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Controlling Emissions from Industrial Boilers
Background:

On June 4, 2010 the U.S. Environmental Protection Agency (US EPA) published in the Federal Register its proposed National Emission Standards for Hazardous Air Pollutants for Industrial, Commercial, and Institutional Boilers (ICI) and Process Heaters; 75 FR 32006-32073. The long-awaited rule would reduce emissions of toxic air pollutants from new and existing industrial, commercial, and institutional boilers and process heaters at major and area source facilities, also known as national emission standards for hazardous air pollutants (NESHAPs). A major source facility emits or has the potential to emit 10 or more tons per year (tpy) of any single air toxic or 25 tpy or more of any combination of air toxics. An area source facility emits or has the potential to emit less than 10 tons per year (tpy) of any single air toxic or less than 25 tpy of any combination of air toxics. The proposed rules would reduce emissions of a number of toxic air pollutants, including mercury, other metals, and organic air toxics, including dioxins. Most major source boilers and process heaters covered by the proposed major source rule are located at industrial facilities, and EPA estimates that there are approximately 13,555 boilers and process heaters at major sources in the United States. EPA has identified 11 different subcategories of boilers and process heaters based on the design of the various types of units, and the proposed rule would include specific requirements for each subcategory. The proposal would establish emission limits for: mercury, dioxin, particulate matter (PM) (as a surrogate for non-mercury metals), hydrogen chloride (HCl) (as a surrogate for acid gases), and carbon monoxide (CO) (as a surrogate for non-dioxin organic air toxics). EPA estimates that implementation of the rulemaking, as proposed, would reduce nationwide emissions from major source boilers and process heaters by: 15,000 pounds per year of mercury; 3,200 tpy of non-mercury metals; 37,000 tpy of HCl; 50,000 tpy of PM; 340,000 tpy of SO2; 722 grams per year of dioxin; and 1,800 tpy of volatile organic compounds.

Most area source boilers covered by the proposed area source rule are located at commercial and institutional facilities, and EPA estimates that there are approximately 183,000 existing area source boilers at 92,000 facilities in the United States. EPA is proposing to regulate area source boilers based on boiler design, and the proposal would set different requirements for large and small boilers. Large boilers have a heat input capacity equal to or greater than 10 million British thermal units per hour (Btu per hr), while small boilers have a heat input capacity less than 10 million Btu per hour. The proposed rule would establish standards to address emissions of mercury, particulate matter (PM) (as a surrogate for non- mercury metals), and carbon monoxide (CO) (as a surrogate for organic air toxics). For existing large boilers the proposal would require the following: coal-fired units would be required to meet emission limits for mercury and CO, biomass and oil-fired units would need to meet limits for CO, and all area source facilities with large boilers would be required to conduct an energy assessment to identify cost- effective energy conservation measures. Existing small boilers would not be required to meet emission limits. They would be required to meet a work practice standard by performing a boiler tune-up every 2 years. EPA estimates that the proposal would reduce nationwide emissions from existing and new area source boilers by approximately: 1,500 tons per year (tpy) of total air toxics; 1,500 pounds per year of mercury; 250 tpy of non-mercury metals; 9 tpy of polycyclic organic matter (POM); and 7,600 tpy of PM.

 

Proposed ICI Boiler MACT Emission Limits:

Compliance Options: The June 4th ICI Boiler MACT proposal is expected to be finalized by February 21, 2011 which sets the clock for a three year compliance window. In light of the compliance schedule the following emission control technology options are available to sources as a potential compliance strategy is developed. Please note links to case studies and more information where available.

  1. Particulate Control
    1. Pulse Jet Fabric Filter (PJFF)
    2. Electostatic Precipitators (ESPs)
      1. Upgrade/Enlarge ESP
      2. Add flue gas conditioning
    3. Wet ESP
    4. Wet Venturi Scrubber
    5. Electrified Filter Bed (EFB)
    6. Recyclone
  2. Acid Gas Controls
    1. Dry Scrubber
      1. Spray Dry Absorber (SDA)
      2. Circulating Dry Scrubber (CDS)
    2. Wet Scrubber
    3. Direct Sorbent Injection (DSI)
    4. Wet ESP
    5. Wet Venturi Scrubber
  3. Mercury Controls
    1. Activated Carbon Injection (ACI)
    2. Wet Scrubber
      1. Wet FGD re-emission additive
    3. Sorbent(s)
    4. Change fuel to lower Hg content
  4. CO/VOC Controls
    1. Oxidation Catalyst
    2. Regenerative oxidation catalyst
    3. SCR- to maintain NOx compliance
    4. Thermal Oxidizer
    5. Upgrade air system
    6. Install high energy burners
  5. Dioxin/Furans
    1. ACI
    2. Oxidation Catalyst
    3. PJFF + Powdered Activated Carbon (PAC) (replace ESP)
    4. Wet ESP
    5. SDA
    6. Wet Scrubber
    7. SCR
    8. Change fule to a lower Cl content
  6. Monitoring Options
    1. CO CEMS
    2. PM CEMS
    3. Sorbent Traps
    4. Hg CEMS
    5. Bag leak detection
    6. Opacity
    7. Predictive maintenance
    8. Portable Analyzers (e.g. stationary engines & other industrial applications)
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