Hans Bengtsson, AZZ Welding Services, Sweden

Weld Overlay
High Temperature Corrosion in Biomass Combustion
World Bioenergy Conference
Hans Bengtsson
2014-06-05
www.azz.com/wsi-europe
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AZZ® at a Glance
AZZ® incorporated
HQ:
Fort Worth Texas, USA
Employees: 3,400
Locations:
49
Market cap: $ 1,05bn
AZZ is listed on the NYSE (AZZ)
Galvanizing
Electrical & Industrial
WSI/SMS
Markets: Refining, Nuclear, Fossil power, Waste to
Energy, Chemical/Industrial processing, Pulp/Paper,
Steel manufacturing processing
• Steel manufacturing
WSI Global Footprint
www.azz.com/wsi-europe
WSI
Innovative maintenance through automatic
weld repair solutions
• PQR/WPS development (600+ procedures)
• Welding plans (1500+) / repair plans
• 2013: 800 scopes executed in 35 countries
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Our capabilities
WSI is a specialized global service company offering innovative maintenance through
Automated Weld Repair Solutions that extend the lifetime and maximize the value of
our customers' assets in the Energy Industry
Qualified QA programs
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Requirements/technical review
WPS/PQR
Craft qualification certificates
Testing/inspection procedures and material inspection reports
Non-Nuclear Quality Assurance Programs
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NBIC certified R, S, U, U2
EN ISO 3834 – 3
ASME Section I and VIII, Div. 1 & 2
Ad 2000 Merkblatt HPO, TRD 201
Safety
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Automation that allows safety performance
PPE to reduce risk and fatigue
Highly skilled and qualified craft and qualified HSE managers Example quality
Certificate
Human performance-based prevention
Ad 2000 Merkblatt
Safety equipment and plans
HPO, TRD 201
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Our products
Field Services
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Waterwall overlay, re-overlay
Tie in
Shop fabrication
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Panel
Tubes
superheater, evaporator, etc
Welding engineers involved
in every step of our work
Inspection and maintenance program:
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QA Inspectors
Welding engineer
Field services – on site weld overlay
Tie-in finishing after replacement
www.azz.com/wsi-europe
Shop products - fabrication of front and floor tube panel
using UNIFUSE® 625/CS overlay tubes and membrane bar
Lakeside UK - Boiler, October 2013
UT Readings – Ultrasone Testing
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Biomass challenges
Biomass as collected/harvested and dried
Semi-processed biomass (pellets, etc)
The ready availability of waste biomass in many countries differs from one to other:
Straw
Differnt wood sources
Corrosion on biomass facilities has
turned into a real challenge. Every
plant shows different behaviour:
• Operational parameters
• Waste composition
• Relative new technology
Harvested product – depending
on the area: pine, eucaliptus,
olive, rice, etc
Black liqour or mixed fuel also
containing municipal waste, industrial
waste, animal residues, sewage, etc
www.azz.com/wsi-europe
Need to establish a relationship
between: manufacturers, end
user, maintenance providers, R&D
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Biomass fuel and boiler
Biomass fuel
• Chemical composition: agricultural wastes typically contain more alkali metals and
chlorine than conventional fuels
• Fuel characteristic: chips, rejected wood, straw, or fuel characteristic in general may
cause ashes leading to erosion
• Fuel procedence: harvested fuel as in pine and eucaliptus brings also sand, leading
to erosion
Corrosion
Chlorine causing accelerated
corrosion and fouling
www.azz.com/wsi-europe
Erosion
Every plant may have a dominant
wear phenomena, depending on
fuel, operational paramenters, etc
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Corrosion problem at waterwall and superheater
1) Chlorine, potassium, sodium and sulfur ashes deposited on pressure boundary
bringing heat steam to higher temperature levels
2) Surrounding corrosive flue gases
3) Operational temperature factors: depending on the temperature:
- Alkali salts molten on tube surface reacting with protective oxides
- Alkali salts forming low melting temp. eutectics with other ash materials
(ex. KCl is more corrosive than NaCl and has a lower melting temperature)
Improve metallurgy on
evaporator and SH tubes,
heat exchangers and hot
gas paths
Fuel characteristics:
Reduce chlorine content
by mixing or using
additives
Operational parameter:
Reduction of steam and
metal temperatures
Metal alloy for corrosion protection has to be commercial available, economically
efficient and easy to apply
www.azz.com/wsi-europe
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Protection for Waterwall
Welding overlay with alloy 625 ON-SITE
Welding overlay with alloy 625 on shop panels for replacement + on site TIE-IN
On site weld overlay on both
CS or on old 625 is possible
Old fatigued alloy 625 grinded off until smooth
surface, then automatic weld overlay
Panel replacement when tube
thickness is too low.
Replacement panels protected
Shop panel protection
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on-site installation + tie-in
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sCases from boilers in Sweden
Improve metallurgy on pressure parts shop and field both:
• Preventive
• Currative
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Showcase- MW Power- Vattenfall- Jordbro plant
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MW Power-Vattenfall Jordbro Biomass power station
Alloy 625 panel weld overlay field (~250m²) and shop (~80m²)
Project execution in September 2012
Main dimensional boiler data - NEW BUILD on-line June 2010
• Fuel: waste wood and forest residue
• 63MWth / 82 bar / +473 °C
• Boiler efficiency > 90%; Particulate emissions < 15mg/Nm3
• NOx-emissions < 70 mg/MJ
• Fuel need: 20.5 tons at 100% load
• Bottom fly ashes: 1.2 tons/hour
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The challenge
First major maintenance, July 2011: significant erosion/corrosion
tube wastage were detected down to 2,0mm
After the outage decision to upgrade CS water panels with 625
Revision 2012, WOL ~250m² projected, 9 days inside the boiler
Existing panels with < 4,0mm tube wall thickness replaced
~80m² panels provided with 625 shop overlay
www.azz.com/wsi-europe
Bubbling fluidized bed (BFB)
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Showcase- MW Power- Vattenfall- Jordbro plant
Scope of work
• Field overlay above refractory cutline up to elevation 18,5 m
• Replacement of ~80m² prior to weld overlay
• Target area 9,2 m to 18,1 m: ~250m² proj.
