Metal Dusting Corrosion Initiation in Conversion of Natural Gas to Synthesis Gas
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Transcript of Metal Dusting Corrosion Initiation in Conversion of Natural Gas to Synthesis Gas
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Metal dusting corrosion initiation in
conversion of natural gas to
synthesis gas
Professor Hilde Venvik
Department of Chemical Engineering, NTNU
2011-11-03
http://www.sintef.no/Projectweb/TGTC2011/ -
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inGAP is a National Centre of Research-based Innovation (SFI),appointed by the Norwegian Research Council.
inGAP's vision is value creation in natural-gas processes throughrational design of processes and products based on atomistic andmechanistic insight in catalyst and reactor parameters under operativeconditions
inGAP has very successfully developed research on natural gasprocessing in the international frontline and maintains excellentcontacts and technology transfer with partner industries;- 2010 mid-term evaluation of all CRI (SFI) centres.
inGAPs partners include UiO, SINTEF, Statoil, Borealis, Ineos andHalldor Topse AS (Denmark).
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Acknowledgement
PhD student P.V.D.S. (Daham) Gunawardana, Professor AndersHolmen, Professor De Chen, Department of Chemical Engineering
Senior scientist John Walmsley, Ingvar Kvande, SINTEF Materialsand Chemistry, Trondheim, Norway
Thoa Thi Minh Nguyen, Halldor Topse AS, Kgs. Lyngby, Denmark.
Jorun Zahl Albertsen, Bente Krogh, Emil Edwin, Iver Espen Pedersen,Statoil Research Centre, Trondheim, Norway 4, Arkitekt Ebbells vei
10, 7005.
Professor Unni Olsbye, University of Oslo, Norway
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Outline
What is metal dusting?
Important existing knowledge
Our approach to metal dusting
Recent results in metal dusting
Conclusions and outlook
Koksdannelse ved cracking,A. Holmen, O. A. Lindvg,
SINTEF Kjemi, 1980
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Metal dusting corrosion:
A potentially catastrophic materials degradation phenomenon
Affects process equipment applied in natural gas conversion atelevated temperature
Occurs due to the decomposition of carbon
containing molecules to form carbon on the inner surfaces of theequipment
Proceeds by dissolution of carbon in the alloy, carbide formation and
carbide decomposition
Eventually turns the alloy into fine particles
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[1]
[2]
1.
Experimentalandthe
oreticalinvestigations
ofmetaldustingcorrosioninplantexposed
nickel-basedalloys.J
.Z.Albertsen;PhDthesisatNTNU,2007:0
5.
2.
Corrosionbycarbon
andnitrogen-Metald
usting,carburizationandnitridation;
WoodheadPublishingLimited,Cambridge.
Metal dusting @ Statoil Tjeldbergodden
methanol plant
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What is metal dusting?
1. Carbon formation oninner surfaces
2. Carbide phaseformation anddecomposition cycleswithin the material
hemispherical pits
uniform attack
3. Material is graduallyturned into a dustl ikecorrosion product
also contains carbidesand oxides
Metal dusting in a
heat exchanger forsynthesis gas made
by a large grained
alloy 800Top: wall segment
Bottom: Uniformly attackedsurface with coke andcarburized zones
Metal dusting in
a drain line of a Ni
based alloy located
in a steam
superheaterExample of pit formation
50 m
50 m
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Which processes and units can be
affected by metal dusting? Syngas production for ammonia, methanol/DME, GTL,
steam crackers, high-temperature fuel cells
Could save $500 million to $1.3 billion per year in thehydrogen industry if prevented Increased industrial productivity by enabling machinery to
function with fewer maintenance shutdowns. Such savings will
become increasingly important as hydrogen is used more as asource of energy (Argonne national laboratory, US)
Plant conditions natural gas reforming: Reduction of costs is a natural target
Decrease the steam content in the process gas while increasingthe overall reformer capacity
Steam/carbon ratio decreased Risk for metal dusting in heat
recovery units will be higher
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22 C O C C O
2 2C O H C H O
4 22C H C H
2 2 2CO H O CO H
3 3C M C
The thermodynamic driving force
Carburizing atmosphere
High carbon activity (ac>1)
Critical T-range: 400-1000C
{ , , }Ni Fe CrM
2
2
,1 1 ( ) H C O
C
H O
p pa K T
p
2
2
,2 2
( )( ) C O
C
C O
pa K T
p
4
2
,3 3 2( ) ( )
C H
C
H
p
a K Tp
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The kinetic control of carbon formation
The extent of carbon formation is determined by the surface on whichthe carbon forms; i.e. unwanted catalytic reactions
Metallic phases (particles) known to activate CO (CH4) and to formcarbides; i.e. Ni, Fe, Co,
The metals are important in steel/HT-alloys
Carbon formationanalogous to onNi(Fe)-basedcatalysts
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Carbon formation on Ni observed in situ at
Halldor Topsoe AS
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Selective synthesis
of CNF/CNT
CNT/CNF as
catalyst supports
Pt/CNF
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Metal dusting prevention
Adjustment or careful selection of process parameters(T, P, C)
Development of new, metal dusting resistant, alloys
Application of coatings to protect the underlyingmetal/alloy matrix (Cr-, Al- surface oxide layer)
Mixing process gas with low concentration of sulfurcompounds (H2S, CS2, (CH3)2S2, etc.)
