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T.J. Schildhauer, May 2009
Fluidised Bed Methanation Technology for Improved Production of SNG from Coal
International Conference on Clean Coal Technologies, Dresden, 18 May 2009
T.J. Schildhauer, S. BiollazPaul Scherrer Institut Villigen, Switzerland
T.J. Schildhauer, May 2009
Outline
• Why convert coal to SNG? (What is SNG?)
• State of art in SNG from coal: fixed bed methanation
• Learnings from coal gasification and methanation for “biomass-to-SNG”
• Learnings from “biomass-to-SNG” for future coal gasification and methanation
• Conclusions and Outlook
T.J. Schildhauer, May 2009
Why convert carbonaceous material to SNG?
• Synthetic Natural Gas (SNG) is a versatile energy carrier that is interchangeable with Natural Gas (> 95% methane, high HHV)
• SNG can be distributed via the NG grid • Many applications in industry, for de-central electricity production and as
fuel, e.g. in CNG cars• Higher “chemical efficiency” achievable than for FT• Less selectivity issues• Process is less complex (not necessarily high pressure process)
T.J. Schildhauer, May 2009
State of the art: Fixed bed methanation (I)
• In operation since 1984, input is lignite• 14 Lurgi-Gasifiers (150 MWth each)• Fixed bed methanation (Lurgi)
Great Plains Synfuels Plant
http://www.dakotagas.com/
T.J. Schildhauer, May 2009
State of the art: Fixed bed methanation (II)
• Adiabatic fixed bed reactors with intermediate cooling and product gas recycle (here the TREMP® process by Haldor Topsoe A/S, Denmark)• Temperature profiles show catalyst deactivation due to sintering
Rostrup-Nielsen et al., Applied Catalysis A: General 330 (2007) 134–138
T.J. Schildhauer, May 2009
Chemical/cold gas efficiency along the process chain
FeedstockProducer gas CH4 , CO2
Heat
Heat
Autothermal Gasification:Losses depend on the gasifier outlettemperature.
Exothermic Methanation:Losses depend on selectivity and producergas composition. The higher the methanefraction, the higher the chemical efficiency!
Gasifier Methanation
T.J. Schildhauer, May 2009
Is there a price to pay for higher efficiency?
• Higher chemical or cold gas efficiency asks for lower gasifier outlet temperatures and higher methane content in the producer gas
• From the Biomass-to-SNG process we know that lower temperatures in the gasifier and more methane means:- not only H2 S and COS, but also organic sulphur compounds such asmercaptans, thiophenes
- potentially higher ethylene (C2 H4 ) contents• Under fixed bed conditions, ethylene tends to form
carbon whiskers on nickel catalysts• Additional potential for catalyst deactivation!
Czekaj et al., Applied Catalysis A: General 329 (2007) 68 – 78
T.J. Schildhauer, May 2009
How about fluidised bed methanation?
• Comflux methanation technology for SNG production (70 & 80ies)• Demo plant in 20 MWSNG scale running on CO/H2 mixtures
T.J. Schildhauer, May 2009
Operation experience of demo & pilot plants (Comflux) Good starting point for bio syngas investigations
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] 20 MW Demo plant2 kW Pilot plant
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H2 /CO ratio [-]
Target area for biomass
Target area for biomass
T.J. Schildhauer, May 2009
Methane from wood: Producing SNG in pipeline quality
CHP Plant Güssing; 8 MWth , 2 MWel
Gas conditioning
SNG (CH4 )
FluidizedCatalyst
Bed
H2 4%CO 0.5%CO2 47.5%CH4 40%C2H4 0%N2 8% Gas
cleaning
H2 37%CO 25%CO2 18%CH4 10%C2H4 3%N2 6%S-speciestars
T.J. Schildhauer, May 2009
FluidizedCatalyst
Bed
Gas cleaning
> 1000h stable run with real gas (10 kW slip stream)
fully automated set-up of PSI
T.J. Schildhauer, May 2009
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CH
4, C
O2 [
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[vol
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s_ch4
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Stable run with real gas on 10 kW scale
Schildhauer et al., Annual Scientific Report PSI (2008)
T.J. Schildhauer, May 2009
Why does it work? (Toolbox for investigation)
- Measuring dense phase concentration profiles by means of a moveable sampling tube allows to gain insight into the „heart of methanation“
- Taking catalyst samples oxygen-free from the reactor allows sample characterisation by:
XRD, chemisorption, TPO/TPR etc.
GC
GAS
Sampling points
Seemann et al., Applied Catalysis A: General 313 (2006) 14 – 21
T.J. Schildhauer, May 2009
Why does it work ? (Dominant effects)
At end of catalyst bed, mixing of dense and bubble phase
Mass transfer between dense and bubble phase
Hydrogen reacts with Cs on catalyst surface (internal regeneration)
CO2 first by Boudouard (Cs !), then readsorption, then by methanation
Kopyscinski et al., Chemical Engineering Technology 32 (2007) 343 – 347
T.J. Schildhauer, May 2009
Methanation Options for SNG Synthesis Fixed bed vs. fluidised bed methanation
Fixed Bed Fluidised bed+ State of the art - Hot spot- Formation of carbon whiskers if
C2 H4 present in the feed
+ Good temperature control+ No formation of carbon whiskers
if C2 H4 present in the feed- Attrition resistant catalyst necessary- Scale-up more complex
T.J. Schildhauer, May 2009
Acquiring experience in up scaling PSI does R&D on methanation and gas cleaning in Güssing (A)
1 MWSNG PDU:• gas pre-treatment• methanation• H2 /CO2 separation Process Development Unit (PDU)
T.J. Schildhauer, May 2009
Conclusion and Outlook
• In SNG production, higher overall chemical efficiency asks for lower gasifier outlet temperatures and higher methane contents
• Lower gasifier temperatures and more methane means often: more ethylene contents (catalyst deactivation due to carbon formation!)
• Fluidised bed methanation allows converting (unsaturated) hydrocarbons into SNG, without harming the methanation catalyst (experiment in 10 kW scale during 1000h)
• It is expected that PSI’s methanation technology is quite robust towards producer gases from e.g. low temperature coal gasification
• A proof-of-concept of PSI’s first generation methanation technology on the 1 MW scale is on the way (commissioning ongoing, 60h run so far)
T.J. Schildhauer, May 2009
Acknowledgments• Our partners: CTU, TU Vienna, repotec, Biomassekraftwerk Güssing• European Union (DG TREN)• swisselectric research, VSG, EGO, GVM, Gaznat• Swiss Federal Office of Energy (BfE)• CCEM, ETH domain (ETH-Rat)
T.J. Schildhauer, May 2009
Research cooperations in SNG from wood
KonsortiumMethan aus Holz
Bio-SNG
CCEM2nd Gen. Biogas
Swisselectric research
EU DG TREN
Swiss Federal Office of Energy (BFE)VSGEGOGVM
Gaznat
ETH-Domain
T.J. Schildhauer, May 2009
Carbon- and sulphur-species in raw gas from gasifiers Mainly depending on gasification temperature
C1 C2 – C5 BTEX >C7 (tars)
C
S
H2 S
COS
mercaptanes
thiophenes
Low temperature gasification: (800 - 900 °C)High temperature
gasification: (1200 - 1600 °C)
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