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carbamate corrosion at moderate T & p?
3

carbamate corrosion at moderate T & p?

carbamate corrosion at moderate T & p?

(OP)
Dear all,
carbamate is known as corrosive agent in urea plants, where high pressure and temperature are applied.
But what about mixtures of CO2,NH3, water at moderate temperatures (10 - 80°C) and moderate pressure (1 - 10 bara)?
I am asking because when quering for 'carbamate corrosion' or related topics, one always gets results related to urea production, at harsh conditions.
From a first sight, I'd say, carbon steel is OK for the NH3-dominated, alkaline mixtures at moderate conditions. On the other hand, I can't find supportive feedbacks.
What do you think?
Thanks a lot!

RE: carbamate corrosion at moderate T & p?

I don't believe google knows much about this problem.
Suggest you start with this NiDI publication, and maybe contact them for expert consulting help.

"Everyone is entitled to their own opinions, but they are not entitled to their own facts."

RE: carbamate corrosion at moderate T & p?

(OP)
Ironic metallurgist, thanks a lot.

RE: carbamate corrosion at moderate T & p?

The situation you are talking about is prevalent in ARU overhead circuits. That is a common feature in many refineries. Consult the Corrosion Handbook Vol 13 for further guidance.

DHURJATI SEN
Kolkata, India

RE: carbamate corrosion at moderate T & p?

DS,

As far as I know carbamates are unique to urea process; I have not heard of it in refinery. Correct me if I am mistaken.

"Everyone is entitled to their own opinions, but they are not entitled to their own facts."

RE: carbamate corrosion at moderate T & p?

(OP)
IM,

carbamate occur as first reaction product in processes dealing with CO2, NH3 and water, including carbon capture by NH3.
I don't know about ARUs

Demser

RE: carbamate corrosion at moderate T & p?

I was not referring to carbamate at all. I was answering the 2nd line only.

Quote (But what about mixtures of CO2,NH3, water at moderate temperatures (10 - 80°C) and moderate pressure (1 - 10 bara)?)


In the Amine Regeneration Column, after the rich amine is stripped, the overhead gas consists of H20, H2S, CO2 & NH3, the last one as a result of slippage from secondary units like OHCU.

This CO2 and NH3 give lot of pain in the overhead circuits.

DHURJATI SEN
Kolkata, India

RE: carbamate corrosion at moderate T & p?

(OP)
DS and IM:

In the meantime, I learned about the publication of C.P. Dillon in "Materials Performance" (Dec 1999, p.74f), who mentions several applications - besides Urea - where carbamates are discussed as corrosive agents: alkylamine production, NH3 stripping (alkanolamine, ethyleneamine production), CO compressor with CH3NH2-based odorant (traces of CO2)etc. And also processes dealing with CS2 + NH3, giving thio-carbamate.
The is very little information on temperature or pressure thresholds above which carbamate becomes corrosive for processes others than Urea.

Regards,
Demser

RE: carbamate corrosion at moderate T & p?

Thanks demser & DS, I learned something useful today.

"Everyone is entitled to their own opinions, but they are not entitled to their own facts."

RE: carbamate corrosion at moderate T & p?

2
Here is a simple review for MOC in Urea plant.

Several Urea licensors (Stamicarbon, Saipem, KBR, Uhde, Urea Casale, etc.) are often using specific materials (i.e., Safurex®, ASME Code Case 2295-2-UNS S32906, Alloy 2RE69, X2CrNiMoN 25 22 2 or Type 310MoLN) instead of conventional material (316L SS) in Carbamate circuits (reactor, HP-scrubber, stripper, carbamate pool condenser, etc.) of Urea Plant since 1997-2000.

CS in Urea Processes is typically used for utility services and products (i.e., steam, water, air, etc.).

The HMB Tables should be evaluated for more detail MOC.

Additional References (other than above answers) for Ammonia-Urea Services
- ANSI STD K61.1 Safety Requirements for the Storage and Handling of Anhydrous Ammonia
- Code of Federal Regulations, Title 29, OSHA Chapter XVII, Part 1910.111 (29 CFR 1910.111)
- MTI MS-6 Materials Selector for Ammonia and Caustic Soda
- NSC 1-251 National Safety Council
- NACE Paper 07195
- NACE MP, Protection of CS Tanks containing 32% Urea Mixture, Jan. 2010, p28-30
- Urea licensors‘ manuals

Thomas Eun

RE: carbamate corrosion at moderate T & p?

(OP)
Hello Thomas,

thank you very much for the Additional References, and NACE 07195 in particular.

Regards,
Demser

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