Post on 14-Jul-2020
transcript
Challenges in power production
with biomass -
High-temperature corrosion
Chemistry in Energy Technology
March 11 – 15, 2019
Presented
by
Patrik Yrjas
Power production principle by combustion
- cooking water.....
Large-scale combustion techniques
Pulverized fuel firing – adapted
mainly for coal
Grate fired boilers – today
mainly for waste and smaller
scale biomass boilers
Fluidised bed boilers – suitable
for different kinds of fuels
Sumitomo SHI FW
(former Amec Foster Wheeler)
Fluidised bed boilers
Important for Finland, three major manufacturers
located here:
Sumitomo SHI FW (former Amec Foster Wheeler
Energia Oy) – BFB, CFB
Andritz Oy – BFB, CFB, recovery boilers
Valmet Technologies Oy - BFB, CFB, recovery boilers
CYMIC multi-fuel boiler
TSE, Naantali, FinlandSteam 144 / 130 kg/s
164 / 44 bar
555 / 555 C
390 MWth
(142 MWe, 244 MWheat)
Fuels: Wood biomass,
agrofuel, peat,
coal, SRF
Start-up: Fall 2017
Courtesy of Valmet Technologies Oy
Corrosion in power boilers
Wet corrosion of colder areas before stack (e.g. acid
dew point, hygroscopic deposits)
Corrosion of refractory material
Corrosion of steam side material/tubing
Corrosion on fire side material/tubing
- The major reason for efficiency limitations and
operational problems
- Rule of thumb: 10 ºC steam temperature increase,
increase plant efficiency by 2 %
Challenges in biomass combustion
High-temperature corrosionHigh-temperature corrosion refers to a chemical attack from
gases, solid or molten salts, or molten metals, typically at
temperatures > 300°C, but limit not strict. Examples of high-
temperature corrosion:
• Gas phase corrosion• Chlorination
• Oxidation
• Carburization
• Sulphidation
• Nitridation
• Solid and melt phase corrosion• Deposit composition and change (gas, fuel mix, etc)
Picture taken from: www.modernpowersystems.com
Source: Frandsen et al.
Slagging, fouling, and corrosion
Factors affecting corrosion
Material temperature
Steel composition
Deposit composition
Gas composition
Temperatures Wall tubes and drum
Temperature of supersaturated steam
(depends on pressure) ~ 300°C
Material temperature at walls +50°C
Superheaters
Steam ~ 400°C → 550°C (…600°C?)
Material
Radiation area+ 50°C
Convection area + 20-35°C
Economizers
Pre-heating of water max ~300°C
Air-pre-heaters
Pre heating of air (~120°C ±)
Steels
Most commonly used steels
Non alloy
Low alloy
High alloy
Stainless
And when ordinary steels are not enough
Composite =compound materials
Overlay welding
Metal spraying
Refractories
SteelsAlloying
Steels are made by combining iron (Fe) and carbon (C) which include
other elements as impurities or alloyed in purpose
Carbon content in steels usually 0,05-1%
– Cast iron (gjutjärn), if C > 2%
– The most important alloying element
– Affects the formation of microstucture (ferritic, martensitic, austenitic)
– Affects wide range of mechanical properties and fabrication characterization
C content increases C content decreases
tensile strenght toughness
hardness ductility
Classic improvers: Cr and Ni Cr: added to the steel to increase resistance to corrosion and
oxidation through Cr2O3 formation
Ni: tendency to form austenite results in a great toughness and high
strength at both high and low temperatures. Nickel also improves
resistance to oxidation and corrosion
Others: Mn, Mo, and Nb Mn: an austenite forming element, which improves hot working
properties and increases strength, toughness and hardenability (MnS
vs. FeS)
Mo: improves resistance to pitting corrosion, especially by chlorides
and sulphur chemicals
Nb: carbide stabilization, which tends to minimize the occurrence of
inter-granular corrosion; strengthens steels and alloys for high
temperature service
Steels
Grouping of steels
16Mo3, 13CrMo4-5, SA-209 Gr- T1,Low alloy steels 10CrMo9-10,
(Cr + Mo + Ni + Cu + V + Nb/Cb) > 5% 7CrMoVTiB10-10 SA-213 Gr. T11, T12, T22
High alloy steels, ferritic X10CrMoVTiB10-10 SA-213 Gr. T91, SA-335Gr. P91
Min. 13% Cr and max. 3% Ni
Stainless steels,1.4016, 1.4006, 1.4005 430, 410, 416
Min. 18% Cr and 3-6% Niferritic and martensitic
Stainless steels, 1.4162 (LDX 2101),austenitic-ferritic 1.4462 S32101, S32205
Min. 18% Cr and min. 7% Ni
Stainless steels, SA-213 TP347H,austenitic X7CrNiNb18-10 TP310HCbN
More Cr, Ni, Mo, Ce...
