Stationary Source Controls & Source Sampling

1. Stationary Source Controls & Source Sampling Marti Blad, PhD, PE

2. What we will learn • Control of air pollution is possible • Physical, chemical or biological • Control of air pollution is not perfect • “Shell game” • Control mechanisms for particles are different from those that control gasses • Examples of types of controls • How air pollution control devices work • Sampling of point sources

3. Stationary Source Control • Philosophy of pollution prevention • Modify the process: use different raw materials • Modify the process: increase efficiency • Recover and reuse: less waste = less pollution • Philosophy of end-of-pipe treatment • Collection of waste streams • Add-on equipment at emission points • AP control of stationary sources • Particulates • Gases

4. Particulate Control Technologies • Remember this order: • Settling chambers • Cyclones • ESPs (electrostatic precipitators) • Spray towers • Venturi scrubbers • Baghouses (fabric filtration) • All physical processes

7. Settling Chambers • “Knock-out pots” • Simplest, cheapest, no moving parts • Least efficient • large particles only • Creates solid-waste stream • Can be reused • Picture on next slide

9. Cyclones • Inexpensive, no moving parts • More efficient than settling chamber • still better for larger particles • Single cyclone or multi-clone design • In series or in parallel • Creates solid-waste stream • Picture next slide

13. ESPs • Electrostatic precipitator • More expensive to install, • Electricity is major operating cost • Higher particulate efficiency than cyclones • Can be dry or wet • Plates cleaned by rapping • Creates solid-waste stream • Picture on next slide

14. Electrostatic Precipitator Concept

15. Electrostatic Precipitator

16. Electrostatic Precipitator

17. Spray Towers • Water or other liquid “washes out” PM • Less expensive than ESP but more than cyclone, still low pressure drop • Variety of configurations • Higher efficiency than cyclones • Creates water pollution stream • Can also absorb some gaseous pollutants (SO2)

18. Spray Tower

19. Venturi Scrubber • High intensity contact between water and gas => high pressure drop • Venturi action modified spray tower • High removal efficiency for small particles • Creates water pollution stream • Can also absorb some gaseous pollutants (SO2)

20. Venturi Scrubber Detail illustrates cloud atomization from high-velocity gas stream shearing liquid at throat

22. Baghouses • Fabric filtration – vacuum cleaner • High removal efficiency for small particles • Not good for wet or high temperature streams • Uses fabric bags to filter out PM • Inexpensive to operate • Bags cleaned by periodic shaking or air pulse • Creates solid-waste stream

25. Baghouse in a Facility

26. Pulse-Air-Jet Type Baghouse

28. Stationary Source Controls:Gaseous Pollutants and Air Toxics

29. Controlling Gaseous Pollutants: SO2 & NOx • Modify Process • Switch to low-sulfur coals • Desulfurize coal (washing, gasification) • Increase efficiency • Low-NOx burners • Recover and Reuse (heat) • staged combustion • flue-gas recirculation

30. Controlling Gaseous Pollutants: CO & VOCs • Wet/dry scrubbers • Absorbers • NOx and SOx included • Proper operating conditions • Thermal and catalytic oxidation • Chemical • Carbon adsorption • Physical

31. VOC / CO Process Control • Keep combustion HOT • Reuse & recycle heat • Control cold start-ups, shut-downs, wet inputs • wood-fired, chemical incinerators, boilers • Increase residence time of gas in combustor • Unfortunately, things that reduce NOxtend to increase VOC’s • Atmosphere in air combustion 78% N2

32. Scrubbers / Absorbers • SO2 removal: “FGD” (flue gas desulfurization) • Lime/soda ash/citrate absorbing solutions • Can create useable by-product OR solid waste stream • NOx removal—catalytic and non-catalytic • Catalyst = facilitates chemical reaction • Ammonia-absorbing solutions • Process controls favored over this technology • CO & CO2 removal • Some VOC removal

34. Thermal Oxidation • Chemical change = burn • CO2 and H2O ideal end products of all processes • Flares (for emergency purposes) • Incinerators • Direct • Catalytic = improve reaction efficiency • Recuperative: heat transfer between inlet /exit gas • Regenerative: switching ceramic beds that hold heat, release in air stream later to re-use heat

35. Flares

36. Catalytic Oxidation

37. Carbon Adsorption • Will do demonstration shortly • Good for organics (VOCs) • Both VOCs and carbon can be recovered when carbon is regenerated (steam stripping) • Physical capture • Adsorption • Absorption

39. Adsorb Absorb

40. Controlling Air Toxics • “Technology-based” approach • Maximum achievable control technology (MACT) • Based on emissions levels already being achieved by better-controlled and lower-emitting sources in an industry • Provides level economic playing field • In setting MACT standards, EPA does not generally prescribe a specific control technology

41. What is source sampling? • Sample air pollutants at the source • Stacks, vents, pt. of compliance, etc. • Sample specific pollutants • Standard methods/protocols • Determine amount of a pollutant emitted • Pollutant concentration • Mass pollutant per unit volume exhaust gas • Pollutant mass rate • Mass pollutant emitted over a time interval

42. Why is source sampling done? • Evaluate process efficiency • Evaluate equipment & control performance • Calculate process material balances • Evaluate process economics • Input of models (point source) • Regulatory compliance verification/permit review

43. Before Sampling Sources • Plan what will be done • Describe sampling objective, pollutants & site • Identify responsible persons • Sampling locations & access • Standard methods • CFR, ASTM, AAC • Sample type (grab, integrated or instrument) • Methods – field sampling & lab analyses • QA/QC requirements (field and lab) • Health & safety considerations (plan) • Each test is done 3 times

44. Standard Methods – Basic • Method 1 • Sample port location & number of ports, determine absence of cyclonic flow • Method 2 • Stack gas velocity & flow rate • Method 3 • Gas MW & composition (%O2, %N2, %CO2) • Method 4 • Moisture content of stack gas • Method 5 • total particulate emissions • Method 9 • visual determination of opacity

45. Standard Methods – Gases • Method 6 • Sulfur dioxide • Method 7 • Nitrogen oxides • Method 10 • Carbon dioxide • Other methods • Hydrocarbons • Hydrochloric acid • Hydrogen sulfide • Fluoride • Dioxins & furans • PCBs, PAHs, Formaldehyde (HCHO), others

46. Continuous Emission Monitoring • Real-time detection of emissions gases • Carbon dioxide • Nitrogen oxides • Sulfur oxides • Hydrogen chloride • Total hydrocarbons • Real time measure of flow and temperature • Continuous monitoring of opacity

47. Total Hydrocarbon Setup Continuous Emission Monitoring (cont.)

48. CO • NO • NOx • SO2 • THCs • Flow • Temperature Continuous Emission Monitoring (cont.)

49. Is this something you should do? • Source sampling is • Involved • Expensive • Time consuming • Source sampling requires • Specialized training, experience & equipment • Laboratory support capacity • Significant QA/QC

50. What should you be able to do? • Know if it is being planned right • Know if it is being done right • Know if it is reported right • What resources are available • CARB • Smoke school