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Thermochemical Biomass Gasification Technologies and
ProductsRalph P. Overend
Stanford University: Global Climate and Energy Project (GCEP)
April 27, 2004
Outline
• Types of Gasification• Shared conventions• Why biomass gasification behavior is not at
all coal like• Thermochemical Process Technologies
– Pressurized water gasification• R&D needs and issues• Examples of NREL research
Biomass Gasification Systems• Three distinct process configurations
– Biological – Anaerobic Digestion (AD) • Water streams with soluble or slurry biomass high in
BOD/COD– Thermochemical pyrolysis and gasification
• Dry biomass resources – High pressure and temperature water gasification
• Aqueous solutions or slurries of biomass
• Technological Maturity– Thermochemical and AD go back to the end of the 19th
Century. Have been commercialised.– High pressure water gasification technology is an
emerging technology - which has yet to get beyond the bench and pilot unit.
Carlota Perez, a researcher at Britain's University of Sussex, in her book “Technological Revolutions and Financial Capital: The Dynamics of Bubbles and Golden Ages” (Edward Elgar, 2002).
Economist “A survey of the IT industry, page 4, May 10 -16
Useful shared knowledge• Energy units will be in the SI system
– 5 and 10% error: GJ = Million Btu, short ton = tonne• Biomass definitions and usage
– Mainly lignocellulosics I.e. wood straw and stalks• food/fibre residues are also mainly lignocellulosics composed
of cellulose/hemicellulose and lignin• Energy content (dry basis) is more or less constant at 18.6 GJ/t
or 5 MWth/t• Apart from solar dried straw materials most green biomass has
50% total mass basis water.• Volumetric energy densities of bulk material is very low
despite the cell wall density being about 1.5 g/cm3.
– Bituminous Coal or crude oil for example, has a volume of 30 dm3 GJ-1, while solid wood has around 90 dm3 GJ-1, in chip form it is 250 dm3 GJ-1 for hardwood species. Cereal straw has even less energy density, and the volumes required range from 450 dm3 GJ-1 (for large round bales) to 1.2 m3 GJ-1 (for chopped straw).
1792 and all that• Murdoch (1792) coal
distillation• London gas lights 1802• Blau gas – Fontana 1780• 1900s Colonial power• MeOH 1913 BASF• Fischer Tropsch 1920s• Vehicle Gazogens WWII• SASOL 1955 - Present• GTL 1995 – Present• Hydrogen – Future?
Historic Gasification
PyrolysisPyrolysis• Thermal conversion (destruction) of organics in the absence of oxygen • In the biomass community, this commonly refers to lower temperature
thermal processes producing liquids as the primary product• Possibility of chemical and food byproducts
GasificationGasification• Thermal conversion of organic materials at elevated temperature and
reducing conditions to produce primarily permanent gases, with char, water, and condensibles as minor products
• Primary categories are partial oxidation and indirect heating
Basic DefinitionsBasic Definitions
Gasification
Pyrolysis
Reduction
Combustion
Gas, Tar, Water
Ash
Biomass
Air
C + CO2 = 2COC + H2O = CO + H2
C + O2 = CO24H + O2 = 2H2O
Updraft Gasifier
Pyrolysis
Reduction
Combustion
