08 gasification & liquid fuel synthesis
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John Jechura – jjechura@mines.eduUpdated: January 4, 2015
Gasification & Liquid Fuel Synthesis
Topics
• Principles of gasification
Gasification vs. combustion
• Gasifier & associated process configurations
• Products from syngas
Fisher‐Tropsch (FT) Synthesis
2
Thermochemical Conversions
• Pyrolysis 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
• Gasification Thermal conversion of organic materials at elevated temperature and reducing conditions to produce primarily permanent gases, with char, water, & condensables as minor products
Primary categories are partial oxidation and indirect heating
4
Distinction between produced gas
• Town Gas
Gas produced from coal, about 50% hydrogen, 3%‐6% carbon monoxide, & the rest mostly methane & carbon dioxide
• Synthesis Gas (Syngas)
Mixture of hydrogen & carbon monoxide
• Synthetic Natural Gas (SNG)
Mixture of mostly methane from syngas
• Producer Gas
Partial oxidation of coke with humidified air
• Water Gas
50/50 mixture of hydrogen & carbon monoxide
5
Principles of Gasification
Gasification Purification Low Btu GasCO, H2, N2
Feed
AirSteam
Contaminants
Gasification Purification Medium Btu GasCO, H2
Feed
OxygenSteam
Contaminants
Gasification Purification Medium Btu GasCO, H2
Feed
HeatSteam
Contaminants
Hydro-Gasification Purification High Btu GasCO, H2, CH4
Feed
HeatHydrogen
Contaminants
Catalytic Gasification Purification & Separation SNGCH4
Feed
Steam
Contaminants
6
Simplistic view of gasification
Biomass Gasification: Fundamentals & ApplicationsAshwani Gupta, webinar, December 7, 2010.
7
Stoichiometric Considerations
2 2
2
2 2 2
C O CO1
C O CO21
H O H O2
• Oxygen consumed (exothermic)
• Water‐gas reactions (endothermic)
• Bourdourd reaction (endothermic)
• Hydro‐gasification
• Water‐gas shift reaction
• Methanation reaction
2 2
2 2 2
C H O CO HC 2H O CO 2H
2C CO 2CO
2 4C 2H CH
2 2 2CO H O H CO
2 4 21 1
C H O CH CO2 2
8
Gasification vs. Combustion
Biomass Gasification: Fundamentals & ApplicationsAshwani Gupta, webinar, December 7, 2010.
9
Gasification vs. Combustion
Biomass Gasification: Fundamentals & ApplicationsAshwani Gupta, webinar, December 7, 2010.
10
Coal is not the only feedstock
Biomass Gasification: Fundamentals & ApplicationsAshwani Gupta, webinar, December 7, 2010.
11
Alcohol Synthesis
Biomass
Flue Gas
Dryer
Scrubber
Sludge(Waste)
CO2
Sulfur
Acid Gas Cleanup
Air
Gasifier
Solids(Waste)
Steam
Alcohol Separation
Methanol & Water
Ethanol
MixedAlcohols
Steam
Reformer
Air
Compressor
Water to recycle
Compressor
Example Thermochemical Conversion
Personal communication Ryan Davis, NREL. November 2009.
