Developments in oxy-combustion technologies

Toby Lockwood

High temperature materials in pulverised coal technology

Kyle Nicol

24th

April 2014, 2pm AEST (Melbourne, Australia)

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Developments in oxyfuel

combustion of coal

Toby Lockwood

IEA Clean Coal Centre

Oxyfuel concept

• Eliminate N2 from combustion for purer stream of CO

2

(>90% dry)

• Combustion air replaced with a mixture of pure oxygen

and recycle flue gases

Conventional plant + ASU

+ CPU + flue gas recycle

Advantages

• Based on combining established technologies

• Straightforward retrofit

• Minimal interference with steam cycle

• High capture rates possible (98-99%)

• Low water use

• Reduced boiler size possible

• Potentially easier flue gas scrubbing

But:

• Energy penalty is significant (7-10 %pts) due to air

separation and CO2 purification/compression

• Capital cost

• Corrosion and air ingress issues

• Altered combustion properties

Flue gas recycle

Possible recycle locations:

• Hot recycle before FGD: High SOx = corrosion risk

• Recycle post FGD: Thermal penalty

• Dry recycle post FGC: Even bigger penalty, but needed for

coal drying/transport

• Usually post FGD for 2˚ stream, post FGC for 1˚

• Dry deSOx is another solution for hot recycle

Combustion

CO2 has very different properties to N

2:

• 1.7 x density: altered mass flows and heating rate

• 1.6 x specific heat: lower flame temperature, ignition

delay

• Active in IR spectrum: higher thermal radiation

• Reduced diffusivity of O2 and volatiles

• Gasification reactions

Oxyfuel flames are

less stable and can

detach from burner.

Flue gas RR is first

recourse to stabilise

combustion.

Air

Oxyfuel

Combustion: Recycle ratio

• Reduce flue gas dilution to match air flame temperature

• ~27-29% oxygen needed for wet recycle

• Also reduces ignition delay and stabilises flame

Combustion: Oxyfuel burners

Oxyfuel tailored burners needed for optimum

performance:

• Increase recirculation of hot exhaust with swirl or quarl

geometry

• Account for altered density/volumes on aerodynamics

• Pure oxygen injection

Alstom RWTH Aachen

Combustion fundamentals

Gasification reactions:

CO2 + C → 2CO

H2O + C → CO + H

2

Clarifying effect on each combustion stage helps improve

CFD models:

• Coal drying: largely unaffected

• Devolatilisation: similar yield, slightly longer duration

• Ignition: Slightly delayed even at same flame temperature

• Char combustion: Gasification only significant at high

temperature and low oxygen. But highly endothermic, so

total char consumption is little affected.

Pollutants

• Up to 75% less NOx due to NO reburning and lack of N2

• More SO2 retained in ash

• Species in recycled flue gas are concentrated up to 3-4

times (equivalent to combustion without nitrogen)

• No stack emissions: Mainly an issue for CO2 purification

and corrosion

Low temperature corrosion

Dew point raised by around 30˚C due to high H2O and SO

3.

Serious issue for oxyfuel pilots:

• Preheater, economiser, FGD, FGC and CPU at risk

• Avoid stagnation and leaks: Use purges and welded joints

• Stainless steels or coatings employed

• FGC can be Ni alloy

• Parts of CPU are plastic

Ciuden Schwarze Pumpe

High temperature corrosion

Several mechanisms for worse superheater corrosion:

• High CO2: carburisation (brittle metal carbides)

• High SOx: sulphidation

• High H2O: volatises Cr, aids diffusion through scale

• Hot corrosion: SOx forms molten salts with Na/K

• Many studies show higher corrosion rates

but no consensus

• Fundamental chemistry is unchanged

• Peak hot corrosion at higher temperature

• Water vapour has a significant influence

Oxygen production: Cryogenic ASU

Cryogenic air separation is an established technology

for >4000 tpd O2:

• Air is compressed and cooled to dew point

• 500 MW plant needs ~1000 tpd = 2 x largest units built

• Low purity O2 is optimum (~97%)

• Energy intensive: 10-15% of gross output, but potential

for further optimisation

• Flexibility limitations

Air Pre-

cooling

TSA

Drying

Cooled

<-170˚C ~5 bar Distillation

O2 N2

Cryogenic ASU: Optimisation

• Significant efficiency gains

made for oxyfuel ASU

• More complex process

cycles such as triple column

distillation

• Further optimisation forecast

for next few years

Liquid oxygen storage

Storing oxygen can allow operating cost saving:

• Off-peak: Use cheaper power to produce O2

• Peak: Use stored O2 and turn down ASU

• Capital intensive so need volatile market

• Can also improve ASU ramping/turndown

Ion transport membranes

Possibility for lower energy oxygen production, pre-

commercialisation:

