Municipal Solid Waste Incineration by po2933

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									Thermochemical Conversion
Technologies
Combustion Types
Incineration (energy recovery through
 complete oxidation)
  – Mass Burn
  – Refuse Derived Fuel
Pyrolysis
Gasification
Plasma arc (advanced thermal
 conversion)
Gasification
 Partial oxidation process using air, pure
  oxygen, oxygen enriched air, hydrogen, or
  steam
 Produces electricity, fules (methane,
  hydrogen, ethanol, synthetic diesel), and
  chemical products
 Temperature > 1300oF
 More flexible than incineration, more
  technologically complex than incineration or
  pyrolysis, more public acceptance
Flexibility of Gasification
Pyrolysis
 Thermal degradation of carbonaceous materials
 Lower temperature than gasification (750 – 1500oF)
 Absence or limited oxygen
 Products are pyrolitic oils and gas, solid char
 Distribution of products depends on temperature
 Pyrolysis oil used for (after appropriate post-
  treatment): liquid fuels, chemicals, adhesives, and
  other products.
 A number of processes directly combust pyrolysis
  gases, oils, and char
Pyrolyzer—Mitsui R21
Thermoselect (Gasification and
Pyrolysis)
 Recovers a synthesis gas, utilizable glass-like
  minerals, metals rich in iron and sulfur from
  municipal solid waste, commercial waste,
  industrial waste and hazardous waste
 High temperature gasification of the organic
  waste constituents and direct fusion of the
  inorganic components.
 Water, salt and zinc concentrate are produced
  as usable raw materials during the process
  water treatment.
 No ashes, slag or filter dusts
 100,000 tpd plant in Japan operating since
  1999
Thermoselect
(http://www.thermoselect.com/index.cfm)
Fulcrum Bioenergy MSW to Ethanol Plant
Plasma Arc
 Heating Technique using electrical arc
 Used for combustion, pyrolysis, gasification, metals
  processing
 Originally developed by SKF Steel in Sweden for
  reducing gas foriron manufacturing
 Plasma direct melting reactor developed by
  Westinghouse Plasma Corp.
 Further developed for treating hazardous feedstocks
  (Contaminated soils, Low-level radioactive waste,
  Medical waste)
 Temperatures (> 1400oC) sufficient to slag ash
 Plasma power consumption 200-400 kWh/ton
 Commercial scale facilities for treating MSW in Japan
Plasma Arc Technology in Florida
 Green Power Systems is proposing to build
  and operate a plasma arc facility to process
  1,000 tons per day of municipal solid waste
  (garbage) in Tallahassee, Florida.
 Geoplasma is proposing to build a similar
  facility for up to 3,000 tons of solid waste per
  day in St. Lucie County, claims 120 MW will
  be produced
 Health risks, economics, and technical issues
  still remain
Process
Heated using
  – direct current arc plasma for high T organic
    waste destruction and gasification and
  – Alternating current powered, resistance
    hearing to maintain more even T
    distribution in molten bath
Waste Incineration -
Advantages
• Volume and weight reduced (approx. 90% vol. and
  75% wt reduction)
• Waste reduction is immediate, no long term
  residency required
• Destruction in seconds where LF requires 100s of
  years
• Incineration can be done at generation site
• Air discharges can be controlled
• Ash residue is usually non-putrescible, sterile, inert
• Small disposal area required
• Cost can be offset by heat recovery/ sale of energy
Waste Incineration -
Disadvantages
High capital cost
Skilled operators are required
 (particularly for boiler operations)
Some materials are noncombustible
Some material require
 supplemental fuel
Waste Incineration -
Disadvantages
 Air contaminant potential (MACT standards have
  substantially reduced dioxin, WTE 19% of Hg
  emissions in 1995 – 90% reduction since then)
 Volume of gas from incineration is 10 x as great
  as other thermochemical conversion processes,
  greater cost for gas cleanup/pollution control
 Public disapproval
   Risk imposed rather than voluntary
   Incineration will decrease property value
     (perceived not necessarily true)
   Distrust of government/industry ability to
     regulate
Carbon and Energy
Considerations
 Tonne of waste creates 3.5 MW of energy
  during incineration (eq. to 300 kg of fuel oil)
  powers 70 homes
 Biogenic portion of waste is considered CO2
  neutral (tree uses more CO2 during its
  lifecycle than released during combustion)
 Unlike biochemical conversion processes,
  nonbiogenic CO2 is generated
 Should not displace recycling
WTE Process
Three Ts
Time
Temperature
Turbulence
System Components
Refuse receipt/storage
Refuse feeding
Grate system
Air supply
Furnace
Boiler
Energy/Mass Balance

