Corrosion experiments in amine solutions

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Corrosion experiments in amine

solutions

Andreas Grimstvedt Process technology

SINTEF Materials and chemistry

Wenle He

Applied mechanics and corrosion SINTEF Materials and chemistry

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Contents of presentation

Background

Apparatus for corrosion experiments

Results experiments MEA

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Background

Corrosion problem on the equipments in amine based CO2 capture process Corrosion is influenced by many parameters:

Type and concentration of amine Gas concentration (O2, CO2)

Temperature Steel

Fluid flow

Products from corrosion and degradation Corrosion and degradation inhibitors

Corrosion of steel and degradation of amines:

Degradation product can be chelating agents for iron ions. Iron ions can catalyze the degradation of amines.

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Corrosion in aqueous systems with CO

2 − +

+

Fe

e

Fe

2

2

2

2

2

H

+

+

e

H

Anode reaction Cathode reaction

• Carbamate (primary and secondary amines) • Heat stabile salts

• Degradation products

• Break down of protective layer (Fe2O3, Fe3O4,FeCO3 etc)

A. Ikeda, M. Ueda and S. Mukai, CO2Behavior of Carbon and Cr Steels, In Advances in CO2Corrosion (1984)

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Apparatus and Corrosion rate measurements

EC-Rotating disk electrode EC-autoclave, 1L Pipe-autoclave, 1.5L 5L-autoclave

RT~80ºC, atm, flow RT~150ºC, 2 bar RT~500ºC, 10 bar RT~500ºC, 10 bar

Rcorr by EC (LPR, EIS) Rcorr vs time,

Rcorr vs liquid flow

Rcorr by weight loss Rcorr by weight loss

Rcorrin 6 bottles Rcorr by weight loss

Rcorr by EC (LPR, EIS) Rcorr vs time

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Rotating disc electrode

2 / 1 3 / 1 6 / 1 61 . 1 ω ν δ = D

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Autoclave Glass beaker Plastic Wood Platinum counter electrode Saturated calomel reference electrode Salt bridge Gas outlet Gas inlet 316 L Working electrode Magnet

Stirrer and heater Amine solution Thermocouple

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Material

Environments

Corrosion rate measurements

Carbon steel: ST 52

Stainless steels: 316L, 13Cr

Solutions: MEA, DETA 30 %, 50 %,

new and degraded Temperature: 40 ºC

Gases: open air 100 % CO2

4 % CO2+N2

4 % CO2 +12 % O2

Liquid flow: rotating disk electrode

•Tafel Polarization

•Linear Polarization Resistance (LPR) •Impedance

•Weight Loss

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Steel St 52 was corroded at low potentials

At higher potentials the metal became passive.

-1.0 -0.5 0.0 0.5 1.0 1.5 -1.00 0.00 1.00 2.00 3.00 4.00 i / mA cm-2 E / V SC E Polarization curve

St 52 corrosion in 30 % MEA with

4 % CO2 at 40 ºC, pH 10.50

Potential pH diagram

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Comparison of Corrosion

Rates measurements

0.59 Impedance (nondestructive)

0.63 Linear Polarization (nondestructive)

0.80 Tafel Extrapolation Corrosion rate mm / year Measurements y = -0.2689x - 0.9182 y = 0.0993x - 0.6757 -1.2 -1.0 -0.8 -0.6 -0.4 -0.2 -4 -3 -2 -1 0 1 2 log (| i |/mA cm-2) E/ VSC E y = 75.266x - 0.801 -0.815 -0.81 -0.805 -0.8 -0.795 -0.79

-2.0E-04 -1.5E-04 -1.0E-04 -5.0E-05 0.0E+00 5.0E-05 1.0E-04 1.5E-04 I / Acm-2 E/ V SC E 0 10 20 30 40 0 20 40 60 80 100 Z'/ ohm cm2 Z' '/ o h m cm 2 Rs Rs+Rct

Corrosion rates were determined by current, linear polarization resistance and impedance resistance

St 52 corrosion in 30 % MEA

with 4 % CO2 at 40 ºC,

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Effect of CO

2

partial pressure and

O

2

on corrosion rates

0.46 439 4 % CO2 + 12 % O2 0.42 482 4 % CO2 0.59 339 100 % CO2 Corrosion rate mm / year Charge transfer resistance

Rct, ohm cm2 Gas 0 40 80 120 160 200 0 100 200 300 400 500 Z'/ ohm cm2 Z' '/ ohm cm 2 100 % CO2 4 % CO2 4 % CO2 12 % O2 St 52 corrosion in 30 % MEA with 4 % CO2 at 40 ºC, pH 10.50

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Effect of MEA concentration on

corrosion rates

Corrosion in MEA with CO2 at

40 ºC, 100 rpm 0.008 1.10 0.48 4% CO2 + 12 %O2 0.005 0.85 0.35 4% CO2 50% MEA 50% MEA 30% MEA Gases/Solution 13Cr St 52 St 52 Material

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Effect of amine

degradation and flow

St 52 corrosion in 30 % MEA with CO2 at 40 ºC

0.0 0.4 0.8 1.2 1.6 0 500 1000 1500 2000 2500 Rotation rate/ rpm Co rr os io n r a te/ mm y e a r -1 4 % CO2 + 16 % O2 4 % CO2 Fresh MEA pH 10.50 1.2 1.6 2.0 2.4 0 500 1000 1500 2000 2500 Rotation rate/ rpm Co rro sio n rate/ mm yea r -1 4 % CO2 + 12 % O2 4 % CO2

Corrosion rates were increased by amine degradation, flow, oxygen presence

1.6 2.0 2.4 2.8 0 500 1000 1500 2000 2500 Rotation rate/ rpm Corrosion rate / mm yea r -1 4 % CO2 + 12 % O2 4 % CO2

Degraded MEA (air, 10 days) pH 9.77

Degraded MEA (air+2% CO2, 10 days)

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Corrosion in

Diethylenetriamine (DETA)

No Corrosion when oxygen was present!

Heavy Corrosion when oxygen was removed. Mainly Corrosion was in the solution.

Corrosion ra te/ mm y -1 316L corrosion in 2.5 M DETA at 135 ºC (α=0.5)

Corrosion rates were measured by weight loss

Open air system CO2purged through amine CO2purged over amine

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-1.5 -1 -0.5 0 0.5 1 1.5 -2.0 -1.0 0.0 1.0 2.0 i/ mA cm-2 E/ V SC E 40 °C 80 °C

At 80 °C the 316L Steel shows active and passive behavior

-1.5 -1 -0.5 0 0.5 1 1.5 -2.0 -1.0 0.0 1.0 2.0 i/ mA cm-2 E/ V SC E Measurement on Pt 316L corrosion in 2.5 M DETA

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Almost no corrosion was observed for 316L and 13 Cr steel in MEA.

St 52 was not corroded in MEA without CO2 present.

The corrosion rate of ST 52 was increased with concentration of CO2 and MEA.

Corrosion rate was increased by degradation of MEA.

Corrosion rate was increased when O2 was present.

Corrosion rate was increased by increasing fluid convection with O2 present.

316L was corroded in DETA

Figure

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