• Based on perovskite ceramic membranes

• Air feed is 800-900˚C and >13 bar

• 5 tpd pilot from Air Products, 100 tpd pilot this year

• Modular design: Stacks of flat wafers

• Requires integration with gas turbines to realise

efficiency potential (1-2% pts)

Flue gas purification: CPU

No standard for CO2 purity. Pilot CPU have aimed for very

high purity CO2 (>99%):

• High level of dehydration (ppm levels) required to prevent

pipeline corrosion: Temperature swing adsorption used

• Very low O2 required for EOR

• O2, N

2, Ar add to compression energy

• Hg damages Al heat exchangers: Sorbent guard bed

• SOx/NOx, pipeline and compressor corrosion: Several

polishing technologies demonstrated

FG compression,

cooling + flash or

distillation

FGC Drying Cold Box:

Liquefaction,

distillation

CO2 Flue gas ~30 bar

Flue gas purification: CPU

Callide CPU

2NO + O2 → 2NO

2

2NO2 + H

2O → HNO

2 + HNO

3

‘Autorefrigeration’ by

product CO2

NaOH

SOx/NOx removal

Low volume/high pressure FG aids SOx/NOx removal. PPM

levels of SOx and NOx achieved by various means:

• Air Products: Sour compression. Exploits the catalysis of

SO2 oxidation by NO at high pressure:

NO2 + SO

2 → NO + SO

3

• Air Liquide: low pressure scrubs with NaOH or Na2CO

3

and distillation of NO2

• Linde: Cold scrub with ammonia water or NaOH at 15 bar

(LICONOX). Conversion of NOx to fertilisers or nitrogen

gas possible.

• Praxair: Activated carbon

Vent gas purification

Waste gases from distillation contain some CO2 and O

2

• Use polymer membranes or pressure swing adsorption

• Recover O2 for boiler and reduce ASU power

• Increase CO2 capture rate from 90 to 98%, reduce

capture cost per ton

Air Liquide: Membrane

Praxair: VPSA

Thermal integration of plant

Energy savings possible from thermal integration of boiler,

steam cycle, ASU, and CPU.

• ASU compressor heat for feedwater heating: 7 to 9% of

ASU energy recovered, ~0.4%pts in plant efficiency

• Lesser gains from CPU compressor heat

• Steam used for ASU/CPU sorbent regeneration

Coil wound HX for

ASU heat recovery

Oxyfuel pilot projects

ANL/BHP

ANL/EERC IFRF

IHI

Canmet

B&W/AL

IVD-Stuttgart

PowerGen

Jupiter

B&W

Enel

RWE-npower

Oxyxoal UK

Alstom

VattenfallCiuden CFB

Ciuden PC

Callide

0.1

1

10

100

1980 1985 1990 1995 2000 2005 2010 2015

Gro

ss o

utp

ut

(MW

e o

r M

Wt/

3)

Combustion pilot

Pilot with CPU

Schwarze Pumpe (2008)

Vattenfall 30 MWt plant in Germany was first full-chain pilot.

• Lignite-fired, 9 t/hr of CO2 produced

• Multiple burner tests, corrosion tests, plant control…

• Brief storage trial (road transport)

Es.CO2, Ciuden (2011)

30 MWt oxyCFB (Foster Wheeler) and 20 MWt oxyPC units.

• Air Liquide CPU: Full flue gas dehydration, 6% to pure CO2

• Up to 40% oxygen used in CFB

• Testing anth/petcoke blends, CFB deSOx, CPU/boiler

integration…

Air Oxy

Callide (2012)

100 MWt full-chain oxyfuel PC retrofit (IHI) from consortium

of utilities, manufacturers, and mining company.

• CPU takes ~15% of flue gas: 75 tpd liquid CO2

• Local Callide bituminous coal, no FGD

• Generates electricity to grid

Demonstration projects: Futuregen 2.0

• 167 MWe gross retrofit from consortium of energy and

mining companies (plant design: B&W and Air Liquide).

• FEED completed Dec 2013, start construction this year?

• $1 bn of CAPEX from DOE. Illinois meeting O&M deficit

• 98% capture yields 1.1 Mt CO2/yr

• 21.5% (HHV) design efficiency

• FGD by circulating dry scrubber

• 50 km CO2 pipeline to onshore saline aquifer

Other demonstrations

• Compostilla, Spain: 300 MW gross SC oxyCFB project,

FEED completed, seeking funding

• Young Dong, Korea: 100 MW retrofit, FEED completed,

government funding withdrawn

• WhiteRose, UK: 450 MW gross USC plant. FEED contract

awarded Oct 2013, finalist for £1 bn UK government

funding

• ENEL, Italy: feasibility study for 320 MW net pressurised

plant

China:

• 35 MWt HUST pilot, 200 MW FEED underway

• Several other large demos in early stages of planning

Pressurised oxyfuel

At high pressures:

• Latent heat of water vapour is recovered at temperature

usable for feedwater preheating

• Reduced air ingress

• Reduced fan power

• Reduces wet compression in CPU (shifted upstream)

ENEL operate a 5 MWt pilot, 50 MWt pilot and demo planned:

• Coal slurry

• Flameless combustion

• Low emissions

• Ash runs off as slag

Costs

• ASU is largest additional plant cost (14-20% of total

capex)

• Estimates of postcombustion and oxyfuel costs are

similar (~80% increase in COE)

• Oxyfuel potentially lower cost retrofit

Summary

• Oxyfuel ready for demonstration

• Main boiler issue is corrosion: May restrict fuel use or

recycle path

• Cryo ASU has potential for further optimisation and

integration with steam cycle

• CPU offers less potential for energy gains but lower

cost flue gas cleaning possible

• Minimum energy penalty of 6-7%pts through plant

integration and other optimisation

• Capital cost estimates equivalent to post-combustion

• Next generation systems could include pressurised

combustion and O2 production by membranes

High temperature steels and nickel

alloys in pulverised coal technology

Kyle Nicol

Introduction

Most of coal-fired power plant are pulverised type

▲ Electrical efficiency = ▼ coal use & ▼ environmental

impact & can favour plant economics

▲ steam temperature = ▲ electrical efficiency

Steam temperature limited by materials

Commercial Steels

1880s - Ferritic steels: Proven and peaked at <565ºC

1960s - Martensitic steels:

9% chromium in <600ºC superheat

11-12% chromium in <620ºC reheat

1990s - Austenitic steels: Excellent up to 665ºC, but

limited to thin-section

Cyclic Operation

Cyclic operation results in cracks

Methods can accurately predict component lifetime

Preventative action can be economically favourable

Commercial boiler steels

Boiler component and steam

temperature

Materials Fireside

corrosion

resistance

Steamside

oxidation

resistance

Creep

resistance

Fatigue

resistance

PWHT Comments

Tube: Waterwall <480°C Ferritic: T11, T12 Low Very Low Very Low Very Low No None

Tube: Waterwall <565°C Ferritic: T22, T23, T24 Moderate Low Low Low No SCC of T24

Tube: Superheater and

reheater 550-575°C

Ferritic: T22, T23, T24

Moderate Moderate Low -

Moderate

Low -

Moderate

No SCC of T24

Martensitic: T91 Yes Type IV

Tube: Superheater and

reheater <600°C

Martensitic: T92, E911,

T122, NF12, SAVE12

High High Very High

(superheat

) High

(reheat)

Very High

(superheat)

High

(reheat)

Yes Type IV

Austenitic: 347HFG, 310 Yes DMW

Tube: Reheater <620°C Austenitic: Super 304H,

Esshete 1250, 17-14

CuMo, Sanicro 28,

NF709, HR3C, SAVE 25

Very High Very High Moderate Moderate Yes DMW

Pipe: Headers <580°C and <22

MPa

Martensitic: P91 Moderate Moderate High Moderate Yes Type IV

Pipe: Header <600°C and 22-25

MPa

Martensitic: P92, E911,

P122

High High Very High High Yes Type IV

Pipe: Headers <620°C and <10

MPa

Martensitic: NF12,

SAVE12

Very High Very High High Moderate Yes Type IV

Pipe: Superheat <600°C and

22-25 MPa

Martensitic: P92, E911,

P122

None High Very High Very High Yes Type IV

Pipe: Reheat <620°C and <10

MPa

Martensitic: NF12,

SAVE12

None Very High Moderate Moderate Yes Type IV

Furnace floors, upper furnace

walls, convection pass

enclosures and economisers

Ferritic: High carbon

grades, chromoly steels

Moderate None Low Low Yes None

Baffles, supports, hanger

fittings, oil burner impellers,

soot-blower clamps and

hangers

Austenitic: 25Cr-20Ni,

25Cr-12Ni

High None Moderate Moderate Yes None

Commercial turbine steels

Steam turbine component Materials

Steamside

oxidation

resistance

Creep

resistance

Fatigue

resistance Comments

HP/IP Rotor <620°C Martensitic: 9-12CrMoVNbN, 9-12CrWCo,

E, FB2, TR1150, TOS110 High High High

Single material to

avoid DMW.

HP/IP Rotor <593°C Martensitic: TR1100, TOS107 Moderate Moderate Moderate

HP/IP Rotor <566°C

Ferritic: 1CrMoV

Martensitic:, 11CrMoVTaN (TOS101),

12CrMoVW, 12CrMoVNbN,

26NiCrMoV11.5

Low Low Low

LP Rotor <600°C Martensitic: 3.5NiCrMoV Moderate Moderate Moderate

LP Rotor <566°C Martensitic: NiCrMoV Low Low Low

Blades <620°C Martensitic: 9-12CrWCo High High High Coatings may be

applied to protect

against erosion, but

not corrosion.

