API PUBL 4772-2008 Measuring Particulate Emissions from Combustion Sources《燃烧源中颗粒排放物的测量》.pdf

1、Measuring Particulate Emissions from Combustion SourcesAPI PUBLICATION 4772 SEPTEMBER 2008Measuring Particulate Emissions from Combustion SourcesRegulatory and Scientific Affairs DepartmentAPI PUBLICATION 4772 SEPTEMBER 2008Special NotesAPI publications necessarily address problems of a general natu

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11、f Regulatory and Scientific Affairs, API, 1220 L Street, NW, Washington D.C. 20005.Table of Contents Section PageExecutive Summary 1 Introduction: Filterable and Condensable Particulate Emissions. 4 Principal Measurement Approaches. 4 Filter/Impinger System: Directly Sampling Stack Gas. 4Dilution Sa

12、mpling System: Replicating Ambient Air 5 Condensable Particulate Formation 5 Conventional Measurements: Filter/Impinger Sampling. 6 EPA Method 5 6 EPA Methods 5B and 5F 7 EPA Method 17.8 EPA Method 201A8Sulfuric Acid Emission Measurements 9 EPA Methods 6 and 8 9 Controlled Condensation System. 10 Im

13、portance of Measuring PM 2.5 and Condensable Emissions. 11 EPA Method 202 and its Modifications12 South Coast Air Quality Management District Methods 5.1 and 5.2 14 An Alternate Approach: Replicating the Atmosphere with Dilution System Sampling 14 Dilution System Sampling Results. 17 Mass Emissions

14、18 Chemical Speciation. 18 Quantitation and Precision 20 Guidance for Source Operators: Which Method Do I Use and When? . 20 References. 24 Executive Summary The principal measurement methods for sampling particulate matter (PM) from stationary combustion sources generally consist of a sampling trai

15、n that includes a heated filter maintained at a variety of elevated temperatures, followed by a series of aqueous impinger solutions used to collect material that is in the vapor phase within the stack, but could condense and form PM immediately after entering the atmosphere. These two fractions are

16、 commonly referred to as “filterable” (e.g. fly ash or catalyst fines) and “condensable” (e.g. sulfuric acid, semi-volatile organics, or ammonium sulfates), PM. Since the early 1970s, the EPA has proposed a number of methods to determine PM emitted from combustion sources and these are discussed in

17、this report. Most of the attention was initially centered on measuring filterable PM as this material was considered to comprise the major fraction of PM emissions subject to removal by control technology. The EPA methods and their variants differ primarily in the temperature of the collecting filte

18、r, leading to accumulation of different amounts of material on the filter (depending upon the species present in the stack gas). A summary of the operating temperatures and impact on condensables accumulation (Table 1) indicates the biases that can occur between the principal PM measurement methods

19、employed today. Table 1. PM Emissions Measurement Methods & Filter Temperatures: Will the Component Be Collected on the Filter? Method Filter Temperature, oF Catalyst Fines/Ash H2SO4NH4Sulfates EPA 5 EPA 5B, 5F EPA 17 EPA OTM 27 SCAQMD 5.1/5.2 Dilution Sampler 248 25 320 10 Stack temp. Stack temp. 1

20、90 Ambient Yes Yes Yes Yes Yes Yes Some No No* No* Some Yes Yes Yes No* No* Yes Yes *Stack temperatures are generally 500 oF for units without wet scrubbers. Units equipped with wet scrubbers have stack temperatures 500 oF) precedes a cooled condensation coil that lowers the filtered sample gas temp

21、erature to 167-185 oF, below the dew point of sulfuric acid. Droplets of condensed sulfuric acid are collected and rinsed from the coil while the SO2passes on and is collected in peroxide solution impingers. There are several published variations of the method, differing in the filter temperature an

22、d sulfate analysis procedures employed (Maddalone, 1979, Cheney, 1984). In contrast to the bias found for Method 8, the additional presence of ammonia in the sample stream does not contribute a positive bias to the sulfuric acid measurements using this method (England, 2008). This method has not bee

23、n widely used for refinery source testing despite the fact that the EPA recognizes controlled condensation as a valid test method (Myers, 2007) and provides the method as NCASI Method 8A in the list of Conditional Test Methods provided in the EMC section of the EPA website (www.epa.gov/ttn/EMC). As

24、such, operators of refinery combustion units are encouraged to insist that regulatory agencies accept it for testing inasmuch as the current EPA Methods 6 and 8 are subject to a positive bias and not sufficiently accurate at low SO2concentrations. Figure 3. Controlled Condensation Method Sampling Tr

25、ain (SO3) (Maddalone, 1979) Measuring Particulate Emissions from Combustion Sources 11 Importance of Measuring PM 2.5 Emissions and Condensable PM The EPAs increasing concern about the health effects of inhaling PM ultimately led to the development of new National Ambient Air Quality Standards (NAAQ

26、S) for fine PM, defined as having an aerodynamic diameter equal to or less than 2.5 microns equal to or less than 2.5 microns as measured by EPA Reference Methods (Federal Register, 1997). This occurred along with the development of new emission sampling methods, Methods 201 and 201A that included i

27、n-stack cyclones ahead of an in-stack filter (Figure 4) to quantify different PM size fractions: total PM, PM 10 and PM 2.5. These methods were designated as Conditional Test Method 40 (CTM 040) and, more recently, as Other Test Method 027 (OTM 027). At the same time, advances in emissions control t

