AIR POLLUTION CONTROL TECHNOLOGY HANDBOOK - CHAPTER 5 potx

Source Testing 5.1 INTRODUCTION Source testing is measuring the air pollutant concentration and/or quantity at a source or stack. The terminology implies using test methods to measure concentration on a one-time or snapshot basis, as opposed to continuously monitoring the source as discussed in Chapter 6. Source testing may be performed to provide design data or to measure performance of a process, or it may be prescribed on a periodic basis to demonstrate compliance with air permit emission limitations. Most source test pro- cedures require labor to set up the test, collect samples, and analyze the results. 5.2 CODE OF FEDERAL REGULATIONS The gospel of source testing is the Code of Federal Regulations, 40 CFR Part 60, Appendix A. 1 Very specific test procedures with step-by-step instructions are detailed in the CFR. A list of source test methods that are described in the CFR is provided in Table 5.1. These procedures have been tested, reviewed, and adopted by the EPA as the reference source test methods for a number of pollutants in a variety of applications. The universality of these test methods makes it easy for those practicing in the field to know just how a source test was conducted, and understand its limitations, just by giving a shorthand reference such as “Method 8.” Of course, the CFR test methods cannot be applied to all possible applications because it would have been impossible to evaluate and fund the research required for all circumstances. It would be an inefficient use of public funds for the EPA to sponsor research for test methods that cover unusual operating conditions for a unique process, and it is impossible to predict future processes, conditions, and improvements. Sometimes experience, judgment, and skill are needed to modify the test method to overcome a limitation that arises in a specific application. In such cases, test reports can reference the test method and describe the modification. 5.3 REPRESENTATIVE SAMPLING TECHNIQUES 5.3.1 G ASEOUS P OLLUTANTS One of the fundamentals in source testing for air contaminants is to obtain a representative sample of the gas stream. This is easy to do for gaseous pollutants, since molecules of gas can be assumed to be evenly distributed throughout the gas stream due to mixing and diffusion. It is highly unlikely that gaseous pollutants will segregate in a moving gas stream. A simple probe can be used to withdraw a sample. Due care must be used to avoid pulling a sample from a nonrepresentative location, such as just downstream of an injection point. 5 9588ch05 frame Page 59 Wednesday, September 5, 2001 9:45 PM © 2002 by CRC Press LLC TABLE 5.1 Code of Federal Regulations Source Test Methods Method Description 1 Sample and velocity traverses for stationary sources 1A Sample and velocity traverses for stationary sources with small stacks or ducts 2 Determination of stack gas velocity and volumetric flow rate (Type S pitot tube) 2A Direct measurement of gas volume through pipes and small ducts 2B Determination of exhaust gas volume flow rate from gasoline vapor incinerators 2C Determination of stack gas velocity and volumetric flow rate in small stacks or ducts (standard pitot tube) 2D Measurement of gas volumetric flow rates in small pipes and ducts 3 Gas analysis for carbon dioxide, oxygen, excess air, and dry molecular weight 3A Determination of oxygen and carbon dioxide concentrations in emissions from stationary sources (instrumental analyzer procedure) 4 Determination of moisture content in stack gases 5 Determination of particulate emissions from stationary sources 5A Determination of particulate emissions from the asphalt processing and asphalt roofing industry 5B Determination of nonsulfuric acid particulate matter from stationary sources 5C Reserved 5D Determination of particulate emissions from positive-pressure fabric filters 5E Determination of particulate emissions from the wool fiberglass insulation manufacturing industry 5F Determination of nonsulfate particulate matter from stationary sources 5G Determination of particulate emissions from wood heaters from a dilution tunnel sampling location 5H Determination of particulate emissions from wood heaters from a stack location 6 Determination of sulfur dioxide emissions from stationary sources 6A Determination of sulfur dioxide, moisture, and carbon dioxide emissions from fossil-fuel combustion sources 6B Determination of sulfur dioxide and carbon dioxide daily average