Showing papers on "NOx published in 1973"

Reduction of sulfur trioxide and nitrogen oxides by secondary fuel injection

Abstract: Tests with an experimental laboratory burner showed that sulfur trioxide can be reduced to SO2, and nitrogen oxides to nitrogen, by the injection and combustion of a clean secondary fuel downstream of the primary combustion zone. Sulfur trioxide and nitrogen oxides from fuels containing sulfur or nitrogen are formed in the primary flame by free radical reactions involving such species as the O atom. These reactions can apparently be reversed by a secondary combustion, which lowers the O2 concentration. Our results suggest that this method of pollution abatement, which, for brevity, we call “reburning”, may, with further development, be applicable for the reduction of SO2 and NOx emissions from coal- or oil-fired furnaces, boilers, and incinerators, wherever the primary flame must be operated at excess air.

Catalytically-supported thermal combustion

Abstract: A method for the catalytically-supported thermal combustion of carbonaceous fuel comprising the adiabatic combustion of at least a portion of the fuel admixed with air in the presence of a solid oxidation catalyst at an operating temperature 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 by low amounts of atmospheric pollutants, especially oxides of nitrogen.

Odd Nitrogen in the Atmosphere

Abstract: Sources and sinks for atmospheric odd nitrogen are discussed and detailed calculations are presented for the altitude range 0–80 km. The mixing ratio of odd nitrogen is approximately 2×10−9 throughout the troposphere and increases in the stratosphere to a value of order 2×10−8 at 40 km. The dominant atmospheric forms of odd nitrogen are HNO3, NO2 and NO. Nitric acid is the major form below 25 km. Nitric oxide is the most abundant constituent during the day and at night is efficiently converted to NO2 below 65 km. Possible modification of stratospheric NOx by supersonic aircraft is discussed and it is concluded that the consequences may be detectable if the globally averaged source of NO from stratospheric aviation should exceed 4×107 molecules cm−2 sec−1.

Gas turbine engine with means for reducing the formation and emission of nitrogen oxides

Abstract: Means for reducing the formation and emission of nitrogen oxides in a gas turbine engine provide for bleeding and cooling a portion of the airflow pressurized by the compressor. The cooled compressor bleed airflow is then introduced into the primary combustion zone of the combustor in order to reduce the flame temperature effecting a reduction in the rate of formation of oxides of nitrogen.

Process for disposal of oxides of nitrogen

Abstract: A process for converting gases containing oxides of nitrogen into gases which may be safely vented to the atmosphere wherein the gases containing the oxides of nitrogen (NOx) are mixed with excess combustible products obtained by burning a hydrocarbon fuel with less than its stoichiometric requirements of oxygen, the mixture thus obtained is cooled to avoid temperatures substantially above 2,000 DEG F. but not below about 1,200 DEG F., the combustible material remaining after substantially all of the oxides of nitrogen have been reduced to nitrogen are oxidized, so that the resulting gas, substantially free of NOx and carbon monoxide (CO), may be vented to the surrounding atmosphere without contamination of the environment and without smoke or other particulate matter.

Two stage combustion process

Abstract: A method is disclosed which encompasses a two stage combustion process wherein a carbonaceous fuel, which when burned with stoichiometric amount of air has an adiabatic flame temperature of at least 3,300* F., admixed with air is partially combusted in a thermal zone. The effluent is quenched and then contacted with a solid oxidation catalyst to combust or oxidize the fuel under essentially adiabatic conditions. The operating temperature of the catalyst is preferably 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, for example at a temperature of about 1,500* to 3,200* F. The resulting effluent is characterized by high thermal energy useful for generating power and by low amounts of atmospheric pollutants, especially oxides of nitrogen.

Ozonolysis Rates of Some Atmospheric Gases

Abstract: Rate constants were measured for the gas phase reactions of ppm concentrations of ozone in air with acetylene, acetaldehyde and toluene as 8.6 ± 0.9, 3.4 ± 0.5 and 1.2 ± 0.6 × 10-20 cm3 molecule-1 sec.-1, respectively, using the O3/NO chemiluminesence detector. Toluene, xylene, methane and carbon monoxide were also investigated and upper limits for the rate constants were obtained. Combination with data on olefins and oxides of nitrogen gives a quantitative assessment of the various contributions to the removal of atmospheric ozone.

Catalytic treatment of recycle gases for an internal combustion engine

Abstract: A small catalyst reactor section is mounted in association with the exhaust gas outlet means in order to obtain heat transfer and rapid warm-up for oxidation catalyst maintained in the reactor that will, in turn, provide conversion for a hydrocarbon containing crankcase vent stream being returned from the crankcase vent means to the engine intake manifold system. In addition, means may be provided for passing a regulated portion of exhaust gases into and through the same reactor in order to supply resulting CO2 and water vapor as generally inert material to the engine intake and to the combustion zones for reducing flame front temperatures and effecting reductions in NOx emissions.

