High temperature corrosion of candidate

materials for industrial boilers in biomass

combustion

Jiri Krejcik and Josef Cizner

16. February 2010, Oslo

SVÚM a.s.Research Centre Bechovice

190 11 Prague 9 CZECH REPUBLIC

Corrosion test of candidate steels Corrosion test of candidate steels and alloys for biomass combustionand alloys for biomass combustion

a) Laboratory test in model environment (presented in the NGBW conference in Milan)

b) Field test on 5 different types of biomass combustion(co-combustion) boilers

Type

Steam temperature [°C]

Pressure [bar]

Performance [t/h]

1 Biocel Paskov, CZ bark (wood chips) + coal + mine gas

grade-fired 486 83 50

2 Mondi Štětí, CZ bark + lignite

circumfluid 535 94 220

3 Växjö Energi AB, S wood chips + peat

circumfluid 535 100 90

4 TTS Třebíč, CZ straw

grade-fired water heating boiler 4

5 Dalkia Krnov, CZ lignite + wood chips (pollard - 2006)

lgnifluid 445 37,2 75

Chemical composition [ %] Material Cr Ni Mo Mn Other

Low alloy steels 15Mo3 15 020

– – 0,30 0,52 C 0,16; Si 0,26

13CrMo4 4 15121

0,96 0,07 0,48 0,46 C 0,12; Si 0,21

10CrMo9 10 (T22) 15313

2,10 – 0,92 0,43 C 0,12; Si 0,22

T23 ▲ 2,3 – 0,15 0,27 C 0,06; Si 0,15; V 0,2; W 1,58; Nb 0,06; B 0,005; N 0,02; Al 0,02

T24 2,3 – 0,96 0,52 C 0,08; Si 0,3; P 0,005; S 0,001; Al 0,02; Al 0,02; N 0,007; V 0,23; B 0,0025; Ti 0,070

High alloy steels

T92 9,15 0,26 0,50 0,46 W 1,7;Si 0,22; Nb 0,6; N 0,05; V 0,2; B 0,003; C 0,11

X20CrMoV12 1 10,45 0,70 0,88 0,60 C 0,18; Si 0,22; V 0,26 Esshete 1250 14,90 9,65 0,94 6,25 C 0,084; Si 0,58; Nb 0,86; V 0,22; B 0,004 TP 347 H 17,60 10,70 – 1,84 Si 0,29; C 0,05, Nb 0,6 Ni-base alloys

SAN 28 * 27,00 31,00 3,50 2,0 C 0,02; Si 0,07; Cu 1,0

Alloy 625 * 22,00 Bal. 9,00 – Fe 3,0; Nb 3,5; C 0,025

* chemical composition range

boiler TTS Třebíč

▲ boiler TTS Třebíč, Växjö and Krnov

Test samples - cuts of tubes from candidate materials fixed on the bar made from AISI 310 steel.

Uncooled samples were installed into boilers.

Area: pulp and paper industryMoving - grate boilerPerformance: 50 t/hProduced steam: 486 °C/83 barFuel:bark (saw dust) + bark from deposit

(with earth) + coal - mine gas

Location of the test samples in boiler Paskov (CZ)

Time: 580 °C - 4 224 h, 7 032 h, 9 832 h640 °C - 4 224 h

coal-mine gas

natural gas SH1

SH2 LUVO1

LUVO2

ECO1

ECO2

DHD

bark

DMD

Electrofilter

airwatersteam

corrosion samplesgas temperature 580 °C

corrosion samplesgas temperature 640 °C

samples 600 °C

Location of the test samples in boiler Štětí (CZ)

Area: pulp and paper industryCircumfluid – Foster WheelerPerformance: 220 t/hProduced steam: 535°C/94 barFuel:50 % bark + 50 % lignite

Time: 8 760 h, 17 520 h, 31 370 hTemperature: 600 °C

Samples (SH1-SH2)Gas temperature 540°C

Samples (SH2-SH3)Gas temperature 580°C

Location of the test samples in boiler Växjö (S)

Area: heat and electricity generationBoiler: Sandvik IICircumfluidPerformance: 90 t/hProduced steam: 535 °C/100 barFuel:wood chips + peat

Time: 6 240 h, 15 000 h, 23 760 hTemperature: 540 °C and 580 °C

samples 500 °C

Location of the test samples boiler Třebíč (CZ)

