Nitrogen oxides, analyzer

There may be many types of chemical species of interest for a given test. The most common types of analyzers associated with combustion equipment are contained in a rack or cabinet as seen in Figure 33.4. The typical analyzers found in one of these cabinets are a paramagnetic oxygen analyzer, infrared absorpfion carbon monoxide analyzer, UBH analyzer, and a chemiluminescent nitrogen oxide analyzer. Commercial sulfur dioxide analyzers based on infrared or ultraviolet absorption are also readily available to fit into one of these racks. The... 

The NO analyzer is based on the principles of chemiluminescence to determine continuously the NO concentration in the sample gas stream. The analyzer should contain a NOg-to-NO converter, which converts the nitrogen dioxide (NO9) in the sample gas to nitrogen oxide (NO). An NOg-to-NO converter is not necessary if data are presented to demonstrate that the NO9 portion of the exhaust gas is less than 5 percent of the total NO9 concentration. 

Air emissions at point of discharge should be monitored continuously for fluorides and particulates and aimually for ammonia and nitrogen oxides. Monitoring data should be analyzed and reviewed at regular intervals and compared with the operating standards so that any necessary corrective actions can be taken. Records of monitoring results should be kept in an acceptable format. The results should be reported to the responsible authorities and relevant parties, as required. 

Gases analyzed include hydrocarbons, carbon monoxide, carbon dioxide, sulfur dioxide, sulfur trioxide, nitrogen oxides (also nitrous oxide, N2O), hydrogen chloride, hydrogen cyanide, ammonia, etc. 

A similar device with Nasicon solid electrolyte Na3Sc(P04)3 is used when analyzing the concentration of nitrogen oxides in air. The electrochemical system in this sensor can be formnlated as... 

Zhao et al. [74] developed a kinetic model to analyze the removal of nitrogen oxides in a pulsed corona discharge in NO/N2 mixtures. They considered reactions of NO and N02 with N and O atoms and with excited N2(A3S) molecules. 

Before 1970, most of the data for nitrogen oxides were obtained by continuous measurements with a colorimetric analyzer that was similar in principle to the colorimetric oxidant analyzer shown in Figure 6-8. The scrubbing agent is a mixture of -(l-naphthyl)ethylenediamine, sulfanilic acid, and acetic acid in aqueous solution. The color is produced when both nitrogen dioxide and nitrites react with this reagent to form an azo dye. The color is not affected by nitric oxide in the air sample. 

The calibration of a chemiluminescent analyzer using these standards is verified when both the nitrogen dioxide and nitric oxide channels respond similarly to charges from the (ylinder of diluted nitric oxide. Agreement with the response of the nitric oxide channel should also be obtained when the standard nitric oxide mixture is titrated with a previously established source of ozone. Chemiluminescent instruments have simplified monitoring of nitrogen oxides, but accurate calibration requires well-trained personnel. 

RR) E-J. Murphy, "Comparison of Methods for Detecting and Analyzing Fumes from Explosives , USBurMines R1 51133(1961). A comparative study of several analytical methods for determining carbon monoxide and nitrogen oxides in toxic gases produced by detonation of explosives... 

Due to the manner in which fuel is oxidized in UMR, the byproduct exhaust gases contain no oxides of nitrogen. The nitrogen oxide concentrations were below the detection limit of the gas analyzer, roughly 0.03 ppm. 

In recent years, the effects of acid rain on lake water, heavy metals contaminated soils and structural materials have been widely discussed (1). Sulfur and nitrogen contained in fossil fuels are released into the atmosphere by combustion. Sulfur and nitrogen oxides dissolve in rain drops as bisulfite, sulfite and nitrite ions. These components are further oxidized into sulfate and nitrate ions. Since these species lower pH, it is important to accurately determine them in rain water. However, these ions are difficult to analyze because they rapidly oxidize in the presence of catalysts such as ferric and manganous ions. Light, temperature, and pH also affect the oxidation rate of S(IV). 

Difficulties are encountered in determining NO2 using the ozone-chemiluminescence technique due to the non-specific conversion of several nitrogen oxides/oxyacids on the Mo catalyst. Use of FeS04 f°r N02-to-N0 conversion has been described, but humidity-dependent sorption/desorption effects have been reported, e.g., PAN (11). Alternatively, a commercial NO2 analyzer based on surface chemiluminescence of NO2 in the presence of a luminol solution, has been introduced which exhibits the requisite sensitively and selectivity. 

