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1
Corrosion in Black Liquor Pyrolysis and Combustion Gas Environments
Preet M. SinghInstitute of Paper Science and Technology
Atlanta, Georgia
Colloquium on BL Combustion and GasificationPark City, UtahMay 13th, 2003
Recovery Boiler
To stackElectrostaticprecipitator
Primary
Secondary
TertiaryAir delivery:
Black liquor
Smelt
Economizer
BoilerSuperheater
Screen Tubes
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2
Differences in Fireside Tube Surface Corrosion
“Corrosive” Area“Non-Corrosive” Area
Thermocouples and Gas-line for Environment Sampling
Filters for Gas-line
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3
Instrumentation for Boiler Environment Characterization
0
5
10
15
20
25
30
1 foot 1 inch Waterwall surface
% i
n D
ry G
ases
High Corrosion Area Low Corrosion Area
Hydrogen Sulfide in RB
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4
0
0.1
0.2
0.3
0.4
0.5
0.6
1 foot 1 inch Waterwall surface
% i
n D
ry G
ases
High Corrosion Area Low Corrosion Area
Methyl Mercaptan in RB
Average Gas Composition at Waterwall Surface - Boiler #1
Gas Species High Corr. Area Low Corr. Area
N2 24.8 % 38.6 %CO2 18.8 % 13.4 %CO 11.7 % 9.2 %H2 2.4 % 1.4 %O2 2.9 % 4.4 %
CH4 4.0 % 0.8 %H2S 18 % 3.8 %
SO2/COS 0.2 % 0.18 %Meth. Mercaptan 0.17 % 0.02 %
65% Solids-Black liquor is sprayed on side-walls
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Black Liquor “Pyrolysis” on Waterwall Tubes - High Local Concentrations of Sulfur Bearing Gases
High Corrosion Of Waterwall Due to Black Liquor Spray in Boiler #1
Recovery Boiler #2
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Locations of Cut-line Corrosion in a BoilerMid-Furnace Corrosion
Composite Tubes
High Corrosion Areas
Rear Wall
Front WallRight Wall
(South)Left Wall(North)
C-Steel Tubes
Primary Airports
Secondary Airports
Auxiliary Burners
Liquor Guns
Locations of Mid-Furnace Corrosion Boiler #4
Gas Sampling PortComposite Tubes
(High Corrosion Rate)
Front Wall
Rear Wall
Left Wall
1
113 1 115 1
113 115RLM
RLT
RCM 34’
RCT 41’
LB 25’
LF 25’
RLBRCB 27’
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Gases at Waterwall SurfaceMid Furnace - Boiler #5 (North Wall)
65 - 68% Solids-Black liquor
Gas Species % in HighCorr. Area
% in LowCorr. Area
% 12' AboveHigh Corr
N2 10.60 40.62 46.74CO2 14.23 17.71 17.87CO 27.95 13.57 13.98H2 12.04 6.67 5.16O2 0.27 0.52 0.55
CH4 4.42 1.82 1.59H2S 0.91 0.81 0.86
SO2/COS 0.20 0.10 0.12CH3SH 0.030 0.023 .013(CH3)2S 0.033 0.028 0.033
CS2 0.0012 0.0018 0.0024(CH3)2S2 0.0019 0.0012 0.0009
When black liquor is sprayed or ends-up intentionally or unintentionally on waterwalls
local pyrolysis of black liquor on waterwall surface
Higher concentrations of sulfur bearing gases locally
higher sulfidation or corrosion of carbon steel waterwalls in these areas
Corrosion in Lower Furnace
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Corrosion Kinetics
Thermobalance for RB Simulation Tests
DifferentGasesMass Flow Meters
and Controllers
Gas outlet
Furnace
Thermocouple
Gas inlet
CathetometerQuartz spring
Test Coupon
Platinum wire
EndcapPyrex tube
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Effect of Temperature
C-Steel, SA-210 at 320oC and 400°C in High Corrosion Gases From RB#1
C-Steel, SA-210 @ 320 and 400°C in High-RB#1 Gases
0
10
20
30
40
50
60
0 4 8 12 16Time, days
Wt.