emissions from fossil-fuel combustion sources 6C Determination of sulfur dioxide emissions from stationary sources (instrumental analyzer procedure) 7 Determination of nitrogen oxide emissions from stationary sources 7A Determination of nitrogen oxide emissions from stationary sources — ion chromatographic method 7B Determination of nitrogen oxide emissions from stationary sources (ultraviolet spectrophotometry) 7C Determination of nitrogen oxide emissions from stationary sources — alkaline- permanganate/colorimetric method 7D Determination of nitrogen oxide emissions from stationary sources — alkaline- permanganate/ion chromatographic method 7E Determination of nitrogen oxide emissions from stationary sources (instrumental analyzer method) 8 Determination of sulfuric acid mist and sulfur dioxide emissions from stationary sources 9588ch05 frame Page 60 Wednesday, September 5, 2001 9:45 PM © 2002 by CRC Press LLC 9 Visual determination of the opacity of emissions from stationary sources 9 Alt. 1 Determination of the opacity of emissions from stationary sources remotely by LIDAR 10 Determination of carbon monoxide emissions from stationary sources 10A Determination of carbon monoxide emissions in certifying continuous emission monitoring systems at petroleum refineries 10B Determination of carbon monoxide emissions from stationary sources 11 Determination of hydrogen sulfide content of fuel gas streams in petroleum refineries 12 Determination of inorganic lead emissions from stationary sources 13A Determination of total fluoride emissions from stationary sources — SPADNS zirconium lake method 13B Determination of total fluoride emissions from stationary sources — specific ion electrode method 14 Determination of fluoride emissions from potroom roof monitors for primary roof monitors for primary aluminum plants 15 Determination of hydrogen sulfide, carbonyl sulfide, and carbon disulfide emissions from stationary sources 15A Determination of total reduced sulfur emissions from sulfur recovery plants in petroleum refineries 16 Semicontinuous determination of sulfur emissions from stationary sources 16A Determination of total reduced sulfur emissions from stationary sources (impinger technique) 16B Determination of total reduced sulfur emissions from stationary sources 17 Determination of particulate emissions from stationary sources (in-stack filtration method) 18 Measurement of gaseous organic compound emissions by gas chromatography 19 Determination of sulfur dioxide removal efficiency and particulate, sulfur dioxide, and nitrogen oxides emission rates 20 Determination of nitrogen oxides, sulfur dioxide, and diluent emissions from stationary gas turbines 21 Determination of volatile organic compound leaks 22 Visual determination of fugitive emissions from material sources and smoke emissions from flares 23 Determination of polychlorinated dibenzo-p-dioxins and polychlorinated dibenzofurans from stationary sources 24 Determination of volatile matter content, water content, density, volume solids, and weight solids of surface coatings 24A Determination of volatile matter content and density of printing inks and related coatings 25 Determination of total gaseous nonmethane organic emissions as carbon 25A Determination of total gaseous organic concentration using a nondispersive infrared analyzer 26 Determination of hydrogen chloride emissions from stationary sources 27 Determination of vapor tightness of gasoline delivery tank using pressure–vacuum test 28 Certification and auditing of wood heaters 28A Measurement of air-to-fuel ratio and minimum achievable burn rates for wood-fired appliances TABLE 5.1 (continued) Code of Federal Regulations Source Test Methods Method Description 9588ch05 frame Page 61 Wednesday, September 5, 2001 9:45 PM © 2002 by CRC Press LLC The primary consideration for gaseous pollutant sampling is that the sample is not contaminated, or decontaminated, by incompatibility with the materials of the sampling device or container. Teflon, stainless steel, and glass sample lines and containers often are used to avoid reactions with pollutants. 