Pure oxygen supply to an internal combustion engine

Abstract: A method for decreasing hydrocarbons and oxides of nitrogen emanating from the exhaust system of an internal combustion engine involves supplying substantially pure oxygen to the air intake means of the engine. Such pure oxygen may be passed from a tank in which it is stored to the air intake means of the engine. The pure oxygen may be created by storing a chemical compound in a chamber and heating the chamber so that the compound may release the oxygen, or oxygen can be created by electrolytically decomposing water, passing oxygen generated by such decomposition into a storage tank coupled to the air intake means of the engine.

Emission control process and system

Abstract: An emission control system is disclosed for reducing gaseous emissions contained in exhaust gases from combustion processes, whether internal or external. The system is applicable to the exhaust systems of wheeled vehicles, stationary internal combustion engines, diesel engines and external combustion systems. The system is primarily useful in the removal of nitrogen oxides from combustion exhaust gases. The combustion gases containing oxides of nitrogen are contacted with a nitrogen-containing compound or compounds which provide nascent hydrogen, an electron acceptor, resulting in reduction of the oxides of nitrogen. Ammonia, hydrazine, primary, secondary and tertiary amines are exemplary of the compounds which may be used. An oxidation unit is preferably used in conjunction with the system for reduction of oxides of nitrogen to substantially reduce unburned hydrocarbons and carbon monoxide contained in the combustion exhaust gases. Combustion exhaust gases from an internal or external combustion process, containing unburned hydrocarbons, carbon monoxide and oxides of nitrogen, are introduced into an oxidation unit, catalytic or thermal, wherein the unburned hydrocarbons and carbon monoxide are oxidized to carbon dioxide and water. The gases exiting from the oxidation zone are then contacted with a nitrogen-containing compound or compounds which react with the nitrogen oxides. For wheeled vehicles the emission control system is connected to the ignition lock assemkly so that, when the ignition is turned on, the emission control system is activated.

Method for removing the oxides of nitrogen as air contaminants

Abstract: A method for treating a stream of combustion effluents, containing NOx and other contaminants, said method comprising the steps of first contacting the stream with a sufficient amount of hydrocarbon in the presence of oxygen at a temperature ranging from 400 to 2,700*C. for sufficient time to substantially reduce the NOx to molecular nitrogen; contacting the reduced stream with sufficient oxygen at a temperature ranging from 400 to 2,700*C. for a time sufficient to substantially oxidize all other contaminants to an oxidized state. It has been found that this reduction can also be carried out in an intermittent manner in which the reducing hydrocarbon-oxygen mixture can be shut off for hours at a time with continuing NO- removal (the self-contained reductant mode).

Parametric test results of a swirl-can combustor

Abstract: Pollutant levels of oxides of nitrogen, unburned hydrocarbons, and carbon monoxide were measured for three models of an experimental, annular swirl can combustor. The combustor was 1.067 meters in outer diameter, incorporated 120 modules, and was specifically designed for elevated exit temperature performance. Test conditions included combustor inlet temperatures of 589, 756 and 839 K, inlet pressures of 3 to 6.4 atmospheres, reference velocities of 21 to 38 meters per second and combustor equivalence ratios, based on total combustor flows of 0.206 to 1.028. Maximum oxides of nitrogen emission index values occurred at an equivalence ratio of 0.7 with lower values measured for both higher and lower equivalence ratios. Oxides of nitrogen concentrations, to the 0.7 level with 756 K inlet air, were correlated for the three models by a combined parameter consisting of measured flow and geometric parameters. Effects of the individual parameters comprising the correlation are also presented.

Effect of inlet-air humidity, temperature, pressure, and reference Mach number on the formation of oxides of nitrogen in a gas turbine combustor

Abstract: Tests were conducted to determine the effect of inlet air humidity on the formation of oxides of nitrogen (NOx) from a gas turbine combustor. Combustor inlet air temperature ranged from 506 K (450 F) to 838 K (1050 F). The tests were primarily run at a constant pressure of 6 atmospheres and reference Mach number of 0.065. The NOx emission index was found to decrease with increasing inlet air humidity at a constant exponential rate: NOx = NOx0e-19H (where H is the humidity and the subscript 0 denotes the value at zero humidity). the emission index increased exponentially with increasing normalized inlet air temperature to the 1.14 power. Additional tests made to determine the effect of pressure and reference Mach number on NOx showed that the NOx emission index varies directly with pressure to the 0.5 power and inversely with reference Mach number.

Formation of hydrocarbons and oxides of nitrogen in automobile engines.