Gai
n, m
g/cm
² High - RB#1-400CHigh - RB#1-320C
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SA210 in HC Gases at 320oC
SA210 in HC Gases at 320oC
100.00
0.0
95.89
4.11
Spot #1
100.00
0.00
97.92
2.08
Spot #3 Spot #6
100.00Total
14.89O
74.54Fe
10.57S
At%Element
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SA210 in HC Gases at 400oC
SA210 in HC Gases at 400oC
O
Fe
S
Element
0.00
94.6
1.55
Spot #1
0.00
48.24
49.53
Spot #2
0.00
46.72
51.94
Spot #5 Spot #10
25.12
68.02
6.86
At%
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Effect of Temperature on Corrosion Rate of 304 SS in Gases Containing Only H2S and H2
Source – IPST Corrosivity Database
304SS in H2S + H2 Gas Mixtures (Partial Pressure of O2 = 0.0)
0.1
1
10
100
1000
200 300 400 500 600 700Temperature (oC)
Cor
rosio
n R
ate
(mpy
)
Effect of Gas Composition
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Lower Furnace Gas Compositions Used in Laboratory Tests
87.20.000.000.020.361.180.000.000.00.012.0High Corrosivity w/o O2 (HC)
43.60.000.000.000.230.5421.800.1010.119.74.0Low Sulfur (LS)
70.50.000.000.052.045.990.000.006.10.014.7High Sulfur (HS)
N2CS2CH32SCH3SHCOSH2SCOCH4O2CO2H2
1.00E-362.17E-143.60E-344.32E-11High Corrosivity w/o O2 (HC)
3.33E-362.97E-133.92E-291.68E-10Low Sulfur (LS)
6.12E-033.59E-136.12E-037.14E-10High Sulfur (HS)
PO2PS2PO2PS2
320oC480oCLower Furnace Recovery Boiler Gases
(HS) High Sulfur Containing RB Gases
0.2
12.1
1.40.1
1.7 0.90
5
10
15
20
25
30
35
40
304-L SA210 I-625 304-L SA210 I-625
Alloy
Cor
rosi
on R
ate
(mpy
)
HS-Gases at 480 oC HS-Gases at 320 oC
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(LS) Lower Sulfur Containing RB Gases
0.68
16.89
1.99 0.96 0.84 1.100
5
10
15
20
25
30
35
40
304-L SA210 I-625 304-L SA210 I-625
Alloy
Cor
rosi
on R
ate
(mpy
)
LS-Gases at 480 oC LS-Gases at 320 oC
(HC) Low Oxygen Containing RB Gases
9.5
36.4
13.8
1.1
29.3
1.5
0
5
10
15
20
25
30
35
40
304-L SA210 I-625 304-L SA210 I-625
Alloy
Cor
rosi
on R
ate
(mpy
)
HC-Gases at 480 oC
HC-Gases at 320 oC
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Effect of Sulfur Partial Pressure on Corrosion Rate of 304 SS in Gases Containing Only H2S and H2 at 400oC
Corrosion Rate of 304 SS at 400oC as a function of Sulfur Partial Pressure in (H2S + H2) Gas Mixtures
0.00
0.50
1.00
1.50
2.00
2.50
3.00
3.50
4.00
4.50
5.00
1.0E-15 1.0E-13 1.0E-11 1.0E-09 1.0E-07 1.0E-05 1.0E-03
Partial Pressure of Sulfur (atm.)