Gas, Tar, Water
Ash
Biomass
Air
C + CO2 = 2COC + H2O = CO + H2
C + O2 = CO24H + O2 = 2H2O
Updraft Gasifier
Freeboard
Fluid Bed
PlenumAir/Steam
Biomass
Ash
Cyclone
Fluid-Bed Gasifier
Freeboard
Fluid Bed
PlenumAir/Steam
Biomass
Ash
Cyclone
Fluid-Bed Gasifier
Secondary
Circulating Fluid-Bed Gasifier
Fly Ash
Bottom Ash
Biomass
Air/Steam
GasifierPrimaryCyclone
CycloneSecondary
Circulating Fluid-Bed Gasifier
Fly Ash
Bottom Ash
Biomass
Air/Steam
GasifierPrimaryCyclone
Cyclone
Fly Ash
Bottom Ash
Biomass
Air/Steam
GasifierPrimaryCyclone
Cyclone
Biomass
Pyrolysis
Reduction
Combustion
Gas, Tar, Water
AshAir
C + CO2 = 2COC + H2O = CO + H2
C + O2 = CO24H + O2 = 2H2O
Downdraft Gasifier
Biomass
Pyrolysis
Reduction
Combustion
Gas, Tar, Water
AshAir
C + CO2 = 2COC + H2O = CO + H2
C + O2 = CO24H + O2 = 2H2O
Downdraft Gasifier
Biomass
N2 or Steam
Furnace
Char
Recycle Gas
Flue Gas
Entrained Flow Gasifier
Air
Biomass
N2 or Steam
Furnace
Char
Recycle Gas
Flue Gas
Entrained Flow Gasifier
Air
Biomass in the coalifaction seriesafter van Krevelen
• Young coal?– Retains polymeric
identity • Cellulose• Hemicellulose• Lignin
– Polymers are normal!• E.g. Glass transition
temperatures –melting behaviour
• Decomposition starts at 250 C
Single wood particle pyrolysis
Advances in Thermochemical Fundamentals
• Prior to 1975 there were only slow pyrolysis processes – charcoal production
• So-called fast pyrolysis decoupled the physical phenomena of heat and mass transfer from the chemistry resulting in– Phenomenological understanding of the chemical
processes– Knowledge of primary rate process rate constants– Applied catalysis knowledge to govern some pathway
outcomes (Levoglucosan vs hydroxy acetaldehyde)– High yield (theoretical?) production of charcoal
Understanding the Phenomena
Controlling Thermochemistry
Lede-scheme
Conversion to active species
Time to maximum active
Biomass Thermal Regimes time required for pyrolysis
• Region I – essentially heat and mass transfer free.-kinetic model– Horizontal lines also for a
infinitesimal thin sample• Region II – heat transfer
limit Bi 0.2• Region III – Thermally
thick• Region IV – thermal wave
regime Bi > 10KM Bryden, KW Ragland & CJ Rutland. 2002. Modeling thermally thick pyrolysis of wood. Biomass and Bioenergy 22(1) 41-53.
Biot number Bi relates the heat transfer resistance inside and at the surface of a body.
Updraft Gasifier• Thermal Region III-IV• Limited throughput due to
materials of construction at grate 150 kg m-2 h-1 of dry biomass
• Product gas very high in tars.
• Maximum diameter of 3 –4 m due to material flow issues.
• Good for direct use of gas in a combustor
Downdraft – co-current gasificationalso open core versions
• Thermal regime III• diameter < 1.5 m• throughput 300 kg m-2 h-1
of dry biomass• from 100 kWth to 2 MWth
input.• Commercial in India and
China.• DOE/NREL with CPC
forestry projects.
Community Power Corporation’sCommunity Power Corporation’sBioMaxBioMax 15 Modular15 Modular BiopowerBiopower SystemSystem
Fluidised Bed Gasifiers
• High heat transfer region II or III depending on particle size
• Factory assembled up to 3 m diameter
• 1500 kg m-2 h-1 of dry biomass
