Showing papers on "NOx published in 1975"

Global ozone balance in the natural stratosphere

Abstract: The method of instantaneous rates is a three-dimensional model that takes the observed distribution of atmospheric species and temperature as input data. The distribution of radiation over wavelength, photochemical rate constants, and reaction rates are evaluated in each cell of the three-dimensional grid. For certain problems of restricted scope, definite answers can be given by this approach. For example, it is shown that the Chapman reactions and air motions are insufficient to give a global ozone balance; these factors account for only about 20 percent of the ozone produced below 45 km. There must be other photochemical or chemical reactions that destroy natural stratospheric ozone. The water reactions (H, HO, and HOO radicals) balance about 10 percent of the ozone produced below 45 km. Recently observed concentrations of nitrogen dioxide at up to 36-km elevations are close to those required to destroy the remaining 70 percent of naturally produced ozone. Until enough measurements are made to characterize the vertical, latitudinal, and seasonal distribution of nitrogen dioxide, it will not be known whether yet other substances (such as chlorine, bromine, and metallic oxide particles) play a significant (10 percent or more) role in the natural ozone balance. (auth)

Reduction of gaseous pollutants in combustion flue gas

Abstract: Fuel is burned in a primary combustion chamber with less than the air required for stoichiometric combustion so that the combustion gases have a high carbon monoxide (CO) and a hydrocarbon content and the temperature of the gases is held below that at which significant nitrogen oxides (NOx) would be produced. The combustion gases are then passed through a secondary combustion zone in which more air is injected into the gas stream to oxidize the CO and hydrocarbons to carbon dioxide (CO2). The secondary burner comprises a plurality of foraminous tubes through which secondary air is emitted. Combustion in the secondary zone is maintained at a temperature below that at which nitrogen oxides (NOx) will be produced in significant quantities.

Catalytic Combustion: An Important Consideration for Future Applications

Abstract: Many problems in practical combustion devices are caused by the need to establish a near-stoichiometric zone which aids in the achievement of stable, highly-efficient combustion. For example, if operation at low equivalence ratios (φ ∼ 0.6) were practical, NOx, emission and combustion chamber cooling requirements could be reduced. The present work describes the results of a large-scale experiment where combustion stability was achieved through the use of a catalytic bed within the reaction zone (i.e., catalytic combustion). Since this scheme requires design of a system which results in uniform fuel-air mixing and a uniform velocity profile, the exhaust gases closely approximate isothermal plug flow, thus avoiding many additional current system disadvantages due to severe temperature gradients. Testing was conducted at pressures up to 10.5 atmospheres and exhaust temperatures up to 1589 °K. Performance trends with fuel-air ratio, inlet temperature, reference velocity and pressure were obtained. A ...

Method of reducing emission of pollutants from multi-cylinder engine

Abstract: NOx concentration in the exhaust gas is reduced by supplying an extremely rich air-fuel mixture to half of the cylinders and an extremely lean mixture to the remaining cylinders. HC and CO in the exhaust are oxidized in a reactor due to existence of excess air left after combustion of the lean mixture.

NO, NO2 and HNO3 below 35 km in the atmosphere

Abstract: Experimental data on NO, NO2 and HNO3 in the atmosphere are reviewed. The low abundance of nitric acid in the tropospheric gas phase is emphasized, as well as the high variability of NOx in the low stratosphere and in the troposphere. Some model-predicted distributions of these odd-nitrogen molecules are presented. Areas of agreement and of disagreement between theory and experiment are indicated.

Method and apparatus for reducing NOx from furnaces

Abstract: NO x 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 of combusting nitrogen-containing fuels

Abstract: A method for combusting nitrogen-containing fuel by: combusting a first fuel-air mixture in the presence of a catalyst in a first stage, operated fuel-rich so that the amount of air in the first stage is substantially less than the amount needed for complete combustion; adding additional air to the effluent gas from the first stage to form a second mixture with an amount of air at least sufficient to combust fully the effluent from the first stage; and then combusting the second mixture in a second stage. The first mixture is sufficiently fuel-rich, and the second mixture contains sufficient additional air, so that the combustion temperature in the first stage is below a temperature that would result in any substantial formation of oxides of nitrogen or other fixed nitrogen compounds from atmospheric nitrogen present in the mixture being combusted, and the second stage temperature also is below that for substantial nitrogen oxide formation therefrom. The method serves to suppress formation of nitrogen oxides from the nitrogen-containing compounds in the fuel.

