Showing papers on "NOx published in 1985"

Absorption of NOx gases

Abstract: Oxidation of nitric oxide is an important step in NOx absorption. Recent advances namely catalytic oxidation and the use of slrong oxidizing agents have been reviewed. The refinements which have been made in the kinetics of NO oxidation have been discussed. Several liquid phase absorbents have been suggested for the NO removal, particularly for the purpose of pollution abatement. Different models for NO oxidation using nitric acid have been analysed and the limitations of published information have been brought out. Absorption of tetravalent nitrogen oxide (NO2 and N2O4) has received considerable attention. The absorbents include water, nitric and sulfuric acids, sodium hydroxide, sodium sulfite and sodium chlorite. Absorption in water and nitric acid is important in the manufacture of nitric acid. The published information on the mechanism of NO2 and N2O4 absorption in water has been critically analysed. The problem of nitrous acid decomposition has been analysed on the basis of film theory. The predicti...

Response of chemiluminescence NOx analyzers and ultraviolet ozone analyzers to organic air pollutants

Abstract: A chemiluminescent NO/sub x/ analyzer and an ultraviolet photometry ozone analyzer were found to respond to a number of organic pollutants and mixtures in purified air. Two types of interferences were observed with the NO/sub x/ analyzer. A small positive interference as NO was observed with organosulfur compounds. Positive interferences as NO/sub 2/ were observed with nitric acid, methyl nitrate, peroxyacetyl nitrate, N/sub 2/O/sub 5/ (in O/sub 3/-NO/sub 2/ mixtures in the dark), certain nitro aromatics (nitrocresol), and chlorine-containing compounds (ClNO/sub x/) but not with peroxybenzoyl nitrate. The ultraviolet photometry ozone analyzer gave a positive response to ozone-free atmospheres containing aromatic compounds including styrene, methylstyrene, o-cresol, and nitrocresol. Since many aromatic compounds absorb light at approx. 254 nm, methods other than UV photometry should be employed to measure ozone in atmospheres containing these aromatics.

An outdoor smog chamber and modeling study of toluene–NOx photooxidation

Abstract: An experimental investigation of the gas-phase photooxidation of toluene–NO_x–air mixtures at part-per-million concentrations has been carried out in a 65-m^3, outdoor smog chamber to assess our understanding of the atmospheric chemistry of toluene. In addition, six CO-NO_x–air irradiations were conducted to characterize the chamber with regard to any wall radical sources. Measured parameters in the toluene–NO_x experiments included O_3, NO, NO_2, HNO_3, peroxyacetyl nitrate (PAN), CO, toluene, benzaldehyde, o-cresol, m-nitrotoluene, peroxybenzoyl nitrate (PBZN), temperature, relative humidity, aerosol size distributions, and particulate organic carbon. Predictions of the reaction mechanism of Leone and Seinfeld [7] are found to be in good agreement with the data under a variety of initial conditions. Additional simulations are used to investigate various mechanistic pathways in areas where our understanding of toluene chemistry is still incomplete.

The photochemistry of synoptic-scale ozone synthesis Implications for the global tropospheric ozone budget

Abstract: The oxidation of nonmethane hydrocarbons represents a source of tropospheric ozone that is primarily confined to the boundary layers of several highly industrialized regions. (Each region has an area greater than one million km2). Using a photochemical model, the global tropospheric ozone budget is reexamined by including the in-situ production from these localized regimes. The results from these calculations suggest that the net source due to this photochemistry, which takes place on the synoptic scale, is approximately as large as the amount calculated for global scale photochemical processes which consider only the oxidation of methane and carbon monoxide. Such a finding may have a considerable impact on our understanding of the tropospheric ozone budget. The model results for ozone show reasonable agreement with the climatological summer distribution of ozone and the oxides of nitrogen at the surface and with the vertical distribution of ozone and nonmethane hydrocarbons obtained during a 1980 field program.

Reactive nitrogen compounds in the Arctic

Abstract: Measurements of NO, NOx (NO + NO2), and NOy (NOx + 2N2O5 + NO3 + HONO + HO2NO2 + PAN + R-ONOx) were made in March 1983 between 200 and 12,000 m altitude on several flights in the Arctic and from Spitsbergen, Norway, to Cologne, West Germany. NO values were always below the detection limit (10 ppt); NOx values (determined with a FeSO4 converter) were high, ∼600 ppt, in the boundary layer and generally decreased sharply with altitude, although distinct strata of high NOx were observed at altitudes up to 8000 m. NOy (measured with a 425°C Mo converter) showed altitude profiles similar to NOx profiles with boundary layer values as high as 1500 ppt. Ratios of NOx to NOy were 0.81 near the surface and 0.46 at 6400 m, probably owing to higher levels of PAN or other organic compounds in the free troposphere. The possible global impact of high concentrations of reactive nitrogen compounds in the Arctic is discussed.

