T TNO Environment, Energy and Process Innovation Jaap Koppejan Reducing corrosion and ash deposition in Dutch WtE plants ACERC conference, 20-21 Feb, Salt

Jaap Koppejan

t

TNO Environment, Energy and Process Innovation

Reducing corrosion and ash deposition in Dutch WtE plants

ACERC conference, 20-21 Feb, Salt Lake City

Feb 20, 2003Reducing corrosion and ash deposition in waste incinerators 2t

Content

• General info on Dutch waste incineration

sector

• Corrosion processes

• Corrosion reduction measures


Waste to Energy plants in the Netherlands • 11 installations, total capacity approx. 5.5 Mton• Existing WtE plants were retrofitted in 90’s• Very low emissions


Emission limits (dry m3, 11% O2)Component Emission limit

total dust 5 mg/m3

HCl 10 mg/m3

HF 1 mg/m3

CO 50 mg/m3

VOC 10 mg/m3

SO2 40 mg/m3

NOx 70 mg/m3

Sum of heavy metals 1 mg/m3

Cd 0,05 mg/m3

Hg 0,05 mg/m3

PCDD's + PCDF's 0,1 ng I-TEQ/m3


WtE plants in the NetherlandsProcessing capacity

E-Power output

Heat output

Number of lines

Date of operation

kton/yr MWe MWth

Alkmaar 465 42 3 1995

Amsterdam 840 80 4 1993

Rotterdam 380 26 4 1962

Rijnmond 1150 108 100 (distilled water) 7 1972 (6 lines)1995 (1 line)

Roosendaal 67 14 MWth 2 1972

Dordrecht 240 9 4 1972 / 1992

Moerdijk 600 195 Steam to CHP 3 1997

Nijmegen 340 28 2 1987/1995

Arnhem 360 25 75 (district Heating) 3 1985/1990/1991

Hengelo 285 26 2 1997

Wijster 720 48 3 1996


Need for increased availability• Typical:

• steam conditions 40 Bar/400°C, efficiency 22%• Availability in hours/year: 90%

• 1 day production loss equals about 125,000 $

corrosion in first pass and boiler is major reason for production loss.

• Higher steam conditions needed for higher efficiencies (e.g. 100 Bar/500°C)

Corrosion and deposition problems


Overview of corrosion processes in WtE-boilers

Boiler water wall

Ceramic Lining

Grate

~700°C

Boiler: 400°C/ 40 Bar

900-1100°C

Generation of Volatile chlorides

Super heaters

chlorides+CO

chlorides+H2O

gasNaClZnCl2

Sulphatesof NaCland ZnCl2

NaCl(g)> NaCl(s)

Cl-gas corrosionNaCl+ SO2 + O2 = Na2SO4 + Cl2Fe + Cl2 = FeCl2FeCl2 + O2 = Fe3O4 + Cl2

Ev EvS S Ec Ec


Typical temperatures in boilers of WtE-plants

Boilerpart Steam T metal °C T gas °C

Waterwall, evaporator

265 °C ~ 300°C ~ 1100-700 °C

Evaporator tubes

265 °C ~ 300 °C ~ 800-700 °C

Superheater 400 °C ~ 450 °C ~ 700-600 °C


Typical corrosion in Dutch WtE plants

Evaporator Superheater

Metal temperature

~ 250-300 °C ~ 400-530 °C

Construction Membrane wall Tube bundles

Material C-steel (St.35.8)

Alloy (15Mo3)

Typical corrosion velocities

0,15-0,30 mm/y 0,20-0,40 mm/y


Corrosion on water walls

1. CO corrosion at locations with reducing

conditions


CO corrosion on furnace walls

Carbon steel corrosion at 450 °C


Corrosion on water walls

1. CO corrosion at locations with reducing conditions

2. Corrosion by metal chloride deposits

3. Erosion due to high dust loads and high local

velocities

4. Missing refractory tiles


Corrosion on superheater tubes


Corrosion on superheater tubes

1. Corrosion by Cl2 or HCl containing gas (active

oxidation)

2. Corrosion by metal chloride deposits

3. Erosion due to high dust loads and local high

velocities

4. Sulphate corrosion (less influence)


Active oxidation from Cl in gas at 500 C, no SO2

1. 2NaCl + Fe2O3 + ½ O2 = Na2Fe2O4 + Cl2

2. Fe + Cl2 = FeCl2 , attaching Fe3O4

layerMetal chloride T4 (°C)

FeCl2 536

FeCl3 167

CrCl2 741

CrCl3 611

NiCl2 607


Corrosion reduction measures

1. Combustion conditions

2. Boiler cleaning mechanisms

3. Materials used

4. Boiler design


1. Combustion conditions

• Improvement of air distribution

• Optimisation of combustion behaviour

• Better flue gas temperature control


2. Improved boiler cleaning mechanism

• Removal/adaptation of soot blowers

• Optimisation of boiler tube cleaning system

• Cleaning with dynamite/gas explosions

• Water jet cleaning


Cleaning with explosives

since Period [w eeks]

E-M Wijster No

Tw ence Yes 6

AVR-Rotterdam Yes (2002) 4

AVR-Rijnmond 1-6 Yes (1999) 18

AVR-Rijnmond 0 Yes (1999)

HVC Alkmaar Yes

GDA A'dam Yes (1999) 7

AZN Moerdijk No -

ARN Weurt Yes 9

GEVUDO Dordrecht No

AVRAVIRA Duiven Yes 5


Effect of cleaning with explosives

0

50

100

150

200

250

300

350

400

450

500

550

600

650

700

750

jan-01 feb-01 apr-01 jun-01 jul-01 sep-01 nov-01 dec-01 feb-02 apr-02 mei-02 jul-02 sep-02

date

Flu

e g

as

tem

pe

ratu

re


3. More advanced materials

• Cladding Alloy 625


steel 15Mo3 tube corrosion

Steal 15Mo3

02468

10121416

Metal temperature (C)

Co

rro

sio

n (

mm

)

5000 uur 10000 uur 20000 uur


Alloy 625 tube corrosionAlloy 625

0,0

0,2

0,4

0,6

0,8

1,0

1,2

300 325 350 375 400 425 450 475 500 525 550 575 600 625 650

Metal Temperature (C)

Co

rro

sio

n (

mm

)

5000 uur 10000 uur 20000 uur


• Composite tubes for super heaters

• Advanced refractory on membrane walls, e.g. SiC tiles or better fixation

3. More advanced materials• Cladding, e.g. Alloy 625


4. Adaptations of design:

• Super heater configuration

2

2

1B

1B

1A

1A

Gas

Gas


Changing configuration of super heater bundles

Temperatures and corrosion of 15Mo3/St35.8

200

250

300

350

400

450

500

550

600

400 450 500 550 600 650 700 750 800

Flue gas temperature °C

Ste

am

te

mp

era

ture

°C

123

Much corrosion

Little corrosion


4. Adaptations of design:

• Super heater bundle configuration

• Water injection in steam system

• Increasing refractory area or cladding in

first pass

• Water cooled grate (if sufficient heating

value)


Summary: Good experiences exist in the Netherlands with

• Optimization of combustion process (case

specific)

• Improved boiler tube cleaning

• Improved materials and constructions (cladding,

superheater configuration)

Documents

T TNO Environment, Energy and Process Innovation Jaap Koppejan Reducing corrosion and ash deposition in Dutch WtE plants ACERC conference, 20-21 Feb, Salt