ash related challenges from a boiler manufacturer’s point ...users.abo.fi/maengblo/fpk_ii_2016/ash...
TRANSCRIPT
Ash related challenges from a boilermanufacturer’s point of view
FPK II course 2016Sonja Enestam
2
Contents� Valmet Technologies� Fuels
– Trends– Challenges
� Ash related challenges– Fouling and slagging– Bed agglomeration– Corrosion
� The significance of corrosion
� How do we tackle issues of corrosion?- Questions and solutions
� Case Naantali
ValmetLeading global developer and supplier ofprocess technologies, automation andservices for the pulp, paper and energyindustries
Converting renewable resources intosustainable results
2016 © Valmet4
End-products
Services
Automation
Technologies
Rawmaterials
Customerindustries
Heat Electricity Chem pulpDiss pulp Mech pulp Paper Board Tissue
Biogas Biofuels Biochemicals New paper gradesBiomaterials
Energy production Biofuel refining Pulp Paper
Waste Recycled paper
Pulp
Agro Wood
Energy Paper
December 31 2013 © Valmet |5
Valmet’s Road to Becoming a Global MarketLeader
1942Rauma-Raahe
1951Valmet
1951-1995Several M&As
1968-1996Several M&As i.e.1986 KMW1987 Wärtsilä paper finishing machinery1992 Tampella Papertech
1999Metso createdthrough merger ofValmet and Rauma
Key acquisitions2000 Beloit Technology2006 Kvaerner Pulping
Kvaerner Power2009 Tamfelt
End of 2013Demerger toValmet and Metso
1797 Tamfelt1856 Tampella1858 Beloit1860 KMW1868 Sunds
Defibrator
2016
Unique offering covers process technology,automation and services
© Valmet6
Paper• Recycled fiber lines• Tailor-made board and paper machines• Modularized board and paper machines• Tissue production lines• Modernizations and grade conversions• Standalone products
Focus in customer benefits
Customer
Pulp and Energy• Complete pulp mills• Sections and solutions for pulp production• Multifuel boilers• Biomass and waste gasification• Emission control systems• Biotechnology solutions e.g. for
producing bio fuels
Automation• Distributed control systems• Quality control systems• Analyzers and measurements• Performance solutions• Process simulators• Safety solutions• Industrial Internet solutions
Services• Spare parts and consumables• Paper machine clothing and
filter fabrics• Rolls and workshop services• Mill and plant improvements• Maintenance outsourcing• Services energy and
environmental solutions
Key figures 2015
2016 © Valmet7
Net sales by areaNet sales by business lineOrders receivedEUR 2,878 millionNet salesEUR 2,928 millionEBITA before NRI1EUR 182 millionEBITA margin (before NRI1)6.2%Employees12,306Market position#1-2 Services#1-3 Pulp & paper automation#1-2 Pulp#1-3 Energy#1 Paper, board, tissue
39%
8%31%
23%
ServicesAutomationPulp and EnergyPaper
21%
11%
45%
10%
13%
North AmericaSouth AmericaEMEAChinaAsia-Pacific
1) NRI = non-recurring itemsStable business = Services and Automation business linesCapital business = Pulp and Energy, and Paper business lines
20168
Valmet location
© Valmet
• Over 100 service centers• 80 sales offices• 34 production units• 16 technology centers
Strong global presence close to our customers140 locations in 33 countries
Our pulp and energy technology offering
2016 © Valmet9
Pulp Recovery Energy Biotechnologies
400 boilers and environmentalprotection systems delivered
300 complete fiber lines and 350recovery islands delivered
• Wood handlingsystems
• Cooking systems• Complete fiber lines• Pulp drying systems
• Evaporation systems• Recovery islands
• Circulating fluidizedbed boilers (CYMIC)
• Bubbling fluidizedbed boilers (HYBEX)
• Biomass and wastegasification
• Oil and gas boilers• Waste heat recovery• Air pollution control
systems
