United States Office of Air Quality Environmental Protection Planning and Standards Agency Research Triangle Park NC 27711 A,r EPA-450/3-84-16 September 1984 Development and Evaluation of Method 5B— Background Information for Proposed Reference Method ------- EPA-450/3-84{16 Development and Evaluation of Method 5B—Background Information for Proposed Reference Method Emission Standards and Engineering Division U.S. ENVIRONMENTAL PROTECTION AGENCY Office of Air and Radiation Office of Air Quality Planning and Standards Research Triangle Park, NC 27711 September 1984 ------- This report has been reviewed by the Emission Standards and Engineering Division of the Office of Air Quality Planning and Standards, EPA, and approved for publication. Mention of trade names or commercial products is not intended to constitute endorsement or recommendation for use. Copies of this report are avialable through the Library Services Office (MD-35), U.S. Environmental Protection Agency, Research Triangle Park, N.C. 27711, or from National Technical Information Services, 5285 Port Royal Road, Springfield, Virginia 22161. ------- Introduction On June 11, 1979, the Environmental Protection Agency (EPA) promulgated standards of performance for new electric utility steam generating units. In the preamble to the regulation (44 FR 33580), EPA acknowledged that using Method 5 to sample for particulate matter in gas streams containing large amounts of sulfuric acid mist could lead to collection of condensed sulfuric acid mist as part of the particulate sample. Because particulate control devices, that were identified as best emission reduction systems, do not remove sulfuric acid mist, EPA concluded that the particulate matter sample should not include the condensed acid mist and agreed to develop a test procedure that would allow the measurement of nonsulfuric acid particulate matter (NSAPM). Two approaches can be used to measure NSAPM. One is to use a sampling procedure that collects particulate but does not collect sulfuric acid, and the other is to use the existing sampling procedure (Method 5) and then remove any condensed sulfuric acid from the sample. Conceptually, the first approach seems easier, but it presents some difficult problems in execution. The physical state of sulfuric acid in the stack depends on three variables, the temperature of the gas, the concentration of water vapor, and the concentration of sulfur trioxide ($03). As an example, at 155°C and 10 percent water vapor, a gas stream can contain about 82 ppm of uncondensed $03, but at 150°C and 10 percent water vapor, a gas stream can contain only about 52 ppm. This makes it obvious that one needs to control the temperature of the sampling system very precisely and evenly to prevent the collection of condensed sulfuric acid, but the sampling equipment used with Method 5 does not lend itself ------- readily to this kind of precise temperature control. Higher sampling temperatures could be used, but construction materials become a problem. Removing condensed sulfuric acid after sampling has two major advantages: (1) It allows the tester greater flexibility in the choice of sampling equipment and conditions, and (2) it confines operations requiring very precise control to the laboratory. For these reasons, the second approach, that of removing any condensed sulfuric acid after the sample is collected, was chosen as the more promising one. Of the possible procedures for removing condensed sulfuric acid, the two most commonly used are: (1) heating the samples in an oven to evaporate the sulfuric acid