recovery boiler superheater tube corrosion and cracking ...whitty/blackliquor/colloquium2006... ·...
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Recovery Boiler Superheater TubeCorrosion and Cracking Studies
Jim Keiser, Gorti Sarma, Kim Choudhury and Adam Willoughby -Oak Ridge National Laboratory
Joey Kish, Laurie Frederick and Doug Singbeil - PapricanFrançois Jetté - Domtar Inc
Peter Gorog - Weyerhaeuser Company
7th International Colloquium on Black Liquor Combustion and Gasification
July 31-August 2, 2006; Jyväskylä, Finland
2BLG Colloquium, SH, August 2006 Finland
The DOE Funded Project “Materials For Industrial Heat Recovery Systems” Has Addressed Several Topics
Recuperators on aluminum melting furnaces
Primary air port cracking
Mid-furnace corrosion
Superheater tube corrosion and cracking
3BLG Colloquium, SH, August 2006 Finland
Our Study Of Degradation Of Superheater Materials Includes A Number Of Tasks
Examination of cracked or corroded superheater tubes
Industry survey of experience with carbon steel and alternate superheater tube materials
Study of mechanical cycling and temperature of superheater tubes
Laboratory corrosion studies of alternate superheater materials
Exposure of superheater corrosion probes with alternate materials
4BLG Colloquium, SH, August 2006 Finland
Potential Benefits From Study Of Superheater Tube Materials
Operation of recovery boilers at higher steam temperatures and pressures offers the potential for more efficient operation
To achieve the potential efficiency benefits, structural materials must have sufficient corrosion resistance for the environments they will encounter
This study should provide clear, objective data on the corrosion resistance of candidate alloys to expected HP/HT boiler superheater environments
From the information collected it should be possible to make materials recommendations for superheater sections as a function of temperature
5BLG Colloquium, SH, August 2006 Finland
During A Shutdown, Fourteen Tube Sections Were Removed From The Intermediate Superheater For Examination
Fig 16
The tube sections removed included the weld attaching the tube to the load-bearing member.
6BLG Colloquium, SH, August 2006 Finland
The Superheater Tubes Of Interest Were In The Intermediate Bank On The Right Side Of The Boiler
1/2 19/2
13/14
17/18
15/16
7/8 23/2
11/12
9/10
5/6
3/4
21/2
ScreenTubes
SuperheaterBanks
Roof
Instrument Box
Sootblower
7BLG Colloquium, SH, August 2006 Finland
The Tubes Were Thoroughly Examined To See If There Was Any Evidence Of Cracking
The remnants of the high crown seal box were ground off the tubes without removing any of the tube material
A dye penetrant examination was conducted on each of the tubes – no crack indications were found
A magnetic particle inspection was conducted on a few of the tubes - no crack indications were found
Cross sections were cut from each of the tubes at the 3, 6, 9 and 12 o’clock positions just below the tube to crown weld
The cross sections were examined microscopically in the as-polished and etched conditions
8BLG Colloquium, SH, August 2006 Finland
Cracks Were Found In The 3 And 9 O’clock Positions On The Tube From Platen 8
One crack advanced about 20% of the way through the tube wall.
9BLG Colloquium, SH, August 2006 Finland
Cracks Were Also Found In The First Tube From Platens 11 and 12
Both cracks were associated with the weld.
10BLG Colloquium, SH, August 2006 Finland
The Second Tube In Platen 14 Was Cracked
Crack originated in the heat affected zone and advanced about 20% through the tube wall.
11BLG Colloquium, SH, August 2006 Finland
Two Failed Tubes, Found During The Hydro Following The Fall, 2004 Shutdown, Have Also Been Examined
These tubes were from the opposite side of the superheater platens from where several previous failures had occurred
Welds attaching the tubes to the support were ground off then a dye penetrant test was done
Dye penetrant examinations revealed large cracks
Cross sections of the tubes were examined metallographically
Fig 10
12BLG Colloquium, SH, August 2006 Finland
Cracks On These Tubes Followed The Weld HAZ Along The Tube To High Crown Seal Weld
The through-wall cracks appear to follow the bottom of the weld of the
tube to the high crown seal box.
