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 H

+

e

−

⇔

H

Anode reaction Cathode reaction

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

• Degradation products

• Break down of protective layer (Fe₂O₃, Fe₃O₄,FeCO₃etc)

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

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

R_corr vs liquid flow

R_corr by weight loss R_corr by weight loss

R_corrin 6 bottles R_corr by weight loss

R_corr by EC (LPR, EIS) R_corr 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 % CO₂at 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 % CO₂at 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 CO₂at

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 CO₂at 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