SVÚM a.s.
Research Centre Bechovice
190 11 Prague 9
CZECH REPUBLIC
High temperature corrosion of candidate materials
for industrial boilers in biomass combustion
Jiri Krejcik and Josef Cizner
16. February 2010, Oslo
Corrosion test of candidate steels and
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
1
2
3
4
5
Biocel Paskov, CZ
bark (wood chips) +
coal + mine gas
Mondi Štětí, CZ
bark + lignite
Växjö Energi AB, S
wood chips + peat
TTS Třebíč, CZ
straw
Dalkia Krnov, CZ
lignite + wood chips
(pollard - 2006)
Type
Steam
temperature [°C]
Pressure
[bar]
Performance
[t/h]
grade-fired
486
83
50
circumfluid
535
94
220
circumfluid
535
100
90
grade-fired
lgnifluid
water heating boiler
445
37,2
4
75
Chemical composition [ %]
Material
Low alloy steels
15Mo3
15 020
13CrMo4 4
15121
10CrMo9 10 (T22)
15313
Cr
Ni
Mo
Mn
Other
–
–
0,30
0,52 C 0,16; Si 0,26
0,96
0,07
0,48
0,46 C 0,12; Si 0,21
2,10
–
0,92
0,43 C 0,12; Si 0,22
T23 ▲
2,3
–
0,15
0,27
T24 
2,3
–
0,96
C 0,06; Si 0,15; V 0,2; W 1,58;
Nb 0,06; B 0,005; N 0,02; Al 0,02
C 0,08; Si 0,3; P 0,005; S 0,001; Al 0,02;
0,52
Al 0,02; N 0,007; V 0,23; B 0,0025; Ti 0,070
High alloy steels
T92
X20CrMoV12 1
Esshete 1250
TP 347 H
Ni-base alloys
SAN 28 *
Alloy 625 *
*

W 1,7;Si 0,22; Nb 0,6;
N 0,05; V 0,2; B 0,003; C 0,11
0,60 C 0,18; Si 0,22; V 0,26
6,25 C 0,084; Si 0,58; Nb 0,86; V 0,22; B 0,004
1,84 Si 0,29; C 0,05, Nb 0,6
9,15
0,26
0,50
10,45
14,90
17,60
0,70
9,65
10,70
0,88
0,94
–
27,00
22,00
31,00
Bal.
3,50  2,0
9,00
–
chemical composition range
boiler TTS Třebíč
▲ boiler TTS Třebíč, Växjö and Krnov
0,46
C 0,02; Si 0,07; Cu 1,0
 3,0; Nb 3,5; C 0,025
Test samples - cuts of tubes from candidate materials fixed on
the bar made from AISI 310 steel.
Uncooled samples were installed into boilers.
Location of the test samples in boiler Paskov (CZ)
DHD
SH2
LUVO1
SH1
ECO1
Electrofilter
coal-mine gas
natural gas
bark
DMD
ECO2
LUVO2
corrosion samples
gas temperature 580 °C
Area: pulp and paper industry
Moving - grate boiler
Performance: 50 t/h
Produced steam: 486 °C/83 bar
Fuel:bark (saw dust) + bark from deposit
(with earth) + coal - mine gas
air
water
steam
corrosion samples
gas temperature 640 °C
Time: 580 °C - 4 224 h, 7 032 h, 9 832 h
640 °C - 4 224 h
Location of the test samples in boiler Štětí (CZ)
samples 600 °C
Area: pulp and paper industry
Circumfluid – Foster Wheeler
Performance: 220 t/h
Produced steam: 535°C/94 bar
Fuel:50 % bark + 50 % lignite
Time: 8 760 h, 17 520 h, 31 370 h
Temperature: 600 °C
Location of the test samples in boiler Växjö (S)
Samples (SH1-SH2)
Gas temperature 540°C
Samples (SH2-SH3)
Gas temperature 580°C
Area: heat and electricity generation
Boiler: Sandvik II
Circumfluid
Performance: 90 t/h
Produced steam: 535 °C/100 bar
Fuel:wood chips + peat