Cor
rosi
on R
ate
(mpy
Source – IPST Corrosivity Database
Phase Stability Diagrams for Fe, Ni, and Cr in Presence of O2 and S2 at 320oC
1.00E-362.17E-14High Corrosivity w/o O2 (HC)
3.33E-362.97E-13Low Sulfur (LS)
6.12E-033.59E-13High Sulfur (HS)
PO2PS2
320oCLower Furnace
Recovery Boiler Gases
0-5-10-15-20-25-30-35-40
0
-5
-10
-15
-20
-25
-30
-35
-40
log pS2(g)
log pO2(g)Constant value:T / °C = 320.00
Predominance Diagram for Ni-O-S System
Ni(FCC)Ni(FCC)NiONiO
NiS(A)NiS(A)
NiS2NiS2
Ni3S2Ni3S2NiSO4NiSO4
0-5-10-15-20-25-30-35-40
0
-5
-10
-15
-20
-25
-30
-35
-40
log pS2(g)
log pO2(g)Constant value:T / °C = 320.00
Predominance Diagram for Cr-O-S System
Cr2O3Cr2O3
Cr2S3Cr2S3
Cr2(SO4)3Cr2(SO4)3
0-5-10-15-20-25-30-35-40
0
-5
-10
-15
-20
-25
-30
-35
-40
log pS2(g)
log pO2(g)Constant value:T / °C = 320.00
Predominance Diagram for Fe-O-S System
Fe2O3Fe2O3Fe3O4Fe3O4
FeSFeS
FeS2FeS2
Fe2S3Fe2S3
FeSO4FeSO4
Fe2(SO4)3Fe2(SO4)3
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Phase Stability Diagrams for Fe, Ni, and Cr in Presence of O2 and S2 at 480oC
3.60E-344.32E-11High Corrosivity w/o O2 (HC)
3.92E-291.68E-10Low Sulfur (LS)
6.12E-037.14E-10High Sulfur (HS)
PO2PS2
480oCLower Furnace
Recovery Boiler Gases
0-5-10-15-20-25-30-35-40
0
-5
-10
-15
-20
-25
-30
-35
-40
log pS2(g)
log pO2(g)Constant value:T / °C = 480.00
Predominance Diagram for Ni-O-S System
Ni(FCC)Ni(FCC) NiONiO
NiS0.84NiS0.84NiS(A)NiS(A)
NiS2NiS2
Ni3S2Ni3S2
NiSO4NiSO4
0-5-10-15-20-25-30-35-40
0
-5
-10
-15
-20
-25
-30
-35
-40
log pS2(g)
log pO2(g)Constant value:T / °C = 480.00
Predominance Diagram for Cr-O-S System
Cr2O3Cr2O3
CrS1.17CrS1.17
Cr2S3Cr2S3
Cr2(SO4)3Cr2(SO4)3
0-5-10-15-20-25-30-35-40
0
-5
-10
-15
-20
-25
-30
-35
-40
log pS2(g)
log pO2(g)Constant value:T / °C = 480.00
Predominance Diagram for Fe-O-S System
Fe(A)Fe(A) Fe2O3Fe2O3
Fe3O4Fe3O4
Fe0.877SFe0.877S
FeSFeS
FeS2FeS2
Fe2S3Fe2S3
FeSO4FeSO4
Fe2(SO4)3Fe2(SO4)3
What About Gasifiers?
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Low Temperature Gasifier Environment
27.5481H2O (v)Water vapor
15.2311CO2Carbon dioxide
9.9051COCarbon monoxide
44.6459H2Hydrogen sulfide
0.0008(CH3)2S2Dimethyl disulfide
0.0012(CH3)2SDimethyl sulfide
0.0122CH3SHMethyl Mercaptan
1.4789H2SHydrogen sulfide
0.0395C3H6Propane
0.0987C2H4Propene
0.0526C2H6Ethane
0.9862CH4Methane
% Wet basis
Chemical formulaGas Component
7-day results
7-day Weight gain vs. alloy
0
20
40
60
80
100
120
304 304b 310 7-mo 601I 50Cr-50Fe
alloy
wei
ght g
aine
d (m
g/cm
^2)
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AcknowledgmentsDr. Safaa Al-Hassan
Jorge Perdomo
Jamshad Mahmood,
Tony Clandra
DOE - (DE-FC36-95GO10092)
AF&PA
ORNL - 85X-SY627V
Mill Personnel
IPST Member Companies