Showing papers on "NOx published in 1983"

Nitrogen oxides in the troposphere: Global and regional budgets

Abstract: The cycle of nitrogen oxides in the troposphere is discussed from both global and regional perspectives. Global sources for NO(x) are estimated to be of magnitude 50 (+ or - 25) x 10 to the 12th gm N/yr. Nitrogen oxides are derived from combustion of fossil fuels (40 percent) and biomass burning (25 percent) with the balance from lightning and microbial activity in soils. Estimates for the rate of removal of NOx based on recent atmospheric and precipitation chemistry data are consistent with global source strengths derived here. Industrial and agricultural activities provide approximately two thirds of the global source for NOx. In North America, sources from combustion of fossil fuels exceed natural sources by a factor of 3-13. Wet deposition removes about one third of the combustion source of NOx over North America, while dry deposition removes a similar amount. The balance is exported from the continent. Deposition of nitrate in precipitation over eastern Canada and the western Atlantic is clearly influenced by sources of NOx in the eastern United States.

A two‐dimensional photochemical model of the atmosphere: 2. The tropospheric budgets of the anthropogenic chlorocarbons CO, CH4, CH3Cl and the effect of various NO x sources on tropospheric ozone

Abstract: This paper presents two-dimensional photochemical model simulations that show the influence of the various NOx sources from industry, lightning, the stratosphere, and aircraft on the tropospheric distributions of NOx, HNO3, and O3. We found that, by far, the best agreement with the global observations is obtained if the industrial sources are included in the calculations. Industrial activities have led to substantial increases of ozone concentrations in the lower troposphere of the northern hemisphere. Emissions of NOx by high-flying aircraft have only a small effect on ozone concentrations in the troposphere. The ability of the model to simulate the global distributions of the long-lived chlorocarbons CFCl3 and CF2Cl2 indicates that the interhemispheric exchange is rather well described. The model confirms an earlier finding by Rowland et al. (1982) that the CF2Cl2 emission rates estimated by the Chemical Manufacturers Association (CMA) may be 35–40% lower for the period 1976 through 1980. The model also supports the earlier finding of Hyson et al. (1980) that CFCl3 is apparently increasing roughly 10% faster than the CMA emission rates can account for during the period 1976 through 1980. Although this disparity could be explained by assuming 10% higher emission rates for CFCl3 during the period, the behavior of the interhemispheric gradient indicates that errors in the determination of the absolute concentrations could also be an explanation. The ability of the model to simultaneously simulate measured distributions of the shorter-lived chlorocarbons CH3CCl3, CH2Cl2, C2HCl3, and C2Cl4 indicates that its average OH concentrations are also about correct. Based on these OH concentrations, the model tropospheric budgets of CO, CH4, and CH3Cl are calculated. The computed losses of CO, CH4, and CH3Cl by reaction with OH are 2.1×1015 g CO yr−1, 3.2×1014 g CH4 yr−1, and 1.9× 012 g CH3Cl yr−1, respectively.

Formation of nitrous acid and nitric oxide in the heterogeneous dark reaction of nitrogen dioxide and water vapor in a smog chamber

Abstract: The dark reaction of NOx and H2O vapor in 1 atm of air was studied for the purpose of elucidating the recently discussed unknown radical source in smog chambers. Nitrous acid and nitric oxide were found to be formed by the reaction of NO2 and H2O in an evacuable and bakable smog chamber. No nitric acid was observed in the gas phase. The reaction is not stoichiometric and is thought to be a heterogeneous wall reaction. The reaction rate is first order with respect to NO2 and H2O, and the concentrations of HONO and NO initially increase linearly with time. The same reaction proceeds with a different rate constant in a quartz cell, and the reaction of NO2 and H218O gave H18ONO exclusively. Taking into consideration the heterogeneous reaction of NO2 and H2O, the upper limit of the rate constant of the third-order reaction NO + NO2 + H2O → 2HONO was deduced to be (3.0 ± 1.4) × 10−10 ppm−2-min−1, which is one order of magnitude smaller than the previously reported value. Nitrous acid formed by the heterogeneous dark reaction of NO2 and H2O should contribute significantly to both an initially present HONO and a continuous supply of OH radicals by photolysis in smog chamber experiments.

