Showing papers on "NOx published in 1974"

Photochemical reactions initiated by and influencing ozone in unpolluted tropospheric air

Abstract: This paper presents theoretical arguments in favour of OH-concentrations larger than 10 6 molecules cm ?3 in the sunlit lower troposphere even if allowance is made for heterogeneous removal of OH, HO 2 and HNO 3 molecules. The OH-concentrations, presented in this paper, were calculated considering for the first time the photochemical effect of both scattered and direct radiation at ground levels and adopting recent accurate data for the quantum efficiency of O( 1 D) production in the ozone photolysis near 310 nm. The significant role played by OH in the atmospheric carbon, nitrogen and possibly sulphur cycles is discussed. Low background mixing ratios of NOx molecules (< 10 ?9 ) in the unpolluted atmosphere are calculated. The oxidation of NH3, initiated by the reaction with OH, may provide a significant source of tropospheric NOx-molecules, if its rate constant is about 10 ?13 cm 3 s ?1 near the ground. The conversion of NO 2 into HNO 3 , followed by heterogeneous removal of HNO 3 , is the most important tropospheric sink for NO x -molecules. The photodissociation of ozone in ultraviolet light between 300 and 330 nm, which leads to the formation of the excited O( 1 D) atom, “drives” several sequences of reactions treated in this study. Several chains of reactions, involving carbon and nitrogen compounds, lead to large rates of formation and destruction of ozone in the troposphere. These rates partly balance each other. Whether there is a net production or destruction of ozone in the troposphere cannot be determined at present. Ozone is a very active, catalytic component in the tropospheric chemical systems. Globally, the combustion source of CO for the year 1970 is more than 20% of the natural source of CO as provided by the oxidation of biologically produced CH 4 . For middle latitudes of the Northern Hemisphere the combustion source is about equal to the natural source. However, too little is known about homogeneous and heterogeneous reactions affecting the methane oxidation products. DOI: 10.1111/j.2153-3490.1974.tb01951.x

Response of commercial chemiluminescent nitric oxide-nitrogen dioxide analyzers to other nitrogen-containing compounds

Abstract: Commercial chemiluminescent oxides of nitrogen analyzers employing carbon or molybdenum converters are nonspecific for determination of nitrogen dioxide (NO/sub 2/) The instruments not only measure NO/sub 2/, but also simultaneously respond nearly quantitatively to peroxyacetyl nitrate (PAN), and a variety of other organic nitrates and nitrites Furthermore, they respond nonquantitatively to compounds such as nitroethane and nitric acid The implications of these observations are not serious for most ambient air analyses where the concentrations of the interfering nitrogenous compounds are low relative to NO/sub 2/ levels However, for highly quantitative ambient air or smog chamber measurements under circumstances where relatively low concentrations of NO/sub 2/ occur simultaneously with high concentrations of PAN and other nitrogen-containing compounds, corrections for interference by these compounds can be significant In the absence of such corrections, the NO/sub x/ mode of commercial chemiluminescent analyzers must be viewed to the good approximation as measuring total gas phase ''oxides of nitrogen,'' not simply the sum of NO and NO/sub 2/

HOx, NOx, and ClOx: Their Role in Atmospheric Photochemistry

Abstract: Sources of atmospheric odd nitrogen and hydrogen are reviewed and their role m ozone photochemistry is discussed. A model, containing few adjustable parameters, gives good agreement with observed d...

The Role of Energy-Releasing Kinetics in NOx Formation: Fuel-Lean, Jet-Stirred CO-Air Combustion

Abstract: Oxides of nitrogen concentrations, temperatures and mass flow rates near reactor blowout have been measured for chemically rate-limited, fuel-lean combustion of carbon monoxide with moist air in a jet-stirred reactor at 0.5 and 1 atmosphere. Comparisons with predictions obtained by modeling the jet-stirred reactor as a micromixed perfectly stirred reactor are used to examine the detailed influences of energy-releasing kinetic processes on NOx formation. Reaction radical intermediates and, in particular, oxygen atoms are shown to play a key role in this influence. For fuel-lean combustion, under conditions of intense turbulence and backmixing, super-equilibrium concentrations of oxygen atoms cause N2 O to act as an important intermediate leading to NOx formation. Measurements indicating the influence of finite mixing on experimental reactor performance and NOx emissions are presented as well.