• Bed medium can be catalytic e.g. olivine
• Commercially available
CarbonaCarbona Project: Skive, DenmarkProject: Skive, Denmark
BIOMASSBIOMASS
ASHASH
AIRAIR
ASHASH
POWERPOWER
HEATHEAT
FUELFUELFEEDINGFEEDING
GASIFIERGASIFIERTAR CRACKERTAR CRACKER
GAS COOLERGAS COOLER GAS COOLERGAS COOLERSTACKSTACK
HEAT RECOVERYHEAT RECOVERY
GAS TANKGAS TANK
GAS ENGINE(S)GAS ENGINE(S)
Indirect (Allothermal) systems
• Thermal region III• Gasifier/pyrolyzer very
high through put approx 10 t m-2 h-1
– Combustor limiting
• FERCO – Burlington• TUV in Gussing• MTCI – Thermochem
using product gas fired vessel for soda liquor
FERCO GASIFIERFERCO GASIFIER-- BURLINGTON, VTBURLINGTON, VT
350 TPD350 TPD
Gasification ApplicationsGasification Applications
• Heat• District heating• Plant steam• Institutional heating
• Combined heat and power• Pulp and paper industry• District heating/electricity
• Electricity only• Cofiring - ash segregation• Integrated gasification combined cycle
• Synthesis gas• Oxygenates - methanol, ethanol, DME, etc.• Fischer-Tropsch Liquids• Hydrogen• Methane• Chemicals
Synthesis Gas Synthesis Gas -- Examples Examples of Conversion Processesof Conversion Processes
• Oxygenates• Methanol, DME, Mobil MTG• Mixed alcohols
• Snamprogetti/Topsoe, Lurgi, Dow, IFP/Idemitsu• Modified Fischer Tropsch - ethanol
• Dow, Pearson Technologies• Biochemical (fermentation)
• Mississippi State University, University of Arkansas• Hydrocarbon fuels
• Methane• Fischer Tropsch
• Iron based - Sasol Synthoil• Cobalt based - Shell middle distillate synthesis (SMDS)
• Hydrogen• Methane steam reforming• High and low temperature shift• H2 separation
SyngasCO + H2
Methanol
H2OWGSPurify
H2N2 over Fe/FeO
(K2O, Al2O3, CaO)NH3
Cu/ZnOIsosynthesis
ThO2 or ZrO2
i-C4
Alkali-doped
ZnO/Cr2 O
3
Cu/ZnO; Cu/ZnO/Al2 O3
CuO/CoO/Al2 O3
MoS2
MixedAlcohols
Oxosynthesis
HCo(CO)4
HCo(CO)3 P(Bu3 )
Rh(CO)(PPh3 )3
AldehydesAlcohols
Fischer-Tropsch
Fe, C
o, R
u
WaxesDiesel
OlefinsGasoline
Ethanol
Co, Rh
FormaldehydeAg
DME
Al 2O
3
zeolites
MTOMTG
OlefinsGasoline
MTBEAcetic Acid
carb
onyla
tion
CH3O
H +
COCo
, Rh,
Ni
M100M85DMFC
Direct Use
hom
olog
atio
nCo
isob
utyl
ene
acid
ic io
n ex
chan
ge
High Pressure Water Gasification
Liquid water based gasification
HawaiiCarbonSCSawdust/StarchHawaiiCarbonSCGlucoseTwenteNoneSCGlyc/GluNEDONiSCMixed PolymersWatanabeZrO2SCGlucose/CelluloseJ. Gas. Co“metal”SCSewage sludgeKarlsruhenoneSC500Baby FoodBattelleCu/Ni21350Cow manure/Corn fiberBattelleRu/TiO221350CarbohydrateU. WiscRaney Ni/Sn5.6265Sorb/Glyc/EtGlyU Wisc.Pt/Al2O35.1225Glu/Sorb/Glyc
SourceCatalystMPaoCFeedstock
Research and Development AreasResearch and Development Areas(not all(not all--inclusive)inclusive)
• Feed characterization• Materials handling
• Storage• Conveying• Moisture control• Comminution• Feeding
• Gasification• Kinetics• Phase equilibria• CFD modeling
• Gas cleanup• Tar, ammonia, water• Particulates, ash• Residual carbon control• Integrated process specific species• Gas separations
• Process integration• Prime mover systems• Catalytic syngas conversion
• Sensors and controls• LCA and TE modeling
U.S. DOE - Office of Biomass Program Biomass Conversion Platforms
Syngas Platform“Thermo-chemical”
