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					Greener Solid Waste Practices:
An Environmental Sustainability Program
Davis, California (September 17-18, 2007)


Thermal Conversion of Solid
Waste
G.M. Savage, L.F. Diaz, and L.L. Eggerth
CalRecovery, Inc.
Concord, California USA

GSavage@calrecovery.com
Outline
• Some Important Concepts
• General Types of Thermal Technologies
• Overview:
  – International
  – USA
• Conclusions
Introduction
• Focus of presentation:
  – description of some thermal technologies that
    have been demonstrated and some that are
    under development
  – presentation is a high level overview only
Thermal Processes
• Direct combustion (CH + O2  CO2 + H2O)
• Pyrolysis (thermal process occurs in the
  absence of O2/air)
• Gasification (sub-stoichiometric air)
• Plasma arc (very high temperature gas)
Example of Typical California Solid Waste
Management Infrastructure Designed to
Achieve High Waste Diversion Rates
                                                                                              Yard Waste,
 Diversion from Disposal (%)




                               90
                                                                                              Wood Waste,
                               80
                                                                                              Concrete,
                               70
                                                                     Food Waste               & Kraft Paper
                               60
                               50
                               40
                                                                 Paper & Containers
                                              Food Waste
                               30
                                           Mixed Paper
                               20
                               10      Yard Waste
                                    Containers & Newspaper
                                0

                                                                                         Construction &
                                       Residential               Commercial
                                                                                       Demolition/Self-Haul

                                       High                                                     Low

                                                         Degree of Municipal Control
Examples of Recovering Energy
from Solid Wastes
                                                                                                 Steam
                                                                                Steam Boiler
                                                                Direct
                                                                                and Turbine/     Electricity
                                                              Combustion         Generator
                                              Fuel
Source-                                   Materials
Separated                                                           Ash
              Pre-Processing (i.e.,    (e.g., wood, crop                                  Medium- or High-
Organics                                   residues)                                          Quality
                  front-end)                                   Biogasification/
              (mechanical and/or                                                             Fuel Gas
                                                                  Anaerobic
                   manual)                                        Digestion

                                                                        Sludge
                                                                                               Low-/Medium-
                Non-combustible
                                                                    Thermal                    Quality Fuel Gas
                Process Residues
                                                                 Gasification/
                                                             Pyrolysis/Liquefaction
                                               Fuel
                                            Materials            Char             Liquid Fuel/Residue
Mixed MSW      Pre-Processing (i.e.,
                                       (e.g., paper, food)
                   front-end)                                                                                  Steam
               (mechanical and/or                                 Fluidized            Steam Boiler
                    manual)                                          Bed               and Turbine/            Electricity
                                                                 Combustor              Generator
                                                                          Ash
            Recyclables    Non-combustible
                           Process Residues                                                Liquid Fuel
                                                              Ethanol Production

                                                                     Residue
Comparison of Solid Waste
Characterization Worldwide (% wet wt)
    Location                Putres-   Paper    Metals   Glass   Plastics,   Textiles   Ceramics,   Wt (g)/
                             cibles                             Rubber,                  Dust,      cap/
                                                                Leather                 Stones      day
    Bangalore, India         75.2       1.5      0.1     0.2       0.9        3.1        19.0        400
    Israel                   71.3      24.8      1.1     1.0       0.8        1.0         1.8        400
    Manila, Philippines      45.5      14.5      4.9     2.7       8.6        1.3        27.5        400
    Asunción, Paraguay       60.8      12.2      2.3     4.6       4.4        2.5        13.2        460
    Seoul, Korea             22.3      16.2      4.1    10.6       9.6        3.8        33.4a     2,000a
    Vienna, Austria          23.3      33.6      3.7    10.4       7.0        3.1        18.9b      1,180
    Mexico City, Mexico      59.8c     11.9      1.1     3.3       3.5        0.4        20.0        680
    Paris, France            16.3      40.9      3.2     9.4       8.4        4.4        17.4       1,430
    Australia                23.6      39.1      6.6    10.2       9.9                    9.0       1,870
    Sunnyvale, California    39.4d     40.8      3.5     4.4       9.6        1.0         1.3       2,000
a
    Includes briquette ash (average).
b   Includes “all others.”
c   Includes small amounts of wood, hay, and straw.
d   Includes garden waste.
Comparison of Thermal Characteristics of
MSW and Those Needed for Self-Sustained
Combustion                                                              100

                                                              10         90

                                                         20                   80

                                                    30                         70

                                               40                                   60
                  Ash (%)                                                                           Moisture Content (%)
                                          50                                         50

                                     60                                                   40

                                 70                                                            30

                            80                                                                      20

                           90                                                                        10

                     100
                                10    20        30            40   50    60    70    80        90 100

                                                Volatile Solids (%)


   Area of Self-Sustained Combustion                                          Typical Values for Many Industrialized Countries

   Typical Values for Developing Countries
Type of Treatment of MSW in
Europe (2004)
European Union
• Recent legislation regarding SWM – the
  Landfill Directive:
  – bans disposal of untreated organic materials
    into landfills
Targets for Biodegradable Waste
Diversion (Landfill Directive) in the EU
 Target Date *                 % of Biodegradable Waste
                               Allowed to Landfill (% of
                                  quantities in 1995)
 2006 (2010)                             75%
 2009 (2013)                             50%
 2016 (2020)                             35%
 * The directive allows for a 4-year derogation for Member States that
 were landfilling more than 80% of the biodegradable waste in 1995
WTE in the EU
               50 million tons of MSW
                thermally treated in 420
                plants produced:

