Liquid CO2 storage tank - material and corrosion issue

[cyria]

Dear all

Liquid co2 storage tank with 7 bar and -50oC.
Liquid co2 is almost 99%.
I know if there is no water, there is no risk of co2 corrosion.
However it is not sure, there is no water content.
Is it possible to use carbon steel and coating such as zinc silicate type?
Is it practical to calculate the corrosion rate with De Waard equation?
I really wonder is there any corrosion risk under current situation,(very low temperature)?
If you have any standard, rule, technical background or experience about it, it would be very helpful.

 

[psafety]

Recheck that temp at a leak/depressurization I think it'll exceed the min temp of carbon.

 

[BenThayer]

where is your source of water? and at -50°C, wouldn't it be ice?

the liquid CO2 bullets we had (worked at a site where we produced/recovered ~600 Ton / Day from an ammonia process a decade ago) we used mole sieve to remove any water and condensed and stored the Liquid CO2 at about -15°F and ~ 200 psig. memory might be a bit fuzzy on exact temp and pressure but you can look it up easy enough.

regarding leak/depressurization, we had it in just relatively mild carbon steel. if you get a major leak/depressurization, you are headed for a solid anyways. besides, the coincident temperature pressure should not be an issue. we were always more concerned with loss of refrigeration than a leak.

 

[psafety]

Yes the temperature is critical as the metal freezes. I am very well aware of the potential. May I cite:

http://onlinelibrary.wiley.com/doi/10.1002/prs.680130405/references

It does happen.

 

[SJones]

There are no CO2 corrosion prediction models that will work for the conditions stated. There needs to be sufficient water content to form a separate aqueous phase for corrosion to occur (which will then freeze). So check your water content and process engineering models to see whether a distinct aqueous phase, as opposed to a dispersion, can be achieved.

Steve Jones
Materials & Corrosion Engineer

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

 

[BenThayer]

psafety,

thanks for the info. did the event you cited occur because of the CO2 essentially undergoing a rapid boiling similar to a BLEVE. May I cite:

http://www.criticalprocesses.com/BLEVE.htm

http://www.eiga.org/index.php?id=18...nload&tx_abdownloads_pi1[uid]=1600&no_cache=1

would a better metallurgy protect against that type of boil-off or is it a relief device sizing question?

thanks.

 

[psafety]

CS minimum temp is -20F I think. I was involved in the following inspections. We went to 304SS, best I remember a nozzle weld failed the rapid release lifted the vessel off the supports and immediately froze, fractured and turned into a missle. Since the paper was published I assume I can share what was written. As the paper stated we found stress fatique in most of these vessels and replaced all. Yes, you can say it was similar to a BLEVE. In safety we say Murphy is an optimist. If building a new vessel consider the content of that report.

 

[maddocks]

You're going to want to check out the depressuring scenario. Water isn't going to be an issue but the resulting temperatures from depressuring will potentially push you into stainless. Without an aqueous phase, corrosion isn't generally considered to be an issue.