before weighing, and (2) weighing the samples to constant weight, then chemically measuring the condensed sulfuric acid and subtracting its weight. These two techniques were compared using particulate samples collected at a coal-fired power plant burning a very high sulfur coal and equipped with a wet scrubber. For this set of samples, the two techniques gave comparable results for NSAPM. Each technique has its own advantages and disadvantages. The heating technique is relatively quick and simple, but it is not specific for condensed sulfuric acid since any substance that has a similar boiling point would also be evaporated. The analysis/subtraction technique is more specific since there are very few interferences with the chemical measurement, but it is more time consuming and requires a very accurate weighing of the sample while it still contains sulfuric acid. This can be difficult because sulfuric acid is very hygroscopic, and the samples may ------- not reach constant weight. Because the heating technique seemed to have fewer problems, it was the technique chosen for initial development. Method Development A working method tentatively entitled Method 5B was drafted. The method allowed the tester the option of collecting samples at any temperature up to 260°C, but specified that the samples be returned to the laboratory and heated in a laboratory oven at 160°C for 3 hours before desiccating and weighing. To determine the effect of sample collection temperature, a series of comparative tests were conducted at three different sites. Two of the test sites were coal-fired boilers, and the other was an oil-fired boiler. The sulfur content of the fuel varied according to site. A series of paired samples were collected at each site using a dual train system. The filter and sample probe of one train was maintained at 121° +_ 25°C as specified in Method 5, while the filter and probe of the other train was maintained at 160° _+ 25°C. The samples from all sites were first desiccated at room temperature and then weighed. Following this initial weighing, samples from some sites were extracted with isopropyl alcohol (IPA) to remove the sulfuric acid. The IPA extract was then analyzed for sulfuric acid by barium-thorin titration and the resultant weight of sulfuric acid was subtracted from the initial sample weights. Samples from other sites were heated to 160°C for 3 hours, desiccated, and weighed. All samples from a particular site were treated in the same manner. ------- The results from these tests are summarized in Tables 1-3. As expected, the initial sample weights of the samples filtered at 121°C were consistently higher than those filtered at 160°C. This can easily be seen from the tables. However, after both pairs of samples were treated to remove the condensed sulfuric acid, this relationship did not really change. Although the differences between Method 5 and 5B samples became smaller, the samples collected by Method 5 were still consistently higher than those collected by Method 5B. This can also be seen clearly from the tables. Although the reason for this difference could not be determined, it was apparently related to the relative amounts of condensed sulfuric acid collected with the sample. The Environmental Monitoring and Systems Laboratory of EPA conducted similar tests concurrent with the testing described above. Their report also concluded that "sampling below the acid dew point and failure to keep the particulate material dry during sampling cause a positive bias in the sample results - a bias that is not removed by washing with