                - 20 million MWh of electricity

                - 50 million MWh of heat
               In 2005, 13 countries
                produced 12.7 million tons of
                RDF or SRF
 Fundamentals of Modern Waste
 Incineration (EU)
      Volume reduction               Energy               Segregation of
       and inertization             recovery                pollutants



    Controlled
     feeding                      (24 %
                                  power,



                                                 filter
                                >50% CHP)
                                low dioxin
                                                                           HCl
    Optimized                                               Fly ash        HBr
    combustion
      control                                                              Hg
                                                                           SO2

                                               Inertization Recovery of
                      Utilization                disposal   Cl, Br, Hg,
                                                (storage)     gypsum
Source: Vehlow, J. Germany
Management of Boiler and
Filter Ash in Europe
•   Extraction/sintering
•   Fusion/vitrification
•   Stabilization
•   Filler in asphalt (NL)
•   „Utilization„ in salt mine (D)
•   Storage for future use
 Source: Vehlow, J., 2006
MSW Management in the
United States (2003)




 Source: US EPA
Number of Waste-to-Energy Facilities
in the United States (1982 to 2004)




 Source: 2005-2006 Municipal Waste Combustion in the United States,
 8th Edition, E.B. Berenyi
Thermal Gasification/Pyrolysis –
System Schematic

                          Pyrolysis (syn) gas
   Organic Feed
                  Pyrolysis
                                         Pyrolytic Oil
                   Reactor


                        Char (e.g., carbon black)
         Heat
Gasification
• Carbon in waste or biomass reacts with steam and
  oxygen (from air) at sub-stoichiometric conditions
• Primary reactions:
  –   C + O2 -> CO2 (exothermic)
  –   C + H2O -> CO + H2 (endothermic, water gas)
  –   C + CO2 -> 2 CO (endothermic)
  –   CO + H2O -> CO2 + H2 (exothermic, generator gas)
• Resulting synthesis gas (syngas) can be used for:
  – energy production in IC engines or turbines
  – synthesis of chemicals
  – hydrogen production
IC Engine Firing Syngas




                          Gasifier (rt) and Gas Conditioner (lt)
 Engine and Dynamometer
Gasification as Front-end Plant




Source: Bilitewski, B., 2006
Pyrolysis
• Endothermic reaction of organic fraction of
  waste, biomass, or liquid waste in the
  absence of oxygen at high temperature and
  pressure
• Organic matter is transformed to a gas,
  liquid, and a solid (char)
• Temperature and pressure levels affect the
  relative ratios of gas, liquid, and solid
Thermal Gasification/Pyrolysis
• Several pilot plants have been operated
• Reliability and maturity of the technology
  has not been demonstrated at full-scale
• Major issues deal with solid residues
  produced, gas clean-up, quality of liquid
  fuel, and air emissions
 Pyrolysis (or Gasification) and
 Melting System in Japan


                   Melting

Gasification


                  Slag


 Source:
Matsuto, T.
Slag and Metal in Japan




About 150 melting systems in operation in 2002 in Japan

Source: Matsuto, T.
Fischer-Tropsch (FT) Process
• Proven technology, originally invented in
  Germany in 1920s
• Catalyzed chemical reaction where
  hydrogen and carbon monoxide are
  converted to liquid hydrocarbons
• Typical catalysts based on Fe and Co
• Main objective is to produce a synthetic
  substitute to petroleum
Plasma Arc
• Energy that is added causes neutral atoms
  of gas to split (5,000 to 10,000 degrees C)
• As atoms split a plasma of positively and
  negatively charged atoms and electrons is
  formed
• Need high voltage to generate electric arc,
  two electrodes (cathode and anode) and
  gas (helium, air)
Plasma -- Commercial
Applications
• Welding and cutting
• Steel melting furnaces
• Some hazardous and radioactive wastes
  treated
Plasma -- Application to SW
• Small unit operating in a cruise ship for about 3
  years
• Some propose to “gasify” the waste and use gas
  to generate electricity
• Several “start-up” companies during the last few
  years, most operate pilot plants
• Concerns about gas cleaning and solid residue
  produced
• Unproven on commercial scale in United States
Plasma -- Application to SW
• One or two facilities operating in Japan
• One facility in Utashinai, Japan processes
  a fraction (segregated) of residential
  waste mixed with ASR
• Gas produced is burned in a boiler to
  produce steam and generate electricity
  with a steam turbine
Plasma -- Application to SW in
Japan




        Facility in Utashinai, Japan
Plasma -- Application to SW in
Japan




  Facility processes a selected fraction of residential waste and ASR
Plasma -- Application to SW in
Japan




                                       Main reactor


 Partial view of processing facility
Plasma -- Application to SW in
Japan


                     Steam turbine




     Slag removal




                     Solid residue
Conclusions

• Direct combustion (massburn)-- well
  developed, substantial history; many systems
  producing steam/electricity
• Fluidized bed -- under development, sporadic
  history; interest is primarily a function of fossil
  fuel prices and air pollution regulations
Conclusions (cont.)

• Thermal gasification -- under development, sporadic
  history; interest is a function of fossil fuel prices
• With current emphasis on sustainability, highest and
  best use of materials, and system integration, a
  number of design criteria/conditions must be
  considered when planning and implementing energy
  recovery from waste

				
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posted:4/23/2011
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