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1.
This paper is directed to people who are involved in the measurement of gas turbine exhaust emissions and as a consequence in the establishment of standard reference gases and attendant analytical procedures. Several problems exist in connection with the establishment of these standards: A number of standard reference gases have been developed by the National Bureau of Standards for use in the automotive industry which are also suitable for gas turbine exhaust measurements. However, there is a need for additional standard reference materials such as NO in nitrogen, intermediate levels of CO 2 in air, and higher concentrations of CO in nitrogen and propane in air. There is difficulty in maintaining certain reference materials with confidence in assay, particularly due to instability in the cylinder. Instrumental operational problems with flame ionization detector type units exist. Of particular importance is the difference in response per carbon atom in different organic molecules and the difference in response of a test sample as a function of the oxygen content of the sample. Instrumental method problems such as converter efficiency in chemiluminescence units measuring NO 2 and calibration techniques involving CO to CH 4 conversion, also must be considered. A number of problems occur in the use of wet chemical reference methods such as the phenoldisulfonic acid method for the determination of NO x. These include both efficiency of collection, conversion of NO to NO 2, and subsequent analysis. This paper considers the development of standards for the measurement of NO x, CO, CO 2, total hydrocarbons, and O 2 and reviews the state-of-the-art with respect to these problems and their resolution. 相似文献
2.
The Saltzman Phenoldisulfonic Acid and Nondispersive Infrared methods have been compared for the determination of oxides of nitrogen in automobile exhaust. The main purpose of this investigation was to determine whether the Nondispersive Infrared method could be used as a possible replacement for the Saltzman method. Results show that the Nondispersive Infrared analyzer can be used to measure NO x in exhaust gases with advantages over both the Saltzman and Phenoldisulfonic Acid methods. These advantages include simplicity, speed, less complicated analytical technique, and the fact that it is better adapted to be carried out by technicians at the test site. 相似文献
3.
Several wet chemical methods have been used or suggested for the determination of SO 2 concentrations in air pollution work. These include the iron-O-phenanthroline procedure reported by Stephens and Lindstrom, the Scaringelli-modified West-Gaeke method and the Schulze method. This paper describes a laboratory study to evaluate the usefulness of the iron-o-phenanthroline procedure and is directed to individuals concerned with the analysis of gases from the exhaust of gas turbine engines and other combustion processes, including stationary power plants. The variables considered were: range of usefulness in terms of concentration of SO 2, efficiency of collection, effect of contaminants, specifically oxides of nitrogen, olefin and aldehyde and effect of storage prior to spectrophctometric measurement. The Stephens-Lindstrom method was found to be suitable for measuring higher levels of SO 2 concentrations. It can accurately measure amounts totalling 6000 µl of SO 2 and above whereas the other mentioned methods are generally used for lower levels. Collection efficiency was satisfactory. Contaminants, particularly oxides of nitrogen, are a problem only at low levels of SO 2. NO 2 interference may be eliminated by absorption of the NO 2 on Ultraport S impregnated with ANEDA/H 2SO 4 solution. Temperature control during SO 2 addition is necessary. Storage of exposed reagents prior to measurement produce only small errors if stored at 0°C or at room temperature. 相似文献
4.
A new procedure for determining nitrogen oxides in automobile exhaust has been developed. The new procedure was included in a Bureau of Mines comparative study that aimed at evaluating various widely used methods for determining NO x in auto exhaust. The methods included in the evaluation study follow: (1) Static oxidation in tank (ST method). The method involves oxidation of NO in residence with O 2 in a stainless steel tank. (2) Bureau of Mines method (BM method). The method involves application of the ST procedure in exhaust samples from which the hydrocarbons have been removed by combustion over catalyst. (3) Chevron Research method (CR method), as described in the literature. (4) Phenoldisulfonic acid method (PDS method), as described in the literature. The principal objective of this study was to generate experimental evidence which would lead to defining an optimum procedure for converting NO, present in exhaust gas, into NO 2; this conversion is desired so that the total of NO + NO 2 can be determined quantitatively in the form of NO 2. In pursuing this objective, the procedures prescribed by the foregoing methods were comparatively tested. The results indicated that all four methods are subject to error, the extent of which depends on the conditions employed. The BM method was superior from the standpoint of accuracy because it was less affected by interferences due to hydrocarbon-NO 2 reactions. 相似文献
5.
