Coal Facilitation of Renewable Energy Alternatives

Larry BaxterBrigham Young University

Provo, UT 84602

Global Climate and Energy ProgramAdvanced Coal Workshop

March 15-16, 2005

Environmental Impacts

Coal Facilitates Renewable Energy

• Coal-biomass integrated systems (pcc, igcc, etc.) advantages relative to dedicated plants• Increased

• Availability• Efficiency• Reliability

• Decreased • Cost (capital, operating, and power production)• Risk (technical, financial, project)• Implementation time

Cofiring is a Cross Cutting Option

Combustion

Oxyfuel

Gasification

Liquefaction

Fuel CellsC

ofiri

ng

US CO2 Emissions

• Coal Facts and Figures:• 1 Billion Tons of Coal

Consumed

• Coal generates 54% of US Electricity

• ~ 1200 Coal-Fired Power Plants

15% of Coal Emissions

Transportation32%Electric

Other 4%

ElectricCoal 30%

Industrial21%

Other13%

Potential Biomass Contribution

400

450

500

550

600

650

1990 1995 2000 2005 2010

Car

bon

Em

issi

ons

(106 m

etri

c to

ns)

Year

Kyoto Protocol

Cofiring Scenario

Status Quo

Cofiring Reduces Net CO2 Emissions

1

1.5

2

2.5

3

3.5

4

0% 20% 40% 60% 80% 100%

40%

60%

80%

100%

120%

140%

Eff

icie

ncy

Mul

tiplie

r

Effective Reduction in CO2 Emissions

Po

wer

Pla

nt E

ffic

ienc

y

Thermodynamic Limit

FutureTechnology

100% Efficient

Cofiring Effectively Reduces Net CO2Emissions

1

1.04

1.08

1.12

0% 2.5% 5% 7.5% 10% 12.5%

38%

39%

40%

41%

42%

ExistingFacilities

Best Proven Technology

Eff

icie

ncy

Mul

tiplie

r

Effective Reduction in CO2 Emissions

Pow

er P

lant

Eff

icie

ncy

Biomass Energy Economics

Typical biomass Cost

(US$ per ton)

Cost of Electricity compared to feedstock prices,

with various conditions, incentives, or subsidies

Typical Cost of Energy from Conventional Co-firing Combustion

Acknowledgement: Graph provided by Antares Group Inc

PTC – proposed production tax credit

Incentive, e.g., Green Pricing Premium

Biomass Cofiring Best Uses Resource

0.4

0.5

0.6

0.7

0.8

0.9

1

Effic

ienc

y/C

oal E

ffici

ency

Cofired Units(demonstation and optimized)

Dedicated Unit Increasing Size

10 MWe 60 MWe

US Commercial Experience• Over 40 commercial demonstrations (>100 world wide)• Broad combination of fuel (residues, energy crops,

herbaceous, woody), boiler (pc, stoker, cyclone), and amounts (1-20%).

• Good documentation on fuel handling, storage, preparation.

• Modest information on efficiency, emissions, economics.

• Almost no information on fireside behaviors, SCR impacts, etc.

Fuel Properties2.0

1.5

1.0

0.5

0.0

H:C

Mol

ar R

atio

1.00.80.60.40.20.0

O:C Molar Ratio

SemianthraciteBituminous Coal

Subbituminous CoalLignite

Anthracite

Cellulose

Average BiomassWood

Grass

Lignin anthracite semianthracite bituminous coal subbituminous coal lignite peat biomass black liquor

average values

Peat

Black Liquor

Typical Fuel Properties

Coal & Biomass Elemental Compositions Differ

Black Thunder Pittsburgh #8

Imperial Wheat Straw Red Oak Wood Chips

C

H

N

S

Cl

Ash

O (diff)

COAL:

BIOMASS:

Pittsburgh #8

7.8% Ash

Imperial Wheat Straw

15.4% Ash

Red Oak

1.3% Ash

Black Thunder

7.2% Ash

SiO2

Al2O3

TiO2

Fe2O3

CaO

MgO

Na2O

P2O5

K2O

SO3

Cl

COAL:

BIOMASS:

Coal & Biomass Ash Compositions Differ

Commercial Fuel Mix Varies

Woodland Fuel Mix, Spring-Summer 1993

0%

20%

40%

60%

80%

100%

23-A

pr

30-A

pr

7-M

ay

14-M

ay

21-M

ay

28-M

ay

4-Ju

n

11-J

un

18-J

un

25-J

un

2-Ju

l

9-Ju

l

16-J

ul

23-J

ul

30-J

ul

6-A

ug

13-A

ug

20-A

ug

27-A

ug

EucalyptusAlmondCoffeeMich CalPit MixPitsSawdustShellsPruningsPine DustWhite PineWEYCOUWW