13BLG Colloquium, SH, August 2006 Finland
Cross Sections Of The Tubes Show Through Wall Cracks In The HAZ With Secondary Cracking
14BLG Colloquium, SH, August 2006 Finland
To Study The Cyclic Stresses, Strain Gauges Were Installed In October, 2003 On The First Tube Of Two Platens
Three strain gauges were installed on each tube
The strain gauges were 120° apart at 6, 10 and 2 o’clock
The strain gauges are rated for service up to 750°C
A data point is collected from each strain gauge once per second
A thermocouple was also installed on each tube
Fig 22
15BLG Colloquium, SH, August 2006 Finland
The Tubes Were Installed So The Strain Gauges Were Just Below The Tube To High Crown Seal Weld
Photos showing the installation of superheater tube with strain gauges. In the picture on the left, the #2 tube has been installed in platen 14, but the hole is still empty where tube #1 with the strain gauges will be installed. In the center photo, the #1 tube with strain gauges is in position, and in the picture on the right, the tube is welded in place and the strain gauge and thermocouple wires extend through a specially made opening.
16BLG Colloquium, SH, August 2006 Finland
The Strain Gauge Data For A Typical Day Of Operation Shows Intermittent Periods Of Activity
Strain gauge data for a typical day of “clean” boiler operation. The strain associated with the largest of the oscillations is not sufficient to initiate fatigue cracks. However, these oscillations could promote growth of existing cracks.
-400
-350
-300
-250
-200
-150
-100
-50
0
7:30 8:00 8:30 9:00 9:30 10:00 10:30 11:00 11:30 12:00 12:30 13:00 13:30 14:00 14:30 15:00
time
stra
in
Tube 4 SG1
Tube 4 SG2
Tube 4 SG3
Tube 14 SG1
Tube 14 SG2
Tube 14 SG3
Tube 5 SG1
Tube 5 SG2
Tube 5 SG3
17BLG Colloquium, SH, August 2006 Finland
Plotting The Data Over A Shorter Period Reveals A Swinging Motion Is Caused By The Sootblowers
Five sootblower cycles are shown, note the activity induced by each sootblower begins on platen 5 then moves to platen 14 then back to platen 5.
Ashdown 2 Strain Gauges May 17, 2004
-400
-350
-300
-250
-200
-150
-100
-50
0
8:19 8:20 8:21 8:22 8:23 8:24 8:25 8:26 8:27 8:28 8:29 8:30 8:31 8:32 8:33 8:34 8:35 8:36 8:37 8:38 8:39
time
Stra
in (M
pa)
Tube 5 SG1 Tube 5 SG2 Tube 5 SG3 Tube 14 SG1 Tube 14 SG2 Tube 14 SG3
18BLG Colloquium, SH, August 2006 Finland
This Superheater Has A Plugging Problem And The Extent Of Plugging Is Reflected In The Strain Gauge Activity
Number of cycles (strain changes of at least 20 units) over a three month period showing varying amounts of plugging in the intermediate superheater area.
Ashdown 2 Strain Gauge Daily Total Cycles March -May 2004
0
500
1000
1500
2000
25003/
1/04
3/3/
043/
5/04
3/7/
043/
9/04
3/11
/04
3/13
/04
3/15
/04
3/17
/04
3/19
/04
3/21
/04
3/23
/04
3/25
/04
3/27
/04
3/29
/04
3/31
/04
4/2/
044/
4/04
4/6/
044/
8/04
4/10
/04
4/12
/04
4/14
/04
4/16
/04
4/18
/04
4/20
/04
4/22
/04
4/24
/04
4/26
/04
4/28
/04
4/30
/04
5/2/
045/
4/04
5/6/
045/
8/04
5/10
/04
5/12
/04
5/14
/04
5/16
/04
5/18
/04
5/20
/04
5/22
/04
5/24
/04
5/26
/04
5/28
/04
5/30
/04
No
of C
ycle
s
SG5-1 SG5-2 SG5-3 SG14-1 SG14-2 SG14-3
March 1 April 13 May 18
Ashdown 2 Strain Gauge Daily Total Cycles March -May 2004
0
500
1000
1500
2000
25003/
1/04
3/3/
043/
5/04
3/7/
043/
9/04
3/11
/04
3/13
/04
3/15
/04
3/17
/04
3/19
/04
3/21
/04
3/23
/04
3/25
/04
3/27
/04
3/29
/04
3/31
/04
4/2/
044/
4/04
4/6/
044/
8/04
4/10
/04
4/12
/04
4/14
/04
4/16
/04
4/18
/04
4/20
/04
4/22
/04
4/24
/04
4/26
/04
4/28
/04
4/30
/04
5/2/
045/
4/04
5/6/
045/
8/04
5/10
/04
5/12
/04
5/14
/04
5/16
/04
5/18
/04
5/20
/04
5/22
/04
5/24
/04
5/26
/04
5/28
/04
5/30
/04
No
of C
ycle
s
SG5-1 SG5-2 SG5-3 SG14-1 SG14-2 SG14-3
March 1 April 13 May 18
19BLG Colloquium, SH, August 2006 Finland
The Effect Of Plugging Is Clearly Indicated In The 15 Minute Data Plots For The Three Dates
Strain gauge data for 15 minute period on the three dates indicated on the previous slide. Note the suppression of oscillations on April 13 when
the superheater appears to be badly plugged.