Special alloys, 2.4856
for e.g. Ni based (Sanicro 63, Alloy 625)
Fe, C, Mn, Si
EN materials ASME/ASTM materials
Non alloy steels P235GH, P265GH SA/A-210 Gr. A-1 and C, SA-106 Gr. B and C
Non alloy steels (Fe+C), carbon steels
May include manganese (Mn) and silicon (Si)
Very good availability, easy to weld
Price ~ 1,5 €/kg (P265GH)
Max design (material) temperature
– For pressure parts 450 oC
– For non-pressure parts 480 oC
Scaling temperature in air at 500 oC or little higher400
500
600
700
800
900
1000
1100
Grouping and use of steels
Examples of useFurnace walls, superheaters, boiler bank,
economizers, air preheaters (temperature below ~ 450 °C)
Grouping of steels
High alloy steels, ferritic X10CrMoVTiB10-10 SA-213 Gr. T91, SA-335Gr. P91
Min. 13% Cr and max. 3% Ni
Stainless steels,1.4016, 1.4006, 1.4005 430, 410, 416
Min. 18% Cr and 3-6% Niferritic and martensitic
Stainless steels, 1.4162 (LDX 2101),austenitic-ferritic 1.4462 S32101, S32205
Min. 18% Cr and min. 7% Ni
Stainless steels, SA-213 TP347H,austenitic X7CrNiNb18-10 TP310HCbN
More Cr, Ni, Mo, Ce...
Special alloys, 2.4856
for e.g. Ni based (Sanicro 63, Alloy 625)
Fe, C, Mn, Si
Cr, Mo, Ni, Cu, V, Nb/Cb
EN materials ASME/ASTM materials
Low alloy steels
16Mo3, 13CrMo4-5,10CrMo9-10,
7CrMoVTiB10-10
SA-209 Gr- T1,
SA-213 Gr. T11, T12, T22
Non alloy steels P235GH, P265GH SA-210 Gr. A-1 and C, SA-106 Gr. B and C
Low alloy ferritic steels
Molybdenum (Mo), chromium (Cr), vanadium (V), nickel (Ni)
Mo increases high temperature strength (0.5-1.0%)
increases both strength and resistance to scaling (0.5-2.5%)
increases creep strength at higher temperatures (max. 0.3%)
Use depending on strength values up to 575 °C
Very good availability
Price ~ 1,8 €/kg (16Mo3) to 3,3 €/kg (7CrMoVTiB10-10)
Requirements for welding increases with increasing alloying
elements
400
500
600
700
800
900
1000
1100
Cr
V
Mo
Cr
Grouping and use of steels
Examples of use
Furnace walls, superheaters, screen
tubes, boiler bank, economizers
Stainless steels,1.4016, 1.4006, 1.4005 430, 410, 416
Min. 18% Cr and 3-6% Niferritic and martensitic
Stainless steels, 1.4162 (LDX 2101),austenitic-ferritic 1.4462 S32101, S32205
Min. 18% Cr and min. 7% Ni
Stainless steels, SA-213 TP347H,austenitic X7CrNiNb18-10 TP310HCbN
More Cr, Ni, Mo, Ce...