IPA or by heating to 316°C." While the source of this positive bias is unknown, it is clear that samples should not be collected at temperatures below the acid dew point. Therefore, the working draft of Method 5B was revised to require that samples be collected at temperatures of 160° + 25°C. However, some questions remained as to the most suitable temperature for conditioning the filters in the laboratory prior to weighing. ------- Table 1. COAL-FIRED BOILER NUMBER 1 RATIO OF CONCENTRATION TO REFERENCE CONDITION (Method 5B - Following I PA Extraction) Sample method Analysis condition Ambient I PA extraction 5 1.54 1.15 r~ SB 1.03 1.00 Table 2. COAL-FIRED BOILER NUMBER 2 RATIO OF CONCENTRATION TO REFERENCE CONDITION (Method 5B - Heated to 160°C) Sampl e method Analysis condition Ambient Oven heat - 160°C 5 2.58 1.60 5B 1.07 1.00 Table 3. OIL-FIRED BOILER RATIO OF CONCENTRATION TO REFERENCE CONDITION (Method 5B - Heated to 160°C) Sampl e method Analysis condition Ambient Oven heat - 160°C b 6.73 2.00 5B 3.80 1.00 ------- Using the revised draft of Method 5B, EPA began a second test program to evaluate the consistency of the method and to determine the effects of different conditioning temperatures on the measured NSAPM. Tests were conducted at two different sources. The first was a coal-fired boiler equipped with an electrostatic precipitator and a flue gas desulfurization unit, and the second was an oil-fired unit equipped with a mechanical dust collector. Both units were burning fuels with relatively high sulfur contents, ranging from 2.4 to 3.5 percent sulfur. Samples were collected with a sampling system, called a quad train, which allows the tester to collect four simultaneous samples divided into two pairs, each pair of which is collected under the same conditions. The advantage of this system is that a large number of paired samples can be collected in a relatively brief period of time. This minimizes the effect of temporal variations in source emissions making comparison between sampling methods easier. A more complete explanation of this sampling system and it's operation can be found in the emission test reports. The detailed sampling and analytical matrices for the coal-fired boiler are shown in Tables 4 and 5, and for the oil-fired boiler in Tables 6 and 7. All the samples were collected with the filter and probe operated at 160°F except for those samples where the probe was heated to 204°F. There were two basic patterns of analysis. Most samples were desiccated at ambient temperature and weighed, and then conditioned in a laboratory oven at temperatures varying from 160°C to 316°C for periods of 6 to 24 hours before being desiccated and reweighed. The remaining samples were ------- Table 4. SAMPLE MATRIX FOR COAL-FIRED BOILER Run no. 1 2 3 4 5 6 7 8 9 10 Sampl e train no. 1A IB 1C ID 2A 2B 2C 2D 3A 3B 3C 3D ' 4A 4B 4C 4D 5A 5B 5C 5D 6A 6B 6C 6D 7A 7B 7C 7D 8A 8B 8C 8D 9A 9B 9C 9D 10A 10B IOC 10D MSB 160°C (320°F) X X X X X X X X X X X X X X X X X X X X X X X X Sampl e method3 M5B-P400 160°-204°C (320°-400°F) X X X X X X X X M5W 160°C (320°F) X X X X X X X X a M5B - Probe and filter heated to 160°C (320°F). M5B-P400 - Probe heated to 204°C; filter heated to 160°C. M5W - Probe and filter heated to 160°C; water rinse of nozzle, probe, and front filter holder glassware. ------- Table 5. ANALYTICAL MATRIX FOR COAL-FIRED BOILER Run no. 1 2 3 4 5 6 7 8 9 10 Samp! e train no. 1A IB 1C ID 2A 2B 2C 2D 3A 3B 3C 3D 4A 4B 4C 4D 5A 5B 5C 50 6A 6B 6C 6D Sampl e method Thermogravi metric conditionings Ambient 160° 232° 316°C MSB X MSB X M5BW