Ashdown 2 Strain Gauges May 18, 2004
-400
-350
-300
-250
-200
-150
-100
-50
0
2:30 2:31 2:32 2:33 2:34 2:35 2:36 2:37 2:38 2:39 2:40
time
stra
in
Tube 4 SG1 Tube 4 SG2 Tube 4 SG3 Tube 14 SG1 Tube 14 SG2 Tube 14 SG3
Ashdown 2 Strain Gauges April 13, 2004
-400
-350
-300
-250
-200
-150
-100
-50
0
1:00 1:01 1:02 1:03 1:04 1:05 1:06 1:07 1:08 1:09 1:10
time
stra
in
Tube 5 SG1 Tube 5 SG2 Tube 5 SG3 Tube 14 SG1 Tube 14 SG2 Tube 14 SG3
Ashdown 2 Strain Gauges March 1, 2004
-400
-350
-300
-250
-200
-150
-100
-50
0
1:20 1:21 1:22 1:23 1:24 1:25 1:26 1:27 1:28 1:29 1:30
time
stra
in
Tube 5 SG1 Tube 5 SG2 Tube 5 SG3 Tube 14 SG1 Tube 14 SG2 Tube 14 SG3
Ashdown 2 Strain Gauges May 18, 2004
-400
-350
-300
-250
-200
-150
-100
-50
0
2:30 2:31 2:32 2:33 2:34 2:35 2:36 2:37 2:38 2:39 2:40
time
stra
in
Tube 4 SG1 Tube 4 SG2 Tube 4 SG3 Tube 14 SG1 Tube 14 SG2 Tube 14 SG3
Ashdown 2 Strain Gauges April 13, 2004
-400
-350
-300
-250
-200
-150
-100
-50
0
1:00 1:01 1:02 1:03 1:04 1:05 1:06 1:07 1:08 1:09 1:10
time
stra
in
Tube 5 SG1 Tube 5 SG2 Tube 5 SG3 Tube 14 SG1 Tube 14 SG2 Tube 14 SG3
Ashdown 2 Strain Gauges March 1, 2004
-400
-350
-300
-250
-200
-150
-100
-50
0
1:20 1:21 1:22 1:23 1:24 1:25 1:26 1:27 1:28 1:29 1:30
time
stra
in
Tube 5 SG1 Tube 5 SG2 Tube 5 SG3 Tube 14 SG1 Tube 14 SG2 Tube 14 SG3
March 1, 2005
April 13, 2005 May 18, 2005
20BLG Colloquium, SH, August 2006 Finland
The Daily Averages Of Strain Gauge Measurements Give Some Indication Of Loading On The Tubes
Ashdown 2 Daily Averages per Strain Gauge Jan 2004 to June 2005
-350
-300
-250
-200
-150
-100
-50
01-
Jan-
04
16-J
an-0
4
31-J
an-0
4
15-F
eb-0
4
1-M
ar-0
4
16-M
ar-0
4
31-M
ar-0
4
15-A
pr-0
4
30-A
pr-0
4
15-M
ay-0
4
30-M
ay-0
4
14-J
un-0
4
29-J
un-0
4
14-J
ul-0
4
29-J
ul-0
4
13-A
ug-0
4
28-A
ug-0
4
12-S
ep-0
4
27-S
ep-0
4
12-O
ct-0
4
27-O
ct-0
4
11-N
ov-0
4
26-N
ov-0
4
11-D
ec-0
4
26-D
ec-0
4
10-J
an-0
5
25-J
an-0
5
9-Fe
b-05
24-F
eb-0
5
11-M
ar-0
5
26-M
ar-0
5
10-A
pr-0
5
25-A
pr-0
5
10-M
ay-0
5
25-M
ay-0
5
T5-1 T5-2 T5-3 T14-1 T14-2 T14-3T = Tube
Ashdown 2 Daily Averages per Strain Gauge Jan 2004 to June 2005
-350
-300
-250
-200
-150
-100
-50
01-
Jan-
04
16-J
an-0
4
31-J
an-0
4
15-F
eb-0
4
1-M
ar-0
4
16-M
ar-0
4
31-M
ar-0
4
15-A
pr-0
4
30-A
pr-0
4
15-M
ay-0
4
30-M
ay-0
4
14-J
un-0
4
29-J
un-0
4
14-J
ul-0
4
29-J
ul-0
4
13-A
ug-0
4
28-A
ug-0
4
12-S
ep-0
4
27-S
ep-0
4
12-O
ct-0
4
27-O
ct-0
4
11-N
ov-0
4
26-N
ov-0
4
11-D
ec-0
4
26-D
ec-0
4
10-J
an-0
5
25-J
an-0
5
9-Fe
b-05
24-F
eb-0
5
11-M
ar-0
5
26-M
ar-0
5
10-A
pr-0
5
25-A
pr-0
5
10-M
ay-0
5
25-M
ay-0
5
T5-1 T5-2 T5-3 T14-1 T14-2 T14-3T = Tube
21BLG Colloquium, SH, August 2006 Finland
Laboratory Corrosion Studies Of Alternate Materials Are Being Conducted At Paprican
Objective– Determine relative corrosion resistance of candidate tube
alloys in simulated HP/HT recovery boiler superheater environments
Approach– Crucible test method using horizontal three-zone furnaces
Variables– Alloy composition (materials); temperature; time