Method and apparatus for turbine system combustor temperature

Abstract: A method and apparatus for operating a gas turbine system are disclosed utilizing an adiabatic combustion process, employing combustion of a pre-mixed carbonaceous fuel-air admixture in a combustion zone. The combustion and the combustion zone are maintained at an approximately constant temperature by selective control of the fuel-to-air ratio over a period of turbine operation during which the fuel demand or the combustion air temperature varies. Such combustion is conducted in the presence of an oxidation catalyst and the combustion zone including the catalyst is maintained at an approximately constant temperature. In a mode of operation which is preferred when conditions permit, such temperature is substantially above the instantaneous auto-ignition temperature of the fuel-air admixture but below a temperature that would result in any substantial formation of oxides of nitrogen. The resulting effluent is characterized by high thermal energy useful for generating power and may be low in atmospheric pollutants, including oxides of nitrogen.

Trace Gas Analysis of Power Plant Plumes Via Aircraft Measurement: O3, NOx, and SO2 Chemistry

Abstract: The gaseouis plume from an isolated 1000-megawatt power plant was systematically examined from a single engine aircraft to determine the extent to which NO x and SO 2 , chemistry occurs as a function of distance. The concentrations of ambient ozone, water vapor, and hydroxyl free radicals are indicated to be of major importance in defining the chemistry of power plant plumes during summertime conditions.

Process for removing noxious gas pollutants from effluent gases by irradiation

Abstract: Noxious gas pollutants including NOx and SO2 can be removed from effluent gases effectively and efficiently by regulating the NOx/SO2 concentration ratio so as to be in the region of 0.1 3.0, preferably 0.5 - 1.5, before the gases are irradiated with an ionizing radiation or ultraviolet light. Convenient processes for carrying out said regulation include a process in which a pretreating means for removing NOx or SO2 partly is placed before a reaction chamber. Circulation of the effluent gases between the reaction chamber and the collecting means, keeping the temperature in the collecting means at below the decomposition point of the reaction products, is efficacious for enhancing efficiency in removing said pollutants from the effluent gases.

Removal of ozone from the atmosphere by soil and vegetation

Abstract: OZONE is the principal constituent of the photochemical smog that plagues many cities in the United States. Produced by the action of sunlight on the hydrocarbons and oxides of nitrogen emitted by vehicles and industry, concentrations of ozone greater than 25×1011 molecules cm−3 (1×1011 molecules cm−3 =0.4 parts per hundred million = 8 µg m−3), used as evidence of photochemical smog1, have been observed in Los Angeles for more than two decades2. Because of lower air temperatures, less sunshine and fewer vehicles, photochemical pollution was considered unlikely to occur in Western Europe but concentrations indicative of photochemical smog have now been reported from Germany3, the Netherlands4,5 and southern England6,7 on calm, sunny days. High concentrations of ozone cause respiratory difficulties in humans8 and damage many plants9 including crops10.

Effect of Ammonia in Gaseous Fuels On Nitrogen Oxide Emissions

Abstract: The effect of ammonia in the fuel on NOx emissions was investigated through laboratory experiments and field burner tests. It was found that the degree of conversion of pm-monia to NOx was a strong function of excess air, ammonia content in the fuel, and of the degree of mixing in the flame. In premixed laboratory flames concentrations of NOx above the peak equilibrium amounts were produced. In furnace diffusion flames the conversion to NOx was much less. At substoichiometric air-fuel ratios all the ammonia appears to pyrolize, forming N2, and only very little NOx. Several methods for burning ammonia to produce low NOx emissions were investigated.

Process for selective reduction of oxides of nitrogen

Abstract: Oxides of nitrogen are selectively removed from air-polluting exhaust gases from nitric acid manufacturing plants by reaction with preferably a stoichiometric amount of ammonia in the presence of an acid-resistant aluminosilicate molecular sieve composition as catalyst.