Time: 6 240 h, 15 000 h, 23 760 h
Temperature: 540 °C and 580 °C
Location of the test samples boiler Třebíč (CZ)
samples 500 °C
Area: heat generation
Boiler: VESKO-S
Performance: 5 MW
Fuel: 100% wheat straw
Time: 2 000 h, 4 747 h
Temperature: 500 °C
Location of the test samples at the instalation of Krnov (CZ)
samples 450 °C
Area: heat and electricity generation
Ingnifluid - ČKD Dukla Prague
Performance: 75 t/h
Produced steam: 445°C/37,2 bar
Fuel: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, CZ
Analysis of deposit
Installation
2006
Mg
0,38
Al
1,82
Si
Ca
4,05 10,65
K
1,30
Na
1,91
Cl
0,05
S
O
7,09 64,12
2. Company: MONDI PACKAGING, Štětí, CZ
Analysis of deposit
Installation
2006
2007
2008
2009
Mg
Al
Si
Ca
0,12 13,70 21,30 6,88
1,04 16,18 8,84 28,80
0,10 4,32 7,24 22,44
0,17 8,36 9,24 17,33
K
0,74
0,80
0,20
0,71
Na
0,08
0,60
0,03
0,15
Cl
0,20
0,12
0,16
0,22
S
0,79
7,01
6,37
1,60
O
52,40
25,11
53,14
59,74
3. Company: VÄXJÖ Energi AB, S
Analysis of deposit
Installation
SH1 - SH2
2006
SH2 - SH3
SH1 - SH2
2007
SH2 - SH3
SH1 - SH2
2008
SH2 - SH3
SH1 - SH2
2009
SH2 - SH3
Mg
3,94
2,46
0,96
0,42
0,48
0,63
0,56
0,68
Al
Si
Ca
K
5,71 12,15 19,64 4,02
1,38 5,32 12,30 15,27
5,19 8,85 21,86 3,54
1,17 7,81 18,77 4,01
0,77 1,58 8,47 1,29
0,82 1,80 13,12 2,53
2,89 6,02 24,28 3,36
2,14 8,02 19,35 2,33
Na
0,79
1,20
0,59
1,60
0,30
0,59
0,81
0,52
Cl
S
O
0,33 9,12 33,01
0,12 5,64 47,87
0,87 8,46 40,10
1,03 13,96 42,84
1,47 0,87 39,75
0,88 1,25 27,03
0,44 1,99 55,31
0,30 1,46 61,28
4. Company: TTS, Třebíč, CZ
Analysis of deposit
Installation
2006
2007
2009
Mg
1,35
0,32
0,31
Al
Si
Ca
0,16 26,13 13,55
1,79 20,36 13,29
1,33 11,40 11,88
K
4,11
1,52
4,48
Na
0,03
0,04
0,22
Cl
1,19
1,38
1,16
S
O
0,80 46,82
0,63 57,23
0,54 66,51
5. Company: DALKIA Krnov, CZ
Analysis of deposit
Installation
2006
2007
2008
2009
Mg
Al
Si
Ca
9,58 11,28 18,46 8,42
0,14 8,88 6,53 8,43
1,00 10,14 6,66 8,72
0,04 8,68 5,60 11,22
K
2,10
1,04
0,18
1,42
Na
6,14
0,36
0,03
0,38
Cl
3,93
0,03
0,02
0,17
S
5,94
0,25
2,31
2,89
O
32,10
68,77
66,51
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
BIOCEL Paskov 580 °C
4,5
10CrMo9 10
13CrMo4 4
15 Mo3
T92
X20CrMoV12 1
E 1250
347H
SAN28
625
2 000
Weight loss [g/m 2]
Tubes thickness reduction [mm]
2 500
1 500
1 000
500
4
3,5
3
2,5
2
1,5
1
0,5
0
0
0
2000
4000
6000
Time [h]
8000
10000
10
o9
M
Cr
10
2
T9
M
Cr
0
X2
1
12
V
o
0
25
1
E
7H
34
N
SA
28
5
62
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
MONDI PACKAGING, Štětí - 600 °C
4 500
10CrMo9 10
13CrMo4 4
15 Mo3
T92
X20CrMoV12 1
E 1250
347H
SAN28
625
4 000
Weight changes [g/m 2]
3 500
3 000
2 500
2 000
1 500
1 000
500
0
-500
0
5000
10000
15000
20000
25000
30000
35000
Time [h]
High alloy martensitic and austenitic steels and Ni-base alloys have
very good corrosion resistance.