Special alloys, 2.4856
for e.g. Ni based (Sanicro 63, Alloy 625)
Fe, C, Mn, Si
Cr, Mo, Ni, Cu, V, Nb/Cb
EN materials ASME/ASTM materials
(Cr + Mo + Ni + Cu + V + Nb/Cb) > 5%
High alloy steels,
ferritic X10CrMoVNb9-1 SA-213 Gr. T91, SA-335Gr. P91
Low alloy steels
16Mo3, 13CrMo4-5,10CrMo9-10,
7CrMoVTiB10-10
SA-209 Gr- T1,
SA-213 Gr. T11, T12, T22
Non alloy steels P235GH, P265GH SA-210 Gr. A-1 and C, SA-106 Gr. B and C
Grouping of steels
High alloy ferritic steels
Alloying elements over 5%
Economical use up to 600 ˚C
Limited availability
Challenging in welding
Price ~ 7-9 €/kg (X10CrMoVNb9-1)
400
500
600
700
800
900
1000
1100
Grouping and use of steels
Superheaters, main steam pipes
Examples of use
Stainless steels, 1.4162 (LDX 2101),austenitic-ferritic 1.4462 S32101, S32205
Min. 18% Cr and min. 7% Ni
Stainless steels, SA-213 TP347H,austenitic X7CrNiNb18-10 TP310HCbN
More Cr, Ni, Mo, Ce...
Special alloys, 2.4856
for e.g. Ni based (Sanicro 63, Alloy 625)
Fe, C, Mn, Si
Cr, Mo, Ni, Cu, V, Nb/Cb
EN materials ASME/ASTM materials
(Cr + Mo + Ni + Cu + V + Nb/Cb) > 5%
24
Min. 13% Cr and max. 3% Ni
Stainless steels,
ferritic and martensitic 1.4016, 1.4006, 1.4005 430, 410, 416
High alloy steels,
ferritic
X10CrMoVTiB10-10 SA-213 Gr. T91, SA-335Gr. P91
Low alloy steels
16Mo3, 13CrMo4-5,10CrMo9-10,
7CrMoVTiB10-10
SA-209 Gr- T1,
SA-213 Gr. T11, T12, T22
Non alloy steels P235GH, P265GH SA-210 Gr. A-1 and C, SA-106 Gr. B and C
Grouping of steels
Ferritic and martensitic stainless steels
Ferritic (min. 13% Cr, max. 3% Ni)
Good corrosion resistance
Cheap price
Poor weldability
High tendency to embrittlement
NOT FOR PRESSURE BEARING PARTS
Martensitic (min. 13% Cr, max. 3% Ni)
Higher carbon content than with ferritic
Martensitic structure with heat treatment
Good strength-toughness properties
Moderate corrosion resistance
400
500
600
700
800
900
1000
1100
Grouping and use of steels
Martensitic stainless steels for e.g. to
turbine components and steam lines
Ferritic stainless steels not for pressure bearing parts
But are used for e.g in recovery boiler ash hoppers
Examples of use
Stainless steels, SA-213 TP347H,austenitic X7CrNiNb18-10 TP310HCbN
More Cr, Ni, Mo, Ce...