Apparatus for elimination of nitrogen oxides from combustion waste gases

Abstract: Nitrogen oxides (NOx) are removed from combustion waste gases by injecting gas (NH 3 ) into the combustion waste gases in the presence of a metallic catalyst to deoxidize the nitrogen oxides to nitrogen and water, within a reaction tower having the catalysts moving through the reaction tower, so that thereafter the dust may be separated from the catalysts and the catalysts may be regenerated continuously, so that the regenerated catalysts may be returned to the reaction tower. The catalyst moves in a substantially closed path, and preferable downwardly through the reaction tower, with the ammonia gas and combustion waste gases moving in cross current through the reaction tower, with mixing being enhanced by a plurality of angled baffle plates. Regeneration is accomplished by washing the catalysts, particularly ferrous catalysts with water to remove ferric sulfates, thereafter providing ferrous sulfates on the surface of the ferrous catalysts, and thereafter heating the catalysts with combustion gases separate from the ammonia gases, to dry the catalysts prior to their moving into the portion of the reaction tower having therein the mixed ammonia gas and combustion waste gases.

Fuel-water vapor premix for low nox burning

Abstract: A method and apparatus for burning fuels with air, with reduced production of NOx, involves the premixing of water vapor with the fuel prior to the burning operation. Because of the low retention of water vapor at low temperatures, means are provided for preheating the fuel and spraying water into the fuel so that water vapor will be taken up by the heated fuel in sufficient quantity to provide the desired results. Various embodiments of apparatus are illustrated.

Method for simultaneous removal of SOx and NOx

Abstract: Waste gas containing sulfur oxide (SOx) and nitrogen oxide (NOx) is mixed with an ozone-containing gas to have the value x of NOx fall in the range of 1.2 to 2.5 and thereafter brought into contact with an aqueous solution containing sulfuric acid, nitric acid and an iron compound to be deprived of SOx and NOx. To the solution with which the waste gas has been brought into contact, air or oxygen is added to effect oxidation of the part of said oxides still remaining therein in an unoxidized state and regenerate the activity of the iron compound functioning as a catalyst. Part of the solution to which the addition of air or oxygen has been made is recycled as the solution for the purpose of contact with waste gas.

Metal dissolution process

Abstract: Evolution of NOx fumes during dissolution of metal values in mineral acid solutions of nitric acid can be eliminated by the addition of small quantities of hydrogen peroxide to the acid solution.

Method and apparatus for nox analysis

Abstract: OF THE DISCLOSURE Disclosed herein is an apparatus and method for NOx analysis in which a sample gas is introduced into a sample cell and mixed with oxygen to induce conversion of NO to NO2. After a given time, prior to complete con-version of NO to NO2, the absorbance and the time rate of change of absorbance is measured. The time rate of change of absorbance is indicative of the initial NO concentration in the sample gas; and the sum of the absorbance and the time rate of change of absorbance is indicative of the initial NOx concentration in the gas. A better indication of the initial NOx concentration can be obtained from the sum of the absorbance and the square root of the time rate of change of absorbance.

Preliminary Study of the Catalytic Combustor Concept as Applied to Aircraft Gas Turbines

Abstract: A catalytic combustor operating at low-equivalence ratios throughout was evaluated in terms of combustion efficiency and exhaust emissions using JP-4-fueled aircraft gas turbines. Measured nitrogen oxide concentrations were below 2 ppM (two orders of magnitude below that expected from conventional combustors) for all operating conditions tested. A definite trend of increasing NOx levels was noted for increasing exhaust temperatures, though the levels were still below the 2 ppM concentration. Virtually 100 percent combustion efficiency was obtained at combustor inlet temperatures above 700 F and fuel-air ratios above 0.02. Specific heat release rates of 3.5 million BTU/atm-hr-cu ft were achieved with high efficiency. Catalytic bed pressure drops were about 1 percent of the combustor static pressure at 44 ft/sec reference velocity and 2400 F exhaust temperature. Carbon monoxide and hydrocarbon emissions sharply increased at fuel-air ratios less than 0.0212 or exhaust temperatures less than 2000 F.