22BLG Colloquium, SH, August 2006 Finland
Alternate Materials For Superheater Corrosion Studies (Alloy Sets For Different Test Conditions)
- - -1018Bal.SS 347H
1- - -9Bal.SA213 T91
Low Temperature Alloy Set (A1)
High Temperature Alloy Set (A2)
0 [3.4Al]61295.1Alloy 693
1.53233Bal.Alloy 33
3.53127Bal.Alloy 28
- - -2025Bal.SS 310H
1.53233Bal.Alloy 33
3.53127Bal.Alloy 28
- - -2025Bal.SS 310H
- - -1018Bal.SS 347H
MoNiCrFeAlloy
23BLG Colloquium, SH, August 2006 Finland
Salt Deposit Mixture
525
(977)
24.44.98.46.156.2D1
SO4CO3ClKNa
FMT
°C
(°F)
Chemical Composition (wt.%)No.
Simulates typical deposit in coastal/closed-cycle mill
“Worst Case” salt deposit mixture
24BLG Colloquium, SH, August 2006 Finland
Salt Deposit Melting BehaviorTe
mpe
ratu
re D
iffer
ence
(°C
/mg)
Temperature (°C)
FMT = 525 °C20 °C/min
25BLG Colloquium, SH, August 2006 Finland
FY 2006 Test Matrix
530 °C510 °C336N2D1A1
Influence of Expose Time (Corrosion Kinetics)
N2
Cover
Gas
N2
Cover
Gas
560 °C336D1A2
Furnace
3
Furnace
2
Furnace
1
t
(h)
Salt
Deposit
Alloy
Set
Influence of Temperature
336h168h24h510D1A1
Furnace
3
Furnace
2
Furnace
1
T
(°C)
Salt
Deposit
Alloy
Set
26BLG Colloquium, SH, August 2006 Finland
Superheater Corrosion Probe
6 materials and a total of 15 samples, each about 10 cm (4 inches) long and 5 cm (2 inches) OD
Spring loaded to hold samples tightly together
Air cooled
Exposed in location where maximum boiler gas temperature is approximately 650°C (1200°F)
Temperature gradient is expected to be at least 75C°
Plan for 1000 or 1500 h exposure
Probes will be exposed in two mills
27BLG Colloquium, SH, August 2006 Finland
Materials Used For Samples Offer A Wide Range Of Composition And Corrosion Resistance
0.5 Ti 1.5 Nb
3.20.02Bal295.4Alloy 693
0.4 N0.011.6313332Alloy 33 weld overlay
1.0 Cu0.023.53127BalAlloy 28
0.5202552310S
0.50.089.517Bal347H
0.22 V0.0130.060.110.950.28.30BalT91
OtherAlNbCMoNiCrFeAlloyNominal compositions in wt %
28BLG Colloquium, SH, August 2006 Finland
Schematic Of Superheater Corrosion Probe
29BLG Colloquium, SH, August 2006 Finland
All 15 Samples Are Interlocking And Have Two Thermocouples On Each
30BLG Colloquium, SH, August 2006 Finland
SummaryCracks developed in superheater tubes in the heat affected zones of welds attaching the tube to the support structure
Strain gauges on the superheater tubes showed amplitude of current tube swinging is not sufficient to cause fatigue cracking
Laboratory corrosion studies of alternate superheater tube materials are being conducted in environments that duplicate current conditions as well as those of a boiler operating at higher steam temperatures and pressures
Air cooled superheater corrosion probes which will expose samples of alternate superheater tube materials are being prepared for exposure in two mills under conditions that simulate the temperature and chemical environment of a boiler operating at higher steam temperatures and pressures