28、echnology resulted in the development of improved wet scrubbers and wet ESPs capable of capturing fine PM. The PM 2.5 fraction of the total PM emissions had a large component of condensable PM, as the physics of condensation leads to the formation of small-size particles. Consequently, the EPA recon

29、sidered methods for determining condensable PM and returned to their original proposal for Method 5, including aqueous impingers after the heated filter to collect the condensable PM. With the promulgation of this method, the EPA believed that it had procedures to quantify the emissions of condensab

30、le PM and filterable PM into the atmosphere, as well as the means to determine the effectiveness of control technologies designed to reduce them (Myers, 2006). 12 API Publication 4772 Figure 4. EPA OTM 027 Sampling Train (U.S. EPA, 2004) EPA Method 202 and its Modifications The method promulgated by

31、 the EPA for measuring condensables was published as Method 202. Method 202 measures condensable PM by bubbling a pre-filtered gas sample through a series of impingers partially filled with water and placed in an ice bath. The impinger solutions are then evaporated and dried to determine the net res

32、idue weight. The method includes a number of blanks (de-ionized water, dichloromethane, and a filter) used to correct the test results. In an attempt to correct some of the difficulties present in the original draft first proposed in 1971, the new method included a nitrogen purge of the impingers af

33、ter completion of the test to remove any residual SO2from solution to prevent its conversion to sulfate. The inclusion of a different solvent, dichloromethane, was also thought to result in improved extraction of any organic condensable PM present. In the years following its publication, this method

34、 was widely adopted by state and local regulatory agencies for compliance testing to measure condensable PM in a sampling train along with filterable PM, thereby determining total PM emissions. However, it soon became apparent that measurements of condensable PM made with Method 202 were higher than

35、 anticipated for gas-fired sources, and its accuracy was questioned (Corio, 2000). Evidence grew that the nitrogen purge was very important but not effective in preventing conversion of dissolved SO2to condensed sulfates, which subsequently could react with dissolved ammonia to form ammonium sulfate

36、s prior to actual analysis. In addition, any NH3in the emissions gas, either as a consequence of its use as a Measuring Particulate Emissions from Combustion Sources 13 particle conditioning agent for ESPs or as ammonia slip from installed nitrogen oxides control technology, reacts with SO2in the im

37、pinger solutions to increase the measured sulfates and further bias the apparent condensable emissions rate. In response to these concerns, research studies were carried out to modify Method 202 to avoid conversion of SO2 to sulfate in the impinger solutions (Richards, 2005). In this optimized Metho

38、d 202 (Figure 5), the gas entering the sampling train is first contacted on the surface of an indirect condenser to a temperature below 68 oF using cold water recirculated from the impinger case. With this modification, the only contact between gaseous SO2 and condensed water is with condensed mater

39、ial on the surfaces of the indirect heat exchanger. A large knockout or dry impinger follows the condenser to quickly separate the sample gas from the condensed water. The sample gas stream then passes through two empty Greenberg-Smith impingers to ensure complete droplet knockout and condensable PM

40、 formation upstream of the condensable PM filter. The filter collection is combined with the rinses of the empty Greenberg-Smith impingers. All of the condensed material is then extracted from the combined sample and analyzed in accordance with standard Method 202 analytical procedures. Laboratory t

41、ests have shown that this procedure avoids artifact formation in gas streams containing SO2, NOx, and NH3 (up to 15 ppm) associated with the standard method. While these results are promising, very few field tests have been carried out to establish the method on a firm basis. As evaluation and possi

42、ble modifications of optimized Method 202 is ongoing, readers are advised to consult the EPA website to learn of new developments regarding the current status of optimized Method 202. EPA has termed this method as OTM 028 and has made it available on its website. 14 API Publication 4772 Figure 5. Op

43、timized EPA Method 202 Sampling Train (Richards, 2005) South Coast Air Quality Management District Method 5.2 While it is not the intention of this report to review the various state and local regulatory approaches to measuring PM emissions, no report would be complete without mentioning the South C

44、oast Air Quality Management District (SCAQMD) method for measuring filterable and condensable PM, Method 5.2 (SCAQMD, 1989). Although this method uses the same equipment as EPA Method 5, this method specifies that the external filter to be maintained at about 190 oF. Due to the low filter temperatur

45、e, SO3in the flue gas will be collected as sulfuric acid and ammonium sulfates (where the stack gas contains ammonia) on the filter. Hence, collected condensables cause a positive bias in the filterable portion using Method 5.2. This bias can be very significant (50%) for FCC units operating in the

46、SCAQMD due to very low stack emissions limits for PM. An Alternate Approach: Replicating the Atmosphere with Dilution System Sampling The methods described in the preceding pages are all based on collecting filterable PM on a filter maintained at various elevated temperatures and subsequently collec

47、ting any condensable PM in an aqueous impinger solution. Needless to say, this does not replicate the conditions or correspond to the processes leading to the formation of PM in the atmosphere downwind from Measuring Particulate Emissions from Combustion Sources 15 these sources. Researchers have long been interested in developing a PM source test method that more closely represents PM formation phenomena that occur as the exiting stack gas interacts with the atmosphere. This has been achieved for mobile source emissions measurements, which have been quantified since the 19