thermal plant boiler presentation
DESCRIPTION
A thermal plant Boiler detailTRANSCRIPT
COATING TECHNOLOGIES FOR BOILERS IN
POWER PLANTSSRINIVASAN SHANKAR- SHANKAR ASSOCIATES
BoilersSuper heaters
COATING TECHNOLOGIES FOR
CORROSION PROTECTION OF
BOILERS
BACKGROUND• Increase in demand for energy leads to higher operating temperature and
more demanding operating conditions in boilers
• As a result higher erosion/corrosion rates of metallic components of
boilers for plant is being observed
SOLUTION• Coating technologies are flexible solutions to protect the
different zones of the plant with the most cost-effective
approach
Coating tree
On site
During manufacturing
Erosion resistance
Boiler
High temperature
(< 450 °C)
Very High temperature
(>450°C)
Erosion
(Blowers)
Superheaters Grid
Water jackets
Themocouple pits
Ancillary components
Boilers
COATING TECHNOLOGIES FOR
CORROSION PROTECTION OF
BOILERS
COATING TECHNOLOGIES FOR
CORROSION PROTECTION OF
BOILERS
Super heater (during
manufacturing)
Thermocouple pits
Metallurgical bonding
Low dilution (< 2%)
Advanced materials available
Laser welding
Boiler (on-site and during
manufacturing)
Super heater (during
manufacturing)
Water jackets
High Thickness (>2mm)
Metallurgical bondingArc welding
Boiler (on-site and during
manufacturing)
Superheater (no bending)
High deposition rate
Suitable for on-site applications
Large selection of material
available
Thermal spray
COATING TECHNOLOGIES
COATING TECHNOLOGIES FOR
CORROSION PROTECTION OF
BOILERS
Blowers
Super heater
Grid components (Fluidized
bed)
•For specific applications
•Not weldableHard material•CrC – NiCr
•Stellite 6
Super heater (during
manufacturing)
Thermocouple pits
•Advanced materials
•Resistance at higher
temperature (compared to
IN625)
•Difficult to weld
Co-Cr-Ni-Al
Boiler (on-site and during
manufacturing)
Super heater (during
manufacturing) T <450 °C
•Standard, proven materials
•Large reference lists
•Easy-to-weld material
Ni-Cr-Mo•IN 625
•Hastelloy
MATERIAL SELECTION
COATING TECHNOLOGIES FOR
CORROSION PROTECTION OF
BOILERS
THERMAL SPRAY
• Two processes: HVOF and Wire Spray
• Flexible technologies easy to transfer on-site
• Large selection of applicable materials
• “Cold”, robust application process
• High productivity, both automatic and manual
• Lower cost
THERMAL SPRAY
TECHNOLOGIES FOR CORROSION
PROTECTION OF BOILERS
THERMAL SPRAY• The intrinsic limit of thermal spray coatings is the
residual porosity of the deposited layer.
IMPROVING STRATEGIES
• Porosity reduction through technology development
(HVOF vs. Wire Spray)
• Porosity sealing
TS Processes: a comparisonTS Processes: a comparison
0
1000
2000
3000
4000
0 200 400 600
Velocity (m/s)
Tem
pera
ture
(C
°)
arc
flame
VPS
HP/
HVOF
APS
Wire SprayWire Spray
HP/HVOFHP/HVOF20 lbs/hr (5 kg/hr)
Powder InputKerosene
Oxygen
Water
Cooling
Water
Cooling
Particle
3300-3900 FPS
(1000-1200 m/s)
Gas
1800-2000 m/s
3100 K
(a.u
.) Temperature
Velocity
Pressure
Chamber
Nozzle
Barrel
3100 K
2500 K
1800 m/s
1 MPa
0.13 MPa
Zone of powder
injection
TS Processes: a comparisonTS Processes: a comparison
• Not suitable for manual operation
• More complex to install on site
• More expensive
• Higher porosity• Lower bond strength
Limitations
• Better bond strength• Very low porosity
• Low running cost• High productivity• High thickness• Easy operation on
site• Suitable for manual
operation
Advantages
>7010-30 Tensile bond strength (MPa)
< 15 to 10Coating porosity (%)
28002500Gas stream temperature (°C)