Effect of hydrogen injection stability and emissions of an experimental premixed prevaporized propane burner

Abstract: Hydrogen in quantities up to 5 percent by weight of the total fuel flow was injected into a premixed propane burner. The hydrogen was either premixed with the propane and air upstream of the burner or introduced as a torch at the flameholder. Emissions of total nitrogen oxides, carbon monoxide, and unburned hydrocarbon are reported as are combustion efficiencies and lean blowout limits. To maintain at least 99 percent combustion efficiency at a 700 K inlet mixture temperature with no hydrogen added, it was necessary to burn with a propane equivalence ratio of 0.525. When 4 percent hydrogen was premixed with the propane and air, a combustion efficiency greater than 99 percent was recorded at a propane equivalence ratio of 0.425. The total nitrogen oxides (NOx) emissions corresponding to these two conditions were 0.8 g NO2/kg equivalent propane and 0.44 g NO2/kg equivalent propane, respectively. The hydrogen torch did not reduce NOx emissions.

Effect of fuel properties on performance of a single aircraft turbojet combustor

Abstract: The performance of a single-can JT8D combustor was investigated with a number of fuels exhibiting wide variations in chemical composition and volatility. Performance parameters investigated were combustion efficiency, emissions of CO, unburned hydrocarbons and NOx, as well as liner temperatures and smoke. At the simulated idle condition no significant differences in performance were observed. At cruise, liner temperatures and smoke increased sharply with decreasing hydrogen content of the fuel. No significant differences were observed in the performance of an oil-shale derived JP-5 and a petroleum-based Jet A fuel except for emissions of NOx which were higher with the oil-shale JP-5. The difference is attributed to the higher concentration of fuel-bound nitrogen in the oil-shale JP-5.

Process for removing oxides of nitrogen and sulfur from exhaust gases

Abstract: The present invention relates to a process for wet-treating an exhaust gas which comprises simultaneously removing a nitrogen oxide (NOx) and a sulfur oxide (SOx) from an exhaust gas containing these oxides by treating exhaust gas containing oxides of nitrogen and sulfur with a lime or limestone slurry containing alkali metal or alkaline earth metal iodide.

Apparatus for NOx control using steam-hydrocarbon injection

Abstract: This invention describes a furnace system for the reduction of nitrogen oxide containing gases which utilizes a two-chambered refractory lined furnace. Fuel gas and stoichiometric air is introduced into the first chamber to provide an ambient temperature sufficient for the reaction of steam and hydrocarbon gases which are introduced into the first chamber to provide a reducing atmosphere. The nitrogen oxide (NOx) containing gases are also introduced into the first chamber where the NOx is reduced. The gases then pass into the second chamber where they are rapidly cooled to a temperature below that at which there is thermo-regeneration of nitrogen oxides. Additional air is supplied to the second chamber for the combustion of combustible gases remaining therein after reduction, care being taken that the temperature never rises above the temperature at which there is substantial regeneration of nitrogen oxides.

A study of NOx emission characteristics in two stage combustion

Abstract: To suppress the emission of NO x a new technique for two stage combustion has been developed and the formation of NO x by this combustion process examined by changing the combustion mode. The combustion is divided into two parts, a primary and a secondary stage. In the primary stage, partial combustion is carried out for a much higher fuel-air equivalence ratio than that of usual staged combustion. After promoting partial combustion, secondary air is supplied to complete combustion in the secondary combustion chamber. Nitrogen compounds such as HCN, NH 3 , and NO are formed in the primary stage, and these are converted to NO x in the exhaust gas at a high conversion rate. When NO is added to a fuel, the greater part is converted to HCN in the primary fuel-rich combustion, and a relatively small quantity of NH 3 is also formed. Interactions between NO, HCN, NH 3 and other species, including carbon compounds, are strongly suggested in fuel-rich flames. HCN and NH 3 may be formed through several different reactions. These nitrogen compounds can be reduced by carrying out the primary combustion at a high fuel-air equivalence ratio and premixed rate. The rate of conversion of the nitrogen compounds to NO x is not affected but Thermal NO is significantly suppressed by the combustion modifications in the secondary stage. By applying this combustion technique to a practical boiler, successful reduction of NO x is obtained.

The effects of selected air pollutants on clearance of titanic oxide particles from the lungs of rats.

