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AIR POLLUTION CONTROLS

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					AIR POLLUTION CONTROLS

        Chapter 24
         A.P.E.S.
        Is Dilution the Solution?
• Years ago polluting
  factors were moved to
  more remote locations
• Used taller smokestacks
  to disperse pollution
  further up into air so it
  would dissipate over a
  wide area & come down
  in “harmless traces”
    PARTICULATE REMOVAL
           (2 types)
1. Filters
   – Cotton or fiberglass
     cloth traps particles
     from effluent stream
     (waste gas), allowing
     clean air to pass thru.
   – Similar to filter on car
     or vacuum- but bigger
     and more of them.
   – Often stored in a
     “baghouse”
     PARTICULATE REMOVAL
2. Electrostatic precipitators
   – Most common in
     powerplants
   – Ash passes over
     electrodes & pick up an
     electrostatic surface charge
   – Ash particles passed along
     & accumulate on a
     collecting plate that is
     removed and disposed of
     as solid waste in landfill
   – 99% effective- depends on
     particle size, chemistry,
     strength of electric field
   – Still poses solid waste
     problems
            SULFUR REMOVAL
                (6 types)
1. Fuel Switching
   •   Use low sulfur fuel from
       softer coal
       •   Will affect jobs in areas
           that mine harder coals
   •   Natural gas
       •   Difficult to ship,
           expensive
   •   Nuclear power
       •   Uncertain dangers
   •   Alt. Energy source
       •   Becoming more
           competitive
          SULFUR REMOVAL
2. Fuel Cleaning
  •   Coal can be crushed,
      washed, and gasified
      to remove sulfur
  •   Creates water
      pollution that must be
      cleaned- expensive
           SULFUR REMOVAL
3. Limestone Injection
   •   Mix limestone with coal
       before going to boiler
   •   CaCO3 reacts with sulfur
       to make CaSO3, CaSO4,
       or gypsum.
   •   Sometimes produces a
       residue called slag that
       reduces efficiency & must
       be disposed of
                  SULFUR REMOVAL
4.       Fluidized Bed Combustion
     •      1 meter thick layer of coal &
            limestone cover perforated plate
     •      Air is forced up thru perforation
            to push coal & limestone up-
            making it seem like a fluid.
     •      Oil is sprayed into mix to “start
            the fire”
     •      Steam/water pipes are
            immersed in mix
     •      This makes burning more
            efficient & prevents build up of
            slag
     •      90% of sulfur is captured by
            limestone & nitrogen cmpds are
            reduced due to lower
            temperatures used.
     •      Can use cheaper fuel (lignite)
            SULFUR REMOVAL
5. Flue Gas Scrubbing (wet
   scrubbing)
   – Crushed limestone, lime
     slurry, or alkali (sodium
     bicarbonate) are injected
     into gas stream
   – Inexpensive & effective
   – Maintenance is difficult-
     chip off plaster like residue
     regularly
   – Causes metal erosion of
     pipes
   – Dispose of solid waste
           SULFUR REMOVAL
6. Dry alkali injection
   •   Spray dry sodium
       bicarbonate into
       gases
   •   Expensive
   •   Trade off- reduce air
       pollution problem but
       increase solid
       waste/water problem
       when wastes have to
       be disposed of.
NITROGEN OXIDE REMOVAL
• Staged burners
  – Burn at slower rate
    reduces NOx
• Catalytic converters
  – Use platinum-
    palladium-rhodium to
    remove 90% of NOx,
    hydrocarbons, & CO
    from your cars exhaust
               CLEAN AIR ACT
• 1963- 1st national air
  pollution legislation
• Revamped in 1970’s
   – Identified 6 criteria
     pollutants
   – Est. national ambient
     air quality standards
     (NAAQS)
       • Primary standards-
         protect human health
       • Secondary standards-
         protect property,
         crops, climate,
         visibility, personal
         comfort
                        CLEAN AIR ACT
• Extensively revamped in 1990
   – Acid rain
       • Cut SO2 by more than ½ from
         1990-2000
   – Urban smog
       • ↓ tailpipe emissions, deadlines est.
         for cities that do not meet
         standards
   – Toxic Air Pollutants
       • Factories must reduce toxic
         pollutant production by 90% by
         2003
   – Ozone Protection
       • CFC’s & CCl4 phased out.
         Recovery & recycling programs for
         CFCs est. Hydrofluorocarbons
         phased out by 2030
   – Marketing pollution rights
       • Corporations can offset their
         pollution levels by buying, selling,
         and banking pollution
   – Volatile organic cmpds
              CLEAN AIR ACT
• And yes… Changed again in 1997
• Ambient ozone standards lowered from 0.12 ppm(1 hr
  avg) to 0.08 ppm (8 hr avg)
• Soot & dust emissions apply to particles 2.5 microns vs.
  10 previously
• Cap and Trade program devised by President Bush is
  designed to allow utilities not in compliance with EPA
  NAAQS to buy, sell, or trade pollution credits for sulfur
  dioxide, nitrogen dioxide and particulates. The expense
  of these credits is a strong incentive to utilities to
  decrease their emissions to reduce their overall costs.
• A timeline of the Clean Air Act:
• http://www.edf.org/documents/2695_cleanairact.htm
                    Clean Air Act                      http://www.epa.gov/air/oaq_caa.html




