Coal Technologies
Coal Technologies
Coal Technologies
Duration: 00:12:51
Link: http://coe-
jaguar.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
- 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
• 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) 5
SASOL in South Africa
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Comparison of Processes
DIRECT INDIRECT
LIQUEFACTION LIQUEFACTION
Adds hydrogen to break down Complete breakdown of coal
the coal with steam and oxygen
Dissolves in a solvent followed Sulfur is removed from the
by hydrocracking syngas
Operates at 450 C and 170 bars Syngas reacted over catalyst at
Light products are distilled 300 C and 20 bars
Medium and heavy distillates Produces a lighter suite of
obtained from vacuum distillation products; high quality gasoline
Liquid yields of 70% of the dry and petrochemicals
weight of coal feed Oxygenated chemicals
Further upgrade is needed for
use as transportation fuels
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Indirect Liquefaction
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CTL Costs
• 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….
• 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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