5.3.2 V ELOCITY AND P ARTICULATE T RAVERSES Volumetric flow rate in a duct or stack is measured using a pitot tube to detect the difference between the static and dynamic pressure difference created by the velocity head at several points in the duct. Details of the tip of a pitot tube are shown in Figure 5.1. The measured pressure difference is used to calculate velocity. The key is to position the pitot tube at the correct points in the duct so that the average velocity is determined. This is done by positioning the pitot tube at the centroid of equal-area segments of the duct. Method 1 (CFR) provides tables for probe positions based on this principle. Figure 5.2 is an example of sampling points for a circular stack cross section. Figure 5.3 is an example for a rectangular duct. Note that the two lines of sampling points lie at 90°. For a circular duct, this requires at least two sampling ports at 90°. For small diameter stacks, the pitot tube can reach across the stack to pick up the points on the far side. For large diameter stacks, it is easier to reach no more than half way across the stack, so four sampling ports are provided to allow shorter sampling probes. FIGURE 5.1 Pitot tube for velocity measurement. 9588ch05 frame Page 62 Wednesday, September 5, 2001 9:45 PM © 2002 by CRC Press LLC Similarly, because each sampling position is representative of a small area of the duct or stack, particulate samples are withdrawn at the same traverse points at which velocity measurements are made. However, because particles do not neces- sarily follow the streamlines of gas flow and because gravity can act on particles in a horizontal duct, Method 1 recommends more traverse points for particulate sam- pling than for a simple velocity traverse. The minimum number of sample points for traverses depends on the proximity of the test port to flow disturbances in the duct, and to a lesser extent, the duct size. The minimum number of sample points for a velocity traverse is illustrated in Figure 5.4. The minimum number of samples to be taken for a particulate traverse is illustrated in Figure 5.5. 5.3.3 I SOKINETIC S AMPLING Extracting a particulate sample from a moving gas stream using a probe in a duct requires that the sample be taken at the same velocity as the gas flow, i.e., isokinet- ically. If the velocity of the sample is higher than that of the gas flow, then excess FIGURE 5.2 Traverse point locations for a round duct. The stack cross-section is divided into 12 equal areas with the location of traverse points indicated. FIGURE 5.3 Traverse point locations for a rectangular duct. 9588ch05 frame Page 63 Wednesday, September 5, 2001 9:45 PM © 2002 by CRC Press LLC gas moving toward the probe will divert toward the probe and be collected with the sample. Meanwhile, particles with sufficient momentum will tend to continue trav- eling in a straight line, leaving the gas flow streamlines and will not be carried into the sampling probe, as illustrated in Figure 5.6a. This produces a sample that, after measuring the collected gas volume and weighing the collected particulate filter, has an erroneously low particulate concentration. Similarly, if the sample velocity is too low, excess gas is diverted away from the probe while particles are carried into the probe, as illustrated in Figure 5.6b, resulting in an erroneously high particulate concentration. The correct isokinetic sample flow rate is determined by conducting a velocity traverse prior to collecting a particulate sample. During the particulate sample, the FIGURE 5.4 Minimum number of sample points for a velocity traverse. FIGURE 5.5 Minimum number of sample points for a particulate traverse. 9588ch05 frame Page 64 Wednesday, September 5, 2001 9:45 PM © 2002 by CRC Press LLC collected gas volume is measured with a gas meter. After the sample is taken and as data are being evaluated, the sample velocity as a percentage of gas velocity is determined and reported as a quality check on the particulate sample. REFERENCES 1. Code of Federal Regulations, 40 CFR Part 60, Appendix A, Office of the Federal Register, National Archives and Records Administration, Washington, D.C., July 1, 1993. FIGURE 5.6 Reason for isokinetic sampling. 9588ch05 frame Page 65 Wednesday, September 5, 2001 9:45 PM © 2002 by CRC Press LLC . location, such as just downstream of an injection point. 5 958 8ch 05 frame Page 59 Wednesday, September 5, 2001 9: 45 PM © 2002 by CRC Press LLC TABLE 5. 1 Code of Federal Regulations Source Test Methods . Measurement of air- to-fuel ratio and minimum achievable burn rates for wood-fired appliances TABLE 5. 1 (continued) Code of Federal Regulations Source Test Methods Method Description 958 8ch 05 frame. FIGURE 5. 4 Minimum number of sample points for a velocity traverse. FIGURE 5. 5 Minimum number of sample points for a particulate traverse. 958 8ch 05 frame Page 64 Wednesday, September 5, 2001