Abstract: A procedure utilizing the lung clearance kinetics of titanic oxide (TiO2) particles was used to determine the effects of inhaled sulphur dioxide (SO2) and nitrogen oxides (NO x) on particle clearance. The procedure is reproducible and mainly tests clearance mechanisms involving alveolar macrophages and the mucociliary transport system at the alveolobronchial clearance pathway. At low SO2 or NOx exposures enhanced particle clearance was observed. Lung clearance was depressed at 15 and 24 ppm of NO2 after 22 exposures as well as at 20 ppm of SO2 after 11 exposures, and also at 1 ppm of SO2 after 25 exposures. Dose-response curves for the SO2 and NOx exposures showed differences explainable by the routes by which these gases reach the alveolar macrophages.

An Experimentally Verified NOx Emission Model for Gas Turbine Combustors

Abstract: An analytical model has been developed to simulate the thermal NOx emission processes in various gas turbine combustors for a variety of fuels. The NOx emissions predicted by the model are in excellent agreement with available laboratory and field data. Its capability to simulate the water injection process accurately has been demonstrated previously. Comprehensive understanding of the NOx emission processes in gas turbine combustors has been gained through the current analytical studies. NOx emissions as influenced by ambient humidity, changes in combustor geometry, type of fuel used and changes in operating parameters can now be evaluated quantitatively through a priori prediction and have been verified by available laboratory and field data. The analytical model has also been demonstrated to be a powerful guidance tool in directing the experimental testing program in an effort to reduce NOx emissions from gas turbine combustors.Copyright © 1975 by ASME

Prevaporization and premixing to obtain low oxides of nitrogen in gas turbine combustors

Abstract: Tests were conducted to determine the effectiveness of prevaporization and premixing in reducing the formation of oxides of nitrogen in a gas turbine type combustor using liquid JP-5 fuel at the supersonic cruise condition. The combustor inlet temperature was 833 K (1500 R) at a pressure of 4 atmospheres and a reference velocity of 46 m/sec (150 ft/sec). An order of magnitude reduction in nitric oxide emissions was achieved. Nitric oxide emission indices as low as 0.6 gm NO2/kg fuel were measured at an equivalence ratio of 0.29 with one percent combustion inefficiency without vitiation of the mixer stream.

Reactivities of complex hydrocarbon mixtures

Abstract: Complex hydrocarbon mixtures were reacted for several hours in the presence of nitrogen oxides in a large ultraviolet irradiation chamber. The hydrocarbons were reacted at concentrations of 5, 10, and 20 ppM C in mixes containing /sup 1//2 or 1 ppM NOx. Rates of oxidation of nitric oxide, nitrogen dioxide dosage, hydrocarbon consumption, eye irritation, and yields of peroxyacetyl nitrate (PAN), formaldehyde, and oxidant were measured. If aromatics are substituted for olefins in a hydrocarbon mixture, there is a decrease in both oxidant and PAN dosages. Eye irritation increased with increasing aromatics. These reactivity parameters decreased by replacing aromatics with paraffins. (Air Pollut. Abstr.)

Generation of nitrogen oxide pollutants during C02 enrichment of glasshouse atmospheres

Abstract: SummaryThe propane and kerosene burners used in glasshouses to provide an enriched CO2 content of the atmosphere generate nitrogen oxides by heat-induced combination of atmospheric N2 and O2. Concentrations of 30–40 pphm† of nitric oxide, and about 10 pphm of nitrogen dioxide, were detected.Nitrogen oxides have recently been recognized as pollutants which can damage plants in pphm concentrations, especially in the presence of sulphur dioxide. The concentrations detected here are just below the threshold expected to cause damage if species of NOx were the only pollutants, but in the presence of small amounts of SO2 some foliar lesions might be expected.

Nox reducing agent feeding apparatus

Abstract: PURPOSE: In an apparatus for reducing NOx in gas by feeding a NOx reducing agent into combustion gases, the NOx reducing agent is continuously fed, in required volume, into desired portions of the high temperature combustion gas. COPYRIGHT: (C)1977,JPO&Japio

Outdoor smog chamber studies. Effect of hydrocarbon reduction on nitrogen dioxide

Abstract: A 312 cu m (11,018 cu ft) Teflon film outdoor smog chamber was constructed in rural North Carolina. The chamber was operated with natural conditions of solar radiation, temperature and relative humidity which existed at the time of a run. Ninety-two 12-hour runs using propylene and oxides of nitrogen were conducted to assess the performance of the system. A photochemical model, in which only the light intensity magnitude and pattern and the rate of heterogeneous surface reactions were changed, was used to compare the outdoor results with those of three indoor chambers. Good agreement was found in all cases. One-hundred-thirty 12-hour runs were conducted using a simulated urban hydrocarbon mix and oxides of nitrogen. Reduction of the hydrocarbon concentration resulted in reductions of nitrogen dioxide (NO/sub 2/) maximum concentration and, for large reductions, the daytime NO/sub 2/ dosage. Other factors investigated included NO/sub 2/ to NO ratio at constant NOx, effect of slow dilution, and results of extended 24-hour and 36-hour runs. (GRA)