400-700120-200Particles velocity ( m/s )At the impact
>2000450Gas stream velocity ( m/s )
HP/HVOFWire FlameThermal spray process
TS Processes: a comparisonTS Processes: a comparisonMicrostructure of as coated material Microstructure of as coated material –– IN625IN625
High Pressure Wire Spray HVOF
TS Processes: a comparisonTS Processes: a comparisonMicrostructure after exposure in boilerMicrostructure after exposure in boiler
A) WIRE SPRAY IN 625A) WIRE SPRAY IN 625
At 400 °C – 1000 h At 500 °C – 1000 h
TS Processes: a comparisonTS Processes: a comparisonMicrostructure after exposure in boilerMicrostructure after exposure in boiler
B) HVOF IN 625B) HVOF IN 625
At 400 °C – 1000 h At 600 °C – 1000 h
THERMAL SPRAY TECHNOLOGIES FOR
CORROSION PROTECTION OF BOILERS
SealSeal WWWW
• IN625 layer deposited
with High pressure wire
spray
• High temperature sealing
with ceramic aluminum
slurry (sacrificial layer)
• Max. metal temp.: 300 °C
THERMAL SPRAY TECHNOLOGIES FOR
CORROSION PROTECTION OF BOILERS
SEAL WW
• High Pressure wire spray is a proven technology able toproduce reproducible coatingsalso in harsh condition
• Slurry sealing is fast, unexpensive and can bereapplied at each plant stop
THERMAL SPRAY TECHNOLOGIES FOR
CORROSION PROTECTION OF BOILERS
SEAL WW APPLICATIONS
Flameseal WW has been applied on waterwalls of power plant boilrs
• More than 5000 m2 in exercise
• 150 – 1500 ton/day
• Tsteam : 240 – 280 °C
• Tfumes : 700 – 950 °C
• Metal waste (uncoated): 0.3 – 0.7 mm/y
• Metal waste (coated): < 50 µm/y
THERMAL SPRAY TECHNOLOGIES FOR
CORROSION PROTECTION OF BOILERS
Uncoated pipes Seal WW Coated pipes
-3
-2,5
-2
-1,5
-1
-0,5
0
0,5
1
0 2 4 6
Operating years
Thic
kness losses
(m
m)
Corrosion of tubes
protected with
Flameseal
Corrosion of
uncoated tubes
-3
-2,5
-2
-1,5
-1
-0,5
0
0,5
1
0 2 4 6
Operating years
Thic
kness losses
(m
m)
Corrosion of tubes
protected with
Flameseal
Corrosion of
uncoated tubes
THERMAL SPRAY TECHNOLOGIES FOR
CORROSION PROTECTION OF BOILERS
Micrographic examination of a
scale of coating extracted after 4
years of service in a Municipal
waste boiler operating at 30 bar.
No corrosion in the IN 625
layer
Limited corrosion growth at
the interface
THERMAL SPRAY TECHNOLOGIES FOR
CORROSION PROTECTION OF BOILERS
AlloyAlloy HH
• Corrosion resistant layer
deposited with HVOF
• Large selection of material
applicable
• No sealing required
• Max. metal temp.: 400 °C
THERMAL SPRAY TECHNOLOGIES FOR
CORROSION PROTECTION OF BOILERS
ALLOY H
• HVOF produces thermal spray coatings of superior quality
• With optimized equipment can beapplied on very large surfaces as, forexamples, on boiler panels prior toassembly of the boiler
• It is also possible to install on site HVOF equipment, if boiler dimensions are large enough
COATING TECHNOLOGIES FOR
CORROSION PROTECTION OF BOILERS
Super heater (in blower area)
Grid components
•For specific applications
•As overlay coating on Alloy
H525
Hard material•CrC – NiCr
•Stellite 6
Boiler panels for high S fuel
Power plant boilers
• Composition similar to
Hastelloy C276
•Ni-Cr 50-50
Alloy H 555
Alloy H5050
Boiler panels
Water jackets
• Composition similar to IN 625Alloy H 525
Alloy H Applications
THERMAL SPRAY TECHNOLOGIES FOR
CORROSION PROTECTION OF BOILERS
• 320 MW ENEL boilers for use with S-
containing fuels (i.e. ori-mulsion) and
reducing combustion conditions
• No thickness losses after 5 years
operations
ALLOY H5050 APPLICATIONS
CLADDING TECHNOLOGIES FOR