M5BW M5B-P400J M5B-P400J MSB MSB M5BW M5BW MSB MSB MSB MSB M5B-P400 M5B-P400 MSB MSB MSB M5B M5B MSB M5BW M5BW 7A IM5B-P400 7B IM5B-P400 7C M5B 7D M5B 8A M5BW 8B M5BW 8C MSB 8D MSB 9A MSB 9B MSB 9C MSB -P 400 9D M5B-P400 10A MSB 108 MSB IOC MSB 10D M5B X (24) X X (24) X X X (24) X X X X (24) X X (24) X (24) X (24) X (24) X Ambient 232° 316°C X X X X (24) X (24) X (24) X (24) X Ambient 316°C X X (24) X X X (24) X (24) 1 Water soluble sulfate determination*5 X X X X X X X X a Thermogravimetric conditioning of probe rinse and filter fractions at indicated temperatures after initial desiccation and ambient weights were obtained. The designation (24) for selected samples indicates a heat period of 24 hours. All other samples were heat-conditioned for 6 hours. b In this procedure, the mass of total water soluble sulfates in the sample was determined and subtracted from the total sample mass. NOTE:, All back halves represent a modified Method 8, with analysis for sulfates as sulfuric acid and sulfur dioxide. 8 ------- Table 6. SAMPLE MATRIX FOR OIL-FIRED BOILER Run no. 1 2 3 4 5 6 7 8 9 10 Sampl e train no. 1A IB 1C ID 2A 2B 2C 2D 3A 3B 3C 3D 4A 4B 4C 4D 5A 5B 5C 5D 6A 6B 6C 6D 7A 7B 7C 7D 8A 8B 8C 8D 9A 9B 9C 90 IDA 10B IOC 10D MSB 160°C (320°F) X X X X X X X X X X X X X X X X X X X X X X X X X X Sample method3 M5B-P400 160°-204°C (320°-400°F) X X X X X X X X M5W 160°C (320°F) X X X X X X a MSB - Probe and filter heated to 160°C. M5B-P400 - Probe heated to 204°C; filter heated to 160°C. M5W - Probe and filter heated to 160°C; water rinse of nozzle, probe, and front filter holder glassware. 9 ------- Table 7. ANALYTICAL MATRIX FOR OIL-FIRED BOILER Run no. 1 2 3 4 b 6 V 8 9 10 1 Sample I Sample train no. I method 1A IB 1C ID 2A 2B 2C 2D 3A 3B 3C 4D 4A 4B 4C 4D 5A 5B 5C 5D 6A 68 6C 6D 7A 7B 7C 7D 8A 8B 8C 8D 9A 98 9C 9D 10A 10B IOC 10D Thermogra vi metric conditioning3 Ambient 160° 232° 316°C M5BW | M5BW MSB X MSB 1 X MSB MSB M5BW M5BW MSB MSB M5B-P400 M5B-P400 M5B-P400 M5B-P400 MSB MSB MSB MSB MSB MSB MSB MSB MSB MSB M5BW MSB M5BW MSB M5B M5B-P400 MSB M5B-P400 MSB MSB MSB MSB MSB M5B-P400 MSB M5B-P400 X (24) X (24) X X X X X X X X X X X (24) X (24) X (24) X X (24) X Ambient 232° 316°C X (24) X (24) X X X X X X X X Ambi ent 316°C Water soluble sulfate determination^ X X X X X (24) X (24) X X X X Thermogravimetric conditioning of probe rinse and filter fractions at indicated temperatures after initial desiccation and ambient weights were obtained. The designation (24) for selected samples indicates a heat period of 24 hours. All other samples were heat-conditioned for 6 hours. in this procedure, the mass of total water-soluble sulfates in the sample was determined and subtracted from the total sample mass. NOTE: All back halves represent a modified Method 8, with analysis for sulfates as sulfuric acid and sulfur dioxide. 10 ------- treated with ammonium hydroxide to convert any sulfuric acid to ammonium sulfate before the total particulate matter was weighed. The water soluble sulfate content was then measured by a separate method and subtracted from the total particulate matter weight. This procedure, identified as Method 5W here, is a modification of a procedure used by the Texas Air Control Board. The full text of the procedure can be found in the emission test reports. Discussion The results from the coal-fired boiler test are summarized in Table 8, and the results from the oil-fired boiler test are summarized in Table 9. The average and 95 percent confidence interval for the average of these data are shown graphically in Figures 1 and 2. There