weld overlay high temperature corrosion in biomass ... · pdf fileweld overlay high...

www.azz.com/wsi-europe 1

Weld Overlay

High Temperature Corrosion in Biomass Combustion

World Bioenergy Conference

Hans Bengtsson

2014-06-05


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)

Markets: Refining, Nuclear, Fossil power, Waste to

Energy, Chemical/Industrial processing, Pulp/Paper,

Steel manufacturing processing

• Steel manufacturingWSI

Innovative maintenance through automatic

weld repair solutions

• PQR/WPS development (600+ procedures)

• Welding plans (1500+) / repair plans

• 2013: 800 scopes executed in 35 countries

WSI Global Footprint

Galvanizing

Electrical & Industrial

WSI/SMS


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• Requirements/technical review

• WPS/PQR

• Craft qualification certificates

• Testing/inspection procedures and material inspection reports

Non-Nuclear Quality Assurance Programs• 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• Automation that allows safety performance

• PPE to reduce risk and fatigue

• Highly skilled and qualified craft and qualified HSE managers

• Human performance-based prevention

• Safety equipment and plans

Example quality

Certificate

Ad 2000 Merkblatt

HPO, TRD 201


Our products

Lakeside UK - Boiler, October 2013

UT Readings – Ultrasone Testing

Welding engineers involved

in every step of our work

Shop products - fabrication of front and floor tube panel

using UNIFUSE® 625/CS overlay tubes and membrane bar

Field services – on site weld overlay

Tie-in finishing after replacement

Field Services• Waterwall overlay, re-overlay

• Tie in

Shop fabrication• Panel

• Tubes

• superheater, evaporator, etc

Inspection and maintenance program:• QA Inspectors

• Welding engineer


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

Harvested product – depending

on the area: pine, eucaliptus,

olive, rice, etc

Corrosion on biomass facilities has

turned into a real challenge. Every

plant shows different behaviour:

• Operational parameters

• Waste composition

• Relative new technology

Need to establish a relationship

between: manufacturers, end

user, maintenance providers, R&D Black liqour or mixed fuel also

containing municipal waste, industrial

waste, animal residues, sewage, etc


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 Erosion

Every plant may have a dominant

wear phenomena, depending on

fuel, operational paramenters, etc

Chlorine causing accelerated

corrosion and fouling


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)

Operational parameter:

Reduction of steam and

metal temperatures

Fuel characteristics:

Reduce chlorine content

by mixing or using

additives

Improve metallurgy on

evaporator and SH tubes,

heat exchangers and hot

gas paths

Metal alloy for corrosion protection has to be commercial available, economically

efficient and easy to apply


Protection for Waterwall

Welding overlay with alloy 625 ON-SITE

Welding overlay with alloy 625 on shop panels for replacement + on site TIE-IN

Shop panel protection on-site installation + 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


Improve metallurgy on pressure parts shop and field both:

• Preventive

• Currative

sCases from boilers in Sweden


Showcase- MW Power- Vattenfall- Jordbro plant

• 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

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 Bubbling fluidized bed (BFB)


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

• Thickness on progress

• Thickness

• Chemistry: PMI

• Sealing: copper sulfate



Showcase- ENA AB-Enköping-Sweden

Background

•Boiler type: Vibrating grate Burmeister & Wein Energy 80 MW.

•Steam pressure: 101 bar

•Temperature: 540C

•Production: District heating and power

•Fuel: 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


Field weld overlay

Showcase- ENA AB-Enköping-Sweden


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


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

cross section of a worn 625 overlay waterwall sample

0,5 mm

1,5 mm

Alloy 625

CS tube SEM and EDX on localized corrosion pit on alloy

625 overlay to understand chem. compositions at

different chloride complex phases

30 μm

Severe corroded T22 superheater tube in a

biomass boiler burning hog fuel


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


• Words from the CUSTOMERS

• "Solid and professional project execution by WSI"


• Vattenfall

• Euromaint

• ENA Energi

• SYSAV

• Coor Service Management

• E.ON Händelöverket

• Umeå Energi

• Billerud AB

• INEOS A/S

• Fortum Högdalen AB

• Renova

• Boliden Mineral AB

• Halmstad Energi & Miljö

• Södra Cell AB

• Valmet (Metso) Power AB

• Foster Wheeler Oy

• BW Völund

• Andritz

• Rautaruki Steel Oy

WSI referens project Nordic 2004 – up to day


Future

Inconel 625 limitation:

• Metal temperature

• Erosion/Abrasion properties

WSI has a R&D development program for alternative alloys

Questions!


THANK YOU!

weld overlay high temperature corrosion in biomass ... · pdf fileweld overlay high...

Documents