pre-combustion technology for coal-fired power plants
TRANSCRIPT
Pre-Combustion Technology for
Coal-fired Power Plants
Thomas F. EdgarUniversity of Texas-Austin
IEAGHG International CCSSummer School
July, 2014
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Introduction
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CO2 Absorption/Stripping of Power Plant Flue Gas
Flue Gas
With 90% CO2
RemovalS
tripp
er
Flue
Gas InRich
Solvent
CO2 for
Transport
& Storage
LP Steam
Ab
sorb
erLean
Solvent
Use 30% of
power plant output
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The Basic Chemistry of Gasification
CxHy + H2O + O2 → aH2 + xCO
For example:
4 CH + 2 H2O + O2 4 H2 + 4 CO (Hydrocarbon) (Water) (Oxygen) (Hydrogen) (Carbon Monoxide)
Water Shift Reaction: CO + H2O => CO2 + H2
4Source: GE
Combustion vs. Gasification
Combustion
• SO2 is scrubbed out of stack gas – reacted with limestone to form gypsum
• NOx controlled with low NOx
burners and selective catalytic reduction (SCR)
• Fly ash removed via ESP or bag filters
• Hg can be removed by contacting flue gas with activated carbon
Gasification
• H2S removed from syngas and converted to solid sulfur or sulfuric acid (Claus Process)
• NH3 washes out of gas with water, thermal NOx controlled by diluent injection, optional SCR for deeper NOx removal
• Ash converted to inert glassy slag
• >90% of Hg removed by passing high pressure syngas thru activated carbon bed
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FutureGen Plant Schematic
Syngas H2
http://www.psenterprise.com/consulting/r_and_d/images/vpdm_futuregen.png 7
Coal Gasification Emissions
• Sulfur in coal reduced to H2S– Elemental sulfur is recovered – salable product
– 99.4% removal efficiencies, no sludge
• Nitrogen in fuel is converted to N2, NH3, and small amounts of HCN
• Metals either contained in glasslike slag or water stream – 10x fewer air emissions
• 15-20% less CO2 due to increased efficiencies
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IGCC vs. Conventional Pulverized
Coal Combustion (PCC)
• 20-50% lower water usage, compared to PCC
• CO2 under pressure takes less energy to remove than from PCC flue gas (Gas volume is <1% of flue gas from same MW size PCC)
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IGCC with CO2 Capture
Fuel is gasified and a synthesis gas is produced. The gas primarily consists of CO, H2, and H2O.
Source: VATTENFALL
110
IGCC with CO2 Capture
2 The synthesis gas is cleaned from residuals.
Source: VATTENFALL11
IGCC with CO2 Capture
3 The CO and H2O are converted in a shift reactor to CO2 and H2. Source: VATTENFALL
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IGCC with CO2 Capture
4 The gas is cleaned from sulfur after the shift reactor. Source: VATTENFALL
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IGCC with CO2 Capture
5Carbon dioxide is separated from the synthesis gas in an absorption process. The carbon dioxide is transported to a storage site. The remaining gas (mainly hydrogen) is combusted.
Source: VATTENFALL14
1. TYPE OF BED
2. OPERATING PRESSURE
3. SLAGGING, NON-SLAGGING
LURGI (FIXED BED, HIGH P, NON-SLAGGING)
KOPPERS-TOTZEK (ENTRAINED BED, LOW P, SLAGGING)
WELLMAN-GALUSHA (FIXED, LOW P, NON-SLAGGING)
WINKLER (FLUIDIZED, LOW P, NON-SLAGGING)
1st Generation Gasifiers
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Kellog Brown
and Root (KBR) 17
Current Gasifier Types
Manufacturer Gasifier type Application
ConocoPhillips Coal- water slurry feed,
Oxygen blown, refractory
lined gasifier
wide range of coal
General Electric Energy
(GE)
Coal-water slurry feed, O2
blown, refractory lined
gasifier
bituminous coal, pet-
coke or blend of pet coke
with low rank coal
Kellog Brown and Root
(KBR)
dry feed, air blown
transport reactor
low rank coal
Mitsubishi Heavy
Industry (MHI)
dry feed, air blown low rank coal
Shell dry feed, coal is crushed,
dried and fed into gasifier,
oxygen blown, waterwall
in gasifier
wide variety of feedstock
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IGCC Plants in the US
The Tampa Electric IGCC Project
Mulberry, Florida, 1996
Using: GE Energy Gasification
Output: 250 MWe
The Wabash River IGCC Project
West Terre Haute, Indiana, 1995
Using: The ConocoPhillips E-Gas
Gasification process
Output: 262 MWe
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Implementing New Technologies
• Advanced Gasification– Transport Gasifier in oxygen-blown mode
• Oxygen Separation– Advanced ion transport membranes
• Hydrogen Production– Membrane separation from CO2
• Gas Cleanup– Remove sulfur, mercury, chlorides, ammonia
• Hydrogen Turbines
• Fuel Cells
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Theoretical Limit
Ceramic Vanes
and Blades
Ceramic Vanes
Precooled Air
Conventional
Cooling
IGCC station performance
Efficient Pollutant Removal
Pre-Combustion
PM, Hg, Su
Pulverized coal
• Pollutants are removed after the coal is
burned
• The gas volume treated is 300 times the
gas volume of an IGCC plant
• Combustion produces large quantities
of waste & consumes more water than
IGCC
IGCC
• Gasification cleans the syngas before
combustion
• High pressure & low volume provide
favorable economics for pollutant
removal
• IGCC offers increased fuel diversity,
reduced emissions, and increased
siting & permitting flexibility
Boiler
SCRESP/
FF
Carbon
Injection
FF
FGD
WESP
CO2
Source: GE 22
IGCC Concluding Remarks
• Gasification is a well-known process• The CO2 is separated and the decarbonized gaseous fuel is used for
the gas turbine
Advantages• Proven CO2 separation technology• Co-production of hydrogen for power and/or other uses
Disadvantages• IGCC is unfamiliar technology for electrical utilities• IGCC without CO2 capture has generally higher costs than pulverized
coal combustion but could change in the future for new plants/new technology
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