Special alloys, 2.4856
for e.g. Ni based (Sanicro 63, Alloy 625)
Fe, C, Mn, Si
Cr, Mo, Ni, Cu, V, Nb/Cb
Min. 18% Cr and 3-6% Ni
EN materials ASME/ASTM materials
(Cr + Mo + Ni + Cu + V + Nb/Cb) > 5%
27
Min. 13% Cr and max. 3% Ni
Stainless steels, austenitic-ferritic
X2CrNi23-4, X2CrNiMoN22-5-3
SA/A-789 S1803
Stainless steels,
ferritic and martensitic 1.4016, 1.4006, 1.4005 430, 410, 416
High alloy steels,
ferritic
X10CrMoVTiB10-10 SA-213 Gr. T91, SA-335Gr. P91
Low alloy steels
16Mo3, 13CrMo4-5,10CrMo9-10,
7CrMoVTiB10-10
SA-209 Gr- T1,
SA-213 Gr. T11, T12, T22
Non alloy steels P235GH, P265GH SA-210 Gr. A-1 and C, SA-106 Gr. B and C
Grouping of steels
Austenitic-ferritic stainless steels = Duplex steels
1) Lean duplex (LDX 2101)
2) ”Acid proof” duplex (2205)
3) Super duplex (2507)
Magnetic
Good corrosion resistance (especially against stress
corrosion cracking) and strength
Operating temperature below 300 oC (in pressure vessels
max. 250 oC )400
500
600
700
800
900
1000
1100
Grouping and use of steels
Used in evaporators (T > 150 °C), containers
and in pipings
www.outokumpu.com
www.ranflexmetals.com
Examples of use
Special alloys, 2.4856
for e.g. Ni based (Sanicro 63, Alloy 625)
Fe, C, Mn, Si
Cr, Mo, Ni, Cu, V, Nb/Cb
Min. 18% Cr and 3-6% Ni
Min. 18% Cr and min. 7% Ni
EN materials ASME/ASTM materials
(Cr + Mo + Ni + Cu + V + Nb/Cb) > 5%
Min. 13% Cr and max. 3% Ni
Stainless steels, austenitic
X7CrNiNb18-10 SA-213 TP347H, TP310HCbN
Stainless steels, austenitic-ferritic
X2CrNi23-4, X2CrNiMoN22-5-3
SA/A-789 S1803
Stainless steels,
ferritic and martensitic 1.4016, 1.4006, 1.4005 430, 410, 416
High alloy steels,
ferritic
X10CrMoVTiB10-10 SA-213 Gr. T91, SA-335Gr. P91
Low alloy steels
16Mo3, 13CrMo4-5,10CrMo9-10,
7CrMoVTiB10-10
SA-209 Gr- T1,
SA-213 Gr. T11, T12, T22
Non alloy steels P235GH, P265GH SA-210 Gr. A-1 and C, SA-106 Gr. B and C
Grouping of steels
Austenitic stainless steels
Low carbon grade, L = C < 0,03%
Normal grade, C < 0,08%
Sensitization area 550-750 ˚C
Stabilized grades for temperatures between 550 and 750 ˚C
Not magnetic
High-strength and ductile
Brittleness in long-term, high temperature use
Challenges in bending
Limited availability of special grades (TP310HCbN,
347HFG, 253Ma)
400
500
600
700
800
900
1000
1100
Grouping and use of steels
Hottest superheaters, pipings
Plates, superheater ties, refractory anchors, tube shields…
(high T > 550°C)
Black liquor line, evaporator, vessels, cyclones
Examples of use
Fe, C, Mn, Si
Cr, Mo, Ni, Cu, V, Nb/Cb
Min. 18% Cr and 3-6% Ni
Min. 18% Cr and min. 7% Ni
More Cr, Ni, Mo, Ce...
EN materials ASME/ASTM materials
(Cr + Mo + Ni + Cu + V + Nb/Cb) > 5%
Min. 13% Cr and max. 3% Ni
Non ferrous alloys,
for e.g. Ni based
2.4856
(Sanicro 63, Alloy 625)
Stainless steels, austenitic
X7CrNiNb18-10 SA-213 TP347H, TP310HCbN
Stainless steels, austenitic-ferritic
X2CrNi23-4, X2CrNiMoN22-5-3
SA/A-789 S1803
Stainless steels,
ferritic and martensitic 1.4016, 1.4006, 1.4005 430, 410, 416
High alloy steels X10CrMoVTiB10-10 SA-213 Gr. T91, SA-335Gr. P91
Low alloy steels
16Mo3, 13CrMo4-5,10CrMo9-10,
7CrMoVTiB10-10
SA-209 Gr- T1,
SA-213 Gr. T11, T12, T22
Non alloy steels P235GH, P265GH SA-210 Gr. A-1 and C, SA-106 Gr. B and C
Grouping of steels
Special alloys, for e.g. Ni-based alloys
Iron not anymore the main element
To be used in really aggressive corrosive
environments
Applications: compound / composite tube + overlay
weldings
When ordinary steels are not
enough...