• Title I - Air Pollution Prevention and Control
     –   Part A - Air Quality and Emission Limitations
     –   Part B - Ozone Protection (replaced by Title VI)
     –   Part C - Prevention of Significant Deterioration of Air Quality
     –   Part D - Plan Requirements for Nonattainment Areas
• Title II - Emission Standards for Moving Sources
     – Part A - Motor Vehicle Emission and Fuel Standards
     – Part B - Aircraft Emission Standards
     – Part C - Clean Fuel Vehicles                  Be familiar with which
                                                     part does what…
•   Title III - General
•   Title IV - Acid Deposition Control
•   Title V - Permits
•   Title VI - Stratospheric Ozone Protection
              CAFÉ standards
• Energy Policy and Conservation Act of 1975 created
  Corporate Average Fuel Economy (CAFÉ) for vehicles.
• Intended to reduce fuel consumption and emissions
• Vehicles fuel efficiency 27.5mpg and trucks SUVS
  20.7mpg (22.7mpg by 2007)
• Reduce emissions NO to .07 g/mile
• Reduce sulfur emissions from 300 ppm to 30 ppm
• Effects: higher prices for vehicles, reduce pollutants by
  2 millions tons /year.
   CAFÉ Standards (updated 2011)
       http://www.nhtsa.gov/staticfiles/rulemaking/pdf/cafe/CAFE-
                         GHG_Fact_Sheet.pdf
                        TRUCKS                  CARS
2009                    23.1mpg                 27.5mpg
2010                    23.5mpg                 27.5mpg
2011                    24.1mpg                 30.2mpg
2012                    25.4mpg                 33.3mpg
2013                    26.0mpg                 34.2mpg
2014                    26.6mpg                 34.9mpg
2015                    27.5mpg                 36.2mpg
2016                    28.8mpg                 37.8mpg
Comparison of 1970 and 1999 Emissions
                    Other Countries…
             THE GOOD                            THE BAD & THE UGLY

• Sweden, W. Germany cut sulfur           • Many other countries do not have
  emissions by 2/3                          air pollution controls or legislation.
• Austria & Switzerland over 2/3 &        • China- almost entire pop. uses
  they control motorcycle emissions         coal cakes to heat home; some
• 26 of 37 cities on the Global             places have particulate levels 9x
  Environmental Monitoring System           those of max U.S. standards
  have decreased particulate levels       • S. Poland, N. Czech Republic
• 20 out of 37 have decreased sulfur        covered in smog most of the time,
  emissions                                 acid rain huge, gardens
• Cubatao, Brazil was called “Valley        contaminated
  of Death” due to dangerous              • Copsa Mica, Romania- notorious
  pollution from oil refinery, chemical     “black town” from mining dust, birth
  & fertilizer companies, steel plant;      defects, decreased life expectancy
  end of military rule allowed people
  to voice concern, invested money
  & reduced pollution significantly.

				
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posted:8/22/2012
language:English
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