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Municipal Solid Waste Incineration

Municipal Solid Waste Incineration. Combustion Types. Incineration (energy recovery through complete oxidation) Mass Burn Refuse Derived Fuel Pyrolysis Gasification Plasma arc (advanced thermal conversion). Gasification.

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Municipal Solid Waste Incineration

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  1. Municipal Solid Waste Incineration

  2. Combustion Types • Incineration (energy recovery through complete oxidation) • Mass Burn • Refuse Derived Fuel • Pyrolysis • Gasification • Plasma arc (advanced thermal conversion)

  3. Gasification • Partial oxidation process using air, pure oxygen, oxygen enriched air, or steam • Carbon converted into syngas • More flexible than incineration • More public acceptance

  4. Flexibility of Gasification

  5. Pyrolysis • Thermal degradation of carbonaceous materials • Lower temperature than gasification • Absence or limited oxygen • Products are gas, liquid, solid char • Distribution of products depends on temperature

  6. 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

  7. Environmental Considerations • Tonne of waste creates 3.5 MW of energy (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) • Should not displace recycling

  8. Waste Incineration - Disadvantages • High capital cost • Skilled operators are required (particularly for boiler operations) • Some materials are noncombustible • Some material require supplemental fuel • Public disapproval • Risk imposed rather than voluntary • Incineration will decrease property value (perceived not necessarily true) • Distrust of government/industry ability to regulate

  9. Three Ts • Time • Temperature • Turbulence

  10. System Components • Refuse receipt/storage • Refuse feeding • Grate system • Air supply • Furnace • Boiler

  11. Energy/Mass Balance Energy Loss (Radiation) Flue Gas Waste Mass Loss (unburned C in Ash)

  12. Flue Gas Pollutants • Particulates • Acid Gases • NOx • CO • Organic Hazardous Air Pollutants • Metal Hazardous Air Pollutants

  13. 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) 

  14. Metals • Removed with particulates • Mercury remains volatilized • Tough to remove from flue gas • Remove source or use activated carbon (along with dioxins)

  15. 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

  16. 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

  17. Air Pollution Control • Remove certain waste components • Good Combustion Practices • Emission Control Devices

  18. Devices • Electrostatic Precipitator • Baghouses • Acid Gas Scrubbers • Wet scrubber • Dry scrubber • Chemicals added in slurry to neutralize acids • Activated Carbon • Selective Non-catalytic Reduction

  19. Stoichiometric Insufficient O2 Excess Air Role of Excess Air – Control Three Ts T Amount of Air Added

  20. Stoichiometric Insufficient O2 Excess Air Role of Excess Air – Cont’d Increasing Moisture Amount of Air Added

  21. 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

  22. 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

  23. Schematic Presentation of Bottom Ash Treatment

  24. Ash Reuse Options • Construction fill • Road construction • Landfill daily cover • Cement block production • Treatment of acid mine drainage

  25. Refuse Boiler Fabric Filter Stack Spray Dryer Tipping Floor Ash Conveyer Metal Recovery Mass Burn Facility – Pinellas County

  26. Overhead Crane

  27. Turbine Generator

  28. Fabric Filter

  29. Return to Home page Updated August 2005

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