Examples of steelsW
eig
ht-
%Low
alloy
High alloy
steels Austenitic stainless steelsNi-based
alloys
Source: Cha et al.
Increasing Cr and Ni content
Increasing material costs
Steels
Combustion of biomass
Purpose:
To produce heat and electricity without increasing
the net-CO2 concentration in the atmosphere
Availability
Replace fossil fuels
F. Frandsen
Biomass sources
Tree derived - wood, branches, stumps, bark,
sawdust
Straw and energy crops (miscanthus, willow,
poplar, etc.)
Waste derived – demolition wood, agrofuels,
food processing residues (rice husk, bagasse,
corn cobs, etc.), and others
Note; biofuels often connected to processed
biomass such as ethanol, biodiesel, etc.
Biomass - ash forming matter
0
1
2
3
4
5
6
7
8
9
10
Wei
ght
% (
db
)
Rest
P
S
Cl
Na
K
Ca
Si
Based on data from the ÅA database: https://web.abo.fi/fak/tkf/ook/bransle/
Ash chemistry of different fuel types
Coal => silicate based ash chemistry, Na, S and
Ca (in FBC when used for desulphurization)
Biomass => Ca, K, Na, S, and Cl (+Si in some
cases)
Agrofuels => Si, Ca, K, P, S and Cl
Waste fuels => .......... + Zn and Pb (+Br)
Challenging fuel mixesAmec Foster Wheeler´s fuel system:
Courtesy of Amec Foster Wheeler
Challenging fuel mixesValmet´s fuel system:
Corrosion by metal chloride and
sulphate deposits
Deposition of sulphates and chlorides occurs by:
• condensation from the gas phase
• attachment of small sticky particles
PbS
O4
Inner scale
Outer scale
Ref. Rainer Backman
The salt system melting stairs
Importance of composition to T0
Fe2O3
Corrosion mechanism
- ”active oxidation”
Fe
Metal/Fe, e.g. low alloyed steel, 16Mo3
KCl
O2, (H2O)
Cl-, Cl2
FeCl2
Fe2O3
Cl-
HCl
Cl2?
HCl, Cl2KOH
p(O2)increases
p(Cl2)increases
Cr2O3
Corrosion mechanism of Fe/Cr-steels
- initiation to ”active oxidation”
Fe/Cr
Metal; Fe/Cr, e.g. stainless steel, AISI347 (19% Cr)
KCl
O2, (H2O)
Cl-, Cl2MeCl2
Me2O3
Cl-
HCl
Cl2?
HCl, Cl2
K2CrO4
p(O2)increases
p(Cl2)increases
Cr2O3
KOH
Me = Fe, Cr
Active oxidation
First and most cited corrosion reaction mechanism
? Driving force for the chlorine diffusion
? The molecular sizes of O2, Cl-, HCl, Cl2, CrCl2,
FeCl2
Facts:
FeCl2, Fe2O3, Cr2O3
and K2CrO4 have
been identified as
corrosion products
Fe2O3
Corrosion mechanism
- ”active oxidation”
Fe
Metal/Fe, e.g. low alloyed steel, 16Mo3
KCl
O2, (H2O)
Cl-, Cl2
FeCl2
Fe2O3
Cl-
HCl
Cl2?
HCl, Cl2KOH
p(O2)increases
p(Cl2)increases
What can we do....?
Some research tools Laboratory methods
Furnace tests; materials exposed to synthetic ashes
at high temperature and a controlled gas atmosphere
Other used methods, e.g. DTA/TGA studies, camera,
isotopes (e.g. O18 and O16) etc.