Area: heat generationBoiler: VESKO-SPerformance: 5 MWFuel: 100% wheat straw

Time: 2 000 h, 4 747 hTemperature: 500 °C

Location of the test samples at the instalation of Krnov (CZ)

samples 450 °C

Area: heat and electricity generationIngnifluid - ČKD Dukla PraguePerformance: 75 t/hProduced steam: 445°C/37,2 barFuel:lignite + 20% pollard - 2006

lignite + wood chips - other years

Time: 1 560 h, 7 440 h, 9 456 h, 14 124 h, 21 647 h

Temperature: 450 °C

Analysis of deposit

Deposit was taken from the location of samples

(scratched off from the surface of overheating tubes).

Analysis of elements was carried out by EMPA

analyzer, most important is the content of Cl

(chlorides) and S.

1. Company: BIOCEL Paskov, CZBIOCEL Paskov, CZ

Analysis of deposit

Installation Mg Al Si Ca K Na Cl S O

2006 0,38 1,82 4,05 10,65 1,30 1,91 0,05 7,09 64,12

2. Company: MONDI PACKAGING, Štětí, CZMONDI PACKAGING, Štětí, CZ

Analysis of deposit

Installation Mg Al Si Ca K Na Cl S O

2006 0,12 13,70 21,30 6,88 0,74 0,08 0,20 0,79 52,40 2007 1,04 16,18 8,84 28,80 0,80 0,60 0,12 7,01 25,11 2008 0,10 4,32 7,24 22,44 0,20 0,03 0,16 6,37 53,14 2009 0,17 8,36 9,24 17,33 0,71 0,15 0,22 1,60 59,74

3. Company: VÄXJÖ Energi AB, SÄXJÖ Energi AB, S

Analysis of deposit

Installation Mg Al Si Ca K Na Cl S O

SH1 - SH2 3,94 5,71 12,15 19,64 4,02 0,79 0,33 9,12 33,01 2006

SH2 - SH3 2,46 1,38 5,32 12,30 15,27 1,20 0,12 5,64 47,87 SH1 - SH2 0,96 5,19 8,85 21,86 3,54 0,59 0,87 8,46 40,10

2007 SH2 - SH3 0,42 1,17 7,81 18,77 4,01 1,60 1,03 13,96 42,84 SH1 - SH2 0,48 0,77 1,58 8,47 1,29 0,30 1,47 0,87 39,75

2008 SH2 - SH3 0,63 0,82 1,80 13,12 2,53 0,59 0,88 1,25 27,03 SH1 - SH2 0,56 2,89 6,02 24,28 3,36 0,81 0,44 1,99 55,31

2009 SH2 - SH3 0,68 2,14 8,02 19,35 2,33 0,52 0,30 1,46 61,28

4. Company: TTS, Třebíč, CZTTS, Třebíč, CZ

Analysis of deposit

Installation Mg Al Si Ca K Na Cl S O

2006 1,35 0,16 26,13 13,55 4,11 0,03 1,19 0,80 46,82 2007 0,32 1,79 20,36 13,29 1,52 0,04 1,38 0,63 57,23 2009 0,31 1,33 11,40 11,88 4,48 0,22 1,16 0,54 66,51

5. Company: DALKIA Krnov, CZDALKIA Krnov, CZ

Analysis of deposit

Installation Mg Al Si Ca K Na Cl S O

2006 9,58 11,28 18,46 8,42 2,10 6,14 3,93 5,94 32,10 2007 0,14 8,88 6,53 8,43 1,04 0,36 0,03 0,25 68,77 2008 1,00 10,14 6,66 8,72 0,18 0,03 0,02 2,31 66,51 2009 0,04 8,68 5,60 11,22 1,42 0,38 0,17 2,89 67,20

Evaluation

Weight changes of test samples were evaluated during the

down - time of boilers.

On diagrams are corrosion curves, corrosion rate is

depending on kind of biomass and temperature.

