Showing papers on "NOx published in 1982"

The Tropospheric Cycle of NOX

Abstract: The tropospheric chemistry, budget, and distribution of NOX are reviewed. For surface air, the chemistry of NOX can conveniently be separated into daytime and nighttime processes. During the day, NOX is removed mainly via NO2 + OH + M → HNO3 + M. During the night, some of the NO2 is converted first to NO3 then to N2O5, which can be removed by moist surfaces thereby forming dissolved NO3. Estimates indicate that this reaction mechanism taking place within nighttime fogs of clouds could remove NOX as efficiently as the daytime reaction with OH. The final sink for removal of NO from the atmosphere is predominately by NO3 deposition, mostly by rainout. A smaller fraction appears as dry deposition. The total NO3 deposition in 1964 is estimated to have been (24 ± 916) x 1O12 g N yr -1. The geographical pattern for the measured total deposition is also shown. The sources of NOX, both natural and man made, totaled (40 ± 20) x 1O12 g N yr -1. Its geographical distribution is also estimated. Existing measurements provide a vertical profile of NOX for continental midlatitudes; it appears to be dominated by anthropogenic sources.

Nitric Oxide Formation During Pulverized Coal Combustion

Abstract: Data on the overall conversion of coal-nitrogen to NOx were obtained at 1250 K and 1750 K for a residence time of one second. The conversion of coal-nitrogen to NOx decreased monotonically with increasing fuel/oxygen equivalence ratio and decreased slightly with increasing temperature. Oxidation experiments were also carried out on char in order to separate the contribution to NOx emissions of the char from that of the volatiles. The char used was prepared by the pyrolysis of coal at a temperature and residence time corresponding to those of oxidation experiments. The conversion to NOx of char-nitrogen was lower than the corresponding value for coal-nitrogen. It was found that volatilized nitrogen compounds accounted for a major fraction of NOx produced from coal-nitrogen, especially at high temperatures and low fuel/oxygen equivalence ratios.

Diesel NOx emissions—A simple correlation technique forintake air effects

Abstract: A correlation technique for the effects of intake gas addition (N2, O2, Ar), exhaust gas recirculation and elevated intake air temperature on diesel NOx emissions is presented. NOx emissions were obtained from two different single-cylinder divided-chamber diesel engines operating over a wide range of engine speeds, loads, and intake air compositions and temperatures. Since the major portion of the combustion event in diesel engines is diffusion controlled in a manner similar to that in steady spray flames, variations in the calculated stoichiometric adiabatic flame temperature are used to correlate NOx emissions. The NOx correlation yields an apparent activation energy which is relatively independent of engine speed, load or combustion chamber configuration, indicating that the NOx kinetics are not significantly altered by variations of the air-fuel mixing process. However, this apparent activation energy is considerably lower than the one obtained for steady-spray flames. Several possible reasons for this difference are discussed. In the absence of detailed theoretical models describing the diesel combustion process, the simple flame-temperature correlation provides a useful method of correlating and predicting the effects of intake air composition and temperature on NOx emissions from divided-chamber diesel engines.

Method and apparatus for burning high nitrogen-high sulfur fuels

Abstract: A method of minimizing the production of SOx and NOx in the burning of a fuel containing significant amounts of SOx and NOx precursors in which the fuel is treated to remove significant amounts of SOx precursors without the removal of significant amounts of NOx precursors and the fuel is thereafter burned in a two-stage, rich-lean burning step in which significant amounts of the NOx precursors are converted to N2. Treating the fuel to remove SOx precursors is preferrably carried out in the presence of an oxidizing agent, such as H2 O2, a reducing agent, such as hydrogen, and/or steam, and still more preferably, the oxidizing agent, the reducing agent and steam are generated by burning an auxiliary fuel and passing the effluent thereof to the step of treating the fuel to remove SOx precursors.

Process through which soot intermixes into lubricating oil of a diesel engine with exhaust gas recirculation

Abstract: Diesel engines equipped with exhaust gas recirculation reduce NOx emissions: however, engine combustion causes large amounts of soot to be produced. This soot intermixes with the contaminates lubricants thereby adversely affecting engine durability. The behavior of soot with EGR and the process by which soot intermixes with lubricant was investigated. The study indicates that the amount of soot intermixing with lubricants is related to exhaust smoke and the EGR rate. Most of the soot intermixes with the oil film on the cylinder wall. Intermixing with blow-by gas is very small.