• Pyrolysis solutions forbio-oil production
• LignoBoost for ligninextraction
• Steam treated pelletsproduction lines
• Biomass prehydrolysisfor further refining tofuels or chemicals
Fuel use in electricity and heat production inFinland 2012–2013
9 March, 2016 © Valmet | Author / Title10
DD
DD
DD
Source: Statistics on production of electricity and heat, Statistics Finlandand Electricity statistics, Finnish Energy Industries
Com
bust
ion
Bio-energy technologies are in transition
11
heat
steamCombustion
electricity
waste
wood
peat
fossil
New bio products
agro
heat
steam
Bio gas
Bio oil
Bio coal
Lignin
Gasification
Pyrolysis
Torrefaction
LignoBoost
Combustion
Fuel
hand
ling
and
pre
-pro
cess
ing
electricityagro
waste
wood
peat
fossil
Chemical orbiochemical
Ethanol
New bio products
12
The trend: From coal and peat to biofuels andrecycled fuels
Coal Peat
Wood chips
Forest residueRecycled fuel
Agro
13
Parameters steering the fuel choiceBalancing economy and sustainability
EconomyEnvironmental regulations-CO2 trade-green energy benefitsEthical aspectsFuel availabilityPriceFuel quality andcombustibility-emissions-corrosion-ash quality-bed sintering
14
Fuel
pric
e[€
/MW
h]
Level of challenge
1 5 10
The fuel dilemma
Agro biomass• Straw• Sunflowerhulls• Corn Stover• Miscanthus
Wood biomass• Northern wood• Pulp&Paper
sludges• Wood pellets
•
Recycled fuels• Packaging
waste• Recycledwood
Fast growing wood• Willow
Eucalyptus•
FossilHard coal•
Fuel properties
� Heating valueMoisture
� Physicalcharacteristics
� Ash content
� Ash composition– Cl, S, Ca, K, Na, Pb, Zn,
P…
15
• Furnace dimensions• Air / fuel ratio• Use of flue gas recirculation
S.Enestam
• Fuel feeding• HSE
• Fouling and slagging propensity• Ash handling
• Fouling propensity• Corrosivity• Bed agglomeration• Emissions• Ash quality
Fuel related challenges
� Fuel feeding� Agglomeration� Slagging & Fouling� Corrosion� Ash quality� Emissions
16S.Enestam
17
Low melting ash
Low melting silicatesformed with the bed
material
Fouling
Corrosion
Bed sintering
Na+
Slagging
The influence of fuel composition on thecombustibility
K+
Low melting ash
Na+
Zn2+
Pb2+ Cl-
Corrosive environment
S
Ca
S.Enestam
Fouling
Bed sintering
Slagging
Corrosion
18
Typical analyses of different types of fuelsminimum – average – maximum
Peat Woodchips
Scandinavian
Bark Demolitionwood
SRF AGRO(Straw, Barley)
Moisture [wt-%] 10– 45 – 65 10 – 45 – 60 0.3 – 50 – 65 5 – 10 – 30 5 – 35 – 55 5 – 10 – 20
Ash(815C)
[wt-% ofds] 2 – 6 – 18 0.2 – 1.5 – 4 0.1 – 4.0 – 13 1 – 3.5 – 13 10 – 18 – 26 4 – 6,5 – 12
HHVdry [MJ/kg] 17 – 22 – 23 19 – 21– 26 15.5 – 20 – 33 18 – 19.5 – 21 15.0 – 19.5 – 25 16.5 – 18.5 – 19
LHVwet [MJ/kg] 5 – 11 – 21,5 1.5 – 10 – 17 4.1 – 9.1 – 20.9 13 – 14.5 – 15.5 8.5 – 11 – 17 13.5 – 15 – 15,5
S [wt-% ofds] 0.1 – 0.2 – 0.8 0.01 – 0.04 –
0.09 0.01 – 0.05 – 0.2 0.01 – 0.07 – 0.15 0.1 – 0.5 – 0.7 <0.08 – 0.08 – 0.2
Cl [wt-% ofds]
0.02 – 0.04 –0.25
<0.01 – 0.01 –0.01
<0.01– 0.07 –0.32 0.01 – 0.07 – 0.26 0.2 – 0.7 – 1.6 0.15– 0.3 – 1
Na [mg/kg ofds] 25 – 580 – 2500 5 – 160 – 520 5 – 380 – 1520 300 – 850 – 1800 3050 – 7800 –
12000 < 200– 240 – 1000
K [mg/kg ofds]
150 – 850 –4200 10 – 850 – 1900 25 – 1700 – 4500 400 – 850 – 2350 2800 – 4800 – 6600
6000 – 12 000 –22 000
Pb [mg/kg ofds] 2 – 8 – 30 <5 1 – 10 – 30 10 – 150– 650 1 – 50 – 110 < 5
Zn [mg/kg ofds] 5 – 30 – 150 30 – 35 – 40 100 – 1600 –
5800 100 – 1800 – 12000 200 – 400 – 600 30 – 35 – 40
Fuel related challenges
19
� Fuel feeding� Agglomeration� Slagging & Fouling� Corrosion� Ash quality� Emissions
Agglomeration mechanism
= fuel =ash =sand
21
Agglomeration mechanism
� Bed particle (B)� Sticky material (A) consists mostly of
