Gasification & Liquid Fuel Synthesis
John Jechura – jjechura@mines.edu
Updated: January 4, 2015
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
Contaminants
Feed
Gasification
Steam
Purification
Low Btu Gas
CO, H2, N2
Air
Contaminants
Feed
Gasification
Steam
Purification
Medium Btu Gas
CO, H2
Oxygen
Contaminants
Feed
Gasification
Steam
Purification
Medium Btu Gas
CO, H2
Heat
Contaminants
Feed
Hydro-Gasification
Hydrogen
Purification
High Btu Gas
CO, H2, CH4
Heat
Contaminants
Feed
Catalytic Gasification
Purification & Separation
SNG
CH4
Steam
6
Simplistic view of gasification
Biomass Gasification: Fundamentals & Applications
Ashwani Gupta, webinar, December 7, 2010.
7
Stoichiometric Considerations
• Oxygen consumed (exothermic)
• Hydro‐gasification
C  O2  CO2
1
C  O2  CO
2
1
H2  O2  H2O
2
C  H2O  CO  H2
C  2 H2O  CO2  2 H2
C  2 H2  CH4
• Water‐gas shift reaction
CO  H2O  H2  CO2
• Water‐gas reactions (endothermic)
• Methanation reaction
1
1
C  H2O  CH4  CO2
2
2
• Bourdourd reaction (endothermic)
C  CO2  2 CO
8
Gasification vs. Combustion
Biomass Gasification: Fundamentals & Applications
Ashwani Gupta, webinar, December 7, 2010.
9
Gasification vs. Combustion
Biomass Gasification: Fundamentals & Applications
Ashwani Gupta, webinar, December 7, 2010.
10
Coal is not the only feedstock
Biomass Gasification: Fundamentals & Applications
Ashwani Gupta, webinar, December 7, 2010.
11
Example Thermochemical Conversion
Flue Gas
Gasifier
Reformer
Biomass
Scrubber
Dryer
Compressor
Solids
(Waste) Air
Sludge
(Waste)
Steam
Water to recycle
Steam
Acid Gas Cleanup
Air
Alcohol Separation
Ethanol
CO2
Sulfur
Alcohol
Synthesis
Compressor
Mixed
Alcohols
Methanol & Water
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)
,R
h
Aldehydes
Alcohols
Ethanol
DME
ca
CH rbon
y
3O
H latio
Co
+C n
,R
O
h,
Ni
zeolites
MTO
MTG
Olefins
Gasoline
se
sis
(K2O, Al2O3, CaO)
H2
e
th
yn
NH3
N2 over Fe/FeO
)
os
u3
) 4 (B
Ox
CO ) 3P 3) 3
o( O Ph
HC o(C )(P
HC (CO
Rh
H2O
WGS
Purify
Methanol
U
ect
Co
ThO2 or ZrO 2
Cu/ZnO
Acetic Acid
Di r
Syngas
CO + H2
3
• Isosynthesis
i-C4
Isosynthesis
Ag
isobutylene
acidic ion exchange
• Oxosynthesis
Formaldehyde
hom
Co ologa
tion
• Olefins
MTBE
Fischer-Tropsch
d
l 2O
pe
/A
do
nO
li 3
/Z 3
ka
r 2O Cu l 2O
Al
/C ; A
O nO O/
Zn /Z Co
Cu uO/
C oS 2
M
• Mixed alcohols
Mixed
Alcohols
Fe, Co, Ru
• Ethanol
Olefins
Gasoline
Al2O3
Waxes
Diesel
• Fischer Tropsch Liquids
M100
M85
DMFC
22
Fischer‐Tropsch for Liquid Fuel Synthesis
• Set of reactions that “recreates” linear alkanes from syngas
2n  1H2  nCO  CnH2n2  nH2O
• Distribution of compounds well described by Anderson‐Schulz‐Flory distribution
Wn  n1     n1
2
where  represents
chain growth probability
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
“High quality diesel via the Fischer-Tropsch process – a review”
M.E. Dry, Journal of Chemical Technology & Biotechnology, v 77, pp 43-50
27
Fischer‐Tropsch Chain Growth & Kinetics
• General rate expressions
 For Co:
 For Fe:
rate  k
rate  k
pH2 pCO
1  b pCO 
2
pH2 pCO
pCO  a pH2O
• Water slows down rate for iron‐based catalysts
“High quality diesel via the Fischer‐Tropsch process – a review”
M.E. Dry, Journal of Chemical Technology & Biotechnology, v 77, pp 43‐50
28
Fischer‐Tropsch – More Than Alkanes
“High quality diesel via the Fischer‐Tropsch process – a review”
M.E. Dry, Journal of Chemical Technology & Biotechnology, v 77, pp 43‐50
29
Fischer‐Tropsch Process Considerations
http://www.eia.gov/todayinenergy/detail.cfm?id=15071
30
Production of Diesel
“High quality diesel via the Fischer‐Tropsch process – a review”
M.E. Dry, Journal of Chemical Technology & Biotechnology, v 77, pp 43‐50
31
Production of Gasoline, Diesel, & Chemicals
“High quality diesel via the Fischer‐Tropsch process – a review”
M.E. Dry, Journal of Chemical Technology & Biotechnology, v 77, pp 43‐50
32