Process for reduction of oxides of nitrogen

Abstract: An improved process for reducing the concentration of oxides of nitrogen (NOx) in a waste stream is provided wherein an effluent stream containing oxides of nitrogen (NOx) is burned at a temperature greater than about 2000° F. and less than about 3000° F. with an effective amount of an oxygen containing gas and a stoichiometric excess of a hydrocarbon, based on the total amount of available oxygen, to provide a combustion effluent. The combustion effluent is thereafter contacted, at a temperature in the range of from about 1600° F. to about 1800° F., with an effective amount of a gaseous stream containing less than 21 volume percent oxygen to substantially oxidize all combustibles present in the combustion effluent and provide an oxidation effluent substantially free of oxides or nitrogen (NOx) and combustibles. The oxidation efluent 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.

The effect of the vanadium component on the life of the WO3-TiO2 catalyst used for the reduction of NOx with NH3.

Abstract: The 5000-h life test of the WO3–TiO2 catalyst for the reduction of NOx with NH3 has been investigated in real flue gases containing vanadium and SOx on a pilot plant. When the present catalyst was used in a residual-oil-fired-boiler flue gas, steady activities over 90% of NOx reduction were achieved for 5000 h at 400 °C (space velocity: 2700 h−1). On the other hand, when the catalysts were taken out of the reactors at certain intervals and studied by means of a laboratory reactor, they were much more active than fresh catalyst at lower temperatures (250–350 °C). Also, the SO2 oxidation efficiency increased with the reaction time. This activation was considered to be due to the vanadium component in the flue gas.

The Potential effects of increased methane on atmospheric ozone

Abstract: Using a one dimensional atmospheric model, we investigate the possible influence of an increase in atmospheric methane on ozone. The couplings between methane and the catalytic destruction of ozone by NOx, HOx, and ClX are discussed. Our model calculations suggest that doubling the ground-level flux of methane, with fixed atmospheric temperatures and currently recommended chemical reaction rates, would increase the total ozone column by 3.5%. Calculations showing the very significant moderating effects of a methane increase on ozone perturbations due to N2O and chlorofluorocarbons are discussed.

Method and apparatus for combustion with a minimum of NOx emission

Abstract: A method an apparatus for combustion with a minimum of NOx emission in various industrial furnaces and boilers. By injecting air for combustion into a furnace through the burner tile or air baffle in the deviated flow pattern asymmetrical with respect to the burner tile or baffle axis, the quick mixing of the air and fuel in early stages of combustion is suppressed to provide for a relatively gentle combustion and allow the burnt gas self-circulation to take place effectively, thereby minimizing the emission of nitrogen oxides.

Platinum gold catalyst for removing NOx and NH3 from gas streams

Abstract: Selective reduction of NO x with NH 3 as well as decomposition of excess NH 3 is provided over a wide temperature range by a platinum-gold catalyst

Influence of Oxides of Nitrogen on Crop Growth and Yield: An Overview

Abstract: Automobiles and power generating facilities are the major sources of oxides of nitrogen (NO X ). These sources also emit sulfur dioxide (SO 2 ) and hydrocarbons, which in combination with NO X contribute to the production of ozone (O 3 ). Consequently, oxides of nitrogen are rarely present alone in polluted air masses. Both nitric oxide (NO) and nitrogen dioxide (NO 2 ) can either be toxic to or metabolized by plants. The rate of uptake of the pollutants and the physiological state of the plant determine whether the NO X will be injurious or beneficial. Oxides of nitrogen are less phytotoxic than SO 2 or O 3 and the concentrations of NO X that presently occur in most agricultural areas do not pose a threat to crop productivity. However, exposure to NO X in combination with SO 2 and/or O 3 can alter plant metabolism and productivity at concentrations that would not produce such effects if the pollutants were present alone. Consequently, the effects of NO X on crop growth and yield are minimal in comparison with the effects of NO X in combination with SO 2 and O 3 .