Sugar Platform “Bio-chemical”
FuelsChemicals & Materials
BiomassCombined Heat & Power
Residues
Clean Gas
Conditioned SynGas
Sugar Feedstocks
FeedstockHandling
EnzymaticHydrolysis of
Cellulose
EthanolRecovery
Heat & Power
Generation
Fermentationfor Bioproducts
PretreatmentGasification/Pyrolysis
Gas Conditioning& Separation
Synthesis Multi-sugarFermentation
FuelEthanol
BioproductsExportElectricity
Hydrogen &Bioproducts
Fuels/Products
LigninProducts
SugarIntermediates
SugarIntermediates
LigninIntermediates
Residues
MBMSMBMS
TMBMSTMBMS
Gasification (TCUF)Gasification (TCUF)
Engine TestingEngine Testing
EmissionsEmissionsMonitoringMonitoring
NREL FacilitiesNREL Facilities
ThermochemicalThermochemical Process Development Unit (TCPDU)Process Development Unit (TCPDU)
Biomass Feed
8-in. FluidizedBed Reactor
Hopper/Feeder
Controller
SuperheatedSteam
ThermalCracker
Cyclones
Char
Settling Tank
Aqueous Effluent
Scrubber
BlowerCoalescing
Filter
Wet scrubbedSyngas
Base Configuration
75 100 125 150 175 2000
2e+4
4e+4
6e+4
8e+4
1e+5 78
91,92
104 116
128
142 152 166 178
192 216
94
108 202
78 - benzene91,92 - toluene94 - phenol104 - styrene108 - cresol116 - indene128 - naphthalene
142 - methylnaphthalenes152 - acenaphthalene166 - flourene178 - anthracene/phenanthrene192 - methylanthracene?202 - pyrene/flouranthene216 - benzo(a)flourene
Averaged mass spectrum (TMBMS) of tars from indirect wood gasification
TCPDU Process Conditions and TCPDU Process Conditions and Product Gas CompositionProduct Gas Composition
GC analysis of Port 3 (vol. %, N2- and steam-free)
hydrogen 26.9 ± 1.4 methane 15.6 ± 0.2 carbon monoxide 26.7 ± 1.4 carbon dioxide 23.5 ± 0.8 ethylene 4.1 ± 0.1 ethane 0.68 ± 0.07 acetylene 0.47 ± 0.04 propylene 0.32 ± 0.04 1-butene 0.16 ± 0.04 H2/CO ratio 1.0 ± 0.1 Tar concentrations by TMBMS (ppmv,
w/ steam and N2) benzene 1732 ± 165 toluene 715 ± 89 cresol 216 ± 44 naphthalene 327 ± 33 phenanthrene 72 ± 7
Average gas composition from indirect wood gasification in TCPDU
2/11 to 2/28/03
TCPDU process parameters 11-Feb-03 to 28-Feb-03steam feed rate (kg/h) 20.0 ± 0.2biomass feed rate (kg/h) 10.5 ± 0.9fluid bed T (ºC) 615 ± 1thermal cracker T (ºC) 775 ± 2product gas flow rate (kg/h) 8.2 ± 0.8material balance 98.9±10%
m /z
5 0 7 5 1 0 0 1 2 5 1 5 0 1 7 5 2 0 0 2 2 5
Inte
nsity
(arb
.)
- 2 0 0 0 0
- 1 5 0 0 0
- 1 0 0 0 0
- 5 0 0 0
0
5 0 0 0
1 0 0 0 0
1 5 0 0 0
2 0 0 0 0
2 5 0 0 0
C O 2 ( /1 0 )
b e n z e n e
t o lu e n e n a p h t h a le n e
p y r e n e
Difference Mass Spectrum (catalyst outlet-inlet) showing destruction of
biomass gasifier tars
Gas Flow Rate
0.35-0.4 kg/hr 7-18 kg/hr
WHSV (weight of feed/hr / weight of catalyst)
1.6 hr-1 0.16-0.48 hr-1
Temperature
700-900°C 850°C
5 cm bench-scale reformer – March, 2001 30 cm pilot-scale reformer – April 2002
Experimental ApproachExperimental Approach
Additional Information• Biobased Products and Bioenergy Initiative
www.bioproducts-bioenergy.gov• Biopower Program
www.eren.doe.gov/biopower• Biofuels Program
www.ott.doe.gov/biofuels
The National Bioenergy Center is funded by the
Office of Biomass Program within theU.S. Department of Energy
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