K, Ca, Si, Na� The melting temperature of the
sticky material is < 800 °C
B
B
A
Bed Agglomeration -> solutions
� Inert bed material: AggloStop� Bed temperature: < 750 °C� Bed material removal� Additives
Date Author Title22
Ref. Piotrowska, Åbo Akademi
Sand
Sticky silicatesand/or
phosphates
K SiBed Agglomeration
Solution� Bed temperature: < 750 °C
Ref. D.Lindberg, Åbo Akademi University, 2013
Na
06.02.2013
24
AggloStopDiabase as an alternative bed material
Mineral Diabase B(wt-%)
Natural sand A(wt-%)
Quartz (SiO2) < 0,1 40
Feldspar (KAlSi3O8) - 20Feldspar (NaAlSi3O8+CaAl2Si2O8) 50 40
Pyrokseeni (XYSi2O6) 25 -
Biotite(K(Mg,Fe)3(AlSiO10)(OH)2)
6 -
Olivine (Mg,Fe)2SiO4) 15 -
Magnetite (Fe3O4) 4 -
Fouling & slagging
25
Slagging
Fouling
26
Influence of fuel composition and processconditions
� Amount of ash in the fuel and composition of the ash– Ash melting behavior => stickiness of the ash– Condensable matter
� Increased temperature => increased slagging and fouling, oftencaused by increased load
� Often leads to a ”snow ball” effect progressing with the flue gas flow inthe boiler
� Swirls caused by the air feeding system can cause areas with highslagging in the furnace– CFD modelling
� The fuel feeding system in combination with the air feeding can movethe combustion too high up in the furnace– Both systems can be optimized with CFD modelling
27
Effects of fouling
� Reduced heat transfer => Decreased efficiency of the boiler� Increased need for sootblowing (steam consumption)� Increased corrosion risk
– Without deposits usually no corrosion– All deposits are not corrosive
� Plugging of the boiler– Unavailability
� Partial plugging leads to increased flow velocity which in turn leads toerosion– Tube leakages– Unavailability
© Valmet /
28
Avoiding slagging and fouling� Correct boiler design based on the fuel properties
– Empty pass in waste boilers– Correct placement on heat exchangers– Tube spacing of heat exchangers
� Understanding of fuel ash properties– Avoiding difficult fuel mixtures at high loads– Avoiding certain fuel fuels
� Limiting the furnace temperature– By recirculating flue gas
� Furnace cleaning– Avoiding the snow ball effect
� Optimization of sootblowing– Sufficient amount of superheaters– Right type of superheaters– Sufficient soot blowing, 1/d -> 1/ shift
� Boiler cleaning at annual shut down© Valmet /
29
Corrosion
30 S.Enestam
Change ofmaterial
→ Price
Fuel mixtureBoileravailability
→ Economy
Superheaterplacement
→ Design
Final steamtemperatureand pressure
→ Efficiency
The influence of corrosion on boiler technologyand plant efficiency
Different corrosion types – BFB boilers
Date Author Title31
Alkali chlorideinduced corrosion
Heavy metal inducedcorrosion
Dew pointcorrosion
Erosion-corrosion
Erosion-corrosion
Different corrosion types – CFB boilers
Date Author Title
INTERNAL
32
Erosion-corrosion
Alkali chlorideinduced corrosion
Alkali chlorideinduced corrosion
Heavy metal chlorideinduced corrosion
Dew pointcorrosion
Corrosion types – Recovery boilers
33
Alkali chlorideinduced corrosion
Sulphidaton
Acidic sulphates
34
Corrosionmechanisms
Protectiveness of the oxide layer
Ref: B-J Skrifvars9 March, 2016 © Valmet | Author / Title35
Steel
Compact steel-oxide layer- protects from further oxidation- requires the presence of oxygen
Steel
Does not work if- the steel-oxide layer breaks- oxygen is abscent- the steel-oxide layer is porous
Cr2O3 Fe2O3(Cr,Fe)2O3
protectivep-type
poorly protectiven-type
The oxide formed on FeCr steel consists of a corundum-type solid solution,(Cr, Fe)2O3. The Cr/Fe ratio determines whether it is protective (as Cr2O3)or poorly protective (as Fe2O3).
