Title: Coal Cowboy
Duration: 00:12:51
Link: http://coejaguar.engr.utexas.edu/mediasite
/Viewer/?peid=1ed1281cb87e405
d93db5389ceb34760
Conversion of Coal to Liquid
(CTL) Fuels
• Several very old processes… since
WWII
• Same general theme: increase H/C
ratio
• Can make a wide variety of
hydrocarbon products (e.g. synthetic
crude or synfuel)
• Two basic methods: direct and indirect
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Advantages of Coal To Liquid
(CTL) Fuels
• CTL Improves national and economic security
• Lessens dependence on foreign oil
• Uses domestic resources and produces more
jobs for Americans
• Provides environmental benefits
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- Cleaner fuels that reduce NOx and particulate emissions
- Enables use of higher efficiency engines
Is capable of capturing CO2 emissions
Provides geographic diversity as energy source
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Coal Liquefaction
• Very expensive
• Liquefaction attractive for transportation
fuel
• Indirect liquefaction commercially proven
(>50 yrs)
• Acid gas removal by amines (CO2, H2S)
• S removal by Claus Process
H2S + O2 = H2O + SO2
H2S + SO2 = S + H2O
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Direct Liquefaction of Coal
Attractive Because of
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Low transportation cost
Less chemical transformation required
Higher efficiency than high Btu gas production
Easy to store
Less water required for manufacture
However, processing slurries at high
temperature and pressure presents difficulties
with equipment life and solid/liquid separation
(still not commercial)
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SASOL in South Africa
Indirect Coal liquefaction is proven technology
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South Africa’s SASOL Co. developed a commercial
coal liquids industry (fuel plus chemicals)
The plant produces about 150,000 barrels daily at
its second plant
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Coal To Liquids in China
Concerned about increasing dependence on oil imports and its impact on
economic growth and national security, China is making a massive $6
billion investment in new coal liquefaction plants.
Planned $2 billion Shenhua facility will eventually produce 50,000 barrels
daily of diesel fuel and gasoline.
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Two Basic Approaches To Convert
Coal To A Liquid Fuel
1. Direct Liquefaction:
• Dissolves coal in a solvent at elevated
temperature and pressure
• Combined with hydrogen gas and a catalyst
2. Indirect Liquefaction:
• Involves first gasifying coal, followed by
reacting carbon monoxide and hydrogen
together
nCO + (2n+1)H2 = CnH2n+2 + nH2O
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Comparison of Processes
DIRECT
LIQUEFACTION
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Adds hydrogen to break down
the coal
Dissolves in a solvent followed
by hydrocracking
Operates at 450 C and 170 bars
Light products are distilled
Medium and heavy distillates
obtained from vacuum distillation
Liquid yields of 70% of the dry
weight of coal feed
Further upgrade is needed for
use as transportation fuels
INDIRECT
LIQUEFACTION
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Complete breakdown of coal
with steam and oxygen
Sulfur is removed from the
syngas
Syngas reacted over catalyst at
300 C and 20 bars
Produces a lighter suite of
products; high quality gasoline
and petrochemicals
Oxygenated chemicals
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Indirect Liquefaction
• Fischer-Tropsch Indirect Liquefaction Process
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Yields high quality transportation fuels plus other
products
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Schematic diagram of different coal liquefaction processes.
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CTL Costs
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Coal-based liquid fuel becomes viable when the per-barrel
price of oil is expected to exceed the $70-100 range for
20+ years
CTL has high front-end capital cost
- A 50,000 barrel-a-day plant would cost over $3 billion to construct
The product refinement process is three to four times more
expensive than refining an equivalent amount of oil
The cost of sequestering the captured CO2 would increase
the price of the end product by $10-20 a barrel.
The imposition of a carbon cap and trade policy would also
raise the cost of fuel produced with CTL technology
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CTL is Very Water-Intensive
• CTL requires ~7:1 water to fuel ratio
– ~7 gallons of water per gallon of fuel produced
– Water scarcity can be a limiting factor for CTL plant
permitting
• Conventional gasoline
– 1-2.5 gallons of water per gallon of fuel produced
• Irrigated Biofuels
– 1000 gallons of water per gallon of fuel
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Liquids Fuels Summary….
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Proven technologies
All processes require adding hydrogen
All processes remove sulfur and ash
Product include liquid, gas, and combustible
solid(char)
• Several long-standing commercial processes
(e.g., S. Africa - SASOL)
• So far no large-scale use without government
support
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Coal to Liquids Summary….
• Good promise because of very large coal
deposits in the world
• Numerous processes that can generate a
wide variety of products
• Environmental issues include some
hazardous wastes and byproducts
• Does not yet effectively compete with natural
gas or oil production … requires some form of
subsidy
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