Mechanism and rates of the gas phase oxidations of sulfur dioxide and the nitrogen oxides in the atmosphere

Abstract: As our knowledge of the atmospheric chemistry of the SO/sub 2/, NO, and NO/sub 2/ continues to grow, it becomes increasingly clear that many different chemical reactions contribute to the oxidation of these oxides in the atmosphere. Solution phase and gas phase chemistry are both important to acid rain development, and gas-solid, gas-liquid, liquid-solid as well as simple gaseous molecule interactions are seemingly important in some circumstances as well. The evaluation of the mechanism and rates of solution phase and heterogeneous pathways for SO/sub 2/ and NOx oxidation within the troposphere, the significance of surface removal processes, and the transport and diffusion processes are much less amenable to simple laboratory studies and quantification. Although a significant wealth of important and necessary information related to SO2 and NOx chemistry has been defined in recent years and a reasonable depth of knowledge of the many fundamental gas phase processes exists today, many uncertainties still remain in this, the simplest of the research areas related to acid rain development.

Gas sensor and method of using same

Abstract: An electrochemical sensor (10) capable of determining the partial pressure of various gases (e.g., CO, CO2, H2S, alcohol vapors, hydrocarbons, NOx, etc.) and, optionally, substantially concurrently, but independently, oxygen content in gases and liquids. The sensor (10) measures the amount of chemisorbent species formed either electrochemically by partial reduction (such as "Reduced-CO2" in the case of CO2) or partial oxidation (in the case of alcohol) or non-electro-chemically via specific adsorption (in the case of CO and hydrocarbons) on platinum or other metals. The charge required to oxidize this chemisorbed species is proportional to the amount of adsorbate on the electrode surface which is made a reproducible and reliable function of the partial pressure of the gas to be measured. By the proper selection of the sensor (10) construction and electrical parameters, high sensitivity, fast response time, and high selectivity can be obtained.

Staged fuel and air for low NOx burner

Abstract: A low NO x burner for a furnace and a method of operating the burner involving a primary and secondary combustion zone wherein staged fuel and air to both combustion zones is provided. By injection of from about 40 to 60% of the liquid or gaseous hydrocarbon fuel along with about 90% of the total air required to a first reaction zone and injection of the remaining fuel with the remaining 10% of the air to a secondary reaction zone the formation of NO x is significantly suppressed. Such a burner is useful in minimizing NO x emissions for a variety of furnace types including both natural draft and forced draft furnaces.

Effect of Oxygen Enrichment on the Performance and Emissions of I.D.I. Diesel Engines

Abstract: The purpose of this study was to determine the effect of the partial pressure of O sub 2 in the intake charge of an I.D.I. diesel engine on the various operating parameters and the exhaust emissions. The oxygen content in the intake was varied between 21% and 40% by volume. Engine performance and emissions were evaluated at constant engine speed and injection timing while fueling was varied. The research revealed that enriching the intake air with oxygen led to a large decrease in ignition delay and reduced combustion noise. The fuel economy, the power output and the exhaust temperature remained almost constant. HC and CO emissions decreased and smoke levels dropped substantially, while NOx emissions increased pro-rata with the O sub 2 added. Theoretical analysis using the Zel' dovich kinetics showed that nitric oxide emissions are sensitive to "mean NO-formation temperature" and the combustion duration associated with this temperature, and, to a lesser extent, the atomic oxygen concentration. The theoretical analysis revealed close correlation between calculated and measured NO emissions.

Process of conversion for disposal of chemically bound nitrogen in industrial waste gas streams

Abstract: An improved process for disposal of chemically bound nitrogen in industrial waste streams is provided wherein a effluent stream containing chemically bound nitrogen, such as ammonia stream, is contacted with an effective amount of oxygen containing gas and a stoichiometric excess of a hydrocarbon, based on the total amount of available oxygen, at a temperature greater than about 2000° F. or less than 3000° F., to provide a combustion effluent. The combustion effluent is thereafter contacted with an effective amount of a gaseous stream containing less oxygen than that which supports flame propagation at a temperature in the range of from about 1600° F. to about 1800° F., to substantially oxidize all combustibles present in the combustion effluent and provide an oxidation effluent substantially free of oxides of nitrogen (NOx) and combustibles. The oxidation effluent may be cooled in heat exchange equipment to recover energy, recycled to support the combustion and/or the oxidation of the combustibles, or vented to the atmosphere.

