Performance Improvements for Oxy-Coal Combustion Technology

Performance Improvements for Oxy-Coal Combustion Technology

John Wheeldon Technical Executive, Electric Power Research Institute Second Oxy-Combustion Conference Yeppoon, Queensland 12th to 15th September 2011

2 © 2011 Electric Power Research Institute, Inc. All rights reserved.

• Multiple societal benefits offered by electricity: elevates quality of life – Projected generation 25.0 x 109 MWh in 2020, 35.2 x 109 MWh in 2035

14%

18%

5%

21%

42%Nuclear

Renewables

Liquids

Natural gas

Coal

16% hydro 2% others • Without fossil fuels nuclear is the only mass generator.

• Can renewables supply all power required at acceptable cost?

• Diversity of supply essential to cost control.

• The challenge is how to strike a balance between protecting the environment and keeping electricity affordable.

Source: DOE-EIA International Energy Outlook 2010

World Power Generation: 2007 18.8 x 109 MWh

Worldwide Demand for Electricity Increasing


EPRI’s PRISM-MERGE Analysis

• Two portfolios: full- and limited-technologies reduce CO2 emissions to ~1905 levels by 2050, an 80% reduction.

• Levels match those of proposed US legislation, which also values CO2 at $25/ton.

• Limited portfolio: no CCS or plug-in electric vehicles (PEVs) and nuclear remains at 2007 levels. Heavily dependent on gas.

• Full portfolio: coal and gas with CCS, expansion of PEVs, and increased nuclear power.

• By 2050 full portfolio COE increases 80% relative to 2007 prices: limited portfolio COE increases 210%.

www.epri.com

US Data 2007 1905

Population, millions ~296 ~84.2 CO2, billion tons ~6000 ~1200 CO2, tons/capita 20.3 14.3

2050

~ 419 ~1200

2.9


Assumptions Used in Economic Calculations

• Unless stated otherwise – Capacity factor 85% – Coal price $1.71/GJ ($1.8/MBtu) and coal is sub-bituminous – Gas price $4.71/GJ ($5.0/MBtu) – Cost of CO2 emitted $26.5/tonne ($25/ton) – Cost of CO2 transmission and storage $10/tonne ($9.1/ton).

• Cost of electricity levelized over 30 years. • Plants located in Kenosha, Wisconsin and incorporate state-of-the art

environmental controls. • Ultra-supercritical (USC) pulverized coal steam conditions

290 bar/600 C/620 C (4200 psia/1110 F/1150 F). • Advanced ultra-supercritical (A-USC) pulverized coal steam conditions

345 bar/730 C/760 C (5000 psia/1350 F/1400 F). • 7FB (60 Hz) gas turbine firing temperature 1430 C (2600 F)


Points to Bear in Mind

• Results are preliminary. • Based on different studies adjusted to common basis: close to equal

footing but more work required. • Costs include projected realistic improvements: objective to show

potential of technologies. • It is a snap shot: technologies will evolve and costs will change. • New technologies and innovations will emerge. • Demonstration essential to prove technology and improve designs:

only the most cost-effective will be commercialized. • Development activities need to be focused on commercial offering by

2025 otherwise coal may miss the boat.

Source: Shell


CO2 Emissions from Current Power Plants

USC PC 2 x 7FB

Net output, MW 750 550 Capacity factor, % 85 85 TPC, $M 1900 440 TPC, $/kW 2540 800 Efficiency, % (HHV) 39.1 46.8 lb CO2/MWh emitted 1820 848 Cost of electricity, $/MWh Capital 42.6 11.9 Fixed O&M 5.9 0.8 Variable O&M 3.1 1.7 Fuel 15.7 36.5 CO2 S&T CO2 emitted 22.8 10.6 TOTAL 90.1 61.5 Dispatch cost, $/MWh 41.6 48.8

2 x 7FB

550 40

440 800 42.4 936

25.3 1.8 1.7 40.4

11.7 80.9 53.8


Making CO2 Emissions from USC Equivalent to those from NGCC

0

20

40

60

80

100

120

140

USC USC + PCC NGCC

Co

st, $

/MW

h

COE Dispatch

USC + PCC with 65% capture efficiency achieving CO2 emissions of 850 lb/MWh, same as NGCC

USC dispatch not affected


Effect of ∼98% Post-Combustion CO2 Capture

Capture cases have CO2 emissions of 46 lb/MWh NGCC is now coal equivalent

USC dispatch reduced slightly


When CO2 Capture Included, Higher Generating Efficiency Lowers Levelized Cost of Electricity

30

40

50

60

70

30 35 40 45 50

CO

E In

crea

se o

ver

Cas

e W

ith

ou

t CC

S, %

Generating Efficiency Without CCS, % (HHV)

Pittsburgh #8 PRB

35% - DOE target

Based on current post-combustion capture (PCC) technology with KS-1. Oxy-combustion projected to be similar.

Relative COE will fall as technologies improve.