Växjö Energi AB - 540 °C
Växjö Energi AB - 580 °C
3000
Weight loss [g/m 2]
2200
1800
1400
3300
10CrMo9 10
13CrMo4 4
15 Mo3
T92
X20CrMoV12 1
E 1250
347H
SAN28
625
T23
2700
Weight loss [g/m 2]
2600
1000
2100
10CrMo9 10
13CrMo4 4
15 Mo3
T92
X20CrMoV12 1
E 1250
347H
SAN28
625
T23
1500
900
600
300
200
-200 0
5000
10000
15000
20000
25000
-300 0
Time [h]
5000
10000
15000
20000
25000
Time [h]
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
Třebíč 500 °C
K rnov – 450°C
2500
250
10CrMo9 10
13CrMo4 4
15 Mo3
T92
X20CrMoV12 1
E1250
347H
SAN28
625
T23
T24
1500
1000
2
200
g /m
Weight loss [g/m 2]
2000
150
100
50
0
15313
X 20C rMoV12 1
625
500
15121
E 1250
T 23
15020
T P 347 H
T 92
S AN28
0
0
1000
2000
3000
4000
5000
Time [h]
Only Ni-base alloys and austenitic
steels have good corrosion resistance
Good corrosion resistance of all test
materials - low temperature
Evaluation 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 corrosion
EPMA microanalysis and metallography were used for the
study of corrosion mechanism.
Low alloy steels
EPMA microanalysis of corrosion layers
Outer corrosion layer [wt %]
Fe
60
O
36
Cl
2
S
1,75
Inner corrosion layer [wt %]
Fe
50
O
38
Cr
7
Cl
0,3
S
0,4
Mechanism of initiation and growth of inner
oxidic 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
W% 100
O
W%
S
W%
Cl 80
W%
Cr
W%
Fe
W% 60
Mo
1 point - 10 µm
A (15313,540)
- z kor. vrs. do ZM
10CrMo9 10 -Vz.è.
540
°C - Växjö
100.0
100.0
100.0
100.0
100.0
100.0
basic
material
(BM)
corrosion layer
[%]
40
20
Pt Nº
0
10
20
0
0
0
0
0
0
W% 5
S
W%
Cl
W%
Cr 4
5.000
5.000
5.000
1 point - 2 µm
Vz.è. A (15313,540)
- z kor.°C
vrs. -pøes
penetraci do ZM
10CrMo9
10 - 540
Växjö
corrosion layer
penetration
BM
3
[%]
2
1
Pt Nº
0
1
5
10
0
0
0
Martensitic steels
T 92, X20CrMoV12 1
Outer corrosion layer [wt %]
Fe
55
O
41
Cr
0,3
Cl
1,7
S
7,6
Inner corrosion layer [wt %]
Fe
30-50
O
35
Cr
20
W
0,9
Cl
0,2
S
7
Mechanism of growth of inner corrosion layer
Penetration of O, S and Cl into basic material, prefentially
carbide particles are attacked
Corrosion layer - thickness
Penetration to BM
Växjö
X20CrMoV12 1 - Paskov
W%100
O
W%
S
W%
Cr 80
W%
Fe
W%
Mo
W% 60
W
100.0
100.0
100.0
100.0
100.0
100.0
11 point
point -- 10
10 µm
µm
T92 - MondiVz.è. T92 H
outer corrosion layer
inner corrosion layer
BM
[%]
40
20
Pt Nº
0
10
20
0
0
0
0
0
0
Austenitic steels
Outer corrosion layer [wt %]
Fe
59
O
37
Cr
0,5
Cl
2,0
S
1,5
Inner corrosion layer [wt %]
Fe
O
Cr
Ni
Mo
Cl
S
36
37
27
2,0
1,4
0,3
2,4
Mechanism of initiation and growth of inner
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
100
W%
O
W%
S
W%
Cl 80
W%
Cr
W%
Fe
60
W%
Mo
100.0
100.0
100.0
100.0
100.0
100.0
Vz.è. E (E1250,540) - z kor. vrs. do ZM
Växjö - E1250 - 540 °C
1 point - 2 µm
corrosion layer
penetration
BM
[%]
40
20
0
Pt Nº
10
20
0
0
0
0
0
0
W% 2
S
W%
Cl
2.000
2.000
Vz.è. E (E1250,540) - z kor. vrs. pøes penetraci do ZM
E1250540 °C - Växjö
1 point - 2 µm
corrosion
layer
penetration
BM
%
1
Pt Nº
0
1
10
0
0
Ni-base alloys
SAN 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 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
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!