metal dusting corrosion initiation in conversion of natural gas to synthesis gas

8/13/2019 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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Depth length (nm)

0 10 20 30 40

In

tensity

0

500

1000

1500

2000

2500


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


Depth length (nm)0 10 20 30 40

Intensity

0

500

1000

1500

2000

2500


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!

metal dusting corrosion initiation in conversion of natural gas to synthesis gas

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