13
Gasifier configurations –Counter‐Current Moving Bed
http://www.netl.doe.gov/technologies/coalpower/turbines/refshelf/handbook/1.2.1.pdf
14
Gasifier configurations – Fluidized Bed
http://www.netl.doe.gov/technologies/coalpower/turbines/refshelf/handbook/1.2.1.pdf
15
Gasifier configurations – Entrained Flow
http://www.netl.doe.gov/technologies/coalpower/turbines/refshelf/handbook/1.2.1.pdf
16
Direct vs. Indirect Gasification
http://www1.eere.energy.gov/ba/pba/pdfs/bio_gasification.pdf
17
SilvaGas Indirect Gasifier
http://rentechinc.com/silvaGas.php
18
Gas Cleanup Technologies
• Particulate removal
Cyclones
Wet scrubbing
• Gas conditioning
Tar removal /destruction
CO2 & H2S removal
• Solvent systems – amines, Selexol, …
19
IGCC – Integrated Gasification Combined Cycle
20
Syngas Products
• Hydrogen
• Methanol and its derivatives (NH3, DME, MTBE formaldehyde, acetic acid, MTG, MOGD, TIGAS)
• Fischer Tropsch Liquids
• Ethanol
• Mixed alcohols
• Olefins
• Oxosynthesis
• IsosynthesisSyngasCO + H2
Methanol
H2OWGSPurify
H2N2 over Fe/FeO
(K2O, Al2O3, CaO)NH3
Cu/ZnOIsosynthesis
ThO2 or ZrO2
i-C4
Alkali-doped
ZnO/Cr2 O3
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
Al2O
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
ge22
Fischer‐Tropsch for Liquid Fuel Synthesis
2 2 2 22 1 H CO C H H On nn n n
• Set of reactions that “recreates” linear alkanes from syngas
• Distribution of compounds well described by Anderson‐Schulz‐Flory distribution
where representschain growth probability
2 1n 1 nnW
23
Fischer‐Tropsch for Liquid Fuel Synthesis
• Chain growth probability shifts from light products to wax
24
Fischer‐Tropsch for Liquid Fuel Synthesis
• History
Original process commercialized in Germany in 1936. Used by Germany & Japan during World War II to produce substitute fuels
Sasol. Largest scale implementation series of plants operated by Sasol in South Africa. Required during time of apartheid.
Shell Middle Distillate Synthesis. 12,000 barrels per day Shell facility converts natural gas into low‐sulfur diesel fuels and food‐grade wax in Bintulu, Malaysia.
Ras Laffan, Qatar. Based on the Sasol technology, using cobalt catalysts at 230oC. Includes "Dolphin Gas Project" plant, converting natural gas to petroleum liquids at a rate of 140,000 barrels/day, with additional production of 120,000 barrels of oil equivalent in natural gas liquids and ethane. Was scheduled to commission in 2010.
Rentech. • Demonstration F‐T plant Commerce City, CO. Commercial scale facilities had been planned for Rialto, CA, & Natchez, MS.
• Abanded projects 2012. Sold technology in 2013.
Three GTL facilities proposed in US: Lake Charles, LA (large scale); Karns City, PA; Ashtabula, OH• December 2013 Shell cancelled plans for another facility in LA because of high capital costs & market uncertainties for natural gas & liquid product prices
25
Fischer‐Tropsch Process Considerations
• Catalyst types HTFT (High‐Temperature Fischer‐Tropsch)
• Iron‐based catalyst• 330oC‐350oC• Used extensively by Sasol in their Coal‐to‐Liquid (CTL) plants
LTFT (Low‐Temperature Fischer‐Tropsch)• cobalt based catalyst• 250oC or less• Shell’s integrated Gas‐to‐Liquid (GTL) plant in Bintulu, Malaysia.
• Product types Predominantly straight‐chain alkanes. Lesser amounts of 1‐alkenes & alcohols. Properties best for distillate fuels (jet, diesel) & wax
• Low octane gasoline. Isomerization required• May hydrocrack was for increased fuel production
26
Fischer‐Tropsch Reactor Types
27
“High quality diesel via the Fischer-Tropsch process – a review”M.E. Dry, Journal of Chemical Technology & Biotechnology, v 77, pp 43-50
Fischer‐Tropsch Chain Growth & Kinetics
• General rate expressions
For Co:
For Fe:
• Water slows down rate for iron‐based catalysts
28
2H CO
2CO
rate1
p pk
b p
2
2
H CO
CO H O
ratep p
kp a p
“High quality diesel via the Fischer‐Tropsch process – a review”M.E. Dry, Journal of Chemical Technology & Biotechnology, v 77, pp 43‐50
Fischer‐Tropsch – More Than Alkanes
29
“High quality diesel via the Fischer‐Tropsch process – a review”M.E. Dry, Journal of Chemical Technology & Biotechnology, v 77, pp 43‐50
Fischer‐Tropsch Process Considerations
30
http://www.eia.gov/todayinenergy/detail.cfm?id=15071
Production of Diesel
31
“High quality diesel via the Fischer‐Tropsch process – a review”M.E. Dry, Journal of Chemical Technology & Biotechnology, v 77, pp 43‐50
Production of Gasoline, Diesel, & Chemicals
32
“High quality diesel via the Fischer‐Tropsch process – a review”M.E. Dry, Journal of Chemical Technology & Biotechnology, v 77, pp 43‐50
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