Incineration3   MSW Combustion
III.   Flue Gases
  1. Heat Content
  2. Composition, Temperature - Higher T important for plume lift, waster condensing problem for public (visual)
    1. Know BTU in waste
    2. Know gas composition
    3. With either flue gas Temp or Enthalpy known, the other can be calculated
  3. Pollutants of concern
    1. Particulates
    2. Acid Gases (SOx, HCl, HFl)
    3. NOx, primarily NO and NO2
    4. Carbon Monoxide, organics (PIC)
    5. Heavy Metals
    6. Carbon dioxide not significant, if all MSW burned, it would contribute <2% of that produced during E production in US
  4. Emission Control
    1. Remove or alter certain waste stream components, mercury in batteries, HM, Yard waste
    2. Regulate combustion efficiency (design and operate furnace to maximize conversion of organic matter to CO2 and water) Good Combustion Practices, GCP
    3. Use properly maintained and operated emission control devices, Best demonstrated technology
  5. Particulates (smoky fire)
    1. Solid - noncombustable materials released into flue gas as fly ash, Dia <1 micron to 100s of microns, inorganic oxides, Heavy metals, unburned matter
    2. Condensable - refuse vaporized after passing out of system, cool, condense, ex: mercury, organic compounds
    3. Causes
      1. Too low of a comb T (incomplete comb)
      2. Insuff. oxygen or overabundant EA (too high T)
      3. Insuff mixing or residence time
      4. To much turbulence, entrainment of particulates
    4. Control
      1. Electrostatic precipitator - after heat recovery, ESP induces a charge particulates, gas stream passes between plates w/ opposite charge, particulates attracted to plat, 93% removal of dia <2u, 99.8% removal of larger, cannot always meet stds
      2. Fabric Filters, FF (baghouses) - like vac cleaner, flue gas pulled thru densely woven fabric, superior effic >99.99% (>effic for smaller diam.)
        1. Tech of choice for new MWC
  6. Acid Gases
    1. From Cl, S, N, Fl in refuse (in plastics, textiles, rubber, yd waste, paper)
    2. Uncontrolled incin - 18-20% HCl with pH 2
    3. Acid gas scrubber (SO2, HCl, HFl) usually ahead of ESP or baghouse
      1. Wet scrubber - older type of system, good mercury removal (cools gas) but generates waste water
      2. Spray dryer - inject reagent slurry into a vessel where the water I the slurry evaporates, cooling the flue gas and allowing the acid gases to react with the reagent, produces dry powder collected by ESP or FF
        1. BDT for use with ESP and FF
      3. Dry Scrubber Injectors - introduces a totally dry, highly pulverized lime sorbent into flue gas or in-furnace, easy to retrofit existing units but limited efficiency (98%)
      4. 95% removal of HCl, HFl - 95% required
      5. 86% removal of SO2 - 80% required

 
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