Thermodynamic chemical equilibrium
calculations
Melting evaluations of salts, deposits and ashes
Pilot/bench-scale tests
Full-scale measurements
Temperature controlled corrosion and deposit probes
Sampling and SEM/EDX-analyses
High-temperature material exposure
testsSteels are cut to 20 mm x 20 mm in our workshop or delivered. Pretreated and covered with a synthetic
ash/salt/real ash. Five samples exposed at a time in a tube furnace with chosen atmosphere and
temperature. Afterwards steel samples are casted in resin, cut off the reveal cross-section and polished
and washed.
Pre-melted salt
Result treatment
Salt
Steel
Pasta Oxide layer
Oxide layer
Steel
Epoxy
Oxide layer
Steel
Steel
Salt particles
Salt particles
max.
min.
average
etc.
The cleaned cross-sections are studied in the SEM/EDX and the
oxide layer thickness (corrosion layer) is determined over the cross-
section. From the data we get differnt oxide layers values: mean,
max, min, median etc.
0
50
100
150
200
250
300
350
400
450
500
0 20 40 60 80 100 120 140 160
Oxide layer thickness, [µm]
Co
un
ts
Maxim
um
valu
e
Mo
st
co
mm
on
valu
e
Avera
ge
Med
ian
180
Counts as a function of oxide layer
thickness
53This figure shows the statistics as calculated from the measured oxide layer
thicknesses., mean median, min and max values can be determined
0
100
200
300
400
500
600
0 50 100 150 200 250 300
Oxide layer thickness, [µm]
Co
un
ts
Maxim
um
valu
e
Mo
st
co
mm
on
valu
e
Avera
ge
Med
ian
Counts as a function of oxide layer thicknessType 2
Percentage of counts as a function of oxide
layer thicknessDistribution of oxide layer
0
0,5
1
1,5
2
2,5
3
3,5
4
4,5
5
0 50 100 150 200 250
Thickness of oxide layer [µm]
%
Ash with no Cl
No ash
Ash with Cl
Examples of corrosion results, 168 h
(21% O2, 79% N2)
(Skrifvars et al. 2008)
0
20
40
60
80
100
120
140
Co
rro
sio
n layer
thic
kn
ess, m
m 1.3% Cl T0=522°C
0
20
40
60
80
100
120
140
Co
rro
sio
n la
ye
r th
ick
ne
ss
, m
m 0.3% Cl T0=526°C
0
20
40
60
80
100
120
140
Co
rro
sio
n layer
thic
kn
ess, m
m 0% Cl T0 = 835°C
0
20
40
60
80
100V
ikt-
%
Rest
Nb
Mn
Mo
Ni
Cr
Fe
Samples with KCl on 304L
K2CrO4
MeCl2
500°C
20 μm
Cr Fe
Ni O
K Cl
Cr Fe Mn Mo Ni Si nCr/nFe
304L (wt.%) 19.19 70.21 2.02 0.32 7.72 0.47
304L (at.%) 20.33 69.24 2.04 0.18 7.27 0.94 0.29
SEM-results; importance of pre-melting
10CrMo, 10%KCl + K2SO4 500oC
Salt prepared without melting
Salt molten for homogeneity
Waste case: Experimental – materials
and conditions
Fe; 96.0
Fe; 68.7
Cr; 2.2
Cr; 18.1 Ni; 10.9
0 % 20 % 40 % 60 % 80 % 100 %
10CrMo9-10
AISI 347
59
Compound Melting temp. Temperatures Time Atmosphere
ZnCl2 318 ºC 250 ºC
PbCl2 501 ºC 350 ºC 168 h ambient
ZnO 1975 ºC 450 ºC
PbO 888 ºC 550 ºC
Results – oxide layer thickness
x- the oxide layer thickness under the detection limit
60
80
33
5
240
356
7
38
5 4
108
70
9
0
50
100
150
200
250
300
350
400
250 350 450 350 450 550 550 550
Mean
oxid
e la
yer
thic
kn
ess
µm
Temperature ºC
10CrMo
AISI347
xx x x
ZnCl2 PbCl2 ZnO PbO
XX
XX
KCl
Results – oxide layer thickness evaluation (450 ºC)
61Internal attack steel
Oxide layerOxide layer
steel
0
1
2
3
4
5
0 50 100 150 200 250 300 350
Oxide layer thickness µm
PbCl2 (Type 2)
10CrMo
AISI347
0
1
2
3
4
5
0 50 100 150 200 250 300 350
Dis
trib
uti
on
%
Oxide layer thickness µm
ZnCl2 (Type 1)
mean 5 µm
mean 108 µm
mean 35 µm
mean 240 µm
Another case study:
Questions
Are Pb- and Zn- chloride mixtures corrosive at
lower temperatures (300, 350 ºC)?
