High Temperature Oxidation and Corrosion of Gas Turbine Materials in Burner Rig Exposures

Joy SumnerAdriana Encinas-Oropesa

Nigel J. SimmsJohn E. Oakey

Cranfield University

8th International Charles Parsons Turbine

ConferenceSeptember 2011

BackgroundIntegrated Gasification Combined

Cycle (IGCC) Plants:

Combined Cycle Plants

• Higher efficiency (coupling steam

and gas turbines (GTs))

IGCC

• Syngas from solid fuels

• Integration of gas cleaning to meet

environmental legislation

GT lifetime limited by

• Hot corrosion: alkali metals, SOx

• Erosion: particles

• Deposition: particles, vapour

• Creep and fatigue

• Synergistic effects

O2

supplyGasifier

Particle remover

Shift reactor

Combustor

can

Heat exchanger

Sulphur removal

FuelSteam

Bottom ash

CO2

absorber

CO2

desorberH2 co-

production

Compressor

Steam turbine

GT

Fly ash

Steam

Sulphur

CO2

compressor

CO2

storage

~

~

Air

Cooler Steam

BackgroundTraditionally, industrial gas

turbines operate on natural gas /

oil-derived fuels

• Low in ash, alkali metals, etc

• Increasing fuel cost

Alternative fuels

• Gasified coal & biomass

• Lower calorific value syngases

• More ash, S, alkali metals, etc

Higher gas operating

temperatures

• Increase power plant efficiency

Result:

• Components exposed to hotter,

dirtier combusted gas stream

0.01

0.1

1

10

100

Wt% wet Wt% dry Wt% daf Wt% daf Wt% daf Wt% daf Wt% daf Wt% daf Wt% daf

Water

content

Ash Volatiles C H O N S Cl

Fuel parameter

%

Willow Poplar

Fir/pine/spruce Miscanthus

Wheat Olive waste

Coal

0

5000

10000

15000

20000

25000

Al Ba Ca Fe K Mg Mn Na P Si Ti

Element

Co

ncen

trati

on

(m

g/k

g d

ry)

Willow Poplar

Fir/pine/spruce Miscanthus

Wheat Olive waste

Coal

UK/US Collaboration on Advanced Materials for Low Emission Power Plants

5 year project established between:

• UK Department of Energy and Climate Change (DECC)

• US Department of Energy (DOE)

Project aims:

• Study new gas turbine operating environments

• Study response of materials for hot gas path components

• Quantifying & ranking materials’ corrosion resistance

• Creating an information database for future models

Talk aims:

• Describe burner rig exposures designed to simulate GT

environments

• Assess corrosion of current state-of-the-art materials

Experimental Details: MaterialsUnder this programme:

• 24 materials systems exposed:

• 8 state-of-the-art alloys (bare

or coated)

• 9 corrosion resistant/bond

coatings

• 2 thermal barrier coatings

Wt. %

Material Ni Cr Co Al Ti Ta Mo W B C Other

Haynes

230

57 22 5 0.3 - - 2 14 0.015 0.1 Si: 0.4, Mn: 0.5

La: 0.02, Fe: 3

IN939 48 22.5 19 1.9 3.7 1.4 - 2 0.009 0.15 Nb: 1, Zr: 0.09

IN738LC 62 16 8.5 3.4 3.4 1.7 1.7 2.6 0.01 0.11 Nb: 0.9, Zr: 0.05

CM247LC 62 8.1 9.2 5.6 0.7 3.2 0.5 9.5 0.015 0.07 Hf: 1.4, Zr: 0.015

4 tests:

• Combustion gas

environments simulating 4

different fuels

• Up to 1000 hours

• In a high velocity burner rig

• Total of nearly 700 air-

cooled samples exposed

Focus on 4 materials & 3 tests

Experimental Details: Test Conditions

Parameter Units Test 1 Test 2 Test 3

Simulates Contaminated

Diesel

IGCC H2-rich IGCC

Entry Gas Temp. °C 1180 1180 1250

Gas Velocity ms-1 50 50 50

Dust Type - - Sieved PF fly

ash

-

Dust Load ppm.mg-1.h-1 - 2 -

SOX vppm 300 300 300

HCl vppm - - -

H2O vol.% 8.7 8.7 ~20

Na ppb 125 125 125

K ppb 125 125 125

Syngas upper contaminant limits determined:

• Extrapolated from current NG limits

• Corrected for reduced fuel calorific content

• Variables standardised for ease of comparison

Comment on Accelerated Tests

• Large metal losses:

• Up to 2-3 mm in 1000 hours

• Why?

• Burner rig runs an accelerated test

• Operates under atmospheric pressure

• But need the same alkali sulphate

dew points as a real gas turbine

• Therefore need more salt in the

system

• Increases the vapour pressure in the

gas stream

• Increases the deposition flux

• Therefore much higher corrosion rates

than in standard gas turbines

g

isi

ip

ppm ,.

dShDii /

i

iinis

CT

BApp exp,

ṁ, flux of condensed gaseous component, i

βi, mass transfer coefficient of component, i

pi, partial pressure of component, i

ps,i, saturation pressure of component, i

p, flue gas pressure

ρg, flue gas density

Sh, Sherwood number

Di, diffusion coefficient of component, i

d, diameter on which component, i, condenses

pn, 105 Pa

Ai, Bi, Ci, constants

T, absolute temperature

Experimental Details:Burner Rig

Water cooling Dilution & cooling air

Dilution &

cooling airWater

cooling

Vent

Temperature &

pressure monitoring,

gas analysisTemperature monitored

air-cooled probes

Air

Air

SO2

Liquid/vapour

contaminants

Natural

Gas

Particle

feeder

Samples exposed for:

• 300 hours

• 700 hours

• 1,000 hours

Experimental Details:Statistical Assessment of Damage via Image Analysis

XXXXXXXXXXXXXX

XXXXXXXXXXXXXX

x3

Thermocouple measures

cooling air exit temp.