The properties of the protective oxide
Reactions that convert protective chromium-rich oxide to non-protectiveiron-rich oxide play a key part in high temperature corrosion…
Ref.: HTC, Chalmers
Corrosion mechanisms
Gas phase corrosion
Solid phase corrosion
Molten phase corrosion
37
© Metso38
WIND
Solidparticles
Moltenparticles
Gaseousparticles
LEE
Corrosion mechanisms
SH tube
Gas phase corrosion
• Gas molecules reacting directly with the tube material• No condensation due to• tube temperature• concentration in the gas
• HCl, H2S, Cl2, KCl, NaCl, PbCl2 ,ZnCl2
Cor
rosi
onra
te,i
py
0.240”
0.180”
0.120”
0.060”
480 570 660 750 840 930Temperature, OF
CS304LSS
H2S induced corrosion
39
Molten phase corrosion
40
• Molten deposit on the tube surface
• Better contact with tube surface
• Faster reaction
• Catastrophic corrosion rates
• Occurs when Tmat > T0 ofthe deposit
• Rule of thumb: Tmat< T0
Thethicknessof the oxide,mm
Steel: T91Time: 168 h
450 500 525 550 575 600
0102030405060708090
100
Ash 5, T0= 884oCAsh 6, T0= 834oC
Ash 7, T0= 625oCAsh 8, T0= 526oC
Ash 9, T0= 621oCAsh 10, T0= 522oC
No AshTemperature, oC
The influence of melt formation in the deposit
41
Method
Condensation behavior of zinc and lead, S.Enestam201042
0
10
20
30
40
50
60
70
80
90
100
100
150
200
250
300
350
400
450
500
550
600
650
700
750
800
850
900
950
1000
Am
ount
ofm
elt[
wt%
]
Temperature [°C]
Alkali saltAlkali salt + PbCl2Alkali salt + ZnCl2
(Na,K,SO4,Cl)
The influence of deposit composition on ashmelting behaviour
Solid phase corrosion
• Solid deposit reacting with the tubematerial• Condensed material• Impacted material• KCl, NaCl, PbCl2 ,ZnCl2,
sulphates, sulphides, carbonates
43
T0= 801°CT0= 771°C
160
140
120
100
80
60
40
20
0450 500 525 550 575
600
Thethicknessof the oxide,mm
Temperature, oC15: KCl
17: NaCl
Steel: T91
Solid phase corrosion
44
Method
Corrosion mechanisms – alkali chloride induced corrosion
2012 /S.Enestam45
Metal
Fe2O3
KCl
FeCl2
Fe2O3
KOH
Cl-
HCl
Metal
Cr2O3
KCl
MeCl2
Me2O3Cl-
Me = Cr, Fe
K2CrO4
HCl
Fe2O3 Cr2O3
304L exposed in the presence of KCl and H2O at600°C for 1hr
KClFe2O3
K2CrO4
Fe2O3 (Cr,Fe)2O3
Ref: Jonsson et al, Oxidation of metals, 72:213-239 (2009)
Corrosivity of alkali chlorides on two steels
47
No salt
NaClKCl0
20
40
60
80
100
450 500 525 550 575 600
Cor
rosi
onpr
oduc
tlay
er[µ
m]
T[C]
102 186
No salt
NaClKCl0
20
40
60
80
100
450 500 525 550 575 600
Cor
rosi
onpr
oduc
tlay
er[µ
m]
T[C]
10CrMo9-10
AISI 347
S.Enestam
NaCl and KCl equally corrosive onthe tube surface
Cr2O3 more protectivethan Fe2O3
Steel composition
48
Grade Category Cr Mo Ni Others Relativepricea
Typical use(boiler part)
10CrMo9-10 Low alloy 2.25 1 - 2.3 Superheaters
AISI 347 Standardstainless steel 19 - 10 Nb 6.7 Superheaters
a May 2011
S.Enestam