Nickel base nox reducing catalytic structure

Abstract: A system for reducing NOx gases found in the exhaust stream of the internal combustion engine is provided which includes an internal combustion engine having associated therewith a means for supplying fuel and oxygen to the engine, a manifold system for directing or channeling the exhaust gases from the engine, and a NOx reducing catalyst assembly communicating with the manifold which includes a housing having a NOx reducing catalytic structure of apertured thin metal foil positioned therein which comprises a durable, chromium containing corrosion resistant nickel base substrate having on at least one surface, an effective amount of a NOx reducing catalyst selected from the group consisting of iron, nickel, cobalt, copper, manganese and mixtures thereof.

NOx Emissions From Industrial Boilers: Potential Control Methods

Abstract: Future regulations may limit emissions of NOx from industrial/commercial boilers as well as utility boilers. The potential methods of control for these boilers are the same as those for utility boilers—low excess air, flue gas recycle, and two stage combustion. Low excess air and flue gas recycle can control NOx from thermal fixation. Two stage combustion controls both thermal and fuel NOx . Further development work is needed to apply these combustion modification procedures to industrial/commercial boilers in which volumetric heat release rate is normally quite high.

Measurement of gaseous emissions from a turbofan engine at simulated altitude conditions

Abstract: Gaseous emission from a TFE 731-2 turbofan engine were measured over a range of fuel-air ratios from idle to full power at simulated from near sea level to 13,200 m. Carbon monoxide and unburned hydrocarbon emissions were highest at idle and lowest at high power settings; oxides of nitrogen exhibited the reverse trend. Carbon monoxide and unburned hydrocarbon levels decreased with increasing altitude. Oxides of nitrogen emissions were successfully correlated by a parametric group of combustor operating variables.

Apparatus for measuring no{11 {11 concentrations

Abstract: In this apparatus, the concentration of NOx constituents in a gaseous sample is measured by reacting those constituents with ozone to obtain a chemiluminescent reaction. The ozone is obtained from an electrically energizable ozonator closely coupled to the reaction chamber. By energizing the ozonator periodically, the luminescence obtained in the reaction chamber is caused to pulsate. Accordingly, by measuring the a.c. component of the signal obtained from a photo-detector coupled to the chamber, a measure of NOx concentration is obtained, this measurement being relatively insensitive to changes to the dark current of the photo-detector.

The jet engine design that can drastically reduce oxides of nitrogen

Abstract: The NOx pollution problem of hydrogen fueled turbojets and supersonic combustion ramjets (scramjets) was investigated to determine means of substantially alleviating the problem. Since the NOx reaction rates are much slower than the energy producing reactions, the NOx production depends mainly on the maximum local temperatures in the combustor and the NOx concentration is far from equilibrium at the end of a typical combustor (L approximately 1 ft). In diffusion flames, as used in present turbojets and scramjets combustor designs, the maximum local temperature occurs at the flame and is equal to the stoichiometric value. Whereas, in the heat conduction flames, wherein the flame propagates due to a heat conduction process away from the flame to the cooler oncoming premixed unburnt gases, the maximum temperature is lower than in the diffusion flame. Hence the corresponding pollution index is also lower.

Power generation wherein sulfur and nitrogen oxides are removed

Abstract: A sulfur bearing carbonaceous fuel, particularly a low BTU gaseous fuel, is burned in a deficiency of air in the combustion zone of a boiler to form a reducing gas containing H 2 and CO in an amount in excess of that required to reduce the generated SO x to H 2 S and COS. The oxides of sulfur and nitrogen are, in part, converted to H 2 S, N 2 and/or NH 3 during heat transfer in the boiler. The balance is passed through a catalyst chamber where sulfur species are converted to H 2 S and oxides of nitrogen to N 2 and/or NH 3 . The formed H 2 S is extracted from the flue gas prior to venting to the atmosphere and recovered as free sulfur. Catalytic conversion is carried out at a temperature from about 300° to 800° F.

Low NOx emission burners

Abstract: The invention discloses a low NOx emission burner for use with an apparatus in which the material or materials are heated by the heat radiated from the radiation surface which is heated by the combustion by the burners. The secondary air injection ports or outlets are so arranged as to inject the secondary air upon the radiation surface to control the combustion, thereby reducing the release of NOx without producing CO and soot.