Rich Amine Corrosion 1

[Xeros]

hi,

i'm Xeros.

Fluid is consist of Water and Rich Amine containing CO2.

I think that Rich Amine (salt??)could be dissolved in water and this solution is corrosive.

Is it right?

If this fluid is corrosive, I want to get the information & reference of corrosion mechnism and material requirement preventing the corrosion.

Best regards,

 

[0707]

Amine Corrosion
5.1.1.1.1 Description of Damage

a) Amine corrosion refers to the general and/or localized corrosion that occurs principally on carbon steel in amine treating processes. Corrosion is not caused by the amine itself, but results from dissolved acid gases (CO2 and H2S), amine degradation products, Heat Stable Amine Salts (HSAS) and other contaminants.

b) Stress corrosion cracking of carbon steel in amine services is discussed in 5.1.2.2.

5.1.1.1.2 Affected Materials

Primarily carbon steel. 300 Series SS are highly resistant.
5.1.1.1.3 Critical Factors

a) Corrosion depends on design and operating practices, the type of amine, amine concentration, contaminants, temperature and velocity.

b) Amine corrosion is very closely tied to the operation of the unit. With a few exceptions, carbon steel is suitable for most components in a properly designed and operated unit. Most problems can be traced to faulty design, poor operating practices or solution contamination.

c) Corrosion is also dependent on the type of amine used. In general, alkanolamine systems can be rated in order of aggressiveness from most to least as follows: monoethanolamine (MEA), diglycolamine (DGA), diisopropylamine (DIPA), diethanolamine (DEA), and methyldiethanolamine (MDEA).

d) Lean amine solutions are generally not corrosive because they have either low conductivity and or high pH. However, an excessive accumulation of heat stable amine salts (HSAS) above about 2%, depending on the amine, can significantly increase corrosion rates.

e) Ammonia, H2S and HCN accelerate corrosion in the regenerator overhead condenser and outlet piping as well as reflux piping, valves and pumps.

f) Corrosion rates increase with increasing temperature, particularly in rich amine service. Temperatures above about 220oF (104oC) can result in acid gas flashing and severe localized corrosion if the pressure drop is high enough.

g) Process stream velocity will influence the amine corrosion rate and nature of attack. Corrosion is generally uniform however high velocities and turbulence will cause localized thickness losses. For carbon steel, common velocity limits are generally limited to 3 to 6 fps for rich amine and about 20 fps for lean amine.

Refª “API RECOMMENDED PRACTICE 571” Damage Mechanisms Affecting
Fixed Equipment in the Refining Industry

REGARDS

LUIS

 

[dcasto]

The rich to lean exchanger and down stream is where the corrosion is most active because the CO2 and H2S are going in the revese direction of the chemical reaction or they are coming out of solution.

In practice, smaller amine units use mild carbon steel because corrosion rates are not drastic. As the unit gets larger and the exchangers get big, then the rich amine is placed on the tube side made of 304 SS. Even the rich amine flash tank is made of mild carbon steel with .250 in corrosion allowance. Make sure all lines and vessels in rich service are stress relieved.