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

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

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

14. Particulates Solid Condensable Causes Control
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) 

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

16. Acid Gases
From Cl, S, N, Fl in refuse (in plastics, textiles, rubber, yd waste, paper)
Uncontrolled incineration % HCl with pH 2
Acid gas scrubber (SO2, HCl, HFl) usually ahead of ESP or baghouse
Wet scrubber
Spray dryer
Dry scrubber injectors

17. 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

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

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

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

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

22. 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

23. 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

24. Schematic Presentation of Bottom Ash Treatment

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

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

27. Overhead Crane

30. Turbine Generator

31. Fabric Filter

33. Return to Home page
Updated August 2005