Two integrated sampling and analysis methods for determining NO x emissions in electric utility plants were developed and field tested. The collection systems consist of: a 4.0% potassium permanganate-2.0% sodium hydroxide solution in restricted-orifice impingers, and a 5A° molecular sieve in midget impingers. Sample analysis is accomplished by a colorimetric or ion-chromatographic procedure with the alkaline-permanganate method and by a colorimetric procedure with the molecular sieve method. The alkalinepermanganate method gives excellent agreement with the EPA reference method, Method 7, for NO x measurements. The molecular sieve method shows a significant negative bias relative to Method 7. It is anticipated that the permanganate methods will be proposed as alternates to Method 7, for NO x determinations, under the EPA New Source Performance Standards. 相似文献
6.
The effect of ammonia in the fuel on NO x emissions was investigated through laboratory experiments and field burner tests. It was found that the degree of conversion of pm-monia to NO x 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 NO x above the peak equilibrium amounts were produced. In furnace diffusion flames the conversion to NO x was much less. At substoichiometric air-fuel ratios all the ammonia appears to pyrolize, forming N 2, and only very little NO x. Several methods for burning ammonia to produce low NO x emissions were investigated. 相似文献
7.
We analyse the air quality data measured at a green area of Buenos Aires City (Argentina) during 38 days in winter. We study the relationships between ambient concentrations of nitric oxide (NO), nitrogen dioxide (NO 2), ozone (O 3) and nitrogen oxides (NO x=NO+NO 2). The variation of the level of oxidant (OX=O 3+NO 2) with the NO x is obtained. It can be seen that the level of OX at a given location is made up of two contributions: one independent and another dependent on the NO x concentration. The first one can be considered as a regional contribution, equivalent to the background O 3 concentration and the second one as a local contribution that depends on the level of primary pollution. Local oxidant sources may include direct NO 2 emissions, the reaction of NO with O 2 at high-NO x levels, and the emission of species that promote the conversion of NO to NO 2. The final category of emissions may include the nitrous acid (HONO) that is emitted directly in vehicle exhaust. Finally, we present a diurnal variation of the local as well as regional contributions and the dependence of the last one on wind direction. 相似文献
8.
ABSTRACT This article presents the results of an industrial-scale study (on 400 MW e lignite fired unit) of simultaneous NO x, SO 2, and Hg T removal in FGD absorber with oxidant injection (NaClO 2) into flue gas. It was confirmed that the injection of sodium chlorite upstream the FGD (Flue Gas Desulfurization) absorber oxidize NO to NO 2, Hg 0 to Hg 2+, and enhancing NO x and Hg T removal efficiency from exhaust gas in FGD absorber. Mercury removal efficiency grows with the rise of degree of oxidation NO to NO 2 and was limited by the phenomenon of re-emission. For NO x removal the most critical parameters is slurry pH and temperature. There was no negative effect on sulfur dioxide removal efficiency caused by oxidant injection in tested FGD absorber. Based on the data provided, NO x and Hg T emissions can be reduced by adjusting the FGD absorber operating parameters combined with oxidant injection. 相似文献
9.
A new convenient measurement method of nitrogen oxides (NO x) in the ambient air was developed. The collection of NO x is performed by an annular diffusion scrubber coated with a mixture of titanium dioxide (TiO 2) and hydroxyapatite (Ca 10(PO 4) 6(OH) 2) and the analysis is carried out by ion chromatography with conductivity detection. Under ultraviolet light (UV) illumination, TiO 2 produces reactive oxygen species such as super oxide (O 2−), hydroxyl radical (OH·) and peroxyhydroxyl radical (HO 2·), by which nitric oxide (NO) is oxidized to nitrogen dioxide (NO 2), and is further oxidized to nitric acid (HNO 3). The yielded HNO 3 and NO 2 are effectively adsorbed on the surface of TiO 2 and hydroxyapatite. The collection efficiencies of NO and NO 2 by the annular diffusion scrubber coated with the catalysts under UV illumination are higher than 98%, respectively, at the air flow rate of 0.2–1.0 l min −1. After the collection of NO x, by feeding deionized water into the annular diffusion scrubber, HNO 3 and NO 2 which adsorbed on the catalysts are extracted as forms of nitrite ion (NO 2−) and nitrate ion (NO 3−). The extraction efficiencies of NO and NO 2 are almost 100%. The activity of the washed catalysts can be completely recovered by drying with the purified air. Further, a simultaneous separated measurement of NO and NO 2 can be performed by utilizing the UV illumination dependence. This method was applied to the measurement of NO x in the ambient air. The NO x concentration measured by this method was in good agreement with that obtained using the chemiluminescence NO x analyzer. 相似文献
10.