Method for removing nitrogen oxide contained in exhaust gas of gasoline engine

Abstract: PURPOSE:To efficiently perform denitration by bringing NOx into contact with a catalyst under the presence of O2 to oxidize and absorb it and stopping the pass of exhaust gas at the point of time when the absorption efficiency of the catalyst is reduced and using a gaseous reducing agent to reduce NO2 of the catalyst. CONSTITUTION:Exhaust gas discharged from a manifold is introduced into an oxidizing catalyst to convert CO into CO2 and introduced into either catalyst of the parallel catalysts A, B and NOx is oxidized and absorbed to the catalyst under the presence of O2. Various metals such as Mn and Fe, oxide thereof and composite oxide are used as the catalyst. When exhaust gas is introduced into the catalyst layer of one hand for a specified time and absorption efficiency is reduced, the flow of exhaust gas is changeovered to the catalyst layer of the other hand and H2 is introduced into the catalyst layer wherein exhaust gas is not flowed from an H2 generator to remove NOx and the catalyst is regenerated.

Mutagenic activity of irradiated toluene nitrogen oxide (NOx)/water/air mixtures

Abstract: Irradiated mixtures of toluene/NO/sub x//H/sub 2/O/air were brought to a steady-state distribution of reactants and products in a 22.7 m/sup 3/ flow-mode smog chamber, and the effluent was tested for mutagenic activity by exposing Salmonella typhimurium strains TA100 and TA98 to it. Two different product distributions were examined, with that corresponding to a longer extent of reaction yielding a greater mutagenic response. Vapor-phase concentrations for several aldehydes, cresols, peroxyacetyl nitrate, toluene, nitrogen oxides, ozone, and particulate matter were obtained for the reaction chamber and exposure chamber air masses. Calculations were made as to the total quantity of each product species that deposited into the biotesting medium. This information was used to speculate on what may have caused the mutagenic response.

Oxides of nitrogen and their impact upon vegetation.

Abstract: Annual and daily levels of the two major oxides of nitrogen (NOX), nitric oxide (NO) and nitrogen dioxide (NO2) are still rising in the atmosphere of the urban environment and in close proximity to automobile and airport traffic. Although oxides of nitrogen give rise to other phytotoxic pollutants such as ozone they are also in their own right damaging to plant health. This injury is not normally visible but is reflected in poorer growth and loss of productivity in terms of value and amenity. Few if any reviews have considered the effects of atmospheric concentrations of NOX as separate phytotoxic agents especially at the metabolic level. This paper is an attempt to remedy this deficiency and to promote an understanding of the problem.

Method for removing nitrogen oxide from nitrogen oxide-containing gas

Abstract: PURPOSE: To efficiently remove NOx, by contacting NOx with a catalyst in the presence of O 2 to oxidize and absorb the same by the catalyst and stopping the flowing of exhaust gas at the point of time when absorbing efficiency was lowered to contact the catalyst with a reducing agent to recover the oxidizing/ absorbing capacity thereof. CONSTITUTION: NOx-containing exhaust gas is introduced into a catalyst A through a cock C 1 to react NOx in exhaust gas in the catalyst in the coexistence of O 2 to be absorbed by the catalyst. The exhaust gas is discarded into the atmosphere through a cock C 2 while NOx is exhausted. At the point of time when the removing capacity of the catalyst was lowered, the cocks C 1 , C 2 are changed over and exhaust gas is introduced into a catalyst B. During this time, reducing gas such as H 2 is introduced into the catalyst A through a cock C 3 to reduce NOx absorbed and oxidized in the catalyst. The treated gas issued from the catalyst A is discarded into the atmosphere but, when there is the unreacted reducing agent, the treated gas is introduced into the catalyst B to oxidize the reducing agent. COPYRIGHT: (C)1987,JPO&Japio

Solid fuel and a process for its combustion

Abstract: A solid carbonaceous fuel containing up to 10% wt of calcium compounds and 0.1 to 5% wt of added iron added as oxide, carbonate or elemental iron or as as substantially halogen and sulphate-free iron-containing substances forming iron oxide or carbonate under furnace conditions. The additives act synergistically to reduce NOx.