CORROSION PROTECTION OF BOILERS
CLAD
• Clad is a family of coating produced by arc cladding
• Proven technology possible to transfer on-site
• Metallurgical bonding
• Standardized process, widely accepted by the
industry
• Possible both automatic and manual application
• Temperature resistance up to 400-450 °C
CLADDING TECHNOLOGIES FOR
CORROSION PROTECTION OF BOILERS
• A large reference list of CLADapplications is available, mainlyusing IN 625 alloy; CLAD hasbeen applied both in boilers and in superheaters
• Application costs can be reducedplanning the cladding during the construction of the components
CLAD APPLICATIONS
CLADDING TECHNOLOGIES FOR
CORROSION PROTECTION OF BOILERS
Clad Coated Panel
area in boiler :
•Tsteam: 250 °C
•Tfumes: 1020 °C
Position: at the end of
the postcombustion
(Picture taken after 2 years in
service)
CLADDING TECHNOLOGIES FOR
CORROSION PROTECTION OF BOILERS
APPLICATIONS
Clad has been applied on superheater and boilers:
• 150 – 1500 ton/day
• Tsteam : 350 – 450 °C
• Tfumes : 700 – 950 °C
• Metal waste (uncoated): 1 – 3 mm/y
• Metal waste (coated): < 0.1 – 0.3 mm/y
CLADDING TECHNOLOGIES FOR
CORROSION PROTECTION OF BOILERS
Corrosion phoenomena
on clad IN625:
Superheater tube
operating at metal
temperature of 520 °C
COATING TECHNOLOGIES FOR
CORROSION PROTECTION OF BOILERS
Micrographic examination of a 2-
layers coating composed by:
•1 mm Clad
•0.5 mm Seal
after 1000 h corrosion test @ 500°C
No corrosion at the
interface of the two layers
No corrosion growth at the
interface with base metal
Large selection of materials available as top coat !
COATING TECHNOLOGIES FOR
CORROSION PROTECTION OF BOILERS
EROSION PROTECTION OF BLOWERS AND BURNERS AREA
Flam H 834 is the result of exhaustive research in which chemical composition and coating
process are optimised to reach maximum microhardness values.
This process is suitable for pieces subject to severe high temperature erosion. Blowers of
coal burning power plants are coated with Flam H 834
CHEMICAL COMPOSITION
Chrome Carbide (Cr3C2) 75%
Nichel Chrome 25%
TECHNICAL PROPERTIES
Excellent erosion resistance
Excellent corrosion resistance at high
temperature
PHYSICAL PROPERTIES
Microhardness (HV 300) 800÷÷÷÷1000 HV
Porosity < 1%
Bond strength > 60 Mpa
LASER TECHNOLOGIES FOR
CORROSION PROTECTION OF BOILERS
LasercladLaserclad
• Advanced alloy layer deposited
with laser cladding technology,
developed by CESI
• Low dilution – fine microstructure
– metallurgical bonding
• Suitable for superheaters and
critical parts of boilers
Ni-Cr-Co alloy laser cladding on
thermocouple sheaths of incinerators for
high temperature operation
Laser cladding of Co-Cr-Ni alloy (28%-29%-bal.) on thermocouple
sheaths: sheath diam. 22 mm; coated length 550 mm; two layers
laser cladding; cladding average thickness 1.5 mm
LASER TECHNOLOGIES FOR
CORROSION PROTECTION OF BOILERS
Superheater bundlemanufactured withLaserclad tubes
Thermocouple pits
coated with Laserclad
LASER TECHNOLOGIES FOR CORROSION
PROTECTION OF BOILERS
Transition between
coated and
uncoated area in a
superheater tube
(after 6 months):
•Tsteam: 350 °C
•Tfumes: 1020 °C
COATING TECHNOLOGIES FOR
CORROSION PROTECTION OF BOILERS
COATING TECHNOLOGIES - SUMMARY
Boilers (on site and
manufacturing)
SH
1.2 m2/shift2450Clad
Boilers
(manufacturing)
SH (no bending)
8 m2/shift0.4350 -
400Alloy H
Boilers
Optimal on site
10 m2/shift0.5300 Seal WW
ApplicationsNominal
Productivity
(for one torch)
Thickness
(mm)
Max. T
( °C)
Technology