Coal Gasification (for Power Generation_comparision Technology)

Coal Gasification 101

Dr. Jeff [email protected]

2© 2005 Electric Power Research Institute, Inc. All rights reserved.

Outline

• What is coal?• What is coal gasification?• What can you do with it?• Gasification-based power plants compared to other fossil

fuel power generation options• A few words on CO2 capture


U.S. Forecasts Largest Coal Generation Capacity Installation in 40 Years

0123456789

1011121314151617181920

1940 1945 1950 1955 1960 1965 1970 1975 1980 1985 1990 1995 2000 2005 2010 2015 2020 2025Source: U.S. Department of Energy NETL & Annual Energy Outlook 2005.

Cap

acity

Add

ed (G

Ws) Capacity Addition

Levels Not Seen in 40 Years

Industry Growth Trend Not Seen in

50 Years

20 YearMarket Trough

U.S. Coal Capacity Additions, 1940 U.S. Coal Capacity Additions, 1940 –– 20252025


Carbon

Ash (rock)

Sulfur

Nitrogen

Hydrogen

Mercury

Water


U.S. Coal Basins


Typical U.S. Coal Analysis(Coal Properties Differ Markedly)

Pittsburgh #8 Illinois #6 Wyoming ND Lignite

Ultimate AnalysisMoisture 5.2 12.2 30.24 26.80Carbon 73.8 61.0 48.18 45.82Hydrogen 4.9 4.25 3.31 3.11Nitrogen 1.4 1.25 0.70 0.70Chlorine 0.07 0.07 0.01 N/ASulfur 2.13 3.28 0.37 0.69Oxygen 5.4 11.0 11.87 14.68Ash 7.1 6.95 5.32 8.20

Higher Heating Value-as Received(Btu/lb) 13,260 10,982 8,340 7,810


What happens when coal burns?

• Carbon => CO2 (carbon dioxide)• Ash => flyash• Sulfur => SO2, SO3 (SOx)• Nitrogen => N2 and NOx• Hydrogen => H2O• Mercury => Hg, HgCl2• Water => water vapor (H2O)


What is gasification?

• Similar to combustion (burning) but with less than half the amount of oxygen needed to fully burn the coal

• Combustion: excess air• Gasification: excess fuel (by a lot!!)


Combustion & Gasification Products






Combustion vs Gasification

• H2S & COS are easily removed from syngas and converted to solid sulfur or sulfuric acid

• NH3 washes out of gas with water, thermal NOx controlled by diluent injection in GT

• Ash is converted to glassy slag which is inert and usable

• >90% of Hg removed by passing high pressure syngas thru activated carbon bed

• SO2 & SO3 is scrubbed out of stack gas – reacted with lime to form gypsum

• NOx controlled with low NOx burners and catalytic conversion (SCR)

• Large volume of flyash & sludge

• Hg can be removed by contacting flue gas with activated carbon



Dakota Gasification Gasifier

• The dry ash (non-slagging) Lurgi gasifier is used in Dakota Gasification’s lignite-to-natural gas plant

• The Lurgi process was developed in the 1930s, and was the only “mature” gasification process available when the Dakota project was initiated (circa 1980)

• The Lurgi process operates at relatively low temperature and has some undesirable characteristics– Cannot handle coal fines, produces tars & phenols as

well as syngas, bottom ash instead of slag• Since 1980 several “second generation” gasification

processes have been developed which avoid some of the Lurgi process’ undesirable characteristics


The 3 Major Types of Gasification Processes

1. Moving-Bed Gasifier(e.g., Lurgi)

2. Fluidized-Bed Gasifier (e.g., KBR/Southern)

3. Entrained-Flow Gasifier (e.g., GE Energy, ConocoPhillips, Shell, Siemens)


What can you do with coal gasification?

• Produce Electricity– In a Gas Turbine-based Combined Cycle power plant– Emissions approaching that of a natural gas fired power plant

• Make Fuels– Sasol has been making gasoline from coal since the 1950s in

Republic of South Africa – Dakota Gasification has been making “synthetic’ natural gas from

lignite since the 1980s• Make Chemicals

– Eastman Chemicals has been doing this since 1980s• Make Fertilizer

– Coffeyville Resources in Kansas makes ammonia-based fertilizer from petroleum coke



Steam Cycles vs “Combined” Cycles

• Steam Cycles have – a boiler – a steam turbine

• Referred to as “Rankine” cycle, fossil boiler, “fossil steam” plant, “conventional coal” plant

• Combined Cycles (the “CC” in IGCC) have – a Gas Turbine – a “heat recovery steam generator” (HRSG)– a steam turbine


Conventional Coal Plant

100 MW

14 MW

86 MW

41 MW

45 MW

41 % Efficiency (LHV basis)