Abstract: The basic mechanisms responsible for the production of nitrogen oxide and hydrocarbon emissions from automotive spark-ignition engines are reviewed. It is shown how the formation of nitric oxide is rate controlled in the high-temperature burned gases inside the engine cylinder. A mathematical model which predicts nitric oxide emissions for given engine design and operating variables is then described. In contrast, the hydrocarbons are formed when the flame quenches at the cylinder head and piston walls. The magnitude of these quench layers and crevices and the boundary layer aerodynamics by which the hydrocarbon-rich gases exit the cylinder are discussed. /Author/

Instantaneous photochemical rates in the global stratosphere

Abstract: Starting with the average actual distribution of ozone (Dutsch [15]) and temperature in the stratosphere, we have calculated the solar intensity as a function of wavelength and the instantaneous rates (molecules cm−3 sec−1) for each Chapman reaction and for each of several reactions of the oxides of nitrogen. The calculation is similar to that ofBrewer andWilson [5]. These reaction rates were calculated independently in each volume element in spherical polar coordinates defined by ΔR=1 km from zero to 50, δϑ=5° latitude, and δo=15° longitude (thus including day and night conditions). Calculations were made for two times: summer-winter (January 15) and spring-fall (March 22). As input data we take observed solar intensities (Ackerman [1]) and observed, critically evaluated. constants for elementary chemical and photochemical reactions; no adjustable parameters are employed. (These are not ‘photochemical equilibrium’ calculations.) According to the Chapman model, the instantaneous, integrated, world-wide rate of formation of ozone from sunlight is about five times faster than the rate of ozone destruction, and locally (lower tropical stratosphere) the rate of ozone formation exceeds the rate of destruction by a factors as great as 1000. The global rates of increase of ozone are more than 50 times faster thanBrewer andWilson's [5] estimate of the average annual transfer rate of ozone to the troposphere. The rate constants of the Chapman reactions are believed to be well-enough known that it is highly improbable that these discrepancies are, due to erroneous rate constants. It is concluded that something else besides neutral oxygen species is very important in stratospheric ozone photochemistry. The inclusion of a uniform concentration of the oxides of nitrogen (NOx as, NO and NO2) averaging 6.6×10−9 mole fraction gives a balance between global ozone formation and destruction rates. The inclusion of a uniform mole fraction of NOx at 28×10−9 also gives a global balance. These calculations support the hypethesis (Crutzen [10],Johnston [24]) that the oxides of nitrogen are the most important factor in the global, natural ozone balance. Several authors have recently evaluated the natural source strength of NOx in the stratosphere; the projected fleets of supersonic transports would constitute an artificial source of NOx about equal to the natural value, thus promising more or less to double an active natural stratospheric ingredient.

Catalytic preparation of NO

Abstract: A method and apparatus for converting oxides of nitrogen to nitric oxide is disclosed wherein the gas to be treated is passed through a plurality of alumina tubes each containing a wire of catalytic material which is wound into and through the tubes. The wire, preferably platinum, is connected to a source of electrical energy for resistively heating the wire. In its fashion, the gas to be treated flowing through the tubes is forced into intimate contact with the heated wire of catalyst material to speed the reaction and conversion of the gas to nitric oxide.

Incineration of nitrogenous materials

Abstract: A process for incineration of nitrogenous waste materials in a manner which minimizes NOx pollution. A nitrogenous waste material, such as TNT, is burned with a fuel and less than a stoichiometric quantity of air in the presence of a catalyst in a fluid bed. Secondary air is added to the gaseous products, and the resulting gas mixture is burned to yield a stack gas which has minimal amounts of NOx, carbon monoxide and hydrocarbons. Nickel or a compound thereof is preferred as the catalyst.

Iron oxide sorbents for regenerative sorption of Nox

Abstract: The use of iron oxide sorbents to remove oxides of nitrogen (NOx) from gaseous mixtures containing small amounts of NOx such as the exhaust from an internal combustion engine or flue gases, without interference from carbon oxides or water vapor and thermally regenerable at relatively low temperatures, are disclosed. A preferred sorbent is supported ferric oxide for sorption of NOx from gaseous mixtures containing oxygen. Ferrous or ferrosoferric oxide sorbents are also suitable in the presence or absence of oxygen.

The effect of water injection on nitric oxide emissions of a gas turbine combustor burning ASTM Jet-A fuel

Abstract: Tests were conducted to determine the effect of water injection on oxides of nitrogen (NOx) emissions of a full annular, ram induction gas turbine combustor burning ASTM Jet-A fuel. The combustor was operated at conditions simulating sea-level takeoff and cruise conditions. Water at ambient temperature was injected into the combustor primary zone at water-fuel ratios up to 2. At an inlet-air temperature of 589 K (600 F) water injection decreased the NOx emission index at a constant exponential rate: NOx = NOx (o) e to the -15 W/F power (where W/F is the water-fuel ratio and NOx(o) indicates the value with no injection). The effect of increasing combustor inlet-air temperature was to decrease the effect of the water injection. Other operating variables such as pressure and reference Mach number did not appear to significantly affect the percent reduction in NOx. Smoke emissions were found to decrease with increasing water injection.