are some noticeable differences in the results from the two separate tests. Perhaps, the most striking is that the samples from the coal-fired boiler experienced the largest weight change going from ambient conditioning to conditioning at 160°C, while the samples from the oil-fired boiler showed the greatest change between conditioning at 225°C and 316°C. As expected, the particulate weight measured by Method 5W was, in general, lower than that measured after heating, though those samples heated to 316°C showed relatively good agreement. This was expected since Method 5W measures all water soluble sulfates and not just sulfuric acid. It also indicated that ammonium sulfate which decomposes at 279°C was probably present in the samples. 11 ------- Table 8. COMPARISON OF FILTERABLE PARTICULATE CONCENTRATION FROM A COAL-FIRED BOILER AFTER HEAT CONDITIONING AT INDICATED TEMPERATURES^ Run no. 1A IB 2C& 2D 3C 3D 4A 48 5A 5Bb 5C 5D 6A 6B 7C 7D 8Cb 8D 9A& 9B lOAb 10B lOCb 10D Sample type M5B MSB M5B MSB MSB MSB MSB MSB MSB MSB MSB MSB MSB MSB MSB MSB MSB MSB MSB MSB MSB MSB MSB MSB Average Ambi ent Total weight, *r9 25.9 79.7 56.6 34.3 . 58.8 69.6 26.7 26.7 47.6 46.2 54.0 48.2 33.6 33.8 80.0 86.3 92.3 88.8 57.1 58.2 45.0 38.5 85.4 77.3 Concen- tration, mg/dNm^ 12.0 37.6 28.5 17.5 18.9 22.0 7.8 7.9 14.2 13.9 16.6 14.8 10.6 10.7 25.5 26.5 29.5 27.3 17.3 17.8 13.5 11.7 26.3 23.1 „ 18-8 ac = 7.8 N = 24 160°C Total weight, mg 13.9 16.0 18.2 11.8 — — . 21.1 16.3 24.4 19.5 28.6 31.3 19.0 19.7 _ 25.5 27.7 Concen- tration, mg/dNm3 6.4 7.5 9.2 6.0 _ ^ 6.3 4.9 7.7 6.1 9.1 9.6 6.1 6.1 _ 7.7 8.4 c 7'2 ac = 1.4 N = 14 232°C Total weight, mg 8.8 10.3 19.4 9.1 _ 12.1 17.1 17.9 17.1 16.4 20.9 15.5 22.4 30.4 19.7 18.5 25.4 24.8 22.3 30.1 29.4 Concen- tration, mg/dNm3 4.1 4.9 9.8 4.6 3.5 5.1 5.4 5.3 5.0 6.6 4.9 7.2 9.3 6.3 5.7 7.8 7.5 6.8 9.3 8.8 6.4 0C = 1.9 N = 20 | 316°C Total weight, mg 6.9 8.9 14.6 5.4 13.1 26.6 11.0 11.2 14.7 13.9 13.2 13.2 17.8 11.6 13.6 26.5 15.5 12.3 18.5 20.5 21.2 19.2 25.9 22.6 Concen- tration, mg/dNm 3.2 4.2 7.4 2.8 4.2 8.4 3.2 3.3 4.4 4.2 4.1 4.1 5.6 3.7 4.3 8.1 5.0 3.8 5.6 6.3 6.4 5.8 8.0 6.7 5.1 a~ = 1.7 N = 25 ------- Table 8. COMPARISON OF FILTERABLE PARTICIPATE CONCENTRATION FROM A COAL-FIRED BOILER AFTER HEAT CONDITIONING AT INDICATED TEMPERATURES* ._ (Continued) 1 1 Samp! e Run no. | type 2A*5 IM5B-P400 2B IM5B-P400 4~C JM5B-P400 | 4D IM5B-P400 7A JM5B-P400 | 7B IM5B-P400 9~CE JM5B-P400 | 9D JM5B-P400 Average I AmTT Total weight, mg 1 29.1 26.2 1 40.8 27.2 [ 4b.4 38.0 I 3176 39.0 a( K 'ent Concen- tration, mg/dNm3 14.2 13.0 12.0 7.9 14.1 11.6 10.0 12.0 11.8 : = 2.1 = 8 16( Total weight, mg 17.2 12.6 w» 26.5 20.5 c )"C Concen- tration, mg/dNm3 8.4 6.3 8.0 6.3 : 7.2 >c = 1.1 N = 4 23; Total weight mg 17.3 8.7 18.6 22.0 19.3 20.1 oc F ,oc Concen- tration, mg/dNm3 8.4 4.3 5.5 6.7 5.9 6.2 , 6.2 ' = 1.4 1 = 6 31f Total | weight, I mg 1 14.1 7.0 15.8 12.4 15.7 17.1 15.4 17.9 ac r 56C Concen- tration, mg/dNm3 6.9 3.5 4.7 3.6 4.8 5.2 4.9 5.5 , 4.9 ' = 1.1 J = 8 a Includes both filter and probe rinse fractions. b Heat conditioning intervals for these samples were 24 hours; all others were 6 hours. c Standard deviation with N-l weighting for sample data. d Number of data points. ------- Table 9. COMPARISON OF FILTERABLE PARTICIPATE CONCENTRATION FROM AN OIL-FIRED BOILER AFTER HEAT CONDITIONING AT INDICATED TEMPERATURESa Run no. 1C ID 2A& 2Bb 3A 3B 1 4C 4D 5A 5B 5Ch 5Db Samp! e type M5B M5B M5B M5B M5B M5B M5B M5B M5B M5B M5B M5B Ambient Total weight, mg 336.7 309.3 389.7 378.0 356.9 376.6 348.6 346.0 235.5 230.9 219.2 217.9 Concen- tration, mg/dNm3 