PASKOV 640 °C/4224 h - metallography evaluation

0

0,5

1

1,5

2

2,5

3

3,5

4

4,5

10CrM

o9 10 T92

X20CrM

oV121

E1250

347H

SAN28 625

Tu

bes

th

ickn

ess

red

uct

ion

[m

m]

BIOCEL Paskov 580 °C

0

500

1 000

1 500

2 000

2 500

0 2000 4000 6000 8000 10000Time [h]

Wei

gh

t lo

ss

[g/m

2 ]

10CrMo9 1013CrMo4 415 Mo3T92X20CrMoV12 1E 1250347HSAN28625

Martensitic and austenitic steels have the equal corrosion resistance in both temperatures, corrosion resistance of low alloy steels is unacceptable.

The best corrosion resistance have Ni-base alloys

High alloy martensitic and austenitic steels and Ni-base alloys havevery good corrosion resistance.

MONDI PACKAGING, Štětí - 600 °C

-500

0

500

1 000

1 500

2 000

2 500

3 000

3 500

4 000

4 500

0 5000 10000 15000 20000 25000 30000 35000

Time [h]

Wei

gh

t ch

ang

es [

g/m

2 ]

10CrMo9 1013CrMo4 415 Mo3T92X20CrMoV12 1E 1250347HSAN28625

Växjö Energi AB - 580 °C

-300

300

900

1500

2100

2700

3300

0 5000 10000 15000 20000 25000

Time [h]

Wei

gh

t lo

ss [

g/m

2 ]

10CrMo9 1013CrMo4 415 Mo3T92X20CrMoV12 1E 1250347HSAN28625T23

Växjö Energi AB - 540 °C

-200

200

600

1000

1400

1800

2200

2600

3000

0 5000 10000 15000 20000 25000

Time [h]

Wei

gh

t lo

ss [

g/m

2 ]

10CrMo9 1013CrMo4 415 Mo3T92X20CrMoV12 1E 1250347HSAN28625T23

At temperature 540 °C - low alloy steels + martensitic steel T92 have very low corrosion resistance

At temperature 580 °C - corrosion resistance of low alloy + both martensitic steels is very low - the effect of Cl+S

The best – austenitic steels and Ni-base alloys

0

50

100

150

200

250

g/m

2

K rnov – 450°C

15313 15121 15020 T 92X 20C rMoV12 1 E 1250 T P 347 H S AN28625 T 23

Třebíč 500 °C

0

500

1000

1500

2000

2500

0 1000 2000 3000 4000 5000

Time [h]

Wei

gh

t lo

ss [

g/m

2 ]

10CrMo9 1013CrMo4 415 Mo3T92X20CrMoV12 1E1250347HSAN28625T23T24

Only Ni-base alloys and austenitic steels have good corrosion resistance

Good corrosion resistance of all test materials - low temperature

Evaluation of corrosion rateEvaluation of corrosion rate

Corrosion rate of low alloy steels has the linear character and the weight changes of samples are much higher as compared to other test materials (except of Dalkia Krnov) .

Austenitic steels and Ni-base alloys have the best corrosion resistance and the weight changes are very low in all cases.

The behaviour of martensitic steels is different and depends on the combustion atmosphere in boiler (deposit):

* In atmosphere with higher content of S (no Cl) - martensitic steels have very good corrosion resistance - similar to austenitic steels and Ni-base alloys (Biocel Paskov, Mondi Štětí).

* Different situation is in atmosphere with Cl (Třebíč) and Växjö (Cl + S), the corrosion resistance of martensitic steels is low and is similar to low alloy steels (except X20CrMoV12 1 at lower temperature 540 °C Växjö).

Mechanism of corrosionMechanism of corrosion

EPMA microanalysis and metallography were used for the

study of corrosion mechanism.

Fe O Cl S

60 36 2 1,75

Low alloy steelsLow alloy steelsEPMA microanalysis of corrosion layers

Inner corrosion layer [wt %]

Fe O Cr Cl S

50 38 7 0,3 0,4

Outer corrosion layer [wt %]

Mechanism of initiation and growth Mechanism of initiation and growth ofof inner inner

oxidic layeroxidic layer

Initiation - attack of carbide particles distributed on grain

boundaries and equally distributed in matrix - transformation to oxides (with S, Cl) .

Documentation of this mechanism is shown on steel 10CrMo9 10

boiler Paskov (mainly sulphidation)

boiler Växjö (combination of S and Cl corrosion).

