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