Method for removing nitrogen oxide in diesel exhaust gas

Abstract: PURPOSE:To perform efficient denitration, by contacting NOx-containing gas with a catalyst in the presence of O2 to oxidize and absorb NOx by the catalyst and stopping the exhaust gas when absorbing efficiency is lowered to allow a reducing agent to flow and performing the reductive removal of accumulated NOx. CONSTITUTION:The exhaust gas from an engine is introduced into one of catalysts 1-a, 1-b and Nox is oxidized and absorbed by the catalyst in the presence of O2 while a gaseous reducing agent such as H2 is generated by a H2- generator 2 to be introduced into the catalyst, through which no exhaust gas flows, through a sump 5. NOx oxidized and absorbed by the catalyst is reduced and removed by the reducing agent and the catalyst is regenerated. The catalyst 1-a, 1-b are periodically changed over at the point of time when absorbing efficiency was lowered. By this method, because the reducing agent is used only in an amount necessary for reducing NOx absorbed by the catalyst, a small quantity of the reducing agent is sufficient.

Determination of nitrate by a flow system with a chemiluminescent nitrogen oxide (NOx) analyzer

Abstract: Amelioration de la sensibilite de la methode par reduction des nitrates en oxyde nitrique. Limite de detection: 1ng NO 3 − /ml pour un echantillon de 5 ml

Nitric oxide formation from thermal and fuel-bound nitrogen sources in a turbulent nonpremixed syngas flame

Abstract: Nitric oxide formation from thermal and FBN sources is studied in a turbulent nonpremixed syngas flame using laser diagnostic techniques and turbulent combustion modeling. The well-characterized syngas flame (produced by a central jet of CO/H2/N2/CH4/NH3 fuel in a co-flowing air stream) is experimentally analyzed with laser velocimetry, pulsed Raman scattering and NO probe sampling. Data for the mean and rms fluctuations of axial velocity, temperature, major species concentrations, density and mixture fraction are presented, along with yields of nitric oxide from thermal and fuel-bound nitrogen sources. A turbulent combustion model based upon time-averaged Navier-Stokes equations with k-∈ turbulence closure gives results in reasonable agreement with experiment for axial velocity and mixture fraction. This model is based upon equilibrium chemistry with an assumed shape mixture fraction pdf. It overpredicts the average temperature by as much as 250 K and underpredicts the yield of thermal NOx by a factor of 3. A simplified kinetic mechanism involving the production and destruction of NO and NH2 successfully predicts the experimentally observed trends in NOx yield from NH3 added to the syngas fuel, although the yield of NOx from NH3 is overpredicted by about 50%. Most of the theory/data discrepancies may be a result of neglecting superequilibrium radical concentrations in the theory.

A model investigation of the impact of increases in anthropogenic NOx emissions between 1967 and 1980 on tropospheric ozone

Abstract: The impact of anthropogenic NOx emission on tropospheric ozone has been investigated. Two statistical models were used for estimating annual global emissions of NOx and for driving the trend in the emission for the years 1966-1980. Both models show a steady increase in the NOx emission, except for two brief periods of leveling off: after 1973 and after 1978. The impact was estimated by calculating the rates of emissions as functions of latitude, longitude, and year, with a one-dimensional (latitudinal) model, which included coupled tropospheric photochemistry and diffusive meridional transport. Steady-state photochemical calculations with prescribed NOx emissions appropriate for 1966 and 1980 indicate an ozone increase of 8-11 percent in the Northern Hemisphere, a result compatible with the rise in ozone suggested by the observations.

Apparatus for catalytic cleaning of exhaust gases from a furnace system

Abstract: Apparatus for catalytic cleaning of the exhaust gases of furnace systems. For selectively eliminating nitrogen oxides in the exhaust gases of furnace systems, chemical compounds, such as ammonia in vapor form, are introduced into the exhaust gases emerging from the furnace systems. The exhaust gases are then passed through a catalytic converter, which initiates and/or accelerates the reaction of the oxides of nitrogen with the admixed chemical compounds. In different zones in the catalytic converter, the exhaust gases that are to be treated catalytically and of at least one current of cleaning gas are passed in a countercurrent. The location of the catalyst zones through which the exhaust gases and the cleaning gas, respectively, flow is varied continuously or intermittently. The catalytic converter has catalyst elements disposed in a carrier, and the carrier and the gas connections relative to one another.

Process and apparatus for removing oxides of nitrogen and sulfur from combustion gases

Abstract: A process for lowering the molar ratio of NO to NO2 in flue gas by converting a portion of flue gas nitric oxide (NO) to nitrogen dioxide (NO2), for removing the associated oxides of sulfur (SOx) and nitrogen (NOx) from the flue gas prior to discharge of the flue gas into the atmosphere and an apparatus for practicing the process.

