the measured data that a gas turbine combustor, designed with the hybrid combustion concept, has the best potential to be a near-term viable combustor in meeting the EPA proposed gas turbine emission regulations. The experimental effort thus far has focused on the emission characteristics. Other areas of the design, such as the vaporization of liquid fuels, require additional development work prior to the incorporation of this concept into a viable system for an engine application.