185.0 168.9 196.5 190.5 186.8 199.2 201.8 196.5 165.0 163.5 167.2 163.7 reiTT 1 Total weight, mg 283.6 265.6 337.9 327.7 311.1 332.4 319.8 317.5 201.2 196.0 186.1 183.5 Concen- tration, mg/dNm3 155.8 145.1 170.4 165.2 162.8 175.8 185.2 180.3 141.0 138.8 142.0 137.9 2~3T°C Total weight, mg 266.1 251.0 1 326.6 304.2 298.2 317.1 310.6 306.2 185.4 182.8 178.5 173.7 Concen- tration, mg/dNm3 1 1 146.2 137.0 1 1 164.7 153.3 1 1 156.0 167.7 179.8 173.9 129.9 129.5 136.2 130.5 316 ( otal I weight, mg 194.8 226.1 1 1 222.2 175.9 251.1 241.7 r— "•"• 1 1 1 241.1 234.6 152.6 120.0 103.7 113.3 C Concen- tration, mg/dNm3 107.0 123.5 I 112.0 88.7 131.4 127.8 139.6 133.2 106.9 85.0 79.1 85.1 ------- Table 9. COMPARISON OF FILTERABLE PARTICIPATE CONCENTRATION FROM AN OIL-FIRED BOILER AFTER HEAT CONDITIONING AT INDICATED TEMPERATURES^ (Continued) Run no. 6Ab 6Bb 6C 6D 7B 7D 8Ab 8C 9A& 9Bb 9C 9D 10A IOC Sampl e type M5B M5B M5B MSB M5B M5B M5B M5B M5B MSB MSB MSB MSB MSB Average Ambient Total weight, mg 229.3 216.8 169.6 186.1 221.9 215.5 156.8 112.6 252.9 261.2 204.7 224.6 260.6 210.0 Concen- tration, mg/dNm3 161.1 155.3 140.0 150.3 159.0 157.3 181.1 131.5 171.7 180.9 151.8 162.3 171.8 159.6 169.9 a = 18.3 N = 26 160°C Total weight, mg - - 105.6 89.8 - Concen- tration, mg/dNm3 121.9 104.9 r 151.9 a = 23.0 N = 14 232°C Total weight, mg 182.8 168.3 135.1 145.1 152.1 153.0 100.2 84.9 - 203.1 176.8 Concen- tration, mg/dNm3 128.5 120.6 111.6 117,2 109.0 111.7 115.7 99.2 133.9 134.4 135.7 a = 22.3 N = 22 316°C Total weight, mg 127.5 101.2 104.8 113.0 101.6 93.5 51.5 51.2 117.5 116.7 122.1 119.3 157.8 123.5 Concen- tration, mg/dNm3 89.6 72.5 86.5 91.3 72.8 68.2 59.5 59.8 79.8 80.8 90.6 86.2 104.0 93.8 r 94.4 a = 22.5 N = 26 ------- Table 9. COMPARISON OF FILTERABLE PARTICULATE CONCENTRATION FROM AN OIL-FIRED BOILER AFTER HEAT CONDITIONING AT INDICATED TEMPERATURESa (Continued) Run no. 3C 3D 4A 4B 8B 8D 10B 10D Sampl e type M5B-P400 M5B-P400 M5B-P400 M5B-P400 1 M5B-P400 M5B-P400 M5B-P400 M5B-P400 Average Ambient 160"C 232UC 316UC Total weight, mg 335.2 351.4 398.9 398.0 111.5 105.5 226.1 213.8 Concen- tration, rng/dNm-^ 211.1 193.8 202.2 194.0 134.5 133.2 151.6 158.8 172.4 a = 31.4 N = 8 Total weight, mg 296.8 314.3 369.1 365.6 87.9 85.3 - Concen- tration, mg/dNm3 186.9 173.4 187.1 178.2 106.0 107.7 r 156.5 a = 38.8 N = 6 Total weight, mg 284.2 300.3 357.7 349.9 79.3 74.2 179.9 181.6 Concen- tration, mg/dNm3 179.0 165.6 181.3 170.5 95.7 93.7 120.7 134.9 c 142-7 a = 36.4 N = 8 Total weight, mg 230.8 245.7 291.5 276.8 59.1 55.7 136.0 124.7 Concen- tration, mg/dNm3 145.3 135.5 147.7 134.9 71.3 70.3 91.2 92.6 r 111.1 ° = 33.1 N = 8 a Includes both filter and probe rinse fractions. b Heat conditioning intervals for these samples were 24 hours, all others were 6 hours. c Standard deviation with N-l weighing for sample data. d Number of data points. ------- 30 AMBIENT 20 CC t- UJ CJ O o 10 160 100 160-232 °C ._. IUU-£..4< AMBIENT 160232- 316 °C I 160°C 1 160 232 °C \ 160- 232-316 °C f i MSB-—>-OVEN OVEN HEAT HEAT OVEN MSB »OV£N OVEN OVEN M5W HEAT P400 HEAT HEAT HEAT SAMPLE/ANALYSIS CONDITIONS Figure 1. Coal-fired boiler. ------- 210 — AMB .» . AMBIENT ENT 16C °C — i ' • — j 170 160 150 — 140 — a 5 130 — cc UJ £120^- o cj 110 — 100 — 90 — 80 — 70 60 1SO°C 160-232 °C 160-232 °C 160-232- 316 °C -1 160-232- 31S"°C I MSB- • QVF.W HEAT OVEN HEAT OVEN HEAT MSB- P400 •OVEN HEAT OVEN HEAT OVEN HEAT M5W SAMPLE/ANALYSIS CONDITIONS Figure 2. Oil-fired boiler. 