• Tie-in work
QA/QC – work conducted in accordance with
• EN 288
• EN-ISO 15614-1
• TUV Merkblatt 1156
Quality/Control
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Thickness on progress
Thickness
Chemistry: PMI
Sealing: copper sulfate
www.azz.com/wsi-europe
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Showcase- ENA AB-Enköping-Sweden
Background
•Boiler type:
•Steam pressure:
•Temperature:
•Production:
•Fuel:
Vibrating grate Burmeister & Wein Energy 80 MW.
101 bar
540C
District heating and power
Bio fuels mainly residues from logging, waste from sawmills and
paper mills
•Why Alloy 625 Weld Overlay?
The boiler has been boosted with approximately 10% RT chips since yr 2010.
Because of the lower price of RT-chips compared to other bio fuels, the plant has plans
to change to 100% RT chips. To make sure the tubes in the boiler can cope with the
increased use of RT-chips, improvement of tube metallurgy has to be carried out.
Alloy 625 panel weld overlay in field
2012 July:
~310m²
2013 July:
~250m2
www.azz.com/wsi-europe
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Showcase- ENA AB-Enköping-Sweden
Field weld overlay
www.azz.com/wsi-europe
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Protection for superheaters
Welding overlay with alloy 625 for straw and waste wood (temp. limited to 400-540C)
Welding overlay with alloy 310 for recovery boilers
Tig wash process for a smooth surface and to improve ductility. Superheater and or evaporator
bundle made with Unifuse® 360 tubes welded together + manual tie-in
No porosity, no disbonding due to metallurgical bond to base material
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Weld overlay corrosion
At high temperatures, Cr2O3 protective layer
is attacked / volatilized by molten salts, allowing
chlorine to attack (ex. as in T22)
Weld overlay to protect against salt deposit. WOL
Life depends on temperature:
• Corrosion (due to flue gas flow, salt deposits)
• Erosion /corrosion
Severe corroded T22 superheater tube in a
biomass boiler burning hog fuel
1,5 mm
Alloy 625
30 μm
CS tube
0,5 mm
cross section of a worn 625 overlay waterwall sample
www.azz.com/wsi-europe
SEM and EDX on localized corrosion pit on alloy
625 overlay to understand chem. compositions at
different chloride complex phases
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SEM and EDX results
The chemical compositions (wt%) at different phases are:
1: 68% Pb, 11% Mo, 6% Cr, 3% Fe, 3% Ni, 4% S, 3% Cl, and trace elements
2: 63% Pb, 9% S, 6% Cl, 7% Cr, 5% Mo, 2% Fe, 3% Ni, 2% Na, and trace elements
3: 31% Cr, 24% Ni, 2% Fe, 27% Pb, 6% Zn, 5% S, 1% Cl, and trace elements
4: 32% Pb, 14% Cr, 8% Ni, 5% Fe, 10% Mo, 7% Zn, 9% Cl, 5% K, 3% Na, 3% S, and trace elements
5: 52% Pb, 11% K, 13% S, 7% Cl, 6% Mo, 4% Na, 4% Cr, 2% Ni, and trace elements
6: 34% Ni, 23% Cr, 3% Fe, 23% Pb, 7% Zn, 6% Mo, 2% Cl, and trace elements
7: 49% Pb, 12% K, 3% Na, 13% S, 7% Cl, 5% Cr, 6% Mo, 3% Ni, and trace elements
8: 30% Cr, 28% Pb, 13% Ni, 11% Zn, 7% Mo, 6% Cl, 2% K, and trace elements
9: 26% Pb, 22% Ni, 16% Cr, 11% Zn, 7% Cl, 5% Mo, 7% Na, 3% Fe, and trace elements
10: 27% Pb, 19% Cr, 14% Ni, 13% Zn, 9% Mo, 5% Cl, 4% Na, 2% K, and trace elements
11: 54% Ni, 24% Cr, 6% Pb, 5% S, 6% Fe, and trace elements
12: 27% Cr, 19% Ni, 19% Pb, 15% Zn, 9% Mo, 5% Cl, 2% K, 2% Fe, and trace elements
The composition of the deposit and corrosion
products can vary significantly from plant to
plant. In this case, heavy metal corrosion deposits
(Zn and/or Pb) suggest that the corrosion mechanism is
fluxing by molten chloride salts
www.azz.com/wsi-europe
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Showcase- MW Power- Vattenfall- Jordbro plant
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Words from the CUSTOMERS
"Solid and professional project execution by WSI"
WSI referens project Nordic 2004 – up to day
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www.azz.com/wsi-europe
Södra Cell AB
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Valmet (Metso) Power AB•
Foster Wheeler Oy
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BW Völund
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Andritz
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Rautaruki Steel Oy
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Billerud AB
INEOS A/S
Fortum Högdalen AB
Renova
Boliden Mineral AB
Halmstad Energi & Miljö
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Vattenfall
Euromaint
ENA Energi
SYSAV
Coor Service Management
E.ON Händelöverket
Umeå Energi
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Future
Inconel 625 limitation:
• Metal temperature
• Erosion/Abrasion properties
WSI has a R&D development program for alternative alloys
Questions!
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THANK YOU!
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