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