18 ------- One of the principal purposes of the testing program was to estimate the repeatability of Method 58. As shown in Figures 1 and 2, the precision (which also includes temporal variations) of the method varies somewhat with the method of analysis. The poorest precision was usually produced by ambient conditioning followed by weighing while Method 5W usually showed the best precision. Some care must be exercised when analyzing the precision of the samples taken at the oil-fired boiler, because there were a number of process upsets during these tests which caused substantial variations in the emission rate from test to test. These variations between runs tend to obscure the variation between samples within a run. To eliminate this between-run variation, the standard deviation for the samples within a run were averaged over all runs for the different analytical techniques and plotted along with the 95 percent confidence interval of the average in Figures 3 and 4. These figures show that the samples from the oil-fired boiler follow a similar pattern to that of the coal-fired boiler. When the results from the samples collected with the probe at 204°C are compared with those collected with the probe at 160°C, one can see that the samples collected with the higher temperature probe weigh less after ambient conditioning. This indicates that the higher probe temperature is successful in reducing the amount of condensed sulfuric acid collected. This is not unreasonable since it is more difficult to maintain an even temperature throughout the length of the probe, and the higher overall temperature is more likely to ensure that the gas stream does not contact any sections of the probe that are cooler than 160°C. However, after 19 ------- IN3 O 15 u 10 — AMBIENT ~* UJ a a cc < c a 5 f- 0 _^_ < 160232- AMB 160 232 °C 316oC 160 °C 1 i : • • IENT i i 160 232 °C OC i > 160-232- 316 °C 1 < 1 1 i M5B — frOVEN OVEN OVEN M5B »• OVEN OVEN OVEN M5W HEAT HEAT HEAT P400 HEAT HEAT HEAT SAMPLE/ANALYSIS CONDITIONS Figure 3. Coal-fired boiler. ------- 20 ro E U ;S 15 cn E 2: o ^~ | 10 IU a a cn a < 5 I- co 0 AMBIENT T ^ 160 °C 4 160 °C 160-232- AMBENT 316 °C 160- 232 °C < ( i i ( I 160 232 °C -r 160-232- 4 - 316°C < _ y t i MSB — *OVEN OVEN OVEN M5B- — * OVEN OVEN OVEN M5W HEAT HEAT HEAT P400 HEAT HEAT HEAT SAMPLE/ANALYSIS CONDITION Figure 4. Oil-fired boiler. ------- conditioning the samples at temperatures of 160°C or higher, this difference in weight disappears. This is shown clearly in Tables 10 and 11. These tables are summaries of the data which have been normalized using Method 58 samples conditioned at 160°C as the reference. Conclusions Samples collected at 160°C will contain minimal amounts of sulfuric acid compared to samples collected at 120°C (250°F). While heating the probe to 204°C during sampling is even more effective in preventing condensed sulfuric acid from collecting on the sample, the extra effort required to maintain this temperature in the probe is not justified since any condensed sulfuric acid can be satisfactorily removed by heating the sample in an oven after collection. The repeatability of the measurement is improved by heating the samples to 160°C after collection as compared to ambient conditioning, but there is little or no gain in precision upon heating to higher temperatures. Although, of all the methods tested, Method 5W showed the best repeatability, it cannot distinguish between sulfuric acid and other water soluble sulfates and is not a suitable technique for measuring NSAPM from electric utility boilers. Collecting samples for NSAPM at a probe and filter temperature of 160°C and conditioning these samples at 160°C prior to weighing is