Blades <593°C Martensitic: 9CrWCo, R26 Moderate Moderate Moderate

Blades <566°C Ferritic: 1.25CR-0.5Mo (cast)

Martensitic: Alloy 422, 10CrMoVNb Low Low Low

Inner casing and vale body <620°C

Martensitic: 9CrMo(W)VNbN, CB2,

12CrMoVCbN (cast or forged), 9-12CrW,

12CrWCo (cast)

Austenitic: 19Cr12.5NiNbMoC (CF8C-

Plus)

High High High

Thermal coefficient of

casings must be

similar. Inner casing and vale body <593°C Martensitic: 9Cr1MoVNb, 10CrMoVNb Moderate Moderate Moderate

Inner casing and vale body <566°C

Ferritic: 2.25CR-1Mo (cast), 1.25CR-

0.5MoV (cast), 1.25CR-0.5Mo (cast)

Martensitic: 10CrMoVNb, 9CrMoVNb

Low Low Low

Outer casing <600°C Ferritic: 2.25Cr-1Mo (cast) Negligible Moderate Moderate None

Outer casing <566°C Ferritic: 1.25Cr-0.5Mo (cast) Negligible Low Low

Valve internals and turbine nozzles

<620°C Martensitic: 9-10CrW, 12CrWCo High High High

None

Valve internals and turbine nozzles

<593°C

Martensitic: 9Cr1MoVNb cast,

10CrMoVNb, 12Cr1MoVNbN Moderate Moderate Moderate

Valve internals and turbine nozzles

<566°C

Ferritic: 2.25CR-1Mo (cast), CrMoV

Martensitic: 10CrMoVNb (cast) Low Low Low

Bolts <620°C Martensitic: 9-12CrMoV,

Nickel alloy: IN718, A286 Negligible High High

Thermal coefficient

must be similar to that

of casings.

High stress relaxation

resistance

Bolts <593°C Martensitic: Refractory 26

Nickel alloy: Nimonic 85A Negligible Moderate Moderate

Bolts <565°C Martensitic: Alloy 422, 9-12CrMoV,

Nickel alloy: Nimonic 80A, IN718 Negligible Low Low

Raising the steel barrier to 650ºC

580

590

600

610

620

630

640

650

660

670

Thin-section superheater

and reheater (all pressures)

Thick-section, superheater

header, pipe and valves

(high pressure)

Thick-section, reheater

header, pipe and valves

(low pressure)

Steam turbine

Ste

am

te

mpera

ture

(°C

)

State-of-the-art materials 650°C Steels

Advanced Ultrasupercritical (700ºC)

Advanced ultrasupercritical (AUSC) steam at 700ºC permit

>50% η, achieved with high cost nickel based alloys

Advanced Ultrasupercritical (700ºC)

199

8

199

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200

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200

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200

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201

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6

China: Stage 3b (operate FSDP)

China: Stage 3a (build FSDP)

China: Stage 2 (CTF)

China: Stage 1 (inc long-term creep)

China: Stage 1 (exc long-term creep)

India: Stage 3b (operate FSDP)

India: Stage 1, 2 and 3a (build FSDP)

Japan: Stage 3b (operate FSDP)

Japan: Stage 3a (build FSDP)

Japan: Stage 2 (CTF)

Japan: Stage 1 (inc long-term creep)

Japan: Stage 1 (exc long-term creep)

USA: Stage 3b (operate FSDP)

USA: Stage 3a (build FSDP)

USA: Stage 2 (CTF)

USA: Stage 1 (inc long-term creep)

EU: Stage 3b (operate FSDP)

EU: Stage 3a (build FSDP)

EU: Stage 2 (CTF)

EU: Stage 1 (inc long-term creep)

EU: Stage 1 (exc long-term creep)

Conclusions

If cycling older plant then re-assess material

lifetimes to avoid catastrophic failure

1880-2010s: 600ºC steels = <47% ŋ (net, LHV)

2020s: 650ºC steels = 48-50% ŋ (net, LHV)

2030s: 700ºC nickel alloys = 50-53% ŋ (net, LHV)

Materials development give tangible benefits

Next Webinar

Upgrading the efficiency of worlds coal fleet to reduce

carbon dioxide emissions

Wednesday 14th

May 2014 Midday UK time

Ian Barnes

Thank you for listening

Questions?

Toby Lockwood

toby.lockwood@iea-coal.org

Kyle Nicol

kyle.nicol@iea-coal.org

46