1. Thermochemical Conversion Technologies

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, 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

4. Flexibility of Gasification

5. 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

6. Pyrolyzer—Mitsui R21

7. 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

8. Thermoselect (

9. Fulcrum Bioenergy MSW to Ethanol Plant
Construction on Fulcrum Bioenergy municipal solid waste to ethanol plant, Sierra BioFuels, is set to begin in the 4th quarter of Located in the Tahoe-Reno Industrial Center, in the City of McCarran, Storey County, Nevada, the plant will convert 90,000 tons of MSW into 10.5 million gallons of ethanol per year.

10. 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 kWh/ton
Commercial scale facilities for treating MSW in Japan

11. 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

12. 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

15. 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

16. Waste Incineration - Disadvantages
High capital cost
Skilled operators are required (particularly for boiler operations)
Some materials are noncombustible
Some material require supplemental fuel

17. 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

18. 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

19. WTE Process

20. Three Ts
Time
Temperature
Turbulence

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

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

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

25. 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) 

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

27. 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

28. 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

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

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

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

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

33. 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

34. 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

35. Schematic Presentation of Bottom Ash Treatment

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

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

38. Overhead Crane

41. Turbine Generator

42. Fabric Filter

44. 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