Steel 10CrMo9 10 - Paskov

Steel 10CrMo9 10 - Växjö

Vz.è. A (15313,540) - z kor. vrs. do ZM

100.0100.0100.0100.0100.0100.0

000000

W%O

W%S

W%Cl

W%Cr

W%Fe

W%Mo

Pt Nº

10 20

100

80

60

40

20

0

[%]

corrosion layer

basicmaterial

(BM)

1 point - 10 µm

10CrMo9 10 - 540 °C - Växjö

Vz.è. A (15313,540) - z kor. vrs. pøes penetraci do ZM

5.0005.0005.000

000

W%S

W%Cl

W%Cr

Pt Nº

1 10

5

4

3

2

1

05

corrosion layer penetration BM

1 point - 2 µm

10CrMo9 10 - 540 °C - Växjö

[%]

corrosion layer

Fe O Cr Cl S

55 41 0,3 1,7 7,6

Martensitic steelsMartensitic steelsT 92, X20CrMoV12 1

Inner corrosion layer [wt %]

Fe O Cr W Cl S

30-50 35 20 0,9 0,2 7

Outer corrosion layer [wt %]

Mechanism of growth Mechanism of growth of of inner corrosion inner corrosion

layerlayer

Penetration of O, S and Cl into basic material, prefentially carbide particles are attacked

Växjö

Corrosion layer - thickness Penetration to BM

X20CrMoV12 1 - Paskov

Vz.è. T92 H

100.0100.0100.0100.0100.0100.0

000000

W%O

W%S

W%Cr

W%Fe

W%Mo

W%W

Pt Nº

10 20

100

80

60

40

20

[%]

1 point - 10 µm

T92 - Mondi

inner corrosion layer BM

1 point - 10 µm

outer corrosion layer

100

80

60

40

20

0

[%]

Fe O Cr Cl S

59 37 0,5 2,0 1,5

Austenitic steelsAustenitic steels

Inner corrosion layer [wt %]

Fe O Cr Ni Mo Cl S

36 37 27 2,0 1,4 0,3 2,4

Outer corrosion layer [wt %]

Mechanism of initiation and growth of Mechanism of initiation and growth of

inner corrosion layerinner corrosion layer

Initiation - attack of carbide particles and transformation to oxides.

Oxidation along austenitic grain boundaries.

Paskov 347H - 580 °C sulphidation

Växjö E1250 - 540 °C S and Cl corrosion

Paskov - 347H

Växjö

Vz.è. E (E1250,540) - z kor. vrs. do ZM100.0100.0100.0100.0100.0100.0

000000

W%O

W%S

W%Cl

W%Cr

W%Fe

W%Mo

Pt Nº

10 20

Växjö - E1250 - 540 °C

1 point - 2 µm

100

80

60

40

20

0

[%]

penetration BM corrosion layer

Vz.è. E (E1250,540) - z kor. vrs. pøes penetraci do ZM2.0002.000

00

W%S

W%Cl

Pt Nº

1 10

2

0

penetration BM

1 point - 2 µm

E1250- 540 °C - Växjö

%

corrosionlayer

1

Ni-base alloysNi-base alloysSAN 28, 625

Alloys 625 - application for the atmosphere with Cl in waste incineration plants.Corrosion layers are very thin, much more thinner as compared to other test materials.

Mechanism of corrosionMechanism of corrosion

Observed only one very thin layer - up to 6 µm.

Inner corrosion layer [wt %]

Ni Cr O Mo Cl S

2,5-30 24-27 43 0,8-11 1,2 4,5

Penetration of O, S and Cl into basic material - attack of carbide particles and transformation into oxides (with S, Cl).

Växjö

C O N C L U S I O N C O N C L U S I O N

Tests of candidate materials with uncooled samples from low alloy,

martensitic and A-steels and two Ni-base alloys show the effect of: corrosion atmosphere (content of sulphates, chlorides in deposit) temperature (temperature of combustion gases)

Metallographic analysis demonstrates the initiation of corrosion on

carbide particles and selective corrosion of the surface with corrosion

along grain boundaries in all test materials at higher temperatures (over

500°C). In corrosion products O, Cl and S were found, and penetration of

Cr, W, Mo, Ni from basic material was analysed (depending on chemical

composition of material)

Austenitic steels and Ni-base alloys have very good corrosion resistance

with thin corrosion layer. In low alloy steels and martensitic steels (except

of lower temperatures on Dalkia Krnov boiler) high corrosion rate with

thick corrosion layer was observed.

Thank you for your attention!