No salt
ZnOPbO
KClZnCl2
PbCl2
0
20
40
60
80
100
120
140
250 300 350 400 450 500 550
Cor
rosi
onpr
oduc
tlay
er[μ
m]
T[°C]
Corrosion test: Low alloy steel 10CrMo9-10The influence of Pb and Zn
49
356384240
S.Enestam
Different corrosion types – CFB boilers
Date Author Title
INTERNAL
50
Erosion-corrosion
Alkali chlorideinduced corrosion
Alkali chlorideinduced corrosion
Heavy metal chlorideinduced corrosion
Dew pointcorrosion
Dewpoint corrosionDewpoint of acidic gases
1
10
100
1000
0 20 40 60 80 100 120 140 160 180 200
Dewpoint temperature (°C)
Con
cent
ratio
n(p
pm)
H2SO4HCl
HNO3
Dewpoint corrosion
� Dewpoint corrosion is usually caused by sulfuric acid (H2SO4), since ithas the highest dewpoint of all the acid gases in the flue gases– Dewpoint between 120 - 180 °C with normal fuels– Other acids condense only at temperatures below 80 °C
� The concentration of condensing sulfuric acid depends on thetemperature and moisture content– Concentration typically between 65% and 75%– Temperature close to boiling point
� Sulfuric acid condensed at dewpoint is very corrosive� Alternative corrosion mechanism: corrosion caued by hygroscopic
salts such as CaCl2, ZnCl2, NH4Cl
© Metso
The corrosion rate is influenced by
53
– Flue gas composition
Tflue gas
– Flue gas temperature– Solid and/or molten fly ash– Deposit composition
Steel grade
Material temperature
The corrosivity of theenvironment
Tmat
The corrosivity of theenvironment
54
Technical solutions
Corrosion -> solutions
1. Superheater material and temperature- Price v.s. life time v.s. efficiency and profitability
- Coatings, overlay weld. E.g. Ni based coatings in waste combustion
2. Tube shields – most corrosive locations
3. Superheater location
4. Superheater design
5. Fuel mixture: Co-firing or additives
6. Gasification
55S.Enestam
Superheaters
565.5.2011 / REt
Water-steam cycle, preassure vessle weight aprox.600tn, 100km tubing
SSHPSH2PSH1
Boiler bank
Eco3Eco2Eco1
PAH3SAH3SAH2PAH2PAH1SAH1
TSH
28/10/2011
57
Kymin Voima,Kuusankoski,Finland
Steam 269 MWth107 kg/s114 bar541 °C
Fuels Bark, forest residue,sludge, peat, gas, oil
Start-up 2002
HYBEX boilerBubbling Fluidized Bed (BFB) technology
INTERNAL
HYBEX boilerBubbling Fluidized Bed (BFB) technology
INTERNAL
Furnace:
• Width 12 m
• Depth 11 m
• Height 36 m
Furnace membrane tubes 26 km
Superheater tubes 35 km
Economizer tubes 15 km
Connection tubes 2 km
Weight of pressure parts 1600 ton
Typical boiler materials
60
a May 2011 c Modified with Nb
Grade Category Cr Mo Ni Others Relativepricea
Typical use(boiler part)
P265GH Non-alloy - - - 1.0 Eco, furnace, boilerbank
16Mo3 Low alloy - 0.3 - 1.1 Furnace,boiler bank
13CrMo44 Low alloy 1 0.5 - 1.8 Superheaters
10CrMo9-10 Low alloy 2.25 1 - 2.3 Superheaters