Abstract In this study, experiments were performed with a bench-scale tube-type wet electrostatic precipitator (wESPs) to investigate its effectiveness for the removal of mass- and number-based diesel particulate matter (DPM), hydrocarbons (HCs), carbon monoxide (CO), and oxides of nitrogen (NO x) from diesel exhaust emissions. The concentration of ozone (O 3) present in the exhaust that underwent a nonthermal plasma treatment process inside the wESP was also measured. A nonroad diesel generator operating at varying load conditions was used as a stationary diesel emission source. The DPM mass analysis was conducted by means of isokinetic sampling and the DPM mass concentration was determined by a gravimetric method. An electrical low-pressure impactor (ELPI) was used to quantify the DPM number concentration. The HC compounds, n-alkanes, and polycyclic aromatic hydrocarbons (PAHs) were collected on a moisture-free quartz filter together with a PUF/XAD/PUF cartridge and extracted in dichloromethane with sonication. Gas chromatography (GC)/mass spectroscopy (MS) was used to determine HC concentrations in the extracted solution. A calibrated gas combustion analyzer (Testo 350) and an O 3 analyzer were used for quantifying the inlet and outlet concentrations of CO and NO x (nitric oxide [NO] + nitrogen dioxide [NO 2]), and O 3 in the diesel exhaust stream. The wESP was capable of removing approximately 67–86% of mass- and number-based DPM at a 100% exhaust volumetric flow rate generated from 0- to 75-kW engine loads. At 75-kW engine load, increasing gas residence time from approximately 0.1 to 0.4 sec led to a significant increase of DPM removal efficiency from approximately 67 to more than 90%. The removal of n-alkanes, 16 PAHs, and CO in the wESP ranged from 31 to 57% and 5 to 38%, respectively. The use of the wESP did not significantly affect NO x concentration in diesel exhaust. The O 3 concentration in diesel exhaust was measured to be less than 1 ppm. The main mechanisms responsible for the removal of these pollutants from diesel exhaust are discussed. 相似文献
11.
介绍了中小型工业窑炉生产过程中排放NOx的现状,并针对NOx的治理问题,从工程应用角度,简述了湿法和干法净化NOx的原理和化学反应过程。讨论了NOx排放特性和NOx废气中NO2/NOx比例的问题。提出了影响NOx治理的主要因素,包括吸收剂、吸附剂、催化剂和设备的部分应用参数,并结合工程实例指出工程需要注意的问题。介绍了多项采用湿法和干法净化NOx的工程应用项目,丰富了中小工业窑炉NOx废气的治理的实践经验,为中小工业窑炉排放NOx治理奠定了基础。 相似文献
12.
Abstract For at least 30 years, ozone (O 3) levels on weekends in parts of California’s South Coast (Los Angeles) Air Basin (SoCAB) have been as high as or higher than on weekdays, even though ambient levels of O 3 precursors are lower on weekends than on weekdays. A field study was conducted in the Los Angeles area during fall 2000 to test whether proposed relationships between emission sources and ambient nonmethane hydrocarbon (NMHC) and oxides of nitrogen (NO x) levels can account for observed diurnal and day-of-week variations in the concentration and proportions of precursor pollutants that may affect the efficiency and rate of O 3 formation. The contributions to ambient NMHC by motor vehicle exhaust and evaporative emissions, estimated using chemical mass balance (CMB) receptor modeling, ranged from 65 to 85% with minimal day-of-week variation. Ratios of ambient NO x associated with black carbon (BC) to NO x associated with carbon monoxide (CO) were approximately 1.25 ± 0.22 during weekdays and 0.76 ± 0.07 and 0.52 ± 0.07 on Saturday and Sunday, respectively. These results demonstrate that lower NO x emissions from diesel exhaust can be a major factor causing lower NO x mixing ratios and higher NMHC/NO x ratios on weekends. Nonmobile sources showed no significant day-of-week variations in their contributions to NMHC. Greater amounts of gasoline emissions are carried over on Friday and Saturday evenings but are, at most, a minor factor contributing to higher NMHC/NO x ratios on weekend mornings. 相似文献
13.