            Energy Loss (Radiation)



                           Flue Gas
Waste




            Mass Loss (unburned
            C in Ash)
Flue Gas Pollutants
Particulates
Acid Gases
NOx
CO
Organic Hazardous Air Pollutants
Metal Hazardous Air Pollutants
Particulates
 Solid
 Condensable
 Causes
   –   Too low of a comb T (incomplete comb)
   –   Insufficient oxygen or overabundant EA (too high T)
   –   Insufficient mixing or residence time
   –   Too much turbulence, entrainment of particulates
 Control
   – Cyclones - not effective for removal of small particulates
   – Electrostatic precipitator
   – Fabric Filters (baghouses)
Metals
Removed with particulates
Mercury remains volatilized
Tough to remove from flue gas
Remove source or use activated carbon
 (along with dioxins)
Acid Gases
 From Cl, S, N, Fl in refuse (in plastics,
  textiles, rubber, yd waste, paper)
 Uncontrolled incineration - 18-20% HCl with
  pH 2
 Acid gas scrubber (SO2, HCl, HFl) usually
  ahead of ESP or baghouse
  – Wet scrubber
  – Spray dryer
  – Dry scrubber injectors
Nitrogen removal
Source removal to avoid fuel NOx
 production
T < 1500 F to avoid thermal NOx
Denox sytems - selective catalytic
 reaction via injection of ammonia
Air Pollution Control
Remove certain waste components
Good Combustion Practices
Emission Control Devices
Devices
 Electrostatic Precipitator
 Baghouses
 Acid Gas Scrubbers
   – Wet scrubber
   – Dry scrubber
   – Chemicals added in slurry to neutralize acids
 Activated Carbon
 Selective Non-catalytic Reduction
Role of Excess Air – Control
Three Ts
                       Stoichiometric



 T




     Insufficient O2            Excess Air
              Amount of Air Added
Role of Excess Air – Cont’d

                     Stoichiometric




                                           Increasing Moisture




   Insufficient O2            Excess Air
       Amount of Air Added
            Role of Excess Air – Cont’d

                                     Stoichiometric


                                            NOx
              T
  Optimum T
     Range
(1500 – 1800 oF) PICs/Particulates

                   Insufficient O2            Excess Air
                        Amount of Air Added
Ash
 Bottom Ash – recovered from combustion
  chamber
 Heat Recovery Ash – collected in the heat
  recovery system (boiler, economizer,
  superheater)
 Fly Ash – Particulate matter removed prior to
  sorbents
 Air Pollution Control Residues – usually
  combined with fly ash
 Combined Ash – most US facilities
  combine all ashes
Schematic Presentation of
Bottom Ash Treatment
Ash Reuse Options
Construction fill
Road construction
Landfill daily cover
Cement block production
Treatment of acid mine drainage
                                             Refuse Boiler
    Stack        Fabric Filter
                          Spray Dryer
                                                             Tipping
                                                             Floor
Ash Conveyer




               Metal Recovery


      Mass Burn Facility – Pinellas County
Overhead Crane
Turbine Generator
Fabric Filter
Conclusions
 Combustion remains predominant thermal
  technology for MSW conversion with
  realized improvements in emissions
 Gasification and pyrolysis systems now in
  commercial scale operation but industry
  still emerging
 Improved environmental data needed on
  operating systems
 Comprehensive environmental or life cycle
  assessments should be completed
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Updated August 2008

								
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