X10CrMoVNb9-1 High alloy ferritic 9 1 V, Nb 5.4 Superheaters
AISI 347 Standard stainlesssteel
19 - 10 Nb 6.7 Superheaters
AISI 310 (Modc) High Cr stainlesssteel
25 - 21 N, Nb 10.0 Superheaters
Incr
ease
dco
rros
ion
resi
stan
ce
The influence of Tfg, Tmat and material on corrosion
Date Author Title61
Tfg ≈ 775 °C
Tfg ≈ 1100 °C
Removable cladProbe body Air in
Air out
Test materials
The influence of Tfg, Tmat and material on corrosion
Date Author Title62
493 °C
533 °C
572 °C
495 °C
533 °C
572 °C
Probe 1 (WIND )Stainless steel
Probe 2 (WIND)Stainless steel
0, no corrosion
0, no corrosion1, slight corrosion
3, severe corrosion2, moderate corrosion
4, severe corrosion
Tfg ≈ 775 °C
Tfg ≈ 1100 °C
475 °C
491 °C
4, severe corrosion
4, severe corrosion
Probe 1 (WIND )Low alloy steel
Probe 2 (WIND )Low alloy steel
Date Author Title INTERNAL63
Calculation of the corrosivityof the environment
Empirical data data
Material selection based on fuelcomposition
Date Author Title INTERNAL64
Calculation of the corrosivityof the environment
Empirical data data
• Reference follow-up• Laboratory tests• Probe tests
SteaMaxPlant and fuel specific corrosion prediction
9 March, 2016 © Valmet | Author / Title
Use- Selection of superheater materials- Optimization of steam temperature- Optimization of fuel mixtures and fuel
limits- Evaluation of the corrosivity of fuels and
fuel mixtures- Estimation of corrosion rate and
superheater life length- Trouble shooting
Based on- Composition of fuels and fuel mixtures- Boiler design and superheater placement- Valmet in-house tool for estimating corrosivity- Empirical data from more than 1300 laboratory corrosion tests and more than 45 full
scale plants
SteaMax corrosion evaluationsR&D Expertise
Furnace wall corrosion and ower lay weldingTypical problem in boilers burning waste and waste wood=> Low alloy base material over lay welded with Ni-based alloy
66
Corrosion -> solutions
1. Superheater material and temperature- Price v.s. life time v.s. efficiency and profitability
- Coatings, overlay weld. E.g. Ni based coatings in waste combustion
2. Tube shields – most corrosive locations
3. Superheater location
4. Superheater design
5. Fuel mixture: Co-firing or additives
6. Gasification
67S.Enestam
Tube shieldsMost corrosive locations
Date Author Title INTERNAL68
Superheater locationReduced concentration of gaseous, corrosive chloride in the vicinity of tube surfaces
Date Author Title69
Empty pass Loop sealsuperheater
Superheater designReduce probability of contact between tube surface and corrosive chloridesDouble tube superheater design=> Reduced condensation of
corrrosive compounds
Date Author Title70
Steam
Pressurebearingtube
Target surface temperatureis determined by theenvironment (fuels, flue gastemperature, steamtemperature,...)