Reactive nitrogen species emission from the exhausts of gasoline and diesel vehicles, including nitrogen oxides (NO x) and nitrous acid (HONO), contributes as a significant source of photochemical oxidant precursors in the ambient air. Multiple laboratory and on-road exhaust measurements have been performed to estimate the NO x emission factors from various vehicles and their contribution to atmospheric pollution. Meanwhile, HONO emission from vehicle exhaust has been under-measured despite the fact that HONO can contribute up to 60% of the total hydroxyl budget during daytime and its formation pathway is not fully understood. A profound traffic-induced HONO to NO x ratio of 0.8%, established by Kurtenbach et al. since 2001, has been widely applied in various simulation studies and possibly linked to under-estimation of HONO mixing ratios and OH radical budget in the morning. The HONO/NO x ratios from direct traffic emission have become debatable when it lacks measurements for direct HONO emission from vehicles upon the fast-changing emission reduction technology. Several recent studies have reported updated values for this ratio. This study has reported the measurement of HONO and NO x emission as well as the estimation of exhaust-induced HONO/NO x ratios from gasoline and diesel vehicles using different chassis dynamometer tests under various real-world driving cycles. For the tested gasoline vehicle, which was equipped with three-way catalyst after-treatment device, HONO/NO x ratios ranged from 0 to 0.95 % with very low average HONO concentrations. For the tested diesel vehicle equipped with diesel particulate active reduction device, HONO/NO x ratios varied from 0.16 to 1.00 %. The HONO/NO x ratios in diesel exhaust were inversely proportional to the average speeds of the tested vehicles. Implications: Photolysis of HONO is a dominant source of morning OH radicals. Conventional traffic-induced HONO/NOx ratio of 0.8% has possibly linked to underestimation of the total HONO budget and consequently underestimation of OH radical budget. The recently reported HONO/NOx ratio of ~1.6% was used to stimulate HONO emission, which resulted in increased HONO concentrations during morning peak hours and its impact of 14% OH increment in the morning. However, the results were still lower than the measured concentrations. More studies should be conducted to establish an updated traffic-induced HONO/NOx ratio. 相似文献
14.
研究了有氧条件下氮氧化物在生物滤塔内的传质机理,结果表明,当含NOx废气中氧气含量为20%、氧化度为80%时,被生物滤塔内微生物吸附分解的NOx仅占被净化的NOx的12%左右,而88%左右的NOx没有被微生物及时分解,而是转入液相中形成NO3-和NO2-.在此基础上,提出了采用生物滤塔和硝酸盐脱除反应器(nitrate... 相似文献
15.
An explicit NO x chemistry method has been implemented in AERMOD version 15181, ADMSM. The scheme has been evaluated by comparison with the methodologies currently recommended by the U.S. EPA for Tier 3 NO 2 calculations, that is, OLM and PVMRM2. Four data sets have been used for NO 2 chemistry method evaluation. Overall, ADMSM-modeled NO 2 concentrations show the most consistency with the AERMOD calculations of NO x and the highest Index of Agreement; they are also on average lower than those of both OLM and PVMRM2. OLM shows little consistency with modeled NO x concentrations and markedly overpredicts NO 2. PVMRM2 shows performance closer to that of ADMSM than OLM; however, its behavior is inconsistent with modeled NO x in some cases and it has less good statistics for NO 2. The trend in model performance can be explained by examining the features particular to each chemistry method: OLM can be considered as a screening model as it calculates the upper bound of conversion from NO to NO 2 possible with the background O 3 concentration; PVMRM2 includes a much-improved estimate of in-plume O 3 but is otherwise similar to OLM, assuming instantaneous reaction of NO with O 3; and ADMSM allows for the rate of this reaction and also the photolysis of NO 2. Evaluation with additional data sets is needed to further clarify the relative performance of ADMSM and PVMRM2. Implications: Extensive evaluation of the current AERMOD Tier 3 chemistry methods OLM and PVMRM2, alongside a new scheme that explicitly calculates the oxidation of NO by O3 and the reverse photolytic reaction, shows that OLM consistently overpredicts NO2 concentrations. PVMRM2 performs well in general, but there are some cases where this method overpredicts NO2. The new explicit NOx chemistry scheme, ADMSM, predicts NO2 concentrations that are more consistent with both the modeled NOx concentrations and the observations. 相似文献
16.
Emissions from diesel-powered construction equipment are an important source of nitrogen oxides (NO x) and particulate matter (PM). A new emission inventory for construction equipment emissions is developed based on surveys of diesel fuel use; the revised inventory is compared to current emission inventories. California's OFFROAD model estimates are 4.5 and 3.1 times greater, for NO x and PM respectively, than the fuel-based estimates developed here. The most relevant uncertainties are the overall amount of construction activity/diesel fuel use, exhaust emission factors for PM and NO x, and the spatial allocation of emissions to county level and finer spatial scales. Construction permit data were used in this study to estimate spatial distributions of emissions; the resulting distribution is well correlated with population growth. An air quality model was used to assess the impacts of revised emission estimates. Increases of up to 15 ppb in predicted peak ozone concentrations were found in southern California. Elemental carbon and fine particle mass concentrations were in better agreement with observations using revised emission estimates, whereas negative bias in predictions of ambient NO x concentrations increased. 相似文献
17.