Effect of H2O2 on homogeneous gas phase NO reduction reaction with NH3

Abstract: To study the effect of H2O2 on NO reduction with NH3, the homogeneous gas phase reaction of NH3NOH2O2O2 was investigated in a Pyrex flow reactor over the temperature range from 500°C to 600°C under one atmospheric pressure. H2O2 accelerated the NO reduction by NH3 and caused it to be induced at a temperature of 500°C. In the absence of O2, NOx reduction ratio of more than 90% was obtained for NH3/NO5 and H2O2/NO1 at 550°C. In the presence of O2 or an excess of H2O2, two side reactions, which cause the NOx reduction ratio to decrease, occur. One of the side reactions is NO oxidation with H2O2. It was found experimentally that NO2 inhibited NO reduction and that H2O2 was an NO oxidizing agent, as well as an NH3 decomposing agent. The other side reaction was the formation of NO and NO2, which resulted from the oxidation of NH3 with O2. Under the conditions of our experiments, the amount of O2 in our reaction system was extremely high compared to the amounts of NO, NH3 and H2O2 in the system. Thus NOx was assumed to be produced by the oxidation of the NO reducing radicals, which were produced by the reaction of NH3 with H2O2.

The role of the atmosphere in nitrogen cycling

Abstract: In this work an analysis of the sources, atmospheric concentration, chemical reactions and sinks of the principal atmospheric nitrogen compounds is made. Atmospheric emissions of N2O and NH3 are almost entirely due to biological activity on the continents and in the oceans. The combustion of fossil fuels and biomass is the principal source of NOx. The only relevant chemical transformations in the troposphere are the oxidation of NOx to NO3 - and the formation of ammonium salts. Only 10% of the NH3 emitted is oxidized. Washout of NH4 + and NO3 - by rainfall is the principal mechanism for removing nitrogen compounds from the atmosphere. Part of the N2O enters the stratosphere and part must be removed in the biosphere by processes not yet established.

Reciprocating internal-combustion engine of low-temperature catalytic-combustion type

Abstract: In a reciprocating internal-combustion engine of a low-temperature catalytic-combustion type, catalyst layers which act at low catalyst temperatures of about 500° C. or downwards to permit combustion of a gaseous air-fuel mixture are formed or secured on the inner wall surfaces of each combustion chamber of the engine, whereby low-temperature catalytic combustion of the air-fuel mixture is made possible in quench layer formed along the inner wall surfaces of each combustion chamber separate from its piston-sliding region, whereby incomplete combustion is prevented, a regular operation is made possible even with a dilute gas mixture having air-fuel ratio exceeding the limit of misfire in the conventional engines, the fuel efficiency is enhanced and the reduction in hydrocarbon, CO and NOx in exhaust gas is attained as well.

Low NOx Combustion Systems for Burning Heavy Residual Fuels and High-Fuel-Bound Nitrogen Fuels

Abstract: Novel combustor concepts were designed for dry reduction of thermal NOx, control of NOx from fuels containing high levels of organic nitrogen, and control of smoke from low hydrogen content fuels. These combustor concepts were tested by burning a wide variety of fuels including a middle distillate (ERBS), a petroleum based heavy residual, a coal derived synthetic (SRC-II), and various ratios of blends of these fuels which included nitrogen doping with pyridine. 1 ref.

Method for removal of nitrogen oxide

Abstract: PURPOSE:To obtain a catalyst of high heat resistance having sufficient activity at elevated temp over a long period of time in performing catalytic reduction of NOX in the presence of NH3 by forming the carrier of catalysts of composite oxides contg P as a constituting element CONSTITUTION:This catalyst contains both components of A) >=1 kinds of 3- or 4-element composite oxides consisting of Ti, P, Si and/or Zr, and B) oxides of >=1 kinds of W, Ce, Sn Here, the component A per se has activity for the NOX in waste gases, and also plays the role of a carrier This is a solid acid and exhibits marked acidity not observed in respective independent oxides, and has high heat resistance coupled with high specific surface area With the P in the component A, various effects can be observed; above all, it suppresses particularly the oxidation of NH3 to NOX and the crystallization of catalyst components As a result, it maintains high activity for a long period of time

Effect of Water and Carbon Dioxide in Chemiluminescent Measurement of Oxides of Nitrogen

Abstract: The results of studies on the quenching effects of H/sub 2/O and CO/sub 2/ at levels of interest in exhaust gas analyses are presented. The use of a semipermeable membrane type dryer as a means of removing the water interference has also been evaluated using moist mixtures of a) NO in nitrogen, b) NO/sub 2/ in air, and c) actual exhaust samples.