XXXXXXXXXXXXXX

XXXXXXXXXXXXXX

XXXXXXXXXXXXXX

XXXXXXXXXXXXXX

XXXXXXXXXXXXXX

XXXXXXXXXXXXXX

Cooling air in

0

50

100

150

200

0 10 20 30

-∆G

M /µ

m

Data Point Number

-400

-300

-200

-100

0

100

-2 0 2

∆G

M /µ

m

Std. Normal Prob.

Hot air

out

Results:Samples Pre- and Post-Exposure

Pre-exposure

Post-exposure

Image Analysis Results:The Effect of Exposure Time

0

20

40

60

80

100

120

0 200 400 600 800 1000

GM

L /µ

m

time /hours

Good Metal Loss for CM247LC after Test 2 exposure at 755 °C

-50

150

350

550

0 200 400 600 800 1000

GM

L /µ

m

Time /hours

Good Metal Loss for CM247LC after Test 2 exposure at 955 °C

-700

-600

-500

-400

-300

-200

-100

0

0 20 40 60 80 100

ΔG

M /µ

m

Probability /%

Change in Good Metal with Time (Test 2 exposure, 955 °C)

300 hours

700 hours

1000 hours

SEM & EDX Results:The Effect of Exposure Time (Test 2, 955 °C)

300 hours

Al

Co

Cr

S

Hf

Ni

O

90 µm

700 hours

Al

Co

Cr

Ni

O

S

100 µm

1000 hours

Al

Co

Cr

Hf

Ni

O

S

100 µm

Hf

SEM & EDX Results:The Effect of Exposure Time (Test 2, 955 °C)

300 hours

Al

Co

Cr

S

Hf

Ni

O

90 µm

700 hours

Al Hf

Co

Cr

Ni

O

S

300 µm

1000 hours

300 µm

Al

Co

Cr

Hf

Ni

O

S

Image Analysis Results:The Effect of Test & Exposure Temperature

0

500

1000

1500

1 2 3

GM

L /µ

m

Test

Effect of Test on CM247LC GML (1000 hour exposure)

955 °C

755 °C

-2000

-1500

-1000

-500

0

0 20 40 60 80 100

∆G

M /µ

m

Probability /%

Cumulative Probability ΔGM after 1000 h exposure (955 °C)

test 1 (995 °C)

test 2 (955 °C)

test 3 (955 °C)

-250

-200

-150

-100

-50

0

0 20 40 60 80 100

∆G

M /µ

m

Probability (%)

Cumulative Probability ΔGM after 1000 h exposure (755 °C)

test 1 (755 °C)

test 2 (755 °C)

test 3 (755 °C)

Image Analysis Results:Comparison to Other Alloys

-1100

-900

-700

-500

-300

-100

100

0 20 40 60 80 100

∆G

M /µ

m

Probability (%)

Cumulative Probability ΔGM after 1000 h Test 3 Exposure at 955 °C

IN939

Haynes 230

IN738LC

CM247LC0

200

400

600

800

1000

IN939 Haynes 230 IN738LC CM247LC

GM

L /µ

m

GML after 1000 hours exposure to Test 3 conditions at 955 °C

Conclusions• The severity of the corrosion and oxidation conditions varied between

the three tests

Test 2 (IGCC conditions including ash particles) appeared least

aggressive

Impacting fly ash removed corrosive deposits?

• Different types of hot corrosion seen

Type I: internal oxidation & sulfidation, lower incubation GMLs

Type II: pitting, higher incubation GML

Mixed mode

• CM247LC has a high fraction of Al

Should provide good oxidation protection

Areas of incubation seen in Type I

However, performs poorly under hot corrosion conditions

(cf. Haynes 230, IN939, IN738LC)

Effect of low Cr content

Looking Forward

UK-US Project

• 20 systems being characterised

• Developing a greater understanding of the distribution

of corrosion damage around samples

Moving on the H2-IGCC (Framework 7) project

• Assess different combusted syngas environments

• Study state-of-the-art and advanced materials

systems

Acknowledgements

This work was carried out under the UK/US Collaboration on Advanced

Materials for Low Emission Power Plants programme of research.

UK activities funded by:

• the Department for Innovation, Universities & Skills

• the Department for Business, Enterprise and Regulatory Reform,

• Alstom Power and Siemens (UK).

US activities funded by:

• Department of Energy

• Siemens Power Generation Inc.

-700

-500

-300

-100

0 50 100

ΔG

M /

µm

Probability /%b)

300 hours700 hours1000 hours -120

-100

-80

-60

-40

-20

0

0 50 100

ΔG

M /

µm

Probability /%

300 hours700 hours1000 hours

c)

a) Mount

Damaged regions

Sample

Reference notch

755 °C

HfAl

Co

Cr

S

Ni

O

90 µm

955 °C

700 µm

Al

Co

Cr

S

Hf

Ni

O

SEM & EDX Results:Effect of Exposure Temperature (700 h, Test 3)