Method and apparatus for reducing NOx in exhaust gases from fluidized-bed boiler

Abstract: Temperature of exhaust gases from a fluidized-bed boiler is lowered by means of heat exchange and dust entrained in the exhaust gases is efficiently collected by a dust collector. Part of the gases discharged from the dust collector are mixed with heated combustion air and are charged into a fluidized bed. Therefore, problems caused by dust entrained in the exhaust gases to be mixed with the combustion air as well as the cold corrosion problem can be substantially solved so that the technique for reducing the NOx contents in the exhaust gases from the fluidized-bed boiler is satisfactorily established.

Verfahren zur Minderung von NOx-Emissionen in Rauchgasen

Abstract: Processes for lowering NOx emissions in flue gases. The authors survey processes currently under development for reducing NOx emission levels of combustion units. Primary measures, i.e. acting upon the combustion process itself, do not suffice to meet the recently stiffened limiting emission values; particular attention is therefore paid to secondary measures involving the flue gases. The article describes both wet processes and dry catalytic and non-catalytic processes, some of which can also be employed for simultaneous removal of NOx and SO2. In view of the fast large-scale implementation demanded, only a few, already extensively developed processes will presumable be accepted, and will play a considerable role on an industrial scale.

Method and apparatus for reducing NOx in internal combustion engine

Abstract: A method of reducing the amount of nitrogen oxides (NOx) in an internal combustion engine in which the air/fuel ratio is controlled higher than a theoreticl air/fuel ratio during normal operation of a vehicle, characterized in that the air/fuel ratio is controlled lower than the theoretical air-fuel ratio for a predetermined period of time during acceleration from the start of acceleration, the control being effected by means for detecting an accelerated state of the vehicle, means for measuring the lapse of time during acceleration from the start of acceleration and means for performing an acceleration increment correction upon detection of acceleration.

Method of removing oxides of sulfur and oxides of nitrogen from exhaust gases

Abstract: A continuous method is presented for removing both oxides of sulfur and oxides of nitrogen from combustion or exhaust gases with the regeneration of the absorbent. Exhaust gas is cleaned of particulates and HCl by a water scrub prior to contact with a liquid absorbent that includes an aqueous solution of bisulfite and sulfite ions along with a metal chelate, such as, an iron or zinc aminopolycarboxylic acid. Following contact with the combustion gases the spent absorbent is subjected to electrodialysis to transfer bisulfite ions into a sulfuric acid solution while splitting water with hydroxide and hydrogen ion migration to equalize electrical charge. The electrodialysis stack includes alternate layers of anion selective and bipolar membranes. Oxides of nitrogen are removed from the liquid absorbent by air stripping at an elevated temperature and the regenerated liquid absorbent is returned to contact with exhaust gases for removal of sulfur oxides and nitrogen oxides.

Determination of carbon balances for smog chamber terpene oxidation experiments using a 14C tracer technique

Abstract: In the last decade, numerous studies of monoterpene hydrocarbons in the presence of ozone and oxides of nitrogen have been completed. Although insights about the reactivity of terpenes have been gained, and several products have been identified in the gas and aerosol phases, carbon balances have been generally poor. This paper describes a radiotracer technique which accounts for carbon-containing compounds in a smog chamber at the conclusion of a photooxidation or ozonolysis reaction. Instead of attempting to identify individual products, gas-phase compounds were separated from aerosols, and each phase was analyzed by a liquid scintillation counter. A carbon balance of 79 to 97% was obtained with 14C-α-pinene and ozone using this technique. The significance of the results are discussed in terms of the 14C-α-pinene concentrations used in this study, which were lower than concentrations used previously by one to four orders of magnitude. In spite of the lower concentrations, the gaseous and aerosol fractions observed in the present investigation are comparable to those observed by others. Possible reaction products are discussed with respect to likely mechanisms for α-pinene oxidation.

EFFECT OF Nb2O5 ADDITION ON THE CATALYTIC ACTIVITY OF FeOx FOR REDUCTION OF NOx WITH NH3 AND O2

Abstract: Niobium oxide, Nb2O5, remarkably enhanced the catalytic activity of FeOx for the reduction of NOx with NH3 and O2. Thus, for the reduction catalyzed by FeOx containing a small amount of Nb2O5, the conversion attained 90–100% in contrast to less than 40% for the reduction catalyzed by FeO without Nb2O5. The catalytic activity of the mixed oxide was scarcely affected by addition of SO2 to the reaction gas.