Exhaust emissions from uncontrolled vehicles and related equipment using internal combustion engines. Final report. Part 5. Heavy-duty farm, construction, and industrial engines

Abstract: Test data, documentation, and discussion on detailed emissions characterization of eight diesel engines and four gasoline engines, as well as estimated emission factors and national emissions impact for farm, construction, and industrial applications are reported as part of a study of exhaust emissions from uncontrolled vehicles and related equipment using internal combustion engines The exhaust products measured include total hydrocarbons, carbon monoxide, carbon dioxide, nitric oxide, oxygen, particulates, and smoke Sulfur oxide emissions, evaporative losses of gasoline, and crankcase vent hydrocarbon emissions are estimated rather than measured Emission factors and national impact are computed separately for each of the three applications for total hydrocarbons, CO, NOx, aldehydes, particulates, and SOx The categories of engines covered in the report appear to make some significant, but not major, contributions to national pollutant totals from man-made sources

Controlling NOx Emissions From Steam Generators

Abstract: The information presented is directed to those individuals concerned with reducing nitrogen oxides (NO x ) emissions from gas, oil, or coal fired utility steam generators. First, this paper present...

Purification of exhaust gas

Abstract: There are provided an improved thermal reactor apparatus for, and an improved method of, purifying exhaust gases, particularly from a motor vehicle, wherein thermal oxidation and catalytic oxidation of the CO and HC contents of the exhaust gases and/or catalytic reduction of the NOx contents of the exhaust gases are effected within an environment such that at least some of the components of the reactor exposed to the exhaust gases are coated with and/or made of a catalytic alloy capable of acting as a catalyst for oxidation of the CO and HC contents of the exhaust gases and for reduction of the NOx contents of the exhaust gases. In the preferable embodiment of the invention, the above mentioned environment comprises an upper stream zone occupied by a rich reducing gas mixture, including the starting exhaust gases, and a lower stream zone occupied by a rich oxidizing gas mixture, including the resultant gases from the upper stream zone and additional air.

Catalytic reducing decomposition of oxides of nitrogen

Abstract: The oxides of nitrogen in an exhaust gas are reductively decomposed over a catalyst of cerium oxide or uranium oxide in the presence of ammonia.

Effect of water vapor and nitrogen oxides upon the ozone layer

Abstract: A theoretical meridional model of the O3 layer is presented. Two-dimensional transport by eddies and mean motion is considered together with photochemical reactions involving O, N, and H. The model is used to evaluate the effect of increased contents of H2O and NOx in the stratosphere. It is found that a doubling of stratospheric humidity will reduce the total amount of O3 by less than 1 %, while a doubling of NOx will result in an 18 % reduction for middle latitudes and summer. A 10 % increase in NOx will reduce the total O3 by about 2.8%. The relations between UV radiation and total O3 are described, in particular, for wavelengths of biological interest (290 to 320 nm). A 1% decrease in total O3 will result in a 2 % increase in erythemogenic UV radiation.

Combustor process for low-level NOx and CO emissions

Abstract: A new combustion process wherein combustion efficiency is retained while reducing inlet air temperature to the combustor so as to obtain both reduced nitrogen oxides emissions and reduced CO emissions. A new combination of combustion apparatus and heat utilization apparatus are also provided.

Possible effects of a fleet of supersonic transports on the stratospheric ozone shield

Abstract: The possibility that large quantities of water and various oxides of nitrogen (NOx) can be injected into the stratosphere by a fleet of SST's has raised concern over the possibility of a reduction in the ozone (O3) shield. Calculating such a reduction requires knowledge of the roles of NOx and H2O in the natural O3 budget. Initially, not enough was known either of the background densities of NOx or of many of the rate constants involved to make quantitative statements of the effect of NOx and H2O on the O3 budget. Recently, many of the rate constants required in a quantitative analysis have become known. These results incorporated into model calculations with natural sources of NOx and observed H2O mixing ratios tend to indicate that these constituents play an important role in the O3 budget in the natural stratosphere. At the same time, recent measurements of NO, NO2, and HNO3 have become available. The HNO3 measurements by several different groups appear to be mutually consistent. The results of both the NO measurements and the NO2 measurements, however, differ by an order of magnitude. Although the rate data available are not of sufficient accuracy to resolve the discrepancy between the measurements, it does appear that there will be a reduction in stratospheric O3 caused mainly by HOx or NOx catalysis or both. A semiquantitative analysis for a fleet of SST's suggests a decrease in the column density of O3 of 0.5–5%.