Process for reducing oxides nitrogen in the exhaust gas from internal combustion engines

Abstract: The process comprises the step of passing the nitrogen oxides through a zone maintained at conditions at which said nitrogen oxides will be reduced, said zone including a substantially rigid catalytic member of a metal support or substrate plated with one or more members selected from the group consisting of copper, nickel, iron, and chromium and having, at least in part, an oxidized surface that catalytically promotes the reduction of the oxides of nitrogen as they pass through said zone.

The Effect of Water on Nitric Oxide Production in Gas Turbine Combustors

Abstract: The NOx emission index from the combustion of distallate type fuels is a function of the amount of water that is present in the primary zone. A simple analysis based on modified Zeldovich kinetics was used to predict the magnitude of the NOx reduction due to water. All empirical and theoretical data that were evaluated fit the expressionPercent NOx reduction = (1 – exp (CHH)) 100where CH = 22 ± 8 and H is the absolute humidity. This expression can be used to predict the quantity of water that is required to achieve a desired level of NOx reduction. Emission data that are collected at varying ambient humidities can thus be corrected to a common reference level. Methanol combustion was used to illustrate a particular application of the semiempirical calculational technique. It was shown that the NOx emissions from methanol combustion are equivalent to those obtained by adding 8.7 percent water to the combustion air of a kerosine type fuel. The NOx emissions from methanol combustion, on an equal space rate basis, are a factor of 4 lower than from kerosine type fuels. Corrections for ambient temperature and pressure are also required. Thus, in addition to the humidity correction, a technique for correcting NOx measurements to commonly accepted reference ambient conditions of temperature and pressure is presented in this paper.Copyright © 1975 by ASME

Porous Silica Beads-A Catalyst Support for Removal of Exhaust Gas Pollutants

Abstract: By using low silica compositions and by carefully controlling heat treatment and leaching conditions it has been possible to make high pore volume, thermally stable, strong porous silica beads (PSB) in the 1-5 mm size range. Because of these properties one of the potential applications for the material is as a support for automotive exhaust gas catalysts. Ruthenium and platinum have been supported on PSB and evaluated for NOx reduction and for the oxidation of carbon monoxide and unburned hydrocarbons, respectively. Ruthenium on PSB was found to form a very active and selective catalyst for NOx reduction to nitrogen, and exhibited a different reactivity of CO and H2 than that observed with ruthenium supported on alumina. Platinum supported on PSB has a lower alumina catalyst. Certain features of the PSB based catalysts have not yet been fully evaluated to prove their commercial utility. /Author/

Method for removing nitrogen oxides in gases

Abstract: PURPOSE: A method for removing nitrogen oxides (NOx) contained in gases with a very cheap management cost. COPYRIGHT: (C)1977,JPO&Japio

Process for r emoval of nitrogen exides and sulfur oxides in exhaust gas

Abstract: PURPOSE: NOX and SOX contained in combustion gas of boilers or the like, exhaust sintering gas of steel plants, and exhaust gas of acid pickling plants are removed. COPYRIGHT: (C)1976,JPO&Japio

The Formation of Oxides of Nitrogen in the Combustion of Droplets and Sprays of Some Liquid Fuels

Abstract: Data are given on the formation of NO and NO∞. in the forward stagnation region of flames surrounding burning cylinders simulating the droplet combustion of n-heptane and ethanol. Temperature profiles are also given and it was found that the maximum yields of NO and NO∞ were situated towards the lean side of the maximum flame temperature. In addition HCN concentrations have been measured. It has been shown that considerable NO is formed near the liquid surface by a prompt-NO mechanism. The addition of fuel-nitrogen in the form of pyridine enhanced the level of NO but did not increase the amount of HCN formed Measurements of NO in the spray combustion of gas oil and gas oil doped with pyridine and quinoline were made. With the low levels of additives used it was observed that 100% conversions of the nitrogen compound to NO were obtained.

Method of two-stage burning for suppressing generation of nitrogen oxi des

Abstract: PURPOSE: To provide the afore-identified method, with which the generation of NOx is suppressed by carrying out combustion at an extremely low temperature than the theoretical combustion temperature. COPYRIGHT: (C)1977,JPO&Japio