Does the added sulphur influence on Pb- and
Zn-chloride induced corrosion?
Background - sulphur may decrease KCl induced
corrosion according to:
2KCl + SO2 + H2O +1/2O2 K2SO4 + 2HCl
Corrosion Tests Simulated flue gas composition 1:
15% CO2, 5% O2, 15% H2O, 500 ppm SO2, rest N2
Simulated flue gas composition 2:
15% CO2, 5% O2, 15% H2O, rest N2
Salts: PbCl2 (Tmelt = 501 ºC) and 52 KCl + 48 PbCl2 wt% (molar ratio 4:1, T0 = 411 ºC),
59 KCl + 28 PbCl2 + 13 ZnCl2 wt% (molar ratio 8:1:1, T0 = 210 ºC)
Test duration: 168 h
Steels: non-alloy and low-alloy
Test matrix: 24 samples
Steel Gas 1 - 300°C Gas 2 - 300°C Gas 1 - 350°C Gas 2 - 350°C
P235GH PbCl2 , PbCl2+KCl PbCl2 , PbCl2+KCl PbCl2+KCl,
ZnCl2+PbCl2+KCl
PbCl2+KCl,
ZnCl2+PbCl2+KCl
10CrMo PbCl2 , PbCl2+KCl PbCl2 , PbCl2+KCl PbCl2+KCl,
ZnCl2+PbCl2+KCl
PbCl2+KCl,
ZnCl2+PbCl2+KCl
16Mo3 PbCl2 , PbCl2+KCl PbCl2 , PbCl2+KCl PbCl2+KCl,
ZnCl2+PbCl2+KCl
PbCl2+KCl,
ZnCl2+PbCl2+KCl
Material Fe Cr Ni Mn Si Mo C N Ti V Nb Al P S Cu Co
10CrMo9-10 95,96 2,24 0,45 0,25 1,00 0,07 0,01 0,01
P235GH 97,17 0,30 0,30 1,20 0,35 0,08 0,16 0,01 0,03 0,02 0,02 0,02 0,03 0,02 0,30
16Mo3 98,70 0,30 0,30 0,35 0,35 0,90 0,20 0,01 0,03 0,01 0,30
SEM images of 16Mo3 exposed to
PbCl2/KCl at 300 °C
no SO2
SO2
100µm
200µm
200µm
100µm
SEM images of 16Mo3 exposed to
PbCl2/KCl at 350 °C
no SO2
SO2
Corrosion test results
10CrMo16Mo3
P235GH
0.0
50.0
100.0
150.0
200.0
Pb
Cl2
KC
l+P
bC
l2
KC
l+P
bC
l2
KC
l+P
bC
l2+
Zn
Cl2
Pb
Cl2
KC
l+P
bC
l2
KC
l+P
bC
l2
KC
l+P
bC
l2+
Zn
Cl2
300°C 350°C 300°C 350°C
15%CO2, 5%O2, 15%H2O, restN2
15%CO2, 5%O2, 15%H2O,500ppm SO2, rest N2
110
223 8 13
20
140 130
2 7 119
120
182 7 9
Corrosion layer thickness
10CrMo 16Mo3 P235GH
µm
SEM/EDX analyses of 16Mo3 exposed
to PbCl2/KCl at 350°C. No SO2.