Monitoring data from the UK Automatic Urban and Rural Network are used to investigate the relationships between ambient levels of ozone (O 3), nitric oxide (NO) and nitrogen dioxide (NO 2) as a function of NO x, for levels ranging from those typical of UK rural sites to those observed at polluted urban kerbside sites. Particular emphasis is placed on establishing how the level of ‘oxidant’, OX (taken to be the sum of O 3 and NO 2) varies with the level of NO x, and therefore to gain some insight into the atmospheric sources of OX, particularly at polluted urban locations. The analyses indicate that the level of OX at a given location is made up of NO x-independent and NO x-dependent contributions. The former is effectively a regional contribution which equates to the regional background O 3 level, whereas the latter is effectively a local contribution which correlates with the level of primary pollution. The local oxidant source has probable contributions from (i) direct NO 2 emissions, (ii) the thermal reaction of NO with O 2 at high NO x, and (iii) common-source emission of species which promote NO to NO 2 conversion. The final category may include nitrous acid (HONO), which appears to be emitted directly in vehicle exhaust, and is potentially photolysed to generate HO x radicals on a short timescale throughout the year at southern UK latitudes. The analyses also show that the local oxidant source has significant site-to-site variations, and possible reasons for these variations are discussed. Relationships between OX and NO x, based on annual mean data, and fitted functions describing the relative contributions to OX made by NO 2 and O 3, are used to define expressions which describe the likely variation of annual mean NO 2 as a function of NO x at 14 urban and suburban sites, and which can take account of possible changes in the regional background of O 3. 相似文献
18.
A manual procedure Is outlined which utilizes an alkaline permanganate sampling train for the simultaneous collection of nitrogen and sulfur oxides from stationary sources. Dependent on anticipated concentrations, samples of up to an hour duration may be taken. Analysis of the collected NO x and SO x is straightforward, tailored for needed accuracy and minimum employment time. For oxides of nitrogen, the formed nitrites of collection are converted to nitrates. The total nitrate is then reduced to nitrite, diazotized and coupled to form a red dye. This is all accomplished with a commercially available "ready-made" reagent. The oxides of sulfur are determined by the turbidimetric barium sulfate procedure. Data are shown comparing the proposed method from numerous types of emission sources, both with accepted methods and newer instrumental techniques. The ability to sample simultaneously for NO x and SO x has many advantages, i.e., power plants, boilers, and other sources where both gases are of interest for compliance and/or source Inventory purposes. 相似文献
19.
在一种详细的表面反应机理中加入了包含贵金属催化剂与助催化剂的硫中毒基元反应,建立了新的三效催化转化器催化反应机理。利用该机理进行了稳态工况数值模拟,得到了各排气污染物起燃温度与转化效率随尾气中SO2浓度的变化情况。采用灰色关联分析了SO2浓度与各排气组分转化效率的关联度,结果表明,SO2浓度对C3H6与NOx转化效率影响最大。对三效催化转化器的催化剂活性设计具有重要的参考价值,并对其工况设计及优化提供了指导。 相似文献
20.
The nitrogen-containing products of smog chamber reactions have been the subject of much controversy. Concern has arisen over nitrogen products because of the almost universally poor nitrogen balance reported for irradiated mixtures of hydrocarbons and nitrogen oxides. Some possible nitrogen-containing products, such as molecular nitrogen, nitrous oxide, and nitroolefins have been investigated and shown to be unimportant. The nitrogen products most often measured are peroxyacetyl nitrate and residual nitrogen dioxide. These two products rarely comprise more than 70% of the initial nitrogen at the end of an experiment, and often account for less than 50%. Previous experiments in which total nitrate was determined in the gas phase and on the vessel walls at the end of irradiation have shown very good nitrogen balances. The assumption has been made that the nitrate arises from nitric acid formed on the walls by adsorbed N 2O 5. In the work reported here, all major nitrogen-containing compounds have been monitored continuously for the first time. Nitric oxide and nitrogen dioxide have been monitored by chemilumines-cence and automated Saltzman techniques. Methyl, ethyl, and peroxyacetyl nitrate have been determined by gas chromatogra-phy. Two methods, one continuous and one integrated, have been specially developed to measure nitric acid both in the smog chambers and in the atmosphere. Continuous determination of these compounds yields good nitrogen balances throughout the irradiations. Profiles of the nitrogen-containing species from irradiated HC/ NO x mixtures are discussed in terms of nitrogen products and nitrogen balance. Differences in product distribution for different hydrocarbon systems are also considered. Using rate information from the nitrogen compound profiles, important reactions leading to nitrogen-containing products are identified. Interference with the chemiluminescent technique by HON0 2, PAN, and C 2H 5ONO 2 is discussed. 相似文献
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