EPA Method 25 Determination Of Total Gaseous Nonmethane Organic Emissions As Carbon
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ID： |
BE0D3680B52644BE9FC32848D200A0FE |
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文件大小(MB)： |
0.2 |
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页数： |
48 |
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文件格式： |
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日期： |
2000-2-12 |
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文本摘录（文本识别可能有误，但文件阅览显示及打印正常，pdf文件可进行文字搜索定位）：
1201,METHOD 25 - DETERMINATION OF TOTAL GASEOUS NONMETHANE,ORGANIC EMISSIONS AS CARBON,1.0 Scope and Application.,1.1 Analytes.,Analyte CAS No. Sensitivity,Total gaseous nonmethane,organic compounds,(TGNMO),N/A Dependent upon,analytical equipment,1.2 Applicability.,1.2.1 This method is applicable for the determination,of volatile organic compounds (VOC) (measured as total,gaseous nonmethane organics (TGNMO) and reported as carbon),in stationary source emissions. This method is not,applicable for the determination of organic particulate,matter.,1.2.2 This method is not the only method that applies,to the measurement of VOC. Costs, logistics, and other,practicalities of source testing may make other test methods,more desirable for measuring VOC contents of certain,effluent streams. Proper judgment is required in,determining the most applicable VOC test method. For,example, depending upon the molecular composition of the,organics in the effluent stream, a totally automated,semicontinuous nonmethane organics (NMO) analyzer interfaced,directly to the source may yield accurate results. This,1202,approach has the advantage of providing emission data,semicontinuously over an extended time period.,1.2.3 Direct measurement of an effluent with a flame,ionization detector (FID) analyzer may be appropriate with,prior characterization of the gas stream and knowledge that,the detector responds predictably to the organic compounds,in the stream. If present, methane (CH4) will, of course,also be measured. The FID can be used under any of the,following limited conditions: (1) where only one compound is,known to exist; (2) when the organic compounds consist of,only hydrogen and carbon; (3) where the relative percentages,of the compounds are known or can be determined, and the FID,responses to the compounds are known; (4) where a consistent,mixture of the compounds exists before and after emission,control and only the relative concentrations are to be,assessed; or (5) where the FID can be calibrated against,mass standards of the compounds emitted (solvent emissions,for example).,1.2.4 Another example of the use of a direct FID is,as a screening method. If there is enough information,available to provide a rough estimate of the analyzer,accuracy, the FID analyzer can be used to determine the VOC,content of an uncharacterized gas stream. With a sufficient,buffer to account for possible inaccuracies, the direct FID,1203,can be a useful tool to obtain the desired results without,costly exact determination.,1.2.5 In situations where a qualitative/quantitative,analysis of an effluent stream is desired or required, a gas,chromatographic FID system may apply. However, for sources,emitting numerous organics, the time and expense of this,approach will be formidable.,2.0 Summary of Method.,2.1 An emission sample is withdrawn from the stack at,a constant rate through a heated filter and a chilled,condensate trap by means of an evacuated sample tank. After,sampling is completed, the TGNMO are determined by,independently analyzing the condensate trap and sample tank,fractions and combining the analytical results. The organic,content of the condensate trap fraction is determined by,oxidizing the NMO to carbon dioxide (CO2) and quantitatively,collecting in the effluent in an evacuated vessel; then a,portion of the CO2 is reduced to CH4 and measured by an FID.,The organic content of the sample tank fraction is measured,by injecting a portion of the sample into a gas,chromatographic column to separate the NMO from carbon,monoxide (CO), CO2, and CH4; the NMO are oxidized to CO2,reduced to CH4, and measured by an FID. In this manner, the,1204,variable response of the FID associated with different types,of organics is eliminated.,3.0 Definitions. [Reserved],4.0 Interferences.,4.1 Carbon Dioxide and Water Vapor. When carbon,dioxide (CO2) and water vapor are present together in the,stack, they can produce a positive bias in the sample. The,magnitude of the bias depends on the concentrations of CO2,and water vapor. As a guideline, multiply the CO2,concentration, expressed as volume percent, times the water,vapor concentration. If this product does not exceed 100,the bias can be considered insignificant. For example, the,bias is not significant for a source having 10 percent CO2,and 10 percent water vapor, but it might be significant for,a source having 10 percent CO2 and 20 percent water vapor.,4.2. Particulate Matter. Collection of organic,particulate matter in the condensate trap would produce a,positive bias. A filter is included in the sampling,equipment to minimize this bias.,5.0 Safety.,5.1 Disclaimer. This met……
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