Surface temperature is achievedby controlling the tube heattransfer characteristics withadditional, coaxial layers
Single tube designLife length < 1 year
Double tube designLife length > 3 years
71
Comparison of deposit compositions(XRF)
05
101520253035404550
Na2
O
MgO
Al2
O3
SiO
2
P2O
5
SO3 Cl
K2O
CaO
TiO
2
CuO Zn
O
PbO
wt-%
Sample 1Sample 2Sample 3Sample 4Sample 5Sample 6Sample 7Sample 8
05
101520253035404550
Na2
O
MgO
Al2
O3
SiO
2
P2O
5
SO3 Cl
K2O
CaO
TiO
2
CuO Zn
O
PbO
wt-%
Sample 1Sample 2Sample 3Sample 4Sample 5Sample 6
OLD DESIGN NEW DESIGN
72
E.ON Norrköping EfW PlantP14Steam: 75 MW / 6,5 MPa / 470 CFuels: MSW, industrial waste,
demolition wood,sewage sludge, TDF
Norrköping Händelö site# Type Fuel MWth
P11 Grate Demolition wood 117P12 Grate Coal,TDF 125P13 CFB Bio, TDF 125P14 CFB Waste 75
Ways to minimize corrosionModification of the combustion environment
• AdditivesØ Sulphur
Ø Aluminium sulfate Al2(SO4)3
Ø Ferric sulfate Fe2(SO4)3
Ø Ammonium sulfate (NH4)2SO4
• Co-combustionØ Peat
Ø Coal
Ø Sludge
Date Author Title73
Corrosion management by sulphur addition
� The sulphate eliminates alkali chlorides in the gas phase andattaches to superheater surfaces forming a protective coat andneutralize the effects of alkalichloride in the process
� Sulfate decomposes at high temperature:Fe2(SO4)3 => 2 Fe3+ + 3 SO4
2-
� Alkali chloride reacts with sulfur trioxide or dioxide2MCl(g,c)+ SO3(g)+ H2O (g) => M2SO4 (g,c)+ 2 HCl (g)
2MCl(g,c)+ SO2(g)+ ½ O2 (g)+ H2O (g) => M2SO4 (g,c)+ 2 HCl (g)where M is Na or K
74
CorroStop Additives
02/05/2013
Slow downcorrosion of
superheaters
Measuresand
remedies
Measuresand
remedies
Fuel mixture - additive
�On-line sampling and analysis of the corrosivity ofthe flue gas
� Provides information for fuel blend and additivecontrol
75
Corrored Analyzer
02/05/2013
Sensor+
additive
Sensor+
additive
CorroStop Additives• CorroStop™ – liquid solution
Aluminiumsulfate Al2(SO4)3 or Ferric sulfate Fe2(SO4)315-30 % liquid solutionsSpraying through nozzles before superheaters
CorroStop+™ – elementary sulphurSulphur content > 95 %0,5 – 3,2 mm granulatesAddition to fuel feeding screws
Valmet corrosion management
The influence of fuel mixture on corrosion
76
Corrosive bio fuel mixture requiresstainless steel in the hottestsuperheaters
Adding sulphur rich fuel (e.g. peat) orS-additive enables the use of lowalloy superheater material
GasificationRecycled waste gasification plant for Lahti Energia Oy
77
à Metso delivery: waste gasificationprocess, gas boiler, flue gascleaning system with auxiliary andautomation systems
à 2 gasification lines: 50 MW ofelectricity and 90 MW of district heat
à High-efficiency (gas boiler 121 bar,540 C) conversion of recycledwaste to energy and reduction offossil fuels
à Waste is turned into combustiblegas, which is cooled, cleaned andcombusted in a high-efficiency gasboiler to produce steam for a steamturbine
Corrosion related plant optimization
� Efficiency
� Availability
� Maintenance costs
� Investment costs
78
Maximize steam T and p
Minimize shut-downs due tocorrosion, fouling or bedsinteringMinimize the need for tubereplacement (=minimizecorrosion)Optimize material choice(Good enough material but nottoo good)
Corrosion control is a piece of a big puzzle of economics
792012 /S.Enestam
Corrosioncontrol
FUE
LC
OS
T
0
0.5
1
1.5
2
2.5
3
3.5
PO
WE
RV
ALU
E
FUEL
QU
ALIT
Y
Plant availability
Maintenance costs
Investment costPlant efficiency
Plantprofitability
Turun SeudunEnergiantuotantoCYMIC boiler
3/9/201681
Turun Seudun Energiantuotanto, Naantali, Finland
Naantali Raisio Turku Kaarina
� Turun Seudun Energiantuotanto (TSE) is a utility company owned bylocal municipalities and Fortum
� TSE provides district heating for the owner municipalities andelectricity
9 March, 2016 © Valmet | Author / Title82
Turun Seudun Energiantuotanto, Naantali, FinlandCYMIC boiler
9 March, 2016 © Valmet | Author / Title83
CYMIC boiler - Circulating Fluidized Bed (CFB) technology
Steam 144 / 130 kg/s164 / 44 bar555 / 555 °C390 MW th
Fuels: Wood biomass,agro biomass, peat,coal , SRF
Start-up 2017