New Instrumentation for Airborne Acid Rain Research

Abstract: Instrumental methods have been developed for continuously measuring sulfur dioxide, aerosol sulfur, nitrogen oxides, nitric acid, and ammonia from an aircraft sampling platform. Emphasis has been on modifications to reduce limits of detection to allow sampling at ambient concentrations in the vicinity of clouds. Characterizations based on ambient sampling data, in conjunction with data on cloud water composition and knowledge of the interphase behavior of nitrogen and sulfur oxides and oxyacids, will be used for quantitative evaluation of species contributions to the ionic content of precipitation. A flame photometric instrument with enhanced sensitivity for airborne measurements of both gaseous and aerosol sulfur compounds has been designed and constructed. Ambient airborne levels of less than 1 ppb may be detected using sensitivity enhancement, and effects of pressure changes on instrumental response have been eliminated. Sensitive, real-time measurements of NOx and HNO3 have been achieved by m...

Process of controlling NOx in FCC flue gas in which an SO2 oxidation promotor is used

Abstract: NOx in flue gas from a regenerator in which an SO2 oxidation promoter is present is controlled by mixing ammonia with flue gas and passing the mixture through a combustion zone

Formation of Atmospheric Acidity

Abstract: Atmospheric oxidation is a natural process which is largely driven by photochemistry. In the case of oxides of nitrogen and sulphur emitted from the combustion of fossil fuels, oxidation leads to the formation of strong acids which cause acidification of rain in areas far removed from their source. The mechanisms of the various oxidation processes are dealt with in this paper. They can occur in the gas phase, in liquid droplets or possibly on the surface of some aerosol particles. They are very complex and involve free radicals, such as the hydroxyl radical, strong oxidant molecules, such as ozone and hydrogen peroxide and transition metal catalysts.

Formation of nitrogen oxides in catalytic oxidation of pyridine

Abstract: Formation of nitrogen oxides in the oxidation of pyridine on a platinum/Al2O3 catalyst has been studied. At 270–350°C the reaction of the oxidation of pyridine is zero order with respect to pyridine, NOx concentration being independent of the steady state concentration of pyridine. When pyridine is totally oxidized at 350–520°C an increase in its initial concentration affects only insignificantly the concentration, of NOx since the degree of the conversion of bound nitrogen to oxides sharply falls.

Dry Low NOx Combustion System for Utility Gas Turbine

Abstract: A Dry Low NOx combustion system has been developed for a 80 MW gas turbine operating on natural gas and on distillate oil. The system, employing two-stage combustion and multimode operation, meets the New Source Performance Standards (NSPS) for NOx emissions across much of the load range for both fuels. Mid-load smoke, NOx, and carbon monoxide emissions on distillate oil require further development. This paper outlines the emissions performance of the system for Dry Low NOx applications, specifically in terms of NSPS NOx requirements. Machine data, in addition to test stand data, support the conclusions.Copyright © 1983 by ASME

Improved Low-NOx, rich-lean combustor

Abstract: A low-NOx combustor 12 is provided with a rich, primary burn zone 42 for burning a rich fuel mixture and a subsequent, secondary burn zone 62 for burning a relatively lean fuel mixture NOx formation is inhibited in the rich burn zone by oxygen deficiency, and inhibited in the lean burn zone by a low temperature of combustion reaction

Method for removing acidic components including nitrogen oxide from waste gases

Abstract: A method of simultaneously removing SOx and NOx from waste gases. Using a known desulfurization process the waste gases free of the acidic components are contacted with an oxidizing agent in the gas phase for the oxidation of the oxygen of nitrogen contained in the waste gases. The formed NO2 is absorbed in a subsequent absorbing stage under previous addition of NH3 and the thereby obtained absorbing product is oxidized to form ammonium nitrate in a subsequent oxidation stage with atmospheric oxygen and then reconveyed into the desulfurization process.