the best technique for measuring NSAPM from electric utility boilers. The conditioning temperature of 160°C provides the best compromise between 22 ------- Table 10. COAL-FIRED BOILER RATIO OF CONCENTRATION TO REFERENCE CONDITION (MSB heated to 160°C) Condition Samp! e Analysis 1. Ambient desiccation 2. Oven heat: Sequenced 160°C 232°C 315°C 3. Water extraction M5B 2.61 1.00 0.89 0.71 -- M5B-P400 1.64 1.00 0.86 0.68 M5W -- 0.71 23 ------- Table 11. OIL-FIRED BOILER RATIO OF CONCENTRATION TO REFERENCE CONDITION (MSB heated to 160°C) Condition Analysis Sampl e 1. Ambient desiccation 2. Oven heat: Sequenced 160°C 232°C 315°C 3. Water extraction M5B 1.12 1.00 0.89 0.62 __ M5B-P400 1.13 1.03 0.94 0.73 -- M5W -- -- -- — 0.55 24 ------- a temperature high enough to evaporate any condensed sulfuric acid but not so high as to decompose or evaporate other materials which are intended to be counted as particulate matter. Bibliography 1. Pierce, R.R. Estimating Acid Dew Points in Stack Gases. Chemical Engineering. Vol. No.: 125-128. April 1977. 2. PEDCo Environmental. Summary Report: Compound Evaluation of Methods 5 and 17. Prepared for U.S. Environmental Protection Agency. Research Triangle Park, N.C. February 1983. 56 p. 3. Cornett, C.L. and W.H. McDonald (Monsanto Research Corporation). Emission Test Report. Caterpillar Tractor Company, East Peoria, Illinois. Prepared for U.S. Environmental Protection Agency. Research Triangle Park, N.C. EMB Report 81-IBR-14. June 1982. 4. Cornett, C.L. and R.G. Beer. (Monsanto Research Corporation). Emission Test Report. DuPont Corporation, Parkersburg, West Virginia. Prepared for U.S. Environmental Protection Agency. Research Triangle Park, N.C. February 1982. Emission Measurement Branch Report 80-IBR-12. 5. Day, D.R. (Monsanto Research Corporation). Emission Test Report. Boston Edison Company, Everett, Massachusetts. Prepared for U.S. Environmental Protection Agency. Research Triangle Park, N.C. July 1980. Emission Measurement Branch Report 81-IBR-15. 25 ------- 6. Prohaska, J. (PEDCo Environmental). Evaluation of Method 5B at a Coal-Fired Boiler. Prepared for U.S. Environmental Protection Agency. Research Triangle Park, N.C. September 1983. Emission Measurement Branch Report . 7. Prohaska, J. (PEDCo Environmental). Evaluation of Method 5B at an Oil-Fired Boiler. Prepared for U.S. Environmental Protection Agency. Research Triangle Park, N.C. September 1983. Emission Measurement Branch Report . 26 ------- TECHNICAL REPORT DATA (Please read Instructions on the reverse before completing) 2. 3. RECIPIENT'S ACCESSION NO. 4. TITLE AND SUBTITLE Development and Evaluation of Method 5B - Background Information for Proposed Reference Method 5. REPORT DATE September 1984 6. PERFORMING ORGANIZATION CODE Gary McAlister 8. PERFORMING ORGANIZATION REPORT NO. ND ADORES Emission Measurement Branch Emission Standards and Engineering Division U.S.E.P.A. Research Triangle Park, North Carolina 27711 10. PROGRAM ELEMENT NO. 11. CONTRACT/GRANT NO. G AGENCY NAME AND ADDRESS 13. TYPE OF REPORT ANO PERIOD COVERED Same as above 14. SPONSORING AGENCY CODE EPA 200/04 6. ABSTRACT This report discusses the development of Method 5B. Results from tests at fossil-fuel-fired boilers are summarized and compared. KEY WORDS AND DOCUMENT ANALYSIS DESCRIPTORS 18. DISTRIBUTION STATEMENT Release unlimited b.lDENTIFIERS/OPEN ENDED TERMS 19. SECURITY CLASS (ThisReport) Unclassified !0. SECURITY CLASS (Thispage) Unclassified EPA Form 2220-1 (Rev. 4-77) PREVIOUS EDITION is OBSOLETE c. cos AT I Field/Group 21. NO. OF PAGES 21 22. PRICE ------- ...w— ------- |