An investigation of the adsorption of oxides of nitrogen on respirable mineral dusts and the effects on their cytotoxicity.

Abstract: As part of a wider study of the effects of oxides of nitrogen on the health of coal workers, experiments examining the adsorption of nitrogen dioxide and nitric oxide on coal and other mineral dusts have been carried out together with a study of the effects of adsorption of these gases on the cytotoxicity of the dusts. Both nitric oxide and nitrogen dioxide were found to adsorb readily on all dusts examined. When airborne coal mine dusts collected at coalfaces were examined, measurable quantities of adsorbed oxides of nitrogen were observed. Adsorption of nitrogen dioxide on to kaolinites produced a small but significant decrease in cytotoxicity. Small decreases in the cytotoxicity of coal and quartz dusts were also observed after adsorption of nitrogen dioxide, but these were not significant. No significant or systematic changes in cytotoxicity were observed following nitric oxide adsorption.

Catalytic combustor of gas turbine

Abstract: PURPOSE:To improve thermal efficiency of a gas turbine combustor and reduce Nox, by performing follow up combustion of the catalytic combustor in accordance with a load of a turbine. CONSTITUTION:A total quantity of fuel of a gas turbine catalytic combustor is obtained by operating a flow control valve 28 provided to a fuel main pipe 9 and controlling a flow of fuel flowing in the pipe 9 through a signal from a gas turbine output signal setter 32. Such flow controlled fuel in a fuel main pipe 9 is distributed to the respective catalytic combustors by operation of opening and closing valves 16-19 opened and closed by a gas turbine output signal 33. In this way, the fuel, whose flow is controlled in accordance with a load of a gas turbine, is further distributed to the catalytic combustor in accordance with the load of the turbine, and catalytic combustion is performed in accordance with the load of the gas turbine.

石炭の低NOx化燃焼に対する基礎的検討:生成NO, HCNおよびNH 3 の反応挙動におよぼす石炭灰の触媒作用

Abstract: In order to establish a low NOx fluidized-bed coal combustor, the emission of NO, HON and NH3 formed in gasification reaction of coal with O2 and H2O is desired. Here, the catalysis of coal ash for reduction of NO with CO or H2, hydro-lysis of HCN and decomposition of NH3 in the presence of CO, H2, H2O and H2S were investigated. Ashes employed were those from Taiheiyo coal (JAPAN) and Datung coal (P. R. China). Also, SiO2, Al2O3, CaO and Fe2O3, which are main components in coal ash, were prepared by precipitation or decomposition of each raw salt, and em-ployed. The experiments were carried out using a flow type packed bed reactor under atmospheric pressure at 700-950°C . The inlet gases were mixtures of various compo-sitions of NO (0, 500ppm), HCN (0, 500ppm), NH3 (0, 500ppm), H2S (0, 500ppm), H2 (0, 2. 5%), CO (0, 10%), H2O (0-10%) and N2 balanced, and the total flow rate was 1000Ncm3/min for 1. 0m, e of ash or metal oxide with average diameter of 1.0mm.The main results obtained were as follows:1) The reduction of NO to NH3 with H2 or CO-H2O and the hydrolysis reaction of HCN to NH3 were catalyzed by each ash, but the decomposition of NH3 was only catalyzed by Datung coal ash.2) CaO and Fe2O3 gave high catalytic activity for the reactions of N-compounds; CaO promoted the reduction of NO to NH3 with H2 or CO-H2O, and the hydrolysis of HCN to NH3. Fe2O3 promoted the reduction of NO to NH3, and the hydrolysis of HCN to NH3 below 900°. Above 900°, Fe2O3 promoted the denitrification of NO, HCN and NH3 to N2.The denitrification rate over Fe2O3 was accelerated with the presence of H2S. SiO2 and Al2O3 gave no catalysis.3) In the atmospheres of the first-step combustion under the air ratio less than 1, two kinds of coal ash employed gave a good catalytic activity for the conversion of NO and HCN to NH3, but it was induced that the sufficient coversion of NO, HCN and NH3 to N2 was very difficult except the coal ash containing a large quantity of Fe2O3.4) For a very low NOx combustion of coal, it was concluded that it was sufficiently effective to convert NH3 formed at the first-step combustion under a low air ratio to N2, using artificial or natural iron oxide as a catalyst, before the perfect combustion of the second-step.