Major Technical Cofiring Issues• Fireside Issues

• Pollutant Formation• Carbon Conversion• Ash Management• Corrosion• SCR and other

downstream impacts

• Balance of Process Issues• Fuel Supply and

Storage• Fuel Preparation• Ash Utilization

Lab and field work indicate there are no irresolvable issues, but there are poor

combinations of fuel, boiler, and operation.

NOx Behavior Complex

200

150

100

50

0

Axia

l dist

ance

(cm

)

-20 0 20Radial distance (cm)

500

450

450

450 450

450

400

400

400

400

400 400

400

350 350 350

350

350

350

3

50

350

300

300

250 2

00

200

150

150

100 100

50

50

200

150

100

50

0

Axia

l dist

ance

(cm

)

-20 0 20Radial distance (cm)

450 450

450

400 400

400

400

400

400

400 400 400

400

400

350

350

300 250 250 200 200

150 150 100

100 50 50

200

150

100

50

0

-30 -20 -10 0 10 20 30

600

6

00

600 600

550

550 550

550 500

500

450

450

400

400

400 350

350

350

300

300

250 250

200

150

100 100 100 50 50

Straw (φ = 0.6) Coal (φ = 0.9) 70:30 Straw:Coal (φ = 0.9

NO

NH3

Cofiring Deposition

Deposits Dissimilar to Fuel

SiO2 Al2O3 TiO2 Fe2O3 CaO MgO Na2O K2O P2O5 SO30

10

20

30

40

50

60

Mas

s P

erce

nt [-

]

Fuel

Ceiling/Corner Deposit

Composition Maps Support Corrosion Hypothesis

Cl S Fe

100% Imperial Wheat Straw

85% E. Kentucky 15% Wheat Straw

Fuel Properties Predict Corrosion

Increasing Time

Vapor depositionVapor deposition flux [g/m2/h]

Oxygen Isosurfaces

Basic Compounds Poison CatalystsCatalyst Activity vs. Na Poison Amount

0.000.100.200.300.400.500.600.700.800.901.00

0 0.5 1 1.5 2 2.5 3

Poison Ratio (Na:V)

Act

ivity

(k/k

0)

BYU wetBYU dryChen et al.

20

18

16

14

12

10

8

6

K, c

m

3/g

*s

590580570560550540530520

Temp, K

Light sulfatedA = 27045 +/- 7580Ea = 34556 +/- 1270

FreshA = 17736 +/- 21500Ea = 34640 +/- 5720

24-hour sulfatedA = 28527 +/- 18400Ea = 34737 +/- 2920

24-hour sulfatedLightly sulfatedFreshfit 24-hour sulfatedfit lightly sulfatedfit freshUC_24HSKUC lightly sulfatedUC_KF

1.0

0.9

0.8

0.7

0.6

0.5

0.4

NO

Con

vers

ion

340320300280260240

Temperature (OC)

M1 Catalyst Fresh Fresh Fit Exposed 2063 hr Exposed 2063 hr Fit Exposed 3800 hr Exposed 3800 hr Fit

Conclusions• Major technical issues include fuel handling, storage,

and preparation; NOx formation; deposition; corrosion; carbon conversion; striated flows; effects on ash; impacts on SCR and other downstream processes.

• Importance of these issues depends strongly on fuel, operating conditions, and boiler design.

• Proper choices of fuels (coal and biomass) and operating conditions can minimize or eliminate most impacts for most fuels.

• Ample short-term demonstrations illustrate fuel handling feasibility. Paucity of fireside and long-term data.

• Cofiring residuals is a no-regrets process in almost all implementations.

How does this talk grow corn?

Research Issues• Fundamentals

• Behavior of inorganics• Materials• Impurities/Emissions (N, S, Hg, etc.)

• Process Issues• Pressure• Matrix Effects

• Radical Changes• Processes that have stable, condensed-phase

effluents under conditions accessible on earth.

Acknowledgements• Financial support provided by the DOE/EE, EPRI,

NREL, BYU, a dozen individual companies.• Work performed by research group including four other

faculty members, two post docs, ten graduate students, 30 undergraduate students.