Cl K
O Pb Fe
Fe-chlorides may decrease the melting point (312 °C)
A ring of studied steel is located in the probe tip
Ring temperature can be adjusted
Weight loss → Annual tube wall thickness loss (mm/year)
Cross section analyses → Corrosion and deposit
chemistry
Corrosion probe:
full-scale measurements
Field tests – probe measurements cont.
After exposure…
Detached probe ringUnexposed ring Ring after oxide removal
Corrosion probe fitted with 3 sample rings
Courtesy of Tor Laurén, ÅA
Cross-cut Section and Studies in
Scanning Electron Microscope (SEM)
Cross-section SEM-image of 10CrMo
oxide layer3 – 6 µm
2 h
560 C
Risk of probe failure
Result after first trial (1h 40 min) and the new probe
Earlier trialat the sameboiler
Temperature loggings of test rings in corrosion
probe – steady in short-term
540
545
550
555
560
565
570
575
580
585
590
20:00 20:15 20:30 20:45 21:00 21:15 21:30 21:45 22:00
Tsp (ring1)Tlog (ring2)
Time
°C
540
545
550
555
560
565
570
575
580
585
590
24.4.2009 25.4.2009 26.4.2009 27.4.2009 28.4.2009 29.4.2009 30.4.2009
Tlog (ring2)
Tset (ring1)
°C
Date
Temperature loggings of test rings in corrosion
probe – sometimes difficult to control in long-term
0.0
0.5
1.0
1.5
2.0
2.5
3.0
0 50 100 150 200 250 300
Cal
cula
ted
Mat
eri
al L
oss
[µ
m/h
]
Exposure time [h]
10CrMo
Sanicro 28
Calculated Corrosion Rate as Function of Time and Material
Long Time Exposure Included (560°C)
Remarks on full-scale tests Give data under real conditions
Short time exposure can be used for calculating a corrosion index
With short time exposure it is possible to test a larger test matrix at less expenses and with less risk of probe failure
It is also possible to have a good control of test conditions at short time tests
A challenge to control temperature of several test rings on one probe with just one temperature controller
Different ring materials behaves different during long term exposure, which can make bigger differences in material temperatures on the same probe
For more reliable corrosion rate measurement longer exposure times than 2h is needed (at least in this type of boiler)
Camera experimental set up
Sanicro 63 with KCl @ 548oC, air ambient,
first 90 min (1 frame/2 min)
One test run
Additional....
Related vocabulary
Tensile strength, draghållfasthet, tensión de rotura, murtolujuus
– The maximum amount of tensile stress that material can take before failure
– Rm [MPa]
Yield strength, sträckhållfasthet, límite de fluencia, myötölujuus
– The stress at which a material begins to deform plastically (non-reversible)
– Rp0.2 [MPa]
Impact strength, slaghållfasthet, resistensia al impacto, iskulujuus
– the ability of a material to absorb shock and impact energy without breaking
– testing of susceptibility to brittle fracture
Creep, krypning, deformación por fluencia lenta, viruminen
– slow failure mechanism (at high temperatures), may take years to occur
– a time-dependent, permanent deformation that occurs under stress
Sensitization, sensibilisering, sensibilización, herkistyminen
– precipitation of carbides at grain boundaries, causing the steel to be susceptible to
intergranular corrosion or intergranular stress corrosion cracking
http://www.hindawi.com/journals/ijelc/2013/970835/fig10/
Creep
Sensitization
http://sirius.mtm.kuleuven.be/Research/corr-o-scope/hcindex2/rltd2.htmhttp://www4.hcmut.edu.vn/~dantn/TWI/jk81.html
Ferritic:
Body
centered
structure
Austenitic:
Face
centered
structure
http://tenerife-training.net/Tenerife-News-Cycling-Blog/wp-
content/uploads/2008/11/hcp-fcc-bcc-close-packed-structures.jpg