Piping Corrosion 1

[CGarcia]

Greetings from Venezuela everyone,

I recently joined a consulting company involved in the gas treating area, specifically amine treating.

In order to minimize the problem of wet CO2 corrosion in natural gas streams, in Venezuela it is required a natural gas quality of less of 8.5% molar of CO2 and less than 7lb H2O/MMSCF (Although, future governmental regulations will decrease the CO2 requirement to 2% molar).

Now, I have a doubt regarding the wet CO2 corrosion issue. Let`s say I have a natural gas stream rich in CO2 (10% molar) and H2O (130 lb H2O MMSCF), and I dehydrate the current to very low levels of H2O (less than 7 lb H2O/MMSCF) without removing the CO2. Would I still have problems with CO2 corrosion in an unsaturated gas stream? Why?

Any help would be appreciated. Thanks.

 

[dcasto]

No, it takes freewater to make carboxylic acid. There is some concerns about gaurenteeing the gas stream has no freewater. Acid base reactions take place in a liquid phase to exchange H+.

There have been many post concerning CO2 concentration and SCC on pipelines. A lot of people I work with limit the partial pressure of C02 to 25 psia or 2.5% at 1000 psia line pressure when there is frewater. Look at a 100% CO2 pipeline made out of carbon steel, no issue because the CO2 has been dehydrated. Co2 operating above its criticle pressure becomes hydroscopic and will hold more water in the gas phase that at pressures below its criticle point.

 

[SJones]

Your principal problems will come from dehydration upsets and shut ins leading to the question 'how much corrosion allowance do I put on the carbon steel equipment'. Try a search of these forums using 'corrosion allowance' as the search term.

Steve Jones
Materials & Corrosion Engineer

http://www.pdo.co.om/pdo/