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Corrosiveness of contaminated CO2 stream on HDPE  

Thread by Tim on 11 Mar 2009 at 08:42:29 
Hello everyone,

From the information that I gathered here and elsewhere I know that the corrosiveness and permeability of a pure CO2 stream through a HDPE is low and HDPE is resistent to pure CO2.

What I want to know is what the corrosiveness is of CO2 in the presence of water > forming carbonic acids and what the reaction with HDPE is.

Further, what if the CO2 stream contains small % of H2S, SOx, NOx,O2, H2, CH4, etc (with H2O), what will happen with the HDPE then (corrosiveness, permeability,chemical reactions between each other and HDPE, etc).

I am keen on learning more about this!

Thanks!

Tim

    Comment by Rodney on 13 Mar 2009 at 16:31:11  | |responses: 1|
    Tim,

    HDPE is corrosion resistant to supercritical saturated CO2 (for examples 100 bar 25 degrees Celsius and almost saturated with water), since the pH of carbonic acid is in the range of 3 to 4. Carbonic acid is even in these circumstances a weak acid.

    Sulphuric acid is a nasty one. For a given concentration sulphuric acid is 500.000 times stronger than Carbonic Acid. For long term operation at very low pH, fluoro polymers (PVDF, ETFE) maybe better.

    Note that in high pressure applications the above materials are used in combination with stronger structural materials, such as metals. In that case, the situation at the metal - polymer interface is important for the overall life time. You can think of corrosion reaction with metal, pressure built-up in voids (giving rise to delamination), etc. This is also reason why real composite materials (i.e. glass reinforced epoxy, GRE) are sometimes preferable over polymer - metal laminates: they have the intrinsic potential to be more stable on the long term (at least if the pH does not become too low).

    Rodney

      Comment by Tim on 24 Mar 2009 at 15:07:24  | |responses: 0|
      Rodney,

      Could we get in contact with each other via mail?

      I still have some questions remaining about the transport of impure CO2 transport.

      You can reply and put "send me email notifications on replies....." and still hide it for public. The moderator can then share emails, still safe way to get i ntouch.

      Thanks Tim