1. 1 CE 583 - Air Pollution Measurements, Emission Estimates Jeff Kuo, Ph.D., P.E. jkuo@fullerton.edu

2. 2 Content Representative Samples Concentration Determination and Averaging Standard Analytical Methods Determine Pollutant Flow Rate Isokinetic Sampling Emission Factors Visible Emission

3. 3 Introduction to Air Pollution Measurement Ambient monitoring vs. Source testing Concentration vs. Emission rate Why source testing: Compliance Performance evaluation/guarantees Problems for measurements Representative sample Correct concentration Not an easy task

4. 4 Components of ambient or source sampling devices

5. 5 Representative Samples Ambient Monitoring The public has free access and C is the highest. Power, rain, constant T, easy access, safety. CO measurement: street level, downtown. Source Testing V and C = f(t, location) Near the bend on the inside of a duct: low Far enough down- and up-stream of disturbance >8x downstream, >4x upstream Practically hard to achieve

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8. 8 Representative Samples… Inlet device to exclude unwanted materials: bug screen. TSP (< 50  ): prior to 1987 PM 10 : 1987 PM 2.5 : 1997 Gas may condense in sampling device or reacts with the encountered solids. SO 2 will react with alkaline solids on a filter, thus increase the weight of the solids collected. Probes are heated Grab sample: react with sample container and modify its content during transit?

9. 9 Concentration Determination Some can be done by real-time instrument – mostly optically (light absorbance by the compound, but subject to interference). Gas containing SO 2 is passed through a dilute solution of NaOH, and then the solution is thru acid-base titration. CO 2 can be an interference. SO 2 + 2NaOH  Na 2 SO 3 + H 2 O CO 2 + 2NaOH  Na 2 CO 3 + H 2 O Average C of real-time instruments (done electronically)

10. 10 Averaging Particulate (and other gases) measurements are not real-time but averaging instruments.

11. 11 Averaging (Example 4.2) A PM 2.5 sampler: an inlet exclude particles > 2.5 , a filter, a flow meter, and a suitable housing. Q = 16.7 L/min,  t = 24 hr,  w filter = 0.0005g C = 21  g/m 3 < 25  g/m 3 (NAAQS 24-hr average) High quality weighing and sample humidity control are critical. Can not used to assess hourly variations. 16.7 L/min ~ average human breathing rate. What is our PM 2.5 intake rate?

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13. 13 Standard Analytical Methods EPA has standard sampling methods for various pollutants – often different for ambient monitoring than for source testing. Table 4.1: for ambient monitoring. The methods define the pollutants such as West-Gaeke method for SO 2 (different from Method 6 for source testing). For EPA, there is a reference method for each major pollutant. Equivalent methods are commonly used by local or states (simpler/cheaper). Particulate Matter TSP is mainly for lead measurement. PM 10 and PM 2.5 for compliance with NAAQS.

14. 14 Standard Analytical Methods… Pb A TSP filter is extracted using NO 3 and HCl to dissolve Pb. The extract is then analyzed by atomic absorption (AA). SO 2 (West-Gaeke method) Known air volume is bubble through a solution of sodium tetrachloromercurate to form a complex. The solution is treated with pararosaniline, turns into read-purple, and then determined in a colorimeter. [HgCl 4 ] 2- + 2SO 2 ---> [Hg(SO 3 ) 2 ] 2- + 4Cl - + 4H +

15. 15 Standard Analytical Methods… Ozone Ozone in air reacts with ethylene in a chemiluminescent reaction, measured with a photomultiplier tube. CO Measured by nondispersive IR (NDIR) absorption. Filters are used to obtain a specific wavelength band at which CO strongly absorbs.

16. 16 Standard Analytical Methods… Hydrocarbon (non-methane) The gas is pass through a FID (flame ionization detector) where HC burns in a hydrogen flame. Part of the sample is diverted to GC where methane is quantified. The difference is non-methane HC. NO 2 NO 2 is converted to NO, which is then reacted with ozone. Light from this chemiluminescent reaction is measured. A parallel sample is run without conversion of NO 2 to NO – NO reading.

17. 17 Determine Pollutant Mass/Molar Flow Rate Pollutant molar flow rate = (molar flow rate of gas) x (pollutant molar concentration in gas) Example 4.3: In method 6 testing of a stack, SO 2 = 600 ppm, V= 40 ft/s, D = 5 ft, T = 450 o F, P = 1 atm. What is the SO 2 flow rate (averaging of C and V may be needed)?

18. 18 Determine Pollutant Mass/Molar Flow Rate

19. 19 Isokinetic Sampling In stack sampling for particulates, one must maintain isokinetic flow into the sampling probe – the gas V inside the probe (V n ) = the gas V in the stack where the sample is taken (V s ). V n >V s : gas stream will bend into the nozzle and the inertia of the particles will carry some of them past the nozzle, even though gas they were in will be collected – underestimate of C (top fig.).

20. 20 Emission Factors Emission Factors (EPA document AP-42) Emission testing is expensive Testing not feasible (for poorly-defined source) Estimate of emission from new facilities. EF for coal combustion w/o control equipment Furnace TypeAll particles PM 10 SO x NO x CO PC, wall-fired dry bottom10A2.3A38S21.70.5 PC, wall-fired wet bottom7A2.6A38S340.5 Hand-fired156.231S9.1275

21. 21 Emission Factors – Example 4.4 Estimate emission from a 500-MW power plant. Thermal efficiency = 35%. Boiler = PC, wall- fired, dry bottom type. Pittsburgh seam coal is used (ash = 8.7%, S = 1.6%, heating value = 13,600 Btu/lb dry). Additional information about coal: Appendix C and back cover.

22. 22 Emission Factors – Example 4.4

23. 23 Visible Emission If particle C is high enough, the plume becomes visible. As plume flows downstream, the plume’s opacity (optical density) decreases. Measuring opacity is easy (observers or electro- optical device), but relating opacity to mass emission rate in the plume is hard. Visual measurements of plume opacity have played a major role in air pollution control.

24. 24 Visible Emission Professor Ringleman devised a system in 1890 – marked five grids of various densities on a piece of white cardboard (Ringleman #1 = 20% opacity, Ringleman #5 = 100% opacity) – used prior to 1970. A continued interest of using optical method. For example, large sources are often required to install in- stack electro-optical detectors for continuous monitoring.