Capture only. Transportation and storage costs also reduced by improved efficiency


Effect of Increasing Coal Plant Generating Efficiency

0

20

40

60

80

100

120

140

USC PCC USC OXY A-USC OXY NGCC PCC NGCC PCC 40% CF

Co

st, $

/MW

h

Cost of electricity Dispatch cost

Oxy cases based on 660-MW USC PC with projected enhancements to ASU. All CCS cases have CO2 emissions of 46 lb/MWh


Source of Power Losses from OXY USC

MW Air-blown USC

OXY USC

Gross output 697.8 700.1 Power block 19.0 16.7 ASU (1) 71.7 CPU 67.3 BOP 21.8 26.5 Losses 40.8 182.2 Net output 657.0 517.9

(1) Includes projected improvements

ASU + CPU = 139 MW, 20% of gross output


Two Approaches to Lowering Cost of CCS

Evolutionary approach: improved current technologies to be as cost-effective as possible.

Revolutionary approach: develop new technologies with potential to lower cost of CCS.


Effect of CO2 Purity and Capture Efficiency on Oxy-Combustor Performance

Base Case 1 Case 2

CO2 captured, % 90 90 98 CO2 purity, vol. % >99.99 98.7 >99.99 O2 content, vol. % <20 ppm 0.4 vol. % <20 ppm Net output, MW 509 510 501 TPC, $M 2360 2360 2380 Efficiency, % (HHV) 31.5 31.5 31.0 lb CO2/MWh emitted 230 230 46 COE, $/MWh 125.7 125.5 126.8

Dispatch cost, $/MWh 35.0 34.9 34.0

Case 3A Case 3B

100 90 84.4 84.4

4.1 vol. % 4.1 vol. % 505 511

2290 2280 31.2 31.6

0 229 122.3 122.4

33.4 34.9

Little difference in alternative CO2 purification approaches. High oxygen not acceptable for EOR applications and may not satisfy pipeline purity criteria.


Revolutionary Developments

• Chemical looping offers ∼20 percent reduction so COE would be around $100/MWh – For NGCC with PCC COE is around $75/MWh.

• Ion Transfer Membrane is a new technological approach that lowers cost of oxygen production.

• Extensive activity to develop improved technologies to capture CO2 from flue gas where partial pressure is only ∼0.12 bar (1.7 psi) – Technologies include membranes, solvents, and sorbents

– Could these be adapted to capture/separate oxygen from either atmospheric or pressurized air?

– For example, the metal-organic framework materials have very high specific surface and a very large number of structural variations.

• Replacing steam with supercritical CO2 as working fluid – Potentially adds 3% points to efficiency as well as lowering capital cost.


Evolutionary Improvements

• For low sulfur coal, remove FGD and capture acid gases in CPU. – Neutralize sulfuric, nitric, and hydrochloric acids in limestone digester

– Potential by-product sales but fickle market.

• Improve compressor designs to lower power losses – Designed to handle acid gases

– All power plant technologies benefit but coal more so as CO2/MWh higher.

• Do steam turbine drives offer advantages?

• Identify most cost-effective heat integration measures through rigorous modeling

– In USA, DOE is funding the Carbon Capture and Storage Simulation Initiative

– Studies must be realistic and comply with boiler design and operational requirements.


Evolutionary Improvements (continued)

• Complete materials development programs identifying most cost effective materials especially for water walls: also US DOE funded project.

• Pressurized operation. Lower capital costs, less energy consumed in recycle, recovery of latent heat at higher pressure.

• Cyclone burners displaced because of high NOX emissions but oxy-combustion mechanism and CPU can over come this – Coarser fuel using crushers not mills so lower maintenance and power

consumption.

• Oxy flue gas contains ∼4.5 wt % of oxygen delivered by ASU and is ∼25 vol.% of CPU vent stream – Using membrane to remove oxygen lowers ASU duty.


Evolutionary Improvements (continued)

• Eliminate pipeline by storing CO2 on own reservation – Can save ∼$5/MWh: may influence plant location.

• Limiting water usage becoming increasingly important – Oxy has inherent advantage over PCC: maximize it.

• Ideas may not be additive; achieving one may preclude another – Again good modeling capability may help establish the optimal benefits.

• Reduce recycle and increase oxygen content of combustion gas – CFB well suited to this: intrinsic heat dissipation through solids circulation – Boiler cost reduced ∼30% and recycle gas rate by ∼70%.

• Accommodate design changes to reduce load at when COE peaks – For 3 hours in July electricity in Texas selling for over $3000/MWh. By

switching off ASU (72 MW) and using LOX, revenues increase by $648k

– Or vent some CO2 and pay the levy.


Need for Demonstration

• Once the most economic design options are identified they need to be demonstrated to prove that they are operationally practical – Economic benefits could be negated by increased maintenance costs.

• Demonstration is an essential step to commercialization – Design and operational experience identifies cost reduction measures

• But it is expensive so how can cost be reduced? – Likely still need public private partnership but cost can be limited by

retrofitting an existing unit.

• EPRI has been investigating the cost of retrofitting post-combustion CO2 capture technology and is now preparing to do something similar for oxy combustion – Compared to new unit study identified capital savings of up to $3300/kW.


Closing Comments

• Reducing CO2 emissions is a formidable challenge and will come with a marked increase in the cost of electricity.

• To minimize the cost increase all power generation technologies will need to play a part including coal with CCS – Fuel diversity is essential to keep electricity prices competitive.

• Oxy-combustion appears to be a cost-competitive coal option, but in keeping with all technologies costs must be reduced – Technology innovations are needed – Reality-based modeling can help sort through the options.

• Technology needs to be commercially available around 2025 so it is essential that demonstration projects come into service in the next 5 to 8 years.


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Performance Improvements for Oxy-Coal Combustion Technology