Gas Turbine

Photo source: Siemens


Gas Turbine “simple cycle”

100 MW

38 MW

62 MW

38% Efficiency (LHV basis)


Combined Cycle

100 MW

Fuel

38 MW19 MW

62 MW

22 MW

21 MW to condenser

40 MW

19 + 38 = 57 MW 57% Efficiency! (LHV basis)


15MW 79MW

30MW49MW

47MW21MW

9MW

Net Coal to Power: 30 + 21 – 9 = 42% (LHV basis)

17MW

100MW

IGCC schematic from US DOE26 MW


Comparison to other fossil fuel power generation options

• Emissions• Greenhouse gases• Cost of Electricity


Emissions Comparison – State-of-the-Art Coal Combustion, IGCC, and NGCC Values represent technology capability, not permit levels

0.0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

NGCC+SCR

IGCC+S

CR

IGCC

SCPC+SCR

SCPC+SCR

lb/M

W-h

r

NOxSO2PM

PRB

Bituminous


Emissions Comparison with Older Coal Plants and Federal Standards

250 US plants exceeded these levels in 2004

0

2

4

6

8

10

12

14

16

18

NGCC+SCR

IGCC+S

CR

IGCC

SCPC+SCR

SCPC+SCR

2006

NSPS

PC-old

lb/M

W-h

r

NOxSO2PM


Solid Waste Comparison(Based on nominal 500 MW plant size)

0

50

100

150

200

250

300

350

400

450

PC-Sub

PC-USC

CFB IGCC PC-Sub

PC-USC

CFB IGCC PC-Sub

PC-USC

CFB IGCC PC-Sub

PC-USC

CFB IGCC

Solid

Was

te, l

b/M

Wh

SulfurSpent SorbentAsh/Slag

Pittsburgh #8 Illinois #6 TX LigniteWyoming PRB


Makeup Water Comparison

0

1

2

3

4

5

6

7

8

9

10

PC CFB IGCC

Mak

eup

Wat

er, g

pm/M

W


Atmospheric CO2 Trends

Source: CSIRO Atmospheric Research,

www.cmar.csiro.au

Peak of last Ice Age - 20,000 yrs ago


CO2 Emissions without CO2 Capture

0

200

400

600

800

1,000

1,200

PC-Sub PC-Super PC-Ultra NGCC IGCC PC-old

CO

2 E

mis

sion

s (k

g/M

W-h

r)


IGCC with CO2 Removal and OptionalHydrogen Co-Production

O2 N2

Air

BFW

BFWSteam

Steam Turbine

HRSG

CoalPrep

Gas CoolingGasificationC + H2O = CO + H2

Sulfur and CO2

Removal

Air Separation

Unit

GasTurbine

Air

Hydrogen

CO2 to use or sequestrationSulfur

ShiftCO+ H2O = CO2 + H2


FutureGen Project

• A 275 MW (nominal) IGCC with CO2 capture and H2export– Coal gasification followed by water-gas shift reaction– 90% of CO2 will be removed from syngas,

compressed to circa 2000 psia and injected into deep geologic formations for sequestration

– Remaining syngas will be primarily H2• Small slipstream will upgraded to high purity H2 and sold

“over the fence”• Balance will be fired in an advanced combined cycle

• Site selection RFP issued in March 2006• Operation targeted to begin in 2012


Pulverized Coal (PC) with CO2 Removal

CO2 to useor SequestrationFresh Water

PCBoiler SCR

SteamTurbine

CO2Removal

MEA

Coal Flue Gasto StackESP FGDAir

Fly Ash Gypsum/Waste


CO2 Capture Comparison

Exhaust or Syngas

Pressure

CO2 Volumetric Concentration

CO2 Partial Pressure

Natural Gas Combined Cycle Exhaust

14.7 psia 4% 0.6 psia

Supercritical Coal Boiler Exhaust

14.7 psia 13% 1.9 psia

IGCC Syngas 825 psia 40% 330 psia


Impact of CO2 CaptureResults from recent IEA & US DOE studies on bituminous coal adjusted to standard EPRI economic inputs, $2/MMBtu coal, 85% capacity factor, 2005 USD

49.6 52.045.7 46.1

11.6

16.321.3 19.0

0

10

20

30

40

50

60

70

80

GE IGCC Shell IGCC SCPC-IEA SCPC-DOE

30-y

ear L

evel

ized

Cos

t of E

lect

ricity

, $/M

Whr

Delta for CaptureWithout Capture

Range of Uncertainty

Range of Uncertainty

(Excludes cost of emission

allowances and CO2 pipeline to

sequestration site)

The End

Documents

Coal Gasification (for Power Generation_comparision Technology)