Natural and Anthropogenic Sources of Oxides of Nitrogen (NOx) for the Troposphere.

Abstract: : This paper lists all known sources of oxides of nitrogen (NOx) in the free troposphere to enable evaluation to be made of the significance of aircraft injections of NOx for tropospheric photochemistry. Sources considered include the combustion of fossil fuels and biomass, lightning (summarizing the results of a parallel study by Kowalczyk and Bauer), transport from the stratosphere, and cosmic ray ionization. The results are provided in a form convenient for two-dimensional computation with extension to three-dimensional application. Data apply to 1975, with a projection to 1990.

Decomposing method for nox

Abstract: PURPOSE:To reduce and decompose NOX efficiently while suppressing the oxidation of SOX by treating waste gases contg NOX and SOX with NH3 in the presence of the catalysts prepd by firing the moldings consisting of specific compsns of TiO2, a V compd, and phosphate of alkaline earth metals, zinc, etc CONSTITUTION:A raw material of TiO2 (eg; titanium hydroxide), a V compd (eg; V2O5) and phosphate of metals of >=1 kinds of alkaline earth metals, zinc, Al, etc are mixed The mixing ratios are 100ptswt the TiO2, 01-3ptswt the V compd (value in terms of V2O5), and 01-5ptswt the phosphate (value in terms of tertiary salt) and are 01-25ptswt the phosphate with respect to 1ptwt of the V compd Next, water and molding assistants such as silica sol, glass powder, or the like are added according to need to this mixture, thence the mixture is molded and dried, after which the moldings are fired at 300- 700 degC, whereby the catalysts are prepd Next, waste gases contg NOX and SOX and the NH3 of 06-2 times mole the NOX are flowed through this catalyst bed under 200-600 degC temp conditions, whereby the NOX is reduced and decomposed

NOx reduction for gas turbines by water injection into the combustion chamber

Abstract: The air storage gas turbine power plant operated by the process for NO the condensate from the container (13), optionally after passing through a recuperator (6), into the combustion chambers (8, 9) of the gas turbine (1) is introduced.

Impact of coupled perturbations of atmospheric trace gases on Earth's climate and ozone

Abstract: We have studied the effects on the ozone concentration and surface temperature, of perturbations in the atmospheric content of nitrous oxide, methane, carbon dioxide and chlorofluorocarbons (CFC). The sensitivity study has been carried out with a radiative-convective-photochemical model. The doubling of carbon dioxide concentration has the effect of warming the troposphere and cooling the stratosphere. As a result of this cooling, the change of ozone columnar density produced by 10 ppb of chlorine amount to 9.3% as compared to −10.9% obtained without temperature feedback. Perturbation in nitrous oxide correspond to an increase in NOx of the stratosphere with consequent ozone reduction while doubling the methane concentration correspond to a slight increase in columnar density. The effect of the increased methane concentration in the stratosphere contributes to reduce the effect of CFC due to the enhanced formation of HCl. The perturbation of these two minor constituents appreciably increase the greenhouse effect to 2.30 from 1.67°, obtained when carbon dioxide alone is considered.

Nox control apparatus for city garbage incinerator

Abstract: PURPOSE:To make it possible to operate the city garbage incinerator under a low NOX condition by a method wherein an operating means for choking the air-fuel ratio by measuring the densities of NOX and O2 in the exhaust gas from the incinerator is provided and the quantity of air blown into the incinerator is reduced CONSTITUTION:An algorithm block 3 for controlling NOX receives from a gas chromatograph a signal relating to the density of O2 and a signal relating to the density of NOX in the exhaust gas and generates an output signal eta for correcting the air-fuel ratio in accordance with a specific algorithm Said algorithm first detects the density of O2 in the exhaust gas and when the detected value is below a permissible value of O2, it generates the output signal eta directed to increase the air- fuel ratio On the other hand, it generates the output signal eta directed to choke the air-fuel ratio only when the average value of O2 is above the permissible value thereof and the average value of NOX is above the permissible value of NOX The output signal from the algorithm block 3 is given as one of inputs to a multiplier 61 and corrects the quantity of air under a fire grate so that the air-fuel ratio changes in accordance with the density of O2 and the average value of NOX