A more direct study of the reaction between CO and NO2 was made by Brown and Crist [485], who used a KCl coated Pyrex reaction vessel fitted with a greaseless valve to avoid decomposition of the NO2. In order also to avoid complications due to gas phase dissociation of the NO2, its pressure was kept very low (<0.5 torr), and the reaction times were kept comparatively short. Amounts of reaction were measured by freezing and then analyzing for the product CO2 by vacuum sublimation from the nitrogen oxides. In order to obtain measurable amounts of reaction under the conditions stated, it was necessary to employ high concentrations of CO. Even then the partial pressures of CO2 in the products were less than 30 microns, and often as little as 5 microns, so that good experimental technique was required. It was confirmed that the reaction was second order over some two- to three-fold variation of the partial pressures of CO and NO2. Mean rate coefficients between 500 and 563 K are given in Table 57. 

Instrumentation for the research was developed prior to formulation of the problem. This fortunate situation arose because the instruments were developed for monitoring the lower atmosphere for ozone, nitric oxide, and nitrogen dioxide these compounds are usually present in polluted atmospheres at concentrations below 1 p.p.m. by volume. On hand were an automatic recording nitrogen dioxide analyzer (11), a neutral potassium iodide oxidant recorder (5), and an ozone photometer (Model 53 ultraviolet, Harold Kruger Instruments, San Gabriel, Calif.). Each of these instruments has a sensitivity of 1 to 2 p.p.hm. parts of carrier gas at atmospheric pressure. Without their prior development, the photochemical study would have been impossible. 

A series of laboratory experiments was conducted in which galvanized steel samples were exposed to NO2 in air and irradiated propylene/nitrogen oxides/air mixtures in the absence and presence of SO2. Dew was produced periodically on the test panels, and, at the end and/or during the experiments, panels were sprayed with either deionized water or an ammonium bisulfate solution (pH of 3.5). Gas phase concentrations were monitored, and dew and rain rinse samples were analyzed for nitrite, nitrate, sulfite, sulfate, formaldehyde, and zinc. 

A urease packed bed reactor combined with an ammonia electrode is being used in a blood urea nitrogen (BUN) analyzer marketed since 1976 by the Kimble Division of Owens-Illinois (USA). Urease is bound to aluminum oxide particles. The reaction is conducted at pH 7.5. In order to obtain a high sensitivity for the ammonia electrode, the product stream leaving the reactor is mixed with NaOH until a pH of 11 is attained (Watson and Keyes, 1976). 

Today, we often use the NO-O3 chemiluminescence nitrogen oxides (NO ) analyzer for determining NO concentration in the atmosphere. In the atmosphere, especially at rural sites, NO dominates the formation of O3 known as a toxic substance. " It is important that we understand atmospheric chemistry including O3 formation and the changes in atmospheric NO concentration. High sensitivity and quick response are required on the NO-O3 chemiluminescence NO analyzer for that purpose. However, commercial NO < analyzers generally have insufficient sensitivity for the measurement of NO concentration at the low levels, which are often observed in remote region such as rural sites. 

Continuous analysis instruments equipped with flame ionization, chemiluminescence, and infrared detectors were used to measure the concentrations of total hydrocarbons, nitrogen oxides and carbon monoxide, respectively. The concentration of total hydrocarbons was measured by a JUM FID 3-300 hydrocarbon analyzer with a flame ionization detector. NO, NO2 and NOx was measured by an ECO Physics CLD 700 EL-ht chemiluminescence detector. CO was measured with either a Beckman Industrial Model 880 non-dispersive infrared instrument or an NDIR instrument from Maihak (UNOR 6N). 

In electric power generating stations, restricting the NO (nitrogen oxide compounds) emissions from the flue gas to acceptable levels is important, because NO, compounds contribute to air pollution. Typically, on-line analyzers are used to measure the NO, in the flue gas from the boilers. 

Nitrogen has an odd number of electrons on the outer shell just like phosphorus. However, the nitrogen oxide radicals formed similarly to the phosphorus oxide radicals are cracked very quickly in the hot analyzing chamber in compari-... 

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