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Our (non-metallurgical) approach
Any better predictive tools for the carbon formation is animmediate cash saver, therefore
Understand the initiation of the carbon formation Where does the first carbon form and what is the structure and
composition of these sites?
Can these sites be manipulated_
Develop experimental procedures that are informative yetrepresentative Shorten the phenomenological time scale from months/years to
hours/days Control the alloy composition and pretreatment
Apply advanced characterization tools
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Effect of oxidation pretreatment
conditions on a commercial alloy Inconel alloy 601:
(5863%Ni, 2125%Cr, balance-Fewith Al, C, Mn, S, Si, Cu)
As-received and polished samples
3 oxidation atmospheres:
100% O2
0.5% O2 in Ar 10 % steam 90% Ar
Oxidation temperatures:
540 C - 980 C
Initial test in different carburizationactivity at 550 C for 20h :
10% CO in Ar (infinite ac)
10% CO-10%SteamAr (finite ac)Tme (min)
0 100 200 600 650 700 750 800
Temperature(oC)
0
200
400
600
800
1000
1200 6 h dwell
Rapid cooling in Ar
5minpurgewith
oxidationgas
10oC/min ramp
540o
C
760oC
980oC
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Results
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The harsher the oxidation conditions the higher the carbon formation
As-received 100% O2 0.5% O2 ArAll samples subjected to 10% CO in Ar (infinite ac)
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Oxide surface formed under harsh conditions (p-O2, T) is less denseand with more defects
100% O2 0.5% O2 Ar
Characterization by scanning electron microscopy (SEM)
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Advanced characterization
Depth profiling of oxide layer composition and structure bycombined Ar sputtering, Auger spectroscopy and SEM
Behavior of polished (1um) surfaces in different oxidation conditions(Inconel 601)
Depth length (nm)
0 10 20 30 40
Intensity
0
500
1000
1500
2000
2500
[O] of 100%O2oxidation at 540
oC for 6h
[Cr] of 100%O2oxidation at 540o
C for 6h
[Al] of 100%O2oxidation at 540o
C for 6h
[O] of 0.5%O2-in-Ar oxidation at 540
oC for 6h
[Cr] of 0.5%O2-in-Ar oxidation at 540oC for 6h
[Al] of 0.5%O2-in-Ar oxidation at 540oC for 6h
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Behavior of polished (1um) surfaces in different oxidation conditions(Inconel 601)
Depth length (nm)
0 10 20 30 40
In
tensity
0
500
1000
1500
2000
2500
[O] of 100%O2oxidation at 540
oC for 6h
[Cr] of 100%O2oxidation at 540
o
C for 6h
[Al] of 100%O2oxidation at 540
o
C for 6h
[O] of 0.5%O2-in-Ar oxidation at 540
oC for 6h
[Cr] of 0.5%O2-in-Ar oxidation at 540
oC for 6h
[Al] of 0.5%O2-in-Ar oxidation at 540
oC for 6h
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Advanced characterization
Depth profiling of oxide layer composition and structure bycombined Ar sputtering, Auger spectroscopy and SEM
Resistance to carbon formationappears correlated with high
O and Cr in outer layer
Results so far inconsistentwith respect to Al
Behavior of polished (1um) surfaces in different oxidation conditions(Inconel 601)
Depth length (nm)0 10 20 30 40
Intensity
0
500
1000
1500
2000
2500
[O] of 100%O2oxidation at 540
oC for 6h
[Cr] of 100%O2
oxidation at 540o
C for 6h
[Al] of 100%O2oxidation at 540o
C for 6h
[O] of 0.5%O2-in-Ar oxidation at 540oC for 6h
[Cr] of 0.5%O2-in-Ar oxidation at 540oC for 6h
[Al] of 0.5%O2-in-Ar oxidation at 540oC for 6h
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Carbon formation observed under conditions applied extends fromlittle/no observable carbon to thick deposits of filamentous carbon
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Some conclusions
Preparation/pretreatment protocols are very important Polishing
Oxidation conditions
Dense Cr-containing oxide is more protective Pre-polished samples treated in H2O/Ar at the lowest temperature
appear to have the best resistance
Actual catalyst remains to be identified
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Thank you for your attention!