Internal Corrosion for dry CO2 pipelines 1

[tag10]

For a carbon steel pipeline, internal corrosion is a significant risk to the pipeline integrity in case of insufficient dewatering of the CO2 composition. Free water combined with the high CO2 partial pressure may give rise to extreme corrosion rates, primarily due to the formation of carbonic acid.

In my case, the fluid composition contains:
-(CO2) Vol% >99.6;
-(H2O) ppmv <500;
CO2 Transportation is done at:
- more then 40 degress C;
- more the 120 bar.

How can I predict the corrosion rates with sufficient precision, in order to choose the CS MATERIAL? Can you give me a recommendation (or a software) in order to solve this issue.

Thanks for your advice.

 

[SJones]

If you condense liquid water, corrosion rates will be BIG! It doesn't need a model to tell you that. Clearly, you can readily choose carbon steel provided that you have an appropriate corrosion control strategy based on high reliability dehydration coupled with effective response to transgressions of the operating envelope. If you must model, NORSOK M-506 or FREECORP are probably your best bets.

Steve Jones
Materials & Corrosion Engineer

http://www.linkedin.com/pub/8/83b/b04

 

[grampi1]

I think what he is asking is what dewpoint he needs to achieve in dehydration to assure no water can drop out. Fr that he needs access to a process engineer who can run an equation of state simulator. Generally, a good TEG plant can do the job for CO2 pipelines.

 

[tag10]

Mr. SJones,

Thanks for your answer.
Please be informed that I do not have condensate liquid water.
According to the parameters mention by me (T>40 degress C and P>120 bar), CO2 Transportation is done at supercritical state.
In this case (supercritical state of CO2), I think that NORSOK M-506 or FREECORP are not the best sollutions...

According to fluid's composition (CO2) Vol% >99.6 and (H2O) ppmv <500, it is very difficult for me to say that the corrosion will appear or not.
In order to be sure that I will not have BIG corrosion rates, I was interested to know, how can I predict the corrosion rates (with sufficient precision) in order to be sure, that the carbon steel can be used for the piping MATERIAL.

 

[tag10]

Mr. grampi1,

As you now the density of CO2 depends by temperature and pressure...
I am interested to know, if CO2 composition (mention by me in the above message) could become aggressive at different temperatures and pressures...
Until now, I did not find an answer regarding to simulation of CO2 process. Can you recommend me a document or software?

If there is no problem with corrosion rate, then I will have to take into consideration all scenarios (for example depressurizing CO2 from high pressure)...

 

[SJones]

No water condensation = negligible corrosion as evidenced by the numerous carbon steel CO2 pipelines already in existence. Review NACE Corrosion 2003, Paper 03345 which concludes that modelling is very unreliable in CO2 transportation.

Steve Jones
Materials & Corrosion Engineer

http://www.linkedin.com/pub/8/83b/b04

 

[strider6]

If a gas is "dry" you'll not have corrosion, see below taken from NORSOK M001 Material Selection:

"A gas is considered dry when the water dew point at the actual pressure is at least 10 °C lower than the actual operation temperature for the system"

"For pipelines with dry gas or non-corrosive fluids, no corrosion allowance is required. Corrosion during installation and testing prior to start-up shall be considered"

http://www.standard.no/PageFiles/1194/M-001.pdf

hope this help

S

Corrosion & Rust Prevention Control

 

[tag10]

strider6,
Thank you very much for your info.

According to your recommendation (NORSOK M001 Material Selection), I found that it necessary to insulate the piping, in order to be above to the water dew point, at the actual pressure... What do you think about this solution (insulation)? Is it normal?

How can I take into consideration the Corrosion during installation and testing prior to start-up? Do you know a procedure or something else?

Thanks.

 

[tag10]

Mr. SJones,

Thanks for your info.

I have looked on "NACE Corrosion 2003, Paper 03345" (page 933) and I found that maximum water content is better to be 50 ppm. In my case (500 ppm) it is difficult to predict the corrosion value... According to Mr.strider6 recommendation, I solved the a part from the issue...

I didn't find any information (see "NACE Corrosion 2003, Paper 03345", page 933) regarding to selection of piping material, in case of -79 deg C (when dry ice will appear). The document present only the ordinary CMn steel at minimum operating temperature -46 deg C... Until now I did not find any info about -79 deg C. Do you know an example? Thanks!

 

[SJones]

NACE 2010, Paper 10193 suggests that, at 75.8 bar and 40 deg C, 2000 ppm m H2O is the threshold for appearance of an aqueous phase. That should give you a risk assessment starter in that water solubility will increase with both pressure and temperature.

Steve Jones
Materials & Corrosion Engineer

http://www.linkedin.com/pub/8/83b/b04

 

[BenThayer]

not sure how much corrosion you might get during start-up and shutdown as you pressure up or heat up the piping, etc.

to me, to focus only on steady state normal operation is often a mistake.

i have had lots of equipment be designed "correctly" but would fail during a mistake during commissioning or shutdown.